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Sample records for monogenetic volcanic fields

  1. Volcanic hazard assessment in monogenetic volcanic fields

    OpenAIRE

    Bartolini, Stefania

    2014-01-01

    [eng] 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 volcanic crisis. The impact of a natural event, as a volcanic eruption, can s...

  2. Morphometric characterization of monogenetic volcanic cones of the Chichinautzin and Michoacán-Guanajuato monogenetic volcanic fields in Mexico

    Science.gov (United States)

    Zarazua-Carbajal, Maria Cristina; De la Cruz-Reyna, Servando; Mendoza-Rosas, Ana Teresa

    2014-05-01

    Morphometric characterization of volcanic edifices is one of the main approaches providing information about a volcano eruptive history, whether it has one or more eruptive vents or if it had any sector collapses. It also provides essential information about the physical processes that modify their shapes during periods of quietness, and quite significantly, about the volcanoes' ages. In the case of monogenetic activity, a volcanic field can be characterized by the size and slope distributions, and other cone's morphometric parameter distributions that may provide valuable information about the temporal evolution of the volcanic field. The increasingly available high-resolution digital elevation models and the continuously developing computer tools have allowed a faster development and more detailed morphometric characterization techniques. We present here a methodology to readily obtain diverse volcanic cone shape parameters from the contour curves such as mean slope, slope distribution, dimensions of the cone and crater, crater location within the cone, orientation of the cone's principal axis, eccentricity, and other morphological features using an analysis algorithm that we developed, programmed in Python and ArcPy. Preliminary results from the implementation of this methodology to the Chichinautzin and Michoacán-Guanajuato monogenetic volcanic fields in Mexico have permitted a preliminary estimation of the age distribution of some of the cones with an acceptable correlation with the available radiometric ages. A large part of the Chichinautzin region DEM was obtained from a LIDAR survey by the Mexican National Institute of Statistics and Geography (INEGI).

  3. Basaltic ignimbrites in monogenetic volcanism: the example of La Garrotxa volcanic field

    Science.gov (United States)

    Martí, J.; Planagumà, L. l.; Geyer, A.; Aguirre-Díaz, G.; Pedrazzi, D.; Bolós, X.

    2017-05-01

    Ignimbrites are pyroclastic density current deposits common in explosive volcanism involving intermediate and silicic magmas and in less abundance in eruptions of basaltic central and shield volcanoes. However, they are not widely described in association with monogenetic volcanism, where typical products include lava flows, scoria and lapilli fall deposits, as well as various kinds of pyroclastic density current deposits and explosion breccias. In La Garrotxa basaltic monogenetic volcanic field, part of the Neogene-Quaternary European rift system located in the northeast of the Iberian Peninsula, we have identified a particular group of pyroclastic density current deposits that show similar textural characteristics to silicic ignimbrites, indicating an overlap in transport and depositional processes. These deposits can be clearly distinguished from other pyroclastic density current deposits generated during phreatomagmatic phases that typically correspond to thinly laminated units with planar-to-cross-bedded stratification. The monogenetic ignimbrite deposits correspond to a few meters to several tens of meters thick units rich in lithic- and lapilli scoria fragments, with an abundant ash matrix, and internally massive structure, emplaced along valleys and gullies, with run-out distances up to 6 km and individual volumes ranging from 106 to 1.5 × 107 m3. The presence of flattened scoria and columnar jointing in some of these deposits suggests relatively high emplacement temperatures, coinciding with available paleomagnetic data that suggests an emplacement temperature around 450-500 °C. In this work, we describe the main characteristics of these pyroclastic deposits that were generated by a number of phreatomagmatic episodes. Comparison with similar deposits from silicic eruptions and previous examples of ignimbrites associated with basaltic volcanism allows us to classify them as `basaltic ignimbrites'. The recognition in monogenetic volcanism of such

  4. 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.

  5. 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

  6. Cluster Analysis of vents in monogenetic volcanic fields, Lunar Crater Volcanic Field (Nevada)

    Science.gov (United States)

    Tadini, A.; Cortes, J. A.; Valentine, G. A.; Johnson, P. J.; Tibaldi, A.; Bonali, F. L.

    2012-12-01

    Monogenetic volcanic fields pose a serious risk to human activities and settlements due to their high occurrence around the world and because of the type of eruptive activity that they exhibit. The need of adequate tools to better undertake volcanic hazard assessment for volcanic fields, especially from a spatial point of view, is of key importance at the time of mitigate such hazard. Among these tools, a better understanding of the spatial distribution of cones and vents and any structural/tectonical relationship are essential to understand the plumbing system of the field and thus help to predict the likelihood location of future eruptions. In this study we have developed a spatial methodology, which is the combination of various methodologies developed for volcanic textures and other clustering goals [1,2], to study the clustering of volcanic vents and their relation with structural features from satellite images. The methodology first involves the statistical identification and removal of spatial outliers using a predictive elliptical area [2] and the generation of randomly distributed points in the same predictive area. A comparison of the Near Neighbor Distance (NND) between the generated data and the data measured in a volcanic field is used to determine whether the vents are clustered or not. If the vents are clustered, a combination of hierarchical clustering and K-means [3] is then used to identify the clusters and their related vents. Results are then further constrained with the study of lineaments and other structural features that can be affected and related with the clusters. The methodology was tested in the Lunar Crater Volcanic Field, Nevada (USA) and successfully has helped to identify tectonically controlled lineaments from those that are resultant of geomorphological processes such the drainage control imposed by the cone clusters. Theoretical approaches has been developed before to constrain the plumbing of a volcanic field [4], however these

  7. 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.

  8. 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

  9. 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 (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, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the

  10. Monogenetic volcanism: personal views and discussion

    Science.gov (United States)

    Németh, K.; Kereszturi, G.

    2015-11-01

    Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures. They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar-diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes. The common interplay between internal, such as the physical-chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes. In spite of this volcanic facies complexity, we defend the term "monogenetic volcano" and highlight the term's value, especially to express volcano morphotypes. This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km3) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches. This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism.

  11. 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

  12. GIS methods applied to the degradation of monogenetic volcanic fields: A case study of the Holocene volcanism of Gran Canaria (Canary Islands, Spain)

    Science.gov (United States)

    Rodriguez-Gonzalez, A.; Fernandez-Turiel, J. L.; Perez-Torrado, F. J.; Aulinas, M.; Carracedo, J. C.; Gimeno, D.; Guillou, H.; Paris, R.

    2011-11-01

    Modeling of volcanic morphometry provides reliable measurements of parameters that assist in the determination of volcanic landform degradation. Variations of the original morphology enable the understanding of patterns affecting erosion and their development, facilitating the assessment of associated hazards. A total of 24 volcanic Holocene eruptions were identified in the island of Gran Canaria (Canary Islands, Spain). 87% of these eruptions occurred in a wet environment while the rest happened in a dry environment. 45% of Holocene eruptions are located along short barrancos (S-type, less than 10 km in length), 20% along large barrancos (L-type, 10-17 km in length) and 35% along extra-large barrancos (XL-type, more than 17 km in length). The erosional history of Holocene volcanic edifices is in the first stage of degradation, with a geomorphic signature characterized by a fresh, young cone with a sharp profile and a pristine lava flow. After intensive field work, a careful palaeo-geomorphological reconstruction of the 24 Holocene eruptions of Gran Canaria was conducted in order to obtain the Digital Terrain Models (DTMs) of the pre- and post-eruption terrains. From the difference between these DTMs, the degradation volume and the incision rate were obtained. The denudation of volcanic cones and lava flows is relatively independent both their geographical location and the climatic environment. However, local factors, such as pre-eruption topography and ravine type, have the greatest influence on the erosion of Holocene volcanic materials in Gran Canaria. Although age is a key factor to help understand the morphological evolution of monogenetic volcanic fields, the Gran Canaria Holocene volcanism presented in this paper demonstrates that local and regional factors may determine the lack of correlation between morphometric parameters and age. Consequently, the degree of transformation of the volcanic edifices evolves, in many cases, independently of their age.

  13. Crystallisation condition of the Quaternary basanites of volcanic centre Black Rock, monogenetic field Lunar Crater

    Science.gov (United States)

    Turova, Mariia; Plechov, Pavel; Scherbakov, Vasily; Larin, Nikolay

    2017-04-01

    The Lunar Crater volcanic field is located in a tension zone Basin and Range Province (USA). This tension is connected with dives oceanic plate under the continental plate [1]. Lunar Crater consists of flows basalt, basanite, trachybasalt has a different age [2]. In this work we investigate the youngest rock - basanite. The basanite is highly crystalline consisting of about megacrysts (3-10 cm) 30-60 wt% phenocrysts ( 800-1500 µm) and microphenocrysts (100-800 µm) and 40-60% microlites (stress and style of tectonism of the Basin and Range province of the western United States //Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences. - 1981. - T. 300. - №. 1454. - C. 407-434. 2. Wood, X., and Keinle, Y., 1990, Volcanoes of North America: Cambridge,United Kingdom, Cambridge University Press, 354 p. 3. Nimis P. Clinopyroxene geobarometry of magmatic rocks. Part 2. Structural geobarometers for basic to acid, tholeiitic and mildly alkaline magmatic systems //Contributions to Mineralogy and Petrology. - 1999. - T. 135. - №. 1. - C. 62-74. 4. Ballhaus C., Berry R. F., Green D. H. High pressure experimental calibration of the olivine-orthopyroxene-spinel oxygen geobarometer: implications for the oxidation state of the upper mantle //Contributions to Mineralogy and Petrology. - 1991. - T. 107. - №. 1. - C. 27-40.

  14. 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

    the need to arrange and coordinate geoeducational projects locally and globally around common geological assets such as monogenetic volcanic fields. We also provide a conceptual model to link various sites of monogenetic volcanic fields along a volcanologically valid holistic geoconservation and geoeducation programs that are scientifically well-established. Well-preserved maar craters such as Harrat Hutaymah (A) and erosionally enlarged maars such as Tabah (B) are internationally significant geotopes of volcanic geoheritage sites of Saudi Arabia

  15. Origin of temporal compositional trends in monogenetic vent eruptions: Insights from the crystal cargo in the Papoose Canyon sequence, Big Pine Volcanic Field, CA

    Science.gov (United States)

    Gao, Ruohan; Lassiter, John C.; Ramirez, Gabrielle

    2017-01-01

    Many monogenetic vents display systematic temporal-compositional variations over the course of eruption. Previous studies have proposed that these trends may reflect variable degrees of crustal assimilation, or melting and mixing of heterogeneous mantle source(s). Discrimination between these two endmember hypotheses is critical for understanding the plumbing systems of monogenetic volcanoes, which pose a significant volcanic hazard in many areas. In this study, we examine the Papoose Canyon (PC) monogenetic vent in the Big Pine Volcanic Field (BPVF), which had been well characterized for temporal-compositional variations in erupted basalts. We present new major and trace element and Sr-Nd-Pb-O isotopic data from the PC "crystal cargo" (phenocrysts and xenoliths). Comparison of "crystal cargo" and host basalt provides new constraints on the history of magma storage, fractionation, and crustal contamination that are obscured in the bulk basalts due to pre- and syn-eruptive magma mixing processes. The abundances of phenocrysts and ultramafic xenoliths in the PC sequence decrease up-section. Olivine and clinopyroxene phenocrysts span a wide range of Mg# (77-89). The majority of phenocrysts are more evolved than olivine or clinopyroxene in equilibrium with their host basalts (Mg# = 68- 71, equilibrium Fo ≈ 85- 89). In addition, the ultramafic xenoliths display cumulate textures. Olivine and clinopyroxene from ultramafic xenoliths have Mg# (73-87) similar to the phenocrysts, and lower than typical mantle peridotites. Sr-Nd-Pb isotope compositions of the xenoliths are similar to early PC basalts. Finally, many clinopyroxene phenocrysts and clinopyroxene in xenoliths have trace element abundances in equilibrium with melts that are more enriched than the erupted basalts. These features suggest that the phenocrysts and xenoliths derive from melt that is more fractionated and enriched than erupted PC basalts. Pressure constraints suggest phenocrysts and ultramafic

  16. Geology and geochemistry of Pelagatos, Cerro del Agua, and Dos Cerros monogenetic volcanoes in the Sierra Chichinautzin Volcanic Field, south of México City

    Science.gov (United States)

    Agustín-Flores, Javier; Siebe, Claus; Guilbaud, Marie-Noëlle

    2011-04-01

    This study focuses on the geology and geochemistry of three closely-spaced monogenetic volcanoes that are located in the NE sector of the Sierra Chichinautzin Volcanic Field near México City. Pelagatos (3020 m.a.s.l.) is a small scoria cone (0.0017 km 3) with lava flows (0.036 km 3) that covered an area of 4.9 km 2. Cerro del Agua scoria cone (3480 m.a.s.l., 0.028 km 3) produced several lava flows (0.24 km 3) covering an area of 17.6 km 2. Dos Cerros is a lava shield which covers an area of 80.3 km 2 and is crowned by two scoria cones: Tezpomayo (3080 m.a.s.l., 0.022 km 3) and La Ninfa (3000 m.a.s.l., 0.032 km 3). The eruptions of Cerro del Agua and Pelagatos occurred between 2500 and 14,000 yr BP. The Dos Cerros eruption took place close to 14,000 yr BP as constrained by radiocarbon dating. Rocks from these three volcanoes are olivine-hypersthene normative basaltic andesites and andesites with porphyritic, aphanitic, and glomeroporphyritic textures. Their mineral assemblages include olivine, clinopyroxene, and orthopyroxene phenocrysts (≤ 10 vol.%) embedded in a trachytic groundmass which consists mainly of plagioclase microlites and glass. Pelagatos rocks also present quartz xenocrysts. Due to their high Cr and Ni contents, and high Mg#s, Pelagatos rocks are considered to be derived from primitive magmas, hence the importance of this volcano for understanding petrogenetic processes in this region. Major and trace element abundances and petrography of products from these volcanoes indicate a certain degree of crystal fractionation during ascent to the surface. However, the magmas that formed the volcanoes evolved independently from each other and are not cogenetically related. REE, HFSE, LILE, and isotopic (Sr, Nd, and Pb) compositions point towards a heterogeneous mantle source that has been metasomatized by aqueous/melt phases from the subducted Cocos slab. There is no clear evidence of important crustal contributions in the compositions of Pelagatos and

  17. Studying monogenetic volcanoes with Terrestrial Laser Scanner: Case study at Croscat volcano (Garrotxa Volcanic Zone, Spain)

    Science.gov (United States)

    Geyer Traver, A.; Garcia-Selles, D.; Peddrazzi, D.; Barde-Cabusson, S.; Marti, J.; Muñoz, J.

    2013-12-01

    Monogenetic basaltic zones are common in many volcanic environments and may develop under very different geodynamic conditions. Despite existing clear similarities between the eruptive activity of different monogenetic volcanic fields, important distinctions may arise when investigating in detail the individual eruptive sequences. Interpretation of the deposits and consequently, the reconstruction and characterization of these eruptive sequences is crucial to evaluate the potential hazard in case of active areas. In diverse occasions, erosional processes (natural and/or anthropogenic) may partly destroy these relatively small-sized volcanic edifices exposing their internal parts. Furthermore, despite human activity in volcanic areas is sometimes unimportant due to the remote location of the monogenetic cones, there are places where this form of erosion is significant, e.g. Croscat volcano (Catalan Volcanic Field, Spain). In any case, when studying monogenetic volcanism, it is usual to find outcrops where the internal structure of the edifices is, for one or other reason, well exposed. However, the access to these outcrops may be extremely difficult or even impossible. During the last years, it has been demonstrated that the study of outcrops with problematic or completely restricted access can be carried out by means of digital representations of the outcrop surface. Digital outcrops make possible the study of those areas with natural access limitations or safety issues and may facilitate visualization of the features of interest over the entire outcrop, as long as the digital outcrop can be analysed while navigated in real- time, with optional displays for perspective, scale distortions, and attribute filtering. In particular, Terrestrial Laser Scanning (TSL) instruments using Light Detection And Ranging technology (LIDAR) are capable of capturing topographic details and achieve modelling accuracy within a few centimetres. The data obtained enables the creation of

  18. Geochemical characterization of a Quaternary monogenetic volcano in Erciyes Volcanic Complex: Cora Maar (Central Anatolian Volcanic Province, Turkey)

    Science.gov (United States)

    Gencalioglu-Kuscu, Gonca

    2011-11-01

    Central Anatolian Volcanic Province (CAVP) is a fine example of Neogene-Quaternary post-collisional volcanism in the Alpine-Mediterranean region. Volcanism in the Alpine-Mediterranean region comprises tholeiitic, transitional, calc-alkaline, and shoshonitic types with an "orogenic" fingerprint. Following the orogenic volcanism, subordinate, within-plate alkali basalts ( sl) showing little or no orogenic signature are generally reported in the region. CAVP is mainly characterized by widespread calc-alkaline andesitic-dacitic volcanism with orogenic trace element signature, reflecting enrichment of their source regions by subduction-related fluids. Cora Maar (CM) located within the Erciyes pull-apart basin, is an example to numerous Quaternary monogenetic volcanoes of the CAVP, generally considered to be alkaline. Major and trace element geochemical and geochronological data for the CM are presented in comparison with other CAVP monogenetic volcanoes. CM scoria is basaltic andesitic, transitional-calc-alkaline in nature, and characterized by negative Nb-Ta, Ba, P and Ti anomalies in mantle-normalized patterns. Unlike the "alkaline" basalts of the Mediterranean region, other late-stage basalts from the CAVP monogenetic volcanoes are classified as tholeiitic, transitional and mildly alkaline. They display the same negative anomalies and incompatible element ratios as CM samples. In this respect, CM is comparable to other CAVP monogenetic basalts ( sl), but different from the Meditterranean intraplate alkali basalts. Several lines of evidence suggest derivation of CM and other CAVP monogenetic basalts from shallow depths within the lithospheric mantle, that is from a garnet-free source. In a wider regional context, CAVP basalts ( sl) are comparable to Apuseni (Romania) and Big Pine (Western Great Basin, USA) volcanics, except the former have depleted Ba contents. This is a common feature for the CAVP volcanics and might be related to crustal contamination or source

  19. Creating global comparative analyses of tectonic rifts, monogenetic volcanism and inverted relief

    Science.gov (United States)

    van Wyk de Vries, Benjamin

    2016-04-01

    I have been all around the world, and to other planets and have travelled from the present to the Archaean and back to seek out the most significant tectonic rifts, monogenetic volcanoes and examples of inverted relief. I have done this to provide a broad foundation of the comparative analysis for the Chaîne des Puys - Limagne fault nomination to UNESCO world Heritage. This would have been an impossible task, if not for the cooperation of the scientific community and for Google Earth, Google Maps and academic search engines. In preparing global comparisons of geological features, these quite recently developed tools provide a powerful way to find and describe geological features. The ability to do scientific crowd sourcing, rapidly discussing with colleagues about features, allows large numbers of areas to be checked and the open GIS tools (such as Google Earth) allow a standardised description. Search engines also allow the literature on areas to be checked and compared. I will present a comparative study of rifts of the world, monogenetic volcanic field and inverted relief, integrated to analyse the full geological system represented by the Chaîne des Puys - Limagne fault. The analysis confirms that the site is an exceptional example of the first steps of continental drift in a mountain rift setting, and that this is necessarily seen through the combined landscape of tectonic, volcanic and geomorphic features. The analysis goes further to deepen the understanding of geological systems and stresses the need for more study on geological heritage using such a global and broad systems approach.

  20. 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

  1. The use of digital outcrops to study monogenetic volcanoes: Case study at Croscat volcano (Garrotxa Volcanic Zone, Spain)

    Science.gov (United States)

    Geyer, Adelina; García-Sellés, David; Pedrazzi, Dario; Barde-Cabusson, Stéphanie; Martí, Joan; Muñoz, Josep Anton

    2014-05-01

    During the last years, it has been demonstrated that the study of outcrops with difficult or completely restricted access can be carried out by means of digital representations of the outcrop surface. Furthermore, the study of digital outcrops may facilitate visualization of the features of interest over the entire outcrop, as long as the digital outcrop can be analysed while navigating in real-time, with optional displays for perspective, scale distortions, and attribute filtering. In particular, Terrestrial Laser Scanning (TSL) instruments using Light Detection And Ranging technology (LIDAR) are capable of capturing topographic details and achieve modelling accuracy within a few centimetres. The data obtained permits the creation of detailed 3-D terrain models of larger coverage and accuracy than conventional methods and with almost complete safety of the operators. Here we show digital outcrops may be useful to perform the description of the internal structure of exposed volcanic edifices. A further advantageous application is the estimate of erosion rates and patterns that may be helpful in terms of hazard assessment or preservation of volcanic landscapes. We use as an example of application the Croscat volcano, a monogenetic edifice of the La Garrotxa volcanic field (Spain), which quarrying jobs have exposed the internal part of the volcano leading to a perfect view of its interior but making difficult the access to the upper parts. The Croscat volcano is additionally one of the most emblematic symbols of the La Garrotxa Volcanic Zone Natural Park being its preservation a main target of the park administration.

  2. Petrogenesis and metal budget of Pelagatos volcano in the Chichinautzin monogenetic field, Mexico: A Melt Inclusion Study

    Science.gov (United States)

    Roberge, J.; Mercer, C. N.; Kent, A. J.; Guilbaud, M.

    2013-12-01

    Melt inclusions are now widely used to quantify pre-eruptive volatile contents and to track the compositional evolution of magma. In recent years, the use of melt inclusions has also increased markedly for research in economic geology. Melt inclusions are becoming a powerful tool to track metal contents in ore-forming magmatic reservoirs and metals like Ag, Cu, Li, Mo, Sn, Pb, W, Zn are now commonly included in trace element analyses. Investigating metal reservoirs in currently active volcanic systems provides insight into the conditions that favor mineralization in ore-forming deposits compared to barren systems. In this work, we present volatiles (H2O, CO2, S, Cl) and major and trace element contents of olivine-hosted melt inclusion from 4 samples spanning the entire eruption of Pelagatos scoria cone. Pelagatos is a small and young (less than 14 000 years B.P.) monogenetic volcano within the Sierra Chichinautzin volcanic field located in the central portion of the Trans Mexican Volcanic Belt (south-east of Mexico City). The melt inclusions are basaltic andesite to andesite in composition, with 1.84 - 6.02 wt% MgO, 51.95 - 59.21 wt% SiO2 and 0.64 - 1.55 wt% K2O. The H2O varies from 0.5 to 4.3 wt% whereas CO2 varies from below detection up to 976 ppm. Sulfur contents vary from 35 to 1451 ppm, showing a decrease with increasing MgO content suggesting that S is being lost with progressive differentiation, but since S concentrations do not correlate with any other gas phase (H2O, CO2, Cl) we hypothesize that it partitioned into an immiscible fluid or mineral phase. On the other hand, Cl contents are broadly constant (900 to 1267 ppm), and shows no correlation with MgO or K2O. All analyzed metals (Ag, Cu, Li, Mo, Sn, Pb, W, Zn ) behave incompatibly showing a positive correlation with La. Cu (18 to 82 ppm), Pb (2 to 8 ppm) Zn (30 to 107 ppm) and Mo correlate positively together indicating that fractional crystallization concentrates these elements. These results provide

  3. Modern analogues for Miocene to Pleistocene alkali basaltic phreatomagmatic fields in the Pannonian Basin: "soft-substrate" to "combined" aquifer controlled phreatomagmatism in intraplate volcanic fields Research Article

    Science.gov (United States)

    Németh, Károly; Cronin, Shane; Haller, Miguel; Brenna, Marco; Csillag, Gabor

    2010-09-01

    The Pannonian Basin (Central Europe) hosts numerous alkali basaltic volcanic fields in an area similar to 200 000 km2. These volcanic fields were formed in an approximate time span of 8 million years producing smallvolume volcanoes typically considered to be monogenetic. Polycyclic monogenetic volcanic complexes are also common in each field however. The original morphology of volcanic landforms, especially phreatomagmatic volcanoes, is commonly modified. by erosion, commonly aided by tectonic uplift. The phreatomagmatic volcanoes eroded to the level of their sub-surface architecture expose crater to conduit filling as well as diatreme facies of pyroclastic rock assemblages. Uncertainties due to the strong erosion influenced by tectonic uplifts, fast and broad climatic changes, vegetation cover variations, and rapidly changing fluvio-lacustrine events in the past 8 million years in the Pannonian Basin have created a need to reconstruct and visualise the paleoenvironment into which the monogenetic volcanoes erupted. Here phreatomagmatic volcanic fields of the Miocene to Pleistocene western Hungarian alkali basaltic province have been selected and compared with modern phreatomagmatic fields. It has been concluded that the Auckland Volcanic Field (AVF) in New Zealand could be viewed as a prime modern analogue for the western Hungarian phreatomagmatic fields by sharing similarities in their pyroclastic successions textures such as pyroclast morphology, type, juvenile particle ratio to accidental lithics. Beside the AVF two other, morphologically more modified volcanic fields (Pali Aike, Argentina and Jeju, Korea) show similar features to the western Hungarian examples, highlighting issues such as preservation potential of pyroclastic successions of phreatomagmatic volcanoes.

  4. Eruption processes and deposit characteristics at the monogenetic Mt. Gambier Volcanic Complex, SE Australia: implications for alternating magmatic and phreatomagmatic activity

    Science.gov (United States)

    van Otterloo, Jozua; Cas, Raymond A. F.; Sheard, Malcolm J.

    2013-08-01

    The ˜5 ka Mt. Gambier Volcanic Complex in the Newer Volcanics Province, Australia is an extremely complex monogenetic, volcanic system that preserves at least 14 eruption points aligned along a fissure system. The complex stratigraphy can be subdivided into six main facies that record alternations between magmatic and phreatomagmatic eruption styles in a random manner. The facies are (1) coherent to vesicular fragmental alkali basalt (effusive/Hawaiian spatter and lava flows); (2) massive scoriaceous fine lapilli with coarse ash (Strombolian fallout); (3) bedded scoriaceous fine lapilli tuff (violent Strombolian fallout); (4) thin-medium bedded, undulating very fine lapilli in coarse ash (dry phreatomagmatic surge-modified fallout); (5) palagonite-altered, cross-bedded, medium lapilli to fine ash (wet phreatomagmatic base surges); and (6) massive, palagonite-altered, very poorly sorted tuff breccia and lapilli tuff (phreato-Vulcanian pyroclastic flows). Since most deposits are lithified, to quantify the grain size distributions (GSDs), image analysis was performed. The facies are distinct based on their GSDs and the fine ash to coarse+fine ash ratios. These provide insights into the fragmentation intensities and water-magma interaction efficiencies for each facies. The eruption chronology indicates a random spatial and temporal sequence of occurrence of eruption styles, except for a "magmatic horizon" of effusive activity occurring at both ends of the volcanic complex simultaneously. The eruption foci are located along NW-SE trending lineaments, indicating that the complex was fed by multiple dykes following the subsurface structures related to the Tartwaup Fault System. Possible factors causing vent migration along these dykes and changes in eruption styles include differences in magma ascent rates, viscosity, crystallinity, degassing and magma discharge rate, as well as hydrological parameters.

  5. Crystal Zoning Constrains on the Processes and Time Scales Involved in Monogenetic Mafic Volcanism (Tenerife, Canary Islands)

    Science.gov (United States)

    Albert, H.; Costa Rodriguez, F.; Marti, J.

    2014-12-01

    Most of the historical eruptive activity in Tenerife has been relatively mafic and mildly-explosive monogenetic eruptions, and thus it seems that this activity is the most likely in the near future. Here we investigate the processes and time scales that lead to such eruptions with the aim to better interpret and plan for any possible unrest in the island. We focus on three historical eruptions: Siete Fuentes (December 31 1704-January 1705), Fasnia (January 5-January 13 1705) and Arafo (February 2-February 26 1705) issued from a 10 km long basaltic fissure eruption oriented N45E and covering an area of 10.4 km2. The erupted volume increases by 5-fold from the first to the last eruption. All magmas are tephritic, although the bulk-rock becomes more mafic with time due to accumulation of olivine with Cr-spinel inclusions, and clinopyroxene rather than to the appearance of a truly more primitive melt. Olivine core compositions of the three eruptions range between Fo79 and Fo87. Frequency histograms show three main populations: at Fo79-80, Fo80-82 and Fo84-87 displaying normal and reverse zoning. Thermodynamic calculations show that only cores with Fo80-82 are in equilibrium with the whole rock. Clinopyroxene phenocrysts can have large pools of matrix glass and show rims of different composition. Only the rims, with Mg#84-86, are in equilibrium with the whole-rock. Considering olivine cores and clinopyroxene rims in equilibrium we obtained a temperature range of 1150-1165°C, and MELTS calculations suggest pressures of 1 to 5 kbar. The variety of olivine core populations reflects mixing and mingling between three different magmas, and their proportions have changed with time from Siete Fuentes to Arafo. Most crystals have complex zoning profiles that record two events: (1) one of magma mixing/mingling at depth, (2) another of magma transport and ascent to the surface. Magma mixing at depth ranges from about 3 months to two years and is similar for the three eruptions

  6. The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: tectonically anomalous forearc volcanism in an urban setting

    Science.gov (United States)

    Evarts, Russell C.; Conrey, Richard M.; Fleck, Robert J.; Hagstrum, Jonathan T.; O'Connor, Jim; Dorsey, Rebecca; Madin, Ian P.

    2009-01-01

    More than 80 small volcanoes are scattered throughout the Portland-Vancouver metropolitan area of northwestern Oregon and southwestern Washington. These volcanoes constitute the Boring Volcanic Field, which is centered in the Neogene Portland Basin and merges to the east with coeval volcanic centers of the High Cascade volcanic arc. Although the character of volcanic activity is typical of many monogenetic volcanic fields, its tectonic setting is not, being located in the forearc of the Cascadia subduction system well trenchward of the volcanic-arc axis. The history and petrology of this anomalous volcanic field have been elucidated by a comprehensive program of geologic mapping, geochemistry, 40Ar/39Ar geochronology, and paleomag-netic studies. Volcanism began at 2.6 Ma with eruption of low-K tholeiite and related lavas in the southern part of the Portland Basin. At 1.6 Ma, following a hiatus of ~0.8 m.y., similar lavas erupted a few kilometers to the north, after which volcanism became widely dispersed, compositionally variable, and more or less continuous, with an average recurrence interval of 15,000 yr. The youngest centers, 50–130 ka, are found in the northern part of the field. Boring centers are generally monogenetic and mafic but a few larger edifices, ranging from basalt to low-SiO2 andesite, were also constructed. Low-K to high-K calc-alkaline compositions similar to those of the nearby volcanic arc dominate the field, but many centers erupted magmas that exhibit little influence of fluids derived from the subducting slab. The timing and compositional characteristics of Boring volcanism suggest a genetic relationship with late Neogene intra-arc rifting.

  7. The Chaîne des Puys and Limagne Fault World Heritage project: a global partnership for raising the profile of monogenetic volcanism and rifting

    Science.gov (United States)

    Olive-Garcia, C.

    2013-12-01

    The present Chaîne des Puys and Limagne Fault World Heritage project represents a global partnership for raising the profile of monogenetic volcanism and rifting. From the 19th Century the Chaîne des Puys and Limagne Fault have been at the centre of discussion about the nature of volcanoes, and the origin of rifts. Part of this interest was due to the action of landowners and government agents such as Montlosier and Desmarest (who first realised that the chain were volcanoes), and national leaders such as Napoleon I, who was instrumental in the visit of Humphrey Davey and Michael Farady in 1805. The chain features largely in Scrope's 'Considerations on v olcanoes' 1825, and of Bonney's 'Volcanoes their structure and significance' of 1899. The fault escarpment is discussed at length by Lyell in Principles of Geology (1830), although they did not recognise it yet as a rift. The area has seen the development of a modern scientific-government-private partnership in geoscience research and education that has developed in parallel with the growth of a earth science centre of excellence, now the Laboratoire Magmas et Volcans. In addition, local owners and users have taken an important part in the development of this partnership to help create a sustainable management of the area. Partnerships have been developed with other sites around the world to share best practice, especially in managing inhabited natural sites. For over 30 years the area has been part of the evolving Auvergne Region Natural Volcano Park, for five years the central Puy de Dôme is a 'Grande site de France', equivalent to a national monument. Educational attractions grew up first as private - scientific partnerships (e.g. Lemptégy, Volvic, Maison de la Pierre) and then with greater public input like Vulcania and the Puy de Dome. The channelling of visitors has been accomplished by improved access by bus, and a new cog-railway up the Puy de Dôme. I present an overview of the UNESCO project, and show

  8. Explosive Volcanic Activity at Extreme Depths: Evidence from the Charles Darwin Volcanic Field, Cape Verdes

    Science.gov (United States)

    Kwasnitschka, T.; Devey, C. W.; Hansteen, T. H.; Freundt, A.; Kutterolf, S.

    2013-12-01

    Volcanic eruptions on the deep sea floor have traditionally been assumed to be non-explosive as the high-pressure environment should greatly inhibit steam-driven explosions. Nevertheless, occasional evidence both from (generally slow-) spreading axes and intraplate seamounts has hinted at explosive activity at large water depths. Here we present evidence from a submarine field of volcanic cones and pit craters called Charles Darwin Volcanic Field located at about 3600 m depth on the lower southwestern slope of the Cape Verdean Island of Santo Antão. We examined two of these submarine volcanic edifices (Tambor and Kolá), each featuring a pit crater of 1 km diameter, using photogrammetric reconstructions derived from ROV-based imaging followed by 3D quantification using a novel remote sensing workflow, aided by sampling. The measured and calculated parameters of physical volcanology derived from the 3D model allow us, for the first time, to make quantitative statements about volcanic processes on the deep seafloor similar to those generated from land-based field observations. Tambor cone, which is 2500 m wide and 250 m high, consists of dense, probably monogenetic medium to coarse-grained volcaniclastic and pyroclastic rocks that are highly fragmented, probably as a result of thermal and viscous granulation upon contact with seawater during several consecutive cycles of activity. Tangential joints in the outcrops indicate subsidence of the crater floor after primary emplacement. Kolá crater, which is 1000 m wide and 160 m deep, appears to have been excavated in the surrounding seafloor and shows stepwise sagging features interpreted as ring fractures on the inner flanks. Lithologically, it is made up of a complicated succession of highly fragmented deposits, including spheroidal juvenile lapilli, likely formed by spray granulation. It resembles a maar-type deposit found on land. The eruption apparently entrained blocks of MORB-type gabbroic country rocks with

  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. Volcanism-sedimentation interaction in the Campo de Calatrava Volcanic Field (Spain): a magnetostratigraphic and geochronological study

    Science.gov (United States)

    Herrero-Hernández, Antonio; López-Moro, Francisco Javier; Gallardo-Millán, José Luis; Martín-Serrano, Ángel; Gómez-Fernández, Fernando

    2015-01-01

    This work focuses on the influence of Cenozoic volcanism of the Campo de Calatrava volcanic field on the sedimentation of two small continental basins in Spain (Argamasilla and Calzada-Moral basins). The volcanism in this area was mainly monogenetic, according to the small-volume volcanic edifices of scoria cones that were generated and the occurrence of tuff rings and maars. A sedimentological analysis of the volcaniclastic deposits led to the identification of facies close to the vents, low-density (dilute) pyroclastic surges, secondary volcanic deposits and typical maar deposits. Whole-rock K/Ar dating, together with palaeomagnetic constraints, yielded an age of 3.11-3.22 Ma for the onset of maar formation, the deposition finished in the Late Gauss-Early Matuyana. Using both techniques and previous paleontological data allowed it to be inferred that the maar formation and the re-sedimentation stage that occurred in Argamasilla and Calzada-Moral basins were roughly coeval. The occurrence of syn-eruption volcaniclastic deposits with small thicknesses that were separated by longer inter-eruption periods, where fluvial and lacustrine sedimentation was prevalent, together with the presence of small-volume volcanic edifices indicated that there were short periods of volcanic activity in this area. The volcanic activity was strongly controlled by previous basement faults that favoured magma feeding, and the faults also controlled the location of volcanoes themselves. The occurrence of the volcanoes in the continental basins led to the creation of shallow lakes that were related to the maar formation and the modification of sedimentological intra-basinal features, specifically, valley slope and sediment load.

  11. 40Ar/39Ar dating, geochemistry, and isotopic analyses of the quaternary Chichinautzin volcanic field, south of Mexico City: implications for timing, eruption rate, and distribution of volcanism

    Science.gov (United States)

    Arce, J. L.; Layer, P. W.; Lassiter, J. C.; Benowitz, J. A.; Macías, J. L.; Ramírez-Espinosa, J.

    2013-12-01

    Monogenetic structures located at the southern and western ends of the Chichinautzin volcanic field (Trans-Mexican Volcanic Belt, Central Mexico) yield 40Ar/39Ar ages ranging from 1.2 Ma in the western portion of the field to 1.0-0.09 Ma in the southern portion, all of which are older than the volcanic field. These new ages indicate: (1) an eruption rate of 0.47 km3/kyr, which is much lower than the 11.7 km3/kyr previously estimated; (2) that the Chichinautzin magmatism coexisted with the Zempoala (0.7 Ma) and La Corona (1.0 Ma) polygenetic volcanoes on the southern edge of Las Cruces Volcanic Range (Trans-Mexican Volcanic Belt); and confirm (3) that the drainage system between the Mexico and Cuernavaca basins was closed during early Pleistocene forming the Texcoco Lake. Whole-rock chemistry and Sr, Nd, and Pb isotopic data indicate heterogeneous magmatism throughout the history of Chichinautzin activity that likely reflects variable degrees of slab and sediment contributions to the mantle wedge, fractional crystallization, and crustal assimilation. Even with the revised duration of volcanism within the Chichinautzin Volcanic Field, its eruption rate is higher than most other volcanic fields of the Trans-Mexican Volcanic Belt and is comparable only to the Tacámbaro-Puruaran area in the Michoacán-Guanajuato Volcanic Field to the west. These variations in eruption rates among different volcanic fields may reflect a combination of variable subduction rates of the Rivera and Cocos plates along the Middle America Trench, as well as different distances from the trench, variations in the depth with respect to the subducted slab, or the upper plate characteristics.

  12. Magmatic Evolution in the Los Tuxtlas Volcanic Field, Veracruz, Mexico

    Science.gov (United States)

    Koster, A.; Kobs-Nawotniak, S. E.

    2012-12-01

    Magma evolution within the Los Tuxtlas Volcanic Field (LTVF) is poorly understood. The LTVF is a basaltic, monogenetic field in Veracruz, Mexico, that contains approximately 400 vents and has been active for the last 7 Ma, including a sub-Plinian eruption in 1793. The field is structurally controlled, with cones forming NW-SE lines consistent with local extension. By understanding magmatic evolution through ascent, storage, and mixing, it is possible to more accurately predict future trends in the system. Samples from two alignments of cinder cones located between San Martin Tuxtlas volcano and Laguna Catemaco were analyzed petrographically and geochemically. Geochemical data were plotted in Fenner and Harker diagrams to identify trends, including fractional crystallization and magma recharge. Mineral modes were calculated via point counting in thin sections, and micro-textural variations were noted. Cone morphometry was used as a rough proxy for age along with field relationships to develop an approximate order of events along the alignments. Preliminary data suggest that the aligned vents are part of a linked magmatic plumbing system undergoing periodic recharge.

  13. 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.

  14. 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.

  15. Controls on volcanism at intraplate basaltic volcanic fields

    Science.gov (United States)

    van den Hove, Jackson C.; Van Otterloo, Jozua; Betts, Peter G.; Ailleres, Laurent; Cas, Ray A. F.

    2017-02-01

    A broad range of controlling mechanisms is described for intraplate basaltic volcanic fields (IBVFs) in the literature. These correspond with those relating to shallow tectonic processes and to deep mantle plumes. Accurate measurement of the physical parameters of intraplate volcanism is fundamental to gain an understanding of the controlling factors that influence the scale and location of a specific IBVF. Detailed volume and geochronology data are required for this; however, these are not available for many IBVFs. In this study the primary controls on magma genesis and transportation are established for the Pliocene-Recent Newer Volcanics Province (NVP) of south-eastern Australia as a case-study for one of such IBVF. The NVP is a large and spatio-temporally complex IBVF that has been described as either being related to a deep mantle plume, or upper mantle and crustal processes. We use innovative high resolution aeromagnetic and 3D modelling analysis, constrained by well-log data, to calculate its dimensions, volume and long-term eruptive flux. Our estimates suggest volcanic deposits cover an area of 23,100 ± 530 km2 and have a preserved dense rock equivalent of erupted volcanics of least 680 km3, and may have been as large as 900 km3. The long-term mean eruptive flux of the NVP is estimated between 0.15 and 0.20 km3/ka, which is relatively high compared with other IBVFs. Our comparison with other IBVFs shows eruptive fluxes vary up to two orders of magnitude within individual fields. Most examples where a range of eruptive flux is available for an IBVF show a correlation between eruptive flux and the rate of local tectonic processes, suggesting tectonic control. Limited age dating of the NVP has been used to suggest there were pulses in its eruptive flux, which are not resolvable using current data. These changes in eruptive flux are not directly relatable to the rate of any interpreted tectonic driver such as edge-driven convection. However, the NVP and other

  16. Spatial analysis of the Los Tuxtlas Volcanic Field (LTVF) and hazard implications

    Science.gov (United States)

    Sieron, K.; Alvarez, D.

    2013-05-01

    The Tuxtlas volcanic field (LTVF) is located in the southern part of Veracruz state (Mexico) adjacent to the Gulf of Mexico and consists of 4 large volcanic edifices, 3 of them considered inactive and the active San Martin shield volcano. The monogenetic volcanoes belonging to the younger series are represented by hundreds of scoria cones and tens of maars and tuff cones, all of which show ages less than 50,000 years. In comparison to other monogenetic fields, the scoria cone density is quite elevated with 0.2 cones/km2, although the highest scoria cone density can be observed along narrow zones corresponding to the main NW-SE fault system where it reaches 0.7 cones/km2. Scoria cones occur as single edifices and in clusters and show individual edifice volumes of 0.0009 km3 to 0.2 km3, cone heights varying between 21.39 m and 299.21 m. Lava flows associated to scoria cones originate especially along the main NW-SE trending main fault and present run out distances up to 11 kilometers. Only few radiocarbon and Ar-Ar dates exist for the LTVF, mostly because of the high cone density and dense vegetation of the Los Tuxtlas region. Therefore, morphological parameters were used to estimate relative ages. In consequence, the scoria cones can be subdivided into four age groups; the members of each group do not seem to follow any particular trend and are rather scattered throughout the field. The explosive (or wet) equivalents of the mainly basaltic strombolian scoria cones are explosion craters, such as maars and tuff cones, show the highest concentration along the border of the two main geological units to the S of the area with the highest scoria cone concentration. Although the relatively small scale strombolian eruptions associated to scoria cone emplacement do not represent a considerable hazard for the surrounding population, lava flows can easily extent to the main urban zones accommodating about 262,384 inhabitants. Within the area prone to maar formation, the hazard

  17. 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.

  18. Physical Volcanology and Hazard Analysis of a Young Volcanic Field: Black Rock Desert, Utah, USA

    Science.gov (United States)

    Hintz, A. R.

    2009-05-01

    The Black Rock Desert volcanic field, located in west-central Utah, consists of ~30 small-volume monogenetic volcanoes with compositions ranging from small rhyolite domes to large basaltic lava flow fields. The field has exhibited bimodal volcanism for > 9 Ma with the most recent eruption of Ice Springs volcano ˜ 600 yrs ago. Together this eruptive history along with ongoing geothermal activity attests to the usefulness of a hazard assessment. The likelihood of a future eruption in this area has been calculated to be ˜ 8% over the next 1 Ka (95% confidence). However, many aspects of this field such as the explosivity and nature of many of these eruptions are not well known. The physical volcanology of the Tabernacle Hill volcano, suggests a complicated episodic eruption that may have lasted up to 50 yrs. The initial phreatomagmatic eruptions at Tabernacle Hill are reported to have begun ~14 Ka. This initial eruptive phase produced a tuff cone approximately 150 m high and 1.5 km in diameter with distinct bedding layers. Recent mapping and sampling of Tabernacle Hill's lava field, tuff cone and intra-crater deposits were aimed at better constraining the eruptive history, physical volcanology, and explosive energy associated with this eruption. Blocks ejected during the eruption were mapped and analyzed to yield minimum muzzle velocities of 60 - 70 meters per second. These velocities were used in conjunction with an estimated shallow depth of explosion to calculate an energy yield of ˜ 0.5 kT.

  19. 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

  20. 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

  1. Paleosecular variation of directions from lava flows of the Xalapa Volcanic Field, Veracruz, Mexico

    Science.gov (United States)

    Alva-Valdivia, Luis; Gonzalez-Rangel, Antonio; Caballero-Miranda, Cecilia; Rodriguez, Sergio; Morales, Wendy

    2010-05-01

    We collected 21 monogenetic type lava flows (316 specimens) in the Xalapa Volcanic Field, eastern part of the Mexican Volcanic Belt. Geochronological results of twelve Ar-Ar determinations range from late Pleistocene to Holocene. The ages fall into three groups, those older than 2.0 Ma, those between 0.25-0.40 Ma and those less than approximately 0.1 Ma. All the samples were demagnetized by thermal and AF treatment, showing mostly a single stable component of magnetization with unblocking temperature above 530°C and/or 40-60 mT. We calculate the mean direction (D= 359.70°, I=27.4°, k=24, 95=7.7°) and the VGP to compare and integrate with previous paleosecular variation analyses. The paleosecular variation parameter, upper and lower limit are: SF=14.6, SU=17.5 and SL=11.2, respectively. So, the VGP dispersion is consistent with the expected value of latitude-dependent variation of McFadden for the last 5My.

  2. 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.

  3. Field-trip guide to a volcanic transect of the Pacific Northwest

    Science.gov (United States)

    Geist, Dennis; Wolff, John; Harpp, Karen

    2017-08-01

    The Pacific Northwest region of the United States provides world-class and historically important examples of a wide variety of volcanic features. This guide is designed to give a broad overview of the region’s diverse volcanism rather than focusing on the results of detailed studies; the reader should consult the reference list for more detailed information on each of the sites, and we have done our best to recognize previous field trip leaders who have written the pioneering guides. This trip derives from one offered as a component of the joint University of Idaho- Washington State University volcanology class taught from 1995 through 2014, and it borrows in theme from the classic field guide of Johnston and Donnelly-Nolan (1981). For readers interested in using this field guide as an educational tool, we have included an appendix with supplemental references to resources that provide useful background information on relevant topics, as well as a few suggestions for field-based exercises that could be useful when bringing students to these locations in the future. The 4-day trip begins with an examination of lava flow structures of the Columbia River Basalt, enormous lava fields that were emplaced during one of the largest eruptive episodes in Earth’s recent history. On the second day, the trip turns to the High Lava Plains, a bimodal volcanic province that transgressed from southeast to northwest from the Miocene through the Holocene, at the northern margin of the Basin and Range Province. This volcanic field provides excellent examples of welded ignimbrite, silicic lavas and domes, monogenetic basaltic lava fields, and hydrovolcanic features. The third day is devoted to a circumnavigation of Crater Lake, the result of one of the world’s best-documented caldera-forming eruptions. The caldera walls also expose the anatomy of Mount Mazama, a stratovolcano of the Cascade Range. The last day is spent at Newberry Volcano, a back-arc shield volcano topped by a

  4. 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.

  5. 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

  6. Sr, Nd and Pb isotope and geochemical data from the Quaternary Nevado de Toluca volcano, a source of recent adakitic magmatism, and the Tenango Volcanic Field, Mexico

    Science.gov (United States)

    Martínez-Serrano, Raymundo G.; Schaaf, Peter; Solís-Pichardo, Gabriela; Hernández-Bernal, Ma. del Sol; Hernández-Treviño, Teodoro; Julio Morales-Contreras, Juan; Macías, José Luis

    2004-11-01

    Volcanic activity at Nevado de Toluca (NT) volcano began 2.6 Ma ago with the emission of andesitic lavas, but over the past 40 ka, eruptions have produced mainly lava flows and pyroclastic deposits of predominantly orthopyroxene-hornblende dacitic composition. In the nearby Tenango Volcanic Field (TVF) pyroclastic products and lava flows ranging in composition from basaltic andesite to andesite were erupted at most of 40 monogenetic volcanic centers and were coeval with the last stages of NT. All volcanic rocks in the study area are characterized by a calc-alkaline affinity that is consistent with a subduction setting. Relatively high concentrations of Sr (>460 ppm) coupled with low Y (45 km) that underlies the volcanoes of the study area, the geochemical and isotopic patterns of these rocks indicate low interaction with this crust. NT volcano was constructed at the intersection of three fault systems, and it seems that the Plio-Quaternary E-W system played an important role in the ascent and storage of magmas during the recent volcanic activity in the two regions. Chemical and textural features of orthopyroxene, amphibole and Fe-Ti oxides from NT suggest that crystallization of magmas occurred at polybaric conditions, confirming the rapid upwelling of magmas.

  7. The Pali Aike Volcanic Field, Patagonia: slab-window magmatism near the tip of South America

    Science.gov (United States)

    D'Orazio, Massimo; Agostini, Samuele; Mazzarini, Francesco; Innocenti, Fabrizio; Manetti, Piero; Haller, Miguel J.; Lahsen, Alfredo

    2000-06-01

    The Pali Aike Volcanic Field (PAVF) represents the southernmost occurrence of the Cenozoic back-arc Patagonian Plateau Lavas. Its activity (Pliocene-Recent) started forming tabular lavas followed by the growth of about 470 essentially monogenetic volcanic centers (tuff-rings, maars, spatter and scoria cones). Azimuths of cone alignment, cone elongation and morphologic lineations show prevailing ENE-WSW and NW-SE trends. Erupted products consist mainly of alkaline basalt and basanite, with minor olivine basalt. PAVF rocks are quite primitive in composition (average Mg#=66, Ni=220 ppm and Cr=313 ppm) with relatively high TiO 2 (average 3.0 wt.%). Ultramafic garnet- and/or spinel-bearing xenoliths are found within PAVF volcanics. Chondrite-normalized REE patterns are significantly LREE-enriched and almost rectilinear [(La/Yb) N=10.9-21.0]. Primordial mantle-normalized distributions of incompatible trace elements, as well as Sr and Nd isotope ratios ( 87Sr/ 86Sr=0.70317-0.70339, 143Nd/ 144Nd=0.51290-0.51294), show values typical of intra-plate basalts, despite the fact that these rocks occur only 200 km east of the Andean Cordillera. Primary magmas were generated from a fertile garnet-bearing asthenospheric source at P=1.9-2.9 GPa and T=1420-1470°C. The data suggest a geodynamic model that implies sub-slab asthenosphere flow through a slab window, which started opening below this sector of South America 14 m.y. ago as a consequence of the collision of the Chile Ridge with the Chile Trench. The trailing edge of the Nazca Plate crossed below the Pali Aike area at 9-10 Ma, that is 6-5 m.y. before the onset of the volcanic activity. We hypothesize that this time delay resulted from changes in the kinematics of the South America-Scotia transform plate boundary which only allowed the Pali Aike magmas to rise after about 4 m.y.

  8. 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

  9. The Zuni-Bandera Volcanic Field, NM: An Analog for Exploring Planetary Volcanic Terrains

    Science.gov (United States)

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

    2010-12-01

    The Zuni-Bandera volcanic field, near Grants, New Mexico, is comprised of volcanic deposits from several basaltic eruptions during the last million years. This vent field exhibits a diverse group of coalesced lava flows and displays well-preserved volcanic features including a’a and pahoehoe flows, collapsed lava tubes, cinder cones and low shields. The McCartys flow is a 48-km long inflated basalt flow and is the youngest in the field at around 3000 years old. Over the last three years we have used the Zuni-Bandera volcanic field, and the McCartys flow in particular, as a terrestrial analog for exploring planetary volcanic fields, and understanding the role of lava sheet inflation in flow field development. We have conducted three different styles of analog tests, 1) basic field science focused on understanding lava sheet inflation, 2) mission operations tests related to EVA design and real-time modification of traverse plans, and 3) science enabling technology tests. The Zuni-Bandera field is an ideal location for each style of analog test because it provides easy access to a diverse set of volcanic features with variable quality of preservation. However, many limitations must also be considered in order to maximize lessons learned. The McCartys flow displays well-preserved inflation plateaus that rise up to 15 m above the surrounding field. The preservation state enables textures and morphologies indicative of this process to be characterized. However, the pristine nature of the flow does not compare well with the much older and heavily modified inflated flows of Mars and the Moon. Older flows west of McCartys add value to this aspect of analog work because of their degraded surfaces, development of soil horizons, loose float, and limited exposure of outcrops, similar to what might be observed on the Moon or Mars. EVA design tests and science enabling technology tests at the Zuni-Bandera field provide the opportunity to document and interpret the relationships

  10. Linking magma composition with volcano size and eruptive style in basaltic monogenetic systems

    Science.gov (United States)

    Smith, I. E.; McGee, L. E.; Cronin, S. J.

