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Sample records for basalt volcanic field

  1. Heavy minerals in basalt maares and diatremes of South-Slovak alkali basaltic volcanic field

    International Nuclear Information System (INIS)

    A heavy mineral is one with a density that is greater than 2.8 g/cm3. Heavy mineral suites are usually used for determination of provenance and history of sedimentary and metamorphic rocks. The present study is focused on heavy minerals from pyroclastic rocks collected in maars and diatremes from the South Slovakian alkali basalt volcanic field. Practical part describes sampling strategy and methods of heavy mineral separation. Heavy minerals association from maar Hodejov and Filakovo as well as from diatremes Surice and Tachty were studied. The results indicates, that the samples are suitable for further research like geochronology, definition of possible heavy minerals source rocks and sedimentology analyses. This work will help us to get new information about alkali basalt volcanism in Southern Slovakia. (author)

  2. Numerical simulation of basaltic lava flows in the Auckland Volcanic Field, New Zealand—implication for volcanic hazard assessment

    OpenAIRE

    Kereszturi, G.; Volcanic Risk Solutions, Institute of Agriculture and Environment, Massey University, New Zealand; Cappello, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Ganci, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Procter, J.; Volcanic Risk Solutions, Institute of Agriculture and Environment, Massey University, New Zealand; Németh, K.; Volcanic Risk Solutions, Institute of Agriculture and Environment, Massey University, New Zealand; Del Negro, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Cronin, S. J.; Volcanic Risk Solutions, Institute of Agriculture and Environment, Massey University, New Zealand

    2014-01-01

    Monogenetic volcanic fields, such as the Auckland Volcanic Field (AVF), New Zealand, are common on the Earth’s surface and are typically dominated by basaltic lava flows up to 10 s of km long. In monogenetic volcanic fields located in close proximity to human population and infrastructure, lava flows are a significant threat. In this study, lava flow emplacement conditions for some basaltic eruptions of the AVF were reconstructed using the thermo-rheological MAGFLOW model. Eight existi...

  3. Preliminary K/Ar geochronology of the Crater Basalt volcanic field (CBVF, northern Patagonia

    Directory of Open Access Journals (Sweden)

    Z. Pécskay

    2007-03-01

    Full Text Available The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a multistage history of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.

  4. The Mantle and Basalt-Crust Interaction Below the Mount Taylor Volcanic Field, New Mexico

    Science.gov (United States)

    Schrader, Christian M.; Crumpler, Larry S.; Schmidt, Marick E.

    2010-01-01

    The Mount Taylor Volcanic Field (MTVF) lies on the Jemez Lineament on the southeastern margin of the Colorado Plateau. The field is centered on the Mt. Taylor composite volcano and includes Mesa Chivato to the NE and Grants Ridge to the WSW. MTVF magmatism spans approximately 3.8-1.5 Ma (K-Ar). Magmas are dominantly alkaline with mafic compositions ranging from basanite to hy-basalt and felsic compositions ranging from ne-trachyte to rhyolite. We are investigating the state of the mantle and the spatial and temporal variation in basalt-crustal interaction below the MTVF by examining mantle xenoliths and basalts in the context of new mapping and future Ar-Ar dating. The earliest dated magmatism in the field is a basanite flow south of Mt. Taylor. Mantle xenolith-bearing alkali basalts and basanites occur on Mesa Chivato and in the region of Mt. Taylor, though most basalts are peripheral to the main cone. Xenolith-bearing magmatism persists at least into the early stages of conebuilding. Preliminary examination of the mantle xenolith suite suggests it is dominantly lherzolitic but contains likely examples of both melt-depleted (harzburgitic) and melt-enriched (clinopyroxenitic) mantle. There are aphyric and crystal-poor hawaiites, some of which are hy-normative, on and near Mt. Taylor, but many of the more evolved MTVF basalts show evidence of complex histories. Mt. Taylor basalts higher in the cone-building sequence contain >40% zoned plagioclase pheno- and megacrysts. Other basalts peripheral to Mt. Taylor and at Grants Ridge contain clinopyroxene and plagioclase megacrysts and cumulate-textured xenoliths, suggesting they interacted with lower crustal cumulates. Among the questions we are addressing: What was the chemical and thermal state of the mantle recorded by the basaltic suites and xenoliths and how did it change with time? Are multiple parental basalts (Si-saturated vs. undersaturated) represented and, if so, what changes in the mantle or in the tectonic

  5. Quaternary basaltic volcanism in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina

    Pleistocene times. These basalts mark the end of a period of shallow subduction of the Nazca slab beneath the Payenia province and volcanism in the Nevado volcanic field apparently followed the downwarping slab in a north-northwest direction ending in the Northern Segment. The northern Payenia basalts...

  6. Preliminary K/Ar geochronology of the Crater Basalt volcanic field (CBVF, northern Patagonia

    Directory of Open Access Journals (Sweden)

    Z. Pécskay

    2007-11-01

    Full Text Available The Crater Basalt volcanic field is one of the Quaternary intraplate basaltic fields in northern Patagonia. A systematic geological, volcanological and geochronological study of CBVF indicates a multistage history of eruptions of basaltic volcanoes. K/Ar dating, using whole rock samples shows that the measured analytical ages are fully consistent with the available stratigraphic control. The radiometric ages fall into three distinct, internally consistent age groups, which give evidence that there were at least three major episodes of volcanic activity, at about 1.0 Ma, 0.6 Ma and 0.3 Ma ago. The age differences appear to be just significant, even although less than 10 % radiogenic argon was found in the isotope analysis of whole rock samples.El campo volcánico del Basalto Cráter (CVBC constituye uno de los campos basálticos cuaternarios de intraplaca de la Patagonia septentrional. El estudio sistemático de la geología, volcanología y geocronología del CVBC muestra una historia eruptiva multiepisódica de volcanes basálticos. Las dataciones K-Ar realizadas sobre roca total son coherentes con el control estratigráfico. Las edades obtenidas para el Basalto Cráter permiten distinguir tres episodios diferentes, pero individualmente coherentes, de actividad volcánica, ocurridos hace ~1,0 Ma; 0,6 Ma y 0,3 Ma. Las diferencias de edad parecen ser significativas, aún cuando el contenido de argón radiogénico determinado en los análisis de roca total resultó menor al 10 %.

  7. Magmatic inclusions in rhyolites, contaminated basalts, and compositional zonation beneath the Coso volcanic field, California

    Science.gov (United States)

    Bacon, C.R.; Metz, J.

    1984-01-01

    Basaltic lava flows and high-silica rhyolite domes form the Pleistocene part of the Coso volcanic field in southeastern California. The distribution of vents maps the areal zonation inferred for the upper parts of the Coso magmatic system. Subalkalic basalts (Coso volcanic field contain sparse andesitic inclusions (55-61% SiO2). Pillow-like forms, intricate commingling and local diffusive mixing of andesite and rhyolite at contacts, concentric vesicle distribution, and crystal morphologies indicative of undercooling show that inclusions were incorporated in their rhyolitic hosts as blobs of magma. Inclusions were probably dispersed throughout small volumes of rhyolitic magma by convective (mechanical) mixing. Inclusion magma was formed by mixing (hybridization) at the interface between basaltic and rhyolitic magmas that coexisted in vertically zoned igneous systems. Relict phenocrysts and the bulk compositions of inclusions suggest that silicic endmembers were less differentiated than erupted high-silica rhyolite. Changes in inferred endmembers of magma mixtures with time suggest that the steepness of chemical gradients near the silicic/mafic interface in the zoned reservoir may have decreased as the system matured, although a high-silica rhyolitic cap persisted. The Coso example is an extreme case of large thermal and compositional contrast between inclusion and host magmas; lesser differences between intermediate composition magmas and inclusions lead to undercooling phenomena that suggest smaller ??T. Vertical compositional zonation in magma chambers has been documented through study of products of voluminous pyroclastic eruptions. Magmatic inclusions in volcanic rocks provide evidence for compositional zonation and mixing processes in igneous systems when only lava is erupted. ?? 1984 Springer-Verlag.

  8. Megacrystic pyroxene basalts sample deep crustal gabbroic cumulates beneath the Mount Taylor volcanic field, New Mexico

    Science.gov (United States)

    Schmidt, Mariek E.; Schrader, Christian M.; Crumpler, Larry S.; Rowe, Michael C.; Wolff, John A.; Boroughs, Scott P.

    2016-04-01

    Distributed over the ~ 2.3 m.y. history of the alkaline and compositionally diverse Mount Taylor Volcanic Field (MTVF), New Mexico is a widespread texturally distinct family of differentiated basalts that contain resorbed megacrysts (up to 3 cm) of plagioclase, clinopyroxene, and olivine ± Ti-magnetite ± ilmenite ± orthopyroxene. These lavas have gabbroic cumulate inclusions with mineral compositions similar to the megacrysts, suggesting a common origin. Gabbroic and megacrystic clinopyroxenes form positive linear arrays in TiO2 (0.2-2.3 wt.%) with respect to Al2O3 (0.7-9.3 wt.%). Plagioclase (An41-80) from representative thin sections analyzed for 87Sr/86Sr by laser ablation ICP-MS range from 0.7036 to 0.7048. The low 87Sr/86Sr plagioclases (0.7036 to 0.7037) are associated with high Ti-Al clinopyroxenes. Likewise, the higher 87Sr/86Sr plagioclases (0.7043 to 0.7047) are associated with the low-Al clinopyroxenes. Taken together, the pyroxene and plagioclase megacrysts appear to track the differentiation of a gabbroic pluton (or related plutons) from alkaline to Si-saturated conditions by fractional crystallization and crustal assimilation. Clinopyroxene-liquid geobarometry calculations suggest that crystallization occurred near the crust-mantle transition at an average of ~ 1200 °C and 12-13 kbar. The distribution of the megacrystic pyroxene basalts suggests that a gabbroic intrusive body underlies subregions of the MTVF that have generated silicic magmas. The gabbro is interpreted to be a significant heat and mass input into the lower crust that is capable of driving the petrogenesis of diverse silicic compositions (through fractionation and crustal assimilation), including mugearites, trachytes, trachy-andesites and dacites, high-Si rhyolites, and topaz rhyolites of the MTVF.

  9. Sedimentology, eruptive mechanism and facies architecture of basaltic scoria cones from the Auckland Volcanic Field (New Zealand)

    Science.gov (United States)

    Kereszturi, Gábor; Németh, Károly

    2016-09-01

    Scoria cones are a common type of basaltic to andesitic small-volume volcanoes (e.g. 10- 1-10- 5 km3) that results from gas-bubble driven explosive eruptive styles. Although they are small in volume, they can produce complex eruptions, involving multiple eruptive styles. Eight scoria cones from the Quaternary Auckland Volcanic Field in New Zealand were selected to define the eruptive style variability from their volcanic facies architecture. The reconstruction of their eruptive and pyroclastic transport mechanisms was established on the basis of study of their volcanic sedimentology, stratigraphy, and measurement of their pyroclast density, porosity, Scanning Electron Microscopy, 2D particle morphology analysis and Visible and Near Visible Infrared Spectroscopy. Collection of these data allowed defining three end-member types of scoria cones inferred to be constructed from lava-fountaining, transitional fountaining and Strombolian type, and explosive Strombolian type. Using the physical and field-based characteristics of scoriaceous samples a simple generalised facies model of basaltic scoria cones for the AVF is developed that can be extended to other scoria cones elsewhere. The typical AVF scoria cone has an initial phreatomagmatic phases that might reduce the volume of magma available for subsequent scoria cone forming eruptions. This inferred to have the main reason to have decreased cone volumes recognised from Auckland in comparison to other volcanic fields evolved dominantly in dry eruptive condition (e.g. no external water influence). It suggests that such subtle eruptive style variations through a scoria cone evolution need to be integrated into the hazard assessment of a potentially active volcanic field such as that in Auckland.

  10. Basaltic volcanic episodes of the Yucca Mountain region

    International Nuclear Information System (INIS)

    The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs

  11. Spectroscopy of olivine basalts using FieldSpec and ASTER data: A case study from Wadi Natash volcanic field, south Eastern Desert, Egypt

    Science.gov (United States)

    Madani, Ahmed

    2015-10-01

    This paper aims at revealing the spectral characteristics of the olivine basalts exposed at Wadi Natash area, Egypt, using FieldSpec spectroradiometer. It also evaluates band ratios and fusion techniques for mapping purposes using ASTER data. Several volcanic episodes occurred during Early- to Late-Cretaceous are recorded in the study area. Early-Cretaceous olivine basalts are highly carbonated. Late-Cretaceous eruptions took place throughout several volcanic cones aligned in NW direction. Based on FieldSpec measurements and petrographic data, two groups of olivine basalt namely `A' and `B' are recognized. Fresh olivine basalt (group A) is characterized by low flat spectral profile with overall low reflectance values (˜20%). Spectral profile of altered olivine basalt (group B) shows moderate reflectance values (˜37%) with four little absorption features around the 1.10, 1.40, 2.00 and 2.35 μm wavelength regions. These absorption features are attributed mainly to the presence of chlorite and carbonate alteration products as indicated by petrographic examination. ASTER false colour composite band ratio image (3/2:R, 8/1:G and 8/5:B) discriminates easily the fresh and altered basalts by deep blue and reddish blue colours respectively. Image fusion between previously mentioned FCC ratios image and high spatial resolution ASTER panchromatic image are carried out using brovey and HSV transformation methods. Visual and statistical assessment methods proved that HSV fusion image yields better image interpretability results compared to brovey image. It improves the spatial resolution of original FCC ratios image with acceptable spectral preservation. The present study proved the usefulness of FieldSpec spectral profiles and the processed ASTER data for discriminating different olivine basalt groups exposed at the study area.

  12. Trace Element Geochemistry of Basaltic Tephra in Maar Cores; Implications for Centre Correlation, Field Evolution, and Mantle Source Characteristics of the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Hopkins, J. L.; Leonard, G.; Timm, C.; Wilson, C. J. N.; Neil, H.; Millet, M. A.

    2014-12-01

    Establishing volcanic hazard and risk management strategies hinges on a detailed understanding of the type, timing and tephra dispersal of past eruptions. In order to unravel the pyroclastic eruption history of a volcanic field, genetic links between the deposits and eruption source centre need to be established. The Auckland Volcanic Field (AVF; New Zealand) has been active for ca. 200 kyr and comprises ca. 53 individual centres covering an area of ca. 360km2. These centres show a range of sizes and eruptive styles from maar craters and tuff rings, to scoria cones and lava flows consistent with both phreatomagmatic and magmatic eruptions. Superimposition of the metropolitan area of Auckland (ca. 1.4 million inhabitants) on the volcanic field makes it critically important to assess the characteristics of the volcanic activity, on which to base assessment and management of the consequent hazards. Here we present a geochemical approach for correlating tephra deposits to their source centres. To acquire the most complete stratigraphic record of pyroclastic events, maar crater cores from different locations, covering various depths and thus ages across the field were selected. Magnetic susceptibility and x-ray density scanning of the cores was used to identify the basaltic tephra horizons, which were sampled and in-situ analysis of individual shards undertaken for major and trace elements using EPMA and LA-ICP-MS techniques, respectively. Our results show that tephra shard trace element ratios are comparable and complementary to the AVF whole rock database. The use of specific trace element ratios (e.g. Gd/Yb vs. Zr/Yb) allows us to fingerprint and cross correlate tephra horizons between cores and, when coupled with newly acquired 40Ar-39Ar age dating and eruption size estimates, correlate horizons to their source centres. This integrated style of study can provide valuable information to help volcanic hazard management and forecasting, and mitigation of related risks.

  13. Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (western Turkey) using cosmogenic 3He and 10Be

    Science.gov (United States)

    Heineke, Caroline; Niedermann, Samuel; Hetzel, Ralf; Akal, Cüneyt

    2015-04-01

    The Kula volcanic field is the youngest volcanic province in western Anatolia and covers an area of about 600 km2 around the town Kula (Richardson-Bunbury, 1996). Its alkali basalts formed by melting of an isotopically depleted mantle in a region of long-lived continental extension and asthenospheric upwelling (Prelevic et al., 2012). Based on morphological criteria and 40Ar/39Ar dating, four phases of Quaternary activity have been distinguished in the Kula volcanic field (Richardson-Bunbury, 1996; Westaway et al., 2006). The youngest lava flows are thought to be Holocene in age, but so far only one sample from this group was dated by 40Ar/39Ar at 7±2 ka (Westaway et al., 2006). In this study, we analysed cosmogenic 3He in olivine phenocrysts from three basalt flows and one cinder cone to resolve the Holocene history of volcanic eruptions in more detail. In addition, we applied 10Be exposure dating to two quartz-bearing xenoliths found at the surface of one flow and at the top of one cinder cone. The exposure ages fall in the range between ~500 and ~3000 years, demonstrating that the youngest volcanic activity is Late Holocene in age and therefore distinctly younger than previously envisaged. Our results show that the Late Holocene lava flows are not coeval but formed over a period of a few thousand years. We conclude that surface exposure dating of very young volcanic rocks provides a powerful alternative to 40Ar/39Ar dating. References Prelevic, D., Akal, C. Foley, S.F., Romer, R.L., Stracke, A. and van den Bogaard, P. (2012). Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey. Journal of Petrology, 53, 1019-1055. Richardson-Bunbury, J.M. (1996). The Kula Volcanic Field, western Turkey: the development of a Holocene alkali basalt province and the adjacent normal-faulting graben. Geological Magazine, 133, 275-283. Westaway, R., Guillou, H., Yurtmen, S., Beck, A

  14. Basaltic Lava Flow vs. Welded Basaltic Ignimbrite: Determining the Depositional Nature of a Volcanic Flow in the Akaroa Volcanic Complex

    Science.gov (United States)

    Sexton, E. A.; Hampton, S.

    2014-12-01

    Welded basaltic ignimbrites are one of the rarest forms of ignimbrites found on Earth and can often have characteristics that are indistinguishable from those of basaltic lava flows. This study evaluates a basaltic volcanic flow in a coastal cliff sequence in Raupo Bay, Akaroa Volcanic Complex, Banks Peninsula, New Zealand. The Raupo Bay coastal cliff sequence is comprised of 4 units, termed L1, L2, L3, and A, capped by loess. L1 and L2 are basaltic lavas, L3 proximal scoria deposits, which thin inland, and Unit A, a flow with unusual characteristics, which is the focus of this study. Field mapping, sampling, geochemical analysis and petrology were utilized to characterize units. Further detailed structural analysis of Unit A was completed, to determine the nature of the basal contact, variations in welding throughout the unit and the relationship of the layer to the underlying topography. From these analyses it was found: Unit A is thickest in a paleo-valley and thins and mantles higher topography, welding in the unit increases downwards forming topographic controlled columnar jointing, the top of the unit is brecciated and grades into the lower welded/jointed portion, the basal contact is sharp overlying a regional airfall deposit, the unit has a notably distinct geochemical composition from the underlying stratigraphic units, Unit A contains flattened and sheared scoria clasts, has aligned bubbles, and lava lithics. Further thin section analysis of Unit A identified flattened clast boundaries and microlite rimming around phenocrysts. In comparing these features to previous studies on basaltic lavas and ignimbrites it is hypothesized that Unit A is a welded basaltic ignimbrite that was channelized by paleo-topography on the outer flanks of the Akaroa Volcanic Complex. This study furthers the characterization of basaltic ignimbrites and is the first to recognize basaltic ignimbrites within the Akaroa Volcanic Complex.

  15. Tools and techniques for developing tephra stratigraphies in lake cores: A case study from the basaltic Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Hopkins, Jenni L.; Millet, Marc-Alban; Timm, Christian; Wilson, Colin J. N.; Leonard, Graham S.; Palin, J. Michael; Neil, Helen

    2015-09-01

    Probabilistic hazard forecasting for a volcanic region relies on understanding and reconstructing the eruptive record (derived potentially from proximal as well as distal volcanoes). Tephrostratigraphy is commonly used as a reconstructive tool by cross-correlating tephra deposits to create a stratigraphic framework that can be used to assess magnitude-frequency relationships for eruptive histories. When applied to widespread rhyolitic deposits, tephra identifications and correlations have been successful; however, the identification and correlation of basaltic tephras are more problematic. Here, using tephras in drill cores from six maars in the Auckland Volcanic Field (AVF), New Zealand, we show how X-ray density scanning coupled with magnetic susceptibility analysis can be used to accurately and reliably identify basaltic glass shard-bearing horizons in lacustrine sediments and which, when combined with the major and trace element signatures of the tephras, can be used to distinguish primary from reworked layers. After reliably identifying primary vs. reworked basaltic horizons within the cores, we detail an improved method for cross-core correlation based on stratigraphy and geochemical fingerprinting. We present major and trace element data for individual glass shards from 57 separate basaltic horizons identified within the cores. Our results suggest that in cases where major element compositions (SiO2, CaO, Al2O3, FeO, MgO) do not provide unambiguous correlations, trace elements (e.g. La, Gd, Yb, Zr, Nb, Nd) and trace element ratios (e.g. [La/Yb]N, [Gd/Yb]N, [Zr/Yb]N) are successful in improving the compositional distinction between the AVF basaltic tephra horizons, thereby allowing an improved eruptive history of the AVF to be reconstructed.

  16. Thermal models for basaltic volcanism on Io

    Science.gov (United States)

    Keszthelyil, L.; McEwen, A.

    1997-01-01

    We present a new model for the thermal emissions from active basaltic eruptions on Io. While our methodology shares many similarities with previous work, it is significantly different in that (1) it uses a field tested cooling model and (2) the model is more applicable to pahoehoe flows and lava lakes than fountain-fed, channelized, 'a'a flows. This model demonstrates the large effect lava porosity has on the surface cooling rate (with denser flows cooling more slowly) and provides a preliminary tool for examining some of the hot spots on Io. The model infrared signature of a basaltic eruption is largely controlled by a single parameter, ??, the average survival time for a lava surface. During an active eruption surfaces are quickly covered or otherwise destroyed and typical values of ?? for a basaltic eruption are expected to be on the order of 10 seconds to 10 minutes. Our model suggests that the Galileo SSI eclipse data are consistent with moderately active to quiescent basaltic lava lakes but are not diagnostic of such activity. Copyright 1997 by the American Geophysical Union.

  17. Lead and strontium isotopic evidence for crustal interaction and compositional zonation in the source regions of Pleistocene basaltic and rhyolitic magmas of the Coso volcanic field, California

    Science.gov (United States)

    Bacon, C.R.; Kurasawa, H.; Delevaux, M.H.; Kistler, R.W.; Doe, B.R.

    1984-01-01

    The isotopic compositions of Pb and Sr in Pleistocene basalt, high-silica rhyolite, and andesitic inclusions in rhyolite of the Coso volcanic field indicate that these rocks were derived from different levels of compositionally zoned magmatic systems. The 2 earliest rhyolites probably were tapped from short-lived silicic reservoirs, in contrast to the other 36 rhyolite domes and lava flows which the isotopic data suggest may have been leaked from the top of a single, long-lived magmatic system. Most Coso basalts show isotopic, geochemical, and mineralogic evidence of interaction with crustal rocks, but one analyzed flow has isotopic ratios that may represent mantle values (87Sr/86Sr=0.7036,206Pb/204Pb=19.05,207Pb/204Pb=15.62,208Pb/204Pb= 38.63). The (initial) isotopic composition of typical rhyolite (87Sr/86Sr=0.7053,206Pb/204Pb=19.29,207Pb/204Pb= 15.68,208Pb/204Pb=39.00) is representative of the middle or upper crust. Andesitic inclusions in the rhyolites are evidently samples of hybrid magmas from the silicic/mafic interface in vertically zoned magma reservoirs. Silicic end-member compositions inferred for these mixed magmas, however, are not those of erupted rhyolite but reflect the zonation within the silicic part of the magma reservoir. The compositional contrast at the interface between mafic and silicic parts of these systems apparently was greater for the earlier, smaller reservoirs. ?? 1984 Springer-Verlag.

  18. Pliocene Basaltic Volcanism in The East Anatolia Region (EAR), Turkey

    Science.gov (United States)

    Oyan, Vural; Özdemir, Yavuz; Keskin, Mehmet

    2016-04-01

    East Anatolia Region (EAR) is one of the high Plateau which is occurred with north-south compressional regime formed depending on continent-continent collision between Eurasia and Arabia plates (Şengör and Kidd, 1979). Recent studies have revealed that last oceanic lithosphere in the EAR have completely depleted to 20 million years ago based on fission track ages (Okay et al. 2010). Our initial studies suggest that extensively volcanic activity in the EAR peaked in the Pliocene and continued in the same productivity throughout Quaternary. Voluminous basaltic lava plateaus and basaltic lavas from local eruption centers occurred as a result of high production level of volcanism during the Pliocene time interval. In order to better understand the spatial and temporal variations in Pliocene basaltic volcanism and to reveal isotopic composition, age and petrologic evolution of the basaltic volcanism, we have started to study basaltic volcanism in the East Anatolia within the framework of a TUBITAK project (project number:113Y406). Petrologic and geochemical studies carried out on the Pliocene basaltic lavas indicate the presence of subduction component in the mantle source, changing the character of basaltic volcanism from alkaline to subalkaline and increasing the amount of spinel peridotitic melts (contributions of lithospheric mantle?) in the mantle source between 5.5-3.5 Ma. FC, AFC and EC-AFC modelings reveal that the while basaltic lavas were no or slightly influenced by crustal contamination and fractional crystallization, to more evolved lavas such as bazaltictrachyandesite, basalticandesite, trachybasalt might have been important processes. Results of our melting models and isotopic analysis data (Sr, Nd, Pb, Hf, 18O) indicate that the Pliocene basaltic rocks were derived from both shallow and deep mantle sources with different melting degrees ranging between 0.1 - 4 %. The percentage of spinel seems to have increased in the mantle source of the basaltic

  19. The biological consequences of flood basalt volcanism

    Science.gov (United States)

    Clapham, M.

    2012-12-01

    Flood basalt eruptions are among the largest environmental perturbations of the Phanerozoic. The rapid release of CO2 from a large igneous province would have triggered a chain of events that can include climate warming, ocean acidification, reduced seawater carbonate saturation, and expanded oceanic anoxia. Those stressors have widely negative impacts on marine organisms, especially on calcified taxa, by affecting their respiratory physiology and reducing energy available for growth and reproduction. Many Phanerozoic extinctions, most notably the end-Permian and end-Triassic mass extinctions, coincided with flood basalt eruptions and shared distinctive patterns of taxonomic and ecological selectivity. In these extinctions, highly active organisms were more likely to survive because they possess physiological adaptations for maintaining internal pH during activity, which also proves useful when buffering pH against ocean acidification. In contrast, species that did not move and had low metabolic rates, such as brachiopods and sponges, suffered considerable losses during these extinctions. Heavily-calcified organisms, especially corals, were particularly vulnerable; as a result, ocean acidification and saturation state changes from flood basalt eruptions often triggered crises in reef ecosystems. This characteristic pattern of selectivity during "physiological" extinctions that closely coincided with flood basalts provides a template for assessing the causes of other extinction events. Because these crises also provide deep time analogues for the ongoing anthropogenic crisis of warming, ocean acidification, and expanded anoxia, the selectivity patterns can also help constrain "winners" and "losers" over upcoming decades.

  20. Reappraisal of the significance of volcanic fields

    Science.gov (United States)

    Cañón-Tapia, Edgardo

    2016-01-01

    "Volcanic field" is a term commonly used to loosely describe a group of volcanoes. Often, it is implicitly assumed that the volcanoes on a volcanic field are small, monogenetic and dominantly basaltic, but none of those attributes is indispensable on some definitions of the term. Actually, the term "volcanic field" can be used to describe a group of purely monogenetic edifices, a group of mixed monogenetic and polygenetic edifices, or even a group formed only by purely polygenetic edifices. Differences between each of those alternatives might be important, but the extent to which those differences are truly relevant remains still to be explored. Furthermore, there are several limitations on the current knowledge of this type of volcanic activity that explain the lack of a comprehensive effort to study volcanic fields in global contexts. In this work, issues concerning current definitions of a volcanic field are examined, and some criteria that can be used to distinguish volcanic fields from non-field volcanoes are suggested. Special attention is given to the role played by spatial scale on such a distinction. Also, the tectonic implications of their spatial distribution are explored. In particular, it is shown that volcanic fields are an important component of volcanic activity at a global scale that is closely associated to diffuse plate boundaries, and might well be considered the archetypical volcanic form of such tectonic scenarios.

  1. Flood basalt volcanism during the past 250 million years

    Science.gov (United States)

    Rampino, Michael R.; Stothers, Richard B.

    1988-01-01

    A chronology of the initiation dates of major continental flood basalt volcanism is established from published potassium-argon (K-Ar) and argon-argon (Ar-Ar) ages of basaltic rocks and related basic intrusions. The dating is therefore independent of the biostratigraphic and paleomagnetic time scales. Estimated errors of the initiation dates of the volcanic episodes determined from the distributions of the radiometric ages are, approximately, + or - 4 percent. There were 11 distinct episodes during the past 250 million years. Sometimes appearing in pairs, the episodes have occurred quasi-periodically with a mean cycle time of 32 + or - 1 (estimated error of the mean) million years. The initiation dates of the episodes are close to the estimated dates of mass extinctions of marine organisms. Showers of impacting comets may be the cause.

  2. Effect of Miocene basaltic volcanism in Shanwang (Shandong Province, China) on environmental changes

    Institute of Scientific and Technical Information of China (English)

    GUO; ZhengFu; LIU; JiaQi; CHEN; XiaoYu

    2007-01-01

    Miocene (16-10 Ma) basalts, together with significantly well-preserved fossils (including animal and plant fossils) in the contemporaneously tephra-rich Maar sediments, are located in Shanwang volcanic region, Shandong Province, China. Distribution area of the basaltic eruption products is about 240 km2. Detailed field observations indicate that most of basaltic rocks are fissure eruptive products and some are central eruptives constrained by linear faults. The well-preserved fossils in the lacustrine deposits have been considered to be a result of mass mortalities. Based on physically volcanologic modeling results, eruption column of the basaltic fissure activities in the Shanwang volcanic region is estimated to have entered the stratosphere. Petrographic observations indicate that the basalts have porphyritic textures with phenocrysts of olivine, pyroxene, plagioclase feldspar and alkali feldspar setting in groundmass of plagioclase feldspar, alkali feldspar, quartz, apatite and glass. Based on observations of tephra, tuff and tuffites collected in the Maar sediments of the Shanwang area, we determined major element oxide concentrations and volatile composition of melt inclusions in phenocrysts and matrix glasses by electron microprobe analysis. Volatile (including S, Cl, F and H2O) concentrations erupted into the stratosphere were estimated by comparing pre- and post-eruptive volatile concentrations. Our determination results show that contents of S, Cl, F and H2O emitted into the stratosphere were 0.18%-0.24%, 0.03%-0.05%, 0.03%-0.05% and 0.4%-0.6%, respectively, which was characterized by high-S contents erupted. Amounts of volatiles emitted in the Shanwang volcanic region are much higher than those in eruptions which had a substantial effect on climate and environment. According to the compositions and amounts of the volatiles erupted from the Miocene basaltic volcanism in Shanwang, we propose a hypothesis that volatile-rich basaltic volcanism could result in

  3. Bimodal magmatism, basaltic volcanic styles, tectonics, and geomorphic processes of the eastern Snake River Plain, Idaho

    Science.gov (United States)

    Hughes, S.S.; Smith, R.P.; Hackett, W.R.; McCurry, M.; Anderson, S.R.; Ferdock, G.C.

    1997-01-01

    Geology presented in this field guide covers a wide spectrum of internal and surficial processes of the eastern Snake River Plain, one of the largest components of the combined late Cenozoic igneous provinces of the western United States. Focus is on widespread Quaternary basaltic plains volcanism that produced coalescent shields and complex eruptive centers that yielded compositionally evolved magmas. The guide is constructed in several parts beginning with discussion sections that provide an overview of the geology followed by road directions, with explanations, for specific locations. The geology overview briefly summarizes the collective knowledge gained, and petrologic implications made, over the past few decades. The field guide covers plains volcanism, lava flow emplacement, basaltic shield growth, phreatomagmatic eruptions, and complex and evolved eruptive centers. Locations and explanations are also provided for the hydrogeology, groundwater contamination, and environmental issues such as range fires and cataclysmic floods associated with the region.

  4. Thermal and mass implications of magmatic evolution in the Lassen volcanic region, California, and minimum constraints on basalt influx to the lower crust

    Science.gov (United States)

    Guffanti, M.; Clynne, M.A.; Muffler, L.J.P.

    1996-01-01

    We have analyzed the heat and mass demands of a petrologic model of basaltdriven magmatic evolution in which variously fractionated mafic magmas mix with silicic partial melts of the lower crust. We have formulated steady state heat budgets for two volcanically distinct areas in the Lassen region: the large, late Quaternary, intermediate to silicic Lassen volcanic center and the nearby, coeval, less evolved Caribou volcanic field. At Caribou volcanic field, heat provided by cooling and fractional crystallization of 52 km3 of basalt is more than sufficient to produce 10 km3 of rhyolitic melt by partial melting of lower crust. Net heat added by basalt intrusion at Caribou volcanic field is equivalent to an increase in lower crustal heat flow of ???7 mW m-2, indicating that the field is not a major crustal thermal anomaly. Addition of cumulates from fractionation is offset by removal of erupted partial melts. A minimum basalt influx of 0.3 km3 (km2 Ma)-1 is needed to supply Caribou volcanic field. Our methodology does not fully account for an influx of basalt that remains in the crust as derivative intrusives. On the basis of comparison to deep heat flow, the input of basalt could be ???3 to 7 times the amount we calculate. At Lassen volcanic center, at least 203 km3 of mantle-derived basalt is needed to produce 141 km3 of partial melt and drive the volcanic system. Partial melting mobilizes lower crustal material, augmenting the magmatic volume available for eruption at Lassen volcanic center; thus the erupted volume of 215 km3 exceeds the calculated basalt input of 203 km3. The minimum basalt input of 1.6 km3 (km2 Ma)-1 is >5 times the minimum influx to the Caribou volcanic field. Basalt influx high enough to sustain considerable partial melting, coupled with locally high extension rate, is a crucial factor in development of Lassen volcanic center; in contrast. Caribou volcanic field has failed to develop into a large silicic center primarily because basalt supply

  5. Stratigraphical framework of basaltic lavas in Torres Syncline main valley, southern Parana-Etendeka Volcanic Province

    Science.gov (United States)

    Rossetti, Lucas M.; Lima, Evandro F.; Waichel, Breno L.; Scherer, Claiton M.; Barreto, Carla J.

    2014-12-01

    The Paraná-Etendeka Volcanic Province records the volcanism of the Early Cretaceous that precedes the fragmentation of the South-Gondwana supercontinent. Traditionally, investigations of these rocks prioritized the acquisition of geochemical and isotopic data, considering the volcanic stack as a monotonous succession of tabular flows. Torres Syncline is a tectonic structure located in southern Brazil and where the Parana-Etendeka basalts are well preserved. This work provides a detailed analysis of lithofacies and facies architecture, integrated to petrographic and geochemical data. We identified seven distinct lithofacies grouped into four facies associations related to different flow morphologies. The basaltic lava flows in the area can be divided into two contrasting units: Unit I - pahoehoe flow fields; and Unit II - simple rubbly flows. The first unit is build up by innumerous pahoehoe lava flows that cover the sandstones of Botucatu Formation. These flows occur as sheet pahoehoe, compound pahoehoe, and ponded lavas morphologies. Compound lavas are olivine-phyric basalts with intergranular pyroxenes. In ponded lavas and cores of sheet flows coarse plagioclase-phyric basalts are common. The first pahoehoe lavas are more primitive with higher contents of MgO. The emplacement of compound pahoehoe flows is related to low volume eruptions, while sheet lavas were emplaced during sustained eruptions. In contrast, Unit II is formed by thick simple rubbly lavas, characterized by a massive core and a brecciated/rubbly top. Petrographically these flows are characterized by plagioclase-phyric to aphyric basalts with high density of plagioclase crystals in the matrix. Chemically they are more differentiated lavas, and the emplacement is related to sustained high effusion rate eruptions. Both units are low TiO2 and have geochemical characteristics of Gramado magma type. The Torres Syncline main valley has a similar evolution when compared to other Large Igneous Provinces

  6. Morphology and development of pahoehoe flow-lobe tumuli and associated features from a monogenetic basaltic volcanic field, Bahariya Depression, Western Desert, Egypt

    Science.gov (United States)

    Khalaf, Ezz El Din Abdel Hakim; Hammed, Mohamed Saleh

    2016-01-01

    The dimensions, landforms, and structural characteristics of pahoehoe flow-lobe tumuli from Bahariya Depression are collectively reported here for the first time. The flow-lobe tumuli documented here characterize hummocky flow surfaces. These tumuli are characterized by low, dome-like mounds, lava-inflation clefts, and squeeze ups. Flow-lobe tumuli are of various shapes and sizes, which are affected by the mechanism of inflation because they formed in response to the increase of pressure within the flow when the flow's crust becomes thicker. The tumuli often appear isolated or in small groups in the middle sectors of the lava flows, whereas in the distal sectors they form large concentration, suggesting the presence of complex lava tubes inside of the flow. Tumuli exhibited by El Bahariya lava flows are between 3.0 and 50 m in length and up to 5.0 m in height with lenticular geometry in aerial view. The flow emplacement of flow-lobe tumuli is controlled by variations in local characteristics such as nature of the substrate, flow orientation, slope, interferrence with other lobes, and rate of lava supply. Their presence generally towards the terminal ends of flow fields suggests that they seldom form over the clogged portions of distributary tubes or pathways. Thus, localized inflations that formed over blockages in major lava tubes result in formation of flow-lobe tumuli. The three-tiered (crust-core-basal zone) internal structure of the flow-lobe tumuli, resembling the typical distribution of vesicles in P-type lobes, confirms emplacement by the mechanism of inflation. All the available data show that the morphology and emplacement mechanism of the studied flow-lobe tumuli may be analogous to similar features preserved within topographically confined areas of the Hawaiian and Deccan hummocky lava flows. Considering the age of the studied volcanic fields (˜22 Ma) it is most probable that the structures described here may be amongst the oldest recognized examples

  7. Constraining the onset of flood volcanism in Isle of Skye Lava Field, British Paleogene Volcanic Province

    Science.gov (United States)

    Angkasa, Syahreza; Jerram, Dougal. A.; Svensen, Henrik; Millet, John M.; Taylor, Ross; Planke, Sverre

    2016-04-01

    In order to constrain eruption styles at the onset of flood volcanism, field observations were undertaken on basal sections of the Isle of Skye Lava Field, British Paleogene Volcanic Province. This study investigates three specific sections; Camus Ban, Neist Point and Soay Sound which sample a large area about 1500 km2 and can be used to help explain the variability in palaeo-environments at the onset of flood volcanism. Petrological analysis is coupled with petrophysical lab data and photogrammetry data to create detailed facies models for the different styles of initiating flood basalt volcanism. Photogrammetry is used to create Ortho-rectified 3D models which, along with photomontage images, allow detailed geological observations to be mapped spatially. Petrographic analyses are combined with petrophysical lab data to identify key textural variation, mineral compositions and physical properties of the volcanic rocks emplaced during the initial eruptions. Volcanism initiated with effusive eruptions in either subaerial or subaqueous environments resulting in tuff/hyaloclastite materials or lava flow facies lying directly on the older Mesozoic strata. Volcanic facies indicative of lava-water interactions vary significantly in thickness between different sections suggesting a strong accommodation space control on the style of volcanism. Camus Ban shows hyaloclastite deposits with a thickness of 25m, whereas the Soay Sound area has tuffaceous sediments of under 0.1m in thickness. Subaerial lavas overly these variable deposits in all studied areas. The flood basalt eruptions took place in mixed wet and dry environments with some significant locally developed water bodies (e.g. Camus Ban). More explosive eruptions were promoted in some cases by interaction of lavas with these water bodies and possibly by local interaction with water - saturated sediments. We record key examples of how palaeotopography imparts a primary control on the style of volcanism during the

  8. Pahoehoe-a‧a transitions in the lava flow fields of the western Deccan Traps, India-implications for emplacement dynamics, flood basalt architecture and volcanic stratigraphy

    Science.gov (United States)

    Duraiswami, Raymond A.; Gadpallu, Purva; Shaikh, Tahira N.; Cardin, Neha

    2014-04-01

    Unlike pahoehoe, documentation of true a‧a lavas from a modern volcanological perspective is a relatively recent phenomenon in the Deccan Trap (e.g. Brown et al., 2011, Bull. Volcanol. 73(6): 737-752) as most lava flows previously considered to be a‧a (e.g. GSI, 1998) have been shown to be transitional (e.g. Rajarao et al., 1978, Geol. Soc. India Mem. 43: 401-414; Duraiswami et al., 2008 J. Volcanol. Geothermal. Res. 177: 822-836). In this paper we demonstrate the co-existence of autobrecciation products such as slabby pahoehoe, rubbly pahoehoe and a‧a in scattered outcrops within the dominantly pahoehoe flow fields. Although volumetrically low in number, the pattern of occurrence of the brecciating lobes alongside intact ones suggests that these might have formed in individual lobes along marginal branches and terminal parts of compound flow fields. Complete transitions from typical pahoehoe to 'a‧a lava flow morphologies are seen on length scales of 100-1000 m within road and sea-cliff sections near Uruli and Rajpuri. We consider the complex interplay between local increase in the lava supply rates due to storage or temporary stoppage, local increase in paleo-slope, rapid cooling and localized increase in the strain rates especially in the middle and terminal parts of the compound flow field responsible for the transitional morphologies. Such transitions are seen in the Thakurwadi-, Bushe- and Poladpur Formation in the western Deccan Traps. These are similar to pahoehoe-a‧a transitions seen in Cenozoic long lava flows (Undara ˜160 km, Toomba ˜120 km, Kinrara ˜55 km) from north Queensland, Australia and Recent (1859) eruption of Mauna Loa, Hawaii (a‧a lava flow ˜51 km) suggesting that flow fields with transitional tendencies cannot travel great lengths despite strong channelisation. If these observations are true, then it arguably limits long distance flow of Deccan Traps lavas to Rajahmundry suggesting polycentric eruptions at ˜65 Ma in

  9. Geology and petrology of the basalts of Crater Flat: applications to volcanic risk assessment for the Nevada Nuclear Waste Storage investigations

    International Nuclear Information System (INIS)

    Volcanic hazard studies of the south-central Great Basin, Nevada, are being conducted for the Nevada Nuclear Waste Storage Investigations. This report presents the results of field and petrologic studies of the basalts of Crater Flat, a sequence of Pliocene to Quaternary-age volcanic centers located near the southwestern part of the Nevada Test Site. Crater Flat is one of several basaltic fields constituting a north-northeast-trending volcanic belt of Late Cenozoic age extending from southern Death Valley, California, through the Nevada Test Site region to central Nevada. The basalts of Crater Flat are divided into three distinct volcanic cycles. The cycles are characterized by eruption of basalt magma of hawaiite composition that formed cinder cone clusters and associated lava flows. Total volume of erupted magma for respective cycles is given. The basalts of Crater Flat are sparsely to moderately porphyritic; the major phenocryst phase is olivine, with lesser amounts of plagioclase, clinopyroxene, and rare amphibole. The consistent recurrence of evolved hawaiite magmas in all three cycles points to crystal fractionation from more primitive magmas at depth. A possible major transition in mantle source regions through time may be indicated by a transition from normal to Rb-depleted, Sr-enriched hawaiites in the younger basaltic cycles. The recurrence of small volumes of hawaiite magma at Crater Flat supports assumptions required for probability modeling of future volcanic activity and provides a basis for estimating the effects of volcanic disruption of a repository site in the southwestern Nevada Test Site region. Preliminary data suggest that successive basalt cycles at Crater Flat may be of decreasing volume but recurring more frequently

  10. Measurement of the Dielectric Properties of Volcanic Scoria and Basalt at 9370 MHz

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yongchun; WANG Shijie; OUYANG Ziyuan; LI Xiongyao

    2005-01-01

    Dielectric data for volcanic scoria and basalt on the earth at microwave frequency are extremely sparse, and also crucial for volcanic terrains imaging, and development. In consideration of their similarity to lunar regolith (soils and rocks) in chemical and mineral composition, the dielectric data is significative for passive and active microwave remote sensing on the Moon. This study provides the data about the dielectric properties of three kinds of scoria and two kinds of basalt in China. The method put forward in this paper is also applicable for measuring the dielectric properties of dry rocks and other granular ground materials with low complex dielectric constants. Firstly, the authors measured the ε' and tanδvalues of strip specimens prepared from the mixture of scoria or basalt powder and polythene with the resonant cavity perturbation method at 9370 MHz. Secondly, from the ε' and tanδ values of the mixture, the ε's and ranδs values of solid scoria and basalt were calculated using Lichtenecker's mixture formulae. Finally, the effective complex dielectric constants, ε'e and tanδe, of scoria at different bulk densities were calculated. The results have shown that the ε's and tancδs values of all solid basaltic materials measured (both solid basaltic scoria or basalt) are approximately 7 and 0.05, respectively. With increasing bulk density of scoria, the ε'e and tanδe values of scoria increase significantly.

  11. Volcanic hazard assessment in monogenetic volcanic fields

    OpenAIRE

    Bartolini, Stefania

    2014-01-01

    Tesi realitzada a l'Institut de Ciències de la Terra “Jaume Almera” (ICTJA-CSIC) One of the most important tasks of modern volcanology, which represents a significant socio-economic implication, is to conduct hazard assessment in active volcanic systems. These volcanological studies are aimed at hazard that allows to constructing hazard maps and simulating different eruptive scenarios, and are mainly addressed to contribute to territorial planning, definition of emergency plans or managing...

  12. Age, distance, and geochemical evolution within a monogenetic volcanic field: Analyzing patterns in the Auckland Volcanic Field eruption sequence

    Science.gov (United States)

    Corvec, Nicolas Le; Bebbington, Mark S.; Lindsay, Jan M.; McGee, Lucy E.

    2013-09-01

    The Auckland Volcanic Field (AVF) is a young active monogenetic basaltic field, which contains ˜50 volcanoes scattered across the Auckland metropolitan area. Understanding the temporal, spatial, and chemical evolution of the AVF during the last c.a. 250 ka is crucial in order to forecast a future eruption. Recent studies have provided new age constraints and potential temporal sequences of the past eruptions within the AVF. We use this information to study how the spatial distribution of the volcanic centers evolves with time, and how the chemical composition of the erupted magmas evolves with time and space. We seek to develop a methodology which compares successive eruptions to describe the link between geochemical and spatiotemporal evolution of volcanic centers within a monogenetic volcanic field. This methodology is tested with the present day data of the AVF. The Poisson nearest neighbor analysis shows that the spatial behavior of the field has been constant overtime, with the spatial distribution of the volcanic centers fitting the Poisson model within the significance levels. The results of the meta-analysis show the existence of correlations between the chemical composition of the erupted magmas and distance, volume, and time. The apparent randomness of the spatiotemporal evolution of the volcanic centers observed at the surface is probably influenced by the activity of the source. The methodology developed in this study can be used to identify possible relationships between composition trends and volume, time and/or distance to the behavior of the source, for successive eruptions of the AVF.

  13. Eruptive History and Chemical Evolution of the Precaldera and Postcaldera Basalt-Dacite Sequences, Long Valley, California: Implications for Magma Sources, Current Seismic Unrest, and Future Volcanism

    Science.gov (United States)

    Bailey, Roy A.

    2004-01-01

    The Long Valley Volcanic Field in east-central California straddles the East Sierran frontal fault zone, overlapping the Sierra Nevada and western Basin and Range Provinces. The volcanic field overlies a mature mid-Tertiary erosional surface that truncates a basement composed mainly of Mesozoic plutons and associated roof pendants of Mesozoic metavolcanic and Paleozoic metasedimentary rocks. Long Valley volcanism began about 4 Ma during Pliocene time and has continued intermittently through the Holocene. The volcanism is separable into two basalt-rhyolite episodes: (1) an earlier, precaldera episode related to Long Valley Caldera that climaxed with eruption of the Bishop Tuff and collapse of the caldera; and (2) a later, postcaldera episode structurally related to the north-south-trending Mono-Inyo Craters fissure system, which extends from the vicinity of Mammoth Mountain northward through the west moat of the caldera to Mono Lake. Eruption of the basalt-dacite sequence of the precaldera basalt-rhyolite episode peaked volumetrically between 3.8 and 2.5 Ma; few basalts were erupted during the following 1.8 m.y. (2.5?0.7 Ma). Volcanism during this interval was dominated by eruption of the voluminous rhyolites of Glass Mountain (2.2?0.8 Ma) and formation of the Bishop Tuff magma chamber. Catastrophic rupture of the roof of this magma chamber caused eruption of the Bishop Tuff and collapse of Long Valley Caldera (760 ka), after which rhyolite eruptions resumed on the subsided caldera floor. The earliest postcaldera rhyolite flows (700?500 ka) contain quenched globular basalt enclaves (mafic magmatic inclusions), indicating that basaltic magma had reentered shallow parts of the magmatic system after a 1.8-m.y. hiatus. Later, at about 400 ka, copious basalts, as well as dacites, began erupting from vents mainly in the west moat of the caldera. These later eruptions initiated the postcaldera basalt-rhyolite episode related to the Mono-Inyo Craters fissure system, which

  14. Quickly erupted volcanic sections of the Steens Basalt, Columbia River Basalt Group: Secular variation, tectonic rotation, and the Steens Mountain reversal

    Science.gov (United States)

    Jarboe, N.A.; Coe, R.S.; Renne, P.R.; Glen, J.M.G.; Mankinen, E.A.

    2008-01-01

    The Steens Basalt, now considered part of the Columbia River Basalt Group (CRBG), contains the earliest eruptions of this magmatic episode. Lava flows of the Steens Basalt cover about 50,000 km2 of the Oregon Plateau in sections up to 1000 m thick. The large number of continuously exposed, quickly erupted lava flows (some sections contain over 200 flows) allows for small loops in the magnetic field direction paths to be detected. For volcanic rocks, this detail and fidelity are rarely found outside of the Holocene and yield estimates of eruption durations at our four sections of ??2.5 ka for 260 m at Pueblo Mountains, 0.5 to 1.5 ka for 190 m at Summit Springs, 1-3 ka for 170 m at North Mickey, and ??3 ka for 160 m at Guano Rim. That only one reversal of the geomagnetic field occurred during the eruption of the Steens Basalt (the Steens reversal at approximately 16.6 Ma) is supported by comparing 40Ar/39Ar ages and magnetic polarities to the geomagnetic polarity timescale. At Summit Springs two 40Ar/39Ar ages from normal polarity flows (16.72 ?? ?? 0.29 Ma (16.61) and 16.92 ?? ?? 0.52 Ma (16.82); ?? ?? equals 2s error) place their eruptions after the Steens reversal, while at Pueblo Mountains an 40Ar/39Ar age of 16.72 ?? ?? 0.21 Ma (16.61) from a reverse polarity flow places its eruption before the Steens reversal. Paleomagnetic field directions yielded 50 nontransitional directional-group poles which, combined with 26 from Steens Mountain, provide a paleomagnetic pole for the Oregon Plateau of 85.7??N, 318.4??E, K = 15.1, A95 = 4.3. Comparison of this new pole with a reference pole derived from CRBG flows from eastern Washington and a synthetic reference pole for North America derived from global data implies relative clockwise rotation of the Oregon Plateau of 7.4 ?? 5.0?? or 14.5 ?? 5.4??, respectively, probably due to northward decreasing extension of the basin and range. ?? 2008 by the American Geophysical Union.

  15. Age and petrology of the Tertiary As Sarat volcanic field, southwestern Saudi Arabia

    Science.gov (United States)

    du Bray, E.A.; Stoeser, D.B.; McKee, E.H.

    1991-01-01

    Harrat As Sarat forms the second smallest and southernmost of the basalt fields of western Saudi Arabia and is part of a voluminous Red Sea rift-related continental alkali basalt province. The rocks of the As Sarat were emplaced during the first stage of Red Sea rifting and represent the northernmost extension of the Tertiary Trap Series volcanics that occur mainly in the Yemen Arab Republic and Ethiopia. The field consists of up to 580 m of basalt flows, that are intruded by basaltic plugs, necks, minor dikes, and highly evolved peralkaline trachyte intrusions. K-Ar ages indicate that the As Sarat field formed between 31 and 22 Ma and contains an eruption hiatus of one million years that began about 25 Ma ago. Pre-hiatus flows are primarily hypersthene normative intersertal subalkaline basalt, whereas the majority of post-hiatus flows are nepheline normative alkali basalt and hawaiite with trachytic textures. Normative compositions of the basalts are consistent with their genesis by partial melting at varying depths. Trace element abundances in the basalt indicate that varying degrees of partial melting and fractional crystallization (or crystal accumulation) had major and minor roles, respectively, in development of compositional variation in these rocks. Modeling indicates that the pre-hiatus subalkaline basalts represent 8-10 percent mantle melting at depths of about 70 km and the post-hiatus alkali basalts represent 4-9 percent mantle melting at depths greater than 70 km. ?? 1991.

  16. New Data on mid-Miocene Rhyolite Volcanism in Eastern Oregon Extend Early, co-CRBG Rhyolite Flare up and Constrain Storage Sites of Grande Ronde Flood Basalts

    Science.gov (United States)

    Streck, M. J.; Ferns, M. L.; McIntosh, W. C.

    2015-12-01

    The classical view of relating mid-Miocene rhyolites of the tri-state area of Oregon, Nevada, and Idaho to the flood basalts of the Columbia River Basalt was that a mantle plume impinging along the Oregon-Idaho border first causes eruption of the flood basalts but shortly thereafter causes generation of rhyolites at the McDermitt volcanic field from which then hot-spot track rhyolites developed progressively younging towards Yellowstone. More recent work reveals rhyolites as old as found at McDermitt (~16.5 Ma) to occur along a wide E-W tangent along the Oregon-Nevada-Idaho border. And now, our data extend such early rhyolites (>16 Ma) to several locations further north within and in the periphery of the Lake Owyhee Volcanic Field (LOVF) adding to the geographically orphaned old age of 16.7 Ma of the Silver City Rhyolite, Idaho. Hence, the rhyolite flare-up associated with flood basalt magmatism occurred within a circular area of ~400 km centered 100 km NNE of McDermitt. Consequently, no south-to-north progression exists in the onset of rhyolite volcanism; instead, rhyolites started up at the same time over this large area. Province-wide rhyolite volcanism was strongest between ~16.4 and 15.4 Ma coincident with eruptions of the most voluminous member of the CRBG - the Grande Ronde Basalt (GRB). Field evidence for such bimodal volcanism consists of intercalated local GRB units with the Dinner Creek Tuff and Littlefield Rhyolite in the Malheur River Gorge corridor. GRB eruption sites exist and were likely fed from reservoirs residing below or near rhyolitic chambers. Presently, we have petrological evidence for pinning down GRB storages sites to areas from where rhyolites of the Dinner Creek Tuff and lava flows of the Littlefield Rhyolite erupted. In summary, input of GRG and other CRBG magmas were driving co-CRBG rhyolite volcanism which in turn may have influenced whether flood basalt magmas erupted locally or travelled in dikes to more distally located areas.

  17. Evidence of pre-Columbian settlements in the forest of the Tuxtla Volcanic Field, Veracruz, Mexico

    OpenAIRE

    Araceli Zamora-Camacho; Juan Manuel Espíndola; Peter Schaaf; Angel Ramírez; María de Lourdes Godínez Calderón

    2015-01-01

    The basaltic Los Tuxtlas Volcanic Field (LTVF) is located at the western margin of the Gulf of Mexico in the State of Veracruz, Mexico. The field is a massif composed of four large volcanic structures and hundreds of scoria cones, lava domes and maars. This area was in the past covered by a dense forest in whose margins flourished several of the ancient cities of importance in central and southern Veracruz. Within the forest no enduring archeological ruins have been found; but ...

  18. X-ray microspectroscopy of sulfur in basaltic glass inclusions. Inference on the volcanic sulfur emissions

    Science.gov (United States)

    Métrich, N.; Susini, J.; Galoisy, L.; Calas, G.; Bonnin-Mosbah, M.; Menez, B.

    2003-03-01

    It is commonly accepted that sulfur is carried out as sulfide (S^{II-}) or/and sulfate (S^{VI}) by Earth mantlederived melts, before being released as SO2 and/or H2S in volcanic emissions. By analyzing reference compounds and a selection of minute glass inclusions in olivine crystals using μXANES (X-ray Near Edge Structure) spectroscopy at the sulfur K-edge, we demonstrated the ubiquitous presence of sulfite (S^{IV}) in addition to sulfate (S^{VI}) in these rare inclusions representative of oxidized and water rich-basaltic magmas, prior to loss of sulfur and water. The sulfide (S^{II-}) when exists is minor. We proposed that sulfite (S^{IV}) acts as an intermediate, metastable species which results in partitioning of sulfur into the volcanic gas emissions.

  19. A depleted, not ideally chondritic bulk Earth: The explosive-volcanic basalt loss hypothesis

    Science.gov (United States)

    Warren, Paul H.

    2008-04-01

    It has long been customary to assume that in the bulk composition of the Earth, all refractory-lithophile elements (including major oxides Al 2O 3 and CaO, all of the REE, and the heat-producing elements Th and U) occur in chondritic, bulk solar system, proportion to one another. Recently, however, Nd-isotopic studies (most notably Boyet M. and Carlson R. W. (2006) A new geochemical model for the Earth's mantle inferred from 146Sm- 142Nd systematics. Earth Planet. Sci. Lett.250, 254-268) have suggested that at least the outer portion of the planet features a Nd/Sm ratio depleted to ˜0.93 times the chondritic ratio. The primary reaction to this type of evidence has been to invoke a "hidden" reservoir of enriched matter, sequestered into the deepest mantle as a consequence of primordial differentiation. I propose a hypothesis that potentially explains the evidence for Nd/Sm depletion in a very different way. Among the handful of major types of differentiated asteroidal meteorites, two (ureilites and aubrites) are ultramafic restites so consistently devoid of plagioclase that meteoriticists were once mystified as to how all the complementary plagioclase-rich matter (basalt) was lost. The explanation appears to be basalt loss by graphite-fueled explosive volcanism on roughly 100-km sized planetesimals; with the dispersiveness of the process dramatically enhanced, relative to terrestrial experience, because the pyroclastic gases expand into vacuous space (Wilson L. and Keil K. (1991) Consequences of explosive eruptions on small Solar System bodies: the case of the missing basalts on the aubrite parent body. Earth Planet. Sci. Lett.104, 505-512). By analogy with lunar pyroclastic products, the typical size of pyroclastic melt/glass droplets under these circumstances will be roughly 0.1 mm. Once separated from an asteroidal or planetesimal gravitational field, droplets of this size will generally spiral toward the Sun, rather than reaccrete, because drag forces such the

  20. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    Science.gov (United States)

    Vazquez, Jorge A.; Woolford, Jeff M

    2015-01-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  1. Geochemical discrimination of the geotectonic environment of basaltic-andesitic volcanic rocks associated with the Laochang polymetallic ore deposit at Lancang, Yunnan

    Institute of Scientific and Technical Information of China (English)

    GAO Jianguo

    2006-01-01

    The Laochang polymetallic ore deposit at Lancang is one of the well known ancient ore deposits associated with volcanic rocks in the Sanjiang (Tri-river) region of Southwest China. Volcanic rocks are dominated by alkali basalt and trachyte basalt. There has long been a controversy on the environment of formation of basalts. Some scholars hold that the basalts were formed in a continental environment, some thought they were formed in an oceanic environment and others considered that the basalts were emplaced in a back-arc basin. This study focuses on the geochemical characteristics of the basalts on the basis of their major elements, REEs and trace elements. At the same time, strongly incompatible elements such as Ta, Th and Hf and their ratios were used to differentiate the geotectonic settings of basalts. The results showed that the basalts in the region studied were formed in a continental rift environment.

  2. Basaltic Clasts in Y-86032 Feldspathic Lunar Meteorite: Ancient Volcanism far from the Procellarum Kreep Terrane

    Science.gov (United States)

    Yamaguchi, A.; Takeda, H.; Nyquist, L. E.; Bogard, D.; Karouji, Y.; Ebihara, M.

    2008-01-01

    Lunar meteorite, Y-86032 is a fragmental or regolith breccia enriched in Al2O3 (28-31 wt%) and having very low concentrations of REEs and Th, U [e.g., 1]. Nyquist et al. [2] suggested that Y- 86032 contains a variety of lithologies not represented by the Apollo samples. They found clasts with old Ar-Ar ages and an ancient Sm-Nd age, and negative Nd indicating a direct link to the primordial magma ocean. Importantly, the final lithification of the Y-86032 breccia was likely >3.8-4.1 Ga ago. Therefore, any lithic components in the breccia formed prior to 3.8 Ga, and lithic components in breccia clasts in the parent breccia formed even earlier. Here we report textures and mineralogy of basaltic and gabbroic clasts in Y- 86032 to better understand the nature of ancient lunar volcanism far from the Procellarum KREEP Terrain (PKT) [3] and the central nearside.

  3. The `Strawberry Volcanic Field' of Northeastern Oregon: Another Piece of the CRB Puzzle?

    Science.gov (United States)

    Steiner, A. R.; Streck, M. J.

    2010-12-01

    The Mid to Late Miocene Strawberry Volcanics field (SVF) located along the southern margin of the John Day valley of NE Oregon, comprise a diverse group of volcanic rocks ranging from basalt to rhyolite. The main outcrop area of the SVF (3,400 km2) is bordered by units from the Columbia River Basalt Group (CRBG), with the main CRB units to the north, the Picture Gorge Basalt to the east and Steens Basalt to the south. The geographic position and age of the Strawberry Volcanics make a genetic relationship to CRB volcanism likely, yet little is known about this diverse volcanic field. This research aims at refining the stratigraphic and age relationships as well as the petrology and geochemistry of magmas associated with the SVF. Previous investigations (e.g. Robyn, 1977) found that the SVF was active between 20 to 10 Ma with the main pulse largely being coeval with the 15 Ma CRBG eruptions. Lavas and tuffs from the SVF are calc-alkaline with low FeO*/MgO (~ 2.56 wt. %), high Al2O3 (~ 16.4 wt. %), low TiO2 (~ 1.12 wt.%), and span the entire compositional range from basalt to rhyolite (47-78 wt. % SiO2) with andesite as the dominant lithology. Basaltic lavas from the SVF have compositional affinities to earlier Steens Basalt, and some trace element concentrations and ratios are indistinguishable from those of CRBG lavas (e.g. Zr, Ba, Sr, and Ce/Y). Andesites are calc-alkaline, but contrary to typical arc (orogenic) andesites, SVF andesites are exceedingly phenocryst poor (Strawberry Volcanics are largely the product of hot-spot related basaltic magmas interacting with the continental crust. The range in compositions from calc-alkaline andesite to rhyolite may be attributed to the hybridization of mantle-derived and crustal melts, with the more evolved compositions reflecting greater proportions of crustally derived material and/or higher degrees of differentiation. Furthermore, since the earliest SVF eruption is 3 Ma older than the proposed onset of the CRBG (~ 17 Ma

  4. Appraisal and evolution of hydrochemical processes from proximity basalt and granite areas of Deccan Volcanic Province (DVP) in India

    Science.gov (United States)

    Sonkamble, Sahebrao; Sahya, Ashalata; Mondal, N. C.; Harikumar, P.

    2012-05-01

    SummaryThis paper deals with a systematic hydrochemical study carried out at proximity basalt and granite areas of Deccan Volcanic Province (DVP) in India to assess groundwater quality and evaluate the hydrochemical processes. A total of 40 groundwater samples were collected equally from these areas and analyzed. Results showed that the groundwaters rich in alkaline earth in the basalt and alkali rich element in the granite. The dominancy of cations was observed as Ca2+ > Mg2+ > Na+ > K+ in the basalt and Na+ > Mg2+ > K+ > Ca2+ in the granite, whereas anions as HCO3->Cl>SO42- and Cl>HCO3->SO42-, respectively. Hydrochemical processes were identified with the helps of ion exchange, carbonate weathering and dissolution, multiple ionic ratios, and silicate weathering, which shown the predominance of carbonate, dolomite, calcite and silicate (anorthite) weathering in basalt, but in granite, silicate (alkali feldspar) weathering was dominated. Factor analysis also showed that there were multiple processes acting on groundwaters, were separated from the main cluster. Salinity, Sodium Absorption Ratio (SAR), Soluble Sodium Percentage (SSP), Residual Sodium Carbonate (RSC), Kelley's Ratio (KR) and Permeability Index (PI) in well samples showed that groundwater in basalt was more suitable for irrigation purposes. Further, a digital elevation model (DEM) was generated using Global mapper (8.0 version) software, which aided to decipher the thickness of basalt trap, and vertical transition zone of basaltic (trap) and granitic (basement) aquifer at this DVP comprising with the well depths and groundwater chemistry.

  5. A 3D model of crustal magnetization at the Pinacate Volcanic Field, NW Sonora, Mexico

    Science.gov (United States)

    García-Abdeslem, Juan; Calmus, Thierry

    2015-08-01

    The Pinacate Volcanic Field (PVF) is located near the western border of the southern Basin and Range province, in the State of Sonora NW Mexico, and within the Gulf of California Extensional Province. This volcanic field contains the shield volcano Santa Clara, which mainly consists of basaltic to trachytic volcanic rocks, and reaches an altitude of ~ 1200 m. The PVF disrupts a series of discontinuous ranges of low topographic relief aligned in a NW direction, which consist mainly of Proterozoic metamorphic rocks and Proterozoic through Paleogene granitoids. The PVF covers an area of approximately 60 by 55 km, and includes more than 400 well-preserved cinder cones and vents and eight maar craters. It was active from about 1.7 Ma until about 13 ka. We have used the ages and magnetic polarities of the volcanic rocks, along with mapped magnetic anomalies and their inverse modeling to determine that the Pinacate Volcanic Field was formed during two volcanic episodes. The oldest one built the Santa Clara shield volcano of basaltic and trachytic composition, and occurred during the geomagnetic Matuyama Chron of reverse polarity, which also includes the normal polarity Jaramillo and Olduvai Subchrons, thus imprinting both normal and reverse magnetization in the volcanic products. The younger Pinacate series of basaltic composition represents monogenetic volcanic activity that extends all around the PVF and occurred during the subsequent geomagnetic Brunhes Chron of normal polarity. Magnetic anomalies toward the north of the Santa Clara volcano are the most intense in the PVF, and their inverse modeling indicates the presence of a large subsurface body magnetized in the present direction of the geomagnetic field. This suggests that the magma chambers at depth cooled below the Curie temperature during the Brunhes Chron.

  6. Cross-arc geochemical variations in volcanic fields in Honduras C.A.: progressive changes in source with distance from the volcanic front

    Science.gov (United States)

    Patino, Lina C.; Carr, Michael J.; Feigenson, Mark D.

    A geochemical traverse across Honduras reveals the heterogeneity of the mantle underneath Central America. Alkali basalts from Lake Yojoa (170km behind the front) have low 87Sr/86Sr but high La/Yb, and elevated incompatible trace element abundances, consistent with derivation from a normal mid-ocean ridge basalt source mantle via low degrees of melting. These lavas lack evidence for an enriched source thought to be intermingled with normal mid-ocean ridge basalt source mantle beneath most of Central America. The amplitude of the subducted slab signature decreases smoothly with distance from the volcanic front. Lavas from Zacate Grande, the area nearest to the volcanic front (17 km behind the arc), display large ion lithophile element enrichment and high field strength element depletion indicating the involvement of subducted material in magma genesis. Components of subducted material are not evident in lavas from Lake Yojoa, the area furthest from the arc. Basalts and basaltic andesites from Tegucigalpa, 102 km behind the volcanic front, are geochemically intermediate between those of Lake Yojoa and Zacate Grande. The lavas from Tegucigalpa show a decreased influence of the subduction component, and are affected by assimilation-fractional crystallization processes at shallow depths. The gradual decrease in the subducted component from the volcanic front to Zacate Grande, Tegucigalpa and finally Lake Yojoa contrasts with the abrupt decrease documented for southeast Guatemala, the only other area in Central America where a cross-arc transect has been studied.

  7. A brief comparison of lava flows from the Deccan Volcanic Province and the Columbia-Oregon Plateau Flood Basalts: Implications for models of flood basalt emplacement

    Indian Academy of Sciences (India)

    Ninad Bondre; Raymond A Duraiswami; Gauri Dole

    2004-12-01

    The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a atter of great interest as well as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note, however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. In this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces, and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation of lava flow morphology from all CFB provinces.

  8. A Plagioclase Ultraphyric Basalt group in the Neogene flood basalt piles of eastern Iceland: Volcanic architecture and mode of emplacement

    Science.gov (United States)

    Oskarsson, B. V.; Riishuus, M. S.

    2013-12-01

    3D photogrammetry in conjunction with ground mapping was applied in order to assess the architecture of a Plagioclase Ultraphyric Basalt (PUB) group in eastern Iceland, namely the Grænavatn group. The ~10 Myr old group is exposed in steep glacially carved fjords and can be traced over 60 km along strike. Two feeder dikes have been found and show that the group erupted along the trend of the dike swarm associated with the Breiddalur central volcano. The group has 9--14 flows where thickest, and thins to about 3--4 flows up-dip to the east within the distance of 15-20 km from the source. We have estimated the volume of the group to exceed 40 km3. The flows have mixed architecture of simple and compound morphology. The flow lobes have thicknesses from 1--24 m and many reach lengths over 1000 m. The surface morphology varies from rubbly to scoriaceous, but is dominantly of pahoehoe style. The internal structure of the lava flows is well preserved and the flows display abundant vesicle cylinders. The modal percentage of An-rich plagioclase macrocrysts varies from 25--50 % and they are in the range of 5--30 mm. The aspect ratio of the group and the nature of the flows indicate fissure-fed eruptions. A thick flow found at the base of the group in various locations seems to record the largest eruption episode in the formation of the group. This phase is also the most abundant in macrocryst. An asymmetric buildup is seen in one location and may have characterized the general buildup of the group. The general morphology of the lava flows suggests low viscous behavior, at odds with the high crystal content. Petrographic observations and mineral chemistry shows that the plagioclase macrocrysts are very calcic (An80-85) and in disequilibrium with the groundmass and plagioclases therein (An50-70). Thus the apparent lava rheology and emplacement of the PUBs was likely achieved due to fast ascent of the magma through the crust and transfer of heat from the primitive macrocrysts

  9. Pollution and paradigms: lessons from Icelandic volcanism for continental flood basalt studies

    Science.gov (United States)

    Grattan, John

    2005-02-01

    This paper is based on the premise that research into the environmental impact of continental flood basalt (CFB) volcanism has paid insufficient attention to the potential ecosystem damage that would result from the direct deposition of hundreds of megatons (Tg) of sulphur and other volatiles. The environmental impacts of the 1783 Laki Fissure eruption are reviewed in outline. It is shown that in a relatively brief period of volcanic activity, volatiles emitted by the eruption damaged and destroyed vegetation from the Arctic Ocean to the Mediterranean. Air pollution was so intense that human health was affected and the national death rate increased dramatically in both England and France. It is proposed that the events of 1783 may be used as a paradigm for the environmental impacts of a CFB lava flow, and the emissions of 1783 are scaled up to illustrate this point. Thus, if a Laki style event were to erupt for a year it would approach the physical scale of a single episode of the Roza flow in the Columbia River CFB and potentially yield 576 Tg of sulphur gases which could have been oxidised into approximately 945 Tg of aerosol. This could generate a tropospheric aerosol mass of approximately 708 Tg H 2SO 4. The ecosystem impact of the deposition of acids on this scale would be profound and, as with the actual Laki event, be continental in scale. All parts of the plant life cycle would be disrupted, including photosynthesis and fruiting. Inevitably, with the disruption of food webs animals would also be affected. Poorly buffered inland waters would be acidified, as would Boreal soils, reducing their biodiversity. In our already polluted and interdependent world, any future event on this scale would have serious consequences for human health and trade.

  10. Rare-earth element geochemistry and the origin of andesites and basalts of the Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Cole, J.W.; Cashman, K.V.; Rankin, P.C.

    1983-01-01

    Two types of basalt (a high-Al basalt associated with the rhyolitic centres north of Taupo and a "low-Al" basalt erupted from Red Crater, Tongariro Volcanic Centre) and five types of andesite (labradorite andesite, labradorite-pyroxene andesite, hornblende andesite, pyroxene low-Si andesite and olivine andesite/low-Si andesite) occur in the Taupo Volcanic Zone (TVZ), North Island, New Zealand. Rare-earth abundances for both basalts and andesites are particularly enriched in light rare-earth elements. High-Al basalts are more enriched than the "low-Al" basalt and have values comparable to the andesites. Labradorite and labradorite-pyroxene andesites all have negative Eu anomalies and hornblende andesites all have negative Ce anomalies. The former is probably due to changing plagioclase composition during fractionation and the latter to late-stage hydration of the magma. Least-squares mixing models indicate that neither high-Al nor "low-Al" basalts are likely sources for labradorite/labradorite-pyroxene andesites. High-Al basalts are considered to result from fractionation of olivine and clinopyroxene from a garnet-free peridotite at the top of the mantle wedge. Labradorite/labradorite-pyroxene andesites are mainly associated with an older NW-trending arc. The source is likely to be garnet-free but it is not certain whether the andesites result from partial melting of the top of the subducting plate or a hydrated lower portion of the mantle wedge. Pyroxene low-Si andesites probably result from cumulation of pyroxene and calcic plagioclase within labradorite-pyroxene andesites, and hornblende andesites by late-stage hydration of labradorite-pyroxene andesite magma. Olivine andesites, low-Si andesites and "low-Al" basalts are related to the NNE-trending Taupo-Hikurangi arc structure. Although the initial source material is different for these lavas they have probably undergone a similar history to the labradorite/labradorite-pyroxene andesites. All lavas show evidence

  11. Geologic map of the Simcoe Mountains Volcanic Field, main central segment, Yakama Nation, Washington

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2015-01-01

    Mountainous parts of the Yakama Nation lands in south-central Washington are mostly covered by basaltic lava flows and cinder cones that make up the Simcoe Mountains volcanic field. The accompanying geologic map of the central part of the volcanic field has been produced by the U.S. Geological Survey (USGS) on behalf of the Water Resources Program of the Yakama Nation. The volcanic terrain stretches continuously from Mount Adams eastward as far as Satus Pass and Mill Creek Guard Station. Most of the many hills and buttes are volcanic cones where cinders and spatter piled up around erupting vents while lava flows spread downslope. All of these small volcanoes are now extinct, and, even during their active lifetimes, most of them erupted for no more than a few years. On the Yakama Nation lands, the only large long-lived volcano capable of erupting again in the future is Mount Adams, on the western boundary.

  12. The geochemical characteristics of basaltic and acidic volcanics around the Myojin depression in the Izu arc, Japan

    Science.gov (United States)

    Haraguchi, S.; Tamaki, K.; Kato, Y.; Machida, S.

    2012-12-01

    Around the Myojin Depression, westside of the Myojin-sho caldera in the Izu arc, seamounts are circular distributed and hydrothermal activity with sulfide deposition are found from the Baiyonneise Caldera, one of seamounts at the northern side. Some knoll chains distribute in the eastside of the Myojin Depression, and connect between these knolls. This circulator distribution of seamounts and connected knoll chains considered to the dykes are similar to the geographical features of the Kuroko Depositions in the Hokuroku Region, Northwest Japan (Tanahashi et al., 2008). Hydrothermal activities are also found from the other rifts (Urabe and Kusakabe 1990). Based on these observations, the cruise KT09-12 by R/V Tansei-Maru, Ocean Research Institute (ORI), University of Tokyo, investigated in the Myojin Rift. During the cruise, basaltic to dacitic volcanic rocks and some acidic plutonic rocks were recovered by dredge system. Herein, we present petrographical and chemical analyses of these rock samples with sample dredged by the cruise MW9507 by R/V MOANA WAVE, and consider the association with hydrothermal activities and depositions. Dredges during the cruise KT09-12 were obtained at the Daini-Beiyonneise Knoll at the northern side, Daisan-Beiyonneise Knoll at the southern side, and the Dragonborn Hill, small knoll chains, at the southeastern side of the depression. Many volcanic rocks are basalt, and recovered mainly from the Dragonborn Hill. Andesite and dacite was recovered from the Daini- and the Daini-Bayonneise Knoll. Tonalites were recovered from the Daisan-Bayonneise Knoll. Basalts from the Dragonborn Hill show less than 50% of SiO2 and more than 6 wt% and 0.88 wt% of MgO and TiO2 content. Basalts from the rift zone show depleted in the volcanic front (VF) side and enriched in the reararc (RA) side. The Dragonborn Hill is distributed near the VF, and basalts show depleted geochemical characteristics. However, these characteristics are different from the basalts

  13. The eruptive history of the Tequila volcanic field, western Mexico: ages, volumes, and relative proportions of lava types

    Science.gov (United States)

    Lewis-Kenedi, Catherine B.; Lange, Rebecca A.; Hall, Chris M.; Delgado-Granados, Hugo

    2005-06-01

    The eruptive history of the Tequila volcanic field (1600 km2) in the western Trans-Mexican Volcanic Belt is based on 40Ar/39Ar chronology and volume estimates for eruptive units younger than 1 Ma. Ages are reported for 49 volcanic units, including Volcán Tequila (an andesitic stratovolcano) and peripheral domes, flows, and scoria cones. Volumes of volcanic units ≤1 Ma were obtained with the aid of field mapping, ortho aerial photographs, digital elevation models (DEMs), and ArcGIS software. Between 1120 and 200 kyrs ago, a bimodal distribution of rhyolite (~35 km3) and high-Ti basalt (~39 km3) dominated the volcanic field. Between 685 and 225 kyrs ago, less than 3 km3 of andesite and dacite erupted from more than 15 isolated vents; these lavas are crystal-poor and show little evidence of storage in an upper crustal chamber. Approximately 200 kyr ago, ~31 km3 of andesite erupted to form the stratocone of Volcán Tequila. The phenocryst assemblage of these lavas suggests storage within a chamber at ~2 3 km depth. After a hiatus of ~110 kyrs, ~15 km3 of andesite erupted along the W and SE flanks of Volcán Tequila at ~90 ka, most likely from a second, discrete magma chamber located at ~5 6 km depth. The youngest volcanic feature (~60 ka) is the small andesitic volcano Cerro Tomasillo (~2 km3). Over the last 1 Myr, a total of 128±22 km3 of lava erupted in the Tequila volcanic field, leading to an average eruption rate of ~0.13 km3/kyr. This volume erupted over ~1600 km2, leading to an average lava accumulation rate of ~8 cm/kyr. The relative proportions of lava types are ~22 43% basalt, ~0.4 1% basaltic andesite, ~29 54% andesite, ~2 3% dacite, and ~18 40% rhyolite. On the basis of eruptive sequence, proportions of lava types, phenocryst assemblages, textures, and chemical composition, the lavas do not reflect the differentiation of a single (or only a few) parental liquids in a long-lived magma chamber. The rhyolites are geochemically diverse and were likely

  14. Using Spatial Density to Characterize Volcanic Fields on Mars

    Science.gov (United States)

    Richardson, J. A.; Bleacher, J. E.; Connor, C. B.; Connor, L. J.