    2012-12-01

    Magma composition, volcano size and eruptive style (together with vent locations) are the definitive parameters of basaltic monogenetic systems. These variables are not independent, but the relationships between them are complex. Monogenetic volcano fields that episodically erupt small-volume, discrete magma batches such as the Auckland Volcanic Field (AVF, northern New Zealand), typically represent primary mantle melts variably modified by near source processes. In such cases, where the volume of magma is small, eruption styles are strongly controlled by the interaction of magma with the surficial environment and this is determined by both magma volume and its rise rate. The magmatic compositional extremes of primitive magmas in the AVF define a spectrum ranging from strongly silica-undersaturated nephelinite to sub-alkalic basalt. Nephelinites are low SiO2 (~40 wt.%), highly incompatible-element enriched compositions, representing very low degrees of partial melting (indicates that all of these magmas are sourced within the same general mantle region at depths of 80-70 km. The two compositional extremes also define extremes in volume of magma and ultimately magma flux at the surface. The surficial environment of the AVF is characterized by highly water saturated sediments of variable competency and many pressurized aquifer systems. Where there is a combination of small volumes and low flux rates, environmental factors dominate and phreatomagmatic explosive eruptions ensue, forming tuff cones, rings and maars. Larger volumes and flux rates result in dry eruptions forming cinder cones and lava fields. Thus at a fundamental level defining magma source characteristics and temporal or spatial variation in these (such as cyclic or evolutionary trends) can inform better long term forecasts of surface eruption processes and thus should be more closely examined in hazard studies of monogentic fields.

  11. 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

  12. 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.

  13. Tectonic and magmatic controls on the location of post-subduction monogenetic volcanoes in Baja California, Mexico, revealed through spatial analysis of eruptive vents

    Science.gov (United States)

    Germa, Aurélie; Connor, Laura J.; Cañon-Tapia, Edgardo; Le Corvec, Nicolas

    2013-12-01

    Post-subduction (12.5 Ma to less than 1 Ma) monogenetic volcanism on the Baja California peninsula, Mexico, formed one of the densest intra-continental areas of eruptive vents on Earth. It includes about 900 vents within an area ˜700 km long (N-S) and 70 to 150 km wide (W-E). This study shows that post-subduction volcanic activity was distributed along this arc and that modes exist in the volcano distribution, indicating that productivity of the magma source region was not uniform along the length of the arc. Vent clustering, vent alignments, and cone elongations were measured within eight monogenetic volcanic fields located along the peninsula. Results indicate that on a regional scale, vent clustering varies from north to south with denser spatial clustering in the north on the order of 1.9 × 10-1 vents/km2 to less dense clustering in the south on the order of 7.8 × 10-2 vents/km2. San Quintin, San Carlos, Jaraguay, and Santa Clara are spatially distinct volcanic fields with higher eruptive vent densities suggesting the existence of individual melt columns that may have persisted over time. In contrast, the San Borja, Vizcaino, San Ignacio, and La Purisima vent fields show lower degrees of vent clustering and no obvious spatial gaps between fields, thus indicating an area of more distributed volcanism. Insight into the lithospheric stress field can be gained from vent alignments and vent elongation measurements. Within the fields located along the extinct, subduction-related volcanic arc, elongation patterns of cinder cones and fissure-fed spatter cones, vent clusters, and vent alignments trend NW-SE and N-S. Within the Santa Clara field, located more to the west within the forearc, elongation patterns of the same volcanic features trend NE-SW. These patterns suggest that magmatism was more focused in the forearc and in the northern part of Baja California than in its southern region. Within the extinct arc, magma ascent created volcano alignments and elongate

  14. Lithofacies, eruptive phases and processes of Udo monogenetic multiple volcano near Jeju Island, South Sea, Korea

    Institute of Scientific and Technical Information of China (English)

    HWANG Sang-koo

    2004-01-01

    A monogenetic multiple volcano was emergent on Udo island, 3 km offthe sea shore of the eastern promontory of Jeju Island, South Sea,Korea. All of the preserved volcanic successions occur in a regular pattern of sequences,representing an excellent example of an eruptive cycle. The island represents volcanic stratigraphy that comprises a horseshoe-shaped tuff cone, a nested cinder cone on the crater floor of the tuff cone,and basalt lavas which extend northwest from the moat between tuff and cinder cones. The volcanic stratigraphy suggests eruptive styles that start with emergent Surtseyan eruption, progressing through Strombolian eruption and end with lava effusion.

  15. The anatomy of a cinder cone: preliminary paleomagnetic, rock magnetic, structural, and petrologic data from the La Cienega volcano, Cerros del Rio volcanic field, northern New Mexico

    Science.gov (United States)

    Petronis, M. S.; Foucher, M.; Lineline, J.; Van Wyk de Vries, B.

    2011-12-01

    The Cerros del Rio volcanic field is one of several middle Pliocene to Pleistocene basaltic volcanic fields of the axial Rio Grande Rift in central and northern New Mexico. It is a monogenetic volcanic field that comprises about 60 cinder-spatter cones, occupies ~ 700 km2, and ranges in age from 2.7 Ma to 1.1 Ma. Eruptive centers are typically central vent volcanoes, ranging from low-relief shields to steep-sided, breached cinder and spatter cone remnants. They represent short eruptive events that likely were derived from rapidly evolving reservoir-conduit systems. Mining activity has exposed the volcanic plumbing system of the Cienega Mine cinder cone, just west of Santa Fe, NM. Here, geologists from France and USA have been investigating the exposed roots of this eviscerated Pliocene volcano to investigate magma conduit geometry, magma flow structures, and eruption patterns. We are testing models for magma transport and volcano construction using a variety of field and laboratory tools. Common models of volcanic construction envision the magma feeder as a dike or pipe-like conduit transporting molten rock from a deep reservoir to the eruptive vent. We posit that small volcanic pluming systems are inherently more complex and actually involve numerous feeder geometries throughout the volcano lifespan. Our preliminary work suggests that the simple exteriors of some cinder cones hide a long life and complex history, both of which would change the appreciation of the related volcanic hazards in active systems. The Cienega Mine cinder cone consists of several meter- to decimeter-wide intrusions that connect to eruptive centers. These intrusions show a continuity of brittle to ductile structures from their margins to interiors. We have collected samples across each intrusion as well as along strike for anisotropy of magnetic susceptibility (AMS) and petrographic analysis in order to establish magma flow patterns. AMS results yield a remarkably consistent dataset that

  16. Radar Imaging of Volcanic Fields and Sand Dune Fields: Implications for VOIR

    OpenAIRE

    Elachi, C.; Blom, R; Daily, M.; Farr, T; Saunders, R. S.

    1980-01-01

    A number of volcanic fields and sand dune fields in the western part of North America were studied using aircraft and Seasat synthetic aperture radar images and LANDSAT images. The capability of radars with different characteristics (i.e., frequency, polarization and look angles was assessed to identify and map different volcanic features, lava flows and sand dune types. It was concluded that: (1) volcanic features which have a relatively large topographic expression (i.e., cinder cones, coll...

  17. Spatio-temporal evolution of the Tuxtla Volcanic Field

    Science.gov (United States)

    Kobs Nawotniak, S. E.; Espindola, J.; Godinez, L.

    2010-12-01

    Mapping of the Tuxtla Volcanic Field (TVF), located in Veracruz, Mexico, through the use of digital elevation models, aerial photography, and field confirmation has found 353 distinct cones, 4 large composite volcanoes, and 42 maars. Eruptive activity in the TVF began in the late Miocene, underwent a quiescent period approximately 2.6-0.8 Ma, and continues into historic times with the most recent eruption occurring at San Martín Tuxtla volcano in 1793. The covariance of the minimum cone separation in the TVF indicates that, despite the influence of clear vent alignments following regional faulting trends, the field as a whole is anticlustered. Dividing the cones by morphometric age shows that while the older cones have an anti-clustered distribution, the younger cones (Catemaco. These areas of concentrated volcanism roughly correspond to the locations of two gravity anomalies previously identified in the area. While the average height/width ratio is equal between the two clusters, the cones in the eastern group are significantly smaller than their counterparts in the western group. The maars of the TVF are mostly located within the younger volcanic series, west of Laguna Catemaco, and have an anticlustered distribution; many of the maars are evenly spaced along curved lines, where they are weakly grouped according to crater diameter. Results indicate volcanism TVF has undergone continued spatial restriction over time, concentrating in the western half of the TVF with the onset of the eruption of the younger volcanic series 0.8 Ma and further contracting along the principle fault system within the last 50 Ka.

  18. 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

  19. Earthquake prediction using extinct monogenetic volcanoes: A possible new research strategy

    Science.gov (United States)

    Szakács, Alexandru

    2011-04-01

    Volcanoes are extremely effective transmitters of matter, energy and information from the deep Earth towards its surface. Their capacities as information carriers are far to be fully exploited so far. Volcanic conduits can be viewed in general as rod-like or sheet-like vertical features with relatively homogenous composition and structure crosscutting geological structures of far more complexity and compositional heterogeneity. Information-carrying signals such as earthquake precursor signals originating deep below the Earth surface are transmitted with much less loss of information through homogenous vertically extended structures than through the horizontally segmented heterogeneous lithosphere or crust. Volcanic conduits can thus be viewed as upside-down "antennas" or waveguides which can be used as privileged pathways of any possible earthquake precursor signal. In particular, conduits of monogenetic volcanoes are promising transmitters of deep Earth information to be received and decoded at surface monitoring stations because the expected more homogenous nature of their rock-fill as compared to polygenetic volcanoes. Among monogenetic volcanoes those with dominantly effusive activity appear as the best candidates for privileged earthquake monitoring sites. In more details, effusive monogenetic volcanic conduits filled with rocks of primitive parental magma composition indicating direct ascent from sub-lithospheric magma-generating areas are the most suitable. Further selection criteria may include age of the volcanism considered and the presence of mantle xenoliths in surface volcanic products indicating direct and straightforward link between the deep lithospheric mantle and surface through the conduit. Innovative earthquake prediction research strategies can be based and developed on these grounds by considering conduits of selected extinct monogenetic volcanoes and deep trans-crustal fractures as privileged emplacement sites of seismic monitoring stations

  20. 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.

  1. Influence of the substrate on maar-diatreme volcanoes — An example of a mixed setting from the Pali Aike volcanic field, Argentina

    Science.gov (United States)

    Ross, Pierre-Simon; Delpit, Séverine; Haller, Miguel J.; Németh, Károly; Corbella, Hugo

    2011-04-01

    The morphologic parameters, pyroclastic deposits and evolution of maar-diatreme volcanoes are affected by the type of environment in which they are emplaced. End-member cases are a hard substrate (rocks) and a soft substrate (unconsolidated volcaniclastic or sedimentary deposits). In this paper, we present an example of a volcanic complex emplaced in a mixed hard-soft setting from the Pali Aike volcanic field (PAVF) near the Argentina-Chile border. The Plio-Pleistocene PAVF is an alkaline, mafic, back-arc monogenetic field which contains over 100 phreatomagmatic volcanoes. The studied volcanic complex contains two large coalescent maars overlain by scoria and spatter. The 1.4 × 1.3 km East Maar has better exposures than the shallower, 1.9 km-wide West Maar and seems to have been less modified by post-eruptive processes. The tephra rim of the East Maar was studied in detail and we infer it was produced mostly by base surges from phreatomagmatic eruption columns, with rare instances of intercalated scoria fall layers. Based on regional information, the general pre-maar stratigraphy is dominated by sedimentary and volcaniclastic rocks of the Magallanes Basin, including a thick poorly consolidated upper unit dating from the Miocene. These are overlain by Plio-Pleistocene fluvio-glacial deposits and PAVF lavas, some of which are exposed in the East Maar just below the phreatomagmatic deposits. All of these units are represented as lithic clasts in the tephra rim of the East Maar, the most abundant being the clasts from the earlier basaltic lavas and rock fragments derived from the glacial deposits. There is no specific evidence for a deep diatreme under the East Maar, and in this particular case, the mixed environment seems to have produced a maar-diatreme volcano typical of a soft substrate.

  2. Subglacial and Subaqueous Monogenetic Volcanoes, Thermal and Morphological Contrasts

    Science.gov (United States)

    Gudmundsson, M. T.; Jarosch, A. H.

    2012-12-01

    Tuyas, tindars (hyaloclastite ridges), sheets and various types of smaller mounds are the main types of monogenetic volcanic edifices formed in eruptions within glaciers. Similar landforms can be created in subaqueous to emergent eruptions. Differences in confinement by ice on the one hand and water on the other may provide a diagnostic tool to differentiate between the two environments. In marine or lake environments a stable water level can be assumed in most cases. Within glaciers the level of englacial lakes may wary considerably, depending on drainage mechanisms and possible shifts during eruption between subglacial and supraglacial drainage. A combined study of (1) the morphology of predominantly basaltic tuyas in Iceland, (2) thermal constraints on ice melting and size of depression in glacier surface around a growing volcano, (3) ice flow patterns of Pleistocene ice sheets as recorded by striations, and (4) ice flow modeling, provides insight into some of the characteristics unique to subglacially formed volcanoes. In the modeling it is assumed that the ice sheet in which the tuyas formed was warm-based, although it may well have been polythermal. The results show that the tuyas tend to be elongated in the direction of ice flow at the time of eruption. A progression towards lowering of the passage zone away from vent area in the down-flow direction is also indicated. These patterns are also predicted by the ice flow modeling, since inflow of ice on the up-slope side is much greater than from the sides or from the down-slope side, effectively preventing significant extension of a growing lava delta in the up-flow direction of the glacier. Another aspect of the large scale edifice morphology that may be a useful diagnostic is the level of erosion. Islands formed in monogenetic eruptions in the ocean or large lakes are eroded by wave action. Surtsey off the south coast of Iceland has a lava cap but has lost more than half of its area since formation in 1963

  3. A mantle plume below the Eifel volcanic fields, Germany

    OpenAIRE

    Ritter, Joachim R. R.; Jordan, Michael; Christensen, Ulrich R.; Achauer, Ulrich

    2001-01-01

    We present seismic images of the upper mantle below the Quaternary Eifel volcanic fields, Germany, determined by teleseismic travel time tomography. The data were measured at a dedicated network of more than 200 stations. Our results show a columnar low P-velocity anomaly in the upper mantle with a lateral contrast of up to 2%. The 100 km wide structure extends to at least 400 km depth and is equivalent to about 150–200 K excess temperature. This clear evidence for a plume below a region of c...

  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. Alberca De Guadalupe Maar Crater, Zacapu Basin : A Rare Type of Volcano within the Michoacán-Guanajuato Volcanic Field, México

    Science.gov (United States)

    Kshirsagar, P. V.; Siebe, C.; Guilbaud, M. N.; Salinas, S.

    2014-12-01

    Phreato-magmatic vents (esp. maar craters) are rare in the ~40,000 Km2 Plio-Quaternary monogenetic Michoacán-Guanajuato Volcanic Field (MGVF) located in the central part of the Mexican Volcanic Belt. In contrast to >1000 scoria cones, only 2 dozen phreato-magmatic monogenetic vents (e.g. tuff cones, tuff rings, and maars) have been identified. About half of these form a cluster near Valle de Santiago in the Lerma river valley at the northern margin of the MGVF, while the others occur in a rather scattered fashion. Here we discuss the origin of Alberca de Guadalupe maar crater, one of the three phreato-magmatic vents (in addition to El Caracol and Alberca de Los Espinos) that occur within the boundaries of the inter-montane lacustrine Zacapu basin, a tectonic graben bound by an ENE-WSW normal fault system. The maar crater came into existence between 20,000 and 23,000 y BP, forming a 140 m deep hole in the otherwise planar surrounding ground of theearly Pleistocene lava flows of Cerro Pelón.The maar crater has a diameter of ~1 Km and bears a 9 m deep lake. Eruptive products include typical surge deposits that are best exposed around the rim and inner crater walls. They are poorly sorted (Mdø= -1.56 to -3.75, ø= 1.43 to 3.23), rich in accidental lithics (angular andesitic lava and ignimbrite clasts) constituting 51-88% of the deposit with few juveniles (basaltic andesite with phenocrysts of plagioclase, olivine, and pyroxene in a quenched glassy matrix; SiO2=54-58 wt. %). Dry surge units are friable and clast-supported, in contrast the wet surge units are fairly indurated and bear accretionary lapilli. Bedding is frequently distorted by ballistic impact-sag structures. The entire construct is disrupted by an E-W trending regional fault, downthrowing the northern part by ~30 m.The unusual formation of this maar crater in the semi-arid highlands of Zacapu was favored by the local hydrological and topographical conditions. Such conditions still prevail in several

  6. Space Radar Image of Pinacate Volcanic Field, Mexico

    Science.gov (United States)

    1994-01-01

    This spaceborne radar image shows the Pinacate Volcanic Field in the state of Sonora, Mexico, about 150 kilometers (93 miles) southeast of Yuma, Arizona. The United States/Mexico border runs across the upper right corner of the image. More than 300 volcanic vents occur in the Pinacate field, including cinder cones that experienced small eruptions as recently as 1934. The larger circular craters seen in the image are a type of volcano known as a 'maar', which erupts violently when rising magma encounters groundwater, producing highly pressurized steam that powers explosive eruptions. The highest elevations in the volcanic field, about 1200 meters (4000 feet), occur in the 'shield volcano' structure shown in bright white, occupying most of the left half of the image. Numerous cinder cones dot the flanks of the shield. The yellow patches to the right of center are newer, rough-textured lava flows that strongly reflect the long wavelength radar signals. Along the left edge of the image are sand dunes of the Gran Desierto. The dark areas are smooth sand and the brighter brown and purple areas have vegetation on the surface. Radar data provide a unique means to study the different types of lava flows and wind-blown sands. This image was acquired by Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) onboard the space shuttle Endeavour on April 18, 1994. The image is 57 kilometers by 48 kilometers (35 miles by 30 miles) and is centered at 31.7 degrees north latitude, 113.4 degrees West longitude. North is toward the upper right. The colors are assigned to different radar frequencies and polarizations of the radar as follows: red is L-band, horizontally transmitted and received; green is L-band, horizontally transmitted, vertically received; and blue is C-band, horizontally transmitted, vertically received. SIR-C/X-SAR, a joint mission of the German, Italian, and United States space agencies, is part of NASA's Mission to Planet Earth.

  7. Radar imaging of volcanic fields and sand dune fields: Implications for VOIR

    Science.gov (United States)

    Elachi, C.; Blom, R.; Daily, M.; Farr, T.; Saunders, R. S.

    1980-01-01

    A number of volcanic fields and sand dune fields in the western part of North America were studied using aircraft and Seasat synthetic aperture radar images and LANDSAT images. The capability of radars with different characteristics (i.e., frequency, polarization and look angles was assessed to identify and map different volcanic features, lava flows and sand dune types. It was concluded that: (1) volcanic features which have a relatively large topographic expression (i.e., cinder cones, collapse craters, calderas, etc.) are easily identified; (2) lava flows of different ages can be identified, particularly on the L-band images; and (3) sand dunes are clearly observed and their extent and large scale geometric characteristics determined, provided the proper imaging geometry exists.

  8. Magmatic Processes in Monogenetic Eruptions, Procida Island, Campi Flegrei, Italy: Geochemical Evidence From Melt Inclusions

    Science.gov (United States)

    Severs, M. J.; Fedele, L.; Esposito, R.; Bodnar, R.; Petrosino, P.; Lima, A.; de Vivo, B.; Shimizu, N.

    2008-12-01

    Campi Flegrei is an active volcanic complex located in the greater Naples area, which has produced more than 50 eruptions over the past 60,000 years. These have ranged from small eruptions such as Monte Nuovo eruption of 1538 CE to extremely large eruptions such as the Campanian Ignimbrite (150-200 DRE; Barbieri et al., 1978). The volcanic field includes the mainland area located to the west of Naples and also the two islands of Ischia and Procida. The volcanic products range from basalts to shoshonitic phonolites and trachytes, with the more evolved magmas being more abundant. Three eruptive units from Procida Island have been studied to observe geochemical trends over time within a small area and to better understand magmatic processes between monogenetic eruptions. Juvenile samples from Pozzo Vecchio, Breccia Museo, and Solchiara were collected to examine the geochemistry of the mineral phases present and melt inclusions (MIs) found within the phenocrysts. Solchiara contained phenocrysts of olivine and clinopyroxene, whereas Breccia Museo and Pozzo Vecchio samples contained clinopyroxene and sanidine as the dominant phenocryst phases. Melt inclusions from Solchiara have narrow compositional ranges in major and trace elements (i.e., CaO, TiO2, Zr, Dy, La) over a large range in SiO2 contents (47 to 55 wt%) while MI from the Breccia Museo have a limited range of SiO2 contents (57 to 61 wt%) with a wider range for major and trace elements (i.e., FeO, Al2O3, CaO, La, Th, Rb). Pozzo Vecchio MI from clinopyroxene and sanidine define different chemical compositions, but petrographic evidence does not suggest a xenocrystic origin for either mineral phase. This suggests that Pozzo Vecchio is the result of magma mixing. Modeling of fractional crystallization of olivine, clinopyroxene, and sanidine are capable of producing most of the trends in major and trace elements between the most primitive samples to the most evolved samples. Volatile concentrations between the

  9. 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

  10. 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.

  11. Geochemistry of high-potassium rocks from the mid-Tertiary Guffey volcanic center, Thirtynine Mile volcanic field, central Colorado

    Science.gov (United States)

    Wobus, Reinhard A.; Mochel, David W.; Mertzman, Stanley A.; Eide, Elizabeth A.; Rothwarf, Miriam T.; Loeffler, Bruce M.; Johnson, David A.; Keating, Gordon N.; Sultze, Kimberly; Benjamin, Anne E.; Venzke, Edward A.; Filson, Tammy

    1990-07-01

    The Guffey volcanic center is the largest within the 2000 km2 mid-Tertiary Thirtynine Mile volcanic field of central Colorado. This study is the first to provide extensive chemical data for these alkalic volcanic and subvolcanic rocks, which represent the eroded remnants of a large stratovolcano of Oligocene age. Formation of early domes and flows of latite and trachyte within the Guffey center was followed by extrusion of a thick series of basalt, trachybasalt, and shoshonite flows and lahars. Plugs, dikes, and vents ranging from basalt to rhyolite cut the thick mafic deposits, and felsic tuffs and tuff breccias chemically identical to the small rhyolitic plutons are locally preserved. Whole-rock major and trace element analyses of 80 samples, ranging almost continuously from 47% to 78%SiO2, indicate that the rocks of the Guffey center are among the most highly enriched in K2O (up to 6%) and rare earth elements (typically 200-300 ppm) of any volcanic rocks in Colorado. These observations, along with the relatively high concentrations of Ba and Rb and the depletion of Cr and Ni, suggest an appreciable contribution of lower crustal material to the magmas that produced the Thirtynine Mile volcanic rocks.

  12. 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

  13. Stress fields of the overriding plate at convergent margins and beneath active volcanic arcs.

    Science.gov (United States)

    Apperson, K D

    1991-11-01

    Tectonic stress fields in the overriding plate at convergent plate margins are complex and vary on local to regional scales. Volcanic arcs are a common element of overriding plates. Stress fields in the volcanic arc region are related to deformation generated by subduction and to magma generation and ascent processes. Analysis of moment tensors of shallow and intermediate depth earthquakes in volcanic arcs indicates that the seismic strain field in the arc region of many convergent margins is subhorizontal extension oriented nearly perpendicular to the arc. A process capable of generating such a globally consistent strain field is induced asthenospheric corner flow below the arc region.

  14. Magnetotelluric data, Taos Plateau Volcanic Field, New Mexico

    Science.gov (United States)

    Ailes, Chad E.; Rodriguez, Brian D.

    2010-01-01

    The population of the San Luis Basin region of northern New Mexico is growing. Water shortfalls could have serious consequences. Future growth and land management in the region depend on accurate assessment and protection of the region's groundwater resources. An important issue in managing the groundwater resources is a better understanding of the hydrogeology of the Santa Fe Group and the nature of the sedimentary deposits that fill the Rio Grande rift, which contain the principal groundwater aquifers. The shallow unconfined aquifer and the deeper confined Santa Fe Group aquifer in the San Luis Basin are the main sources of municipal water for the region. The U.S. Geological Survey (USGS) is conducting a series of multidisciplinary studies of the San Luis Basin. Detailed geologic mapping, high-resolution airborne magnetic surveys, gravity surveys, an electromagnetic survey called magnetotellurics (MT), and hydrologic and lithologic data are being used to better understand the aquifers. This report describes a regional east-west MT sounding profile acquired in late July 2009 across the Taos Plateau Volcanic Field where drillhole data are sparse. Resistivity modeling of the MT data can be used to help map changes in electrical resistivity with depths that are related to differences in rock types. These various rock types help control the properties of aquifers. The purpose of this report is to release the MT sounding data collected along the east-west profile. No interpretation of the data is included.

  15. Ancient Mudflows in the Tuxtla Volcanic Field, Veracruz, Mexico

    Science.gov (United States)

    Espindola, J.; Zamora-Camacho, A.; Godinez, M.

    2011-12-01

    The Tuxtla Volcanic Field (TVF) is a basaltic volcanic enclave in eastern Mexico at the margin of the Gulf of Mexico. Due to the high rates of precipitation floods and mudflows are common. Resulting from a systematic study of geologic hazard in the TVF we found several mudflow deposits that impacted pre-Columbian settlements. Sections of the deposits were observed in detail and sampled for granulometric studies. The deposits contained materials suitable for dating: ceramic shards and some of them charcoal fragments. Shards from the interior of the deposit were collected and placed in black bags to prevent the action of light and to be analyzed by thermoluminiscense (TL), the charcoal samples were dated using standard radiocarbon methods (C-14). The sites were dubbed La Mojarra (18°37.711', 95°18.860'), Revolución (18° 35.848', 95°11.412'), Pisatal (18°36.618', 95°10.634'), and Toro Prieto (18°38.229, 95°12.037'). These places were named after the nearby villages the first two, lake Pisatal the third and Toro Prieto creek the fourth. All the deposits occur close to the margins of riverbeds or lakes. Samples of these sites yielded ages of 1176±100 (TL), 1385±70 (C-14), 1157±105 (TL), 2050+245-235 (C-14), respectively. These locations have undergone recurrent floods in the last decades, showing that these phenomena impact the same areas over centuries. The dates mentioned are important because, no vestiges of human settlements had been reported in the area, which in the past was covered by a dense forest. The settlements must have been very small and depended of such cities as nearby Matacapan an important city with strong ties to Teotihuacán in central Mexico. The ages agree with the findings of archeologic studies in Matacapan, which indicate that the population became increasingly ruralized since the late classic period (≈ 600-800 AD).

  16. 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 (δ18Ozrc<4.7 ‰). Despite the growing data set of low-δ18O melts within, and proximal to, the Snake River Plain (SRP) Large Igneous Province, debate persists regarding both the mechanisms for low-δ18O magma petrogenesis, and their relative influence in the SRP. The LOVF is associated with widespread silicic volcanism roughly concurrent with the eruption of the Steens-Columbia River Basalt Group between ~17-15Ma. Silicic activity in the LOVF is limited to 16-15Ma, when an estimated 1100km3 of weakly peralkaline to metaluminous rhyolitic lavas and ignimbrites erupted from a series of fissures and calderas. Geographically, the LOVF overlaps the Oregon-Idaho Graben (OIG), and straddles the 87Sr/86Sr= 0.704 line which, together with the 0.706 line to the east, delineate the regional transition from the North American Precambrian 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

  17. Magnetotelluric Imaging of Hasandaǧ-Karacadaǧ Monogenetic Cluster, Central Anatolia, Turkey

    Science.gov (United States)

    Uslular, Göksu; Bülent Tank, Sabri; Özaydın, Sinan; Karaş, Mustafa; Gençalioǧlu-Kuşcu, Gonca; Sandvol, Eric

    2017-04-01

    Hasandaǧ stratovolcano is one of the most devastating volcanic edifices in the Central Anatolia, Turkey. The volcano has been studied for decades but there is still no consensus on its origin. To provide new insight on Hasandaǧ, there is also a need for geophysical explorations (e.g. seismology, magnetotelluric-MT) within the region. As a part of collaborative multidisciplinary project (CD-CAT: Continental Dynamics/Central Anatolian Tectonics) funded by NSF, we conducted 25 MT (360 Hz - 0.0002 Hz) measurements to reveal the electrical conductivity structure of the volcanic region between Hasandaǧ and Karacadaǧ stratovolcanoes. By means of two- and three-dimensional numerical modelling attempts based on several state-of-the-art algorithms, the MT data were utilized to create SW-NE trending profiles that visualize to a depth of 50-km of the subsurface structure. Prior to two-dimensional modelling, dimensionality analyses (i.e. geo-electric strike angle determination following Groom and Bailey decomposition for single-site and multi-site cases, phase tensors and induction vectors) were performed. Preliminary findings lead us to suggest that (i) there is a highly conductive body from 20 km to 40 km depth beneath the monogenetic field (i.e. Eǧrikuyu) between Hasandaǧ and Karacadaǧ. This may correspond to the possible depth at which widespread mildly-alkaline basalts are formed due to the decompression melting of heterogeneous mantle (mixing of mostly subduction-modified lithospheric and partially upwelling asthenospheric). (ii) Relatively low conductive body at shallow depth possibly due to the presence of buried ignimbrite. (iii) One of the maar with a deep source (diatreme-like) may still store hot fluids that result from highly conductive body, and here would be a suitable prospect area for geothermal exploration. (iv) low to high conductivity boundary underneath the Tuz Gölü fault appear as a barrier for fluid flow.

  18. 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.

  19. 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.

  20. The Western Arabian intracontinental volcanic fields as a potential UNESCO World Heritage site

    Science.gov (United States)

    Németh, Károly; Moufti, Mohammed R.

    2017-04-01

    UNESCO promotes conservation of the geological and geomoprhological heritage through promotion of protection of these sites and development of educational programs under the umbrella of geoparks among the most globally significant ones labelled as UNESCO Global Geoparks. UNESCO also maintains a call to list those natural sites that provide universal outstanding values to demonstrate geological features or their relevance to our understanding the evolution of Earth. Volcanoes currently got a surge in nomination to be UNESCO World Heritage sites. Volcanic fields in the contrary fell in a grey area of nominations as they represents the most common manifestation of volcanism on Earth hence they are difficult to view as having outstanding universal values. A nearly 2500-km long 300-km wide region of dispersed volcanoes located in the Western Arabian Penninsula mostly in the Kingdom of Saudi Arabia form a near-continuous location that carries universal outstanding value as one of the most representative manifestation of dispersed intracontinental volcanism on Earth to be nominated as an UNESCO World Heritage site. The volcanic fields formed in the last 20 Ma along the Red Sea as group of simple basaltic to more mature and long-lived basalt to trachyte-to-rhyolite volcanic fields each carries high geoheritage values. While these volcanic fields are dominated by scoria and spatter cones and transitional lava fields, there are phreatomagmatic volcanoes among them such as maars and tuff rings. Phreatomagmatism is more evident in association with small volcanic edifices that were fed by primitive magmas, while phreatomagmatic influences during the course of a larger volume eruption are also known in association with the silicic eruptive centres in the harrats of Rahat, Kishb and Khaybar. Three of the volcanic fields are clearly bimodal and host small-volume relatively short-lived lava domes and associated block-and-ash fans providing a unique volcanic landscape commonly not

  1. The Temporal and Spatial Association of Faulting and Volcanism in the Cerros del Rio Volcanic Field - Rio Grande Rift, USA

    Science.gov (United States)

    Thompson, R. A.; Hudson, M. R.; Minor, S. A.; McIntosh, W. C.; Miggins, D. P.; Grauch, V.

    2008-12-01

    The Plio-Pleistocene Cerros del Rio volcanic field (CdRVF) in northern New Mexico is one of the largest ( greater than 700 square kilometers) predominantly basaltic and andesitic volcanic centers of the Rio Grande rift; it records the late-stage, volcano-tectonic evolution of the SW part of the Espanola Basin. The CdRVF reflects both regional proclivity toward Pliocene basaltic volcanism following protracted Neogene extensional tectonism and localized eruptive response to migration of basin- bounding faults. Approximately 180 cubic kilometers of flat lying to gently dipping basalt, andesite, and minor dacite lava flows and pyroclastic deposits of the CdRVF were erupted from more than 50 exposed vents between 2.8 Ma and 1.14 Ma. Subsurface interpretations of drill hole data and incised canyon exposures of the Rio Grande show that volcanic deposits are interbedded with Santa Fe Group sediments deposited in actively subsiding sub-basins of the southernmost Espanola Basin. Major basin-bounding faults in this area strike north to northwest, dip basinward, and have mostly dip-slip and subordinate strike-slip displacement. Although major basin-bounding faults were active prior to the onset of volcanism in the CdRVF, protracted extension resulted in a westward migration of graben-bounding faults. Phases of coeval volcanism at 2.8-2.6 Ma, 2.5-2.2 Ma, and 1.5-1.1 Ma, decreased in eruptive volume through time and are delineated on the basis of mapped stratigraphy, argon geochronology, paleomagnetic and aeromagnetic properties, and record a syntectonic westward migration of eruptive centers. The alignment of vent areas with mapped faults strongly suggests deep magmatic sources utilized local structures as conduits (i.e. faults and fractures developed in response to regional stress). However, some near-surface feeder dikes associated with eroded cinder cones record orientations that are not typically correlative with regional fault patterns suggesting near-surface conduits are

  2. Geology and geochemistry of volcanic centers within the eastern half of the Sonoma volcanic field, northern San Francisco Bay region, California

    Science.gov (United States)

    Sweetkind, Donald S.; Rytuba, James J.; Langenheim, V.E.; Fleck, Robert J.

    2011-01-01

    Volcanic rocks in the Sonoma volcanic field in the northern California Coast Ranges contain heterogeneous assemblages of a variety of compositionally diverse volcanic rocks. We have used field mapping, new and existing age determinations, and 343 new major and trace element analyses of whole-rock samples from lavas and tuff to define for the first time volcanic source areas for many parts of the Sonoma volcanic field. Geophysical data and models have helped to define the thickness of the volcanic pile and the location of caldera structures. Volcanic rocks of the Sonoma volcanic field show a broad range in eruptive style that is spatially variable and specific to an individual eruptive center. Major, minor, and trace-element geochemical data for intracaldera and outflow tuffs and their distal fall equivalents suggest caldera-related sources for the Pinole and Lawlor Tuffs in southern Napa Valley and for the tuff of Franz Valley in northern Napa Valley. Stratigraphic correlations based on similarity in eruptive sequence and style coupled with geochemical data allow an estimate of 30 km of right-lateral offset across the West Napa-Carneros fault zones since ~5 Ma.

  3. Field-trip guides to selected volcanoes and volcanic landscapes of the western United States

    Science.gov (United States)

    ,

    2017-06-23

    The North American Cordillera is home to a greater diversity of volcanic provinces than any comparably sized region in the world. The interplay between changing plate-margin interactions, tectonic complexity, intra-crustal magma differentiation, and mantle melting have resulted in a wealth of volcanic landscapes.  Field trips in this guide book collection (published as USGS Scientific Investigations Report 2017–5022) visit many of these landscapes, including (1) active subduction-related arc volcanoes in the Cascade Range; (2) flood basalts of the Columbia Plateau; (3) bimodal volcanism of the Snake River Plain-Yellowstone volcanic system; (4) some of the world’s largest known ignimbrites from southern Utah, central Colorado, and northern Nevada; (5) extension-related volcanism in the Rio Grande Rift and Basin and Range Province; and (6) the eastern Sierra Nevada featuring Long Valley Caldera and the iconic Bishop Tuff.  Some of the field trips focus on volcanic eruptive and emplacement processes, calling attention to the fact that the western United States provides opportunities to examine a wide range of volcanological phenomena at many scales.The 2017 Scientific Assembly of the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) in Portland, Oregon, was the impetus to update field guides for many of the volcanoes in the Cascades Arc, as well as publish new guides for numerous volcanic provinces and features of the North American Cordillera. This collection of guidebooks summarizes decades of advances in understanding of magmatic and tectonic processes of volcanic western North America. These field guides are intended for future generations of scientists and the general public as introductions to these fascinating areas; the hope is that the general public will be enticed toward further exploration and that scientists will pursue further field-based research.

  4. 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.

  5. The Maar-Diatreme System in a Mixed "Hard/Soft-Rock" Setting: an Example from the Pali Aike Volcanic Field, Argentina

    Science.gov (United States)

    Delpit, S.; Ross, P.

    2009-05-01

    The eruptive processes in diatremes remain poorly understood compared to those at other volcano types, because these processes occur at depth. Except for maar-diatreme volcanoes formed during kimberlitic eruptions, volcanologists agree that these systems are of phreatomagmatic origin. The origin of kimberlitic diatremes is more contentious, but studying non kimberlitic equivalents can be a good approach to better understand kimberlitic diatremes considering their numerous common characteristics. The geometry of maar-diatreme systems is strongly influenced by their setting in "hard-rock" or "soft-rock" environments (Lorenz, 2003, Geolines 15:72-83). Formation of maar-diatreme systems in "hard-rock" environments, like in the West Eifel Volcanic Field of Germany, is largely described in the literature but emplacement in "soft-rock" environments or mixed settings is not. In the case of "hard-rock" environments external water is provided by fracture aquifers. The eruption products are juvenile clasts and country rock fragments. The inner crater walls of the maar, and the diatreme walls, have steep slopes. In the case of "soft- rock" environments, water is contained in the sediment pores and the walls tend to be at lower angles. We recently conducted field work on maars, cinder cones and spatter rings of the Pali Aike Volcanic Field of southern Argentina as part of the Potrok Aike Maar Lake Sediment Archive Drilling Project (PASADO). These Quaternary monogenetic volcanoes were emplaced in a mixed "hard/soft-rock" environment containing young glacial sediments, basaltic lava flows, partly consolidated fluviatile sediments, and older indurated sedimentary rocks. The mixed environment of emplacement is reflected in a phreatomagmatic deposit on the inner slope of a tephra ring exposing some lapilli-tuff layers. The lapilli fraction comprises approximately 40% lithics on average (visual estimate): at least half of the fraction is composed of basaltic lava derived from a pre

  6. 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

  7. 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.

  8. Paleomagnetic evidence for an episodic eruptive history of the Cerros del Rio volcanic field, New Mexico

    Science.gov (United States)

    Hudson, M. R.; Thompson, R. A.

    2011-12-01

    The Pliocene to Quaternary (~2.6-1.14 Ma) Cerros del Rio volcanic field of northern New Mexico forms a dissected basaltic plateau sourced by multiple eruptive centers. Paleomagnetic data compliment geologic mapping, geochronologic and geochemical data to define the spatial and temporal eruptive history of Cerros del Rio volcanic deposits. The preserved stratigraphic sequence reflects three principal phases of volcanism; 1) 2.7-2.6 Ma, 2) 2.5-2.2 Ma, and 3) 1.5-1.1 Ma. Paleomagnetic data collected from 85 sites that span the area of the volcanic field largely sample phase-1 deposits that record the Guass normal-polarity chron or phase-2 deposits that record the Matuyama reversed-polarity chron. A grand mean of individual sites (excluding transitional directions) is D = 352.8°, I = 49.7°, k= 14, a95 = 3.9. However, normal- and reversed-polarity group means are not statistically antipodal, with the normal-polarity inclination being significantly shallower than an expected (55°) dipole inclination. This failed reversal test suggests that paleosecular variation has not be fully averaged within both polarity groups, despite a basis on abundant data from multiple eruptive centers. Compared to variation recorded by the full volcanic field, site directions from individual eruptive centers have restricted dispersion, indicating that the centers formed quickly relative to paleosecular variation. Grouping data within individual eruptive centers to calculate eruptive-group means (EGM), directions of the normal- and reversed-polarity EGM remain skewed from antipodal. Modal analysis demonstrates the presence of multiple directional clusters among the normal-polarity EGM whereas the frequency distribution of reversed polarity EGM are symmetrical about their maximum. These paleomagnetic directional characteristics indicate that voluminous phase-1 deposits of the Cerros del Rio volcanic field probably erupted episodically during short time intervals and that several individual

  9. The role of phreatomagmatism in a Plio-Pleistocene high-density scoria cone field: Llancanelo Volcanic Field (Mendoza), Argentina

    Science.gov (United States)

    Risso, Corina; Németh, Károly; Combina, Ana María; Nullo, Francisco; Drosina, Marina

    2008-01-01

    The Plio-Pleistocene Llancanelo Volcanic Field, together with the nearby Payun Matru Field, comprises at least 800 scoria cones and voluminous lava fields that cover an extensive area behind the Andean volcanic arc. Beside the scoria cones in the Llancanelo Field, at least six volcanoes show evidence for explosive eruptions involving magma-water interaction. These are unusual in the context of the semi-arid climate of the eastern Andean ranges. The volcanic structures consist of phreatomagmatic-derived tuff rings and tuff cones of olivine basalt composition. Malacara and Jarilloso tuff cones were produced by fallout of a range of dry to wet tephra. The Malacara cone shows more evidence for a predominance of wet-emplaced units, with a steep slump-slope characterized by many soft-sediment deformation structures, such as: undulating bedding planes, truncated beds and water escape features. The Piedras Blancas and Carapacho tuff rings resulted from explosive eruptions with deeper explosion loci. These cones are hence dominated by lapilli tuff and tuff units, emplaced mainly by wet and/or dry pyroclastic surges. Carapacho is the only centre that appears to have started with phreatomagmatic eruptions, with lowermost tephra being rich in non-volcanic country rocks. The presence of deformed beds with impact sags, slumping textures, asymmetrical ripples, dunes, cross- and planar lamination, syn-volcanic faulting and accretionary lapilli beds indicate an eruption scenario dominated by excessive water in the transportational and depositional regime. This subordinate phreatomagmatism in the Llancanelo Volcanic Field suggests presence of ground and/or shallow surface water during some of the eruptions. Each of the tuff rings and cones are underlain by thick, fractured multiple older lava units. These broken basalts are inferred to be the horizons where rising magma interacted with groundwater. The strong palagonitization at each of the phreatomagmatic cones formed hard beds

  10. Cenozoic diatreme field in Chubut (Argentina) as evidence of phreatomagmatic volcanism accompanied with extensive Patagonian plateau basalt volcanism?

    Institute of Scientific and Technical Information of China (English)

    Károly Németh; Ulrike Martin; Miguel J. Haller; Viviana L Alric

    2007-01-01

    @@ In Patagonia, Argentina, at the northern border of the Patagonian Cenozoic mafic plateau lava fields, newly discovered diatremes stand about 100 m above the surrounding plain. These diatremes document phreatomagmatic episodes associated with the formation of the volcanic fields. The identified pyroclastic and intrusive rocks are exposed lower diatremes of former phreatomagmatic volcanoes and their feeding dyke systems.These remotely located erosional remnants cut through Paleozoic granitoids and Jurassic/Cretaceous alternating siliciclastic continental successions that are relatively easily eroded. Plateau lava fields are generally located a few hundreds of metres above the highest level of the present tops of the preserved diatremes suggesting a complex erosional history and potential interrelation-ships between the newly identified diatremes and the surrounding lava fields. Uprising magma from theunderlying feeder dyke into the diatreme root zone intruded the clastic debris in the diatremes, inflated them and mingled with the debris to form subterranean peperite. The significance of identifying diatremes in Patagonia are twofold: 1) in the syn-eruptive paleoenvironment, water was available in various "soft-sediments", commonly porous, media aquifer sources, and 2) the identified abundant diatremes that form diatreme fields are good source candidates for the extensive lava fields with phreatomagmatism facilitating magma rise with effective opening of fissures before major lava effusions.

  11. Volcanic hazard assessment in the Phlegraean Fields: A contribution based on stratigraphic and historical data

    Energy Technology Data Exchange (ETDEWEB)

    Rosi, M.; Santacroce, R. (Universita di Pisa (Italy) Gruppo Nazionale per la Vulcanologia, Roma (Italy))

    1984-01-01

    Phenomena occurring since 1982 in the Phlegraean fields, interpreted as precursors of a potential renewal of volcanic activity, have forced the authors to anticipate some conclusions of a volcanic-hazard study based on the reconstruction of past eruptions in the area, to serve as basis for civil defense preparedness plans. The eruptive history of the Phlegraean Fields suggests a progressive decrease with time in the strength of eruptive phenomena paralleling a migration of vents towards the center of the Phlegraean caldera. Studies concerning the volcanic risk zonation were therefore concentrated on activities during the last 4,500 years and two eruptions (Monte Nuovo and Agnano Monte Spina), that occurred in 1538 and 4,400 years B.P., respectively were selected as the reference eruptions from which possible eruption scenarios were drawn.

  12. Timing and nature of volcanic particle clusters based on field and numerical investigations

    Science.gov (United States)

    Bagheri, Gholamhossein; Rossi, Eduardo; Biass, Sébastien; Bonadonna, Costanza

    2016-11-01

    Aggregation processes are known to play an important role in volcanic particle dispersal and sedimentation. They are also a primary source of uncertainty in ash dispersal forecasting since fundamental questions, such as the timing and deposition dynamics of volcanic aggregates, still remain unanswered. Here, we applied a state-of-the-art combination of field and numerical strategies to characterize volcanic aggregates. We introduce a new category of aggregates observed with high-speed-high-resolution videos, namely cored clusters. Cored clusters are mostly sub-spherical fragile aggregates that have never been observed in the deposits nor on adhesive tape as they typically break at impact with the ground. They consist of a core particle (200-500μm) fully covered by a thick shell of particles field-based evidence of the so-called rafting effect, in which the sedimentation of coarse ash in cored clusters is delayed due to aggregation.

  13. Petrologic and petrographic variation of youthful eruptive products in the Tuxtla Volcanic Field, Veracruz, Mexico

    Science.gov (United States)

    Parrish, C. B.; Kobs Nawotniak, S. E.; Fredrick, K. C.; Espindola, J.

    2010-12-01

    The Tuxtla Volcanic Field (TVF) is located near the Gulf of Mexico in the southern part of the state of Veracruz, Mexico. Volcanism in the region began around 7 Ma and has continued until recent times with the volcano San Martín Tuxtla’s latest eruptions in AD 1664 and 1793. The TVF rocks are mainly of alkaline composition and have been divided into two separate volcanic series, an older and younger. The TVF is a structural high located between the Veracruz Basin to the southwest and the Gulf of Mexico to the northeast, characterized by relatively thin crust with the depth to the Moho around 28 to 34 km. The TVF is unique because it is isolated from the nearest volcanic fields (the Mexican Volcanic Belt, Central American Volcanic Belt and the Eastern Alkaline Province) by at least 230km and because of the on-going debate over its magmatic origin. Many models have been proposed to explain the TVF’s alkaline nature in a unique location with most linking it either to the subduction of the Cocos plate to the west of Mexico and/or to extensional faulting in the region. The purpose of our study was to determine systematic changes in the youthful volcanic deposits across the TVF. Regional and local mapping was conducted and lava and scoria samples were collected from seven sites associated with two vent clusters in the TVF. Mapping of the easternmost cluster of deposits suggests chronological emplacement of the deposits through superposition and vent location and morphology. The petrography of lava and tephra deposits may further indicate magmatic origins and other factors influencing the development of the field, including chronology and possible mixing and/or differentiation. Previous published studies analyzed samples near the San Martin Tuxtla volcanic center. Their data is used as a comparative reference for these samples, most of which were collected from another, younger cluster east of Laguna Catemaco. From this study, a better understanding of past eruptive

  14. Volcanic ash layers in blue ice fields (Beardmore Glacier Area, Antarctica): Iridium enrichments

    Science.gov (United States)

    Koeberl, Christian

    1988-01-01

    Dust bands on blue ice fields in Antarctica have been studied and have been identified to originate from two main sources: bedrock debris scraped up from the ground by the glacial movement (these bands are found predominantly at fractures and shear zones in the ice near moraines), and volcanic debris deposited on and incorporated in the ice by large-scale eruptions of Antarctic (or sub-Antractic) volcanoes. Ice core studies have revealed that most of the dust layers in the ice cores are volcanic (tephra) deposits which may be related to some specific volcanic eruptions. These eruptions have to be related to some specific volcanic eruptions. These eruptions have to be relatively recent (a few thousand years old) since ice cores usually incorporate younger ice. In contrast, dust bands on bare blue ice fields are much older, up to a few hundred thousand years, which may be inferred from the rather high terrestrial age of meteorites found on the ice and from dating the ice using the uranium series method. Also for the volcanic ash layers found on blue ice fields correlations between some specific volcanoes (late Cenozoic) and the volcanic debris have been inferred, mainly using chemical arguments. During a recent field expedition samples of several dust bands found on blue ice fields at the Lewis Cliff Ice Tongue were taken. These dust band samples were divided for age determination using the uranium series method, and chemical investigations to determine the source and origin of the dust bands. The investigations have shown that most of the dust bands found at the Ice Tongue are of volcanic origin and, for chemical and petrological reasons, may be correlated with Cenozoic volcanoes in the Melbourne volcanic province, Northern Victoria Land, which is at least 1500 km away. Major and trace element data have been obtained and have been used for identification and correlation purposes. Recently, some additional trace elements were determined in some of the dust band

  15. Field-trip guide to mafic volcanism of the Cascade Range in Central Oregon—A volcanic, tectonic, hydrologic, and geomorphic journey

    Science.gov (United States)

    Deligne, Natalia I.; Mckay, Daniele; Conrey, Richard M.; Grant, Gordon E.; Johnson, Emily R.; O'Connor, Jim; Sweeney, Kristin

    2017-08-16

    The Cascade Range in central Oregon has been shaped by tectonics, volcanism, and hydrology, as well as geomorphic forces that include glaciations. As a result of the rich interplay between these forces, mafic volcanism here can have surprising manifestations, which include relatively large tephra footprints and extensive lava flows, as well as water shortages, transportation and agricultural disruption, and forest fires. Although the focus of this multidisciplinary field trip will be on mafic volcanism, we will also look at the hydrology, geomorphology, and ecology of the area, and we will examine how these elements both influence and are influenced by mafic volcanism. We will see mafic volcanic rocks at the Sand Mountain volcanic field and in the Santiam Pass area, at McKenzie Pass, and in the southern Bend region. In addition, this field trip will occur during a total solar eclipse, the first one visible in the United States in more than 25 years (and the first seen in the conterminous United States in more than 37 years).The Cascade Range is the result of subduction of the Juan de Fuca plate underneath the North American plate. This north-south-trending volcanic mountain range is immediately downwind of the Pacific Ocean, a huge source of moisture. As moisture is blown eastward from the Pacific on prevailing winds, it encounters the Cascade Range in Oregon, and the resulting orographic lift and corresponding rain shadow is one of the strongest precipitation gradients in the conterminous United States. We will see how the products of the volcanoes in the central Oregon Cascades have had a profound influence on groundwater flow and, thus, on the distribution of Pacific moisture. We will also see the influence that mafic volcanism has had on landscape evolution, vegetation development, and general hydrology.

  16. 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).

  17. Rapid uplift in Laguna del Maule volcanic field of the Andean Southern Volcanic zone (Chile) 2007-2012

    Science.gov (United States)

    Feigl, Kurt L.; Le Mével, Hélène; Tabrez Ali, S.; Córdova, Loreto; Andersen, Nathan L.; DeMets, Charles; Singer, Bradley S.

    2014-02-01

    The Laguna del Maule (LdM) volcanic field in Chile is an exceptional example of postglacial rhyolitic volcanism in the Southern Volcanic Zone of the Andes. By interferometric analysis of synthetic aperture radar (SAR) images acquired between 2007 and 2012, we measure exceptionally rapid deformation. The maximum vertical velocity exceeds 280 mm yr-1. Although the rate of deformation was negligible from 2003 January to 2004 February, it accelerated some time before 2007 January. Statistical testing rejects, with 95 per cent confidence, four hypotheses of artefacts caused by tropospheric gradients, ionospheric effects, orbital errors or topographic relief, respectively. The high rate of deformation is confirmed by daily estimates of position during several months in 2012, as measured by analysis of signals transmitted by the Global Positioning System (GPS) and received on the ground at three stations around the reservoir forming the LdM. The fastest-moving GPS station (MAU2) has a velocity vector of [-180 ± 4, 46 ± 2, 280 ± 4] mm yr-1 for the northward, eastward and upward components, respectively, with respect to the stable interior of the South America Plate. The observed deformation cannot be explained by changes in the gravitational load caused by variations in the water level in the reservoir. For the most recent observation time interval, spanning 44 d in early 2012, the model that best fits the InSAR observations involves an inflating sill at a depth of 5.2 ± 0.3 km, with length 9.0 ± 0.3 km, width 5.3 ± 0.4 km, dip 20 ± 3° from horizontal and strike 14 ± 5° clockwise from north, assuming a rectangular dislocation in a half-space with uniform elastic properties. During this time interval, the estimated rate of tensile opening is 1.1 ± 0.04 m yr-1, such that the rate of volume increase in the modelled sill is 51 ± 5 million m3 yr-1 or 1.6 ± 0.2 m3 s-1. From 2004 January to 2012 April the total increase in volume was at least 0.15 km3 over the 5.2-yr

  18. Measurements and Slope Analyses of Quaternary Cinder Cones, Camargo Volcanic Field, Chihuahua, Mexico

    Science.gov (United States)

    Gallegos, M. I.; Espejel-Garcia, V. V.

    2012-12-01

    The Camargo volcanic field (CVF) covers ~3000 km2 and is located in the southeast part of the state of Chihuahua, within the Basin and Range province. The CVF represents the largest mafic alkali volcanic field in northern Mexico. Over a 300 cinder cones have been recognized in the Camargo volcanic field. Volcanic activity ranges from 4.7 to 0.09 Ma revealed by 40Ar/39Ar dating methods. Previous studies say that there is a close relationship between the cinder cone slope angle, due to mechanical weathering, and age. This technique is considered a reliable age indicator, especially in arid climates, such as occur in the CVF. Data were acquired with digital topographic maps (DRG) and digital elevation models (DEM) overlapped in the Global Mapper software. For each cone, the average radius (r) was calculated from six measurements, the height (h) is the difference between peak elevation and the altitude of the contour used to close the radius, and the slope angle was calculated using the equation Θ = tan-1(h/r). The slope angles of 30 cinder cones were calculated showing angles ranging from 4 to 15 degrees. A diffusion model, displayed by an exponential relationship between slope angle and age, places the ages of these 30 cones from 215 to 82 ka, within the range marked by radiometric methods. Future work include the analysis of more cinder cones to cover the whole CVF, and contribute to the validation of this technique.

  19. 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

  20. 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

  1. 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.

  2. 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.

  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. Contributions to Astrogeology: Geology of the lunar crater volcanic field, Nye County, Nevada

    Science.gov (United States)

    Scott, D. H.; Trask, N. J.

    1971-01-01

    The Lunar Crater volcanic field in east-central Nevada includes cinder cones, maars, and basalt flows of probably Quaternary age that individually and as a group resemble some features on the moon. Three episodes of volcanism are separated by intervals of relative dormancy and erosion. Changes in morphology of cinder cones, degree of weathering, and superposition of associated basalt flows provide a basis for determining the relative ages of the cones. A method has been devised whereby cone heights, base radii, and angles of slope are used to determine semiquantitatively the age relationships of some cinder cones. Structural studies show that cone and crater chains and their associated lava flows developed along fissures and normal faults produced by tensional stress. The petrography of the basalts and pyroclastics suggests magmatic differentiation at depth which produced interbedded subalkaline basalts, alkali-olivine basalts, and basanitoids. The youngest flows in the field are basanitoids.

  5. 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

  6. Geology, geochronology, and paleogeography of the southern Sonoma volcanic field and adjacent areas, northern San Francisco Bay region, California

    Science.gov (United States)

    Wagner, D.L.; Saucedo, G.J.; Clahan, K.B.; Fleck, R.J.; Langenheim, V.E.; McLaughlin, R.J.; Sarna-Wojcicki, A. M.; Allen, J.R.; Deino, A.L.

    2011-01-01

    Recent geologic mapping in the northern San Francisco Bay region (California, USA) supported by radiometric dating and tephrochronologic correlations, provides insights into the framework geology, stratigraphy, tectonic evolution, and geologic history of this part of the San Andreas transform plate boundary. There are 25 new and existing radiometric dates that define three temporally distinct volcanic packages along the north margin of San Pablo Bay, i.e., the Burdell Mountain Volcanics (11.1 Ma), the Tolay Volcanics (ca. 10-8 Ma), and the Sonoma Volcanics (ca. 8-2.5 Ma). The Burdell Mountain and the Tolay Volcanics are allochthonous, having been displaced from the Quien Sabe Volcanics and the Berkeley Hills Volcanics, respectively. Two samples from a core of the Tolay Volcanics taken from the Murphy #1 well in the Petaluma oilfield yielded ages of 8.99 ?? 0.06 and 9.13 ?? 0.06 Ma, demonstrating that volcanic rocks exposed along Tolay Creek near Sears Point previously thought to be a separate unit, the Donnell Ranch volcanics, are part of the Tolay Volcanics. Other new dates reported herein show that volcanic rocks in the Meacham Hill area and extending southwest to the Burdell Mountain fault are also part of the Tolay Volcanics. In the Sonoma volcanic field, strongly bimodal volcanic sequences are intercalated with sediments. In the Mayacmas Mountains a belt of eruptive centers youngs to the north. The youngest of these volcanic centers at Sugarloaf Ridge, which lithologically, chemically, and temporally matches the Napa Valley eruptive center, was apparently displaced 30 km to the northwest by movement along the Carneros and West Napa faults. The older parts of the Sonoma Volcanics have been displaced at least 28 km along the RodgersCreek fault since ca. 7 Ma. The Petaluma Formation also youngs to the north along the Rodgers Creek-Hayward fault and the Bennett Valley fault. The Petaluma basin formed as part of the Contra Costa basin in the Late Miocene and was

  7. Volcanic sulfur dioxide index and volcanic explosivity index inferred from eruptive volume of volcanoes in Jeju Island, Korea: application to volcanic hazard mitigation

    Science.gov (United States)

    Ko, Bokyun; Yun, Sung-Hyo

    2016-04-01

    Jeju Island located in the southwestern part of Korea Peninsula is a volcanic island composed of lavaflows, pyroclasts, and around 450 monogenetic volcanoes. The volcanic activity of the island commenced with phreatomagmatic eruptions under subaqueous condition ca. 1.8-2.0 Ma and lasted until ca. 1,000 year BP. For evaluating volcanic activity of the most recently erupted volcanoes with reported age, volcanic explosivity index (VEI) and volcanic sulfur dioxide index (VSI) of three volcanoes (Ilchulbong tuff cone, Songaksan tuff ring, and Biyangdo scoria cone) are inferred from their eruptive volumes. The quantity of eruptive materials such as tuff, lavaflow, scoria, and so on, is calculated using a model developed in Auckland Volcanic Field which has similar volcanic setting to the island. The eruptive volumes of them are 11,911,534 m3, 24,987,557 m3, and 9,652,025 m3, which correspond to VEI of 3, 3, and 2, respectively. According to the correlation between VEI and VSI, the average quantity of SO2 emission during an eruption with VEI of 3 is 2-8 × 103 kiloton considering that the island was formed under intraplate tectonic setting. Jeju Island was regarded as an extinct volcano, however, several studies have recently reported some volcanic eruption ages within 10,000 year BP owing to the development in age dating technique. Thus, the island is a dormant volcano potentially implying high probability to erupt again in the future. The volcanoes might have explosive eruptions (vulcanian to plinian) with the possibility that SO2 emitted by the eruption reaches stratosphere causing climate change due to backscattering incoming solar radiation, increase in cloud reflectivity, etc. Consequently, recommencement of volcanic eruption in the island is able to result in serious volcanic hazard and this study provides fundamental and important data for volcanic hazard mitigation of East Asia as well as the island. ACKNOWLEDGMENTS: This research was supported by a grant [MPSS

  8. Eifel maars: Quantitative shape characterization of juvenile ash particles (Eifel Volcanic Field, Germany)

    Science.gov (United States)

    Rausch, Juanita; Grobéty, Bernard; Vonlanthen, Pierre

    2015-01-01

    The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of the West Eifel Volcanic Field (WEVF), in contrast to deposits in the East Eifel Volcanic Field (EEVF), lack the diagnostic criteria of typical phreatomagmatic deposits. The aim of this study was to determine quantitatively the shape of WEVF and EEVF maar ash particles in order to infer the governing eruption style in Eifel maar volcanoes. The quantitative shape characterization was done by analyzing fractal dimensions of particle contours (125-250 μm sieve fraction) obtained from Scanning electron microscopy (SEM) and SEM micro-computed tomography (SEM micro-CT) images. The fractal analysis (dilation method) and the fractal spectrum technique confirmed that the WEVF and EEVF maar particles have contrasting multifractal shapes. Whereas the low small-scale dimensions of EEVF particles (Eppelsberg Green Unit) coincide with previously published values for phreatomagmatic particles, the WEVF particles (Meerfelder Maar, Pulvermaar and Ulmener Maar) have larger values indicating more complex small-scale features, which are characteristic for magmatic particles. These quantitative results are strengthening the qualitative microscopic observations, that the studied WEVF maar eruptions are rather dominated by magmatic processes. The different eruption styles in the two volcanic fields can be explained by the different geological and hydrological settings found in both regions and the different chemical compositions of the magmas.

  9. 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

  10. 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.

  11. 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.

  12. 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...

  13. 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...

  14. Crustal thickness at the Tuxtla Volcanic Field (Veracruz, Mexico) from receiver functions

    Science.gov (United States)

    Zamora-Camacho, A.; Espindola, V. H.; Pacheco, J. F.; Espindola, J. M.; Godinez, M. L.

    2010-09-01

    The Tuxtla Volcanic Field (TVF) is a structure of basaltic rocks on the western margin of the Gulf of Mexico in the Mexican State of Veracruz. Located some 150 km from the easternmost tip of the Mexican Volcanic Belt, its tectonic relationship is still unclear. The volcanism, mostly alkaline, is younger than 7 Ma and has given origin to hundreds of cinder and scoria cones, maars and four large composite volcanoes, one of which, San Martín Tuxtla, erupted explosively in 1793. Due to its volcanological importance, it has been the subject of several geological studies, none of which focused on its crustal structure. Moreover, because the seismicity level in the area is relatively low, no broadband seismometers of Mexico's National Seismological Service are currently installed in the area. In this paper we present the results of the analyses of 24 teleseismic events occurring between 2004 and 2008 recorded in two broadband stations deployed around San Martín volcano. The aim of this study was to determine the depth to the Moho, any major intracrustal interface in the area, and a velocity model by means of receiver function analysis. The results show that the crustal thickness in the area varies between roughly 28 and 34 km. The receiver functions at one station suggest a second interface at a depth between 10 and 14 km. This interface is probably the contact between an upper sedimentary layer and the transitional crust found elsewhere in the margins of the Gulf of Mexico. The determination of the crustal thickness in the TVF is of importance to characterize the area and as a framework to pursue further studies of this volcanic field.

  15. A distinct source and differentiation history for Kolumbo submarine volcano, Santorini volcanic field, Aegean arc.

    Science.gov (United States)

    Klaver, Martijn; Carey, Steven; Nomikou, Paraskevi; Smet, Ingrid; Godelitsas, Athanasios; Vroon, Pieter

    2016-08-01

    This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely-operated vehicle that were analyzed for major element, trace element and Sr-Nd-Hf-Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave-bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52-60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low (206)Pb/(204)Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field.

  16. Volcanic Hazard Education through Virtual Field studies of Vesuvius and Laki Volcanoes

    Science.gov (United States)

    Carey, S.; Sigurdsson, H.

    2011-12-01

    Volcanic eruptions pose significant hazards to human populations and have the potential to cause significant economic impacts as shown by the recent ash-producing eruptions in Iceland. Demonstrating both the local and global impact of eruptions is important for developing an appreciation of the scale of hazards associated with volcanic activity. In order to address this need, Web-based virtual field exercises at Vesuvius volcano in Italy and Laki volcano in Iceland have been developed as curriculum enhancements for undergraduate geology classes. The exercises are built upon previous research by the authors dealing with the 79 AD explosive eruption of Vesuvius and the 1783 lava flow eruption of Laki. Quicktime virtual reality images (QTVR), video clips, user-controlled Flash animations and interactive measurement tools are used to allow students to explore archeological and geological sites, collect field data in an electronic field notebook, and construct hypotheses about the impacts of the eruptions on the local and global environment. The QTVR images provide 360o views of key sites where students can observe volcanic deposits and formations in the context of a defined field area. Video sequences from recent explosive and effusive eruptions of Carribean and Hawaiian volcanoes are used to illustrate specific styles of eruptive activity, such as ash fallout, pyroclastic flows and surges, lava flows and their effects on the surrounding environment. The exercises use an inquiry-based approach to build critical relationships between volcanic processes and the deposits that they produce in the geologic record. A primary objective of the exercises is to simulate the role of a field volcanologist who collects information from the field and reconstructs the sequence of eruptive processes based on specific features of the deposits. Testing of the Vesuvius and Laki exercises in undergraduate classes from a broad spectrum of educational institutions shows a preference for the

  17. Investigation of the Galatian volcanic complex in the northern central Turkey using potential field data

    Science.gov (United States)

    Bilim, Funda

    2011-03-01

    The Galatia volcanic complex (GVC) is one of two important volcanic complexes located in central Anatolia, Turkey. The study of potential field data can yield useful information about the subsurface magnetisation and density distribution. In this paper, a study of the thermal structural setting of the GVC using the analysis and interpretation of aeromagnetic data is presented. Volcanic rocks are the main cause of the magnetic anomalies that occur in the study region. A Curie-point-depth (CPD) map was constructed using the azimuthally averaged power spectrum of aeromagnetic anomaly data that was reduced-to-the-pole transformed (RTP); the map shows high geothermal potential for the GVC. The Curie point depths vary from about 6.74 km to 16.9 km and are consistent with the results of previous geothermal studies. The GVC exhibits low CPD and high heat-flow values (>100 mW m -2). The CPD suggested that deep-seated magnetised sources continue downward up to 10 km (inside the upper crust). A horizontal gradient analytic signal (HGAS) map exhibits the images and locations of deep-seated magnetised sources. In addition, the CPD and average Moho depth (33 km, calculated from gravity anomaly data) are used to determine the presence of magnetic and non-magnetic crust in two cross sections taken from the GVC. The results presented should shed considerable light on some aspects of geothermal exploration in the GVC.

  18. Paleogene volcanism in Central Afghanistan: Possible far-field effect of the India-Eurasia collision

    Science.gov (United States)

    Motuza, Gediminas; Šliaupa, Saulius

    2017-10-01

    A volcanic-sedimentary succession of Paleogene age is exposed in isolated patches at the southern margin of the Tajik block in the Ghor province of Central Afghanistan. The volcanic rocks range from basalts and andesites to dacites, including adakites. They are intercalated with sedimentary rocks deposited in shallow marine environments, dated biostratigraphically as Paleocene-Eocene. This age corresponds to the age of the Asyābēd andesites located in the western Ghor province estimated by the 40Ar/39Ar method as 54 Ma. The magmatism post-dates the Cimmerian collision between the Tajik block (including the Band-e-Bayan block) and the Farah Rod block located to the south. While the investigated volcanic rocks apparently bear geochemical signatures typical to an active continental margin environment, it is presumed that the magmatism was related to rifting processes most likely initiated by far-field tectonics caused by the terminal collision of the Indian plate with Eurasia (Najman et al., 2017). This event led to the dextral movement of the Farah Rod block, particularly along Hari Rod (Herat) fault system, resulting in the development of a transtensional regime in the proximal southern margin of the Tajik block and giving rise to a rift basin where marine sediments were interbedded with pillow lavas intruded by sheeted dyke series.

  19. 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.

  20. The Maars of the Tuxtla Volcanic Field: the Example of 'laguna Pizatal'

    Science.gov (United States)

    Espindola, J.; Zamora-Camacho, A.; Hernandez-Cardona, A.; Alvarez del Castillo, E.; Godinez, M.

    2013-12-01

    Los Tuxtlas Volcanic Field (TVF), also known as Los Tuxtlas massif, is a structure of volcanic rocks rising conspicuously in the south-central part of the coastal plains of eastern Mexico. The TVF seems related to the upper cretaceous magmatism of the NW part of the Gulf's margin (e.g. San Carlos and Sierra de Tamaulipas alkaline complexes) rather than to the nearby Mexican Volcanic Belt. The volcanism in this field began in late Miocene and has continued in historical times, The TVF is composed of 4 large volcanoes (San Martin Tuxtla, San Martin Pajapan, Santa Marta, Cerro El Vigia), at least 365 volcanic cones and 43 maars. In this poster we present the distribution of the maars, their size and depths. These maars span from a few hundred km to almost 1 km in average diameter, and a few meters to several tens of meters in depth; most of them filled with lakes. As an example on the nature of these structures we present our results of the ongoing study of 'Laguna Pizatal or Pisatal' (18° 33'N, 95° 16.4'W, 428 masl) located some 3 km from the village of Reforma, on the western side of San Martin Tuxtla volcano. Laguna Pisatal is a maar some 500 meters in radius and a depth about 40 meters from the surrounding ground level. It is covered by a lake 200 m2 in extent fed by a spring discharging on its western side. We examined a succession of 15 layers on the margins of the maar, these layers are blast deposits of different sizes interbedded by surge deposits. Most of the contacts between layers are irregular; which suggests scouring during deposition of the upper beds. This in turn suggests that the layers were deposited in a rapid series of explosions, which mixed juvenile material with fragments of the preexisting bedrock. We were unable to find the extent of these deposits since the surrounding areas are nowadays sugar cane plantations and the lake has overspilled in several occassions.

  1. Raton-Clayton Volcanic Field magmatism in the context of the Jemez Lineament

    Science.gov (United States)

    Schrader, C. M.; Pontbriand, A.

    2013-12-01

    The Raton-Clayton Volcanic Field (RCVF) was active from 9 Ma to approximately 50 Ka and stretches from Raton, New Mexico in the west to Clayton, New Mexico in the east. The field occurs in the Great Plains at the northeastern end of the Jemez Lineament, a major crustal feature and focus of volcanism that extends southwest to the Colorado Plateau in Arizona and encompasses five other major volcanic fields. Jemez Lineament magmatism is temporally related to Rio Grande Rift magmatism, though it extends NE and SW from the rift itself, and it has been suggested that it represents an ancient crustal suture that serves as a conduit for magmatism occurring beneath the larger region of north and central New Mexico (Magnani et al., 2004, GEOL SOC AM BULL, 116:7/8, pp. 1-6). This study extends our work into the RCVF from prior and ongoing work in the Mount Taylor Volcanic Field, where we identified different mantle sources with varying degrees of subduction alteration and we determined some of the crustal processes that contribute to the diversity of magma chemistry and eruptive styles there (e.g., AGU Fall Meeting, abst. #V43D-2884 and #V43D-2883). In the RCVF, we are analyzing multiple phases by electron microprobe and plagioclase phenocrysts and glomerocrysts by LA-ICPMS for Sr isotopes and trace elements. We are undertaking this investigation with the following goals: (1) to evaluate previous magma mixing and crustal assimilation models for Sierra Grande andesites (Zhu, 1995, unpublished Ph.D. dissertation, Rice University; Hesse, 1999, unpublished M.S. thesis, Northern Arizona University); (2) to evaluate subduction-modified mantle as the source for RCVF basanites (specifically those at Little Grande); and (3) to assess the possible role of deep crustal cumulates in buffering transitional basalts. In the larger context, these data will be used to evaluate the varying degree of subduction-modification and the effect of crustal thickness on magmatism along the Jemez

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

    Science.gov (United States)

    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.

  3. Geology and radiocarbon ages of Tláloc, Tlacotenco, Cuauhtzin, Hijo del Cuauhtzin, Teuhtli, and Ocusacayo monogenetic volcanoes in the central part of the Sierra Chichinautzin, México

    Science.gov (United States)

    Siebe, Claus; Arana-Salinas, Lilia; Abrams, Michael

    2005-03-01

    Tláloc, Tlacotenco, Cuauhtzin, Hijo del Cuauhtzin, Teuhtli, and Ocusacayo monogenetic volcanoes located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were studied to further refine attendant volcanic hazards in this heavily populated region. Based on fieldwork and Landsat imagery interpretation, a geologic map was produced, morphometric parameters characterizing the cones and lava flows were determined, and the areal extent and volumes of erupted products were estimated. The longest lava flow was produced by Tlacotenco and reached 9.5 km from its source; total areas covered by lava flows from each eruption range between 12.8 km 2 (Tlacotenco) and 54.4 km 2 (Tláloc); and total erupted volumes range between 0.26 and 1.36 km 3 per volcano. Radiocarbon measurements of a paleosol underneath an ash layer from the Tláloc scoria cone yielded an age of 6200 years BP, while charcoal found within block-and-ash flow and lahar deposits from Cuauhtzin dome yielded ages of 7360 and 8225 years BP, respectively. The Tlacotenco dacite lava flow overlies Popocatépetl's Tutti Frutti Plinian pumice fall deposit dated at 14,000 years BP and is therefore younger than this prominent stratigraphic marker. On the other hand, Teuhtli and Hijo del Cuauhtzin scoria cones and the Ocusacayo andesite lava flows are overlain by the Tutti Frutti and therefore older than 14,000 years BP. These new dates together with other published dates for scoria cones in the SCVF imply that the previously determined recurrence interval during the Holocene for monogenetic eruptions in the SCVF of <1700 years [Siebe, C., Rodríguez-Lara, V., Schaaf, P., Abrams, M., 2004a. Radiocarbon ages of Holocene Pelado, Guespalapa, and Chichinautzin scoria cones, south of Mexico_City: implications for archaeology and future hazards. Bull. Volcanol. 66, 203-225.] needs to be corrected to <1250 years. This means that the time of quiescence since the last eruption of the SCVF

  4. 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

  5. Volcano-tectonics of the Al Haruj Volcanic Province, Central Libya

    Science.gov (United States)

    Elshaafi, Abdelsalam; Gudmundsson, Agust

    2016-10-01

    The Al Haruj intra-continental Volcanic Province (AHVP), located at the south-western margin of the Sirt Basin, hosts the most extensive and recent volcanic activity in Libya - which is considered typical for plate interiors. From north to south the AHVP is divided into two subprovinces, namely Al Haruj al Aswad and Al Haruj al Abiyad. The total area of the AHVP is around 42,000 km2. Despite the great size of the AHVP, its volcano-tectonic evolution and activity have received very little attention and are poorly documented and understood. Here we present new field data, and analytical and numerical results, on the volcano-tectonics of the AHVP. The length/thickness ratio of 47 dykes and volcanic fissures were measured to estimate magmatic overpressure at the time of eruption. The average dyke (length/thickness) ratio of 421 indicates magmatic overpressures during the associate fissure eruptions of 8-19 MPa (depending on host-rock elastic properties). Spatial distributions of 432 monogenetic eruptions sites/points (lava shields, pyroclastic cones) in the AHVP reveal two main clusters, one in the south and another in the north. Aligned eruptive vents show the dominating strike of volcanic fissures/feeder-dykes as WNW-ESE to NW-SE, coinciding with the orientation of one of main fracture/fault zones. Numerical modelling and field observations suggest that some feeder-dykes may have used steeply dipping normal-fault zones as part of their paths to the surface.

  6. 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.

  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. Preliminary isostatic gravity map of the Sonoma volcanic field and vicinity, Sonoma and Napa Counties, California

    Science.gov (United States)

    Langenheim, V.E.; Roberts, C.W.; McCabe, C.A.; McPhee, D.K.; Tilden, J.E.; Jachens, R.C.

    2006-01-01

    This isostatic residual gravity map is part of a three-dimensional mapping effort focused on the subsurface distribution of rocks of the Sonoma volcanic field in Napa and Sonoma counties, northern California. This map will serve as a basis for modeling the shapes of basins beneath the Santa Rosa Plain and Napa and Sonoma Valleys, and for determining the location and geometry of faults within the area. Local spatial variations in the Earth's gravity field (after accounting for variations caused by elevation, terrain, and deep crustal structure explained below) reflect the distribution of densities in the mid to upper crust. Densities often can be related to rock type, and abrupt spatial changes in density commonly mark lithologic boundaries. High-density basement rocks exposed within the northern San Francisco Bay area include those of the Mesozoic Franciscan Complex and Great Valley Sequence present in the mountainous areas of the quadrangle. Alluvial sediment and Tertiary sedimentary rocks are characterized by low densities. However, with increasing depth of burial and age, the densities of these rocks may become indistinguishable from those of basement rocks. Tertiary volcanic rocks are characterized by a wide range in densities, but, on average, are less dense than the Mesozoic basement rocks. Isostatic residual gravity values within the map area range from about -41 mGal over San Pablo Bay to about 11 mGal near Greeg Mountain 10 km east of St. Helena. Steep linear gravity gradients are coincident with the traces of several Quaternary strike-slip faults, most notably along the West Napa fault bounding the west side of Napa Valley, the projection of the Hayward fault in San Pablo Bay, the Maacama Fault, and the Rodgers Creek fault in the vicinity of Santa Rosa. These gradients result from juxtaposing dense basement rocks against thick Tertiary volcanic and sedimentary rocks.

  9. 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 %.

  10. Short-time electrical effects during volcanic eruption: Experiments and field measurements

    Science.gov (United States)

    Büttner, Ralf; Zimanowski, Bernd; Röder, Helmut

    2000-02-01

    Laboratory experiments on the fragmentation and expansion of magmatic melt have been performed using remelted volcanic rock at magmatic temperatures as magma simulant. A specially designed dc amplifier in combination with high speed data recording was used to detect short-time electrostatic field effects related to the fragmentation and expansion history of the experimental system, as documented by simultaneous force and pressure recording, as well as by high-speed cinematography. It was found that (1) the voltage-time ratio of electrostatic field gradients (100 to 104 V/s) reflects different physical mechanisms of fragmentation and expansion and (2) the maximum voltage measured in 1 m distance (-0.1 to -180 V) can be correlated with the intensity of the respective processes. Based on these experimental results, a field method was developed and tested at Stromboli volcano in Italy. A 0.8 m rod antenna was used to detect the dc voltage against local ground (i.e., the electrostatic field gradient), at a distance of 60 to 260 m from the respective vent. Upwind position of the detection site was chosen to prevent interference caused by contact of charged ash particles with the antenna. A standard 8 Hz geophone was used to detect the accompanying seismicity. Three types of volcanic activity occurred during the surveillance operation; two of these could be clearly related to specific electrical and seismical signals. A typical delay time was found between the electrical and the seismical signal, corresponding to the seismic velocity within the crater deposits. Using a simple first-order electrostatic model, the field measurements were recalibrated to the laboratory scale. Comparison of field and laboratory data at first approximation revealed striking similarities, thus encouraging the further development of this technique for real-time surveillance operation at active volcanoes.

  11. 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.

  12. Magnetic links among lava flows, tuffs and the underground plumbing system in a monogenetic volcano, derived from magnetics and paleomagnetic studies

    Science.gov (United States)

    Urrutia-Fucugauchi, Jaime; Trigo-Huesca, Alfonso; Pérez-Cruz, Ligia

    2012-12-01

    A combined study using magnetics and paleomagnetism of the Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a 'magnetic' link between the lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that the lava and ash tuff carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  13. 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

  14. 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).

  15. SIR-A radar images of sand dunes and volcanic fields

    Science.gov (United States)

    Blom, R.; Elachi, C.; Evans, D.

    1982-01-01

    Shuttle Imaging Radar (SIR-A) synthetic aperture radar images of sand dunes and volcanic fields are presented and preliminary interpretation provided. The SIR-A images are compared with Seasat images where available. Unvegetated sand dunes are recorded as black areas on SIR-A images due to the specular reflection away from the sensor at the SIR-A incidence angle. Even a very small amount of vegetation provides some backscatter, however. Interdune areas frequently contain rough lag gravels which outline the dunes. Lava flows are typically very rough surfaces which are bright areas on radar images. Cinder cones are smooth and therefore black on the image unless they have a blocky crater rim at the SIR-A incidence angle. Ash dunes and ash fields are smooth and imaged as dark areas.

  16. Origin and formation of neck in a basin landform: Examples from the Camargo volcanic field, Chihuahua (México)

    Science.gov (United States)

    Aranda-Gómez, José Jorge; Housh, Todd B.; Luhr, James F.; Noyola-Medrano, Cristina; Rojas-Beltrán, Marco Antonio

    2010-11-01

    The term "neck in a basin" (NIB) landform is proposed for volcanic structures characterized by nearly circular to elliptical open basins, located near the headwater of small streams or drainages, which contain small volcanic necks and/or erosion remnants of one (or more) cinder cones. NIB landforms are typically 400-1000 m in diameter and 30-100 m deep and are invariably surrounded by steep walls cut into one or more basaltic lava flows. NIB landforms lack evidence for a primary volcanogenic origin through either collapse or youthful eruptive activity. In the Pliocene portion (4 - 2 Ma) of the Plio-Quaternary Camargo volcanic field of Chihuahua (México), they are relatively numerous and are best developed at the margins of a gently sloping (3-5°) basaltic lava plateau and near major fault scarps. Mature NIB landforms have ring-like circular drainage patterns and central elevations marked by small volcanic necks and associated radial dikes intruded into basaltic scoria-fall and /or agglutinate deposits. We interpret NIB landforms to be erosional in origin. They develop where a cinder cone is surrounded by one or more sheet-like lava flows from one or more separate subsequent vents. Once eruptive activity ceases at the younger volcano(es), fluvial erosion gradually produces a ring-like drainage pattern along the contact between the lava and the older cinder cone. As a response to a marked contrast in resistance to erosion between lava flows and unconsolidated or poorly lithified pyroclastic deposits, the older cinder cone is preferentially eroded. In this manner, a ring-shaped, steep sided erosional basin, preformed by the scoria cone, is produced; eventually fluvial erosion exposes the central neck and dikes. The volume, relief, and age of the volcanic field are key factors in the formation and preservation of a NIB landform. They form in volcanic fields where lava emissions are sufficiently vigorous to engulf earlier cinder cones. Relief and associated high rates

  17. Geology of the Mid-Miocene Rooster Comb Caldera and Lake Owyhee Volcanic Field, eastern Oregon: Silicic volcanism associated with Grande Ronde flood basalt

    Science.gov (United States)

    Benson, Thomas R.; Mahood, Gail A.

    2016-01-01

    The Lake Owyhee Volcanic Field (LOVF) of eastern Oregon consists of rhyolitic caldera centers and lava fields contemporaneous with and spatially related to Mid-Miocene Columbia River flood basalt volcanism. Previous studies delineated two calderas in the southeastern part of LOVF near Owyhee Reservoir, the result of eruptions of two ignimbrites, the Tuff of Leslie Gulch and the Tuff of Spring Creek. Our new interpretation is that these two map units are differentially altered parts of a single ignimbrite produced in a major phreatomagmatic eruption at ~ 15.8 Ma. Areas previously mapped as Tuff of Spring Creek are locations where the ignimbrite contains abundant clinoptilolite ± mordenite, which made it susceptible to erosion. The resistant intracaldera Tuff of Leslie Gulch has an alteration assemblage of albite ± quartz, indicative of low-temperature hydrothermal alteration. Our new mapping of caldera lake sediments and pre- and post-caldera rhyolitic lavas and intrusions that are chemically similar to intracaldera Tuff of Leslie Gulch point to a single ~ 20 × 25 km caldera, which we name the Rooster Comb Caldera. Erosion of the resurgently uplifted southern half of the caldera created dramatic exposures of intracaldera Tuff of Leslie Gulch cut by post-caldera rhyolite dikes and intrusions that are the deeper-level equivalents of lava domes and flows that erupted into the caldera lake preserved in exposures to the northeast. The Rooster Comb Caldera has features in common with more southerly Mid-Miocene calderas of the McDermitt Volcanic Field and High Rock Caldera Complex, including formation in a basinal setting shortly after flood basalt eruptions ceased in the region, and forming on eruption of peralkaline ignimbrite. The volcanism at Rooster Comb Caldera postdates the main activity at McDermitt and High Rock, but, like it, begins ~ 300 ky after flood basalt volcanism begins in the area, and while flood basalts don't erupt through the silicic focus, are

  18. 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

  19. 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.

  20. Geology and K-Ar dating of the Tuxtla Volcanic Field, Veracruz, Mexico

    Science.gov (United States)

    Nelson, Stephen A.; Gonzalez-Caver, Erika

    1992-12-01

    The Tuxtla Volcanic Field (TVF) is located on the coast of the Gulf of Mexico in the southern part of the state of Veracruz, Mexico. Volcanism began about 7 my ago, in the Late Miocene, and continued to recent times with historical eruptions in ad 1664 and 1793. The oldest rocks occur as highly eroded remnants of lava flows in the area surrounding the historically active cone of San Martín Tuxtla. Between about 3 and 1 my ago, four large composite volcanoes were built in the eastern part of the area. Rocks from these structures are hydrothermally altered and covered with lateritic soils, and their northern slopes show extensive erosional dissection that has widened preexisting craters to form erosional calderas. The eastern volcanoes are composed of alkali basalts, hawaiites, mugearites, and benmoreites, with less common calc-alkaline basaltic andesites and andesites. In the western part of the area, San Martín Tuxtla Volcano and its over 250 satellite cinder cones and maars produced about 120 km3 of lava over the last 0.8 my. A ridge of flank cinder cones blocked drainage to the north to form Laguna Catemaco. Lavas erupted from San Martín and its flank vents are restricted to compositions between basanite and alkali basalt. The alignment of major volcanoes and flank vents along a N55°W trend suggests an extensional stress field in the crust with a minimum compressional stress orientation of N35° E. In total, about 800 km3 of lava has been erupted in the TVF in the last 7 my. This gives a magma output rate of about 0.1 km3/1000 year, a value smaller than most composite cones, but similar to cinder cone fields that occur in central Mexico. Individual eruptions over the last 5000 years had volumes on the order of 0.1km3, with average recurrence intervals of 600 years. The alkaline compositions of the TVF lavas contrast markedly with the calc-alkaline compositions erupted in the subduction-related Mexican Volcanic Belt to the west, leading previous workers to

  1. 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.

  2. 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

  3. Petrology of the alkaline rocks of the Macau Volcanic Field, NE Brazil

    Science.gov (United States)

    Ngonge, Emmanuel Donald; de Hollanda, Maria Helena Bezerra Maia; Pimentel, Márcio Martins; de Oliveira, Diógenes Custódio

    2016-12-01

    The Macau Volcanic Field (MVF) in the Borborema Province, NE Brazil, contains multiple centres of volcanic activity of Early to Late Cenozoic ages. We present element and Sr-Nd-Pb isotope geochemical data for four of the few most prominent basalt types of this volcanic field: Serrote Preto-type, Serra Aguda-type, Pico do Cabugi-type and Serra Preta-type, in order to assess their magmatic history from source to crystallization and the evolution of the mantle beneath the Borborema Province. The basalts are basically sodic nephelinitic-basanitic-alkali olivine basalts enriched in LILE and in Nb-Ta. The Serra Preta, Cabugi and Serra Aguda types demonstrate compositions close to primitive characteristics with 10% < MgO < 15 wt.% and 200 ppm < Ni < 500 ppm, and experienced limited fractional crystallization of olivine-clinopyroxene-plagioclase-oxides with negligible wall-rock assimilation. Rb/Sr and Ba/Rb constraints support the generation of SiO2-undersaturated magmas from mantle melting of amphibole-bearing peridotites with minor phlogopite. The source for the basanites and alkali basalts is estimated to be a garnet-bearing domain around the lithosphere-asthenosphere boundary (80-93 km deep), while the nephelinites are derived from the adiabatic asthenosphere at 105 km with temperatures of 1480 °C. Their incompatible trace element patterns and Sr-Nd-Pb isotopic compositions are similar to FOZO and EM-type OIB magmas. From the comparison of data with those of the Ceará-Mirim dyke swarm we propose that there is a ubiquitous FOZO reservoir in the SCLM beneath the Borborema Province. This FOZO signature characterized the upwelling asthenosphere during the lithospheric extension and thinning at the opening of the Equatorial Atlantic and is clearly represented in the Mesozoic olivine tholeiites of Ceará-Mirim. The upwelled asthenosphere cooled as a rigid SCLM since the Cretaceous and has preserved its FOZO signature evident in the Macau Cenozoic basalts. The EM signatures

  4. 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.

  5. Structural analysis and thermal remote sensing of the Los Humeros Volcanic Complex: Implications for volcano structure and geothermal exploration

    Science.gov (United States)

    Norini, G.; Groppelli, G.; Sulpizio, R.; Carrasco-Núñez, G.; Dávila-Harris, P.; Pellicioli, C.; Zucca, F.; De Franco, R.

    2015-08-01

    The Los Humeros Volcanic Complex (LHVC) is an important geothermal target in the Trans-Mexican Volcanic Belt. Understanding the structure of the LHVC and its influence on the occurrence of thermal anomalies and hydrothermal fluids is important to get insights into the interplay between the volcano-tectonic setting and the characteristics of the geothermal resources in the area. In this study, we present a structural analysis of the LHVC, focused on Quaternary tectonic and volcano-tectonic features, including the areal distribution of monogenetic volcanic centers. Morphostructural analysis and structural field mapping revealed the geometry, kinematics and dynamics of the structural features in the study area. Also, thermal infrared remote sensing analysis has been applied to the LHVC for the first time, to map the main endogenous thermal anomalies. These data are integrated with newly proposed Unconformity Bounded Stratigraphic Units, to evaluate the implications for the structural behavior of the caldera complex and geothermal field. The LHVC is characterized by a multistage formation, with at least two major episodes of caldera collapse: Los Humeros Caldera (460 ka) and Los Potreros Caldera (100 ka). The study suggests that the geometry of the first collapse recalls a trap-door structure and impinges on a thick volcanic succession (10.5-1.55 Ma), now hosting the geothermal reservoir. The main ring-faults of the two calderas are buried and sealed by the widespread post-calderas volcanic products, and for this reason they probably do not have enough permeability to be the main conveyers of the hydrothermal fluid circulation. An active, previously unrecognized fault system of volcano-tectonic origin has been identified inside the Los Potreros Caldera. This fault system is the main geothermal target, probably originated by active resurgence of the caldera floor. The active fault system defines three distinct structural sectors in the caldera floor, where the

  6. Combining Geological and Geophysical Data in Volcanic Hazard Estimation for Dominica, Lesser Antilles

    Science.gov (United States)

    George, O.; Latchman, J. L.; Connor, C.; Malservisi, R.; Connor, L.

    2014-12-01

    Risk posed by volcanic eruptions are generally quantified in a few ways; in the short term geophysical data such as seismic activity or ground deformation are used to assess the state of volcanic unrest while statistical approaches such as spatial density estimates are used for long term hazard assessment. Spatial density estimates have been used in a number of monogenetic volcanic fields for hazard map generation and utilize the age, location and volumes of previous eruptions to calculate the probability of a new event occurring at a given location within this field. In a previously unpublished study, spatial density estimates of the Lesser Antilles volcanic arc showed the island of Dominica to have the highest likelihood of future vent formation. In this current study, this technique was used in combination with relocated seismic events occurring beneath Dominica within the last ~ 20 years as well as InSAR images of ground deformation to generate a hazard map which not only takes into consideration the past events but also the current state of unrest. Here, geophysical data serve as a weighting factor in the estimates with those centers showing more vigorous activity receiving stronger favorability in the assessment for future activity. In addition to this weighting, the bandwidth utilized in the 2D-radially symmetric kernel density function was optimized using the SAMSE method so as to find the value which best minimizes the error in the estimate. The end results of this study are dynamic volcanic hazards maps which will be readily updatable as changes in volcanic unrest occurs within the system.

  7. The VORISA Project: An Integrated Approach to Assessing Volcanic Hazard and Risk in the Kingdom of Saudi Arabia

    Science.gov (United States)

    Lindsay, J. M.; Moufti, R.

    2013-12-01

    The Kingdom of Saudi Arabia has numerous large monogenetic volcanic fields, known locally as 'Harrat'. The largest of these, Harrat Rahat, produced a basaltic fissure eruption in 1256 AD with lava flows travelling within 20 km of the Islamic holy city Al-Madinah. With over 900 visible basaltic and trachytic vents and periodic seismic swarms indicating stalled eruptions, an understanding of the risk of future eruptions in this volcanic field is vital. To systematically address this need we developed the Volcanic Risk in Saudi Arabia (VORISA) Project, a 3-year, multi-disciplinary international research collaboration that integrates geological, geophysical, hazard and risk studies. Detailed mapping and geochemical studies are being combined with new and existing age determinations to determine the style and sequence of events during past basaltic and trachytic eruptions. Data from gravity and magnetotelluric surveys are being integrated with microearthquake data from an 8-station borehole seismic research array to geophysically characterise the structure and nature of the crust, and thus constrain possible physical controls on magma propagation. All available data are being synthesised in hazard models to determine patterns in eruption frequency, magnitude, and style of past activity, as well as the probable location and style of a future event. Combined with geospatial vulnerability data, these hazard models, which include a reconstruction of the 1256 AD eruption, enable us to calculate and communicate volcanic risk to the city of Al-Madinah.

  8. Field Courses for Volcanic Hazards Mapping at Parícutinand Jorullo Volcanoes (Mexico)

    Science.gov (United States)

    Victoria Morales, A.; Delgado Granados, H.; Roberge, J.; Farraz Montes, I. A.; Linares López, C.

    2007-05-01

    During the last decades, Mexico has suffered several geologic phenomena-related disasters. The eruption of El Chichón volcano in 1982 killed >2000 people and left a large number of homeless populations and severe economic damages. The best way to avoid and mitigate disasters and their effects is by making geologic hazards maps. In volcanic areas these maps should show in a simplified fashion, but based on the largest geologic background possible, the probable (or likely) distribution in time and space of the products related to a variety of volcanic processes and events, according to likely magnitude scenarios documented on actual events at a particular volcano or a different one with similar features to the volcano used for calibration and weighing geologic background. Construction of hazards maps requires compilation and acquisition of a large amount of geological data in order to obtain the physical parameters needed to calibrate and perform controlled simulation of volcanic events under different magnitude-scenarios in order to establish forecasts. These forecasts are needed by the authorities to plan human settlements, infrastructure, and economic development. The problem is that needs are overwhelmingly faster than the adjustments of university programs to include courses. At the Earth Science División of the Faculty of Engineering at the Universidad Nacional Autónoma de México, the students have a good background that permits to learn the methodologies for hazards map construction but no courses on hazards evaluations. Therefore, under the support of the university's Program to Support Innovation and Improvement of Teaching (PAPIME, Programa de Apoyo para la Innovación y Mejoramiento de la Enseñanza) a series of field-based intensive courses allow the Earth science students to learn what kind of data to acquire, how to record, and process in order to carry out hazards evaluations. This training ends with hazards maps that can be used immediately by the

  9. Eruptive History of the Rhyolitic Guangoche Volcano, Los Azufres Volcanic Field, Central Mexico

    Science.gov (United States)

    Rangel Granados, E.; Arce, J. L.; Macias, J. L.; Layer, P. W.

    2014-12-01

    Guangoche is a rhyolitic and polygenetic volcano with a maximum elevation of 2,760 meters above sea level. It is situated to the southwest of the Los Azufres Volcanic Field (LAVF), in the central sector of the Trans-Mexican Volcanic Belt. Guangoche volcano is the youngest volcano described within the LAVF. It shows a horseshoe shaped crater open to the south, with a central lava dome. Its eruptive history during late Pleistocene has been intense with six explosive eruptions that consists of: 1) A southwards sector collapse of the volcano that generated a debris avalanche deposit with megablocks of heterogenous composition; 2) A plinian-type eruption that generated a pumice fall deposit and pyroclastic density currents by column collapse at 30.6 ka; 3) A plinian-type eruption "White Pumice Sequence" (29 ka) that developed a 22-km-high eruptive column, with a MDR of 7.0 x 107 kg/s (vol. = 0.53 km3); 4) A dome-destruction event, "Agua Blanca Pyroclastic Sequence" at 26.7 ka, that deposited a block-and-ash flow deposit; 5) A subplinian-plinian type eruption "Ochre Pyroclastic Sequence" (<26 ka) with an important initial phreatomagmatic phase, that generated pyroclastic density currents and pumice fallouts. The subplinian-plinian event generated a 16-km-high eruptive column, with a MDR of 1.9 x 107 kg/s, and magma volume of 0.38 km3; 6) The eruptive history ended with a subplinian eruption (<<26 ka), that generated a multilayered fall deposit, that developed a 11-km-high eruptive column, with a MDR of 2.9 x 106 kg/s and a magma volume of 0.26 km3. Volcanic activity at Guangoche volcano has been intense and future activity should not be discarded. Unfortunately, the last two events have not been dated yet. Guangoche rhyolitic magma is characterized by low-Ba contents suggesting crystal mush extraction for their genesis.

  10. 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

  11. Neogene-Quaternary Volcanic forms in the Carpathian-Pannonian Region: a review

    Science.gov (United States)

    Lexa, Jaroslav; Seghedi, Ioan; Németh, Karoly; Szakács, Alexandru; Koneĉny, Vlastimil; Pécskay, Zoltan; Fülöp, Alexandrina; Kovacs, Marinel

    2010-09-01

    Neogene to Quaternary volcanic/magmatic activity in the Carpathian-Pannonian Region (CPR) occurred between 21 and 0.1 Ma with a distinct migration in time from west to east. It shows a diverse compositional variation in response to a complex interplay of subduction with rollback, back-arc extension, collision, slab break-off, delamination, strike-slip tectonics and microplate rotations, as well as in response to further evolution of magmas in the crustal environment by processes of differentiation, crustal contamination, anatexis and magma mixing. Since most of the primary volcanic forms have been affected by erosion, especially in areas of post-volcanic uplift, based on the level of erosion we distinguish: (1) areas eroded to the basement level, where paleovolcanic reconstruction is not possible; (2) deeply eroded volcanic forms with secondary morphology and possible paleovolcanic reconstruction; (3) eroded volcanic forms with remnants of original morphology preserved; and (4) the least eroded volcanic forms with original morphology quite well preserved. The large variety of volcanic forms present in the area can be grouped in a) monogenetic volcanoes and b) polygenetic volcanoes and their subsurface/intrusive counterparts that belong to various rock series found in the CPR such as calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) and alkalic types including K-alkalic, shoshonitic, ultrapotassic and Na-alkalic. The following volcanic/subvolcanic forms have been identified: (i) domes, shield volcanoes, effusive cones, pyroclastic cones, stratovolcanoes and calderas with associated intrusive bodies for intermediate and basic calclkaline volcanism; (ii) domes, calderas and ignimbrite/ash-flow fields for felsic calc-alkaline volcanism and (iii) dome flows, shield volcanoes, maars, tuffcone/tuff-rings, scoria-cones with or without related lava flow/field and their erosional or subsurface forms (necks/ plugs, dykes, shallow intrusions

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. Lithosphere versus asthenosphere mantle sources at the Big Pine Volcanic Field, California

    Science.gov (United States)

    Gazel, Esteban; Plank, Terry; Forsyth, Donald W.; Bendersky, Claire; Lee, Cin-Ty A.; Hauri, Erik H.

    2012-06-01

    Here we report the first measurements of the H2O content of magmas and mantle xenoliths from the Big Pine Volcanic Field (BPVF), California, in order to constrain the melting process in the mantle, and the role of asthenospheric and lithospheric sources in this westernmost region of the Basin and Range Province, western USA. Melt inclusions trapped in primitive olivines (Fo82-90) record surprisingly high H2O contents (1.5 to 3.0 wt.%), while lithospheric mantle xenoliths record low H2O concentrations (whole rock 500 ka, to cooler (˜1220°C) and shallower melting (˜1 GPa) conditions in younger magmas. The estimated depth of melting correlates strongly with some trace element ratios in the magmas (e.g., Ce/Pb, Ba/La), with deeper melts having values closer to upper mantle asthenosphere values, and shallower melts having values more typical of subduction zone magmas. This geochemical stratification is consistent with seismic observations of a shallow lithosphere-asthenosphere boundary (˜55 km depth). Combined trace element and cryoscopic melting models yield self-consistent estimates for the degree of melting (˜5%) and source H2O concentration (˜1000 ppm). We suggest two possible geodynamic models to explain small-scale convection necessary for magma generation. The first is related to the Isabella seismic anomaly, either a remnant of the Farallon Plate or foundered lithosphere. The second scenario is related to slow extension of the lithosphere.

  18. Impact of reduced near-field entrainment of overpressured volcanic jets on plume development

    Science.gov (United States)

    Saffaraval, Farhad; Solovitz, Stephen A.; Ogden, Darcy E.; Mastin, Larry G.

    2012-01-01

    Volcanic plumes are often studied using one-dimensional analytical models, which use an empirical entrainment ratio to close the equations. Although this ratio is typically treated as constant, its value near the vent is significantly reduced due to flow development and overpressured conditions. To improve the accuracy of these models, a series of experiments was performed using particle image velocimetry, a high-accuracy, full-field velocity measurement technique. Experiments considered a high-speed jet with Reynolds numbers up to 467,000 and exit pressures up to 2.93 times atmospheric. Exit gas densities were also varied from 0.18 to 1.4 times that of air. The measured velocity was integrated to determine entrainment directly. For jets with exit pressures near atmospheric, entrainment was approximately 30% less than the fully developed level at 20 diameters from the exit. At pressures nearly three times that of the atmosphere, entrainment was 60% less. These results were introduced into Plumeria, a one-dimensional plume model, to examine the impact of reduced entrainment. The maximum column height was only slightly modified, but the critical radius for collapse was significantly reduced, decreasing by nearly a factor of two at moderate eruptive pressures.

  19. 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.

  20. Field-trip guide to Columbia River flood basalts, associated rhyolites, and diverse post-plume volcanism in eastern Oregon

    Science.gov (United States)

    Ferns, Mark L.; Streck, Martin J.; McClaughry, Jason D.

    2017-08-09

    The Miocene Columbia River Basalt Group (CRBG) is the youngest and best preserved continental flood basalt province on Earth, linked in space and time with a compositionally diverse succession of volcanic rocks that partially record the apparent emergence and passage of the Yellowstone plume head through eastern Oregon during the late Cenozoic. This compositionally diverse suite of volcanic rocks are considered part of the La Grande-Owyhee eruptive axis (LOEA), an approximately 300-kilometer-long (185 mile), north-northwest-trending, middle Miocene to Pliocene volcanic belt located along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the (1) flood basalt-dominated Columbia Plateau on the north, (2) bimodal basalt-rhyolite vent complexes of the Owyhee Plateau on the south, (3) bimodal basalt-rhyolite and time-transgressive rhyolitic volcanic fields of the Snake River Plain-Yellowstone Plateau, and (4) the High Lava Plains of central Oregon.This field-trip guide describes a 4-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the Columbia River Basalt Group and coeval and compositionally diverse volcanic rocks associated with the early “Yellowstone track” and High Lava Plains in eastern Oregon. Beginning in Portland, the Day 1 log traverses the Columbia River gorge eastward to Baker City, focusing on prominent outcrops that reveal a distal succession of laterally extensive, large-volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Basalt formations of the CRBG. These “great flows” are typical of the well-studied flood basalt-dominated Columbia Plateau, where interbedded silicic and calc-alkaline lavas are conspicuously absent. The latter part of Day 1 will highlight exposures of middle to late Miocene silicic ash-flow tuffs, rhyolite domes, and

  1. 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.

  2. Stress Field and Dike Propagation within a Partially Submerged Volcanic Edifice

    Science.gov (United States)

    Tait, S.; Taisne, B.; Manga, M.; Pasquet, E.; Limare, A.; Bhat, H.

    2013-12-01

    In order to better understand dike propagation within and flank collapse on volcanic islands, we performed a set of analogue laboratory experiments. We created conic edifices of gelatin and measured their deformation under their own weight whilst we varied the level to which they were partially submerged. In most experiments the lower part of the edifice was submerged in water while the upper part was surrounded by air, but in some cases oil was used as the fluid surrounding the upper part of the edifice in order to change density differences. The gelatin was typically made of a sugar (or glycerol) solution so that it was approximately 10-30% denser than water, and its strength was varied by using different gelatin concentrations. The strain field was visualized from the birefringence pattern created by placing the gelatin between sheets of polarising film with the directions crossed. One first order feature of the strain field is an approximately elliptical shaped extensional region, centered below the summit and at approximately sea-level. The second feature is a region of strong sub-horizontal shear in the lower most part of the edifice, close to the lower, rigid no-slip boundary. We also observed the behaviour of dikes injected into the base of the edifice from below: these dikes were filled with water or salt solution so that they had variable amounts of positive buoyancy with respect to the edifice. If all, or a very large fraction, of the edifice was submerged, the dike typically propagated vertically and erupted at the summit. If the edifice was only partially submerged, however, the dikes typically switched from dominantly vertical to horizontal propagation and erupted on the flanks of the edifice, very often at sea level.

  3. Relation of compositions of deep fluids in geothermal activity of Pleistocene-Holocene volcanic fields of Lesser Caucasus

    Science.gov (United States)

    Meliksetian, Khachatur; Lavrushin, Vassily; Shahinyan, Hrach; Aidarkozhina, Altin; Navasardyan, Gevorg; Ermakov, Alexander; Zakaryan, Shushan; Prasolov, Edward; Manucharyan, Davit; Gyulnazaryan, Shushan; Grigoryan, Edmond

    2017-04-01

    It is widely accepted, that geothermal activity in the conductive heat flow processes, such as volcanism and hydrothermal activity, is manifestation of the thermal mass transfer process in the Earth's crust, where geothermal and geochemical processes are closely connected. Therefore, geochemistry and isotope compositions of thermal mineral waters within and on periphery of volcanic clusters may represent key indicators for better understanding of geothermal activity in geodynamically active zones. Geochemical features of heat and mass transport in hydrothermal systems related to active volcanic and fault systems in continental collision related orogenic elevated plateaus such as Anatolian-Armenian-Iranian highlands are still poorly understood. In this contribution we attempt to fill these gaps in our knowledge of relations of geochemical and geothermal processes in collision zones. We present new data on chemical compositions, trace element geochemistry of thermal waters of Lesser Caucasus, (Armenia) as well as isotope analysis of free gases such as {}3He/{}4He, {}40Ar/{}36Ar, δ{}13?(CO{}2), nitrogen δ{}15N(N{}2) and oxygen and hydrogen isotopes in water phases (δD, δ{}18O). To reveal some specific features of formation of fluid systems related to thermal activity in the areas of collision related active volcanism and active geodynamics a complex geochemical (SiO{}2, K-Na, Na-Li, Li-Mg) and isotope geothermometers (δ{}18O(CaCO{}3) - δ{}18O(H{}2O)) were applied. The distribution of δ{}13?(??{}2) values in free gases of mineral waters of Armenia demonstrates that gases related to Quaternary volcanic fields are characterized by relatively light δ{}13?(CO{}2) values close to mantle derived gases, while on periphery of volcanic systems relatively heavy values of δ{}13?(CO{}2) indicate strong influence of metamorphic and sedimentary derived carbon dioxide. Distribution of nitrogen isotopes δ{}15N(N{}2) demonstrate an inverse correlation with δ{}13?(CO{}2

  4. The interplay between tectonics and volcanism: a key to unravel the nature of Andean geothermal systems

    Science.gov (United States)

    Cembrano, J. M.