    2012-01-01

    We introduce a new tool to planetary geology for quantifying the spatial arrangement of vent fields and volcanic provinces using non parametric kernel density estimation. Unlike parametricmethods where spatial density, and thus the spatial arrangement of volcanic vents, is simplified to fit a standard statistical distribution, non parametric methods offer more objective and data driven techniques to characterize volcanic vent fields. This method is applied to Syria Planum volcanic vent catalog data as well as catalog data for a vent field south of Pavonis Mons. The spatial densities are compared to terrestrial volcanic fields.

  15. Eruptive Productivity of the Ceboruco-San Pedro Volcanic Field, Nayarit, Mexico

    Science.gov (United States)

    Frey, H. M.; Lange, R. A.; Hall, C. M.; Delgado-Granados, H.

    2002-12-01

    High-precision 40Ar/39Ar geochronology coupled with GIS spatial analysis provides constraints on magma eruption rates over the past 1 Myr of the Ceboruco-San Pedro volcanic field (1870 km2), located in the Tepic-Zacoalco rift in western Mexico. The volcanic field is part of the Trans Mexican Volcanic arc and is dominated by the andesitic-dacitic stratocone of Volcan Ceboruco and includes peripheral fissure-fed flows, domes, and monogenetic cinder cones. The ages of these volcanic features were determined using 40Ar/39Ar laser step-heating techniques on groundmass or mineral separates, with 78% of the 52 analyses yielding plateau ages with a 2 sigma error < 50 kyrs. The volumes were determined using high resolution (1:50,000) digital elevation models, orthophotos, and GIS software, which allowed for the delineation of individual volcanic features, reconstruction of the pre-eruptive topography, and volume calculations by linear interpolation. The relative proportions of the 80 km3 erupted over the past 1 Myr are 14.5% basaltic andesite, 64.5% andesite, 20% dacite, and 1% rhyolite, demonstrating the dominance of intermediate magma types (in terms of silica content). Overall, there appears to be no systematic progression in the eruption of different magma types (e.g., basalt, andesite, dacite, etc.) with time. However, more than 75% of the total volume of lava within the Ceboruco-San Pedro volcanic field erupted in the last 100 kyrs. This reflects the youthfulness of Volcan Ceboruco, which was constructed during the last 50 kyrs and has a present day volume of 50 +/- 2.5 km3, accounting for 81% of the andesite and 50% of the dacite within the volcanic field. Eleven cinder cones, ranging from the Holocene to 0.37 Ma, display a narrow compositional range, with 52-58 wt% SiO2, 3-5.5 wt% MgO, and relatively high TiO2 concentrations (0.9-1.8 wt%). The total volume of the cinder cones is 0.83 km3. No lavas with < 51 wt% SiO2 have erupted in the past 1 Myr. Peripheral

  16. Decreasing Magmatic Footprints of Individual Volcanos in a Waning Basaltic Field

    Energy Technology Data Exchange (ETDEWEB)

    G.A> Valentine; F.V. Perry

    2006-06-06

    The distribution and characteristics of individual basaltic volcanoes in the waning Southwestern Nevada Volcanic Field provide insight into the changing physical nature of magmatism and the controls on volcano location. During Pliocene-Pleistocene times the volumes of individual volcanoes have decreased by more than one order of magnitude, as have fissure lengths and inferred lava effusion rates. Eruptions evolved from Hawaiian-style eruptions with extensive lavas to eruptions characterized by small pulses of lava and Strombolian to violent Strombolian mechanisms. These trends indicate progressively decreasing partial melting and length scales, or magmatic footprints, of mantle source zones for individual volcanoes. The location of each volcano is determined by the location of its magmatic footprint at depth, and only by shallow structural and topographic features that are within that footprint. The locations of future volcanoes in a waning system are less likely to be determined by large-scale topography or structures than were older, larger volume volcanoes.

  17. Very long pahoehoe inflated basaltic lava flows in the Payenia volcanic province (Mendoza and la Pampa, Argentina

    Directory of Open Access Journals (Sweden)

    Giorgio Pasquarè

    2008-03-01

    Full Text Available Extremely long basaltic lava flows are here presented and described. The flows originated from the great, polygenetic, fissural Payen Volcanic Complex, in the Andean back-arc volcanic province of Payenia in Argentina. The lava flows outpoured during the Late Quaternary from the summit rift of a shield volcano representing the first volcanic centre of this complex. One of these flows presents an individual tongue-like shape with a length of 181 km and therefore is the longest known individual Quaternary lava flow on Earth. Leaving the flanks of the volcano this flow reached the Salado river valley at La Pampa and, in its distal portion, maintained its narrow and straight shape without any topographic control over a flat alluvial plain. It has a hawaiite composition with low phenocryst content of prevailing olivine and minor plagioclase. Rare Earth element patterns are typical of Na-alkaline basalts, but incompatible trace element patterns and Sr -Nd isotope ratios, suggest a geodynamic setting transitional to the orogenic one. The flow advanced following the thermally efficient "inflation" mechanism, as demonstrated by a peculiar association of well developed morphological, structural and textural features. The temperature of 1130-1160°C and the viscosity of 3-73 Pa*s, calculated by petrochemical data, may be considered, together with a very low cooling rate and a sustained and long lasting effusion rate, the main causes of the extremely long transport system of this flow. Both the extreme length of the flow and the partial lack of topographic control may provide new constraints on the physics of large inflated flows, which constitute the largest volcanic provinces on Earth and probably also on the terrestrial planets.

  18. A petrologic study of the Teanaway Basalt: Eocene slab window volcanism in central WA

    Science.gov (United States)

    Roepke, E.; Tepper, J. H.; Ivener, D.

    2013-12-01

    The Teanaway Basalt (TB) includes subaerial basalt to andesite flows, mafic to felsic tuffs, and rhyolite domes in the Central Cascades of Washington State. These volcanics overlie the extensive ~47 Ma Teanaway Dike Swarm (TDS) that cuts the underlying Swauk Formation. This study focuses on the tectonic setting of eruption and geochemical variations relating to geography and stratigraphy within the TB. The western-most area of the TB, Easton Ridge (ER), is compared with the eastern-most area of the TB, Liberty Ridge (LR) - 40 km to the east of ER. The bimodal TB consists predominantly of basaltic andesite and andesite (45.3-63.1 wt% SiO2) with subordinate rhyolite (75.9-79.4 wt% SiO2). The mafic rocks classify as primarily medium-K tholeiites (0.1-3.0 wt% K2O), but a few samples classify as alkaline. Enrichment in LILE and depletion in HFSE on spidergrams are indicative of an arc setting. However, compared with the modern Cascade Arc, the TB is distinctly higher in Fe2O3T (8.8-17.1 wt%) and TiO2 (1.1-2.7 wt%), and distinctly lower in Al2O3 (11.2-14.6) and K2O, with a similar range of Mg #s (0.15-0.48). Most tectonic discrimination plots characterize the TB as MORB, but some indicate an arc or within-plate setting. Preliminary Pb isotopic data (206Pb/204Pb = 19.13-19.19, 207Pb/204Pb = 15.62-15.64, and 208Pb/204Pb = 38.78-38.90) indicate the TB and TDS are more enriched than Cascade Arc rocks in 206Pb/204Pb and 208Pb/204Pb. Overall, these geochemical data are consistent with a model in which asthenospheric mantle ascending through a slab window interacts with mantle wedge that has previously acquired arc chemical traits. The existence of a slab window in this region during the mid-Eocene is compatible with plate reconstructions and evidence of extension that have been attributed to subduction of the Resurrection-Kula ridge (Haeussler et al., 2003). Harker plots show lavas at LR are generally more enriched than those at ER in Fe2O3T (11.9-17.1 wt% vs 8.8-15.7 wt%) Mn

  19. Depth of volcanic basalt degassing forecasted from CO2 fluid inclusions

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Fluid inclusions have recorded the history of degassing in basalt. Some fluid inclusions in olivine and pyroxene phenocrysts of basalt were analyzed by micro-thermometry and Raman spectroscopy in this paper. The experimental results showed that many inclusions are present almost in a pure CO2 system. The densities of some CO2 inclusions were computed in terms of Raman spectroscopic characteristics of CO2 Fermi resonance at room temperature. Their densities change over a wide range, but mainly between 0.044 g/cm3 and 0.289 g/cm3. Their micro-thermometric measurements showed that the CO2 inclusions examined reached homogenization between 1145.5℃ and 1265℃. The mean value of homogenization temperatures of CO2 inclusions in basalts is near 1210℃. The trap pressures (depths) of inclusions were computed with the equation of state and computer program. Distribution of the trap depths makes it know that the degassing of magma can happen over a wide pressure (depth) range, but mainly at the depth of 0.48 km to 3.85 km. This implicates that basalt magma experienced intensive degassing and the CO2 gas reservoir from the basalt magma also may be formed in this range of depths. The results of this study showed that the depth of basalt magma degassing can be forecasted from CO2 fluid inclusions, and it is meaningful for understanding the process of magma degassing and constraining the inorganogenic CO2 gas reservoir.

  20. The Carrán-Los Venados volcanic field and its relationship with coeval and nearby polygenetic volcanism in an intra-arc setting

    Science.gov (United States)

    Bucchi, Francisco; Lara, Luis E.; Gutiérrez, Francisco

    2015-12-01

    Understanding the relationship between monogenetic and polygenetic volcanism has been a long-standing goal in volcanology, especially in cases where these two styles of volcanism are coeval and geographically adjacent. We studied the Carrán-Los Venados (CLV) volcanic field and made comparisons with published data on CLV's polygenetic neighbor Puyehue-Cordón Caulle (PCC) in the Southern Andean arc, using quantitative tools and recent numerical simulations of magma reservoir formation. CLV is a basaltic to basaltic andesitic volcanic field composed of 65 post-glacial scoria cones and maars and a 1-km-high Pleistocene stratovolcano, whereas PCC is a basaltic to rhyolitic composite volcano. Our results point to three main differences between CLV and PCC: (1) the CLV magmas differentiate at low-crustal reservoirs, followed by rapid ascent to the surface, while the PCC magmas stagnate and differentiate in lower- and upper-crustal reservoirs; (2) CLV is elongated in the NE direction while PCC is elongated in the NW direction. Under the current stress field (N60°E σHmax), these two volcanic alignments correspond, respectively, to local extensional and compressive deformation zones within the arc; and (3), the post-glacial CLV magma flux was estimated to be 3.1 ± 1.0 km3/ky, which is similar to the average magma flux estimated for PCC; however, the PCC magma flux is estimated at approximately twice this value during peak eruptive periods (5.5 ± 1.1 km3/ky). Based on numerical simulations, CLV is in a limit situation to create and sustain a mush-type upper-crustal reservoir containing highly crystalline magma, which is however not eruptible. The PCC volcanic system would have been able to create a stable reservoir containing eruptible silicic magma during periods of peak magma flux. We postulate that monogenetic volcanism occurs at CLV due to both low magma flux and an extensional/transtensional regime that favors rapid magma rise without storage and differentiation in

  1. Catastrophic volcanism

    Science.gov (United States)

    Lipman, Peter W.

    1988-01-01

    Since primitive times, catastrophes due to volcanic activity have been vivid in the mind of man, who knew that his activities in many parts of the world were threatened by lava flows, mudflows, and ash falls. Within the present century, increasingly complex interactions between volcanism and the environment, on scales not previously experienced historically, have been detected or suspected from geologic observations. These include enormous hot pyroclastic flows associated with collapse at source calderas and fed by eruption columns that reached the stratosphere, relations between huge flood basalt eruptions at hotspots and the rifting of continents, devastating laterally-directed volcanic blasts and pyroclastic surges, great volcanic-generated tsunamis, climate modification from volcanic release of ash and sulfur aerosols into the upper atmosphere, modification of ocean circulation by volcanic constructs and attendent climatic implications, global pulsations in intensity of volcanic activity, and perhaps triggering of some intense terrestrial volcanism by planetary impacts. Complex feedback between volcanic activity and additional seemingly unrelated terrestrial processes likely remains unrecognized. Only recently has it become possible to begin to evaluate the degree to which such large-scale volcanic processes may have been important in triggering or modulating the tempo of faunal extinctions and other evolutionary events. In this overview, such processes are examined from the viewpoint of a field volcanologist, rather than as a previous participant in controversies concerning the interrelations between extinctions, impacts, and volcanism.

  2. Subduction zone mantle enrichment by fluids and Zr-Hf-depleted crustal melts as indicated by backarc basalts of the Southern Volcanic Zone, Argentina

    Science.gov (United States)

    Holm, Paul M.; Søager, Nina; Alfastsen, Mads; Bertotto, Gustavo W.

    2016-10-01

    We aim to identify the components metasomatizing the mantle above the subducting Nazca plate under part of the Andean Southern Volcanic Zone (SVZ). We present new major and ICP-MS trace element and Sr, Nd and high-precision Pb isotope analyses of primitive olivine-phyric alkali basalts from the Northern Segment Volcanic Field, part of the Payenia province in the backarc of the Transitional SVZ. One new 40Ar-39Ar age determination confirms the Late Pleistocene age of this most northerly part of the province. All analysed rocks have typical subduction zone type incompatible element enrichment, and the rocks of the Northern Segment, together with the neighbouring Nevado Volcanic Field, have isotopic compositions intermediate between adjacent Transitional SVZ arc rocks and southern Payenia OIB-type basaltic rocks. Modelling the Ba-Th-Sm variation we demonstrate that fluids as well as 1-2% melts of upper continental crust (UCC) enriched their mantle sources, and La-Nb-Sm variations additionally indicate that the pre-metasomatic sources ranged from strongly depleted to undepleted mantle. Low Eu/Eu* and Sr/Nd also show evidence for a UCC component in the source. The contribution of Chile Trench sediments to the magmas seems insignificant. The Zr/Sm and Hf/Sm ratios are relatively low in many of the Northern Segment rocks, ranging down to 17 and 0.45, respectively, which, together with relatively high Th/U, is argued to indicate that the metasomatizing crustal melts were derived by partial melting of subducted UCC that had residual zircon, in contrast to the UCC melts added to Transitional SVZ arc magmas. Mixing between depleted and undepleted mantle, enriched by UCC and fluids, is suggested by Sr, Nd and Pb isotopes of the Northern Segment and Nevado magmas. The metasomatized undepleted mantle south of the Northern Segment is suggested to be part of upwelling OIB-type mantle, whereas the pre-metasomatically depleted mantle also can be found as a component in some arc

  3. New Insights to the Mid Miocene Calc-alkaline Lavas of the Strawberry Volcanics, NE Oregon Surrounded by the Coeval Tholeiitic Columbia River Basalt Province

    Science.gov (United States)

    Steiner, A. R.; Streck, M. J.

    2013-12-01

    The Strawberry Volcanics (SV) of NE Oregon were distributed over 3,400 km2 during the mid-Miocene and comprise a diverse volcanic suite, which span the range of compositions from basalt to rhyolite. The predominant composition of this volcanic suite is calc-alkaline (CA) basaltic andesite and andesite, although tholeiitic (TH) lavas of basalt to andesite occur as well. The coeval flood basalts of the Columbia River province surround the SV. Here we will discuss new ages and geochemical data, and present a new geologic map and stratigraphy of the SV. The SV are emplaced on top of pre-Tertiary accreted terranes of the Blue Mountain Province, Mesozoic plutonic rocks, and older Tertiary volcanic rocks thought to be mostly Oligocene of age. Massive rhyolites (~300 m thick) are exposed mainly along the western flank and underlie the intermediate composition lavas. In the southern portion of this study area, alkali basaltic lavas, thought to be late Miocene to early Pliocene in age, erupted and overlie the SV. In addition, several regional ignimbrites reach into the area. The 9.7 Ma Devine Canyon Tuff and the 7.1 Ma Rattlesnake Tuff also overlie the SV. The 15.9-15.4 Ma Dinner Creek Tuff is mid-Miocene, and clear stratigraphic relationships are found in areas where the tuff is intercalated between thick SV lava flows. All of the basalts of the SV are TH and are dominated by phenocryst-poor (≤2%) lithologies. These basalts have an ophitic texture dominated by plagioclase, clinopyroxene and olivine (often weathered to iddingsite). Basalts and basaltic andesites have olivine Fo #'s ranging from 44 at the rims (where weathered to iddingsite) and as high as 88 at cores. Pyroxene Mg #'s range from 65 to 85. Andesites of the SV are sub-alkaline, and like the basalts, are exceedingly phenocryst-poor (≤3%) with microphenocrysts of plagioclase and lesser pyroxene and olivine, which occasionally occur as crystal clots of ~1-3 mm instead of single crystals. In addition, minimal

  4. Precaldera lavas of the southeast San Juan Volcanic Field: Parent magmas and crustal interactions

    Science.gov (United States)

    Colucci, M. T.; Dungan, M. A.; Ferguson, K. M.; Lipman, P. W.; Moorbath, S.

    1991-07-01

    Early intermediate composition volcanic rocks of the Oligocene (circa 34-29 Ma) southeast San Juan volcanic field, southern Colorado, comprise the Conejos Formation. Conejos lavas include both high-K calc-alkaline and alkaline magma series (54-69% SiO2) ranging in composition from basaltic andesite (basaltic trachyandesite) to dacite (trachydacite). The subsequent Platoro caldera complex (29-27 Ma) was superimposed on a cluster of broadly precursory Conejos stratocones. Precaldera volcanism occurred in three pulses corresponding to three time-stratigraphic members: (1) the Horseshoe Mountain member, (2) the Rock Creek member, and (3) the Willow Mountain member. Each member exhibits distinctive phenocryst modes and incompatible trace element contents. Horseshoe Mountain lavas (hornblende-phyric) have relatively low alkali and incompatible element abundances, Rock Creek lavas (anhydrous phenocrysts) and ash-flow tuffs have the highest abundances, and Willow Mountain lavas (diverse mineralogy) are intermediate. All Conejos lavas exhibit low ratios of lead (206Pb/204Pb = 17.5 to 18.2) and neodymium (ɛNd = -8 to -4) isotopes and high 87Sr/86Sr (0.7045 to 0.7056) compared to depleted asthenospheric mantle. These values lie between those of likely mantle compositions and the isotopic composition of Proterozoic crust of the southern Rocky Mountains. Mafic lavas of the Horseshoe Mountain member have the lowest Pb and Nd isotope ratios among Conejos members but trend toward higher isotopic values with increasing degrees of differentiation. Compositions within the Rock Creek series trend toward higher Pb and lower Nd isotope ratios with increasing SiO2. Willow mountain volcanic sequences define diverse chemical-isotopic correlations. We interpret the chemical and isotopic differences observed between mafic lavas of each member to reflect derivation from compositionally distinct mantle derived parent magmas that have experienced extensive deep level crustal contamination

  5. Volcanic field elongation, vent distribution and tectonic evolution of continental rift: The Main Ethiopian Rift example

    Science.gov (United States)

    Mazzarini, Francesco; Le Corvec, Nicolas; Isola, Ilaria; Favalli, Massimiliano

    2015-04-01

    Magmatism and faulting operate in continental rifts and interact at a variety of scales, however their relationship is complex. The African rift, being the best example for both active continental rifting and magmatism, provides the ideal location to study the interplay between the two mechanisms. The Main Ethiopian Rift (MER), which connects the Afar depression in the north with the Turkana depression and Kenya Rift to the south, consists of two distinct systems of normal faults and its floor is scattered with volcanic fields formed by tens to several hundreds monogenetic, generally basaltic, small volcanoes and composite volcanoes and small calderas. The distribution of vents defines the overall shape of the volcanic field. Previous work has shown that the distribution of volcanic vents and the shape of a field are linked to its tectonic environment and its magmatic system. In order to distinguish the impact of each mechanism, we analyzed four volcanic fields located at the boundary between the central and northern MER, three of them (Debre Zeyit, Wonji and Kone) grew in the rift valley and one (Akaki) on the western rift shoulder. The elongation and shape of the fields were analyzed based on their vent distribution using the Principal Component Analysis (PCA), the Vent-to-Vent Distance (VVD), and the two dimensional symmetric Gaussian kernel density estimate methods. We extracted from these methods several parameters characterizing the spatial distribution of points (e.g., eccentricity (e), eigenvector index (evi), angular dispersion (Da)). These parameters allow to define at least three types of shape for volcanic fields: strong elongate (line and ellipse), bimodal/medium elongate (ellipse) and dispersed (circle) shapes. Applied to the natural example, these methods well differentiate each volcanic field. For example, the elongation of the field increases from shoulder to rift axis inversely to the angular dispersion. In addition, the results show that none of

  6. Geologic and geophysical investigations of the Zuni-Bandera volcanic field, New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Ander, M.E.; Heiken, G.; Eichelberger, J.; Laughlin, A.W.; Huestis, S.

    1981-05-01

    A positive, northeast-trending gravity anomaly, 90 km long and 30 km wide, extends southwest from the Zuni uplift, New Mexico. The Zuni-Bandera volcanic field, an alignment of 74 basaltic vents, is parallel to the eastern edge of the anomaly. Lavas display a bimodal distribution of tholeiitic and alkalic compositions, and were erupted over a period from 4 Myr to present. A residual gravity profile taken perpendicular to the major axis of the anomaly was analyzed using linear programming and ideal body theory to obtain bounds on the density contrast, depth, and minimum thickness of the gravity body. Two-dimensionality was assumed. The limiting case where the anomalous body reaches the surface gives 0.1 g/cm/sup 3/ as the greatest lower bound on the maximum density contrast. If 0.4 g/cm/sup 3/ is taken as the geologically reasonable upper limit on the maximum density contrast, the least upper bound on the depth of burial is 3.5 km and minimum thickness is 2 km. A shallow mafic intrusion, emplaced sometime before Laramide deformation, is proposed to account for the positive gravity anomaly. Analysis of a magnetotelluric survey suggests that the intrusion is not due to recent basaltic magma associated with the Zuni-Bandera volcanic field. This large basement structure has controlled the development of the volcanic field; vent orientations have changed somewhat through time, but the trend of the volcanic chain followed the edge of the basement structure. It has also exhibited some control on deformation of the sedimentary section.

  7. 3-D high-speed imaging of volcanic bomb trajectory in basaltic explosive eruptions

    Science.gov (United States)

    Gaudin, D.; Taddeucci, J; Houghton, B. F.; Orr, Tim R.; Andronico, D.; Del Bello, E.; Kueppers, U.; Ricci, T.; Scarlato, P.

    2016-01-01

    Imaging, in general, and high speed imaging in particular are important emerging tools for the study of explosive volcanic eruptions. However, traditional 2-D video observations cannot measure volcanic ejecta motion toward and away from the camera, strongly hindering our capability to fully determine crucial hazard-related parameters such as explosion directionality and pyroclasts' absolute velocity. In this paper, we use up to three synchronized high-speed cameras to reconstruct pyroclasts trajectories in three dimensions. Classical stereographic techniques are adapted to overcome the difficult observation conditions of active volcanic vents, including the large number of overlapping pyroclasts which may change shape in flight, variable lighting and clouding conditions, and lack of direct access to the target. In particular, we use a laser rangefinder to measure the geometry of the filming setup and manually track pyroclasts on the videos. This method reduces uncertainties to 10° in azimuth and dip angle of the pyroclasts, and down to 20% in the absolute velocity estimation. We demonstrate the potential of this approach by three examples: the development of an explosion at Stromboli, a bubble burst at Halema'uma'u lava lake, and an in-flight collision between two bombs at Stromboli.

  8. Volcanology, geochemistry and age of the Lausitz Volcanic Field

    Science.gov (United States)

    Büchner, J.; Tietz, O.; Viereck, L.; Suhr, P.; Abratis, M.

    2015-11-01

    The Lausitz (Lusatia) Volcanic Field is part of the Central European Volcanic Province, and its magmas represent an alkaline trend from olivine nephelinites and basanites to trachytes and phonolites, typical for intraplate settings. Neighbouring volcanic fields are the České Středohoří Mountains to the south-west and the Fore-Sudetic Basin in Lower Silesia to the east. More than 1000 volcanic structures associated with approximately 500 vents have been located within this volcanic field. Residuals of scoria cones, lava lakes, lava flows and maar-diatreme in filling occur in situ near the level of the original syn-volcanic terrain. In more deeply eroded structures, volcanic relicts outcrop as plugs or feeders. Evolved rocks occur as monogenetic domes or intrusions in diatremes, while their volcaniclastic equivalents are rare. Twenty-three localities were dated using the 40Ar/39Ar method. The ages range from 35 to 27 Ma, with a focus around 32-29 Ma, indicating Late Eocene and mainly Oligocene volcanism for the LVF. Differentiated rocks appear to be slightly younger than less differentiated. No geographical age clusters are apparent.

  9. Monogenetic volcanic fields and their geoheritage values of western Saudi Arabia and their implication to holistic geoeducation projects locally and globally (Invited)

    Science.gov (United States)

    Nemeth, K.; Moufti, R.

    2013-12-01

    Monogeneitc volcanic fields are the most common manifestation of volcanism on Earth and other planets. They composed of small volume and short lived volcanoes each of them with a relatively simple eruption history. In spite of recent researches demonstrated complex, repeated and geochemically distinct eruption histories commonly associated with te formation of small-volume volcanoes, they are still considerred as volcanoes that are in human-scale and therefore ideal to use them as educational tools or part of volcanic geoheritage projects including geopark developments. In the western margin of the Kingdom of Saudi Arabia there are at least 9 intracontinental volcanic fields subparalell with the Red Sea Rift ranging from alkaline basaltic to basalt-trachyte bimodal dispersed volcanic systems. Among these volcanic fields the geoheritage value of three fields were recently evaluated and proposed that they are suitable for further development to establish the first volcanic geoparks in the Arabian Peninsula in the area of 1) Al Madinah (AMVF) 2) Kishb (KVF) and 3) Hutaymah Volcanic Fields (HVF). The AMVF offers a natural concept based on specific volcanic precinct ordering of its volcanic geoheritages from the most accessable and most common volcanism that is historically significant (eg. scoria and lava spatter cones with extensive lava fields) toward a more adventure geotourism style approach in remote, less common but more destructive type of volcanism (eg. trachytic explosion craters). In the contrary, the KVF is a perfect site where phreatomagmatic volcanism and their consequences were identified as a major driving force for further geopark developments. The HVF with its rich archaeological and cultural sites and superbly exposed variously eroded tuff rings and maars offer a good location to develop geoeducation programs to highlight short- and long-term climatic and hydrologic changes in an area a volcanic field evolved. The three Saudi projects also demonstrate

  10. Vulnerability of shallow ground water and drinking-water wells to nitrate in the United States: Model of predicted nitrate concentration in shallow, recently recharged ground water -- Input data set for basalt and volcanic rocks (gwava-s_vrox)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data set represents the presence or absence of basalt and volcanic rocks in the conterminous United States. The data set was used as an input data layer for a...

  11. Internal architecture of the Tuxtla volcanic field, Veracruz, Mexico, inferred from gravity and magnetic data

    Science.gov (United States)

    Espindola, Juan Manuel; Lopez-Loera, Hector; Mena, Manuel; Zamora-Camacho, Araceli

    2016-09-01

    The Tuxtla Volcanic Field (TVF) is a basaltic volcanic field emerging from the plains of the western margin of the Gulf of Mexico in the Mexican State of Veracruz. Separated by hundreds of kilometers from the Trans-Mexican Volcanic Belt to the NW and the Chiapanecan Volcanic Arc to the SE, it stands detached not only in location but also in the composition of its rocks, which are predominantly alkaline. These characteristics make its origin somewhat puzzling. Furthermore, one of the large volcanoes of the field, San Martin Tuxtla, underwent an eruptive period in historical times (CE 1793). Such volcanic activity conveys particular importance to the study of the TVF from the perspective of volcanology and hazard assessment. Despite the above circumstances, few investigations about its internal structure have been reported. In this work, we present analyses of gravity and aeromagnetic data obtained from different sources. We present the complete Bouguer anomaly of the area and its separation into regional and residual components. The aeromagnetic data were processed to yield the reduction to the pole, the analytic signal, and the upward continuation to complete the interpretation of the gravity analyses. Three-dimensional density models of the regional and residual anomalies were obtained by inversion of the gravity signal adding the response of rectangular prisms at the nodes of a regular grid. We obtained a body with a somewhat flattened top at 16 km below sea level from the inversion of the regional. Three separate slender bodies with tops 6 km deep were obtained from the inversion of the residual. The gravity and magnetic anomalies, as well as the inferred source bodies that produce those geophysical anomalies, lie between the Sontecomapan and Catemaco faults, which are proposed as flower structures associated with an inferred deep-seated fault termed the Veracruz Fault. These fault systems along with magma intrusion at the lower crust are necessary features to

  12. Igneous Rocks of the East Pacific Rise: The alkali volcanic suite appear to be differentiated from a tholeiitic basalt extruded from the mantle.

    Science.gov (United States)

    Engel, A E; Engel, C G

    1964-10-23

    The apical parts of large volcanoes along the East Pacific Rise (islands and seamounts) are encrusted with rocks of the alkali volcanic suite (alkali basalt, andesine- and oligoclase-andesite, and trachyte). In contrast, the more submerged parts of the Rise are largely composed of a tholeiitic basalt which has low concentrations of K, P, U, Th, Pb, and Ti. This tholeiitic basalt is either the predominant or the only magma generated in the earth's mantle under oceanic ridges and rises. It is at least 1000-fold more abundant than the alkali suite, which is probably derived from tholeiitic basalt by magmatic differentiation in and immediately below the larger volcanoes. Distinction of oceanic tholeiites from almost all continental tholeiites is possible on the simple basis of total potassium content, with the discontinuity at 0.3 to 0.5 percent K(2)O by weight. Oceanic tholeiites also are readily distinguished from some 19 out of 20 basalts of oceanic islands and seamount cappings by having less than 0.3 percent K(2)O by weight and more than 48 percent SiO(2). Deep drilling into oceanic volcanoes should, however, core basalts transitional between the oceanic tholeiites and the presumed derivative alkali basalts. The composition of the oceanic tholeiites suggests that the mantle under the East Pacific Rise contains less than 0.10 percent potassium oxide by weight; 0.1 part per million of uranium and 0.4 part of thorium; a potassium:rubidium ratio of about 1200 and a potassium: uranium ratio of about 10(4).

  13. Primitive magmas at five Cascade volcanic fields: Melts from hot, heterogeneous sub-arc mantle

    Science.gov (United States)

    Bacon, C.R.; Bruggman, P.E.; Christiansen, R.L.; Clynne, M.A.; Donnelly-Nolan, J. M.; Hildreth, W.

    1997-01-01

    Major and trace element concentrations, including REE by isotope dilution, and Sr, Nd, Pb, and O isotope ratios have been determined for 38 mafic lavas from the Mount Adams, Crater Lake, Mount Shasta, Medicine Lake, and Lassen volcanic fields, in the Cascade arc, northwestern part of the United States. Many of the samples have a high Mg# [100Mg/(Mg + FeT) > 60] and Ni content (>140 ppm) such that we consider them to be primitive. We recognize three end-member primitive magma groups in the Cascades, characterized mainly by their trace-element and alkali-metal abundances: (1) High-alumina olivine tholeiite (HAOT) has trace element abundances similar to N-MORB, except for slightly elevated LILE, and has Eu/Eu* > 1. (2) Arc basalt and basaltic andesite have notably higher LILE contents, generally have higher SiO2 contents, are more oxidized, and have higher Cr for a given Ni abundance than HAOT. These lavas show relative depletion in HFSE, have lower HREE and higher LREE than HAOT, and have smaller Eu/Eu* (0.94-1.06). (3) Alkali basalt from the Simcoe volcanic field east of Mount Adams represents the third end-member, which contributes an intraplate geochemical signature to magma compositions. Notable geochemical features among the volcanic fields are: (1) Mount Adams rocks are richest in Fe and most incompatible elements including HFSE; (2) the most incompatible-element depleted lavas occur at Medicine Lake; (3) all centers have relatively primitive lavas with high LILE/HFSE ratios but only the Mount Adams, Lassen, and Medicine Lake volcanic fields also have relatively primitive rocks with an intraplate geochemical signature; (4) there is a tendency for increasing 87Sr/86Sr, 207Pb/204Pb, and ??18O and decreasing 206Pb/204Pb and 143Nd/144Nd from north to south. The three end-member Cascade magma types reflect contributions from three mantle components: depleted sub-arc mantle modestly enriched in LILE during ancient subduction; a modern, hydrous subduction component

  14. Short-lived eruptive episodes during the construction of a Na-alkalic basaltic field (Perşani Mountains, SE Transylvania, Romania)

    Science.gov (United States)

    Seghedi, Ioan; Popa, Răzvan-Gabriel; Panaiotu, Cristian G.; Szakács, Alexandru; Pécskay, Zoltán

    2016-10-01

    The Perşani Mts. basaltic field covers >176 km2 (~22 × 8 km) and is one of the youngest and biggest monogenetic volcanic fields in Southeastern Europe. It consists of 21 monogenetic volcanic centers, most of which were built on a basement of Miocene rhyolitic tuffs and Mesozoic sedimentary rocks. 40Ar/39Ar dating shows that the eruptions took place in five episodes: 1220, 1142, 1060, 800, and 683 ka. An additional undated episode at 1060-800 ka has been identified using volcanological observations. Initial phreatomagmatic activity was commonly followed by explosive Strombolian/Hawaiian phases that deposited agglutinated spatter around the vents along with massive-to-bedded unconsolidated scoria and lapilli. Some volcanoes lack evidence for magmatic explosive activity, while others lack evidence for the initial phreatomagmatic phase. During most eruptions, the final activity was the effusion of lava flows that in some cases deformed (or partially destroyed) the volcanic edifices. The erupted volumes varied greatly from one episode to other, without showing any pattern: the highest volumes are recorded in deposits from the third pulse (1060 ka). The volcanoes are located close to faults and always on their footwall blocks, and it is inferred that the regional tectonic stress regime controlled both the timing and spacing of volcanic activity in the volcanic field.

  15. Mafic monogenetic vents at the Descabezado Grande volcanic field (35.5°S-70.8°W): the northernmost evidence of regional primitive volcanism in the Southern Volcanic Zone of Chile

    Science.gov (United States)

    Salas, Pablo A.; Rabbia, Osvaldo M.; Hernández, Laura B.; Ruprecht, Philipp

    2016-06-01

    In the Andean Southern Volcanic Zone (SVZ), the broad distribution of mafic compositions along the recent volcanic arc occurs mainly south of 37°S, above a comparatively thin continental crust (≤~35 km) and mostly associated with the dextral strike-slip regime of the Liquiñe-Ofqui Fault Zone (LOFZ). North of 36°S, mafic compositions are scarce. This would be in part related to the effect resulting from protracted periods of trapping of less evolved ascending magmas beneath a thick Meso-Cenozoic volcano-sedimentary cover that lead to more evolved compositions in volcanic rocks erupted at the surface. Here, we present whole-rock and olivine mineral chemistry data for mafic rocks from four monogenetic vents developed above a SVZ segment of thick crust (~45 km) in the Descabezado Grande volcanic field (~35.5°S). Whole-rock chemistry (MgO > 8 wt%) and compositional variations in olivine (92 ≥ Fo ≥ 88 and Ni up to ~3650 ppm) indicate that some of the basaltic products erupted through these vents (e.g., Los Hornitos monogenetic cones) represent primitive arc magmas reaching high crustal levels. The combined use of satellite images, regional data analysis and field observations allow to recognize at least 38 mafic monogenetic volcanoes dispersed over an area of about 5000 km2 between 35.5° and 36.5°S. A link between ancient structures inherited from pre-Andean tectonics and the emplacement and distribution of this mafic volcanism is suggested as a first-order structural control that may explain the widespread occurrence of mafic volcanism in this Andean arc segment with thick crust.

  16. Occurrence of an unknown Atlantic eruption in the Chaîne des Puys volcanic field (Massif Central, France)

    Science.gov (United States)

    Jouannic, G.; Walter-Simonnet, A. V.; Bossuet, G.; Cubizolle, H.; Boivin, P.; Devidal, J. L.; Oberlin, C.

    2014-08-01

    A volcanic ash layer, called MF1, was recently identified in Holocene sediments from the Gourgon and Molhiac peat bogs (Monts du Forez, French Massif Central). This ash layer consists of colorless shards with a heterogeneous trachytic to rhyolitic composition. The trace elements analyzed by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) attest to a local origin. Radiocarbon dating of peat samples taken within and below the ash layer indicates the best age at 6339 ± 61 cal yr BP, i.e. an age contemporaneous with the volcanic activity of Montchal, Montcineyre and Pavin volcanoes from the Chaîne des Puys volcanic field. These volcanoes are characterized by basaltic and trachytic products, thus the rhyolitic composition of MF1 tephra suggests that it is likely originated from an unknown eruption. These results again confirm the interest of studying the distal volcanic ash fallouts in order to establish or specify records of past eruptions of volcanic fields. Identification of this new tephra layer also provides an additional tephrochronological marker for Eastern French Massif Central.

  17. Spatio-volumetric hazard estimation in the Auckland volcanic field

    Science.gov (United States)

    Bebbington, Mark S.

    2015-05-01

    The idea of a volcanic field `boundary' is prevalent in the literature, but ill-defined at best. We use the elliptically constrained vents in the Auckland Volcanic Field to examine how spatial intensity models can be tested to assess whether they are consistent with such features. A means of modifying the anisotropic Gaussian kernel density estimate to reflect the existence of a `hard' boundary is then suggested, and the result shown to reproduce the observed elliptical distribution. A new idea, that of a spatio-volumetric model, is introduced as being more relevant to hazard in a monogenetic volcanic field than the spatiotemporal hazard model due to the low temporal rates in volcanic fields. Significant dependencies between the locations and erupted volumes of the observed centres are deduced, and expressed in the form of a spatially-varying probability density. In the future, larger volumes are to be expected in the `gaps' between existing centres, with the location of the greatest forecast volume lying in the shipping channel between Rangitoto and Castor Bay. The results argue for tectonic control over location and magmatic control over erupted volume. The spatio-volumetric model is consistent with the hypothesis of a flat elliptical area in the mantle where tensional stresses, related to the local tectonics and geology, allow decompressional melting.

  18. Volcanic ash aggregation: new insights from field and numerical experiments

    Science.gov (United States)

    Rossi, Eduardo; Bagheri, Gholamhossein; Bonadonna, Costanza

    2015-04-01

    Particle aggregation is considered as a key process that may affect dispersal and sedimentation of volcanic ash, with significant implications for the associated hazards. So far the theoretical description of volcanic ash aggregation is commonly related to the solution of the Smoluchowski Coagulation Equations, a set of Ordinary Differential Equations (ODEs) which basically describe the change in time of an initial grain-size distribution due to the interaction of "single" particles. Nevertheless, field data show that this general description lacks of completeness, mainly due to the peculiarities of the volcanic context with respect to other fields (aerosol and pollution sciences). We propose an improvement of the general theoretical model in order to take into account the new insights from field observations. In particular, we focused on the problem of different densities between single particles and aggregates. This algorithm has been applied to observed volcanic eruptions (i.e. Eyjafjallajokull 2010, Sakurajima 2013 and Mt. Saint Helens 1980) in order to investigate the sensitiveness of the model with respect to the input parameters (total grain-size distribution, collision kernels, sticking efficiencies). Constrains on these parameters come from field observations and laboratory experiments.

  19. Multiple Brunhes Chron Excursions Recorded in the Eifel Volcanic Field

    Science.gov (United States)

    Singer, B. S.; Guillou, H.; Zhang, X.; Schnepp, E.; Hoffman, K. A.

    2006-12-01

    Volcanic records of excursional geomagnetic field behavior, in particular paleointensity estimates, are fragmentary for the Pleistocene. The West Eifel volcanic field is unique in that 12 of 66 measured lava flow sites record Virtual Geomagnetic Poles (VGPs) clustered between 34 to 45° N and 30 to 50° E (over Iraq). Paleointensities of 37 lavas reveal that 9 transitionally magnetized and four normally magnetized lavas are SINT-800 centered on the broad low during which the Big Lost excursion occurred. These lava flows thus record snapshots of the behavior of the total vector field experienced at this site during one of the most complex periods of geodynamo instability of the Brunhes Chron. Our findings suggest that four temporally distinctive excursions are recorded between 626 and 528 ka and that each weakening of the geodynamo during this period revealed a non-dipole field which consistently produced VGPs over Iraq.

  20. Cenozoic volcanic rocks of Saudi Arabia

    Science.gov (United States)

    Coleman, R.G.; Gregory, R.T.; Brown, G.F.

    2016-01-01

    The Cenozoic volcanic rocks of Saudi Arabia cover about 90,000 km2, one of the largest areas of alkali olivine basalt in the world. These volcanic rocks are in 13 separate fields near the eastern coast of the Red Sea and in the western Arabian Peninsula highlands from Syria southward to the Yemen Arab Republic.

  1. Petrologic insights into basaltic volcanism at historically active Hawaiian volcanoes: Chapter 6 in Characteristics of Hawaiian volcanoes

    Science.gov (United States)

    Helz, Rosalind L.; Clague, David A.; Sisson, Thomas W.; Thornber, Carl R.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

    2014-01-01

    Study of the petrology of Hawaiian volcanoes, in particular the historically active volcanoes on the Island of Hawai‘i, has long been of worldwide scientific interest. When Dr. Thomas A. Jaggar, Jr., established the Hawaiian Volcano Observatory (HVO) in 1912, detailed observations on basaltic activity at Kīlauea and Mauna Loa volcanoes increased dramatically. The period from 1912 to 1958 saw a gradual increase in the collection and analysis of samples from the historical eruptions of Kīlauea and Mauna Loa and development of the concepts needed to evaluate them. In a classic 1955 paper, Howard Powers introduced the concepts of magnesia variation diagrams, to display basaltic compositions, and olivine-control lines, to distinguish between possibly comagmatic and clearly distinct basaltic lineages. In particular, he and others recognized that Kīlauea and Mauna Loa basalts must have different sources.

  2. Preliminary paragenetic interpretation of the Quaternary topaz rhyolite lava domes of the Blackfoot volcanic field, southeastern Idaho

    Science.gov (United States)

    Lochridge, W. K., Jr.; McCurry, M. O.; Goldsby, R.

    2015-12-01

    The Quaternary topaz rhyolite lava domes of the bimodal, basalt-dominated Blackfoot volcanic field (BVF), SE Idaho occur in three clusters. We refer to these as the China Hat lava dome field (southernmost; ~ 57 ka), and the 1.4 to 1.5 Ma Sheep Island and White Mountain (northernmost) lava dome fields. The rhyolites and surrounding, more voluminous basalt lavas closely resemble coeval Quaternary rocks erupted to the north along the Eastern Snake River Plain segment of the Yellowstone-Snake River Plain volcanic track. However rhyolites in BVF are distinguished by having more evolved Sr- and Nd-isotopic ratios, as well as having phenocryst assemblages that includes hydrous phases (biotite and hornblende), thorite, and vapor-phase topaz. This study seeks to improve our understanding of the unique conditions of magma evolution that led to these differences. We focus on textural features of major and accessory phenocrysts as a basis for inferring paragenesis for rhyolites from the China Hat lava dome field. Preliminary work indicates that there are three sequentially formed populations of textures among magmatic phases: 1. population of anhedral quartz and plagioclase; 2. population of euhedral grains that includes quartz, sandine, plagioclase, biotite, hornblende, Fe-Ti oxides, zircon and apatite; 3. boxy cellular (skeletal?) sanidine and quartz. We speculate that the first population are resorbed antecrysts, the second formed prior to eruption as autocrysts (at or near equilibrium?), and the third formed soon before or during eruption.

  3. Constraints on the origin and evolution of magmas in the Payún Matrú Volcanic Field, Quaternary Andean back-arc of western Argentina

    DEFF Research Database (Denmark)

    Hernadno, I R; Aragón, E; Frei, Robert;

    2014-01-01

    basalt (La/Nb = 0·8–1·5, La/Ba = 0·05–0·08). The Sr–Nd isotopic compositions of the basaltic to trachytic rocks range between 0·703813 and 0·703841 (87Sr/86Sr) and 0·512743 and 0·512834 (143Nd/144Nd). Mass-balance and Rayleigh fractionation models support the proposed origin of the trachytes...... that the basaltic lavas originated in the asthenospheric mantle, probably within the spinel stability field and beneath an attenuated continental lithosphere in the back-arc area. The lack of a slab-fluid signature in the Payún Matrú Volcanic Field rocks, along with unpublished and published geophysical results...

  4. Magma evolution and ascent at the Craters of the Moon and neighboring volcanic fields, southern Idaho, USA: implications for the evolution of polygenetic and monogenetic volcanic fields

    Science.gov (United States)

    Putirka, Keith D.; Kuntz, Mel A.; Unruh, Daniel M.; Vaid, Nitin

    2009-01-01

    The evolution of polygenetic and monogenetic volcanic fields must reflect differences in magma processing during ascent. To assess their evolution we use thermobarometry and geochemistry to evaluate ascent paths for neighboring, nearly coeval volcanic fields in the Snake River Plain, in south-central Idaho, derived from (1) dominantly Holocene polygenetic evolved lavas from the Craters of the Moon lava field (COME) and (2) Quaternary non-evolved, olivine tholeiites (NEOT) from nearby monogenetic volcanic fields. These data show that NEOT have high magmatic temperatures (1205 + or - 27 degrees C) and a narrow temperature range (50 degrees C). Prolonged storage of COME magmas allows them to evolve to higher 87Sr/86Sr and SiO2, and lower MgO and 143Nd/144Nd. Most importantly, ascent paths control evolution: NEOT often erupt near the axis of the plain where high-flux (Yellowstone-related), pre-Holocene magmatic activity replaces granitic middle crust with basaltic sills, resulting in a net increase in NEOT magma buoyancy. COME flows erupt off-axis, where felsic crustal lithologies sometimes remain intact, providing a barrier to ascent and a source for crustal contamination. A three-stage ascent process explains the entire range of erupted compositions. Stage 1 (40-20 km): picrites are transported to the middle crust, undergoing partial crystallization of olivine + or - clinopyroxene. COME magmas pass through unarmored conduits and assimilate 1% or less of ancient gabbroic crust having high Sr and 87Sr/86Sr and low SiO2. Stage 2 (20-10 km): magmas are stored within the middle crust, and evolve to moderate MgO (10%). NEOT magmas, reaching 10% MgO, are positively buoyant and migrate through the middle crust. COME magmas remain negatively buoyant and so crystallize further and assimilate middle crust. Stage 3 (15-0 km): final ascent and eruption occurs when volatile contents, increased by differentiation, are sufficient (1-2 wt % H2O) to provide magma buoyancy through the

  5. The Satah Mountain and Baldface Mountain volcanic fields: Pleistocene hot spot volcanism in the Anahim Volcanic Belt, west-central British Columbia, Canada

    Science.gov (United States)

    Kuehn, Christian; Guest, Bernard; Russell, James K.; Benowitz, Jeff A.

    2015-03-01

    The Satah Mountain and Baldface Mountain volcanic fields (SMVF, BMVF) comprise more than three dozen small volcanic centers and erosional remnants thereof. These fields are located in the Chilcotin Highland of west-central British Columbia, Canada, and are spatially associated with the Anahim Volcanic Belt (AVB), a linear feature of alkaline to peralkaline plutonic and volcanic centers of Miocene to Holocene ages. The AVB has been postulated to be the track of a hot spot passing beneath the westward moving Cordilleran lithosphere. We test the AVB hot spot model by applying whole-rock 40Ar/39Ar geochronology ( n = 24) and geochemistry. Whole-rock chemical compositions of volcanic rock samples ( n = 59) from these two fields suggest a strong geochemical affinity with the nearby Itcha Range shield volcano; however, SMVF and BMVF centers are mostly small in volume (interaction of the potential hot spot with (pre)existing fracture systems in vicinity of the Itcha Range.

  6. Influences on the variability of eruption sequences and style transitions in the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Kereszturi, Gábor; Németh, Károly; Cronin, Shane J.; Procter, Jonathan; Agustín-Flores, Javier

    2014-10-01

    Monogenetic basaltic volcanism is characterised by a complex array of eruptive behaviours, reflecting spatial and temporal variability of the magmatic properties (e.g. composition, eruptive volume, magma flux) as well as environmental factors at the vent site (e.g. availability of water, country rock geology, faulting). These combine to produce changes in eruption style over brief periods (minutes to days) in many eruption episodes. Monogenetic eruptions in some volcanic fields often start with a phreatomagmatic vent-opening phase that later transforms into "dry" magmatic explosive or effusive activity, with a strong variation in the duration and importance of this first phase. Such an eruption sequence pattern occurred in 83% of the known eruption in the 0.25 My-old Auckland Volcanic Field (AVF), New Zealand. In this investigation, the eruptive volumes were compared with the sequences of eruption styles preserved in the pyroclastic record at each volcano of the AVF, as well as environmental influencing factors, such as distribution and thickness of water-saturated semi- to unconsolidated sediments, topographic position, distances from known fault lines. The AVF showed that there is no correlation between ejecta ring volumes and environmental influencing factors that is valid for the entire AVF. In contrary, using a set of comparisons of single volcanoes with well-known and documented sequences, resultant eruption sequences could be explained by predominant patterns of the environment in which these volcanoes were erupted. Based on the spatial variability of these environmental factors, a first-order susceptibility hazard map was constructed for the AVF that forecasts areas of largest likelihood for phreatomagmatic eruptions by overlaying topographical and shallow geological information. Combining detailed phase-by-phase breakdowns of eruptive volumes and the event sequences of the AVF, along with the new susceptibility map, more realistic eruption scenarios can be

  7. Temperature dependence of basalt weathering

    Science.gov (United States)

    Li, Gaojun; Hartmann, Jens; Derry, Louis A.; West, A. Joshua; You, Chen-Feng; Long, Xiaoyong; Zhan, Tao; Li, Laifeng; Li, Gen; Qiu, Wenhong; Li, Tao; Liu, Lianwen; Chen, Yang; Ji, Junfeng; Zhao, Liang; Chen, Jun

    2016-06-01

    The homeostatic balance of Earth's long-term carbon cycle and the equable state of Earth's climate are maintained by negative feedbacks between the levels of atmospheric CO2 and the chemical weathering rate of silicate rocks. Though clearly demonstrated by well-controlled laboratory dissolution experiments, the temperature dependence of silicate weathering rates, hypothesized to play a central role in these weathering feedbacks, has been difficult to quantify clearly in natural settings at landscape scale. By compiling data from basaltic catchments worldwide and considering only inactive volcanic fields (IVFs), here we show that the rate of CO2 consumption associated with the weathering of basaltic rocks is strongly correlated with mean annual temperature (MAT) as predicted by chemical kinetics. Relations between temperature and CO2 consumption rate for active volcanic fields (AVFs) are complicated by other factors such as eruption age, hydrothermal activity, and hydrological complexities. On the basis of this updated data compilation we are not able to distinguish whether or not there is a significant runoff control on basalt weathering rates. Nonetheless, the simple temperature control as observed in this global dataset implies that basalt weathering could be an effective mechanism for Earth to modulate long-term carbon cycle perturbations.

  8. Compositional and Microtextural Analysis of Basaltic Feedstock Materials Used for the 2010 ISRU Field Tests, Mauna Kea, Hawaii

    Science.gov (United States)

    Marin, N.; Farmer, J. D.; Zacny, K.; Sellar, R. G.; Nunez, J.

    2011-12-01

    This study seeks to understand variations in composition and texture of basaltic pyroclastic materials used in the 2010 International Lunar Surface Operation-In-Situ Resource Utilization Analogue Test (ILSO-ISRU) held on the slopes of Mauna Kea Volcano, Hawaii (1). The quantity and quality of resources delivered by ISRU depends upon the nature of the materials processed (2). We obtained a one-meter deep auger cuttings sample of a basaltic regolith at the primary site for feed stock materials being mined for the ISRU field test. The auger sample was subdivided into six, ~16 cm depth increments and each interval was sampled and characterized in the field using the Multispectral Microscopic Imager (MMI; 3) and a portable X-ray Diffractometer (Terra, InXitu Instruments, Inc.). Splits from each sampled interval were returned to the lab and analyzed using more definitive methods, including high resolution Powder X-ray Diffraction and Thermal Infrared (TIR) spectroscopy. The mineralogy and microtexture (grain size, sorting, roundness and sphericity) of the auger samples were determined using petrographic point count measurements obtained from grain-mount thin sections. NIH Image J (http://rsb.info.nih.gov/ij/) was applied to digital images of thin sections to document changes in particle size with depth. Results from TIR showed a general predominance of volcanic glass, along with plagioclase, olivine, and clinopyroxene. In addition, thin section and XRPD analyses showed a down core increase in the abundance of hydrated iron oxides (as in situ weathering products). Quantitative point count analyses confirmed the abundance of volcanic glass in samples, but also revealed olivine and pyroxene to be minor components, that decreased in abundance with depth. Furthermore, point count and XRD analyses showed a decrease in magnetite and ilmenite with depth, accompanied by an increase in Fe3+phases, including hematite and ferrihydrite. Image J particle analysis showed that the

  9. Optimal likelihood-based matching of volcanic sources and deposits in the Auckland Volcanic Field

    Science.gov (United States)

    Kawabata, Emily; Bebbington, Mark S.; Cronin, Shane J.; Wang, Ting

    2016-09-01

    In monogenetic volcanic fields, where each eruption forms a new volcano, focusing and migration of activity over time is a very real possibility. In order for hazard estimates to reflect future, rather than past, behavior, it is vital to assemble as much reliable age data as possible on past eruptions. Multiple swamp/lake records have been extracted from the Auckland Volcanic Field, underlying the 1.4 million-population city of Auckland. We examine here the problem of matching these dated deposits to the volcanoes that produced them. The simplest issue is separation in time, which is handled by simulating prior volcano age sequences from direct dates where known, thinned via ordering constraints between the volcanoes. The subproblem of varying deposition thicknesses (which may be zero) at five locations of known distance and azimuth is quantified using a statistical attenuation model for the volcanic ash thickness. These elements are combined with other constraints, from widespread fingerprinted ash layers that separate eruptions and time-censoring of the records, into a likelihood that was optimized via linear programming. A second linear program was used to optimize over the Monte-Carlo simulated set of prior age profiles to determine the best overall match and consequent volcano age assignments. Considering all 20 matches, and the multiple factors of age, direction, and size/distance simultaneously, results in some non-intuitive assignments which would not be produced by single factor analyses. Compared with earlier work, the results provide better age control on a number of smaller centers such as Little Rangitoto, Otuataua, Taylors Hill, Wiri Mountain, Green Hill, Otara Hill, Hampton Park and Mt Cambria. Spatio-temporal hazard estimates are updated on the basis of the new ordering, which suggest that the scale of the 'flare-up' around 30 ka, while still highly significant, was less than previously thought.

  10. Increased thyroid cancer incidence in a basaltic volcanic area is associated with non-anthropogenic pollution and biocontamination.

    Science.gov (United States)

    Malandrino, Pasqualino; Russo, Marco; Ronchi, Anna; Minoia, Claudio; Cataldo, Daniela; Regalbuto, Concetto; Giordano, Carla; Attard, Marco; Squatrito, Sebastiano; Trimarchi, Francesco; Vigneri, Riccardo

    2016-08-01

    The increased thyroid cancer incidence in volcanic areas suggests an environmental effect of volcanic-originated carcinogens. To address this problem, we evaluated environmental pollution and biocontamination in a volcanic area of Sicily with increased thyroid cancer incidence. Thyroid cancer epidemiology was obtained from the Sicilian Regional Registry for Thyroid Cancer. Twenty-seven trace elements were measured by quadrupole mass spectrometry in the drinking water and lichens (to characterize environmental pollution) and in the urine of residents (to identify biocontamination) in the Mt. Etna volcanic area and in adjacent control areas. Thyroid cancer incidence was 18.5 and 9.6/10(5) inhabitants in the volcanic and the control areas, respectively. The increase was exclusively due to the papillary histotype. Compared with control areas, in the volcanic area many trace elements were increased in both drinking water and lichens, indicating both water and atmospheric pollution. Differences were greater for water. Additionally, in the urine of the residents of the volcanic area, the average levels of many trace elements were significantly increased, with values higher two-fold or more than in residents of the control area: cadmium (×2.1), mercury (×2.6), manganese (×3.0), palladium (×9.0), thallium (×2.0), uranium (×2.0), vanadium (×8.0), and tungsten (×2.4). Urine concentrations were significantly correlated with values in water but not in lichens. Our findings reveal a complex non-anthropogenic biocontamination with many trace elements in residents of an active volcanic area where thyroid cancer incidence is increased. The possible carcinogenic effect of these chemicals on the thyroid and other tissues cannot be excluded and should be investigated. PMID:26438396

  11. Increased thyroid cancer incidence in a basaltic volcanic area is associated with non-anthropogenic pollution and biocontamination.

    Science.gov (United States)

    Malandrino, Pasqualino; Russo, Marco; Ronchi, Anna; Minoia, Claudio; Cataldo, Daniela; Regalbuto, Concetto; Giordano, Carla; Attard, Marco; Squatrito, Sebastiano; Trimarchi, Francesco; Vigneri, Riccardo

    2016-08-01

    The increased thyroid cancer incidence in volcanic areas suggests an environmental effect of volcanic-originated carcinogens. To address this problem, we evaluated environmental pollution and biocontamination in a volcanic area of Sicily with increased thyroid cancer incidence. Thyroid cancer epidemiology was obtained from the Sicilian Regional Registry for Thyroid Cancer. Twenty-seven trace elements were measured by quadrupole mass spectrometry in the drinking water and lichens (to characterize environmental pollution) and in the urine of residents (to identify biocontamination) in the Mt. Etna volcanic area and in adjacent control areas. Thyroid cancer incidence was 18.5 and 9.6/10(5) inhabitants in the volcanic and the control areas, respectively. The increase was exclusively due to the papillary histotype. Compared with control areas, in the volcanic area many trace elements were increased in both drinking water and lichens, indicating both water and atmospheric pollution. Differences were greater for water. Additionally, in the urine of the residents of the volcanic area, the average levels of many trace elements were significantly increased, with values higher two-fold or more than in residents of the control area: cadmium (×2.1), mercury (×2.6), manganese (×3.0), palladium (×9.0), thallium (×2.0), uranium (×2.0), vanadium (×8.0), and tungsten (×2.4). Urine concentrations were significantly correlated with values in water but not in lichens. Our findings reveal a complex non-anthropogenic biocontamination with many trace elements in residents of an active volcanic area where thyroid cancer incidence is increased. The possible carcinogenic effect of these chemicals on the thyroid and other tissues cannot be excluded and should be investigated.

  12. Geochemistry and petrogenesis of the Gallego Volcanic Field, Solomon Islands, SW Pacific and geotectonic implications

    Science.gov (United States)

    Petterson, M. G.; Haldane, M. I.; Smith, D. J.; Billy, D.; Jordan, N. J.

    2011-08-01

    The Upper Miocene to present day Gallego Volcanic Field (GVF) is located in northwest Guadalcanal, Solomon Islands, SW Pacific, and potentially includes the offshore Savo volcano. The GVF is a multi-centred complex covering an area of ~ 800 km 2 on Guadalcanal and a further ~ 30 km 2 on the island of Savo, north of west Guadalcanal. GVF volcanism is characterised by effusive eruptions of lava, intrusion of sub-volcanic plutons, as well as pyroclastic flow and fall deposits dominated by block and ash flow deposits. Geochemical analysis of a representative suite of samples from the GVF demonstrates that the GVF comprise largely a 'main suite' of basalts to andesites and minor trachyandesites. The predominant mineralogy of the GVF comprises plagioclase, amphibole, clinopyroxene and magnetite-ilmenite. Associated with the 'main suite' are cognate nodules composed of hornblendite, gabbros, and clinopyroxenite. Interpretation of major and trace element geochemistry and petrographic studies suggests that fractionation was dominated by early clinopyroxene, and later amphibole + clinopyroxene + minor plagioclase. Geochemical features such as the incompatibility of Sr suggest that plagioclase largely crystallised en-masse late in the fractionation sequence. The presence of amphibole and late fractionation of plagioclase is suggestive of derivation from initially water-rich magmas. The region is characterised by strong geographically-related geochemical variations as evidenced by the Woodlark (and Manus) basins: basalts become more arc-like within the ocean basins with decreasing distance to the subducting trench. The GVF-Savo volcanoes are spatially and geochemically affected by deep N-S fractures that show some evidence of sympathetic geochemical variations with distance from the trench (e.g. Sr/Y ratios). Comparison with a range of international data for Th/Nb vs Pb/Nb and Dy/Yb vs SiO 2 indicate that: amphibole was indeed a strong controlling phase on magmatic evolution

  13. The Hawaiian Volcano Observatory: a natural laboratory for studying basaltic volcanism: Chapter 1 in Characteristics of Hawaiian volcanoes

    Science.gov (United States)

    Tilling, Robert I.; Kauahikaua, James P.; Brantley, Steven R.; Neal, Christina A.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

    2014-01-01

    In the beginning of the 20th century, geologist Thomas A. Jaggar, Jr., argued that, to fully understand volcanic and associated hazards, the expeditionary mode of studying eruptions only after they occurred was inadequate. Instead, he fervently advocated the use of permanent observatories to record and measure volcanic phenomena—at and below the surface—before, during, and after eruptions to obtain the basic scientific information needed to protect people and property from volcanic hazards. With the crucial early help of American volcanologist Frank Alvord Perret and the Hawaiian business community, the Hawaiian Volcano Observatory (HVO) was established in 1912, and Jaggar’s vision became reality. From its inception, HVO’s mission has centered on several goals: (1) measuring and documenting the seismic, eruptive, and geodetic processes of active Hawaiian volcanoes (principally Kīlauea and Mauna Loa); (2) geological mapping and dating of deposits to reconstruct volcanic histories, understand island evolution, and determine eruptive frequencies and volcanic hazards; (3) systematically collecting eruptive products, including gases, for laboratory analysis; and (4) widely disseminating observatory-acquired data and analysis, reports, and hazard warnings to the global scientific community, emergency-management authorities, news media, and the public. The long-term focus on these goals by HVO scientists, in collaboration with investigators from many other organizations, continues to fulfill Jaggar’s career-long vision of reducing risks from volcanic and earthquake hazards across the globe.

  14. 39Ar/40Ar Chronology and Volumes of Eruptive Products Over the Last 1 Myr in the Tequila Volcanic Field, Jalisco, Mexico

    Science.gov (United States)

    Lewis-Kenedi, C. B.; Lange, R. A.; Hall, C. M.; Delgado-Granados, H.

    2002-12-01

    The Tequila volcanic field, located within the western Trans-Mexican arc, covers an area of 1036 km2 and includes a central, andesitic stratocone, Volc\\­_{a}n Tequila, as well as cinder cones, domes, and fissure-fed flows. Sixty-nine high precision 39Ar-40Ar dates reveal that major activity in the Tequila volcanic field began at approximately 1 Ma. From 1 Ma to 200 ka, rhyolite (> 73 wt. % SiO2) and alkali basalt (­š 51 wt. % SiO2) were the only compositions erupted in significant volumes (29 +/- 5.7 km3 and 12 +/- 1.2 km3, respectively). At approximately 200 ka, the andesite comprising Volc\\­_{a}n Tequila erupted within 30-40 kyr, producing a volume of 30 +/- 2.0 km3. Additional andesitic flows (11 +/- 1.4 km3) erupted to the northwest and southeast of the stratocone between 140 and 20 ka. The total volume of dacite that erupted at the Tequila volcanic field is small (1.3 +/- 0.03 km3) and occurred largely (88%) within the last 70 kyrs. Unlike the andesites and dacites, the basalts and rhyolites did not erupt within narrow time intervals, but extruded over the entire last 1 Myr, producing a total volume of 12.6 +/- 1.2 km3 and 32 +/- 6.1 km3, respectively. This detailed eruptive history, combined with the observed phenocryst assemblages (0-10 vol. %) in the small-volume andesite, dacite, and alkali basalt flows, suggest that they were erupted directly from the lower (or middle) crust, without prior storage in an upper crustal chamber. In contrast, the voluminous burst of andesitic volcanism that produced the phenocryst-rich (35-45 vol. %) lavas of Volc\\­_{a}n Tequila was likely fed from a short-lived (­š 40 kyrs) upper crustal chamber. This scenario is supported by the complex, disequilibrium textures seen in the phenocryst assemblage of the Volc\\­_{a}n Tequila lavas, indicative of magma mingling within an upper crustal chamber (Wallace and Carmichael, 1994). The total volume of erupted material at the Tequila volcanic field is 89 +/- 12 km3, of which

  15. The Relative Rates of Secondary Hydration in Basalt and Rhyolite, and the use of δD as a Paleoclimate Indicator: Implications for Paleoenvironmental and Volcanic Degassing Studies

    Science.gov (United States)

    Seligman, A. N.; Bindeman, I. N.

    2014-12-01

    The δD-H2O correlation is important for volcanic degassing and secondary hydration trends. We utilize the caibration of the TC/EA - MAT 253 continuous flow system, which permits us to analyze wt.% H2O and its δD extracted from 1-8 mg of glass with as little as 0.1 wt% H2O. Tephra that has been secondarily hydrated with meteoric water is widely used as a paleoenvironmental tool, but the rate of secondary hydration, the relative amounts of primary magmatic (degassed) and secondary meteoric water, and the retention of primary and secondary δD values are not well understood. To quantify these processes, we use a natural experiment involving dated Holocene tepha in Kamchatka and Oregon. Our research illustrates the drastic difference in hydration rates between silicic (hydrated after ~1.5 ka) and mafic tephra, which is not hydrated in the Holocene (similar to results for submarine volcanic glasses), and andesitic tephra with intermediate degrees of hydration. The 0.05-7.3 ka basaltic scoria from Klyuchevskoy volcano retains ≤0.45 wt.% primary magmatic H2O, with δD values from -99 to -121 ‰. Four other 0.05-7.6 ka basaltic tephra units from Kamchatka with 65 wt.% have higher (1.5 -3.4) wt.% H2O and δD values between -115 - -160 ‰. We interpret the lower δD values and higher water contents (opposite of the magmatic degassing trend) to be a characteristic of secondary hydration in regions of higher latitude such as Kamchatka and Oregon. We are also investigating 7.7 ka Mt. Mazama tephra in Oregon that are known to be fully hydrated and cover nearly 5000 km2 northeast of Crater Lake and range in elevation from ~1.3-1.9 km to understand the δD and δ18O details of the hydrated water's correspondence with local Holocene meteoric waters. In the future, we plan to use a combination of δD in mid-high latitude precipitation to delineate δD-H2O hydration trends to better understand the distinction between primary magmatic and secondary meteoric water in volcanic

  16. Combining probabilistic hazard assessment with cost-benefit analysis to support decision making in a volcanic crisis from the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Sandri, Laura; Jolly, Gill; Lindsay, Jan; Howe, Tracy; Marzocchi, Warner

    2010-05-01

    One of the main challenges of modern volcanology is to provide the public with robust and useful information for decision-making in land-use planning and in emergency management. From the scientific point of view, this translates into reliable and quantitative long- and short-term volcanic hazard assessment and eruption forecasting. Because of the complexity in characterizing volcanic events, and of the natural variability of volcanic processes, a probabilistic approach is more suitable than deterministic modeling. In recent years, two probabilistic codes have been developed for quantitative short- and long-term eruption forecasting (BET_EF) and volcanic hazard assessment (BET_VH). Both of them are based on a Bayesian Event Tree, in which volcanic events are seen as a chain of logical steps of increasing detail. At each node of the tree, the probability is computed by taking into account different sources of information, such as geological and volcanological models, past occurrences, expert opinion and numerical modeling of volcanic phenomena. Since it is a Bayesian tool, the output probability is not a single number, but a probability distribution accounting for aleatory and epistemic uncertainty. In this study, we apply BET_VH in order to quantify the long-term volcanic hazard due to base surge invasion in the region around Auckland, New Zealand's most populous city. Here, small basaltic eruptions from monogenetic cones pose a considerable risk to the city in case of phreatomagmatic activity: evidence for base surges are not uncommon in deposits from past events. Currently, we are particularly focussing on the scenario simulated during Exercise Ruaumoko, a national disaster exercise based on the build-up to an eruption in the Auckland Volcanic Field. Based on recent papers by Marzocchi and Woo, we suggest a possible quantitative strategy to link probabilistic scientific output and Boolean decision making. It is based on cost-benefit analysis, in which all costs

  17. Seismic Activity at tres Virgenes Volcanic and Geothermal Field

    Science.gov (United States)

    Antayhua, Y. T.; Lermo, J.; Quintanar, L.; Campos-Enriquez, J. O.

    2013-05-01

    The volcanic and geothermal field Tres Virgenes is in the NE portion of Baja California Sur State, Mexico, between -112°20'and -112°40' longitudes, and 27°25' to 27°36' latitudes. Since 2003 Power Federal Commission and the Engineering Institute of the National Autonomous University of Mexico (UNAM) initiated a seismic monitoring program. The seismograph network installed inside and around the geothermal field consisted, at the beginning, of Kinemetrics K2 accelerometers; since 2009 the network is composed by Guralp CMG-6TD broadband seismometers. The seismic data used in this study covered the period from September 2003 - November 2011. We relocated 118 earthquakes with epicenter in the zone of study recorded in most of the seismic stations. The events analysed have shallow depths (≤10 km), coda Magnitude Mc≤2.4, with epicentral and hypocentral location errors geothermal explotation zone where there is a system NW-SE, N-S and W-E of extensional faults. Also we obtained focal mechanisms for 38 events using the Focmec, Hash, and FPFIT methods. The results show normal mechanisms which correlate with La Virgen, El Azufre, El Cimarron and Bonfil fault systems, whereas inverse and strike-slip solutions correlate with Las Viboras fault. Additionally, the Qc value was obtained for 118 events. This value was calculated using the Single Back Scattering model, taking the coda-waves train with window lengths of 5 sec. Seismograms were filtered at 4 frequency bands centered at 2, 4, 8 and 16 Hz respectively. The estimates of Qc vary from 62 at 2 Hz, up to 220 at 16 Hz. The frequency-Qc relationship obtained is Qc=40±2f(0.62±0.02), representing the average attenuation characteristics of seismic waves at Tres Virgenes volcanic and geothermal field. This value correlated with those observed at other geothermal and volcanic fields.

  18. Evidence of magma activation beneath the Lunayyir basaltic field (Saudi Arabia from attenuation tomography

    Directory of Open Access Journals (Sweden)

    I. Koulakov

    2014-06-01

    Full Text Available We present a seismic attenuation model for the crust beneath the Cenozoic basaltic field of Lunayyir (western Saudi Arabia, where a strong seismic swarm occurred in 2009. The tomography inversion uses the envelope shape of the S wave seismograms from over 300 strong events (M > 3.5. The resulting attenuation structures appear to be consistent with the distribution of seismic velocities. The obtained 3-D attenuation model distinguishes the low-attenuation zones down to 5 km depth corresponding to the rigid basaltic cover. At greater depths, we detect a high-attenuation anomaly coinciding with the main seismicity cluster. We propose that this zone corresponds to the upper part of the conduit area ascending from deeper magma sources. According to the distributions of local events, fluids and melts from this conduit appear to reach a depth of ~2 km, but were not able to reach the surface and cause the eruption in 2009.

  19. Inverse modeling for field-scale hydrologic and transport parameters of fractured basalt

    International Nuclear Information System (INIS)

    A large-scale test of infiltration into a thick sequence Of fractured Snake River Plain basalts was performed during the summer of 1994 on the Idaho National Engineering Laboratory. Monitoring of moisture and tracer movement during this test provided a set of quantitative measurements from which to obtain a field-scale hydrologic description of the fractured basalts. An inverse modeling study using these quantitative measurements was performed to obtain the representative hydrologic description. This report describes the results of the inverse modeling study and includes the background and motivation for conducting the infiltration test; a brief overview of the infiltration test; descriptions of the calibration targets chosen for the simulation study, the simulation model, and the model implementation; and the simulation results with comparisons to hydrologic and tracer breakthrough data obtained from the infiltration test

  20. Basaltic cannibalism at Thrihnukagigur volcano, Iceland

    Science.gov (United States)

    Hudak, M. R.; Feineman, M. D.; La Femina, P. C.; Geirsson, H.

    2014-12-01

    Magmatic assimilation of felsic continental crust is a well-documented, relatively common phenomenon. The extent to which basaltic crust is assimilated by magmas, on the other hand, is not well known. Basaltic cannibalism, or the wholesale incorporation of basaltic crustal material into a basaltic magma, is thought to be uncommon because basalt requires more energy than higher silica rocks to melt. Basaltic materials that are unconsolidated, poorly crystalline, or palagonitized may be more easily ingested than fully crystallized massive basalt, thus allowing basaltic cannibalism to occur. Thrihnukagigur volcano, SW Iceland, offers a unique exposure of a buried cinder cone within its evacuated conduit, 100 m below the main vent. The unconsolidated tephra is cross-cut by a NNE-trending dike, which runs across the ceiling of this cave to a vent that produced lava and tephra during the ~4 Ka fissure eruption. Preliminary petrographic and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) analyses indicate that there are two populations of plagioclase present in the system - Population One is stubby (aspect ratio 2.1), subhedral to euhedral, and has much higher Ba/Sr ratios. Population One crystals are observed in the cinder cone, dike, and surface lavas, whereas Population Two crystals are observed only in the dike and surface lavas. This suggests that a magma crystallizing a single elongate population of plagioclase intruded the cinder cone and rapidly assimilated the tephra, incorporating the stubbier population of phenocrysts. This conceptual model for basaltic cannibalism is supported by field observations of large-scale erosion upward into the tephra, which is coated by magma flow-back indicating that magma was involved in the thermal etching. While the unique exposure at Thrihnukagigur makes it an exceptional place to investigate basaltic cannibalism, we suggest that it is not limited to this volcanic system. Rather it is a process that likely

  1. Post-rift flood-basalt-like volcanism on the Newfoundland Basin nonvolcanic margin: The U event mapped with spectral decomposition

    Science.gov (United States)

    Deemer, S.; Hurich, C.; Hall, J.

    2010-10-01

    Diabase sills emplaced at less than .5 km depth (presently ~ 7 km) are imaged throughout the Newfoundland Basin as an extraordinarily high amplitude package of seismic reflections historically referred to as the U event. The sills are extensive, covering roughly 20,000 km 2, and represent a post-rift voluminous magmatic episode along an otherwise nonvolcanic rifted margin. Spectral decomposition is used to estimate a total magmatic volume at roughly 1000-2000 km 3. On an individual basis the major sills are comparable to flows in flood basalt volcanic environments. A proposed mechanism for generating these large volumes of magma which are also very limited in time to perhaps only two major intrusive episodes (2 sills) is the approach of the Canary and Madeira hot spots. Suppressed volcanism while the hot spots traveled under full thickness continental lithosphere of Newfoundland resulted in a local accumulation of magma which was suddenly released when the hot spots approached thinned lithosphere at the eastern edge of the Grand Banks. The emplacement of the sills 'anticipated' the arrival of the hot spots geographically.

  2. Basaltic rocks from the Andean Southern Volcanic Zone: Insights from the comparison of along-strike and small-scale geochemical variations and their sources

    Science.gov (United States)

    Hickey-Vargas, Rosemary; Holbik, Sven; Tormey, Daniel; Frey, Frederick A.; Moreno Roa, Hugo

    2016-08-01

    The origin of spatial variations in the geochemical characteristics of volcanic rocks erupted in the Andean Southern Volcanic Zone (SVZ) has been studied by numerous researchers over the past 40 years. Diverse interpretations for along-strike, across-strike, and small-scale variations have been proposed. In this paper, we review geochemical data showing along-strike geochemical variations and address the processes causing such trends. We compare large- and small-scale changes of the same geochemical parameters in basaltic rocks in order to use spatial scale as a tool for isolating processes that may have the same result. Along-strike geochemical variations in the SVZ are expected, due to 1) greater thickness or age of the sub-arc continental crust and mantle lithosphere in the Northern SVZ (NSVZ; 33°S-34°30‧S) and Transitional SVZ (TSVZ; 34°30‧S-37°S) compared with the Central SVZ (CSVZ; 37°S-41.5°S) and Southern SVZ (SSVZ: 41.5°S-46°S); and 2) along-strike changes of the subducting Nazca plate and overlying asthenosphere. Basalts and basaltic andesites erupted at volcanic front stratovolcanoes define several along-strike geochemical trends: 1) higher 87Sr/86Sr and lower 143Nd/144Nd at volcanoes in the NSVZ compared with the TSVZ, CSVZ, and SSVZ; 2) higher and more variable La/Yb at volcanoes in the NSVZ and TSVZ compared with the CSVZ and SSVZ; 3) lower 87Sr/86Sr for a given 143Nd/144Nd at volcanoes in the TSVZ compared with the CSVZ and SSVZ; and 4) large values for time-sensitive subduction tracers such as 10Be/9Be and (238U/230Th) at some volcanoes in the CSVZ, but not in the NSVZ and TSVZ. Geochemical parameters that distinguish the TSVZ from the CSVZ and SSVZ are also found within the CSVZ at small basaltic eruptive centers (SEC) aligned with the Liquiñe-Ofqui Fault System (LOFS), which extends from 38°S to the southernmost SVZ. Our interpretation is that CSVZ magmas with strong time-sensitive subduction tracers represent the ambient subduction

  3. Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M.; Vaniman, D.T.; Carr, W.J.