    2013-05-01

    Field mapping combined with seismic data document the interplay between tectonics and volcanism in the Andes. In the Central Volcanic Zone (CVZ) of northern Chile (22-24°S), Pleistocene east-west shortening and a thick crust (50-70 km) are associated with major composite dacitic-andesitic volcanoes and a few monogenetic basaltic eruptive centers. CVZ stratovolcanoes are devoided of flank vents; clusters of minor eruptive centers are uncommon. Composite volcanoes and minor eruptive centers are coeval with a NS-striking system of reverse faults and fault-propagation folds. Although dextral strike-slip crustal seismicity is recorded between 18 and 21°S, evidence for long-term, margin-parallel strike-slip deformation is absent. In contrast, volcanoes of the Southern Volcanic Zone (SVZ), between 38 and 46°S are built on a much thinner crust (30-40 km) during intra-arc dextral transpression. Crustal seismicity shows dextral strike-slip focal mechanisms. There, a wide variety of volcanic forms and compositions coexist along the same volcanic arc. Volcanoes range from single monogenetic cones lying on master faults to major composite volcanoes organized into either NE- or NW-trending chains, oblique to the continental margin. Flank vents and elongated clusters of minor eruptive centers are common. Compositions range from primitive basalts at minor eruptive centers, to highly evolved magmas at mature stratovolcanoes. I hypothesize that the kinematics of fault-fracture networks under which magma is transported through the crust is one fundamental factor controlling the wide variety of volcanic forms, volcanic alignment patterns and rock compositions along a single volcanic arc. As a first approximation, a thicker crust favors magma differentiation processes whereas a thinner crust prevents it. Likewise, whereas bulk intra-arc compression (vertical σ3) enhances longer residence times of magmas in the CVZ, strike-slip deformation (horizontal σ3) in SVZ provides

  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. Geologic Map of Part of the Uinkaret Volcanic Field, Mohave County, Northwestern Arizona

    Science.gov (United States)

    Billingsley, George H.; Hamblin, W. Kenneth; Wellmeyer, Jessica L.; Dudash, Stephanie L.

    2001-01-01

    The geologic map of part of the Uinkaret Volcanic Field is one product of a cooperative project between the U.S. Geological Survey, the National Park Service, and the Bureau of Land Management to provide geologic information about this part of the Grand Canyon-Parashant Canyon National Monument of Arizona. The Uinkaret Volcanic Field is a unique part of western Grand Canyon where volcanic rocks have preserved the geomorphic development of the landscape. Most of the Grand Canyon, and parts of adjacent plateaus have already been mapped. This map completes one of the remaining areas where uniform quality geologic mapping was needed. A few dozen volcanoes and lava flows within the Grand Canyon are not included in the map area, but their geologic significance to Grand Canyon development is documented by Hamblin (1994) and mapped by Billingsley and Huntoon (1983) and Wenrich and others (1997). The geologic information in this report may be useful to resource managers of the Bureau of Land Management for range management, biological, archaeological, and flood control programs. The map area lies within the Shivwits, Uinkaret, and Kanab Plateaus, which are subplateaus of the Colorado Plateaus physiographic province (Billingsley and others, 1997), and is part of the Arizona Strip north of the Colorado River. The nearest settlement is Colorado City, Arizona, about 58 km (36 mi) north of the map area (fig. 1). Elevations range from about 2,447 m (8,029 ft) at Mount Trumbull, in the northwest quarter of the map area, to about 732 m (2,400 ft) in Cove Canyon, in the southeast quarter of the map area. Vehicle access is via the Toroweap and Mount Trumbull dirt roads (fig. 1). Unimproved dirt roads traverse other parts of the area except in designated wilderness. Extra fuel, two spare tires, and extra food and water are highly recommended for travelers in this remote area. The U.S. Bureau of Land Management, Arizona Strip Field Office, St. George, Utah manages most of the area. In

  7. 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.

  8. 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

  9. 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

  10. 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.

  11. 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 Pb...

  12. Combining long- and short-term probabilistic volcanic 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

    2012-04-01

    By using BET_VH, we propose a quantitative probabilistic hazard assessment for base surge impact in Auckland, New Zealand. Base surges resulting from phreatomagmatic eruptions are among the most dangerous phenomena likely to be associated with the initial phase of a future eruption in the Auckland Volcanic Field. The assessment is done both in the long-term and in a specific short-term case study, i.e. the simulated pre-eruptive unrest episode during Exercise Ruaumoko, a national civil defence exercise. The most important factors to account for are the uncertainties in the vent location (expected for a volcanic field) and in the run-out distance of base surges. Here, we propose a statistical model of base surge run-out distance based on deposits from past eruptions in Auckland and in analogous volcanoes. We then combine our hazard assessment with an analysis of the costs and benefits of evacuating people (on a 1 × 1-km cell grid). In addition to stressing the practical importance of a cost-benefit analysis in creating a bridge between volcanologists and decision makers, our study highlights some important points. First, in the Exercise Ruaumoko application, the evacuation call seems to be required as soon as the unrest phase is clear; additionally, the evacuation area is much larger than what is recommended in the current contingency plan. Secondly, the evacuation area changes in size with time, due to a reduction in the uncertainty in the vent location and increase in the probability of eruption. It is the tradeoff between these two factors that dictates which cells must be evacuated, and when, thus determining the ultimate size and shape of the area to be evacuated.

  13. 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

  14. 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

  15. Paleomagnetic Study of a Miocene Deformation in a Region Close to the Camargo Volcanic Field, Chihuahua, Mexico

    Science.gov (United States)

    Wogau-Chong, K.; Bohnel, H.; Aranda Gomez, J.

    2009-05-01

    The Sierra the Aguachile is a Miocene volcanic sequence located in the SE of Chihuahua State NW of the Camargo volcanic field and belongs to the Agua Mayo Group, which unconformably overlays Mesozoic calcareous units. The Sierra de Aguachile sequence defines a structure that may be interpreted as a plunging fold, which could be the result of a reactivation of the San Marcos Fault. This major fault is well known more to the east but may extend into the study area where it would be covered by the younger volcanic sequences; its main activity has been reported to be during the the Neocomian with reactivation phases in the Paleogene and Miocene. To test if the observed structure is the result of a tectonic deformation that happened after the emplacement of the volcanic sequence, a paleomagnetic study was carried out. A total of 14 sites were sampled from different parts of the structure, all in the capping ignimbrite layers. Site mean directions were determined using AF demagnetization. The fold test was applied to analyze if the remanence was acquired in situ or before the proposed folding. Precision parameters k before and after application of the tectonic corrections are 25.38 and 31.43, respectively. This indicates that the Sierra de Aguachile indeed was folded after emplacement of the ignimbrites, which restricts the age of the corresponding tectonic event to be younger than 31.3 +/- 0.7 Ma. Due to the gentle folding though, the difference in precision parameters is not significant at the 95% probability level.

  16. The Origin of ‘OIB-Type’ Magmas in the Central Mexican Volcanic Belt

    Science.gov (United States)

    Straub, S. M.; Gomez-Tuena, A.; Zellmer, G. F.; Cai, Y.; Stuart, F. M.; Espinasa-Perena, R.; Langmuir, C. H.; Goldstein, S. L.

    2009-12-01

    Many models consider a primary mantle origin of high-Mg andesites, but the subarc mantle of arcs producing high-Mg andesites remains poorly defined. In the monogenetic volcanic field of Sierra Chichinautzin (central Mexican Volcanic Belt), high-Mg andesites are spatially and temporally intimately associated with mildly alkaline basalts and basaltic andesites, variously referred to as ‘OIB-type’, ‘intraplate’ or ‘high-Nb arc basalts’ (Wallace and Carmichael 1999, Contrib Mineral Petrol; Schaaf et al. 2005, J Petrol). ‘OIB-type’ magmas and high-Mg andesites have erupted within a few hundreds to thousands of years from vents only a few kilometers apart, or may even have erupted jointly from single vents. It has been suggested that these ‘OIB-type’ magmas were melts from subarc mantle yet unmodified by subduction fluxes while high-Mg andesites were produced from mantle sources residual to the ‘OIB-type’ magmas. In order to test this model, we investigated ‘OIB-type’ magmas erupting from three young and closely spaced monogenetic volcanoes in the Sierra Chichinautzin Volcanic Field (V. Chichinautzin, V. Suchiooc, Cuescomates vent). The primitive olivine-phyric alkaline basalts and basaltic andesites (SiO2 = 49.6-53.5 wt%; Mg#=62-68 and MgO= 6.5-8.3 wt%) have high Ni (97-179 ppm), Nb (18-34 ppm), Nb/La (0.9-1.2) and 3He/4He ratios (R/Ra = 7.3-8.0) typical of near-primary mantle magmas unaffected by the passage through the ~47 km thick continental crust. However, all ‘OIB-type’ magmas contain high-Ni olivines that are indicative of siliceous slab melts infiltrating and reacting with peridotite mantle (Straub et al., 2008, G-cubed; Wang & Gaetani 2008, Contrib Mineral Petrol). Significant slab additions to the mantle source of the ‘OIB-type’ magmas are further confirmed by Sr-Nd-Pb systematics. We suggest that ‘OIB-type’ arc magmas reflect fertilization of a pre-existing MORB-type subarc mantle by enriched, little fractionated slab

  17. 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

  18. Quaternary bimodal volcanism in the Niğde Volcanic Complex (Cappadocia, central Anatolia, Turkey): age, petrogenesis and geodynamic implications

    Science.gov (United States)

    Aydin, Faruk; Schmitt, Axel K.; Siebel, Wolfgang; Sönmez, Mustafa; Ersoy, Yalçın; Lermi, Abdurrahman; Dirik, Kadir; Duncan, Robert

    2014-11-01

    The late Neogene to Quaternary Cappadocian Volcanic Province (CVP) in central Anatolia is one of the most impressive volcanic fields of Turkey because of its extent and spectacular erosionally sculptured landscape. The late Neogene evolution of the CVP started with the eruption of extensive andesitic-dacitic lavas and ignimbrites with minor basaltic lavas. This stage was followed by Quaternary bimodal volcanism. Here, we present geochemical, isotopic (Sr-Nd-Pb and δ18O isotopes) and geochronological (U-Pb zircon and Ar-Ar amphibole and whole-rock ages) data for bimodal volcanic rocks of the Niğde Volcanic Complex (NVC) in the western part of the CVP to determine mantle melting dynamics and magmatic processes within the overlying continental crust during the Quaternary. Geochronological data suggest that the bimodal volcanic activity in the study area occurred between ca. 1.1 and ca. 0.2 Ma (Pleistocene) and comprises (1) mafic lavas consisting of basalts, trachybasalts, basaltic andesites and scoria lapilli fallout deposits with mainly basaltic composition, (2) felsic lavas consisting of mostly rhyolites and pumice lapilli fall-out and surge deposits with dacitic to rhyolitic composition. The most mafic sample is basalt from a monogenetic cone, which is characterized by 87Sr/86Sr = 0.7038, 143Nd/144Nd = 0.5128, 206Pb/204Pb = 18.80, 207Pb/204Pb = 15.60 and 208Pb/204Pb = 38.68, suggesting a moderately depleted signature of the mantle source. Felsic volcanic rocks define a narrow range of 143Nd/144Nd isotope ratios (0.5126-0.5128) and are homogeneous in Pb isotope composition (206Pb/204Pb = 18.84-18.87, 207Pb/204Pb = 15.64-15.67 and 208Pb/204Pb = 38.93-38.99). 87Sr/86Sr isotopic compositions of mafic (0.7038-0.7053) and felsic (0.7040-0.7052) samples are similar, reflecting a common mantle source. The felsic rocks have relatively low zircon δ18O values (5.6 ± 0.6 ‰) overlapping mantle values (5.3 ± 0.3 %), consistent with an origin by fractional crystallization

  19. Compositional and Textural Analysis of Maar-Diatreme Volcanic Deposits at Hopi Buttes Volcanic Field (AZ) Using GigaPan Panoramic and Thermal Infrared Imagery

    Science.gov (United States)

    Lee, R.; Graettinger, A. H.; Weinell, M.; Hughes, C. G.

    2016-12-01

    Basaltic maar-diatreme volcanoes are produced when rising magma interacts with groundwater and produces a maar crater at the ground surface. This crater is underlain by a diatreme, a downward-tapering conical structure filled with a mixture of fragments of intruded magma, fractured host rock, and clasts recycled through repeated discrete subsurface explosions. The debris of the diatreme records the mixing processes caused by subsurface explosions and is the source for ejected material that forms maar tephra rings. Determining the variable depths and lateral locations of these explosions and how energy is dissipated in the subsurface is critical to understanding how maar-diatreme eruptions progress. The Hopi Buttes Volcanic Field (HBVF) in the Navajo Nation, Arizona, USA, contains several diatremes and incised tephra rings with heterolithic clasts 10 mm - 10 m in size, and are well-exposed near-vertical to vertical outcrops. Our ability to measure the length scales and distribution of textures produced by subsurface explosions in these diatremes is limited by the physical accessibility of the exposures, due to both the verticality of the outcrops and the cultural sensitivity of the site. Quantifying the number and locations of explosions is dependent on our ability to investigate the full diatreme outcrop, and not just what can be accessed through traditional field observations. We present a novel field and computer-based technique for both quantitatively and qualitatively characterizing the composition and texture of maar-diatreme deposits in vertical outcrops. This technique uses a combination of field-collected multispectral thermal infrared (TIR) image data and visible wavelength GigaPan imagery to characterize the compositional and textural variations over a whole outcrop. To increase the spatial and spectral resolution of the TIR data, a super-resolution technique will be applied. The technique provides a simple and efficient method to augment the study of the

  20. 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.

  1. 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

  2. Geochemical constraints on the relationship between the Miocene-Pliocene volcanism and tectonics in the Palaoco and Fortunoso volcanic fields, Mendoza Region, Argentina: New insights from 40Ar/39Ar dating, Sr-Nd-Pb isotopes and trace elements

    Science.gov (United States)

    Dyhr, Charlotte T.; Holm, Paul M.; Llambías, Eduardo J.

    2013-10-01

    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 Pb isotopes of the Palaoco and nearby Río Grande rocks require a strong arc-like component in the mantle that is absent or weak in both Early Miocene (Fortunoso Group) and Pleistocene alkaline lavas (Llancanelo Group) erupted in the same area. We evaluate the relative roles of varying mantle source compositions and crustal contamination in the generation of geochemically very different lavas from the Palaoco, Fortunoso and Río Grande volcanic fields, north of the Payún Matrú Volcano. The source for the Early Miocene Fortunoso(I) basalts was a OIB-type mantle devoid of subduction zone input. This type of OIB-like volcanic activity terminated due to a change from an extensional to a compressional tectonic regime. Towards the end of the Miocene renewed alkaline volcanism at Fortunoso (II) display a transition to arc-type incompatible element enrichment. Shortly after the calc-alkaline Palaoco volcanism started with a very strong geochemical arc-signature including Ba/La ≈ 60 and La/Nb = 2-3. After a quiesence of 1 Ma the major part of the voluminous Late Palaoco basalts were erupted around 7.5 Ma over a few hundred ka. These are less enriched in Ba and Sr and have compositions like many Holocene rocks of the Southern Volcanic Zone. Isotopically the Fortunoso I and Palaoco rocks are distinct. Regional volcanism of the Charilehue, Huincán I and II mostly has a moderate arc-type enrichment indicating incipient arc developments. However, Palaoco and La Brea at (c. 35°S) show full geochemical arc-signature, and we infer that a frontal arc was established. The subsequent development in the Palaoco-Río Grande area encompasses renewed late Pliocene calc-alkaline low volume

  3. Isotopically (δ13C and δ18O) heavy volcanic plumes from Central Andean volcanoes: a field study

    Science.gov (United States)

    Schipper, C. Ian; Moussallam, Yves; Curtis, Aaron; Peters, Nial; Barnie, Talfan; Bani, Philipson; Jost, H. J.; Hamilton, Doug; Aiuppa, Alessandro; Tamburello, Giancarlo; Giudice, Gaetano

    2017-08-01

    Stable isotopes of carbon and oxygen in volcanic gases are key tracers of volatile transfer between Earth's interior and atmosphere. Although important, these data are available for few volcanoes because they have traditionally been difficult to obtain and are usually measured on gas samples collected from fumaroles. We present new field measurements of bulk plume composition and stable isotopes (δ13CCO2 and δ18OH2O+CO2) carried out at three northern Chilean volcanoes using MultiGAS and isotope ratio infrared spectroscopy. Carbon and oxygen in magmatic gas plumes of Lastarria and Isluga volcanoes have δ13C in CO2 of +0.76‰ to +0.77‰ (VPDB), similar to slab carbonate; and δ18O in the H2O + CO2 system ranging from +12.2‰ to +20.7‰ (VSMOW), suggesting significant contributions from altered slab pore water and carbonate. The hydrothermal plume at Tacora has lower δ13CCO2 of -3.2‰ and δ18OH2O+CO2 of +7.0‰, reflecting various scrubbing, kinetic fractionation, and contamination processes. We show the isotopic characterization of volcanic gases in the field to be a practical complement to traditional sampling methods, with the potential to remove sampling bias that is a risk when only a few samples from accessible fumaroles are used to characterize a given volcano's volatile output. Our results indicate that there is a previously unrecognized, relatively heavy isotopic signature to bulk volcanic gas plumes in the Central Andes, which can be attributed to a strong influence from components of the subducting slab, but may also reflect some local crustal contamination. The techniques we describe open new avenues for quantifying the roles that subduction zones and arc volcanoes play in the global carbon cycle.

  4. 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

  5. Revised stratigraphy and eruption rates of Ceboruco stratovolcano and surrounding monogenetic vents (Nayarit, Mexico) from historical documents and new radiocarbon dates

    Science.gov (United States)

    Sieron, Katrin; Siebe, Claus

    2008-09-01

    erupted from Ceboruco's crater on average every 143 years during the last 1000 years. In contrast, a monogenetic eruption forming either a scoria cone or a dome has occurred in the area surrounding Ceboruco on average every 1000 years during the Holocene. During the period between AD 1000 and AD 1500 Ceboruco displayed an elevated activity experiencing a rhyodacite plinian eruption (3-4 km 3 DRE) followed by the emplacement of six andesitic/dacitic lava flows also with a total volume of 3-4 km 3. All these figures indicate that the Ceboruco volcanic region is one of the most active areas in the entire Trans-Mexican Volcanic Belt. Consequently, production of a detailed volcanic hazard map and implementation of other preventive measures aimed at reducing potential losses in case of renewed volcanic activity should be mandatory.

  6. 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 (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.

  7. 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.

  8. Crustal deformation and magmatic processes at Laguna del Maule volcanic field (Chile): Geodetic measurements and numerical models

    Science.gov (United States)

    Le Mével, Hélène

    The Laguna del Maule (LdM) volcanic field in Chile is an exceptional example of postglacial rhyolitic volcanism in the Southern Volcanic Zone of the Andes. Since 2007, LdM has experienced an unrest episode characterized by high rates of deformation measured by interferometric analysis of synthetic aperture radar (SAR) images acquired between 2007 and 2016, and data from the Global Positioning System (GPS) recorded since 2012 at five stations. The inflating region includes most of the 16--km-by--14--km ring of rhyolitic domes and coulees. The fastest-moving GPS station (MAU2) has a velocity vector of [[special character omited]72 +/- 4, 19 +/- 1, 194 +/- 3] mm/yr between 2012 and 2016 for the eastward, northward, and upward components, respectively. First, we model the InSAR observations assuming a rectangular dislocation in a half space with uniform elastic properties. The best time function for modeling the InSAR data set is a double exponential model with rates increasing from 2007 through 2010 and decreasing slowly since 2011. Modeling of historical uplift at Yellowstone, Long Valley, and Three Sisters volcanic fields suggests a common temporal evolution of vertical displacement rates. We hypothesize that magma intruding into an existing silicic magma reservoir is driving the surface deformation and present a new dynamic model to describe this process. A Newtonian fluid characterized by its viscosity, density, and pressure flows through a vertical conduit, intruding into a reservoir embedded in an elastic domain and leading to time-dependent surface deformation. Using a grid-search optimization, we minimize the misfit to the InSAR displacement data by varying the three parameters governing the analytical solution: the characteristic timescale tauP for magma propagation, the injection pressure, and the inflection time when the acceleration switches from positive to negative. For a spheroid with semi-major axis a = 6200 m, semi-minor axis c = 100 m, located at a

  9. 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.

  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 nd epsilon;Nd near-15 is predominant in anhydrous, two-pyroxene dacites; hydrous rhyolites, rhyodacites, and dacites with epsilon;Nd below-10 are dominated by a second component; hydrous rocks 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. LiDAR observations of an Earth magmatic plumbing system as an analog for Venus and Mars distributed volcanism

    Science.gov (United States)

    Richardson, Jacob; Connor, Charles; Malservisi, Rocco; Bleacher, Jacob; Connor, Laura

    2014-05-01

    Clusters of tens to thousands of small volcanoes (diameters generally system of these clusters can constrain magma ascent processes as well as the regional magma production budget and heat flux beneath each cluster. Unfortunately, directly observing the plumbing systems of volcano clusters on Mars and Venus eludes our current geologic abilities. Because erosion exposes such systems at the Earth's surface, a better understanding of magmatic processes and migration can be achieved via field analysis. The terrestrial plumbing system of an eroded volcanic field may be a valuable planetary analog for Venus and Mars clusters. The magmatic plumbing system of a Pliocene-aged monogenetic volcanic field, emplaced at 0.8 km depth, is currently exposed as a sill and dike swarm in the San Rafael Desert of Central Utah, USA. The mafic bodies in this region intruded into Mesozoic sedimentary units and now make up the most erosion resistant units as sills, dikes, and plug-like conduits. Light Detection and Ranging (LiDAR) can identify volcanic units (sills, dikes, and conduits) at high resolution, both geomorphologically and with near infrared return intensity values. Two Terrestrial LiDAR Surveys and an Airborne LiDAR Survey have been carried out over the San Rafael volcanic swarm, producing a three dimensional point cloud over approximately 36 sq. km. From the point clouds of these surveys, 1-meter DEMs are produced and volcanic intrusions have been mapped. Here we present reconstructions of the volcanic instrusions of the San Rafael Swarm. We create this reconstruction by extrapolating mapped intrustions from the LiDAR surveys into a 3D space around the current surface. We compare the estimated intrusive volume to the estimated conduit density and estimates of extrusive volume at volcano clusters of similar density. The extrapolated reconstruction and conduit mapping provide a first-order estimate of the final intrustive/extrusive volume ratio for the now eroded volcanic field

  12. Volcanic hazard assessment at Deception Island

    Science.gov (United States)

    Bartolini, S.; Sobradelo, R.; Geyer, A.; Martí, J.

    2012-04-01

    Deception Island is the most active volcano of the South Shetland Islands (Antarctica) with more than twenty eruptions recognised over the past two centuries. The island was formed on the expansion axis of the Central Bransfield Strait and its evolution consists of constructive and destructive phases. A first a shield phase was followed by the construction of a central edifice and formation of the caldera with a final monogenetic volcanism along the caldera rim. The post-caldera magma composition varies from andesitic-basaltic to dacitic. The activity is characterised by monogenetic eruptions of low volume and short duration. The eruptions show a variable degree of explosivity, strombolian or phreatomagmatic, with a VEI 2 to 4, which have generated a wide variety of pyroclastic deposits and lavas. It is remarkable how many phases of phreatic explosive eruptions are associated to the emission of large ballistic blocks. Tephra record preserved in the glacier ice of Livingston Island or in marine sediments show the explosive power of the phreatomagmatic phases and the wide dispersal of its finest products in a great variety of directions of the prevailing winds. Also it is important to highlight the presence of different lahar deposits associated with some of these eruptions. In this contribution we present the guidelines to conduct a short-term and long-term volcanic hazard assessment at Deception Island. We apply probabilistic methods to estimate the susceptibility, statistical techniques to determine the eruption recurrence and eruptive scenario, and reproduce the effects of historical eruptions too. Volcanic hazard maps and scenarios are obtained using a Voris-based model tool (Felpeto et al., 2007) in a free Geographical Information System (GIS), a Quantum GIS.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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

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

    Indian Academy of Sciences (India)

    Ahmed Madani

    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 red-dish 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 Field-Spec spectral profiles and the processed ASTER data for discriminating different olivine basalt groups exposed at the study area.

  4. 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.

  5. Exploration of the Rotokawa geothermal field, Taupo volcanic zone, New Zealand

    Energy Technology Data Exchange (ETDEWEB)

    Browne, P.R.L. (Univ. of Auckland (New Zealand))

    1988-11-10

    The Rotokawa geothermal field is located 7 km east of Wairakei, New Zealand, and has been investigated for its sulphur resources and power potential over the past 50 years. Exploration of the field has slow and mostly unsystematic. The depths of the drill holes are less than 50 m until 1964. Since 1965 the exploration has been carried out systematically. Three, one and four exploration wells were drilled in 1965-66, 1977, and 1984-86 respectively. Finding Jurassic greywackes and argillites at a depth of 2200 m below a thick (ca. 900 m)sequence of two pyroxene andesite lava flows had an important significance, because the Jurassic rocks are the basement rocks for the North Island. The Rotokawa geothermal field represents an important resource with an assessed potential of 49 MW (proven), 100 MW (probable) and 200 MW (possible), though these figures are considered to be probably optimistic. Further exploratory drilling is needed. The main development problems at this stage are: (1) encountering good subsurface permeability, (2) identifying and combating corrosive CO{sub 2}-rich fluids, (3) determining the most favorable reinjection conditions; this is a problem, ironically enhanced by the hot temperature and the consequently high silica contents of the thermal fluids, (4) establishing an acceptable development plan for the field which accommodates the requirements of both the sulphur mining interests, the power producers, and especially the Ngati Tahu maori owners of the land. 24 refs., 2 figs., 2 tabs.

  6. 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..

  7. 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.

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

    Science.gov (United States)

    Eppler, Dean B.

    2015-01-01

    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.

  9. Crater lakes of the Pali Aike Volcanic Field as key sites for paleoclimatic and paleoecological reconstructions in southern Patagonia, Argentina

    Science.gov (United States)

    Zolitschka, Bernd; Schäbitz, Frank; Lücke, Andreas; Corbella, Hugo; Ercolano, Bettina; Fey, Michael; Haberzettl, Torsten; Janssen, Stephanie; Maidana, Nora; Mayr, Christoph; Ohlendorf, Christian; Oliva, Gabriel; Paez, Marta M.; Schleser, Gerhard H.; Soto, Julio; Tiberi, Pedro; Wille, Michael

    2006-07-01

    Sedimentary records from crater lakes are of major scientific interest because they provide continuous high-resolution climatic and environmental archives. From a limnogeological survey of crater lakes performed in the Pali Aike Volcanic Field (52°S, southeastern Patagonia, Santa Cruz, Argentina), two deep crater lakes have been recognized: Laguna Potrok Aike (100 m water depth) and Laguna Azul (56 m water depth). Physico-chemical analyses of these closed lake systems demonstrate that Laguna Azul has a dimictic and thermally stratified freshwater body, whereas Laguna Potrok Aike is a subsaline polymictic lake. Both have an oxygen-rich water column from top to bottom. Laguna Potrok Aike in particular is enriched in Na, P, and Cl. The morphometry suggests that Laguna Azul is of Holocene age, whereas the potential sediment infill of Laguna Potrok Aike may comprise 250 m to a mid-Pleistocene age (770 ka). Several aerial and subaquatic lake level terraces at Laguna Potrok Aike point to lake level fluctuations triggered by prior hydrological changes. Although fine-grained sediments of both lakes are not varied, they may eventually provide a detailed terrestrial record of past environmental and climatic variations for this southern mid-latitude region.

  10. 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

  11. 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

  12. 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

  13. 40Ar/39Ar Ages for the Sentinel-Arlington Volcanic Field, Southwestern Arizona

    Science.gov (United States)

    Cave, S. R.; Greeley, R.; Champion, D. E.; Turrin, B. D.

    2007-12-01

    The Sentinel Plains lava field and proximate small (history as well as the timing of the ancient Gila River interactions that led to the development of the Painted Rock transverse drainage. The absolute timing was determined in order datermine causal relationships with local tectonism. The SAVF basal contact is ~30 m above the Holocene surface where exposed along the current river channel; and the lavas show similar amounts mantling by aeolian dust, development of pedogenic calcium carbonate, and subsequent incision by radial ephemeral drainages. Relative timing of eruptive events was determined by stratigraphic and embayment relationships. Continuity of distal flows exposed in cross-sections to their source vents could be established using field work, and confirmed using geomagnetic secular variation and geochemical analyses. Edifices generally corresponded to discreet geomagnetic inclination, declination, and paleointensity values. Older eruptive events exhibited normal polarity, while stratigraphically younger events exhibited reversed polarity. Most lavas were alkali olivine basalt with a range of unnormalized SiO2 weight percentages ranging from 47.16-51.48. Geochronology using 40Ar/39Ar method revealed an age of 1.94 +/- 0.85 Ma for Painted Rock Low Shield (New Mexico Geochronology Research Laboratory), 1.64 +/- 0.14 Ma for Theba Low Shield (Rutgers University) and 1.24 +/- 0.040 Ma for Wild Horse Low Shield (Rutgers University). Some ages were precise enough to correspond to the Matuyama reversed polarity epoch, with SAVF initiation possibly within the Olduvai normal polarity event. These dates represent an overall improvement in precision and accuracy over previous dates (values corresponding to 6.20 Ma to 1.28 Ma) collected in the late 1970s and early 1980s using K-Ar technique. The 40Ar/39Ar ages correspond to expected magnetic polarities and stratigraphic sequences.

  14. Comparing and Reconciling Traditional Field and Photogeologic Mapping Techniques: Lessons from the San Francisco Volcanic Field, Arizona

    Science.gov (United States)

    Skinner, J. A., Jr.; Eppler, D. B.; Bleacher, J. E.; Evans, C. A.; Feng, W.; Gruener, J.; Hurwitz, D. M.; Janoiko, B.; Whitson, P.

    2014-01-01

    Cartographic products and - specifically - geologic maps provide critical assistance for establishing physical and temporal frameworks of planetary surfaces. The technical methods that result in the creation of geologic maps vary depending on how observations are made as well as the overall intent of the final products [1-3]. These methods tend to follow a common linear work flow, including the identification and delineation of spatially and temporally discrete materials (units), the documentation of their primary (emplacement) and secondary (erosional) characteristics, analysis of the relative and absolute age relationships between these materials, and the collation of observations and interpretations into an objective map product. The "objectivity" of a map is critical cross comparison with overlapping maps and topical studies as well as its relevance to scientific posterity. However, the "accuracy" and "correctness" of a geologic map is very subject to debate. This can be evidenced by comparison of existing geologic maps at various scales, particularly those compiled through field- and remote-based mapped efforts. Our study focuses on comparing the fidelity of (1) "Apollo-style" geologic investigations, where typically non-geologist crew members follow static traverse routes established through pre-mission planning, and (2) "traditional" field-based investigations, where geologists are given free rein to observe without preplanned routes. This abstract summarizes the regional geology wherein our study was conducted, presents the geologic map created from traditional field mapping techniques, and offers basic insights into how geologic maps created from different tactics can be reconciled in support of exploratory missions. Additional abstracts [4-6] from this study discuss various exploration and science results of these efforts.

  15. Hydrothermal alteration in oceanic ridge volcanics: A detailed study at the Galapagos Fossil Hydrothermal Field

    Science.gov (United States)

    Ridley, W.I.; Perfit, M.R.; Josnasson, I.R.; Smith, M.F.

    1994-01-01

    The Galapagos Fossil Hydrothermal Field is composed of altered oceanic crust and extinct hydrothermal vents within the eastern Galapagos Rift between 85??49???W and 85??55???W. The discharge zone of the hydrothermal system is revealed along scarps, thus providing an opportunity to examine the uppermost mineralized, and highly altered interior parts of the crust. Altered rocks collected in situ by the submersible ALVIN show complex concentric alteration zones. Microsamples of individual zones have been analysed for major/minor, trace elements, and strontium isotopes in order to describe the complex compositional details of the hydrothermal alteration. Interlayered chlorite-smectite and chlorite with disequilibrium compositions dominate the secondary mineralogy as replacement phases of primary glass and acicular pyroxene. Phenocrysts and matrix grains of plagioclase are unaffected during alteration. Using a modification of the Gresens' equation we demonstrate that the trivalent rare earth elements (REEs) are relatively immobile, and calculate degrees of enrichment and depletion in other elements. Strontium isotopic ratios increase as Sr concentrations decrease from least-altered cores to most-altered rims and cross-cutting veins in individual samples, and can be modeled by open system behaviour under low fluid-rock ratio (metal sulfides beneath the seafloor is probably a result of fluid mixing and cooling. If, as suggested here, the discharge zone alteration occurred under relatively low fluid-rock ratios, then this shallow region must play an important role in determining the exit composition of vent fluids in marine hydrothermal systems. ?? 1994.

  16. Time lag between deformation and seismicity along monogenetic volcanic unrest periods: The case of El Hierro Island (Canary Islands)

    Science.gov (United States)

    Lamolda, Héctor; Felpeto, Alicia; Bethencourt, Abelardo

    2017-07-01

    Between 2011 and 2014 there were at least seven episodes of magmatic intrusion in El Hierro Island, but only the first one led to a submarine eruption in 2011-2012. In order to study the relationship between GPS deformation and seismicity during these episodes, we compare the temporal evolution of the deformation with the cumulative seismic energy released. In some of the episodes both deformation and seismicity evolve in a very similar way, but in others a time lag appears between them, in which the deformation precedes the seismicity. Furthermore, a linear correlation between decimal logarithm of intruded magma volume and decimal logarithm of total seismic energy released along the different episodes has been observed. Therefore, if a future magmatic intrusion in El Hierro Island follows this behavior with a proper time lag, we could have an a priori estimate on the order of magnitude the seismic energy released would reach.

  17. 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.

  18. Evolution of the Latir volcanic field, Northern New Mexico, and its relation to the Rio Grande Rift, as indicated by potassium-argon and fission track dating

    Science.gov (United States)

    Lipman, Peter W.; Mehnert, Harald H.; Naeser, Charles W.

    1986-05-01

    Remnants of the Latir volcanic field and cogenetic plutonic rocks are exceptionally exposed along the east margin of the present-day Rio Grande rift by topographic and structural relief in the Sangre de Cristo Mountains of northern New Mexico. Evolution of the magmatic system associated with the Latir field, which culminated in eruption of a regional ash flow sheet (the Amalia Tuff) and collapse of the Questa caldera 26 m.y. ago, has been documented by 74 new potassium-argon (K-Ar) and fission track (F-T) ages. The bulk of the precaldera volcanism, ash flow eruptions and caldera formation, and initial crystallization of the associated shallow granitic batholith took place between 28 and 25 Ma; economically important molybdenum mineralization is related to smaller granitic intrusions along the south margin of the Questa caldera at about 23 Ma. Interpretation of the radiogenic ages within this relatively restricted time span is complicated by widespread thermal resetting of earlier parts of the igneous sequence by later intrusions. Many samples yielded discordant ages for different mineral phases. Thermal blocking temperatures decrease in the order: K-Ar sanidine > K-Ar biotite > F-T zircon ≫ F-T apatite. The F-T results are especially useful indicators of cooling and uplift rates. Upper portions of the subvolcanic batholith, that underlay the Questa caldera, cooled to about 100°C within about a million years of emplacement; uplift of the batholith increases to the south along this segment of the Sangre de Cristo Mountains. Activity in the Latir volcanic field was concurrent with southwest directed extension along the early Rio Grande rift zone in northern New Mexico and southern Colorado. The geometry of this early rifting is compatible with interpretation as back arc extension related to a subduction system dipping gently beneath the cordilleran region of the American plate. The Latir field lies at the southern end of a southward migrating Tertiary magmatic

  19. Distribution and size of lava shields on the Al Haruj al Aswad and the Al Haruj al Abyad Volcanic Systems, Central Libya

    Science.gov (United States)

    Elshaafi, Abdelsalam; Gudmundsson, Agust

    2017-05-01

    The Al Haruj Volcanic Province (AHVP) consists of two distinct volcanic systems. In the north is the system of Al Haruj al Aswad, covering an area of 34,200 km2, while in the south the system of Al Haruj al Abyad, covering an area of 7,850 km2. The systems have produced some 432 monogenetic volcanoes, primarily scoria (cinder) cones, lava shields, and maars. The density distribution of the volcanoes in each system, plotted as eruption points or sites, has a roughly elliptical surface expression, suggesting similar plan-view geometry of the magma sources, here suggested as deep-seated reservoirs. More specifically, the Al Haruj al Aswad magma reservoir has major and minor axes of 210 km and 119 km, respectively, and an area of 19,176 km2, the corresponding figures for the Haruj al Abyad reservoir being 108 km and 74 km, for the axes, and 6209 km2 for the area. We measured 55 lava shields on the AHVP. They are mostly restricted to the northern and southern parts of AHVP and date from late Miocene to (at least) the end of Pleistocene, while some may have been active into Holocene. In fact, although primarily monogenetic, some of the lava shields show evidence of (possibly Holocene) fissure eruptions in the summit parts. The early lava shields tend to be located at the edges of volcanic systems and with greater volumes than later (more central) shields. The average lava shield basal diameter is 4.5 km and height 63 m. There is strong linear correlation between lava shield volume and basal area, the coefficient of determination (R2) being about 0.75. When 22 Holocene Icelandic lava shields are added to the dataset, for comparison, the correlation between volume and basal area becomes R2 = 0.95. Numerical models suggest that the local stress fields favoured rupture and dyke injection at the margins of the source reservoirs during late Miocene - early Pliocene, in agreement with the distribution of the early, large-volume shields.

  20. Mercury isotopic composition of hydrothermal systems in the Yellowstone Plateau volcanic field and Guaymas Basin sea-floor rift

    Science.gov (United States)

    Sherman, L.S.; Blum, J.D.; Nordstrom, D.K.; McCleskey, R.B.; Barkay, T.; Vetriani, C.

    2009-01-01

    To characterize mercury (Hg) isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the Yellowstone Plateau volcanic field and vent chimney samples from the Guaymas Basin sea-floor rift. These samples provide an initial indication of the variability in Hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle-derived magmas. Fluid samples from Ojo Caliente hot spring in Yellowstone range in δ202Hg from - 1.02‰ to 0.58‰ (± 0.11‰, 2SD) and solid precipitate samples from Guaymas Basin range in δ202Hg from - 0.37‰ to - 0.01‰ (± 0.14‰, 2SD). Fluid samples from Ojo Caliente display mass-dependent fractionation (MDF) of Hg from the vent (δ202Hg = 0.10‰ ± 0.11‰, 2SD) to the end of the outflow channel (&delta202Hg = 0.58‰ ± 0.11‰, 2SD) in conjunction with a decrease in Hg concentration from 46.6pg/g to 20.0pg/g. Although a small amount of Hg is lost from the fluids due to co-precipitation with siliceous sinter, we infer that the majority of the observed MDF and Hg loss from waters in Ojo Caliente is due to volatilization of Hg0(aq) to Hg0(g) and the preferential loss of Hg with a lower δ202Hg value to the atmosphere. A small amount of mass-independent fractionation (MIF) was observed in all samples from Ojo Caliente (Δ199Hg = 0.13‰ ±1 0.06‰, 2SD) but no significant MIF was measured in the sea-floor rift samples from Guaymas Basin. This study demonstrates that several different hydrothermal processes fractionate Hg isotopes and that Hg isotopes may be used to better understand these processes.

  1. 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.

  2. Preliminary Seismic Velocity Structure Results from Ambient Noise and Teleseismic Tomography: Laguna del Maule Volcanic Field, Chile

    Science.gov (United States)

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

    2016-12-01

    Laguna del Maule Volcanic Field is a large, restless, rhyolitic system in the Southern Andes that is being heavily studied through several methods, including seismology, by a collaborative team of research institutions. A temporary array of 52 seismometers from OVDAS (the Southern Andean Volcano Observatory), PASSCAL (Portable Array Seismic Studies of the Continental Lithosphere), and the University of Wisconsin-Madison was used to collect the 1.3 years worth of data for this preliminary study. Ambient noise tomography uses surface wave dispersion data obtained from noise correlation functions (NCFs) between pairs of seismic stations, with one of each pair acting as a virtual source, in order to image the velocity structure in 3-D. NCFs were computed for hour-long time windows, and the final NCFs were obtained with phase-weighted stacking. The Frequency-Time Analysis technique was then utilized to measure group velocity between station pairs. NCFs were also analyzed to detect temporal changes in seismic velocity related to magmatic activity at the volcano. With the surface wave data from ambient noise, our small array aperture limits our modeling to the upper crust, so we employed teleseismic tomography to study deeper structures. For picking teleseismic arrivals, we tested two different correlation and stacking programs, which utilize adaptive stacking and multi-channel cross-correlation, to get relative arrival time data for a set of high quality events. Selected earthquakes were larger than magnitude 5 and between 30 and 95 degrees away from the center of the array. Stations that consistently show late arrivals may have a low velocity body beneath them, more clearly visualized via a 3-D tomographic model. Initial results from the two tomography methods indicate the presence of low-velocity zones at several depths. Better resolved velocity models will be developed as more data are acquired.

  3. Petrological and geochemical evolution of the Tolbachik volcanic massif, Kamchatka, Russia

    Science.gov (United States)

    Churikova, Tatiana G.; Gordeychik, Boris N.; Iwamori, Hikaru; Nakamura, Hitomi; Ishizuka, Osamu; Nishizawa, Tatsuji; Haraguchi, Satoru; Miyazaki, Takashi; Vaglarov, Bogdan S.

    2015-12-01

    Data on the geology, petrography, and geochemistry of Middle-Late-Pleistocene rocks from the Tolbachik volcanic massif (Kamchatka, Klyuchevskaya group of volcanoes) are presented and compared with rocks from the neighboring Mount Povorotnaya, Klyuchevskaya group basement, and Holocene-historical Tolbachik monogenetic cones. Two volcanic series of lavas, middle-K and high-K, are found in the Tolbachik massif. The results of our data analysis and computer modeling of crystallization at different P-T-H2O-fO2 conditions allow us to reconstruct the geochemical history of the massif. The Tolbachik volcanic massif started to form earlier than 86 ka based on K-Ar dating. During the formation of the pedestal and the lower parts of the stratovolcanoes, the middle-K melts, depleted relative to NMORB, fractionated in water-rich conditions (about 3% of H2O). At the Late Pleistocene-Holocene boundary, a large fissure zone was initiated and the geodynamical regime changed. Upwelling associated with intra-arc rifting generated melting from the same mantle source that produced magmas more enriched in incompatible trace elements and subduction components; these magmas are high-K, not depleted relative to N-MORB melts with island arc signatures and rift-like characteristics. The fissure opening caused degassing during magma ascent, and the high-K melts fractionated at anhydrous conditions. These high-K rocks contributed to the formation of the upper parts of stratovolcanoes. At the beginning of Holocene, the high-K rocks became prevalent and formed cinder cones and associated lava fields along the fissure zone. However, some features, including 1975-1976 Northern Breakthrough, are represented by middle-K high-Mg rocks, suggesting that both middle-K and high-K melts still exist in the Tolbachik system. Our results show that fractional crystallization at different water conditions and a variably depleted upper mantle source are responsible for all observed variations in rocks within

  4. Geomorphological evidence of the influence of pre-volcanic basement structure on emplacement and deformation of volcanic edifices at the Cofre de Perote Pico de Orizaba chain and implications for avalanche generation

    Science.gov (United States)

    Concha-Dimas, Aline; Cerca, Mariano; Rodríguez, Sergio R.; Watters, Robert J.

    2005-12-01

    Pre-volcanic structure of the basement influences volcanism distribution and avalanche generation in volcanic edifices. Therefore, systematic studies of basement structure below volcanic chains are necessary to understand the deformation effects observed in the surface and vice versa. Based on a compilation of pre-existing data, interpretation of aerial photographs and satellite images, and a collection of structural data we analyzed morphological and structural features of the Cofre de Perote-Pico de Orizaba (CP-PO) volcanic chain and its basement. We have identified three sets of regional lineaments that are related to basement trends. (1) NW 55° SE fractures are parallel to anticline folds observed in Cretaceous rocks that originated during Laramide shortening. These folds present an abrupt morphology observed only in the eastern flank but that is likely to continue below the volcanic chain. (2) NE 55° SW fractures are parallel to normal faults at the basement. We infer that these basement faults confine the CP-PO chain within a stepped graben with a total normal displacement of about 400 m. These faults have been active through time since they have affected volcanic deposits and induced the emplacement of monogenetic vents. Notably, lineaments of monogenetic vents concentrate where the basement is relatively shallow. (3) Another set of faults, oriented N-S, has been observed affecting the scarce basement outcrops at the western flank of the chain covered by lacustrine deposits. Lineaments measured in the volcanic edifice of Pico de Orizaba correlate with the regional trends. In particular, the NE 55° SW alignment of monogenetic vents and fractures at Pico de Orizaba suggest that the same dike trend exists within the volcanic edifice. A normal fault with similar orientation was documented at the NE continuation of an alignment crossing the volcanic edifice along the Jamapa canyon. In the absence of magmatic activity related to collapses, the displacement of

  5. Diverse mantle and crustal components in lavas of the NW Cerros del Rio volcanic field, Rio Grande Rift, New Mexico

    Science.gov (United States)

    Duncker, K. E.; Wolff, J. A.; Harmon, R. S.; Leat, P. T.; Dickin, A. P.; Thompson, R. N.

    1991-09-01

    Products of Pliocene (2 4 Ma) mafic to intermediate volcanism in the northwestern Cerros del Rio, a dominantly mafic volcanic field in the Española Basin of the Rio Grande Rift (RGR), range from 49% to 63% SiO2 and exhibit diversity in silica saturation, trace-element patterns, and isotopic compositions. Tholeiites, which are largely confined to west of the Rio Grande, have trace-element abundances that resemble those of oceanic basalts, but with mild depletions in Nb and Ta, and high 87Sr/86Sr, low 143Nd/144Nd, and high δ18O compared to typical OIB. They are regarded as asthenospherically-derived magmas contaminated with continental crust. Alkali basalts and hawaiites erupted from vents east of the Rio Grande are geochemically distinct, having generally higher overall incompatible-element abundances, but with pronounced depletions in K, Rb, Nb and Ta with respect to Th and LREE. Spatially-associated benmoreites, mugearites and latites (collectively termed “evolved” lavas) have similar trace-element characteristics to the mafic mildly-alkaline compositions, but are typically not as depleted in K. Hawaiites and evolved lavas exhibit a good negative correlation of 143Nd/144Nd with SiO2, due to interaction with lower continental crust. The most silicic “evolved” lavas carry the highest proportions of crustal material, and consequently have higher K/Th than the related hawaiites. Several (mostly mafic) lavas contain abundant crustally-derived resorbed quartz xenocrysts in O-isotope disequilibrium with the host magma. The δ18O values of xenocrystic quartz range over 4‰, indicating a variety of quartz-bearing crustal contaminants beneath the Española Basin. The hawaiites, with their unusual combination of trace-element enrichments and depletions, cannot be generated by any process of fractionation or crustal contamination superposed on a common mantle source type (oceanic or arc-source). It is a regional mantle source type, inasmuch as it was also present

  6. 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

  7. Continuous in-situ measurements of volcanic gases at Pisciarelli-Phelgrean Field (Italy): a new experimental approach

    Science.gov (United States)

    Wiersberg, T.; Somma, R.; Rocco, A.; Quattrocchi, F.; Zimmer, M.; de Natale, G.; de Natale, P.; Boschi, E.

    2009-04-01

    We present a new experimental approach for continuous real-time monitoring of volcanic gases. The realization of this new set-up based on the experience derived from several earlier short-time gas monitoring campaigns carried out in 2006, 2007 and 2008 at different sites (Tor Caldara, Latium Region, Central Italy; Solfatara and Pisciarelli, Campania Region, Souther Italy). The monitoring station is now implemented at a fumarole field in Pisciarelli, about 1 km SE of the Solfatara volcano. Fumarolic gas is continuously pumped through 200m Teflon © tube with a membrane pump (pumping rate 400cc/min) into a small field laboratory, where the gas phase is analyzed minutely by means of a quadrupole mass spectrometer for H2, H2S, CH4, N2, O2, Ar, He, and CO2 and with a tuneable diode laser spectrometer. Further analytical devices may be added in the future. Off-line gas samples are taken regularly to crosscheck the gas composition with a gas chromatograph and for noble gas analysis. Prior to gas analysis, gaseous water is condensed in a water trap placed in a cooling box in close vicinity to the fumarole. The water is removed from the trap in regular intervals (2 h) by a peristaltic pump. The amount of water is determined directly in the trap by measuring the rise of the water level in intervals of 5 minutes. Knowledge of the gas flow and the amount of water would enables us to determine the gas/water ratio of fumarolic gases, however, the actual fumarole temperature (December 2008) at Pisciarelli is 95.8°C, thus water condensation has already occurred prior to gas sampling. The gas from the Pisciarelli fumarole is dominated by CO2 (>98.5 vol.-%), followed by N2, H2S, O2, H2, Ar, CH4 and He. O2 and partly N2 and Ar are due to atmospheric contamination of the system. The air-free calculated gas composition is in good agreement with already published gas composition data. Within the time of investigation, no significant variations were detected in the composition of the

  8. The 3D Distribution of Magma Bodies that Fed the Paraná Silicic Volcanics, Brazil: A Combination of Field Evidence, Textural Analysis, and Geothermobarometry

    Science.gov (United States)

    Harmon, L.; Gualda, G. A. R.; Gravley, D. M.

    2016-12-01

    The Paraná Silicic Volcanics include some of the largest eruptive deposits known in the geological record. However, we know very little about the magma bodies that fed these eruptions. Combining physical volcanology, geochemistry, and geothermobarometry techniques, we aim to find the sources of extinct magma bodies to build a 3D view of the magma structure at the time by discovering storage conditions, eruption styles, and post-eruption alteration. The approach elucidates temporal and spatial eruption styles and sequences of the silicic units that make up the Palmas unit of the Serra Geral formation, Brazil. We use field investigations to determine the history of volcanic deposits, domes, and changes in eruptive style; we map and characterize volcanic deposits based on thickness (thicker is proximal to source) and distribution of effusive (proximal to source) and explosive deposits. We focus on several exposed canyons that exhibit either exclusively explosive or effusive, or a clear progression from explosive to effusive deposits. The progression from explosive to effusive indicates a system change from explosively energetic to effusively waning. Additionally, observation of pervasive flow banding in both effusive and explosive deposits indicates rheomorphic flow through many portions of the field area, an indicator of hot emplacement. Geochemical work focuses on the pre-eruptive magma conditions to determine the depth of magma bodies. We utilize glass bearing samples of both the explosively deposited juvenile blob-like structures and obsidian samples to determine crystallization depth. The glass is variably altered, via silicification and devitrification processes, with the blobs more greatly silicified than the obsidian. We use rhyolite-MELTS geothermobarometry when pristine glass can be found. Initial results indicate shallow ( 80 MPa) storage conditions for the explosively erupted blobs. The combination of techniques builds a 3D understanding of extinct super

  9. Inverse steptoes in Las Bombas volcano, as an evidence of explosive volcanism in a solidified lava flow field. Southern Mendoza-Argentina

    Science.gov (United States)

    Risso, Corina; Prezzi, Claudia; Orgeira, María Julia; Nullo, Francisco; Margonari, Liliana; Németh, Karoly

    2015-11-01

    Here we describe the unusual genesis of steptoes in Las Bombas volcano- Llancanelo Volcanic Field (LVF) (Pliocene - Quaternary), Mendoza, Argentina. Typically, a steptoe forms when a lava flow envelops a hill, creating a well-defined stratigraphic relationship between the older hill and the younger lava flow. In the Llancanelo Volcanic Field, we find steptoes formed with an apparent normal stratigraphic relationship but an inverse age-relationship. Eroded remnants of scoria cones occur in ;circular depressions; in the lava field. To express the inverse age-relationship between flow fields and depression-filled cones here we define this landforms as inverse steptoes. Magnetometric analysis supports this inverse age relationship, indicating reverse dipolar magnetic anomalies in the lava field and normal dipolar magnetization in the scoria cones (e.g. La Bombas). Negative Bouguer anomalies calculated for Las Bombas further support the interpretation that the scoria cones formed by secondary fracturing on already solidified basaltic lava flows. Advanced erosion and mass movements in the inner edge of the depressions created a perfectly excavated circular depression enhancing the ;crater-like; architecture of the preserved landforms. Given the unusual genesis of the steptoes in LVF, we prefer the term inverse steptoe for these landforms. The term steptoe is a geomorphological name that has genetic implications, indicating an older hill and a younger lava flow. Here the relationship is reversed.

  10. [The influence of insulin on contamination of the common carp Cyprinus carpio by the monogenetic fluke Dactylogyrus vastator].

    Science.gov (United States)

    Mikriakov, B P; Mikriakov, D B; Stepanova, M A

    2011-01-01

    The influence of insulin on the contamination of the carp Cyprinus carpio with the monogenetic fluke Dactylogyrus vastator is studied. Fishes reacted to the introduction of the hormon by the decrease in the degree of intensity of infection and by the increase in the number of lifeless parasites on gills, by contrast to control fishes and fishes processed with stress hormones (adrenaline and cortisol). We assume that the decrease in the abundance index in live monogenetic fluke and the increase in the number of lifeless oness is caused by the deficiency of nutrients accessible for the growth and development caused by activation of hormone-induced anabolic processes and stimulation of mechanisms of immune protection.

  11. Phenocryst complexity in andesites and dacites from the Tequila volcanic field, Mexico: resolving the effects of degassing vs. magma mixing

    Science.gov (United States)

    Frey, Holli M.; Lange, Rebecca A.

    2011-08-01

    The petrology of five phenocryst-poor (2-5%) andesites and dacites, all of which were erupted from different short-lived, monogenetic vents, is compared to that of phenocryst-rich (10-25%) andesites erupted from the adjacent stratovolcano, Volcán Tequila, in the Mexican arc. Despite differences in phenocryst abundances, these magmas have comparable phase assemblages (plagioclase + orthopyroxene + titanomagnetite + ilmenite + apatite ± augite ± hornblende), and similarly wide variations in phenocryst compositions, coupled to complex zoning patterns. For the phenocryst-poor lavas, equilibrium pairs of two Fe-Ti oxides lead to a narrow range of calculated temperatures for each sample that range from 934 (±24) to 1,073 (±6)°C and oxygen fugacities that range from +0.1 to +0.7 log units relative to the Ni-NiO buffer. Application of the plagioclase-liquid hygrometer to each sample at these calculated temperatures leads to maximum melt water concentrations of 4.6-3.1 wt% during plagioclase crystallization, indicating that the magmas were fluid saturated at depths ≥6.4-4.5 km. There is a wide, continuous range in the composition of plagioclase (≤44 mol% An) and orthopyroxene (≤16% Mg#) phenocrysts in each sample, which is consistent with a loss of dissolved water (≤2.8 wt%) from the melt phase during degassing as the magmas ascended rapidly to the surface. Evidence is presented that shows the effect of dissolved water is to reduce the activity of MgO relative to FeO in the melt phase, which indicates that degassing will also affect the Mg# of pyroxene phenocrysts, with higher melt water concentrations favoring Fe-rich pyroxene. Both plagioclase and orthopyroxene commonly display diffusion-limited growth textures (e.g., skeletal and hopper crystals, large interior melt hollows, and swallow tails), which are consistent with large undercoolings produced by degassing-induced crystallization. Therefore, degassing is proposed as a possible cause for the phenocryst

  12. A combined field and numerical approach to understanding dilute pyroclastic density current dynamics and hazard potential: Auckland Volcanic Field, New Zealand

    Science.gov (United States)

    Brand, Brittany D.; Gravley, Darren M.; Clarke, Amanda B.; Lindsay, Jan M.; Bloomberg, Simon H.; Agustin-Flores, Javier; Németh, Károly

    2014-04-01

    The most dangerous and deadly hazards associated with phreatomagmatic eruptions in the Auckland Volcanic Field (AVF; Auckland, New Zealand) are those related to volcanic base surges - dilute, ground-hugging, particle laden currents with dynamic pressures capable of severe to complete structural damage. We use the well-exposed base surge deposits of the Maungataketake tuff ring (Manukau coast, Auckland), to reconstruct flow dynamics and destructive potential of base surges produced during the eruption. The initial base surge(s) snapped trees up to 0.5 m in diameter near their base as far as 0.7-0.9 km from the vent. Beyond this distance the trees were encapsulated and buried by the surge in growth position. Using the tree diameter and yield strength of the wood we calculate that dynamic pressures (Pdyn) in excess of 12-35 kPa are necessary to cause the observed damage. Next we develop a quantitative model for flow of and sedimentation from a radially-spreading, dilute pyroclastic density currents (PDCs) to determine the damage potential of the base surges produced during the early phases of the eruption and explore the implications of this potential on future eruptions in the region. We find that initial conditions with velocities on the order of 65 m s- 1, bulk density of 38 kg m- 3 and initial, near-vent current thicknesses of 60 m reproduce the field-based Pdyn estimates and runout distances. A sensitivity analysis revealed that lower initial bulk densities result in shorter run-out distances, more rapid deceleration of the current and lower dynamic pressures. Initial velocity does not have a strong influence on run-out distance, although higher initial velocity and slope slightly decrease runout distance due to higher rates of atmospheric entrainment. Using this model we determine that for base surges with runout distances of up to 4 km, complete destruction can be expected within 0.5 km from the vent, moderate destruction can be expected up to 2 km, but much

  13. Paleomagnetic secular variation study of Ar-Ar dated lavas flows from Tacambaro area (Central Mexico): Possible evidence of Intra-Jaramillo geomagnetic excursion in volcanic rocks

    Science.gov (United States)

    Peña, Rafael Maciel; Goguitchaichvili, Avto; Guilbaud, Marie-Noëlle; Martínez, Vicente Carlos Ruiz; Rathert, Manuel Calvo; Siebe, Claus; Reyes, Bertha Aguilar; Morales, Juan

    2014-04-01

    More than 350 oriented paleomagnetic cores were obtained for rock-magnetic and paleomagnetic analysis from radiometrically dated (40Ar-39Ar) magmatic rocks occurring in the southern segment (Jorullo and Tacámbaro areas) of the Michoacán-Guanajuato Volcanic Field in the Trans-Mexican Volcanic Belt. Most of the lavas (37) stem from monogenetic volcanoes dated at less than 4 Ma. Two additional sites were sampled from the plutonic basement dated at 33-30 Ma. Primary remanences carried by low-Ti titanomagnetites allowed to determining 34 reliable site-mean directions of mostly normal (27) but also reversed (7) polarities. The mean directions of these two populations are antipodal, and suggest neither major vertical-axis rotations with respect to the North America craton nor tilting in the region for the last 4 Ma (rotation and flattening of the inclination parameters being less than -5.9 ± 3.8 and 0.1 ± 3.9, respectively). The corresponding paleomagnetic pole obtained for Pliocene-Pleistocene times is PLAT = 83.4°, PLON = 2.4° (N = 32, A95 = 2.7°). Virtual geomagnetic poles also contribute to the time averaged field global database and to the paleosecular variation (PSV) investigations at low latitudes from lavas for the last 5 Ma, showing a geomagnetic dispersion value that is in agreement with available PSV models. When comparing the magnetic polarities and corresponding radiometric ages of the studied sites with the Cenozoic geomagnetic polarity time scale (GPTS), a good correlation is observable. This finding underscores the suitability of data obtained on lavas in Central Mexico for contributing to the GPTS. Furthermore, the detection of short-lived geomagnetic features seems possible, since the possible evidence of Intra-Jaramillo geomagnetic excursion could be documented for the first time in these volcanic rocks.

  14. The Volatile Element Evolution of Intra-plate Alkaline Rocks as Recorded by Apatite: An Example from the Hegau Volcanic Field (Southwest Germany)

    Science.gov (United States)

    Von Der Handt, A.; Rahn, M. K. W.; Wang, L. X.; Marks, M. A. W.

    2014-12-01

    The role of volatiles in the petrogenesis of alkaline intra-plate magmas has been the subject of an increasing number of experimental studies. The study of naturally occurring rocks and their volatile contents is often complicated by syn- and post-eruptive degassing and alteration processes. Minerals that incorporate volatiles into their structure such as apatites are often more faithful recorders of the pre-eruptive volatile budget. The Hegau volcanic field in Southwest Germany is part of the Central European Volcanic Province, lies around 60-70 km to the east of the Upper Rhine graben and of Miocene age. Three main lithological units can be distinguished (1) olivine melilites (2) phonolites and (3) the "Deckentuff" series referring to a series of diatreme-filling pipe breccias and lapilli tuff layers. Carbonatites occur subordinately in the Hegau province. Earlier radiometric age dating suggested distinct phases of volcanic activity of Deckentuffs, melilites and phonolites with little overlap, but new apatite fission-track and (U-Th)/He age data suggest a synchronous activity. Apatite is an abundant accessory phase in the Deckentuff and phonolite series and we investigated its major, trace and volatile element composition by EPMA, SIMS and cathodoluminescence imaging. Pronounced core-rim zoning of apatite in places attests that diffusional equilibration was very limited and they likely retained their primary compositions. This allows us to trace the entire magmatic evolution of the Hegau province from its most primitive to most evolved products as well as resolve it in time by combining age dating with compositional analysis. Apatite compositions fall along the OH-F join with low Cl-contents (<0.5 wt%). Volatile contents (Cl, OH, S) are highest in most primitive compositions and decrease with further evolution while F increases. Multiple magmatic cycles can be discerned with a general trend to the more evolved phonolite compositions toward the end of volcanic

  15. The Late Pliocene mafic lavas from the Camusú Aike volcanic field (˜50°S, Argentina): Evidence for geochemical variability in slab window magmatism

    Science.gov (United States)

    D'Orazio, M.; Innocenti, F.; Manetti, P.; Haller, M. J.; Di Vincenzo, G.; Tonarini, S.

    2005-01-01

    The Camusú Aike volcanic field (CAVF), part of the discontinuous N-S-trending belt of Cenozoic mafic lava formations that occur in a backarc position along extra-Andean Patagonia, is located in southern Patagonia (˜50°S, Santa Cruz province), approximately 70 km east of the extensive Meseta de las Vizcachas and just south of the upper Río Santa Cruz valley. The CAVF volcanics cover a surface of ˜200 km 2 and occur mainly as lava flows and scoria cones. They are subdivided into two groups: Group I volcanics are high-TiO 2, low-Mg# olivine-hypersthene-normative basalts and trachybasalts that erupted at about 2.9 Ma; Group II lavas are much less abundant, more primitive basaltic andesites that erupted at about 2.5 Ma. Both groups show a within-plate geochemical signature, though it is more marked in Group I lavas. The main geochemical characteristics, age, and location of CAVF volcanics are consistent with the slab window opening model proposed by different authors for the genesis of the Miocene-Recent mafic magmatism of Patagonia south of 46.5°S. The whole-rock geochemical and Sr-Nd isotope features of Group I lavas ( 87Sr/ 86Sr=0.7035-0.7037; 143Nd/ 144Nd=0.51288-0.51291) indicate a genetic link between these lavas and the primitive basalts in southernmost Patagonia (Pali Aike volcanic field and Estancia Glencross area), which have been interpreted as melting products of an isotopically depleted asthenosphere. The relatively evolved compositions of the erupted Group I magmas are modeled by a polybaric crystal fractionation process without significant involvement of crustal contamination. The more primitive Group II lavas are strongly depleted in incompatible elements, have slightly higher (LREE+Ba+Th+U)/HFSE ratios, and have more enriched Sr-Nd isotope compositions ( 87Sr/ 86Sr≈0.7039; 143Nd/ 144Nd≈0.51277) that are more akin to the Patagonian basalts farther to the north. The most likely explanation for the geochemical features of Group II lavas is the

  16. Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field, Taupo Volcanic Zone, New Zealand

    Science.gov (United States)

    Rissmann, C.; Christenson, B.; Werner, C.; Leybourne, M.; Cole, J.; Gravley, D.

    2012-01-01

    Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20a of production (116MW e). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (Wm -2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20a of production, current CO2 emissions equated to 111??6.7T/d. Observed heat flow was 70??6.4MW, compared with a pre-production value of 122MW. This 52MW reduction in surface heat flow is due to production-induced drying up of all alkali-Cl outflows (61.5MW) and steam-heated pools (8.6MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali-Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18MW (from 25MW to 43.3??5MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20a of production, with an observed heat flow of 26.7??3MW and a CO 2 emission rate of 39??3T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali-Cl outflows once contributed significantly to the natural surface heat flow (~50%) they contributed little (99% of the original CO 2

  17. Genesis and evolution of the Cerro Prieto Volcanic Complex, Baja California, Mexico

    Science.gov (United States)

    García-Sánchez, L.; Macías, J. L.; Sosa-Ceballos, G.; Arce, J. L.; Garduño-Monroy, V. H.; Saucedo, R.; Avellán, D. R.; Rangel, E.; Layer, P. W.; López-Loera, H.; Rocha, V. S.; Cisneros, G.; Reyes-Agustín, G.; Jiménez, A.; Benowitz, J. A.

    2017-06-01

    The Cerro Prieto Volcanic Complex (CPVC), located in northwestern Mexico, is the only surface manifestation of the Cerro Prieto Geothermal Field, the third largest producer of geothermal energy in the world. This geothermal field and the Salton Sea in the USA sit in a pull-apart basin that belongs to the trans-tensional tectonic zone that includes the San Andreas Fault system and the Salton Trough basin to the NW and the East Pacific Rise to the SE. In spite of its strategic importance in the generation of geothermal energy, the origin of Cerro Prieto and its relationship with the geothermal reservoir were unknown. In this contribution, we discuss the origin, evolution, and mechanisms of formation of this small monogenetic volcano and the magmas that fed the system. The volcanic complex is located on top of the Cerro Prieto left lateral fault to the northwest of the Cerro Prieto Geothermal Field. The complex consists of a lava cone and a series of domes (˜0.15 km3) protruding from Tertiary sandstones and recent unconsolidated sediments of the alluvial plain of the Colorado River. The Cerro Prieto Volcanic Complex consists of seven stratigraphic units emplaced in a brief time span around 78-81 ka. Its activity began with the extrusion of a dacitic lava that came into contact with water-saturated sediments, causing brecciation of the lava. The activity continued with the emplacement of dacitic domes and a dyke that were destroyed by a phreatic explosion emplacing a lithic-rich breccia. This phreatic explosion formed a 300-m-wide and 40-m-deep circular crater. The activity then migrated ˜650 m to the SW where three dacitic lava domes were extruded and ended with the emplacement of a fissure-fed lava flow. Subsequent remobilization of the rocks in the complex has generated debris and hyperconcentrated flow deposits interbedded with fluviatile sediments in the surrounding terrain. All rocks of the CPVC are dacites with phenocrysts of plagioclase, orthopyroxene, and Fe

  18. 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

  19. Volcanism and sedimentation along the western margin of the Rio Grande rift between caldera-forming eruptions of the Jemez Mountains volcanic field, north-central New Mexico, USA

    Science.gov (United States)

    Jacobs, Elaine P.; WoldeGabriel, Giday; Kelley, Shari A.; Broxton, David; Ridley, John

    2016-11-01

    The Cerro Toledo Formation (CTF), a series of intracaldera rhyolitic dome complexes and their associated extracaldera tephras and epiclastic sedimentary deposits, records the dynamic interplay between volcanic, tectonic, and geomorphic processes that were occurring along the western margin of the Rio Grande rift between major caldera-forming eruptions of the Bandelier Tuff 1.65-1.26 Ma. The Alamo Canyon and Pueblo Canyon Members differ significantly despite deposition within a few kilometers of each other on the Pajarito Plateau. These differences highlight spatial distinctions in vent sources, eruptive styles, and depositional environments along the eastern side of the Jemez Mountains volcanic field during this ca. 400,000 year interval. Intercalated pyroclastic fall deposits and sandstones of the Pueblo Canyon Member reflect deposition with a basin. Thick Alamo Canyon Member deposits of block-and-ash-flow tuff and pyroclastic fall deposits fill a paleovalley carved into coarse grained sedimentary units reflecting deposition along the mountain front. Chemistry and ages of glass from fall deposits together with clast lithologies of sedimentary units, allow correlation of outcrops, subsurface units, and sources. Dates on pyroclastic fall deposits from Alamo Canyon record deep incision into the underlying Otowi Member in the southern part of the Pajarito Plateau within 100 k.y. of the Toledo caldera-forming eruption. Reconstruction of the CTF surface shows that this period of rapid incision was followed by aggradation where sediments largely filled pre-existing paleocanyons. Complex sequences within the upper portion of the Otowi Member in outcrop and in the subsurface record changes in the style of eruptive activity during the waning stages of the Toledo caldera-forming eruption.

  20. 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.

  1. Subterranean fragmentation of magma during conduit initiation and evolution in the shallow plumbing system of the small-volume Jagged Rocks volcanoes (Hopi Buttes Volcanic Field, Arizona, USA)

    Science.gov (United States)

    Re, Giuseppe; White, James D. L.; Muirhead, James D.; Ort, Michael H.

    2016-08-01

    Monogenetic volcanoes have limited magma supply and lack long-lived sustained magma plumbing systems. They erupt once, often from multiple vents and sometimes over several years, and are rarely or never re-activated. Eruptive behavior is very sensitive to physical processes (e.g., volatile exsolution, magma-water interaction) occurring in the later stages of magma ascent at shallow crustal depths (flowing through dikes fragmented and conduits were formed. We have identified three main types of fragmental deposits, (1) buds (which emerge from dikes), (2) pyroclastic massifs, and (3) diatremes; these represent three different styles and intensities of shallow-depth magma fragmentation. They may develop successively and at different sites during the evolution of a monogenetic volcano. The deposits consist of a mixture of pyroclasts with varying degrees of welding and country-rock debris in various proportions. Pyroclasts are commonly welded together, but also reveal in places features consistent with phreatomagmatism, such as blocky shapes, dense groundmasses, and composite clasts (loaded and cored). The extent of fragmentation and the formation of subterranean open space controlled the nature of the particles and the architecture and geometry of these conduit structures and their deposits.

  2. 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.

  3. 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.

  4. 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.

  5. Intermediate composition magma production in an intracontinental setting: Unusual andesites and dacites of the mid-Miocene Santa Rosa-Calico volcanic field, Northern Nevada

    Science.gov (United States)

    Brueseke, Matthew E.; Hart, William K.

    2009-11-01

    The mid-Miocene Santa Rosa-Calico volcanic field (SC) of northern Nevada provides an outstanding example of the role open-system magmatic processes play in producing calc-alkaline and tholeiitic andesite-dacite magmas in an intracontinental setting. SC volcanism commenced at ˜ 16.7 Ma and is associated with the initial manifestations of the Yellowstone hotspot, the Columbia River-Steens flood basalt event(s), and the formation of the Northern Nevada rift. Locally a diverse package of magmatic products ranging from tholeiitic basalt to high-Si rhyolite was produced during an ˜ 2 myr duration. Within this package are the products of at least four distinct intermediate composition magmatic systems that may represent as much as 40% of the SC volcanic pile. These help differentiate the SC from contemporaneous Oregon Plateau volcanic fields (e.g. McDermitt, Lake Owyhee, Northwest Nevada) that are dominated by bimodal basalt-rhyolite assemblages. All SC intermediate units are characterized by textural and mineralogic complexities including xenoliths and xenocrysts of local crust and crystal clots of plagioclase ± clinopyroxene ± orthopyroxene ± oxide. SC intermediate units are dominantly tholeiitic, but include lava flows with transitional to calc-alkaline affinities. Relative to locally erupted Steens Basalt, SC intermediate lava flows have similar elemental enrichments and depletions, but dissimilar Sr and Nd isotopic compositions. These isotopic differences, coupled with the abundant disequilibrium features and variable incompatible element ratios, indicate that open system magmatic processes played a major role in the genesis of the intermediate units. SC silicic magmas were produced primarily via upper crustal melting of chemically and isotopically heterogeneous Cretaceous granitoid. Interaction between fractionating mafic Steens flood basalt magmas and the more evolved crustal melts ± assimilation of local upper crust provides a general template for the

  6. Channel and tube flow features associated with the Twin Craters Lava Flow, Zuni-Bandera Volcanic Field, NM: Insights into similar features on Mars

    Science.gov (United States)

    Samuels, R.; deWet, A.; Bleacher, J. E.; von Meerscheidt, H. C.; Hamilton, C.; Garry, W. B.

    2013-12-01

    The Zuni-Bandera Volcanic Field lies near the center of the Jemez lineament that extends from central Arizona to northeastern New Mexico. The Jemez lineament is a result of rifting in the Earth's crust and is associated with volcanic activity that spans the last 16 Ma. The youngest volcanic activity associated with the lineament includes basaltic lava that was erupted 3 ka ago to form the McCartys Flow. The Twin Craters flow is moderately older (18.0 ka), but it also well-preserved and provides an ideal location to investigate volcanic processes and landforms. In this study, we combined detailed field observations and mapping with remote sensing to better understand variations in morphology along the transport system of the flow . The Twin Craters flow is characterized as an aā and tube-fed pāhoehoe flow with braided or branching tubes and channels; and associated aā and pāhoehoe break-outs. It is possible that the variations in morphology along the same transport structure might be related to pre-flow slope, which might have also been variable along flow. Shatter ring features are thought to be related to changes in eruption rate, and therefore, local flux through the system. However, over-pressurization of the tube might also be related to changes in local discharge rate associated with the ponding and release of lava within the transport system that may be due to interactions between the lava and obstacles along the flow's path (see Mallonee et al., this meeting). Many of these features are similar to features present in the Tharsis Montes region of Mars and particularly on the southern apron of Ascraeus Mons. The detailed description of the morphology of the Twin Craters Lava Flow and the understanding of the emplacement mechanisms will be crucial in identifying the processes that formed the Ascraeus flows and channels. This will aid in determining if the lava surface textures are directly related to eruption conditions or if they have been significantly

  7. Remote Sensing as a First Step in Geothermal Exploration in the Xilingol Volcanic Field in NE China

    Science.gov (United States)

    Peng, F.; Huang, S.; Xiong, Y.

    2013-12-01

    Geothermal energy is a renewable and low-carbon energy source independent of climate change. It is most abundant in Cenozoic volcanic areas where high temperature can be obtained within a relatively shallow depth. Geological structures play an important role in the transfer and storage of geothermal energy. Like other geological resources, geothermal resource prospecting and exploration require a good understanding of the host media. Remote sensing (RS) has the advantages of high spatial and temporal resolution and broad spatial coverage over the conventional geological and geophysical prospecting techniques, while geographical information system (GIS) has intuitive, flexible, and convenient characteristics. In this study, RS and GIS techniques are utilized to prospect the geothermal energy potential in Xilingol, a Cenozoic volcanic area in the eastern Inner Mongolia, NE China. Landsat TM/ETM+ multi-temporal images taken under clear-sky conditions, digital elevation model (DEM) data, and other auxiliary data including geological maps of 1:2,500,000 and 1:200,000 scales are used in this study. The land surface temperature (LST) of the study area is retrieved from the Landsat images with a single-channel algorithm. Prior to the LST retrieval, the imagery data are preprocessed to eliminate abnormal values by reference to the normalized difference vegetation index (NDVI) and the improved normalized water index (MNDWI) on the ENVI platform developed by ITT Visual Information Solutions. Linear and circular geological structures are then inferred through visual interpretation of the LST maps with references to the existing geological maps in conjunction with the computer automatic interpretation features such as lineament frequency, lineament density, and lineament intersection. Several useful techniques such as principal component analysis (PCA), image classification, vegetation suppression, multi-temporal comparative analysis, and 3D Surface View based on DEM data are

  8. The polycyclic Lausche Volcano (Lausitz Volcanic Field) and its message concerning landscape evolution in the Lausitz Mountains (northern Bohemian Massif, Central Europe)

    Science.gov (United States)

    Wenger, Erik; Büchner, Jörg; Tietz, Olaf; Mrlina, Jan

    2017-09-01

    The Tertiary Lausitz Volcanic Field covers a broad area encompassing parts of Eastern Saxony (Germany), Lower Silesia (Poland) and North Bohemia (Czech Republic). Volcanism was predominantly controlled by the volcano-tectonic evolution of the Ohře Rift and culminated in the Lower Oligocene. This paper deals with the highest volcano of this area, the Lausche Hill (792.6 m a.s.l.) situated in the Lausitz Mountains. We offer a reconstruction of the volcanic edifice and its eruptive history. Its complex genesis is reflected by six different eruption styles and an associated petrographic variety. Furthermore, the Lausche Volcano provides valuable information concerning the morphological evolution of its broader environs. The remnant of an alluvial fan marking a Middle Paleocene-Lower Eocene (62-50 Ma) palaeo-surface is preserved at the base of the volcano. The deposition of this fan can be attributed to a period of erosion of its nearby source area, the Lausitz Block that has undergone intermittent uplift at the Lausitz Overthrust since the Upper Cretaceous. The Lausche Hill is one of at least six volcanoes in the Lausitz Mountains which show an eminent low level of erosion despite their Oligocene age and position on elevated terrain. These volcanoes are exposed in their superficial level which clearly contradicts their former interpretation as subvolcanoes. Among further indications, this implies that the final morphotectonic uplift of the Lausitz Mountains started in the upper Lower Pleistocene ( 1.3 Ma) due to revived subsidence of the nearby Zittau Basin. It is likely that this neotectonic activity culminated between the Elsterian and Saalian Glaciation ( 320 ka). The formation of the low mountain range was substantially controlled by the intersection of the Lausitz Overthrust and the Ohře Rift.

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

    DEFF Research Database (Denmark)

    Søager, Nina

    The extensive Quaternary volcanism in the Payenia volcanic province, Mendoza, Argentina, is investigated in this study by major and trace element analyses, Sr, Nd, Hf and Pb-isotopic analyses and Zr-Hf isotope dilution data on samples from almost the entire province. The samples are mainly...... in basalts from all the studied volcanic fields in Payenia is signs of lower crustal contamination indicating assimilation of, in some cases, large amounts of trace element depleted, mafic, plagioclase-bearing rocks. The northern Payenia is dominated by backarc basalts erupted between late Pliocene to late...

  10. Volcanic gas

    Science.gov (United States)

    McGee, Kenneth A.; Gerlach, Terrance M.

    1995-01-01

    In Roman mythology, Vulcan, the god of fire, was said to have made tools and weapons for the other gods in his workshop at Olympus. Throughout history, volcanoes have frequently been identified with Vulcan and other mythological figures. Scientists now know that the “smoke" from volcanoes, once attributed by poets to be from Vulcan’s forge, is actually volcanic gas naturally released from both active and many inactive volcanoes. The molten rock, or magma, that lies beneath volcanoes and fuels eruptions, contains abundant gases that are released to the surface before, during, and after eruptions. These gases range from relatively benign low-temperature steam to thick hot clouds of choking sulfurous fume jetting from the earth. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other volcanic gases are hydrogen sulfide, hydrochloric acid, hydrogen, carbon monoxide, hydrofluoric acid, and other trace gases and volatile metals. The concentrations of these gas species can vary considerably from one volcano to the next.

  11. 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

  12. Paleomagnetic and geochemical applications to tectonics and Quaternary geology: Studies at Coso Volcanic Field, California and the Channelled Scabland, Washington

    Science.gov (United States)

    Pluhar, Christopher J.

    At the Coso Range, CA we used paleomagnetism to reveal the long-term history and kinematics of deformation resulting from distributed transtension of the Eastern California shear zone (ECSZ). Pliocene lavas and sediments deposited in and around the Wild Horse Mesa record and result from the initiation of deformation along the ECSZ in this area. Geochemical analyses, geochronologic, and stratigraphic constraints provide new information about the initiation and evolution of volcanism in this region. Following emplacement of the volcanics, distributed faulting has accommodated dextral shear of the ECSZ by 12°--22° of rotation of fault-bounded blocks in the Wild Horse Mesa and tilting in the Coso geothermal area. This partitioning of block kinematic style probably results from partitioning of slip of the master faults at depth that control block motion of the shallow crust. A calculation based upon some simple assumptions about block geometry indicates that at least 1.5 km of dextral slip is accommodated across the Wild Horse Mesa. Magnetostratigraphic studies of the Cold Creek bar at Hanford, WA constrain the timing of deposition of cataclysmic flood deposits resulting from jokulhlaups like the Missoula floods and similar processes. Abundant evidence for reversed polarity sediments confirm previous studies suggesting onset of cataclysmic floods prior to the last major magnetic polarity reversal (0.78 Ma). A normal polarity zone bracketed by reversed polarity at eastern Cold Creek bar extends the chronology back to before the Jaramillo subchron (0.99--1.07 Ma) suggesting that the climatic and physiographic elements for cataclysmic floods were in place in the Pacific Northwest by about 1.1 Ma.

  13. Spatial distribution of cones and satellite-detected lineaments in the Pali Aike Volcanic Field (southernmost Patagonia): insights into the tectonic setting of a Neogene rift system

    Science.gov (United States)

    Mazzarini, Francesco; D'Orazio, Massimo

    2003-07-01

    The relationships between the distribution and morphometric features of eruptive structures (scoria and spatter cones, maar, tuff rings) and the fracture network were investigated in the Pliocene-Quaternary Pali Aike Volcanic Field (southernmost Patagonia, Argentina-Chile). The alkali basaltic/basanitic magmas which erupted in this area have nearly primary magma compositions and often bear mantle xenoliths; hence magma ascent from deep-seated reservoirs was probably very fast, with no significant stagnation at crustal levels. Field surveys and satellite image analysis led to the identification of up to 467 eruptive structures and four main NW-SE, NE-SW, E-W and N-S fracture systems. The spatial distribution of eruptive cones and fractures was investigated through the computation of power-law exponents ( Df) for self-similar clustering. The self-similarity of cones and fractures was defined between lower and upper cut-offs which were in turn related to the thickness of the fractured mechanical layer. The fractal character of cones and fracture distribution (clustering) in the Pali Aike Volcanic Field area was thus correlated with crustal thickness. The self-similarity of fractures was used to establish the relative chronology of the detected fracture systems. The self-similar clustering exponent is highest in the E-W and NW-SE fracture systems ( Df=1.78 and 1.77, respectively), and lowest in the N-S system ( Df=1.65). The self-similar clustering of eruptive structures is well defined ( Df=1.45). The intense volcano-tectonic activity in the Pali Aike area marks a major Pliocene-Quaternary phase in the development of the Magellan Neogene Rift System.

  14. 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

  15. Models of volcanic eruption hazards

    Energy Technology Data Exchange (ETDEWEB)

    Wohletz, K.H.

    1992-01-01

    Volcanic eruptions pose an ever present but poorly constrained hazard to life and property for geothermal installations in volcanic areas. Because eruptions occur sporadically and may limit field access, quantitative and systematic field studies of eruptions are difficult to complete. Circumventing this difficulty, laboratory models and numerical simulations are pivotal in building our understanding of eruptions. For example, the results of fuel-coolant interaction experiments show that magma-water interaction controls many eruption styles. Applying these results, increasing numbers of field studies now document and interpret the role of external water eruptions. Similarly, numerical simulations solve the fundamental physics of high-speed fluid flow and give quantitative predictions that elucidate the complexities of pyroclastic flows and surges. A primary goal of these models is to guide geologists in searching for critical field relationships and making their interpretations. Coupled with field work, modeling is beginning to allow more quantitative and predictive volcanic hazard assessments.

  16. 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.

  17. 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

  18. Mantle Origin of Silicic Calc-alkaline Basalts to Andesites in the Central Mexican Volcanic Belt

    Science.gov (United States)

    Straub, S. M.; Zellmer, G. F.; Gómez-Tuena, A.; Stuart, F.; Espinasa-Perena, R.; Cai, Y.

    2011-12-01

    The Quaternary central Mexican Volcanic Belt, constructed on ~50 km thick continental crust, erupts a broad spectrum of basaltic to dacitic calc-alkaline magmas with the arc-typical high ratios of large-ion lithophile to high-field strength elements. In order to understand their genesis, we investigated high-Mg# olivine-phyric calc-alkaline basalts to andesites from Holocene monogenetic volcanoes Tuxtepec (50.2 wt% SiO2; 9.7 wt% MgO), Yecahuazac (53.1;8.0), Suchiooc Cone (53.2;9.2), Guespalapa (54.4-61.2;5.3-7.9) and Cuatepel (55.6-58.9;5.4-7.5), and as well as one basaltic andesite from composite volcano Popocateptl (56.7;6.9). The high 3He/4He (7.3 ± 0.3 Ra; n=16) of olivine phenocrysts that crystallize at upper crustal levels, and the limited range of Sr-Nd-Hf isotope ratios preclude any significant crustal contamination of these magmas. Moreover, small, but significant differences in Sr-Nd-Hf isotope ratios and the variations of olivine phenocrysts in the Fo-Ni space conclusively rule out that these magmas were related through fractional crystallization. Consequently, the basaltic to andesitic magmas must originate from the sub-arc mantle. Building on the high-Ni content of the olivines that by far exceed Ni abundances of olivines in partial melts of peridotite, we propose that the subarc MVB mantle contains segregations of silica-excess and silica-deficient 'reaction pyroxenites' that formed through infiltration of highly reactive silicic fluids or melts from slab. Upon melting, the pyroxenites produce dacitic and basaltic initial melts, respectively, that mix in variable proportions during ascent through mantle and crust. This genetic model links the silica enrichment of the arc magmas directly to the silica flux from slab, with no requirement for any significant melt silica increase in the overlying crust.

  19. Revised ages for tuffs of the Yellowstone Plateau volcanic field: Assignment of the Huckleberry Ridge Tuff to a new geomagnetic polarity event

    Science.gov (United States)

    Lanphere, M.A.; Champion, D.E.; Christiansen, R.L.; Izett, G.A.; Obradovich, J.D.

    2002-01-01

    40Ar/39Ar ages were determined on the three major ash-flow tuffs of the Yellowstone Plateau volcanic field in the region of Yellowstone National Park in order to improve the precision of previously determined ages. Total-fusion and incremental-heating ages of sanidine yielded the following mean ages: Huckleberry Ridge Tuff-2.059 ?? 0.004 Ma; Mesa Falls Tuff-1.285 ?? 0.004 Ma; and Lava Creek Tuff-0.639 ?? 0.002 Ma. The Huckleberry Ridge Tuff has a transitional magnetic direction and has previously been related to the Reunion Normal-Polarity Subchron. Dating of the Reunion event has been reviewed and its ages have been normalized to a common value for mineral standards. The age of the Huckleberry Ridge Tuff is significantly younger than lava flows of the Reunion event on Re??union Island, supporting other evidence for a normal-polarity event younger than the Reunion event.

  20. Paleomagnetism and 40Ar/39Ar geochronology of the Plio-Pleistocene Boring Volcanic Field: Implications for the geomagnetic polarity time scale and paleosecular variation

    Science.gov (United States)

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

    2017-01-01

    Paleomagnetic directions and 40Ar/39Ar ages have been determined for samples of lava flows from the same outcrops, where possible, for 84 eruptive units ranging in age from 3200 ka to 60 ka within the Boring Volcanic Field (BVF) of the Pacific Northwest, USA. This study expands upon our previous results for the BVF, and compares the combined results with the current geomagnetic polarity time scale (GPTS). Lava flows with transitional directions were found within the BVF at the Matuyama-Brunhes and Jaramillo-Matuyama polarity boundaries, and replicate ages corresponding to these and other boundaries have been newly ascertained. Although the BVF data generally agree with GPTS chronozone boundaries, they indicate that onset of the Gauss-Matuyama transition and Olduvai subchron occurred significantly earlier than given in the current time scale calibration. Additional comparisons show that the BVF results are consistent with recent statistical models of geomagnetic paleosecular variation.

  1. 大兴安岭-太行山重力梯度带以西的第四纪火山活动%Quaternary Volcanic Activities in the West of the Daxing′anling-Taihangshan Gravity Lineament

    Institute of Scientific and Technical Information of China (English)

    樊祺诚; 赵勇伟; 陈生生; 李霓; 隋建立

    2015-01-01

    Quaternary volcanic activities in the west of the Daxing'anling-Taihangshan gravity lineament stretch,from north to south,across two different geotectonic setting,the Xing'an Mongolian orogenic belt and the North China Craton.The volcanic activities generated three volcanic clusters with various sizes:Nuominhe volcanic cluster and Chaoerhe-Halahahe volcanic cluster in the north,Abaga volcanic cluster and Dalinuoer volcanic cluster in the middle,and Datong volcanic cluster and Wulanhada volcanic cluster in the south.These volcanic clusters consist mainly of monogenetic volcanos with the cone number from dozens to more than 200.For example,the Abaga-Dalinuoer volcanic field in Inner Mongolia ex-tends northwestward into the adjacent Dariganga lava plateau of Mongolia,forming the largest Cenozoic volcanic fields in eastern Asia.Thus,the west of Daxing'anling-Taihangshan gravity lineament is a key place to (1 )discuss origin and tec-tonic setting of intra-continent volcanic activity,and (2)study differential evolutions between the east and west sides of the Daxing'anling-Taihangshan gravity lineament and between the Xing'an Mongolian orogenic belt and the North China Craton.%大兴安岭—太行山重力梯度带以西的第四纪火山活动自北往南贯穿兴蒙造山带和华北克拉通2个大地构造单元,可以分为北、中、南三部分,展现规模不等的火山群:北部诺敏河火山群和绰尔河—哈拉哈河火山群,中部阿巴嘎火山群和达里诺尔火山群,南部大同火山群和乌兰哈达火山群。这些火山群主要由单成因火山组成,少则几十座,多则200余座,如阿巴嘎火山群向北延入蒙古达里干加,构成亚洲东部面积最大的新生代火山区。因此,大兴安岭—太行山重力梯度带以西的第四纪火山成为探讨大陆内部火山活动构造背景与成因机制的重要场所,也是获取大兴安岭—太行山重力梯度带东西两侧和兴

  2. Volcanic Catastrophes

    Science.gov (United States)

    Eichelberger, J. C.

    2003-12-01

    The big news from 20th century geophysics may not be plate tectonics but rather the surprise return of catastrophism, following its apparent 19th century defeat to uniformitarianism. Divine miracles and plagues had yielded to the logic of integrating observations of everyday change over time. Yet the brilliant interpretation of the Cretaceous-Tertiary Boundary iridium anomaly introduced an empirically based catastrophism. Undoubtedly, decades of contemplating our own nuclear self-destruction played a role in this. Concepts of nuclear winter, volcanic winter, and meteor impact winter are closely allied. And once the veil of threat of all-out nuclear exchange began to lift, we could begin to imagine slower routes to destruction as "global change". As a way to end our world, fire is a good one. Three-dimensional magma chambers do not have as severe a magnitude limitation as essentially two-dimensional faults. Thus, while we have experienced earthquakes that are as big as they get, we have not experienced volcanic eruptions nearly as great as those preserved in the geologic record. The range extends to events almost three orders of magnitude greater than any eruptions of the 20th century. Such a calamity now would at the very least bring society to a temporary halt globally, and cause death and destruction on a continental scale. At maximum, there is the possibility of hindering photosynthesis and threatening life more generally. It has even been speculated that the relative genetic homogeneity of humankind derives from an evolutionary "bottleneck" from near-extinction in a volcanic cataclysm. This is somewhat more palatable to contemplate than a return to a form of Original Sin, in which we arrived at homogeneity by a sort of "ethnic cleansing". Lacking a written record of truly great eruptions, our sense of human impact must necessarily be aided by archeological and anthropological investigations. For example, there is much to be learned about the influence of

  3. 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).

  4. Magma displacements under insular volcanic fields, applications to eruption forecasting: El Hierro, Canary Islands, 2011-2013

    Science.gov (United States)

    García, A.; Fernández-Ros, A.; Berrocoso, M.; Marrero, J. M.; Prates, G.; De la Cruz-Reyna, S.; Ortiz, R.

    2014-04-01

    Significant deformations, followed by increased seismicity detected since 2011 July at El Hierro, Canary Islands, Spain, prompted the deployment of additional monitoring equipment. The climax of this unrest was a submarine eruption first detected on 2011 October 10, and located at about 2 km SW of La Restinga, southernmost village of El Hierro Island. The eruption ceased on 2012 March 5, after the volcanic tremor signals persistently weakened through 2012 February. However, the seismic activity did not end with the eruption, as several other seismic crises followed. The seismic episodes presented a characteristic pattern: over a few days the number and magnitude of seismic event increased persistently, culminating in seismic events severe enough to be felt all over the island. Those crises occurred in 2011 November, 2012 June and September, 2012 December to 2013 January and in 2013 March-April. In all cases the seismic unrest was preceded by significant deformations measured on the island's surface that continued during the whole episode. Analysis of the available GPS and seismic data suggests that several magma displacement processes occurred at depth from the beginning of the unrest. The first main magma movement or `injection' culminated with the 2011 October submarine eruption. A model combining the geometry of the magma injection process and the variations in seismic energy release has allowed successful forecasting of the new-vent opening.

  5. 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.

  6. Detailed geologic field mapping and radiometric dating of the Abanico Formation in the Principal Cordillera, central Chile: Evidence of protracted volcanism and implications for Cenozoic tectonics

    Science.gov (United States)

    Mosolf, J.; Gans, P. B.; Wyss, A. R.; Cottle, J. M.

    2011-12-01

    Many aspects of the long-term evolution of intra-arc processes remain poorly understood, including temporal trends in magmatism, temporal and spatial patterns of volcanism, and styles of arc deformation. The Abanico Formation in the Principal Cordillera of central Chile is a thick, well-exposed section of volcanogenic strata providing a superb locale for the investigation of continental arc dynamics over a 60+ myr timescale. In this study, eight new litho-stratigraphic members of the Abanico Formation are described and mapped in the Río Tinguiririca river area. Mapping and field observations show the Abanico Formation measures up to ~2.5 km in composite stratigraphic thickness. The lower ~1.1 km of the section (> 46 Ma) is dominated by andesitic breccias interbedded with andesite, basaltic andesite, and olivine basalt lavas. The upper 1.4 km of the section (volcanics composed mainly of andesite, basaltic andesite, and basalt lavas. A strong deformational overprint has tilted, folded, and faulted the Abanico map units. Fold axes and reverse faults, both east and west directed, are generally N-S trending. Reverse faults achieve up to ~50 Ma of stratigraphic separation, placing Campanian strata on Miocene rocks with up to ~2 km of vertical throw. The Abanico Formation is also offset by numerous steeply-dipping, oblique-slip faults with 100+ meters of slip. The Abanico Formation is interpreted to have been emplaced within an active arc, with progressively more evolved material being erupted up section during the Campanian to Miocene, followed by more mafic volcanism during the Pliocene and Quaternary. Radiometric ages bounding intra-formational unconformities imply that shortening commenced no later than the early Miocene, with an older deformational episode possibly preceding it. Results of this study clearly demonstrate the age of the Abanico Formation extends from Campanian to Miocene, requiring a significant revision of the current mid-Tertiary age paradigm for

  7. A micro-scale investigation of melt production and extraction in the upper mantle based on silicate melt pockets in ultramafic xenoliths from the Bakony-Balaton Highland Volcanic Field (Western Hungary)

    DEFF Research Database (Denmark)

    Bali, Eniko; Zanetti, A.; Szabo, C.;

    2008-01-01

    Mantle xenoliths in Neogene alkali basalts of the Bakony-Balaton Highland Volcanic Field (Western Hungary) frequently have melt pockets that contain silicate minerals, glass, and often carbonate globules. Textural, geochemical and thermobarometric data indicate that the melt pockets formed at rel...

  8. 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.).

  9. Coexistence of pumice and manganese nodule fields-evidence for submarine silicic volcanism in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    -generation mine-sites of manganese nodules, of high abundance and paramarginal ore grade, seem to be closely related to the pumice field. Circumstantial evidence, i.e. juxtaposed pumice and nodule fields in the vicinity of three major fracture zones (73 degrees E...

  10. 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

  11. Rapid pre-eruptive thermal rejuvenation in a large silicic magma body: the case of the Masonic Park Tuff, Southern Rocky Mountain volcanic field, CO, USA

    Science.gov (United States)

    Sliwinski, J. T.; Bachmann, O.; Dungan, M. A.; Huber, C.; Deering, C. D.; Lipman, P. W.; Martin, L. H. J.; Liebske, C.

    2017-05-01

    Determining the mechanisms involved in generating large-volume eruptions (>100 km3) of silicic magma with crystallinities approaching rheological lock-up ( 50 vol% crystals) remains a challenge for volcanologists. The Cenozoic Southern Rocky Mountain volcanic field, in Colorado and northernmost New Mexico, USA, produced ten such crystal-rich ignimbrites within 3 m.y. This work focuses on the 28.7 Ma Masonic Park Tuff, a dacitic ( 62-65 wt% SiO2) ignimbrite with an estimated erupted volume of 500 km3 and an average of 45 vol% crystals. Near-absence of quartz, titanite, and sanidine, pronounced An-rich spikes near the rims of plagioclase, and reverse zoning in clinopyroxene record the reheating (from 750 to >800 °C) of an upper crustal mush in response to hotter recharge from below. Zircon U-Pb ages suggest prolonged magmatic residence, while Yb/Dy vs temperature trends indicate co-crystallization with titanite which was later resorbed. High Sr, Ba, and Ti concentrations in plagioclase microlites and phenocryst rims require in-situ feldspar melting and concurrent, but limited, mass addition provided by the recharge, likely in the form of a melt-gas mixture. The larger Fish Canyon Tuff, which erupted from the same location 0.7 m.y. later, also underwent pre-eruptive reheating and partial melting of quartz, titanite, and feldspars in a long-lived upper crustal mush following the underplating of hotter magma. The Fish Canyon Tuff, however, records cooler pre-eruptive temperatures ( 710-760 °C) and a mineral assemblage indicative of higher magmatic water contents (abundant resorbed sanidine and quartz, euhedral amphibole and titanite, and absence of pyroxene). These similar pre-eruptive mush-reactivation histories, despite differing mineral assemblages and pre-eruptive temperatures, indicate that thermal rejuvenation is a key step in the eruption of crystal-rich silicic volcanics over a wide range of conditions.

  12. Fake ballistics and real explosions: field-scale experiments on the ejection and emplacement of volcanic bombs during vent-clearing explosive activity

    Science.gov (United States)

    Taddeucci, J.; Valentine, G.; Gaudin, D.; Graettinger, A. H.; Lube, G.; Kueppers, U.; Sonder, I.; White, J. D.; Ross, P.; Bowman, D. C.

    2013-12-01

    Ballistics - bomb-sized pyroclasts that travel from volcanic source to final emplacement position along ballistic trajectories - represent a prime source of volcanic hazard, but their emplacement range, size, and density is useful to inverse model key eruption parameters related to their initial ejection velocity. Models and theory, however, have so far focused on the trajectory of ballistics after leaving the vent, neglecting the complex dynamics of their initial acceleration phase in the vent/conduit. Here, we use field-scale buried explosion experiments to study the ground-to-ground ballistic emplacement of particles through their entire acceleration-deceleration cycle. Twelve blasts were performed at the University at Buffalo Large Scale Experimental Facility with a range of scaled depths (burial depth divided by the cubic root of the energy of the explosive charge) and crater configurations. In all runs, ballistic analogs were placed on the ground surface at variable distance from the vertical projection of the buried charge, resulting in variable ejection angle. The chosen analogs are tennis and ping-pong balls filled with different materials, covering a limited range of sizes and densities. The analogs are tracked in multiple high-speed and high-definition videos, while Particle Image Velocimetry is used to detail ground motion in response to the buried blasts. In addition, after each blast the emplacement position of all analog ballistics was mapped with respect to the blast location. Preliminary results show the acceleration history of ballistics to be quite variable, from very short and relatively simple acceleration coupled with ground motion, to more complex, multi-stage accelerations possibly affected not only by the initial ground motion but also by variable coupling with the gas-particle mixture generated by the blasts. Further analysis of the experimental results is expected to provide new interpretative tools for ballistic deposits and better

  13. Growth, destruction and volcanic facies architecture of three volcanic centres in the Miocene Uşak-Güre basin, western Turkey: Subaqueous-subaerial volcanism in a lacustrine setting

    Science.gov (United States)

    Karaoğlu, Özgür; Helvacı, Cahit

    2012-11-01

    Early to Mid-Miocene extension in western Anatolia, related to plate tectonic motions, resulted in the development of a number of normal fault-bounded sedimentary basins as well as different styles and compositions of volcanic activity. The Uşak and Güre basins accumulated a thick fluvio-lacustrine fill in which three distinct volcanic edifices (Elmadağ, İtecektepe and Beydağı) and their deposits can overlap with each other and with the sediments produced by the background sedimentation. In addition, complete facies architectures of small-volume (monogenetic) volcanoes have been recognised in association with the three large complex (polygenetic) volcanoes providing a complex mixed siliciclastic and volcaniclastic basin infill in the respective basins where volcanism took place. All three volcanic centres display a complex succession of effusive and explosive volcanisms and their reworked deposits, with abundant evidences of magma-water interaction such as peperites for non-explosive magma-water interaction with the lacustrine water-saturated sediment and standing water body in a large alkaline lake. During the constructive phase, proximal successions of pyroclastic flows, pyroclastic falls, and rarely surge deposits are associated with distally-emplaced debris flow deposits, sometimes of mixed volcanogenic and terrestrial origins, and are interbedded with lacustrine sediments of the Inay Group. All three volcanic centres then experienced a phase of volcano growth and degradation between 17 and 15 Ma ago, most likely related to a combination of tectonic movements on NE-SW-trending basement faults, which triggered multiple flank collapses and volcanic debris avalanches (Elmadağ), and voluminous ignimbrite eruptions that triggered caldera formation (İtecektepe and Beydağı volcanic centres). Lacustrine conditions persisted during the destruction and post-destruction stages of the volcano's evolution, as evidenced by indications of magma-water interactions

  14. Scientific Drilling in a Central Italian Volcanic District

    Directory of Open Access Journals (Sweden)

    Paola Montone

    2007-09-01

    Full Text Available The Colli Albani Volcanic District, located 15 km SE of Rome (Fig. 1, is part of the Roman Magmatic Province, a belt of potassic to ultra-potassic volcanic districts that developed along the Tyrrhenian Sea margin since Middle Pleistocene time (Conticelli and Peccerillo, 1992; Marra et al., 2004; Giordano et al., 2006 and references therein. Eruption centers are aligned along NW-SE oriented majorextensional structures guiding the dislocation of Meso-Cenozoic siliceous-carbonate sedimentary successions at the rear of the Apennine belt. Volcanic districts developed in structural sectors with most favorable conditions for magma uprise. In particular, the Colli Albani volcanism is located in a N-S shear zone where it intersects the extensional NW- and NE-trending fault systems. In the last decade, geochronological measurements allowed for reconstructions of the eruptive history and led to the classification as "dormant" volcano. The volcanic history may be roughly subdivided into three main phases marked by different eruptive mechanisms andmagma volumes. The early Tuscolano-Artemisio Phase (ca. 561–351 ky, the most explosive and voluminous one, is characterized by five large pyroclastic flow-forming eruptions. After a ~40-ky-long dormancy, a lesser energetic phase of activity took place (Faete Phase; ca. 308–250 ky, which started with peripheral effusive eruptions coupled with subordinate hydromagmatic activity. A new ~50-ky-long dormancypreceded the start of the late hydromagmatic phase (ca. 200–36 ky, which was dominated by pyroclastic-surge eruptions, with formation of several monogenetic or multiple maars and/or tuff rings.

  15. 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

    and Sr–Nd isotopic compositions of the basaltic lavas and Payún Matrú rocks indicate that the trachytes of Payún Matrú are the result of fractional crystallization of basaltic parent magmas without significant upper crustal contamination, and that the basalts have a geochemical similarity to ocean island...... 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...

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

    DEFF Research Database (Denmark)

    Søager, Nina

    primitive basalts and trachybasalts but also more evolved samples from the retroarc region and the larger volcanoes Payún Matrú and Payún Liso are presented. The samples cover a broad range of compositions from intraplate lavas similar to ocean island basalts to arc andesites. A common feature found...... 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...... the literature. The Nevado basalts have been modelled by 4-10 % melting of a primitive mantle added 1-5 % upper continental crust. In the southern Payenia province, intraplate basalts dominate. The samples from the Payún Matrú and Río Colorado volcanic fields are apparently unaffected by the subducting slab...

  17. 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.

  18. Oxygen isotope evolution of the Lake Owyhee volcanic field, Oregon, and implications for low-δ18O magmas of the Snake River Plain - Yellowstone hotspot

    Science.gov (United States)

    Blum, T.; Kitajima, K.; Nakashima, D.; Valley, J. W.

    2013-12-01

    The Snake River Plain - Yellowstone (SRP-Y) hotspot trend is one of the largest known low-δ18O magmatic provinces, yet the timing and distribution of hydrothermal alteration relative to hotspot magmatism remains incompletely understood. Existing models for SRP-Y low-δ18O magma genesis differ regarding the timing of protolith alteration (e.g. Eocene vs. present), depth at which alteration occurs (e.g. 15 km vs. Owyhee volcanic field (LOVF) of east central Oregon to further identify magmatic oxygen isotope trends within the field. These data offer insight into the timing of alteration and the extent of the greater SRP-Y low-δ18O province, as well as the conditions that generate large low-δ18O provinces. 16-14 Ma silicic volcanism in the LOVF is linked to the pre-14 Ma SRP-Y hotspot, with volcanism partially overlapping extension in the north-south trending Oregon-Idaho Graben (OIG). Ion microprobe analyses of zircons from 16 LOVF silicic lavas and tuffs reveal homogeneous zircons on both the single grain and hand sample scales: individual samples have 2 S.D. for δ18O ranging from 0.27 to 0.96‰ (SMOW), and sample averages ranging from 1.8 to 6.0‰, excluding texturally chaotic and/or porous zircons which have δ18O values as low as 0.0‰. All low-δ18O LOVF magmas, including the caldera-forming Tuff of Leslie Gulch and Tuff of Spring Creek, are confined to the OIG, although not all zircons from within the OIG have low δ18O values. The presence and sequence of low-δ18O magmas in the LOVF and adjacent central Snake River Plain (CSRP) cannot be explained by existing caldera subsidence or pre-hotspot source models. These data, however, combined with volumetrically limited low-δ18O material in the adjacent Idaho Batholith and Basin and Range, are consistent with low-δ18O magmas generated by the superposition of high hotspot-derived thermal fluxes on active extensional structures (OIG extension in the LOVF, and Basin and Range rifting in the CSRP) thereby

  19. Volcanic hazard management in dispersed volcanism areas

    Science.gov (United States)

    Marrero, Jose Manuel; Garcia, Alicia; Ortiz, Ramon

    2014-05-01

    Traditional volcanic hazard methodologies were developed mainly to deal with the big stratovolcanoes. In such type of volcanoes, the hazard map is an important tool for decision-makers not only during a volcanic crisis but also for territorial planning. According to the past and recent eruptions of a volcano, all possible volcanic hazards are modelled and included in the hazard map. Combining the hazard map with the Event Tree the impact area can be zoned and defining the likely eruptive scenarios that will be used during a real volcanic crisis. But in areas of disperse volcanism is very complex to apply the same volcanic hazard methodologies. The event tree do not take into account unknown vents, because the spatial concepts included in it are only related with the distance reached by volcanic hazards. The volcanic hazard simulation is also difficult because the vent scatter modifies the results. The volcanic susceptibility try to solve this problem, calculating the most likely areas to have an eruption, but the differences between low and large values obtained are often very small. In these conditions the traditional hazard map effectiveness could be questioned, making necessary a change in the concept of hazard map. Instead to delimit the potential impact areas, the hazard map should show the expected behaviour of the volcanic activity and how the differences in the landscape and internal geo-structures could condition such behaviour. This approach has been carried out in La Palma (Canary Islands), combining the concept of long-term hazard map with the short-term volcanic scenario to show the expected volcanic activity behaviour. The objective is the decision-makers understand how a volcanic crisis could be and what kind of mitigation measurement and strategy could be used.