    1983-03-01

    Volcanism studies of the Nevada Test Site (NTS) region are concerned with hazards of future volcanism with respect to underground disposal of high-level radioactive waste. The hazards of silicic volcanism are judged to be negligible; hazards of basaltic volcanism are judged through research approaches combining hazard appraisal and risk assessment. The NTS region is cut obliquely by a N-NE trending belt of volcanism. This belt developed about 8 Myr ago following cessation of silicic volcanism and contemporaneous with migration of basaltic activity toward the southwest margin of the Great Basin. Two types of fields are present in the belt: (1) large-volume, long-lived basalt and local rhyolite fields with numerous eruptive centers and (2) small-volume fields formed by scattered basaltic scoria cones. Late Cenozoic basalts of the NTS region belong to the second field type. Monogenetic basalt centers of this region were formed mostly by Strombolian eruptions; Surtseyean activity has been recognized at three centers. Geochemically, the basalts of the NTS region are classified as straddle A-type basalts of the alkalic suite. Petrological studies indicate a volumetric dominance of evolved hawaiite magmas. Trace- and rare-earth-element abundances of younger basalt (<4 Myr) of the NTS region and southern Death Valley area, California, indicate an enrichment in incompatible elements, with the exception of rubidium. The conditional probability of recurring basaltic volcanism and disruption of a repository by that event is bounded by the range of 10{sup -8} to 10{sup -10} as calculated for a 1-yr period. Potential disruptive and dispersal effects of magmatic penetration of a repository are controlled primarily by the geometry of basalt feeder systems, the mechanism of waste incorporation in magma, and Strombolian eruption processes.

  4. 1992-93 Results of geomorphological and field studies Volcanic Studies Program, Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Wells, S.G.

    1993-10-01

    Field mapping and stratigraphic studies were completed of the Black Tank volcanic center, which represents the southwestern most eruptive center in the Cima volcanic field of California. The results of this mapping are presented. Contacts between volcanic units and geomorphic features were field checked, incorporating data from eight field trenches as well as several exposures along Black Tank Wash. Within each of the eight trenches, logs were measured and stratigraphic sections were described. These data indicate that three, temporally separate volcanic eruptions occurred at the Black Tank center. The field evidence for significant time breaks between each stratigraphic unit is the presence of soil and pavement-bounded unconformities.

  5. A geologic and anthropogenic journey from the Precambrian to the new energy economy through the San Juan volcanic field

    Science.gov (United States)

    Yager, Douglas B.; Burchell,; Johnson, Raymond H.

    2010-01-01

    The San Juan volcanic field comprises 25,000 km2 of intermediate composition mid-Tertiary volcanic rocks and dacitic to rhyolitic calderas including the San Juan–Uncompahgre and La Garita caldera-forming super-volcanoes. The region is famous for the geological, ecological, hydrological, archeological, and climatological diversity. These characteristics supported ancestral Puebloan populations. The area is also important for its mineral wealth that once fueled local economic vitality. Today, mitigating and/or investigating the impacts of mining and establishing the region as a climate base station are the focuses of ongoing research. Studies include advanced water treatment, the acid neutralizing capacity (ANC) of propylitic bedrock for use in mine-lands cleanup, and the use of soil amendments including biochar from beetle-kill pines. Biochar aids soil productivity and revegetation by incorporation into soils to improve moisture retention, reduce erosion, and support the natural terrestrial carbon sequestration (NTS) potential of volcanic soils to help offset atmospheric CO2 emissions. This field trip will examine the volcano-tectonic and cultural history of the San Juan volcanic field as well as its geologic structures, economic mineral deposits and impacts, recent mitigation measures, and associated climate research. Field trip stops will include a visit to (1) the Summitville Superfund site to explore quartz alunite-Au mineralization, and associated alteration and new water-quality mitigation strategies; (2) the historic Creede epithermal-polymetallic–vein district with remarkably preserved resurgent calderas, keystone-graben, and moat sediments; (3) the historic mining town of Silverton located in the nested San Juan–Silverton caldera complex that exhibits base-metal Au-Ag mineralization; and (4) the site of ANC and NTS studies. En route back to Denver, we will traverse Grand Mesa, a high NTS area with Neogene basalt-derived soils and will enjoy a soak

  6. Petrogenesis of basaltic volcanic rocks from the Pribilof Islands, Alaska, by melting of metasomatically enriched depleted lithosphere, crystallization differentiation, and magma mixing

    Science.gov (United States)

    Chang, J.M.; Feeley, T.C.; Deraps, M.R.

    2009-01-01

    The Pribilof Islands, Alaska, are located in the Bering Sea in a continental intraplate setting. In this study we examine the petrology and geochemistry of volcanic rocks from St. Paul (0??54-0??003 Ma) and St. George (2??8-1??4 Ma) Islands, the two largest Pribilof Islands. Rocks from St. George can be divided into three groups: group 1 is a high-MgO, low-SiO. 2 suite composed primarily of basanites; group 2 is a high-MgO, high-SiO 2 suite consisting predominantly of alkali basalts; group 3 is an intermediate- to low-MgO suite that includes plagioclase-phyric subalkali basalts and hawaiites. Major and trace element geochemistry suggests that groups 1 and 2 formed by small-degree partial melting of amphibole-bearing to amphibole-free garnet peridotite. Group 1 rocks were the earliest melts produced from the most hydrous parts of the mantle, as they show the strongest geochemical signature of amphibole in their source. The suite of rocks from St. Paul ranges from 14??4 to 4??2 wt % MgO at relatively constant SiO 2 contents (43??1-47??3 wt %). The most primitive St. Paul rocks are modeled as mixtures between magmas with compositions similar to groups 1 and 2 from St. George Island, which subsequently fractionated olivine, clinopyroxene, and spinel to form more evolved rocks. Plagioclase-phyric group 3 rocks from St. George are modeled as mixtures between an evolved melt similar to the evolved magmas on St. Paul and a fractionated group 2 end-member from St. George. Mantle potential temperatures estimated for primitive basanites and alkali basalts are ???1400??C and are similar to those of mid-ocean ridge basalts (MORB). Similarly, 87Sr/. 86Sr and 143Nd/. 144Nd values for all rocks are MORB-like, in the range of 0??702704-0??703035 and 0??513026-0??513109, respectively. 208Pb/. 204Pb vs 206Pb/. 204Pb values lie near the MORB end-member but show a linear trend towards HIMU (high time-integrated 238U/. 204Pb). Despite isotopic similarities to MORB, many of the major and

  7. Closer look at lunar volcanism

    International Nuclear Information System (INIS)

    Although the American Apollo and Soviet Luna missions concentrated on mare basalt samples, major questions remain about lunar volcanism. Lunar field work will be indispensable for resolving the scientific questions about ages, compositions, and eruption processes of lunar volcanism. From a utilitarian standpoint, a better knowledge of lunar volcanism will also yield profitable returns in lunar base construction (e.g., exploitation of rille or lava-tube structures) and in access to materials such as volatile elements, pure glass, or ilmenite for lunar industry

  8. 40Ar/39Ar geochronology, paleomagnetism, and evolution of the Boring volcanic field, Oregon and Washington, USA

    Science.gov (United States)

    Fleck, Robert J.; Hagstrum, Jonathan T.; Calvert, Andrew T.; Evarts, Russell C.; Conrey, Richard M.

    2014-01-01

    The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.

  9. Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations. Volume II

    International Nuclear Information System (INIS)

    Volcanic hazard investigations during FY 1984 focused on five topics: the emplacement mechanism of shallow basalt intrusions, geochemical trends through time for volcanic fields of the Death Valley-Pancake Range volcanic zone, the possibility of bimodal basalt-rhyolite volcanism, the age and process of enrichment for incompatible elements in young basalts of the Nevada Test Site (NTS) region, and the possibility of hydrovolcanic activity. The stress regime of Yucca Mountain may favor formation of shallow basalt intrusions. However, combined field and drill-hole studies suggest shallow basalt intrusions are rare in the geologic record of the southern Great Basin. The geochemical patterns of basaltic volcanism through time in the NTS region provide no evidence for evolution toward a large-volume volcanic field or increases in future rates of volcanism. Existing data are consistent with a declining volcanic system comparable to the late stages of the southern Death Valley volcanic field. The hazards of bimodal volcanism in this area are judged to be low. The source of a 6-Myr pumice discovered in alluvial deposits of Crater Flat has not been found. Geochemical studies show that the enrichment of trace elements in the younger rift basalts must be related to an enrichment of their mantle source rocks. This geochemical enrichment event, which may have been metasomatic alteration, predates the basalts of the silicic episode and is, therefore, not a young event. Studies of crater dimensions of hydrovolcanic landforms indicate that the worst case scenario (exhumation of a repository at Yucca Mountain by hydrovolcanic explosions) is unlikely. Theoretical models of melt-water vapor explosions, particularly the thermal detonation model, suggest hydrovolcanic explosion are possible at Yucca Mountain. 80 refs., 21 figs., 5 tabs

  10. Status of volcanic hazard studies for the Nevada Nuclear Waste Storage Investigations. Volume II

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M.; Wohletz, K.H.; Vaniman, D.T.; Gladney, E.; Bower, N.

    1986-01-01

    Volcanic hazard investigations during FY 1984 focused on five topics: the emplacement mechanism of shallow basalt intrusions, geochemical trends through time for volcanic fields of the Death Valley-Pancake Range volcanic zone, the possibility of bimodal basalt-rhyolite volcanism, the age and process of enrichment for incompatible elements in young basalts of the Nevada Test Site (NTS) region, and the possibility of hydrovolcanic activity. The stress regime of Yucca Mountain may favor formation of shallow basalt intrusions. However, combined field and drill-hole studies suggest shallow basalt intrusions are rare in the geologic record of the southern Great Basin. The geochemical patterns of basaltic volcanism through time in the NTS region provide no evidence for evolution toward a large-volume volcanic field or increases in future rates of volcanism. Existing data are consistent with a declining volcanic system comparable to the late stages of the southern Death Valley volcanic field. The hazards of bimodal volcanism in this area are judged to be low. The source of a 6-Myr pumice discovered in alluvial deposits of Crater Flat has not been found. Geochemical studies show that the enrichment of trace elements in the younger rift basalts must be related to an enrichment of their mantle source rocks. This geochemical enrichment event, which may have been metasomatic alteration, predates the basalts of the silicic episode and is, therefore, not a young event. Studies of crater dimensions of hydrovolcanic landforms indicate that the worst case scenario (exhumation of a repository at Yucca Mountain by hydrovolcanic explosions) is unlikely. Theoretical models of melt-water vapor explosions, particularly the thermal detonation model, suggest hydrovolcanic explosion are possible at Yucca Mountain. 80 refs., 21 figs., 5 tabs.

  11. The ~ 2000 yr BP Jumento volcano, one of the youngest edifices of the Chichinautzin Volcanic Field, Central Mexico

    Science.gov (United States)

    Arce, J. L.; Muñoz-Salinas, E.; Castillo, M.; Salinas, I.

    2015-12-01

    The Chichinautzin Volcanic Field is situated at the southern limit of the Basin of Mexico and the Metropolitan area of Mexico City, the third most populated city around the world. The Chichinautzin Volcanic field holds more than 220 monogenetic volcanoes. Xitle is the youngest of these with an estimated age of 1.6 ky BP. Xitle's eruptive activity took place during the Mesoamerican Mexican Pre-classic period and is related to the destruction of Cuicuilco Archaeological Site, the oldest civilization known in Central Mexico. However, there are still several regional cones that have not been dated. Based on 14C ages, stratigraphic and geomorphologic criteria, we conclude that the Jumento volcano, located to the west of Xitle, is one of the youngest cones of the Chichinautzin Volcanic Field. The Jumento volcano has a basaltic andesite composition, and its eruptive activity was initially hydromagmatic, followed by Strombolian and finally effusive events occurred recorded through: (1) a sequence of hydromagmatic pyroclastic surges and ashfall layers emplaced at a radius of > 5 km from the crater with charcoal fragments at its base; this activity built the Jumento's cone with slopes of 32°; and (2) lava flows that breached the southern part of the cone and flowed for up to 2.5 km from the vent. The resulting 14C ages for this volcano yielded a maximum age of ~ 2 ky BP. Morphometric analysis indicates that the state of degradation of Jumento cone is similar to the Xitle, suggesting that the Jumento could be in the state of degradation of a volcanic structure of similar age or younger adding credence to the probable radiocarbon age of ~ 2 ky BP for the Jumento edifice.

  12. The Pliocene-Quaternary Buffalo Valley volcanic field, Nevada: Post-extension, intraplate magmatism in the north-central Great Basin, USA

    Science.gov (United States)

    Cousens, Brian; Wetmore, Stacey; Henry, Christopher D.

    2013-12-01

    The Buffalo Valley volcanic field consists of Pliocene through Quaternary lava flows and spatter cones located south of Battle Mountain and adjacent to the Fish Creek Mountains, north-central Nevada. The volcanic rocks are split into two groups by age and geochemistry. The Pliocene sequence (4.02 to 2.75 Ma) consists of olivine- and plagioclase-bearing alkali basaltic lava flows with minor pyroclastic deposits, found primarily along the south flank of Battle Mountain and also at the north end of the Fish Creek Mountains and within the Fish Creek Mountains caldera. The Quaternary series (1.99 to 1.14 Ma) includes nearly a dozen trachybasaltic spatter cones with short lava flows erupted along the northwest flank of the Fish Creek Mountains. Normalized rare earth element and incompatible element plots for both groups are light rare earth and Nb-Ta enriched, resembling alkali basalts from ocean islands, but the Quaternary lavas are more light rare earth element-enriched and cross the Pliocene basalt patterns at Eu. Radiogenic and stable isotope ratios are consistent with an asthenospheric mantle source, and the rare earth element patterns indicate a shift from melting in the spinel to garnet peridotite field with time. Basaltic rocks from other intraplate fields in the Great Basin, including the Lunar Crater and Cima fields, only include lavas that originated at depth in the garnet peridotite field. Buffalo Valley is located at the margin of a proposed lithospheric drip (delamination) and within a zone of lithospheric thinning that extends across northern Nevada, both of which may control where melting in the asthenosphere may occur. The proximity to the edge of Precambrian-Phanerozoic lithosphere boundary may also be a factor in melt generation.

  13. The roles of fractional crystallization, magma mixing, crystal mush remobilization and volatile-melt interactions in the genesis of a young basalt-peralkaline rhyolite suite, the greater Olkaria volcanic complex, Kenya Rift valley

    Science.gov (United States)

    Macdonald, R.; Belkin, H.E.; Fitton, J.G.; Rogers, N.W.; Nejbert, K.; Tindle, A.G.; Marshall, A.S.

    2008-01-01

    The Greater Olkaria Volcanic Complex is a young (???20 ka) multi-centred lava and dome field dominated by the eruption of peralkaline rhyolites. Basaltic and trachytic magmas have been erupted peripherally to the complex and also form, with mugearites and benmoreites, an extensive suite of magmatic inclusions in the rhyolites. The eruptive rocks commonly represent mixed magmas and the magmatic inclusions are themselves two-, three- or four-component mixes. All rock types may carry xenocrysts of alkali feldspar, and less commonly plagioclase, derived from magma mixing and by remobilization of crystal mushes and/or plutonic rocks. Xenoliths in the range gabbro-syenite are common in the lavas and magmatic inclusions, the more salic varieties sometimes containing silicic glass representing partial melts and ranging in composition from anorthite ?? corundum- to acmite-normative. The peralkaline varieties are broadly similar, in major element terms, to the eruptive peralkaline rhyolites. The basalt-trachyte suite formed by a combination of fractional crystallization, magma mixing and resorption of earlier-formed crystals. Matrix glass in metaluminous trachytes has a peralkaline rhyolitic composition, indicating that the eruptive rhyolites may have formed by fractional crystallization of trachyte. Anomalous trace element enrichments (e.g. ??? 2000 ppm Y in a benmoreite) and negative Ce anomalies may have resulted from various Na- and K-enriched fluids evolving from melts of intermediate composition and either being lost from the system or enriched in other parts of the reservoirs. A small group of nepheline-normative, usually peralkaline, magmatic inclusions was formed by fluid transfer between peralkaline rhyolitic and benmoreitic magmas. The plumbing system of the complex consists of several independent reservoirs and conduits, repeatedly recharged by batches of mafic magma, with ubiquitous magma mixing. ?? The Author 2008. Published by Oxford University Press. All

  14. Sedimentation architecture of the volcanically-dammed Alf valley in the West Eifel Volcanic Field, Germany

    Science.gov (United States)

    Eichhorn, Luise; Lange, Thomas; Engelhardt, Jörn; Polom, Ulrich; Pirrung, Michael; Büchel, Georg

    2015-04-01

    In the southeastern part of the Quaternary West Eifel Volcanic Field, the Alf valley with its morphologically wide (~ 500 m) and flat valley bottom is visibly outstanding. This flat valley bottom was formed during the Marine Isotope Stage 2 due to fluviolacustrine sediments which deposited upstream of a natural volcanic dam. The dam consisted of lava and scoria breccia from the Wartgesberg Volcano complex (Cipa 1958, Hemfler et al. 1991) that erupted ~ 31 BP (40Ar/ 39Ar dating on glass shards, Mertz, pers. communication 2014). Due to this impoundment, the Alf creek turned into a dendritic lake, trapping the catchment sediments. The overall aim is to create the sedimentation architecture of the Alf valley. In comparison to maar archives like Holzmaar or Meerfelder Maar in the vicinity, the fluviolacustrine sediments of the Alf valley show clay-silt lamination despite the water percolation. This archive covers the transition from the Last Glacial Maximum to Early Holocene (Pirrung et al. 2007). Focus of this study is the creation of a 3D model by applying the program ESRI ArcGIS 10.2 to reconstruct the pre-volcanic Alf valley. Moreover, the sedimentation architecture is reconstructed and the sediment fill quantified. Therefore, the digital elevation model with 5 m resolution from the State Survey and Geobasis Information of Rhineland-Palatinate, polreduced magnetic data measured on top of the Strohn lava stream, shear seismic data and core stratigraphies were utilized. Summarizing previous results, Lake Alf had a catchment area of ~ 55 km² (Meerfelder Maar: 1.27 km²) and a surface area of 8.2 km² (Meerfelder Maar: 0.24 km²) considering a maximum lake water level of 410 m a.s.l.. In the deepest parts (~ 50 m) of Lake Alf, lake sediments are laminated, up to 21 m thick and show a very high sedimentation rate ~ 3 mm a-1 (Dehner Maar ~ 1.5 mm a-1, (Sirocko et al. 2013)). The sediments become coarser upstream und stratigraphically above the fine-grained lake sediments

  15. Emplacement history and inflation evidence of a long basaltic lava flow located in Southern Payenia Volcanic Province, Argentina

    Science.gov (United States)

    Bernardi, Mauro I.; Bertotto, Gustavo W.; Jalowitzki, Tiago L. R.; Orihashi, Yuji; Ponce, Alexis D.

    2015-02-01

    The El Corcovo lava flow, from the Huanul shield volcano in the southern Mendoza province (central-western Argentina) traveled a distance of 70 km and covered a minimum area of ~ 415 km2. The flow emplacement was controlled both by extrinsic (e.g., topography) and intrinsic (e.g., lava supply rate, lava physicochemical characteristics) factors. The distal portion of the lava flow reached the Colorado River Valley, in La Pampa Province, where it spread and then was confined by earlier river channels. Cross-sections through the flow surveyed at several localities show two vesicular layers surrounding a dense central section, where vesicles are absent or clustered in sheet-shaped and cylindrical-shaped structures. Lavas of the El Corcovo flow are alkaline basalts with low values of viscosity. The morphological and structural characteristics of the flow and the presence of landforms associated with lava accumulation are the evidence of inflation. This process involved the formation of a tabular sheet flow up to 4 m of thick with a large areal extent in the proximal sectors, while at terminal sectors frontal lobes reached inflation values up to 10 m. The numerous swelling structures present at these portions of the flow suggest the movement of lava in lava tubes. We propose that this aspect and the low viscosity of the lava allowed the flow travel to a great distance on a gentle slope relief.

  16. Geothermal Fields on the Volcanic Axis of Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Mercado, S.; Gonzalez, A.

    1980-12-16

    At present in Mexico, geothermal energy is receiving a great impulse due to the excellent results obtained in the Cerro Prieto geothermal field, in which a geothermoelectric plant is operated. This plant has four units of 37.5 MW each, with a total capacity of 150 MW, and under program 470 MW more by 1984. The Government Institution, Comisi6n Federal de Electricidad, is in charge of the exploration and exploitation of geothermal fields as well as construction and operation of power plants in Mexico. By this time CFE has an extensive program of exploration in the central part of Mexico, in the Eje Neovolcdnico. In this area, several fields with hydrothermal alteration are under exploration, like the Michoac6n geothermal area, where Los Azufres geothermal field is being developed. Seventeen wells have been drilled and twelve of them presented excellent results, including two dry steam wells. In other areas, such as Arar6, Cuitzeo, San Agustln del Maiz,Ixtldn de Los Hervores and Los Negritos, geological, geophysical and geochemical explorations have been accomplished, including shallow well drilling with good results. Another main geothermal area is in the State of Jalisco with an extension of 5,000 m2, where La Primavera geothermal field shows a lot of volcanic domes and has an intensive hydrothermal activity. Deep wells have been drilled, one of them with a bottom temperature of 29OOC. Other fields in this area, like San Narcos, Hervores de La Vega, La Soledad, Villa Corona, etc., have a good geothermal potential. A new geothermal area has been explored recently in the eastern part of the country named Los Humeros, Puebla. In this area studies are being made and there are plans for well drilling exploration by the beginning of 1981. Like this one, there are many other areas in the country in which 300 hydrothermal alteration zones are been classified and 100 of them are considered economically exploitable.

  17. Wave field decomposition of volcanic tremor at Pacaya Volcano, Guatemala

    Science.gov (United States)

    Lanza, F.; Waite, G. P.; Kenyon, L. M.

    2013-12-01

    A dense, small-aperture array of 12 short-period seismometers was deployed on the west flank of Pacaya volcano (Guatemala) and operated for 14 days in January 2011. The data were used to investigate the properties of the volcanic tremor wave field at the volcano. Volcanic tremor has been proven to be a powerful tool for eruption forecasting, therefore, identifying its source locations may shed new light on the dynamics of the volcano system. A preliminary spectral analysis highlights that most of the seismic energy is associated with six narrow spectral peaks between 1 and 6 Hz. After taking topography into account, we performed frequency-slowness analyses using the MUSIC algorithm and the semblance technique with the aim to define and locate the different components contributing to the wave field. Results show a complex wave field, with possibly multiple sources. We identify peaks at frequencies < 2 Hz as being related to anthropogenic sources coming from the N- NW direction where the geothermal plant and San Vincente Pacaya village are located. Azimuth measurements indicate that the 3 Hz signal propagates from the SE direction and it has been attributed to the new vent on the southeast flank of Pacaya Volcano. However, the presence of secondary peaks with azimuths of ˜ 200°, 150° and 70° seems to suggest either nonvolcanic sources or perhaps the presence of structural heterogeneities that produce strong scattered waves. At higher frequencies, results show effects of array aliasing, and therefore have not been considered in this study. The dispersive properties of the wave field have been investigated using the Spatial Auto-Correlation Method (SPAC). The dispersion characteristics of Rayleigh waves have been then inverted to find a shallow velocity model beneath the array, which shows a range of velocities from about 0.3 km/s to 2 km/s, in agreement with slowness values of the frequency bands considered. In detail, apparent velocities of 1-2 km/s dominate at

  18. Eruptive history, petrology, and petrogenesis of the Joe Lott Tuff Member of the Mount Belknap Volcanics, Marysvale volcanic field, west-central Utah

    Science.gov (United States)

    Budding, Karin E.

    1982-01-01

    The Joe Lott Tuff Member of the Mount Belknap Volcanics is the largest rhyolitic ash-flow tuff sheet in the Marysvale volcanic field. It was erupted 19 m.y. ago, shortly after the changeover from intermediate-composition calc-alkalic volcanism to bimodal basalt-rhyolite volcanism. Eruption of the tuff resulted in the formation of the Mount Belknap Caldera whose pyroclastic intracaldera stratigraphy parallels that in the outflow facies. The Joe Loft Tuff Member is a composite ash-flow sheet that changes laterally from a simple cooling unit near the source to four distinct cooling units toward the distal end. The lowest of these units is the largest and most widespread; it is 64 m thick and contains a basal vitrophyre. Eruption of the lower unit led to the initial collapse of the caldera. The lower unit is followed upward by a 43 m middle unit, a 26 m pink-colored unit which is separated by a prominent air- fall layer, and a 31 m upper unit. The Joe Loft Tuff Member is an alkali rhyolite with 75.85-77.31 wt. % silica and 8.06-9.32 wt. % K2O+Na2O; the agpaitic index (Na2O+ K2O/Al2O3) is .77-.98. The tuff contains about I% phenocrysts of quartz, sanidine, oligoclase, augite, apatite, zircon, sphene, biotite, and oxidized Fe-Ti oxides. The basal vitrophyre contains accessory allanite, chevkinite, and magnesiohastingsite. The main cooling units are chemically and mineralogically zoned indicating that the magma chamber restratified prior to each major eruption. Within each of the two thickest cooling units, the mineralogy changes systematically upwards; the Or content and relative volume of sanidine decreases and An content of plagioclase increases. The basal vitrophyre of the lower unit has a bulk composition that lies in the thermal trough near the minima of Or-Ab-Q at 1 kb PH2O. Microprobe analyses of feldspar and chemical modeling on experimental systems indicate that pre-eruption temperatures were near 750?C and that the temperature increased during the eruption of

  19. Longevity of Yellowstone hotspot volcanism: Isotopic evidence linking the Siletzia LIP (56 Ma) and early Columbia River Basalt Group (17 Ma) mantle sources

    Science.gov (United States)

    Pyle, D. G.; Duncan, R. A.; Wells, R. E.; Graham, D. W.; Hanan, B. B.; Harrison, B. K.; Haileab, B.

    2015-12-01

    Siletzia is a Paleocene-Eocene accreted terrane of submarine and subaerially erupted mafic lavas exposed in the Cascadia forearc. This large igneous province [LIP] is exposed in multiple volcanic sections from Vancouver Island, B.C., to southern Oregon [~700 km]. We estimate Siletzia magmatism at ~2.3 x 106 km3 west of the Cascades and may reach 4.6 x 106 km3 if correlative with Alaskan Yakutat terrane and significant portions of the LIP filled the Oregon Embayment. 40Ar-39Ar ages show the bulk of Siletzia erupted over a 6-7 Myr interval beginning at 56 Ma, implying eruption rates of 0.3-0.7 km3/yr. In Oregon, Siletz River volcanism began in the south [56-53 Ma] and migrated northward [54-50 Ma]. Concurrent eruptions of Metchosin and Crescent basalts do not show a southerly age progression. Therefore, Siletzia likely erupted south of the Kula-Farallon spreading center with ridge collision at or north of the Metchosin igneous complex. Isotopic data for 29 Siletzia lavas have initial 7/6Sr 0.7030-0.7037, ΕNd +4.9 - +7.7, 6/4Pb 18.70-19.94, 7/4Pb 15.49-15.63 and 8/4Pb 38.27-39.53. Olivine yield 3He/4He from 9.4 to 13.7 (R/Ra) and high MgO lavas display a narrow 187Os/188Os range (0.131-0.134) when age corrected. Both He and Os tracers are elevated above typical depleted MORB mantle and indicate plume involvement. Pb-Pb and Pb-Nd arrays suggest 3 mantle components for Siletzia volcanism: a depleted source with isotopic and trace element characteristics expected for spreading center lavas (i.e., Ku-Fa) influenced by a plume, a HIMU contaminant (i.e., high 6/4Pb; low 7/6Sr) confined to southern Siletzia, and a plume source (6/4Pb 19.00; 7/4Pb 15.55; 8/4Pb 38.60; 7/6Sr; 0.7033; ΕNd +6.4; γOs +5.0). Siletzia plume mantle is a close match to recent Yellowstone plume estimates based on early CRBG lavas. Mounting geophysical and geochemical evidence supports the contention that Siletzia is an early product of the Yellowstone hot spot in a sub-oceanic setting.

  20. Geochemistry of the late Holocene rocks from the Tolbachik volcanic field, Kamchatka: Quantitative modelling of subduction-related open magmatic systems

    Science.gov (United States)

    Portnyagin, Maxim; Duggen, Svend; Hauff, Folkmar; Mironov, Nikita; Bindeman, Ilya; Thirlwall, Matthew; Hoernle, Kaj

    2015-12-01

    We present new major and trace element, high-precision Sr-Nd-Pb (double spike), and O-isotope data for the whole range of rocks from the Holocene Tolbachik volcanic field in the Central Kamchatka Depression (CKD). The Tolbachik rocks range from high-Mg basalts to low-Mg basaltic trachyandesites. The rocks considered in this paper represent mostly Late Holocene eruptions (using tephrochronological dating), including historic ones in 1941, 1975-1976 and 2012-2013. Major compositional features of the Tolbachik volcanic rocks include the prolonged predominance of one erupted magma type, close association of middle-K primitive and high-K evolved rocks, large variations in incompatible element abundances and ratios but narrow range in isotopic composition. We quantify the conditions of the Tolbachik magma origin and evolution and revise previously proposed models. We conclude that all Tolbachik rocks are genetically related by crystal fractionation of medium-K primary magmas with only a small range in trace element and isotope composition. The primary Tolbachik magmas contain ~ 14 wt.% of MgO and ~ 4% wt.% of H2O and originated by partial melting (~ 6%) of moderately depleted mantle peridotite with Indian-MORB-type isotopic composition at temperature of ~ 1250 °C and pressure of ~ 2 GPa. The melting of the mantle wedge was triggered by slab-derived hydrous melts formed at ~ 2.8 GPa and ~ 725 °C from a mixture of sediments and MORB- and Meiji-type altered oceanic crust. The primary magmas experienced a complex open-system evolution termed Recharge-Evacuation-Fractional Crystallization (REFC). First the original primary magmas underwent open-system crystal fractionation combined with periodic recharge of the magma chamber with more primitive magma, followed by mixing of both magma types, further fractionation and finally eruption. Evolved high-K basalts, which predominate in the Tolbachik field, and basaltic trachyandesites erupted in 2012-2013 approach steady-state REFC

  1. Two- and three-dimensional gravity modeling along western continental margin and intraplate Narmada-Tapti rifts: Its relevance to Deccan flood basalt volcanism

    Indian Academy of Sciences (India)

    Somdev Bhattacharji; Rajesh Sharma; Nilanjan Chatterjee

    2004-12-01

    magma chambers along the western continental margin and the intraplate Narmada-Tapti rifts at estimated depths between 6 and 8 km from the surface (consistent with geological, petrological and geochemical models) appear to be the major reservoirs for Deccan flood basalt volcanism at approximately 65 Ma.

  2. Oxygen Isotope Character of the Lake Owyhee Volcanic Field, Oregon

    Science.gov (United States)

    Blum, T.; Strickland, A.; Valley, J. W.

    2012-12-01

    Oxygen isotope analyses of zircons from lavas and tuffs from the Lake Owyhee Volcanic Field (LOVF) of east central Oregon unequivocally demonstrate the presence of mid-Miocene low-δ18O magmas (δ18OzrcPrecambrian continental crust to the east to younger Phanerozoic accreted terranes to the west. Here we report high accuracy ion microprobe analyses of δ18O in zircons using a 10-15μm spot, with average spot-to-spot precision ±0.28‰ (2SD), to investigate intra-grain and intra-unit δ18Ozrc trends for LOVF rhyolites. Due to its high closure temperature, chemical and physical resistance, and slow oxygen diffusion rates, zircon offers a robust record of magmatic oxygen isotope ratios during crystallization and provides constraints on the petrogenesis of Snake River Plain (SRP) low-δ18O melts. Individual zircons from LOVF rhyolites show no evidence of core-rim δ18O zoning, and populations exhibit ≤0.42‰ (2SD) intra-unit variability. Unit averages range from 2.2 to 4.3‰, with the lowest values in caldera-forming ignimbrites, but all units show evidence of crystallization from low-δ18O melts. Quartz and feldspar analyses by laser fluorination (precision ±0.20‰, 2SD) indicate δ18Oqtz ranges between 5.7 and 6.8‰, and δ18OKfs between -5.4 and +6.7‰. Δ18O(qtz-zrc) ranges from 2.1-2.5‰, while Δ18O(Kfs-zrc) varies from 2.3 to -7.7‰. Quartz values are consistent with equilibration at magmatic temperatures, however, at least some feldspars have undergone subsolidus exchange and feldspar or whole rock δ18O values are not reliably igneous. The observed low-δ18Ozrc values document high temperature interaction of magmatic protoliths with meteoric waters. Current models to account for low-δ18O SRP rhyolites include remelting of hydrothermally altered cogenetic volcanic and subvolcanic rocks, or partial melting of deeper-seated low-δ18O source rocks altered either by SRP hot spot activity or during an earlier event. The SRP represents the greatest known

  3. Status of volcanism studies for the Yucca Mountain Site Characterization Project

    International Nuclear Information System (INIS)

    Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. Geophysical data are described for the YMR and are used as an aid to understand the distribution of basaltic volcanic centers. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. The long time of activity and characteristic small volume of the Postcaldera basalt of the YMR result in one of the lowest eruptive rates in a volcanic field in the southwest United States. Chapter 5 summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Chapter 6 summarizes the history of volcanism studies (1979 through early 1994), including work for the Yucca Mountain Site Characterization Project and overview studies by the state of Nevada and the Nuclear Regulatory Commission. Chapter 7 summarizes probabilistic volcanic hazard assessment using a three-part conditional probability model. Chapter 8 describes remaining volcanism work judged to be needed to complete characterization studies for the YMR. Chapter 9 summarizes the conclusions of this volcanism status report

  4. Status of volcanism studies for the Yucca Mountain Site Characterization Project

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.; Perry, F.; Murrell, M.; Poths, J.; Valentine, G.A. [Los Alamos National Lab., NM (United States); Wells, S. [Univ. of California, Riverside, CA (United States); Bowker, L.; Finnegan, K. [Univ. of Nevada, Las Vegas, NV (United States); Geissman, J.; McFadden, L.

    1995-02-01

    Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. Geophysical data are described for the YMR and are used as an aid to understand the distribution of basaltic volcanic centers. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the Basin and Range province. The long time of activity and characteristic small volume of the Postcaldera basalt of the YMR result in one of the lowest eruptive rates in a volcanic field in the southwest United States. Chapter 5 summarizes current concepts of the segregation, ascent, and eruption of basalt magma. Chapter 6 summarizes the history of volcanism studies (1979 through early 1994), including work for the Yucca Mountain Site Characterization Project and overview studies by the state of Nevada and the Nuclear Regulatory Commission. Chapter 7 summarizes probabilistic volcanic hazard assessment using a three-part conditional probability model. Chapter 8 describes remaining volcanism work judged to be needed to complete characterization studies for the YMR. Chapter 9 summarizes the conclusions of this volcanism status report.

  5. Hydrous basalt-limestone interaction at crustal conditions: Implications for generation of ultracalcic melts and outflux of CO2 at volcanic arcs

    Science.gov (United States)

    Carter, Laura B.; Dasgupta, Rajdeep

    2015-10-01

    High degassing rates for some volcanoes, typically in continental arcs, (e.g., Colli Albani Volcanic District, Etna, Vesuvius, Italy; Merapi, Indonesia; Popocatepetl, Mexico) are thought to be influenced by magma-carbonate interaction in the crust. In order to constrain the nature of reaction and extent of carbonate breakdown, we simulated basalt-limestone wall-rock interactions at 0.5-1.0 GPa, 1100-1200 °C using a piston cylinder and equal mass fractions of calcite (CaCO3) and a hydrous (∼4 wt.% H2O) basalt in a layered geometry contained in AuPd capsules. All experiments produce melt + fluid + calcite ± clinopyroxene ± plagioclase ± calcic-scapolite ± spinel. With increasing T, plagioclase is progressively replaced by scapolite, clinopyroxene becomes CaTs-rich, and fluid proportion, as inferred from vesicle population, increases. At 1.0 GPa, 1200 °C our hydrous basalt is superliquidus, whereas in the presence of calcite, the experiment produces calcite + clinopyroxene + scapolite + melt. With the consumption of calcite with increasing T and decreasing P, melt, on a volatile-free basis, becomes silica-poor (58.1 wt.% at 1.0 GPa, 1100 °C to 34.9 wt.% at 0.5 GPa, 1200 °C) and CaO-rich (6.7 wt.% at 1.0 GPa, 1100 °C to 43.7 wt.% at 0.5 GPa, 1200 °C), whereas Al2O3 drops (e.g., 19.7 at 1100 °C to 12.8 wt.% at 1200 °C at 1.0 GPa) as clinopyroxene becomes more CaTs-rich. High T or low P melt compositions are 'ultracalcic,' potentially presenting a new hypothesis for the origin of ultracalcic melt inclusions in arc lava olivines. Wall-rock calcite consumption is observed to increase with increasing T and decreasing P. At 0.5 GPa, our experiments yield carbonate assimilation from 21.6 to 47.6% between 1100 and 1200 °C. Using measured CO2 outflux rates for Mts. Vesuvius, Merapi, Etna and Popocatepetl over a T variation of 1100 to 1200 °C at 0.5 GPa, we calculate 6-92% of magmatic input estimates undergo this extent of assimilation, suggesting that up to ∼3

  6. Characterization of the sub-continental lithospheric mantle beneath the Cameroon volcanic line inferred from alkaline basalt hosted peridotite xenoliths from Barombi Mbo and Nyos Lakes

    Science.gov (United States)

    Pintér, Zsanett; Patkó, Levente; Tene Djoukam, Joëlle Flore; Kovács, István; Tchouankoue, Jean Pierre; Falus, György; Konc, Zoltán; Tommasi, Andréa; Barou, Fabrice; Mihály, Judith; Németh, Csaba; Jeffries, Teresa

    2015-11-01

    We carried out detailed petrographic, major and trace element geochemical, microstructural and FTIR analyses on eight characteristic ultramafic xenoliths from Nyos and Barombi Mbo Lakes in the continental sector of the Cameroon Volcanic Line (CVL). The studied xenoliths are spinel lherzolites showing lithologies similar to the other xenoliths reported previously along the CVL. They have protogranular and porphyroclastic textures. One of the Barombi xenolith contains amphibole, which had not been previously reported in this locality. Amphibole is common in the Nyos xenoliths suite. Peridotite xenoliths from both localities show some chemical heterogeneity, but Barombi xenoliths generally are less depleted in basaltic elements with respect to Nyos xenoliths. Trace element compositions of Nyos spinel lherzolites show a moderately depleted initial (premetasomatic) composition and variable enrichment in REE. Evidence for both modal and cryptic metasomatism is present in Nyos xenoliths. Rare earth element patterns of clinopyroxene suggest that interaction between mafic melts and the upper mantle occurred beneath the Nyos locality. Barombi Mbo xenoliths, on the other hand, record a small degree of partial melting. The Barombi Mbo xenoliths have weak, dominantly orthorhombic olivine crystal preferred orientations, whereas Nyos ones have strong axial-[010] patterns, which may have formed in response to transpression. Nominally anhydrous mantle minerals (NAMs) of the Barombi Mbo xenoliths show generally higher bulk concentrations of 'water' (70-127 ppm) than Nyos xenoliths (32-81 ppm). The Barombi Mbo xenoliths could originate from a juvenile segment of the lithospheric mantle, which had been originally part of the asthenosphere. It became a part of the lithosphere in response to thermal relaxation following the extension, forming a weakly deformed lower lithospheric mantle region along the CVL. The Nyos xenoliths, however, represent a shallow lithospheric mantle bearing

  7. Residence, resorption and recycling of zircons in Devils Kitchen rhyolite, Coso Volcanic Field, California

    Science.gov (United States)

    Miller, J.S.; Wooden, J.L.

    2004-01-01

    Zircons from the Devils Kitchen rhyolite in the Pleistocene Coso Volcanic field, California have been analyzed by in situ Pb/U ion microprobe (SHRIMP-RG) and by detailed cathodoluminescence imaging. The zircons yield common-Pb-corrected and disequilibrium-corrected 206Pb/238U ages that predate a previously reported K-Ar sanidine age by up to 200 kyr, and the range of ages exhibited by the zircons is also approximately 200 kyr. Cathodoluminescence imaging indicates that zircons formed in contrasting environments. Most zircons are euhedral, and a majority of the zircons are weakly zoned, but many also have anhedral, embayed cores, with euhedral overgrowths and multiple internal surfaces that are truncated by later crystal zones. Concentrations of U and Th vary by two orders of magnitude within the zircon population, and by 10-20 times between zones within some zircon crystals, indicating that zircons were transferred between contrasting chemical environments. A zircon saturation temperature of ???750??C overlaps within error a previously reported phenocryst equilibration temperature of 740 ?? 25??C. Textures in zircons indicative of repeated dissolution and subsequent regrowth are probably caused by punctuated heating by mafic magma input into rhyolite. The overall span of ages and large variation in U and Th concentrations, combined with calculated zircon saturation temperatures and resorption times, are most compatible with crystallization in magma bodies that were emplaced piecemeal in the crust at Coso over 200 kyr prior to eruption, and that were periodically rejuvenated or melted by subsequent basaltic injections. ?? Oxford University Press 2004; all rights reserved.

  8. Pleistocene high-silica rhyolites of the Coso volcanic field, Inyo County, California.

    Science.gov (United States)

    Bacon, C.R.; Macdonald, R.; Smith, R.L.; Baedecker, P.A.

    1981-01-01

    The high-silica rhyolite domes and lava flows of the bimodal Pleistocene part of the Coso volcanic field provide an example of the early stages of evolution of a silicic magmatic system of substantial size and longevity. Major and trace element compositions are consistent with derivation from somewhat less silicic parental material by liquid state differentiation processes in compositionally and thermally zoned magmatic systems. Seven chemically homogeneous eruptive groups can be distinguished on the basis of trace element and K/Ar data. The oldest two groups are volumetrically minor and geochemically distinct from the younger groups, all five of which appear to have evolved from the same magmatic system. Erupted volume-time relations suggest that small amounts of magma were bled from the top of a silicic reservoir at a nearly constant long-term rate over the last 0.24Ma. The interval of repose between eruptions appears to be proportional to the volume of the preceding eruptive group. This relationship suggests that eruptions take place when some parameter which increases at a constant rate reaches a critical value; this parameter may be extensional strain accumulated in roof rocks. Extension of the lithosphere favors intrusion of basalt into the crust, attendant partial melting, and maintenance of a long-lived silicic magmatic system. The Coso silicic system may contain a few hundred cubic kilometers of magma. The Coso magmatic system may eventually have the potential for producing voluminous pyroclastic eruptions if the safety valve provided by rapid crustal extension becomes inadequate to 1) defuse the system through episodic removal of volatile-rich magma from its top and 2) prohibit migration of the reservoir to a shallow crustal level.-from Authors

  9. Geologic field-trip guide to Lassen Volcanic National Park and vicinity, California

    Science.gov (United States)

    Muffler, L. J. Patrick; Clynne, Michael A.

    2015-07-22

    This geologic field-trip guide provides an overview of Quaternary volcanism in and around Lassen Volcanic National Park in northern California. The guide begins with a comprehensive overview of the geologic framework and the stratigraphic terminology of the Lassen region, based primarily on the “Geologic map of Lassen Volcanic National Park and vicinity” (Clynne and Muffler, 2010). The geologic overview is then followed by detailed road logs describing the volcanic features that can readily be seen in the park and its periphery. Twenty-one designated stops provide detailed explanations of important volcanic features. The guide also includes mileage logs along the highways leading into the park from the major nearby communities. The field-trip guide is intended to be a flexible document that can be adapted to the needs of a visitor approaching the park from any direction.

  10. Isotopic and trace element constraints on the petrogenesis of lavas from the Mount Adams volcanic field, Washington

    Science.gov (United States)

    Jicha, B.R.; Hart, G.L.; Johnson, C.M.; Hildreth, W.; Beard, B.L.; Shirey, S.B.; Valley, J.W.

    2009-01-01

    Strontium, Nd, Pb, Hf, Os, and O isotope compositions for 30 Quaternary lava flows from the Mount Adams stratovolcano and its basaltic periphery in the Cascade arc, southern Washington, USA indicate a major component from intraplate mantle sources, a relatively small subduction component, and interaction with young mafic crust at depth. Major- and trace-element patterns for Mount Adams lavas are distinct from the rear-arc Simcoe volcanic field and other nearby volcanic centers in the Cascade arc such as Mount St. Helens. Radiogenic isotope (Sr, Nd, Pb, and Hf) compositions do not correlate with geochemical indicators of slab-fluids such as (Sr/P)n and Ba/Nb. Mass-balance modeling calculations, coupled with trace-element and isotopic data, indicate that although the mantle source for the calc-alkaline Adams basalts has been modified with a fluid derived from subducted sediment, the extent of modification is significantly less than what is documented in the southern Cascades. The isotopic and trace-element compositions of most Mount Adams lavas require the presence of enriched and depleted mantle sources, and based on volume-weighted chemical and isotopic compositions for Mount Adams lavas through time, an intraplate mantle source contributed the major magmatic mass of the system. Generation of basaltic andesites to dacites at Mount Adams occurred by assimilation and fractional crystallization in the lower crust, but wholesale crustal melting did not occur. Most lavas have Tb/Yb ratios that are significantly higher than those of MORB, which is consistent with partial melting of the mantle in the presence of residual garnet. ??18O values for olivine phenocrysts in Mount Adams lavas are within the range of typical upper mantle peridotites, precluding involvement of upper crustal sedimentary material or accreted terrane during magma ascent. The restricted Nd and Hf isotope compositions of Mount Adams lavas indicate that these isotope systems are insensitive to crustal

  11. Isotopic and trace element constraints on the petrogenesis of lavas from the Mount Adams volcanic field, Washington

    Science.gov (United States)

    Jicha, Brian R.; Hart, Garret L.; Johnson, Clark M.; Hildreth, Wes; Beard, Brian L.; Shirey, Steven B.; Valley, John W.

    2009-02-01

    Strontium, Nd, Pb, Hf, Os, and O isotope compositions for 30 Quaternary lava flows from the Mount Adams stratovolcano and its basaltic periphery in the Cascade arc, southern Washington, USA indicate a major component from intraplate mantle sources, a relatively small subduction component, and interaction with young mafic crust at depth. Major- and trace-element patterns for Mount Adams lavas are distinct from the rear-arc Simcoe volcanic field and other nearby volcanic centers in the Cascade arc such as Mount St. Helens. Radiogenic isotope (Sr, Nd, Pb, and Hf) compositions do not correlate with geochemical indicators of slab-fluids such as (Sr/P) n and Ba/Nb. Mass-balance modeling calculations, coupled with trace-element and isotopic data, indicate that although the mantle source for the calc-alkaline Adams basalts has been modified with a fluid derived from subducted sediment, the extent of modification is significantly less than what is documented in the southern Cascades. The isotopic and trace-element compositions of most Mount Adams lavas require the presence of enriched and depleted mantle sources, and based on volume-weighted chemical and isotopic compositions for Mount Adams lavas through time, an intraplate mantle source contributed the major magmatic mass of the system. Generation of basaltic andesites to dacites at Mount Adams occurred by assimilation and fractional crystallization in the lower crust, but wholesale crustal melting did not occur. Most lavas have Tb/Yb ratios that are significantly higher than those of MORB, which is consistent with partial melting of the mantle in the presence of residual garnet. δ 18O values for olivine phenocrysts in Mount Adams lavas are within the range of typical upper mantle peridotites, precluding involvement of upper crustal sedimentary material or accreted terrane during magma ascent. The restricted Nd and Hf isotope compositions of Mount Adams lavas indicate that these isotope systems are insensitive to crustal

  12. Correlating the end-Triassic mass extinction and basalt volcanism of the Central Atlantic Magmatic Province at the 100,000-year level by high-precision U-Pb age determinations

    Science.gov (United States)

    Schoene, Blair; Guex, Jean; Bartolini, Annachiara; Schaltegger, Urs; Blackburn, Terrence J.

    2010-05-01

    The end-Triassic mass extinction is one of the five largest extinctions in Earth history, though considerable uncertainty remains in terms of its duration, causes and effects. Many workers suggest that the extinction was related directly or indirectly to adverse climate following the onset of the Central Atlantic Magmatic Province (CAMP), which erupted > 2.5x106 km3 of basalt in less than 1 Ma. However, there remains a need for precise and accurate geochronology to correlate the onset of CAMP volcanism, recorded uniquely in terrestrial sections, with the well-documented marine extinction event. We provide new chemical abrasion ID-TIMS U-Pb age determinations on ash bed and basaltic zircons using the well-calibrated EARTHTIME 202Pb-205Pb-233U-235U tracer solution, yielding data that are up to 70% more precise compared to single-Pb/single-U tracers. We show that the Triassic-Jurassic boundary (TJB) and end-Triassic biological crisis from two independent marine stratigraphic sections in northern Peru and in Nevada (USA) correlate with the onset of terrestrial flood volcanism in the Central Atlantic Magmatic Province (CAMP) to <150 ka. Ash bed samples reveal complicated U-Pb systematics, showing ranges in 206Pb/238U zircon dates of up to 2 Ma, representing a range of growth histories prior to eruption. Therefore, we use the youngest single closed-system zircon to approximate the eruption date. Three volcanic ash beds from the Pucara basin, northern Peru, bracket the TJB to a 206Pb/238U age of 201.31 ± 0.18/0.31/0.43 Ma (internal uncertainties/ with tracer calibration uncertainty/ with decay constant uncertainties). The first discovered ash bed from the New York canyon, Nevada, 1.5 m above TJB requires a boundary age of less than 201.33 ± 0.13 Ma. We also provide data from two laboratories which yield a new 206Pb/238U zircon age of 201.28 ± 0.02/0.22/0.31 Ma for the North Mtn. basalt, the lowest CAMP basalt from the Fundy basin, Nova Scotia. This narrows the

  13. Geomagnetic field intensity and inclination records from the Hawaiian long basaltic cores: geomagnetic implications

    Science.gov (United States)

    Laj, C. E.; Kissel, C.; Davies, C.; Gubbins, D.

    2009-12-01

    In the long basaltic cores drilled in the Big Island of Hawaii, the sub-horizontal orientation of the flows and their regular accumulation with time, which makes the continuity in time almost comparable with sediments, provides an excellent opportunity to obtain a detailed record of the absolute intensity and inclination of the geomagnetic field from a sequence of lava flows. Here, we report new paleointensity (Thellier and Thellier) and inclination determinations obtained from the analysis of 370 samples from 130 flows in the subaerial part of HSDP2. These new results are combined with previous results obtained from the other long basaltic cores in Hawaii (HSDP1, SOH4 and SOH1) all selected using a set of stringent paleointensity selection criteria (PICRIT-03). In a first step the Sharp and Renne age model was used for correlation of the records. In a second step correlation was refined using some characteristic features of the paleomagnetic records themselves (HSDP 1 and HSDP 2 in particular), which led to a slight modification of the Sharp and Renne age model. The age model was further improved by correlation with the sedimentary SINT-800 record. The results are consistent between these independent records, over the different time intervals where they overlap. This allows construction of the first accurate lava record of absolute intensity and inclination at Hawaii which overlap for almost 75% of this time interval these different records overlap, the results are very consistent and allow to construct an accurate lava record of absolute geomagnetic field intensity and inclination at Hawaii for the last 420 kyr based on at least two independent records over almost. The VADM undergoes large oscillations between about 3 and 16 10^22 A.m*2 with an average values of about 8 10^22 A m^2. When the values corresponding to recognized excursional periods are omitted, the inclination is on the average 29.6°, i.e. about 6° shallower than the GAD value. These results will

  14. Quantifying the morphometric variability of monogenetic cones in volcanic fields: the Virunga Volcanic Province, East African Rift

    Science.gov (United States)

    Poppe, Sam; Grosse, Pablo; Barette, Florian; Smets, Benoît; Albino, Fabien; Kervyn, François; Kervyn, Matthieu

    2016-04-01

    Volcanic cone fields are generally made up of tens to hundreds of monogenetic cones, sometimes related to larger polygenetic edifices, which can exhibit a wide range of morphologies and degrees of preservation. The Virunga Volcanic Province (VVP) developed itself in a transfer zone which separates two rift segments (i.e. Edward and Kivu rift) within the western branch of the East-African Rift. As the result of volcanic activity related to this tectonic regime of continental extension, the VVP hosts eight large polygenetic volcanoes, surrounded by over 500 monogenetic cones and eruptive fissures, scattered over the vast VVP lava flow fields. Some cones lack any obvious geo-structural link to a specific Virunga volcano. Using recent high-resolution satellite images (SPOT, Pléiades) and a newly created 5-m-resolution digital elevation model (TanDEM-X), we have mapped and classified all monogenetic cones and eruptive fissures of the VVP. We analysed the orientation of all mapped eruptive fissures and, using the MORVOLC program, we calculated a set of morphometric parameters to highlight systematic spatial variations in size or morphometric ratios of the cones. Based upon morphological indicators, we classified the satellite cones into 4 categories: 1. Simple cones with one closed-rim crater; 2. Breached cones with one open-rim crater; 3. Complex cones with two or more interconnected craters and overlapping cones; 4. Other edifices without a distinguishable crater or cone shape (e.g. spatter mounds and levees along eruptive fissures). The results show that cones are distributed in clusters and along alignments, in some cases parallel with the regional tectonic orientations. Contrasts in the volumes of cones positioned on the rift shoulders compared to those located on the rift valley floor can possibly be attributed to contrasts in continental crust thickness. Furthermore, higher average cone slopes in the East-VVP (Bufumbira zone) and central-VVP cone clusters suggest

  15. The Giant Lavas of Kalkarindji: rubbly pāhoehoe lava in an ancient continental flood basalt province

    OpenAIRE

    Marshall, Peter E.; Widdowson, Mike; Murphy, David T.

    2016-01-01

    The Kalkarindji continental flood basalt province of northern Australia erupted in the mid Cambrian (c. 511-505 Ma). It now consists of scattered basaltic lava fields, the most extensive being the Antrim Plateau Volcanics (APV) - a semi-continuous outcrop (c. 50,000 km2) reaching a maximum thickness of 1.1 km. Cropping out predominately in the SW of the APV, close to the top of the basalt succession, lies the Blackfella Rockhole Member (BRM). Originally described as ‘basaltic agglomerate’ the...

  16. A newly discovered Pliocene volcanic field on the western Sardinia continental margin (western Mediterranean)

    Science.gov (United States)

    Conforti, Alessandro; Budillon, Francesca; Tonielli, Renato; De Falco, Giovanni

    2016-02-01

    A previously unknown submerged volcanic field offshore western Sardinia (western Mediterranean Sea), has been identified based on swath bathymetric data collected in 2009, 2010 and 2013, and high-resolution seismic profiles collected in 2011 and 2013. About 40 conical-shaped volcanic edifices (maximum width of about 1600 m and maximum height of about 180 m) and several lava outcrops (up to 1,200 m wide) were recognized at 20 to 150 m water depth over an area of 800 km2. The volcanic edifices are mainly eruptive monogenic vents, mostly isolated with a rather distinct shape, or grouped to form a coalescent volcanic body in which single elements are often still recognizable. High-resolution seismics enabled identifying relationships between the volcanic bodies and continental margin successions. The edifices overlie a major erosional surface related to the margin exposure following the Messinian salinity crisis, and are overlain by or interbedded with an early Pliocene marine unit. This seismo-stratigraphic pattern dates the volcanic activity to the early Pliocene, in agreement with the radiometric age of the Catalano island lavas (4.7 Ma) reported in earlier studies. The morphometry of the volcanic bodies suggests that cone erosion was higher at shallow water depths. Indeed, most of the shallow edifices are strongly eroded and flattened at 125 to 130 m water depth, plausibly explained by recurrent sub-aerial exposure during Pleistocene sea-level lowstands, whereas cones in deeper water are much better preserved. Volcanic vents and lava deposits, hereafter named the Catalano volcanic field (CVF), are emplaced along lineaments corresponding to the main directions of the normal fault system, which lowered the Sinis Basin and the western Sardinia continental margin. The CVF represents a volumetrically relevant phase of the late Miocene - Quaternary anorogenic volcanic cycle of Sardinia, which is related to the first stage of the extensional tectonics affecting the island

  17. The structural architecture of the Los Humeros volcanic complex and geothermal field, Trans-Mexican Volcanic Belt, Central Mexico

    Science.gov (United States)

    Norini, Gianluca; Groppelli, Gianluca; Sulpizio, Roberto; Carrasco Núñez, Gerardo; Davila Harris, Pablo

    2014-05-01

    The development of geothermal energy in Mexico is a very important goal, given the presence of a large heat anomaly, associated with the Trans-Mexican Volcanic Belt, the renewability of the resource and the low environmental impact. The Quaternary Los Humeros volcanic complex is an important geothermal target, whose evolution involved at least two caldera events, that alternated with other explosive and effusive activity. The first caldera forming event was the 460 ka eruption that produced the Xaltipan ignimbrite and formed a 15-20 km wide caldera. The second collapse event occurred 100 ka with the formation of the Zaragoza ignimbrite and a nested 8-10 km wide caldera. The whole volcano structure, the style of the collapses and the exact location of the calderas scarps and ring faults are still a matter of debate. The Los Humeros volcano hosts the productive Los Humeros Geothermal Field, with an installed capacity of 40 MW and additional 75 MW power plants under construction. Recent models of the geothermal reservoir predict the existence of at least two reservoirs in the geothermal system, separated by impermeable rock units. Hydraulic connectivity and hydrothermal fluids circulation occurs through faults and fractures, allowing deep steam to ascend while condensate flows descend. As a consequence, the plans for the exploration and exploitation of the geothermal reservoir have been based on the identification of the main channels for the circulation of hydrothermal fluids, constituted by faults, so that the full comprehension of the structural architecture of the caldera is crucial to improve the efficiency and minimize the costs of the geothermal field operation. In this study, we present an analysis of the Los Humeros volcanic complex focused on the Quaternary tectonic and volcanotectonics features, like fault scarps and aligned/elongated monogenetic volcanic centres. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of

  18. King's Bowl Pit Crater, Lava Field and Eruptive Fissure, Idaho - A Multipurpose Volcanic Planetary Analog

    Science.gov (United States)

    Hughes, S. S.; Garry, B.; Kobs-Nawotniak, S. E.; Sears, D. W. G.; Borg, C.; Elphic, R. C.; Haberle, C. W.; Kobayashi, L.; Lim, D. S. S.; Sears, H.; Skok, J. R.; Heldmann, J. L.

    2014-12-01

    King's Bowl (KB) and its associated eruptive fissure and lava field on the eastern Snake River Plain, is being investigated by the NASA SSERVI FINESSE (Field Investigations to Enable Solar System Science and Exploration) team as a planetary analog to similar pits on the Moon, Mars and Vesta. The 2,220 ± 100 BP basaltic eruption in Craters of the Moon National Monument and Preserve represents early stages of low shield growth, which was aborted when magma supply was cut off. Compared to mature shields, KB is miniscule, with ~0.02 km3 of lava over ~3 km2, yet the ~6 km long series of fissures, cracks and pits are well-preserved for analog studies of volcanic processes. The termination of eruption was likely related to proximity of the 2,270 ± 50 BP eruption of the much larger Wapi lava field (~5.5 km3 over 325 km2 area) on the same rift. Our investigation extends early work by R. Greeley and colleagues, focusing on imagery, compositional variations, ejecta distribution, dGPS profiles and LiDAR scans of features related to: (1) fissure eruptions - spatter ramparts, cones, feeder dikes, extension cracks; (2) lava lake formation - surface morphology, squeeze-ups, slab pahoehoe lava mounds, lava drain-back, flow lobe overlaps; and (3) phreatic steam blasts - explosion pits, ejecta blankets of ash and blocks. Preliminary results indicate multiple fissure eruptions and growth of a basin-filled lava lake up to ~ 10 m thick with outflow sheet lava flows. Remnant mounds of original lake crust reveal an early high lava lake level, which subsided as much as 5 m as the molten interior drained back into the fissure system. Rapid loss of magma supply led to the collapse of fissure walls allowing groundwater influx that triggered multiple steam blasts along at least 500 m. Early blasts occurred while lake magma pressure was still high enough to produce squeeze-ups when penetrated by ejecta blocks. The King's Bowl pit crater exemplifies processes of a small, but highly energetic

  19. Distribution and characteristics of volcanic reservoirs in China

    Institute of Scientific and Technical Information of China (English)

    HUANG Yulong; WANG Pujun; CHEN Shuming

    2009-01-01

    About forty productive oil/gas fields hosted in volcanic reservoirs have been found since 1957 in fourteen basins of China. They can be simply subdivided into two groups, the east and the west. Reservoir volcanic rocks of the east group are predominantly composed of Late Jurassic to Early Cretaceous rhyolite and Tertiary basalt, preferred being considered as rift type volcanics developed in the circum-Pacific tectonic regime. Those of the west are Permo-Carboniferous intermediate/basic volcanic rocks, being island-arc type ones developed in paleo-Asian Ocean tectonic regime.

  20. Contemporaneous trachyandesitic and calc-alkaline volcanism of the Huerto Andesite, San Juan Volcanic Field, Colorado, USA

    Science.gov (United States)

    Parat, F.; Dungan, M.A.; Lipman, P.W.

    2005-01-01

    Locally, voluminous andesitic volcanism both preceded and followed large eruptions of silicic ash-flow tuff from many calderas in the San Juan volcanic field. The most voluminous post-collapse lava suite of the central San Juan caldera cluster is the 28 Ma Huerto Andesite, a diverse assemblage erupted from at least 5-6 volcanic centres that were active around the southern margins of the La Garita caldera shortly after eruption of the Fish Canyon Tuff. These andesitic centres are inferred, in part, to represent eruptions of magma that ponded and differentiated within the crust below the La Garita caldera, thereby providing the thermal energy necessary for rejuvenation and remobilization of the Fish Canyon magma body. The multiple Huerto eruptive centres produced two magmatic series that differ in phenocryst mineralogy (hydrous vs anhydrous assemblages), whole-rock major and trace element chemistry and isotopic compositions. Hornblende-bearing lavas from three volcanic centres located close to the southeastern margin of the La Garita caldera (Eagle Mountain - Fourmile Creek, West Fork of the San Juan River, Table Mountain) define a high-K calc-alkaline series (57-65 wt % SiO2) that is oxidized, hydrous and sulphur rich. Trachyandesitic lavas from widely separated centres at Baldy Mountain-Red Lake (western margin), Sugarloaf Mountain (southern margin) and Ribbon Mesa (20 km east of the La Garita caldera) are mutually indistinguishable (55-61 wt % SiO2); they are characterized by higher and more variable concentrations of alkalis and many incompatible trace elements (e.g. Zr, Nb, heavy rare earth elements), and they contain anhydrous phenocryst assemblages (including olivine). These mildly alkaline magmas were less water rich and oxidized than the hornblende-bearing calc-alkaline suite. The same distinctions characterize the voluminous precaldera andesitic lavas of the Conejos Formation, indicating that these contrasting suites are long-term manifestations of San Juan

  1. Paleomagnetism and Rock Magnetic Properties from Quaternary Lavas and Tuffs of the Yellowstone Plateau Volcanic Field

    Science.gov (United States)

    Harlan, S. S.; Morgan, L. A.

    2008-12-01

    We report paleomagnetic and rock magnetic from rhyolite lava flows, ignimbrites, and basalt flows associated with the Yellowstone Caldera, within and surrounding Yellowstone National Park. These data were collected in order to understand sources of magnetic variations observed in high resolution aeromagnetic data reported by Finn and Morgan (2002), and to better understand the evolution of the Yellowstone magmatic system. Most paleomagnetic samples are from volcanic rocks of the third eruptive cycle (1.2 Ma to 0.070 Ma), including the ca. 0.640 Ma Lava Creek Tuff, postcaldera rhyolite flows, and contemporaneous marginal or post-caldera basalt flows. Magnetic intensities for samples ranged from 0.12 A/m to 5.9 A/m, with volume susceptibilities of 2.14x10-4 to 1.45x10-3 SI; Q ratios range from 0.67 to 23.8. As expected, most sites yield well-defined paleomagnetic directions of north declination and moderate positive inclination consistent with remanence acquisition during the Brunhes polarity chron. However, a few sites from older units such as the rhyolites of the Harlequin Lake (0.839 ± 0.007 Ma) and Lewis Canyon (0.853 ± 0.008 Ma) flows, and the basalts from the Junction Butte flow (at Tower Falls, 2.16 ± 0.04 Ma) and Hepburn Mesa (2.2 Ma) yield reverse polarity magnetizations (40Ar/39Ar dates from Obradovich, 1992, and Harlan, unpublished (Hepburn Mesa flow)). Rock magnetic behavior, including high coercivities during AF demagnetization, high laboratory unblocking temperatures, and susceptibility vs. temperature determinations indicate that remanence in the rhyolitic samples is carried by a combination of single or pseudo-single domain magnetite and/or hematite; in the basalt flows magnetite and high-Ti titanomagnetite carrys the remanence. Paleomagnetic results from 46 sites in 27 separate flows yields a grand mean direction with a declination of 356.9° and inclination of 61.9° (k = 35.2, α95 = 4.8°). VGPs calculated from the site-mean directions yield a

  2. Paleomagnetism of the Pleistocene Tequila Volcanic Field (Western Mexico)

    Science.gov (United States)

    Rodríguez Ceja, M.; Goguitchaichvili, A.; Calvo-Rathert, M.; Morales-Contreras, J.; Alva-Valdivia, L.; Rosas Elguera, J.; Urrutia Fucugauchi, J.; Delgado Granados, H.

    2006-10-01

    This paper presents new paleomagnetic results from 24 independent cooling units in Tequila area (western Trans-Mexican Volcanic Belt). These units were recently dated by means of state-of-the-art 40Ar-39Ar method (Lewis-Kenedy et al., 2005) and span from 1130 to 150 ka. The characteristic paleodirections are successfully isolated for 20 cooling units. The mean paleodirection, discarding intermediate polarity sites, is I = 29.6°, D = 359.2°, k = 26, α95 = 7.1°, n = 17, which corresponds to the mean paleomagnetic pole position Plat = 85.8°, Plong = 84.3°, K = 27.5, A95 = 6.9°. These directions are practically undistinguishable from the expected Plestocene paleodirections, as derived from reference poles for the North American polar wander curve and in agreement with previously reported directions from western Trans-Mexican Volcanic Belt. This suggests that no major tectonic deformation occurred in studied area since early-middle Plestocene to present. The paleosecular variation is estimated trough the study of the scatter of virtual geomagnetic poles giving SF = 15.4 with SU = 19.9 and SL = 12.5 (upper and lower limits respectively). These values are consistent with those predicted by the latitude-dependent variation model of McFadden et al. (1991) for the last 5 Myr. The interesting feature of the paleomagnetic record obtained here is the occurrence of an intermediate polarity at 671± 13 ka which may correspond the worldwide observed Delta excursion at about 680-690 ka. This gives the volcanic evidence of this event. Two independent lava flows dated as 362± 13 and 354± 5 ka respectively, yield transitional paleodirections as well, probably corresponding to the Levantine excursion.

  3. Volcanic hazards of the Idaho National Engineering Laboratory and adjacent areas

    Energy Technology Data Exchange (ETDEWEB)

    Hackett, W.R. [WRH Associates, Salt Lake City, UT (United States); Smith, R.P. [Lockheed Idaho Technologies Co., Idaho Falls, ID (United States)

    1994-12-01

    Potential volcanic hazards are assessed, and hazard zone maps are developed for the Idaho National Engineering Laboratory (INEL) and adjacent areas. The basis of the hazards assessment and mapping is the past volcanic history of the INEL region, and the apparent similarity of INEL volcanism with equivalent, well-studied phenomena in other regions of active volcanism, particularly Hawaii and Iceland. The most significant hazards to INEL facilities are associated with basaltic volcanism, chiefly lava flows, which move slowly and mainly threaten property by inundation or burning. Related hazards are volcanic gases and tephra, and ground disturbance associated with the ascent of magma under the volcanic zones. Several volcanic zones are identified in the INEL area. These zones contain most of the volcanic vents and fissures of the region and are inferred to be the most probable sites of future INEL volcanism. Volcanic-recurrence estimates are given for each of the volcanic zones based on geochronology of the lavas, together with the results of field and petrographic investigations concerning the cogenetic relationships of INEL volcanic deposits and associated magma intrusion. Annual probabilities of basaltic volcanism within the INEL volcanic zones range from 6.2 {times} 10{sup {minus}5} per year (average 16,000-year interval between eruptions) for the axial volcanic zone near the southern INEL boundary and the Arco volcanic-rift zone near the western INEL boundary, to 1 {times} 10{sup {minus}5} per year (average 100,000-year interval between eruptions) for the Howe-East Butte volcanic rift zone, a geologically old and poorly defined feature of the central portion of INEL. Three volcanic hazard zone maps are developed for the INEL area: lava flow hazard zones, a tephra (volcanic ash) and gas hazard zone, and a ground-deformation hazard zone. The maps are useful in land-use planning, site selection, and safety analysis.

  4. Phreatomagmatic eruptions through unconsolidated coastal plain sequences, Maungataketake, Auckland Volcanic Field (New Zealand)

    Science.gov (United States)

    Agustín-Flores, Javier; Németh, Károly; Cronin, Shane J.; Lindsay, Jan M.; Kereszturi, Gábor; Brand, Brittany D.; Smith, Ian E. M.

    2014-04-01

    Maungataketake is a monogenetic basaltic volcano formed at ~ 85-89 ka in the southern part of the Auckland Volcanic Field (AVF), New Zealand. It comprises a basal 1100-m diameter tuff ring, with a central scoria/spatter cone and lava flows. The tuff ring was formed under hydrogeological and geographic conditions very similar to the present. The tuff records numerous density stratified, wet base surges that radiated outward up to 1 km, decelerating rapidly and becoming less turbulent with distance. The pyroclastic units dominantly comprise fine-grained expelled grains from various sedimentary deposits beneath the volcano mixed with a minor component of juvenile pyroclasts (~ 35 vol.%). Subtle lateral changes relate to deceleration with distance and vertical transformations are minor, pointing to stable explosion depths and conditions, with gradual transitions between units and no evidence for eruptive pauses. This volcano formed within and on ~ 60 m-thick Plio/Pleistocene, poorly consolidated, highly permeable shelly sands and silts (Kaawa Formation) capped by near-impermeable, water-saturated muds (Tauranga Group). These sediments rest on moderately consolidated Miocene-aged permeable turbiditic sandstones and siltstones (Waitemata Group). Magma-water fuelled thermohydraulic explosions remained in the shallow sedimentary layers, excavating fine-grained sediments without brittle fragmentation required. On the whole, the resulting cool, wet pyroclastic density currents were of low energy. The unconsolidated shallow sediments deformed to accommodate rapidly rising magma, leading to development of complex sill-like bodies and a range of magma-water contact conditions at any time. The weak saturated sediments were also readily liquefied to provide an enduring supply of water and fine sediment to the explosion loci. Changes in magma flux and/or subsequent stabilisation of the conduit area by a lava ring-barrier led to ensuing Strombolian and fire-fountaining eruption

  5. Strong responses of Southern Ocean phytoplankton communities to volcanic ash

    OpenAIRE

    Browning, T.J.; Bouman, H. A.; Henderson, G. M.; Mather, T.A.; D. M. Pyle; Schlosser, Christian; Woodward, E.M.S.; Moore, C. M.

    2014-01-01

    Volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms; however, little direct evidence of stimulatory responses has been obtained in the field. Here we present the results of twenty-one 1-2day bottle enrichment experiments from cruises in the South Atlantic and Southern Ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash. Furthermore, expe...

  6. Impact of Environmental Factors on the Spectral Characteristics of Lava Surfaces: Field Spectrometry of Basaltic Lava Flows on Tenerife, Canary Islands, Spain

    Directory of Open Access Journals (Sweden)

    Long Li

    2015-12-01

    Full Text Available We report on spectral reflectance measurements of basaltic lava flows on Tenerife Island, Spain. Lava flow surfaces of different ages, surface roughness and elevations were systematically measured using a field spectroradiometer operating in the range of 350–2500 nm. Surface roughness, oxidation and lichen coverage were documented at each measured site. Spectral properties vary with age and morphology of lava. Pre-historical lavas with no biological coverage show a prominent increase in spectral reflectance in the 400–760 nm range and a decrease in the 2140–2210 nm range. Pāhoehoe surfaces have higher reflectance values than ʻaʻā ones and attain a maximum reflectance at wavelengths < 760 nm. Lichen-covered lavas are characterized by multiple lichen-related absorption and reflection features. We demonstrate that oxidation and lichen growth are two major factors controlling spectra of Tenerife lava surfaces and, therefore, propose an oxidation index and a lichen index to quantify surface alterations of lava flows: (1 the oxidation index is based on the increase of the slope of the spectral profile from blue to red as the field-observed oxidation level strengthens; and (2 the lichen index is based on the spectral reflectance in the 1660–1725 nm range, which proves to be highly correlated with lichen coverage documented in the field. The two spectral indices are applied to Landsat ETM+ and Hyperion imagery of the study area for mapping oxidation and lichen coverage on lava surfaces, respectively. Hyperion is shown to be capable of discriminating different volcanic surfaces, i.e., tephra vs. lava and oxidized lava vs. lichen-covered lava. Our study highlights the value of field spectroscopic measurements to aid interpretation of lava flow characterization using satellite images and of the effects of environmental factors on lava surface evolution over time, and, therefore, has the potential to contribute to the mapping as well as dating

  7. Stratigraphy, geomorphology, geochemistry and hazard implications of the Nejapa Volcanic Field, western Managua, Nicaragua

    Science.gov (United States)

    Avellán, Denis Ramón; Macías, José Luis; Pardo, Natalia; Scolamacchia, Teresa; Rodriguez, Dionisio

    2012-02-01

    The Nejapa Volcanic Field (NVF) is located on the western outskirts of Managua, Nicaragua. It consists of at least 30 volcanic structures emplaced along the N-S Nejapa fault, which represents the western active edge of the Managua Graben. The study area covers the central and southern parts of the volcanic field. We document the basic geomorphology, stratigraphy, chemistry and evolution of 17 monogenetic volcanic structures: Ticomo (A, B, C, D and E); Altos de Ticomo; Nejapa; San Patricio; Nejapa-Norte; Motastepe; El Hormigón; La Embajada; Asososca; Satélite; Refinería; and Cuesta El Plomo (A and B). Stratigraphy aided by radiocarbon dating suggests that 23 eruptions have occurred in the area during the past ~ 34,000 years. Fifteen of these eruptions originated in the volcanic field between ~ 28,500 and 2,130 yr BP with recurrence intervals varying from 400 to 7,000 yr. Most of these eruptions were phreatomagmatic with minor strombolian and fissural lava flow events. A future eruption along the fault might be of a phreatomagmatic type posing a serious threat to the more than 500,000 inhabitants in western Managua.

  8. Development and relationship of monogenetic and polygenetic volcanic fields in time and space.

    Science.gov (United States)

    Germa, Aurelie; Connor, Chuck; Connor, Laura; Malservisi, Rocco

    2013-04-01

    The classification of volcanic systems, developed by G. P. L. Walker and colleagues, relates volcano morphology to magma transport and eruption processes. In general, distributed monogenetic volcanic fields are characterized by infrequent eruptions, low average output rate, and a low spatial intensity of the eruptive vents. In contrast, central-vent-dominated systems, such as stratovolcanoes, central volcanoes and lava shields are characterized by frequent eruptions, higher average flux rates, and higher spatial intensity of eruptive vents. However, it has been observed that a stratovolcano is often associated to parasitic monogenetic vents on its flanks, related to the central silicic systems, and surrounded by an apron of monogenetic edifices that are part of the volcanic field but independent from the principal central system. It appears from spatial distribution and time-volume relationships that surface area of monogenetic fields reflects the lateral extent of the magma source region and the lack of magma focusing mechanisms. In contrast, magma is focused through a unique conduit system for polygenetic volcanoes, provided by a thermally and mechanically favorable pathway toward the surface that is maintained by frequent and favorable stress conditions. We plan to relate surface observations of spatio-temporal location of eruptive vents and evolution of the field area through time to processes that control magma focusing during ascent and storage in the crust. We choose to study fields that range from dispersed to central-vent dominated, through transitional fields (central felsic system with peripheral field of monogenetic vents independent from the rhyolitic system). We investigate different well-studied volcanic fields in the Western US and Western Europe in order to assess influence of the geodynamic setting and tectonic stress on the spatial distribution of magmatism. In summary, incremental spatial intensity maps should reveal how fast a central conduit

  9. 准噶尔盆地春晖油田石炭系火山岩储层控制因素分析%Controlling factors of the Carboniferous volcanic reservoirs in the Chunhui Oil Field, Junggar Basin

    Institute of Scientific and Technical Information of China (English)

    董臣强

    2014-01-01

    春晖油田石炭系火山岩地层中,油气富集程度与储层发育程度呈正相关关系。研究认为,储层的发育与分布主要受岩相、岩性和构造运动的控制。岩相控制岩性,岩性控制储集空间组合类型,溢流相和火山沉积相围绕爆发相具有环带状分布特点,从火山角砾岩→玄武岩、安山岩→凝灰岩,储集性能逐渐变差;构造运动则控制裂缝的发育及溶蚀作用,断层周边微裂缝发育,沿着微裂缝则溶蚀作用增强,次生孔隙发育。%The Chunhui Oil Field in the Junggar Basin lies in the western part of the Halaalate Mountain tectonic zone, in which the Carboniferous volcanic strata consist dominantly of the volcanic rocks such as tuff, andesite, basalt and volcanic breccias. There is a positive correlation between the hydrocarbon enrichment and reservoir development in the Carboniferous volcanic reservoir rocks from the Chunhui Oil Field. The distribution and development of the volcanic reservoir rocks are primarily controlled by lithofacies, lithology and tectonism. On the whole, the lithofacies may exercise a major control on lithology of the volcanic reservoir rocks, which, in turn, may control the reservoir spaces types. The volcanic rocks in the Chunhui Oil Field exhibit a trend of the girdle pattern of lithofacies changes from the explosive facies through the effusive facies to the volcano-sedimentary facies. The reservoir capacity is gradually getting poor and poor from volcanic breccias to basalt and andesite and finally to tuff. The tectonism is also believed to be a major control on the fissure development and dissolution. The structural stress may give rise to the formation of the cracks or fissures in the brittle rocks, which may greatly improve the reservoir spaces of the Carboniferous volcanic reservoir rocks in the study area.

  10. Interpreting chemical compositions of small scale basaltic systems: A review

    Science.gov (United States)

    McGee, Lucy E.; Smith, Ian E. M.

    2016-10-01

    Small scale basaltic magmatic systems occur in all of the major tectonic environments of planet Earth and are characteristically expressed at the Earth's surface as fields of small monogenetic cones. The chemical compositions of the materials that make up these cones reflect processes of magma generation and differentiation that occur in their plumbing system. The volumes of magmas involved are very small and significantly their compositional ranges reveal remarkably complex processes which are overwhelmed or homogenized in larger scale systems. Commonly, compositions are basaltic, alkalic and enriched in light rare earth elements and large ion lithophile elements, although the spectrum extends from highly enriched nephelinites to subalkalic and tholeiitic basalts. Isotopic analyses of rocks from volcanic fields almost always display compositions which can only be explained by the interaction of two or more mantle sources. Ultimately their basaltic magmas originate by small scale melting of mantle sources. Compositional variety is testament to melting processes at different depths, a range of melting proportions, a heterogeneous source and fractionation, magma mixing and assimilation within the plumbing system that brings magmas to the surface. The fact that such a variety of compositions is preserved in a single field shows that isolation of individual melting events and their ascent is an important and possibly defining feature of monogenetic volcanism, as well as the window their chemical behavior provides into the complex process of melt generation and extraction in the Earth's upper mantle.