  20. 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.

  1. Petrography and geochemistry of achnelithic tephra from Las Herrerías Volcano (Calatrava volcanic field, Spain): Formation of nephelinitic achneliths and post-depositional glass alteration

    Science.gov (United States)

    Carracedo-Sánchez, M.; Sarrionandia, F.; Arostegui, J.; Errandonea-Martin, J.; Gil-Ibarguchi, J. I.

    2016-11-01

    We present the results of a petrographic and geochemical study carried out on a layer of achnelithic tephra outcropping at the base of the volcanic cone of Las Herrerías (Miocene-Quaternary volcanic region of Campo de Calatrava, Spain). The tephra, with a composition of nephelinite and ash (volcanic maar lake. Afterwards, there was no more water circulation through the achnelithic tephra, which was sealed from water by overlying hydrovolcanic tuff deposits. It was this isolation that made possible the preservation of glass to the present day.

  2. 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.

  3. Phosphorus zoning as a recorder of crystal growth kinetics: application to second-generation olivine in mantle xenoliths from the Cima Volcanic Field

    Science.gov (United States)

    Baziotis, I.; Asimow, P. D.; Ntaflos, T.; Boyce, J. W.; McCubbin, F. M.; Koroneos, A.; Perugini, D.; Flude, S.; Storey, M.; Liu, Y. S.; Klemme, S.; Berndt, J.

    2017-07-01

    Composite mantle xenoliths from the Cima Volcanic Field (CA, USA) contain glassy veins that cross-cut lithologic layering and preserve evidence of lithospheric melt infiltration events. Compositions and textures of minerals and glasses from these veins have the potential to place constraints on the rates and extents of reaction during infiltration. We studied glass-bearing regions of two previously undescribed composite xenoliths, including optical petrography and chemical analysis for major and trace elements by electron probe microanalysis and laser-ablation inductively coupled plasma mass spectrometry. The petrogenetic history of each vein involves melt intrusion, cooling accompanied by both wall-rock reaction and crystallization, quench of melt to a glass, and possibly later modifications. Exotic secondary olivine crystals in the veins display concentric phosphorus (P)-rich zoning, P-rich glass inclusions, and zoning of rapidly diffusing elements (e.g., Li) that we interpret as records of rapid disequilibrium events and cooling rates on the order of 10 °C/h. Nevertheless, thermodynamic modeling of the diversity of glass compositions recorded in one of the samples demonstrates extensive reaction with Mg-rich olivine from the matrix before final quench. Our results serve as a case study of methods for interpreting the rates and processes of lithospheric melt-rock reactions in many continental and oceanic environments.

  4. A new genetic interpretation for the Caotaobei uranium deposit associated with the shoshonitic volcanic rocks in the Hecaokeng ore field, southern Jiangxi, China

    Directory of Open Access Journals (Sweden)

    Dong-Sheng Yang

    2017-03-01

    Full Text Available Combined with in-situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS zircon UPb geochronology, published and unpublished literature on the Caotaobei uranium deposit in southern Jiangxi province, China, is re-examined to provide an improved understanding of the origin of the main ore (103 Ma. The Caotaobei deposit lies in the Hecaokeng ore field and is currently one of China's largest, volcanic-related uranium producers. Unlike commonly known volcanogenic uranium deposits throughout the world, it is spatially associated with intermediate lavas with a shoshonitic composition. Uranium mineralization (pitchblende occurs predominantly as veinlets, disseminations, and massive ores, hosted by the cryptoexplosive breccias rimming the Caotaobei crater. Zircons from one latite define four distinct 206Pb/238U age groups at 220–235 Ma (Triassic, 188 Ma (Early Jurassic, 131–137 Ma (Early Cretaceous, and 97–103 Ma (Early-Late Cretaceous transition, hereafter termed mid-Cretaceous. The integrated age (134 ± 2 Ma of Early Cretaceous zircons (group III is interpreted as representing the time of lava emplacement. The age data, together with the re-examination of literature, does not definitively support a volcanogenic origin for the generation of the deposit, which was proposed by the previous workers based mainly on the close spatial relationship and the age similarity between the main ore and volcanic lavas. Drill core and grade-control data reveal that rich concentrations of primary uranium ore are common around the granite porphyry dikes cutting the lavas, and that the cryptoexplosive breccias away from the dikes are barren or unmineralized. These observations indicate that the emplacement of the granite porphyries exerts a fundamental control on ore distribution and thus a genetic link exists between main-stage uranium mineralization and the intrusions of the dikes. Zircon overgrowths of mid-Cretaceous age (99.6

  5. NASA Desert RATS 2010: Preliminary Results for Science Operations Conducted in the San Francisco Volcanic Field, Arizona

    Science.gov (United States)

    Gruener, J. E.; Lofgren, G. E.; Bluethmann, W. J.; Bell, E. R.

    2011-01-01

    The National Aeronautics and Space Administration (NASA) is working with international partners to develop the space architectures and mission plans necessary for human spaceflight beyond earth orbit. These mission plans include the exploration of planetary surfaces with significant gravity fields. The Apollo missions to the Moon demonstrated conclusively that surface mobility is a key asset that improves the efficiency of human explorers on a planetary surface. NASA's Desert Research and Technology Studies (Desert RATS) is a multi-year series tests of hardware and operations carried out annually in the high desert of Arizona. Conducted since 1998, these activities are designed to exercise planetary surface hardware and operations in relatively harsh climatic conditions where long-distance, multi-day roving is achievable

  6. 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; Civetta, Lucia; Webster, Jim D.; Cioni, Raffaello; D'Antonio, Massimo

    2016-04-01

    One of the current stakes in modern volcanology is the definition of magma storage conditions which has direct implications on the eruptive style and thus on the associated risks and the management of likely related crisis. In alkaline differentiated magmas, chlorine (Cl), contrary to H2O, occurs as a minor volatile species but may be used as a geobarometer. Numerous experimental studies on Cl solubility have highlighted its saturation conditions in silicate melts. The NaCl-H2O system is characterized by immiscibility under wide ranges of pressure, temperature and NaCl content (Mount Somma-Vesuvius, Phlegrean Fields and Ischia. We have analysed the products of the representative explosive eruptions of each volcano, including Plinian, sub-Plinian and strombolian events. We have focussed our research on the earliest emitted, most evolved products of each eruption, likely representing the shallower, fluid-saturated portion of the reservoir. As the studied eruptions cover the entire eruptive history of each volcanic system, the results allow better constraining the evolution through time of the shallow plumbing system. We highlighted for Mount Somma - Vesuvius two magma ponding zones, at ~170-200 MPa and ~105-115 MPa, alternatively active in time. For Phlegrean Fields, we evidence a progressive deepening of the shallow reservoirs, from the Campanian Ignimbrite (30-50 MPa) to the Monte Nuovo eruption (115 MPa). Only one eruption was studied for Ischia, the Cretaio eruption, that shows a reservoir at 140 MPa. The results on pressure are in large agreement with literature. The Cl geobarometer may help scientists to define the reservoir dynamics through time and provide strong constraints on pre-eruptive conditions, of utmost importance for the interpretation of the monitoring data and the identification of precursory signals.

  7. Analysis of Volcanic Deposits From the 2001 Eruption of Mt. Cleveland, Alaska Using Multisensor Satellite Data and Field Observations

    Science.gov (United States)

    Smith, S. J.; Dehn, J.; Moore, R. B.

    2003-12-01

    Eruptive characteristics and histories of Aleutian stratovolcanoes are some of the least understood because of their remote locations, yet they have the ability to cripple the heavily traveled air routes in this region. Remote sensing is useful for gathering information on remote eruption deposits and compliments field observations. Mount Cleveland, on the western part of Chuginadak Island, has been one of the most active of these Aleutian volcanoes over the past century, its most recent eruption disrupted air traffic from February to March 2001. Using field observations of pyroclastic fan deposits preceding an a\\'{}a lava flow down the western flank of Mount Cleveland in 2001 this study attempts to associate spectral characteristics of these deposits (from Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), Second European Remote Sensing Satellite (ERS-2), and RADARSAT-1) to similar characteristics around the entire volcano. By also using Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) data this study will present a more accurate chronology of the 2001 eruption. Field observations of the pyroclastic fan deposit reveal the existence of two separate stratigraphic deposits, an initial smooth ˜10-30 m thick a\\'{}a block and ash deposit overlain by a rougher ˜1-15 m thin breadcrust bomb deposit. The southern and northeastern parts of the fan are dominated by the thin breadcrust bomb deposit with an average bomb area of 2.38 m2, while the northwestern part is dominated by very large a\\'{}a blocks with pull-apart fractures and a much larger average block area of 22.44 m2. Initial Landsat 7 ETM+ and photographic analysis of this pyroclastic fan displays a slight coloration difference between the two deposits. The stratigraphic sequence of the pyroclastic fan from 2001 suggests that there was 1) a warm to hot debris flow from the collapse of

  8. 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.

  9. Efficient Exploration and Development of Carboniferous Volcanic Gas Field in Kelameili Area in Junggar Basin%克拉美丽石炭系火山岩气田的高效勘探开发

    Institute of Scientific and Technical Information of China (English)

    董雪梅; 徐怀民; 贺陆明; 任军民; 吴静

    2012-01-01

    Volcanic oil-gas exploration in Junggar basin started in 1950's.In recent years,through comprehensive researches of hydrocarbon accumulation conditions of the Carboniferous volcanic reservoirs,Ludong-Wucaiwan area is chosen as major exploration target to carry out systematic studies and make technological breakthrough,thus deepening the knowledge of volcanic reservoir,establishing the exploration thought of reservoir controls dominated by volcanic rock body,based on which the matched technologies were developed,and the breakthroughs have been made in drilling of volcanic rock body as main target in Dinan bulge.A hundred billion cubic meters of Kelameili gas field with both source and reservoir in Carboniferous system was proved in two years and the first large-scale integrated volcanic gas field in Junggar basin is discovered.Up to now,it has been brought into the scale and efficient production.The Carboniferous volcanic reservoirs have become an important domain for oil-gas exploration in Junggar basin.%准噶尔盆地火山岩油气勘探始于20世纪50年代,近年来通过准噶尔盆地石炭系油气成藏条件综合研究,优选陆东—五彩湾地区作为勘探主战场,展开针对石炭系火山岩的系统研究和技术攻关,不断深化成藏认识,确立了以火山岩岩体控藏的勘探思路,研发了与之相应的配套技术,在滴南凸起上以火山岩岩体为主要目标展开钻探获得突破,探明了千亿方的石炭系自生自储的克拉美丽气田,形成准噶尔盆地第一个大型整装火山岩气田,并已实现规模高效开发。石炭系火山岩已经成为准噶尔盆地油气勘探的重要领域。

  10. Metasomatic origin of garnet orthopyroxenites in the subcontinental lithospheric mantle underlying Pali Aike volcanic field, southern South America

    Science.gov (United States)

    Wang, Jian; Hattori, Keiko H.; Stern, Charles R.

    2008-11-01

    Garnet-bearing orthopyroxenites occur as both discrete xenoliths and as veinlets in peridotite xenoliths that were brought to the surface by Quaternary Pali Aike alkali basalts in the southernmost of the Patagonian plateau lava fields in southern South America. Orthopyroxenites commonly contain Ti-rich minerals and also relict grains of olivine (Ol) and clinopyroxene (Cpx) occurring as inclusions in secondary orthopyroxene (Opx). The secondary Opx contains high TiO2 (0.20-0.59 wt.%), moderate Al2O3 (2.87-5.10 wt.%) and low magnesium numbers (Mg#, 84.5-89.2) compared with Opx in garnet-bearing peridotites. This suggests that secondary Opx formed at the expense of Ol and Cpx during metasomatism by an evolved Ti-rich melt. The orthopyroxenites contain bulk-rock concentrations of Cr, Ni and platinum group elements similar to peridotites, suggesting that these metals were essentially immobile during metasomatism, and that the metasomatizing melt did not introduce these elements. Instead, the metasomatizing melt contributed alkalis, Ti, Si, Al, and S to the orthopyroxenites based on increased concentrations of these elements and mineralogy. Secondary Opx has also been documented in mantle peridotite xenoliths derived from beneath both active arcs and ancient cratons. In comparison with such Opx in these mantle samples, the secondary Opx in the Pali Aike xenoliths contains relatively high Ti and Al and low Mg. High Ti and low Mg in these samples reflect the evolved nature of the metasomatizing melt that originated from the underlying asthenospheric mantle. The type of secondary Opx, typified by these samples, may be common elsewhere in subcontinental mantle lithosphere (SCLM) affected by asthenospheric upwelling.

  11. Paleomagnetic, Anisotropy of Magnetic Susceptibility, and 40AR/39AR Data from the Cienega Volcano, Cerros del Rio Volcanic Field, New Mexico

    Science.gov (United States)

    Foucher, M. S.; Petronis, M. S.; Lindline, J.; Van Wyk de Vries, B.

    2012-12-01

    Cinder cone eruptions are typically interpreted to have formed by the ascension of magma through a simple conduit. Recent field work and laboratory studies on different excavated volcanoes around the world suggest that magma transport within cinder cones can involve a complex system of feeder geometries. We studied the Cienega volcano, a cinder cone in the Cerros del Rio volcanic field, northern New Mexico, in order to better understand the complexity and the evolution of volcanic plumbing systems in the development of cinder cone volcanoes. We hypothesized that cinder cone plumbing systems are inherently complex and involve numerous feeder geometries (e.g. dikes, sills) and flow patterns both towards and away from the central vent complex. The Cienega volcano comprises tephra fall deposits as well as several vents, multiple intrusions, and numerous lava flow sequences. We inspected the magmatic plumbing system using different laboratory methods including paleomagnetic, anisotropy of magnetic susceptibility (AMS), rock magnetic and thin section studies. We collected samples across each outcrop of the feeder system. The dikes are olivine porphyritic basalts with major clinopyroxene, calcic plagioclase feldspar, magnetite, and xenocrystic quartz. Most samples display a trachytic texture with plagioclase crystals showing a preferred orientation parallel to the dike margins. The magnetic information is held predominantly by a cubic phase magnetite with a low- to moderate-Ti composition of Single or Pseudo-Single Domain grains. The AMS results show various flow directions. Three of six dikes yielded magma flow directions away from the vent. The other dikes showed both a subvertical flow, which corresponds to the typical movement of magma in a dike originating from a deeper crustal level, and a downward flow direction. We concluded that magma initially flowed upward from the magma chamber until it encountered flow resistance. At this structural level (the current

  12. 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

    Energy Technology Data Exchange (ETDEWEB)

    F.V. Perry; A. Cogbill; R. Kelley

    2005-08-26

    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{sup -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

  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. Geochemical and zircon isotopic evidence for extensive high level crustal contamination in Miocene to mid-Pleistocene intra-plate volcanic rocks from the Tengchong field, western Yunnan, China

    Science.gov (United States)

    Li, Linlin; Shi, Yuruo; Williams, Ian S.; Anderson, J. Lawford; Wu, Zhonghai; Wang, Shubing

    2017-08-01

    SHRIMP zircon Pb/U dating of Cenozoic volcanic rocks in the Tengchong area, western Yunnan Province, China, shows that the dacite and andesitic breccia lavas from Qushi village were intruded at 480 ± 10 ka and 800 ± 40 ka, respectively. Moreover, Pb/U dating of trachyandesite from Tuantian village and olivine basalt from Wuhe village give weighted mean 206Pb/238U ages of 2.82 ± 0.08 Ma and 12.28 ± 0.30 Ma. Corrections for initial 230Th disequilibrium of zircon were used for the former two younger ages. The Tengchong volcanic rocks have a large range of SiO2 (48.6-66.9 wt.%) and mostly belong to a high-K calc-alkaline series. The lavas originated from heterogeneous sources and were modified by subsequent fractional crystallization. The REE and other trace element patterns of the Tengchong volcanic rocks resemble magmas having a large component of continental crust. All have similar degrees of LREE and HREE fractionation and are enriched in LILE, La, Ce and Pb, with depletions in Nb, Ta, Ti, Sr and P relative to primitive mantle. Zircon δ18O values of 6.96 ± 0.17 and 7.01 ± 0.24‰ and highly varied negative εHf(t) values of - 1.5 to - 11.0 and - 10.3 to - 13.7, as well as the presence of inherited zircon grains in the studied samples, indicate that the magmas contain crustal material on a large scale. The Tengchong volcanic rocks have HFSE ratios (e.g., Nb/Ta, La/Nb, Zr/Y) similar to continental flood basalts, indicative of an intra-plate extensional tectonic setting. Widespread distributed faults might have facilitated upwelling of mantle-derived melts and eruptions from shallow crustal magma chambers to form the large volcanic field.

  15. Magma injection into a long-lived reservoir to explain geodetically measured uplift: Application to the 2007-2014 unrest episode at Laguna del Maule volcanic field, Chile

    Science.gov (United States)

    Le Mével, Hélène; Gregg, Patricia M.; Feigl, Kurt L.

    2016-08-01

    Moving beyond the widely used kinematic models for the deformation sources, we present a new dynamic model to describe the process of injecting magma into an existing magma reservoir. To validate this model, we derive an analytical solution and compare its results to those calculated using the Finite Element Method. A Newtonian fluid characterized by its viscosity, density, and overpressure (relative to the lithostatic value) flows through a vertical conduit, intruding into a reservoir embedded in an elastic domain, leading to an increase in reservoir pressure and time-dependent surface deformation. We apply our injection model to Interferometric Synthetic Aperture Radar (InSAR) data from the ongoing unrest episode at Laguna del Maule (Chile) volcanic field that started in 2007. Using a grid search optimization, we minimize the misfit to the InSAR displacement data and vary the three parameters governing the analytical solution: the characteristic timescale τP for magma propagation, the maximum injection pressure, and the inflection time when the acceleration switches from positive to negative. For a spheroid with semimajor axis a = 6200 m, semiminor axis c = 100 m, located at a depth of 4.5 km in a purely elastic half-space, the best fit to the InSAR displacement data occurs for τP=9.5 years and an injection pressure rising up to 11.5 MPa for 2 years. The volume flow rate increased to 1.2 m3/s for 2 years and then decreased to 0.7 m3/s in 2014. In 7.3 years, at least 187 × 106 m3 of magma was injected.

  16. On the plumbing system of volcanic complexes: field constraints from the Isle of Skye (UK) and FEM elasto-plastic modelling including gravity and tectonics.

    Science.gov (United States)

    Bistacchi, A.; Pisterna, R.; Romano, V.; Rust, D.; Tibaldi, A.

    2009-04-01

    The plumbing system that connects a sub-volcanic magma reservoir to the surface has been the object of field characterization and mechanical modelling efforts since the pioneering work by Anderson (1936), who produced a detailed account of the spectacular Cullin Cone-sheet Complex (Isle of Skye, UK) and a geometrical and mechanical model aimed at defining the depth to the magma chamber. Since this work, the definition of the stress state in the half space comprised between the magma reservoir and the surface (modelled either as a flat surface or a surface comprising a volcanic edifice) was considered the key point in reconstructing dike propagation paths from the magma chamber. In fact, this process is generally seen as the propagation in an elastic media of purely tensional joints (mode I or opening mode propagation), which follow trajectories perpendicular to the least compressive principal stress axis. Later works generally used different continuum mechanics methodologies (analytic, BEM, FEM) to solve the problem of a pressure source (the magma chamber, either a point source or a finite volume) in an elastic (in some cases heterogeneous) half space (bounded by a flat topography or topped by a "volcano"). All these models (with a few limited exceptions) disregard the effect of the regional stress field, which is caused by tectonic boundary forces and gravitational body load, and consider only the pressure source represented by the magma chamber (review in Gudmundsson, 2006). However, this is only a (sometimes subordinate) component of the total stress field. Grosfils (2007) first introduced the gravitational load (but not tectonic stresses) in an elastic model solved with FEM in a 2D axisymmetric half-space, showing that "failure to incorporate gravitational loading correctly" affect the calculated stress pattern and many of the predictions that can be drawn from the models. In this contribution we report on modelling results that include: 2D axisymmetric or true

  17. Effects of deglaciation on the petrology and eruptive history of the Western Volcanic Zone, Iceland

    Science.gov (United States)

    Eason, Deborah E.; Sinton, John M.; Grönvold, Karl; Kurz, Mark D.

    2015-06-01

    New observations and geochemical analyses of volcanic features in the 170-km-long Western Volcanic Zone (WVZ) of Iceland constrain spatial and temporal variations in volcanic production and composition associated with the last major deglaciation. Subglacial eruptions represent a significant portion of the late Quaternary volcanic budget in Iceland. Individual features can have volumes up to ˜48 km3 and appear to be monogenetic. Subaqueous to subaerial transition zones provide minimum estimates of ice sheet thickness at the time of eruption, although water-magma interactions and fluctuating lake levels during eruption can lead to complex lithological sequences. New major and trace element data for 36 glacial and postglacial eruptive units, combined with observations of lava surface quality, passage zone heights, and 3He exposure ages of some glacial units, indicate a maximum in volcanic production in the WVZ during the last major ice retreat. Anomalously high volcanic production rates continue into the early postglacial period and coincide with significant incompatible element depletions and slightly higher CaO and SiO2 and lower FeO content at a given MgO. Subglacial units with strong incompatible element depletions also have lava surfaces that lack evidence of subsequent glaciation. These units likely formed after the onset of deglaciation, when rapidly melting ice sheets increased decompression rates in the underlying mantle, leading to anomalously high melting rates in the depleted upper mantle. This process also can explain the eruption of extremely depleted picritic lavas during the early postglacial period. These new observations indicate that the increased volcanic activity associated with glacial unloading peaked earlier than previously thought, before Iceland was completely ice free.

  18. Faults and volcanoes: Main volcanic structures in the Acambay Graben, Mexico

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Pedrazzi, D.; Suñe-Puchol, I.; Lacan, P.

    2016-12-01

    The Mexican Volcanic Belt (MVB) province is best known by the major stratovolcanoes, such as Popocatepetl and Colima, but most of the province is formed by modest size stratovolcanoes and monogenetic cones. Regional fault systems were developed together with the building of the volcanic province; the most notorious one is Chapala-Tula Fault System (CTFS), which runs parallel to the central sector of the MVB, and thus it is also referred to as the Intra-Arc fault system. Acambay graben (AG) is part of this central system. It is a 20 x 70 km depression located 100 km to the NW of Mexico City, at the easternmost end of the E-W trending CTFS, and was formed as the result of NS to NE oriented extension. Seismically active normal faults, such as the Acambay-Tixmadejé fault, with a mB =7 earthquake in 1912, delimit the AG. The graben includes several volcanic structures and associated deposits ranging in age from Miocene to 3 ka. The main structures are two stratovolcanoes, Altamirano (900 m high) and Temascalcingo (800 m high). There are also several Miocene-Pliocene lava domes, and Quaternary small cinder cones and shield volcanoes. Faulting of the Acambay graben affects all these volcanic forms, but depending on their ages, the volcanoes are cut by several faults or by a few. That is the case of Altamirano and Temascalcingo volcanoes, where the former is almost unaffected whereas the latter is highly dissected by faults. Altamirano is younger than Temascalcingo; youngest pyroclastic deposits from Altamirano are dated at 12-3 ka, and those from Temascalcingo at 40-25 ka (radiocarbon ages). The relatively young ages found in volcanic deposits within the Acambay graben raise the volcanic danger level in this area, originally marked as an inactive volcanic zone, but activity could restart at any time. Supported by DGAPA-PAPIIT-UNAM grant IN-104615.

  19. Archaeological applications of laser-induced breakdown spectroscopy: an example from the Coso Volcanic Field, California, using advanced statistical signal processing analysis

    Energy Technology Data Exchange (ETDEWEB)

    Remus, Jeremiah J.; Gottfried, Jennifer L.; Harmon, Russell S.; Draucker, Anne; Baron, Dirk; Yohe, Robert

    2010-05-01

    Over the past quarter century, multielement chemical analysis has become a common means for attributing the provenance of archaeological materials. The Coso Volcanic Field (CVF) in California, USA, contains at least 38 high-silica rhyolite domes, many of which contain obsidian glass that has been quarried for tools by the indigenous population for more than 12,000 years. Artifacts made from CVF obsidian are found throughout the southwestern United States and geochemical sourcing of CVF obsidian has been an important tool in understanding prehistoric Native American trading patterns. Laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopic technique that has the potential for real-time man-portable chemical analysis in the field. Because LIBS is simultaneously sensitive to all elements, a single laser shot can be used to record the broadband emission spectra, which provides a ''chemical fingerprint'' of a material. Single-shot broadband LIBS spectra were collected using a commercial benchtop LIBS system for 27 obsidian samples from major sites across the CVF and four additional sites in California and western Nevada outside of CVF. Classification of the samples was performed using partial least-squares discriminant analysis (PLSDA), a common chemometric technique suitable for performing regression on high-dimensional data. Provenance identification for the obsidian samples was evaluated for three separate labeling frameworks. The first framework consisted of a binary classification problem to distinguish CVF samples from non-CVF samples. The second approach focused on the CVF samples with labels that corresponded to the eight separate Coso sites encompassed by the 27 samples. In the third analysis, non-CVF samples were excluded, and the remaining 27 CVF samples were labeled based on groupings defined from previous major and trace element chemical studies, which reduces the number of possible classes from eight to four

  20. 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

    Directory of Open Access Journals (Sweden)

    Ronaldo Pierosan

    2011-09-01

    Full Text Available 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 distinguish lava (flow and dome from hypabyssal units. The morphology of ignimbrite crystals allows the distinction between effusive units and ignimbrite, when pyroclasts are obliterated. Co-ignimbritic tuffs are massive, and some show stratifications that suggest deposition by current traction flow. Zircon and apatite saturation temperatures vary from 799°C to 980°C, are in agreement with most temperatures of α-type melts and can be interpreted as minimum liquidus temperature. The viscosities estimation for rhyolitic and trachytic compositions yield values close to experimentally determined melts, and show a typical exponential decay with water addition. The emplacement of Iricoumé volcanics and part of Mapuera granitoids was controlled by ring-faults in an intracratonic environment. A genesis related to the caldera complex setting can be assumed for the Iricoumé-Mapuera volcano-plutonic association in the Pitinga Mining District.O Grupo Iricoumé corresponde ao mais expressivo vulcanismo Paleoproterozóico do Escudo das Guianas, craton Amazônico. As rochas vulcânicas são coexistentes com os granitóides Mapuera, e pertencem ao magmatismo Uatumã. Possuem idades U-Pb em torno 1888 Ma, e assinaturas geoquímicas de magmas tipo-A. As vulcânicas do Iricoumé consistem de traquitos a riolitos porfiríticos, associados a ignimbritos ricos em cristal e tufos co-ignimbríticos de queda e surge. A quantidade e a morfologia dos fenocristais podem ser

  1. Paleointensities of the Auckland Excursion from Volcanic Rocks in New Zealand

    Science.gov (United States)

    Mochizuki, N.; Tsunakawa, H.; Shibuya, H.; Cassidy, J.; Smith, I. E.

    2001-12-01

    Shibuya et al. (1992) reported the Auckland excursion from several basaltic lava flows of monogenetic volcanic centers (forced to introduce correction for thermal alterations in laboratory heating, using low temperature part of the Arai plot. We, therefore, applied the double heating technique (DHT) of Shaw method (Tsunakawa and Shaw, 1994), which was capable of detecting inappropriate results by the ARM correction, to the samples. The low temperature demagnetization (LTD) was combined with DHT (Yamamoto et al., submitted) before AF demagnetization and samples were heated in a vacuum of 10-100 Pa. Sixty-one samples from the five lava flows were subjected to the LTD-DHT Shaw method. Twenty-three of these samples yielded successful results passing the selection criteria. Five out of six paleointensities from the Crater Hill lava were consistent with each other. A mean paleointensity was given to be 10.9+/- 1.9 μ T (N=5) for the Crater Hill lava. Five out of seven paleointensities from the Wiri lava, were consistent and a mean was 10.8+/- 1.2 μ T (N=5). Three samples from the Puketutu lava gave a mean paleointensity of 11.4+/- 0.8 μ T (N=3). These three lava flows, Crater Hill, Wiri and Puketutu lava, all recorded the north-down paleodirection and gave almost the same paleointensities of ~ 11 μ T. This concordance of paleointensities and paleodirections supports the reliability of the paleointensity determination. Four paleointensities were obtained from the Hampton Park lava of the west paleodirection, and gave a mean paleointensity of 10.1+/- 1.1 μ T (N=4). The field strength was comparable to that of the north-down group. Three samples from the McLennan Hills lava of the south paleodirection gave quite low paleointensities, a mean of which was calculated to be 2.4+/- 0.6 μ T (N=3). These five paleointensities from the Auckland excursion are no more than one-fifth of the present-field intensity. The corresponding VDMs range from 0.6x1022 to 2.3*E22Am2, which

  2. 云南腾冲全新世火山岩地球化学特征及其成因%A study on the geochemical characteristics and petrogenesis of Holocene volcanic rocks in the Tengchong volcanic eruption field, Yunnan Province, SW China

    Institute of Scientific and Technical Information of China (English)

    李欣; 刘嘉麒

    2012-01-01

    Studies of major element, trace element and Sr-Nd-Pb isotopic compositions of the Hotocene volcanic rocks in the Tengchong volcanic eruption field, including Heikongshan, Dayingshan and Maanshan volcanic rocks, indicate they are high potassium cale-alkaline series rocks including trachybasalt, basaltic trachyandesite, trachyandensite, and dacite. These rocks are enriched in LILE and LREE, and depleted in Nb-Ta-Ti in mantle-normalized incompatible trace element patterns. They have relatively high "Sr/ "Sr (0.705862-0.710614), low l43Nd/144Nd (0.511941 -0.512526) and relatively high radiogenic Pb isotopes (208Pb/204Pb = 38.962-39. 155, 207Pb/204Pb = 15.620~15.659 and, 206Pb/204Pb = 17. 872-18.269). The geochemical characteristics of the Holocene volcanic rocks in the Tengchong volcanic eruptive field indicate that the magma sources of Heikongshan, Dayingshan, Maanshan are from enriched mantle which possibly resulted from palaeo-oceanic crust subduction. The magma sources of these three volcanoes are same but with different evolution stage. The magma evolution of Dayingshan is higher than that of Heikongshan and Maanshan. The comparison with geochemical characteristics of post - collisional K-rich rocks in South Tibet shows that the magma sources of Holocene volcanic rocks in the Tengchong volcanic eruption field and post-collisional K-rich rocks in South Tibet are different%通过对腾冲火山群的黑空山、打莺山和马鞍山火山岩主量元素、微量元素、Sr-Nd-Pb同位素地球化学的研究表明,腾冲全新世火山岩为高钾钙碱性系列,包括粗面玄武岩、玄武粗安岩、粗面安山岩和英安岩.该套火山岩富集大离子亲石元素和轻稀土元素,亏损Nb-Ta-Ti不相容元素,具有高的87Sr/86Sr比值(0.705862 ~0.710614),低的143Nd/144Nd比值(0.511941~0.512526)和较高的放射性成因Pb同位素组成(208Pb/204Pb =38.962~ 39.155;207Pb/204Pb=15.620 ~ 15.659;206Pb/204Pb=17.872~18.269).主量、微量和同

  3. Geometric Comparisons of Selected Small Topographically Fresh Volcanoes in the Borealis and Elysium Planitia Volcanic Fields, Mars: Implications for Eruptive Styles

    Science.gov (United States)

    Taylor, K.; Sakimoto, S. E. H.; Mitchell, D.

    2002-01-01

    MOLA (Mars Orbiter Laser Altimeter) data from small, topographically fresh volcanoes from the Elysium and Borealis regions were gridded and analyzed using GMT (Generic Mapping Tools) programs. Results compare eruptive styles of the two regions, and draw conclusions about the different volcanic regions. Additional information is contained in the original extended abstract.

  4. Magma-derived CO2 emissions in the Tengchong volcanic field, SE Tibet: Implications for deep carbon cycle at intra-continent subduction zone

    Science.gov (United States)

    Zhang, Maoliang; Guo, Zhengfu; Sano, Yuji; Zhang, Lihong; Sun, Yutao; Cheng, Zhihui; Yang, Tsanyao Frank

    2016-09-01

    Active volcanoes at oceanic subduction zone have long been regard as important pathways for deep carbon degassed from Earth's interior, whereas those at continental subduction zone remain poorly constrained. Large-scale active volcanoes, together with significant modern hydrothermal activities, are widely distributed in the Tengchong volcanic field (TVF) on convergent boundary between the Indian and Eurasian plates. They provide an important opportunity for studying deep carbon cycle at the ongoing intra-continent subduction zone. Soil microseepage survey based on accumulation chamber method reveals an average soil CO2 flux of ca. 280 g m-2 d-1 in wet season for the Rehai geothermal park (RGP). Combined with average soil CO2 flux in dry season (ca. 875 g m-2 d-1), total soil CO2 output of the RGP and adjacent region (ca. 3 km2) would be about 6.30 × 105 t a-1. Additionally, we conclude that total flux of outgassing CO2 from the TVF would range in (4.48-7.05) × 106 t a-1, if CO2 fluxes from hot springs and soil in literature are taken into account. Both hot spring and soil gases from the TVF exhibit enrichment in CO2 (>85%) and remarkable contribution from mantle components, as indicated by their elevated 3He/4He ratios (1.85-5.30 RA) and δ13C-CO2 values (-9.00‰ to -2.07‰). He-C isotope coupling model suggests involvement of recycled organic metasediments and limestones from subducted Indian continental lithosphere in formation of the enriched mantle wedge (EMW), which has been recognized as source region of the TVF parental magmas. Contamination by crustal limestone is the first-order control on variations in He-CO2 systematics of volatiles released by the EMW-derived melts. Depleted mantle and recycled crustal materials from subducted Indian continental lithosphere contribute about 45-85% of the total carbon inventory, while the rest carbon (about 15-55%) is accounted by limestones in continental crust. As indicated by origin and evolution of the TVF

  5. Slab-derived metasomatism in the Carpathian-Pannonian mantle revealed by investigations of mantle xenoliths from the Bakony-Balaton Highland Volcanic Field

    Science.gov (United States)

    Créon, Laura; Delpech, Guillaume; Rouchon, Virgile; Guyot, François

    2017-08-01

    A suite of fifteen peridotite xenoliths from the Bakony-Balaton Highland Volcanic Field (BBHVF, Pannonian Basin, Central Europe) that show abundant petrographic evidence of fluid and melt percolation were studied in order to decipher the formation of their melt pockets and veins. The suite mainly consists of ;fertile; lherzolites (5.8-19.9 vol.% clinopyroxene) and a few harzburgites (1.9-5.4 vol.% clinopyroxene) from well-known localities (Szentbékkálla, Szigliget) and two previously unreported localities (Füzes-tó and Mindszentkálla). Major and trace element data indicate that most of the peridotites record variable degrees of partial melt extraction, up to > 15% for the harzburgites. Subsequently, the xenoliths experienced at least two stages of metasomatic modification. The first stage was associated with percolation of a volatile-bearing silicate melt and resulted in crystallization of amphibole, enrichment in the most incompatible trace elements (Ba, Th, U, Sr), and development of negative Nb-Ta anomalies in clinopyroxene. The second and last metasomatic event, widespread beneath the BBHVF, is associated with the formation of silicate melt pockets, physically connected to a network of melt veins, with large and abundant CO2 vesicles. The glass in these veins has sub-alkaline trachy-andesitic composition and displays an OIB-like trace element signature. Its composition attests to the migration through a supra-subduction zone mantle wedge of silicic melt highly enriched in volatiles (CO2, H2O, Cl, F), LILE, REE and HFSE and consistent with compositions of natural and experimental examples of slab melting-derived magma. In the present case, however, melt was likely derived from melting of oceanic crust and carbonated sediments under conditions where Nb-rich mineral phases were not stable in the residue. A likely scenario for the origin such melts involves melting after subduction ceased as the slab thermally equilibrated with the asthenosphere. Melt

  6. 松南气田火山岩气藏产水特征和控水策略%Water production characteristics and control strategy of volcanic reservoir in Songnan gas field

    Institute of Scientific and Technical Information of China (English)

    常文博; 任宪军; 单玄龙

    2016-01-01

    基于天然气单次闪蒸实验、气藏水化验分析两种方法,区分松辽盆地松南气田气井产水类型;结合气藏精细描述,分析不同气井的产水机理;进一步利用数值模拟,探索火山岩气藏控水策略。松南气田产水可分为凝析水和地层水两种类型,构造高部位火山机构气井产凝析水,构造低部位火山机构气井产地层水。断层引起的底水上窜是造成构造高部位钻井产少量地层水的主要原因。通过数值模拟发现,采气速度越高,边底水锥进越快。松南气田火山岩气藏最优采气速度约在3.6%。根据高部位高配、低部位低配的控水原则,明确了不同类型、不同构造部位火山岩气井合理产量,可有效控制火山岩气井出水,实现气藏稳产。%Based on the gas single flash experiment and gas reservoir water chemical examination,the types of water production of Songnan gas field in Songliao Basin were determined.Combined with fine description of volcan-ic reservoirs,the different water production mechanisms were analyzed.Furthermore,the authors explored the wa-ter control strategy based on numerical simulation.The water production in Songnan gas filed can be divided into two types:condensate water and formation water.The gas wells which drilled the high volcanic edifice produce condensate water,while drilled the low volcanic edifice produce formation water.The bottom water coning along the fault is the primary cause of formation water output from some gas wells drilled the high volcanic edifice.The nu-merical simulation indicated that there is a positive correlation between gas recovery rate and bottom water coning rate.The optimal gas recovery rate in Songnan volcanic gas field is about 3. 6%.According to the water control principle of high production at high structural position and low production at low structural position,the authors cal-culate the reasonable production of volcanic gas

  7. A new rapid and non-destructive method to detect tephra layers and cryptotephras: applying to the first distal tephrostratigraphic record of the Chaîne des Puys volcanic field (France).

    Science.gov (United States)

    Jouannic, Gwénolé; Walter-Simonnet, Anne-Véronique; Bossuet, Gilles; Delabrousse, Eric; Cubizolle, Hervé

    2014-05-01

    Tephrostratigraphy has been considerably developed for 30 years, mainly in palaeo-environmental studies. In such studies, distal tephra layers are important chronological markers, but they are also tools to establish or specify record of past eruptions of a volcanic field. Nowadays, development of effective rapid methods to detect tephra layers in sedimentary records of various compositions is a challenge. Many classic methods for detection of tephra layers, like regular sampling or magnetic susceptibility measurements, have shown their limits. Regular sampling takes a long time, and finding tephra layers remains uncertain. Moreover, magnetic susceptibility maesurements, although it is a non-destructive method, is ineffective when tephra layers are made of volcanic glass shards with differentiated magma composition. X-ray fluorescence (XRF) is also a non-destructive method but it takes a very long time to analyze a core with sufficient high resolution, and measurements only concern the surface of the sediment. We propose a new method allows detection of tephra layers with, for the first time, a 3D resolution: the Computed Tomography Scan (CT- Scan). This method, regularly used in medicine, allows there to obtain pictures of materials density on 3D with inframillimetric measurement ranges. Then, it is possible to detect tephras, cryptotephras (invisible by naked eye), reworked tephra layers even when tephra layers don't outcrop at the surface of the sediment (and are therefore undetectable by usual methods like XRF and magnetic susceptibility). This method has been tried out on tephras sedimented in different types of sediments (silicated, carbonated and organic matter). Our results show that this method is very efficient for peaty environment. Used on coring carried out in Forez Mountains (French Massif Central), CT-Scan allows to detect more tephra layers than usual methods (XRF and magnetic susceptibility). Results presented here allow to build the first

  8. Friction in volcanic environments

    Science.gov (United States)

    Kendrick, Jackie E.; Lavallée, Yan

    2016-04-01

    Volcanic landscapes are amongst the most dynamic on Earth and, as such, are particularly susceptible to failure and frictional processes. In rocks, damage accumulation is frequently accompanied by the release of seismic energy, which has been shown to accelerate in the approach to failure on both a field and laboratory scale. The point at which failure occurs is highly dependent upon strain-rate, which also dictates the slip-zone properties that pertain beyond failure, in scenarios such as sector collapse and pyroclastic flows as well as the ascent of viscous magma. High-velocity rotary shear (HVR) experiments have provided new opportunities to overcome the grand challenge of understanding faulting processes during volcanic phenomena. Work on granular ash material demonstrates that at ambient temperatures, ash gouge behaves according to Byerlee's rule at low slip velocities, but is slip-weakening, becoming increasingly lubricating as slip ensues. In absence of ash along a slip plane, rock-rock friction induces cataclasis and heating which, if sufficient, may induce melting (producing pseudotachylyte) and importantly, vesiculation. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The shear-thinning behaviour and viscoelasticity of frictional melts yield a tendency for extremely unstable slip, and occurrence of frictional melt fragmentation. This velocity-dependence acts as an important feedback mechanism on the slip plane, in addition to the bulk composition, mineralogy and glass content of the magma, that all influence frictional behaviour. During sector collapse events and in pyroclastic density currents it is the frictional properties of the rocks and ash that, in-part, control the run-out distance and associated risk. In addition, friction plays an important role in the eruption of viscous magmas: In the conduit, the rheology of magma is integral

  9. Subsidence in the Parícutin lava field: Causes and implications for interpretation of deformation fields at volcanoes

    Science.gov (United States)

    Chaussard, Estelle

    2016-06-01

    Assessment of volcanic hazards includes interpretation of ground deformation signal, which, at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava. The deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old, but if the lava thickness is great, deformation may still be occurring, possibly leading to misinterpretation of the observed deformation. Here I evaluate the 2007-2011 ground motion of the 1943-1952 lava field of the Parícutin monogenetic cinder cone, Mexico. Interferometric Synthetic Aperture Radar (InSAR) time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5.5 cm/year. There is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness. I estimate these thicknesses in the subsiding areas using pre- and post-eruption topographic maps and show that they reach up to 200 m. A numerical model for lava flow cooling was developed considering radiation and convection from the surface, conductive transfer inside the flow and to the ground, and vesiculation and latent heat generation at the top and bottom of the flow. The model shows that compaction induced by cooling of the thick deposits emplaced ~ 60 years ago explains the observed subsidence when conductive transfer to the ground is considered. These results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement, emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields.

  10. 松南气田营城组火山岩储层建模技术%Geologic modeling of volcanic reservoirs in the Yingcheng Formation of Songnan gas field

    Institute of Scientific and Technical Information of China (English)

    宗畅; 刘华; 王建波

    2012-01-01

    火山岩具有结构复杂、岩性岩相变化快、储层非均质性强等特点,从而使火山岩储层的地质建模工作变得十分复杂。在借鉴松辽盆地徐深气田火山岩储层建模技术和经验的基础上,以松辽盆地松南气田为例,运用建模软件开展了该区的储层建模工作。利用钻井、测井、地震、岩心分析等资料完成了火山岩期次的划分,建立起了松南气田地层格架,并在此基础上,结合综合地质研究成果,建立了该区的构造模型及属性模型。其研究成果与后续开发井钻探结果符合性较好,为气藏开发决策提供了依据。%Volcanic rocks are characterized by complex structure,rapid change of lithology and facies,and strong heterogeneity of reservoirs,thus geologic modeling is very hard.Based on the experiences of the geologic modeling of the volcanic reservoirs in the Xushen gas field,we carried out the geologic modeling of the volcanic reservoirs in the Songnan gas field,Songliao Basin.Various data including drilling,logging,seismic data and core analysis were integrated to perform volcanic period's division and correlation and to establish the stratigraphic framework of the Songnan gas field.These study results,in combination with those of the comprehensive geologic research,were utilized to build structural models and attribute models of the study area.The prediction results have been validated by the follow-up development drilling results.These understandings provided a strong foundation for strategic decision making of gas field development.

  11. Crustal-scale recycling in caldera complexes and rift zones along the Yellowstone hotspot track: O and Hf isotopic evidence in diverse zircons from voluminous rhyolites of the Picabo volcanic field, Idaho

    Science.gov (United States)

    Drew, Dana L.; Bindeman, Ilya N.; Watts, Kathryn E.; Schmitt, Axel K.; Fu, Bin; McCurry, Michael

    2013-01-01

    Rhyolites of the Picabo volcanic field (10.4–6.6 Ma) in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain (SRP), and within a deep (>3 km) borehole near the central axis of the Yellowstone hotspot track. In this study we present new O and Hf isotope data and U–Pb geochronology for individual zircons, O isotope data for major phenocrysts (quartz, plagioclase, and pyroxene), whole rock Sr and Nd isotope ratios, and whole rock geochemistry for a suite of Picabo rhyolites. We synthesize our new datasets with published Ar–Ar geochronology to establish the eruptive framework of the Picabo volcanic field, and interpret its petrogenetic history in the context of other well-studied caldera complexes in the SRP. Caldera complex evolution at Picabo began with eruption of the 10.44±0.27 Ma (U–Pb) Tuff of Arbon Valley (TAV), a chemically zoned and normal-δ18O (δ18O magma=7.9‰) unit with high, zoned 87Sr/86Sri (0.71488–0.72520), and low-εNd(0) (−18) and εHf(0) (−28). The TAV and an associated post caldera lava flow possess the lowest εNd(0) (−23), indicating ∼40–60% derivation from the Archean upper crust. Normal-δ18O rhyolites were followed by a series of lower-δ18O eruptions with more typical (lower crustal) Sr–Nd–Hf isotope ratios and whole rock chemistry. The voluminous 8.25±0.26 Ma West Pocatello rhyolite has the lowest δ18O value (δ18Omelt=3.3‰), and we correlate it to a 1,000 m thick intracaldera tuff present in the INEL-1 borehole (with published zircon ages 8.04–8.35 Ma, and similarly low-δ18O zircon values). The significant (4–5‰) decrease in magmatic-δ18O values in Picabo rhyolites is accompanied by an increase in zircon δ18O heterogeneity from ∼1‰ variation in the TAV to >5‰ variation in the late-stage low-δ18O rhyolites, a trend similar to what is characteristic of Heise and Yellowstone, and which indicates remelting of variably hydrothermally altered tuffs

  12. Melt inclusions are not reliable proxies for magmatic liquid composition: evidence from crystal-poor andesites and dacites in the Tequila volcanic field, Mexico

    Science.gov (United States)

    Frey, H. M.; Lange, R. A.

    2009-12-01

    A compositional study of >200 melt inclusions in plagioclase and orthopyroxene phenocrysts from six crystal-poor (2-5 vol%) andesite and dacite lavas (60-68 wt% SiO2) from the Tequila volcanic field in the Mexico arc is used to evaluate whether melt inclusions in phenocrysts accurately record magmatic liquid compositions. The crystal-poor andesites and dacites were erupted contemporaneously with crystal-poor rhyolites, and there is a continuum in the SiO2 concentration of the erupted magmas. The liquid line of descent defined by the whole-rock compositions ranges from andesite to rhyolite (60-77 wt% SiO2), as illustrated on Harker diagrams. The crystal-poor andesites and dacites are multiply saturated with five to seven mineral phases (plagioclase + orthopyroxene + titanomagnetite + ilmenite + apatite ± augite ± hornblende), most of which crystallized via degassing during magma ascent (Frey and Lange, 2009). By comparison with phase equilibrium experiments from the literature, it is shown that the vast majority of crystals are phenocrysts and not xenocrysts. Textural evidence of rapid crystal growth includes skeletal, hopper, and swallow-tail morphologies and abundant melt inclusions. The inclusions range in size from a few microns to > 50 μm and occur as isolated pockets and extensive channels that mimic the crystal morphology. Inclusions are typically brown glass, with occasional microphenocrysts of titanomagnetite and/or apatite within or adjacent to the melt inclusions. The compositions of the melt inclusions in the plagioclase and orthopyroxene phenocrysts, when plotted on Harker diagrams, vary systematically from one another and from the liquid line of descent defined by the whole rock compositions of erupted magmas. For example, melt inclusions in plagioclase are systematically depleted in Al2O3 relative to the whole rock samples, whereas those in coexisting orthopyroxenes are systematically enriched in Al2O3. The opposite trend is found for FeO, where it

  13. Paleomagnetic Evidence From Volcanic Units of Valsequillo Basin for the Laschamp Geomagnetic Excursion, and Implications for Early Human Occupation in Central Mexico

    Science.gov (United States)

    Rocha, J.; Gogichaishvili, A.; Martin Del Pozzo, A.; Urrutia-Fucugauchi, J.; Soler, A. M.

    2007-12-01

    Alleged human and animal footprints were found within the upper bedding surfaces of the Xalnene volcanic ash layer that outcrops in Valsequillo basin, south of Puebla, Mexico (Gonzalez et al., Quaternary Science Reviews doi: 10.1016/j.quascirev, 2005). The ash has been dated to 40 ka by means of optically stimulated luminescence analysis. This was held as new evidence that America was colonized earlier. We carried out paleomagnetic and rock magnetic analysis of 18 Xalnene ash block and core samples collected at two distinct localities, and nineteen standard paleomagnetic cores belonging to nearby monogenetic volcanoes. Our data yield evidence that both volcanic lava flow and Xalnene ash were emplaced at during the Laschamp geomagnetic event spanning from about 45 to 39 ka. This interpretation indicates that Valsequillo probably remains one of the sites of early human occupation in the Americas, producing evidence of early arrival.

  14. Paleomagnetic and rock-magnetic study on volcanic units of the Valsequillo Basin: implications for early human occupation in central Mexico

    Science.gov (United States)

    Goguitchaichvili, Avto; Pozzo, Ana Lillian Martin-Del; Rocha-Fernandez, Jose Luis; Urrutia-Fucugauchi, Jaime; Soler-Arechalde, Ana Maria

    2009-01-01

    Alleged human and animal footprints were found within the upper bedding surfaces of the Xalnene volcanic ash layer that outcrops in the Valsequillo Basin, south of Puebla, Mexico (Gonzalez et al, 2005). The ash has been dated at 40 ka by optically stimulated luminescence analysis, thereby providing new evidence that America was colonized earlier than the Clovis culture (about 13.5 Ma). We carried out paleomagnetic and rock magnetic analysis on 18 Xalnene ash block and core samples collected at two distinct localities and 19 standard paleomagnetic cores belonging to nearby monogenetic volcanoes. Our data provide evidence that both the volcanic lava flow and Xalnene ash were emplaced during the Laschamp geomagnetic event spanning from about 45 to 39 ka.

  15. Field-trip guide to Mount Hood, Oregon, highlighting eruptive history and hazards

    Science.gov (United States)

    Scott, William E.; Gardner, Cynthia A.

    2017-06-22

    This guidebook describes stops of interest for a geological field trip around Mount Hood volcano. It was developed for the 2017 International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly in Portland, Oregon. The intent of this guidebook and accompanying contributions is to provide an overview of Mount Hood, including its chief geologic processes, magmatic system, eruptive history, local tectonics, and hazards, by visiting a variety of readily accessible localities. We also describe coeval, largely monogenetic, volcanoes in the region. Accompanying the field-trip guidebook are separately authored contributions that discuss in detail the Mount Hood magmatic system and its products and behavior (Kent and Koleszar, this volume); Mount Hood earthquakes and their relation to regional tectonics and the volcanic system (Thelen and Moran, this volume); and young surface faults cutting the broader Mount Hood area whose extent has come to light after acquisition of regional light detection and ranging coverage (Madin and others, this volume).The trip makes an approximately 175-mile (280-kilometer) clockwise loop around Mount Hood, starting and ending in Portland. The route heads east on Interstate 84 through the Columbia River Gorge National Scenic Area. The guidebook points out only a few conspicuous features of note in the gorge, but many other guides to the gorge are available. The route continues south on the Mount Hood National Scenic Byway on Oregon Route 35 following Hood River, and returns to Portland on U.S. Highway 26 following Sandy River. The route traverses rocks as old as the early Miocene Eagle Creek Formation and overlying Columbia River Basalt Group of middle Miocene age, but chiefly lava flows and clastic products of arc volcanism of late Miocene to Holocene age.

  16. Decompressional Volcanism Following Giant Landslide Events at a Miocene Shield- Volcano, Teno, Tenerife: Evidence From Field Observations, Augite and Olivine Chemistry, and Chemical Thermobarometry

    Science.gov (United States)

    Hansteen, T. H.; Longpré, M.; Troll, V. R.; Walter, T. R.

    2006-12-01

    Giant landslides play a major role in the evolution of large oceanic shield-volcanoes around the globe. The removal of a significant portion of the volcanic edifice due to lateral collapse is thought to supersede the effect of erosion and subsidence in the process of island decay. On the other hand, rapid constructional phases appear to frequently follow giant mass-wasting and are generally concentrated in the region affected by the collapse (e.g. Réunion, La Palma, Fogo). The rapid unloading of up to thousands of km3 of near-surface rocks must decompress parts of the volcanic edifice, which in turn may affect the magmatic system [1,2]. Located in north-western Tenerife, Teno is a deeply eroded Miocene shield-volcano which has suffered at least two giant lateral collapses between 5-6 Ma [3]. Incised valleys dissect the structure of the old volcano and expose ancient landslide scars. Extensive debris avalanche deposits typically include juvenile pyroclastic material, suggesting that explosive volcanic activity was contemporaneous with landsliding. Moreover, post- collapse stratigraphy is marked by numerous thick ultramafic lava flows (basanites, ankaramites, picrites, SiO2 volcano may have disrupted any shallow magma reservoir existing prior to the collapse, resulting in pyroclastic activity. The decompression effect may also have triggered the rapid ascent of mafic melts stored at mantle depth, causing mixing of multiple magma batches and the aggregation of their crystal populations. The very steep normal zonation at the rims of many augite and olivine crystals may be attributed to a rapid change in the P-T conditions and/or the melt chemical composition. [1] Presley et al. 1997, Bull Volcanol. [2] Pinet & Jaupart 2005, JVGR. [3] Walter & Schmincke 2002, Int J Earth Sci.[4] Putirka et al. 2003, Am Min.

  17. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.

    2009-08-22

    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean integrates volcanic radiative cooling and responds over a wide range of time scales. The associated processes, especially ocean heat uptake, play a key role in ongoing climate change. However, they are not well constrained by observations, and attempts to simulate them in current climate models used for climate predictions yield a range of uncertainty. Volcanic impacts on the ocean provide an independent means of assessing these processes. This study focuses on quantification of the seasonal to multidecadal time scale response of the ocean to explosive volcanism. It employs the coupled climate model CM2.1, developed recently at the National Oceanic and Atmospheric Administration\\'s Geophysical Fluid Dynamics Laboratory, to simulate the response to the 1991 Pinatubo and the 1815 Tambora eruptions, which were the largest in the 20th and 19th centuries, respectively. The simulated climate perturbations compare well with available observations for the Pinatubo period. The stronger Tambora forcing produces responses with higher signal-to-noise ratio. Volcanic cooling tends to strengthen the Atlantic meridional overturning circulation. Sea ice extent appears to be sensitive to volcanic forcing, especially during the warm season. Because of the extremely long relaxation time of ocean subsurface temperature and sea level, the perturbations caused by the Tambora eruption could have lasted well into the 20th century.

  18. The Timber Mountain magmato-thermal event: An intense widespread culmination of magmatic and hydrothermal activity at the southwestern Nevada volcanic field

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, M.R. Jr.

    1988-05-01

    Eruption of the Rainier Mesa and Ammonia Tanks Members Timber Mountain Tuff at about 11.5 and 11.3 Ma, respectively, resulted in formation of the timber Mountain (TM) caldera; new K-Ar ages show that volcanism within and around the TM caldera continued for about 1 m.y. after collapse. Some TM age magmatic activity took place west and southeast of the TM caldera in the Beatty -- Bullfrog Hills and Shoshone Mountain areas, suggesting that volcanic activity at the TM caldera was an intense expression of an areally extensive magmatic system active from about 11.5 to 10Ma. Epithermal Au-Ag, Hg and fluorite mineralization and hydrothermal alteration are found in both within and surrounding the Timber Mountain -- Oasis Valley caldera complex. New K-Ar ages date this hydrothermal activity between about 13 and 10 Ma, largely between about 11.5 and 10 Ma, suggesting a genetic relation of hydrothermal activity to the TM magmatic system.

  19. Magnetic signature of submarine volcanoes in the Phlegrean Fields-Ischia Ridge (North-Western side of the Bay of Naples, Southern Italy

    Directory of Open Access Journals (Sweden)

    M. Secomandi

    2008-06-01

    Full Text Available This paper presents a study of the Phlegrean Fields-Ischia submarine ridge by the analysis and interpretation of high-resolution aeromagnetic data recently acquired in the Western Procida offshore. The investigated area is located along the ridge connecting Ischia to the Phlegrean Fields and is characterized by the existence of several monogenetic volcanoes aligned on a NE-SW system of faults. The high-resolution magnetic data yielded new information on the area, highlighting particularly the signature of a volcanic body located between Pt. Serra and the Ruommoli shoal. This structure has not been clearly described before and we named it as the Pt. Serra submarine volcano. The computation of the analytic signal and horizontal gradient of the data distinctly located this structure and definined the position of its rims. A 2D modeling and 3D inversion of data provided information on the volcano’s thickness, width and magnetization, disclosing a meaningful igneous body extending down to several hundred meters b.s.l.

  20. Spatial and temporal variations of diffuse CO_{2} degassing at the N-S volcanic rift-zone of Tenerife (Canary Islands, Spain) during 2002-2015 period

    Science.gov (United States)

    Alonso, Mar; Ingman, Dylan; Alexander, Scott; Barrancos, José; Rodríguez, Fátima; Melián, Gladys; Pérez, Nemesio M.

    2016-04-01

    Tenerife is the largest of the Canary Islands and, together with Gran Canaria Island, is the only one with a central volcanic complex that started to grow at about 3.5 Ma. Nowadays the central complex is formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and was partially filled by post-caldera volcanic products. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 Ma (Dóniz et al., 2008). Most of the monogenetic cones are aligned following a triple junction-shaped rift system, as result of inflation produced by the concentration of emission vents and dykes in bands at 120o to one another as a result of minimum stress fracturing of the crust by a mantle upwelling. The main structural characteristic of the southern volcanic rift (N-S) of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Four main volcanic successions in the southern volcanic rift zone of Tenerife, temporally separated by longer periods (˜70 - 250 ka) without volcanic activity, have been identified (Kröchert and Buchner, 2008). Since there are currently no visible gas emissions at the N-S rift, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. We report here the last results of diffuse CO2 efflux survey at the N-S rift of Tenerife, performed using the accumulation chamber method in the summer period of 2015. The objectives of the surveys were: (i) to constrain the total CO2 output from the studied area and (ii) to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for the N-S rift of Tenerife. Soil CO2 efflux values ranged from non-detectable up to 31.7 g m-2 d-1. A spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, did not show an

  1. Volcanic Rocks and Features

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Volcanoes have contributed significantly to the formation of the surface of our planet. Volcanism produced the crust we live on and most of the air we breathe. The...

  2. 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.

  3. 火山温室气体释放通量与观测的研究进展%Research Advances in Greenhouse Gases Degassing from Cenozoic Volcanic Active Fields

    Institute of Scientific and Technical Information of China (English)

    郭正府; 张茂亮; 孙玉涛; 成智慧; 张丽红; 刘嘉麒

    2015-01-01

    火山活动是地球深部碳循环的重要环节,火山区不仅在火山喷发期能够释放温室气体,而且在休眠期也能向大气圈中释放大量的温室气体。在当前全球温室气体减排的背景下,定量化地研究火山区对大气圈温室气体含量增加的贡献,对于识别自然因素和人类因素碳排放的相对规模、为国际碳排放谈判积累基础数据等均具有至关重要的科学价值和现实意义。本文对火山区温室气体的排放方式与特征、温室气体释放通量与成因的研究方法进行了简要概括,并综述了中国新生代典型火山区温室气体释放通量与成因的研究成果。结合国外温室气体排放研究现状,指出深入研究活火山(包括休眠火山)区的温室气体释放通量与成因对于估算火山来源温室气体的释放规模、建立火山未来喷发预测-预警体系、深入理解岩浆脱气过程与机制等问题均具有至关重要的现实意义和科学价值。%Volcanic activities are of great importance to the global deep carbon cycle,which could release large amount of greenhouse gases during both eruptive and quiescent stages,resulting in climatic and environmental changes on local and even global scales.Under the context of global warming,quantitative studies on the contribution of volcanic activities to rising of atmospheric greenhouse gases concentration are critical to discriminating carbon emissions associated with nature and human and to accumulating essential data for geological carbon budget.In this study,we briefly reviewed types,char-acteristics and research methods of greenhouse gases emissions,and the current status of research on fluxes and origin of greenhouse gases emitting from volcanic fields of China.Based on internationally accepted theory in volcanic-related green-house gases,we proposed that,systematic studies on fluxes and origin of greenhouse gases emitting from volcanic activities

  4. 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.

  5. Volcanic geology of Admiralty Bay, King George Island, Antarctica

    Institute of Scientific and Technical Information of China (English)

    邢光福; 王德滋; 金庆民; 沈渭洲; 陶奎元

    2002-01-01

    At Admiralty Bay of central King George Island, Keller Peninsula, Ullman Spur and Point Hennequin are main Tertiary volcanic terranes. Field investigation and isotopic datings indicate that, there occurred three periods of eruptions ( three volcanic cycles) and accompanying N-toward migration of the volcanic center on Keller Peninsula. After the second period of eruptions, the crater collapsed and a caldera was formed, then later eruptions were limited at the northern end of the peninsula and finally migrated to Ullman Spur. Thus Keller Peninsula is a revived caldera, and its volcanism migrated toward E with time. Point Hennequin volcanism happened more or less simultaneously with the above two areas, but has no clear relation in chemical evolution with them, frequently it belongs to another independent volcanic center.

  6. First data on the environment and climate change within the Zhom-Bolok volcanic field (Eastern Sayan Mountains) in the Middle-Late Holocene

    Science.gov (United States)

    Bezrukova, E. V.; Shchetnikov, A. A.; Kuzmin, M. I.; Sharova, O. G.; Kulagina, N. V.; Letunova, P. P.; Ivanov, E. V.; Kraynov, M. A.; Kerber, E. V.; Filinov, I. A.; Levina, O. V.

    2016-05-01

    This paper considers the results of comprehensive lithological, biostratigraphic, and geochemical investigation of sediments in Khara-Nur Lake (Eastern Sayan Mountains) situated in the area of the greatest Holocene eruptions in the Central Asia Region. The age of the basal sediment layer is estimated at 6881 ± 53 years. The local natural environment and climate have undergone great changes since that time. The Holocene volcanic events did not exert a catastrophic impact on the regional landscape, but they caused dramatic changes in the local vegetation. The well-defined correlation of the regional events with the well-known records of the natural environment in the Northern Hemisphere is indicative of the decisive influence of global atmospheric circulation on restructuring the landscape and climate system in the Zhom-Bolok Region in the Middle-Late Holocene.

  7. Volcanic hazard assessment for disposal of high-level radioactive waste

    Energy Technology Data Exchange (ETDEWEB)

    Crowe, B.M.

    1986-12-31

    Volcanic hazards are evaluated through risk assessment, which is a product of probability and consequences. These studies have been completed for a potential waste disposal site in the Nevada Test Site (NTS). Cenozoic volcanism of the NTS region is divided into three distinct episodes. The youngest episode, 3.7 to 0.3 m.y., comprises scattered, monogenetic Strombolian centers of small volume (<1 km{sup 3}). Rates of volcanic activity for the NTS region are estimated to be about 10{sup -6} event/yr, based on vent counts through time and calculation of rates of magma production. The conditional probability of disruption of the possible waste disposal site at the NTS by basaltic volcanism is bounded by the range of 10{sup -8} to 10{sup -10} yr{sup -1}. Consequences, expressed as radiological release levels, were evaluated by assuming disruption of a repository by basaltic magmas fed along narrow dikes. Limits are placed on the volume of waste material incorporated in magma by analogy to the abundance of lithic fragments in basalt scoria and lava. These consequences would be increased if rising magma encountered water and produced magma/water vapor explosions, which can eject large volumes of country rock. Such a mechanism would be important only if the vapor explosions excavated a crater to repository depths (380 m) - an unlikely event, based on the dimensions of hydrovolcanic craters. The total expected release from disruption of a repository by basaltic magma for a 10{sup 4}-yr period is 1.8 Ci for spent fuel and 1.3 Ci for high-level waste. 34 references.

  8. Volcanic hazards to airports

    Science.gov (United States)

    Guffanti, M.; Mayberry, G.C.; Casadevall, T.J.; Wunderman, R.

    2009-01-01

    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. Analysis of a new compilation of incidents of airports impacted by volcanic activity from 1944 through 2006 reveals that, at a minimum, 101 airports in 28 countries were affected on 171 occasions by eruptions at 46 volcanoes. Since 1980, five airports per year on average have been affected by volcanic activity, which indicates that volcanic hazards to airports are not rare on a worldwide basis. The main hazard to airports is ashfall, with accumulations of only a few millimeters sufficient to force temporary closures of some airports. A substantial portion of incidents has been caused by ash in airspace in the vicinity of airports, without accumulation of ash on the ground. On a few occasions, airports have been impacted by hazards other than ash (pyroclastic flow, lava flow, gas emission, and phreatic explosion). Several airports have been affected repeatedly by volcanic hazards. Four airports have been affected the most often and likely will continue to be among the most vulnerable owing to continued nearby volcanic activity: Fontanarossa International Airport in Catania, Italy; Ted Stevens Anchorage International Airport in Alaska, USA; Mariscal Sucre International Airport in Quito, Ecuador; and Tokua Airport in Kokopo, Papua New Guinea. The USA has the most airports affected by volcanic activity (17) on the most occasions (33) and hosts the second highest number of volcanoes that have caused the disruptions (5, after Indonesia with 7). One-fifth of the affected airports are within 30 km of the source volcanoes, approximately half are located within 150 km of the source volcanoes, and about three-quarters are within 300 km; nearly one-fifth are located more than 500 km away from the source volcanoes. The volcanoes that have caused the most impacts are Soufriere Hills on the island of Montserrat in the British West Indies

  9. Inverse Dipolar Magnetic Anomaly Over the Volcanic Cone Linked to Reverse Polarity Magnetizations in Lavas and Tuffs - Implications for the Conduit System

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L. L.; Trigo-Huesca, A.

    2012-12-01

    A combined magnetics and paleomagnetic study of Toluquilla monogenetic volcano and associated lavas and tuffs from Valsequillo basin in Central Mexico provides evidence on a magnetic link between lavas, ash tuffs and the underground volcanic conduit system. Paleomagnetic analyses show that lavas and ash tuffs carry reverse polarity magnetizations, which correlate with the inversely polarized dipolar magnetic anomaly over the volcano. The magnetizations in the lava and tuff show similar southward declinations and upward inclinations, supporting petrological inferences that the tuff was emplaced while still hot and indicating a temporal correlation for lava and tuff emplacement. Conduit geometry is one of the important controlling factors in eruptive dynamics of basaltic volcanoes. However volcanic conduits are often not, or only partly, exposed. Modeling of the dipolar anomaly gives a reverse polarity source magnetization associated with a vertical prismatic body with southward declination and upward inclination, which correlates with the reverse polarity magnetizations in the lava and tuff. The study documents a direct correlation of the paleomagnetic records with the underground magmatic conduit system of the monogenetic volcano. Time scale for cooling of the volcanic plumbing system involves a longer period than the one for the tuff and lava, suggesting that magnetization for the source of dipolar anomaly may represent a long time average as compared to the spot readings in the lava and tuff. The reverse polarity magnetizations in lava and tuff and in the underground source body for the magnetic anomaly are interpreted in terms of eruptive activity of Toluquilla volcano at about 1.3 Ma during the Matuyama reverse polarity C1r.2r chron.

  10. Applications of dip angle and coherence attributes to recognition of volcanic edifice in Songliao Basin

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of the shape and inner structure of volcanic edifice, the dip angle and coherence were selected to recognize the buried volcanic edifices in Songliao Basin. Five volcanic edifices were recognized in both two methods in the first volcanic cycle of Yingcheng Formation and the prediction perfectly corresponds to the drilling results in well XS8 area. The results are satisfying when the prediction method were employed in the exploration and development of Qingshen gas field.

  11. The Quetzalapa Pumice: a voluminous late Pleistocene rhyolite deposit in the eastern Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Rodríguez, Sergio-Raúl; Siebe, Claus; Komorowski, Jean-Christophe; Abrams, Michael

    2002-03-01

    The study area is located in the east part of the Trans-Mexican Volcanic Belt, in the Las Cumbres Volcanic Complex (LCVC) which lies between two large stratovolcanoes: Pico de Orizaba (5700 m a.s.l.) to the south, and Cofre de Perote (4200 m a.s.l.) to the NNE. The most conspicuous structure of the LCVC is a 4-km-diameter circular crater with a dacitic dome in the center, which constitutes the remains of a destroyed stratovolcano. The Quetzalapa Pumice (QP) was produced by a plinian eruption that was dated by the 14C method at 20 000 yr. BP. The eruptive sequence consists predominantly of pumice fall deposits and scarce intra-plinian pyroclastic flow deposits, which crop out on the west flank of the LCVC. The absence of post-plinian ignimbrite deposits is striking. The deposits are well sorted, clast-supported with reverse grading at the base, with a medium to high accessory lithics content. The maximum average thickness of the deposit in the proximal areas is about 15 m and has been divided into three members: the Basal Member (BM), 2 m thick with four submembers (BMf 1, BMf 2, BMf 3, and BMafl), the Intermediate Member (IM), 10 m thick with two submembers (IMpf and IMaf), and the Upper Member (UM), 3 m thick with four submembers (UMpl, UMsdf, UMwaf, and UMpls). The predominant component of the fall deposits is a white, highly vesiculated pumice with 71% SiO 2 content. Plagioclase is the most abundant mineral followed by 1-3-mm-long biotite phenocrysts. The accessory lithics are lavas mostly of andesitic composition. Their abundance increases toward the uppermost levels of the sequence. We calculate a minimum volume of 8.4 km 3 (2.22 km 3 dense rock equivalent), for the entire QP deposit. Isopach and isopleth maps show that the IM deposit has an elongated distribution with a NNE-SSW direction, whereas the UM deposit has a circular distribution. We estimate a maximum eruptive column height for the IM of 20 km. Field studies and isopach and isopleth maps indicate

  12. The Use of Handheld X-Ray Fluorescence (XRF) Technology in Unraveling the Eruptive History of the San Francisco Volcanic Field, Arizona

    Science.gov (United States)

    Young, Kelsey E.; Evans, C. A.; Hodges, K. V.

    2012-01-01

    While traditional geologic mapping includes the examination of structural relationships between rock units in the field, more advanced technology now enables us to simultaneously collect and combine analytical datasets with field observations. Information about tectonomagmatic processes can be gleaned from these combined data products. Historically, construction of multi-layered field maps that include sample data has been accomplished serially (first map and collect samples, analyze samples, combine data, and finally, readjust maps and conclusions about geologic history based on combined data sets). New instruments that can be used in the field, such as a handheld xray fluorescence (XRF) unit, are now available. Targeted use of such instruments enables geologists to collect preliminary geochemical data while in the field so that they can optimize scientific data return from each field traverse. Our study tests the application of this technology and projects the benefits gained by real-time geochemical data in the field. The integrated data set produces a richer geologic map and facilitates a stronger contextual picture for field geologists when collecting field observations and samples for future laboratory work. Real-time geochemical data on samples also provide valuable insight regarding sampling decisions by the field geologist

  13. Precambrian Lunar Volcanic Protolife

    Directory of Open Access Journals (Sweden)

    Jack Green

    2009-06-01

    Full Text Available Five representative terrestrial analogs of lunar craters are detailed relevant to Precambrian fumarolic activity. Fumarolic fluids contain the ingredients for protolife. Energy sources to derive formaldehyde, amino acids and related compounds could be by flow charging, charge separation and volcanic shock. With no photodecomposition in shadow, most fumarolic fluids at 40 K would persist over geologically long time periods. Relatively abundant tungsten would permit creation of critical enzymes, Fischer-Tropsch reactions could form polycyclic aromatic hydrocarbons and soluble volcanic polyphosphates would enable assembly of nucleic acids. Fumarolic stimuli factors are described. Orbital and lander sensors specific to protolife exploration including combined Raman/laser-induced breakdown spectrocsopy are evaluated.

  14. Thermal vesiculation during volcanic eruptions

    Science.gov (United States)

    Lavallée, Yan; Dingwell, Donald B.; Johnson, Jeffrey B.; Cimarelli, Corrado; Hornby, Adrian J.; Kendrick, Jackie E.; von Aulock, Felix W.; Kennedy, Ben M.; Andrews, Benjamin J.; Wadsworth, Fabian B.; Rhodes, Emma; Chigna, Gustavo

    2015-12-01

    Terrestrial volcanic eruptions are the consequence of magmas ascending to the surface of the Earth. This ascent is driven by buoyancy forces, which are enhanced by bubble nucleation and growth (vesiculation) that reduce the density of magma. The development of vesicularity also greatly reduces the ‘strength’ of magma, a material parameter controlling fragmentation and thus the explosive potential of the liquid rock. The development of vesicularity in magmas has until now been viewed (both thermodynamically and kinetically) in terms of the pressure dependence of the solubility of water in the magma, and its role in driving gas saturation, exsolution and expansion during decompression. In contrast, the possible effects of the well documented negative temperature dependence of solubility of water in magma has largely been ignored. Recently, petrological constraints have demonstrated that considerable heating of magma may indeed be a common result of the latent heat of crystallization as well as viscous and frictional heating in areas of strain localization. Here we present field and experimental observations of magma vesiculation and fragmentation resulting from heating (rather than decompression). Textural analysis of volcanic ash from Santiaguito volcano in Guatemala reveals the presence of chemically heterogeneous filaments hosting micrometre-scale vesicles. The textures mirror those developed by disequilibrium melting induced via rapid heating during fault friction experiments, demonstrating that friction can generate sufficient heat to induce melting and vesiculation of hydrated silicic magma. Consideration of the experimentally determined temperature and pressure dependence of water solubility in magma reveals that, for many ascent paths, exsolution may be more efficiently achieved by heating than by decompression. We conclude that the thermal path experienced by magma during ascent strongly controls degassing, vesiculation, magma strength and the effusive

  15. Lung problems and volcanic smog

    Science.gov (United States)

    ... releases gases into the atmosphere. Volcanic smog can irritate the lungs and make existing lung problems worse. ... deep into the lungs. Breathing in volcanic smog irritates the lungs and mucus membranes. It can affect ...

  16. 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.

  17. Modeling volcanic ash dispersal

    CERN Document Server

    CERN. Geneva

    2010-01-01

    The assessment of volcanic fallout hazard is an important scientific, economic, and political issue, especially in densely populated areas. From a scientific point of view, considerable progress has been made during the last two decades through the use of increasingly powerful computational models and capabilities. Nowadays, models are used to quantify hazard...

  18. Multiple sets of information synthesized to describe fractures of volcanic reservoir: Taking volcanic reservoir of the Member 1 of Yingcheng Formation in Xudong Area of Xushen Gas Field as an example.%多信息综合火山岩储层裂缝表征:以徐深气田徐东地区营城组一段火山岩储层为例

    Institute of Scientific and Technical Information of China (English)

    陈欢庆; 胡永乐; 靳久强; 冉启全; 王拥军

    2011-01-01

    从成因角度将徐深气田徐东地区营城组一段火山岩储层裂缝划分为构造裂缝、冷凝收缩裂缝、炸裂缝、溶蚀裂缝、缝合缝、风化裂缝等多种类型.根据动静结合的思路,综合岩心、镜下薄片、常规和FMI测井资料、地震等多信息以及地震相干分析和蚂蚁追踪等技术.对各类型裂缝发育特征进行详细表征.结果表明,上述井震资料的结合可以完成火山岩储层裂缝表征,宏观上沿着徐东地区徐中断裂和徐东断裂裂缝最为发育,大致呈近SN向展布.微观上在发育SN向靠近断裂带裂缝的同时,还发育众多EW向或近EW向的裂缝.对裂缝成因机制分析,研究区目的层火山岩储层裂缝成因影响因素包括构造作用、火山岩性、火山岩体、火山岩相和成岩作用等,其中以构造作用和成岩作用为主.%The volcanic reservoir fractures of the Member 1 of Yingcheng Formation in Xudong Area of Xushen Gas Field are divided according to their origins into tectonic fractures, condensation contracted fractures, exploded fractures, corrosion fractures, stitched fractures and weathering fractures. Synthesizing multiple sets of information from cores, microsections and FMI logging data and using seismic variance and ant tracking technology, we described the characteristics of all kinds of fractures in detail. The results indicated that fractures developed along Xuzhong Faults and Xudong Faults in NS direction in macroscopic view. And many fractures developed along EW direction in microcosmic view at the same time. The analysis of genetic mechanisms of fractures suggested that the fractures of volcanic reservoir of the Member 1 of Yingcheng in Xudong Area of Xushen Gas Field were affected by tectonic processes, volcanic lithology, volcanic bodies, volcanic lithofacies and diagenesis, among which tectonic processes and diagenesis played the leading role.

  19. Recent seismicity detection increase in the Santorini volcanic island complex

    Science.gov (United States)

    Chouliaras, G.; Drakatos, G.; Makropoulos, K.; Melis, N. S.

    2012-04-01

    Santorini is the most active volcanic complex in the South Aegean Volcanic Arc. To improve the seismological network detectability of the seismicity in this region, the Institute of Geodynamics of the National Observatory of Athens (NOA) recently installed 4 portable seismological stations supplementary to the 3 permanent stations operating in the region. The addition of these stations has significantly improved the detectability and reporting of the local seismic activity in the NOA instrumental seismicity catalogue. In this study we analyze quantitatively the seismicity of the Santorini volcanic complex. The results indicate a recent significant reporting increase mainly for events of small magnitude and an increase in the seismicity rate by more than 100%. The mapping of the statistical significance of the rate change with the z-value method reveals that the rate increase exists primarily in the active fault zone perpendicular to the extensional tectonic stress regime that characterizes this region. The spatial distribution of the b-value around the volcanic complex indicates a low b-value distribution parallel to the extensional stress field, while the b-value cross section of the volcanic complex indicates relatively high b-values under the caldera and a significant b-value decrease with depth. These results are found to be in general agreement with the results from other volcanic regions and they encourage further investigations concerning the seismic and volcanic hazard and risk estimates for the Santorini volcanic complex using the NOA earthquake catalogue.

  20. Geochemical, isotopic (Sr-Nd-Pb) and geochronological (Ar-Ar and U-Pb) constraints on Quaternary bimodal volcanism of the Nigde Volcanic Complex (Central Anatolia, Turkey)

    Science.gov (United States)

    Aydin, F.; Siebel, W.; Uysal, I.; Ersoy, E. Y.; Schmitt, A. K.; Sönmez, M.; Duncan, R.

    2012-04-01

    The Nigde Volcanic Complex (NVC) is a major Late Neogene-Quaternary volcanic centre within the Cappadocian Volcanic Province of Central Anatolia. The Late Neogene evolution of the NVC generally initiated with the eruption of extensive andesitic-dacitic lavas and pyroclastic flow deposits, and minor basaltic lavas. This stage was followed by a Quaternary bimodal magma suite which forms Na-alkaline/transitional basaltic and high-K calc-alkaline to alkaline silicic volcanic rocks. In this study, we present new geochemical, isotopic (Sr-Nd-Pb) and geochronological (Ar-Ar and U-Pb) data for the bimodal volcanic suite within the NVC. Recent data suggest that the eruption of this suite took place ranges between ~650 and ~220 ka (Middle-Late Pleistocene). Silicic rocks consisting of rhyolite and associated pumice-rich pyroclastic fall out and surge deposits define a narrow range of 143Nd/144Nd isotope ratios (0.5126-0.5127), and show virtually no difference in Pb isotope composition (206Pb/204Pb = 18.84-18.87, 207Pb/204Pb = 15.64-15.67 and 208Pb/204Pb = 38.93-38.99). 87Sr/86Sr isotopic compositions of the silicic (0.704-0.705) and basaltic rocks (0.703-0.705) are rather similar reflecting a common source. The most mafic sample from basaltic rocks related to monogenetic cones is characterized by 87Sr/86Sr = 0.704, 143Nd/144Nd = 0.5127, 206Pb/204Pb = 18.80, 207Pb/204Pb = 15.60 and 208Pb/204Pb = 38.68. These values suggest a moderately depleted signature of the mantle source. The geochronological and geochemical data suggest that NVC silicic and basaltic rocks are genetically closely related to each other. Mantle derived differentiated basaltic melts which experienced low degree of crustal assimilation are suggested to be the parent melt of the rhyolites. Further investigations will focus on the spatial and temporal evolution of Quaternary bimodal magma suite in the NVC and the genetic relation between silicic and basaltic rocks through detailed oxygen isotope analysis and (U

  1. Aurorae and Volcanic Eruptions

    Science.gov (United States)

    2001-06-01

    1 month, and a very high temperature, more than 1000 K (700 °C). However, the Tvashtar outburst is quite anomalous and has lasted more than one year. The temperature has been estimated at about 1000-1300 K (700-1000 °C); this range is typical for silicate-based volcanism observed on the Earth. The Galileo spacecraft observed the onset of this eruption, and twice again this year. Monitoring of this event by means of ground-based telescopes, as here with ISAAC at the VLT or by the ADONIS Adaptive Optics system on the ESO 3.6-m telescope at La Silla, gives the astronomers a most welcome opportunity to follow more closely the temperature evolution of the eruption and hence provides excellent support to the space observations. The forthcoming arrival on Paranal of NAOS (the adaptive optics system for the VLT) and CONICA (the connected IR camera equipped with an Aladdin detector) will lead to a significant improvement of the achievable image quality. It will be employed for a large variety of astronomical programmes and will, among others, allow the detection and frequent monitoring of a large number of hot spots on the surface of Io . Note [1]: ISAAC registers (infrared) electromagnetic radiation at wavelengths between approx. 1.0 and 5.0 µm which we sense as heat. The human eye registers electromagnetic radiation (light) at shorter wavelengths, from about 0.4 to 0.7 µm. Technical information about the photos PR Photos 21a-d/01 are based on on-target exposures lasting a total of 30 sec (L-band), 44 sec (4.07 µm), 58 sec (3.28 µm) and 58 sec (3.21 µm), respectively. The real observing time is twice as much, with half of the time spent in the off-target chop position. The fields shown measure 72 x 72 arcsec 2 ; 1 pixel = 0.07 arcsec. PR Photo 21e/01 is a colour-coded combination of these four exposures. North is up and East is left. Addendum: About the Jovian aurorae and polar haze Aurorae Borealis and Aurorae Australis ('Northern and Southern Lights') are observed

  2. Exploring Hawaiian Volcanism

    Science.gov (United States)

    Poland, Michael P.; Okubo, Paul G.; Hon, Ken

    2013-02-01

    In 1912 the Hawaiian Volcano Observatory (HVO) was established by Massachusetts Institute of Technology professor Thomas A. Jaggar Jr. on the island of Hawaii. Driven by the devastation he observed while investigating the volcanic disasters of 1902 at Montagne Pelée in the Caribbean, Jaggar conducted a worldwide search and decided that Hawai`i provided an excellent natural laboratory for systematic study of earthquake and volcano processes toward better understanding of seismic and volcanic hazards. In the 100 years since HVO's founding, surveillance and investigation of Hawaiian volcanoes have spurred advances in volcano and seismic monitoring techniques, extended scientists' understanding of eruptive activity and processes, and contributed to development of global theories about hot spots and mantle plumes.

  3. Exploring Hawaiian volcanism

    Science.gov (United States)

    Poland, Michael P.; Okubo, Paul G.; Hon, Ken

    2013-01-01

    In 1912 the Hawaiian Volcano Observatory (HVO) was established by Massachusetts Institute of Technology professor Thomas A. Jaggar Jr. on the island of Hawaii. Driven by the devastation he observed while investigating the volcanic disasters of 1902 at Montagne Pelée in the Caribbean, Jaggar conducted a worldwide search and decided that Hawai‘i provided an excellent natural laboratory for systematic study of earthquake and volcano processes toward better understanding of seismic and volcanic hazards. In the 100 years since HVO’s founding, surveillance and investigation of Hawaiian volcanoes have spurred advances in volcano and seismic monitoring techniques, extended scientists’ understanding of eruptive activity and processes, and contributed to development of global theories about hot spots and mantle plumes.

  4. California's Vulnerability to Volcanic Hazards: What's at Risk?

    Science.gov (United States)

    Mangan, M.; Wood, N. J.; Dinitz, L.

    2015-12-01

    California is a leader in comprehensive planning for devastating earthquakes, landslides, floods, and tsunamis. Far less attention, however, has focused on the potentially devastating impact of volcanic eruptions, despite the fact that they occur in the State about as frequently as the largest earthquakes on the San Andreas Fault Zone. At least 10 eruptions have occurred in the past 1,000 years—most recently in northern California (Lassen Peak 1914 to 1917)—and future volcanic eruptions are inevitable. The likelihood of renewed volcanism in California is about one in a few hundred to one in a few thousand annually. Eight young volcanoes, ranked as Moderate to Very High Threat [1] are dispersed throughout the State. Partially molten rock (magma) resides beneath at least seven of these—Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, and Salton Buttes— causing earthquakes, toxic gas emissions, hydrothermal activity, and (or) ground deformation. Understanding the hazards and identifying what is at risk are the first steps in building community resilience to volcanic disasters. This study, prepared in collaboration with the State of California Governor's Office of Emergency Management and the California Geological Survey, provides a broad perspective on the State's exposure to volcano hazards by integrating mapped volcano hazard zones with geospatial data on at-risk populations, infrastructure, and resources. The study reveals that ~ 16 million acres fall within California's volcano hazard zones, along with ~ 190 thousand permanent and 22 million transitory populations. Additionally, far-field disruption to key water delivery systems, agriculture, utilities, and air traffic is likely. Further site- and sector-specific analyses will lead to improved hazard mitigation efforts and more effective disaster response and recovery. [1] "Volcanic Threat and Monitoring Capabilities

  5. Subdiffusion of volcanic earthquakes

    CERN Document Server

    Abe, Sumiyoshi

    2016-01-01

    A comparative study is performed on volcanic seismicities at Mt.Eyjafjallajokull in Iceland and Mt. Etna in Sicily, Italy, from the viewpoint of science of complex systems, and the discovery of remarkable similarities between them regarding their exotic spatio-temporal properties is reported. In both of the volcanic seismicities as point processes, the jump probability distributions of earthquakes are found to obey the exponential law, whereas the waiting-time distributions follow the power law. In particular, a careful analysis is made about the finite size effects on the waiting-time distributions, and accordingly, the previously reported results for Mt. Etna [S. Abe and N. Suzuki, EPL 110, 59001 (2015)] are reinterpreted. It is shown that spreads of the volcanic earthquakes are subdiffusive at both of the volcanoes. The aging phenomenon is observed in the "event-time-averaged" mean-squared displacements of the hypocenters. A comment is also made on presence/absence of long term memories in the context of t...

  6. 火山岩气藏储层岩相特征及其对储层物性的影响——以徐深气田徐东地区白垩系营城组一段火山岩为例%Lithofacies characteristics of volcanic gas reservoirs and their influence on reservoir physical properties: a case study of Member 1 of Cretaceous Yingcheng Formation in Xudong area of the Xushen gas field

    Institute of Scientific and Technical Information of China (English)

    陈欢庆; 胡永乐; 冉启全; 闫林; 孙作兴

    2011-01-01

    Taking the volcanic reservoir of Member 1 of Yingcheng Formation in Xudong area of the Xushen gas field as an example, the authors studied lithofacies characteristics of the volcanic gas reservoir and their influences on reservoir physical properties with the purpose of effectively forecasting and exploiting the volcanic reservoir.On the basis of identification of volcanic rock types and recognition of volcanic rock bodies by combining geological data with logging data and seismic data, the authors analyzed volcanic lithofacies characteristics and their relationship with reservoir physical properties and forecast the favorable prospecting areas by using data from wells, sections and plane lithofacies.The results indicate that the volcanic reservoir of the Member 1 of Yingcheng Formation in Xudong area of the Xushen gas field was formed by repeated volcanic eruptions, with the lithologies consisting of 10 types.The rhyolite, rhyolite tuff and sedimentary volcanic breccia played the preponderant role.The eruption type in the study area was cranny-center eruption, and crater and volcanic lithofacies were obviously controlled by ruptures.The volcanic bodies were dominated by craters, and different volcanic lithofacies were developed in different positions of volcanic bodies.The volcanic fades inside the volcanic bodies in the study area can be divided into five types and sixteen sub-facies.The results indicate that the volcanic lithology and its combination constitute the basis of the division of volcanic fades, and the spreading of volcanic fades controls the distribution of gas reservoirs.The reservoir development areas include the lower part and upper part and top overflow sub-facies of overflow facies, splash down sub-facies and air falling sub-facies, middle extrusive sub-facies, exterior sub-facies of extrusive facies and volcanic neck sub-facies of volcanic channels facies.The sub-facies of the volcanic reservoir include volcanic sub-lithfacies of volcanic neck

  7. Collaborative studies target volcanic hazards in Central America

    Science.gov (United States)

    Bluth, Gregg J. S.; Rose, William I.

    Central America is the second-most consistently active volcanic zone on Earth, after Indonesia. Centuries of volcanic activity have produced a spectacular landscape of collapsed calderas, debris flows, and thick blankets of pyroclastic materials. Volcanic activity dominates the history, culture, and daily life of Central American countries.January 2002 marked the third consecutive year in which a diverse group of volcanologists and geophysicists conducted focused field studies in Central America. This type of multi-institutional collaboration reflects the growing involvement of a number of U.S. and non-U.S. universities, and of other organizations, in Guatemala and El Salvador (Table 1).

  8. Monitoring and forecasting Etna volcanic plumes

    Directory of Open Access Journals (Sweden)

    S. Scollo

    2009-09-01

    Full Text Available In this paper we describe the results of a project ongoing at the Istituto Nazionale di Geofisica e Vulcanologia (INGV. The objective is to develop and implement a system for monitoring and forecasting volcanic plumes of Etna. Monitoring is based at present by multispectral infrared measurements from the Spin Enhanced Visible and Infrared Imager on board the Meteosat Second Generation geosynchronous satellite, visual and thermal cameras, and three radar disdrometers able to detect ash dispersal and fallout. Forecasting is performed by using automatic procedures for: i downloading weather forecast data from meteorological mesoscale models; ii running models of tephra dispersal, iii plotting hazard maps of volcanic ash dispersal and deposition for certain scenarios and, iv publishing the results on a web-site dedicated to the Italian Civil Protection. Simulations are based on eruptive scenarios obtained by analysing field data collected after the end of recent Etna eruptions. Forecasting is, hence, supported by plume observations carried out by the monitoring system. The system was tested on some explosive events occurred during 2006 and 2007 successfully. The potentiality use of monitoring and forecasting Etna volcanic plumes, in a way to prevent threats to aviation from volcanic ash, is finally discussed.

  9. DECOVALEX-THMC Task D: Long-Term Permeability/Porosity Changes inthe EDZ and Near Field due to THM and THC Processes in Volcanic andCrystaline-Bentonite Systems, Status Report October 2005

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.

    2005-11-01

    The DECOVALEX project is an international cooperativeproject initiated by SKI, the Swedish Nuclear Power Inspectorate, withparticipation of about 10 international organizations. The name DECOVALEXstands for DEvelopment of COupled models and their VALidation againstExperiments. The general goal of this project is to encouragemultidisciplinary interactive and cooperative research on modelingcoupled processes in geologic formations in support of the performanceassessment for underground storage of radioactive waste. Three multi-yearproject stages of DECOVALEX have been completed in the past decade,mainly focusing on coupled thermal-hydrological-mechanicalprocesses.Currently, a fourth three-year project stage of DECOVALEX isunder way, referred to as DECOVALEX-THMC. THMC stands for Thermal,Hydrological, Mechanical, and Chemical processes. The new project stageaims at expanding the traditional geomechanical scope of the previousDECOVALEX project stages by incorporating geochemical processes importantfor repository performance. The U.S. Department of Energy (DOE) leadsTask D of the new DECOVALEX phase, entitled "Long-termPermeability/Porosity Changes in the EDZ and Near Field due to THC andTHM Processes for Volcanic and Crystalline-Bentonite Systems." In itsleadership role for Task D, DOE coordinates and sets the direction forthe cooperative research activities of the international research teamsengaged in Task D.

  10. U-series data of recent volcanism at an Axial Volcanic Ridge (Invited)

    Science.gov (United States)

    van Calsteren, P. W.; Thomas, L. E.; Jc024 Shipboard Party

    2010-12-01

    The spreading rate of the Mid Atlantic Ridge, at the area around 45°N is 11mm/y. This is appropriate scaling for mantle horizontal flow and vertical upwelling. However, the accretion of oceanic crust within the median valley graben (MVG), occurs episodically on timescales much longer than years. During the 2008 JC024 cruise various geophysical and bathymetry datasets were collected as well as photographic and video evidence and some 270 rock samples, using ship-borne instruments, a deep-towed platform TOBI and a tethered ROV Isis both in demersal mode and 'flying' at 100m above the seafloor. We1 could identify the overall 'hour-glass' shape of the MVG, the location of the AVR, 'flat-top' features and some smooth areas on either side. Overall we1 counted some 8000 conical or dome-shaped hummocks, which are arranged in lineaments, mostly parallel to the spreading axis. We1 deduced that each hummock is an individual monogenetic volcano. Smooth areas between the AVR and the median valley boundary faults may indicate sheet flows which are probably burying the subsiding hummocks. For Dive 91, we1 used a MS2000 high-resolution multi-beam bathymetry echo-sounder on Isis flying at an altitude of 100m above the seafloor; to construct a bathymetry map with a vertical resolution of 20cm and a horizontal precision of 5m over an area of ˜3km2. The high-resolution bathymetry allows us to deduce that volcano dimensions average around 300m diameter, ˜150m altitude, and 0.005km3 volume and to count ˜100 volcanoes. Visual observations using the camera systems on Isis showed that individual volcanoes are essentially piles of pillow lavas, usually ˜1m diameter and >2m long of various types, sometimes leaving >10% gaps between pillows, sometimes interlocking somewhat deformed pillows. Small protrusions, 10-50cm long, which are numerous on some pillows, could be fairly easily broken off using the pincers on the hydraulic arms of Isis, and returned to the surface. Uncertainty remains

  11. CHARACTERISTICS OF CARBONIFEROUS VOLCANIC RESERVOIRS IN THE 6th AND 7th AREAS OF KARAMAY OIL FIELD%克拉玛依油田六七区石炭系火山岩储层特征

    Institute of Scientific and Technical Information of China (English)

    罗雪; 罗明高; 林军; 袁述武; 乐园; 陈忠云

    2013-01-01

    Characteristics of lithology,physical and pore structure of the Carboniferous volcanic rocks in the 6th and the 7th districts of Karamay oil field are studied through observation and analysis of drilling cores of 665.56 meters long from 32 drilling wells,470 thin sections,666 physical analysis samples and 82 drilling wells logging data.It is showed that burial depth of layers,lithology and fractures are 3 main factors influencing the reservoirs in this area,and the most favorable reservoir is located in the south of the 6 district and the middle of the 7 district.Pyroclastic rock and sedimentary rock are the main rock types in the area and the major lithology of volcanic rock reservoir is breccias lava and basalt characteristic of low porosity and permeability.Reservoir space is dominated by stoma,intercrystal pore,vug and pre-existing fractures.The favorable reservoir mainly distributes in the south and northwest of 6 district and in the middle of 7 district.%针对32口井665.56 m岩心、470块岩矿薄片、666个物性分析样品以及82口井测井等资料,对克拉玛依油田六七区石炭系火山岩的岩性、物性以及孔隙结构特征进行了研究,结果表明该区影响火山岩储层的主要因素主要有地层埋深、岩性以及裂缝影响,最有利的储集区位于六区南部和七中区.研究区岩石类型主要为火山熔岩类、火山碎屑岩类和沉积岩类,火山岩储层主要岩性为角砾熔岩和玄武岩;孔隙度、渗透率较低;储集空间以气孔、晶间孔、溶蚀孔和原生裂缝为主;有利火山岩储层主要分布于六区南部、西北部以及七中区.

  12. Volcanic hazard assessment at the Campi Flegrei caldera

    OpenAIRE

    Mastrolorenzo, G.; Pappalardo, L; C. Troise; S. Rossano; Panizza, A; G. De Natale

    2006-01-01

    Previous and new results from probabilistic approaches based on available volcanological data from real eruptions of Campi Flegrei, are assembled in a comprehensive assessment of volcanic hazards at the Campi Flegrei caldera, in order to compare the volcanic hazards related to the different types of events. Hazard maps based on a very wide set of numerical simulations, produced using field and laboratory data as input parameters relative to the whole range of fallout and pyrocl...

  13. Volcanism on Mars. Chapter 41

    Science.gov (United States)

    Zimbelman, J. R.; Garry, W. B.; Bleacher, J. E.; Crown, D. A.

    2015-01-01

    Spacecraft exploration has revealed abundant evidence that Mars possesses some of the most dramatic volcanic landforms found anywhere within the solar system. How did a planet half the size of Earth produce volcanoes like Olympus Mons, which is several times the size of the largest volcanoes on Earth? This question is an example of the kinds of issues currently being investigated as part of the space-age scientific endeavor called "comparative planetology." This chapter summarizes the basic information currently known about volcanism on Mars. The volcanoes on Mars appear to be broadly similar in overall morphology (although, often quite different in scale) to volcanic features on Earth, which suggests that Martian eruptive processes are not significantly different from the volcanic styles and processes on Earth. Martian volcanoes are found on terrains of different age, and Martian volcanic rocks are estimated to comprise more than 50% of the Martian surface. This is in contrast to volcanism on smaller bodies such as Earth's Moon, where volcanic activity was mainly confined to the first half of lunar history (see "Volcanism on the Moon"). Comparative planetology supports the concept that volcanism is the primary mechanism for a planetary body to get rid of its internal heat; smaller bodies tend to lose their internal heat more rapidly than larger bodies (although, Jupiter's moon Io appears to contradict this trend; Io's intense volcanic activity is powered by unique gravitational tidal forces within the Jovian system; see "Volcanism on Io"), so that volcanic activity on Mars would be expected to differ considerably from that found on Earth and the Moon.

  14. Volcanic Ash Nephelometer Probe Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Advanced dropsondes that could effectively be guided through atmospheric regions of interest such as volcanic plumes may enable unprecedented observations of...

  15. Volcanic Eruptions and Climate

    Science.gov (United States)

    Robock, A.

    2012-12-01

    Large volcanic eruptions inject sulfur gases into the stratosphere, which convert to sulfate aerosols with an e-folding residence time of about one year. The radiative and chemical effects of these aerosol clouds produce responses in the climate system. Observations and numerical models of the climate system show that volcanic eruptions produce global cooling and were the dominant natural cause of climate change for the past millennium, on timescales from annual to century. Major tropical eruptions produce winter warming of Northern Hemisphere continents for one or two years, while high latitude eruptions in the Northern Hemisphere weaken the Asian and African summer monsoon. The Toba supereruption 74,000 years ago caused very large climate changes, affecting human evolution. However, the effects did not last long enough to produce widespread glaciation. An episode of four large decadally-spaced eruptions at the end of the 13th century C.E. started the Little Ice Age. Since the Mt. Pinatubo eruption in the Philippines in 1991, there have been no large eruptions that affected climate, but the cumulative effects of small eruptions over the past decade had a small effect on global temperature trends. The June 13, 2011 Nabro eruption in Eritrea produced the largest stratospheric aerosol cloud since Pinatubo, and the most of the sulfur entered the stratosphere not by direct injection, but by slow lofting in the Asian summer monsoon circulation. Volcanic eruptions warn us that while stratospheric geoengineering could cool the surface, reducing ice melt and sea level rise, producing pretty sunsets, and increasing the CO2 sink, it could also reduce summer monsoon precipitation, destroy ozone, allowing more harmful UV at the surface, produce rapid warming when stopped, make the sky white, reduce solar power, perturb the ecology with more diffuse radiation, damage airplanes flying in the stratosphere, degrade astronomical observations, affect remote sensing, and affect

  16. System of Volcanic activity

    Directory of Open Access Journals (Sweden)

    P. HÉDERVARI

    1972-06-01

    Full Text Available A comparison is made among the systems of B. G.
    Escher (3, of R. W. van Bemmelen (1 and that of the author (4. In this
    connection, on the basis of Esclier's classification, the terms of "constructiv
    e " and "destructive" eruptions are introduced into the author's system and
    at the same time Escher's concept on the possible relation between the depth
    of magma-chamber and the measure of the gas-pressure is discussed briefly.
    Three complementary remarks to the first paper (4 011 the subject of system
    of volcanic activity are added.

  17. The volcanic and geochemical development of São Nicolau, Cape Verde Islands

    DEFF Research Database (Denmark)

    Duprat, Helene Inga; Holm, Paul Martin; Sherson, Jacob Friis;

    2007-01-01

    We present 34 new age results from 40 Ar/39 Ar incremental heating analyses of groundmass separates from volcanic rocks from São Nicolau, Cape Verde. Combining the age results with field observations, we show that the volcanic activity that formed the island occurred in four separate stages: 1: >6...... of 207 volcanic rocks representing all volcanic activity stages is presented. The rocks are alkaline and mostly primitive (MgO >8 wt.%) basic to ultrabasic ranging from nephelinites through basanites to picrobasalts. Evolved rocks range to phonolites. During all four volcanic stages predominantly high Mg...... assumed. With more ages of only around 50 ka the youngest volcanic rocks found on the island indicate that stage 4 may still be active. The cyclieity of São Nico volcanism suggests that mantle plume material arrived under São Nicolau in batches separated by nonfertile material....

  18. Halogen Chemistry in Volcanic Plumes (Invited)

    Science.gov (United States)

    Roberts, Tjarda

    2017-04-01

    only partially constrained by available observations. Reactions on aerosol are a key driver of the chemistry and are affected by uncertainties in both the HOBr reactive uptake coefficient and the aerosol surface area. Recent work has explored the reactive uptake of HOBr on sulfate-rich aerosol, whilst field-measurements at Mt Etna have aimed to quantify the size-resolved primary aerosol emission, towards improving model representations of this highly non-linear volcanic plume halogen chemistry.

  19. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  20. 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 < 1m diameter lava coils. Lineations are generally straight and parallel each other, sometimes for over 100 meters. The boundaries between plateaus and depressions are also lineated and tilted to angles sometimes approaching vertical. Plateau-parallel cracks, sometimes containing squeeze-ups, mark the boundary between tilted crust and plateau. Some plateau depressions display level floors with hummocky surfaces, while some are bowl shaped with floors covered in broken lava slabs. The lower walls of pits sometimes display lateral, sagged lava wedges. Infrequently, pit floors display the upper portion of a tumulus from an older flow. In some places the surface crust has been disrupted forming a slabby texture. Slabs are typically on the scale of a meter or less across and no less than 7-10 cm thick. The slabs preserve the lineated textures of the undisturbed plateau crust. It appears that this style of terrain represents the emplacement of an extensive sheet that experiences inflation episodes within preferred regions where lateral spreading of the sheet is inhibited, thereby forming plateaus. Rough surfaces represent inflation-related disruption of pahoehoe lava and not a a lava. Depressions are often the result of non-inflation and can be clearly identified by lateral

  1. Uranium series, volcanic rocks

    Science.gov (United States)

    Vazquez, Jorge A.

    2014-01-01

    Application of U-series dating to volcanic rocks provides unique and valuable information about the absolute timing of crystallization and differentiation of magmas prior to eruption. The 238U–230Th and 230Th-226Ra methods are the most commonly employed for dating the crystallization of mafic to silicic magmas that erupt at volcanoes. Dates derived from the U–Th and Ra–Th methods reflect crystallization because diffusion of these elements at magmatic temperatures is sluggish (Cherniak 2010) and diffusive re-equilibration is insignificant over the timescales (less than or equal to 10^5 years) typically associated with pre-eruptive storage of nearly all magma compositions (Cooper and Reid 2008). Other dating methods based on elements that diffuse rapidly at magmatic temperatures, such as the 40Ar/39Ar and (U–Th)/He methods, yield dates for the cooling of magma at the time of eruption. Disequilibrium of some short-lived daughters of the uranium series such as 210Po may be fractionated by saturation of a volatile phase and can be employed to date magmatic gas loss that is synchronous with volcanic eruption (e.g., Rubin et al. 1994).

  2. Volcanic Eruptions and Climate

    Science.gov (United States)

    LeGrande, Allegra N.; Anchukaitis, Kevin J.

    2015-01-01

    Volcanic eruptions represent some of the most climatically important and societally disruptive short-term events in human history. Large eruptions inject ash, dust, sulfurous gases (e.g. SO2, H2S), halogens (e.g. Hcl and Hbr), and water vapor into the Earth's atmosphere. Sulfurous emissions principally interact with the climate by converting into sulfate aerosols that reduce incoming solar radiation, warming the stratosphere and altering ozone creation, reducing global mean surface temperature, and suppressing the hydrological cycle. In this issue, we focus on the history, processes, and consequences of these large eruptions that inject enough material into the stratosphere to significantly affect the climate system. In terms of the changes wrought on the energy balance of the Earth System, these transient events can temporarily have a radiative forcing magnitude larger than the range of solar, greenhouse gas, and land use variability over the last millennium. In simulations as well as modern and paleoclimate observations, volcanic eruptions cause large inter-annual to decadal-scale changes in climate. Active debates persist concerning their role in longer-term (multi-decadal to centennial) modification of the Earth System, however.

  3. Geodynamical evolution of Central Andes at 24°S as inferred by magma composition along the Calama-Olacapato-El Toro transversal volcanic belt

    Science.gov (United States)

    Matteini, M.; Mazzuoli, R.; Omarini, R.; Cas, R.; Maas, R.

    2002-11-01

    crustal signatures. At the same time, the eastern sector of the Puna plateau experienced westward underthrusting of the Brazilian shield and upper crustal brittle deformation. Partial melts from underthrust upper crustal wedges mixed with lower crustal magmas to produce lavas at Aguas Calientes and Quevar. During Pliocene to Quaternary, delamination of the lithosphere and lowermost crust promoted a widespread monogenetic ocean island basalt-type and shoshonitic volcanism.

  4. Amazonian volcanism inside Valles Marineris on Mars

    Science.gov (United States)

    Brož, Petr; Hauber, Ernst; Wray, James J.; Michael, Gregory

    2017-09-01

    The giant trough system of Valles Marineris is one of the most spectacular landforms on Mars, yet its origin is still unclear. Although often referred to as a rift, it also shows some characteristics that are indicative of collapse processes. For decades, one of the major open questions was whether volcanism was active inside the Valles Marineris. Here we present evidence for a volcanic field on the floor of the deepest trough of Valles Marineris, Coprates Chasma. More than 130 individual edifices resemble scoria and tuff cones, and are associated with units that are interpreted as lava flows. Crater counts indicate that the volcanic field was emplaced sometime between ∼0.4 Ga and ∼0.2 Ga. The spatial distribution of the cones displays a control by trough-parallel subsurface structures, suggesting magma ascent in feeder dikes along trough-bounding normal faults. Spectral data reveal an opaline-silica-rich unit associated with at least one of the cones, indicative of hydrothermal processes. Our results point to magma-water interaction, an environment of astrobiological interest, perhaps associated with late-stage activity in the evolution of Valles Marineris, and suggest that the floor of Coprates Chasma is promising target for the in situ exploration of Mars.