  11. Volcanism and Oil & Gas In Northeast China

    Institute of Scientific and Technical Information of China (English)

    Shan Xuanlong

    2000-01-01

    Based on study on the relation with volcanic rock and oil & gas in Songliao Basin and Liaohe Basin in northeast China, author proposes that material from deep by volcanism enrichs the resources in basins, that heat by volcanism promotes organic matter transforming to oil and gas, that volcanic reservoir is fracture, vesicular, solution pore, intercrystal pore.Lava facies and pyroclastic facies are favourable reservoir. Mesozoic volcanic reservoir is majority of intermediate, acid rock,but Cenozoic volcanic reservoir is majority of basalt. Types of oil and gas pool relating to volcanic rock include volcanic fracture pool, volcanic unconformity pool, volcanic rock - screened pool, volcanic darpe structural pool.

  12. Bimodal basalt-rhyolite magmatism in the central and western Snake River Plain, Idaho and Oregon

    Science.gov (United States)

    McCurry, M.; Bonnichsen, B.; White, C.; Godchaux, M.M.; Hughes, S.S.

    1997-01-01

    The purpose of this trip is to examine Miocene to Pleistocene basalt and rhyolite flows, ignimbrites and hypabyssal intrusions in a transect from the western Snake River Plain graben across the older part of the Snake River Plain "hot-spot-track." The earlier, dominantly explosive rhyolitic phase of volcanism will be examined primarily in the Cassia Mountains, near Twin Falls, Idaho. The second day of the field trip will focus on the Graveyard Point intrusion, a strongly differentiated diabase sill in easternmost Oregon. This late Tertiary sill is well exposed from floor to roof in sections up to 150 m thick, and is an example of the type of solidified shallow magma chamber that may be present beneath some Snake River Plain basalt volcanoes. The field trip will conclude with an examination of the diverse styles of effusive and explosive basaltic volcanism in the central and western Snake River Plain.

  13. Geologic Investigations Spurred by Analog Testing at the 7504 Cone-Sp Mountain Area of the San Francisco Volcanic Field

    Science.gov (United States)

    Bleacher, J. E.; Eppler, D. B.; Needham, D. H.; Evans, C. A.; Skinner, J. A.; Feng, W.

    2015-12-01

    The SP Mountain area of the San Francisco Volcanic Field, AZ, has been used as an analog mission development site for NASA since 1998. This area consists of basaltic cinder cones, lava flows and maar craters that have been active since mid-Miocene, with the youngest events occurring within the last 10,000 years. The area has been used because its geologic and topographic resemblance to lunar and Martian terrains provides an ideal venue for testing hardware and science operations practices that might be employed on planetary surfaces, as well as training astronauts in field geology. Analog operations have often led to insights that spurred new scientific investigations. Most recently, an investigation of the 7504 cone was initiated due to perceptions that Apollo-style traverse plans executed during the Desert RATS 2010 mission had characterized the area incorrectly, leading to concerns that the Apollo traverse planning process was scientifically flawed. This investigation revealed a complex history of fissure eruptions of lava and cinders, cinder cone development, a cone-fill-and-spill episode, extensive rheomorphic lava flow initiation and emplacement, and cone sector collapse that led to a final lava flow. This history was not discernible on pre-RATS mission photogeology, although independent analysis of RATS 2010 data and samples develped a "75% complete solution" that validated the pre-RATS mission planning and Apollo traverse planning and execution. The study also pointed out that the development of scientific knowledge with time in a given field area is not linear, but may follow a functional form that rises steeply in the early period of an investigation but flattens out in the later period, asymptotically approaching a theoretical "complete knowledge" point that probably cannot be achieved. This implies that future human missions must be prepared to shift geographic areas of investigation regularly if significant science returns are to be forthcoming.

  14. Rheology and Morphology of a Trachybasaltic Lava Flow: a Case Study from the Cima Volcanic Field (CA)

    Science.gov (United States)

    Soldati, A.; Beem, J. R.; Robertson, T.; Gomez, F. G.; Whittington, A. G.

    2015-12-01

    Subliquidus rheology of a trachybasaltic lava was measured in the laboratory for the first time. Field observations of the parent flow focused on surface morphology characterization, which was later quantified in terms of surface roughness. The studied lava flow was emitted during the Holocene by a monogenetic cinder cone in the Cima Volcanic Field (CA). Surface morphology transitions from smooth pahoehoe ropes near the vent to jagged `a`a blocks over the majority of the flow. A variety of 2 m2 outcrops were photographed using a hand-held DSLR camera, and their surface texture was reconstructed with photogrammetry. The roughness of each outcrop, effectively described by the standard deviation between the real photogrammetric point cloud and the best-fitting surface, was quantified at different spatial scales, ranging from 0.5 cm to 200 m. We found that the roughness of the flow increases linearly as spatial resolution decreases, with a slope break corresponding to the average size of the outcrop lava blocks. The rheology of Cima lavas was determined by concentric cylinder viscometry in the 1220 °C to 1160 °C temperature range. The obtained rheological flow curves indicate a Bingham rheology, with clearly detected yield strength ranging from 25 Pa at the higher temperatures up to 650 Pa at the lower temperatures. Plagioclase crystallization begins at 1170 °C, likely playing a key role in promoting yield strength escalation. Viscosity increases by one order of magnitude (from 94 to 1116 Pa·s) over the 60 °C span of cooling considered, remaining consistently lower than most basaltic melts due to the high alkali content (6 wt%). The rheological and morphological results are being integrated, in order to assess if it is possible to identify the rheological fingerprint of the active flow on the preserved flow morphology. The composition-dependence of the morphological pahoehoe to `a`a transition in a rheological map is being assessed by comparing our results to

  15. CO{sub 2} mineral trapping: an experimental study on the carbonation of basalts from the eastern Deccan Volcanic Province, India

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Nishi; Pathak, Vamdev; Shrivastava, J.P. [Department of Geology, University of Delhi, Delhi 110007 (India)

    2013-07-01

    Rock specimens from Deccan flood basalts have been reacted in the laboratory under high pCO{sub 2} (5 and 10 bars), total pressure (vessel pressure between 10 and 20 bars), and temperature (100 and 200 deg. C) conditions for 50, 60, 70, and 80 hours. XRD and SEM-EDS analyses show that calcite, aragonite, siderite and magnesite, and clays are derived from the alteration of Deccan basalts under water-saturated, hydrothermal-like conditions. Alteration reactions were accompanied by significant variation in the pH of the reacting aqueous solution, dependent upon time, pCO{sub 2}, and temperature variables of the experiment. Neo-formed secondary products also include significant amounts of smectite, chlorite, and smectite/chlorite mixed layer clays. (authors)

  16. A field investigation of the basaltic ring structures of the Channeled Scabland and the relevance to Mars

    Science.gov (United States)

    Kestay, Laszlo P.; Jaeger, Windy L.

    2015-01-01

    The basaltic ring structure (BRS) is a class of peculiar features only reported in the Channeled Scabland of eastern Washington State. They have been suggested to be good analogs, however, for some circular features on Mars. BRSs are found where Pleistocene floods scoured the Columbia River Basin, stripping off the uppermost part of the Miocene Columbia River Basalt Group and exposing structures that were previously embedded in the lava. The “Odessa Craters,” near Odessa, WA, are 50–500-m-wide BRSs that are comprised of discontinuous, concentric outcrops of subvertically-jointed basalt and autointrusive dikes. Detailed field investigation of the Odessa Craters in planform and a cross-sectional exposure of a similar structure above Banks Lake, WA, lead us to propose that BRSs formed by concurrent phreatovolcanism and lava flow inflation. In this model, phreatovolcanic (a.k.a., “rootless”) cones formed on a relatively thin, active lava flow; the lava flow inflated around the cones, locally inverting topography; tensile stresses caused concentric fracturing of the lava crust; lava from within the molten interior of the flow exploited the fractures and buried the phreatovolcanic cones; and subsequent erosive floods excavated the structures. Another population of BRSs near Tokio Station, WA, consists of single-ringed, raised-rimmed structures that are smaller and more randomly distributed than the Odessa Craters. We find evidence for a phreatovolcanic component to the origin as well, and hypothesize that they are either flood-eroded phreatovolcanic cones or Odessa Crater-like BRSs. This work indicates that BRSs are not good analogs to the features on Mars because the martian features are found on the uneroded surfaces. Despite this, the now superseded concepts for BRS formation are useful for understanding the formation of the martian features.

  17. Spurious behavior in volcanic records of geomagnetic field reversals

    Science.gov (United States)

    Carlut, Julie; Vella, Jerome; Valet, Jean-Pierre; Soler, Vicente; Legoff, Maxime

    2016-04-01

    Very large directional variations of magnetization have been reported in several lava flows recording a geomagnetic reversal. Such behavior could reflect real geomagnetic changes or be caused by artifacts due to post-emplacement alteration and/or non-ideal magnetic behavior. More recently, a high resolution paleomagnetic record from sediments pleads also for an extremely rapid reversal process during the last reversal. Assuming that the geomagnetic field would have moved by tens of degrees during cooling of moderate thickness lava flows implies brief episodes of rapid changes by a few degrees per day that are difficult to reconcile with the rate of liquid motions at the core surface. Systematical mineralogical bias is a most likely explanation to promote such behavior as recently reconsidered by Coe et al., 2014 for the rapid field changes recorded at Steens Mountain. We resampled three lava flows at La Palma island (Canarias) that are sandwiched between reverse polarity and normal polarity flows associated with the last reversal. The results show an evolution of the magnetization direction from top to bottom. Thermal demagnetization experiments were conducted using different heating and cooling rates. Similarly, continuous demagnetization and measurements. In both cases, we did not notice any remagnetization associated with mineralogical transformations during the experiments. Magnetic grain sizes do not show any correlation with the amplitude of the deviations. Microscopic observations indicate poor exsolution, which could suggests post-cooling thermochemical remagnetization processes.

  18. Basalt: Biologic Analog Science Associated with Lava Terrains

    Science.gov (United States)

    Lim, D. S. S.; Abercromby, A.; Kobs-Nawotniak, S. E.; Kobayashi, L.; Hughes, S. S.; Chappell, S.; Bramall, N. E.; Deans, M. C.; Heldmann, J. L.; Downs, M.; Cockell, C. S.; Stevens, A. H.; Caldwell, B.; Hoffman, J.; Vadhavk, N.; Marquez, J.; Miller, M.; Squyres, S. W.; Lees, D. S.; Fong, T.; Cohen, T.; Smith, T.; Lee, G.; Frank, J.; Colaprete, A.

    2015-12-01

    This presentation will provide an overview of the BASALT (Biologic Analog Science Associated with Lava Terrains) program. BASALT research addresses Science, Science Operations, and Technology. Specifically, BASALT is focused on the investigation of terrestrial volcanic terrains and their habitability as analog environments for early and present-day Mars. Our scientific fieldwork is conducted under simulated Mars mission constraints to evaluate strategically selected concepts of operations (ConOps) and capabilities with respect to their anticipated value for the joint human and robotic exploration of Mars. a) Science: The BASALT science program is focused on understanding habitability conditions of early and present-day Mars in two relevant Mars-analog locations (the Southwest Rift Zone (SWRZ) and the East Rift Zone (ERZ) flows on the Big Island of Hawai'i and the eastern Snake River Plain (ESRP) in Idaho) to characterize and compare the physical and geochemical conditions of life in these environments and to learn how to seek, identify, and characterize life and life-related chemistry in basaltic environments representing these two epochs of martian history. b) Science Operations: The BASALT team will conduct real (non-simulated) biological and geological science at two high-fidelity Mars analogs, all within simulated Mars mission conditions (including communication latencies and bandwidth constraints) that are based on current architectural assumptions for Mars exploration missions. We will identify which human-robotic ConOps and supporting capabilities enable science return and discovery. c) Technology: BASALT will incorporate and evaluate technologies in to our field operations that are directly relevant to conducting the scientific investigations regarding life and life-related chemistry in Mars-analogous terrestrial environments. BASALT technologies include the use of mobile science platforms, extravehicular informatics, display technologies, communication

  19. Role of crustal assimilation and basement compositions in the petrogenesis of differentiated intraplate volcanic rocks: a case study from the Siebengebirge Volcanic Field, Germany

    Science.gov (United States)

    Schneider, K. P.; Kirchenbaur, M.; Fonseca, R. O. C.; Kasper, H. U.; Münker, C.; Froitzheim, N.

    2016-06-01

    The Siebengebirge Volcanic Field (SVF) in western Germany is part of the Cenozoic Central European Volcanic Province. Amongst these volcanic fields, the relatively small SVF comprises the entire range from silica-undersaturated mafic lavas to both silica-undersaturated and silica-saturated differentiated lavas. Owing to this circumstance, the SVF represents a valuable study area representative of intraplate volcanism in Europe. Compositions of the felsic lavas can shed some new light on differentiation of intraplate magmas and on the extent and composition of potential crustal assimilation processes. In this study, we provide detailed petrographic and geochemical data for various differentiated SVF lavas, including major and trace element concentrations as well as Sr-Nd-Hf-Pb isotope compositions. Samples include tephriphonolites, latites, and trachytes with SiO2 contents ranging between 53 and 66 wt%. If compared to previously published compositions of mafic SVF lavas, relatively unradiogenic 143Nd/144Nd and 176Hf/177Hf coupled with radiogenic 87Sr/86Sr and 207Pb/204Pb lead to the interpretation that the differentiated volcanic rocks have assimilated significant amounts of lower crustal mafic granulites like the ones found as xenoliths in the nearby Eifel volcanic field. These crustal contaminants should possess unradiogenic 143Nd/144Nd and 176Hf/177Hf, radiogenic 87Sr/86Sr, and highly radiogenic 207Pb/204Pb compositions requiring the presence of ancient components in the central European lower crust that are not sampled on the surface. Using energy-constrained assimilation-fractional crystallisation (EC-AFC) model calculations, differentiation of the SVF lithologies can be modelled by approximately 39-47 % fractional crystallisation and 6-15 % crustal assimilation. Notably, the transition from silica-undersaturated to silica-saturated compositions of many felsic lavas in the SVF that is difficult to account for in closed-system models is also well explained by

  20. Records of magmatic change as preserved in zircon: examples from the Yellowstone Volcanic Field

    Science.gov (United States)

    Rivera, T. A.

    2015-12-01

    Zircon crystals have been used as proxies for their host magmatic composition and as records of the evolution and differentiation of silicic magma systems through the use of integrated techniques such as cathodoluminescence imaging, LA-ICPMS trace element analysis, thermometry, and high-precision CA-IDTIMS U/Pb dating. This petrochronologic approach can aid in identifying crystal populations arising from discrete pulses of magmatism, reconstructing the growth histories of those populations, quantifying the chemical evolution of the host magma, and determining the timing and tempo of that chemical evolution. The Yellowstone Volcanic Field hosts both large and small volume silicic eruptions whose zircon records can provide insights to magmatic processes using a petrochronologic approach. Morphological and thermochemical trends preserved in zircon grains extracted from the three Yellowstone super-eruptions and a small volume precursory eruption indicate that magmatism in the volcanic field is punctuated, characterized by numerous pulses of melting, differentiation, and solidification occurring prior to eruption. U/Pb zircon dating constrains magma assembly to geologically short timescales, with populations of earlier solidified zircon incorporated into the nascent magma just prior to eruption. This requires punctuated intervals of high magmatic flux be superimposed on longer durations of a much lower background flux. Thus super-eruptions within the Yellowstone Volcanic Field result from rapid production and evolution of magma, and preceded by periods of smaller volume magma production that undergo similar differentiation processes over comparable timescales.

  1. The Lathrop Wells volcanic center: Status of field and geochronology studies

    International Nuclear Information System (INIS)

    The purpose of this paper is to describe the status of field and geochronology studies of the Lathrop Wells volcanic center. Our perspective is that it is critical to assess all possible methods for obtaining cross-checking data to resolve chronology and field problems. It is equally important to consider application of the range of chronology methods available in Quaternary geologic research. Such an approach seeks to increase the confidence in data interpretations through obtaining convergence among separate isotopic, radiogenic, and age-correlated methods. Finally, the assumptions, strengths, and weaknesses of each dating method need to be carefully described to facilitate an impartial evaluation of results. The paper is divided into two parts. The first part describes the status of continuing field studies for the volcanic center for this area south of Yucca Mountain, Nevada. The second part presents an overview of the preliminary results of ongoing chronology studies and their constraints on the age and stratigraphy of the Lathrop Wells volcanic center. Along with the chronology data, the assumptions, strengths, and limitations of each methods are discussed

  2. Geochemistry of quaternary volcanism in the Sunda-Banda arc, Indonesia, and three-component genesis of island-arc basaltic magmas

    Science.gov (United States)

    Wheller, G. E.; Varne, R.; Foden, J. D.; Abbott, M. J.

    1987-06-01

    Volcanic rocks of the Sunda and Banda arcs range from tholeiitic through calcalkaline and shoshonitic to leucititic, the widest compositional span of mafic magmatism known from an active arc setting. Mafic rocks in our data set, which includes 315 new analyses of volcanic rocks from twelve Quaternary volcanoes, including Batu Tara in the previously geochemically unknown Flores-Lembata arc sector, are generally similar to those from other island arcs: most contain Flores arc sectors each comprise volcanoes which become progressively more K-rich eastwards, culminating in the leucitite volcanoes Muriah, Soromundi and Sangenges, and Batu Tara, respectively. In the most easterly Banda sector, the volcanics vary from high- to low-K eastwards around the arc. Correlations between geochemistry and 87Sr/ 86Sr values show separate trends for each of the four arc sectors, believed to be the result of involvement of at least three geochemically and isotopically distinct components in the source regions of the arc magmatism. A dominant source component with a low K content and a low 87Sr/ 86Sr value, and common to all sectors, is probably peridotitic mantle. A second component, with low K content but high 87Sr/ 86Sr value, appears to be crustal material. This component is most apparent in the Banda sector, in keeping with that sector's tectonic setting close to Precambrian Australian continental crust, but it is also present to lesser extents in the West Java and Flores sectors. However, the most marked geochemical and isotopic variations shown by the arc volcanics are primarily due to the involvement of a third component, which is rich in K-group elements but has relatively low 87Sr/ 86Sr values. This component appears to be mantle-derived and is least overprinted by crustal material in the Bali sector volcanics where the Pb, Be, U-Th and O isotope characteristics of the rocks support the suggestion that their genesis has not involved incorporation of recently subducted

  3. Spatial and Alignment Analyses for a field of Small Volcanic Vents South of Pavonis Mons Mars

    Science.gov (United States)

    Bleacher, J. E.; Glaze, L. S.; Greeley, R.; Hauber, E.; Baloga, S. M.; Sakimoto, S. E. H.; Williams, D. A.; Glotch, T. D.

    2008-01-01

    The Tharsis province of Mars displays a variety of small volcanic vent (10s krn in diameter) morphologies. These features were identified in Mariner and Viking images [1-4], and Mars Orbiter Laser Altimeter (MOLA) data show them to be more abundant than originally observed [5,6]. Recent studies are classifying their diverse morphologies [7-9]. Building on this work, we are mapping the location of small volcanic vents (small-vents) in the Tharsis province using MOLA, Thermal Emission Imaging System, and High Resolution Stereo Camera data [10]. Here we report on a preliminary study of the spatial and alignment relationships between small-vents south of Pavonis Mons, as determined by nearest neighbor and two-point azimuth statistical analyses. Terrestrial monogenetic volcanic fields display four fundamental characteristics: 1) recurrence rates of eruptions,2 ) vent abundance, 3) vent distribution, and 4) tectonic relationships [11]. While understanding recurrence rates typically requires field measurements, insight into vent abundance, distribution, and tectonic relationships can be established by mapping of remotely sensed data, and subsequent application of spatial statistical studies [11,12], the goal of which is to link the distribution of vents to causal processes.

  4. Shallow magma chamber under the Wudalianchi Volcanic Field unveiled by seismic imaging with dense array

    Science.gov (United States)

    Li, Zhiwei; Ni, Sidao; Zhang, Baolong; Bao, Feng; Zhang, Senqi; Deng, Yang; Yuen, David A.

    2016-05-01

    The Wudalianchi Volcano Field (WDF) is a typical intraplate volcano in northeast China with generation mechanism not yet well understood. As its last eruption was around 300 years ago, the present risk for volcano eruption is of particular public interest. We have carried out a high-resolution ambient noise tomography to investigate the location of magma chambers beneath the volcanic cones with a dense seismic array of 43 seismometers and ~ 6 km spatial interval. Significant low-velocity anomalies up to 10% are found at 7-13 km depth under the Weishan volcano, consistent with the pronounced high electrical-conductivity anomalies from previous magnetotelluric survey. We propose these extremely low velocity anomalies can be interpreted as partial melting in a shallow magma chamber with volume at least 200 km3 which may be responsible for most of the recent volcanic eruptions in WDF. Therefore, this magma chamber may pose a serious hazard for northeast China.

  5. Episodic soil succession on basaltic lava fields in a cool, dry environment

    Science.gov (United States)

    Vaughan, K.L.; McDaniel, P.A.; Phillips, W.M.

    2011-01-01

    Holocene- to late Pleistocene-aged lava flows at Craters of the Moon National Monument and Preserve provide an ideal setting to examine the early stages of soil formation under cool, dry conditions. Transects were used to characterize the amount and nature of soil cover on across basaltic lava flows ranging in age from 2.1 to 18.4 ka. Results indicate that on flows <13 ka, very shallow organic soils (Folists in Soil Taxonomy) are the dominant soil type, providing an areal coverage of up to ∼25%. On flows ≥13.9 ka, deeper mineral soils including Entisols, Aridisols, and Mollisols become dominant and the areal extent increases to ≥95% on flows older than 18.4 ka. These data suggest there are two distinct pedogenic pathways associated with lava flows of the region. The first pathway is illustrated by the younger flows, where Folists dominate. In the absence of a major source of loess, relatively little mineral material accumulates and soils provide only minor coverage of the lava flows. Our results indicate that this pathway of soil development has not changed appreciably over the past ∼10 ka. The second pedogenic pathway is illustrated by the flows older than 13.9 ka. These flows have been subject to deposition of large quantities of loess during and after the last regional glaciation, resulting in almost complete coverage. Subsequent pedogenesis has given rise to Aridisols and Mollisols with calcic and cambic horizons and mollic epipedons. This research highlights the importance of regional climate change on the evolution of Craters of the Moon soilscapes.

  6. Subsurface fluid distribution and possible seismic precursory signal at the Salse di Nirano mud volcanic field, Italy

    OpenAIRE

    Lupi, Matteo; Suski Ricci, Barbara; Kenkel, Johannes; Ricci, Tullio; Fuchs, Florian; Miller, Stephen A.; Kemna, Andreas

    2016-01-01

    Mud volcanoes are geological systems often characterized by elevated fluid pressures at depth deviating from hydrostatic conditions. This near-critical state makes mud volcanoes particularly sensitive to external forcing induced by natural or man-made perturbations. We used the Nirano mud volcanic field as a natural laboratory to test pre- and post-seismic effects generated by distant earthquakes. We first characterized the subsurface structure of the Nirano mud volcanic field with a geoelect...

  7. Geomorphometric analysis of the scoria cones of the San Francisco Volcanic Field using polar coordinate transformation

    Science.gov (United States)

    Vörös, Fanni; Koma, Zsófia; Karátson, Dávid; Székely, Balázs

    2016-04-01

    Scoria cones are often studied using geomorphometric and traditional GIS methods, e.g. aspect, slope histograms, area, cone height/width ratio. In order to enhance the non-symmetric shape components in contrast to the conical forms, we used a new approach in our research: the polar coordinate transformation (PCT) introduced by Székely & Karátson (2004). The study area is the classic cluster of scoria cones at the San Francisco Volcanic Field (SFVF) encompassing roughly 600 scoria cones as well as the San Francisco stratovolcano. Our goal is to analyse the even slight asymmetric shape of the scoria cones, and to generalize our findings. The area is a well-studied volcanic field, with a great number of available geological and geomorphological information, so comparing our PCT results with the data in literature is feasible. Polar coordinate transformation, being a one-to-one transformation, maps the original Cartesian coordinates (X, Y in meters) to radial distance (m) and azimuth (°) values. Our inputs were digitized polygons. We created images in the transformed coordinate system that clearly show the asymmetrical shape of the scoria cones. This asymmetry is found to be related to some extent to denudation, and to the age of the volcanic edifice that correlates with differential erosion. However, original asymmetries related to formation (e.g. rifting, emplacement on slope, eruption variations etc.) are also reasonable. The applied technique allows to define new derivatives of volcano-geomorphological parameters. The resultant scoria cone patterns have been manually categorized, however, the results are suitable for automated classification which is our next purpose. BSz contributed as an Alexander von Humboldt Research Fellow. Székely, B. & Karátson, D. (2004): DEM-based morphometry as a tool for reconstructing primary volcanic landforms: examples from the Börzsöny Mountains, Hungary, Geomorphology 63:25-37.

  8. Boundary of the southwestern Nevada volcanic field from Laczniak and others (1996), for the Death Valley regional ground-water flow system study, Nevada and California

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This digital data set defines the boundary of the southwestern Nevada volcanic field (SWNVF), an area of thick, regionally distributed volcanic rocks within the...

  9. Payenia volcanic province, southern Mendoza, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin; Llambias, Eduardo Jorge

    2013-01-01

    to the low thickness of the lithospheric mantle and preheating of the lower crust by earlier Mio-Pliocene volcanism. Rare earth element modelling of mantle melting calls for enriched source compositions and a beginning of melting within the garnet stability field for all Payenia basalts. The Río Colorado......The Pleistocene to Holocene Payenia volcanic province is a backarc region of 60,000 km2 in Mendoza, Argentina, which is dominated by transitional to alkaline basalts and trachybasalts. We present major and trace element compositions of 139 rocks from this area of which the majority are basaltic...... rocks with 4 to 12 wt.% MgO and 44 to 50 wt.% SiO2. The southern Payenia province is dominated by intraplate basalts and the trace element patterns of the Río Colorado and Payún Matrú lavas suggest little or no influence from subducted slab components. The mantle source of these rocks is similar to some...

  10. Mechanisms of low-flux intraplate volcanic fields - Basin and Range and Northwest Pacific Ocean

    Science.gov (United States)

    Valentine, G.; Hirano, N.

    2009-05-01

    Many fields of small-volume, scattered volcanoes that typically have alkaline affinities occur in intraplate settings. The underlying mechanisms of these intraplate volcanoes are enigmatic; they often do not correlate with anomalous heat sources or upwelling mantle (as in hot spots, mid-ocean ridges, and active continental rifts), or with fluids introduced by actively-subducting lithosphere. We compare the characteristics of two low volume-flux intraplate volcanic fields, one in a continental setting that is characterized by slow extension (western U.S.A.), and the other on the floor of the northwest Pacific Ocean in a region of plate flexure. The comparison supports an interpretation that the fundamental driving mechanism for low magma-flux volcanic fields, which episodically erupt scattered, small-volume volcanoes over millions of years, is regional-scale deformation of compositionally-heterogeneous upper mantle. Deformation serves to mechanically focus partial melts that might be present due to locally-depressed solidus temperatures caused by slightly higher volatile contents, creating sufficient melt buoyancy to trigger magma ascent via magma-driven fractures (dikes). The key role of deformation in collecting magmas and triggering dike ascent and eruption, without influx of new material or heat into the source region, supports the definition of such systems as tectonically-controlled, and is likely applicable at other low-flux, diffuse volcanic fields. Differences in the degree of fractionation and wall-rock contamination in the two fields is related to vertical variations in principal-stress orientation that may cause stalling of ascending dikes.

  11. Transition of basaltic lava from pahoehoe to aa, Kilauea Volcano, Hawaii: Field observations and key factors

    Science.gov (United States)

    Peterson, D.W.; Tilling, R.I.

    1980-01-01

    Nearly all Hawaiian basaltic lava erupts as pahoehoe, and some changes to aa during flowage and cooling; factors governing the transition involve certain critical relations between viscosity and rate of shear strain. If the lava slows, cools, and stops in direct response to concomitant increase in viscosity before these critical relations are reached, it remains pahoehoe. But, if flow mechanics (flow rate, flow dimensions, slope, momentum, etc.) impel the lava to continue to move and deform even after it has become highly viscous, the critical relations may be reached and the lava changes to aa. Typical modes of transition from pahoehoe to aa include: (1) spontaneous formation of relatively stiff clots in parts of the flowing lava where shear rate is highest; these clots grow into discrete, rough, sticky masses to which the remaining fluid lava incrementally adheres; (2) fragmentation and immersion of solid or semi-solid surface crusts of pahoehoe by roiling movements of the flow, forming cores of discrete, tacky masses; (3) sudden renewed movement of lava stored and cooled within surface reservoirs to form clots. The masses, fragments, and clots in these transition modes are characterized by spinose, granulated surfaces; as flow movement continues, the masses and fragments aggregate, fracture, and grind together, completing the transition to aa. Observations show that the critical relation between viscosity and rate of shear strain is inverse: if viscosity is low, a high rate of shear is required to begin the transition to aa; conversely, if viscosity is high, a much lower rate of shear will induce the transition. These relations can be demonstrated qualitatively with simple graphs, which can be used to examine the flow history of any selected finite lava element by tracing the path represented by its changing viscosity and shear rate. A broad, diffuse "transition threshold zone" in these graphs portrays the inverse critical relation between viscosity and shear

  12. Cambrian intermediate-mafic magmatism along the Laurentian margin: Evidence for flood basalt volcanism from well cuttings in the Southern Oklahoma Aulacogen (U.S.A.)

    Science.gov (United States)

    Brueseke, Matthew E.; Hobbs, Jasper M.; Bulen, Casey L.; Mertzman, Stanley A.; Puckett, Robert E.; Walker, J. Douglas; Feldman, Josh

    2016-09-01

    The Southern Oklahoma Aulocogen (SOA) stretches from southern Oklahoma through the Texas panhandle and into Colorado and New Mexico, and contains mafic through silicic magmatism related to the opening of the Iapetus Ocean during the early Cambrian. Cambrian magmatic products are best exposed in the Wichita Mountains (Oklahoma), where they have been extensively studied. However, their ultimate derivation is still somewhat contentious and centers on two very different models: SOA magmatism has been suggested to occur via [1] continental rifting (with or without mantle plume emplacement) or [2] transform-fault related magmatism (e.g., leaky strike-slip faults). Within the SOA, the subsurface in and adjacent to the Arbuckle Mountains in southern Oklahoma contains thick sequences of mafic to intermediate lavas, intrusive bodies, and phreatomagmatic deposits interlayered with thick, extensive rhyolite lavas, thin localized tuffs, and lesser silicic intrusive bodies. These materials were first described in the Arbuckle Mountains region by a 1982 drill test (Hamilton Brothers Turner Falls well) and the best available age constraints from SOA Arbuckle Mountains eruptive products are ~ 535 to 540 Ma. Well cuttings of the mafic through intermediate units were collected from that well and six others and samples from all but the Turner Falls and Morton wells are the focus of this study. Samples analyzed from the wells are dominantly subalkaline, tholeiitic, and range from basalt to andesite. Their overall bulk major and trace element chemistry, normative mineralogy, and Srsbnd Nd isotope ratios are similar to magmas erupted/emplaced in flood basalt provinces. When compared with intrusive mafic rocks that crop out in the Wichita Mountains, the SOA well cuttings are geochemically most similar to the Roosevelt Gabbros. New geochemical and isotope data presented in this study, when coupled with recent geophysical work in the SOA and the coeval relationship with rhyolites, indicates

  13. Field and experimental constraints on the rheology of arc basaltic lavas: the January 2014 Eruption of Pacaya (Guatemala)

    Science.gov (United States)

    Soldati, A.; Sehlke, A.; Chigna, G.; Whittington, A.

    2016-06-01

    We estimated the rheology of an active basaltic lava flow in the field, and compared it with experimental measurements carried out in the laboratory. In the field we mapped, sampled, and recorded videos of the 2014 flow on the southern flank of Pacaya, Guatemala. Velocimetry data extracted from videos allowed us to determine that lava traveled at ˜2.8 m/s on the steep ˜45° slope 50 m from the vent, while 550 m further downflow it was moving at only ˜0.3 m/s on a ˜4° slope. Estimates of effective viscosity based on Jeffreys' equation increased from ˜7600 Pa s near the vent to ˜28,000 Pa s downflow. In the laboratory, we measured the viscosity of a representative lava composition using a concentric cylinder viscometer, at five different temperatures between 1234 and 1199 °C, with crystallinity increasing from 0.1 to 40 vol%. The rheological data were best fit by power law equations, with the flow index decreasing as crystal fraction increased, and no detectable yield strength. Although field-based estimates are based on lava characterized by a lower temperature, higher crystal and bubble fraction, and with a more complex petrographic texture, field estimates and laboratory measurements are mutually consistent and both indicate shear-thinning behavior. The complementary field and laboratory data sets allowed us to isolate the effects of different factors in determining the rheological evolution of the 2014 Pacaya flows. We assess the contributions of cooling, crystallization, and changing ground slope to the 3.7-fold increase in effective viscosity observed in the field over 550 m, and conclude that decreasing slope is the single most important factor over that distance. It follows that the complex relations between slope, flow velocity, and non-Newtonian lava rheology need to be incorporated into models of lava flow emplacement.

  14. Age discrimination among basalt flows using digitally enhanced LANDSAT imagery. [Saudi Arabia

    Science.gov (United States)

    Blodget, H. W.; Brown, G. F.

    1984-01-01

    Digitally enhanced LANDSAT MSS data were used to discriminate among basalt flows of historical to Tertiary age, at a test site in Northwestern Saudi Arabia. Spectral signatures compared favorably with a field-defined classification that permits discrimination among five groups of basalt flows on the basis of geomorphic criteria. Characteristics that contributed to age definition include: surface texture, weathering, color, drainage evolution, and khabrah development. The inherent gradation in the evolution of geomorphic parameters, however, makes visual extrapolation between areas subjective. Therefore, incorporation of spectrally-derived volcanic units into the mapping process should produce more quantitatively consistent age groupings.

  15. Groundmass Crystallinities of Proximal and Distal Lavas from Cinder Cone, Lassen Volcanic Field

    Science.gov (United States)

    Szymanski, M. E.; Teasdale, R.

    2015-12-01

    Cinder Cone is located in the northeast corner of Lassen Volcanic Center, approximately 35 km southeast of Old Station, California. The area consists of a cinder cone constructed of loose scoria, lava flows and a 13-16 km diameter ash deposit. According to radiocarbon ages from trees affected by the lava flows and paleomagnetic data, Cinder Cone erupted in about 1650 AD (1). The youngest products of the Cinder Cone eruption are two Fantastic Lava Beds flows which are basaltic andesite and andesite with olivine (1). Samples were collected along the longest flow from Cinder Cone, the Fantastic Lava Beds Flow 2 (4.5 km) at approximately 0.5 km interval. The samples contain olivine, plagioclase and clinopyroxene phenocrysts in fine grained groundmass with varying vesicularity. Quartz xenocrysts also occur. SEM-Back Scatter Electron images are used to map and quantify groundmass crystallinities along the length of the Fantastic Lava Beds flow 2 and of tephra units. The average area of groundmass plagioclase crystals increases along the length of the lava flow from 94.7 to 292.6 μm2. The number of groundmass plagioclase crystals per area (μm2) decreases from 0.0045 to 0.0018 from proximal to distal samples. Crystals also become blockier in distal samples along the lava flow. The larger number of crystals per area in near vent samples establishes a baseline from which we interpret crystal growth and nucleation to have occurred in the flow channel. Increasing crystal size and a decrease in the number of crystals per area indicates growth dominated nucleation during cooling and crystallization in the flow channel. Relative cooling rates along the length of the flow from proximal to distal samples can be inferred based on groundmass crystallinities, distance travelled and estimates of flow and crystallization rates. (1) Muffler and Clynne, 2015.

  16. Possible earthquake precursor and drumbeat signal detected at the Nirano Mud Volcanic Field, Italy

    Science.gov (United States)

    Lupi, Matteo; Suski Ricci, Barbara; Kenkel, Johannes; Ricci, Tullio; Fuchs, Florian; Miller, Stephen A.; Kemna, Andreas; Conventi, Marzia

    2016-04-01

    We used the Nirano mud volcanic field as a natural laboratory to test pre- and post-seismic effects generated by distant earthquakes. Mud volcanoes are geological systems often characterized by elevated fluid pressures at depth deviating from hydrostatic conditions. This near-critical state makes mud volcanoes particularly sensitive to external forcing induced by natural or man-made perturbations. We first characterized the subsurface structure of the Nirano mud volcanic field with a geoelectrical study. Next, we deployed a broad-band seismic station to understand the typical seismic signal generated at depth. Seismic records show a background noise below 2 s, sometimes interrupted by pulses of drumbeat-like high-frequency signals lasting from several minutes to hours. Drumbeat signal was previously discovered in geysers and at magmatic volcanoes. To date this is the first observation of drumbeat signal observed in mud volcanoes. In 2013 June we recorded a M4.7 earthquake, that occurred approximately 60 km far from our seismic station. According to empirical estimations the Nirano mud volcanic field should not have been affected by the M4.7 earthquake. Yet, before the seismic event we recorded an increasing amplitude of the signal in the 10-20 Hz frequency band. The signal emerged approximately two hours before the earthquake and lasted for about three hours. We performed an analysis of the 95th percentile of the root mean square amplitude of the waveforms for the day of the earthquake. This statistical analysis suggests the presence of a possible precursory signal about 10 minutes before the earthquake indicating the occurrence of enhanced fluid flow in the subsurface that may be related to pressure build up in the preparation zone of the earthquake.

  17. Lava-flow characterization at Pisgah Volcanic Field, California, with multiparameter imaging radar

    Science.gov (United States)

    Gaddis, L.R.

    1992-01-01

    Multi-incidence-angle (in the 25?? to 55?? range) radar data aquired by the NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) at three wavelengths simultaneously and displayed at three polarizations are examined for their utility in characterizing lava flows at Pisgah volcanic field, California. Pisgah lava flows were erupted in three phases; flow textures consist of hummocky pahoehoe, smooth pahoehoe, and aa (with and without thin sedimentary cover). Backscatter data shown as a function of relative age of Pisgah flows indicate that dating of lava flows on the basis of average radar backscatter may yield ambiguous results if primary flow textures and modification processes are not well understood. -from Author

  18. Near field chemical speciation: the reaction of uranium and thorium with Hanford basalt and elevated pH

    International Nuclear Information System (INIS)

    The hydrolysis of radionuclides such as thorium and uranium and their subsequent chemisorption on Hanford basalt have been studied using a variety of techniques, including x-ray photoelectron and infrared spectroscopy. Data obtained to date indicate mixed complexes of uranium and thorium to be on the basalt surface, the complexes being radionuclide oxides, hydrated oxides (hydroxides), and carbonates. These findings are discussed with respect to their importance for input for models describing speciation and dissolution processes involving nuclear waste repository materials such as Hanford basalt. 5 figures, 2 tables

  19. Constraints on the origin and evolution of magmas in the Payún Matrú Volcanic Field, Quaternary Andean Back-arc of Western Argentina

    NARCIS (Netherlands)

    Hernando, I.R.; Aragón, E.; Frei, R.; González, P.D.; Spakman, W.

    2014-01-01

    The Payún Matrú Volcanic Field (Pleistocene–Holocene) is located in the Andean back-arc of the Southern Volcanic Zone, western Argentina, and is contemporaneous with the Andean volcanic arc at the same latitude. It includes two polygenetic, mostly trachytic volcanoes: Payún Matrú (with a summit cald

  20. Origin and potential geothermal significance of China Hat and other late Pleistocene topaz rhyolite lava domes of the Blackfoot Volcanic Field, SE Idaho

    Science.gov (United States)

    McCurry, M. O.; Pearson, D. M.; Welhan, J. A.; Kobs-Nawotniak, S. E.; Fisher, M. A.

    2014-12-01

    The Snake River Plain and neighboring regions are well known for their high heat flow and robust Neogene-Quaternary tectonic and magmatic activity. Interestingly, however, there are comparatively few surficial manifestations of geothermal activity. This study is part of a renewed examination of this region as a possible hidden or blind geothermal resource. We present a testable, integrated volcanological, petrogenetic, tectonic and hydrothermal conceptual model for 57 ka China Hat and cogenetic topaz rhyolite lava domes of the Blackfoot Volcanic Field. This field is well suited for analysis as a blind resource because of its distinctive combination of (1) young bimodal volcanism, petrogenetic evidence of shallow magma storage and evolution, presence of coeval extension, voluminous travertine deposits, and C- and He-isotopic evidence of active magma degassing; (2) a paucity of hot springs or other obvious indicators of a geothermal resource in the immediate vicinity of the lava domes; and (3) proximity to a region of high crustal heat flow, high-T geothermal fluids at 2.5-5 km depth and micro-seismicity characterized by its swarming nature. Eruptions of both basalt and rhyolite commonly evolve from minor phreatomagmatic to effusive. In our model, transport of both magmatic and possible deep crustal aqueous fluids may be controlled by preexisting crustal structures, including west-dipping thrust faults. Geochemical evolution of rhyolite magma is dominated by mid- to upper-crustal fractional crystallization (with pre-eruption storage and phenocryst formation at ~14 km). Approximately 1.2 km3 of topaz rhyolite have been erupted since 1.4 Ma, yielding an average eruption rate of 0.8 km3/m.y. Given reasonable assumptions of magma cumulate formation and eruption rates, and initial and final volatile concentrations, we infer average H2O and CO2 volatile fluxes from the rhyolite source region of ~2MT/year and 340 T/day, respectively. Lithium flux may be comparable to CO2.

  1. Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

    Science.gov (United States)

    Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.

    2015-09-25

    The Bodie Hills is a ~40 by ~30 kilometer volcanic field that straddles the California-Nevada state boundary between Mono Lake and the East Walker River. Three precious metal mining districts and nine alteration zones are delineated in Tertiary-Quaternary volcanic and Mesozoic granitic and metamorphic rocks that comprise the volcanic field. Cumulative production from the mining districts, Bodie, Aurora, and Masonic, is 3.4 million ounces of gold and 28 million ounces of silver. Small amounts of mercury were produced from the Potato Peak, Paramount-Bald Peak, and Cinnabar Canyon-US 395 alteration zones; a native sulfur resource in the Cinnabar Canyon-US 395 alteration zone has been identified by drilling. There are no known mineral resources in the other six alteration zones, Red Wash-East Walker River, East Brawley Peak, Sawtooth Ridge, Aurora Canyon, Four Corners, and Spring Peak. The mining districts and alteration zones formed between 13.4 and 8.1 Ma in predominantly ~15–9 Ma volcanic rocks of the Bodie Hills volcanic field. Ages of hydrothermal minerals in the districts and zones are the same as, or somewhat younger than, the ages of volcanic host rocks.

  2. Determination of the Lithosphere-Asthenosphere Boundary (LAB) beneath the Nógrád-Gömör Volcanic Field by combined geophysical (magnetotellurics) and geochemical methods

    Science.gov (United States)

    Novák, Attila; Klébesz, Rita; Szabó, Csaba; Patkó, Levente; Liptai, Nóra; Kovács, Zoltán; Wesztergom, Viktor; Ádám, Antal; Lemperger, István; Kis, Árpád; Molnár, Csaba; Szendrői, Judit

    2014-05-01

    Understanding the fundamental role of LAB is substantial for the investigation of the geodynamic evolution of the Earth. The LAB depths can be estimated by different geophysical methods (seismology, magnetotellurics), however these depths are controversial. It has been emphasized in the literature that combined geophysical and geochemical approach may lead to better understanding of these depths. The magnetotellurics (MT) is very powerful method because it indicates the sudden increase in conductivity at the LAB. The mantle xenoliths (small fragments of the lithospheric mantle) provide the information to reconstruct their P-T paths. In the Carpathian-Pannon region (CPR) five, well-studied occurrences of mantle xenoliths-bearing Plio-Pleistocene alkali basalts are known, which makes the CPR a very promising area for investigating the inconsistency in the LAB estimates. As a test area Nógrád-Gömör Volcanic Field (NGVF) has been chosen. The host basalt erupted at the NGVF collected mantle xenoliths from a small volume of the upper mantle in a depth of about 40-50 km. The major element geochemistry of the studied xenoliths indicates that most of them represent common lherzolitic mantle, whereas others show strong wehrlitisation process. This metasomatism is supposed to be caused by a migrating mafic melt agent, resulting in the transformation of a large portion of lherzolite to wehrlite beneath the NGVF, possibly just below the crust mantle boundary. In aim to detect the LAB at the research area and find the correlation with petrologic and geochemical results we carried out MT deep soundings. The campaign contained 12 long period MT stations with 3-5 km average spacing along 60 km long profile SSE to NNW direction. This presentation summarizes the preliminary results of the combined geophysical and geochemical approaches to determine the LAB depths.

  3. First-order estimate of the Canary Islands plate-scale stress field: Implications for volcanic hazard assessment

    Science.gov (United States)

    Geyer, A.; Martí, J.; Villaseñor, A.

    2016-06-01

    In volcanic areas, the existing stress field is a key parameter controlling magma generation, location and geometry of the magmatic plumbing systems and the distribution of the resulting volcanism at surface. Therefore, knowing the stress configuration in the lithosphere at any scale (i.e. local, regional and plate-scale) is fundamental to understand the distribution of volcanism and, subsequently, to interpret volcanic unrest and potential tectonic controls of future eruptions. The objective of the present work is to provide a first-order estimate of the plate-scale tectonic stresses acting on the Canary Islands, one of the largest active intraplate volcanic regions of the World. In order to obtain the orientation of the minimum and maximum horizontal compressive stresses, we perform a series of 2D finite element models of plate scale kinematics assuming plane stress approximation. Results obtained are used to develop a regional model, which takes into account recognized archipelago-scale structural discontinuities. Maximum horizontal compressive stress directions obtained are compared with available stress, geological and geodynamic data. The methodology used may be easily applied to other active volcanic regions, where a first order approach of their plate/regional stresses can be essential information to be used as input data for volcanic hazard assessment models.

  4. A new model for the emplacement of Columbia River basalts as large, inflated pahoehoe lava flow fields

    Science.gov (United States)

    Self, S.; Thordarson, Th.; Keszthelyi, L.; Walker, G.P.L.; Hon, K.; Murphy, M.T.; Long, P.; Finnemore, S.

    1996-01-01

    Extensive flows of the Columbia River Basalt (CRB) Group in Washington, Oregon, and Idaho are dominantly inflated compound pahoehoe sheet lavas. Early studies recognized that CRB lavas are compound pahoehoe flows, with textures suggesting low flow velocities, but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks. However, small volume ( pahoehoe flows on Kilauea, Hawai'i, demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger (10-20 km3) pahoehoe flows in Iceland. The vertical distribution of vesicles and other morphologic features within CRB lava flows indicate that they grew similarly by inflation. Small pahoehoe lobes at the base and top of many CRB pahoehoe lava flows indicate emplacement in a gradual, piecemeal manner rather than as a single flood. We propose that each thick CRB sheet flow was active for months to years and that each group of flows produced by a single eruption (a flow field) was emplaced slowly over many years. Copyright 1996 by the American Geophysical Union.

  5. Multiple episodes of hydrothermal activity and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic activity, volcanism and regional extension

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, S.I.; Noble, D.C.; Jackson, M.C. [Univ. of Nevada, Reno, NV (United States)] [and others

    1994-12-31

    Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of hydrothermal alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of hydrothermal activity mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma).

  6. Post-eruptive sediment transport and surface processes on unvegetated volcanic hillslopes - A case study of Black Tank scoria cone, Cima Volcanic Field, California

    Science.gov (United States)

    Kereszturi, Gábor; Németh, Károly

    2016-08-01

    Conical volcanic edifices that are made up from lapilli to block/bomb pyroclastic successions, such as scoria cones, are widespread in terrestrial and extraterrestrial settings. Eruptive processes responsible for establishing the final facies architecture of a scoria cone are not well linked to numerical simulations of their post-eruptive sediment transport. Using sedimentological, geomorphic and 2D fragment morphology data from a 15-ky-old scoria cone from the Cima Volcanic Field, California, this study provides field evidence of the various post-eruptive sediment transport and degradation processes of scoria cones located in arid to semi-arid environments. This study has revealed that pyroclast morphologies vary downslope due to syn-eruptive granular flows, along with post-eruptive modification by rolling, bouncing and sliding of individual particles down a slope, and overland flow processes. The variability of sediment transport rates on hillslopes are not directly controlled by local slope angle variability and the flank length but rather by grain size, and morphological characteristics of particles, such as shape irregularity of pyroclast fragments and block/lapilli ratio. Due to the abundance of hillslopes degrading in unvegetated regions, such as those found in the Southwestern USA, granulometric influences should be accounted for in the formulation of sediment transport laws for geomorphic modification of volcanic terrains over long geologic time.

  7. Noble Gases and Halogens in Icelandic Basalts

    OpenAIRE

    Weston, Bridget

    2013-01-01

    Noble gas and halogen data from a suite of Icelandic samples are presented. Iceland combines hotspot volcanism, a spreading ridge and abundant subglacially erupted samples. This combination allows for samples that erupted under high enough pressures to retain a measurable mantle volatile content, and also display signatures representing interaction between ocean island basalt (OIB) and mid-ocean ridge basalt (MORB) mantle sources.Erupted samples used to determine the mantle’s halogen and nobl...

  8. Preliminary Geochemical and Petrologic Assessment of the Fanney Rhyolite and the Bloodgood Canyon and Apache Springs tuffs, Mogollon-Datil Volcanic Field, New Mexico

    Science.gov (United States)

    Salings, E. E.; Rentz, S. P.; Michelfelder, G.; Sikes, E. R.

    2015-12-01

    Continental arc volcanoes represent a dramatic expression of a significant and fundamental phenomena in global tectonics: the subduction of an oceanic plate beneath a more buoyant continental plate. The subduction of an oceanic plate results in recycling of crustal material into the convecting mantle, partial melting, and primary basalt production. Moreover, during passage through thick continental crust, subduction zone magmas may substantially differentiate and melt crustal rocks giving rise to the great diversity of igneous lithologies characteristic of earth. These are important processes that must be understood in detail in order to interpret the long-term evolution of the earth and continental crust. Here we present variations in the isotopic and trace element composition of volcanic rocks from Bloodgood Canyon and Apache Springs tuffs, and the Fanney Rhyolite located in the western Mogollon-Datil Volcanic Field (MDVF). The project will address several questions. First, are the Bloodgood and Apache Springs tuffs and Fanney Rhyolite petrogenically related, and are these rhyolites expressions of a continental arc ignimbrite flare-up? Second, what petrogenic processes affected differentiation and where is the magma sourced? Finally, to what extent do these units represent a manifestation of the MDVF and the transition from arc magmatism to rifting? The Bloodgood Canyon is a crystal-rich rhyolite tuff containing quartz>k-feldspar>plagioclase>biotite, and pumice and lithic fragments. Rb ranges from 230-330ppm, Sr from 14-83ppm, and 87Sr/86Srm from 0.71619-0.72477.The Apache Springs Tuff is a rhyolite tuff containing quartz>k-feldspar>plagioclase>biotite, and lithics. Rb (228-233ppm) and 87Sr/86Srm (0.71025-0.71056) are restricted, while Sr (105-399ppm) is more variable in composition. The Fanney Creek is a massive rhyolite lava with flow banding and contains quartz phenocryst clusters and k-feldspars. Currently, no data exists for the Apache Springs Tuff.

  9. The correlation between geomagnetic field reversals, Hawaiian volcanism, and the motion of the Pacific plate

    Directory of Open Access Journals (Sweden)

    W. Dong

    1996-06-01

    Full Text Available The correlation between geomagnetic field reversals and volcanism is investigated, according to the speculated consequence on volcanoes of the transient electric currents in the geodynamo, through Joule's heating, before and after every reversal event. We evaluate the temporal variation during the last ~ 70 Ma both of the magma emplacement rate Q(t from the Hawaii hot spot, and of the speed v(t of the Pacific plate, by means of the observed volumes of islands and seamounts along the Hawaii/Emperor Seamounts chain, and their respective radiometric datings. Results confirm expectations. A justification of the volcanic crises that lead to the generation of the large igneous provinces during the last ~ 250 Ma also emerged. We describe in detail the complex pattern of the timings of the different effects. Joule's power is generally responsible for ~ 75-80% of magmatism, and friction power only for ~ 20-25%; but, on some occasions almost ~ 100% is fuelled by friction alone. The visco-elastic coupling between lithosphere and asthenosphere results ~ 96% viscous, and ~ 4% elastic.

  10. Evidences for a volcanic province in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    Based on various lines of evidence such as the widespread occurrence of basalts, pumice, volcanic glass shards and their transformational products (zeolites, palagonites, and smectite-rich sediments), we suggest the presence of a volcanic province...

  11. New Contributions to the Geomagnetic Instability Time Scale: Paleomagnetic study of Tequila and Ceboruco-San Pedro-Amado Nervo Volcanic Fields (Trans Mexican Volcanic Belt)

    Science.gov (United States)

    Rodriguez Ceja, M.; Gogichaishvili, A.; Alva-Valdivia, L.; Rosas Elguera, J.; Calvo, M.; Urrutia-Fucugauchi, J.

    2005-05-01

    The Trans-Mexican Volcanic Belt (TMVB) is one of the largest continental volcanic arcs of the North American plate. It spans about 1000 km from the Pacific to the Gulf of Mexico. Despite the abundance of thick lava sequences with quite high extrusion rates, the TMVB have been relatively little studied from a paleomagnetic point of view. Previous studies were aimed for tectonic evolution of the region rather than documenting fluctuations of Earth's magnetic field in terms of both directions and intensity. We report a detailed paleomagnetic and rock-magnetic study of Tequila and Ceboruco-San Pedro-Amado Nervo volcanic fields. 350 oriented samples belonging to 31 independent cooling units were collected. All these sites were previously dated by means of the state-of-the-art 40Ar-39Ar geochronological method and span from 1.1 Ma to 2 Ky. Rock-magnetic experiments which included continuous susceptibility, isothermal remanence acquisition and hysteresis measurements point to simple magnetic mineralogy. In most of cases, the remanence is carried by Ti-poor titanomagnetite of pseudo-single-domain magnetic structure. The paleodirections of the flow dated as 819±25 ka correspond to a VGP latitude of 18° N. This anomalous field behaviour apparently recorded prior to the Matuyama-Brunhes reversal may coincide with the geomagnetic event, defined as M-B precursor. Two independent lava flows, dated as 623±91 and 614±16 ka respectively, yield reverse paleodirections and one lava flow dated as 690±29 yields transitional paleodirections. It is possible that these lavas erupted during the worldwide observable Big Lost or Delta events.

  12. Group II Xenoliths from Lunar Crater Volcanic Field, Central Nevada: Evidence for a Kinked Geotherm

    Science.gov (United States)

    Roden, M.; Mosely, J.; Norris, J.

    2015-12-01

    Group II xenoliths associated with the 140 Ka Easy Chair Crater, Lunar Crater volcanic field, NV, consist of amphibole rich-inclusions including amphibolites, pyroxenites, and gabbros. Abundant minerals in these inclusions are kaersutite, aluminous (7.3-9.7 wt% Al2O3), calcic clinopyroxene, primarily diopside, and olivine (Mg# 69-73) with accessory spinel, sulfide and apatite. Although most apatites are fluor-hydroxyapatite solid solutions, one xenolith contains Cl- and OH-rich apatite suggesting that Cl may have been an important constituent in the parent magma(s) . The xenoliths show abundant evidence for equilibration at relatively low temperatures including amphibole and orthopyroxene exsolution in clinopyroxene, and granules of magnetite in hercynite hosts. If latter texture is due to exsolution, then this particular Group II xenolith equilibrated at temperatures near or below 500oC or at a depth of about 15 km along a conductive geotherm. It may be that all the Group II xenoliths equilibrated at low temperatures given the abundant exsolution textures although Fe-Mg exchange relations suggest equilibration at temperatures in excess of 800oC. Low equilibration temperatures are in conflict with the unusually high equilibration temperatures, >1200oC (Smith, 2000) displayed by Group I xenoliths from this same volcanic field. Taken at face value, the geothermometric results indicate unusually high temperatures in the upper mantle, normal temperatures in the crust and the possibility of a kinked geotherm in the region. Curiously the LCVF lies in an area of "normal" heat flow, south of the Battle Mountain area of high heat flow but the number of heat flow measurements in the Lunar Crater area is very low (Humphreys et al., 2003; Sass, 2005). References: Humphreys et al., 2003, Int. Geol. Rev. 45: 575; Sass et al., 2005, http://pubs.usgs.gov/of/2005/1207/; Smith, 2000, JGR 105: 16769.

  13. Very long pahoehoe inflated basaltic lava flows in the Payenia volcanic province (Mendoza and la Pampa, Argentina Flujos de lava basáltica pahoehoe muy extendidos en la provincia volcánica Payenia (Mendoza y La Pampa, Argentina

    Directory of Open Access Journals (Sweden)

    Giorgio Pasquarè

    2008-03-01

    Full Text Available Extremely long basaltic lava flows are here presented and described. The flows originated from the great, polygenetic, fissural Payen Volcanic Complex, in the Andean back-arc volcanic province of Payenia in Argentina. The lava flows outpoured during the Late Quaternary from the summit rift of a shield volcano representing the first volcanic centre of this complex. One of these flows presents an individual tongue-like shape with a length of 181 km and therefore is the longest known individual Quaternary lava flow on Earth. Leaving the flanks of the volcano this flow reached the Salado river valley at La Pampa and, in its distal portion, maintained its narrow and straight shape without any topographic control over a flat alluvial plain. It has a hawaiite composition with low phenocryst content of prevailing olivine and minor plagioclase. Rare Earth element patterns are typical of Na-alkaline basalts, but incompatible trace element patterns and Sr -Nd isotope ratios, suggest a geodynamic setting transitional to the orogenic one. The flow advanced following the thermally efficient "inflation" mechanism, as demonstrated by a peculiar association of well developed morphological, structural and textural features. The temperature of 1130-1160°C and the viscosity of 3-73 Pa*s, calculated by petrochemical data, may be considered, together with a very low cooling rate and a sustained and long lasting effusion rate, the main causes of the extremely long transport system of this flow. Both the extreme length of the flow and the partial lack of topographic control may provide new constraints on the physics of large inflated flows, which constitute the largest volcanic provinces on Earth and probably also on the terrestrial planets.En este trabajo se presentan y describen flujos de lava extremadamente largos. Estos flujos se originaron en el complejo volcánico fisural Payen, dentro de la provincia volcánica Payenia en el retroarco andino. Los flujos de lava

  14. Parallel simulation of particle transport in an advection field applied to volcanic explosive eruptions

    Science.gov (United States)

    Künzli, Pierre; Tsunematsu, Kae; Albuquerque, Paul; Falcone, Jean-Luc; Chopard, Bastien; Bonadonna, Costanza

    2016-04-01

    Volcanic ash transport and dispersal models typically describe particle motion via a turbulent velocity field. Particles are advected inside this field from the moment they leave the vent of the volcano until they deposit on the ground. Several techniques exist to simulate particles in an advection field such as finite difference Eulerian, Lagrangian-puff or pure Lagrangian techniques. In this paper, we present a new flexible simulation tool called TETRAS (TEphra TRAnsport Simulator) based on a hybrid Eulerian-Lagrangian model. This scheme offers the advantages of being numerically stable with no numerical diffusion and easily parallelizable. It also allows us to output particle atmospheric concentration or ground mass load at any given time. The model is validated using the advection-diffusion analytical equation. We also obtained a good agreement with field observations of the tephra deposit associated with the 2450 BP Pululagua (Ecuador) and the 1996 Ruapehu (New Zealand) eruptions. As this kind of model can lead to computationally intensive simulations, a parallelization on a distributed memory architecture was developed. A related performance model, taking into account load imbalance, is proposed and its accuracy tested.

  15. Aeromagnetic Expression of Buried Basaltic Volcanoes Near Yucca Mountain, Nevada

    Science.gov (United States)

    O'Leary, D. W.; Mankinen, E.A.; Blakely, R.J.; Langenheim, V.E.; Ponce, D.A.

    2002-01-01

    A high-resolution aeromagnetic survey has defined a number of small dipolar anomalies indicating the presence of magnetic bodies buried beneath the surface of Crater Flat and the Amargosa Desert. Results of potential-field modeling indicate that isolated, small-volume, highly magnetic bodies embedded within the alluvial deposits of both areas produce the anomalies. Their physical characteristics and the fact that they tend to be aligned along major structural trends provide strong support for the hypothesis that the anomalies reflect buried basaltic volcanic centers. Other, similar anomalies are identified as possible targets for further investigation. High-resolution gravity and ground-magnetic surveys, perhaps along with drilling sources of selected anomalies and radiometric age determinations, can provide valuable constraints in estimating potential volcanic hazard to the potential nuclear waste repository at Yucca Mountain.

  16. Paleomagnetism in the Determination of the Emplacement Temperature of Cerro Colorado Tuff Cone, El Pinacate Volcanic Field, Sonora, Mexico.

    Science.gov (United States)

    Rodriguez Trejo, A.; Alva-Valdivia, L. M.; Vidal Solano, J. R.; Garcia Amador, B.; Gonzalez-Rangel, J. A.

    2014-12-01

    Cerro Colorado Maar is located at the World Heritage Site, biosphere reserve El Pinacate and Gran Desierto del Altar, at the NNW region of Sonora, Mexico (in El Pinacate Volcanic Field). It is a tuff cone, about 1 km diameter, result of several phreatomagmatic episodes during the late Quaternary. We report paleomagnetic and rock magnetic properties from fusiform volcanic bombs obtained from the borders of Cerro Colorado. This study is based in the thermoremanent magnetization TRM normally acquired by volcanic rocks, which can be used to estimate the emplacement temperature range. We performed the experiments on 20 lithic fragments (10 cm to 20 cm approximately), taking 6-8 paleomagnetic cores from each. Rock magnetic experiments (magnetic susceptibility vs. temperature (k-T), hysteresis curves and FORC analysis, shows that the main magnetic mineral carriers of magnetization are titanomagnetite and titanohematite in different levels of intergrowth. The k-T curves suggest in many cases, only one magnetic phase, but also in other cases a second magnetic phase. Thermal demagnetization was used to demagnetize the specimens in detailed short steps and make a well-defined emplacement temperature determination ranges. We found that temperature emplacement determination range for these two magnetic phases is between 350-450 °C, and 550-580 °C, respectively. These results are consistent with those expected in an eruption of Surtsey type, showing a distinct volcanic activity compared to the other craters from El Pinacate volcanic field.

  17. Geochemical characteristics of island-arc volcanic rocks in the Nan-Nam Pat-Phetchabun zone, northern Thailand

    Institute of Scientific and Technical Information of China (English)

    SHEN Shangyue; FENG Qinglai; YANG Wenqiang; ZHANG Zhibin; Chongpom Chonglakmani

    2010-01-01

    Late Permian-Early Triassic (P2-T1) volcanic rocks distributed on the eastern side of ocean-ridge and oceanic-island basalts in the Nan-Uttaradit zone were analyzed from aspects of petrographic characteristics, rock assemblage, REE, trace elements, geotectonic setting, etc., indicating that those volcanic rocks possess the characteristic features of island-arc volcanic rocks. The volcanic rock assemblage is basalt-basaltic andesite-andesite. The volcanic rocks are sub-alkaline, dominated by calc-alkaline series, with tholeiite series coming next. The chemical composition of the volcanic rocks is characterized by low TiO2 and K2O and high Al2O3 and Na2O. Their REE patterns are of the flat, weak LREE-enrichment right-inclined type. The trace elements are characterized by the enrichment of large cation elements such as K, Rb and Ba, common enrichment of U and Th, and depletion of Nb, Ta, Zr and Hf. The petrochemical plot falls within the field of volcanic rocks, in consistency with the plot of island-arc volcanic rocks in the Jinsha River zone of China. This island-arc volcanic zone, together with the ocean-ridge/oceanic island type volcanic rocks in the Nan-Uttaradit zone, constitutes the ocean-ridge volcanic rock-island-arc magmatic rock zones which are distributed in pairs, indicating that the oceanic crust of the Nan-Uttaradit zone once was of eastward subduction. This work is of great significance in exploring the evolution of paleo-Tethys in the Nan-Uttaradit zone.

  18. Pyroclastic Density Current Hazards in the Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Brand, B. D.; Gravley, D.; Clarke, A. B.; Bloomberg, S. H.

    2012-12-01

    The most dangerous phenomena associated with phreatomagmatic eruptions are dilute pyroclastic density currents (PDCs). These are turbulent, ground-hugging sediment gravity currents that travel radially away from the explosive center at up to 100 m/s. The Auckland Volcanic Field (AVF), New Zealand, consists of approximately 50 eruptive centers, at least 39 of which have had explosive phreatomagmatic behaviour. A primary concern for future AVF eruptions is the impact of dilute PDCs in and around the Auckland area. We combine field observations from the Maungataketake tuff ring, which has one of the best exposures of dilute PDC deposits in the AVF, with a quantitative model for flow of and sedimentation from a radially-spreading, steady-state, depth-averaged dilute PDC (modified from Bursik and Woods, 1996 Bull Volcanol 58:175-193). The model allows us to explore the depositional mechanisms, macroscale current dynamics, and potential impact on societal infrastructure of dilute PDCs from a future AVF eruption. The lower portion of the Maungataketake tuff ring pyroclastic deposits contains trunks, limbs and fragments of Podocarp trees (strength of the wood, we calculate that dynamic pressures (Pdyn) of 10-75 kPa are necessary to topple trees of this size and composition. Thus the two main criteria for model success based on the field evidence include (a) Pdyn must be >10 kPa nearer than 0.9 km to the vent, and 35 kPa can be expected within 3 km from source, ensuring complete destruction of the area; Pdyn > 15 kPa up to 5 km from source, resulting in heavy structural damage to most buildings and near destruction of weaker buildings; and Pdyn <10 kPa at ~6 km from source, resulting in severe damage to weaker structures at least up to this distance. This exercise illustrates our ability to combine field measurements with numerical techniques to explore controlling parameters of dilute PDC dynamics. These tools can be used to understand and estimate the damage potential and

  19. Preliminary Ambient Noise and Seismic Interferometry Analysis of the Laguna del Maule Volcanic Field, Chile

    Science.gov (United States)

    Wespestad, C.; Thurber, C. H.; Bennington, N. L.; Zeng, X.; Cardona, C.; Keranen, K. M.; Singer, B. S.

    2015-12-01

    Laguna del Maule Volcanic Field is a large, restless, youthful rhyolitic system in the Southern Andes of Chile. We present a preliminary examination of ambient noise data at this site from 12 University of Wisconsin and 6 OVDAS (Southern Andean Volcano Observatory) broadband seismometers for a 3 month period. Ambient noise tomography seeks to correlate pairs of stations, with one station acting as a virtual source and the other a receiver, generating empirical Green's functions between each pair. The noise correlation functions (NCFs) were computed for day-long and hour-long windows, then the final NCFs were obtained from stacking each time window set. The hour-long NCFs converged more rapidly, so this time window was chosen for use in later stages. This study used phase weighted stacking of the NCFs instead of linear stacking in order to achieve a better signal to noise ratio (SNR), although linearly stacked Green's functions were also created to confirm the improvement. Phase weighted stacking can detect signals with weak amplitudes much more clearly than linear stacking by finding coherence of signals in multiple frequency bins and down-weighting the importance of amplitude for correlation (Schimmel and Gallart, 2007). The Frequency-Time Analysis Technique was utilized to measure group velocity, and initial results show it to be about 2 km/s on average. Fluctuations of the average velocity between different station pairs across this dense array will provide a preliminary indication of the location and size of the magma system. This study also applied seismic interferometry using ambient noise to determine temporal changes in seismic velocity occurring at Laguna del Maule. Initial results show temporal changes in seismic velocity correlated to seasonal changes in the hydrologic cycle (rain, snow pack, snow melt, etc.). Current work focuses on identifying changes in seismic velocity associated with ongoing volcanic processes.

  20. Managing a Monogenetic Volcanic Field As a World Heritage Nomination: Implications for Science, Outreach, and Hazards

    Science.gov (United States)

    Olive-Garcia, C.; van Wyk de Vries, B.

    2014-12-01

    Monogenetic volcanoes form a large proportion of the world's volcanoes. They are in all tectonic environments and thus provide a significant link to understand fundamental geological processes such as plate tectonics. The Chaîne des Puys - Limagne fault World Heritage nomination is a prime example of this link where monogenetic volcanism, continental rifting, uplift and erosion are highlighted, and are made understandable to the lay person, though the actions on over 80 aligned monogenetic volcanoes. Such geoheritage is essential for monogenetic and other geological risks to be communicated to the wider public. The current scientific interest on monogenetic volcanoes is quite recent, and because of this, and probably their global distribution but small size, they have not received their due importance from a geoheritage standpoint. Some individual sites and some fields are protected and developed as attractions, but there has been no coherent global strategy for defining monogenetic heritage, or for linking sites. This is starting through the monogenetic commission of IAVCEI, and with wider participation of the IUGS and other bodies. The Chaîne des Puys - Limagne Fault UNESCO project is an example of how public awareness, at a global scale, and be increased through geoheritage. This is done integrating local stakeholders: population, industry, science, landscapers, artists, sports, government. This builds on existing protection and sustainable activities, integrating them with education programs. The result is to create a populace that 'thinks geological', and which leads visitors to also become geologically aware. This is helped by a monogenetic landscape that is easily readable and by links made to other geological sites around the world. We will explain how this process is ongoing. The project started over 35 years ago, and is a long-term vision to develop geological understanding and protection of this unique monogenetic and tectono-volcanic site.

  1. Post-Columbia River Basalt Group stratigraphy and map compilation of the Columbia Plateau, Oregon

    International Nuclear Information System (INIS)

    This report presents the results of reconnaissance mapping of sedimentary deposits and volcanic rocks overlying the Columbia River Basalt. The project area covers parts of the Dalles, Pendleton, Grangeville, Baker, Canyon City, and Bend. The mapping was done to provide stratigraphic data on the sedimentary deposits and volcanic rocks overlying the Columbia River Basalt Group. 160 refs., 16 figs., 1 tab

  2. Growing magma chambers control the distribution of small-scale flood basalts.

    Science.gov (United States)

    Yu, Xun; Chen, Li-Hui; Zeng, Gang

    2015-01-01

    Small-scale continental flood basalts are a global phenomenon characterized by regular spatio-temporal distributions. However, no genetic mechanism has been proposed to explain the visible but overlooked distribution patterns of these continental basaltic volcanism. Here we present a case study from eastern China, combining major and trace element analyses with Ar-Ar and K-Ar dating to show that the spatio-temporal distribution of small-scale flood basalts is controlled by the growth of long-lived magma chambers. Evolved basalts (SiO2 > 47.5 wt.%) from Xinchang-Shengzhou, a small-scale Cenozoic flood basalt field in Zhejiang province, eastern China, show a northward younging trend over the period 9.4-3.0 Ma. With northward migration, the magmas evolved only slightly ((Na2O + K2O)/MgO = 0.40-0.66; TiO2/MgO = 0.23-0.35) during about 6 Myr (9.4-3.3 Ma). When the flood basalts reached the northern end of the province, the magmas evolved rapidly (3.3-3.0 Ma) through a broad range of compositions ((Na2O + K2O)/MgO = 0.60-1.28; TiO2/MgO = 0.30-0.57). The distribution and two-stage compositional evolution of the migrating flood basalts record continuous magma replenishment that buffered against magmatic evolution and induced magma chamber growth. Our results demonstrate that the magma replenishment-magma chamber growth model explains the spatio-temporal distribution of small-scale flood basalts. PMID:26581905

  3. Imaging the deep source of the Rotorua and Waimangu geothermal fields, Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Heise, W.; Caldwell, T. G.; Bertrand, E. A.; Hill, G. J.; Bennie, S. L.; Palmer, N. G.

    2016-03-01

    Magnetotelluric data were recorded in a 45 × 10 km band crossing the Rotorua and Waimangu geothermal fields in the northern part of the Taupo Volcanic Zone in the central North Island of New Zealand. 3-D inverse modelling of these data show that beneath the low resistivity areas marking the near surface geothermal fields, localised electrically conductive zones are present in the crust below about 2.5 and 3.5 km depth at Rotorua and Waimangu, respectively. At increasing depth these conductive zones broaden and appear to merge with a larger conductive zone at 8 km depth situated between the geothermal systems. At Rotorua the top of the conductive zone is situated directly beneath the area of greatest surface heat and gas discharge. At Waimangu the uppermost part of the deeper conductive zone is situated beneath the western part of Lake Rotomahana, also an area of intense surface thermal activity and high heat flux. The localised conductive zones are interpreted to be high temperature (quasi-magmatic) fluids rising from a broader zone of partial melt at deeper levels.

  4. Bibliography of literature pertaining to Long Valley Caldera and associated volcanic fields

    Science.gov (United States)

    Ewert, John W.; Harpel, Christopher J.; Brooks, Suzanna K.; Marcaida, Mae

    2011-01-01

    define the beginning of the Brunhes Chron and helps constrain the Brunhes-Matuyama boundary. The Bishop ash, which was dispersed as far east as Nebraska, Kansas, and Texas, provides an important tephrostratigraphic marker throughout the Western United States. The obsidian domes of both the Mono and Inyo Craters, which were produced by rhyolitic eruptions in the past 40,000 years, have been well studied, including extensive scientific drilling through the domes. Exploratory drilling to 3-km depth on the resurgent dome and subsequent instrumentation of the Long Valley Exploratory Well (LVEW) have led to a number of important new insights. Scientific drilling also has been done within the Casa Diablo geothermal field, which, aside from drilling, has been commercially developed and is currently feeding 40 MW of power into the Southern California Edison grid. Studies in all the above-mentioned volcanic fields have contributed to the extensive scientific literature published on the Long Valley region. Although most of this scientific literature has been published since 1970, a significant amount of historical literature extends backward to the late 1800s. The purpose of this bibliography is to compile references pertaining to the Long Valley region from all time periods and all Earth science fields into a single listing, thus providing an easily accessible guide to the published literature for current and future researchers.

  5. Mantle xenocrysts of Chompolo field of the alkaline volcanics, Aldan shield, South Yakutia.

    Science.gov (United States)

    Nikolenko, Evgeny; Tychkov, Nikolay; Afanasiev, Valentin

    2015-04-01

    New mineralogical and chemical constraints for 10 dikes, veins (360-800m) and pipes (60-110 m) of Chompolo field discovered in 1957-1958 are discussed. Feld is located within Central Aldan Archean and Paleoproterozoic granulite-orthogneiss superterrane of Aldan-Stanovoy Shield, with peak of metamorphism - 2.1-1.9 Ga (Smelov, Timofeev, 2007). Originally (Shilina and Zeitlin 1959) and later (Kostrovitsky and Garanin 1992, Ashchepkov, Vladykin et al. 2001) these rocks were classified as kimberlites by mineralogy including pyrope, Cr spinel, and Cr diopside. Panina and Vladykin (1994), Davies et al, (2006) identified them as lamprophyres and lamproites. The age of Chompolo rocks is pre-Jurassic (Vladimirov et. al., 1989) dated by 40Ar/39Ar as 164.7±1 Ma (233.7±2.2 next plato)(unpublished Ashchepkov). The Rb-Sr isochron for lamprophyre "intrusions 104" indicate later age of 131±4 Ma (Zaitsev, Smelov, 2010). Magmatic bodies (Aldanskaya, Sputnik, Gornaya, Ogonek, Perevalnaya, Kilier-E) were studied during 2012-2013 fieldworks. Most of igneous rocks occur as inequigranular volcanic breccias with micro- or crypto-crystalline groundmass of K feldspar (up to 16.3 wt.% K2O, up to 3.2 wt.% FeO), chlorite, opaque minerals, melanocratic xenocrysts and phenocrysts (garnet, pyroxene, amphibole, Cr spinel, apatite, zircon, mica), and abundant xenogenic fragments of wallrock and crystalline basement. Garnet chemistry records the presence of mantle and crustal material. Mantle garnets lack the common megacryst, wehrlite, and high-temperature lherzolite varieties. Mantle mineralization prevails in the Aldan dike and the Sputnik, Gornaya, and Ogonek pipes, while crustal and elcogitic material is in the Perevalnaya and Kilier-E pipes. The Cr spinel consists of (in wt%) 3.5 to 50.9 Al2O3, 18.6-63.5 wt% Cr2O3, 6.1 to 19.1 MgO, and 0 to 1.61 TiO2. Al and Cr in spinels are in inverse proportion. The Chompolo alkaline volcanic rocks are most similar to the Central Aldan lamproites in trace

  6. Holocene Flows of the Cima Volcanic Field, Mojave Desert, Part 2: Flow Rheology from Laboratory Measurements

    Science.gov (United States)

    Robertson, T.; Whittington, A. G.; Soldati, A.; Sehlke, A.; Beem, J. R.; Gomez, F. G.

    2014-12-01

    Lava flow morphology is often utilized as an indicator of rheological behavior during flow emplacement. Rheological behavior can be characterized by the viscosity and yield strength of lava, which in turn are dependent on physical and chemical properties including crystallinity, vesicularity, and bulk composition. We are studying the rheology of a basaltic lava flow from a monogenetic Holocene cinder cone in the Cima lava field (Mojave Desert, California). The flow is roughly 2.5 km long and up to 700m wide, with a well-developed central channel along much of its length. Samples were collected along seven different traverses across the flow, along with real-time kinematic (RTK) GPS profiles to allow levee heights and slopes to be measured. Surface textures change from pahoehoe ropes near the vent to predominantly jagged `a`a blocks over the majority of the flow, including all levees and the toe. Chemically the lava shows little variation, plotting on the trachybasalt-basanite boundary on the total alkali-silica diagram. Mineralogically the lava is dominated by plagioclase, clinopyroxene and olivine phenocrysts, with abundant flow-aligned plagioclase microcrystals. The total crystal fraction is ~50% near the vent, with higher percentages in the distal portion of the flow. Vesicularity varies between ~10 and more than ~60%. Levees are ~10-15m high with slopes typically ~25-35˚, suggesting a yield strength at final emplacement of ~150,000 Pa. The effective emplacement temperature and yield strength of lava samples will be determined using the parallel-plate technique. We will test the hypothesis that these physical and rheological properties of the lava during final emplacement correlate with spatial patterns in flow morphology, such as average slope and levee width, which have been determined using remote sensing observations (Beem et al. 2014).

  7. Climate Throughout Geologic Time Was Cooled by Sequences of Explosive Volcanic Eruptions Forming Aerosols That Reflect and Scatter Ultraviolet Solar Radiation and Warmed by Relatively Continuous Extrusion of Basaltic Lava that Depletes Ozone, Allowing More Solar Ultraviolet Radiation to Reach Earth

    Science.gov (United States)

    Ward, P. L.

    2015-12-01

    Active volcanoes of all sizes and eruptive styles, emit chlorine and bromine gases observed to deplete ozone. Effusive, basaltic volcanic eruptions, typical in Hawaii and Iceland, extrude large lava flows, depleting ozone and causing global warming. Major explosive volcanoes also deplete ozone with the same emissions, causing winter warming, but in addition eject megatons of water and sulfur dioxide into the lower stratosphere where they form sulfuric-acid aerosols whose particles grow large enough to reflect and scatter ultraviolet sunlight, causing net global cooling for a few years. The relative amounts of explosive and effusive volcanism are determined by the configuration of tectonic plates moving around Earth's surface. Detailed studies of climate change throughout geologic history, and since 1965, are not well explained by greenhouse-gas theory, but are explained quite clearly at OzoneDepletionTheory.info. Ozone concentrations vary substantially by the minute and show close relationships to weather system highs and lows (as pointed out by Dobson in the 1920s), to the height of the tropopause, and to the strength and location of polar vortices and jet streams. Integrating the effects of volcanism on ozone concentrations and the effects of ozone concentrations on synoptic weather patterns should improve weather forecasting. For example, the volcano Bárðarbunga, in central Iceland, extruded 85 km2 of basaltic lava between August 29, 2014, and February 28, 2015, having a profound effect on weather. Most surprising, more than a week before the March 4 eruption of Eyjafjallajökull in 2010, substantial amounts of ozone were released in the vicinity of the volcano precisely when surface deformation showed that magma first began moving up from sills below 4 km depth. Ozone similarly appears to have been emitted 3.5 months before the Pinatubo eruption in 1991. Readily available daily maps of ozone concentrations may allow early warning of an imminent volcanic

  8. Discriminating lava flows of different age within Nyamuragira's volcanic field using spectral mixture analysis

    Science.gov (United States)

    Li, Long; Canters, Frank; Solana, Carmen; Ma, Weiwei; Chen, Longqian; Kervyn, Matthieu

    2015-08-01

    In this study, linear spectral mixture analysis (LSMA) is used to characterize the spectral heterogeneity of lava flows from Nyamuragira volcano, Democratic Republic of Congo, where vegetation and lava are the two main land covers. In order to estimate fractions of vegetation and lava through satellite remote sensing, we made use of 30 m resolution Landsat Enhanced Thematic Mapper Plus (ETM+) and Advanced Land Imager (ALI) imagery. 2 m Pleiades data was used for validation. From the results, we conclude that (1) LSMA is capable of characterizing volcanic fields and discriminating between different types of lava surfaces; (2) three lava endmembers can be identified as lava of old, intermediate and young age, corresponding to different stages in lichen growth and chemical weathering; (3) a strong relationship is observed between vegetation fraction and lava age, where vegetation at Nyamuragira starts to significantly colonize lava flows ∼15 years after eruption and occupies over 50% of the lava surfaces ∼40 years after eruption. Our study demonstrates the capability of spectral unmixing to characterize lava surfaces and vegetation colonization over time, which is particularly useful for poorly known volcanoes or those not accessible for physical or political reasons.

  9. Catastrophic isotopic modification of rhyolitic magma at times of caldera subsidence, Yellowstone plateau volcanic field.

    Science.gov (United States)

    Hildreth, W.; Christiansen, R.L.; O'Neil, J.R.

    1984-01-01

    This Wyoming volcanic field has undergone repeated eruption of rhyolitic magma strongly depleted in 18O. Large calderas subsided 2.0, 1.3 and 0.6 m.y. ago on eruption of ash-flow sheets. More than 60 other rhyolite lavas and tuffs permit reconstruction of the long-term chemical and isotopic evolution of the silicic system. Narrow delta 18O ranges in the ash-flow sheets contrast with wide delta 18O variation in post-caldera lavas. The earliest post-collapse lavas are 3-6per mille lighter than the preceding ash-flow sheets. The 18O depletions were short-lived events that immediately followed caldera subsidence and sequences of post-caldera lavas record partial recovery toward pre-caldera delta 18O values. Contemporaneous extra-caldera rhyolites show no effects of the repeated depletions. Although some contamination by foundering roof rocks seems to be required, water was probably the predominant contaminant.-W.H.B.

  10. Rhyolite thermobarometry and the shallowing of the magma reservoir, Coso volcanic field, California

    Science.gov (United States)

    Manley, C.R.; Bacon, C.R.

    2000-01-01

    The compositionally bimodal Pleistocene Coso volcanic field is located at the western margin of the Basin and Range province ~ 60 km north of the Garlock fault. Thirty-nine nearly aphyric high-silica rhyolite domes were emplaced in the past million years: one at 1 Ma from a transient magma reservoir, one at ~ 0.6 Ma, and the rest since ~ 0.3 Ma. Over the past 0.6 My, the depth from which the rhyolites erupted has decreased and their temperatures have become slightly higher. Pre-eruptive conditions of the rhyolite magmas, calculated from phenocryst compositions using the two-oxide thermometer and the Al-in-hornblende barometer, ranged from 740??C and 270 MPa (2.7 kbar; ~ 10 km depth) for the ~ 0.6 Ma magma, to 770??C and 140 MPa (1.4 kbar; ~ 5.5 km) for the youngest (~ 0.04 Ma) magma. Results are consistent with either a single rhyolitic reservoir moving upward through the crust, or a series of successively shallower reservoirs. As the reservoir has become closer to the surface, eruptions have become both more frequent and more voluminous.

  11. Magnetotelluric Studies of the Laguna del Maule Volcanic Field, Central Chile

    Science.gov (United States)

    Cordell, D. R.; Unsworth, M. J.; Diaz, D.; Pavez, M.; Blanco, B.

    2015-12-01

    Geodetic data has shown that the surface of the Laguna del Maule (LdM) volcanic field in central Chile has been moving upwards at rates >20 cm/yr since 2007 over a 200 km2 area. It has been hypothesized that this ground deformation is due to the inflation of a magma body at ~5 km depth beneath the lake (2.8 km b.s.l.). This magma body is a likely source for the large number of rhyolitic eruptions at this location over the last 25 ka. A dense broadband magnetotelluric (MT) array was collected from 2009 to 2015 and included data from a geothermal exploration project. MT phase tensor analysis indicates that the resistivity structure of the region is largely three-dimensional for signals with periods longer than 1 s, which corresponds to depths >5 km. The MT data were inverted using the ModEM inversion algorithm to produce a three-dimensional electrical resistivity model which included topography. Four primary features were identified in the model: 1) A north-south striking, 10 km by 5 km, low-resistivity zone (inflation centre at a depth of ~5 km (2.8 km b.s.l.) is interpreted as a zone of partial melt which may be supplying material via conduits to account for the observed ground deformation; 2) A shallow low-resistivity feature ~400 m beneath the lake surface (1.8 km a.s.l.) and spatially coincident with the inflation centre is interpreted to be a zone of hydrothermal alteration; 3) A thin, low-resistivity feature to the west of LdM at a depth of ~250 m (2.2 km a.s.l.) is interpreted to be the clay cap of a potential geothermal prospect; 4) A large, low-resistivity zone beneath the San Pedro-Tatara Volcanic Complex to the west of LdM at a depth of ~10 km (8 km b.s.l.) is interpreted to be a zone of partial melt. Further MT data collection is planned for 2016 which will expand the current grid of MT stations to better constrain the lateral extent of the observed features and give greater insight into the dynamics of this restless magma system.

  12. The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups

    Science.gov (United States)

    Óskarsson, Birgir V.; Riishuus, Morten S.

    2014-12-01

    Simple flows (tabular) in the Neogene flood basalt sections of Iceland are described and their mode of emplacement assessed. The flows belong to three aphyric basalt groups: the Kumlafell group, the Hólmatindur group and the Hjálmadalur group. The groups can be traced over 50 km and originate in the Breiðdalur-Thingmuli volcanic zone. The groups have flow fields that display mixed volcanic facies architecture and can be classified after dominating type morphology. The Kumlafell and the Hólmatindur groups have predominantly simple flows of pāhoehoe and rubbly pāhoehoe morphologies with minor compound or lobate pāhoehoe flows. The Hjálmadalur group has simple flows of rubbly pāhoehoe, but also includes minor compound or lobate flows of rubble and 'a'ā. Simple flows are most common in the distal and medial areas from the vents, while more lobate flows in proximal areas. The simple flows are formed by extensive sheet lobes that are several kilometers long with plane-parallel contacts, some reaching thicknesses of ~ 40 m (aspect ratios inflation structures. Their internal structure consists generally of a simple upper vesicular crust, a dense core and a thin basal vesicular zone. The brecciated flow-top is formed by clinker and crustal rubble, the clinker often welded or agglutinated. The simple flows erupted from seemingly short-lived fissures and have the characteristics of cooling-limited flows. We estimate the effusion rates to be ~ 105 m3/s for the simple flows of the Kumlafell and Hólmatindur groups and ~ 104 m3/s for the Hjálmadalur group. The longest flows advanced 15-20 km from the fissures, with lava streams of fast propagating flows inducing tearing and brecciation of the chilled crust. Compound or lobate areas appear to reflect areas of low effusion rates or the interaction of the lava with topographic barriers or wetlands, resulting in chaotic flowage. Slowing lobes with brecciated flow-tops developed into 'a'ā flows. The groups interdigitated

  13. Volcanic sanidinites: an example for the mobilization of high field strength elements (HFSE) in magmatic systems

    Science.gov (United States)

    Aßbichler, Donjá; Heuss-Aßbichler, Soraya; Müller, Dirk; Kunzmann, Thomas

    2016-04-01

    In earth science the mobility of high field strength elements (HFSE) is generally discussed in context of hydrothermal processes. Recent investigations mainly address processes in (late) magmatic-, metamorphic- and submarine hydrothermal systems. They have all in common that H2O is main solvent. The transport of HFSE is suggested to be favored by volatiles, like boron, fluorine, phosphate and sulfate (Jiang et al., 2005). In this study processes in magmatic system are investigated. Sanidinites are rare rocks of igneous origin and are found as volcanic ejecta of explosive volcanoes. They consist mainly of sanidine and minerals of the sodalite group. The very porous fabric of these rocks is an indication of their aggregation from a gaseous magmatic phase. The large sanidine crystals (up to several centimeters) are mostly interlocking, creating large cavities between some crystals. In these pores Zr crystallizes as oxide (baddeleyite, ZrO2) or silicate (zircon, ZrSiO4). The euhedral shape of these minerals is a further indication of their formation out of the gas phase. Furthermore, bubbles in glass observed in some samples are evidence for gas-rich reaction conditions during the formation of the sanidinites. The formation of sanidinites is suggested to be an example for solvothermal processes in natural systems. Solvothermal processes imply the solvation, transport and recrystallization of elements in a gas phase. Results obtained from whole rock analysis from sanidinites from Laacher See (Germany) show a positive correlation between LOI, sulfate, Cl, and Na with the HFSE like Zr. Na-rich conditions seem to ameliorate the solvothermal transport of Zr. All these features point to the formation of sanidinites in the upper part of a magma chamber, where fluid consisting of SO3 and Cl compounds in addition to H2O, CO2 and HFSE (high field strength elements) like Zr accumulate.

  14. Spreading and collapse of big basaltic volcanoes

    Science.gov (United States)

    Puglisi, Giuseppe; Bonforte, Alessandro; Guglielmino, Francesco; Peltier, Aline; Poland, Michael

    2016-04-01

    Among the different types of volcanoes, basaltic ones usually form the most voluminous edifices. Because volcanoes are growing on a pre-existing landscape, the geologic and structural framework of the basement (and earlier volcanic landforms) influences the stress regime, seismicity, and volcanic activity. Conversely, the masses of these volcanoes introduce a morphological anomaly that affects neighboring areas. Growth of a volcano disturbs the tectonic framework of the region, clamps and unclamps existing faults (some of which may be reactivated by the new stress field), and deforms the substratum. A volcano's weight on its basement can trigger edifice spreading and collapse that can affect populated areas even at significant distance. Volcano instability can also be driven by slow tectonic deformation and magmatic intrusion. The manifestations of instability span a range of temporal and spatial scales, ranging from slow creep on individual faults to large earthquakes affecting a broad area. In the frame of MED-SVU project, our work aims to investigate the relation between basement setting and volcanic activity and stability at three Supersite volcanoes: Etna (Sicily, Italy), Kilauea (Island of Hawaii, USA) and Piton de la Fournaise (La Reunion Island, France). These volcanoes host frequent eruptive activity (effusive and explosive) and share common features indicating lateral spreading and collapse, yet they are characterized by different morphologies, dimensions, and tectonic frameworks. For instance, the basaltic ocean island volcanoes of Kilauea and Piton de la Fournaise are near the active ends of long hotspot chains while Mt. Etna has developed at junction along a convergent margin between the African and Eurasian plates and a passive margin separating the oceanic Ionian crust from the African continental crust. Magma supply and plate velocity also differ in the three settings, as to the sizes of the edifices and the extents of their rift zones. These

  15. The Records of the Tectonic Evolution From the Volcanics in Qiangtang Basin, Tibet

    Institute of Scientific and Technical Information of China (English)

    He Zhonghua; Yang Deming; Li Cai; Pu Zhongyu

    2000-01-01

    The volcanism in Qiangtang Basin is very frequent due to the divergence and subduction of the various plates. The study indicates that these volcanics are formed in different tectonic settings: 1 )Hercynian volcanics are mainly basalts and are formed in the intraplate and intercontinental rift. 2 ) Indosinian volcanics markedly vary in the distribution and composition and reflect transitional MORB and island are environments respectively. 3) Yanshanian volcanics consist predominantly of basalts, andesites, dacites and rhyolites and are characterized by calc- alkaline volcanic suite, indicating island arc setting. 4)Himalayan volcanics are complicated and associated with intraplate orogency. The volcanism provides important tectonic information for recognizing the evolution of Qiangtang Basin.

  16. Reflection seismic imaging in the volcanic area of the geothermal field Wayang Windu, Indonesia

    Science.gov (United States)

    Polom, Ulrich; Wiyono, Wiyono; Pramono, Bambang; Krawczyk, CharLotte M.

    2014-05-01

    Reflection seismic exploration in volcanic areas is still a scientific challenge and requires major efforts to develop imaging workflows capable of an economic utilization, e.g., for geothermal exploration. The SESaR (Seismic Exploration and Safety Risk study for decentral geothermal plants in Indonesia) project therefore tackles still not well resolved issues concerning wave propagation or energy absorption in areas covered by pyroclastic sediments using both active P-wave and S-wave seismics. Site-specific exploration procedures were tested in different tectonic and lithological regimes to compare imaging conditions. Based on the results of a small-scale, active seismic pre-site survey in the area of the Wayang Windu geothermal field in November 2012, an additional medium-scale active seismic experiment using P-waves was carried out in August 2013. The latter experiment was designed to investigate local changes of seismic subsurface response, to expand the knowledge about capabilities of the vibroseis method for seismic surveying in regions covered by pyroclastic material, and to achieve higher depth penetration. Thus, for the first time in the Wayang Windu geothermal area, a powerful, hydraulically driven seismic mini-vibrator device of 27 kN peak force (LIAG's mini-vibrator MHV2.7) was used as seismic source instead of the weaker hammer blow applied in former field surveys. Aiming at acquiring parameter test and production data southeast of the Wayang Windu geothermal power plant, a 48-channel GEODE recording instrument of the Badan Geologi was used in a high-resolution configuration, with receiver group intervals of 5 m and source intervals of 10 m. Thereby, the LIAG field crew, Star Energy, GFZ Potsdam, and ITB Bandung acquired a nearly 600 m long profile. In general, we observe the successful applicability of the vibroseis method for such a difficult seismic acquisition environment. Taking into account the local conditions at Wayang Windu, the method is

  17. Distribution and Evolution of Volcanism of the Bolaven Plateau, Southern Laos

    Science.gov (United States)

    Herrin, J. S.; Sieh, K.; Wiwegwin, W.; Charusiri, P.; Singer, B. S.; Singsomboun, K.; Jicha, B.

    2015-12-01

    The Bolaven Plateau of southern Laos hosts a 6000 km2 basaltic volcanic complex erupted through flat-lying Mesozoic non-marine clastic sedimentary rocks. It is among the largest of dozens of isolated intracontinental Neogene-Quaternary volcanic centers in southeast Asia. The most voluminous flow sequences are tholeiitic, but a significant component of alkalic basalt is also present as morphologically younger cinder cones and related flows that cap the Plateau. Two salient aspects of the volcanic field are these: (1) Lava compositions appear to transition temporally from tholeiitic to alkaline, suggesting that the field tapped low-degree partial melts of a fresh mantle source toward the end of its lifespan. Circumstantial evidence for this can be found in abundant spinel lherzolite, wehrlite, and olivine websterite xenoliths within the alkaline basalts. (2) The volcanic center appears to have initiated atop a pre-existing 1000 m high, 90 km wide bedrock plateau, with nearly all visible vents confined to a 30-km wide zone that extends 80-km north to south. Our work on the Bolaven volcanic complex aims at establishment of a geochemical and temporal framework for its evolution. Using field relationships, petrologic and geochemical studies, and 40Ar/39Ar dating, we hope to unravel the genetic and age relationships of these compositionally varied lava sequences. Another objective of our investigation is to assess the possibility that lavas of the Bolaven might mask the heretofore undiscovered impact site of the Australasian tektite strewnfield (see Sieh et al, this meeting). Toward this aim, we will determine whether a sufficient expanse of the volcanic field is younger than the 0.8 Ma tektites. Finally, we intend to constrain the timing of incision of the Bolaven Plateau by the Mekong River and its tributaries.

  18. Geochemical constraints on the relationship between the Miocene-Pliocene volcanism and tectonics in the Palaoco and Fortunoso volcanic fields, Mendoza Region, Argentina

    DEFF Research Database (Denmark)

    Dyhr, Charlotte Thorup; Holm, Paul Martin; Llambias, Eduardo J.

    2013-01-01

    New 40Ar/39Ar analyses constrain the formation of the volcanic succession of Sierra de Palaoco in the present back-arc of the Andean Southern Volcanic Zone (SVZ), near 36°S, to the Late Miocene and assigns them to the Huincán II Formation. The composition of major and trace elements, Sr, Nd and P...

  19. Geochemical evidence for waning magmatism and polycyclic volcanism at Crater Flat, Nevada

    Science.gov (United States)

    Perry, F. V.; Crowe, B. M.

    Petrologic and geochemical studies of basaltic rocks in the Yucca Mountain region are currently focused on understanding the evolution of volcanism in the Crater Flat volcanic field and the mechanisms of polycyclic volcanism at the Lathrop Wells volcanic center, the youngest center in the Crater Flat volcanic field. Geochemical and petrologic data indicate that the magma chambers which supplied the volcanic centers in Crater Flat became situated at greater crustal depths as the field evolved. Deep magma chambers may be related to a waning magma flux that was unable to sustain upper crystal magma conduits and chambers. Geochemical data from the Lathrop Wells volcanic center indicate that eruptive units identified from field and geomorphic relationships are geochemically distinct. The geochemical variations cannot be explained by fractional crystallization of a single magma batch, indicating that several magma batches were involved in the formation of the Lathrop Wells center. Considering the low magma flux in the Yucca Mountain region in the Quaternary, the probability of several magma batches erupting essentially simultaneously at Lathrop Wells in considered remote. It is more likely that the Lathrop Wells center was formed by a series of eruptions that took place over many thousands of years. The geochemical data from Lathrop Wells is consistent with the concept of a complex, polycyclic volcano, which was originally proposed based on geomorphic and soil-development data.

  20. New geochronological constraints of the Lassen segment's regional volcanism

    Science.gov (United States)

    Germa, A.; Connor, C.; Connor, L.; Malservisi, R.; Tavarez, S.; Charbonnier, S. J.; Clynne, M. A.; Perry, C.; Quidelleur, X.; Ricci, J.

    2015-12-01

    The Lassen region is the southernmost active volcanic field in the Cascade Range. Since ~3.5 Ma distributed mafic to intermediate calc-alkaline magmas continuously built hundreds of cinder cones, lava flows, and a few small shield volcanoes. A set of 10 new unspiked K-Ar ages obtained on groundmass separates help reveal the timing of this regional volcanism. Although most lavas show a high atmospheric contamination level and a low K content, significant ages were obtained with this technique. Shields were dated at about 2.5 Ma (Clynne and Muffler, 2010) and are commonly dissected by erosion. However, we obtained a K-Ar age of 374 ± 25 ka for the late lava flow at the summit of Crater Mountain, which is less eroded than the other shields. This indicates that this regional volcano's activity overlapped that of the Lassen Volcanic Center (LVC), and raises questions regarding the ages of other shields. The Caribou Volcanic field (CVF), at the eastern boundary of the Lassen region, was also contemporaneous with the LVC. The field's activity initiated ~425 ka ago, but does not appear to have extended into the Holocene (Clynne and Muffler, 2010). We obtained a K-Ar age of 296 ± 13 ka on the basaltic andesite of Eleanor Lake, extending further the activity of the Caribou sequence. Our K-Ar age of 59 ± 3 ka on a basaltic flow confirms that the Bidwell Spring Chain was active between 20 and 70 ka as previously shown. We dated the basaltic andesite tuya of Turnaround Lake at 4 ± 5 ka. However, this conflicts with the timing of Tuya chain (15-18 ka). Finally, to the south-west of LVC, basalts of Cold Creek Butte yield an age of 207 ± 26 ka, and we dated a basaltic flow from Inskip Hill at ~5 ka. The new ages obtained, especially the Holocene ones, are consistent with magnetotelluric soundings and gravity data that show mid-crustal anomalies in the back-arc (Tavarez, 2015). These data demonstrate that the CVF is still active and has the potential for future eruptions.

  1. Campagne Fournaise 1: Etude de la partie sous-marine du volcan de la Fournaise

    OpenAIRE

    Lenat, J-f

    1990-01-01

    In 1984, a survey of the bathymetry (Seabeam), the gravity and magnetic fields of the submarine east flank of Piton de la Fournaise was performed with R/V "Jean Charcot ". Piton de la Fournaise is one of the most active volcanoes in the world. It is a basaltic shield volcano which occupies the southeast third of Reunion Island in the southwestern Indian Ocean. Three main types of volcanic or volcano-tectonic features have been identified on the Seabeam map.

  2. A geostatistical method applied to the geochemical study of the Chichinautzin Volcanic Field in Mexico

    Science.gov (United States)

    Robidoux, P.; Roberge, J.; Urbina Oviedo, C. A.

    2011-12-01

    The origin of magmatism and the role of the subducted Coco's Plate in the Chichinautzin volcanic field (CVF), Mexico is still a subject of debate. It has been established that mafic magmas of alkali type (subduction) and calc-alkali type (OIB) are produced in the CVF and both groups cannot be related by simple fractional crystallization. Therefore, many geochemical studies have been done, and many models have been proposed. The main goal of the work present here is to provide a new tool for the visualization and interpretation of geochemical data using geostatistics and geospatial analysis techniques. It contains a complete geodatabase built from referred samples over the 2500 km2 area of CVF and its neighbour stratovolcanoes (Popocatepetl, Iztaccihuatl and Nevado de Toluca). From this database, map of different geochemical markers were done to visualise geochemical signature in a geographical manner, to test the statistic distribution with a cartographic technique and highlight any spatial correlations. The distribution and regionalization of the geochemical signatures can be viewed in a two-dimensional space using a specific spatial analysis tools from a Geographic Information System (GIS). The model of spatial distribution is tested with Linear Decrease (LD) and Inverse Distance Weight (IDW) interpolation technique because they best represent the geostatistical characteristics of the geodatabase. We found that ratio of Ba/Nb, Nb/Ta, Th/Nb show first order tendency, which means visible spatial variation over a large scale area. Monogenetic volcanoes in the center of the CVF have distinct values compare to those of the Popocatepetl-Iztaccihuatl polygenetic complex which are spatially well defined. Inside the Valley of Mexico, a large quantity of monogenetic cone in the eastern portion of CVF has ratios similar to the Iztaccihuatl and Popocatepetl complex. Other ratios like alkalis vs SiO2, V/Ti, La/Yb, Zr/Y show different spatial tendencies. In that case, second

  3. A Disequilibrium Melting Spectrum: Partially Melted Crustal Xenoliths from the Wudalianchi Volcanic Field, NE China.

    Science.gov (United States)

    McLeod, C. L.; McGee, L. E.

    2015-12-01

    Disequilibrium melting has been established as a common process occurring during crustal anatexis and thus demonstrates that crustal assimilation by ascending mantle-derived magmas is likley not a closed system. Observations of extreme compositional heterogeneity within partial melts derived from crustal xenoliths have been documented in several recent examples, however, the retention or transfer of elements to and from residues and glasses, and their relative contributions to potential crustal contaminants warrants further investigation. Sampled lavas from the Huoshaoshan volcano in the Holocene Wudalianchi volcanic field of Northeast China contain crustal xenoliths which preserve a spectrum of partial melting both petrographically and geochemically, thus providing an excellent, natural example of crustal anatexis. Correlations exist between the volume of silicic glass preserved within the xenoliths and bulk rock SiO2 (70-83 wt%), Al2O3 (16-8 wt%), glass 87Sr/86Sr (0.715-0.908), abundances of elements common in feldspars and micas (Sr, Ba, Rb) and elements common in accessory minerals (Y, Zr, Nb). These correlations are likely associated with the consumption of feldspars and micas and the varying retention of accessory phases during partial melting. The xenoliths which contain the greater volumes of silicic glass and residual quartz (interpreted as being the most melted) were found within pahoehoe lava, whilst the least melted xenoliths were found within scoria of the summit cone of Huoshaoshan; thus it is interpreted that the extent of melting is linked to the immersion time in the lava. Small-scale (mm) mingling and transfer of material from the enclosing lava to the xenolith is observed, however, modelling of potential contaminant compositions is inconsistent with crustal contamination during lava petrogenesis. It is inferred that crustal contamination in sampled lavas is localized within the open magmatic system and most likely occurs at the contact zone

  4. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    Directory of Open Access Journals (Sweden)

    A. Aiuppa

    2006-11-01

    Full Text Available Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily. Sulphur dioxide (SO2, hydrogen sulphide (H2S, hydrogen chloride (HCl and hydrogen fluoride (HF concentrations in the volcanic plumes (typically several minutes to a few hours old were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3 at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance, reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions

  5. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    Directory of Open Access Journals (Sweden)

    A. Aiuppa

    2007-01-01

    Full Text Available Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basaltic volcano in eastern Sicily, and Vulcano Island, a closed-conduit quiescent volcano in the Aeolian Islands (northern Sicily. Sulphur dioxide (SO2, hydrogen sulphide (H2S, hydrogen chloride (HCl and hydrogen fluoride (HF concentrations in the volcanic plumes (typically several minutes to a few hours old were repeatedly determined at distances from the summit vents ranging from 0.1 to ~10 km, and under different environmental conditions. At both volcanoes, acidic gas concentrations were found to decrease exponentially with distance from the summit vents (e.g., SO2 decreases from ~10 000 μg/m3at 0.1 km from Etna's vents down to ~7 μg/m3 at ~10 km distance, reflecting the atmospheric dilution of the plume within the acid gas-free background troposphere. Conversely, SO2/HCl, SO2/HF, and SO2/H2S ratios in the plume showed no systematic changes with plume aging, and fit source compositions within analytical error. Assuming that SO2 losses by reaction are small during short-range atmospheric transport within quiescent (ash-free volcanic plumes, our observations suggest that, for these short transport distances, atmospheric reactions for H2S and halogens are also negligible. The one-dimensional model MISTRA was used to simulate quantitatively the evolution of halogen and sulphur compounds in the plume of Mt. Etna. Model predictions support the hypothesis of minor HCl chemical processing during plume transport, at least in cloud-free conditions. Larger

  6. Melding Research on the Navajo Volcanic Field into Undergraduate Curriculum to Promote Scientific Literacy

    Science.gov (United States)

    Gonzales, D. A.

    2011-12-01

    This presentation highlights the curricular design and preliminary outcomes of undergraduate research in the Department of Geosciences at Fort Lewis College (FLC), supported by an NSF-RUI project on the Navajo volcanic field (NVF). A prime impact of this project was to support the education and career development of undergraduate students by further developing basic knowledge and skills in the context of authentic inquiry on petrologic-based research topics. Integrating research into the curriculum promoted scientific habits of mind by engaging students as "active agents" in discovery, and the creative development and testing of ideas. It also gave students a sense of ownership in the scientific process and knowledge construction. The initial phase of this project was conducted in Igneous Petrology at FLC in 2010. Eleven students were enrolled in this course which allowed them to work as a team in collaboration with the PI, and engage in all aspects of research to further develop and hone their skills in scientific inquiry. This course involved a small component of traditional lecture in which selected topics were discussed to provide students with a foundation to understand magmatic processes. This was complemented by a comprehensive review of the literature in which students read and discussed a spectrum of articles on Tertiary magmatism in the western United States and the NVF. Invited lectures by leading-scientists in geology provided opportunities for discussions and interaction with professional geologists. All of the students in the class engaged in the active collection of petrologic data in the field and laboratory sessions, and were introduced to the use of state-of-the art analytical tools as part of their experiences. Four students were recruited from the course to design, develop, and conduct long-term research projects on selected petrologic topics in the NVF. This research allowed these students to engage in the "messy" process of testing existing

  7. Style of Plate Spreading Derived from the 2008-2014 Velocity Field Across the Northern Volcanic Zone of Iceland

    Science.gov (United States)

    Drouin, V.; Sigmundsson, F.; Hreinsdottir, S.; Ofeigsson, B.; Sturkell, E.; Einarsson, P.

    2015-12-01

    The Northern Volcanic Zone (NVZ) of Iceland is a subaerial part of the divergent boundary between the North-American and Eurasian Plates. At this latitude, the full spreading between the plates is accommodated by the NVZ. We derived the plate boundary velocity field from GPS campaign and continuous measurements between 2008 and 2014, a time period free of any magma intrusion. Average velocities were estimated in the ITRF08 reference frame. The overall extension is consistent with 18 mm/yr in the 104°N direction spreading, in accordance with the MORVEL2010 plate motion model. We find that a 40km-wide band along the plate boundary accommodates about 75% of the full plate velocities. Within this zone, the average strain rate is approximately 0.35 μstrain/yr. The deformation field and the strain rate are, however, much affected by other sources of deformations in the NVZ. These include magmatic sources at the most active volcanic centers, glacial rebound near the ice-caps and geothermal power-plant water extraction. Magmatic sources include a shallow magma chamber deflation under Askja caldera, as well as under Þeistareykir and eventual deep magma inflation north of Krafla volcano. Vatnajökull ice cap melting causes large uplift and outward displacements in the southern part of the NVZ. The two geothermal power-plants near Krafla are inducing local deflations. Our GPS velocities show a 35° change in the direction of the plate boundary axis north of Askja volcano that we infer to be linked to the geometric arrangement of volcanic systems within the NVZ.We use a simple arctangent model to describe the plate spreading to provide constraints on the location and the locking depth of the spreading axis. For that purpose we divided the area in short overlapping segments having the same amount of GPS points along the plate spreading direction and inverted for the location of the center of the spreading axis and locking depth. With this simple model we can account for most

  8. Revisiting the Jurassic Geomagnetic Reversal recorded in the Lesotho Basalt (Southern Africa)

    CERN Document Server

    Prévot, M; Thompson, J; Faynot, L; Perrin, M; Camps, P; Prevot, Michel; Roberts, Neil; Thompson, John; Faynot, Liliane; Perrin, Mireille; Camps, Pierre

    2003-01-01

    We carried out a detailed and continuous paleomagnetic sampling of the reversed to normal geomagnetic transition recorded by some 60 consecutive flow units near the base of the Lesotho Basalt (183  1 Ma). After alternating field or thermal cleaning the directions of remanence are generally well clustered within flow units. In contrast, the thermal instability of the samples did not allow to obtain reliable paleointensity determinations. The geomagnetic transition is incompletely recorded due to a gap in volcanic activity attested both by eolian deposits and a large angular distance between the field directions of the flows underlying or overlying these deposits. The transition path is noticeably different from that reported in the pioneer work of van Zijl et al. (1962). The most transitional Virtual Geomagnetic Poles are observed after the volcanic hiatus. Once continents are replaced in their relative position 180 Ma ago, the post-hiatus VGP cluster over Russia. However, two successive rebounds f...

  9. The Cerro Bitiche Andesitic Field: petrological diversity and implications for magmatic evolution of mafic volcanic centers from the northern Puna

    Science.gov (United States)

    Maro, Guadalupe; Caffe, Pablo J.

    2016-07-01

    The Cerro Bitiche Andesitic Field (CBAF) is one of the two largest mafic volcanic fields in northern Puna (22-24° S) and is spatially and temporally associated with ignimbrites erupted from some central Andean Altiplano-Puna Volcanic Complex calderas. The CBAF comprises seven scoria cones and widespread high-K calcalkaline lava flows that cover an area of 200 km2. Although all erupted rocks have a relatively narrow chemical range (56-62 % SiO2, 3-6 % MgO), there is a broad diversity of mineral compositions and textures. The least evolved lavas (˜58-61 % SiO2) are high-Mg andesites with scarce (<10 %) microphenocrysts of either olivine or orthopyroxene. The small compositional range and low phenocryst content indicate evolution controlled by low percentages (<10 %) of fractional crystallization of olivine and clinopyroxene of magmas similar to the least evolved rocks from the field, accompanied by assimilation during rapid ascent through the crust. Evolved andesites (˜62 wt% SiO2), on the other hand, are porphyritic rocks with plagioclase + orthopyroxene + biotite and ubiquitous phenocryst disequilibrium textures. These magmas were likely stored in crustal reservoirs, where they experienced convection caused by mafic magma underplating, magma mixing, and/or assimilation. Trace element and mineral compositions of CBAF lavas provide evidence for complex evolution of distinct magma batches.

  10. Evolution and genesis of volcanic rocks from Mutnovsky Volcano, Kamchatka

    Science.gov (United States)

    Simon, A.; Yogodzinski, G. M.; Robertson, K.; Smith, E.; Selyangin, O.; Kiryukhin, A.; Mulcahy, S. R.; Walker, J. D.

    2014-10-01

    This study presents new geochemical data for Mutnovsky Volcano, located on the volcanic front of the southern portion of the Kamchatka arc. Field relationships show that Mutnovsky Volcano is comprised of four distinct stratocones, which have grown over that past 80 ka. The youngest center, Mutnovsky IV, has produced basalts and basaltic andesites only. The three older centers (Mutnovsky I, II, III) are dominated by basalt and basaltic andesite (60-80% by volume), but each has also produced small volumes of andesite and dacite. Across centers of all ages, Mutnovsky lavas define a tholeiitic igneous series, from 48-70% SiO2. Basalts and basaltic andesites have relatively low K2O and Na2O, and high FeO* and Al2O3 compared to volcanic rocks throughout Kamchatka. The mafic lavas are also depleted in the light rare earth elements (REEs), with chondrite-normalized La/Sm arc volcanic rocks worldwide. Radiogenic isotope ratios (Sr, Nd, Pb, Hf) are similar for samples from all four eruptive centers, and indicate that all samples were produced by melting of a similar source mixture. No clear age-progressive changes are evident in the compositions of Mutnovsky lavas. Mass balance and assimilation-fractional crystallization (AFC) modeling of major and rare earth elements (REEs) indicate that basaltic andesites were produced by FC of plagioclase, clinopyroxene and olivine from a parental basalt, combined with assimilation of a melt composition similar to dacite lavas present at Mutnovsky. This modeling also indicates that andesites were produced by FC of plagioclase from basaltic andesite, combined with assimilation of dacite. Dacites erupted from Mutnovsky I and II have low abundances of REEs, and do not appear to be related to mafic magmas by FC or AFC processes. These dacites are modeled as the products of dehydration partial melting at mid-crustal levels of a garnet-free, amphibole-bearing basaltic rock, which itself formed in the mid-crust by emplacement of magma that

  11. Geochemical characteristics of the oceanic island- type volcanic rocks in the Chiang Mai zone, northern Thailand

    Institute of Scientific and Technical Information of China (English)

    SHEN Shangyue; FENG Qinglai; ZHANG Zhibin; CHONGPAN Chonglakmani

    2009-01-01

    The oceanic island volcanic rocks in the Chiang Mai zone, northern Thailand, are usually covered by Lower Carboniferous and Upper Permian shallow-water carbonate rocks, with the Hawaii rocks and potash trachybasalt being the main rock types. The alkaline series is dominant with sub-alkaline series occurring in few cases. The geochemical characteristics are described as follows: the major chemical compositions are characterized by high TiO2, high P2O5 and medium K2O; the rare-earth elements are characterized by right-inclined strong LREE-enrichment patterns; the trace element patterns are of the upward-bulging K-Ti enrichment type; multi-component plots falling within the fields of oceanic island basalts and alkali basalts, belonging to the oceanic island-type volcanic rocks, which are similar to the equivalents in Deqin and Gengma (the Changning-Menglian zone) of Yunnan Province, China.

  12. Feasibility of using the magnetotelluric method for sub- basalt imaging at Kachchh, India%利用大地电磁资料对玄武岩成像的可行性

    Institute of Scientific and Technical Information of China (English)

    Dhananjai Pandey; Lucy MacGregor; Martin Sinha; Satish Singh

    2008-01-01

    The magnetotelluric (MT) method has been among the favorite supporting tools for seismic imaging of sub-salt and sub-basalt targets. In this paper we present an example from Kachchh, India (where basaltic rocks overlie Mesozoic sedimentary rocks), and discuss the feasibility of using MT method as an exploration tool in this geological setting. Our results highlight the difference in magnetotelluric response caused by the thin intra-basalt layering. The key issue addressed in this paper is what MT can and cannot provide in such geological settings. First, we compute apparent resistivity and phase response curves using representative resistivity-depth models and borehole data from the study area. Later, we compare these results to assess the plausibility of using MT to image the sub-volcanic sediments at Kachchh. Finally, we substantiate our discussion through one-dimensional inversion of the field observed MT data from this region that exhibits poor sensitivity of MT for thin basalt layers.

  13. Fracture development within a stratovolcano: The Karaha-Telaga Bodas geothermal field, Java volcanic arc

    Science.gov (United States)

    Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

    2004-01-01

    Karaha-Telaga Bodas, a vapour-dominated geothermal system located in an active volcano in western Java, is penetrated by more than two dozen deep geothermal wells reaching depths of 3 km. Detailed paragenetic and fluid-inclusion studies from over 1000 natural fractures define the liquid-dominated, transitional and vapour-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by ashallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures that developed were filled with carbonates at shallow depths, and by quartz, epidote and actinolite at depths and temperatures over 1 km and 300??C. The system underwent numerous cycles of overpressuring, documented by subhorizontal tensile fractures, anastomosing tensile fracture patterns and implosion breccias. The development of the liquidsystem was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were selectively deposited in fractures that had the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapour-dominated conditions were initiated at this time within a vertical chimney overlying the still hot intrusion. As pressures declined, these conditions spread outward to form the marginal vapour-dominated region encountered in the drill holes. Downward migration of the chimney, accompanied by growth of the marginal vapour-dominated regime, occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. As the liquids boiled off, condensate that formed at the top of the vapour-dominated zone percolated downward and low

  14. Development of a geothermal resource in a fractured volcanic formation: Case study of the Sumikawa Geothermal Field, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Garg, S.K.; Pritchett, J.W.; Stevens, J.L.; Luu, L. [Maxwell Federal Div., Inc., San Diego, CA (United States); Combs, J. [Geo-Hills Associates, Los Altos, CA (United States)

    1996-11-01

    The principal purpose of this case study of the Sumikawa Geothermal Field is to document and to evaluate the use of drilling logs, surface and downhole geophysical measurements, chemical analyses, and pressure transient data for the assessment of a high temperature volcanic geothermal field. The work accomplished during Year 1 of this ongoing program is described in the present report. A brief overview of the Sumikawa Geothermal Field is given. The drilling information and downhole pressure, temperature, and spinner surveys are used to determine feedzone locations, pressures and temperatures. Available injection and production data from both slim holes and large-diameter wells are analyzed to evaluate injectivity/productivity indices and to investigate the variation of discharge rate with borehole diameter. Finally, plans for future work are outlined.

  15. Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA

    Science.gov (United States)

    Muirhead, James D.; Van Eaton, Alexa R.; Re, Giuseppe; White, James D. L.; Ort, Michael H.

    2016-01-01

    Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi Buttes volcanic field, Arizona, to shed light on the nature of its magma feeder system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field- and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other eruptive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 106 m3) and sills (minimum volume of 8.47 × 105 m3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (∼2.75 × 106 m3 total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decimeters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere

  16. Petrology and Geochemistry of Hydrothermally Altered Volcanic Rocks in the Iheya North Hydrothermal Field, Middle Okinawa Trough

    Science.gov (United States)

    Yamasaki, T.

    2015-12-01

    The Iheya North hydrothermal field is located in the middle Okinawa Trough, a young and actively spreading back-arc basin extending behind the Ryukyu arc-trench system in the southeastern margin of the East China Sea. In this hydrothermal field, two scientific drilling expeditions (IODP Exp 331 and SIP CK14-04) were conducted using a deep-sea drilling vessel "Chikyu," and samples from a total of 27 holes were taken. Through these expeditions, Kuroko-type volcanogenic massive sulfide deposits (VMS), hydrothermally altered volcanic rocks, and pumiceous and pelagic sediments were recovered. The recovered core provided important information about the relationship between hydrothermal activity, alteration, and ore mineralization. Whole-rock major element composition and trace element (TE) patterns of pumices were very similar to those of rhyolites in the middle Okinawa Trough (RMO). However, pumices were relatively enriched in chalcophile elements Sr and Nb, which suggest incipient mineralization. Volcanic rock generally demonstrated strong silicification and was greenish pale gray in color. Regardless of severe alteration, some rock displayed major element composition broadly similar to the RMO. Alteration was evidenced by an increase in the content of SiO2 and MgO, and decrease in Al2O3, Na2O, and K2O content. The most striking geochemical feature of altered volcanic rock was the discordance between texture and the degree of modification of TEs. Some samples showed decussate texture occupied by petal-like quartz with severe silicification, but no prominent disturbance of concentration and patterns of TEs were observed. In contrast, samples with well-preserved igneous porphyritic texture showed very low TE content and modification of TE patterns. These results suggest that the modification of texture and composition of TEs, as well as silicification, do not occur by a uniform process, but several processes. This may reflect the differences in temperature and the

  17. The Oldest Known Caldera Associated with the Yellowstone Hotspot: New Geologic Mapping, Geochemistry, and 40Ar/39Ar Geochronology for the Northern McDermitt Volcanic Field, Northern Nevada and Southeastern Oregon

    Science.gov (United States)

    Benson, T. R.; Mahood, G. A.

    2015-12-01

    McDermitt Volcanic Field (MVF) of Nevada and Oregon is one of three major caldera centers associated with Mid-Miocene Steens/Columbia River flood basalts. Pioneering geologic mapping of MVF by Rytuba and McKee (1984) and subsequent work established four main ignimbrites within the field. Our new 40Ar/39Ar ages (FCT=28.02 Ma) are 16.41±0.02 (±2σ) Ma for Tuff of Oregon Canyon, 16.35±0.04 Ma for Tuff of Trout Creek Mountains, 16.30±0.04 Ma for Tuff of Long Ridge, and 15.56±0.08 Ma for Tuff of Whitehorse Creek. We have mapped two previously unrecognized overlapping calderas that we interpret as sources for Tuff of Oregon Canyon and Tuff of Trout Creek. These ~20-km diameter calderas lie north of the well-known McDermitt Caldera; a smaller 7-km caldera that formed on eruption of the Tuff of Whitehorse Creek is nested within them. Argon ages and geochemistry of alkali rhyolite lava domes in the northern MVF define two populations: ~16.6-16.3 Ma associated with the newly recognized calderas, and ~15.5-15.3 Ma outlining the margins of the younger Whitehorse Caldera. Consistent with both ignimbrites erupting from the same evolving magma system, the high-silica alkali rhyolite Tuff of Oregon Canyon lies on compositional trends defined by the Tuff of Trout Creek, which is zoned from a moderately crystal-rich high-silica alkali rhyolite to a strongly porphyritic low-silica alkali rhyolite. They both are distinguished from the Tuff of Long Ridge from McDermitt Caldera by their higher Zr/Rb, and relatively high FeO* concentrations distinguish all MVF ignimbrites from ignimbrites from the nearby High Rock Caldera Complex, where the oldest caldera formed on eruption of the Idaho Canyon Tuff at 16.38±0.02 Ma (Coble and Mahood, in review). The Tuff of Trout Creek rests conformably on the Tuff of Oregon Canyon west and southwest of the calderas, where they overlie a thick stack of Steens Basalt lavas. To the east and southeast the two ignimbrites are separated by as much as

  18. Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA

    Science.gov (United States)

    Muirhead, James D.; Van Eaton, Alexa R.; Re, Giuseppe; White, James D. L.; Ort, Michael H.

    2016-02-01

    Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field- and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated, and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other eruptive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 106 m3) and sills (minimum volume of 8.47 × 105 m3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (˜2.75 × 106 m3 total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decimeters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the important role of shallow sills in active monogenetic fields.

  19. Origin of High-Alumina Basalt, Andesite, and Dacite Magmas.

    Science.gov (United States)

    Hamilton, W

    1964-10-30

    The typical volcanic rocks of most island arcs and eugeosynclines, and of some continental environments, are basalt, andesite, and dacite, of high alumina content. The high-alumina basalt differs from tholeiitic basalt primarily in having a greater content of the components of calcic plagioclase. Laboratory data indicate that in the upper mantle, below the level at which the basaltic component of mantle rock is transformed by pressure to eclogite or pyroxenite, the entire basaltic portion probably is melted within a narrow temperature range, but that above the level of that transformation plagioclase is melted selectively before pyroxene over a wide temperature range. The broad spectrum of high-alumina magmas may represent widely varying degrees of partial melting above the transformation level, whereas narrow-spectrum tholeiite magma may represent more complete melting beneath it.

  20. Reverse Faulting as a Crucial Mechanism for Magma Ascent in Compressional Volcanic Arcs: Field Examples from the Central Andes

    Science.gov (United States)

    Aron, F. A.; Gonzalez, G.; Cembrano, J. M.; Veloso, E. E.

    2010-12-01

    The nature of crustal deformation in active arcs and the feedback mechanisms between tectonics and magma transport constitute fundamental problems in the understanding of volcanic systems. Additionally, for geothermal energy exploration, a better understanding of how crustal architecture and stress field controls fluid ascent and heat transfer from deep levels to the surface is crucial. The Central Andes volcanic belt is an excellent, modern example of such systems but, the scarcity of good outcrops has limited our ability to define the relations between structure and volcanism. In the Salar de Atacama Basin of northern Chile, there are good exposures of folded and faulted Neogene units (continental sediments, volcanic rocks and ignimbrites) and reverse faults spatially and temporally related to volcanic edifices. The subsurface of the study area has been interpreted by previous authors as a thin-skinned, 6-8 km-deep, east-vergent compressional belt. We carried out structural mapping, Digital Elevation Models (DEMs) analyses, strain tensor analyses and fault-related fold kinematic modelling to assess the causal relationship between compressional deformation and magmatism in this region. Field observations indicate that the structures deformed progressively Oligocene-Miocene continental sedimentary units, the upper sedimentary infill of the Salar de Atacama basin (Pliocene-Present), and Pliocene-Pleistocene Ignimbrites. The topographic expression of the compressional belt corresponds to a set of subparallel, asymmetric, fault-related-folds, which can be seen in the field as prominent NS-trending ridges with heights ranging between 50 and 400 m. Furthermore, we found evidence of a ~100 km-long structure along the active magmatic arc, so-called Miscanti Fault. This fault represents the easternmost expression of the above mentioned compressional belt. Pleistocene-Holocene monogenetic cones and strato-volcanoes are located either at the hinge zone of fault

  1. Can we identify source lithology of basalt?

    Science.gov (United States)

    Yang, Zong-Feng; Zhou, Jun-Hong

    2013-01-01

    The nature of source rocks of basaltic magmas plays a fundamental role in understanding the composition, structure and evolution of the solid earth. However, identification of source lithology of basalts remains uncertainty. Using a parameterization of multi-decadal melting experiments on a variety of peridotite and pyroxenite, we show here that a parameter called FC3MS value (FeO/CaO-3*MgO/SiO2, all in wt%) can identify most pyroxenite-derived basalts. The continental oceanic island basalt-like volcanic rocks (MgO>7.5%) (C-OIB) in eastern China and Mongolia are too high in the FC3MS value to be derived from peridotite source. The majority of the C-OIB in phase diagrams are equilibrium with garnet and clinopyroxene, indicating that garnet pyroxenite is the dominant source lithology. Our results demonstrate that many reputed evolved low magnesian C-OIBs in fact represent primary pyroxenite melts, suggesting that many previous geological and petrological interpretations of basalts based on the single peridotite model need to be reconsidered.

  2. Geochemical Characteristics and Metallogenesis of Volcanic Rocks as Exemplified by Volcanic Rocks in Ertix,Xinjiang

    Institute of Scientific and Technical Information of China (English)

    刘铁庚; 叶霖

    1997-01-01

    Volcanic rocks in Ertix,Xinjiang,occurring in the collision zone between the Siberia Plate and the Junggar Plate,are distributed along the Eritix River Valley in northern Xinjiang.The volcanic rocks were dated at Late Paleozoic and can be divided into the spilite-keratophyre series and the basalt-andesite series.The spilite-keratophyre series volcanic rocks occur in the Altay orogenic belt at the southwest margin of the Siberia Plate.In addition to sodic volcanic rocks.There are also associated potassic-sodic volcanic rocks and potassic volcanic rocks.The potassic-sodic volcanic rocks occur at the bottom of the eruption cycle and control the distribution of Pb and Zn deposits.The potassic volcanic rocks occur at the top of the eruption cycle and are associated with Au and Cu mineralizations.The sodic volcanic rocks occur in the middle stage of eruption cycle and control the occurrence of Cu(Zn) deposits.The basalt-andesite series volcanic rocks distributed in the North Junggar orogenic belt at the north margin of the Junggar-Kazakstan Plate belong to the potassic sodic volcain rocks.The volcanic rocks distributed along the Ulungur fault are relatively rich in sodium and poor in potassium and are predominated by Cu mineralization and associated with Au mineralization.Those volcanic rocks distributed along the Ertix fault are relatively rich in K and poor in Na,with Au mineralization being dominant.

  3. Recent eruptive episodes of the Rungwe volcanic field (Tanzania) recorded in lacustrine sediments of the Northern malawi rift

    Science.gov (United States)

    Williams, T. M.; Henney, P. J.; Owen, R. B.

    1993-07-01

    Discrete ash horizons in Holocene sediments from northern Lake Malawi provide evidence of six eruptive episodes within the nearby Rungwe Volcanic Field between c.9000-360 BP. Rare earth element (REE) analyses show the ash layers to be strongly enriched in La, Ce, Pr, Nd, Sm, Tb, Dy, Er, Tm, Yb and Lu, with low Eu/Eu∗ and high La N/Sm N values, relative to the surrounding muds. Mixing calculations suggest possible affinities between the Rungwe ash emissions and silicic volcanics from other important Quaternary centres (e.g. Naivasha) with respect to HREE geochemistry. The LREE spectra are less comparable and may indicate a less fractionated ash assemblage for Rungwe Field. In the absence of clear in situ evidence regarding the timing and frequency of Holocene eruptions at Rungwe, the Lake Malawi sediments may prove a valuable reconstructive tool. However, the direction and extent of ash dispersal is strongly controlled by wind/climatic factors and the retention of a complete record at any single location is unlikely.

  4. Recurrence models of volcanic events: Applications to volcanic risk assessment

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M. [Los Alamos National Lab., Las Vegas, NV (United States); Picard, R.; Valentine, G. [Los Alamos National Lab., NM (United States); Perry, F.V. [New Mexico Univ., Albuquerque, NM (United States)

    1992-03-01

    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km{sup 2} area of Yucca Mountain by ascending basalt magma was bounded by the range of 10{sup {minus}8} to 10{sup {minus}10} yr{sup {minus}1 2}. The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site.

  5. Recurrence models of volcanic events: Applications to volcanic risk assessment

    International Nuclear Information System (INIS)

    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Risk used in this context refers to a combined assessment of the probability and consequences of future volcanic activity. Past studies established bounds on the probability of magmatic disruption of a repository. These bounds were revised as additional data were gathered from site characterization studies. The probability of direct intersection of a potential repository located in an eight km2 area of Yucca Mountain by ascending basalt magma was bounded by the range of 10-8 to 10-10 yr-12. The consequences of magmatic disruption of a repository were estimated in previous studies to be limited. The exact releases from such an event are dependent on the strike of an intruding basalt dike relative to the repository geometry, the timing of the basaltic event relative to the age of the radioactive waste and the mechanisms of release and dispersal of the waste radionuclides in the accessible environment. The combined low probability of repository disruption and the limited releases associated with this event established the basis for the judgement that the risk of future volcanism was relatively low. It was reasoned that that risk of future volcanism was not likely to result in disqualification of the potential Yucca Mountain site

  6. Long-distance lava correlation in the Paraná volcanic province along the Serra Geral cuesta, southeastern Brazil

    Science.gov (United States)

    Hartmann, L. A.; Arena, K. R.; Duarte, S. K.; Pertille, J.

    2013-09-01

    The capability of determining the flow-by-flow stratigraphy and the long-distance correlation of lava flows in large continental volcanic provinces leads to a considerable advance in the understanding of processes related to generation and evolution of the lavas. The Paraná volcanic province is exposed along the Serra Geral cuesta of southern Brazil in a steeply inclined, 1,000-m-high section starting 40-m above sea level. Each of the 10-20 pahoehoe flows and rhyodacite flow units has a unique chemical composition. Integrated with field stratigraphy and gamma-spectrometric measurements, this leads to the establishment of the correct stratigraphic sequence in each of three different vertical sections. The number of flows integrating the three serras is 26 ("serra" is a mountain range in Portuguese). Each serra has basaltic andesites at the base, whereas rhyodacites are intercalated with basaltic andesites at the top. Three basaltic andesite flows and one rhyodacite flow unit are correlated between Serra Umbu and Serra Boa Vista (10 km). In the Serra Faxinal, a thick (170 m) sill at the base correlates with flow 13F, whereas a dike-sill in the Graxaim quarry (24 km distance) correlates with flow 3F. One basaltic andesite and two rhyodacite flow units correlate between Serra Faxinal and Serra Umbu (50 km). The results are most significant for the understanding of large tracts of continental volcanic provinces with use of common geochemical and gamma-spectrometric techniques.

  7. Neogene volcanism in Gutai Mts. (Eastern Carpathains: a review

    Directory of Open Access Journals (Sweden)

    Marinel Kovacs

    2003-04-01

    Full Text Available Two types of volcanism developed in Gutâi Mts. (inner volcanic chain of Eastern Carpathians: a felsic, extensional/“back-arc” type and an intermediate, arc type. The felsic volcanism of explosive origin, consisting of caldera-related rhyolitic ignimbrites and resedimented volcaniclastics, had taken place during Early-Middle Badenian and Early Sarmatian. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The intermediate volcanism, consisting of extrusive (effusive and explosive and intrusive activity, had developed during Sarmatian and Pannonian (13.4-7.0 Ma. It is represented by typical calc-alkaline series, from basalts to rhyolites. Lava flows of basaltic andesites and andesites are predominant, often emplaced in subaqueous environment. Extrusive domes, mainly composed of dacites, are associated to the andesitic volcanic structures. The geochemical study on the volcanic rocks shows the calc-alkaline character of both felsic and intermediate volcanism and typical subduction zones geochemical signatures for the intermediate one. The felsic volcanism shows affinities with subduction-related rocks as well. The main petrogenetic process in Gutâi Mts. was crustal assimilation, strongly constrained by trace element and isotope geochemistry.

  8. Incremental assembly and prolonged consolidation of Cordilleran magma chambers--Evidence from the Southern Rocky Mountain volcanic field

    Science.gov (United States)

    Lipman, Peter W.

    2007-01-01

    Recent inference that Mesozoic Cordilleran plutons grew incrementally during >106 yr intervals, without the presence of voluminous eruptible magma at any stage, minimizes close associations with large ignimbrite calderas. Alternatively, Tertiary ignimbrites in the Rocky Mountains and elsewhere, with volumes of 1–5 × 103 km3, record multistage histories of magma accumulation, fractionation, and solidification in upper parts of large subvolcanic plutons that were sufficiently liquid to erupt. Individual calderas, up to 75 km across with 2–5 km subsidence, are direct evidence for shallow magma bodies comparable to the largest granitic plutons. As exemplified by the composite Southern Rocky Mountain volcanic field (here summarized comprehensively for the first time), which is comparable in areal extent, magma composition, eruptive volume, and duration to continental-margin volcanism of the central Andes, nested calderas that erupted compositionally diverse tuffs document deep composite subsidence and rapid evolution in subvolcanic magma bodies. Spacing of Tertiary calderas at distances of tens to hundreds of kilometers is comparable to Mesozoic Cordilleran pluton spacing. Downwind ash in eastern Cordilleran sediments records large-scale explosive volcanism concurrent with Mesozoic batholith growth. Mineral fabrics and gradients indicate unified flow-age of many pluton interiors before complete solidification, and some plutons contain ring dikes or other textural evidence for roof subsidence. Geophysical data show that low-density upper-crustal rocks, inferred to be plutons, are 10 km or more thick beneath many calderas. Most ignimbrites are more evolved than associated plutons; evidence that the subcaldera chambers retained voluminous residua from fractionation. Initial incremental pluton growth in the upper crust was likely recorded by modest eruptions from central volcanoes; preparation for caldera-scale ignimbrite eruption involved recurrent magma input and

  9. Ship Rock Diatreme: is it a Classical Volcano? New Evidence on Magma Ascent and Emplacement Within the Navajo Volcanic Field

    Science.gov (United States)

    Rotzien, J. R.; Mayhew, B.; Yospin, S.; Beiki, A.; Tewksbury, C.; Hardman, D.; Bank, C.; Noblett, J.; Semken, S.; Kroeger, G.

    2007-12-01

    The Navajo Volcanic Field (NVF) is an area of late-Tertiary volcanism along the New Mexico-Arizona border near the Four Corners region of the American Southwest. Among the roughly 80 exhumed diatremes that comprise the NVF, Ship Rock and The Thumb are two diatremes that present an interesting problem concerning magma ascent and emplacement within the NVF. Are the diatremes remnants of classical volcanoes with underlying magma chambers, or are the diatremes formed from buds off of upward propagating dike swarms? The 2006 Keck Consortium Geophysics Project collected non-invasive gravity and magnetic data to image the subsurface of Ship Rock and The Thumb to suggest constraints concerning the formation of these diatremes within the Navajo Volcanic Field. At Ship Rock, we collected over 120 gravity points spaced 500 m apart along 10 lines. We also collected about 65,000 magnetic points that cover an area of 1,570,000 square meters surrounding Ship Rock. The gravity data reveal gravity lows several kilometers away from Ship Rock, probably as a result of thick sedimentary units close to the surface. A steep gradient of 5 mGal/km separates the gravity lows from a strong gravity high immediately to the southwest of Ship Rock. We interpret this gravity high to be uneven basement topography or a magma chamber at depth; further studies are required to determine which of the interpretations is more likely. The Ship Rock magnetic data show the prominent west and northeast dikes extend well beyond their surface outcrops while the southern dike extends only to its visible termination. The magnetic data we collected at The Thumb along ~18 km of lines reveal a linear northeast-southwest trending magnetic anomaly about 105 to 360 nT in amplitude that crosses the diatreme. We interpret the anomaly to be a dike beneath The Thumb. Models of the total field magnetic data suggest a dike at shallow depths of about 0.1 to 4.8 m and widths of about 0.25 to 1.5 m with a steep dip to the

  10. 40Ar/39Ar geochronology and geochemical reconnaissance of the Eocene Lowland Creek volcanic field, west-central Montana

    Science.gov (United States)

    Dudas, F.O.; Ispolatov, V.O.; Harlan, S.S.; Snee, L.W.

    2010-01-01

    We report geochronological and geochemical data for the calc-alkalic Lowland Creek volcanic field (LCVF) in westcentral Montana. 40Ar/ 39Ar age determinations show that the LCVF was active from 52.9 to 48.6 Ma, with tuff-forming eruptions at 52.9 ?? 0.14 and 51.8 ?? 0.14 Ma. These dates span the age range of vigorous Eocene igneous activity in the Kamloops-Absaroka-Challis belt. The LCVF evolved upward from basal rhyolites (SiO 2>71 wt%) to dacites and andesites (SiO 2 > 62 wt%). Compositional change parallels a transition from early explosive volcanism to late effusive activity. Four geochemical components can be detected in the rocks. A component with 206Pb/204Pb 18.3 and epsilon;Nd>-9 contain a third component; and an andesite with low Nd content and epsilon;Nd near-9 probably contains a fourth component. The first three components probably derive from the lower and middle crust, whereas the fourth is probably from the lithospheric mantle. ?? 2010 by The University of Chicago.

  11. Plio-Pleistocene paleomagnetic secular variation and time-averaged field: Ruiz-Tolima volcanic chain, Colombia

    Science.gov (United States)

    Sánchez-Duque, A.; Mejia, V.; Opdyke, N. D.; Huang, K.; Rosales-Rivera, A.

    2016-02-01

    Paleomagnetic results obtained from 47 Plio-Pleistocene volcanic flows from the Ruiz-Tolima Volcanic Chain (Colombia) are presented. The mean direction of magnetization among these flows, which comprise normal (n = 43) and reversed (n = 4) polarities, is Dec = 1.8°, Inc = 3.2°, α95 = 5.0°, and κ = 18.4. This direction of magnetization coincides with GAD plus a small persistent axial quadrupolar component (around 5%) at the site-average latitude (4.93°). This agreement is robust after applying several selection criteria (α95 < 10º α95 < 5.5º polarities: normal, reversed, and tentatively transitional). The data are in agreement with Model G proposed by McElhinny and McFadden (1997) and the fit is improved when sites tentatively identified as transitional (two that otherwise have normal polarity) are excluded from the calculations. Compliance observed with the above mentioned time-averaged field and paleosecular variation models, is also observed for many recent similar studies from low latitudes, with the exception of results from Galapagos Islands that coincide with GAD and tend to be near sided.

  12. Lava tubes from the Paraná-Etendeka Continental Flood Basalt Province: Morphology and importance to emplacement models

    Science.gov (United States)

    Waichel, Breno L.; Tratz, Eliza B.; Pietrobelli, Gisele; Jerram, Dougal A.; Calixto, Geovane R.; Bacha, Rafael R.; Tomazzolli, Edison R.; da Silva, Wellington B.

    2013-12-01

    Lava tubes are a common feature in active volcanic areas around the world. They are related to pahoehoe and 'a'ā lava flow fields, that are predominantly basaltic, and form as the most efficient mechanism to transport lava in insulated fedder pathways. Continental Flood Basalt Provinces (CFBs) are thick volcanic sequences of predominantly basaltic lava flows and flow fields, which cover huge areas and are often related to continental breakup. The proposed emplacement model for CFB's is synonymous with the inflation processes observed in modern active flows. Although pahoehoe and 'a'ā lava flows are recognized in CFB's provinces, good examples of lava tubes, pipes or tube systems are rarely reported. Lava feeder systems (tube/pipes) are a common feature of modern pahoehoe flow systems so it would be expected to find good examples in CFB's provinces formed by the same emplacement processes. Here we describe the morphology of two lava tube systems discovered in the Paraná CFB Province in Southern Brazil. Comparisons are made with active systems and the importance of CFB lava tube systems, and their recognition in the rock record, are discussed in the context of the current emplacement model.

  13. H 2O in basalt and basaltic andesite glass inclusions from four subduction-related volcanoes

    Science.gov (United States)

    Sisson, T. W.; Layne, G. D.

    1993-06-01

    Total dissolved H 2O and major element abundances were measured in basalt and basaltic andesite glass inclusions in olivine phenocrysts from Quaternary eruptions of four subduction-related volcanoes to test the hypothesis that low-MgO high-alumina basalts contain high H 2O at depth [1] and to reveal any petrogenetically significant correlations between arc basalt compositions and H 2O contents. Total dissolved H 2O (combined molecular H 2O and OH groups) measured by ion microprobe in mafic glass inclusions from the 1974 eruption of Fuego, Guatemala, reaches 6.2 wt.%. Dissolved H 2O contents decrease in more evolved Fuego glasses. Correlations of H 2O with MgO, Na 2O, K 2O, S and Cl indicate that aqueous fluid exsolution during magma ascent forced crystallization and differentiation of residual liquids. Low-K 2O magnesian high-alumina basalt glass inclusions from the 3 ka eruption of Black Crater (Medicine Lake volcano, California) have low H 2O contents, near 0.2 wt.%, which are consistent with the MORB-like character of these and other primitive lavas of the Medicine Lake region. Basalt and basaltic andesite glass inclusions from Copco Cone and Goosenest volcano on the Cascade volcanic front north of Mt. Shasta have H 2O contents of up to 3.3 wt.%. The range of H 2O contents in Cascade mafic magmas is too large to have resulted solely from enrichment by crystallization and indicates the participation of an H 2O-rich component in magma generation or crustal-level modification. Whereas fluid-absent melting of amphibole-bearing peridotite can account for the H 2O in most mafic arc liquids, the very high H 2O/alkali ratios of the 1974 Fuego eruptives suggest that an aqueous fluid was involved in the generation of Fuego basalts.

  14. Geochemical characteristics of Bikou volcanic group and Sr-Nd-Pb isotopic composition: Evidence for breakup event in the north margin of Yangtze plate, Jining era

    Institute of Scientific and Technical Information of China (English)

    LI; YongFei; LAI; ShaoCong; QIN; JiangFeng; LIU; Xin; WANG; Juan

    2007-01-01

    The geodynamic setting of the Bikou volcanic group is a critical question to trace the Precambrain tectonic framework and evolution for the Yangtze plate. This study has suggested that the Bikou volcanic group is composed of several residual oceanic crust units: MORB (mid-ocean ridge basalt), Alk-OIB (alkaline ocean island basalt) and Th-OIB (tholeiitic ocean island basalt) as well as subduction-related volcanic rocks. According to field observation, those distinct rocks occurred collectively in form of tectonic contact, implying that the Bikou volcanic group was an ophiolitic mélange. Coupled with geochronological data, a perished oceanic basin at the northern margin of the Yangtze block during Neoproterozoic was tested by this ophiolitic mélange. Meanwhile, the isogeochemical data suggest that the ocean occurred in the Southern Hemisphere identical to Indian, South Atlantic and South Pacific oceans in terms of their Dupal anomalies, and the original source of the rocks could be probably mixing by EMⅠand EMⅡ component caused by dehydration melting of subducting oceanic crust during subduction process. On the basis of geochemical characteristics of the studied rocks, the Bikou volcanic group could imply that a partial breakup event occurred in the northern margin of Yangtze plate during the Neoproterozoic era.

  15. Tracing volatile loss during the eruption of individual flood basalt flows in the Columbia River Flood Basalt Province

    Science.gov (United States)

    Burton, K. W.; Vye, C.; Gannoun, A.; Self, S.

    2010-12-01

    Continental flood basalt (CFB) volcanism is characterised by the repeated eruption of huge batches of magma, producing enormous basalt provinces (105-106 km3) over relatively brief intervals of time, and delivering large masses of volcanic gas to the atmosphere. The release of gases and aerosols during CFB volcanism is thought to have had a significant impact on the atmosphere, ocean chemistry and climate [1-3]. The key factors influencing atmospheric chemistry and the environmental impact of CFB eruptions are the timing, mechanism and duration of volatile release during individual eruptions, but for the most part such information remains poorly known. The 187Re-187Os isotope system offers a highly sensitive tracer of the evolution of melt chemistry, and of the timing and mechanism of volatile release. This is partly because the contrasting behaviour of Re and Os during melting results in the extreme fractionation of parent/daughter (Re/Os) isotope ratios, thus magmatic phases can yield precise chronological information, and crustal rocks develop highly radiogenic isotope compositions that can be readily traced if assimilated [4]. Partly also because Re behaves as a highly volatile element during sub-aerial volcanism [5]. This study presents 187Re-187Os isotope data for rocks and minerals from two flows in the Columbia River Flood Basalt Group, one of the youngest flood basalt provinces that formed over a 2 million year interval in the Mid-Miocene. The 2,660 km3 Sand Hollow flow field displays small major and trace element variations, both laterally and vertically across the flow, indicative of fractional crystallisation, but the elemental data cannot be used to distinguish source variations and/or crustal contamination. However, Os isotopes indicate systematic crustal contamination over the timescale of an individual eruption, where the earliest formed lavas show the greatest degree of contamination. Isotope and elemental data for phenocryst phases from the 40

  16. Volcanism Studies: Final Report for the Yucca Mountain Project

    Energy Technology Data Exchange (ETDEWEB)

    Bruce M. Crowe; Frank V. Perry; Greg A. Valentine; Lynn M. Bowker

    1998-12-01

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is

  17. A Study on the Forming Conditions of Basalts in Seamounts of the South China Sea

    Institute of Scientific and Technical Information of China (English)

    李兆麟; 梁德华; 等

    1994-01-01

    Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice, dacite, etc.Inclusions in the minerals of the volcanic rocks are main-ly amorphors melt inclusions, which reflects that the volcanic rocks are characterized by submarine eruption and rapid cooling on the seafloor .Furthermore, fluid-melt inclusions have been discovered for the first time in alkali basalts and mantle-derived xenoliths,indicating a process of differentiation between magma and fluid in the course of mantle partial melting .Alkali basalts and inclusions may have been formed in this nonhomogeneous system.Rock-forming temperatures of four seamouns estimated as follows:the Z hongnan seamount alkali basalt 1155-1185℃; the Xianbei seamount alkali basalt 960-1200℃; tholeiitic basalt 1040-1230℃; the Daimao seamount tholeiitic basalt 1245-1280℃; and the Jianfeng seamount trachandestic prmice 880-1140℃. Equilibrium pressures of alkali basalts in the Zhongnan and Xianbei seamounts are 13.57 and 8.8×108 Pa ,respectively. Pyroxene equilibrium tem-peratures of mantle xenoliths from the Xianbei seamount were estimated at 1073-1121℃, and pres-sures ar (15.58-22.47)×108Pa, suggesting a deep-source (e.g.the asthenosphere )for the alkalibasalts.

  18. Paleomagnetism of Upper Jurassic to Lower Cretaceous Volcanic and Sedimentary Rocks From the Western Tarim Basin: Implications for Inclination Shallowing and the ISEA? chron

    Science.gov (United States)

    Cogne, J.; Gilder, S.; Chen, Y.; Tan, X.; Courtillot, V.; Sun, D.; Li, Y.

    2002-12-01

    Stepwise demagnetization isolates a stable magnetic component in 13 sites of basalt flows and baked sediments dated at 113+-1.6 Ma from the Tuoyun section, western Xinjiang Province, China. Except for one flow from the base of the 300 m-thick section, the rest have exclusively reversed polarity. Five of 11 sites of Early Cretaceous red beds that underlie the basalts possess coherent directions that pass both fold and reversals tests. Six sites of Upper Jurassic red beds have a magnetic component that was likely acquired after folding in the Tertiary. The mean paleolatitude of the Lower Cretaceous red beds is 11° lower than that of the Lower Cretaceous basalts suggesting the red beds underestimate the true field inclination. We further test this result by calculating the paleolatitudes to a common point of the available Early Cretaceous to Present paleomagnetic poles from red beds and volcanic rocks from central Asian localities north of the Tibetan plateau. We find that paleolatitudes of volcanic rocks roughly equal the paleolatitudes calculated from the reference Eurasian apparent polar wander path (APWP) and that paleolatitudes of red beds are generally 10° to 20° lower than the paleolatitudes of volcanic rocks and those predicted from the reference curve. Our study suggests that central Asian red beds poorly record the Earth's field inclination, which leads to lower than expected paleolatitudes. Good agreement in paleolatitudes from volcanic rocks and the Eurasian APWP argues against proposed canted and non-dipole field models.

  19. An ancient recipe for flood-basalt genesis.

    Science.gov (United States)

    Jackson, Matthew G; Carlson, Richard W

    2011-07-27

    Large outpourings of basaltic lava have punctuated geological time, but the mechanisms responsible for the generation of such extraordinary volumes of melt are not well known. Recent geochemical evidence suggests that an early-formed reservoir may have survived in the Earth's mantle for about 4.5 billion years (ref. 2), and melts of this reservoir contributed to the flood basalt emplaced on Baffin Island about 60 million years ago. However, the volume of this ancient mantle domain and whether it has contributed to other flood basalts is not known. Here we show that basalts from the largest volcanic event in geologic history--the Ontong Java plateau--also exhibit the isotopic and trace element signatures proposed for the early-Earth reservoir. Together with the Ontong Java plateau, we suggest that six of the largest volcanic events that erupted in the past 250 million years derive from the oldest terrestrial mantle reservoir. The association of these large volcanic events with an ancient primitive mantle source suggests that its unique geochemical characteristics--it is both hotter (it has greater abundances of the radioactive heat-producing elements) and more fertile than depleted mantle reservoirs-may strongly affect the generation of flood basalts.

  20. Timing and composition of continental volcanism at Harrat Hutaymah, western Saudi Arabia

    Science.gov (United States)

    Duncan, Robert A; Kent, Adam J R; Thornber, Carl; Schliedler, Tyler D; Al-Amri, Abdullah M

    2016-01-01

    Harrat Hutaymah is an alkali basalt volcanic field in north-central Saudi Arabia, at the eastern margin of a large Neogene continental, intraplate magmatic province. Lava flow, tephra and spatter cone compositions in the field include alkali olivine basalts and basanites. These compositions contrast with the predominantly tholeiitic, fissure-fed basalts found along the eastern margin of the Red Sea. The Hutaymah lava flows were erupted through Proterozoic arc-associated plutonic and meta-sedimentary rocks of the Arabian shield, and commonly contain a range of sub-continental lithospheric xenoliths, although the lavas themselves show little indication of crustal contamination. Previous radiometric dating of this volcanic field (a single published K–Ar age; 1.8 Ma) is suspiciously old given the field measurement of normal magnetic polarity only (i.e. Brunhes interval, ≤ 780 Ka). We report new age determinations on 14 lava flows by the 40Ar–39Ar laser step heating method, all younger than ~ 850 Ka, to better constrain the time frame of volcanism, and major, trace and rare earth element compositions to describe the chemical variation of volcanic activity at Harrat Hutaymah. Crystal fractionation was dominated by olivine ± clinopyroxene at a range of upper mantle and crustal pressures. Rapid ascent and eruption of magma is indicated by the array of lower crustal and lithospheric xenoliths observed in lava flows and tephra. Modeling suggests 1–7% melting of an enriched asthenospheric mantle source occurred beneath Harrat Hutaymah under a relatively thick lithospheric cap (60–80 km).

  1. Timing and composition of continental volcanism at Harrat Hutaymah, western Saudi Arabia

    Science.gov (United States)

    Duncan, Robert A.; Kent, Adam J. R.; Thornber, Carl R.; Schlieder, Tyler D.; Al-Amri, Abdullah M.

    2016-03-01

    Harrat Hutaymah is an alkali basalt volcanic field in north-central Saudi Arabia, at the eastern margin of a large Neogene continental, intraplate magmatic province. Lava flow, tephra and spatter cone compositions in the field include alkali olivine basalts and basanites. These compositions contrast with the predominantly tholeiitic, fissure-fed basalts found along the eastern margin of the Red Sea. The Hutaymah lava flows were erupted through Proterozoic arc-associated plutonic and meta-sedimentary rocks of the Arabian shield, and commonly contain a range of sub-continental lithospheric xenoliths, although the lavas themselves show little indication of crustal contamination. Previous radiometric dating of this volcanic field (a single published K-Ar age; 1.8 Ma) is suspiciously old given the field measurement of normal magnetic polarity only (i.e. Brunhes interval, ≤ 780 Ka). We report new age determinations on 14 lava flows by the 40Ar-39Ar laser step heating method, all younger than ~ 850 Ka, to better constrain the time frame of volcanism, and major, trace and rare earth element compositions to describe the chemical variation of volcanic activity at Harrat Hutaymah. Crystal fractionation was dominated by olivine ± clinopyroxene at a range of upper mantle and crustal pressures. Rapid ascent and eruption of magma is indicated by the array of lower crustal and lithospheric xenoliths observed in lava flows and tephra. Modeling suggests 1-7% melting of an enriched asthenospheric mantle source occurred beneath Harrat Hutaymah under a relatively thick lithospheric cap (60-80 km).

  2. Geochemistry of meta-volcanic rocks from the Longbohe Cu deposit, Yunnan Province, China: Implications for the genesis and tectonic setting

    Institute of Scientific and Technical Information of China (English)

    CUI Yinliang; QING Dexian; CHEN Yaoguang

    2007-01-01

    The Longbohe Cu deposit, which is located in the southern part of the Honghe ore-forming zone, Yunnan Province, China, belongs to a typical ore field where volcanic rocks are of wide distribution and are associated with Cu mineralization in time and space. The volcanic rocks in the ore field, which have experienced varying degree of alteration or regional metamorphism, can be divided into three types, i.e., meta-andesite, meta-subvolcanic rock and meta-basic volcanic rock in accordance with their mineral assemblages. These three types of volcanic rocks in the ore field are relatively rich in Na and the main samples plot in the area of alkali basalts in the geochemical classification diagram. With the exception of very few elements, these three types of volcanic rocks are similar in the content of trace elements. In comparison to the basalts of different tectonic settings, the meta-volcanic rocks in the ore field are rich in high field strength elements (HFSE) such as Th, Nb, etc. and depleted in large ion lithophile elements (LILE) such as Sr, Ba, etc. and their primary mantle-normalized trace element patterns show remarkable negative Th and Nb anomalies and negative Sr and Ba anomalies. These three types of volcanic rocks are similar in REE content range and chondrite-normalized REE patterns with the exception of Eu anomaly. Various lines of evidence show that these three types of volcanic rocks in the ore field have the same source but are the products of different stages of magmatic evolution, their original magma is a product of partial melting of the metasomatically enriched mantle in the tensional tectonic setting within the continent plate, and the crystallization differentiation plays an important role in the process of magmatic evolution.

  3. Improved techniques in data analysis and interpretation of potential fields: examples of application in volcanic and seismically active areas

    Directory of Open Access Journals (Sweden)

    G. Florio

    2002-06-01

    Full Text Available Geopotential data may be interpreted by many different techniques, depending on the nature of the mathematical equations correlating specific unknown ground parameters to the measured data set. The investigation based on the study of the gravity and magnetic anomaly fields represents one of the most important geophysical approaches in the earth sciences. It has now evolved aimed both at improving of known methods and testing other new and reliable techniques. This paper outlines a general framework for several applications of recent techniques in the study of the potential methods for the earth sciences. Most of them are here described and significant case histories are shown to illustrate their reliability on active seismic and volcanic areas.

  4. Thermal, radioactive and magnetic properties of the lavas of the Mt Melbourne Volcanic Field (Victoria Land, Antarctica

    Directory of Open Access Journals (Sweden)

    Egidio Armadillo

    2009-06-01

    Full Text Available We present the results of measurements of physical properties carried out on mafic lavas from the Mt Melbourne
    Volcanic Field, useful for interpretation of geophysical surveys designed to shed light on the structure of the
    crust. The thermal conductivity is comparable to that of glass and shows a clear negative dependence on porosity.
    The volume heat capacity and the thermal diffusivity are less variable. The concentration of the thermally
    important natural radioactive isotopes was determined by gamma-ray spectrometry. Lavas denoted a rather low
    heat-production rate, and the largest concentration of heat-producing elements (potassium, uranium, thorium
    was found in the trachyte samples. The magnetic susceptibility is more variable than the other physical properties
    and, among the several iron-titanium oxides, it appears primarily controlled by the ulvöspinel-magnetite solid
    solution series.

  5. Stability Evaluation of Volcanic Slope Subjected to Rainfall and Freeze-Thaw Action Based on Field Monitoring

    Directory of Open Access Journals (Sweden)

    Shima Kawamura

    2011-01-01

    Full Text Available Rainfall-induced failures of natural and artificial slopes such as cut slopes, which are subjected to freezing and thawing, have been frequently reported in Hokkaido, Japan. In particular, many failures occur intensively from spring to summer seasons. Despite numerous field studies, explanation of their mechanical behavior based on in situ data has not yet been completely achieved due to the difficulty in grasping failure conditions. This study aims at clarifying the aspects of in-situ volcanic slopes subjected to rainfall and freeze-thaw action. The changes in soil moisture, pore pressure, deformations, and temperatures in the slope were investigated using soil moisture meters, tensiometers, thermocouple sensors, clinometers, settlement gauges, an anemovane, a snow gauge, and a rainfall gauge. The data generated from these measures indicated deformation in the slope examined mainly proceeded during the drainage process according to changes in soil moisture. Based on this data, a prediction method for failures is discussed in detail.

  6. Late Miocene volcanism and intra-arc tectonics during the early development of the Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Ferrari, Luca; Conticelli, Sandro; Vaggelli, Gloria; Petrone, Chiara M.; Manetti, Piero

    2000-03-01

    The early stage of the Trans-Mexican Volcanic Belt (hereafter TMVB) is marked by widespread, mafic to intermediate, volcanism emplaced between 11 and 7 Ma from the Pacific coast to the longitude of Mexico City, to the north of the modern volcanic arc. Petrological and geochronological data support the hypothesis that this volcanism made up a unique late Miocenic central Mexican comagmatic province. Mafic lavas at the mouth of the Gulf of California and along the northwestern sector of the TMVB made up the Nayarit district, which includes calc-alkaline to transitional varieties. The central sector of the TMVB is characterized by two basaltic districts: the Jalisco-Guanajuato and the Queretaro-Hidalgo, which are distinguished from the westernmost ones by their lower Nb/La and generally lower HFSE/LILE values, as well as by spider diagrams characterized by larger negative spikes at Th, Ta, Nb, and Ti. The surface occurrence of the late Miocene basalts appears to be controlled by pre-existing zones of crustal weakness that channeled the mafic magmas. Field observations suggest that these structures have been reactivated in a transtensional fashion induced by differential tectonic motion of crustal blocks to the south and to the north of the TMVB. Starting from ˜12 Ma the TMVB separates a northern tectonic domain, subject to the developing divergent Pacific-North America plate boundary, from a southern tectonic domain, characterized by oblique subduction of the Rivera and Cocos plates. Apparently, far field stresses related to these complex plate boundaries reactivated older suture zones, allowing rapid uprise of mantle-derived magmas. The subduction-related signature shown by Miocene mafic lavas of the Jalisco-Guanajuato district argues against the existence of mantle plumes beneath this sector of the North America plate. On the other hand, the occurrence in the western TMVB and in the Guadalajara region of a large volume of mafic magmas, which sometimes show

  7. Hydrothermal evolution of repository groundwaters in basalt

    International Nuclear Information System (INIS)

    Groundwaters in the near field of a radioactive waste repository in basalt will change their chemical composition in response to reactions with the basalt. These reactions will be promoted by the heat generated by the decaying waste. It is important to predict both the rate and the extent of these reactions, and the secondary minerals produced, because the alteration process controls the chemical environment affecting the corrosion of the canister, the solubility and complexation of migrating radionuclides, the reactivity of the alteration products to radionuclides sorption, and the porosity and permeability of the host rock. A comprehensive review of the literature leads to the preliminary finding that hydrothermally altering basalts in geothermal regions such as Iceland lead to a secondary mineralogy and groundwater composition similar to that expected to surround a repository. Furthermore, laboratory experiments replicating the alteration conditions approximate those observed in the field and expected in a repository. Preliminary estimates were made of the rate of hydration and devitrification of basaltic glass and the zero-order dissolution rate of basaltic materials. The rates were compared with those for rhyolitic glasses and silicate minerals. Preliminary calculations made of mixed process alteration kinetics, involving pore diffusion and surface reaction suggest that at temperatures greater than 1500C, alteration proceeds so rapidly as to become pervasive in normally fractured basalt exposed to higher temperatures in the field. 70 references

  8. Geomagnetic imprint of the Persani volcanism

    Science.gov (United States)

    Besutiu, Lucian; Seghedi, Ioan; Zlagnean, Luminita; Atanasiu, Ligia; Popa, Razvan-Gabriel; Pomeran, Mihai; Visan, Madalina

    2016-04-01

    The Persani small volume volcanism is located in the SE corner of the Transylvanian Depression, at the north-western edge of the intra-mountainous Brasov basin. It represents the south-easternmost segment of the Neogene-Quaternary volcanic chain of the East Carpathians. The alkaline basalt monogenetic volcanic field is partly coeval with the high-K calc-alkaline magmatism south of Harghita Mountains (1-1.6 Ma). Its eruptions post-dated the calc-alkaline volcanism in the Harghita Mountains (5.3-1.6 Ma), but pre-dated the high-K calc-alkaline emissions of Ciomadul volcano (1.0-0.03 Ma). The major volcanic forms have been mapped in previous geological surveys. Still, due to the small size of the volcanoes and large extent of tephra deposits and recent sediments, the location of some vents or other volcanic structures has been incompletely revealed. To overcome this problem, the area was subject to several near-surface geophysical investigations, including paleomagnetic research. However, due to their large-scale features, the previous geophysical surveys proved to be an inappropriate approach to the volcanological issues. Therefore, during the summers of 2014 and 2015, based on the high magnetic contrast between the volcanic rocks and the hosting sedimentary formations, a detailed ground geomagnetic survey has been designed and conducted, within central Persani volcanism area, in order to outline the presence of volcanic structures hidden beneath the overlying deposits. Additionally, information on the rock magnetic properties was also targeted by sampling and analysing several outcrops in the area. Based on the acquired data, a detailed total intensity scalar geomagnetic anomaly map was constructed by using the recent IGRF12 model. The revealed pattern of the geomagnetic field proved to be fully consistent with the direction of magnetisation previously determined on rock samples. In order to enhance the signal/noise ratio, the results were further processed by

  9. Magma Injection Models to Quantify Reservoir Dynamics at Laguna del Maule Volcanic Field, Chile, between 2007 and 2015.

    Science.gov (United States)

    Le Mével, H.; Gregg, P. M.; Feigl, K. L.

    2015-12-01

    Moving beyond the widely used kinematic models for the deformation sources, we present new dynamic models to describe the process of injecting magma into an existing magma reservoir. The 3-dimensional numerical models account for a viscoelastic, gravitationally loaded domain with spatially variable rheological properties. A Newtonian fluid characterized by its viscosity, density, and overpressure (relative to the lithostatic value) intrudes into a viscoelastic solid via a conduit leading to the reservoir. Using the Finite Element Method (FEM), we simultaneously solve the coupled quasi-static elastic and Navier-Stokes governing equations for the solid and the fluid, respectively, using the COMSOL Multiphysics software. The fluid and the solid interact through buoyancy and viscoelastic relaxation, leading to time-dependent deformation. To quantify the "strength" of the source, we define the product of the volume change (in cubic meters) and pressure change (in Pascals) as the "volcanic moment" (in Newton-meters or Joules). This quantity serves as a basis for comparing the calculated displacement fields to analytical solutions. After validating our injection model, we apply it to the ongoing episode of unrest at Laguna del Maule (Chile). Since 2007, the volcanic field there has been deforming at an exceptionally high rate, with vertical velocities up to 200 mm/yr, as measured by GPS and Interferometric Synthetic Aperture Radar (InSAR) between 2013 and 2014, as described recently by Le Mével et al. (2015, Geophys. Res. Lett. http://dx.doi.org/10.1002/2015GL064665). We are modeling the geodetic data to analyze the temporal and spatial evolution of the displacement. These models constrain the mass flux of material into the reservoir and thus its impact on the stress in the crust. Our results contribute to understanding the current unrest episode at Laguna del Maule and to assessing geodetic signals at other active volcanoes.

  10. A New Geomagnetic Field Model for the last 2k years based on high quality archaeomagnetic and volcanic data

    Science.gov (United States)

    Campuzano, Saioa A.; Gómez-Paccard, Miriam; Pavón-Carrasco, Francisco Javier; Osete, María Luisa

    2016-04-01

    The knowledge of the ancient Earth's magnetic field is crucial to understand its origin and future evolution. In this context, the palaeomagnetic studies provide useful information about the past geomagnetic field registered in rocks, lava flows, sediments or archaeological materials. The continuous upgrade of the palaeomagnetic database during the last decade has allowed the generation of global geomagnetic field models based on different palaeomagnetic data and techniques (such as the SHA.DIF.14K, ARCH3K.1, CALS3K.4b, pfm9k.1a models, among others). Some recent studies have pointed out that the archaeointensity database might not be reliable enough, by observing high scatter in the records. Here, we present a new global geomagnetic model for the last 2000 years, SHAQ2K, based on high quality archaeomagnetic and volcanic intensity data. For this purpose we classify the palaeointensity data in two quality categories following widely accepted palaeomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens finally used to calculate the mean intensities. Respect to the modelling process, we use the spherical harmonic analysis in space and cubic b-splines in time, also applying a spatial and temporal regularization which minimizes the energy of the geomagnetic field at the core-mantle boundary. The implications of the differences between this new model and other previously published global geomagnetic models are discussed.

  11. Seismic activity and stress tensor inversion at Las Tres Vírgenes Volcanic and Geothermal Field (México)

    Science.gov (United States)

    Antayhua-Vera, Yanet; Lermo-Samaniego, Javier; Quintanar-Robles, Luis; Campos-Enríquez, Oscar

    2015-10-01

    We analyze local earthquakes occurring between 2003 and 2012 at the Las Tres Vírgenes Volcanic and Geothermal Field (TVVGF) to establish their temporal and spatial distribution, and relationships with local and regional fault systems, water injection, acid stimulation and steam production tests. We obtained focal mechanisms and inverted data for the stress tensor to understand the local and regional stress fields. We analyzed 423 local earthquakes with magnitudes between 0.1 and 2.9 Mc and hypocentral depths from 0.2 to 7.4 km b.s.l. The cutoff depth at ~ 7.4 km possibly delineates the brittle-ductile transition zone. We identified seven swarms (from 1 to 7). Swarms 1 (December 2009), 2 (May 2010), 3 (June-July 2010) and 7 (December 2012) are strongly correlated with injection processes; whereas swarms 5 (April 2012) and 6 (September 2012) are correlated with local tectonic faults. Stress inversion showed NW-SE, E-W and NE-SW extensional orientations (Shmin), in agreement with the local tectonic stress field; while NE-SW compressional orientations (SHmax) are correlated with the regional tectonic stress field.

  12. What is controlling spectral reflectance of lava flows? First results of a field spectrometric survey of volcanic surfaces on Tenerife Island

    Science.gov (United States)

    Li, Long; Kervyn, Matthieu; Solana, Carmen; Canters, Frank

    2014-05-01

    Space-based remote sensing techniques have demonstrated their great value in volcanic studies thanks to their synoptic spatial coverage and the repeated acquisitions. On satellite images, volcanic surfaces display a wide range of colors, and therefore contrasted reflectance spectra. Understanding the factors controlling the spectral reflectance of volcanic materials at different wavelength is essential to mapping volcanic areas. Detailed investigation into spectra of volcanic materials are, however, restricted due to the trade-off between spatial and spectral resolution of space-based sensors, such as Hyperion imagery that allows resolving 220 spectral bands ranging from 400 to 2500 nm with a spatial resolution of 30 meters. In order to better understand reflectance of volcanic materials, especially lava, a field campaign was launched in Tenerife Island, Spain in November 2013 with an ASD FieldSpec 3 to document the reflectance spectra of historical mafic lava flow surfaces. 20 specific lava and lapilli surfaces, with contrasted age, surface roughness, weathering condition and vegetation coverage were characterized, using a systematic recording method documenting the spectra's variability within a 15×15 m2 area. Results show that all the volcanic materials have great differences in spectral reflectance. Among them, lava's reflectance is low but still slightly higher than that of lapilli. Comparison of rough and smooth lava surfaces on the same lava flow suggests that roughness tends to increase the reflectance of lava surfaces. Also, vegetation and lichen alter lava's reflectance in some spectral regions, especially through a rise in the near infrared part of the spectrum. It is therefore suggested that reflectance spectra of lava evolve over time due to weathering processes, such as chemical alteration and growth of lichen and moss. In addition, it is possible to compare field measurements with spectra derived from Hyperion imagery, resulting in a strong match

  13. UNCOVERING BURIED VOLCANOES: NEW DATA FOR PROBABILISTIC VOLCANIC HAZARD ASSESSMENT AT YUCCA MOUNTAIN

    International Nuclear Information System (INIS)

    holes are planned with the goal of sampling each geographic subpopulation of magnetic anomalies in the region (Figure 1). This will result in a more complete characterization of the location, age, volume and composition of buried basaltic features for the purpose of updating the volcanic hazard assessment. Smith and Keenan (2005) suggested that volcanic hazard estimates might be 1-2 orders of magnitude higher than estimated by the DOE expert elicitation in 1996, based on (1) a proposed relationship between recurrence rates in the YMR and the Reveille-Lunar Crater volcanic field to the north, and (2) the implication that a number of so-far-undiscovered buried volcanoes would have a significant impact on hazard estimates. This article presents the new aeromagnetic data and an interpretation of the data that suggests magnetic anomalies nearest the proposed repository site represent buried Miocene basalt that will likely have only a minor impact on the volcanic hazard

  14. Carbonatite associated with ultramafic diatremes in the Avon Volcanic District, Missouri, USA: Field, petrographic, and geochemical constraints

    Science.gov (United States)

    Shavers, Ethan J.; Ghulam, Abduwasit; Encarnacion, John; Bridges, David L.; Luetkemeyer, P. Benjamin

    2016-04-01

    Here we report field, petrographic, and geochemical analyses of the southeast Missouri Avon Volcanic District intrusive rocks and present the first combined textural and geochemical evidence for the presence of a primary magmatic carbonatite phase among ultramafic dikes, pipes, and diatremes of olivine melilitite, alnöite, and calciocarbonatite. The δ13CVPDB values measured for primary calciocarbonatite as well as carbonates in olivine melilitite and alnöite rocks range from - 3.8‰ to - 8.2‰, which are within the typical range of mantle values and are distinct from values of the carbonate country rocks, 0.0‰ to - 1.3‰. The carbonate oxygen isotope compositions for the intrusive lithologies are in the range of 21.5‰ to 26.2‰ (VSMOW), consistent with post-emplacement low temperature hydrothermal alteration or kinetic fractionation effects associated with decompression and devolatilization. Metasomatized country rock and breccia-contaminated igneous lithologies have carbonate δ13CVPDB values gradational between primary carbonatite values and country rock values. Unaltered sedimentary dolomite breccia and mafic spheroids entrained by calciocarbonatite and the lack of microstratigraphic crystal growth typical of carbonate replacement, also exclude the possibility of hydrothermal replacement as the cause of the magmatic-textured carbonates. Rare earth element (REE) patterns for the alnöite, olivine melilitite, and carbonatite are similar to each other with strong light REE enrichment and heavy REE depletion relative to MORB. These patterns are distinct from those of country rock rhyolite and sedimentary carbonate. These data suggest that rocks of the Avon Volcanic District represent a single ultramafic-carbonatite intrusive complex possibly derived from a single mantle source.

  15. Linking hydropedology and ecosystem services: differential controls of surface field saturated hydraulic conductivity in a volcanic setting in central Mexico

    Directory of Open Access Journals (Sweden)

    A. Gómez-Tagle

    2009-03-01

    Full Text Available In this study the variation of field saturated soil hydraulic conductivity (Kfs as key control variable and descriptor of infiltration was examined by means of a constant head single ring infiltrometer. The study took place in five coverage types and land uses in a volcanic setting in central Mexico. The tested hypothesis was that there exist a positive relationship between plant cover and surface Kfs for the study area. The examined coverage types included; Second growth pine-oak forest, pasture land, fallow land, gully and Cupresus afforestation. Results indicate that Kfs did not depend exclusively of plant cover; it was related to surface horizontal expression of the unburied soil horizons and linked to land use history. Therefore the Kfs measured at a certain location did not depend exclusively of the actual land use, it was also influenced by soil bioturbation linked to plant succession patterns and land use management practices history. The hypothesis accounts partially the variation between sites. Kfs under dense plant cover at the Cupresus afforestation was statistically equal to that measured at the fallow land or the gully sites, while second growth pine-oak forest Kfs figures were over an order of magnitude higher than the rest of the coverage types. The results suggest the relevance of unburied soil horizons in the soil hydrologic response when present at the surface. Under these conditions loosing surface soil horizons due to erosion, not only fertility is lost, but environmental services generation potential. A conceptual model within the hydropedological approach is proposed. It explains the possible controls of Kfs, for this volcanic setting. Land use history driven erosion plays a decisive role in subsurface horizon presence at the surface and soil matrix characteristic determination, while plant succession patterns seem to be strongly linked to soil bioturbation and

  16. 'Snake River (SR)-type' volcanism at the Yellowstone hotspot track: Distinctive products from unusual, high-temperature silicic super-eruptions

    Science.gov (United States)

    Branney, M.J.; Bonnichsen, B.; Andrews, G.D.M.; Ellis, B.; Barry, T.L.; McCurry, M.

    2008-01-01

    A new category of large-scale volcanism, here termed Snake River (SR)-type volcanism, is defined with reference to a distinctive volcanic facies association displayed by Miocene rocks in the central Snake River Plain area of southern Idaho and northern Nevada, USA. The facies association contrasts with those typical of silicic volcanism elsewhere and records unusual, voluminous and particularly environmentally devastating styles of eruption that remain poorly understood. It includes: (1) large-volume, lithic-poor rhyolitic ignimbrites with scarce pumice lapilli; (2) extensive, parallel-laminated, medium to coarse-grained ashfall deposits with large cuspate shards, crystals and a paucity of pumice lapilli; many are fused to black vitrophyre; (3) unusually extensive, large-volume rhyolite lavas; (4) unusually intense welding, rheomorphism, and widespread development of lava-like facies in the ignimbrites; (5) extensive, fines-rich ash deposits with abundant ash aggregates (pellets and accretionary lapilli); (6) the ashfall layers and ignimbrites contain abundant clasts of dense obsidian and vitrophyre; (7) a bimodal association between the rhyolitic rocks and numerous, coalescing low-profile basalt lava shields; and (8) widespread evidence of emplacement in lacustrine-alluvial environments, as revealed by intercalated lake sediments, ignimbrite peperites, rhyolitic and basaltic hyaloclastites, basalt pillow-lava deltas, rhyolitic and basaltic phreatomagmatic tuffs, alluvial sands and palaeosols. Many rhyolitic eruptions were high mass-flux, large volume and explosive (VEI 6-8), and involved H2O-poor, low-??18O, metaluminous rhyolite magmas with unusually low viscosities, partly due to high magmatic temperatures (900-1,050??C). SR-type volcanism contrasts with silicic volcanism at many other volcanic fields, where the fall deposits are typically Plinian with pumice lapilli, the ignimbrites are low to medium grade (non-welded to eutaxitic) with abundant pumice lapilli

  17. Mapping the edge of the Cerros del Rio volcanic field, New Mexico: a piece of the puzzle to understanding a potential geothermal resource

    Science.gov (United States)

    Pellerin, L.; Gallegos, M.; Goebel, M.; Murphy, B. S.; Smith, J.; Soto, D.; Swiatlowski, J.; Volk, C.; Welch, M.; Feucht, D. W.; Hollingshaus, B.; Bedrosian, P. A.; McPhee, D. K.

    2012-12-01

    The Cerros del Rio volcanic field located west of Santa Fe, New Mexico spans the southwestern part of the Espanola Basin with the Rio Grande to the west. Underlying the volcanics are the Santa Fe Group sediments, which contain the Ancha Formation, an important aquifer in the region. High temperature gradients in water wells reveal a potential geothermal prospect. In 2012 the Summer of Applied Geophysical Experience (SAGE) program acquired transient electromagnetic (TEM), audiomagnetotelluric (AMT), gravity and ground magnetic data to determine the buried eastern margin of the volcanic field and the connectivity related to the underlying sediments. The roughly EW 5-km long transect was sited from USGS aeromagnetic data to cross the boundary of the Cerros del Rio volcanic field. TEM data collected at ten stations, at 200-400 m spacing, along the transect employed an in-loop configuration with a square 100 m x 100 m transmitter loop and both a Zonge receiver coil and a 5 m square receiver loop. The 5 m loop allowed for the recovery of early-time data that was saturated when using the Zonge coil. AMT data were acquired at eight stations, at 400-500 m spacing, using the Geometric Stratagem system recording from 92 kHz to 10 Hz; a horizontal magnetic dipole transmitter was used to augment low signal strength at around 1 kHz. Gravity data along the profile were acquired using CG-3 and CG-5 Scintrex gravimeters with a station interval >250 m. Magnetic data were acquired with a Geometrics Cesium vapor G-858 magnetometer for about 3500 m along the profile at a 0.5 second sampling rate. Two volcanic flows interbedded with Ancha Formation and overlying Santa Fe Group sediments were identified in both the TEM and AMT modeling. High surface resistivity zones (>300 ohm-m) with depths ranging from ~100 to 300 m define the volcanic flows and correspond to high densities (2.3 to 2.55 g/cm3), while low resistivity zones (<30 ohm-m) correspond to lower densities (~2.1 g/cm3). High

  18. Geology of the Sabie River Basalt Formation in the Southern Kruger National Park

    Directory of Open Access Journals (Sweden)

    R.J. Sweeney

    1986-12-01

    Full Text Available The Sabie River Basalt Formation (SRBF in the central Lebombo is a virtually continuous sequence of basaltic lavas some 2 500 m thick that was erupted 200 - 179 Ma ago. Flows are dominantly pahoehoe in character and vary from 2 m to 20 m in thickness. Dolerite dykes cross-cutting the basalt sequence probably represent feeders to this considerable volcanic event. Volcanological features observed within the SRBF are described. Two chemically distinct basaltic magma types are recognised, the simultaneous eruption of which presents an intriguing geochemical problem as to their origins.

  19. Volcanic edifice alignment detection software in MATLAB: Test data and preliminary results for shield fields on Venus

    Science.gov (United States)

    Thomson, Bradley J.; Lang, Nicholas P.

    2016-08-01

    The scarcity of impact craters on Venus make it difficult to infer the relative ages of geologic units. Stratigraphic methods can be used to help infer the relative ordering of surface features, but the relatively coarse resolution of available radar data means ambiguity about the timing of certain features is common. Here we develop a set of statistical tools in MATLAB to help infer the relative timing between clusters of small shield volcanoes and sets of fractures in the surrounding terrain. Specifically, we employed two variants of the two-point azimuth method to detect anisotropy in the distribution of point-like features. The results of these methods are shown to successfully identify anisotropy at two spatial scales: at the whole-field level and at scales smaller than a set fraction of the mean value. Initial results on the test cases presented here are promising, at least for volcanic fields emplaced under uniform conditions. These methods could also be used for detecting anisotropy in other point-like geologic features, such as hydrothermal vents, springs, and earthquake epicenters.

  20. Geochemistry and Petrogenesis of Volcanic Rocks in the Yeba Formation on the Gangdise Magmatic Arc, Tibet

    Institute of Scientific and Technical Information of China (English)

    Geng Quanru; Pan Guitang; Jin Zhenmin; Wang Liquan; Liao Zhongli

    2005-01-01

    The Early Jurassic bimodal volcanic rocks in the Yeba Formation, situated between Lhasa, Dagzê and Maizhokunggar, composed of metabasalt, basaltic ignimbrite, dacite, silicic tuff and volcanic breccia, are an important volcanic suite for the study of the tectonic evolution of the Gangdise magmatic arc and the Mesozoic Tethys. Based on systematic field investigations, we carried out geochemical studies on representative rock samples. Major and trace element compositions were analyzed for these rock samples by XRF and ICP-MS respectively, and an isotope analysis of Rb-Sr and Sm-Nd was carried out by a MAT 262 mass spectrograph. The results show that the SiO2 contents in lava rocks are 41 %-50.4 % and 64 %-69 %, belonging to calc-alkaline basalt and dacite. One notable feature of the basalt is its low TiO2 content, 0.66 %-1.01 %, much lower than those of continental tholeiite. The ΣREE contents of basalt and dacite are 60.3-135 μg/g and 126.4-167.9 μg/g respectively. Both rocks have similar REE and other trace element characteristics, with enriched LREE and LILE relative to HREE and HFS, similar REE patterns without Eu anomaly. The basalts have depleted Ti, Ta and Nb and slightly negative Nb and Ta anomalies, with Nb*=0.54-1.17 averaging 0.84. The dacites have depleted P and Ti and also slightly negative Nb and Ta anomalies, with Nb*=0.74-1.06 averaging 0.86. Major and trace elemental and isotopic studies suggest that both basalt and dacite originated from the partial melting of the mantle wedge at different degrees above the subduction zone. The spinal lherzolite in the upper mantle is likely to be their source rocks, which might have been affected by the selective metasomatism of fluids with crustal geochemistry. The LILE contents of both rocks were affected by metamorphism at later stages. The Yeba bimodal volcanic rocks formed in a temporal extensional situation in a mature island arc resulting from the Indosinian Gangdise magmatic arc.

  1. Study on lithogeochemistry of Middle Jurassic basalts from southern China represented by the Fankeng basalts from Yongding of Fujian Province

    Institute of Scientific and Technical Information of China (English)

    ZHOU Jincheng; JIANG Shaoyong; WANG Xiaolei; YANG Jinghong; ZHANG Mengqun

    2006-01-01

    There exists an E-W trending Middle Jurassic volcanic zone in southern China. The Fankeng basalts in the Yongding basin of Fujian Province are considered to be a typical example. The Fankeng basalts have TiO2 contents in the range of 1.92%-3.21%. They are classified as high-Ti basalts. They also have higher total Fe (averaging FeO*= 11.09%). The Middle Jurassic Fankeng basalts from southwestern Fujian have obvious distinctive lithogeochemical features from early Cretaceous basalts from southeastern coast of China. They have higher HFSE, such as Th, Nb, Ta, Zr and Ti. Their element ratios related with HFSE, such as Zr/Ba, La/Nb, La/Ta ,Zr/Y, Ti/Y, Ba/Nb, K/Ti and Rb/Zr are similar to those of OIB. The most samples have εNd(T) of -0.70-0.24, which are near chondrite. Some samples have higher εNd(T) of 1.87-3.55.Therefore, these basaltic magmas might be derived from depleted asthenospheric mantle. The lithogeochemical characteristics of the Fankeng basalts may be caused by interaction between asthenosphere and lithosphere at the time. The (Early-)Middle Jurassic basalts and gabbros from southeastern Hunan, southern Jiangxi and northern Guangdong provinces show similar geochemical features to those of the Fankeng basalts from the Yongding of Fujian. Occurrence of these OIB-type basalts in the area may be regarded as the petrological mark of upwelling of asthenosphere at the time. Upwelling of asthenosphere has led to tectonic extension and the formation of rifted basin in the area.

  2. Age of Tertiary volcanic rocks on the West Greenland continental margin

    DEFF Research Database (Denmark)

    Larsen, Lotte M.; Pedersen, Asger Ken; Tegner, Christian;

    2016-01-01

    Radiometric ages for undated parts of the volcanic succession and intrusions in West Greenland were obtained by the 40Ar–39Ar incremental heating method. Acceptable crystallization ages were obtained for 27 samples. Combined with published results the new data provide a volcanic stratigraphy...... correlatable throughout the Nuussuaq Basin. The thick onshore volcanic pile consists of four widespread formations: 62.5–61 Ma picrites (Vaigat Formation), 61–60 Ma depleted basalts (Maligât Formation and the Hellefisk-1 well), 60–58 Ma less-depleted basalts (Svartenhuk Formation) and 56–54 Ma enriched basalts...... (Naqerloq Formation). Two local successions comprise 53.5 Ma alkali basalts (Erqua Formation) and 38.7 Ma transitional basalts (Talerua Member). A central volcano developed on Ubekendt Ejland, leading to the Sarqâta qáqâ gabbro-granophyre intrusion at 57–55 Ma. Pre-break-up volcanism took place further...

  3. Geochemistry of basalts from small eruptive centers near Villarrica stratovolcano, Chile: Evidence for lithospheric mantle components in continental arc magmas

    Science.gov (United States)

    Hickey-Vargas, R.; Sun, M.; Holbik, S.

    2016-07-01

    In the Central Southern Volcanic Zone (CSVZ) of the Andes, the location of stratovolcanoes and monogenetic small eruptive centers (SEC) is controlled by the Liquiñe-Ofqui Fault Zone (LOFZ), a trench-parallel strike-slip feature of over 1000 km length. The geochemistry of basalts from SEC is different from those of stratovolcanoes, and are termed Type 2 and Type 1 basalts, respectively. In the region of Villarrica stratovolcano, contemporaneous SEC are more MgO-rich, and have greater light rare earth element (LREE) enrichment, lower 87Sr/86Sr and 143Nd/144Nd, and lower ratios of large ion lithophile elements (LILE) to LREE and high field strength elements (HFSE). A unique finding in this region is that basalts from one SEC, San Jorge, has Type 1 character, similar to basalts from Villarrica stratovolcano. Type 1 basalts from Villarrica and San Jorge SEC have strong signals from time-sensitive tracers of subduction input, such as high 10Be/9Be and high (238U/230Th), while Type 2 SEC have low 10Be/9Be and (238U/230Th) near secular equilibrium. Based on new trace element, radiogenic isotope and mineral analyses, we propose that Type 1 basaltic magma erupted at San Jorge SEC and Villarrica stratovolcano forms by melting of the ambient actively subduction-modified asthenosphere, while Type 2 SEC incorporate melts of pyroxenite residing in the supra-subduction zone mantle lithosphere. This scenario is consistent with the close proximity of the volcanic features and their inferred depths of magma separation. The pyroxenite forms from arc magma produced during earlier episodes of subduction modification and magmatism, which extend back >300 Ma along this segment of the western South American margin. Type 2 basaltic magmas may reach the surface during LOFZ-related decompression events, and they may also be a normal but episodic part of the magma supply to large stratovolcanoes, resulting in cryptic geochemical variations over time. The presence and mobilization of stored

  4. Volcanism Studies: Final Report for the Yucca Mountain Project

    International Nuclear Information System (INIS)

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt ( than about 7 x 10-8 events yr-1 . Simple probability estimates are used to assess possible implications of not drilling aeromagnetic anomalies in the Amargosa Valley. The sensitivity of the disruption probability to the location of northeast boundaries of volcanic zones near the Yucca Mountain sit

  5. Examining Volcanic Terrains Using In Situ Geochemical Technologies; Implications for Planetary Field Geology

    Science.gov (United States)

    Young, K. E.; Bleacher, J. E.; Evans, C. A.; Rogers, A. D.; Ito, G.; Arzoumanian, Z.; Gendreau, K.

    2015-01-01

    Regardless of the target destination for the next manned planetary mission, the crew will require technology with which to select samples for return to Earth. The six Apollo lunar surface missions crews had only the tools to enable them to physically pick samples up off the surface or from a boulder and store those samples for return to the Lunar Module and eventually to Earth. Sample characterization was dependent upon visual inspection and relied upon their extensive geology training. In the four decades since Apollo however, great advances have been made in traditionally laboratory-based instrument technologies that enable miniaturization to a field-portable configuration. The implications of these advancements extend past traditional terrestrial field geology and into planetary surface exploration. With tools that will allow for real-time geochemical analysis, an astronaut can better develop a series of working hypotheses that are testable during surface science operations. One such technology is x-ray fluorescence (XRF). Traditionally used in a laboratory configuration, these instruments have now been developed and marketed commercially in a field-portable mode. We examine this technology in the context of geologic sample analysis and discuss current and future plans for instrument deployment. We also discuss the development of the Chromatic Mineral Identification and Surface Texture (CMIST) instrument at the NASA Goddard Space Flight Center (GSFC). Testing is taking place in conjunction with the RIS4E (Remote, In Situ, and Synchrotron Studies for Science and Exploration) SSERVI (Solar System Exploration and Research Virtual Institute) team activities, including field testing at Kilauea Volcano, HI..

  6. Preliminary feasibility study on storage of radioactive wastes in Columbia River basalts. Volume II

    Energy Technology Data Exchange (ETDEWEB)

    ,

    1976-11-01

    Volume II comprises four appendices: analytical data and sample locations for basalt flow type localities; Analytical data and sample locations for measured field sections in Yakima basalts; core hole lithology and analytical data; and geophysical logs. (LK)

  7. Volcanostratigraphic Sequences of Kebo-Butak Formation at Bayat Geological Field Complex, Central Java Province and Yogyakarta Special Province, Indonesia

    Directory of Open Access Journals (Sweden)

    Sri Mulyaningsih

    2016-08-01

    Full Text Available Bayat Complex is usually used as a work field for students of geology and other geosciences. The study area is located in the southern part of the Bayat Complex. Administratively, it belongs to Central Java Province and Yogyakarta Special Province. The lithology of Bayat is very complex, composed of various kinds of igneous, sedimentary, metamorphic, and volcanic rocks. Most of previous researchers interpreted Bayat as a melange complex constructed within a subduction zone. Kebo-Butak is one of formations that forms the Bayat field complex. The formation is composed of basalt, layers of pumice, tuff, shale, and carbonaceous tuff. Most of them are known as volcanic rocks. These imply that volcanic activities are more probable to construct the geology of Bayat rather than the subducted melange complex. The geological mapping, supported by geomorphology, petrology, stratigraphy, and geological structures, had been conducted in a comprehensive manner using the deduction-induction method. The research encounters basalt, black pumice, tuff with basaltic glasses fragments, zeolite, argilic clay, as well as feldspathic- and pumice tuff. Petrographically, the basalt is composed of labradorite, olivine, clinopyroxene, and volcanic glass. Black pumice and tuff contain prismatic clinopyroxene, granular olivine, and volcanic glasses. Feldspathic tuff and pumice tuff are crystal vitric tuff due to more abundant feldspar, quartz, and amphibole than volcanic glass. Zeolite comprises chlorite and altered glasses as deep sea altered volcanic rocks. The geologic structure is very complex, the major structures are normal faults with pyrite in it. There were two deep submarine paleovolcanoes namely Tegalrejo and Baturagung. The first paleovolcano erupted effusively producing basaltic sequence, while the second one erupted explosively ejecting feldspathic-rich pyroclastic material. The two paleovolcanoes erupted simultaneously and repeatedly.

  8. 231Pa systematics in postglacial volcanic rocks from Iceland

    Science.gov (United States)

    Turner, Simon; Kokfelt, Thomas; Hoernle, Kaj; Lundstrom, Craig; Hauff, Folkmar

    2016-07-01

    Several recent studies have highlighted the potential of combined 238U-230Th and 235U-231Pa systematics to constrain upwelling rates and the role of recycled mafic lithologies in mantle plume-derived basalts. Accordingly, we present measurements of the 231Pa concentrations from 26 mafic volcanic rocks from Iceland, including off-axis basalts from the Snaefellsnes Peninsula, to complement previously published 238U-230Th-226Ra data. 231Pa concentrations vary from 27 to 624 fg/g and (231Pa/235U) ratios from 1.12 to 2.11 with the exception of one anomalous sample from the Southeast Rift which has a 231Pa deficit with (231Pa/235U) = 0.86. An important new result is that basalts from the Southeast Rift and the Snaefellsnes Peninsula define a trend at relatively low (231Pa/235U) for a given (230Th/238U) ratio. Many of the remaining samples fall in or around the global field for ocean island basalts but those from the Mid-Iceland Belt and the Southwest Rift/Reykjanes Peninsula extend to higher (231Pa/235U) ratios at a given (230Th/238U), similar to mid-ocean ridge basalts. In principle, these lavas could result from melting of peridotite at lower pressures. However, there is no reason to suspect that the Mid-Iceland Belt and the Southwest Rift lavas reflect shallower melting than elsewhere in Iceland. In our preferred model, these lavas reflect melting of garnet peridotite whereas those from the Southeast Rift and the Snaefellsnes Peninsula contain a significant contribution (up to 20%) of melt from garnet pyroxenite. This is consistent with incompatible trace element and radiogenic isotope evidence for recycled oceanic crust in these lavas. There is increasing agreement that the displacement of ocean island basalts to lower (231Pa/235U) ratios at a given (230Th/238U), compared to mid-ocean ridge basalts, reflects the role of recycled mafic lithologies such as garnet pyroxenite as well as higher average pressures of melting. It now seems likely that this interpretation may

  9. Process interpretation of laminated lacustrine sediments from the valley of the river Alf, Quaternary West Eifel Volcanic Field, Germany

    Science.gov (United States)

    Eichhorn, Luise; Pirrung, Michael; Zolitschka, Bernd; Büchel, Georg

    2016-04-01

    High-resolution annually laminated sediment archives from lakes Holzmaar and Meerfelder Maar located in the Quaternary West Eifel Volcanic Field are in the focus of many investigations (e.g. Brauer et al. 2001, Zolitschka 1991). These publications are related to predominantly biogenic varves covering the last ca. 14 ka years, i.e. the Lateglacial and the Holocene. In our study, laminated sediments consisting of clay-silt couplets are presented from paleolake Alf. This paleolake formed in a valley dammed by volcanic products, and covers the Pleniglacial between 31 and 24 ka BP (Pirrung et al. 2007). The focus of our study is the characterization of the structure of clay-silt couplets and the determination of their origin. The applied granulometry revealed mean grain sizes of 10 μm for the light laminae (colors refer to core scan photo) and 14 μm for the dark laminae (both middle silt). X-ray diffraction confirms identical mineral phases for light and dark laminae, with light laminae being clay-enriched containing a higher amount of sericite and chlorite while dark laminae are enriched in quartz. X-ray fluorescence and detrital microfacies analysis on thin sections indicate that calcite dominates in the dark laminae. Microscopically, three different types of silt layers are present. Type I are laminae with homogeneous sublayers, Type II are graded laminae and Type III are laminae with graded sublayers. Processes causing the formation of these silt lamination types can be attributed to repeatedly occurring snow melting, permafrost thawing or rain events linked with sediment delivery from the catchment into the lake. The amount of precipitation and melt water, sediment discharge and density stratification lead to gravity suspension fall out, partial erosion of previously deposited unconsolidated sediments and resuspension in the lake. Brauer, A., et al. (2001). Lateglacial varve chronology and biostratigraphy of lakes Holzmaar and Meerfelder Maar, Germany. Boreas 30

  10. Petrochemistry and origin of basalt breccia from Ban Sap Sawat area, Wichian Buri, Phetchabun, central Thailand

    Directory of Open Access Journals (Sweden)

    Phisit Limtrakun

    2013-08-01

    Full Text Available Thailand is usually considered to be controlled by escape tectonics associated with India-Asia collision during theLate Cenozoic, and basaltic volcanism took place in this extensional period. This volcanism generated both subaqueous andsubaerial lava flows with tholeiitic to alkalic basaltic magma. The subaqueous eruptions represented by the studied WichianBuri basalts, Ban Sap Sawat in particular, are constituted by two main types of volcanic lithofacies, including lava flows andbasalt breccias. The lava flows are commonly porphyritic with olivine and plagioclase phenocrysts and microphenocrysts,and are uncommonly seriate textured. The basalt breccias are strongly vitrophyric texture with olivine and plagioclasephenocrysts and microphenocrysts. Chemical analyses indicate that both lava flows and basalt breccias have similar geochemical compositions, signifying that they were solidified from the same magma. Their chondrite normalized REE patternsand N-MORB normalized patterns are closely analogous to the Early to Middle Miocene tholeiites from central Sinkhote-Alinand Sakhalin, northeastern margin of the Eurasian continent which were erupted in a continental rift environment. The originfor the Wichian Buri basalts show similarity of lava flows and basalt breccias, in terms of petrography and chemical compositions, signifying that they have been formed from the same continental within-plate, transitional tholeiitic magma.

  11. Database compilation for the geologic map of the San Francisco volcanic field, north-central Arizona

    Science.gov (United States)

    Bard, Joseph A.; Ramsey, David W.; Wolfe, Edward W.; Ulrich, George E.; Newhall, Christopher G.; Moore, Richard B.; Bailey, Norman G.; Holm, Richard F.

    2016-01-08

    The main component of this publication is a geologic map database prepared using geographic information system (GIS) applications. The geodatabase of geologic points, lines, and polygons was produced as a compilation from five adjoining map sections originally published as printed maps in 1987 (see references in metadata). Four of the sections (U.S. Geological Survey Miscellaneous Field Studies Maps MF–1957, MF–1958, MF–1959, MF–1960) were created by scanning and geo-referencing stable base map material consisting of mylar positives. The final section (MF–1956) was compiled by hand tracing an enlargement of the available printed paper base map onto mylar using a #00 rapidograph pen, the mylar positive was then digitally scanned and geo-referenced. This method was chosen because the original basemap materials (mylar positives) for the MF–1956 section were unavailable at the time of this publication. Due to the condition of the available MF–1956 map section used as the base (which had previously been folded) the accuracy within the boundary of the MF–1956 section is presumed to be degraded in certain areas. The locations of the degraded areas and the degree of degradation within these areas is unclear. Final compilation of the database was completed using the ArcScan toolset, and the Editor toolset in ESRI ArcMap 10.1. Polygon topology was created from the lines and labels were added to the resultant geological polygons, lines, and points. Joseph A. Bard and David W. Ramsey updated and corrected the geodatabase, created the metadata and web presence, and provided the GIS-expertise to bring the geodatabase and metadata to completion. Included are links to files to view or print the original map sheets and the accompanying pamphlets.

  12. SHRIMP dating of volcanic rock in the Zhangwu-Heishan area, West Liaoning province, China: Its relationship with coal-bearing strata

    Institute of Scientific and Technical Information of China (English)

    Cai Houan; Xu Debin; Li Baofang; Shao Longyi

    2011-01-01

    The Zhangwu-Heishan area is located to the east of the Fuxin-Yixian Basin and is mostly covered with volcanic rock.At various periods,different geologists had varying opinions about their age and periods of volcanic eruptions,especially on sequences between volcanic rock and main coal-beating strata,which affect the direction of searching for coal,as well as prospecting the entire research area.During our study,we carried out detailed field investigations in this research area; observed and recorded the main representative outcrops of volcanic rock.We collected over 20 volcanic rock samples and tested the Sensitive High Resolution Ion Microprobe Ⅱ (SHRIMP Ⅱ) U-Pb isotope age of 11 samples.The age of our volcanic rock samples ranged between 56.0 ± 2.9 and 132.3 ± 2.3 Ma.After taking earlier investigations into consideration,we concluded that,except for a suite of paleogene olivine basalt,the volcanic rock in the Zhangwu-Heishan area is younger than the coal-beating Shahai Formation.It is therefore most unlikely to find coal seams equivalent to those of the early Cretaceous Shahai Formation in Fuxin Basin below volcanic rock.

  13. Emplacement dynamics and lava field evolution of the flood basalt eruption at Holuhraun, Iceland: Observations from field and remote sensing data

    Science.gov (United States)

    Pedersen, Gro; Höskuldsson, Armann; Riishuus, Morten S.; Jónsdóttir, Ingibjörg; Thórdarson, Thorvaldur; Dürig, Tobias; Gudmundsson, Magnus T.; Durmont, Stephanie

    2016-04-01

    The Holuhraun eruption (Aug 2014- Feb 2015) is the largest effusive eruption in Iceland since the Laki eruption in 1783-84, with an estimated lava volume of ~1.6 km3 covering an area of ~83 km2. The eruption provides an unprecedented opportunity to study i) lava morphologies and their emplacement styles, ii) Morphological transitions iii) the transition from open to closed lava pathways and iv) the implication of lava pond formation. This study is based on three different categories of data; field data, airborne data and satellite data. The field data include tracking of the lava advancement by Global Positioning System (GPS) measurements and georeferenced GoPro cameras allowing classification of the lava margin morphology. Furthermore, video footage on-site documented lava emplacement. Complimentary observations have been provided from aircraft platforms and by satellite data. Of particular importance for lava morphology observations are 1-12 m/pixel airborne Synthetic Aperture Radar (SAR) images (x-band), as well as SAR data from TerraSAR-X and COSMO-SkyMed satellites. The Holuhraun lava field comprises a continuum of morphologies from pāhoehoe to 'a'ā, which have varied temporally and spatially. Shelly pāhoehoe lava was the first morphology to be observed (08-29). Spatially, this lava type was not widely distributed, but was emplaced throughout the eruption close to the vent area and the lava channels. Slabby pāhoehoe lava was initially observed the 08-31 and was observed throughout most of the eruption during the high-lava-flux phase of new lava lobe emplacement. 'A'ā lavas were the dominating morphology the first three months of the eruption and was first observed 09-01 like Rubbly pāhoehoe lava. Finally, Spiny pāhoehoe lava was first observed the 09-05 as a few marginal outbreaks along the fairly inactive parts of the 'a'ā lava lobe. However, throughout the eruption this morphology became more important and from mid-November/beginning of December the

  14. Geochemical characterization of oceanic basalts using Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Iyer Sridhar D

    2009-12-01

    Full Text Available Abstract The geochemical discriminate diagrams help to distinguish the volcanics recovered from different tectonic settings but these diagrams tend to group the ocean floor basalts (OFB under one class i.e., as mid-oceanic ridge basalts (MORB. Hence, a method is specifically needed to identify the OFB as normal (N-MORB, enriched (E-MORB and ocean island basalts (OIB. We have applied Artificial Neural Network (ANN technique as a supervised Learning Vector Quantisation (LVQ to identify the inherent geochemical signatures present in the Central Indian Ocean Basin (CIOB basalts. A range of N-MORB, E-MORB and OIB dataset was used for training and testing of the network. Although the identification of the characters as N-MORB, E-MORB and OIB is completely dependent upon the training data set for the LVQ, but to a significant extent this method is found to be successful in identifying the characters within the CIOB basalts. The study helped to geochemically delineate the CIOB basalts as N-MORB with perceptible imprints of E-MORB and OIB characteristics in the form of moderately enriched rare earth and incompatible elements. Apart from the fact that the magmatic processes are difficult to be deciphered, the architecture performs satisfactorily.

  15. Sensitivity of geochemical monitoring for CO2 sequestration in basalt

    Science.gov (United States)

    Zakharova, N. V.; Goldberg, D.; Herron, M.; Grau, J.

    2010-12-01

    Continental flood basalts is a promising target for carbon dioxide (CO2) storage due to high storage capacity, presence of seals, and potential for geochemical trapping which results in binding CO2 into stable carbonate minerals. The success of long-term CO2 storage in igneous rocks highly depends on our ability to monitor mineralization under in situ conditions. The direct chemistry measurements on cores are costly and typically do not provide continuous coverage. In this study we investigate the potential of borehole geochemical logging for monitoring of CO2 mineralization in basalt. Neutron-induced capture gamma ray spectroscopy tools allow obtaining in-situ concentration logs for up to 10 major elements which can be used to construct a quantitative mineralogical model. While this usually provides good bulk mineralogy estimates, detecting small-volume mineral alteration in volcanic rocks remains challenging, especially if borehole conditions are poor. We analyze Schlumberger Elemental Capture Spectroscopy logs and chemical core analysis from the pilot CO2 sequestration project in the Columbia River flood basalt. We use the geochemical spectroscopy logs and quantitative modeling to quantify their sensitivity to secondary mineralization in basalt. We apply statistical analysis to explain the variance in elemental concentrations (and other logs) and establish detection limits for various mineral alteration products in basalt. We use these results to evaluate monitoring capabilities and limitations of geochemical logging for CO2 mineralization after underground injection in basalt and suggest areas for future research.

  16. Geochemical and isotopic characteristics of volcanic rocks from the northern East China Sea shelf margin and the Okinawa Trough

    Institute of Scientific and Technical Information of China (English)

    ZENG Zhigang; YU Shaoxiong; WANG Xiaoyuan; FU Yongtao; YIN Xuebo; ZHANG Guoliang; WANG Xiaomei; CHEN Shuai

    2010-01-01

    Volcanic rocks both from the northern East China Sea (NECS) shelf margin and the northern Okinawa Trough are subalkaline less aluminous,and lower in High Field Strength Elements (HFSE).These rocks are higher in Large Ion Lithophile Elements (LILE),thorium and uranium contents,positive lead anomalies,negative Nb-Ta anomalies,and enrichment in Light Rare Earth Elements (LREE).Basalts from the NECS shelf margin are akin to Indian Ocean Mid-Ocean Ridge Basalt (MORB),and rhyolites from the northern Okinawa Trough have the highest 207Pb/204Pb and 208Pb/204Pb ratios.The NECS shelf margin basalts have lower 87Sr/86Sr ratios,εNd and σ18O than the northern Okinawa Trough silicic rocks.According to 40K-40Ar isotopic ages of basalts from the NECS shelf margin,rifting of the Okinawa Trough may have been active since at least 3.65-3.86 Ma.The origin of the NECS shelf margin basalt can be explained by the interaction of melt derived from Indian Ocean MORB-like mantle with enriched subcontinental lithosphere.The basalts from both sides of the Okinawa Trough may have a similar origin during the initial rifting of the Okinawa Trough,and the formation of basaltic magmas closely relates to the thinning of continental crust.The source of the formation of the northern Okinawa Trough silicic rocks was different from that of the middle Okinawa Trough,which could have been generated by the interaction of basaltic melt with an enriched crustal component.From the Ryukyu island arc to East China,the Cenozoic basalts have apparently increasing trends of MgO contents and ratios of LREE to Heavy Rare Earth Elements (HREE),suggesting that the trace element variabilities of basalts may have been influenced by the subduction of the Philippine Sea plate,and that the effects of subduction of the Philippine Sea plate on the chemical composition of basaltic melts have had a decreasing effect from the Ryukyu island arc to East China.

  17. Holocene flows of the Cima volcanic field, Mojave Desert (California), Part 1: Remote sensing and multi-scale morphometry

    Science.gov (United States)

    Beem, J. R.; Luecke, A.; Polun, S. G.; Robertson, T.; Savage, A.; Soldati, A.; Whittington, A. G.; Gomez, F. G.

    2014-12-01

    Lava flow morphology and texture can provide insight into rheological and other physical properties of the flow. Studies of terrestrial and extra-terrestrial lava flows rely heavily on remotely sensed observations. This research aims to quantify micromorphology and texture of a Holocene lava flow in the Cima volcanic field (eastern California) using digital elevation models and radar backscatter imagery. We are testing the hypothesis that spatial patterns in morphometry and backscatter roughness correspond with varying rheological conditions during emplacement. The site is ideally suited for morphological study owing to the youthfulness of the flow, as well as the lack of vegetation and minimal surface erosion resulting from the high desert climate. The studied lava flow spans approximately 2.5 km and exhibits well defined lobate forms and lava ropes with clear A'a' to Pahoehoe transitions. This study assesses lava flow micromorphology using a very high resolution (5 cm pixel) digital elevation model (DEM). The DEM was constructed from low-altitude aerial photos acquired using a remotely-controlled model aircraft. In addition to the DEM, the resulting orthoimagery provided a basis for distinguishing pristine lava flow surfaces from areas covered by vegetation and/or eolian deposits. Longer-wavelength morphology (spatial scales greater than 1 meter) is analyzed using a 50 cm pixel DEM produced using stereoscopic NAPP aerial photographs. Roughness estimates are compared with radar backscatter images including steeply incident C-band (5.6 cm wavelength) and L-band (24 cm wavelength) satellite data, as well as shallow incidence Ku-band data (1.7 cm wavelength) acquired using a ground-based imaging radar from an adjacent cinder cone. Photogrammetry and radar provide complementary information on lava flow morphology and micromorphological roughness, which are assessed at different spatial scales using general statistics, as well as the local hypsometric integral.

  18. Terrestrial Analog Field Investigations to Enable Science and Exploration Studies of Impacts and Volcanism on the Moon, NEAs, and Moons of Mars

    Science.gov (United States)

    Heldmann, Jennifer Lynne; Colaprete, Anthony; Cohen, Barbara; Elphic, Richard; Garry, William; Hodges, Kip; Hughes, Scott; Kim, Kyeon; Lim, Darlene; McKay, Chris; Osinski, Gordon R.; Petro, Noah; Sears, Derek; Squyres, Steve; Tornabene, Livio

    2013-01-01

    Terrestrial analog studies are a critical component for furthering our understanding of geologic processes on the Moon, near-Earth asteroids (NEAs), and the moons of Mars. Carefully chosen analog sites provide a unique natural laboratory with high relevance to the associated science on these solar system target bodies. Volcanism and impact cratering are fundamental processes on the Moon, NEAs, and Phobos and Deimos. The terrestrial volcanic and impact records remain invaluable for our understanding of these processes throughout our solar system, since these are our primary source of firsthand knowledge on volcanic landform formation and modification as well as the three-dimensional structural and lithological character of impact craters. Regarding impact cratering, terrestrial fieldwork can help us to understand the origin and emplacement of impactites, the history of impact bombardment in the inner Solar System, the formation of complex impact craters, and the effects of shock on planetary materials. Volcanism is another dominant geologic process that has significantly shaped the surface of planetary bodies and many asteroids. Through terrestrial field investigations we can study the processes, geomorphic features and rock types related to fissure eruptions, volcanic constructs, lava tubes, flows and pyroclastic deposits. Also, terrestrial analog studies have the advantage of enabling simultaneous robotic and/or human exploration testing in a low cost, low risk, high fidelity environment to test technologies and concepts of operations for future missions to the target bodies. Of particular interest is the importance and role of robotic precursor missions prior to human operations for which there is little to no actual mission experience to draw upon. Also critical to understanding new worlds is sample return, and analog studies enable us to develop the appropriate procedures for collecting samples in a manner that will best achieve the science objectives.

  19. Terrestrial analog field investigations to enable science and exploration studies of impacts and volcanism on the Moon, NEAs, and moons of Mars (Invited)

    Science.gov (United States)

    Heldmann, J. L.; Colaprete, A.; Cohen, B. A.; Elphic, R. C.; Garry, W. B.; Hodges, K. V.; Hughes, S. S.; Kim, K. J.; Lim, D.; McKay, C. P.; Osinski, G. R.; Petro, N. E.; Sears, D. W.; Squyres, S. W.; Tornabene, L. L.

    2013-12-01

    Terrestrial analog studies are a critical component for furthering our understanding of geologic processes on the Moon, near-Earth asteroids (NEAs), and the moons of Mars. Carefully chosen analog sites provide a unique natural laboratory with high relevance to the associated science on these solar system target bodies. Volcanism and impact cratering are fundamental processes on the Moon, NEAs, and Phobos and Deimos. The terrestrial volcanic and impact records remain invaluable for our understanding of these processes throughout our solar system, since these are our primary source of firsthand knowledge on volcanic landform formation and modification as well as the three-dimensional structural and lithological character of impact craters. Regarding impact cratering, terrestrial fieldwork can help us to understand the origin and emplacement of impactites, the history of impact bombardment in the inner Solar System, the formation of complex impact craters, and the effects of shock on planetary materials. Volcanism is another dominant geologic process that has significantly shaped the surface of planetary bodies and many asteroids. Through terrestrial field investigations we can study the processes, geomorphic features and rock types related to fissure eruptions, volcanic constructs, lava tubes, flows and pyroclastic deposits. Also, terrestrial analog studies have the advantage of enabling simultaneous robotic and/or human exploration testing in a low cost, low risk, high fidelity environment to test technologies and concepts of operations for future missions to the target bodies. Of particular interest is the importance and role of robotic precursor missions prior to human operations for which there is little to no actual mission experience to draw upon. Also critical to understanding new worlds is sample return, and analog studies enable us to develop the appropriate procedures for collecting samples in a manner that will best achieve the science objectives.

  20. 四川周公山-汉王场地区峨眉山玄武岩中流体类型及活动期次%Fluid types and activities of Emeishan basalt in Zhougong mountain-Hanwang field of Sichuan Province.

    Institute of Scientific and Technical Information of China (English)

    侯明才; 王文楷; 张本健; 王维; 李秀华; 邓敏; 裴森奇; 杨毅

    2013-01-01

    来自汉王场-周公山地区周公2井和汉6井峨眉山玄武岩钻井岩心样品显示峨眉山玄武岩有:隐晶玄武岩、杏仁状玄武岩,凝灰岩,火山角砾岩,凝灰角砾岩,绿帘石岩,赤铁矿染玄武岩,红土化玄武岩和脉岩等九种岩石类型.其中发育的杏仁体成分有:赤铁矿杏仁体、绿帘石杏仁体、石英-绿泥石杏仁体、蛋白石-赤铁矿杏仁体、磁铁矿-赤铁矿杏仁体、榍石-玉髓杏仁体、绿帘石-葡萄石-绿泥石杏仁体、钛铁矿-玉髓-绿泥石-玉髓杏仁体等8种,脉体有:长石脉、赤铁矿脉、石英脉、绿帘石脉、绿泥石、榍石脉、方解石脉、玉髓-水铝英石脉、方解石-赤铁矿脉、方解石-绿泥石脉、石英-方解石脉、石英-绿帘石脉、石英-沥青脉、赤铁矿-玉髓-绿泥石脉、绿帘石-绿泥石-玉髓脉等15种.这些脉体和杏仁体形成于峨眉山玄武岩形成演化的不同阶段,喷溢期流体受岩浆原生组分影响,大气降水影响程度低,温度属高-中温,脉体包裹体盐度-温度为正相关,代表性产物为赤铁矿脉;风化期流体主要来源于大气降水,氧化作用和水解作用对脉体的发育产生了很大影响,这一时期δ13C为低-中负值,包裹体盐度、温度低,以水铝英石脉最为典型;进入埋藏期以后,上覆地层水和深部的卤水对岩石进行改造,这一时期的流体属低-中温,包裹体盐度与温度呈负相关,受有机质影响,δ13C呈高负值,以绿帘石脉最为典型.%Samples from Zhougong 2 well and Han 6 well in Zhougong mountain-Hanwang field show that the Emeishan basalt can be divided into 9 types,cryptocrystalline basalt,amygdaloidal basalt,tuff,volcanic breccia,tuff-breccia,epidosite rock,hematitedbasalt,weathered basalt and vein rock.Minerals and with their combinations such as hematite,epidote,quartz-chlorite,opalhematite,magnetite-hematite,sphene-chalcedony,epidote-prehnite-chlorite,and ilmenite

  1. The Early Mesozoic volcanic arc of western North America in northeastern Mexico

    Science.gov (United States)

    Barboza-Gudiño, José Rafael; Orozco-Esquivel, María Teresa; Gómez-Anguiano, Martín; Zavala-Monsiváis, Aurora

    2008-02-01

    Volcanic successions underlying clastic and carbonate marine rocks of the Oxfordian-Kimmeridgian Zuloaga Group in northeastern Mexico have been attributed to magmatic arcs of Permo-Triassic and Early Jurassic ages. This work provides stratigraphic, petrographic geochronological, and geochemical data to characterize pre-Oxfordian volcanic rocks outcropping in seven localities in northeastern Mexico. Field observations show that the volcanic units overlie Paleozoic metamorphic rocks (Granjeno schist) or Triassic marine strata (Zacatecas Formation) and intrude Triassic redbeds or are partly interbedded with Lower Jurassic redbeds (Huizachal Group). The volcanic rocks include rhyolitic and rhyodacitic domes and dikes, basaltic to andesitic lava flows and breccias, and andesitic to rhyolitic pyroclastic rocks, including breccias, lapilli, and ashflow tuffs that range from welded to unwelded. Lower-Middle Jurassic ages (U/Pb in zircon) have been reported from only two studied localities (Huizachal Valley, Sierra de Catorce), and other reported ages (Ar/Ar and K-Ar in whole-rock or feldspar) are often reset. This work reports a new U/Pb age in zircon that confirms a Lower Jurassic (193 Ma) age for volcanic rocks exposed in the Aramberri area. The major and trace element contents of samples from the seven localities are typical of calc-alkaline, subduction-related rocks. The new geochronological and geochemical data, coupled with the lithological features and stratigraphic positions, indicate volcanic rocks are part of a continental arc, similar to that represented by the Lower-Middle Jurassic Nazas Formation of Durango and northern Zacatecas. On that basis, the studied volcanic sequences are assigned to the Early Jurassic volcanic arc of western North America.

  2. Pressure grouting of fractured basalt flows

    International Nuclear Information System (INIS)

    This report describes a field trial of pressure grouting in basalt and presents the results of subsequent coring and permeability measurements. The trial shows that hydraulic conductivity of fractured basalt bedrock can be significantly reduced by pressure injection of cementitious materials. The effectiveness of the pressure grout procedure was evaluated by measuring the change in the hydraulic conductivity of the bedrock. The extent of grout penetration was determined by analyzing postgrout injection drilling chips for the presence of a tracer in the grout and also by examining cores of the treated basalt. Downhole radar mapping indicated major lava flow patterns and follow water movement during a surface infiltration test. A site called Box Canyon, which is northwest of the Idaho National Engineering Laboratory (INEL), was chosen for the study because its surface outcrop geology is similar to the underlying bedrock fracture system at the INEL's Radioactive Waste Management Complex (RWMC)

  3. Semi-automatic delimitation of volcanic edifice boundaries: Validation and application to the cinder cones of the Tancitaro-Nueva Italia region (Michoacán-Guanajuato Volcanic Field, Mexico)

    Science.gov (United States)

    Di Traglia, Federico; Morelli, Stefano; Casagli, Nicola; Garduño Monroy, Victor Hugo

    2014-08-01

    The shape and size of monogenetic volcanoes are the result of complex evolutions involving the interaction of eruptive activity, structural setting and degradational processes. Morphological studies of cinder cones aim to evaluate volcanic hazard on the Earth and to decipher the origins of various structures on extraterrestrial planets. Efforts have been dedicated so far to the characterization of the cinder cone morphology in a systematic and comparable manner. However, manual delimitation is time-consuming and influenced by the user subjectivity but, on the other hand, automatic boundary delimitation of volcanic terrains can be affected by irregular topography. In this work, the semi-automatic delimitation of volcanic edifice boundaries proposed by Grosse et al. (2009) for stratovolcanoes was tested for the first time over monogenetic cinder cones. The method, based on the integration of the DEM-derived slope and curvature maps, is applied here to the Tancitaro-Nueva Italia region of the Michoacán-Guanajuato Volcanic Field (Mexico), where 309 Plio-Quaternary cinder cones are located. The semiautomatic extraction allowed identification of 137 of the 309 cinder cones of the Tancitaro-Nueva Italia region, recognized by means of the manual extraction. This value corresponds to the 44.3% of the total number of cinder cones. Analysis on vent alignments allowed us to identify NE-SW vent alignments and cone elongations, consistent with a NE-SW σmax and a NW-SE σmin. Constructing a vent intensity map, based on computing the number of vents within a radius r centred on each vent of the data set and choosing r = 5 km, four vent intensity maxima were derived: one is positioned in the NW with respect to the Volcano Tancitaro, one in the NE, one to the S and another vent cluster located at the SE boundary of the studied area. The spacing of centroid of each cluster (24 km) can be related to the thickness of the crust (9-10 km) overlying the magma reservoir.

  4. VOLCANIC RISK ASSESSMENT - PROBABILITY AND CONSEQUENCES

    International Nuclear Information System (INIS)

    Risk is the product of the probability and consequences of an event. Both of these must be based upon sound science that integrates field data, experiments, and modeling, but must also be useful to decision makers who likely do not understand all aspects of the underlying science. We review a decision framework used in many fields such as performance assessment for hazardous and/or radioactive waste disposal sites that can serve to guide the volcanological community towards integrated risk assessment. In this framework the underlying scientific understanding of processes that affect probability and consequences drive the decision-level results, but in turn these results can drive focused research in areas that cause the greatest level of uncertainty at the decision level. We review two examples of the determination of volcanic event probability: (1) probability of a new volcano forming at the proposed Yucca Mountain radioactive waste repository, and (2) probability that a subsurface repository in Japan would be affected by the nearby formation of a new stratovolcano. We also provide examples of work on consequences of explosive eruptions, within the framework mentioned above. These include field-based studies aimed at providing data for ''closure'' of wall rock erosion terms in a conduit flow model, predictions of dynamic pressure and other variables related to damage by pyroclastic flow into underground structures, and vulnerability criteria for structures subjected to conditions of explosive eruption. Process models (e.g., multiphase flow) are important for testing the validity or relative importance of possible scenarios in a volcanic risk assessment. We show how time-dependent multiphase modeling of explosive ''eruption'' of basaltic magma into an open tunnel (drift) at the Yucca Mountain repository provides insight into proposed scenarios that include the development of secondary pathways to the Earth's surface. Addressing volcanic risk within a decision

  5. Paleomagnetic results from Cenozoic volcanics of Lusatia, NW Bohemian Massif

    Science.gov (United States)

    Schnabl, P.; Cajz, V.; Tietz, O.; Buechner, J.; Suhr, P.; Pecskay, Z.; Cizkova, K.

    2013-05-01

    Lusatia is situated in the NE continuation of the Ohre Rift (OR) behind Lusatian Overtrust. Compared to the neighbouring volcanic complex of the České stredohorí Mts. (CS) inside the OR. The scattered occurrences of basaltic bodies in Lusatia are spread on wider area. This can be caused by different tectonic development of the regions and from derived erosional conditions. The Lusatian Overtrust, high-order tectonic structure running across the course of the OR, separates Lusatian region into two different geological areas where Cretaceous sediments or granodiorites of Lusatian Massif represent the country rock of the Cenozoic volcanism, respectively. The age of volcanic activity ranges from 19 to 33 Ma, it's proved by newly obtained Ar-Ar data from Freiberg and K-Ar data from Debrecen. Forty two scattered remnants of Cenozoic volcanic products were sampled to get paleomagnetic data. The superficial volcanics with detectable geological position and volcanology were chosen preferentially, several dykes and separate vents were sampled as well. Paleomagnetic research was processed on more than 500 samples which were demagnetized using alternate field in the range 0-80 mT. Q-ratio was counted to prevent the lightning influence - solitary volcanic occurrences build positive morphology and thus, they are prone to be targeted by lightnings. The values of Q-ratio predominantly span from 0.1 to 7.0; those samples having the value over 10, were excluded for evaluation. The mean paleomagnetic direction (MPD) was acquired from several samples on each sampling site. Declination and Inclination show values of 11.8 deg and 62.7 deg (α95 = 9.3 deg) for normal polarity, or 182.1 deg and -59.2 deg (α95 = 6.1 deg) for reverse polarity, respectively,The corresponding paleolatitude of 41.9 deg was counted from the Inclination. This is 1000 km to the South, compared to recent position. The dispersions of the MPD are relatively wide. This coincides well with the idea of long

  6. Age and petrology of the Kalaupapa Basalt, Molokai, Hawaii ( geochemistry, Sr isotopes).

    Science.gov (United States)

    Clague, D.A.

    1982-01-01

    The post-erosional Kalaupapa Basalt on East Molokai, Hawaii, erupted between 0.34 and 0.57 million years ago to form the Kalaupapa Peninsula. The Kalaupapa Basalt ranges in composition from basanite to lava transitional between alkalic and tholeiitic basalt. Rare-earth and other trace-element abundances suggest that the Kalaupapa Basalt could be generated by 11-17% partial melting of a light-REE-enriched source like that from which the post-erosional lavas of the Honolulu Group on Oahu were generated by 2-11% melting. The 87Sr/86Sr ratios of the lavas range from 0.70320 to 0.70332, suggesting that the variation in composition mainly reflects variation in the melting process rather than heterogeneity of sources. The length of the period of volcanic quiescence that preceded eruption of post-erosional lavas in the Hawaiian Islands decreased as volcanism progressed from Kauai toward Kilauea. - Authors

  7. Late Pleistocene to Holocene soil development and environments in the Long Gang Volcanic Field area, Jilin Province, NE China

    Science.gov (United States)

    Sauer, Daniela; Zhang, Xinrong; Knöbel, Jette; Maerker, Lutz

    2014-05-01

    Late Pleistocene to Holocene shifts of climate and vegetation in the Long Gang Volcanic Field in NE China have been reconstructed, e. g. by Steblich et al. (2009), based on Maar lake sediment cores. In this study, we investigated soil development during the Late Pleistocene and Holocene and linked it to the climate and vegetation reported in the literature. Three pedons were described and analyzed on a crater wall surrounding a maar. The lower part of the slope is covered by basic pyroclastics that are obviously younger than the maar itself. Pedon 1 is located on the upper slope, where the younger pyroclastics are not present; thus it developed over the entire Holocene and part of the Late Pleistocene. Pedon 2 is on the toe slope and developed from the young basic pyroclastics. Vegetation remains, charred by fire that was caused by the volcanic ash fall, were found in the lowermost part of the pyroclastics layer, on top of a paleosol. Charcoal fragments were dated to 18950-18830 cal BP (using INTCAL 09). Thus, pedon 2 developed since around 18.9 ka BP, whereas the development of the paleosol that was buried under the pyroclastics (pedon 3), was stopped at this time. Pedons 1 and 2 are Vitric Andosols, developed mainly from basic pyroclastics, as evidenced by the composition of rock fragments in the soils, comprising 78 / 81 mass % lapilli and 22 / 19 mass % gneiss fragments, respectively. Pedon 3 is a Cutanic Luvisol (Chromic) that developed entirely from gneiss fragments produced by the maar explosion. Lab data suggest increasing intensity of pedogenesis in the direction: Pedon 3 (paleosol) < Pedon 2 < Pedon 1, reflected e. g. in increasing Fed/Fet ratios, decreasing molar ratios of (Ca+K+Na)/Al, and decreasing pH. However, it needs to be considered that lapilli are more readily weatherable than gneiss fragments. The profile morphology of the paleosol, characterized by reddish-brown color (7.5YR), strong angular blocky structure and well-expressed illuvial clay

  8. Mylonitic volcanics near Puging, Upper Siang district, Arunachal Pradesh: Evidence of oblique-slip thrusting

    Indian Academy of Sciences (India)

    T K Goswami; P Bhattacharyya; D Bezbaruah

    2016-08-01

    The Abor volcanics of the continental flood basalt affinity are extensively exposed in different parts of the Siang valley. These are associated with Yinkiong Group of rocks of Paleocene–Eocene age and represent syn-sedimentary volcanism in a rift setting. Subsequent folding and thrusting of the Siyom and Rikor sequences above the Yinkiong Group of rocks represent changes from syn-to-post collisionalbrittle-ductile tectonic episodes. Mylonitic Abor volcanics in the thrust contacts are studied at several locations in the north and south of Puging in the Siang valley. Both the Abor volcanics and associated Rikor and Yinkiong Group of rocks preserve meso to micro-scale fabric asymmetries indicating that the thrust contacts are shear zones of brittle-ductile nature containing mylonitic textures of high shear strain.Two distinct hitherto unrecognised shear zones in the north and south of Puging are named as North Puging Shear Zone (NPSZ) and South Puging Shear Zone (SPSZ). The kinematic indicators along the thrust contact indicate oblique slip thrusting of the Rikor and Siyom thrust sheets above the Yinkiong Group of rocks. This paper provides field evidence proving that the compression due the Burmese plate made oblique slip thrusting and zones of mylonitised volcanics possible and associated metasediments were formed. The kinematic indicators in the NPSZ and SPSZ respectively indicate top-to-SSE and top-to-NNW sense of shears.

  9. Geochemical Interpretation of Collision Volcanism

    Science.gov (United States)

    Pearce, Julian

    2014-05-01

    collision type with extreme LILE and significant HFSE enrichment relative to MORB and with large negative Nb-Ta and Ti anomalies. Post-collision volcanism is usually ascribed to combinations of slab detachment, delamination, and slab roll back (orogenic) and extension (post-orogenic). The magma source is typically conductively-heated, sub-continental mantle lithosphere with composition and depth of melting depending on the nature and evolution of the collision zone in question. Geochemical patterns may be similar to those of syn-collision basalts or of intraplate, continental basalts - or transitional between these. This variability in space and time, though problematic for geochemical fingerprinting, can give clues to the polarity and development of the collision zone, for example by highlighting the distribution of subduction-modified mantle lithosphere and hence of pre-collision subduction zones. One characteristic common to this setting is a high crustal input resulting from the presence of a hot, thick 'crustal chemical filter' which is evident on geochemical projections that highlight AFC-type processes. Using this, and other, geochemical features it is possible to develop methodologies to at least partly see through the complexity of collision terranes.

  10. Putative cryptoendolithic life in Devonian pillow basalt, Rheinisches Schiefergebirge, Germany.

    Science.gov (United States)

    Peckmann, J; Bach, W; Behrens, K; Reitner, J

    2008-03-01

    Middle Devonian (Givetian) pillow basalt and inter-pillow breccia from the Rheinisches Schiefergebirge in Germany were found to contain putative biogenic filaments that indicate that life once proliferated within these volcanic rocks. Mineralized filaments are found in carbonate amygdules (vesicles filled by carbonate cement) in the volcanic rock, where they started to form on the internal surface of the once water-filled vesicles. Biogenicity of the filaments is indicated by (1) their size and shape resembling modern microorganisms including a constant diameter along the length of curved filaments, (2) their independence of crystal faces or cleavage planes, (3) branching patterns reminiscent of modern microorganisms, and (4) their spatial clustering and preferential occurrence close to the margin of pillows and in the inter-pillow breccias. A time lag between the deposition of pillow basalt and the activity of endoliths is revealed by the sequence of carbonate cements filling the amygdules. The putative filamentous microorganisms thrived after the formation of early fibrous rim cement, but before later equant calcite spar filled most of the remaining porosity. Microbial clay authigenesis analogous to the encrustation of prokaryotes in modern iron-rich environments led to the preservation of filaments. The filaments predominantly consist of the clay minerals chamosite and illite. Having dwelled in water-filled vesicles, the Devonian basalt-hosted filaments apparently represent cryptoendoliths. This finding suggests that a previously unrecognized niche for life exists within volcanic rock.

  11. Surface Textures and Features Indicative of Endogenous Growth at the McCartys Flow Field, NM, as an Analog to Martian Volcanic Plains

    Science.gov (United States)

    Bleacher, Jacob E.; Crumpler, L. S.; Garry, W. B.; Zimbelman, J. R.; Self, S.; Aubele, J. C.

    2012-01-01

    Basaltic lavas typically form channels or tubes, which are recognized on the Earth and Mars. Although largely unrecognized in the planetary community, terrestrial inflated sheet flows also display morphologies that share many commonalities with lava plains on Mars. The McCartys lava flow field is among the youngest (approx.3000 yrs) basaltic flows in the continental United States. The southwest sections of the flow displays smooth, flat-topped plateaus with irregularly shaped pits and hummocky inter-plateau units that form a polygonal surface. Plateaus are typically elongate in map view, up to 20 m high and display lineations within the glassy crust. Lineated surfaces occasionally display small pahoehoe lava and not a a lava. Depressions are often the result of non-inflation and can be clearly identified by lateral squeeze-outs along the pit walls that form when the rising crust exposes the still liquid core of the sheet. The plains of Tharsis and Elysium, Mars, display many analogous features

  12. CO2 sequestration in basalts: laboratory measurements

    Science.gov (United States)

    Otheim, L. T.; Adam, L.; van Wijk, K.; McLing, T. L.; Podgorney, R. K.

    2010-12-01

    Geologic sequestration of CO2 is proposed as the only promising large-scale method to help reduce CO2 gas emission by its capture at large point sources and subsequent long-term storage in deep geologic formations. Reliable and cost-effective monitoring will be important aspect of ensuring geological sequestration is a safe, effective, and acceptable method for CO2 emissions mitigation. Once CO2 injection starts, seismic methods can be used to monitor the migration of the carbon dioxide plume. To calibrate changes in rock properties from field observations, we propose to first analyze changes in elastic properties on basalt cores. Carbon dioxide sequestration in basalt rocks results in fluid substitution and mixing of CO2 with water and rock mineralizations. Carbon dioxide sequestration in mafic rocks creates reactions such as Mg2SiO 4 + CaMgSi2O 6 + 4CO2 = Mg 3Ca(CO 3) 4 + 3SiO2 whereby primary silicate minerals within the basalt react with carbonic acid laden water to creating secondary carbonate minerals and silicates. Using time-lapse laboratory scale experiments, such as laser generated ultrasonic wave propagation; it is possible to observe small changes in the physical properties of a rock. We will show velocity and modulus measurements on three basalt core samples for different saturation. The ultimate goal of the project is to track seismic changes due to fluid substitution and mineralization. The porosity of our basalts ranges from 8% to 12%, and the P-wave velocity increases by 20% to 40% from dry to water saturated conditions. Petrographic analysis (CT-scans, thin sections, XRF, XRf) will aid in the characterization of the mineral structure in these basalts and its correlation to seismic properties changes resulting from fluid substitution and mineralization.

  13. Vent 7504 of the San Francisco Volcanic Field (SFVF), Arizona: Sample Geochemistry and Implications for Cone Formation

    Science.gov (United States)

    Needham, D. H.; Eppler, D. B.; Bleacher, J. E.; Skinner, J. A.; Evans, C. A.; Feng, W.; Gruener, J. E.; Whitson, P. A.; Janoiko, B. A.; Mertzman, S. A.

    2015-12-01

    Vent 7504 is a complex structure in the SFVF that has 3 unit classes: a central cone with exposed dikes and cinder-covered rheomorphic facies; a SE/NW-trending ridge north of the cone with cinder-covered rheomorphic facies; and three discrete lava flows that emanate to the N from the ridge and to the SW and NW from the cone. Field observations suggest the ridge was the northern crest of an initial, larger cone. The NW portion of this cone was most likely disrupted during a catastrophic breach of lava that had accumulated within the cone; this third of three lava flows carried rafted packages of the rheomorphic cone facies to the NW, forming the linear N ridge. The final phase of pyroclastic activity was concentrated in the SW portion of the original cone, covering the top of the cone with cinders and forming the more traditional conic-shaped construct observed today. This study describes the geochemistry of 9 samples collected from the mapped units (2 from the cone, 1 from the N ridge, 1 from the N lava flow, 2 from the SW lava flow, and 3 from the NW lava flow) to further constrain the formation of Vent 7504. Geochemical analyses including back-scatter electron scanning electron microscopy and laboratory X-ray fluorescence spectroscopy were conducted on the 9 collected samples to measure bulk rock and olivine phenocryst compositions. Major element concentrations in the bulk rock and olivine compositions are strongly clustered in all samples, indicating they likely originated from a single magmatic source. Bulk rock SiO2 (~47.5 wt%) and alkali (Na2O + K2O, ~2.7 wt% + 0.71 wt%) concentrations are consistent with a basaltic classification for these samples. Trends in major elements relative to MgO are observed for the olivine phenocrysts: SiO2, Al2O3, Na2O, and TiO2 remain constant relative to MgO, but strong linear trends are observed in MnO, FeO, and NiO relative to MgO. These linear trends are expected given the potential for bivalent cation exchanges in the

  14. Petrology, Geochemistry and Nd-Sr-Pb Isotopic Properties of Volcanic Rocks in Daheishan Island, Penglai, Shandong Province

    Institute of Scientific and Technical Information of China (English)

    Fu Yongtao; Li Anchun

    2003-01-01

    The major elements, trace elements, K-Ar age and Sr-Nd-Pb isotopic systems of the Cenozoic volcanic rocks in Daheishan Island and Cishan, Penglai, Shandong Province are measured. The volcanic rocks ( olivine-nephelinite and nepheline-basanite ) in Daheishan Island erupted periodically in an interval of 0.32 Ma, from 8.72 Ma, 8.39 Ma, 8.08 Ma to 7.73 Ma. The volcanic rocks are all rich in light REEs. They are similar to the OIB-type alkali basalt in the trace elements normalized model by primordial mantle: rich in high field elements such as Nb and Ta, and imcompatible elements such as Cs, Rb, Ba, Th, U. The volcanic rocks show a depletion of K and Rb elements. It is suggested by the trace elements that the olivine-nephelinite in Daheishan Island is originated from deep resources under the continental mantle. ε Nd (0) values of the volcanic rocks in Daheishan Island and Cisban are 5.31 ~ 8.51 and 7.33 respectively, suggesting that the volcanic rocks are from the depleted mantle resources, which have higher Sm/Nd ratios than the CHUR. 143Nd /144Nd ratios of Daheishan Island olivine-nephelinite and Cishan alkali basalts are 0.512 910 ~ 0.513 074 and 0.513 014 respectively. The 87Sr /86Sr of Daheishan Island volcanic rocks are lower than that of Cishan, 0.703 427 ~ 0.703 482 and 0.703 895 respectively. The Daheishan Island olivinenephelinite has the Pb isotopic values as follows: 206Pb /204pb = 18.028 9 ~ 17.972 8, 207Pb /204pb= 15.435 8 ~ 15.402 2 and 208Pb /204Pb = 38.087 6 ~ 37.997 5, lower than those of Cishan basanite. The Cishan basanite has 206Pb /204pb = 18.240 1, 207Pb /204Pb = 15.564 5 and 208Pb /204pb = 38.535. The authors suggest that the olivine-nephelinite in Daheishan Island is similar to the E-type MORB or Hawaii OIB, and the alkali basalts in Cishan similar to the Kerguelen OIB. The dominant mantle components of DM+PREMA and perhaps DM ( Dupal type ) are the dominant mantle components for volcanic rocks in Daheishan Island and Cishan. The

  15. East Mariana Basin tholeiites: Cretaceous intraplate basalts or rift basalts related to the Ontong Java plume?

    Science.gov (United States)

    Castillo, P.R.; Pringle, M.S.; Carlson, R.W.

    1994-01-01

    Studies of seafloor magnetic anomaly patterns suggest the presence of Jurassic oceanic crust in a large area in the western Pacific that includes the East Mariana, Nauru and Pigafetta Basins. Sampling of the igneous crust in this area by the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Program (ODP) allows direct evaluation of the age and petrogenesis of this crust. ODP Leg 129 drilled a 51 m sequence of basalt pillows and massive flows in the central East Mariana Basin. 40Ar 39Ar ages determined in this study for two Leg 129 basalts average 114.6 ?? 3.2 Ma. This age is in agreement with the Albian-late Aptian paleontologic age of the overlying sediments, but is distinctively younger than the Jurassic age predicted by magnetic anomaly patterns in the basin. Compositionally, the East Mariana Basin basalts are uniformly low-K tholeiites that are depleted in highly incompatible elements compared to moderately incompatible ones, which is typical of mid-ocean ridge basalts (MORB) erupted near hotspots. The Sr, Nd and Pb isotopic compositions of the tholeiites ( 87Sr 86Srinit = 0.70360-0.70374; 143Nd 144Ndinit = 0.512769-0.512790; 206Pb 204Pbmeas = 18.355-18.386) also overlap with some Indian Ocean Ridge MORB, although they are distinct from the isotopic compositions of Jurassic basalts drilled in the Pigafetta Basin, the oldest Pacific MORB. The isotopic compositions of the East Mariana Basin tholeiites are also similar to those of intraplate basalts, and in particular, to the isotopic signature of basalts from the nearby Ontong Java and Manihiki Plateaus. The East Mariana Basin tholeiites also share many petrologic and isotopic characteristics with the oceanic basement drilled in the Nauru Basin at DSDP Site 462. In addition, the new 110.8 ?? 1.0 Ma 40Ar 39Ar age for two flows from the bottom of Site 462 in the Nauru Basin is indistinguishable from the age of the East Mariana Basin flows. Thus, while magnetic anomaly patterns predict that the igneous

  16. Petrology and petrogenesis of the Eocene Volcanic rocks in Yildizeli area (Sivas), Central Anatolia, Turkey

    Science.gov (United States)

    Doğa Topbay, C.; Karacık, Zekiye; Genç, S. Can; Göçmengil, Gönenç

    2015-04-01

    Yıldızeli region to the south of İzmir Ankara Erzincan suture zone is situated on the large Sivas Tertiary sedimentary basin. After the northern branch of the Neotethyan Ocean was northerly consumed beneath the Sakarya Continent, a continent - continent collision occurred between the Anatolide- Tauride platform and Pontides and followed a severe intermediate magmatism during the Late Cretaceous- Tertiary period. This created an east-west trending volcanic belt along the whole Pontide range. In the previous studies different models are suggested for the Eocene volcanic succession such as post-collisional, delamination and slab-breakoff models as well as the arc model for its westernmost parts. We will present our field and geochemical data obtained from the Yıldızeli and its surroundings for its petrogenesis, and will discuss the tectonic model(s) on the basis of their geochemical/petrological aspects. Cenozoic volcanic sequences of Yıldızeli region which is the main subject of this study, overlie Pre-Mesozoic crustal meta-sedimentary group of Kırşehir Massif, Ophiolitic mélange and Cretaceous- Paleocene? flysch-like sequences. In the northern part of Yıldızeli region, north vergent thrust fault trending E-W seperates the ophiolitic mélange complex from the Upper Cretaceous-Paleocene and Tertiary formations. Volcano-sedimentary units, Eocene in age, of the Yıldızeli (Sivas-Turkey) which are intercalated with sedimentary deposits related to the collision of Anatolide-Tauride and a simultaneous volcanic activity (i.e. the Yıldızeli volcanics), exposed throughout a wide zone along E-W orientation. Yıldızeli volcanics consist of basalts, basaltic-andesites and andesitic lavas intercalated flow breccias and epiclastic, pyroclastic deposits. Basaltic andesite lavas contain Ca-rich plagioclase + clinopyroxene ± olivine with minor amounts of opaque minerals in a matrix comprised of microlites and glass; andesitic lavas are generally contain Ca

  17. Newly developed evidence for the original Tethysan island-arc volcanic rocks in the southern segment of the South Lancangjiang Belt

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper re-describes the characteristics of pre-Ordovician (Pt3) metamorphic volcanic rocks in the Huimin-Manlai region of Yunnan Province from the aspects of petrographic characteristics, rock assemblage, petrochemistry, REE, trace elements, lead isotopes and geotectonic setting. The metamorphic volcanic rocks maintain blasto-intergranular and blasto-andesitic textures; the volcanic rocks are characterized by a basalt-andesite-dacite assemblage; the volcanic rocks are basic-intermediate-intermediate-acid in chemical composition, belonging to semi-alkaline rocks, with calc-alkaline series and tholeiite series coexisting, and they are characterized by low TiO2 contents; their REE distribution patterns are of the LREE-enrichment right-inclined type; the volcanic rocks are enriched in large cation elements and commonly enriched in Th and partly depleted in Ti, Cr and P, belonging to the Gondwana type as viewed from their Pb isotopic composition; petrochemically the data points fall mostly within the field of island-arc volcanic rocks. All these characteristics provided new evidence for the existence of original Tethysan island-arc volcanic rocks in the region studied.

  18. Immiscible iron- and silica-rich melt in basalt petrogenesis documented in the Skaergaard intrusion

    DEFF Research Database (Denmark)

    Jakobsen, Jakob Kløve; Veksler, Ilya; Tegner, Christian;

    2005-01-01

    Silicate liquid immiscibility in basalt petrogenesis is a contentious issue. Immiscible iron and silica-rich liquids were reported in melt inclusions of lunar basalt and in groundmass glasses of terrestrial volcanics. In fully crystallized plutonic rocks, however, silicate liquid immiscibility has...... emulsion of silica and iron-rich liquids. On the outcrop scale, silica-rich (melanogranophyre) pods and layers in iron-rich ferrodiorite of the Upper Zone of the Skaergaard intrusion witness segregation of the two liquids. These findings demand that silicate immiscibility is considered in basalt...

  19. Assessing the potential for luminescence dating of basalts

    Science.gov (United States)

    Tsukamoto, S.; Duller, G.A.T.; Wintle, A.G.; Muhs, D.

    2011-01-01

    The possibility of dating basalt using luminescence was tested on four samples with independent age control from Cima volcanic field, California, with the ultimate aim of assessing whether the technique could be used to date sediments on the surface of Mars. Previous analysis of these samples had demonstrated that the infrared stimulated luminescence (IRSL) signal is most suitable for dating as it showed the lowest fading rate among various luminescence signals. In this study, changes in equivalent dose as a function of preheat are described. The ages for the two youngest Cima samples agree with the independent ages based on cosmogenic nuclide measurements (12.0 ?? 0.8 ka). In the two older samples (dated to 320 and 580 ka by K-Ar), the luminescence behaviour is more complex and the form of the IRSL decay curve is seen to vary with dose. Mathematical fitting is used to isolate two components and their intensities are used to produce dose response curves. The slower component yields a larger equivalent dose. However, even using this component and after correction for fading, the ages obtained for the older samples are younger than the K-Ar ages. ?? 2010 Elsevier B.V.

  20. Space-Time-Isotopic Trends of Snake River Plain Basalts

    Science.gov (United States)

    Jean, M. M.; Hanan, B. B.; Shervais, J. W.

    2010-12-01

    The Snake River Plain (SRP) volcanic province is an 800 km track of basalt extending from the Owyhee Plateau to its current terminus, the Yellowstone Plateau. It is one of several late-Tertiary magmatic terranes that also include the Cascades magmatic arc, the Columbia River basalts, and the Oregon Plateau basalts; all of which are adjacent to the Basin and Range Province extensional system (Hughes and McCurry, 2002). This province represents the track of the Yellowstone plume and consists of basalt that is compositionally similar to ocean-island basalt. This basalt overlies a series of rhyolitic eruptive centers (overlapping caldera complexes, ignimbrites, and caldera-filling eruptions) that signal the arrival of the plume head (Christiansen, 2001) and herald the onset of plume-related rhyolitic and basaltic volcanism (Pierce et al., 2002). Observed within the SRP are two basalt types: the dominant low-K olivine tholeiites and less common high-K alkaline basalts. We report new Sr-, Nd-, and Pb-isotopic analyses of these two basalt types from all three SRP provinces: eastern, central, and western. Low-K tholeiites are enriched in 143Nd/144Nd and 86Sr/87Sr and forms a quasi-linear array in Pb-isotope space, along with Craters of the Moon and eastern SRP basalts. High-K lavas are found largely in the western plain, and have a uniquely different isotopic signature. They are depleted in 143Nd/144Nd and 86Sr/87Sr, relative to the low-K tholeiites, and plot closer to the BSE component of Zindler and Hart (1986). They also share the same Pb-isotopic space with high-K basalts from Smith Prairie (Boise River Group 2 of Vetter and Shervais, 1992). One low-K tholeiite - Eureka North, plots with these high alkali basalts. Mass balance models have demonstrated an increasing plume component from the Yellowstone caldera in the east to the craton edge in the west. The lavas analyzed in this study conform remarkably to this model. The mass fraction of plume component in western

  1. Reactive transport models for mineral CO2 storage in basaltic rocks

    Science.gov (United States)

    Aradottir, E. S.; Sonnenthal, E. L.; Bjornsson, G.; Jonsson, H.

    2010-12-01

    CO2 mineral storage in basalts may provide a long lasting, thermodynamically stable and environmentally benign solution to reduce anthropogenic CO2 in the atmosphere. We present here development of reactive transport models of this process with focus on the CarbFix experiment at Hellisheidi geothermal power plant in Iceland. There, up to 2.2 tons/year of purified CO2 of volcanic origin will be dissolved in water and injected at intermediate depths (400-800 m) into relatively fresh basaltic lava. Plans call for a full-scale injection if the experiment is successful. Reactive transport modeling is an important factor in the CarbFix project, providing tools to predict and optimize long-term management of the injection site as well as to quantify the amount of CO2 that has the potential of being mineralized. TOUGHREACT and iTOUGH2 are used to develop reactive fluid flow models that simulate hydrology and mineral alteration associated with injecting dissolved CO2 into basalts. The mineral reactions database in TOUGHREACT has been revised and extended, providing an internally consistent database suitable for mineral reactions of interest for this study. A multiple interacting continua (MINC) dissolution model was developed to simulate the long and short-term dissolution of basaltic glass taking into account dissolution kinetics, leached layer formation and diffusion-limited dissolution rates. Our main focus has been on developing a three dimensional field model of the injection site at Hellisheidi. Hydrological parameters of the model were calibrated using iTOUGH2 to simulate tracer tests that have been ongoing since 2007. Modeling results indicate groundwater velocity in the reservoir to be significantly lower than expected. The slow groundwater velocity may necessitate increasing groundwater flow by producing downstream wells at low rates after CO2 injection has started. The three dimensional numerical model has proven to be a valuable tool in simulating different

  2. Age and Duration of the Paraná-Etendeka Flood Basalts and Related Plumbing System

    Science.gov (United States)

    Renne, P. R.

    2015-12-01

    The Paraná-Etendeka Igneous Province (PEIP) comprises a large volume sequence of continental flood basalts presently distributed assymetrically between South America (mainly southern Brazil but also parts of Uruguay, Paraguay and Argentina) and southwestern Africa (Namibia, Angola), following opening of the South Atlantic ocean. The PEIP is dominated by tholeiitic basalts to basaltic andesites, with subordinate silicic rocks spanning the dacite-trachyte-rhyolite fields, which occur as lava flows, sills and dike swarms as well as intrusive complexes closely related to the eruptive rocks. The PEIP has long been subject of 40Ar/39Ar geochronologic and paleomagnetic studies which led to conclude its rapid formation near the Hauterivian stage (~133 Ma) with onward progression to Barremian from the intrusive equivalents exposed northwards. Two decades after publication of the first 40Ar/39Ar ages for the Paraná flood basalts (Renne et al., 1992) we report here an updated study of the age and duration of this magmatic event. We calibrated a set of sixty published and new results to the calibration of Renne et al. (2011), which indicates an inception age of the volcanism now estimated at 135 ± 1 Ma, before the initiation of sea floor spreading. Lava extrusion progressed over ~2 Ma from south to north. A protracted duration of ~10 Ma inferred by Stewart et al. (1996) for PEIP volcanism is clearly incorrect, as also concluded by Thiede and Vasconcelos (2010). Low-Ti mafic magmas prevailed during the earlier stages followed over time by enhanced dominance of their silicic equivalents. Eruption of the high-Ti (mafic and silicic) magmas initiated simultaneously ~0.5 m.y. later, continuing up to ~133 Ma with injection of the Ponta Grossa dyke swarm. Despite several paleomagnetic polarity intervals recorded by the lava piles in the southern (> 27°S) and central (latitudes of ~24-27°S) domains of the Brazilian PEIP, the paleomagnetic data show small dispersion in agreement

  3. Magma chamber processes in central volcanic systems of Iceland

    DEFF Research Database (Denmark)

    Þórarinsson, Sigurjón Böðvar; Tegner, Christian

    2009-01-01

    New field work and petrological investigations of the largest gabbro outcrop in Iceland, the Hvalnesfjall gabbro of the 6-7 Ma Austurhorn intrusive complex, have established a stratigraphic sequence exceeding 800 m composed of at least 8 macrorhythmic units. The bases of the macrorhythmic units...... olivine basalts from Iceland that had undergone about 20% crystallisation of olivine, plagioclase and clinopyroxene and that the macrorhythmic units formed from thin magma layers not exceeding 200-300 m. Such a "mushy" magma chamber is akin to volcanic plumbing systems in settings of high magma supply...... rate including the mid-ocean ridges and present-day magma chambers over the Iceland mantle plume. The Austurhorn central volcano likely formed in an off-rift flank zone proximal to the Iceland mantle plume during a major rift relocation....

  4. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    OpenAIRE

    Aiuppa, A.; Franco, A.; von Glasow, R.; Allen, A.G.; W. D'Alessandro; Mather, T. A.; Pyle, D. M.; Valenza, M.

    2007-01-01

    Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent) volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basa...

  5. The tropospheric processing of acidic gases and hydrogen sulphide in volcanic gas plumes as inferred from field and model investigations

    OpenAIRE

    Aiuppa, A.; Franco, A.; von Glasow, R.; Allen, A.G.; D’Alessandro, W.; Mather, T. A.; Pyle, D. M.; Valenza, M.

    2006-01-01

    Improving the constraints on the atmospheric fate and depletion rates of acidic compounds persistently emitted by non-erupting (quiescent) volcanoes is important for quantitatively predicting the environmental impact of volcanic gas plumes. Here, we present new experimental data coupled with modelling studies to investigate the chemical processing of acidic volcanogenic species during tropospheric dispersion. Diffusive tube samplers were deployed at Mount Etna, a very active open-conduit basa...

  6. Geochemical characteristics and petrogenesis of Mesozoic basalts from the North China Craton: A case study in Fuxin, Liaoning Province

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Occurrence of Cretaceous basalts in Fuxin County, Liaoning Province provides us an opportunity to understand Mesozoic mantle processes beneath the northern margin of the North China Craton (NNCC). Fuxin Jianguo basalts occur as volcanic channel phases with well-developed columnar jointings and contain few spinel lherzolite and pyroxenite xenoliths. They are poor in silica and rich in alkalis, Ti and Al, belonging to alkaline basalts. In trace element compositions, Jianguo basalts are moderately enriched in LREE and LILE, but not depleted in HFSE. They have low Sr and high Nd and Pb isotopic ratios. These geochemical characteristics suggest that Jianguo basalts originated from the depleted asthenosphere, representing an undifferentiated and uncontaminated primitive magma. Presence of these basalts indicates that the lithosphere beneath the region had thickness less than 65 km at the time of basalt eruption and was mainly composed of fertile pargasite-bearing spinel lherzolite and plagioclase pyroxenite. The voluminous basaltic-andesitic magmatism during the early Jurassic-late Cretaceous time indicates that the commencement and accomplishment of lithosphere thinning in the NNCC was much earlier than that in the southern margin, since the mafic-intermediate volcanism only occurred at the Cretaceous time in the southern margin and the basalts with an asthenosphere isotopic signature at the Tertiary. This shows that highly spatial and temporal heterogeneity existed in the Mesozoic lithosphere evolution.

  7. Intraplate Harrat Volcanism and Neogene Evolution of the Lithosphere-Asthenosphere Boundary beneath Western Saudi Arabia

    Science.gov (United States)

    Kent, A. J.; Duncan, R. A.; Graham, D. W.; Al-Amri, A. M.; Alshalntoni, S. A.

    2015-12-01

    Continental extension is a fundamental plate tectonic process, and extensional environments are associated with significant production of basaltic magmas. Although tholeiitic magmatism produced by mantle decompression is common, dispersed, less voluminous and compositionally variable basaltic and related magmas also occur in association with continental extension. One of the most voluminous, best-preserved and least studied examples of the latter is the volcanic harrats of western Saudi Arabia. Uplift, crustal erosion and harrat volcanism occurred from ~15 Ma to recent over a considerable region of western Arabia. Volcanism trends north from the Red Sea along the Makkah-Madinah-Nafud (MMN) line as a number of discrete harrats, and geophysical evidence suggests this region is underlain by hot upwelling asthenosphere. Larger harrats occur along the central axis of the MMN line, with smaller fields on the periphery. We present initial results of an ongoing study of harrat volcanism, including more than 50 new 40Ar-39Ar ages together with geochemical and isotopic data. Magma storage and fractionation appears to have occurred at a range of crustal levels, including deep storage and transport sufficiently rapid to preserve a range of lithospheric and crustal xenoliths. Melting commenced within the garnet peridotite field, however modeling of REE element abundances suggest that considerable differences exist in the thickness of the overlying lithospheric lid. Thinner lithosphere (line, whereas harrats peripheral to the MMN line have thicker lithosphere (>60-80 km) and magmas result from lower degree melts. The observed variability can be explained by a process of progressively thinning lithosphere along the main axis of the MMN line, as a result of regional lithospheric extension and mantle decompression melting, coupled with northward asthenospheric flow from the Red Sea and/or Afar hot spot.

  8. Depositional model of Permian Luodianian volcanic island and its impact on the distribution of fusulinid assemblage in southern Qinghai, Northwest China

    Institute of Scientific and Technical Information of China (English)

    NIU ZhiJun; XU AnWu; WANG JianXiong; DUAN QiFa; ZHAO XiaoMing; YAO HuaZhou

    2008-01-01

    Pan-riftizational tectonic activity reached climax at Luodianian (Permian) in the East Tethyan Domain,Qinghai-Tibet Plateau. Because of eruptive volcanics and influence of terrigenous materials, a complex volcanic-sedimentary landform formed on the sea floor in southern Qinghai. Four sedimentary facies types were recognized based on detailed field mapping. Spatially, platform facies volcanic-limestone type was located at the center belt approximately trending NWW, surrounded by shallow water slope facies tuff/tuffite type at the two flanks and deep water slope facies breccia/calcirudite at the most outside. The depression facies sandstone-mudstone type, which comprised mainly mudstone, deposited between volcanic islands (platform facies volcanic-limestone type). Based on the field mapping and stratigraphic section data, seven rift-related sedimentary facies were recognized and a depositional model for volcanic island was proposed. It is revealed that some volcanic island chain formed quickly and intermittently in the Qamdo Block during violent eruption, and small carbonate reef, shoal,platform occurred above or on edge of volcanic island, and some slope sedimentary facies surrounded volcano island chain during dormant period of volcanic activities. Three types of fusulinid assemblages were distinguished in the carbonate rocks, which deposited in varied positions of a palaeo-volcanic island: (1) Misellina- Schwagerina assemblage occurred above or on edge of volcanic island, (2) Parafusulina assemblage was located at restricted depression facies among volcanic islands or carbonate platform, and (3) the reworked Pseudofusulina-Schwagerina assemblage occurred at slope facies near margin of volcanic island, which originally deposited in the shallow-water carbonate platform, then collapsed along the volcanic island margin with fusulinid-bearing grain-supported carbonate conglomerate or calcirudite, and finally re-deposited on the deeper slope. The sedimentary sequence

  9. Depositional model of Permian Luodianian volcanic island and its impact on the distribution of fusulinid assemblage in southern Qinghai,Northwest China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pan-riftizational tectonic activity reached climax at Luodianian (Permian) in the East Tethyan Domain, Qinghai-Tibet Plateau. Because of eruptive volcanics and influence of terrigenous materials, a complex volcanic-sedimentary landform formed on the sea floor in southern Qinghai. Four sedimentary facies types were recognized based on detailed field mapping. Spatially, platform facies volcanic-limestone type was located at the center belt approximately trending NWW, surrounded by shallow water slope facies tuff/tuffite type at the two flanks and deep water slope facies breccia/calcirudite at the most outside. The depression facies sandstone-mudstone type, which comprised mainly mudstone, de-posited between volcanic islands (platform facies volcanic-limestone type). Based on the field map-ping and stratigraphic section data, seven rift-related sedimentary facies were recognized and a depo-sitional model for volcanic island was proposed. It is revealed that some volcanic island chain formed quickly and intermittently in the Qamdo Block during violent eruption, and small carbonate reef, shoal, platform occurred above or on edge of volcanic island, and some slope sedimentary facies surrounded volcano island chain during dormant period of volcanic activities. Three types of fusulinid assemblages were distinguished in the carbonate rocks, which deposited in varied positions of a palaeo-volcanic island: (1) Misellina-Schwagerina assemblage occurred above or on edge of volcanic island, (2) Para-fusulina assemblage was located at restricted depression facies among volcanic islands or carbonate platform, and (3) the reworked Pseudofusulina-Schwagerina assemblage occurred at slope facies near margin of volcanic island, which originally deposited in the shallow-water carbonate platform, then collapsed along the volcanic island margin with fusulinid-bearing grain-supported carbonate con-glomerate or calcirudite, and finally re-deposited on the deeper slope. The sedimentary

  10. Maar- and crater lakes of the Long Gang Volcanic Field (N.E. China)—overview, laminated sediments, and vegetation history of the last 900 years

    OpenAIRE

    Jens Mingram; Allen, J. R. M.; C. Brüchmann; Liu, J; Luo, X.(Central China Normal University (HZNU), Wuhan, 430079, China); Jörg F.W. Negendank; Norbert Nowaczyk; Georg Schettler

    2004-01-01

    Maar- and crater lakes have, due to their specific formation and characteristic morphology, a high potential for the development and preservation of seasonally laminated sediments (varves). Within the Long Gang Volcanic Field (LGVF) in N.E. China eight maar- or crater lakes with water depths between 15 and 127 m are located. The seasonal climate with strong influence of the East Asian summer—and winter monsoon and the position of the LGVF at the northern margin of the East Asian dust storm tr...

  11. Assessment of planetary geologic mapping techniques for Mars using terrestrial analogs: The SP Mountain area of the San Francisco Volcanic Field, Arizona

    Science.gov (United States)

    Tanaka, K.L.; Skinner, J.A.; Crumpler, L.S.; Dohm, J.M.

    2009-01-01

    We photogeologically mapped the SP Mountain region of the San Francisco Volcanic Field in northern Arizona, USA to evaluate and improve the fidelity of approaches used in geologic mapping of Mars. This test site, which was previously mapped in the field, is chiefly composed of Late Cenozoic cinder cones, lava flows, and alluvium perched on Permian limestone of the Kaibab Formation. Faulting and folding has deformed the older rocks and some of the volcanic materials, and fluvial erosion has carved drainage systems and deposited alluvium. These geologic materials and their formational and modificational histories are similar to those for regions of the Martian surface. We independently prepared four geologic maps using topographic and image data at resolutions that mimic those that are commonly used to map the geology of Mars (where consideration was included for the fact that Martian features such as lava flows are commonly much larger than their terrestrial counterparts). We primarily based our map units and stratigraphic relations on geomorphology, color contrasts, and cross-cutting relationships. Afterward, we compared our results with previously published field-based mapping results, including detailed analyses of the stratigraphy and of the spatial overlap and proximity of the field-based vs. remote-based (photogeologic) map units, contacts, and structures. Results of these analyses provide insights into how to optimize the photogeologic mapping of Mars (and, by extension, other remotely observed planetary surfaces). We recommend the following: (1) photogeologic mapping as an excellent approach to recovering the general geology of a region, along with examination of local, high-resolution datasets to gain insights into the complexity of the geology at outcrop scales; (2) delineating volcanic vents and lava-flow sequences conservatively and understanding that flow abutment and flow overlap are difficult to distinguish in remote data sets; (3) taking care to

  12. Petrology and U-Pb zircon geochronology of bimodal volcanic rocks from the Maierze Group, northern Tibet: Constraints on the timing of closure of the Banggong-Nujiang Ocean

    Science.gov (United States)

    Fan, Jian-Jun; Li, Cai; Xie, Chao-Ming; Wang, Ming; Chen, Jing-Wen

    2015-06-01

    We present new zircon U-Pb dates, major and trace element chemistry, and Hf isotopic compositions for bimodal volcanic rocks of the Maierze Group (MG) in the Maierze area of the Southern Qiangtang-Baoshan block, northern Tibet. We discuss the implications of these data for the evolution of this region. The MG bimodal volcanic rocks consist of basalts and dacites that yield LA-ICP-MS zircon U-Pb ages of 122 and 120 Ma, respectively. The MG basalts have light rare earth element (LREE)-enriched chondrite-normalized REE patterns (LaN/YbN = 13-14), high Ti/V ratios (45-64), high Zr (190-270 ppm) and Nb (22-41 ppm) concentrations, and Zr/Y ratios (7-9) that are similar to those of within-plate basalts. The MG basalts also have low MgO and total Fe2O3 (TFe2O3) concentrations, significant enrichments in the LREE and the light ion lithophile elements (LILEs; Rb, Ba, Th, U and Pb), and weak depletions in the high field strength elements (HFSE; Nb, Ta, and Ti), all of which are clearly evident in primitive-mantle-normalized multi-element variation diagrams. The MG dacites are more enriched in the LILE (e.g., Rb, Ba, Th, U, K, and Pb) and more depleted in the HFSE (e.g., Nb, Ta, and Ti) than the MG basalts. Moreover, the dacites have variable zircon εHf(t) values (- 6.3 to + 6.3). These features indicate that the parental magma for the MG basalts was likely derived from an enriched lithospheric mantle source that was contaminated by subduction-related fluids or melts. In contrast, the MG dacites were derived from mixing of the MG basaltic magma with a second magma derived from partial melting of the continental crust. The geochemical and Hf isotopic characteristics of the MG bimodal volcanic rocks suggest that they formed during the initial stages of development of a back-arc basin. From south to north, the Bangong-Nujiang suture zone, the Duolong gold-rich porphyry copper deposit, and the Maierze bimodal rocks are interpreted to represent a remnant of a complete volcanic arc

  13. UPDATING AN EXPERT ELICITATION IN THE LIGHT OF NEW DATA: TEN YEARS OF PROBABILISTIC VOLCANIC HAZARD ANALYSIS FOR THE PROPOSED HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY AT YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    The U.S. Department of Energy (DOE) considers volcanism to be a potentially disruptive class of events that could affect the safety of the proposed high-level waste repository at Yucca Mountain. Volcanic hazard assessment in monogenetic volcanic fields depends on an adequate understanding of the temporal and spatial pattern of past eruptions. At Yucca Mountain, the hazard is due to an 11 Ma-history of basaltic volcanism with the latest eruptions occurring in three Pleistocene episodes to the west and south of Yucca Mountain. An expert elicitation convened in 1995-1996 by the DOE estimated the mean hazard of volcanic disruption of the repository as slightly greater than 10-8 dike intersections per year with an uncertainty of about two orders of magnitude. Several boreholes in the region have encountered buried basalt in alluvial-filled basins; the youngest of these basalts is dated at 3.8 Ma. The possibility of additional buried basalt centers is indicated by a previous regional aeromagnetic survey conducted by the USGS that detected approximately 20 magnetic anomalies that could represent buried basalt volcanoes. Sensitivity studies indicate that the postulated presence of buried post-Miocene volcanoes to the east of Yucca Mountain could increase the hazard by an order of magnitude, and potentially significantly impact the results of the earlier expert elicitation. Our interpretation of the aeromagnetic data indicates that post-Miocene basalts are not present east of Yucca Mountain, but that magnetic anomalies instead represent faulted and buried Miocene basalt that correlates with nearby surface exposures. This interpretation is being tested by drilling. The possibility of uncharacterized buried volcanoes that could significantly change hazard estimates led DOE to support an update of the expert elicitation in 2004-2006. In support of the expert elicitation data needs, the DOE is sponsoring (1) a new higher-resolution, helicopter-borne aeromagnetic survey

  14. Paleoproterozoic andesitic volcanism in the southern Amazonian craton (northern Brazil); lithofacies analysis and geodynamic setting

    Science.gov (United States)

    Roverato, Matteo; Juliani, Caetano; Capra, Lucia; Dias Fernandes, Carlos Marcelo

    2016-04-01

    Precambrian volcanism played an important role in geological evolution and formation of new crust. Most of the literature on Precambrian volcanic rocks describes settings belonging to subaqueous volcanic systems. This is likely because subaerial volcanic rocks in Proterozoic and Archean volcano-sedimentary succession are poorly preserved due to erosive/weathering processes. The late Paleoproterozoic Sobreiro Formation (SF) here described, seems to be one of the rare exceptions to the rule and deserves particular attention. SF represents the subaerial expression of an andesitic magmatism that, linked with the upper felsic Santa Rosa F., composes the Uatumã Group. Uatumã Group is an extensive magmatic event located in the Xingú region, southwestern of Pará state, Amazonian Craton (northern Brazil). The Sobreiro volcanism is thought to be related to an ocean-continent convergent margin. It is characterized by ~1880 Ma well-preserved calc-alkaline basaltic/andesitic to andesitic lava flows, pyroclastic rocks and associated reworked successions. The superb preservation of its rock-textures allowed us to describe in detail a large variety of volcaniclastic deposits. We divided them into primary and secondary, depending if they result from a direct volcanic activity (pyroclastic) or reworked processes. Our study reinforces the importance of ancient volcanic arcs and rocks contribution to the terrestrial volcaniclastic sedimentation and evolution of plate tectonics. The volcanic activity that produced pyroclastic rocks influenced the amount of detritus shed into sedimentary basins and played a major role in the control of sedimentary dispersal patterns. This study aims to provide, for the first time, an analysis of the physical volcanic processes for the subaerial SF, based in field observation, lithofacies analysis, thin section petrography and less geochemical data. The modern volcanological approach here used can serve as a model about the evolution of Precambrian

  15. Spatial and Alignment Analyses for a Field of Small Volcanic Vents South of Pavonis Mons and Implications for the Tharsis Province, Mars

    Science.gov (United States)

    Bleacher, Jacob E.; Glaze, Lori S.; Greeley, Ronald; Hauber, Ernst; Baloga, Stephen; Sakimoto, Susan E. H.; Williams, David A.; Glotch, Timothy D.

    2009-01-01

    A field of small volcanic vents south of Pavonis Mons was mapped with each vent assigned a two-dimensional data point. Nearest neighbor and two-point azimuth analyses were applied to the resulting location data. Nearest neighbor results show that vents within this field are spatially random in a Poisson sense, suggesting that the vents formed independently of each other without sharing a centralized magma source at shallow depth. Two-point azimuth results show that the vents display north-trending alignment relationships between one another. This trend corresponds to the trends of faults and fractures of the Noachian-aged Claritas Fossae, which might extend into our study area buried beneath more recently emplaced lava flows. However, individual elongate vent summit structures do not consistently display the same trend. The development of the volcanic field appears to display tectonic control from buried Noachian-aged structural patterns on small, ascending magma bodies while the surface orientations of the linear vents might reflect different, younger tectonic patterns. These results suggest a complex interaction between magma ascension through the crust, and multiple, older, buried Tharsis-related tectonic structures.

  16. SHRIMP zircon U-Pb age and significance of Early Paleozoic volcanic rocks in East Kunlun orogenic belt, Qinghai Province, China

    Institute of Scientific and Technical Information of China (English)

    ZHU; Yunhai; LIN; Qixiang; JIA; Chunxing; WANG; Guocan

    2006-01-01

    Early Paleozoic volcanic rocks in Nuomuhong area occurred as basalt slice and meta-volcanic slice. SHRIMP zircon U-Pb dating of the basalt slice and the meta-volcanic slice show that the age of the basalt slice is 419±5 Ma, and that of the meta-volcanic slice is 401± 6 Ma. These ages directly testify that there existed Early Paleozoic ocean-continent transform in East Kunlun, the basalt slice was formed in an extensional mid-ocean ridge setting and the meta-volcanic rock slice was formed in an extrusion subduction and collision setting. The inherited zircon age of 1734 Ma in volcanic rocks reflects that the base of East Kunlun may be Middle Proterozoic.

  17. Petrography and petrology of Quaternary volcanic rocks from Ghezel Ghaleh, northwest Qorveh

    Directory of Open Access Journals (Sweden)

    Alireza Bajelan

    2014-10-01

    Full Text Available Introduction In the east and northeast of Sanandaj in the Qorveh-Bijar-Takab axis, there are series of basaltic composition volcanoes with Quaternary age. The study area is part of the Sanandaj-Sirjan zone and is located between 47°52' and 47°57' E longitudes and 35°26 and '35°30' N latitudes. Due to the location of the volcanic cone on Pliocene clastic sediments and Quaternary travertine, the age of these volcanoes is considered to be Quaternary. The cones mostly consist of low scoria, ash, volcanic bombs, lapilli deposits and basaltic lava (Moein Vaziri and Aminsobhani, 1985. Petrological and geochemical studies have been carried out to evaluate Quaternary magmatism in the area and to determine the nature of the lithological characteristics, such as the evaluation of source rocks and magma type, degree of partial melting and the tectonic setting of Ghezel Ghaleh rocks (Moein Vaziri, 1997. Simplified geological map of the study area is characterized by ER-Mapper software. Materials and methods In the course of field studies in the region, 40 samples were taken, 30 thin sections were prepared and polished. XRD analyses were performed on some whole rock samples. All major, minor and trace elements were assessed by ICP-MS at Lab Weft Laboratory in Australia. Results Based on the classification of structural zones, the area is located in the Sanandaj-Sirjan zone, hundred kilometers away from the main Zagros thrust along the NW-SE direction. After early Cimmerian orogeny, andesitic volcanic activity took place (Moein Vaziri and Aminsobhani, 1985. A major secondary mineral in these rocks is iddingsite, formed by hydration and oxidation of the olivine (Shelley, 1993. According to SiO2 against Na2O + K2O (TAS diagram (Irvine and Baragar , 1971 and cationic R1 and R2 diagram (De La Roche et el., 1980, volcanic rocks of the area indicate alkaline series. Discussion To obtain more information on the tectonic setting of these rocks, the Zr/Y-Zr diagram

  18. Determination of properties of Proterozoic continental flood basalts of western part from North Qilian Mountains

    Institute of Scientific and Technical Information of China (English)

    夏林圻; 夏祖春; 赵江天; 徐学义; 杨合群; 赵东宏

    1999-01-01

    Proterozoic volcanic rocks of the western part from the North Qilian Mountains are the products of continental rift volcanism, belonging to continental flood basalts, the petrogeochemistry of which apears to suggest that they are derived from sub-lithospheric mantle plume sources, but that they also show evidence of continental lithosphere components involvement. Their formation is the consequences of plume-lithosphere interactions and is precursive to the opening of the North Qilian Early-Paleozoic ocean basin.

  19. Petrographic and geochemical characterization of the Triassic and Jurassic magmatic and volcanic rocks of southeastern Ecuador

    Science.gov (United States)

    Villares, Fabián; Eguez, Arturo; Yanez, Ernesto

    2014-05-01

    Formely, the subandean zone in the southeastern Ecuador involved large volcanic and magmatic rocks included in the Misahualli Formation and Zamora batholith, both as expression of the Jurassic cal-alcaline volcanic arc. The aim of the project carried out by the INIGEMM (Instituto Nacional de Investigación Geológico Minero Metalúrgico) was discriminate the volcanic products including a continuous set going from basalts to ryolithes and volcanoclastic rocks. Geochemical characterization was done using representative 16 whole - rock chemical analysis. The oldest rocks of the investigated area called Pachicutza Unit, include greenish to black, massive basalts and basaltic andesites, locally showing pillows structures. The texture is aphanitic to microporphyritic with slight crystal growth of plagioclase and pyroxenes. The Unit include also local pyroclastic breccias and tuffs showing variable skarnification related to the intrusion of the jurassic Zamora Batholith. Two samples of basalts show tholeiitic affinity, corresponding to an N- MORB, probably representing an early stage in opening of a regional Triassic rift reported since Colombia to Peru in the Andes. These geochemical characteristics are similar to the amphibolites of Monte Olivo Unit in the Real Cordillera. The Jurassic large volcanic assembly of the Misahualli Formation was also differenciated. Basal volcanics include green, subporphyritic andesites and volcanic breccias possibly generated at an early stage of the volcanic arc, caused by a change of extensive to compressive regime. Continental volcano sedimentary and sedimentary rock were discriminate as Nueva Esperanza and Suarez Units, respectively. The volcanosedimentary sequence include massive to laminate tuffs and tuffites of intermediate composition. The sediments of the Suarez Unit include dominant conglomerats and sandstones of fluvial domain. The regional volcanic sequence is completed by the Las Peñas Unit that includes aphanitic to

  20. Bimodal volcanism in a tectonic transfer zone: Evidence for tectonically controlled magmatism in the southern Central Andes, NW Argentina

    Science.gov (United States)

    Petrinovic, I. A.; Riller, U.; Brod, J. A.; Alvarado, G.; Arnosio, M.

    2006-04-01

    This field-based and analytical laboratory study focuses on the genetic relationship between bimodal volcanic centres and fault types of an important tectonic transfer zone in the southern Central Andes, the NW-SE striking Calama-Olacapato-Toro (COT) volcanic belt. More specifically, tectono-magmatic relationships are examined for the 0.55 Ma Tocomar, the 0.78 Ma San Jerónimo and the 0.45 Ma Negro de Chorrillos volcanic centres in the Tocomar area (66°30 W-24°15 S). Structures of the COT volcanic belt, notably NW-SE striking strike-slip faults and NE-SW trending normal faults, accommodated differential shortening between major N-S striking thrust faults on the Puna Plateau. We present evidence that bimodal volcanism was contemporaneous with activity of these fault types in the COT volcanic belt, whereby eruption and composition of the volcanic rocks in the Tocomar and San Jerónimo-Negro de Chorrillos areas appear to have been controlled by the kinematics of individual faults. More specifically, rhyolitic centres such as the Tocomar are associated with normal faults, whereas shoshonitic-andesitic monogenetic volcanoes, e.g., the San Jerónimo and Negro de Chorrillos centres, formed at strike-slip dominated faults. Thus, the eruption of higher viscous rhyolite magmas appears to have been facilitated in tectonic settings characterized by horizontal dilation whereas ascent and effusive volcanic activity of less viscous and hot basaltic andesites to shoshonites were controlled by subvertical strike-slip faults. While the Tocomar rhyolites are interpreted to be derived from an anatectic crustal source, geochemical characteristics of the San Jerónimo and Negro de Chorrillos shoshonitic andesites are in agreement with a deeper source. This suggests that the composition of erupted volcanic rocks as well as their spatial distribution in the Tocomar area is controlled by the activity of specific fault types. Such volcano-tectonic relationships are also evident from older

  1. Multiple Volcanic Episodes of Flood Basalts Caused by Underplating

    Institute of Scientific and Technical Information of China (English)

    ZHU Dan; XU Yi-gang; SONG Xie-yang; HU Rui-zhong

    2008-01-01

    @@ Most Large igneous provinces (LIPs) are emplaced within <10 Ma, with a main pulse of the magmatism in<1 Ma[1]. For example, the Siberian Traps [2] and the Deccan Traps [3] were probably erupted within one million years. Many events, such as the Columbia River event, feature a single pulse of magmatism, followed by a protrac-ted period of magmatism at a much lower rate that is linked to a plume tail[4].

  2. Micromorphological Characterization of Some Volcanic Soil In West Java

    OpenAIRE

    Mahfud Arifin; Rina Devnita

    2014-01-01

    http://dx.doi.org/10.17014/ijog.vol3no4.20082Micromorphological characterization has been studied on six pedons of soils developing in volcanic materials in West Java. The pedons represent deposits of different volcanoes (Mount Tangkuban Perahu, Mount Patuha and Mount Papandayan) with different ages (Pleistocene, Holocene) within two types of volcanisms (andesitic, basaltic), and three agroclimatic zones (A, B1, B2). Undisturbed soil samples were taken from each identifiable horizon for thin ...

  3. Impact of organic carbon on weathering and chemical denudation of granular basalt

    Science.gov (United States)

    Dontsova, Katerina; Zaharescu, Dragos; Henderson, Whitney; Verghese, Sarah; Perdrial, Nicolas; Hunt, Edward; Chorover, Jon

    2014-08-01

    Bench-scale experiments were conducted to determine rates and patterns of coupled organic matter infusion and weathering in a San Francisco volcanic field (Flagstaff, AZ) basalt sample under experimentally-modeled biotic and abiotic condition and to inform larger-scale collaborative studies at the landscape evolution observatory (LEO), Biosphere 2 (Tucson, AZ), where the same basaltic media is being used in a synthetic hillslope experiment. We postulated that mineral transformations depend significantly on the presence of organic carbon compounds including dissolved natural organic matter (DOM), with organic C simultaneously imprinting the chemical and mineralogical properties of primary and secondary solids undergoing incongruent dissolution. The present work reports on solute releases from Flagstaff basalt (FB) along laboratory-controlled gradients in DOM type and concentration. Loamy sand textured FB was subjected to flow-through, saturated column dissolution experiments using influent solutions with and without DOM compounds. Solutions included Ponderosa pine forest soil O-horizon extracts at three target concentrations: 7, 35, and 70 mg L-1 C, malic acid (MA) solutions at 7, 35, 70, and 140 mg L-1 C, and a control without DOM but having comparable inorganic solution composition. Chemical denudation rates for FB dissolution products were calculated from the concentration difference between outflow and inflow solutions. In addition, changes in the composition of the solid phase over the course of the experiment were determined using X-ray diffraction (XRD), X-ray fluorescence (XRF), and selective dissolution (SE). Column experiments supported dissolution rates derived from the literature and indicated a potentially strong effect of plant-derived organic ligands on mineral dissolution congruency and secondary phase precipitation. Both malic acid and DOM enhanced basalt dissolution, with malic acid having larger effect on per unit C basis. The largest relative

  4. Basaltic Martian analogues from the Baikal Rift Zone and Mongolian terranes

    Science.gov (United States)

    Gurgurewicz, J.; Kostylew, J.

    2007-08-01

    In order to compare the results of studies of the western part of the Valles Marineris canyon on Mars there have been done field works on terrestrial surface areas similar with regard to geological setting and environmental conditions. One of the possible terrestrial analogues of the Valles Marineris canyon is the Baikal Rift Zone [1]. Field investigations have been done on the south end of the Baikal Lake, in the Khamar-Daban massif, where the outcrops of volcanic rocks occur. The second part of the field works has been done in the Mongolian terranes: Mandalovoo, Gobi Altay and Bayanhongor, because of environmental conditions being similar to those on Mars. The Mandalovoo terrane comprises a nearly continuous Paleozoic islandarc sequence [2]. In the Gobi Altay terrane an older sequence is capped by younger Devonian-Triassic volcanic-sedimentary deposits [2]. The Bayanhongor terrane forms a northwest-trending, discontinuous, narrow belt that consists of a large ophiolite allochton [3]. The collected samples of basalts derive from various geologic environments. The CORONA satellite-images have been used for the imaging of the Khamar-Daban massif and the Mandalovoo terrane. These images have the same spatial resolution and range as the Mars Orbiter Camera images of the Mars Global Surveyor mission. In the Mandalovoo terrane these images allowed to find an area with large amounts of tectonic structures, mainly faults (part of the Ongi massif), similar to the studied area on Mars. Microscopic observations in thin sections show diversification of composition and structures of basalts. These rocks have mostly a porphyric structure, rarely aphyric. The main components are plagioclases, pyroxenes and olivines phenocrysts, in different proportions. The groundmass usually consist of plagioclases, pyroxenes and opaques. The most diversified are basalts from the Mandalovoo terrane. Infrared spectroscopy has been used to analyse the composition of the rock material and compare

  5. Geochemical and 40Ar/39Ar constraints on the evolution of volcanism in the Woodlark Rift, Papua New Guinea

    Science.gov (United States)

    Catalano, Joseph P.

    The tectonic mechanisms producing Pliocene to active volcanism in eastern Papua New Guinea (PNG) have been debated for decades. In order to assess mechanisms that produce volcanism in the Woodlark Rift, we evaluate the evolution of volcanism in eastern PNG using 40Ar/39Ar thermochronology and whole rock geochemistry. Active volcanism in southeastern Papua New Guinea occurs on the Papuan Peninsula (Mt. Lamington, Mt. Victory and Waiwa), in the Woodlark Rift (Dobu Island, SE Goodenough Island, and Western Fergusson Island), and in the Woodlark Basin. In the Woodlark Basin, seafloor spreading is active and decompression melting of the upper mantle is producing basaltic magmatism. However, the cause of Pliocene and younger volcanism in the Woodlark Rift is controversial. Two hypotheses for the tectonic setting have been proposed to explain Pliocene and younger volcanism in the Woodlark Rift: (1) southward subduction of Solomon Sea lithosphere beneath eastern PNG at the Trobriand Tough and (2) decompression melting of mantle, previously modified by subduction, as the lithosphere undergoes extension associated with the opening of the Woodlark Basin. A comparison of 40Ar/39Ar ages with high field strength element (HFSE) concentrations in primary magmas indicates that HFSE concentrations correlate with age in the Woodlark rift. These data support the hypothesis that Pliocene to active volcanism in the Woodlark Rise and D'Entrecasteaux Islands results from decompression melting of a relict mantle wedge. The subduction zone geochemical signatures (negative HFSE anomalies) in Woodlark Rift lavas younger than 4 m.y. are a relict from older subduction beneath eastern Papua, likely in the middle Miocene. As the lithosphere is extended ahead of the tip of the westward propagating seafloor spreading center in the Woodlark Basin, the composition of volcanism is inherited from prior arc magmatism (via flux melting) and through time evolves toward magmatism associated with a rifting

  6. Mapping Planetary Volcanic Deposits: Identifying Vents and Distingushing between Effects of Eruption Conditions and Local Lava Storage and Release on Flow Field Morphology

    Science.gov (United States)

    Bleacher, J. E.; Eppler, D. B.; Skinner, J. A.; Evans, C. A.; Feng, W.; Gruener, J. E.; Hurwitz, D. M.; Whitson, P.; Janoiko, B.

    2014-01-01

    Terrestrial geologic mapping techniques are regularly used for "photogeologic" mapping of other planets, but these approaches are complicated by the diverse type, areal coverage, and spatial resolution of available data sets. When available, spatially-limited in-situ human and/or robotic surface observations can sometimes introduce a level of detail that is difficult to integrate with regional or global interpretations. To assess best practices for utilizing observations acquired from orbit and on the surface, our team conducted a comparative study of geologic mapping and interpretation techniques. We compared maps generated for the same area in the San Francisco Volcanic Field (SFVF) in northern Arizona using 1) data collected for reconnaissance before and during the 2010 Desert Research And Technology Studies campaign, and 2) during a traditional, terrestrial field geology study. The operations, related results, and direct mapping comparisons are discussed in companion LPSC abstracts [1-3]. Here we present new geologic interpretations for a volcanic cone and related lava flows as derived from all approaches involved in this study. Mapping results indicate a need for caution when interpreting past eruption conditions on other planetary surfaces from orbital data alone.

  7. Mapping Planetary Volcanic Deposits: Identifying Vents and Distinguishing between Effects of Eruption Conditions and Local Storage and Release on Flow Field Morphology

    Science.gov (United States)

    Bleacher, J. E.; Eppler, D. B.; Skinner, J. A.; Evans, C. A.; Feng, W.; Gruener, J. E.; Hurwitz, D. M.; Whitson, P.; Janoiko, B.

    2014-01-01

    Terrestrial geologic mapping techniques are regularly used for "photogeologic" mapping of other planets, but these approaches are complicated by the diverse type, areal coverage, and spatial resolution of available data sets. When available, spatially-limited in-situ human and/or robotic surface observations can sometimes introduce a level of detail that is difficult to integrate with regional or global interpretations. To assess best practices for utilizing observations acquired from orbit and on the surface, our team conducted a comparative study of geologic mapping and interpretation techniques. We compared maps generated for the same area in the San Francisco Volcanic Field (SFVF) in northern Arizona using 1) data collected for reconnaissance before and during the 2010 Desert Research And Technology Studies campaign, and 2) during a traditional, terrestrial field geology study. The operations, related results, and direct mapping comparisons are discussed in companion LPSC abstracts. Here we present new geologic interpretations for a volcanic cone and related lava flows as derived from all approaches involved in this study. Mapping results indicate a need for caution when interpreting past eruption conditions on other planetary surfaces from orbital data alone.

  8. Accessory mineral U-Th-Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

    Science.gov (United States)

    Simon, J.I.; Vazquez, J.A.; Renne, P.R.; Schmitt, A.K.; Bacon, C.R.; Reid, M.R.

    2009-01-01

    We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ??? 230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ???85 ka rhyolites yielded ages between ???100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ???200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (???10's to 100's ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies. ?? The Author(s) 2009.

  9. SYSTHESIS OF VOLCANISM STUDIES FOR THE YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Perry, F. V.; Crowe, G. A.; Valentine, G. A.; Bowker, L. M.

    1997-09-23

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the

  10. SYSTHESIS OF VOLCANISM STUDIES FOR THE YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT

    Energy Technology Data Exchange (ETDEWEB)

    Perry, F. V.; Crowe, G. A.; Valentine, G. A.; Bowker, L. M.

    1997-09-23

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The distribution of Pliocene and Quaternary basaltic volcanic centers is evaluated with respect to tectonic models for detachment, caldera, regional and local rifting, and the Walker Lane structural zone. Geophysical data are described for the YMR and are used as an aid to understand the distribution of past basaltic volcanic centers and possible future magmatic processes. Chapter 4 discusses the petrologic and geochemical features of basaltic volcanism in the YMR, the southern Great Basin and the

  11. Geochemical Characteristics of Cenozoic Jining Basalts of the Western North China Craton: Evidence for the Role of the Lower Crust, Lithosphere, and Asthenosphere in Petrogenesis

    Directory of Open Access Journals (Sweden)

    Kung-Suan Ho

    2011-01-01

    Full Text Available The Jining volcanic field located in the southern margin of the Mongolian plateau and the western North China Block consists of four rock types: quartz tholeiite, olivine tholeiite, alkali olivine basalt and basanite. These rocks have a wide range of K-Ar ages from ~36 to < 0.2 Ma. The early volcanism was voluminous and dominated by flood-type fissure eruptions of tholeiites, whereas the later phase was represented by sparse eruptions of basanitic lavas. Thirty-six samples analyzed in this study show a wide range in SiO2 contents from 44% ~ 54%. They all are sodium-rich and high-Ti basalts that, however, show marked isotopic variations between two end-members: (1 tholeiites that have higher 87Sr/86Sr of 0.7048 ~ 0.7052, and lower _ of -0.8 to -2.4 and Pb isotope ratios (206Pb/204Pb of 16.9 ~ 17.2, 207Pb/204Pb of 15.3 ~ 15.4 and 208Pb/204Pb of 37.1 ~ 37.7; and (2 basanites that have lower 87Sr/86Sr of 0.7035 ~ 0.7044, and higher _ of +1.3 to +4.9 and Pb isotope ratios (206Pb/204Pb of 17.7 ~ 18.0, 207Pb/204Pb of 15.4 ~ 15.5 and 208Pb/204Pb of 37.8 ~ 38.2. Alkali olivine basalt that occurs as a subordinate rock type is geochemically similar to the basanites, but isotopically similar to the tholeiites, characterized by the highest 87Sr/86Sr ratio among the three basaltic suites, coupled with a low Nb/U value (~33. In Sr-Nd-Pb isotopic plots, the tholeiites extend toward the EM1 (i.e., enriched mantle type 1 component, whereas the basanites trend toward the Indian Ocean mid-ocean ridge basalt (MORB field. Adopting the _ model by Morris and Hart (1983, we suggest that the Oligocene tholeiites were generated by high degree melting of an ascended asthenospheric mantle that was contaminated with a large amount of EM1-type continental lithospheric material during the early Cenozoic. On the other hand, the late Tertiary and Quaternary basanites may have originated predominantly from a depleted asthenosphere component with small but variable degrees of

  12. Intracanyon basalt lavas of the Debed River (northern Armenia), part of a Pliocene-Pleistocene continental flood basalt province in the South Caucasus

    Science.gov (United States)

    Sheth, Hetu; Meliksetian, Khachatur; Gevorgyan, Hripsime; Israyelyan, Arsen; Navasardyan, Gevorg

    2015-03-01

    Late Pliocene to Early Pleistocene (~ 3.25-2.05 Ma), 200-400 m thick basalt lavas outcrop in the South Caucasus region, including the Kars-Erzurum Plateau (northeastern Turkey), the Javakheti Plateau (Georgia-Armenia), and the Lori Plateau (northern Armenia). These fissure-fed, rapidly erupted fluid lavas filled pre-existing river valleys over many tens of kilometres. The basalts exposed in the Debed River canyon, northern Armenia, are ~ 200 m thick and of three morphological types: (1) basal pillow basalts and hyaloclastites, overlain by (2) columnar-jointed pahoehoe sheet flows, in turn overlain by (3) slabby pahoehoe and rubbly pahoehoe flows. The lower and middle lavas show evidence for damming of river drainage, like many lavas of the Columbia River flood basalt province, Scotland, Ireland, and Iceland. There is also evidence for syn-volcanic faulting of the early lavas. Related basalts also outcrop in the Gegham Uplands and the Hrazdan River basin in Armenia. This 3.25-2.05 Ma South Caucasus basalt province, covering parts of Turkey, Georgia and Armenia, has an estimated areal extent of ~ 15,000 km2 and volume of ~ 2250 km3. Because its main geological features are remarkably like those of many continental flood basalt (CFB) provinces, we consider it a true, albeit small, CFB province. It is the smallest and youngest CFB in the world. An analogue closely similar in major features is the Late Miocene Altos de Jalisco CFB province in the western Trans-Mexican Volcanic Belt. Both provinces formed during lithospheric pull-apart and transtensional faulting. Their broader significance is in showing flood basalt size distribution to be a continuum without natural breaks, with implications for geodynamic models.

  13. Jarosite occurrence in the Deccan Volcanic Province of Kachchh, western India: Spectroscopic studies on a Martian analog locality

    Science.gov (United States)

    Bhattacharya, Satadru; Mitra, Souvik; Gupta, Saibal; Jain, Nirmala; Chauhan, Prakash; Parthasarathy, G.; Ajai

    2016-03-01

    The sulfate mineral jarosite is considered a key indicator of hydrous, acidic, and oxidizing conditions on the surface of early Mars. Here we report an analog terrestrial locality hosting jarosite from Matanumadh, Kachchh, western India, using detailed spectroscopic studies on weathered basalts of the Deccan Volcanic Province and overlying tuffaceous shales and sandstones of the Matanumadh Formation. Hyperspectral data in the visible/near-infrared (350-2500 nm) to midinfrared (4000-400 cm-1) region of the electromagnetic spectrum and X-ray diffraction patterns have been acquired on samples collected from the field to detect and characterize the hydrous sulfate and phyllosilicate phases present at the studied site. Hydrous sulfates occur in association with Al-rich phyllosilicates (kaolinite) that overlie a zone of Fe/Mg smectites in altered basalts. Jarosite is found within both saprolitic clay horizons altered from the basalt and within variegated sandstone and shale/clay units overlying the saprolite; it mostly occurs as secondary veins with or without gypsum. Jarosite is also seen as coatings on kaolinite clasts of varying shapes and sizes within the tuffaceous variegated sandstone unit. We argue that the overall geological setting of the Matanumadh area, with this unusual mineral assemblage developing within altered basalts and in the overlying sedimentary sequence, mimics the geological environment of many of the identified jarosite localities on Mars and can be considered as a Martian analog from this perspective.

  14. Why Hexagonal Basalt Columns?

    Science.gov (United States)

    Hofmann, Martin; Anderssohn, Robert; Bahr, Hans-Achim; Weiß, Hans-Jürgen; Nellesen, Jens

    2015-10-01

    Basalt columns with their preferably hexagonal cross sections are a fascinating example of pattern formation by crack propagation. Junctions of three propagating crack faces rearrange such that the initial right angles between them tend to approach 120°, which enables the cracks to form a pattern of regular hexagons. To promote understanding of the path on which the ideal configuration can be reached, two periodically repeatable models are presented here involving linear elastic fracture mechanics and applying the principle of maximum energy release rate. They describe the evolution of the crack pattern as a transition from rectangular start configuration to the hexagonal pattern. This is done analytically and by means of three-dimensional finite element simulation. The latter technique reproduces the curved crack path involved in this transition.

  15. Seismic wave propagation through surface basalts - implications for coal seismic surveys

    Science.gov (United States)

    Sun, Weijia; Zhou, Binzhong; Hatherly, Peter; Fu, Li-Yun

    2010-02-01

    Seismic reflection surveying is one of the most widely used and effective techniques for coal seam structure delineation and risk mitigation for underground longwall mining. However, the ability of the method can be compromised by the presence of volcanic cover. This problem arises within parts of the Bowen and Sydney Basins of Australia and seismic surveying can be unsuccessful. As a consequence, such areas are less attractive for coal mining. Techniques to improve the success of seismic surveying over basalt flows are needed. In this paper, we use elastic wave-equation-based forward modelling techniques to investigate the effects and characteristics of seismic wave propagation under different settings involving changes in basalt properties, its thickness, lateral extent, relative position to the shot position and various forms of inhomogeneity. The modelling results suggests that: 1) basalts with high impedance contrasts and multiple flows generate strong multiples and weak reflectors; 2) thin basalts have less effect than thick basalts; 3) partial basalt cover has less effect than full basalt cover; 4) low frequency seismic waves (especially at large offsets) have better penetration through the basalt than high frequency waves; and 5) the deeper the coal seams are below basalts of limited extent, the less influence the basalts will have on the wave propagation. In addition to providing insights into the issues that arise when seismic surveying under basalts, these observations suggest that careful management of seismic noise and the acquisition of long-offset seismic data with low-frequency geophones have the potential to improve the seismic results.

  16. Paleoproterozoic (~1.88Ga) felsic volcanism of the Iricoumé Group in the Pitinga Mining District area, Amazonian Craton, Brazil: insights in ancient volcanic processes from field and petrologic data

    OpenAIRE

    Ronaldo Pierosan; Evandro F. Lima; Lauro V. S. Nardi; Cristina P. de Campos; Bastos Neto, Artur C.; José M.T.M. Ferron; Maurício Prado

    2011-01-01

    The Iricoumé Group correspond to the most expressive Paleoproterozoic volcanism in the Guyana Shield, Amazonian craton. The volcanics are coeval with Mapuera granitoids, and belong to the Uatumã magmatism. They have U-Pb ages around 1880 Ma, and geochemical signatures of α-type magmas. Iricoumé volcanics consist of porphyritic trachyte to rhyolite, associated to crystal-rich ignimbrites and co-ignimbritic fall tuffs and surges. The amount and morphology of phenocrysts can be useful to di...

  17. Volcanic Rocks As Targets For Astrobiology Missions

    Science.gov (United States)

    Banerjee, N.

    2010-12-01

    Almost two decades of study highlight the importance of terrestrial subaqueous volcanic rocks as microbial habitats, particularly in glass produced by the quenching of basaltic lava upon contact with water. On Earth, microbes rapidly begin colonizing glassy surfaces along fractures and cracks exposed to water. Microbial colonization of basaltic glass leads to enhanced alteration through production of characteristic granular and/or tubular bioalteration textures. Infilling of formerly hollow alteration textures by minerals enable their preservation through geologic time. Basaltic rocks are a major component of the Martian crust and are widespread on other solar system bodies. A variety of lines of evidence strongly suggest the long-term existence of abundant liquid water on ancient Mars. Recent orbiter, lander and rover missions have found evidence for the presence of transient liquid water on Mars, perhaps persisting to the present day. Many other solar system bodies, notably Europa, Enceladus and other icy satellites, may contain (or have once hosted) subaqueous basaltic glasses. The record of terrestrial glass bioalteration has been interpreted to extend back ~3.5 billion years and is widespread in modern oceanic crust and its ancient metamorphic equivalents. The terrestrial record of glass bioalteration strongly suggests that glassy or formerly glassy basaltic rocks on extraterrestrial bodies that have interacted with liquid water are high-value targets for astrobiological exploration.

  18. Uranium Series Chronology of the Late Pleistocene Basalt from the Longgang Volcanoes, Jilin Province

    Institute of Scientific and Technical Information of China (English)

    YU Fusheng; HAN Song; MA Zhibang; XIE Ruijie

    2005-01-01

    The Longgang volcanic cluster located in Jilin Province belongs to one of the active volcanic regions in northeast China, and has been active in modem times. In view of the multiple eruptions in history, it is very important to determine the age of each eruption for evaluating the volcanic hazards. Two alkaline basalt samples taken from Dayizishan and Diaoshuihu were analyzed with the U-series component dating after magnetic separation. The ages of the two samples are (71±9) ka and (106±13) ka B.P., respectively. These data indicate that there existed intensive eruption activities during the late Pleistocene.

  19. Origin of Miocene andesite and dacite in the Goldfield-Superstition volcanic province, central Arizona: Hybrids of mafic and silicic magma mixing

    Science.gov (United States)

    Fodor, R. V.; Johnson, Kelly G.

    2016-07-01

    The Miocene Goldfield-Superstition volcanic province (G-SVP), ∼8000 km2 in central Arizona, is composed largely of silicic pyroclastic rocks and lavas, and smaller volumes of alkalic basalt and intermediate-composition lavas. Volcanism began ∼20.5 Ma as sparse rhyolitic and mainly basaltic lavas followed by intermediate lavas, lasting until ∼19 Ma. At that time, ∼1 m.y. of silicic eruptions began, creating most of the G-SVP. Petrologic studies are available for basalts and some for silicic rocks, but petrologic/geochemical information is sparse for intermediate-composition lavas. These latter, andesites and dacites, are the focus of this study, in which we present the processes and sources responsible for their origins. Goldfield-Superstition andesites and dacites have SiO2 ∼56-70 wt.% and Na2O + K2O that qualifies some as trachy-andesite and -dacite. A prominent petrographic feature is plagioclase-phyric texture (∼11-30 vol% plagioclase), where oligoclase-andesine phenocrysts have cores surrounded by corroded, or reacted, zones, mantled by higher An% plagioclase. Where corroded zones are absent, margins are etched, curved, or embayed. Groundmass plagioclase is labradorite, also more calcic than the phenocrysts. Other minerals are quartz (subrounded; embayed), clinopyroxene, amphibole, biotite, and rare titanite and zircon. A salient compositional characteristic that provides insight to andesite-dacite origins with respect to other G-SVP rocks is revealed when using SiO2 as an index. Namely, abundances of many incompatible elements, mainly HFSE and REE, decrease over the low to high SiO2 range (i.e., abundances are lower in dacites than in co-eruptive andesites and underlying alkalic basalts). As examples: G-SVP basalts have ∼50-70 ppm La, and andesites-dacites have ∼59-22 ppm La; for Zr, basalts have ∼225-170 ppm, but most andesites-dacites have ∼180-50; for Y, basalts >20 ppm, andesites-dacites ∼18-9 ppm. To understand these trends of lower

  20. Major element, REE, and Pb, Nd and Sr isotopic geochemistry of Cenozoic volcanic rocks of eastern China: implications for their origin from suboceanic-type mantle reservoirs

    Science.gov (United States)

    Basu, A.R.; Wang, Junwen; Huang, Wankang; Xie, Guanghong; Tatsumoto, M.

    1991-01-01

    Major- and rare-earth-element (REE) concentrations and UThPb, SmNd, and RbSr isotope systematics are reported for Cenozoic volcanic rocks from northeastern and eastern China. These volcanic rocks, characteristically lacking the calc-alkaline suite of orogenic belts, were emplaced in a rift system which formed in response to the subduction of the western Pacific plate beneath the eastern Asiatic continental margin. The rocks sampled range from basanite and alkali olivine basalt, through olivine tholeiite and quartz tholeiite, to potassic basalts, alkali trachytes, pantellerite, and limburgite. These rock suites represent the volcanic centers of Datong, Hanobar, Kuandian, Changbaishan and Wudalianchi in northeastern China, and Mingxi in the Fujian Province of eastern China. The major-element and REE geochemistry is characteristic of each volcanic suite broadly evolving through cogenetic magmatic processes. Some of the outstanding features of the isotopic correlation arrays are as follows: (1) NdSr shows an anticorrelation within the field of ocean island basalts, extending from the MORB end-member to an enriched, time-averaged high Rb Sr and Nd Sr end-member (EM1), (2) SrPb also shows an anticorrelation, similar to that of Hawaiian and walvis Ridge basalts, (3) NdPb shows a positive correlation, and (4) the 207Pb 204Pb vs 206Pb 204Pb plot shows linear arrays parallel to the general trend (NHRL) for MORB on both sides of the geochron, although in the 208Pb 204Pb vs 206Pb 204Pb plot the linear array is significantly displaced above the NHRL in a pattern similar to that of the oceanic island basalts that show the Dupal signatures. In all isotope correlation patterns, the data arrays define two different mantle components-a MORB-like component and an enriched mantle component. The isotopic data presented here clearly demonstrate the existence of Dupal compositions in the sources of the continental volcanic rocks of eastern China. We suggest that the subcontinental mantle

  1. Recurrence models of volcanic events

    International Nuclear Information System (INIS)

    An assessment of the risk of future volcanism has been conducted for isolation of high-level radioactive waste at the potential Yucca Mountain site in southern Nevada. Volcanism studies for the Yucca Mountain Site Characterization Project have progressed to a sufficient degree that it is now prudent to work toward concluding aspects of the work. An advantage of a probabilistic approach to volcanic risk is that it assigns a structured formalism to the problem. This formalism subdivides a complex issue into logical sections. The significance of uncertainty or differences in scientific opinion concerning volcanism issues can be tested for each section of a probabilistic problem. The perspective for making judgement of significance for volcanism studied are the regulatory requirements for assessing the suitability of the potential Yucca Mountain site. This paper attempts to begin the process of helping establish the probabilistic framework for making those judgement. There are three objectives. First, the authors describe the tripartite probability used to define the risk of volcanism and the geologic assumptions required for the probability model. Second, the authors examine and define the first part of this probability, the recurrence of volcanic events. Studies are reviewed from the volcanological literature where time-volume behavior of volcanic centers and fields have been evaluated. These evaluations include both conventional statistical analysis of time-series of volcanic events and applications using newly developing concepts of fractal analysis and deterministic chaos. Third, the authors tabulate past calculations and derive new values for the recurrence of volcanic events using a simple Poison model

  2. Bacterial diversity and successional patterns during biofilm formation on freshly exposed basalt surfaces at diffuse-flow deep-sea vents.

    Science.gov (United States)

    Gulmann, Lara K; Beaulieu, Stace E; Shank, Timothy M; Ding, Kang; Seyfried, William E; Sievert, Stefan M

    2015-01-01

    Many deep-sea hydrothermal vent systems are regularly impacted by volcanic eruptions, leaving fresh basalt where abundant animal and microbial communities once thrived. After an eruption, microbial biofilms are often the first visible evidence of biotic re-colonization. The present study is the first to investigate microbial colonization of newly exposed basalt surfaces in the context of vent fluid chemistry over an extended period of time (4-293 days) by deploying basalt blocks within an established diffuse-flow vent at the 9°50' N vent field on the East Pacific Rise. Additionally, samples obtained after a recent eruption at the same vent field allowed for comparison between experimental results and those from natural microbial re-colonization. Over 9 months, the community changed from being composed almost exclusively of Epsilonproteobacteria to a more diverse assemblage, corresponding with a potential expansion of metabolic capabilities. The process of biofilm formation appears to generate similar surface-associated communities within and across sites by selecting for a subset of fluid-associated microbes, via species sorting. Furthermore, the high incidence of shared operational taxonomic units over time and across different vent sites suggests that the microbial communities colonizing new surfaces at diffuse-flow vent sites might follow a predictable successional pattern.

  3. Basalt Magma, Whisky and Tequila: finely-crafted mixes of small liquid batches that defy the parent liquid concept but whose complexities teach us much

    Science.gov (United States)

    Rubin, K. H.; Sinton, J. M.; Perfit, M. R.

    2015-12-01

    Basalt is the most ubiquitous magma type we know of in the solar system. It comes in various varieties manifested as compositional sub groups, erupts from a wide variety of volcanic systems and tectonic settings, and its eruptions span many order of magnitude in duration and volume. Igneous petrology, thermodynamics, geochemistry, and geodynamical modelling have been used to develop a sophisticated understanding of source lithologies, compositions and formation conditions (e.g., pressure and temperature) for parent melts and their subsequent transport, storage and evolution. These demonstrate some striking systematics as a function of volcano tectonic setting (on Earth). Yet much like Whisky, what makes it into the bottle, or the eruption, is a mixture of different liquids with unique characteristics, sometimes stirred so well that successive batches are indistinguishable, and sometimes stirred more incompletely, preserving small batch characters that are unique. Recently, geochemical and petrological studies in high spatial density within the products of individual eruptions have shown chemical and mineralogical evidence for incompletely mixed heterogeneous magmas in a majority of systems examined, begging the question of when, if ever, is it realistic to speak of a single parent magma composition, and even in cases where it apparently is, if these are instead just more thoroughly stirred multi-parent magmas. For instance, do monogenetic fields really erupt basalts of more varied parent melt compositions than large hot spot and flood basalt eruptions, or are they just more poorly stirred? This presentation will focus on work by ourselves and others constraining spatial and temporal single-eruption basaltic magma histories at different settings, using them to unravel the time and space scales of magma formation and mixing, how these translate to the assembly of an erupted basalt magma, and the implications for deducing things about and from presumed parents.

  4. A study on the geochemical characteristics of Upper Permian continental marginal arc volcanic rocks in the northern segment of South Lancangjiang Belt

    Institute of Scientific and Technical Information of China (English)

    SHEN Shangyue; FENG Qinglai; WEI Qirong; ZHANG Zhibin; ZHANG Hu

    2006-01-01

    Geochemical characteristics of the Upper Permian ( P2 ) continental marginal arc volcanic rocks are described, which have been found recently around the areas of Xiaodingxi and Zangli on the eastern side of the Yunxian-Lincang granite, in terms of rock assemblage, petrochemistry, REE, trace elements, Pb isotopes, geotectonic environment and so on. The volcanic rock assemblage is dominated by basalt-andesite-dacite, with minor trachyte andecite-trachyte; the volcanic rock series is predominated by the calc-alkaline series, with minor tholleiite series and alkaline series rocks; the volcanic rocks are characterized by high Al2O3 and low TiO2 , with K2O contents showing extremely strong polarity; the REE distribution patterns are characterized by LREE enrichment and right-inclined type; trace elements and large cation elements are highly enriched, Ti and Cr are depleted, and P and Nb are partially depleted; the Pb composition is of the Gondwana type; the petrochemical points mostly fall within the field of island-arc volcanic rocks, in consistency with the projection of data points of continental marginal volcanic rocks in the southern segment of the South Lancangjiang Belt and the North Lancangjiang Belt. This continental marginal arc volcanic rock belt, together with the ocean-ridge and ocean-island volcanic rocks and ophiolites in the Changning-Menglian Belt, constitute the ocean-ridge volcanic rock, ophiolite-arc rock-magmatic rock belts which are distributed in pairs, indicating that the Lancangjiang oceanic crust subducted eastwards. This result is of great importance in constraining the evolution of the paleo-Tethys in the Lancangjiang Belt.

  5. Hot Spot Induced Cenozoic Volcanism in the Upper Rajang Valley, Sarawak - Is Borneo Rifting?

    Science.gov (United States)

    Taib, N.

    2010-12-01

    The Upper Rajang Valley covers a large area in the northern interior of the island of Borneo, in the Malaysian state of Sarawak . It is underlain by the Cretaceous to Late Eocene deep to shallow marine sediments of the Rajang Group. Within this area are several Cenozoic volcanic edifices, which to date have been sparsely studied. Two distinct episodes of volcanism are recognized - the first, dated early Eocene, consists of K-rich basalts, and is represented by the Bukit Mersing volcanics, which were erupted conformably onto deep water turbidites of the Rajang Group. The second, far more extensive, is dated Pliocene to Quaternary, and is bimodal, consisting mainly of early dacite and rhyodacite tuffs, with a smaller amount of later basalt, forming several volcanic plateaus and massifs (Hose Mountains, Usun Apau, Linau-Balui, Nieuwenhuis Mountains and others). They lie unconformably over pre-Miocene sediments, the Linau-Balui basalts having been erupted onto Quaternary river terraces. Mantle-normalized REE and incompatible trace element spider plots reveal that the Bukit Mersing basalts have geochemical affinity with Oceanic Island Basalts (OIB) and rift basalts, being enriched in LREEs and Most Incompatible Elements, and no Eu anomaly. Preliminary trace element data for several basalt samples from Usun Apau also show Oceanic Island/Rift affinity. Bimodal volcanism is most often associated with rift environments. Efforts are being made to radiometrically date the volcanics, in part to determine the possibility of future eruptions. The Upper Rajang Valley is remote, covered in tropical rainforest and is very sparsely populated. At this time, there is no information concerning signs of imminent volcanism, such as hot springs and microseismicity.

  6. Clinopyroxene with diverse origins in alkaline basalts from the western Pannonian Basin: Implications from trace element characteristics

    Science.gov (United States)

    Jankovics, M. Éva; Taracsák, Zoltán; Dobosi, Gábor; Embey-Isztin, Antal; Batki, Anikó; Harangi, Szabolcs; Hauzenberger, Christoph A.

    2016-10-01

    Clinopyroxene crystals of various origins occur in the unusually crystal- and xenolith-rich alkaline basalts of the Bondoró-hegy and the Füzes-tó scoria cone, which are the youngest eruptive centres in the Bakony-Balaton Highland Volcanic Field, western Pannonian Basin. The clinopyroxenes show diverse textural and zoning features as well as highly variable major and trace element chemistry. Xenocryst, megacryst and phenocryst crystal populations can be distinguished on the basis of their compositional differences. The trace element patterns of green clinopyroxene cores display a large range in composition and indicate that most of them have a metamorphic origin. Most of them were incorporated from lower crustal mafic granulite wall rocks, while only a few of them are of magmatic origin representing pyroxenite (Type II) cumulates. The colourless clinopyroxene xenocrysts reflect the texturally and geochemically diverse nature of the subcontinental lithospheric mantle beneath the studied area, mainly representing regions characterised by various stages of metasomatism. The colourless and green megacrysts are genetically related to each other, having crystallised as early and late crystallisation products, respectively, from petrogenetically related melts as part of a fractional crystallisation sequence. These melts represent earlier alkaline basaltic magmas (as represented by the Type II xenoliths), having stalled and crystallised near the crust-mantle boundary in the uppermost part of the mantle. This serves as evidence that the deep magmatic systems beneath monogenetic volcanic fields are complex, involving several phases of melt generation, accumulation and fractionation at variable depths. We show that in situ trace element analysis is necessary in order to unravel the origins and relationships of the diverse clinopyroxene populations. Such studies significantly contribute to our understanding of the ascent histories of alkaline basaltic magmas and provide

  7. Volcanic eruptions observed with infrasound

    Science.gov (United States)

    Johnson, Jeffrey B.; Aster, Richard C.; Kyle, Philip R.

    2004-07-01

    Infrasonic airwaves produced by active volcanoes provide valuable insight into the eruption dynamics. Because the infrasonic pressure field may be directly associated with the flux rate of gas released at a volcanic vent, infrasound also enhances the efficacy of volcanic hazard monitoring and continuous studies of conduit processes. Here we present new results from Erebus, Fuego, and Villarrica volcanoes highlighting uses of infrasound for constraining quantitative eruption parameters, such as eruption duration, source mechanism, and explosive gas flux.

  8. Eruption and emplacement of flood basalt. An example from the large-volume Teepee Butte Member, Columbia River Basalt Group

    Energy Technology Data Exchange (ETDEWEB)

    Reidel, S.P. (Washington State Univ., Pullman (United States)); Tolan, T.L. (Portland State Univ., OR (United States))

    1992-12-01

    Flows of the Teepee Butte Member, Grande Ronde Basalt, issued from a vent system in southeastern Washington, northeastern Oregon, and western Idaho. Three distinct basalt flows were erupted: the Limekiln Rapids flow, the Joseph Creek flow, and the Pruitt Draw flow. Together these mappable flows cover more than 52,000 km[sup 2] and have a volume exceeding 5,000 km[sup 3]. A portion of the vent system for the Joseph Creek flow is exposed in cross section in Joseph Canyon, Washington; it is one of the best preserved Columbia River Basalt Group vent complexes known. The vent complex is about 1 km in cross section, 30 m high, and composed of deposits characteristic of Hawaiian-type volcanism. The vent is asymmetrical; the eastern rampart consists of intercalated pyroclastic deposits and thin pahoehoe flows; the western rampart is composed wholly of pahoehoe flows. Flows of the Teepee Butte Member are compositionally homogeneous and were emplaced as sheet flows, each having several local flow units. Our study supports the importance of linear vent systems and the westward Palouse Slope, along with the large-volume lava flows, in controlling the distribution of Columbia River Basalt Group flows. Other factors, including the number of active fissure segments and topography, modified the shape of the flows and the number of flow units. 45 refs., 19 figs., 2 tabs.

  9. A Conceptual Model to Link Anomalously High Temperature Gradients in the Cerros del Rio Volcanic Field to Regional Flow in the Espanola Basin, New Mexico

    Science.gov (United States)

    Fillingham, E. J.; Keller, S. N.; McCullough, K. R.; Watters, J.; Weitering, B.; Wilce, A. M.; Folsom, M.; Kelley, S.; Pellerin, L.

    2015-12-01

    Temperature-depth well data along with electromagnetic (EM) data were collected by students of the Summer of Applied Geophysics Experience (SAGE) 2015 field season in the Espanola Basin, New Mexico. The data from this year, in addition to data acquired since 2013, were used to construct a conceptual east-west cross-section of the Espanola Basin and the adjacent highlands in order to evaluate the regional flow system. Vertical geothermal gradients from several monitoring wells were measured using a thermistor. Anomalously warm geothermal gradients were mapped in the Cerros del Rio volcanic field in the basin just east of the Rio Grande. Temperature gradients are up to 70℃/km, while the background geothermal gradients in the Rio Grande rift zone generally show 28℃-35℃/km. This anomaly extends to the Buckman well field, which supplies water to the city of Santa Fe. Overpumping of this well field has led to subsidence in the past. However, discharge temperature plots indicate that the temperature gradients of the Buckman field may be rebounding as pumping is reduced. Audiomagnetotelluric (AMT) and transient electromagnetic (TEM) data were acquired in the vicinity of three monitoring wells. TEM and AMT methods complement each other with the former having depths of investigation of less than ten to hundreds of meters and AMT having depths of investigation comparable to the wells deeper than 500m. These datasets were used collectively to image the subsurface stratigraphy and, more specifically, the hydrogeology related to shallow aquifers. The EM data collected at these wells showed a trend indicating a shallow aquifer with a shallower resistive layer of approximately 100 ohm-m at 70-100 meters depth. Beneath this resistive layer we resolved a more conductive, clay-rich layer of 10 ohm-m. These resistivity profiles compliment the electrical logs provided by Jet West, which indicate shallower sandstone interbedded with silt on top of more silt-dominant layers. Our

  10. Lunar volcanism in space and time

    Science.gov (United States)

    Head, J. W., III

    1976-01-01

    The role of lunar volcanism in the history of the moon is documented using lunar-orbit and earth-based data along with characterizations derived from Apollo and Luna sample-return missions. Characteristics of mare and highland volcanic features are described, Apollo and Luna results are discussed, and the characteristics of other mare deposits and of other highland features of possible volcanic origin are summarized. Major conclusions are that: (1) there is little unequivocal morphologic evidence for highland volcanism, (2) lunar mare lavas appear to have originated from depths of 100 to 500 km, (3) impact melting does not appear to have been a factor in the generation of mare lavas, (4) mare volcanism was characterized by massive outpourings of very fluid volatile-poor lava analogous to terrestrial flood basalts, (5) mare volcanism took place from 3.83 to about 2.5 billion years ago, (6) the preferential occurrence of mare deposits in large impact basins appears to be generically unrelated to basin formation, and (7) a thicker farside crust may be responsible for the distinctive nearside-farside asymmetry of mare deposits.

  11. Hanford basalt flow mineralogy

    International Nuclear Information System (INIS)

    Mineralogy of the core samples from five core wells was examined in some detail. The primary mineralogy study included an optical examination of polished mounts, photomicrographs, chemical analyses of feldspars, pyroxenes, metallic oxides and microcrystalline groundmasses and determination from the chemical analyses of the varieties of feldspars, pyroxenes and metallic oxides. From the primary mineralogy data, a firm understanding of the average Hanford basalt flow primary mineralogy emerged. The average primary feldspar was a laboradorite, the average pyroxene was an augite and the average metallic oxide was a solid solution of ilmenite and magnetite. Secondary mineralization consisted of vug filling and joint coating, chiefly with a nontronite-beidellite clay, several zeolites, quartz, calcite, and opal. Specific flow units also were examined to determine the possibility of using the mineralogy to trace flows between core wells. These included units of the Pomona, the Umatilla and a high chromium flow just below the Huntzinger. In the Umatilla, or high barium flow, the compositional variation of the feldspars was unique in range. The pyroxenes in the Pomona were relatively highly zoned and accumulated chromium. The high chromium flow contained chromium spinels that graded in chromium content into simple magnetites very low in chromium content. A study of the statistical relationships of flow unit chemical constituents showed that flow unit constituents could be roughly correlated between wells. The probable cause of the correlation was on-going physical-chemical changes in the source magma

  12. Late Cretaceous lithospheric extension in SE China: Constraints from volcanic rocks in Hainan Island

    Science.gov (United States)

    Zhou, Yun; Liang, Xinquan; Kröner, Alfred; Cai, Yongfeng; Shao, Tongbin; Wen, Shunv; Jiang, Ying; Fu, Jiangang; Wang, Ce; Dong, Chaoge

    2015-09-01

    Petrological, geochemical and in-situ zircon U-Pb dating and Hf-isotope analyses have been carried out on a suite of basalt-andesite-rhyolite volcanic rocks exposed in the Liuluocun area, Hainan Island, SE China. Zircon analyses show that these volcanic rocks crystallized in the Early Cretaceous (ca. 102 Ma). The basalts are characterized by low MgO contents and mg-numbers but high rare earth element, high field strength element and large ion lithophile element contents and Nb-Ta negative anomalies. They have relatively uniform Sr-Nd isotope compositions with εNd(t) values of - 4.09 to - 3.63. The andesites show enrichment of high field strength element and rare earth element with negligible Eu anomalies. They have εNd(t) values of - 2.35 to - 3.88 and εHf(t) values of - 9.73 to - 1.13. The rhyolites have high K2O and SiO2 contents. They are characterized by prominent Eu, P and Ti negative anomalies and enrichment in large ion lithophile element, and show εHf(t) values of - 7.51 to + 0.47 and εNd(t) values of - 2.49 to - 2.69. Petrogenetic analysis indicates that the Liuluocun volcanic rocks were produced by incomplete reaction of the mantle wedge peridotite with felsic melts derived from partial melting of subducted sediment. All these characteristics, combined with geological observations, suggest that their formation was related to regional lithospheric extension in the South China Craton during the Early Cretaceous, which may have been caused by subduction of the Paleo-Pacific plate beneath the continental plate of China.

  13. Development of a geothermal resource in a fractured volcanic formation: Case study of the Sumikawa Geothermal Field, Japan. Final report, May 1, 1995--November 30, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Garg, S.K.; Combs, J.; Pritchett, J.W. [and others

    1997-07-01

    The principal purpose of this case study of the Sumikawa Geothermal Field is to document and to evaluate the use of drilling logs, surface and downhole geophysical measurements, chemical analyses and pressure transient data for the assessment of a high temperature volcanic geothermal field. This comprehensive report describes the work accomplished during FY 1993-1996. A brief review of the geological and geophysical surveys at the Sumikawa Geothermal Field is presented (Section 2). Chemical data, consisting of analyses of steam and water from Sumikawa wells, are described and interpreted to indicate compositions and temperatures of reservoir fluids (Section 3). The drilling information and downhole pressure, temperature and spinner surveys are used to determine feedzone locations, pressures and temperatures (Section 4). Available injection and production data from both slim holes and large-diameter wells are analyzed to evaluate injectivity/productivity indices and to investigate the variation of discharge rate with borehole diameter (Section 5). New interpretations of pressure transient data from several wells are discussed (Section 6). The available data have been synthesized to formulate a conceptual model for the Sumikawa Geothermal Field (Section 7).

  14. Characteristics of mix crystal xenolith from basaltic(shoshonitic) volcanic breccia at Maguan Area, Yunnan Province, and their geological significance%云南马关碧(钾)玄质火山角砾岩中矿物混晶包体特征及其地质意义

    Institute of Scientific and Technical Information of China (English)

    黄玉蓬; 刘显凡; 李春辉; 卢秋霞; 陶专; 赵甫峰; 董毅; 邹金汐; 易立文

    2013-01-01

    在云南马关碧(钾)玄质火山角砾岩中发现了一类特殊包体,呈红色与黑色两种.经X射线粉晶衍射鉴定,红色者为以锰铝榴石为主要结晶相的隐晶-非晶质混晶,黑色者为以绿辉石为主要结晶相的隐晶-非晶质混晶.两种矿物混晶包体在一定程度上类似于熔浆玻璃或熔体囊,它们具有同源演化的相似地球化学特征.文中通过对两种矿物混晶包体的显微特征与地球化学分析研究表明,它们是亏损地幔部分熔融的产物,并作为一种不混溶熔体成分被碱性玄武岩浆携带、运移上升.它们代表了石榴石相(榴辉岩相)地幔源区组分,暗示新生代时期软流圈上涌除释放小体积交代熔体交代上地幔使其富集之外,还造成岩石圈地幔拆沉,尖晶石相地幔组分向石榴石相地幔组分转变.另外,据两种混晶包体与其他类型包体和寄主岩岩浆的不同来源,推测马关地区深部岩石圈地幔经交代作用发生过两次转换.首先是由原始地幔向亏损地幔转化,并发生部分熔融,其后是由亏损地幔转化为富集地幔,形成富碱岩浆和与其互不混溶的进一步富集成矿元素的地幔流体.由此暗示滇西地区与富碱斑岩有关的多金属成矿作用即受制于这一深部地质过程与壳幔混染机制.%A special kind of xenolith has been discovered from the basaltic (shoshonitic) volcanic breccia at Maguan area. Yunnan Province. There are two kinds of xenoliths: one is red and the other is black in color. It can be identified by X-ray crystal powder diffraction that the red one is a mixed crystal of aphanites-amorphous material, the major potential component of which is spessartine. while the black one is a mixed crystal of aphanites-amorphous material, major potential component of which is omphacite. To some extent the two kind of mixed crystals are similar to melting glass or melt pockets. It shows that they have the similar geochemical

  15. Nanoparticulate mineral matter from basalt dust wastes.

    Science.gov (United States)

    Dalmora, Adilson C; Ramos, Claudete G; Querol, Xavier; Kautzmann, Rubens M; Oliveira, Marcos L S; Taffarel, Silvio R; Moreno, Teresa; Silva, Luis F O

    2016-02-01

    Ultra-fine and nano-particles derived from basalt dust wastes (BDW) during "stonemeal" soil fertilizer application have been the subject of some concern recently around the world for their possible adverse effects on human health and environmental pollution. Samples of BDW utilized were obtained from companies in the mining district of Nova Prata in southern Brazil for chemical characterization and nano-mineralogy investigation, using an integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/(Energy Dispersive Spectroscopy) EDS/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM)/EDS and granulometric distribution analysis. The investigation has revealed that BDW materials are dominated by SiO2, Al2O3 and Fe2O3, with a complex micromineralogy including alkali feldspar, augite, barite, labradorite, hematite, heulandrite, gypsum, kaolinite, quartz, and smectite. In addition we have identified a number of trace metals such as Cd, Cu, Cr, Zn that are preferentially concentrated into the finer, inhalable, dust fraction and could so present a health hazard in the urban areas around the basalt mining zone. The implication of this observation is that use of these nanometric-sized particulates as soil fertilizer may present different health challenges to those of conventional fertilizers, inviting future work regarding the relative toxicities of these materials. Our investigation on the particle size distribution, nano-particle mineralogy and chemical composition in typical BDW samples highlights the need to develop cleaning procedures to minimise exposure to these natural fertilizing basalt dust wastes and is thus of direct relevance to both the industrial sector of basalt mining and to agriculture in the region.

  16. Nanoparticulate mineral matter from basalt dust wastes.

    Science.gov (United States)

    Dalmora, Adilson C; Ramos, Claudete G; Querol, Xavier; Kautzmann, Rubens M; Oliveira, Marcos L S; Taffarel, Silvio R; Moreno, Teresa; Silva, Luis F O

    2016-02-01

    Ultra-fine and nano-particles derived from basalt dust wastes (BDW) during "stonemeal" soil fertilizer application have been the subject of some concern recently around the world for their possible adverse effects on human health and environmental pollution. Samples of BDW utilized were obtained from companies in the mining district of Nova Prata in southern Brazil for chemical characterization and nano-mineralogy investigation, using an integrated application of advanced characterization techniques such as X-ray diffraction (XRD), High Resolution-Transmission Electron microscopy (HR-TEM)/(Energy Dispersive Spectroscopy) EDS/(selected-area diffraction pattern) SAED, Field Emission-Scanning Electron Microscopy (FE-SEM)/EDS and granulometric distribution analysis. The investigation has revealed that BDW materials are dominated by SiO2, Al2O3 and Fe2O3, with a complex micromineralogy including alkali feldspar, augite, barite, labradorite, hematite, heulandrite, gypsum, kaolinite, quartz, and smectite. In addition we have identified a number of trace metals such as Cd, Cu, Cr, Zn that are preferentially concentrated into the finer, inhalable, dust fraction and could so present a health hazard in the urban areas around the basalt mining zone. The implication of this observation is that use of these nanometric-sized particulates as soil fertilizer may present different health challenges to those of conventional fertilizers, inviting future work regarding the relative toxicities of these materials. Our investigation on the particle size distribution, nano-particle mineralogy and chemical composition in typical BDW samples highlights the need to develop cleaning procedures to minimise exposure to these natural fertilizing basalt dust wastes and is thus of direct relevance to both the industrial sector of basalt mining and to agriculture in the region. PMID:26551199

  17. Facies-controlled volcanic reservoirs of northern Songliao Basin, NE China

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Volcanic rocks of the late Mesozoic are very important reservoirs for the commercial natural gases including hydrocarbon, carbon dioxide and rare gases in the northern Songliao Basin. The reservoir volcanic rocks include rhyolite,andesite, trachyte, basalt and tuff. Facies of the volcanic rocks can be classified into 5 categories and 15 special types.Porosity and permeability of the volcanic reservoirs are facies-controlled. Commercial reservoirs were commonly found among the following volcanic subfacies: volcanic neck (Ⅰ1), underground-explosive breccia (Ⅰ3), pyroclastic-bearing lava flow (Ⅱ3), upper effusive (Ⅲ3) and inner extrusive ones (Ⅳ1). The best volcanic reservoirs are generally evolved in the interbedded explosive and effusive volcanics. Rhyolites show in general better reservoir features than other types of rocks do.

  18. Late Cenozoic volcanism, geochronology, and structure of the Coso Range, Inyo County, California

    Energy Technology Data Exchange (ETDEWEB)

    Duffield, W.A.; Bacon, C.R.; Dalrymple, G.B.

    1980-05-10

    The Coso Range lies at the west edge of the Great Basin, adjacent to the southern part of the Sierra Nevada. A basement complex of pre-Cenozoic plutonic and metamorphic rocks is partly buried by approx.35 km/sup 3/ of late Cenozoic volcanic rocks that were erupted during two periods, as defined by K-Ar dating: (1) 4.0--2.5 m.y., approx.31 km/sup 3/ of basalt, rhyodacite, dacite, andesite, and rhyolite, in descending order of abundance, and (2) < or =1.1 m.y., nearly equal amounts of basalt and rhyolite, most of the rhyolite being < or =0.3 m.y. old. Vents for the volcanic rocks of the younger period are localized on and near a horst of basement rocks within a concavity defined by the distribution of vents of the older period. The alignment of many vents and the presence of a considerable number of roughly north-trending normal faults of late Cenozoic age reflect basin and range tectonics dominated by roughly east-west lithospheric extension. Fumaroles, intermittently active thermal springs, and associated altered rocks occur within and immediately east of the central part of the field of Quaternary rhyolite, in an area characterized by various geophysical anomalies that are evidently related to an active hot-water geothermal system. This system apparently is heated by a reservoir of silicic magma at > or =8-km depth, itself produced and sustained through partial melting of crustal rocks by thermal energy contained in mantle-derived basaltic magma that intrudes the crust in repsonse to lithospheric extension.

  19. Miocene through Holocene Arc and Post-arc Volcanism in the Northern Sierra Nevada and Western Nevada

    Science.gov (United States)

    Cousens, B.; Henry, C. D.; Timmermans, A.; Sylvester, A.; Wise, W.; Prytulak, J.; Stoffers, A. J.; Gupta, V.

    2009-12-01

    , Upsal Hogback and Soda Lake maars, and the Buffalo Valley field. The lavas are poorly-phyric alkalic basalt, trachybasalt, basaltic trachyandesite, and porphyritic rhyolite. Trace element and isotope geochemistry varies from west to east, from post-arc-like compositions to “OIB”-like compositions typical of young Mojave Desert or Lunar Craters volcanic rocks. This gradient probably reflects the dominance of two mantle sources, “Sierran” to the west (arc and post-arc lavas) and “Great Basin” to the east. We suggest that the Sierran source is primarily metasomatized lithospheric mantle, whereas the Great Basin source is in the asthenosphere. In the wake of the westward-migrating slab hinge through the Tertiary, the lithospheric mantle was largely exhausted of fusible components, so that later melting beneath the central Great Basin occurred only in the asthenosphere.

  20. Middle Miocene near trench volcanism in northern Colombia: A record of slab tearing due to the simultaneous subduction of the Caribbean Plate under South and Central America?

    Science.gov (United States)

    Lara, M.; Cardona, A.; Monsalve, G.; Yarce, J.; Montes, C.; Valencia, V.; Weber, M.; De La Parra, F.; Espitia, D.; López-Martínez, M.

    2013-08-01

    Field, geochemical, geochronological, biostratigraphical and sedimentary provenance results of basaltic and associated sediments northern Colombia reveal the existence of Middle Miocene (13-14 Ma) mafic volcanism within a continental margin setting usually considered as amagmatic. This basaltic volcanism is characterized by relatively high Al2O3 and Na2O values (>15%), a High-K calc-alkaline affinity, large ion lithophile enrichment and associated Nb, Ta and Ti negative anomalies which resemble High Al basalts formed by low degree of asthenospheric melting at shallow depths mixed with some additional slab input. The presence of pre-Cretaceous detrital zircons, tourmaline and rutile as well as biostratigraphic results suggest that the host sedimentary rocks were deposited in a platform setting within the South American margin. New results of P-wave residuals from northern Colombia reinforce the view of a Caribbean slab subducting under the South American margin. The absence of a mantle wedge, the upper plate setting, and proximity of this magmatism to the trench, together with geodynamic constraints suggest that the subducted Caribbean oceanic plate was fractured and a slab tear was formed within the oceanic plate. Oceanic plate fracturing is related to the splitting of the subducting Caribbean Plate due to simultaneous subduction under the Panama-Choco block and northwestern South America, and the fast overthrusting of the later onto the Caribbean oceanic plate.

  1. Hydrothermal systems in two areas of the Jemez volcanic field: Sulphur Springs and the Cochiti mining district

    Energy Technology Data Exchange (ETDEWEB)

    WoldeGabriel, G.

    1989-03-01

    K/Ar dates and oxygen isotope data were obtained on 13 clay separates (<2 ..mu..m) of thermally altered mafic and silicic rocks from the Cochiti mining district (SE Jemez Mountains) and Continental Scientific Drilling Project (CSDP) core hole VC-2A (Sulphur Springs, Valles caldera). Illite with K/sub 2/O contents of 6.68%--10.04% is the dominant clay in the silicic rocks, whereas interstratified illite/smectites containing 1.4%--5.74% K/sub 2/O constitute the altered andesites. Two hydrothermal alteration events are recognized at the Cochiti area (8.07 m.y., n = 1, and 6.5--5.6 m.y., n = 6). The older event correlates with the waning stages of Paliza Canyon Formation andesite volcanism (greater than or equal to13 to less than or equal to8.5 m.y.), whereas the younger event correlates with intrusions and gold- and silver-bearing quartz veins associated with the Bearhead Rhyolite (7.54--5.8 m.y.). The majority of K/Ar dates in the hydrothermally altered, caldera-fill rocks of core hole VC-2A (0.83--0.66 m.y., n = 4) indicate that hydrothermal alteration developed contemporaneously with resurgence and ring fracture Valles Rhyolite domes (0.89--0.54 m.y.). One date of 0 +- 0.10 m.y. in acid-altered landslide debris of postcaldera tuffs from the upper 13 m of the core hole probably correlates with Holocene hydrothermal activity possibly associated with the final phases of the Valles Rhyolite (0.13 m.y.).

  2. Mapping and compositional analysis of mare basalts in the Aristarchus region of the Moon using Clementine data

    International Nuclear Information System (INIS)

    The process of accurately defining and outlining mare basalt units is necessary for constraining the stratigraphy and ages of basalt units, which are used to determine the duration and the flux of lunar volcanism. We use a combination of Clementine's five-band ultraviolet/visible data and TiO2 and FeO abundance distribution maps to define homogenous mare basalt units and characterize their compositional variations (with maturity) in the Aristarchus region. With 20 groups of distinct mare basaltic soils identified using the method in this paper, six additional spectrally defined areas and five basaltic units are constructed, and their mineralogic quantization values provide new constraints on their temporal and spatial evolution. Our results indicate that the Aristarchus region has diverse basalt units and a complex history of volcanic evolution. We also demonstrate that the techniques, from which spectrally distinct mare basalts can be mapped, performed well in this study and can be confidently expanded to other mare regions of the Moon. (research papers)

  3. Paleomagnetism of Upper Jurassic to Lower Cretaceous volcanic and sedimentary rocks from the western Tarim Basin and implications for inclination shallowing and absolute dating of the M-0 (ISEA?) chron

    Science.gov (United States)

    Gilder, Stuart; Chen, Yan; Cogné, Jean-Pascal; Tan, Xiaodong; Courtillot, Vincent; Sun, Dongjiang; Li, Yongan

    2003-02-01

    Stepwise demagnetization isolates a stable magnetic component in 13 sites of basalt flows and baked sediments dated at 113.3±1.6 Ma from the Tuoyun section, western Xinjiang Province, China. Except for one flow from the base of the ˜300 m thick section, the rest have exclusively reversed polarity. The sequence correlates with chron M-0 in some geomagnetic polarity time scales, which potentially places the section just before the start of the Cretaceous Long Normal polarity superchron. Five of 11 sites of Early Cretaceous red beds that underlie the basalts possess coherent directions that pass both fold and reversals tests. Six sites of Upper Jurassic red beds have a magnetic component that was likely acquired after folding in the Tertiary. The mean paleolatitude of the Lower Cretaceous red beds is 11° lower than that of the Lower Cretaceous basalts suggesting the red beds underestimate the true field inclination. We further test this result by calculating the paleolatitudes to a common point of the available Early Cretaceous to Present paleomagnetic poles from red beds and volcanic rocks from central Asian localities north of the Tibetan Plateau. We find that paleolatitudes of volcanic rocks roughly equal the paleolatitudes calculated from the reference Eurasian apparent polar wander path (APWP) and that paleolatitudes of red beds are generally 10-20° lower than the paleolatitudes of volcanic rocks and those predicted from the reference curve. Our study suggests that central Asian red beds poorly record the Earth's field inclination, which leads to lower than expected paleolatitudes. Good agreement in paleolatitudes from volcanic rocks and the Eurasian APWP argues against proposed canted and non-dipole field models.

  4. Tracking and understanding volcanic emissions through cross-disciplinary integration of field, textural, geochemical and geophysical data: A textural working group. (Invited)

    Science.gov (United States)

    gurioli, L.

    2013-12-01

    Relating magma ascent to eruption style using information preserved in pyroclastic deposits is a major challenge in modern volcanology. Because magma ascent and fragmentation are inaccessible to direct observation, one way to obtain quantitative information for conduit dynamics is through textural quantification of the sampled products (i.e., full definition of the rock vesicle and crystal properties). Many workers have shown that quantification of vesicle and crystal size distributions yields valuable insights into the processes that created the pyroclasts. However, the physical characteristics of individual pyroclasts must not be considered in isolation from information regarding: (i) the deposits from which they are taken; (ii) their chemistry; (iii) geophysical signatures of the related explosive events; and (iv) results from petrological and/or analogue experiments. As a result, attempts to understand eruption dynamics have increasingly involved the coupling of traditional field and sample-return analyses with geophysical measurements made synchronous with sample collection. In spite of this progress, we remain far from developing a definitive methods that allows us to sample, correlate and/or compare the multitude of parameters that can be measured at an actively building field deposits. As a result, no study has yet been able to correlate all derivable textural parameters with the full range of available multidisciplinary data. To discuss these issues, a working group met during 6-7 November 2012 at the Maison International of the Université Blaise Pascal (Clermont-Ferrand, France). The workshop was supported by the European Science Foundation and was held under the title: 'Tracking and understanding volcanic emissions through cross-disciplinary integration: A textural working group'. Our main objective was to gather an advisory group to define measurements, methods, formats and standards to be applied to integration of geophysical and physical

  5. Age and Geochemical Features of Dredged Basalts from Offshore SW Taiwan: The Coincidence of Intra-Plate Magmatism with the Spreading South China Sea

    Directory of Open Access Journals (Sweden)

    Kuo-Lung Wang

    2012-01-01

    Full Text Available This study reports age and geochemical analyses of basaltic rocks dredged from volcanic seamounts offshore SW Taiwan. 40Ar/39Ar dating results of these rocks show them to be of the early Miocene age of ~22 - 21 Ma. They are evolved alkali basalts that show OIB-type geochemical features similar to post-spreading seamount basalts (14 - 3.5 Ma in the South China Sea (SCS and Miocene intraplate basalts on the Penghu Islands (16 - 8 Ma and NW Taiwan (23 - 9 Ma. Their Sr-Nd-Pb isotope data plot within the range of the SCS seamount basalts that show an EM2-like component in the mantle source. The age and overall geochemical characteristics of the dredged basalts are comparable to those of the Kungkuan basalts, NW Taiwan and Baolai basalts, SW Taiwan, suggesting an extensive alkali basaltic volcanism along the southeastern Eurasian continental margin during the early Miocene that resulted from regional lithospheric extension in association with seafloor spreading in the South China Sea.

  6. Early J2 basalts in SE China: Incipience of large-scale late Mesozoic magmatism

    Institute of Scientific and Technical Information of China (English)

    XIE; Xin; XU; Xisheng; ZOU; Haibo; JIANG; Shaoyong; ZHANG; Ming

    2006-01-01

    Magmatism in SE China was dormant during 204-180 Ma, but was reactivated in 180-170 Ma (early J2), and then became more and more intensive towards the end of early Cretaceous. The small-scale early J2 magmatism is the incipience to long-term and large-scale magmatism in this region. A near east-west (EW) trend volcanic belt was distributed across south Hunan, south Jiangxi and southwest Fujian was formed during early J2 time. Along this belt from the inland toward the coast, the lithology of basalts changes from alkali into tholeiite, and the amount of erupted volcanic rocks and the proportions of rhyolites coexisting with the basalts increase. On the basis of geochemical characteristics of these basalts, we infer that the melting degree of source rocks and the extent of fractional crystallization and crustal contamination all increased whereas the depth of mantle source decreased from the inland to the coast, which led to the variations of geological characteristics of the volcanic belt. In early J2, the western spreading Pacific plate began to subduct underneath SE China continental block, reactivating near EW trend deep fault that was originally formed during the Indosinian event. The stress of the western spreading Pacific plate and the extent of asthenosphere upwelling increased from the inland to the coast, which is consistent with the generation and evolution of early J2 basalts.

  7. Petrogenesis and geodynamic significance of silicic volcanism in the western Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Petrone, C. M.; Ferrari, L.; Orozco, M. A.; Lopez Martinez, M.

    2012-04-01

    Silicic volcanism in the western Trans-Mexican Volcanic Belt (WTMVB) was defined a Pliocene ignimbrite flare-up associated with the rifting of the Jalisco block from mainland Mexico (Frey et al., 2007; GSAB). With the integration of new and published geochronologic, geochemical, and isotope data we revise this interpretation and propose a new petrogenetic model. The oldest silicic volcanism consists of large silicic domes and minor pyroclastic flows (~370 km3) emplaced to the north of Guadalajara above a thick succession of ~11 to 8.7 Ma basaltic lavas, which yielded Ar-Ar and obsidian FT ages of ~7.5 to 5 Ma. Shortly after (4.9 to 2.9 Ma) large amount of rhyolitic lavas and ash flow tuffs (~500 km3) were emplaced in a WNW-ESE trending belt from Guadalajara to Compostela. Rhyolitic domes and flows (~430 km3) were emplaced also in the Pleistocene mostly between Tequila and Guadalajara with the late Pleistocene La Primavera caldera (~35 km3) as the sole explosive volcanic episodes. As a whole, silicic volcanism occurred from Late Miocene to the Pleistocene, and was dominated by dome and lava flows. Most rhyolites have high LILE/HFSE values and negative spikes at Nb, P and Ti. They also show the same Ba/Nb and K/Rb values and slightly higher Rb/Sr ratios as the 11-8 Ma basalts. Rhyolite Sr isotope data (87Sr/86Sr init = 0.70371 - 070598) are only slightly more radiogenic than the 11-8 basalts (87Sr/86Sr init = 0.70349-0.70410), whereas Nd isotope ratios are indistinguishable from them. Sr and Nd isotope ratios of the rhyolites are also similar to the crust nearby, indicating that they can be compatible either with fractional crystallization (FC) of basalts or with crust assimilation/melting. However REE contents are too low to be the result of basalt FC. Isotope and REE data can be successfully modelled with an initial crustal melt which subsequently undergone fractional crystallization of feldspar and quartz. Late Miocene slab detachment and subsequent slab rollback

  8. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

    Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

  9. Magmatic Source Composition and Magmatism of the Volcanic Rocks in the Area of Kuruktag, Southern Xinjiang

    Institute of Scientific and Technical Information of China (English)

    JIANG Changyi; BAI Kaiyin; HI Aizhi; ZHAO Xiaoning; ZHANG Hongbo

    2001-01-01

    In the Sinian-Cambrian strata in the area of Kuruktag, southern Xingjiang, four layers of volcanic rocks occurred in the Early Sinian Beiyixi Formation, Late Sinian Zhamoketi Formation and Shuiquan Formation, and Early Cambrian Xishanbulake Formation, respectively. Volcanics of the Shuiquan Formation and Xishanbulake Formation are of alkali basalt series, those of the Zhamoketi Formation are of alkali basalt series and tholeiite series, and those of the Beiyixi Formation are obviously characterized by bimodal assemblage and mostly belong to alkali volcanics. Multi-element distribution patterns of the rocks show continental tumescence characters of interplate basalt.Fractional crystallization of plagioclase led to negative Eu-anomalies of some volcanics and the cumulation of olivine resulted in high MgO and low SiO2 content of some volcanic rocks. The SiO2 saturability of volcanic rocks of the Xishanbulake Formation and Shuiquan Formation is lower than that of tholeiite of the Zhamoketi Formation. Correspondingly, the abundance of incompatible elements in the first two formations is higher than those in the last formation, and the differences can be attributed to the different degrees of partial melting. The intense fractionation of REE and the obvious depletion of HREE suggest that these volcanic rocks were derived from garnet Iherzolite of the mantle in the continental lithosphere. The Ba/Nb, La/Nb, Ba/La, Ba/Th and Rb/Nb rations demonstrate that these volcanic rocks were exclusively derived from the enriched mantle, mainly the EMI type mantle.

  10. Vapor segregation and loss in basaltic melts

    Science.gov (United States)

    Edmonds, M.; Gerlach, T.M.

    2007-01-01

    Measurements of volcanic gases at Pu'u'O??'o??, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: 1 persistent continuous gas emission, 2 gas piston events, and 3 lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u'O??'o??. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The Large gas bubbles are H2O rich and are generated by open-system degassing at depths of segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone. ?? 2007 The Geological Society of America.

  11. Volatile Evolution of Magma Associated with the Solchiaro Eruption in the Phlegrean Volcanic District (Italy)

    Science.gov (United States)

    Esposito, R.; Bodnar, R. J.; de Vivo, B.; Lima, A.; Fedele, L.; Shimizu, N.; Hunter, J.

    2009-12-01

    The Phlegrean volcanic district (PVD) in southern Italy is one of the best known volcanic hazard areas in the world. More than 1.5 million people live in close proximity to the volcanic centers. The PVD comprises three volcanic fields: the Campi Flegrei caldera and the islands of Ischia and Procida. We studied volatiles plus major and trace elements in the magma associated with the Solchiaro eruption on the Island of Procida, Italy, to gain a better understanding of the relationship between pre-eruptive volatiles and magmatic evolution. The Solchiaro eruption is one of the more primitive products erupted in the PVD and provides information on the source of later more evolved magmas associated with this volcanic system. The composition of the magma before eruption was determined by analyzing 104 melt inclusions (MIs) in forsteritic olivine, glass embayment plus rim glasses, and high vesciculated glasses selected from 4 representative samples. The composition of MIs was recalculated and ranges from basaltic to trachy-basaltic. Among major elements potassium shows the highest variability, from 0.5 to 6 wt%. MI define a continuous trend based on major and minor element compositions. Embayments matrix glass and high vesciculated glasses define a field that suggests a discontinuous process. Compatible to incompatible trace element ratios in early melts are highly variable and represent the melt phase before or at the very beginning of assimilation-fractional crystallization (FCA) processes. Intermediate melt compositions reflect continuing FCA processes, late melt compositions suggest that the FCA process was aborted before eruption. Volatile contents of early melt are highly variable and reflect source heterogeneities, and the melts are interpreted to be undersaturated. Intermediate melts were volatile saturated and H2O-CO2 contents define a degassing path. Depths of trapping of MI range from 4.4 to 2.2 km, and are calculated based on Newman and Lowenstern (2002) and

  12. Experimental Parameters for Wax Modeling of the Deccan Traps Flood Basalt Province

    Science.gov (United States)

    Rader, E. L.; Vanderkluysen, L.; Clarke, A. B.

    2015-12-01

    The Deccan Traps consist of ~1,000,000 km3 of predominantly tholeiitic basaltic lava flows, which cover the western Indian subcontinent. Their eruption occurred over a ~1-3 million year period overlapping with the Cretaceous-Paleogene (K-Pg) boundary and, hence, has been implicated in one of the most significant extinction events in the history of the planet. The extent of environmental impacts caused by flood basalt eruptions is thought to be related, in part, to the amount, species, and timescales of volcanic gases released. Therefore, constraining the effusion rate of Deccan Traps lava flows is fundamental to understanding the K-Pg extinction event. Previous field and experimental work with polyethylene glycol (PEG) wax has shown that effusion rate is a primary factor controlling flow morphology. While sinuous flows and lava domes have been successfully recreated with PEG wax, the two most common morphologies seen in the Deccan Traps (compound and inflated sheet lobes) have not. We used heated PEG-400 wax injected into a tank of chilled water with a peristaltic pump to form experimental eruptions with high flow rate and low viscosity to replicate inflated flow lobes, and low flow rate with higher viscosity for compound flows. Unlike previous experiments, flow rate was varied during a single experiment to examine the effect on flow morphology. The Psi value is used as a scaling parameter to estimate effusion rates for compound and 'simple' inflated flows in the Deccan Traps. When combined with field work for volume estimates of the two flow types, these experiments will provide the best constraint on eruption rates to date.

  13. Sr, Nd, Pb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin; Thirlwall, Matthew F.

    2015-01-01

    The presented Sr, Nd, Hf and double-spike Pb-isotopic analyses of Quaternary basalts from the Payenia volcanic province in southern Mendoza, Argentina, confirm the presence of two distinct mantle types feeding the Payenia volcanism. The southern Payenia mantle source feeding the intraplate-type Río...

  14. Strength of Concrete Containing Basalt Fibre

    Directory of Open Access Journals (Sweden)

    Parvez Imraan Ansari

    2015-04-01

    Full Text Available This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5% of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.

  15. Chemical and Isotopic Constraints on the Origin of Cenozoic Pacific Northwest Volcanism

    Science.gov (United States)

    Carlson, R. W.; Hart, W. K.; Grove, T. L.; Donnelly-Nolan, J. M.; Barr, J. A.; Till, C. B.

    2009-12-01

    Though there is little debate about the connection of Cascade volcanism to subduction of the Juan de Fuca plate, the cause of extensive Neogene volcanism east of the Cascades is not as well understood. Volumetrically, the most significant component of this volcanism, the flood basalts of the Columbia Plateau and Steens Mountain, are dominated by lavas that have suffered extensive crystal fractionation in crustal magma chambers. The evolved, crustally contaminated, nature of most of these basalts makes identification of the primary magma difficult, confounding interpretation of the background cause of the volcanism. Some Steens lavas are relatively undifferentiated (Johnson et al., USGS Open File report 98-0482). These Steens basalts have compositions that are distinguished from younger primitive basalts on the High Lava Plains (HLP) by distinctly lower Al and higher FeO, Ti, Zr and Nb concentrations, but also Mg#s that are too low to be in equilibrium with mantle that has Fo90 olivine. If these are primary magmatic characteristics, they suggest either a more fertile, FeO-rich source, or lower, not higher, degrees of melting at greater depth during the flood basalt era as opposed to the much smaller-volume younger HLP volcanism. Experimental results on primitive Quaternary HLP and Newberry Volcano lavas suggest last equilibration at pressures corresponding to just below the Moho (30-40 km) with water contents that range from substantial (up to 4 wt %) at Newberry to low (Columbia River basalts and most Snake River Plain basalts have Pb isotope compositions strongly displaced from values seen in oceanic basalts plotting instead along a circa 2.5 Ga trend. The shift in Pb (and Sr, Nd, and Hf) isotope composition occurs precisely at the boundary between young accreted terranes to the west and Precambrian North America to the east, suggesting that ancient continental lithospheric mantle is an important source component of Snake River basaltic volcanism. At precisely the

  16. Mapping fumarolic fields in volcanic areas: A methodological approach based on the case study of La Fossa cone, Vulcano island (Italy)

    Science.gov (United States)

    Madonia, Paolo; Cangemi, Marianna; Costa, Michela; Madonia, Ivan

    2016-09-01

    Changes in the activity state of a volcano can be inferred by monitoring the steam flux from fumarolic fields, in terms of 4D (x, y, z, time) variations in temperature and extension of the zone. During the last decades, several studies in this field have been conducted worldwide, and at Vulcano island (Italy) in particular. Both direct and remotely sensed measurements have been used for identifying thermally anomalous areas, but the possible role of the hydrothermal alteration of volcanic products, producing a sealing effect that obscures the surface thermal evidence of fumarolic activity, have never been explored. The novelty of the present study, carried out at La Fossa cone (Vulcano Island), was the integration of direct and remotely sensed temperature measurements with the evaluation of soil permeability, for the precise mapping of areas where shallow hydrothermal circulation could occur even in the absence of surface evidence. The main results of this study concern the role of a coating found on rock surfaces and regolith in introducing mapping errors, especially during diachronic temperature surveys based on remotely sensed measurements.

  17. Synopsis of volcanic stratigraphy

    Science.gov (United States)

    Hammond, P. E.

    1974-01-01

    Volcanic stratigraphic units are mappable layered units composed of volcanic rocks that are formed on land (subaerially) or under water (subaqueously) by volcanic processes. At least ten different types of volcanic stratigraphic units are recognized. The characteristics for each are discussed briefly and some typical examples are illustrated by diagrams to show their salient features.

  18. Olivine Major and Trace Element Compositions in Southern Payenia Basalts, Argentina

    DEFF Research Database (Denmark)

    Søager, Nina; Portnyagin, Maxim; Hoernle, Kaj;

    2015-01-01

    Olivine major and trace element compositions from 12 basalts from the southern Payenia volcanic province in Argentina have been analyzed by electron microprobe and laser ablation inductively coupled plasma mass spectrometry. The olivines have high Fe/Mn and low Ca/Fe and many fall at the end...... by subduction-zone fluids and/or melts. The increasing contributions from the pyroxene-rich source in the southern Payenia basalts are correlated with an increasing Fe-enrichment, which caused the olivines to have lower forsterite contents at a given Ni content. Al-in-olivine crystallization temperatures...

  19. Evidence for a basalt-free surface on Mercury and implications for internal heat.

    Science.gov (United States)

    Jeanloz, R; Mitchell, D L; Sprague, A L; de Pater, I

    1995-06-01

    Microwave and mid-infrared observations reveal that Mercury's surface contains less FeO + TiO2 and at least as much feldspar as the lunar highlands. The results are compatible with the high albedo (brightness) of Mercury's surface at visible wavelengths in suggesting a rock and soil composition that is devoid of basalt, the primary differentiate of terrestrial mantles. The occurrence of a basalt-free, highly differentiated crust is in accord with recent models of the planet's thermal evolution and suggests that Mercury has retained a hot interior as a result of a combination of inefficient mantle convection and minimal volcanic heat loss.

  20. SHRIMP zircon U-Pb dating for volcanic rocks of the Dasi Formation in southeast Hubei Province, middle-lower reaches of the Yangtze River and its implications

    Institute of Scientific and Technical Information of China (English)

    XIE Guiqing; MAO Jingwen; LI Ruiling; ZHOU Shaodong; YE Huishou; YAN Quanren; ZHANG Zusong

    2006-01-01

    The Jinniu Basin in southeast Hubei,located at the westernmost part of middle-lower valley of the Yangtze River, is one of the important volcanic basins in East China. Volcanic rocks in the Jinniu Basin are distributed mainly in the Majiashan Formation, the Lingxiang Formation and the Dasi Formation, consisting of rhyolite, basalt and basaltic andesite, (trachy)-basalt and basaltic trachy-andesite and (trachy)-andesite and (trachy)-dacite and rhyolite respectively, in which the Dasi volcanism is volumetrically dominant and widespread. The Dasi volcanic rocks were selected for SHRIMP zircon U-Pb dating to confirm the timing of volcanism. The results indicate that there exist a large amount of magmatic zircons characterized by high U and Th contents in the volcanic rocks. The concordia ages for 13 points are 128±1Ma (MSWD = 3.0). On account of the shape of zircons and Th/U ratios, this age is considered to represent the crystallization time of the Dasi volcanism. The volcanic rocks in the Dasi, Majiashan and Lingxiang Formations share similar trace element and REE partition patterns as well as Sr-Nd isotopic compositions. In combination with the regional geology, it is proposed that the southeast Hubei volcanic rocks were formed mainly during the Early Cretaceous, just like other volcanic basins in middle-lower Yangtze valley. A lithospheric extension is also suggested for tectonic regime in this region in the Cretaceous Period.

  1. Permian volcanisms in eastern and southeastern margins of the Jiamusi Massif, northeastern China: zircon U-Pb chronology, geochemistry and its tectonic implications

    Institute of Scientific and Technical Information of China (English)

    MENG En; XU WenLiang; YANG DeBin; PEI FuPing; Yu Yang; Zhang XingZhou

    2008-01-01

    LA-ICP-MS zircon U-Pb dating and geochemical data for the Late Paleozoic volcanic rocks from eastern and southeastern margins of the Jiamusi Massif are presented to understand the regional tectonic evolution. Zircons from eight representative volcanic rocks are euhedral-subhedral in shape and dis-play striped absorption and fine-scale oscillatory growth zoning as well as high Th/U ratios (0.33-2.37), implying a magmatic origin. The dating results show that the Late Paleozoic volcanic rocks in the study area can be divided into two stages, I.e., the Early Permian (a weighted mean 206pb/238U age of 288 Ma) and the Middle Permian volcanisms (a weighted mean 206Pb/238U age of 268 Ma). The former is com-posed mainly of basalt, basaltic-andesite, andesite and minor dacite. They are characterized by low SiO2 contents, high Mg# (0.40-0.59), enrichment in Na (Na2O/K2O = 1.26-4.25) and light rare earth elements (LREEs), relative depletion in heavy rare earth elements (HREEs) and high field strength ele-ments (HFSEs), indicating that an active continental margin setting could exist in the eastern margin of the Jiamusi Massif in the Early Permian. The latter consists mainly of rhyolite and minor dacite with high SiO2 (77.23%-77.52%), low MgO (0.11%-0.14%), enrichment in K2O (Na2O/K2O ratios <0.80) and Rb, Th, U and depletion in Eu, Sr, P and Ti, implying a crust-derived origin. Therefore, it is proposed that the Middle Permian volcanic rocks could have formed under the collision of the Jiamusi and the Khanka Massifs.

  2. El Estribo Volcanic Complex: Evolution from a shield volcano to a cinder cone, Pátzcuaro Lake, Michoacán, México

    Science.gov (United States)

    Pola, A.; Macías, J. L.; Osorio-Ocampo, S.; Sosa-Ceballos, G.; Garduño-Monroy, V. H.; Martínez-Martínez, J.

    2015-09-01

    El Estribo Volcanic Complex (EVC) is located in the northern part of the Michoacán-Guanajuato Volcanic Field within the Trans-Mexican Volcanic Belt (TMVB). El Estribo is located at the southern edge of the E-W Pátzcuaro fault that belongs to the Pátzcuaro-Jarácuaro graben, a western extension of the E-W Morelia-Acambay fault system. Stratigraphy, geochronology, chemistry, and mineral assemblages suggest that the volcanic complex was constructed in two periods separated by a ~ 100 ka volcanic hiatus: a) emission of lava flows that constructed a shield volcano between 126 ka, and b) mixed phreatomagmatic to Strombolian activity that formed a cinder cone ~ 28 ka. The magmas that fed these monogenetic volcanoes were able to use the same feeding system. The cinder cone itself was constructed by Strombolian fallouts and remobilized scoria beds, followed by an erosion period, and by a mixed phreatomagmatic to magmatic phase (Strombolian fallouts ending with lava flows). Soft-sedimentary deformation of beds and impact sags, cross-bedding, as well as pitting and hydrothermal cracks found in particles support the phreatomagmatic phase. The erupted magmas through time ejected basaltic andesitic lava flows (56.21-58.88% SiO2) that built the shield volcano and then basaltic andesitic scoria (57.65-59.05% SiO2) that constructed the cinder cone. Although they used the same feeding system, the geochemical data and the mineral chemistry of the magmas indicate that the shield volcano and the cinder cone were fed by different magma batches erupted thousands of years apart. Therefore, the location of El Estribo Volcanic Complex along an E-W fault that has generated two sector collapses of the shield volcano to the north may be directly linked to this complex redistribution of the magmatic paths to the surface. Our findings show that magmatic feeding systems within monogenetic volcanic fields could be long lived, questioning the classic view of the monogenetic nature of their

  3. Geophysical investigations of buried volcanic centers near Yucca Mountain, Southwest Nevada

    International Nuclear Information System (INIS)

    Several aeromagnetic dipolar anomalies occur over flat, alluvial areas near Yucca Mountain that resemble anomalies typically associated with subaerial basaltic volcanic centers. Detailed gravity and ground magnetic data were collected along a surveyed traverse across an aeromagnetic anomaly in Amargosa Valley, south of Yucca Mountain, Nevada. Modeling of the ground magnetic data collected over the largest of these anomalies, the Lathrop Wells aeromagnetic anomaly, indicates that the top of the causative body, most likely basalt, is less than 250 m below the surface. Gravity data indicate an apparent lack of an associated gravity anomaly and suggest that either the causative body may be tuff rather than basalt, or the volume of the body is small. Both drilling and collection of more magnetic and gravity data are necessary because ages and volumes of buried volcanic centers are important constraints for estimating the probability of potential volcanism near the proposed nuclear waste repository at Yucca Mountain

  4. Groundwater flow in a relatively old oceanic volcanic island: the Betancuria area, Fuerteventura Island, Canary Islands, Spain.

    Science.gov (United States)

    Herrera, Christian; Custodio, Emilio

    2014-10-15

    The island of Fuerteventura is the oldest of the Canary Islands' volcanic archipelago. It is constituted by volcanic submarine and subaerial activity and intrusive Miocene events, with some residual later volcanism and Quaternary volcanic deposits that have favored groundwater recharge. The climate is arid, with an average rainfall that barely attains 60 mm/year in the coast and up to 200 mm/year in the highlands. The aquifer recharge is small but significant; it is brackish due to large airborne atmospheric salinity, between 7 and 15 gm(-2)year(-1) of chloride deposition, and high evapo-concentration in the soil. The average recharge is estimated to be less than about 5 mm/year at low altitude and up to 10 mm/year in the highlands, and up to 20 mm/year associated to recent lava fields. Hydrochemical and water isotopic studies, supported by water table data and well and borehole descriptions, contribute a preliminary conceptual model of groundwater flow and water origin in the Betancuria area, the central area of the island. In general, water from springs and shallow wells tends to be naturally brackish and of recent origin. Deep saline groundwater is found and is explained as remnants of very old marine water trapped in isolated features in the very low permeability intrusive rocks. Preliminary radiocarbon dating indicates that this deep groundwater has an apparent age of less than 5000 years BP but it is the result of mixing recent water recharge with very old deep groundwater. Most of the groundwater flow occurs through the old raised volcanic shield of submarine and subaerial formations and later Miocene subaerial basalts. Groundwater transit time through the unsaturated zone is of a few decades, which allows the consideration of long-term quasi-steady state recharge. Transit times are up to a few centuries through the saturated old volcanics and up to several millennia in the intrusive formations, where isolated pockets of very old water may exist.

  5. Atmospheric chemistry in volcanic plumes.

    Science.gov (United States)

    von Glasow, Roland

    2010-04-13

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis.

  6. Petrology and Geochemistry of Jinlongdingzi Active Volcano—the Most Recent Basaltic Explosive Volcano at Longgang

    Institute of Scientific and Technical Information of China (English)

    樊祺诚; 随建立; 等

    2000-01-01

    The Jinlongdingzi active volcano erupted before 1600a,and it is the latest basaltic explosive volcano at Longgang Volcano.Its volcanic products include the Jinlongdingzi Volcanic cone(elevation 999.4m),the lava flow and the widely-spread volcanic pyroclastic sheet(sihai Pyroclastic Sheet),Jinlongdingzi volcanic rocks are trachybasalts with very similar REE patterns and incompatible element patterns,and their 87Sr/86Sr and 143Nd/144Nd ratios range from 0.704846 ot 0.704921 and from 0.512619 to 0.512646,respectively.It is revealed that the trachybasalt has the character of primary magma derived directly from mantle sources with very little evolution and crust contamination during its ascending.The younger mantle xenoliths demonstrate that the mantle source of the Jinlongdingzi Volcao is hydrous,with relatively low temperature.

  7. Radiation shielding concrete made of Basalt aggregates.

    Science.gov (United States)

    Alhajali, S; Yousef, S; Kanbour, M; Naoum, B

    2013-04-01

    In spite of the fact that Basalt is a widespread type of rock, there is very little available information on using it as aggregates for concrete radiation shielding. This paper investigates the possibility of using Basalt for the aforementioned purpose. The results have shown that Basalt could be used successfully for preparing radiation shielding concrete, but some attention should be paid to the choice of the suitable types of Basalt and for the neutron activation problem that could arise in the concrete shield.

  8. Petrogenesis of Volcanic Rocks in the Khabr-Marvast Tectonized Ophiolite: Evidence for Subduction Processes in the South-Western Margin of Central Iranian Microcontinent

    Institute of Scientific and Technical Information of China (English)

    Azam SOLTANMOHAMMADI; Mohammad RAHGOSHAY; Morteza KHALATBARI-JAFARI

    2009-01-01

    The Late Cretaceous Khabr-Marvast tectonized ophiolite is located in the middle part of the Nain-Baft ophiolite belt, at the south-western edge of the central Iranian microcontinent. Although all the volcanic rocks in the study area indicate subduction-related magmatism (e.g. high LILE (large ion lithophile elements)/ HFSE (high field strenght elements) ratios and negative anomalies in Nb and Ta), geological and geochemical data clearly distinguish two distinct groups of volcanic rocks in the tectonized association: (1) group 1 is comprised of hyaloclustic breccias, basaltic pillow iavas, and andesite sheet flows. These rocks represent the Nain-Baft oceanic crust; and (2) group 2 is alkaline iavas from the top section of the ophiolite suite. These lavas show shoshonite affinity, but do not support the propensity of ophiolite.

  9. Laboratory Studies of Ice Nucleation on Volcanic Ash

    Science.gov (United States)

    Tolbert, M. A.; Schill, G. P.; Genareau, K. D.

    2014-12-01

    Ice nucleation on volcanic ash controls both ash aggregation and cloud glaciation, which affect human respiratory health, atmospheric transport, and global climate. We have performed laboratory studies of the depositional and immersion freezing efficiency of three distinct samples of volcanic ash using Raman Microscopy coupled to an environmental cell. Ash from the Fuego (Basaltic Ash, Guatemala), Soufriere Hills (Andesetic Ash, Montserrat), and Taupo (Rhyolitic Ash, New Zealand) volcanoes were chosen to represent different geographical locations and silica content. All ash samples were quantitatively analyzed for both percent crystallinity and mineralogy using X-ray diffraction. We find that all three samples of volcanic ash are excellent depositional ice nuclei, nucleating ice at ice saturation ratios of 1.05 ± 0.1. For immersion freezing, however, only the Taupo ash exhibited efficient heterogeneous ice nucleation activity. Similar to recent studies on mineral dust, we suggest that the mineralogy of volcanic ash may dictate its ice nucleation activity in the immersion mode.

  10. SYSTHESIS OF VOLCANISM STUDIES FOR THE YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT

    International Nuclear Information System (INIS)

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The hazard of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (-7 events per year. Bounding probability estimates are used to assess possible implications of not drilling aeromagnetic anomalies in the Arnargosa Valley and Crater Flat. The results of simulation modeling are used to assess the sensitivity of the disruption probability for the location of northeast boundaries of volcanic zones near the Yucca Mountain site. A new section on modeling of radiological releases associated with surface and subsurface magmatic activity has been added to chapter 6. The modeling results are consistent with past total system performance assessments that show future volcanic and magmatic events are not significant components of repository performance and volcanism is not a priority issue for performance assessment studies

  11. The geology and petrology of Mauna Kea Volcano, Hawaii; a study of postshield volcanism

    Science.gov (United States)

    Wolfe, Edward W.; Wise, William S.; Dalrymple, G. Brent

    1997-01-01

    Mauna Kea Volcano, on the Island of Hawaii, is capped by lavas of alkalic and transitional basalt (Hamakua Volcanics) erupted between approximately 250-200 and 70-65 ka and hawaiite, mugearite, and benmoreite (Laupahoehoe Volcanics) erupted between approximately 65 and 4 ka. These lavas, which form the entire subaerial surface of the volcano, issued from numerous scattered vents and are intercalated on the upper slopes with glacial deposits. The lavas record diminishing magma-supply rate and degree of partial melting from the shield stage through the postshield stage. Much of the compositional variation apparently reflects fractionation of basaltic magma in reservoirs within and beneath the volcano.

  12. State-space approach to evaluate spatial variability of field measured soil water status along a line transect in a volcanic-vesuvian soil

    Directory of Open Access Journals (Sweden)

    A. Comegna

    2010-12-01

    Full Text Available Unsaturated hydraulic properties and their spatial variability today are analyzed in order to use properly mathematical models developed to simulate flow of the water and solute movement at the field-scale soils. Many studies have shown that observations of soil hydraulic properties should not be considered purely random, given that they possess a structure which may be described by means of stochastic processes. The techniques used for analyzing such a structure have essentially been based either on the theory of regionalized variables or to a lesser extent, on the analysis of time series. This work attempts to use the time-series approach mentioned above by means of a study of pressure head h and water content θ which characterize soil water status, in the space-time domain. The data of the analyses were recorded in the open field during a controlled drainage process, evaporation being prevented, along a 50 m transect in a volcanic Vesuvian soil. The isotropic hypothesis is empirical proved and then the autocorrelation ACF and the partial autocorrelation functions PACF were used to identify and estimate the ARMA(1,1 statistical model for the analyzed series and the AR(1 for the extracted signal. Relations with a state-space model are investigated, and a bivariate AR(1 model fitted. The simultaneous relations between θ and h are considered and estimated. The results are of value for sampling strategies and they should incite to a larger use of time and space series analysis.

  13. Volcan Reventador's Unusual Umbrella

    Science.gov (United States)

    Chakraborty, P.; Gioia, G.; Kieffer, S. W.

    2005-12-01

    In the past two decades, field observations of the deposits of volcanoes have been supplemented by systemmatic, and sometimes, opportunistic photographic documentation. Two photographs of the umbrella of the December 3, 2002 eruption of Volcan Reventador, Ecuador, reveal a prominently scalloped umbrella that is unlike any umbrella previously documented on a volcanic column. The material in the umbrella was being swept off a descending pyroclastic flow, and was, therefore, a co-ignimbrite cloud. We propose that the scallops are the result of a turbulent Rayleigh-Taylor (RT) instability with no precedents in volcanology. We ascribe the rare loss of buoyancy that drives this instability to the fact that the Reventador column fed on a cool co-ignimbrite cloud. On the basis of the observed wavelength of the scallops, we estimate a value for the eddy viscosity of the umbrella of 4000 ~m2/s. This value is consistent with a previously obtained lower bound (200 ~m2/s, K. Wohletz, priv. comm., 2005). We do not know the fate of the material in the umbrella subsequent to the photos. The analysis suggests that the umbrella was negatively buoyant. Field work on the co-ignimbrite deposits might reveal whether or not the material reimpacted, and if so, where and whether or not this material was involved in the hazardous flows that affected the main oil pipeline across Ecuador.

  14. Scenarios constructed for basaltic igneous activity at Yucca Mountain and vicinity

    International Nuclear Information System (INIS)

    Basaltic volcanism has been identified as a possible future event initiating a release of radionuclides from a potential repository at the proposed Yucca Mountain high-level waste repository site. The performance assessment method set forth in the Site Characterization Plan (DOE, 1988) requires that a set of scenarios encompassing all significant radionuclide release paths to the accessible environment be described. This report attempts to catalogue the details of the interactions between the features and processes produced by basaltic volcanism in the presence of the presumed groundwater flow system and a repository structure, the engineered barrier system (EBS), and waste. This catalogue is developed in the form of scenarios. We define a scenario as a well-posed problem, starting from an initiating event or process and proceeding through a logically connected and physically possible combination or sequence of features, events, and processes (FEPs) to the release of contaminants

  15. Water in volcanic glass: From volcanic degassing to secondary hydration

    Science.gov (United States)

    Seligman, Angela N.; Bindeman, Ilya N.; Watkins, James M.; Ross, Abigail M.

    2016-10-01

    Volcanic glass is deposited with trace amounts (0.1-0.6 wt.%) of undegassed magmatic water dissolved in the glass. After deposition, meteoric water penetrates into the glass structure mostly as molecular H2O. Due to the lower δD (‰) values of non-tropical meteoric waters and the ∼30‰ offset between volcanic glass and environmental water during hydration, secondary water imparts lighter hydrogen isotopic values during secondary hydration up to a saturation concentration of 3-4 wt.% H2O. We analyzed compositionally and globally diverse volcanic glass from 0 to 10 ka for their δD and H2Ot across different climatic zones, and thus different δD of precipitation, on a thermal conversion elemental analyzer (TCEA) furnace attached to a mass spectrometer. We find that tephrachronologically coeval rhyolite glass is hydrated faster than basaltic glass, and in the majority of glasses an increase in age and total water content leads to a decrease in δD (‰), while a few equatorial glasses have little change in δD (‰). We compute a magmatic water correction based on our non-hydrated glasses, and calculate an average 103lnαglass-water for our hydrated felsic glasses of -33‰, which is similar to the 103lnαglass-water determined by Friedman et al. (1993a) of -34‰. We also determine a smaller average 103lnαglass-water for all our mafic glasses of -23‰. We compare the δD values of water extracted from our glasses to local meteoric waters following the inclusion of a -33‰ 103lnαglass-water. We find that, following a correction for residual magmatic water based on an average δD and wt.% H2Ot of recently erupted ashes from our study, the δD value of water extracted from hydrated volcanic glass is, on average, within 4‰ of local meteoric water. To better understand the difference in hydration rates of mafic and felsic glasses, we imaged 6 tephra clasts ranging in age and chemical composition with BSE (by FEI SEM) down to a submicron resolution. Mafic tephra

  16. Thermal control of low-pressure fractionation processes. [in basaltic magma solidification

    Science.gov (United States)

    Usselman, T. M.; Hodge, D. S.

    1978-01-01

    Thermal models detailing the solidification paths for shallow basaltic magma chambers (both open and closed systems) were calculated using finite-difference techniques. The total solidification time for closed chambers are comparable to previously published calculations; however, the temperature-time paths are not. These paths are dependent on the phase relations and the crystallinity of the system, because both affect the manner in which the latent heat of crystallization is distributed. In open systems, where a chamber would be periodically replenished with additional parental liquid, calculations indicate that the possibility is strong that a steady-state temperature interval is achieved near a major phase boundary. In these cases it is straightforward to analyze fractionation models of the basaltic liquid evolution and their corresponding cumulate sequences. This steady thermal fractionating state can be invoked to explain large amounts of erupted basalts of similar composition over long time periods from the same volcanic center and some rhythmically layered basic cumulate sequences.

  17. A conflict of water and fire: Remote sensing imagery of the Uinkaret Volcanic Field, Grand Canyon, Arizona

    Science.gov (United States)

    Ramsey, Michael S.

    1995-01-01

    The sedimentary geology of the western Grand Canyon consists of gently northeast dipping sandstones, shales, and carbonates. However, due to facies changes within the units, the geomorphology varies from that seen by visitors at the National Park Headquarters. There, the cliff and slope expression of the rocks is replaced in the west by a series of mesas, ridges, and horizontal platforms. The largest of these occurs on the Esplanade Sandstone within the Supai Formation. The Esplanade is formed by slope retreat of the overlying units and resistance to erosion by the underlying limestones. It is onto this platform that the lavas of the Uinkaret Plateau were emplaced. The Uinkaret lava field lies 120 km south of St. George, Utah and is tectonically defined by two major normal faults -- the Hurricane to the west and the Toroweap to the east. The purpose of this investigation was to collect visible, near and thermal infrared data at different periods of the day and year. It is expected that these data will provide the ability to retrieve water temperatures; monitor sediment loads; map and examine any changes in the near shore vegetation communities and understand some of the intricacies of the geology. This paper will serve, to some degree, as a progress report on the Grand Canyon study, since only a fraction of the data has been received and processed thus far. Data from the Thermal Infrared Multispectral Scanner (TIMS) and the Landsat Thematic Mapper simulator (NS001) were acquired simultaneously on April 4, 1994. A second data acquisition occurred on August 27, 1994. Initial analysis of the TIMS data indicates a remarkably noise-free data set with minimal atmospheric attenuation. environments is evident.

  18. Volcanism and soil mercury on Mars - Consequences for terrestrial microorganisms

    Science.gov (United States)

    Siegel, B. Z.; Siegel, S. M.

    1978-01-01

    An earth-Mars depletion formula proposed by Anders and Owen for volatiles is used to calculate a range of putative Hg levels for Martian volcanic soils based upon analyzed samples from Hawaii. The range is about 50-150 microgram per kg. When applied either in conventional or special media (e.g., basalt powder), these levels of Hg are effective inhibitors of the growth of earth microorganisms. Taken together with other hostile chemical and physical factors, volcanic toxicants would appear to provide a further deterrent to the accidental establishment of terrestrial microbiota on Mars.

  19. Spectroscopic mapping of the white horse alunite deposit, Marysvale volcanic field, Utah: Evidence of a magmatic component

    Science.gov (United States)

    Rockwell, B.W.; Cunningham, C.G.; Breit, G.N.; Rye, R.O.

    2006-01-01

    Previous studies have demonstrated that the replacement alunite deposits just north of the town of Marysvale, Utah, USA, were formed primarily by low-temperature (100??-170?? C), steam-heated processes near the early Miocene paleoground surface, immediately above convecting hydrothermal plumes. Pyrite-bearing propylitically altered rocks occur mainly beneath the steam-heated alunite and represent the sulfidized feeder zone of the H2S-dominated hydrothermal fluids, the oxidation of which at higher levels led to the formation of the alunite. Maps of surface mineralogy at the White Horse deposit generated from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data were used in conjunction with X-ray diffraction studies of field samples to test the accuracy and precision of AVIRIS-based mineral mapping of altered rocks and demonstrate the utility of spectroscopic mapping for ore deposit characterization. The mineral maps identified multiple core zones of alunite that grade laterally outward to kaolinite. Surrounding the core zones are dominantly propylitically altered rocks containing illite, montmorillonite, and chlorite, with minor pyrite, kaolinite, gypsum, and remnant potassium feldspar from the parent rhyodacitic ash-flow tuff. The AVIRIS mapping also identified fracture zones expressed by ridge-forming selvages of quartz + dickite + kaolinite that form a crude ring around the advanced argillic core zones. Laboratory analyses identified the aluminum phosphate-sulfate (APS) minerals woodhouseite and svanbergite in one sample from these dickite-bearing argillic selvages. Reflectance spectroscopy determined that the outer edges of the selvages contain more dickite than do the medial regions. The quartz + dickite ?? kaolinite ?? APS-mineral selvages demonstrate that fracture control of replacement processes is more prevalent away from the advanced argillic core zones. Although not exposed at the White Horse deposit, pyrophyllite ?? ordered illite was identified

  20. Mantle potential temperature estimates of basalt from the surface of Venus

    Science.gov (United States)

    Shellnutt, J. Gregory

    2016-10-01

    The crater density and distribution of Venus indicates the average surface age is younger (≤1 Ga) than most terrestrial planets and satellites in the Solar System. The type and rate (i.e. equilibrium, catastrophic or differential) of volcanism associated with the stagnant lid tectonic system of Venus is a first order problem that has yet to be resolved but is directly related to the thermal conditions of the mantle. The calculated primary melt composition of basalt at the Venera 14 landing site is high-Mg basalt to picrite with a mantle potential temperature estimate similar to terrestrial ambient mantle (1370 ± 70 °C). The calculated accumulated fractional melting curves indicate the olivine compositions from the melt have Mg# of 89-91. The results show that the thermal regime required to generate the primary melt composition of the Venera 14 basalt was not anomalously high (i.e. mantle-plume system) but rather consistent with a lithospheric tensional rift system. The juxtaposition of high thermal regime structures (e.g. Beta Regio) and 'ambient' mantle potential temperature estimates of the Venera 14 basalt suggests that the relatively young surface of Venus is the result of volcanism from a combination of thermal systems that resurfaced the planet at variable rates.

  1. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    Science.gov (United States)

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

    2009-01-01

    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain

  2. Devonian Nb-enriched basalts and andesites of north-central Tibet: Evidence for the early subduction of the Paleo-Tethyan oceanic crust beneath the North Qiangtang Block

    Science.gov (United States)

    Zhang, Hongrui; Yang, Tiannan; Hou, Zengqian; Bian, Yeke

    2016-07-01

    The early evolution of the Tethyan Ocean in north-central Tibet is currently poorly constrained. A sequence of volcanic rocks ranging from basic to intermediate in composition has been identified in the Zaduo area of the North Qiangtang Block. SHRIMP U-Pb dating of zircons from a sample of Zaduo andesite suggests an eruption age of Late Devonian (~ 380 Ma). The Zaduo volcanic rocks exhibit geochemical characteristics similar to those of typical Nb-enriched basalts, with relatively high Nb, Ta, and Zr contents, resulting in high Nb/La ratios (0.70-1.08) and Nb/U ratios (10.57-34.37). The relative enrichment in high field strength elements, together with positive εNd(t) values of + 4.6 to + 5.8 and low (87Sr/86Sr)i ratios of 0.70367-0.70532, indicates the Zaduo volcanic rocks were derived from a depleted mantle source metasomatized by silicate melts of a subducted oceanic slab. The occurrence of Nb-enriched volcanic rocks in the North Qiangtang Block suggests that the subduction of Paleo-Tethyan oceanic crust was initiated in the Late Devonian. Available geochronological data from ophiolites surrounding the North Qiangtang Block suggest that the subducted slab is most likely the Longmucuo-Shuanghu Paleo-Tethyan oceanic crust.

  3. Palaeoenvironment reconstruction, volcanic evolution and geochronology of the Cerro Blanco subcomplex, Nevados de Chillan volcanic complex, Central Chile

    OpenAIRE

    Mee, Katy; Gilbert, Jennie S.; McGarvie, David W.; Naranjo, Jose A.; Pringle, Malcolm S.

    2009-01-01

    Nevados de Chillán Volcanic Complex, central Chile, has been active for at least 640 ka—a period spanning a number of glacial and interglacial periods. Geologic mapping, radiometric dating and geochemical analysis have identified six new volcanic units and produced four new 40Ar/39Ar ages for Cerro Blanco, the northern subcomplex of Nevados de Chillán volcano. Compositions range from dacite to basaltic-andesite and a new geologic map is presented. Examination of lava fracture structures on bo...

  4. Hydrogeology of the Azores volcanic archipelago (Portugal)

    Science.gov (United States)

    Cruz, J.; Coutinho, R.; Antunes, P.; Freire, P.

    2009-04-01

    the volcanic edifices slopes. The basal aquifer system is in the coastal area, presenting generally a very low hydraulic gradient. Hydrogeological surveys that have been made in the Azores archipelago points out to more than 1000 springs and wells spread all over the archipelago (950 springs and 83 drilled wells). Spring distribution is heterogeneous, with densities varying between 0.01 springs/km2 at Pico island and 0.72 springs/km2 estimated at Santa Maria. Specific capacity ranges from 1.4x10-2 to 266.7 L/sm, with a median value of 32.3 L/sm. Transmissivity also present a large range, with values ranging between 1.65x10-5 and 4.03x10-1 m2/s, and a median of 3.66x10-2 m2/s. The heterogeneous distribution shown by these values expresses the influence of the hydrogeological characteristics of volcanic terrain, resulting from syngenetic characteristics and secondary processes, like weathering. The highest values are observed in wells drilled in recent basaltic lava flows, which generally are thin and fractured, with frequent clincker levels interbedded, and the lowest data was estimated in the older volcanic formations of Santa Maria island. Groundwater on perched-water bodies, excluding the numerous mineral waters that are spread in several islands of the archipelago, present usually a low mineralization, shown by the electrical conductivity values (36-725 S/cm; median=158.0 S/cm). The average temperature is equal to 15°C. Waters have an average temperature of 15°C and are mainly slightly acid to slightly alkaline, with a pH range from 4.7 to 8.6, but showing a median value of 7.2. The main water types are Na-Cl to Na-HCO3 waters, with numerous samples lying in the intermediate compositional fields that characterize Na-Cl-HCO3 and Na-HCO3-Cl waters. The groundwater composition in the basal aquifer system is usually from the Na-Cl type and presents a higher mineralization, resulting in a median value for electrical conductivity equal to 1044 S/cm, expressing the

  5. Paleoproterozoic felsic volcanism of Iricoumé group, Erepecuru-Trombetas domain, Amazonian central province: Field and petrographic characterization and Pb-Pb zircon geochronology

    Directory of Open Access Journals (Sweden)

    Lúcia Travassos da Rosa Costa

    2013-03-01

    Full Text Available The Iricoumé group consists of very well preserved pyroclastic and effusive volcanic rocks as a part of an extensive volcano-plutonic event, which marked the central part of the Amazonian craton during the Orosirian. Such rocks occur in the southern part of the southwestern of Erepecuru-Trombetas Domain (NW of the Pará state, south of the Guyana Shield. Petrographic study allows distinction of two volcanic types. A dominant explosive volcanism is characterized by pyroclastic rocks (ignimbrites, rheoignimbrites, lapilli-tuff related to surge deposit, and co-ignimbrite fall tuff while a subordinated effusive volcanism is represented by coherent lavas flows and hypabissal rocks (andesites, lamprophyres and latites. Most of the pyroclastic rocks exhibit features of deposition under high temperature suggesting formation in a caldera-related environment. Pb-Pb zircon ages of 1888 +-2.5 and 1889 +-2 Ma have been obtained for the formation of trachydacitic ignimbrites and confirm that the dominant volcanism is part of the Iricoumé group. The Pb-Pb zircon age of 1992 +-3 Ma yielded by an andesite points to the occurrence in the area of an older Orosirian magmatic episode, which has been previously recognized locally southward in the Tapajós domain. These new results constitute a further evidence of the wide extent of the Iricoum group and correlated volcanic rocks in the central part of the Amazonian craton, and reinforce the assumption that this volcanic episode and correlated magmatism may be considered as a silicic large igneous province (SLIP, as previously proposed by some authors.

  6. Xenolitos ultramáficos en el cerro De la Laguna, volcanismo basáltico de retroarco en el sureste de la provincia de Mendoza, Argentina Ultramafic xenoliths in De la Laguna hill, retro-arc basaltic volcanism in the southeast of Mendoza Province, Argentina

    Directory of Open Access Journals (Sweden)

    G. W. Bertotto

    2002-12-01

    Full Text Available Se describen por primera vez xenolitos ultramáficos incluidos en basaltos de retroarco cenozoicos, en el sector extraandino de la provincia de Mendoza. El basalto portador tiene estructura masiva y textura porfírica con asociaciones de fenocristales de olivino-clinopiroxeno y olivino-plagioclasa. Todos los xenolitos ultramáficos son peridotitas en facies de espinela, se reconocieron lherzolitas, wehrlitas y dunitas, en orden de abundancia. Presentan una asociación mineral compuesta por olivino, ortopiroxeno, clinopiroxeno y espinela. Las texturas identificadas son porfiroclástica de Tipo I y porfiroclástica a equigranular de Tipo I. Estos xenolitos tienen zonas de reacción microscópicas mayormente desarrolladas en los ortopiroxenos y clinopiroxenos en el contacto con el basalto. La presencia de reacción indica al menos un evento de desequilibrio. Estas peridotitas representan fragmentos del manto superior situado debajo de la zona estudiada.Ultramafic xenoliths in Cenozoic retro-arc basalts of the extra-Andean sector of Mendoza province are described here for the first time. The host basalt has a massive structure and porphyritic texture with phenocryst assemblages of olivine-clinopyroxene and olivine-plagioclase. All the ultramafic xenoliths are spinel-bearing peridotites; lherzolite, wehrlite and dunite, in order of abundance, have been recognized. The mineral assemblage is olivine-orthopyroxene-clinopyroxene-spinel. Textures are porphyroclastic Type I and porphyroclastic to equigranular Type I. The xenoliths contain microscopic reaction areas, mainly developed in orthopyroxene and clinopyroxene in the contact with basalt. The reaction indicates at least one disequilibrium event. The peridotites are fragments of the upper mantle situated beneath the study area.

  7. Chlorine as a geobarometer tool: Application to the explosive eruptions of the Volcanic Campanian District (Mount Somma-Vesuvius, Phlegrean Fields, Ischia)

    Science.gov (United States)

    Balcone-Boissard, Hélène; Boudon, Georges; Zdanowicz, Géraldine; Orsi, Giovanni; Civett