  5. Submarine Volcanic Morphology of Santorini Caldera, Greece

    Science.gov (United States)

    Nomikou, P.; Croff Bell, K.; Carey, S.; Bejelou, K.; Parks, M.; Antoniou, V.

    2012-04-01

    Santorini volcanic group form the central part of the modern Aegean volcanic arc, developed within the Hellenic arc and trench system, because of the ongoing subduction of the African plate beneath the European margin throughout Cenozoic. It comprises three distinct volcanic structures occurring along a NE-SW direction: Christianna form the southwestern part of the group, Santorini occupies the middle part and Koloumbo volcanic rift zone extends towards the northeastern part. The geology of the Santorini volcano has been described by a large number of researchers with petrological as well as geochronological data. The offshore area of the Santorini volcanic field has only recently been investigated with emphasis mainly inside the Santorini caldera and the submarine volcano of Kolumbo. In September 2011, cruise NA-014 on the E/V Nautilus carried out new surveys on the submarine volcanism of the study area, investigating the seafloor morphology with high-definition video imaging. Submarine hydrothermal vents were found on the seafloor of the northern basin of the Santorini caldera with no evidence of high temperature fluid discharges or massive sulphide formations, but only low temperature seeps characterized by meter-high mounds of bacteria-rich sediment. This vent field is located in line with the normal fault system of the Kolumbo rift, and also near the margin of a shallow intrusion that occurs within the sediments of the North Basin. Push cores have been collected and they will provide insights for their geochemical characteristics and their relationship to the active vents of the Kolumbo underwater volcano. Similar vent mounds occur in the South Basin, at shallow depths around the islets of Nea and Palaia Kameni. ROV exploration at the northern slopes of Nea Kameni revealed a fascinating underwater landscape of lava flows, lava spines and fractured lava blocks that have been formed as a result of 1707-1711 and 1925-1928 AD eruptions. A hummocky topography at

  6. Application of Geographical Information Systems to Lahar Hazard Assessment on an Active Volcanic System

    OpenAIRE

    2010-01-01

    Lahars (highly dynamic mixtures of volcanic debris and water) have been responsible for some of the most serious volcanic disasters and have killed tens of thousands of people in recent decades. Despite considerable lahar model development in the sciences, many research tools have proved wholly unsuitable for practical application on an active volcanic system where it is difficult to obtain field measurements. In addition, geographic information systems are tools that offer a great potenti...

  7. Volcanic studies at Katmai

    Energy Technology Data Exchange (ETDEWEB)

    1989-12-31

    The Continental Scientific Drilling Program (CSDP) is a national effort supported by the Department of Energy, the US Geological Survey, and the National Science Foundation. One of the projects proposed for the CSDP consists of drilling a series of holes in Katmai National Park in Alaska to give a third dimension to the model of the 1912 eruption of Novarupta, and to investigate the processes of explosive volcanism and hydrothermal transport of metals (Eichelberger et al., 1988). The proposal for research drilling at Katmai states that ``the size, youth, elevated temperature, and simplicity of the Novarupta vent make it a truly unique scientific target.`` The National Park Service (NPS), which has jurisdiction, is sympathetic to aims of the study. However, NPS wishes to know whether Katmai is indeed uniquely suited to the research, and has asked the Interagency Coordinating Group to support an independent assessment of this claim. NPS suggested the National Academy of Sciences as an appropriate organization to conduct the assessment. In response, the National Research Council -- the working arm of the Academy -- established, under the aegis of its US Geodynamics Committee, a panel whose specific charge states: ``The proposed investigation at Katmai has been extensively reviewed for scientific merit by the three sponsoring and participating agencies. Thus, the scientific merit of the proposed drilling at Katmai is not at issue. The panel will review the proposal for scientific drilling at Katmai and prepare a short report addressing the specific question of the degree to which it is essential that the drilling be conducted at Katmai as opposed to volcanic areas elsewhere in the world.``

  8. Io. [theories concerning volcanic activity

    Science.gov (United States)

    Johnson, T. V.; Soderblom, L. A.

    1983-01-01

    A report on the continuing investigation of Io is presented. Gravitational resonance is discussed as the cause of Io's volcanism, and the volcanic activity is explained in terms of sulfur chemistry. Theories concerning the reasons for the two main types of volcanic eruptions on Io are advanced and correlated with geographical features of the satellite. The sulfur and silicate models of the calderas are presented, citing the strengths and weaknesses of each. Problems of the gravitational resonance theory of Io's heat source are then described. Finally, observations of Io planned for the Galileo mission are summarized.

  9. Preliminary geochemical characterization of volcanic and geothermal fluids discharged from the Ecuadorian volcanic arc.

    OpenAIRE

    Inguaggiato, S.; Hidalgo, S.; Beate, B.; Bourquin, J.

    2009-01-01

    In Ecuador, magmatism results from the subduction of the Nazca Plate beneath the North Western part of South America (Pennington, 1981; Kellogg and Vega, 1995; Witt et al., 2006). North of 2.5°S, the Ecuadorian Quaternary volcanic arc is characterized by about 60 volcanoes distributed in three different parallel chains. Many of these volcanoes are potentially active or currently in activity and display associated geothermal fields. South of this latitude, no active arc is present in Ecuador. ...

  10. Volcanic hazard impacts to critical infrastructure: A review

    Science.gov (United States)

    Wilson, G.; Wilson, T. M.; Deligne, N. I.; Cole, J. W.

    2014-10-01

    Effective natural hazard risk assessment requires the characterisation of both hazards and vulnerabilities of exposed elements. Volcanic hazard assessment is at an advanced state and is a considerable focus of volcanic scientific inquiry, whereas comprehensive vulnerability assessment is lacking. Cataloguing and analysing volcanic impacts provide insight on likely societal and physical vulnerabilities during future eruptions. This paper reviews documented disruption and physical damage of critical infrastructure elements resulting from four volcanic hazards (tephra fall, pyroclastic density currents, lava flows and lahars) of eruptions in the last 100 years. We define critical infrastructure as including energy sector infrastructure, water supply and wastewater networks, transportation routes, communications, and critical components. Common trends of impacts and vulnerabilities are summarised, which can be used to assess and reduce volcanic risk for future eruptions. In general, tephra falls cause disruption to these infrastructure sectors, reducing their functionality, whilst flow hazards (pyroclastic density currents, lava flows and lahars) are more destructive causing considerable permanent damage. Volcanic risk assessment should include quantification of vulnerabilities and we challenge the volcanology community to address this through the implementation of a standardised vulnerability assessment methodology and the development and use of fragility functions, as has been successfully implemented in other natural hazard fields.

  11. Recent seismicity detection increase in the Santorini volcanic island complex

    Directory of Open Access Journals (Sweden)

    G. Chouliaras

    2012-04-01

    Full Text Available Santorini is the most active volcanic complex in the South Aegean Volcanic Arc. To improve the seismological network detectability of the seismicity in this region, the Institute of Geodynamics of the National Observatory of Athens (NOA recently installed 4 portable seismological stations supplementary to the 3 permanent stations operating in the region. The addition of these stations has significantly improved the detectability and reporting of the local seismic activity in the NOA instrumental seismicity catalogue.

    In this study we analyze quantitatively the seismicity of the Santorini volcanic complex. The results indicate a recent significant reporting increase mainly for events of small magnitude and an increase in the seismicity rate by more than 100%. The mapping of the statistical significance of the rate change with the z-value method reveals that the rate increase exists primarily in the active fault zone perpendicular to the extensional tectonic stress regime that characterizes this region.

    The spatial distribution of the b-value around the volcanic complex indicates a low b-value distribution parallel to the extensional stress field, while the b-value cross section of the volcanic complex indicates relatively high b-values under the caldera and a significant b-value decrease with depth.

    These results are found to be in general agreement with the results from other volcanic regions and they encourage further investigations concerning the seismic and volcanic hazard and risk estimates for the Santorini volcanic complex using the NOA earthquake catalogue.

  12. Eruptive dynamics and hazards associated with obsidian bearing ignimbrites of the Geghama Volcanic Highland, Central Armenia: a textural insight

    Science.gov (United States)

    Matthews, Zoe; Manning, Christina J.

    2017-04-01

    The Geghama Volcanic highland in central Armenia is an ideal setting to study the young ( 750-25 ka [1]) volcanism that characterises the Lesser Caucasus region. The volcanism in the area is bimodal in composition: the eastern highlands are dominated by numerous monogenetic scoria cones, whilst the west shows more evolved volcanism centered on two obsidian bearing, polygenetic domes (Hatis and Gutanasar) [2]. Activity at Hatis and Gutanasar is thought to have spanned 550ka-200ka [3] and produced a range of products including obsidian flows, ignimbrites and basaltic scoria cones, consistent with long lived and complex magma storage systems. During a similar time period there is evidence for the presence of hominin groups in the surrounding region [3] and it is likely that at least some of the volcanic activity at Hatis and Gutanasar impacted on their distribution [4]. A better understanding of the eruptive behaviour of these volcanoes during this period could therefore shed light on the effect of volcanic activity on the dispersal of man through this period. Whilst large regional studies have striven to better understand the timing and source of volcanism in Armenia, there have been few detailed studies on single volcanoes. Obsidian is ubiquitous within the volcanic material of both Gutanasar and Hatis as lava flows, dome deposits and within ignimbrites. This study aims to better understand the eruptive history of Gutanasar, with specific focus upon the determination of the petrogenetic history of obsidian lenses observed within the ignimbrite deposits. Identification of these obsidians as the result of welding or in-situ melting will help constrain eruptive volumes and flow thickness, important for the reconstruction of palaeo-volcanic hazards. In order to interpret how this obsidian was deposited, macro textural analysis is combined with micro textural measurements of microlite crystals. Quantitative measurements of microlites in obsidian can provide significant

  13. Oxygen isotope evolution of the Lake Owyhee volcanic field, Oregon, and implications for the low-δ18O magmatism of the Snake River Plain-Yellowstone hotspot and other low-δ18O large igneous provinces

    Science.gov (United States)

    Blum, Tyler B.; Kitajima, Kouki; Nakashima, Daisuke; Strickland, Ariel; Spicuzza, Michael J.; Valley, John W.

    2016-11-01

    The Snake River Plain-Yellowstone (SRP-Y) hotspot track represents the largest known low-δ18O igneous province; however, debate persists regarding the timing and distribution of meteoric hydrothermal alteration and subsequent melting/assimilation relative to hotspot magmatism. To further constrain alteration relations for SRP-Y low-δ18O magmatism, we present in situ δ18O and U-Pb analyses of zircon, and laser fluorination δ18O analyses of phenocrysts, from the Lake Owyhee volcanic field (LOVF) of east-central Oregon. U-Pb data place LOVF magmatism between 16.3 and 15.4 Ma, and contain no evidence for xenocrystic zircon. LOVF δ18O(Zrc) values demonstrate (1) both low-δ18O and high-δ18O caldera-forming and pre-/post-caldera magmas, (2) relative increases in δ18O between low-δ18O caldera-forming and post-caldera units, and (3) low-δ18O magmatism associated with extension of the Oregon-Idaho Graben. The new data, along with new compilations of (1) in situ zircon δ18O data for the SRP-Y, and (2) regional δ18O(WR) and δ18O(magma) patterns, further constrain the thermal and structural associations for hydrothermal alteration in the SRP-Y. Models for low-δ18O magmatism must be compatible with (1) δ18O(magma) trends within individual SRP-Y eruptive centers, (2) along axis trends in δ18O(magma), and (3) the high concentration of low-δ18O magmas relative to the surrounding regions. When considered with the structural and thermal evolution of the SRP-Y, these constraints support low-δ18O magma genesis originating from syn-hotspot meteoric hydrothermal alteration, driven by hotspot-derived thermal fluxes superimposed on extensional tectonics. This model is not restricted to continental hotspot settings and may apply to several other low-δ18O igneous provinces with similar thermal and structural associations.

  14. Los volcanes y los hombres

    OpenAIRE

    García, Carmen

    2007-01-01

    Desde las entrañas de la tierra, los volcanes han creado la atmósfera, el agua de los océanos, y esculpido los relieves del planeta: son, pues, los zahoríes de la vida. Existen volcanes que los hombres explotan o cultivan, y otros sobre los cuales se han construido observatorios en los que se llevan a cabo avanzadas investigaciones científicas.

  15. Volcanic hazards and aviation safety

    Science.gov (United States)

    Casadevall, Thomas J.; Thompson, Theodore B.; Ewert, John W.; ,

    1996-01-01

    An aeronautical chart was developed to determine the relative proximity of volcanoes or ash clouds to the airports and flight corridors that may be affected by volcanic debris. The map aims to inform and increase awareness about the close spatial relationship between volcanoes and aviation operations. It shows the locations of the active volcanoes together with selected aeronautical navigation aids and great-circle routes. The map mitigates the threat that volcanic hazards pose to aircraft and improves aviation safety.

  16. Volcanic Zone, New Zealand

    Directory of Open Access Journals (Sweden)

    Graham J. Weir

    2001-01-01

    Full Text Available A conceptual model of the Taupo Volcanic Zone (TVZ is developed, to a depth of 25 km, formed from three constant density layers. The upper layer is formed from eruption products. A constant rate of eruption is assumed, which eventually implies a constant rate of extension, and a constant rate of volumetric creation in the middle and bottom layers. Tectonic extension creates volume which can accomodate magmatic intrusions. Spreading models assume this volume is distributed throughout the whole region, perhaps in vertical dykes, whereas rifting models assume the upper crust is thinned and the volume created lies under this upper crust. Bounds on the heat flow from such magmatic intrusions are calculated. Heat flow calculations are performed and some examples are provided which match the present total heat output from the TVZ of about 4200 MW, but these either have extension rates greater than the low values of about 8 ± 4 mm/a being reported from GPS measurements, or else consider extension rates in the TVZ to have varied over time.

  17. DECOVALEX-THMC Project. Task D. Long-Term Permeability/Porosity Changes in the EDZ and Near Field due to THM and THC Processes in Volcanic and Crystalline-Bentonite Systems. Phase 1 Report

    Energy Technology Data Exchange (ETDEWEB)

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)

    2007-02-15

    The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic

  18. 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.

  19. Control estructural en el desarrollo de una concentración anómala de calderas en los Andes de Neuquén: Complejo Volcánico Pino Hachado (38°30' S y 71°O Structural control on the development of an anomalous concentration of calderas in the Neuquén Andes: Pino Hachado volcanic complex (38°30´S-71°W

    Directory of Open Access Journals (Sweden)

    C. Tunstall

    2005-12-01

    controls in fissural monogenetic fields, suggest that additional mechanisms, linked to basement structure, have defined the emplacement of such big volumes of magmas. Aeromagnetic data constitute a first approach to determine basement segmentation active in the region during ancient phases of crustal attenuation. Therefore, final geometry and distribution of the Pino Hachado volcanic complex (38°30´S-71°W, eventhough related to Plio-Quaternary tectonics at the arc zone, are deeply influenced by basement structure.

  20. Hydrocarbon- Generating Model of the Area Covered With Volcanic Rock

    Institute of Scientific and Technical Information of China (English)

    Guo Zhanqian; Zhang Yuwei

    2000-01-01

    The distribution of Oil & gas fields shows their close relationship with the most active tectonic regions. This is not a coincidence but having a scientific reasons. The crustal active regions, refer to the places where the active natural earthquake, volcanic activities, underground water happened, and the areas of the leaking off of natural gas to the surface of the crust. The magma of volcanic activities brings the organic "kitchen range body" hydrocarbon- generating model and inorganic genetic hydrocarbon to the regions covered by volcanic rock. Underground water brings a catalytic hydrocarbongenerating model for organic matter, and the leaking- off of H2 and CO2 contributes a synthetic hydrocarbon - generating model. Volcanic activities bring the assemblage of Source, Reservoir and Seal formed by the sediments and magma the sedimentary basins, and the hydrocarbon - generating system with a "water - volcano" binary structure is formed. All these conditions are favorable and excellent for the formation of oil & gas fields. The distribution of American oil & gas fields have very close relationship with the mines of Fe, Mn, Ct, Mo, W and V, deposits of Zn, Cu, V, Pb, Al and Hg, and the deposits of fluorite, sulfur, potassium salt, phosphate and halite, and the distribution of sulfate- chloride of river water. The reason why few oil & gas fields discovered in the regions covered by volcanic rock in western America maybe because of the view of "inconsistency between petroleum and volcano". Further more, It's very difficult to carry out a geophysical exploration in such kinds of regions.This paper examined a few hydrocarbon-generating models (systems) mentioned above and came up with some fresh ideas on the exploration in the areas covered with volcanic rocks.

  1. Laboratory study of volcanic ash electrification

    Science.gov (United States)

    Alois, Stefano; Merrison, Jonathan

    2016-04-01

    Electrostatic forces play an important role in the dynamics of volcanic plumes, for example in ash dispersion and aggregation phenomena. Field measurements of ash electrification are often technically challenging due to poor access and there lacks an accepted physical theory to describe the electrical charge exchange which occurs during particle contact. The goal of the study is to investigate single particle electrification under controlled conditions using advanced laboratory facilities. A novel technique is presented, based on the use of a laser based velocimeter. Here an electric field is applied and the field-induced drift velocity of (micron-sized) ash grains is measured as well as the particles fall velocity. This allows the simultaneous determination of a suspended grains size and electrical charge. The experiments are performed in a unique environmental wind tunnel facility under controlled low-pressure conditions. Preliminary results of particle electrification will be presented.

  2. 腾冲打鹰山、马鞍山、黑空山熔岩流动方式%LAVA FLOW STYLES IN DAYINGSHAN,MAANSHAN AND HEIKONGSHAN IN TENGCHONG VOLCANIC FIELD

    Institute of Scientific and Technical Information of China (English)

    赵勇伟; 樊祺诚; 李霓; 刘贵; 张柳毅

    2012-01-01

    Based on detailed field investigation, three lava flow styles are identified in the Dayingshan, Maanshan and Heikongshan in the volcanic field of Tengchong: pipe flow, inflated flow and laminar flow. Lava flows of Dayingshan are characterized by pipe flow. Heat lost gradually increased from the core to the edge of the flow pipe, resulting in lava consolidating gradually from the surface to the core. Lava of Maanshan is dominated by plane pahoehoe inflated by aa. The lava,in high temperature,was inflated into the lava tunnel as liquid-gas mixing phase, which generated aa. Heikongshan is featured by typical aa lava flow in the proximal phase and middle phase from the vent. The high-temperature plastic lava carried breccias on its top when advancing in a state of laminar flow,forming typical aa lava flow sections with breccias on the top and bottom and dense lava in the middle. Tn the distal phase,the lava flow formed numerous strip-shaped uplifts of breccias.%对腾冲打鹰山、马鞍山和黑空山的熔岩流进行详细地质勘察,发现存在3类熔岩流动方式:管状流动、“底侵”式流动和层状流动.管状流动出现于打鹰山熔岩中.熔岩管道中的温度由核心向表层递减,当表层冷却固结时,管道中的塑性熔岩继续前进,最终由表及里逐渐固结.马鞍山火山熔岩为渣状熔岩“底侵”结壳熔岩流动.结壳熔岩由表层向底部增生,早期熔岩固结形成结壳熔岩,晚期高温气液混合相的熔岩注入结壳熔岩之下的通道,最终固结形成渣状熔岩.黑空山熔岩为渣状熔岩层状流动.熔岩流顶部自碎形成的渣块在底部塑性致密熔岩的驼动下流动,在火口近源和中源形成顶部和底部都是角砾的渣状熔岩,在熔岩流的远端尽头,形成垂直于熔岩流动方向的条带状隆起.

  3. Exploring Volcanism with Digital Technology in Undergraduate Education

    Science.gov (United States)

    McCoy, F. W.; Parisky, A.

    2016-12-01

    Volcanism as one of the most dynamic geological processes on this planet is also one of the most dramatic for attracting students to the earth sciences. At the University of Hawaii (UH) volcanism is used to attract students into the geosciences, coupled with its significant association to Hawaiian culture and contemporary issues such as those associated with related hazards - example: during the past century five towns were buried by lava flows on the Big Island, another recently threatened with destruction. To bring this dynamism into undergraduate education, UH focuses on field trips and courses to all islands; at Windward Community College (WCC/UH) a focus is provided through a series of field courses (1 credit) to all islands, especially the Big Island. Critical to the WCC effort are computer-generated animations and descriptions of volcanological processes for illustrating concepts undergraduate students find difficult: tumescence as an indicator of an eruption, fractional crystallization, collapse of volcanic edifices, explosive eruptions, weathering processes, hazards and mitigation, all embedded in the evolutionary story of mid-ocean volcanic islands such as those in Hawaii. Field courses require intense field labs, which are significantly assisted by digital platforms that include computer-generated illustrations, descriptions, animations, and more. The consequence for developing geoscientists has been outstanding.

  4. 40Ar/39Ar dating of tuff vents in the Campi Flegrei caldera (southern Italy): Toward a new chronostratigraphic reconstruction of the Holocene volcanic activity

    Science.gov (United States)

    Fedele, L.; Insinga, D.D.; Calvert, A.T.; Morra, V.; Perrotta, A.; Scarpati, C.

    2011-01-01

    The Campi Flegrei hosts numerous monogenetic vents inferred to be younger than the 15 ka Neapolitan Yellow Tuff. Sanidine crystals from the three young Campi Flegrei vents of Fondi di Baia, Bacoli and Nisida were dated using 40Ar/39Ar geochronology. These vents, together with several other young edifices, occur roughly along the inner border of the Campi Flegrei caldera, suggesting that the volcanic conduits are controlled by caldera-bounding faults. Plateau ages of ∼9.6 ka (Fondi di Baia), ∼8.6 ka (Bacoli) and ∼3.9 ka (Nisida) indicate eruptive activity during intervals previously interpreted as quiescent. A critical revision, involving calendar age correction of literature 14C data and available 40Ar/39Ar age data, is presented. A new reference chronostratigraphic framework for Holocene Phlegrean activity, which significantly differs from the previously adopted ones, is proposed. This has important implications for understanding the Campi Flegrei eruptive history and, ultimately, for the evaluation of related volcanic risk and hazard, for which the inferred history of its recent activity is generally taken into account.

  5. Explosive volcanism and associated pressures - Implications for models of endogenically shocked quartz

    Science.gov (United States)

    De Silva, S. L.; Wolff, J. A.; Sharpton, V. L.

    1990-01-01

    The nature of explosive volcanic phenomena and associated pressures, both from field and theoretical perspectives, is discussed. An endogenic origin for shocked quartz at the K/T boundary requires impulsive pressures greater than 60 kbars to be generated during explosive volcanism. Explosive volcanic eruptions which are events of sustained decompression may be initiated by impulsive explosions while the magnitudes of the overpressures are small. These maximum overpressures can be controlled mainly by the tensile strength of the rock surrounding the magma chamber-conduit system. Thus maximum overpressures in the volcanic environment are limited to less than 500 bars which are orders of magnitude less than those required for shock quartz (greater than 60 kbars). This observation is found to be consistent with the complete lack of field or petrographic evidence in support of shock metamorphism associated with volcanic eruptions and their products.

  6. Climatic impact of volcanic eruptions

    Science.gov (United States)

    Rampino, Michael R.

    1991-01-01

    Studies have attempted to 'isolate' the volcanic signal in noisy temperature data. This assumes that it is possible to isolate a distinct volcanic signal in a record that may have a combination of forcings (ENSO, solar variability, random fluctuations, volcanism) that all interact. The key to discovering the greatest effects of volcanoes on short-term climate may be to concentrate on temperatures in regions where the effects of aerosol clouds may be amplified by perturbed atmospheric circulation patterns. This is especially true in subpolar and midlatitude areas affected by changes in the position of the polar front. Such climatic perturbation can be detected in proxy evidence such as decrease in tree-ring widths and frost rings, changes in the treeline, weather anomalies, severity of sea-ice in polar and subpolar regions, and poor grain yields and crop failures. In low latitudes, sudden temperature drops were correlated with the passage overhead of the volcanic dust cloud (Stothers, 1984). For some eruptions, such as Tambora, 1815, these kinds of proxy and anectdotal information were summarized in great detail in a number of papers and books (e.g., Post, 1978; Stothers, 1984; Stommel and Stommel, 1986; C. R. Harrington, in press). These studies lead to the general conclusion that regional effects on climate, sometimes quite severe, may be the major impact of large historical volcanic aerosol clouds.

  7. 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.

  8. Numerical Simulation and Probabilistic Hazard Assessment of Tephra Fallout at Jinlongdingzi Volcano, Longgang Volcanic Field in Jilin Province%龙岗金龙顶子火山空降碎屑物数值模拟及概率性灾害评估

    Institute of Scientific and Technical Information of China (English)

    于红梅; 许建东; 吴建平; 栾鹏; 赵波

    2013-01-01

    空降碎屑物为爆炸式火山喷发产生的一种重要的灾害类型,数值模拟已成为一个快速有效地确定火山灰扩散和沉积范围的方法.本文根据改进的Suzuki (1983)二维扩散模型,编写了基于Windows环境下的火山灰扩散程序.通过对前人资料的分析,模拟了龙岗火山群中最新火山喷发——金龙顶子火山喷发产生的空降碎屑物扩散范围,与实测结果具有很好的一致性,证实了模型的可靠性和参数的合理性.根据该区10年的风参数,模拟了7021次不同风参数时金龙顶子火山灰的扩散范围,以此制作了火山灰沉积厚度超过1cm和0.5cm时的概率性空降碎屑灾害区划图.本文的研究可为龙岗火山区火山危险性分析和灾害预警与对策提供重要的科学依据.%Tephra fallout is an important type of hazard caused by explosive volcanic eruption. Numerical simulation has become a fast and effective approach to assess the dispersion and deposition of tephra fallout. According to a modified 2D diffusion model of Suzuki (1983), we develop a tephra diffusion program that can run in Windows system. Based on previous data, we simulated the diffusion scope of Jinlongdingzi volcanic eruption, which is the latest eruption in Longgang volcanic field. The simulated results are in good agreement with the results from measurement in situ, indicating that the model is reliable and the parameters used in the model are suitable. By using wind profiles of ten years, 7021 simulations under different wind profile were carried out, and then probabilistic hazard maps of tephra fallout were constructed for tephra thickness thresholds of 1 cm and 0.5 cm. This study can provide an important scientific basis to the volcanic hazard analysis and risk mitigation plans countermeasure in Longgang volcanic area.

  9. Geopulsation, Volcanism and Astronomical Periods

    Institute of Scientific and Technical Information of China (English)

    Yang Xuexiang; Chen Dianyou; Yang Xiaoying; Yang Shuchen

    2000-01-01

    Volcanism is mainly controlled by the intermittent release of energy in the earth. As far as the differential rotation of the earth's inner core is concerned, the Galactic Year may change the gravitational constant G, the solar radiative quantity and the moving speed of the solar system and affect the exchange of angular momentum between core and mantle as well as the energy exchange between crust and mantle. As a result, this leads to eruptions of superplumes and magma, and controls the energy flow from core - mantle boundary (CMB) to crust. When the earth' s speed decreases, it will release a huge amount of energy. They are the reason of the correspondence of the volcanic cycles one by one with the astronomical periods one by one. According to the astronomical periods, volcanic eruptions may possibly be predicted in the future.

  10. Volcanic eruptions and solar activity

    Science.gov (United States)

    Stothers, Richard B.

    1989-01-01

    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  11. Geochemical study for volcanic surveillance

    Energy Technology Data Exchange (ETDEWEB)

    Panichi, C.; La Ruffa, G. [Consiglio Nazionale delle Ricerche, International Institute for Geothermal Research Ghezzano, PI (Italy)

    2000-07-01

    For years, geologists have been striving to reconstruct volcanic eruptions from the analysis of pyroclastic deposits and lava flows on the surface of the earth and in the oceans. This effort has produced valuable information on volcanic petrology and magma generation, separation, mixing, crystallisation, and interaction with water in phreatomagmatic and submarine eruptions. The volcanological process are tied to the dynamics of the earth's crust and lithosphere. The mantle, subducted oceanic crust, and continental crust contain different rock types and are sources of different magmas. Magmas consist primarily of completely or partially molten silicates containing volatile materials either dissolved in the melt or as bubbles of gas. The silicate and volatile portions affect the physical properties of magma and, therefore, the nature of a volcanic eruption.

  12. Whose reality counts? Factors affecting the perception of volcanic risk

    Science.gov (United States)

    Haynes, Katharine; Barclay, Jenni; Pidgeon, Nick

    2008-05-01

    Understanding how people perceive risk has become increasingly important for improving risk communication and reducing risk associated conflicts. This paper builds upon findings, methodologies and lessons learned from other fields to help understand differences between scientists, authorities and the public. Qualitative and quantitative methods were used to analyse underlying attitudes and judgements during an ongoing volcanic crisis on the Caribbean Island of Montserrat. Specific differences between the public, authorities and scientists were found to have been responsible for misunderstandings and misinterpretations of information and roles, resulting in differing perceptions of acceptable risk. Difficulties in the articulation and understanding of uncertainties pertaining to the volcanic risk led to a situation in which the roles of hazard monitoring, risk communication and public protection became confused. In addition, social, economic and political forces were found to have distorted risk messages, leading to a public reliance upon informal information networks. The implications of these findings for volcanic risk management and communication are discussed.

  13. Late Holocene lava flow morphotypes of northern Harrat Rahat, Kingdom of Saudi Arabia: Implications for the description of continental lava fields

    Science.gov (United States)

    Murcia, H.; Németh, K.; Moufti, M. R.; Lindsay, J. M.; El-Masry, N.; Cronin, S. J.; Qaddah, A.; Smith, I. E. M.

    2014-04-01

    A "lava morphotype" refers to the recognizable and distinctive characteristics of the surface morphology of a lava flow after solidification, used in a similar way to a sedimentary facies. This classification method is explored on an example volcanic field in the Kingdom of Saudi Arabia, where copious lava outpourings may represent an important transition between monogenetic and flood basalt fields. Here, young and well-preserved mafic lava fields display a wide range of surface morphologies. We focussed on four post-4500 yrs. BP lava flow fields in northern Harrat Rahat (morphotypes down-flow. The morphotypes give insight into intrinsic and extrinsic parameters of emplacement, rheology and dominant flow behavior, as well as the occurrence and character of other lava structures. The Harrat Rahat lava flow fields studied extend up to 23 km from the source, and vary between 1-2 m and 12 m in thickness. Areas of the lava flow fields are between ˜32 and ˜61 km2, with individual flow field volumes estimated between ˜0.085 and ˜0.29 km3. They exhibit Shelly-, Slabby-, and Rubbly-pahoehoe, Platy-, Cauliflower-, and Rubbly-a'a, and Blocky morphotypes. Morphotypes reflect the intrinsic parameters of: composition, temperature, crystallinity and volatile-content/vesicularity; along with external influences, such as: emission mechanism, effusion rate, topography and slope control of flow velocity. One morphotype can transition to another in individual flow-units or lobes and they may dominate zones. Not all morphotypes were found in a single lava flow field. Pahoehoe morphotypes are related to the simple mechanical disaggregation of the crust, whereas a'a morphotypes are related to the transitional emergence and subsequent transitional disappearance of clinker. Blocky morphotypes result from fracturing and auto-brecciation. A'a morphotypes (i.e. platy-, cauliflower-, rubbly-a'a) dominate the lava flow field surfaces in northern Harrat Rahat, which suggests that core

  14. 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.

  15. Large magnitude silicic volcanism in north Afar: the Nabro Volcanic Range and Ma'alalta volcano

    Science.gov (United States)

    Wiart, Pierre; Oppenheimer, Clive

    2005-02-01

    Much of the volcanological work carried out in north Afar (Ethiopia and Eritrea) has focused on the nature of Quaternary basaltic volcanic ranges, which have been interpreted by some as incipient oceanic ridges. However, we show here that comparable volumes of silicic magmas have been erupted in the region. In particular, the virtually undocumented Nabro Volcanic Range, which runs NNE for more than 100 km from the margin of the Danakil Depression to the Red Sea coast, has a subaerial volume of the order of 550 km3, comparable to the volume of the much better known Erta’Ale axial volcanic range. Nabro volcano itself forms part of an enigmatic double caldera structure with a neighbouring volcano, Mallahle. The twin caldera may have formed simultaneously with the eruption of between 20 and 100 km3 of ignimbrite, which is readily identified in Landsat Thematic Mapper imagery. This may have been the largest explosive eruption in north Afar, and is certain to have deposited a regionally distributed tephra layer which could in the future be located in distal sections as a stratigraphic marker. An integrated analysis of optical and synthetic aperture radar imagery, digital topographic data, field observations and limited geochemical measurements, permits here descriptions and first order inferences about the structure, stratigraphy and compositions of several major volcanoes of the Afar Triangle, and a reappraisal of their regional significance.

  16. Structural significance of the south Tyrrhenian volcanism

    Science.gov (United States)

    Gaudiosi, G.; Musacchio, G.; Ventura, G.; de Astis, G.

    2003-04-01

    The southern part of the Tyrrhenian Sea represents a transition from ocenic- (the Tyrrhenian Sea) to continental-domain (the Calabrian Arc) and is affected by active calkalkaline to potassic volcanism (the Eolian Islands). Active extensional tectonics, coupled with the general upwelling of northern Sicily and Calabria continental crust, coexists with active subduction of the Ionian Plate beneath the Calabrian Arc. This has been interpreted as the result of the detachment of the slab beneath the Calbrian Arc. Present-day tectonics is characterized by NE-SW normal faults and NNW- SSE dextral oblique-slip faults. The normal faults form the major peri- Tyrrhenian basins. Refraction and high resolution onshore-offshore wide-angle-reflection profiles, as well as potential field modeling, provide a 3D image of the Moho. Short wave-length undulations characterize the Moho beneath the Aeolian Arch. The major upraise is about 6 km, beneath the Aeolian active volcanic area, and affects all the crustal boundaries. Another sharp crustal thinning is observed beneath the gulf of Patti at the south-eastern edge of the Tyrrhenian basin. We suggest that the graben-like structure, occurring along the Salina-Lipari-Vulcano islands and oriented at high angles to the trench, is lithospheric and can be followed down to Moho depths. NNW-SSE dextral oblique-slip faults, like the Tindari Letojanni fault system, control the Salina-Lipari-Vulcano portion of the Aeolian volcanism and connect the oceanic crust of the Marsili Basin to the Malta Escarpment, through the Etna volcano. Across this lineament seismicity changes from mostly shallow to the west, to deep intra- slab to the east.

  17. Geologic field-trip guide to Mount Shasta Volcano, northern California

    Science.gov (United States)

    Christiansen, Robert L.; Calvert, Andrew T.; Grove, Timothy L.

    2017-08-18

    The southern part of the Cascades Arc formed in two distinct, extended periods of activity: “High Cascades” volcanoes erupted during about the past 6 million years and were built on a wider platform of Tertiary volcanoes and shallow plutons as old as about 30 Ma, generally called the “Western Cascades.” For the most part, the Shasta segment (for example, Hildreth, 2007; segment 4 of Guffanti and Weaver, 1988) of the arc forms a distinct, fairly narrow axis of short-lived small- to moderate-sized High Cascades volcanoes that erupted lavas, mainly of basaltic-andesite or low-silica-andesite compositions. Western Cascades rocks crop out only sparsely in the Shasta segment; almost all of the following descriptions are of High Cascades features except for a few unusual localities where older, Western Cascades rocks are exposed to view along the route of the field trip.The High Cascades arc axis in this segment of the arc is mainly a relatively narrow band of either monogenetic or short-lived shield volcanoes. The belt generally averages about 15 km wide and traverses the length of the Shasta segment, roughly 100 km between about the Klamath River drainage on the north, near the Oregon-California border, and the McCloud River drainage on the south (fig. 1). Superposed across this axis are two major long-lived stratovolcanoes and the large rear-arc Medicine Lake volcano. One of the stratovolcanoes, the Rainbow Mountain volcano of about 1.5–0.8 Ma, straddles the arc near the midpoint of the Shasta segment. The other, Mount Shasta itself, which ranges from about 700 ka to 0 ka, lies distinctly west of the High Cascades axis. It is notable that Mount Shasta and Medicine Lake volcanoes, although volcanologically and petrologically quite different, span about the same range of ages and bracket the High Cascades axis on the west and east, respectively.The field trip begins near the southern end of the Shasta segment, where the Lassen Volcanic Center field trip leaves

  18. PETROGRAPHY-PETROCHEMISTRY OF THE KIZILDAĞ VOLCANICS (DERİNKUYU/NEVŞEHİR-YEŞİLHİSAR/KAYSERİ: PETROGENETIC APPROACH

    Directory of Open Access Journals (Sweden)

    Fuat IŞIK

    2001-01-01

    Full Text Available The Kızıldağ volcanics of Quaternary age outcropps widespreadly in small volume bodies around the Derinkuyu (Nevşehir-Yeşilhisar (Kayseri region, middle Anatolian. These volcanics are grayish black, reddish black colored and aphyric basalt composition. They show hypocrystaline-porphyritic, hyalophilitic flow texture and consist of olivine, pyroxene and plagioclase. Kızıldağ volcanics have calc-alkaline character and MORB - normalized spider diagram indicate enrichment of lithophile elements (Sr, K, Ba and depletion of high field stength elements (Zr, Ti, Y. Also lithophile elements and high field stength elements of Kızıldağ volcanics are similar to continental crust, relatively. Kızıldağ volcanics in the Neogene-Quaternary volcanics, located in the inner Taurid belt, interpretad that they are related to the subduction of the Afro-Arabian plate under the Anatolian plate.

  19. A quantitative model for volcanic hazard assessment

    OpenAIRE

    W. Marzocchi; Sandri, L.; Furlan, C

    2006-01-01

    Volcanic hazard assessment is a basic ingredient for risk-based decision-making in land-use planning and emergency management. Volcanic hazard is defined as the probability of any particular area being affected by a destructive volcanic event within a given period of time (Fournier d’Albe 1979). The probabilistic nature of such an important issue derives from the fact that volcanic activity is a complex process, characterized by several and usually unknown degrees o...

  20. Volcanic forcing in decadal forecasts

    Science.gov (United States)

    Ménégoz, Martin; Doblas-Reyes, Francisco; Guemas, Virginie; Asif, Muhammad; Prodhomme, chloe

    2016-04-01

    Volcanic eruptions can significantly impact the climate system, by injecting large amounts of particles into the stratosphere. By reflecting backward the solar radiation, these particles cool the troposphere, and by absorbing the longwave radiation, they warm the stratosphere. As a consequence of this radiative forcing, the global mean surface temperature can decrease by several tenths of degrees. However, large eruptions are also associated to a complex dynamical response of the climate system that is particularly tricky do understand regarding the low number of available observations. Observations seem to show an increase of the positive phases of the Northern Atlantic Oscillation (NAO) the two winters following large eruptions, associated to positive temperature anomalies over the Eurasian continent. The summers following large eruptions are generally particularly cold, especially over the continents of the Northern Hemisphere. Overall, it is really challenging to forecast the climate response to large eruptions, as it is both modulated by, and superimposed to the climate background conditions, largely driven themselves by internal variability at seasonal to decadal scales. This work describes the additional skill of a forecast system used for seasonal and decadal predictions when it includes observed volcanic forcing over the last decades. An idealized volcanic forcing that could be used for real-time forecasts is also evaluated. This work consists in a base for forecasts that will be performed in the context of the next large volcanic eruption.

  1. Experimental generation of volcanic lightning

    Science.gov (United States)

    Cimarelli, Corrado; Alatorre-Ibargüengoitia, Miguel; Kueppers, Ulrich; Scheu, Bettina; Dingwell, Donald B.

    2014-05-01

    Ash-rich volcanic plumes that are responsible for injecting large quantities of aerosols into the atmosphere are often associated with intense electrical activity. Direct measurement of the electric potential at the crater, where the electric activity in the volcanic plume is first observed, is severely impeded, limiting progress in its investigation. We have achieved volcanic lightning in the laboratory during rapid decompression experiments of gas-particle mixtures under controlled conditions. Upon decompression (from ~100 bar argon pressure to atmospheric pressure), loose particles are vertically accelerated and ejected through a nozzle of 2.8 cm diameter into a large tank filled with air at atmospheric conditions. Because of their impulsive character, our experiments most closely represent the conditions encountered in the gas-thrust region of the plume, when ash is first ejected from the crater. We used sieved natural ash with different grain sizes from Popocatépetl (Mexico), Eyjafjallajökull (Iceland), and Soufrière Hills (Montserrat) volcanoes, as well as micrometric glass beads to constrain the influence of material properties on lightning. We monitored the dynamics of the particle-laden jets with a high-speed camera and the pressure and electric potential at the nozzle using a pressure transducer and two copper ring antennas connected to a high-impedance data acquisition system, respectively. We find that lightning is controlled by the dynamics of the particle-laden jet and by the abundance of fine particles. Two main conditions are required to generate lightning: 1) self-electrification of the particles and 2) clustering of the particles driven by the jet fluid dynamics. The relative movement of clusters of charged particles within the plume generates the gradient in electrical potential, which is necessary for lightning. In this manner it is the gas-particle dynamics together with the evolving particle-density distribution within different regions of

  2. Automatic classification of seismo-volcanic signatures

    Science.gov (United States)

    Malfante, Marielle; Dalla Mura, Mauro; Mars, Jérôme; Macedo, Orlando; Inza, Adolfo; Métaxian, Jean-Philippe

    2017-04-01

    The prediction of volcanic eruptions and the evaluation of their associated risks is still a timely and open issue. For this purpose, several types of signals are recorded in the proximity of volcanoes and then analysed by experts. Typically, seismic signals that are considered as precursor or indicator of an active volcanic phase are detected and manually classified. In this work, we propose an architecture for automatic classification of seismo-volcanic waves. The system we propose is based on supervised machine learning. Specifically, a prediction model is built from a large dataset of labelled examples by the means of a learning algorithm (Support Vector Machine or Random Forest). Four main steps are involved: (i) preprocess the signals, (ii) from each signal, extract features that are useful for the classes discrimination, (iii) use an automatic learning algorithm to train a prediction model and (iv) classify (i.e., assign a semantic label) newly recorded and unlabelled examples. Our main contribution lies in the definition of the feature space used to represent the signals (i.e., in the choice of the features to extract from the data). Feature vectors describe the data in a space of lower dimension with respect to the original one. Ideally, signals are separable in the feature space depending on their classes. For this work, we consider a large set of features (79) gathered from an extensive state of the art in both acoustic and seismic fields. An analysis of this feature set shows that for the application of interest, 11 features are sufficient to discriminate the data. The architecture is tested on 4725 seismic events recorded between June 2006 and September 2011 at Ubinas, the most active volcano of Peru. Six main classes of signals are considered: volcanic tremors (TR), long period (LP), volcano-tectonic (VT), explosion (EXP), hybrids (HIB) and tornillo (TOR). Our model reaches above 90% of accuracy, thereby validating the proposed architecture and the

  3. 火山地层学与火山架构:以长白山火山为例%Volcanostratigraphy and Volcanic Architecture of the Changbaishan Volcanos, NE China

    Institute of Scientific and Technical Information of China (English)

    王璞珺; 衣健; 陈崇阳; 王岩泉

    2013-01-01

    将长白山火山喷出物按成岩方式和岩相可分为柱状节理熔岩、火山碎屑流和火山泥石流等20种基本类型,它们均可构成可识别的19种火山地层单元.火山架构是由被火山地层界面所围限的诸多基本地层单元叠置而成.一个复杂的火山组合体,可以通过界面识别,拆分成若干火山地层单元,从而实现对火山堆积体的分解描述和整体认知.基性火山喷发区常见的5种火山架构(单源火山田、洪泛玄武岩田、熔岩盾火山、中心式火山和层状复合火山),在长白山地区相继发育.本区火山灾害可分为原发和次生2种.原发性灾害指火山再次喷发引发的灾害,巨量天池水可沿火山断裂下渗,使气水-岩浆喷发的可能性和爆炸强度增加,同时还能引发火山泥石流.次生灾害主要源于火山碎屑堆积物的再搬运和熔岩火山体的崩塌.熔岩火山在本区分布最广,但其底座常为3~7 m厚的松散沉积层,这犹如坐落在软地基之上的摩天大厦,是很不稳定的火山架构.熔岩体下伏的这些风化壳型松散层,只要发生流变或差异性沉陷,就会引发山体滑坡和山崩.因此,加强相关基础地质调查,对事关国计民生的重点区段开展次生火山灾害风险评估,势在必行.%Twenty types of volcanic materials ejected from Changbaishan volcanos were classified, such as columnar joint, pyroclastic flow deposits and lahars. Each of them can comprise a stratigraphic unit recognizable in the volcanic successions. Volcanic architectures are composed of these volcanic units bounded by some kind of eruption surfaces or unconformities. Monogenetic volcano fields, flood basalt field, lava shield volcanos, central volcanos and stratovolcanos described by Walker (2000) seem to develop successively from Miocene to Holocene in the area of Changbaishan volcanos. The potential volcanic hazards including both primary and secondary ones should be concerned

  4. Exceptional Volumes of Rejuvenated Volcanism in Samoa

    Science.gov (United States)

    Konter, J. G.; Jackson, M.; Storm, L.

    2010-12-01

    The internal structure of within-plate volcanoes is typically compared to the stages of volcanic evolution in Hawaii. In Samoa, these stages show some differences with the Hawaiian model, in terms of the duration, volume and geochemical composition of the stages. Particularly, the rejuvenated stage of volcanism in Samoa is significantly more voluminous, with increasing geographic coverage with age, completely repaving the island of Savai’i. This unusual outpouring of rejuvenated lavas has previously been proposed to be related to the tectonic setting, near the northern terminus of the Tonga Trench. Therefore, Samoan volcanism might be caused by lithospheric fracturing, a mantle plume, or potentially a combination of the two. We collected new samples from a deeply eroded canyon on Savai’i to determine a time evolution of the transition from shield to eventual rejuvenated lavas. The canyon exposes several hundred meters of lavas, and we collected samples about 200m vertically down into the canyon. These samples are dominantly olivine basalts, and their Pb isotope compositions fall within the compositional field of young rejuvenated lavas on Savai’i and Upolu. This canyon section, therefore, represents a minimum thickness for the rejuvenated lavas of 200m. Assuming eruption of rejuvenated lavas only occurred subaerially, with a universal thickness of 200m, the new data suggest more than one percent of the volume of Savai’i consists of rejuvenated lavas. This is an order of magnitude greater than the largest relative volumes in Hawaii (Kauai), and implies a different cause for rejuvenated volcanism in Samoa. Another feature that suggests different processes may be important is the transition between the shield and rejuvenated stage. Although Samoan volcanoes do not seem to erupt exactly the same rock types as characteristic Hawaiian post-shield stage lavas, there is a definite shift to more evolved compositions (including trachytes) during the later stages of

  5. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    Science.gov (United States)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  6. Supercomputer modeling of volcanic eruption dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, S.W. [Arizona State Univ., Tempe, AZ (United States); Valentine, G.A. [Los Alamos National Lab., NM (United States); Woo, Mahn-Ling [Arizona State Univ., Tempe, AZ (United States)

    1995-06-01

    Our specific goals are to: (1) provide a set of models based on well-defined assumptions about initial and boundary conditions to constrain interpretations of observations of active volcanic eruptions--including movies of flow front velocities, satellite observations of temperature in plumes vs. time, and still photographs of the dimensions of erupting plumes and flows on Earth and other planets; (2) to examine the influence of subsurface conditions on exit plane conditions and plume characteristics, and to compare the models of subsurface fluid flow with seismic constraints where possible; (3) to relate equations-of-state for magma-gas mixtures to flow dynamics; (4) to examine, in some detail, the interaction of the flowing fluid with the conduit walls and ground topography through boundary layer theory so that field observations of erosion and deposition can be related to fluid processes; and (5) to test the applicability of existing two-phase flow codes for problems related to the generation of volcanic long-period seismic signals; (6) to extend our understanding and simulation capability to problems associated with emplacement of fragmental ejecta from large meteorite impacts.

  7. A Volcanic Hydrogen Habitable Zone

    Science.gov (United States)

    Ramirez, Ramses M.; Kaltenegger, Lisa

    2017-03-01

    The classical habitable zone (HZ) is the circular region around a star in which liquid water could exist on the surface of a rocky planet. The outer edge of the traditional N2–CO2–H2O HZ extends out to nearly ∼1.7 au in our solar system, beyond which condensation and scattering by CO2 outstrips its greenhouse capacity. Here, we show that volcanic outgassing of atmospheric H2 can extend the outer edge of the HZ to ∼2.4 au in our solar system. This wider volcanic-hydrogen HZ (N2–CO2–H2O–H2) can be sustained as long as volcanic H2 output offsets its escape from the top of the atmosphere. We use a single-column radiative-convective climate model to compute the HZ limits of this volcanic hydrogen HZ for hydrogen concentrations between 1% and 50%, assuming diffusion-limited atmospheric escape. At a hydrogen concentration of 50%, the effective stellar flux required to support the outer edge decreases by ∼35%–60% for M–A stars. The corresponding orbital distances increase by ∼30%–60%. The inner edge of this HZ only moves out ∼0.1%–4% relative to the classical HZ because H2 warming is reduced in dense H2O atmospheres. The atmospheric scale heights of such volcanic H2 atmospheres near the outer edge of the HZ also increase, facilitating remote detection of atmospheric signatures.

  8. Kamchatkan Volcanic Eruption Response Team (KVERT), Russia: preventing the danger of volcanic eruptions to aviation.

    Science.gov (United States)

    Girina, O.; Neal, Ch.

    2012-04-01

    The Kamchatkan Volcanic Eruption Response Team (KVERT) has been a collaborative project of scientists from the Institute of Volcanology and Seismology, the Kamchatka Branch of Geophysical Surveys, and the Alaska Volcano Observatory (IVS, KB GS and AVO). The purpose of KVERT is to reduce the risk of costly, damaging, and possibly deadly encounters of aircraft with volcanic ash clouds. To reduce this risk, KVERT collects all possible volcanic information and issues eruption alerts to aviation and other emergency officials. KVERT was founded by Institute of Volcanic Geology and Geochemistry FED RAS in 1993 (in 2004, IVGG merged with the Institute of Volcanology to become IVS). KVERT analyzes volcano monitoring data (seismic, satellite, visual and video, and pilot reports), assigns the Aviation Color Code, and issues reports on eruptive activity and unrest at Kamchatkan (since 1993) and Northern Kurile (since 2003) volcanoes. KVERT receives seismic monitoring data from KB GS (the Laboratory for Seismic and Volcanic Activity). KB GS maintains telemetered seismic stations to investigate 11 of the most active volcanoes in Kamchatka. Data are received around the clock and analysts evaluate data each day for every monitored volcano. Satellite data are provided from several sources to KVERT. AVO conducts satellite analysis of the Kuriles, Kamchatka, and Alaska as part of it daily monitoring and sends the interpretation to KVERT staff. KVERT interprets MODIS and MTSAT images and processes AVHRR data to look for evidence of volcanic ash and thermal anomalies. KVERT obtains visual volcanic information from volcanologist's field trips, web-cameras that monitor Klyuchevskoy (established in 2000), Sheveluch (2002), Bezymianny (2003), Koryaksky (2009), Avachinsky (2009), Kizimen (2011), and Gorely (2011) volcanoes, and pilots. KVERT staff work closely with staff of AVO, AMC (Airport Meteorological Center) at Yelizovo Airport and the Tokyo Volcanic Ash Advisory Center (VAAC), the

  9. Geophysical characterization of circular structures in Chubut and Mendoza (Argentina): Impact vs. Volcanism

    Science.gov (United States)

    Prezzi, C.; Orgeira, M. J.; Risso, C.; Acevedo, R.; Ponce, F.; Nullo, F.; Martinez, O.; Rabassa, J.; Margonari, L.; Corbella, H.

    2013-05-01

    This work focuses on two main objectives. One of them is to provide information to discern the genesis of the circular structures present in Bajada del Diablo (Chubut, Argentina) considered as impact craters, and the other one is to contribute to a better knowledge of the circular structures located in the volcanic fields of Llancanelo and Payunia (Mendoza, Argentina). Chubut circular structures have been attributed to the collision of an extraterrestrial body, possibly an asteroid. However, doubts persist about their genesis because of the lack of direct geological evidences. Since detailed geomorphological studies have ruled out an origin by wind deflation, the prevailing alternative hypothesis attributes these circular structures to a volcanic process. On the other hand, the study of the volcanic fields of Payunia and Llancanelo (Mendoza) will contribute to the knowledge of the mechanics of hydromagmatic processes in the area, and the origin of circular structures morphologically similar to those located in Chubut. In the Payunia volcanic field at least 27 cones with evidences of hydromagmatism, in a field of more than 800 pure magmatic cones, have been recognized. This study tries to determine if a relationship between the observed volcanic circular structures and participation of water during the eruption exists. Magnetic and gravity field surveys of the circular volcanic structures in Llancanelo and Payunia volcanic fields were performed in order to determine their relationship with the type of eruption. Electromagnetic, magnetic and gravity field surveys were also carried out in Chubut circular structures. The comparative analysis of geological and geophysical results obtained in the circular structures of Chubut and those obtained in the circular structures in the volcanic areas of Llancanelo and Payunia suggest an impact origin for the circular structures of Chubut.

  10. Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation