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Sample records for basaltic lava flows

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

    Science.gov (United States)

    Sexton, E. A.; Hampton, S.

    2014-12-01

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

  2. Disruption of tephra fall deposits caused by lava flows during basaltic eruptions

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    Brown, R. J.; Thordarson, T.; Self, S.; Blake, S.

    2015-10-01

    Observations in the USA, Iceland and Tenerife, Canary Islands reveal how processes occurring during basaltic eruptions can result in complex physical and stratigraphic relationships between lava and proximal tephra fall deposits around vents. Observations illustrate how basaltic lavas can disrupt, dissect (spatially and temporally) and alter sheet-form fall deposits. Complexity arises through synchronous and alternating effusive and explosive activity that results in intercalated lavas and tephra deposits. Tephra deposits can become disrupted into mounds and ridges by lateral and vertical displacement caused by movement (including inflation) of underlying pāhoehoe lavas and clastogenic lavas. Mounds of tephra can be rafted away over distances of 100 s to 1,000 s m from proximal pyroclastic constructs on top of lava flows. Draping of irregular topography by fall deposits and subsequent partial burial of topographic depressions by later lavas can result in apparent complexity of tephra layers. These processes, deduced from field relationships, have resulted in considerable stratigraphic complexity in the studied proximal regions where fallout was synchronous or alternated with inflation of subjacent lava sheets. These mechanisms may lead to diachronous contact relationships between fall deposits and lava flows. Such complexities may remain cryptic due to textural and geochemical quasi-homogeneity within sequences of interbedded basaltic fall deposits and lavas. The net effect of these processes may be to reduce the usefulness of data collected from proximal fall deposits for reconstructing basaltic eruption dynamics.

  3. Investigating lava-substrate interactions through flow experiments with syrup, wax, and molten basalt

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    Rumpf, M. E.; Lev, E.

    2015-12-01

    Among the many factors influencing the complex process of lava flow emplacement, the interaction with the substrate onto which flow is emplaced plays a central role. Lava flows are rarely emplaced onto smooth or regular surfaces. For example, at Kīlauea Volcano, Hawai'i, lava flows regularly flow over solid rock, vegetation, basaltic or silica sand, and man-made materials, including asphalt and concrete. In situ studies of lava-substrate interactions are inherently difficult, and often dangerous, to carry-out, requiring the design of controllable laboratory experiments. We investigate the effects of substrate grain size, cohesion, and roughness on flow mobility and morphology through a series of flow experiments using analog materials and molten basalt. We have developed a series of experiments that allow for adjustable substrate parameters and analyze their effects on lava flow emplacement. The first set of experiments are performed at the Fluids Mechanics Laboratory at the Lamont-Doherty Earth Observatory and focus on two analog materials: polyethylene glycol (PEG), a commercially available wax, and corn syrup. The fluids were each extruded onto a series of scaled substrate beds to replicate the emplacement of lava in a natural environment. Preliminary experiments demonstrated that irregular topography, particularly topography with a height amplitude similar to that of the flow itself, can affect flow morphology, width, and velocity by acting as local barriers or culverts to the fluid. This is expected from observations of fluid flow in natural environments. A follow-up set of experiments will be conducted in Fall 2015 at the Syracuse University (SU) Lava Project Lab. In this set, we will pour molten basalt directly onto a series of substrates representing natural environments found on the Earth and other rocky bodies in the Solar System. These experiments will allow for analysis of the effects of basaltic composition and high temperatures on lava-substrate heat

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

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

    2015-02-01

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

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

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    Long Li

    2015-12-01

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

  6. Vertical AMS variation within basalt flow profiles from the Xitle volcano (Mexico) as indicator of heterogeneous strain in lava flows

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    Caballero-Miranda, C. I.; Alva-Valdivia, L. M.; González-Rangel, J. A.; Gogitchaishvili, A.; Urrutia-Fucugauchi, J.; Kontny, A.

    2016-02-01

    The within-flow vertical variation of anisotropy of the magnetic susceptibility (AMS) of three basaltic flow profiles from the Xitle volcano were investigated in relation to the lava flow-induced shear strain. Rock magnetic properties and opaque microscopy studies have shown that the magnetic mineralogy is dominated by Ti-poor magnetite with subtle vertical variations in grain size distribution: PSD grains dominate in a thin bottommost zone, and from base to top from PSD-MD to PSD-SD grains are found. The vertical variation of AMS principal direction patterns permitted identification of two to three main lava zones, some subdivided into subzones. The lower zone is very similar in all profiles with the magnetic foliation dipping toward the flow source, whereas the upper zone has magnetic foliation dipping toward the flow direction or alternates between dipping against and toward the flow direction. The K1 (maximum AMS axis) directions tend to be mostly parallel to the flow direction in both zones. The middle zone shows AMS axes diverging among profiles. We present heterogeneous strain ellipse distribution models for different flow velocities assuming similar viscosity to explain the AMS directions and related parameters of each zone. Irregular vertical foliations and transverse to flow lineation of a few samples at the bottommost and topmost part of profiles suggest SD inverse fabric, levels of intense friction, or degassing effects in AMS orientations.

  7. Petrography, age, and paleomagnetism of basaltic lava flows in coreholes at Test Area North (TAN), Idaho National Engineering Laboratory

    International Nuclear Information System (INIS)

    The petrography, age, and paleomagnetism were determined on basalt from 21 lava flows comprising about 1,700 feet of core from two coreholes (TAN CH No. 1 and TAN CH No. 2) in the Test Area North (TAN) area of the Idaho National Engineering Laboratory (INEL). Paleomagnetic studies were made on two additional cores from shallow coreholes in the TAN area. K-Ar ages and paleomagnetism also were determined on nearby surface outcrops of Circular Butte. Paleomagnetic measurements were made on 416 samples from four coreholes and on a single site in surface lava flows of Circular Butte. K-Ar ages were measured on 9 basalt samples from TAN CH No. 1 and TAN CH No. 2 and one sample from Circular Butte. K-Ar ages ranged from 1.044 Ma to 2.56 Ma. All of the samples have reversed magnetic polarity and were erupted during the Matuyama Reversed Polarity Epoch. The purpose of investigations was to develop a three-dimensional stratigraphic framework for geologic and hydrologic studies including potential volcanic hazards to facilities at the INEL and movement of radionuclides in the Snake River Plain aquifer

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

    Indian Academy of Sciences (India)

    Ninad Bondre; Raymond A Duraiswami; Gauri Dole

    2004-12-01

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

  9. Lava flows and volcanic landforms

    Science.gov (United States)

    Tarquini, Simone

    2016-04-01

    Lava flows constitute a large portion of the edifice of basaltic volcanoes. The substantial difference existing between the emplacement dynamics of different basaltic lava flows suggests a relation between the dominant flow dynamic and the overall shape of the ensuing volcano. Starting from the seminal works of Walker (1971, 1973) it is proposed that the rate of heat dissipation per unit volume of lava can be the founding principium at the roots of the emplacement dynamics of lava flows. Within the general framework of the thermodynamics of irreversible processes, a conceptual model is presented, in which the dynamic of lava flows can evolve in a linear or in a nonlinear regime on the basis of the constraint active on the system: a low constraint promotes a linear dynamic (i.e. fluctuations are damped), a high constraint a nonlinear one (i.e. fluctuations are enhanced). Two cases are considered as end-members for a linear and a nonlinear dynamic in lava flows: the typical "Hawaiian" sheet flow and the classic "Etnean" channelized flow (respectively). In lava flows, the active constraint is directly proportional to the slope of the topography and to the thermal conductivity and thermal capacity of the surrounding environment, and is inversely proportional to the lava viscosity and to the supply rate. The constraint indicates the distance from the equilibrium conditions of the system, and determines the rate of heat dissipation per unit volume. In subaerial flows, the heat dissipated during the emplacement is well approximated by the heat lost through radiation, which can be retrieved through remote-sensing techniques and can be used to correlate dynamic and dissipation. The model presented recombines previously unrelated concepts regarding the dynamics and the thermal regimes observed in different lava flows, providing a global consistent picture. References Walker GPL (1971) Compound and simple lava flows and flood basalts. Bull Volcanol 35:579-590 Walker GPL (1973

  10. Chemical weathering of basaltic lava-flow since 300 kyr ago (La Réunion Island ,France)

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    Claude, Christelle; Meunier, Jean-Dominique; Dussouillez, Philippe; Traoré, Daouda; Pelt, Eric; Chabaux, François; Hamelin, Bruno; Colin, Fabrice

    2015-04-01

    Spheroidal weathering (also named corestone-shell systems hereafter called CSC) is a common form of chemical weathering affecting many types of rocks. Here we combine mineralogical observations, geochemistry of major and trace elements to Sr isotopes and U-series as an attempt to constrain the rate of spheroidal weathering of a basaltic flow dated at 292 ±13 ka from Piton de la Fournaise volcano (Réunion Island). Three zones can be characterized : corestones, grey and red shells. Our results show that weathering is increasing from the core to the red shells and is characterized by a loss of alkali elements and Si while Fe, Al and Ti contents remain constant. Total chemical weathering rates, calculated over 292 ka, are two orders of magnitude lower than present-day estimations from streamwater solute fluxes. Our results show that Sr is exported on a time scale of 1 rather than 300 ka. The extrapolation of this behaviour to all mobile elements allows to recalculate a total chemical weathering rate of 270 t/km2/yr, in the range of the present day estimations. Zr and Th appear as the most immobile elements. Uranium, on the opposite, is shown to be depleted in the cores and the grey shells but enriched in the red shells, probably adsorbed on Fe oxydes and halloysite. A U-transport model is used to estimate the weathering age of samples from the core and the grey and red shells. The process of U remobilization occurs on a timescale of ca 290 ka, i.e. the deposition age of the lava flow. The calculated weathering ages increase from the core to the red shells. Weathering rates are 5.5 ± 0.7 m/Ma for the grey shells and 1.4 ± 0.2 m/Ma for the red shells, with an average value of 2.9 ± 0.3 m/Ma. Finally, this result, compared with denudation rates of 3.5 ± 1.7 m/Ma estimated in the same area strenghthens our conclusion regarding a stable, steady state, geomorphological evolution of the site.

  11. Contaminant transfer and hydrodispersive parameters in basaltic lava flows: artificial tracer test and implications for long-term management

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    Bertrand, G.; Celle-Jeanton, H.; Huneau, F.; Baillieux, A.; Mauri, G.; Lavastre, V.; Undereiner, G.; Girolami, L.; Moquet, J. S.

    2015-10-01

    The aim of this paper is to evaluate the vulnerability after point source contamination and characterize water circulations in volcanic flows located in the Argnat basin volcanic system (Chaîne des Puys, French Massif Central) using a tracer test performed by injecting a iodide solution. The analysis of breakthrough curves allowed the hydrodispersive characteristics of the massive lava flows to be determined. Large Peclet numbers indicated a dominant advective transport. The multimodal feature of breakthrough curves combined with high values of mean velocity and low longitudinal dispersion coefficients indicated thatwater flows in an environment analogous to a fissure system, and only slightly interacts with a low porosity matrix (ne < 1%). Combining this information with lava flow stratigraphy provided by several drillings allowed a conceptual scheme of potential contaminant behaviour to be designed. Although lava flows are vulnerable to point source pollution due to the rapid transfer of water within fractures, the saturated scoriaceous layers located between massive rocks should suffice to strongly buffer the transit of pollution through dilution and longer transit times. This was consistent with the low recovery rate of the presented tracer test.

  12. Geochemistry of the Palitana flood basalt sequence and the Eastern Saurashtra dykes, Deccan Traps: clues to petrogenesis, dyke-flow relationships, and regional lava stratigraphy

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    Sheth, Hetu C.; Zellmer, Georg F.; Kshirsagar, Pooja V.; Cucciniello, Ciro

    2013-04-01

    Recent studies of large mafic dyke swarms in the Deccan Traps flood basalt province, India, indicate that some of the correlative lava flows reached several hundred kilometers in length. Here we present field, petrographic, mineral chemical, and whole-rock geochemical (including Sr-Nd isotopic) data on the Palitana lava sequence and nearby dykes in the Saurashtra region of the northwestern Deccan Traps. These rocks are moderately evolved, many with low-Ti-Nb characteristics. We infer that most dykes are notably (and systematically) less contaminated by ancient continental crust than the Palitana flows, but four dykes are equally or significantly more contaminated, with some of the most extreme Sr-Nd isotopic compositions seen in the entire Deccan Traps (initial ɛNd is as low as -18.0). A Bhimashankar-type and a Poladpur-type dyke are present several hundred kilometers from the type section of these magma types in the Western Ghats escarpment. We find no geochemical correlations between the Palitana sequence and three subsurface sequences in NE Saurashtra containing abundant picritic rocks, surface lavas previously studied from Saurashtra, or the Western Ghats sequence. Intriguingly, the Eastern Saurashtra dykes cannot have been feeders to any of these lava sequences. Feeder dykes of these sequences may be located in southwestern or central Saurashtra, or in the Dhule-Nandurbar-Dediapada areas across the Gulf of Cambay, 200-300 km east of Palitana. Our results indicate polycentric flood basalt eruptions not only on the scale of the Deccan Traps province, but also within the Saurashtra region itself.

  13. Numerical simulation of wear of basalt lava spinning rolls

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    A. Lisiecki

    2006-08-01

    Full Text Available Purpose: of this paper: Results of the study of wear phenomena of cascade spinning rolls during stone woolproduction process are described.Design/methodology/approach: The study was based on direct process observations, chemical analysis andtemperature measurements of basalt lava, metallographic examinations of the spinning rolls deposits. It was showedthat the deposits of spinning rolls are worn in very different way, depending on the roll position in rolls cascade.Findings: Predominant wear phenomena of the fully austenitic Grade 310 deposit of spinning roll no 1 is moltenbasalt lava corrosion-oxidation accompanied by low and high cycle thermal fatigue, high temperature basalt lavaerosion at low velocity of basalt lava stream impinging the working surface at high angle. Predominant wearphenomena of the austenitic-ferritic Grade S32304 deposit of spinning roll no 2 is high temperature basalt lava erosionat very high velocity of lava stream impinging the working surface at high angle what is the cause of much faster wearof then spinning roll no 1. High temperature erosion wear is accompanied by molten basalt lava corrosion-oxidationand low and high cycle thermal fatigue processes. Predominant wear phenomena of the austenitic-ferritic GradeS32304 deposits spinning roll no 3 and roll no 4 is high temperature basalt lava abrasion as sprayed by rolls no 1 andno 2 fibers of solidifying basalt lava impinge the working surface of spinning rolls no 3 and no 4.Research limitations/implications: The mechanisms of high temperature erosion demands further investigationsand detailed studies.Practical implications: The wear resistance of basalt lava spinning rolls can be increased.Originality/value: The mechanisms of surface layer wear of basalt lava spinning rolls were determined.

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

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    Giorgio Pasquarè

    2008-03-01

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

  15. Physical modelling of lava flows

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    M. Dragoni

    1997-06-01

    Full Text Available Lava flows are not only a fascinating scientific problem, involving many branches of continuum mechanics and thermodynamics, but are natural events having a strong social impact. A reliable evaluation of volcanic hazard connected with lava flows depends on the availability of physical models allowing us to predict the evolution of these phenomena. In this regard, the rheological properties of lavas are of major importance in controlling the dynamics of lava flows. Lava is a multi-phase and chemically heterogeneous system. This entails a characteristic, non-Newtonian behaviour of lava flows, which is emphasized by the fact that the rheological parameters are strongly temperature dependent and are therefore affected by the progressive cooling of lava after effusion. Physical models of lava flows show us the complex relationships between the many quantities governing this process and in the near future they may allow us to predict the dynamics of lava flows and to take effective measures for the reduction of volcanic risk.

  16. Lava Flows On Ascraeus Mons Volcano

    Science.gov (United States)

    1998-01-01

    margins of the lava flow cool and harden, but the interior remains hot and continues to flow down-hill. Eventually, the eruption stops and the lava inside the tube cools, contracts, and hardens, leaving behind a tube (basically, a long narrow cave).(3) Rough elevated surface. The rough, pitted, and elevated surface across the bottom half of the image is a lava flow. The margins of this feature are somewhat lobate in form, and the entire feature is elevated above its surroundings, indicating that it was the last lava flow to pour through this region.Putting it All Together: Aa and Pahoehoe Lava Flows: Shield volcanoes such as Ascraeus Mons form from relatively fluid lavas. Shield volcanoes on Earth include the well-known Islands of Hawai'i. The kind of lava that is fluid enough to make shield volcanoes is called basalt. This is an iron- and magnesium-rich silicate lava that, when cooled, is usually black or very dark brown.Basalt lava flows come in two main varieties: Aa and Pahoehoe. These are Hawai'ian names. 'Aa' (pronounced 'ah-ah') lava flows have very rough, jumbly surfaces, and they usually lack lava tubes. 'Aa' lava flow surfaces are very rough to walk on-- thus the term 'aa' probably refers to the sound a person might make when walking on a cooled/solidified aa flow in bare feet!'Pahoehoe' (pronounced 'pa-hoy-hoy') is a term that means 'ropey'. The surfaces of pahoehoe lava flows are generally very smooth and billowy. Sometimes they have a ropy texture like melted taffy or caramel. Pahoehoe flows very commonly contain lava tubes.The rough-surfaced flow across the lower half of the MOC image is interpreted to be an 'aa' lava flow, and the smoother surface with a sinuous channel running down its center is interpreted to be a 'pahoehoe' lava flow. Both would indicate that the lavas on Ascraeus Mons, at least at this location, are probably composed of basalt.More Picture Information: This MOC picture is a subframe of image #26705, centered approximately at 11.5o

  17. Benchmarking computational fluid dynamics models for lava flow simulation

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    Dietterich, Hannah; Lev, Einat; Chen, Jiangzhi

    2016-04-01

    Numerical simulations of lava flow emplacement are valuable for assessing lava flow hazards, forecasting active flows, interpreting past eruptions, and understanding the controls on lava flow behavior. Existing lava flow models vary in simplifying assumptions, physics, dimensionality, and the degree to which they have been validated against analytical solutions, experiments, and natural observations. In order to assess existing models and guide the development of new codes, we conduct a benchmarking study of computational fluid dynamics models for lava flow emplacement, including VolcFlow, OpenFOAM, FLOW-3D, and COMSOL. Using the new benchmark scenarios defined in Cordonnier et al. (Geol Soc SP, 2015) as a guide, we model viscous, cooling, and solidifying flows over horizontal and sloping surfaces, topographic obstacles, and digital elevation models of natural topography. We compare model results to analytical theory, analogue and molten basalt experiments, and measurements from natural lava flows. Overall, the models accurately simulate viscous flow with some variability in flow thickness where flows intersect obstacles. OpenFOAM, COMSOL, and FLOW-3D can each reproduce experimental measurements of cooling viscous flows, and FLOW-3D simulations with temperature-dependent rheology match results from molten basalt experiments. We can apply these models to reconstruct past lava flows in Hawai'i and Saudi Arabia using parameters assembled from morphology, textural analysis, and eruption observations as natural test cases. Our study highlights the strengths and weaknesses of each code, including accuracy and computational costs, and provides insights regarding code selection.

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

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

    2014-04-01

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

  19. Lava flows composition of the Daedalia Planum

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    Carli, Cristian; Giacomini, Lorenza; Sgavetti, Maria; Massironi, Matteo

    2010-05-01

    Daedalia Planum is a large lava plain, consisting of more than 1500 km lava flows emplaced over an almost flat terrain in the south-east area of Arsia Mons. The morphology of this region has been studied by Giacomini et al. (Planet.SpaceSci., 2009) and revealed the presence of various features indicative of inflation mechanisms. Thirteen morphologic units have been delineated and the stratigraphic relationships among these units have been established by the authors. Several compositional data indicate that most of the Mars surface appears to consist of tholeiitic basalts where rocks previously identified as andesite may be basaltic rocks coated with alteration rinds (McSween et al., Science, 2009). Some primitive alkaline olivine-rich basaltic rocks have been also recognized by rover exploration (McSween et al., J.Geophys.Res., 2006). The visible and near-infrared reflectance spectra contain electronic absorptions characteristic of mafic minerals including pyroxenes and olivine. These minerals, together with plagioclase, are the major components of lava's rocks. We have analyzed data acquired by the OMEGA orbiter spectrometer of the Mars Express mission. Several OMEGA's images have been studied collecting sets of spectra from each of the thirteen geological units. The spectra indicate a relatively uniform composition of the lavas, characterized by two wide absorption bands (I and II) at about 1000 and 2000 nm, respectively. These spectral features are diagnostic of the presence of pyroxenes, and the continuum removed spectra permit us to recognize the presence of two different pyroxenes . The precise minima positions of band I, between 950 and 1000 nm, and of band II, between 1800 and 2000 nm, suggest the presence in this region of low calcium and subcalcium clinopyroxene, like pigeonite and augite, with variable relative abundances. The presence of these types of pyroxenes suggests a tholeiitic composition of the Daedalia Planum long lava flows, in agreement with

  20. Paleomagnetism of Basaltic Lava Flows in Coreholes ICPP 213, ICPP-214, ICPP-215, and USGS 128 Near the Vadose Zone Research Park, Idaho Nuclear Technology and Engineering Center, Idaho National Engineering and Environmental Laboratory, Idaho

    Science.gov (United States)

    Champion, Duane E.; Herman, Theodore C.

    2003-01-01

    A paleomagnetic study was conducted on basalt from 41 lava flows represented in about 2,300 ft of core from coreholes ICPP-213, ICPP-214, ICPP-215, and USGS 128. These wells are in the area of the Idaho Nuclear Technology and Engineering Center (INTEC) Vadose Zone Research Park within the Idaho National Engineering and Environmental Laboratory (INEEL). Paleomagnetic measurements were made on 508 samples from the four coreholes, which are compared to each other, and to surface outcrop paleomagnetic data. In general, subhorizontal lines of correlation exist between sediment layers and between basalt layers in the area of the new percolation ponds. Some of the basalt flows and flow sequences are strongly correlative at different depth intervals and represent important stratigraphic unifying elements. Some units pinch out, or thicken or thin even over short separation distances of about 1,500 ft. A more distant correlation of more than 1 mile to corehole USGS 128 is possible for several of the basalt flows, but at greater depth. This is probably due to the broad subsidence of the eastern Snake River Plain centered along its topographic axis located to the south of INEEL. This study shows this most clearly in the oldest portions of the cored sections that have differentially subsided the greatest amount.

  1. Numerical simulation of wear of basalt lava spinning rolls

    OpenAIRE

    A. Lisiecki; A. Klimpel; D. Janicki

    2006-01-01

    Purpose: of this paper: Results of the study of wear phenomena of cascade spinning rolls during stone woolproduction process are described.Design/methodology/approach: The study was based on direct process observations, chemical analysis andtemperature measurements of basalt lava, metallographic examinations of the spinning rolls deposits. It was showedthat the deposits of spinning rolls are worn in very different way, depending on the roll position in rolls cascade.Findings: Predominant wear...

  2. Characterizing the physical properties of solidified PEG, an analog for basaltic lava crust

    Science.gov (United States)

    Soule, S. A.; Cashman, K.; Rust, A.

    2001-12-01

    The crust of a basaltic lava flow provides significant resistance to flow and is an important indicator of lava flow dynamics. Analog studies using polyethylene glycol (PEG), such as those by Fink and Griffiths (1990) and Griffiths and Fink (1992), are a useful means to determine the conditions under which different crustal morphologies are produced. To accurately apply the results of these studies to natural systems, we must understand how to scale between basaltic lava and its analog, PEG. The long-term goal of our study is to characterize the physical properties of both materials for the purpose of developing scaling relationships. We have designed a set of experiments to determine the strength and viscosity of solidified PEG. We measure the ductile deformation and failure of PEG under tension and in simple shear. Experiments are conducted with either constant stress or constant strain rate and at a range of temperatures (5 to 25 \\deg C). Tension experiments are conducted on hourglass-shaped PEG casts with failure occurring at the midpoint of the hourglass. Tension is produced by hanging weight (constant stress) or by pulling with a DC servo motor (constant strain rate). Simple shear experiments are conducted by turning a gear frozen into a sheet of PEG. A thinned ring of crust centered around the gear controls the failure location. From constant stress experiments, we measure pre-failure ductile deformation of the PEG to determine its viscosity. Constant strain rate experiments allow us to determine the dependence of PEG strength on strain rate. To determine the physical properties of basaltic crust we are building a furnace capable of melting large quantities of basalt and conducting experiments at high temperature. The experiments conducted on PEG will aid in the design of similar experiments on lava. The results of this study will have applications beyond scaling between analog models and natural systems. The presence or absence of a continuous flow crust

  3. Intracanyon basalt lavas of the Debed River (northern Armenia), part of a Pliocene-Pleistocene continental flood basalt province in the South Caucasus

    Science.gov (United States)

    Sheth, Hetu; Meliksetian, Khachatur; Gevorgyan, Hripsime; Israyelyan, Arsen; Navasardyan, Gevorg

    2015-03-01

    Late Pliocene to Early Pleistocene (~ 3.25-2.05 Ma), 200-400 m thick basalt lavas outcrop in the South Caucasus region, including the Kars-Erzurum Plateau (northeastern Turkey), the Javakheti Plateau (Georgia-Armenia), and the Lori Plateau (northern Armenia). These fissure-fed, rapidly erupted fluid lavas filled pre-existing river valleys over many tens of kilometres. The basalts exposed in the Debed River canyon, northern Armenia, are ~ 200 m thick and of three morphological types: (1) basal pillow basalts and hyaloclastites, overlain by (2) columnar-jointed pahoehoe sheet flows, in turn overlain by (3) slabby pahoehoe and rubbly pahoehoe flows. The lower and middle lavas show evidence for damming of river drainage, like many lavas of the Columbia River flood basalt province, Scotland, Ireland, and Iceland. There is also evidence for syn-volcanic faulting of the early lavas. Related basalts also outcrop in the Gegham Uplands and the Hrazdan River basin in Armenia. This 3.25-2.05 Ma South Caucasus basalt province, covering parts of Turkey, Georgia and Armenia, has an estimated areal extent of ~ 15,000 km2 and volume of ~ 2250 km3. Because its main geological features are remarkably like those of many continental flood basalt (CFB) provinces, we consider it a true, albeit small, CFB province. It is the smallest and youngest CFB in the world. An analogue closely similar in major features is the Late Miocene Altos de Jalisco CFB province in the western Trans-Mexican Volcanic Belt. Both provinces formed during lithospheric pull-apart and transtensional faulting. Their broader significance is in showing flood basalt size distribution to be a continuum without natural breaks, with implications for geodynamic models.

  4. Geochemistry of rare high-nb basalt lavas : are they derived from a mantle wedge metasomatised by slab melts?

    OpenAIRE

    Hastie, Alan R.; Mitchell, Simon F.; Kerr, Andrew C.; Minifie, Matthew J.; Millar, Ian L.

    2011-01-01

    Compositionally, high-Nb basalts are similar to HIMU (high U/Pb) ocean island basalts, continental alkaline basalts and alkaline lavas formed above slab windows. Tertiary alkaline basaltic lavas from eastern Jamaica, West Indies, known as the Halberstadt Volcanic Formation have compositions similar to high-Nb basalts (Nb > 20 ppm). The Halberstadt high-Nb basalts are divided into two compositional sub-groups where Group 1 lavas have more enriched incompatible element concentrations relative t...

  5. Hanford basalt flow mineralogy

    International Nuclear Information System (INIS)

    Mineralogy of the core samples from five core wells was examined in some detail. The primary mineralogy study included an optical examination of polished mounts, photomicrographs, chemical analyses of feldspars, pyroxenes, metallic oxides and microcrystalline groundmasses and determination from the chemical analyses of the varieties of feldspars, pyroxenes and metallic oxides. From the primary mineralogy data, a firm understanding of the average Hanford basalt flow primary mineralogy emerged. The average primary feldspar was a laboradorite, the average pyroxene was an augite and the average metallic oxide was a solid solution of ilmenite and magnetite. Secondary mineralization consisted of vug filling and joint coating, chiefly with a nontronite-beidellite clay, several zeolites, quartz, calcite, and opal. Specific flow units also were examined to determine the possibility of using the mineralogy to trace flows between core wells. These included units of the Pomona, the Umatilla and a high chromium flow just below the Huntzinger. In the Umatilla, or high barium flow, the compositional variation of the feldspars was unique in range. The pyroxenes in the Pomona were relatively highly zoned and accumulated chromium. The high chromium flow contained chromium spinels that graded in chromium content into simple magnetites very low in chromium content. A study of the statistical relationships of flow unit chemical constituents showed that flow unit constituents could be roughly correlated between wells. The probable cause of the correlation was on-going physical-chemical changes in the source magma

  6. Rheology of lava flows on Mercury: an experimental study

    Science.gov (United States)

    Sehlke, A.; Whittington, A. G.

    2014-12-01

    The morphology of lava flows is controlled by the physical properties of the lava and its effusion rates, as well as environmental influences such as surface medium, slope and ambient temperature and pressure conditions. The important rheological properties of lavas include viscosity (η) and yield strength (σy), strongly dependent on temperature (T), composition (X), crystal fraction (φc) and vesicularity (φb). The crystal fraction typically increases as temperature decreases, and also influences the residual liquid composition. The rheological behavior of multi-phase lava flows is expressed as different flow morphologies, for example basalt flows transition from smooth pahoehoe to blocky `a`a at higher viscosities and/or strain rates. We have previously quantified the rheological conditions of this transition for Hawaiian basalts, but lavas on Mercury are very different in composition and expected crystallization history. Here we determine experimentally the temperature and rheological conditions of the pahoehoe-`a`a transition for two likely Mercury lava compositions using concentric cylinder viscometry. We detect first crystals at 1302 ºC for an enstatite basalt and 1317 ºC for a basaltic komatiite composition representative of the northern volcanic plains (NVP). In both cases, we observe a transition from Newtonian to pseudo-plastic response at crystal fractions > 10 vol%. Between 30 to 40 vol%, a yield strength (τ0) around 26±6 and 110±6 Pa develops, classifying the two-phase suspensions as Herschel-Bulkley fluids. The measured increase in apparent viscosity (ηapp) ranges from 10 Pa s to 104 Pa s. This change in rheological properties occurs only in a temperature range up to 100 ºC below the liquidus. By analogy with the rheological conditions of the pahoehoe-`a`a transition for Hawaiian basalts, we can relate the data for Mercury to lava flow surface morphology as shown in Figure 1, where the onset of the transition threshold zone (TTZ) for the

  7. On anomalously magnetic basalt lavas from Stardalur, Iceland

    International Nuclear Information System (INIS)

    In an attempt to explain an exceptionally strong magnetic anomaly near Stardalur, SW-Iceland, a 200 m deep hole was drilled into its centre and the core subjected to various mineralogical and geophysical measurements. In Moessbauer spectra of bulk samples from depths between 45 and 170 m the magnetic phase is predominant and consists of very pure magnetite. The area ratio for the components with hyperfine fields of 46 and 49 T is approximately 2. Comparison with spectra of selected basalt lavas showing similar magnetic properties indicates a distinctive difference. The strong remanent magnetism of the Stardalur samples can be explained by a combination of unusually high concentration in the rocks of pure magnetite, its small grain size and a strong magnetic field appending its formation. It is suggested that both the composition of the magnetic phase and the strong magnetic field were brought about by hydrothermal alteration. (orig.)

  8. Pressure grouting of fractured basalt flows

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2011-01-01

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

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

    OpenAIRE

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

    2016-01-01

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

  11. Natural-Scale Lava Flow Experiments on Video: Variations with Temperature, Slope, and Effusion Rate

    Science.gov (United States)

    Karson, J. A.; Wysocki, R.; Edwards, B. R.; Lev, E.

    2013-12-01

    Investigations of active basaltic lava flows and analog materials show that flow dynamics and final flow morphology are strongly determined by the rapidly evolving rheology of the lava crust which constrains the downslope advance of the lava flow. The non-dimensional factor Ψ (ratio of the time scale of crust formation to advective heat loss) provides a useful means of comparing different flows. The key parameters that control Ψ include the melt viscosity, temperature, effusion rate, and slope. Experimental lava flows, up to several meters long created in the Syracuse University Lava Project permit these variables to be investigated independently and in combination in volume-limited flows (inflated lobes, break-outs, and bubbles (limu o'Pele), that provide additional information on lava crust development. New, continuous flow (cooling-limited) experiments show downslope variations under constant flow conditions.

  12. Pressure grouting of fractured basalt flows

    International Nuclear Information System (INIS)

    This report describes a field trial of pressure grouting in basalt and the results of subsequent coring and permeability measurement activities. The objective was to show that the hydraulic conductivity of fractured basalt bedrock can be significantly reduced by pressure injection of cementitious materials. The effectiveness of the pressure grout procedure was evaluated by measuring the change in the hydraulic conductivity of the bedrock. The extent of grout penetration was established by analyzing postgrout injection drilling chips for the presence of a tracer in the grout and also by examining cores of the treated basalt. Downhole radar mapping was used to establish major lava flow patterns and follow water movement during a surface infiltration test. A site called Box Canyon, which is located northwest of the INEL, was chosen for this study due to the similarity of this surface outcrop geology to that of the underlying bedrock fracture system found at the Radioactive Waste Management Complex. This study showed that hydraulic conductivity of basalt can be reduced through pressure grouting of cementitious material

  13. Eruption rate, area, and length relationships for some Hawaiian lava flows

    Science.gov (United States)

    Pieri, David C.; Baloga, Stephen M.

    1986-01-01

    The relationships between the morphological parameters of lava flows and the process parameters of lava composition, eruption rate, and eruption temperature were investigated using literature data on Hawaiian lava flows. Two simple models for lava flow heat loss by Stefan-Boltzmann radiation were employed to derive eruption rate versus planimetric area relationship. For the Hawaiian basaltic flows, the eruption rate is highly correlated with the planimetric area. Moreover, this observed correlation is superior to those from other obvious combinations of eruption rate and flow dimensions. The correlations obtained on the basis of the two theoretical models, suggest that the surface of the Hawaiian flows radiates at an effective temperature much less than the inner parts of the flowing lava, which is in agreement with field observations. The data also indicate that the eruption rate versus planimetric area correlations can be markedly degraded when data from different vents, volcanoes, and epochs are combined.

  14. Eruption Constraints for a Young Channelized Lava Flow, Marte Vallis, Mars

    Science.gov (United States)

    Therkelsen, J. P.; Santiago, S. S.; Grosfils, E. B.; Sakimoto, S. E. H.; Mendelson, C. V.; Bleacher, J. E.

    2001-01-01

    This study constrains flow rates for a specific channelized lava flow in Marte Vallis, Mars. We measured slope-gradient, channel width, and channel depth. Our results are similar to other recent studies which suggests similarities to long, terrestrial basaltic flow. Additional information is contained in the original extended abstract.

  15. Anisotropy of magnetic susceptibility of Hannuoba basalt, northern China: Constraints on the vent position of the lava sequences

    Science.gov (United States)

    Zhu, Rixiang; Shi, Caidong; Liu, Qingsong

    2003-01-01

    Anisotropy of magnetic susceptibility (AMS) was determined for Hannuoba basaltic samples from 17 flows (21.4 +/- 0.7Ma) distributed in three sections (Jianshaba, Yuershan and Manjing) around Zhangbei, northern China. The results show normal `flow' fabrics with horizontal foliation planes. The typical ratios of the principal AMS axes are 1.01 for the magnetic lineation (L) and 1.02 for the foliation (F), respectively. Magnetic hysteresis loop, isothermal remanence, thermomagnetic properties, and optical observations indicate that pseudo-single domain (PSD) low-titanium magnetite particles dominate the low-field susceptibility of samples. Thus the AMS of the magma at this area is believed to be originated from the lineation of the low-Titanium magnetite particles driven by the lava flow. Since the Kmax trends coincide well with the observed flow directions, the intersection of the mean Kmax trends from these three sites perfectly defines the previously known vent position of the lava sequences.

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Science.gov (United States)

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

    2013-12-01

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

  18. Temperature measurements in carbonatite lava lakes and flows from oldoinyo lengai, Tanzania.

    Science.gov (United States)

    Krafft, M; Keller, J

    1989-07-14

    The petrogenesis of carbonatites has important implications for mantle processes and for the magmatic evolution of mantle melts rich in carbon dioxide. Oldoinyo Lengai, Tanzania, is the only active carbonatite volcano on Earth. Its highly alkalic, sodium-rich lava, although different in composition from the more common calcium-rich carbonatites, provides the opportunity for observations of the physical characteristics of carbonatite melts. Temperature measurements on active carbonatitic lava flows and from carbonatitic lava lakes were carried out during a period of effusive activity in June 1988. Temperatures ranged from 491 degrees to 519 degrees C. The highest temperature, measured from a carbonatitic lava lake, was 544 degrees C. These temperatures are several hundred degrees lower than measurements from any silicate lava. At the observed temperatures, the carbonatite melt had lower viscosities than the most fluid basaltic lavas. The unusually low magmatic temperatures were confirmed with 1-atmosphere melting experiments on natural samples. PMID:17787875

  19. Studies of fluid instabilities in flows of lava and debris

    International Nuclear Information System (INIS)

    At least two instabilities have been identified and utilized in lava flow studies: surface folding and gravity instability. Both lead to the development of regularly spaced structures on the surfaces of lava flows. The geometry of surface folds have been used to estimate the rheology of lava flows on other planets. One investigation's analysis assumed that lava flows have a temperature-dependent Newtonian rheology, and that the lava's viscosity decreased exponentially inward from the upper surface. The author reviews studies by other investigators on the analysis of surface folding, the analysis of Taylor instability in lava flows, and the effect of surface folding on debris flows

  20. Mineral chemistry of Pangidi basalt flows from Andhra Pradesh

    Indian Academy of Sciences (India)

    P V Nageswara Rao; P C Swaroop; Syed Karimulla

    2012-04-01

    This paper elucidates the compositional studies on clinopyroxene, plagioclase, titaniferous magnetite and ilmenite of basalts of Pangidi area to understand the geothermometry and oxybarometry conditions. Petrographic evidence and anorthite content (up to 85%) of plagioclase and temperature estimates of clinopyroxene indicate that the clinopyroxene is crystallized later than or together with plagioclase. The higher An content indicates that the parent magma is tholeiitic composition. The equilibration temperatures of clinopyroxene (1110–1190°C) and titaniferous magnetite and ilmenite coexisting mineral phases (1063–1103°C) are almost similar in lower basalt flow and it is higher for clinopyroxene (900–1110°C) when compared to titaniferous magnetite and ilmenite coexisting mineral phases (748–898°C) in middle and upper basalt flows. From this it can be inferred that the clinopyroxene is crystallized earlier than Fe–Ti oxide phases reequilibration, which indicates that the clinopyroxene temperature is the approximate eruption temperature of the present lava flows. The wide range of temperatures (900–1190°C) attained by clinopyroxene may point out that the equilibration of clinopyroxene crystals initiated from depth till closer to the surface before the melt erupted. Pangidi basalts follow the QFM buffer curve which indicates the more evolved tholeiitic composition. This suggests the parent tholeiitic magma suffered limited fractionation at high temperature under increasing oxygen fugacity in lower basalt flow and more fractionation at medium to lower temperatures under decreasing oxygen fugacity conditions during cooling of middle and upper basalt flows. The variation of oxygen fugacity indicates the oxidizing conditions for lower basalt flow (9.48–10.3) and extremely reducing conditions for middle (12.1–15.5) and upper basalt (12.4–15.54) flows prevailed at the time of cooling. Temperature vs. (FeO+Fe2O3)/(FeO+Fe2O3+MgO) data plots for present

  1. Emplacement of lava flow fields: Application of terrestrial studies to Alba Patera, Mars

    International Nuclear Information System (INIS)

    Morphological data are at present the major source of information for extraterrestrial lavas. Effusion conditions must therefore be inferred from the final shapes of flow fields, generally using terrestrial lavas as analogues and so presupposing similar emplacement regimes on Earth and other planets. Studies of terrestrial lavas suggest that the overall development of flow fields is systematic and that a general, normalized relation can be established linking the final dimensions of a flow field (specifically, average thickness and the ratio of maximum width to maximum length) to underlying slope and eruption duration, independent of explicit knowledge of discharge rate, gravitational acceleration, lava density, and rheology. This relation is applied to lavas on the Martian volcano Alba Patera, on which two distinct planimetric types of lava flow fields are identified, and eruption durations, average discharge rates, and average velocities are obtained. Imposing the constraint of a terrestrial emplacement regime, the model yields internally consistent results for subliquidus lavas and suggests that, at least for basaltic-basaltic andesitic compositions, the essential conditions of eruption may have been similar to those currently observed on Earth

  2. Rheology of lava flows on Mercury: An analog experimental study

    Science.gov (United States)

    Sehlke, A.; Whittington, A. G.

    2015-11-01

    We experimentally determined the rheological evolution of three basaltic analog compositions appropriate to Mercury's surface, during cooling, and crystallization. Investigated compositions are an enstatite basalt, and two magnesian basalts representing the compositional end-members of the northern volcanic plains with 0.19 wt % (NVP) and 6.26 wt % Na2O (NVP-Na). The viscosity-strain rate dependence of lava was quantified using concentric cylinder viscometry. We measured the viscosities of the crystal-free liquids from 1600°C down to the first detection of crystals. Liquidus temperatures of the three compositions studied are around 1360°C, and all three compositions are more viscous than Hawaiian basalt at the same temperature. The onset of pseudoplastic behavior was observed at crystal fractions ~0.05 to 0.10, which is consistent with previous studies on mafic lavas. We show that all lavas develop detectable yield strengths at crystal fractions around 0.20, beyond which the two-phase suspensions are better described as Herschel-Bulkley fluids. By analogy with the viscosity-strain rate conditions at which the pahoehoe to `a`a transition occurs in Kilauea basalt, this transition is predicted to occur at ~1260 ± 10°C for the enstatite basalt, at ~1285 ± 20°C for the NVP, and at ~1240 ± 40°C for the NVP-Na lavas. Our results indicate that Mercury lavas are broadly similar to terrestrial ones, which suggests that the extensive smooth lava plains of Mercury could be due to large effusion rates (flood basalts) and not to unusually fluid lavas.

  3. Geochemistry and genesis of behind-arc basaltic lavas from eastern Nicaragua

    Science.gov (United States)

    Janoušek, V.; Erban, V.; Holub, F. V.; Magna, T.; Bellon, H.; Mlčoch, B.; Wiechert, U.; Rapprich, V.

    2010-05-01

    The petrology and chemistry of the Behind the Volcanic Front (BVF) lavas from eastern mainland Nicaragua and the adjacent Great Corn Island in the Caribbean Sea illustrate the complex nature of sources and processes operating in such a tectonic setting. The older, Early Miocene (˜ 17 Ma) group of low-Ti ( 1.5%) lavas, rich in other HFSE as well, are represented both by alkaline (Quaternary trachybasalts: Volcán Azul and Kukra Hill) and subalkaline (basalts-basaltic andesites: Late Miocene, ˜ 11 Ma Great Corn Island and Quaternary, Pearl Lagoon) volcanic rocks. The Late Miocene and Quaternary high-Ti BVF lavas probably represent small-volume decompression melts of a source similar to that of the OIB-like magmas, most likely upwelling asthenosphere having a strong Galápagos mantle imprint. The positive Sr-Nd isotopic correlation indicates an interaction between this OIB component and a depleted lithospheric mantle modified by a subduction-related influx of Sr and, to a lesser extent, other hydrous fluid-mobile elements. However, the rocks show no recognizable influence of the modern subduction. The feeble trace-element (e.g., slightly elevated Ba, K, and Sr at some localities) and a more pronounced Sr-Li isotopic subduction-related signal stems most likely from the Miocene convergence episode. Subduction of the Galápagos hot-spot tracks in Costa Rica produces magmas that can be readily recognized by their elevated Sr isotopic ratios due to seafloor alteration; the Nd isotopic signature remains unaffected. Such a component with relatively unradiogenic Nd and radiogenic Sr is required in the source of the modern volcanic front lavas but is not needed to explain the variation in the studied BVF dataset. Terrains with multiepisodic subduction history should be considered with caution, as the lavas generated by decompression melting of the asthenospheric source in the back-arc region may bear a geochemical imprint of the fossil and not the modern subduction component

  4. Viscous flow behavior of tholeiitic and alkaline Fe-rich martian basalts

    Science.gov (United States)

    Chevrel, Magdalena Oryaëlle; Baratoux, David; Hess, Kai-Uwe; Dingwell, Donald B.

    2014-01-01

    The chemical compositions of martian basalts are enriched in iron with respect to terrestrial basalts. Their rheology is poorly known and liquids of this chemical composition have not been experimentally investigated. Here, we determine the viscosity of five synthetic silicate liquids having compositions representative of the diversity of martian volcanic rocks including primary martian mantle melts and alkali basalts. The concentric cylinder method has been employed between 1500 °C and the respective liquidus temperatures of these liquids. The viscosity near the glass transition has been derived from calorimetric measurements of the glass transition. Although some glass heterogeneity limits the accuracy of the data near the glass transition, it was nevertheless possible to determine the parameters of the non-Arrhenian temperature-dependence of viscosity over a wide temperature range (1500 °C to the glass transition temperature). At superliquidus conditions, the martian basalt viscosities are as low as those of the Fe-Ti-rich lunar basalts, similar to the lowest viscosities recorded for terrestrial ferrobasalts, and 0.5 to 1 order of magnitude lower than terrestrial tholeiitic basalts. Comparison with empirical models reveals that Giordano et al. (2008) offers the best approximation, whereas the model proposed by Hui and Zhang (2007) is inappropriate for the compositions considered. The slightly lower viscosities exhibited by the melts produced by low degree of mantle partial melting versus melts produced at high degree of mantle partial melting (likely corresponding to the early history of Mars), is not deemed sufficient to lead to viscosity variations large enough to produce an overall shift of martian lava flow morphologies over time. Rather, the details of the crystallization sequence (and in particular the ability of some of these magmas to form spinifex texture) is proposed to be a dominant effect on the viscosity during martian lava flow emplacement and

  5. Constraining Eruptive Conditions From Lava Flow Morphometry: A Case Study With Field Evidence

    Science.gov (United States)

    Bowles, Z. R.; Clarke, A.; Greeley, R.

    2007-12-01

    Volcanism is widely recognized as one of the primary factors affecting the surfaces of solid planets and satellites throughout the solar system. Basaltic lava is thought to be the most common composition based on observed features typical of basaltic eruptions found on Earth. Lava flows are one of the most easily recognizable landforms on planetary surfaces and their features may provide information about eruption dynamics, lava rheology, and potential hazards. More recently, researchers have taken a multi-faceted approach to combine remote sensing, field observations and quantitative modeling to constrain volcanic activity on Earth and other planets. Here we test a number of published models, including empirically derived relationships from Mt. Etna and Kilauea, models derived from laboratory experiments, and theoretical models previously applied to remote sensing of planetary surfaces, against well-documented eruptions from the literature and field observations. We find that the Graetz (Hulme and Felder, 1977, Phil.Trans., 285, 227 - 234) method for estimating effusion rates compares favorably with published eruption data, while, on the other hand, inverting lava flow length prediction models to estimate effusion rates leads to several orders of magnitude in error. The Graetz method also better constrains eruption duration. Simple radial spreading laws predict Hawaiian lava flow lengths quite well, as do using the thickness of the lava flow front and chilled crust. There was no observed difference between results from models thought to be exclusive to aa or pahoehoe flow fields. Interpreting historic conditions should therefore follow simple relationships to observable morphologies no matter the composition or surface texture. We have applied the most robust models to understand the eruptive conditions and lava rheology of the Batamote Mountains near Ajo, AZ, an eroded shield volcano in southern Arizona. We find effusion rates on the order of 100 - 200 cubic

  6. Numerical simulation of lava flows: Applications to the terrestrial planets

    Science.gov (United States)

    Zimbelman, James R.; Campbell, Bruce A.; Kousoum, Juliana; Lampkin, Derrick J.

    1993-03-01

    Lava flows are the visible expression of the extrusion of volcanic materials on a variety of planetary surfaces. A computer program described by Ishihara et al. appears to be well suited for application to different environments, and we have undertaken tests to evaluate their approach. Our results are somewhat mixed; the program does reproduce reasonable lava flow behavior in many situations, but we have encountered some conditions common to planetary environments for which the current program is inadequate. Here we present our initial efforts to identify the 'parameter space' for reasonable numerical simulations of lava flows.

  7. Petrogenesis of Rinjani Post-1257-Caldera-Forming-Eruption Lava Flows

    Directory of Open Access Journals (Sweden)

    Heryadi Rachmat

    2016-08-01

    Full Text Available After the catastrophic 1257 caldera-forming eruption, a new chapter of Old Rinjani volcanic activity beganwith the appearance of Rombongan and Barujari Volcanoes within the caldera. However, no published petrogeneticstudy focuses mainly on these products. The Rombongan eruption in 1944 and Barujari eruptions in pre-1944, 1966,1994, 2004, and 2009 produced basaltic andesite pyroclastic materials and lava flows. A total of thirty-one sampleswere analyzed, including six samples for each period of eruption except from 2004 (only one sample. The sampleswere used for petrography, whole-rock geochemistry, and trace and rare earth element analyses. The Rombonganand Barujari lavas are composed of calc-alkaline and high K calc-alkaline porphyritic basaltic andesite. The magmashows narrow variation of SiO2 content that implies small changes during its generation. The magma that formedRombongan and Barujari lavas is island-arc alkaline basalt. Generally, data show that the rocks are enriched in LargeIon Lithophile Elements (LILE: K, Rb, Ba, Sr, and Ba and depleted in High Field Strength Elements (HFSE: Y, Ti,and Nb which are typically a suite from a subduction zone. The pattern shows a medium enrichment in Light REEand relatively depleted in Heavy REE. The processes are dominantly controlled by fractional crystallization andmagma mixing. All of the Barujari and Rombongan lavas would have been produced by the same source of magmawith little variation in composition caused by host rock filter process. New flux of magma would likely have occurredfrom pre-1944 until 2009 period that indicates slightly decrease and increase of SiO2 content. The Rombongan andBarujari lava generations show an arc magma differentiation trend.

  8. Validating Cellular Automata Lava Flow Emplacement Algorithms with Standard Benchmarks

    Science.gov (United States)

    Richardson, J. A.; Connor, L.; Charbonnier, S. J.; Connor, C.; Gallant, E.

    2015-12-01

    A major existing need in assessing lava flow simulators is a common set of validation benchmark tests. We propose three levels of benchmarks which test model output against increasingly complex standards. First, imulated lava flows should be morphologically identical, given changes in parameter space that should be inconsequential, such as slope direction. Second, lava flows simulated in simple parameter spaces can be tested against analytical solutions or empirical relationships seen in Bingham fluids. For instance, a lava flow simulated on a flat surface should produce a circular outline. Third, lava flows simulated over real world topography can be compared to recent real world lava flows, such as those at Tolbachik, Russia, and Fogo, Cape Verde. Success or failure of emplacement algorithms in these validation benchmarks can be determined using a Bayesian approach, which directly tests the ability of an emplacement algorithm to correctly forecast lava inundation. Here we focus on two posterior metrics, P(A|B) and P(¬A|¬B), which describe the positive and negative predictive value of flow algorithms. This is an improvement on less direct statistics such as model sensitivity and the Jaccard fitness coefficient. We have performed these validation benchmarks on a new, modular lava flow emplacement simulator that we have developed. This simulator, which we call MOLASSES, follows a Cellular Automata (CA) method. The code is developed in several interchangeable modules, which enables quick modification of the distribution algorithm from cell locations to their neighbors. By assessing several different distribution schemes with the benchmark tests, we have improved the performance of MOLASSES to correctly match early stages of the 2012-3 Tolbachik Flow, Kamchakta Russia, to 80%. We also can evaluate model performance given uncertain input parameters using a Monte Carlo setup. This illuminates sensitivity to model uncertainty.

  9. Stochastic modeling of a lava-flow aquifer system

    Science.gov (United States)

    Cronkite-Ratcliff, Collin; Phelps, Geoffrey A.

    2014-01-01

    This report describes preliminary three-dimensional geostatistical modeling of a lava-flow aquifer system using a multiple-point geostatistical model. The purpose of this study is to provide a proof-of-concept for this modeling approach. An example of the method is demonstrated using a subset of borehole geologic data and aquifer test data from a portion of the Calico Hills Formation, a lava-flow aquifer system that partially underlies Pahute Mesa, Nevada. Groundwater movement in this aquifer system is assumed to be controlled by the spatial distribution of two geologic units—rhyolite lava flows and zeolitized tuffs. The configuration of subsurface lava flows and tuffs is largely unknown because of limited data. The spatial configuration of the lava flows and tuffs is modeled by using a multiple-point geostatistical simulation algorithm that generates a large number of alternative realizations, each honoring the available geologic data and drawn from a geologic conceptual model of the lava-flow aquifer system as represented by a training image. In order to demonstrate how results from the geostatistical model could be analyzed in terms of available hydrologic data, a numerical simulation of part of an aquifer test was applied to the realizations of the geostatistical model.

  10. Thicknesses and Volumes of Lunar Mare Basalt Flow Units

    Science.gov (United States)

    Hiesinger, H.; Head, J. W.; Wolf, U.; Jaumann, R.; Neukum, G.

    Reliable estimates of the flow thickness are crucial to our understanding of the vol- umes and the flux of lunar mare basalt volcanism. Previous work on basalt flow unit thicknesses was based on (1) shadow measurements in high-resolution images that were taken under low-sun conditions, (2) in situ observations, e.g. of Hadley Rille at the Apollo 15 landing site, and (3) on studies of the chemical kinetic aspects of lava emplacement and cooling. These studies revealed flow unit thicknesses between 1 and 96 m. Flow unit thicknesses derived from imaging data are on average ~21 m, in contrast to chemical kinetic considerations that yield thicknesses of less than 10 m. We used crater size-distribution measurements to estimate flow unit thicknesses. A large number (~60) of our crater counts show evidence for resurfacing events and these "irregularities" in the crater size distributions are used to infer the thickness of the resurfacing layer, that is the thickness of lava flows in several nearside basins. We find that the average minimum flow unit height of all investigated units is on the order of 34 m (+7/-6 m) and that the average maximum flow unit height is about 53 m (+9/- 9 m). On average the thinnest flow units were detected for units in Mare Insularum, Mare Cognitum, and Mare Nubium, thickest flows are exposed in Mare Tranquilli- tatis and Mare Humorum. Average thicknesses of flow units in Oceanus Procellarum and Mare Imbrium are slightly larger than in Mare Insularum, Mare Cognitum, and Mare Nubium, but are smaller than in Mare Tranquillitatis and Mare Humorum. The minimum average volume of all investigated flow units is~590 km3 and the maximum average volume is~940 km3. Our data indicate that the most voluminous flow units are located in Mare Humorum and Mare Tranquillitatis. As crater counts for units in Mare Serenitatis do not exhibit prominent deflections we conclude that these units have not to been resurfaced with flows thick enough to be detected in the

  11. 40Ar-39Ar age of a lava flow from the Bhimashankar Formation, Giravali Ghat, Deccan Traps

    Indian Academy of Sciences (India)

    Kanchan Pande; S K Pattanayak; K V Subbarao; P Navaneethakrishnan; T R Venkatesan

    2004-12-01

    We report here a 40Ar-39Ar age of 66.0 ± 0.9Ma (2 ) for a reversely magnetised tholeiitic lava flow from the Bhimashankar Formation (Fm.), Giravali Ghat, western Deccan province, India. This age is consistent with the view that the 1.8–2km thick bottom part of the exposed basalt flow sequence in the Western Ghats was extruded very close to 67.4 Ma.

  12. The strain path and emplacement mechanism of lava flows: an example from Salina (southern Tyrrhenian Sea, Italy)

    Science.gov (United States)

    Ventura, Guido

    2001-05-01

    A lava flow from Salina (southern Tyrrhenian Sea) consists of subcircular to ellipsoidal basaltic enclaves dispersed in a dacitic host. A 2D strain and kinematic analysis of the enclaves has been performed in order to determine (a) the relative contribution of the coaxial ( α) and non-coaxial ( γ) components to the bulk flow deformation, (b) the flow vorticity Wk, (c) the strain path and (d) the mechanism of flow emplacement. The axial ratio Rf and the angle φf between the long axis of the enclaves and the transport direction have been measured in 196 sites located at different distances from the vent. In the near vent zone α> γ whereas further from the vent γ> α. α values were always larger than 1, ranging from 1.6 in the near vent zone to 1 at the front. γ values were between 0.2 (at the back) and 2.6 (at the front). Wk was between 0.13 and 1 and increased from the back to the front. The enclaves result from the injection of basalt into dacite. Most of the deformation was acquired during the lava flow emplacement and not during the rise in the conduit (plug flow). The strain path depicted by the enclaves is consistent with that resulting from experimental analogue models and reveals that the lava suffers lateral extension near the vent. Further from the vent, the lava deforms according to an ideal non-coaxial model. The lava emplacement is mainly controlled by the gravity. Evidence of deformation induced by the magma pressure is lacking. Near the vent, the lava behaves as a hyperbolic flow whereas at the front it behaves as a simple shear flow. The mechanism of flow emplacement is consistent with a mixed 'viscous gliding-spreading' transport model at the back and with a 'viscous gliding' model at the front.

  13. Lava Flow Lengths and Historic Eruptive Parameters: Implications for the Volcanic History of the Batamote Mountains, Ajo, Arizona

    Science.gov (United States)

    Bowles, Z. R.; Clarke, A.; Greeley, R.

    2006-12-01

    Lava flow lengths and morphology depend on (1) initial viscocity, (2) rate of effusion, (3) total volume of lava extruded, (4) duration of extrusion, (5) slope of underlying surface, (6) topography, (7) rate of cooling, (8) formation of crust, and (9) other special circumstances such as ponding and flowing into water. Lava flow lengths and assumptions on lava type contain all the information needed to make educated constraints on the eruptive history of a particular volcano. By no means is this a definitive claim of eruptive histories based on present day observations, but an approximation of what might have occurred may be obtained. Lava flow lengths were measured in the Batamote Mountains in Ajo, Arizona and it was determined that this 18 million year old shield volcano erupted with effusion rates of 5 to 10 cubic meters per second, volumes of 0.00001 cubic kilometers, eruption durations on the order of days, lava yield strengths of 5000 Pa, and flow thicknesses of approximately 3 to 6 meters. These calculations add to the body of knowledge covering Arizona historical volcanism and related Basin and Range extension, but conflict with observations of basaltic volcanic fields in this region.

  14. Geochemistry and stratigraphic correlation of basalt lavas beneath the Idaho Chemical Processing Plant, Idaho National Engineering Laboratory

    Science.gov (United States)

    Reed, M.F.; Bartholomay, R.C.; Hughes, S.S.

    1997-01-01

    Thirty-nine samples of basaltic core were collected from wells 121 and 123, located approximately 1.8 km apart north and south of the Idaho Chemical Processing Plant at the Idaho National Engineering Laboratory. Samples were collected from depths ranging from 15 to 221 m below land surface for the purpose of establishing stratigraphic correlations between these two wells. Elemental analyses indicate that the basalts consist of three principal chemical types. Two of these types are each represented by a single basalt flow in each well. The third chemical type is represented by many basalt flows and includes a broad range of chemical compositions that is distinguished from the other two types. Basalt flows within the third type were identified by hierarchical K-cluster analysis of 14 representative elements: Fe, Ca, K, Na, Sc, Co, La, Ce, Sm, Eu, Yb, Hf, Ta, and Th. Cluster analyses indicate correlations of basalt flows between wells 121 and 123 at depths of approximately 38-40 m, 125-128 m, 131-137 m, 149-158 m, and 183-198 m. Probable correlations also are indicated for at least seven other depth intervals. Basalt flows in several depth intervals do not correlate on the basis of chemical compositions, thus reflecting possible flow margins in the sequence between the wells. Multi-element chemical data provide a useful method for determining stratigraphic correlations of basalt in the upper 1-2 km of the eastern Snake River Plain.

  15. Conveying Lava Flow Hazards Through Interactive Computer Models

    Science.gov (United States)

    Thomas, D.; Edwards, H. K.; Harnish, E. P.

    2007-12-01

    As part of an Information Sciences senior class project, a software package of an interactive version of the FLOWGO model was developed for the Island of Hawaii. The software is intended for use in an ongoing public outreach and hazards awareness program that educates the public about lava flow hazards on the island. The design parameters for the model allow an unsophisticated user to initiate a lava flow anywhere on the island and allow it to flow down-slope to the shoreline while displaying a timer to show the rate of advance of the flow. The user is also able to modify a range of input parameters including eruption rate, the temperature of the lava at the vent, and crystal fraction present in the lava at the source. The flow trajectories are computed using a 30 m digital elevation model for the island and the rate of advance of the flow is estimated using the average slope angle and the computed viscosity of the lava as it cools in either a channel (high heat loss) or lava tube (low heat loss). Even though the FLOWGO model is not intended to, and cannot, accurately predict the rate of advance of a tube- fed or channel-fed flow, the relative rates of flow advance for steep or flat-lying terrain convey critically important hazard information to the public: communities located on the steeply sloping western flanks of Mauna Loa may have no more than a few hours to evacuate in the face of a threatened flow from Mauna Loa's southwest rift whereas communities on the more gently sloping eastern flanks of Mauna Loa and Kilauea may have weeks to months to prepare for evacuation. Further, the model also can show the effects of loss of critical infrastructure with consequent impacts on access into and out of communities, loss of electrical supply, and communications as a result of lava flow implacement. The interactive model has been well received in an outreach setting and typically generates greater involvement by the participants than has been the case with static maps

  16. Eruption of Alkaline Basalts Prior to the Calc-alkaline Lavas of Mt. Cleveland Volcano, Aleutian Arc, Alaska

    Science.gov (United States)

    Bridges, D. L.; Nicolaysen, K. P.

    2005-12-01

    Mt. Cleveland is a 1,730 m stratovolcano, located on Chuginadak Island, that has erupted at least 23 times historically, with the latest occurring in August 2005. Major, trace, and REE analyses of 63 samples from Mt. Cleveland, including 8 from proximal cinder cones and 4 from andesitic domes on the lower flanks, identify two distinct lava suites. Modern Cleveland (MC) basalts to dacites (50.5-66.7 wt.% SiO2) exhibit a calc-alkaline differentiation trend. Major element trends suggest crystal fractionation of plagioclase +/- ortho- and clinopyroxene in MC lavas and olivine in cinder cone deposits. Resorption textures on plagioclase and olivine phenocrysts and multiple populations of plagioclase predominate throughout the MC suite suggesting magma mixing is a major process at Cleveland. Frothy white xenoliths of plagioclase + quartz + biotite are encased in glass and erupted as small pumiceous fragments in 2001. The partial resorption of the xenocrysts indicates assimilation is also an active crustal process at Cleveland. MC trace element spider diagrams exhibit a typical arc pattern in which HFS elements including Nb are depleted, and Pb and LIL elements are enriched. Th/La, Sm/La, and Sr, Nd, Pb, and Hf isotopic ratios indicate both a North Pacific MORB and a sediment component in the source of modern Cleveland lavas, consistent with sediment flux estimates of 90 to 95 m3/m/yr and an updip sediment thickness of 1300 to 1400 meters. Average 206Pb/204Pb, 207Pb/204Pb, 87Sr/86Sr, and 143Nd/144Nd values for the calc-alkaline suite are 18.93, 15.58, 0.70345, and 0.51303 respectively. The second suite consists of 3 olivine-rich, mildly alkaline basalts (48.5-49.4 wt.% SiO2), of older stratigraphic position than MC lavas representing deposits from an older phase of activity (ancestral Cleveland, AC). La/Yb, Sr/Y, and Th/Nb ratios indicate lower degrees of partial melting, relative to MC lavas, and suggests presence of garnet in the source region. The AC lavas, however, are

  17. Lava Flow Emplacement Processes and Eruptive Characteristics of the Ontong Java Plateau: Inferences from High-Precision Glass Analysis

    Science.gov (United States)

    Trowbridge, S. R.; Michael, P. J.

    2015-12-01

    High-precision major and volatile element analyses were performed on natural basaltic glass from ODP Leg 192 Sites 1185 and 1187 of the Ontong Java Plateau (OJP) as a way to correlate lava flows within and between ODP drill sites. The ultimate goal is to estimate the dimensions, emplacement style, and eruption characteristics of the high-MgO Kroenke-type lavas: the youngest known flows at the two sites. The 122-Ma Ontong Java Plateau is the largest known magmatic event in Earth's history, yet little is known of the emplacement style (e.g. flow dimensions and durations) of OJP lavas due to its submarine nature and burial beneath hundreds of meters of sediment. Basalt samples were recovered from 110- and 130-m thick core sections from Sites 1185B and 1187A, respectively. Total Kroenke-type lava thickness is 125 m at 1185B and >136 m at 1187. Site 1187A is located 146 km north of Site 1185B and lies ≈50 m shallower than Site 1187. Remarkably, all of the glass compositions from both sites fall on a common liquid line of descent, suggesting that all lavas were the product of a single eruption from a common magma chamber. The range of MgO compositions reflects a 20ºC range in temperature, representing ~1.9% crystallization of olivine + spinel. Using measured phenocryst abundance, we examine whether this crystallization occurred within the magma chamber or during long transport of lavas on the seafloor. More primitive lavas are present in the upper 30 m of Site 1185B (average of ~9.54 wt. % MgO), overlying more fractionated lavas (average of ~9.06 wt. % MgO). Lavas from Site 1187A bridge the gap between the high- and low-MgO groups of 1185B. In contrast to MORB, OJP glasses have no vesicles, suggesting they remained liquid for much longer during flow. Paleoeruption depths calculated from H2O and CO2 contents of glasses show no systematic variation with depth in Core 1185B, and range from ~2130-2650 mbsl, while Site 1187 shows deeper eruption depths of ~2410-3040 mbsl

  18. Depleted basaltic lavas from the proto-Iceland plume, Central East Greenland

    DEFF Research Database (Denmark)

    Waight, Tod Earle; Baker, Joel A.

    2012-01-01

    New geochemical and isotopic data are presented for volumetrically minor, depleted low-Ti basalts that occur in the Plateau Basalt succession of central East Greenland (CEG), formed during the initial stages of opening of the North Atlantic at 55 Ma. The basalts have MORB-like geochemistry (e.g. ...

  19. Estimating rheological properties of lava flows using high-resolution time lapse imaging

    Science.gov (United States)

    James, M. R.; Applegarth, L. J.; Pinkerton, H.; Fryer, T.

    2011-12-01

    During effusive eruptions, property and infrastructure can be threatened by lava flow inundation. In order to maximise the effectiveness of the response to such an event, it is necessary to be able to reliably forecast the area that will be affected. One of the major controls on the advance of a lava flow is its rheology, which is spatially and temporally variable, and depends on many underlying factors. Estimating the rheological properties of a lava flow, and the change in these over space and time is therefore of the utmost importance. Here we report estimates of rheological properties made from geometric and velocity measurements on integrated topographic and image data using the method of Ellis et al. (2004) (Ellis B, Wilson L & Pinkerton H (2004) Estimating the rheology of basaltic lava flows. Lunar & Planetary Science XXXV Abst. 1550). These are then compared to the viscosity predicted from composition and temperature by the GRD model (Giordano D, Russell JK, & Dingwell DB (2008) Viscosity of Magmatic Liquids: A Model. Earth & Planetary Science Letters, 271, 123-134). During the 13 May 2008 - 6 July 2009 eruption of Mt Etna, Sicily, lava flows were emplaced into the Valle del Bove, reaching a maximum length of >6 km. Towards the end of the eruption, multiple channelized aa flows were active simultaneously, reaching tens to hundreds of metres in length. Flow lifetimes were of the order hours to days. In the last month of the eruption, we installed a Canon EOS 450D camera at Pizzi Deneri, on the north side of the Valle del Bove, to collect visible images at 15-minute intervals. On one day, topographic data (using a Riegl LPM-321 terrestrial laser scanner) and thermal images (using a FLIR Thermacam S40) were also collected from this location. The fronts of some of the larger flows were tracked through the time lapse image sequence. Using knowledge of the camera imaging geometry, the pixel tracks were reprojected onto the topographic surface to determine flow

  20. Geochemistry of Spencer-High Point Volcanic Field Lava Flows, Idaho

    Science.gov (United States)

    Iwahashi, G. S.; Hughes, S. S.

    2007-12-01

    Lava flows in Spencer-High Point (SHP) volcanic field, an ~1700 sq km mafic volcanic rift zone located near Yellowstone in the eastern Snake River Plain (ESRP), have been compared physically and chemically to other ESRP olivine tholeiites. Overall, SHP lavas are geochemically similar to other ESRP olivine tholeiites but their geomorphology is entirely different. The structural alignment of vents and fissures in an east-west direction in the Spencer-High Point region contrasts with most of the ESRP volcanic features aligned northwest-southeast. Numerous cinder cones at SHP, features that characterize Craters of the Moon volcanic field, are unusual on most of the eastern Snake River Plain. This study agrees with preliminary geochemical data by Leeman (1982) and Kuntz et al. (1992) suggesting that SHP lavas are typical ESRP basalts. However, a broad range of geochemical compositions exists in the SHP field that is similar to the entire range of ESRP olivine tholeiites. A few of the samples are actually closer in composition to lavas present at Craters of the Moon but only a limited number of samples from vents with physically higher relief, in the central and eastern portions of the field show these evolved chemical compositions. Typically Ta ranges 0.5-4.5ppm, La 20-90ppm, Ba 200-1100ppm and Cr 7-550ppm. Some lava flows in the central and eastern sections of SHP volcanic field also contain crustal xenoliths, implying a prolonged crustal history. These results although preliminary, suggest that the SHP system represents a possible petrologic transition between the dominant ESRP tholeiites and the evolved compositions found at Craters of the Moon.

  1. How Degassing Determined the Crystallization Style of the Lava Flows Produced During the Laki Eruption (South Iceland)

    Science.gov (United States)

    Guilbaud, M.; Blake, S.; Thordarson, T.; Self, S.

    2005-12-01

    Basaltic eruptions mainly produce lava flows. Degassing of basalt as it rises in the conduit can control the late-stage crystallization of the magma. Microlites formed by degassing-induced undercooling may then influence the flow regime of the lava, control the formation of surface morphologies, and thus determine the final extent of the flows. We present evidence that this mechanism operated during the AD1783-84 Laki eruption. During the eruption, 15 km3 of dominantly rubbly pahoehoe lava was emitted from along a fissure system. We studied crystal compositions, morphologies, glass-crystal gradients, glass chemistry and water content, and quantified crystal numbers and sizes. The observations were then compared to models of equilibrium crystallization and finally combined in a temperature-time model of the magma crystallization path. In this paper, we concentrate on showing snapshots of the four stages that controlled the thermal regime, degassing, and crystallization style of the magma. Phenocrysts formed at water under-saturated, low-undercooling conditions in the magma chamber (stage 1). Compositional zoning in plagioclase evidences the control of degassing on the nucleation and growth of plagioclase-clinopyroxene microphenocrysts in the conduit (stage 2). When the magma reached the surface, nucleation rates were significantly raised that there was a burst of crystallization of olivines and plagioclases skeletal microlites, and relative suppression of clinopyroxene crystallization (stage 3). The lava then partially re-equilibrated to equilibrium conditions during further crystallization in the flow (stage 4). The whole crystallization path of the magma during the eruption may have been nearly isothermal, mainly driven by the undercooling induced by degassing during magma ascent. The high density of microlites in lava from the early phases of outflow from the fissure created conditions favouring periodic disruption of the thickening lava crust, and hence

  2. Degassing dynamics of basaltic lava lake at a top-ranking volatile emitter: Ambrym volcano, Vanuatu arc

    Science.gov (United States)

    Allard, Patrick; Burton, Mike; Sawyer, Georgina; Bani, Philipson

    2016-08-01

    Persistent lava lakes are rare on Earth and provide volcanologists with a remarkable opportunity to directly investigate magma dynamics and degassing at the open air. Ambrym volcano, in Vanuatu, is one of the very few basaltic arc volcanoes displaying such an activity and voluminous gas emission, but whose study has long remained hampered by challenging accessibility. Here we report the first high temporal resolution (every 5 s) measurements of vigorous lava lake degassing inside its 300 m deep Benbow crater using OP-FTIR spectroscopy. Our results reveal a highly dynamic degassing pattern involving (i) recurrent (100-200 s) short-period oscillations of the volcanic gas composition and temperature, correlating with pulsated gas emission and sourced in the upper part of the lava lake, (ii) a continuous long period (∼8 min) modulation probably due to the influx of fresh magma at the bottom of the lake, and (iii) discrete CO2 spike events occurring in coincidence with the sequential bursting of meter-sized bubbles, which indicates the separate ascent of large gas bubbles or slugs in a feeder conduit with estimated diameter of 6 ± 1 m. This complex degassing pattern, measured with unprecedented detail and involving both coupled and decoupled magma-gas ascent over short time scales, markedly differs from that of quieter lava lakes at Erebus and Kilauea. It can be accounted for by a modest size of Benbow lava lake and its very high basalt supply rate (∼20 m3 s-1), favouring its rapid overturn and renewal. We verify a typical basaltic arc signature for Ambrym volcanic gas and, based on contemporaneous SO2 flux measurements, we evaluate huge emission rates of 160 Gg d-1 of H2O, ∼10 Gg d-1 of CO2 and ∼8 Gg d-1 of total acid gas (SO2, HCl and HF) during medium activity of the volcano in 2008. Such rates make Ambrym one of the three most powerful volcanic gas emitters at global scale, whose atmospheric impact at local and regional scale may be considerable.

  3. Petrogenesis of eocene lava flows from the chagai arc, Balochistan, Pakistan and its tectonic implications

    International Nuclear Information System (INIS)

    The Eocene Lava flows occur in the northwestern part of an EW trending subduction related-magmatic belt known as Chagai arc in the Western part of Pakistan. The volcanism in this arc was initiated during the Late Cretaceous, which intermittently continued up to the Quaternary period. In the regional geotectonic context this arc belongs to the Tethyan convergence zone and was believed to have formed due to the northward subduction of Arabian oceanic plate below the southern margin of Afghan micro plate and hence considered as an Andean type arc. Although Bocene volcaniclastic rock occurs throughout the Chagai arc but the lava flows only crop out in a NW-SE elongated (1 km x 6 kIn) area in the northwestern part of the Chagai arc. These lava flows are represented by two discrete cycles of eruptions found towards the top of the lower pyroclastic sequence of Saindak Formation of Ecocene age. The older flow is about 100 m thick and extends for 2 km whereas the younger flow is 700 metre thick and extends for more than 6 km. The lava flows are mainly represented by amigdaloidal basaltic-andesites (55.50- 54.53 wt. % SiO/sub 2/) and andesites (57.40-62.79 wt. % SiO/sub 2/) with minor basalt (51.88 wt. % SiO/sub 2/) and dacite (67.81 wt. % SiO/sub 2/). The main textures exhibited by these flows are hypocrystalline, porphyritic, cummulophyric, vitrophyric and sub pilotaxitic. Large phenocrysts ( < 1 mm - 4mm) of plagioclase (An-38-58) and pyroxene are embedded in a micro to criptocrystalline groundmass having the same minerals with devitrified volcanic glass. The phenocrysts groundmass ratio is 35:65. Apatite, hematite, ilmenite and magnetite are common accessory mineral. Petrochemical studies reveal that these volcanics belong to medium to low K-calc- alkaline series. They have low Mg = (39-50), and higher FeO (total)/MgO (1.81-2.78) ratios, which suggest that parent magma of these rock suites was not directly derived from a partially melted mantle source but fractionated in

  4. Melt fractionation during pāhoehoe flow lobe emplacement, Heiðin há lava, SW Iceland

    Science.gov (United States)

    Nikkola, Paavo; Thordarson, Thorvaldur

    2016-04-01

    Melt segregations are vesicular formations of evolved melts generated by in situ closed system fractionation of a host lava. Although they are common in p¯a hoehoe flows, pillow basalts, lava lakes and shallow intrusions, their development is not fully understood. In addition, as the melt segregations are often confined to the scale of a single outcrop, they can be seen as an easily approachable analogue to the crystal-melt fractionation processes generating evolved magmas in the Earth's crust. An eight meter high p¯a hoehoe flow lobe in Heiðin há lava, SW Iceland, was sampled in order to understand the development of the elaborate segregation structures within. The sampled outcrop is a cross-section of a typical Icelandic p¯a hoehoe lava, belonging to a large post-glacial lava shield on Reykjanes Peninsula. The lava core is striped by melt segregations in the form of vertical vesicle cylinders 1-7 cm in diameter, which feed horizontal vesicle sheets higher up in the upper lava core and lower crust. Whole-rock major and trace element results for the 20 samples from the Heiðin há lava reveal a homogenous olivine tholeiitic host lava intersected by segregations of varying composition. The vesicle cylinders in the flow core are only mildly differentiated, but the segregated melt evolves upwards to horizontal vesicle sheets, from which some have experienced an additional enrichment possibly by a gas filter-pressing of the residual liquid in the horizontal sheet. The most evolved segregations are extremely Fe-rich with 19.5 % FeOtot in comparison to the average of 12.4 % FeOtot in the host lava. Consequently, MgO drops from the host lava's 9.5 % to 4.4 % in the segregation sheets. In addition, segregations are enriched by a factor of ˜2-2.5 in TiO2, K2O, P2O5 and incompatible elements Zr, Nb, Y and V. As a consequence of the closed system behavior, geochemical trends are evident between the host lava, vesicle cylinders, and vesicle sheets of different types.

  5. Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation

    Science.gov (United States)

    Lu, Zhiming; Masterlark, Timothy; Dzurisin, D.

    2005-01-01

    Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study transient deformation of the volcano before, during, and after the 1997 eruption. Point source models suggest that a magma reservoir at a depth of 3.2 km below sea level, located beneath the center of the caldera and about 5 km northeast of the 1997 vent, is responsible for observed volcano-wide deformation. The preeruption uplift rate decreased from about 10 cm yr-1 during 1992-1993 to 2 ??? 3 cm yr-1 during 1993-1995 and then to about -1 ??? -2 cm yr-1 during 1995-1996. The posteruption inflation rate generally decreased with time during 1997-2001, but increased significantly during 2001-2003. By the summer of 2003, 30 ??? 60% of the magma volume lost from the reservoir in the 1997 eruption had been replenished. Interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows, most likely due to thermal contraction. Interferograms for periods after the eruption suggest at least four distinct deformation processes: (1) volcano-wide inflation due to replenishment of the shallow magma reservoir, (2) subsidence of the 1997 lava flows, most likely due to thermal contraction, (3) deformation of the 1958 lava flows due to loading by the 1997 flows, and (4) continuing subsidence of 1958 lava flows buried beneath 1997 flows. Our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes.

  6. Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

    Science.gov (United States)

    Kuntz, Mel A.; Spiker, Elliott C.; Rubin, Meyer; Champion, Duane E.; Lefebvre, Richard H.

    1986-03-01

    Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222± 100), Wapi (2270 ± 50), Hells Half Acre (5200 ± 150), Shoshone (10,130 ± 350), North Robbers and South Robbers (11.980 ± 300), and Cerro Grande (13,380 ± 350).

  7. Geology of the Tyrrhenus Mons Lava Flow Field, Mars

    Science.gov (United States)

    Crown, David A.; Mest, Scott C.

    2014-11-01

    The ancient, eroded Martian volcano Tyrrhenus Mons exhibits a central caldera complex, layered flank deposits dissected by radial valleys, and a 1000+ km-long flow field extending to the southwest toward Hellas Planitia. Past studies suggested an early phase of volcanism dominated by large explosive eruptions followed by subsequent effusive activity at the summit and to the southwest. As part of a new geologic mapping study of northeast Hellas, we are examining the volcanic landforms and geologic evolution of the Tyrrhenus Mons flow field, including the timing and nature of fluvial activity and effects on volcanic units. New digital geologic mapping incorporates THEMIS IR (100 m/pixel) and CTX (5 m/pixel) images as well as constraints from MOLA topography.Mapping results to-date include delineation of the boundaries of the flow field, identification and mapping of volcanic and erosional channels within the flow field, and mapping and analysis of lava flow lobes. THEMIS IR and CTX images allow improved discrimination of the numerous flow lobes that are observed in the flow field, including refinement of the margins of previously known flows and identification of additional and smaller lobes. A prominent sinuous rille extending from Tyrrhenus Mons’ summit caldera is a major feature that supplied lava to the flow field. Smaller volcanic channels are common throughout the flow field; some occur in segments along crests of local topographic highs and may delineate lava tubes. In addition to volcanic channels, the flow field surface is characterized by several types of erosional channels, including wide troughs with scour marks, elongate sinuous channels, and discontinuous chains of elongate pits and troughs. High-resolution images reveal the widespread and significant effects of fluvial activity in the region, and further mapping studies will examine spatial and temporal interactions between volcanism and fluvial processes.

  8. MOLA Constraints on Lava Flow Rheologies

    Science.gov (United States)

    Glaze, L. S.; Stofan, E. R.; Baloga, S. M.; McColley, S.; Sakimoto, S.; Mitchell, D.

    2002-01-01

    MOLA data allow us to distinguish the nature of a viscosity change in the presence of degassing. For a 35 km flow in Elysium we conclude that the viscosity increased exponentially at least 50 times, compared to only 10 times if no degassing occurs. Additional information is contained in the original extended abstract.

  9. Modelling lava flows by Cellular Nonlinear Networks (CNN: preliminary results

    Directory of Open Access Journals (Sweden)

    C. Del Negro

    2005-01-01

    Full Text Available The forecasting of lava flow paths is a complex problem in which temperature, rheology and flux-rate all vary with space and time. The problem is more difficult to solve when lava runs down a real topography, considering that the relations between characteristic parameters of flow are typically nonlinear. An alternative approach to this problem that does not use standard differential equation methods is Cellular Nonlinear Networks (CNNs. The CNN paradigm is a natural and flexible framework for describing locally interconnected, simple, dynamic systems that have a lattice-like structure. They consist of arrays of essentially simple, nonlinearly coupled dynamic circuits containing linear and non-linear elements able to process large amounts of information in real time. Two different approaches have been implemented in simulating some lava flows. Firstly, a typical technique of the CNNs to analyze spatio-temporal phenomena (as Autowaves in 2-D and in 3-D has been utilized. Secondly, the CNNs have been used as solvers of partial differential equations of the Navier-Stokes treatment of Newtonian flow.

  10. Numerical simulation of lava flow using a GPU SPH model

    Directory of Open Access Journals (Sweden)

    Eugenio Rustico

    2011-12-01

    Full Text Available A smoothed particle hydrodynamics (SPH method for lava-flow modeling was implemented on a graphical processing unit (GPU using the compute unified device architecture (CUDA developed by NVIDIA. This resulted in speed-ups of up to two orders of magnitude. The three-dimensional model can simulate lava flow on a real topography with free-surface, non-Newtonian fluids, and with phase change. The entire SPH code has three main components, neighbor list construction, force computation, and integration of the equation of motion, and it is computed on the GPU, fully exploiting the computational power. The simulation speed achieved is one to two orders of magnitude faster than the equivalent central processing unit (CPU code. This GPU implementation of SPH allows high resolution SPH modeling in hours and days, rather than in weeks and months, on inexpensive and readily available hardware.

  11. A Comprehensive Paleomagnetic Study on Radiometrically Dated Late Cretaceous Lava Flows from Jalisco Block (Western Mexico)

    Science.gov (United States)

    Rosas-Elguera, J.; Cervantes, M. A.; Gogichaishvili, A.; Morales, J.

    2014-12-01

    Western and central Mexico is segmented by several regional structural systems that bound crustal blocs. Paleomagnetic data from the western and eastern Trans Mexican Volcanic Belt as well as from adjacent terrains are still scarce which limits analyses of the both local and regional-scale tectonic evolution. A combined radiometric and paleomagnetic survey performed on late Cretaceous lava flows demonstrate that vertical-axis rotations characterize the paleotectonic evolution of western-central Mexico. The characteristic paleomagnetic directions determined in this study may be considered of primary (thermoremanent) origin. Multicomponent demagnetization plots were observed in some cases. In general, the polarity obtained for the flows studied is consistent with their stratigraphic position and with the radiometric age determination. The mean inclination is in reasonably good agreement with the expected inclination for the Late Creataceous, as derived from reference poles given by Besse and Courtillot (2002) for the North American craton. The declination, however, is quite different from that expected, which suggests a possible counterclockwise tectonic rotation of at least 12º. Aceptable palointensity determinations were obtained for only eleven individual samples from two basaltic lava flows. The mean virtual dipole moment (VDM) obtained in this study is 4.2 ± 1.2 _ 1022 A m2, which is almost half than the present geomagnetic field strength.

  12. Detection of high-silica lava flows and lava morphology at the Alarcon Rise, Gulf of California, Mexico using automated classification of the morphological-compositional relationship in AUV multibeam bathymetry and sonar backscatter

    Science.gov (United States)

    Maschmeyer, C.; White, S. M.; Dreyer, B. M.; Clague, D. A.

    2015-12-01

    An automated compositional classification by adaptive neuro-fuzzy inference system (ANFIS) was developed to study volcanic processes that create high-silica lava at oceanic ridges. The objective of this research is to determine the existence of a relationship between lava morphology and composition. Researchers from the Monterey Bay Aquarium Research Institute (MBARI) recorded morphologic observations and collected samples for geochemical analysis during ROV dives at the Alarcon Rise in 2012 and 2015. The Alarcon Rise is a unique spreading ridge environment where composition ranges from basaltic to rhyolitic, making it an ideal location to examine the compositional-morphologic relationship of lava flows. Preliminary interpretation of field data indicates that high-silica lavas are typically associated with 3-5 m, blocky pillows at the heavily faulted north end of the Alarcon. Visual analysis of multibeam bathymetry and side-scan sonar backscatter from MBARI AUV D. Allen B. and gridded at 1 m suggests that lava flow morphology (pillow, lobate, sheet) can be distinguished by seafloor roughness. Bathymetric products used by ANFIS to quantify the morphologic-compositional relationship were slope, aspect, and bathymetric position index (BPI, a measure of local height relative to the adjacent terrain). Sonar backscatter intensity is influenced by surface roughness and previously used to distinguish lava morphology. Gray-level co-occurrence matrices (GLCM) were applied to backscatter to create edge-detection filters that recognized faults and fissures. Input data are slope, aspect, bathymetric value, BPI at 100 m scale, BPI at 500 m scale, backscatter intensity, and the first principle component of backscatter GLCM. After lava morphology was classified on the Alarcon Rise map, another classification was completed to detect locations of high-silica lava. Application of an expert classifier like ANFIS to distinguish lava composition may become an important tool in oceanic

  13. Extensive young dacite lava flows between boninite and BABB in a backarc setting: NE Lau Basin

    Science.gov (United States)

    Embley, R. W.; Rubin, K. H.

    2015-12-01

    Several hundred square kilometers of young dacite lava flows mapped by their high acoustic backscatter erupted in several batches in proximity to boninite and back-arc basin basalt (BABB) in the NE Lau Basin, the world's fastest opening back-arc region and a site proposed as a modern analogue in some ophiolite models. Where sampled, these lavas are aphyric, glassy dacites and are not associated with andesite extrusives (commonly observed elsewhere). Several flow fields occur on the flank of the large silicic Niuatahi seamount. Two of the largest lava fields and several smaller ones (~220 km2) erupted as far as 60 km north of Niuatahi. Their occurrence is likely controlled by crustal fractures from the long-term extension in this rear-arc region. Determining thickness of these flows is problematic, but relief of 30-100 m on flow fronts and in collapsed areas yields volume estimates as high as ~7-18 km3 for the northern group. The mean silica content of the largest and best sampled dacite flow field (LL-B) is 65.6 ±0.2%, a remarkably consistent composition for such an extensive flow (~140 km2). Camera tows show lower viscosity flow forms, including many anastomatosing pillow tubes and ropey surfaces, as well as endogenous domes, ridges and lobes (some with "crease-like" extrusion ridges, and inflated lobes with extrusion structures). An enigmatic 2 x 1.5 km, 30-m deep collapse depression could mark an eruption center for the LL-B flow field. Low viscosity flow morphologies on portions of LL-B and a nearby smaller flow field implies high effusion rates during some phases of the eruption(s), which in turn implies some combination of higher than normal liquidus temperature and high water content. Submarine dacite flows have been described in ancient sequences from the Archaean through the Miocene but this is the first modern occurrence of large volume submarine dacite flows. The volume of these young dacite flows implies the presence of large differentiated melt

  14. Volcanic eruptions on Io: Heat flow, resurfacing, and lava composition

    Science.gov (United States)

    Blaney, Diana L.; Johnson, Torrence V.; Matson, Dennis L.; Veeder, Glenn J.

    1995-01-01

    We model an infrared outburst on Io as being due to a large, erupting lava flow which increased its area at a rate of 1.5 x 10(exp 5)/sq m and cooled from 1225 to 555 K over the 2.583-hr period of observation. The inferred effusion rate of 3 x 10(exp 5) cu m/sec for this eruption is very high, but is not unprece- dented on the Earth and is similar to the high eruption rates suggested for early lunar volcanism. Eruptions occur approxi- mately 6% of the time on Io. These eruptions provide ample resurfacing to explain Io's lack of impact craters. We suggest that the large total radiometric heat flow, 10(exp 14) W, and the size and temperature distribution of the thermal anomalies (McEwen et al. 1992; Veeder et al. 1994) can be accounted for by a series of silicate lava flows in various stages of cooling. We propose that the whole suite of Io's currently observed thermal anomalies was produced by multiple, high-eruptive-rate silicate flows within the past century.

  15. Characterization of the natural thermoluminescence emission of lava flows

    OpenAIRE

    Correcher, Virgilio; Garralón, A.; Pozuelo, M.; García Guinea, Javier

    2008-01-01

    We herein report on the natural thermoluminescence (TL) emission of eight lava flows from different volcanic regions that could potentialIy be useful for dating purposes. AH the samples were characterized by means of: (i) x-ray diffraction to determine the components that act as main contributors of the TL response and (ii) gamma-ray spectrometry to identify the natural radionuclides that induce the TL glow curve. In this sense, plagioclases (Na-Ca feldspars) are the most cornmon mineral dete...

  16. 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.

  17. Enriched continental flood basalts from depleted mantle melts: modeling the lithospheric contamination of Karoo lavas from Antarctica

    Science.gov (United States)

    Heinonen, Jussi S.; Luttinen, Arto V.; Bohrson, Wendy A.

    2016-01-01

    Continental flood basalts (CFBs) represent large-scale melting events in the Earth's upper mantle and show considerable geochemical heterogeneity that is typically linked to substantial contribution from underlying continental lithosphere. Large-scale partial melting of the cold subcontinental lithospheric mantle and the large amounts of crustal contamination suggested by traditional binary mixing or assimilation-fractional crystallization models are difficult to reconcile with the thermal and compositional characteristics of continental lithosphere, however. The well-exposed CFBs of Vestfjella, western Dronning Maud Land, Antarctica, belong to the Jurassic Karoo large igneous province and provide a prime locality to quantify mass contributions of lithospheric and sublithospheric sources for two reasons: (1) recently discovered CFB dikes show isotopic characteristics akin to mid-ocean ridge basalts, and thus help to constrain asthenospheric parental melt compositions and (2) the well-exposed basaltic lavas have been divided into four different geochemical magma types that exhibit considerable trace element and radiogenic isotope heterogeneity (e.g., initial ɛ Nd from -16 to +2 at 180 Ma). We simulate the geochemical evolution of Vestfjella CFBs using (1) energy-constrained assimilation-fractional crystallization equations that account for heating and partial melting of crustal wall rock and (2) assimilation-fractional crystallization equations for lithospheric mantle contamination by using highly alkaline continental volcanic rocks (i.e., partial melts of mantle lithosphere) as contaminants. Calculations indicate that the different magma types can be produced by just minor (1-15 wt%) contamination of asthenospheric parental magmas by melts from variable lithospheric reservoirs. Our models imply that the role of continental lithosphere as a CFB source component or contaminant may have been overestimated in many cases. Thus, CFBs may represent major juvenile crustal

  18. DOWNFLOW code and LIDAR technology for lava flow analysis and hazard assessment at Mount Etna

    Directory of Open Access Journals (Sweden)

    Alessandro Fornaciai

    2011-12-01

    Full Text Available The use of a lava-flow simulation (DOWNFLOW probabilistic code and airborne light detection and ranging (LIDAR technology are combined to analyze the emplacement of compound lava flow fields at Mount Etna (Sicily, Italy. The goal was to assess the hazard posed by lava flows. The LIDAR-derived time series acquired during the 2006 Mount Etna eruption records the changing topography of an active lava-flow field. These short-time-interval, high-resolution topographic surveys provide a detailed quantitative picture of the topographic changes. The results highlight how the flow field evolves as a number of narrow (5-15 m wide disjointed flow units that are fed simultaneously by uneven lava pulses that advance within formed channels. These flow units have widely ranging advance velocities (3-90 m/h. Overflows, bifurcations and braiding are also clearly displayed. In such a complex scenario, the suitability of deterministic codes for lava-flow simulation can be hampered by the fundamental difficulty of measuring the flow parameters (e.g. the lava discharge rate, or the lava viscosity of a single flow unit. However, the DOWNFLOW probabilistic code approaches this point statistically and needs no direct knowledge of flow parameters. DOWNFLOW intrinsically accounts for complexities and perturbations of lava flows by randomly varying the pre-eruption topography. This DOWNFLOW code is systematically applied here over Mount Etna, to derive a lava-flow hazard map based on: (i the topography of the volcano; (ii the probability density function for vent opening; and (iii a law for the expected lava-flow length for all of the computational vents considered. Changes in the hazard due to the recent morphological evolution of Mount Etna have also been addressed.

  19. NVP melt/magma viscosity: insight on Mercury lava flows

    Science.gov (United States)

    Rossi, Stefano; Morgavi, Daniele; Namur, Olivier; Vetere, Francesco; Perugini, Diego; Mancinelli, Paolo; Pauselli, Cristina

    2016-04-01

    After more than four years of orbiting Mercury, NASA's MESSENGER spacecraft came to an end in late April 2015. MESSENGER has provided many new and surprising results. This session will again highlight the latest results on Mercury based on MESSENGER observations or updated modelling. The session will further address instrument calibration and science performance both retrospective on MESSENGER and on the ESA/JAXA BepiColombo mission. Papers covering additional themes related to Mercury are also welcomed. Please be aware that this session will be held as a PICO session. This will allow an intensive exchange of expertise and experience between the individual instruments and mission. NVP melt/magma viscosity: insight on Mercury lava flows S. Rossi1, D. Morgavi1, O. Namur2, D. Perugini1, F.Vetere1, P. Mancinelli1 and C. Pauselli1 1 Dipartimento di Fisica e Geologia, Università di Perugia, piazza Università 1, 06123 Perugia, Italy 2 Uni Hannover Institut für Mineralogie, Leibniz Universität Hannover, Callinstraβe 3, 30167 Hannover, Germany In this contribution we report new measurements of viscosity of synthetic komatitic melts, used the behaviour of silicate melts erupted at the surface of Mercury. Composition of Mercurian surface magmas was calculated using the most recent maps produced from MESSENGER XRS data (Weider et al., 2015). We focused on the northern hemisphere (Northern Volcanic Province, NVP, the largest lava flow on Mercury and possibly in the Solar System) for which the spatial resolution of MESSENGER measurements is high and individual maps of Mg/Si, Ca/Si, Al/Si and S/Si were combined. The experimental starting material contains high Na2O content (≈7 wt.%) that strongly influences viscosity. High temperature viscosity measurements were carried out at 1 atm using a concentric cylinder apparatus equipped with an Anton Paar RheolabQC viscometer head at the Department of Physics and Geology (PVRG_lab) at the University of Perugia (Perugia, Italy

  20. Emplacement conditions of the 1256 AD Al-Madinah lava flow field in Harrat Rahat, Kingdom of Saudi Arabia - Insights from surface morphology and lava flow simulations

    Science.gov (United States)

    Kereszturi, Gábor; Németh, Károly; Moufti, Mohammed R.; Cappello, Annalisa; Murcia, Hugo; Ganci, Gaetana; Del Negro, Ciro; Procter, Jonathan; Zahran, Hani Mahmoud Ali

    2016-01-01

    Lava flow hazard modelling requires detailed geological mapping, and a good understanding of emplacement settings and the processes involved in the formation of lava flows. Harrat Rahat, Kingdom of Saudi Arabia, is a large volcanic field, comprising about 1000 predominantly small-volume volcanoes most of which have emitted lava flows of various lengths. A few eruptions took place in this area during the Holocene, and they were located in the northern extreme of the Harrat Rahat, a close proximity to critical infrastructure and population living in Al-Madinah City. In the present study, we combined field work, high resolution digital topography and morphometric analysis to infer the emplacement history of the last historical event in the region represented by the 1256 AD Al-Madinah lava flow field. These data were also used to simulate 1256 AD-type lava flows in the Harrat Rahat by the MAGFLOW lava flow emplacement model, which is able to relate the flow evolution to eruption conditions. The 1256 AD lava flow field extent was mapped at a scale of 1:1000 from a high resolution (0.5 m) Light Detection And Ranging (LiDAR) Digital Terrain Model (DTM), aerial photos with field support. The bulk volume of the lava flow field was estimated at 0.4 km3, while the source volume represented by seven scoria cone was estimated at 0.023 km3. The lava flow covered an area of 60 km2 and reached a maximum length of 23.4 km. The lava flow field comprises about 20.9% of pāhoehoe, 73.8% of 'a'ā, and 5.3% of late-stage outbreaks. Our field observation, also suggests that the lava flows of the Harrat Rahat region are mainly core-dominated and that they formed large lava flow fields by amalgamation of many single channels. These channels mitigated downslope by topography-lava flow and channel-channel interactions, highlighting this typical process that needs to be considered in the volcanic hazard assessment in the region. A series of numerical lava flow simulations was carried out

  1. Possible lava tube system in a hummocky lava flow at Daund, western Deccan Volcanic Province, India

    Indian Academy of Sciences (India)

    Raymond A Duraiswami; Ninad R Bondre; Gauri Dole

    2004-12-01

    A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.

  2. 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.

  3. SHARAD Constrains on Lava Flow Properties at Southeastern Utopia Planitia

    Science.gov (United States)

    Nunes, D. C.

    2012-12-01

    with the middle to upper range of permittivities for basalt, and, therefore, porosity does not dominate the volume of the lobate flow, and supports the morphologic interpretation of the flow and geologic history of this area offered by Russell and Head [2003] and Tanaka et al. [2003]. Russell P. S. and Head J. W. [2003] JGR, 108, 5064. Tanaka K. L. et al. [2005], USGS Sci. Invest. Maps, 2888. Werner S. C. et al. [2011], PSS, 59, 1143-1165.

  4. Incorporation of seawater into mid-ocean ridge lava flows during emplacement

    Science.gov (United States)

    Soule, S. Adam; Fornari, Daniel J.; Perfit, Michael R.; Ridley, W. Ian; Reed, Mark H.; Cann, Johnson R.

    2006-12-01

    Evidence for the interaction between seawater and lava during emplacement on the deep seafloor can be observed in solidified flows at a variety of scales including rapid quenching of their outer crusts and the formation of lava pillars through the body of the flow. Recently, an additional interaction, incorporation of heated seawater (vapor) into the body of a flow, has been proposed. Large voids and vesicles beneath the surface crusts of mid-ocean ridge crest lobate and sheet lava flows and lava drips found within those cavities have been cited as evidence for this interaction. The voids resulting from this interaction contribute to the high porosity of the shallow ocean crust and play an important role in crustal permeability and hydrothermal circulation at mid-ocean ridges, and thus it is important to understand their origin. We analyze lava samples from the fast-spreading East Pacific Rise and intermediate-spreading Galapagos Spreading Center to characterize this process, identify the source of the vapor, and investigate the implications this would have on submarine lava flow dynamics. We find that lava samples that have interacted with a vapor have a zone of increased vesicularity on the underside of the lava crust and a coating of precipitate minerals ( i.e., crystal fringe) that are distinct in form and composition from those crystallized from the melt. We use thermochemical modeling to simulate the reaction between the lava and a vapor and find that only with seawater can we reproduce the phase assemblage we observe within the crystal fringes present in the samples. Model results suggest that large-scale contamination of the lava by mass exchange with the vapor is unlikely, but we observe local enrichment of the lava in Cl resulting from the incorporation of a brine phase separated from the seawater. We suggest that high eruption rates are necessary for seawater incorporation to occur, but the mechanism by which seawater enters the flow has yet to be

  5. New insights into eruptive activity and lava flow hazard at Nyamulagira volcano, D.R.C., from a new GIS-based lava flow map

    Science.gov (United States)

    Smets, B.; Kervyn, M.; Kervyn, F.; D'Oreye, N.; Wauthier, C.

    2010-12-01

    Nyamulagira, located in the western branch of the East African Rift (EAR), is Africa’s most active volcano with one eruption every 2 - 4 years. A map of Nyamulagira lava flows was produced during the 1960’s by Thonnard et al. (1965). This map, which results from the mosaicking of several aerial photographs, contains locally some geographic inaccuracies. The photo-interpretation also led in places to the discrimination of lava units not corresponding to any flow boundaries in the field. Finally, 19 eruptions occurred since this first edition, which causes it to be outdated and of limited use to document the recent eruptive history. Recently, Smets et al. (2010) have produced a new map of lava flows using a combination of optical and radar satellite imagery. This map is GIS-based and can be quickly updated during/after each eruption. Using the new lava flow map of Nyamulagira and a compilation of bibliographic/field information of the last 31 eruptions, the evolution of eruptive activity since the early 1900’s was reconstructed and the volume of erupted lava estimated for each eruption from 1938 to 2010. The spatio-temporal evolution of eruptive activity suggests a strong control from the rift tectonics but also from inherited basement structures on the location, the fissure orientation and the relative lava volume for the successive eruptions. The time lapse after each eruption is strongly correlated with the erupted volume of lava. The 1938-40 eruption is a key event in the volcano recent history, as the corresponding caldera collapse led to an increase of flank eruptions. Nyamulagira flank eruptions systematically destroy large areas of the protected forest of the Virunga National Park, a UNESCO World Heritage in danger since 1994. The lava flows from distal eruptions or from exceptionally high effusion rate or volume events also threaten local population, mainly south of the main edifice near Lake Kivu.

  6. Determination of thermal/dynamic characteristics of lava flow from surface thermal measurements

    Science.gov (United States)

    Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander; Tsepelev, Igor; Kovtunov, Dmitry

    2016-04-01

    Rapid development of ground based thermal cameras, drones and satellite data allows getting repeated thermal images of the surface of the lava flow. Available instrumentation allows getting a large amount of data during a single lava flow eruption. These data require development of appropriate quantitative techniques to link subsurface dynamics with observations. We present a new approach to assimilation of thermal measurements at lava's surface to the bottom of the lava flow to determine lava's thermal and dynamic characteristics. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. Using an adjoint method we develop a numerical approach to the mathematical problem based on the determination of the missing boundary condition and lava flow characteristics. Numerical results show that in the case of smooth input data lava temperature and velocity can be determined with a high accuracy. A noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. The proposed approach to assimilate measured data brings an opportunity to estimate thermal budget of the lava flow.

  7. The identification of basalt flow features from borehole television logs

    International Nuclear Information System (INIS)

    This study investigated whether basalt features found in outcrops and cores could be identified in open borehole walls by the use of the borehole television camera. To answer this question detailed outcrop surveys were carried out in several locations in the Snake River Plain, Idaho. A similar type of survey was also done on several locations in the Snake River Plain, Idaho. A similar type of survey was also done on several cores from the Idaho National Engineering Laboratory, southeast Idaho. Borehole television logs were viewed to find similar basalt features that were noted in cores and outcrops. From these studies it was found that basalt features can be identified in open borehole walls by the borehole television camera. The basalt flows can be divided into four zones: an upper vesicular zone; a columnar zone; a central zone; and a lower vesicular zone. The upper vesicular zone can be further subdivided into four subzones: an upper vesicular subzone; a transitional subzone; a lower vesicular subzone; and a bubble train subzone. Some specific features found in the borehole TV logs were: bubble-trains, vesicle plumes, borehole extensions, and pipe vesicles. The overall distinctions for the zones were based on the vesicularity. An overall pattern of vesicles was found to be a progression of small numerous vesicles at the top of a flow which increase in size, but decrease in number, towards the center of the flow. The opposite is true starting at the bottom of the basalt flow where small vesicles are numerous, but increase in size while decreasing in number towards the center part of the flow. 14 refs., 3 figs

  8. Lava flow identification and ageing by means of LiDAR intensity: the Mt. Etna case

    OpenAIRE

    Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Pareschi, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Favalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Isola, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Tarquini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia

    2006-01-01

    An application of LiDAR (Light Detection and Ranging) intensity for the identification and mapping of different lava flows from the Mt. Etna (Italy) active volcano is described. In September 2004 an airborne LiDAR survey was flown over summit sectors of Mt. Etna. The information derived from LiDAR intensity values was used to compare the lava flows with respect to their age of emplacement. Analysed lava flows vary in age between those dating prior to AD 1610 and those active du...

  9. Fractionation of the platinum-group elments and Re during crystallization of basalt in Kilauea Iki Lava Lake, Hawaii

    Science.gov (United States)

    Pitcher, L.; Helz, R.T.; Walker, R.J.; Piccoli, P.

    2009-01-01

    Kilauea Iki lava lake formed during the 1959 summit eruption of Kilauea Volcano, then crystallized and differentiated over a period of 35??years. It offers an opportunity to evaluate the fractionation behavior of trace elements in a uniquely well-documented basaltic system. A suite of 14 core samples recovered from 1967 to 1981 has been analyzed for 5 platinum-group elements (PGE: Ir, Os, Ru, Pt, Pd), plus Re. These samples have MgO ranging from 2.4 to 26.9??wt.%, with temperatures prior to quench ranging from 1140????C to ambient (110????C). Five eruption samples were also analyzed. Osmium and Ru concentrations vary by nearly four orders of magnitude (0.0006-1.40??ppb for Os and 0.0006-2.01??ppb for Ru) and are positively correlated with MgO content. These elements behaved compatibly during crystallization, mostly likely being concentrated in trace phases (alloy or sulfide) present in olivine phenocrysts or included chromite. Iridium also correlates positively with MgO, although less strongly than Os and Ru. The somewhat poorer correlation for Ir, compared with Os and Ru, may reflect variable loss of Ir as volatile IrF6 in some of the most magnesian samples. Rhenium is negatively correlated with MgO, behaving as an incompatible trace element. Its behavior in the lava lake is complicated by apparent volatile loss of Re, as suggested by a decrease in Re concentration with time of quenching for lake samples vs. eruption samples. Platinum and Pd concentrations are negatively, albeit weakly, correlated with MgO, so these elements were modestly incompatible during crystallization of the major silicate phases. Palladium contents peaked before precipitation of immiscible sulfide liquid, however, and decline sharply in the most differentiated samples. In contrast, Pt appears to have been unaffected by sulfide precipitation. Microprobe data confirm that Pd entered the sulfide liquid before Re, and that Pt is not strongly chalcophile in this system. Occasional high Pt values

  10. Basalt features observed in outcrops, cores, borehole video imagery and geophysical logs, and basalt hydrogeologic study at the Idaho National Engineering Laboratory, Eastern Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Bennecke, W.M.

    1996-10-01

    A study was undertaken to examine permeable zones identified in boreholes open to the underlying basalt and to describe the vertical cross flows present in the boreholes. To understand the permeable zones in the boreholes detailed descriptions and measurements of three outcrops in the Snake River Plain, three cores at the Idaho Chemical Processing Plant (ICPP) at the INEL, and over fifty borehole TV logs from the INEL were carried out. Based on the observations made on the three outcrops an idealized basalt lava flow model was generated that used a set of nomenclature that would be standard for the basalt lava flows studied. An upper vesicular zone, a sometimes absent columnar zone, central zone, and lower vesicular zone make up the basalt lava flow model. The overall distinction between the different zones are based on the vesicle shape size, vesicularity, and fractures present. The results of the studies also indicated that the basalt lava flows at the INEL are distal to medial facies pahoehoe lava flows with close fitting contacts. The most permeable zones identified in these basalts are fractured vesiculated portions of the top of the lava flow, the columnar areas, and basalt-flow contacts in order of importance. This was determined from impeller flowmeter logging at the INEL. Having this information a detailed stratigraphy of individual basalt lava flows and the corresponding permeable units were generated. From this it was concluded that groundwater flow at the ICPP prefers to travel along thin basalt lava flows or flow-units. Flow direction and velocity of intrawell flows detected by flowmeter is controlled by a nearby pumping well.

  11. Basalt features observed in outcrops, cores, borehole video imagery and geophysical logs, and basalt hydrogeologic study at the Idaho National Engineering Laboratory, Eastern Idaho

    International Nuclear Information System (INIS)

    A study was undertaken to examine permeable zones identified in boreholes open to the underlying basalt and to describe the vertical cross flows present in the boreholes. To understand the permeable zones in the boreholes detailed descriptions and measurements of three outcrops in the Snake River Plain, three cores at the Idaho Chemical Processing Plant (ICPP) at the INEL, and over fifty borehole TV logs from the INEL were carried out. Based on the observations made on the three outcrops an idealized basalt lava flow model was generated that used a set of nomenclature that would be standard for the basalt lava flows studied. An upper vesicular zone, a sometimes absent columnar zone, central zone, and lower vesicular zone make up the basalt lava flow model. The overall distinction between the different zones are based on the vesicle shape size, vesicularity, and fractures present. The results of the studies also indicated that the basalt lava flows at the INEL are distal to medial facies pahoehoe lava flows with close fitting contacts. The most permeable zones identified in these basalts are fractured vesiculated portions of the top of the lava flow, the columnar areas, and basalt-flow contacts in order of importance. This was determined from impeller flowmeter logging at the INEL. Having this information a detailed stratigraphy of individual basalt lava flows and the corresponding permeable units were generated. From this it was concluded that groundwater flow at the ICPP prefers to travel along thin basalt lava flows or flow-units. Flow direction and velocity of intrawell flows detected by flowmeter is controlled by a nearby pumping well

  12. An experimental study of the surface thermal signature of hot subaerial isoviscous gravity currents: Implications for thermal monitoring of lava flows and domes

    Science.gov (United States)

    Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

    2012-02-01

    Management of eruptions requires a knowledge of lava effusion rates, for which a safe thermal proxy is often used. However, this thermal proxy does not take into account the flow dynamics and is basically time-independent. In order to establish a more robust framework that can link eruption rates and surface thermal signals of lavas measured remotely, we investigate the spreading of a hot, isoviscous, axisymmetric subaerial gravity current injected at constant rate from a point source onto a horizontal substrate. We performed laboratory experiments and found that the surface thermal structure became steady after an initial transient. We develop a theoretical model for a spreading fluid cooled by radiation and convection at its surface that also predicts a steady thermal regime. We show that, despite the model's simplicity relative to lava flows, it yields the correct order of magnitude for the effusion rate required to produce the radiant flux measured on natural lava flows. For typical thermal lava properties and an effusion rate between 0.1 and 10 m3 s-1, the model predicts a steady radiated heat flux ranging from 108 to 1010 W. The assessed effusion rate varies quasi-linearly with the steady heat flux, with much weaker dependence on the flow viscosity. This relationship is valid only after a transient time which scales as the diffusive time, ranging from a few days for small basaltic flows to several years for lava domes. The thermal proxy appears thus less reliable to follow sharp variations of the effusion rate during an eruption.

  13. Extending Interfield Analysis of Tumuli on Terrestrial Inflated Lava Flows to Mars

    Science.gov (United States)

    Sangha, S. S.; Diniega, S.; Smrekar, S. E.

    2013-12-01

    In our study, we identify and measure tumuli - small-scale, positive topographic features (~10m in width) - on both terrestrial and Martian inflated lava flows. Inflated lava flows are aptly named for their domed, rigid upper crust that insulates and is lifted by a fluid interior. Locally high magmatic pressures arising from the transport of lava through a network of subsurface lava pathways within these flows can cause a section of the upper crust to tilt upwards and outwards on opposite sides of an axial fracture and produce a tumulus. Thus, tumuli can be used as records of a flow's interior structure. We aim to quantitatively investigate hypothesized relationships between tumuli morphometrics (such as tumuli sizes, shapes, and orientations) and larger-scale lava flow emplacement structure (flow directions, placement of flow boundaries, and scale of the flow). Measurements of >2000 tumuli on six diverse terrestrial fields and also >2000 tumuli on seven Martian fields within the Elysium Planitia region suggest that: (1) Tumuli form predominantly over very low slopes (direction, (3) Tumuli mean cross-sectional area does not change while tumuli density in the field increases further from the source vents, due to increasing bifurcations in lava pathways within the distal portions of the flow, and (4) Tumuli elongation (length/width ratio) decreases away from the source vent. Furthermore, basic tumuli dimensions (length, width, elongation, etc.) are strikingly similar between the planets--suggesting commonality in tumuli formation. Additionally, we have not yet found tumuli on Martian lava flows outside of very young flows within Elysium Planitia (<30 Ma). One possible explanation is that tumuli-forming lava flows only have occurred within a specific period of Martian volcanism. Alternatively, inflation features may be very susceptible to degradation and have eroded beyond recognition on older flows. Our study may thus provide information about regional or global

  14. Evidence from lava flows for complex polarity transitions: The new composite Steens Mountain reversal record

    Science.gov (United States)

    Jarboe, N.A.; Coe, R.S.; Glen, J.M.

    2011-01-01

    Geomagnetic polarity transitions may be significantly more complex than are currently depicted in many sedimentary and lava-flow records. By splicing together paleomagnetic results from earlier studies at Steens Mountain with those from three newly studied sections of Oregon Plateau flood basalts at Catlow Peak and Poker Jim Ridge 70-90 km to the southeast and west, respectively, we provide support for this interpretation with the most detailed account of a magnetic field reversal yet observed in volcanic rocks. Forty-five new distinguishable transitional (T) directions together with 30 earlier ones reveal a much more complex and detailed record of the 16.7 Ma reversed (R)-to-normal (N) polarity transition that marks the end of Chron C5Cr. Compared to the earlier R-T-N-T-N reversal record, the new record can be described as R-T-N-T-N-T-R-T-N. The composite record confirms earlier features, adds new west and up directions and an entire large N-T-R-T segment to the path, and fills in directions on the path between earlier directional jumps. Persistent virtual geomagnetic pole (VGP) clusters and separate VGPs have a preference for previously described longitudinal bands from transition study compilations, which suggests the presence of features at the core-mantle boundary that influence the flow of core fluid and distribution of magnetic flux. Overall the record is consistent with the generalization that VGP paths vary greatly from reversal to reversal and depend on the location of the observer. Rates of secular variation confirm that the flows comprising these sections were erupted rapidly, with maximum rates estimated to be 85-120 m ka-1 at Catlow and 130-195 m ka-1 at Poker Jim South. Paleomagnetic poles from other studies are combined with 32 non-transitional poles found here to give a clockwise rotation of the Oregon Plateau of 11.4???? 5.6?? with respect to the younger Columbia River Basalt Group flows to the north and 14.5???? 4.6?? with respect to cratonic

  15. Retrospective validation of a lava-flow hazard map for Mount Etna volcano

    Directory of Open Access Journals (Sweden)

    Ciro Del Negro

    2011-12-01

    Full Text Available This report presents a retrospective methodology to validate a long-term hazard map related to lava-flow invasion at Mount Etna, the most active volcano in Europe. A lava-flow hazard map provides the probability that a specific point will be affected by potential destructive volcanic processes over the time period considered. We constructed this lava-flow hazard map for Mount Etna volcano through the identification of the emission regions with the highest probabilities of eruptive vents and through characterization of the event types for the numerical simulations and the computation of the eruptive probabilities. Numerical simulations of lava-flow paths were carried out using the MAGFLOW cellular automata model. To validate the methodology developed, a hazard map was built by considering only the eruptions that occurred at Mount Etna before 1981. On the basis of the probability of coverage by lava flows, the map was divided into ten classes, and two fitting scores were calculated to measure the overlap between the hazard classes and the actual shapes of the lava flows that occurred after 1981.

  16. Influence of basal slip on the propagation and cooling of lava flows

    Science.gov (United States)

    Melnik, Oleg; Vedeneeva, Elena; Utkin, Ivan

    2015-04-01

    A thin layer approximation is used for studying of viscous gravity currents on the horizontal topography from a point source. The main difference from a self-similar solution obtained in Huppert (1982) is the account for partial slip of lava on the ground surface. We assume that the slip velocity is proportional to the tangential stress in some positive power. This condition is widely used in polymer science and for the flows on superhydrophobic surfaces. This condition is also applicable for lava flows because of a large roughness of volcanic terrains and the presence of unconsolidated material (ash, lapilli). The system of Stokes equations was reduced to a non-linear parabolic differential equation. Its solution was found both numerically and by a reduction to an ODE that describes similarity solution. In the latter case there is a dependence between lava mass growth rate and the power exponent in the friction law. It was shown that the presence of basal slip allows much faster propagation of lava flows in comparison with no-slip condition at the ground surface. Analytical solutions were proved by a good comparison with fully 2D axisymmetric finite volume simulations. Based on the velocity field obtained from a thin layer theory the heat budget of a lava flow was studied for the case of constant lava viscosity. Heat equation was solved in the lava domain with no flux condition at the bottom, radiative and convective fluxes at the free surface and the influx of a fresh magma from a point source. It was shown that due to a strong difference in the velocity profile the distribution of the temperature inside the lava flow is different in the cases of no-slip and partial slip conditions.

  17. Post-emplacement cooling and contraction of lava flows: InSAR observations and thermal model for lava fields at Hekla volcano, Iceland

    Science.gov (United States)

    Wittmann, Werner; Dumont, Stephanie; Lavallee, Yan; Sigmundsson, Freysteinn

    2016-04-01

    Gradual post-emplacement subsidence of lava flows has been observed at various volcanoes, e.g. Okmok volcano in Alaska, Kilauea volcano on Hawaii and Etna volcano on Sicily. In Iceland, this effect has been observed at Krafla volcano and Hekla volcano. The latter was chosen as a case study for investigating subsidence mechanisms, specifically thermal contraction. Effects like gravitational loading, clast repacking or creeping of a hot and liquid core can contribute to subsidence of emplaced lava flows, but thermal contraction is considered being a crucial effect. The extent to which it contributes to lava flow subsidence is investigated by mapping the relative movement of emplaced lava flows and flow substrate, and modeling the observed signal. The slow vegetation in Iceland is advantageous for Interferometric Synthetic Aperture Radar (InSAR) and offers great coherence over long periods after lava emplacement, expanding beyond the outlines of lava flows. Due to this reason, InSAR observations over volcanoes in Iceland have taken place for more than 20 years. By combining InSAR tracks from ERS, Envisat and Cosmo-SkyMed satellites we gain six time series with a total of 99 interferograms. Making use of the high spatial resolution, a temporal trend of vertical lava movements was investigated over a course of over 23 years over the 1991 lava flow of Hekla volcano, Iceland. From these time series, temporal trends of accumulated subsidence and subsidence velocities were determined in line of sight of the satellites. However, the deformation signal of lava fields after emplacement is vertically dominated. Subsidence on this lava field is still ongoing and subsidence rates vary from 14.8 mm/year in 1995 to about 1.0 mm/year in 2014. Fitting a simple exponential function suggests a exponential decay constant of 5.95 years. Additionally, a one-dimensional, semi-analytical model was fitted to these data. While subsidence due to phase change is calculated analytically

  18. Sensibility analysis of VORIS lava-flow simulations: application to Nyamulagira volcano, Democratic Republic of Congo

    Directory of Open Access Journals (Sweden)

    A. M. Syavulisembo

    2015-03-01

    Full Text Available Assessment and management of volcanic risk are important scientific, economic, and political issues, especially in densely populated areas threatened by volcanoes. The Virunga area in the Democratic Republic of Congo, with over 1 million inhabitants, has to cope permanently with the threat posed by the active Nyamulagira and Nyiragongo volcanoes. During the past century, Nyamulagira erupted at intervals of 1–4 years – mostly in the form of lava flows – at least 30 times. Its summit and flank eruptions lasted for periods of a few days up to more than two years, and produced lava flows sometimes reaching distances of over 20 km from the volcano, thereby affecting very large areas and having a serious impact on the region of Virunga. In order to identify a useful tool for lava flow hazard assessment at the Goma Volcano Observatory (GVO, we tested VORIS 2.0.1 (Felpeto et al., 2007, a freely available software (http://www.gvb-csic.es based on a probabilistic model that considers topography as the main parameter controlling lava flow propagation. We tested different Digital Elevation Models (DEM – SRTM1, SRTM3, and ASTER GDEM – to analyze the sensibility of the input parameters of VORIS 2.0.1 in simulation of recent historical lava-flow for which the pre-eruption topography is known. The results obtained show that VORIS 2.0.1 is a quick, easy-to-use tool for simulating lava-flow eruptions and replicates to a high degree of accuracy the eruptions tested. In practice, these results will be used by GVO to calibrate VORIS model for lava flow path forecasting during new eruptions, hence contributing to a better volcanic crisis management.

  19. Evolution of an active lava flow field using a multitemporal LIDAR acquisition

    OpenAIRE

    Favalli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Fornaciai, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Mazzarini, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Harris, A.; Clermont Université, Université Blaise Pascal, Laboratoire Magmas et Volcans, Clermont‐Ferrand, France; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Pareschi, M. T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Tarquini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia

    2010-01-01

    Application of light detection and ranging (LIDAR) technology in volcanology has 7 developed rapidly over the past few years, being extremely useful for the generation 8 of high‐spatial‐resolution digital elevation models and for mapping eruption products. 9 However, LIDAR can also be used to yield detailed information about the dynamics of 10 lava movement, emplacement processes occuring across an active lava flow field, and the 11 volumes involved. Here we present the results...

  20. Effect of Levee and Channel Structures on Long Lava Flow Emplacement: Martian Examples from THEMIS and MOLA Data

    Science.gov (United States)

    Peitersen, M. N.; Zimbelman, J. R.; Christensen, P. R.; Bare, C.

    2003-01-01

    Long lava flows (discrete flow units with lengths exceeding 50 km) are easily identified features found on many planetary surfaces. An ongoing investigation is being conducted into the origin of these flows. Here, we limit our attention to long lava flows which show evidence of channel-like structures.

  1. Deriving Lava Eruption Temperatures on Io Using Lava Tube Skylights

    Science.gov (United States)

    Davies, A. G.; Keszthelyi, L. P.; McEwen, A. S.

    2015-12-01

    The eruption temperature of Io's silicate lavas constrains Io's interior state and composition [1] but reliably measuring this temperature remotely is a challenge that has not yet been met. Previously, we established that eruption processes that expose large areas at the highest temperatures, such as roiling lava lakes or lava fountains, are suitable targets for this task [2]. In this study we investigate the thermal emission from lava tube skylights for basaltic and ultramafic composition lavas. Tube-fed lava flows are known on Io so skylights could be common. Unlike the surfaces of lava flows, lava lakes, and lava fountains which all cool very rapidly, skylights have steady thermal emission on a scale of days to months. The thermal emission from such a target, measured at multiple visible and NIR wavelengths, can provide a highly accurate diagnostic of eruption temperature. However, the small size of skylights means that close flybys of Io are necessary, requiring a dedicated Io mission [3]. We have modelled the thermal emission spectrum for different skylight sizes, lava flow stream velocities, end-member lava compositions, and skylight radiation shape factors, determining the flow surface cooling rates. We calculate the resulting thermal emission spectrum as a function of viewing angle. From the resulting 0.7:0.9 μm ratios, we see a clear distinction between basaltic and ultramafic compositions for skylights smaller than 20 m across, even if sub-pixel. If the skylight is not resolved, observations distributed over weeks that show a stationary and steady hot spot allow the presence of a skylight to be confidently inferred. This inference allows subsequent refining of observation design to improve viewing geometry of the target. Our analysis will be further refined as accurate high-temperature short-wavelength emissivity values become available [4]. This work was performed at the Jet Propulsion Laboratory-California Institute of Technology, under contract to

  2. A hybrid model for leveed lava flows: Implications for eruption styles on Mars

    Science.gov (United States)

    Glaze, Lori S.; Baloga, Stephen M.; Garry, W. Brent; Fagents, Sarah A.; Parcheta, Carolyn

    2009-07-01

    Many channelized lava flows on the plains of Mars have substantial embanking margins and levees inferred to have been stationary while the central channel was active. Levee formation can be attributed to two end-member processes during emplacement: construction during passage of the flow front and growth along the entire length of the flow while it is active. It is shown here that the amount of lava that can be deposited by the flow front alone is limited. Estimates of the levee volume for many Mars plains flows exceed this limit and must have formed by processes that continued after the passage of the front. Experimental studies of analogous laboratory flows also indicate a combination of both modes of emplacement. A model that combines both modes of levee formation is presented, including a method for estimating volumetric flow rate, eruption duration, and viscosity. Six lava flows on the plains of the Tharsis volcanic province are used as illustrative examples. Crustal thicknesses for the six flows examined range from 9 to 23 m. Estimated emplacement times required to cool crusts of these thicknesses range from 1 year to 10 years. Corresponding viscosities are on the order of 105-106 Pa s. Effusion rates range from 25 to 840 m3 s-1 and are all within the range of terrestrial observations. Therefore, the large leveed plains flows on Mars are not dramatically different in eruption rate or lava viscosity from large terrestrial analogs.

  3. Volcanic styles at Alba Patera, Mars: Implications of lava flow morphology to the volcanic history

    Science.gov (United States)

    Schneeberger, D. M.; Pieri, D. C.

    Alba Patera presents styles of volcanism that are unique to Mars. Its very low profile, large areal extent, unusually long and voluminous lava flows, and circumferential graben make it among Mars' most interesting volcanic features. Clues to Alba's volcanic history are preserved in its morphology and stratigraphy. Understanding the relationship of lava flow morphology to emplacement processes should enable estimates of viscosity, effusion rate, and gross composition to be made. Lava flows, with dimensions considered enormous by terrestrial standards, account for a major portion of the exposed surface of Alba Patera. These flows exhibit a range of morphologies. While most previous works have focused on the planimetric characteristics, attention was drawn to the important morphological attributes, paying particular attention to what the features suggest about the emplacement process.

  4. A new tree-ring date for the ``floating island'' lava flow, Mount St. Helens, Washington

    Science.gov (United States)

    Yamaguchi, David K.; Hoblitt, Richard P.; Lawrence, Donald B.

    1990-09-01

    Anomalously narrow and missing rings in trees 12 m from Mount St. Helens' “floating island” lava flow, and synchronous growth increases in trees farther from the flow margin, are evidence that this andesitic flow was extruded between late summer 1799 and spring 1800 a.d., within a few months after the eruption of Mount St. Helens' dacitic layer T tephra. For ease of reference, we assign here an 1800 a.d. date to this flow. The new date shows that the start of Mount St. Helens' Goat Rocks eruptive period (1800 1857 a.d.) resembled the recent (1980 1986) activity in both petrochemical trends and timing. In both cases, an initial explosive eruption of dacite was quickly succeeded by the eruption of more mafic lavas; dacite lavas then reappeared during an extended concluding phase of activity. This behavior is consistent with a recently proposed fluid-dynamic model of magma withdrawal from a compositionally zoned magma chamber.

  5. The Origin of Ina: Evidence for Inflated Lava Flows on the Moon

    Science.gov (United States)

    Garry, W. B.; Robinson, M. S.; Zimbelman, J. R.; Bleacher, J. E.; Hawke, B. R.; Crumpler, L. S.; Braden, S. E.; Sato, H.

    2012-01-01

    Ina is an enigmatic volcanic feature on the Moon known for its irregularly shaped mounds, the origin of which has been debated since the Apollo Missions. Three main units are observed on the floor of the depression (2.9 km across, < or =64 m deep) located at the summit of a low-shield volcano: irregularly shaped mounds up to 20 m tall, a lower unit 1 to 5 m in relief that surrounds the mounds, and blocky material. Analyses of Lunar Reconnaissance Orbiter Camera images and topography show that features in Ina are morphologically similar to terrestrial inflated lava flows. Comparison of these unusual lunar mounds and possible terrestrial analogs leads us to hypothesize that features in Ina were formed through lava flow inflation processes. While the source of the lava remains unclear, this new model suggests that as the mounds inflated, breakouts along their margins served as sources for surface flows that created the lower morphologic unit. Over time, mass wasting of both morphologic units has exposed fresh surfaces observed in the blocky unit. Ina is different than the terrestrial analogs presented in this study in that the lunar features formed within a depression, no vent sources are observed, and no cracks are observed on the mounds. However, lava flow inflation processes explain many of the morphologic relationships observed in Ina and are proposed to be analogous with inflated lava flows on Earth.

  6. Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

    Science.gov (United States)

    Wanless, V.D.; Perfit, M.R.; Ridley, W.I.; Wallace, P.J.; Grimes, Craig B.; Klein, E.M.

    2011-01-01

    Most geochemical variability in MOR basalts is consistent with low- to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR high-silica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H2O concentrations and relatively light oxygen isotope ratios (~ 5.8‰ vs. expected values of ~ 6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in δ18O in residual magma, but assimilation of material initially altered at high temperatures results in lower δ18O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.

  7. The effect of particle size on the rheology of liquid-solid mixtures with application to lava flows: Results from analogue experiments

    Science.gov (United States)

    Gaudio, P.; Ventura, G.; Taddeucci, J.

    2013-08-01

    We investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size (from 63 to 0.5 mm) and volume fraction ϕ (from 0.03 to 0.6). At constant ϕ, finer suspensions display higher viscosities than coarser ones. Shear thinning (flow index n 0.1-0.2 and is more pronounced (stronger departure from the Newtonian behavior) in finer suspensions. Maximum packing and average crystal size displays a nonlinear, positive correlation, while yield stress develops at ϕ > 0.2-0.3 irrespective of the crystal size. We incorporate our results into physical models for flow of lava and show that, with respect to lava flows containing coarser crystals, those with smaller crystals are expected to: 1) flow at lower velocity, 2) have a lower velocity gradient, and 3) be more prone to develop a region of plug flow. Our experimental results explain the observation that phenocryst-bearing and microlite-bearing lavas at Etna volcano (Italy) show smooth pahoehoe and rough aa' surfaces, respectively.

  8. Quantitative reconstruction of thermal and dynamic characteristics of lava flow from surface thermal measurements

    Science.gov (United States)

    Korotkii, Alexander; Kovtunov, Dmitry; Ismail-Zadeh, Alik; Tsepelev, Igor; Melnik, Oleg

    2016-06-01

    We study a model of lava flow to determine its thermal and dynamic characteristics from thermal measurements of the lava at its surface. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. We develop a numerical approach to the mathematical problem in the case of steady-state flow. Assuming that the temperature and the heat flow are prescribed at the upper surface of the model domain, we determine the flow characteristics in the entire model domain using a variational (adjoint) method. We have performed computations of model examples and showed that in the case of smooth input data the lava temperature and the flow velocity can be reconstructed with a high accuracy. As expected, a noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. Also we analyse the influence of optimization methods on the solution convergence rate. The proposed method for reconstruction of physical parameters of lava flows can also be applied to other problems in geophysical fluid flows.

  9. Real-time satellite monitoring of Nornahraun lava flow NE Iceland

    Science.gov (United States)

    Jónsdóttir, Ingibjörg; Þórðarson, Þorvaldur; Höskuldsson, Ármann; Davis, Ashley; Schneider, David; Wright, Robert; Kestay, Laszlo; Hamilton, Christopher; Harris, Andrew; Coppola, Diego; Tumi Guðmundsson, Magnús; Durig, Tobias; Pedersen, Gro; Drouin, Vincent; Höskuldsson, Friðrik; Símonarson, Hreggviður; Örn Arnarson, Gunnar; Örn Einarsson, Magnús; Riishuus, Morten

    2015-04-01

    An effusive eruption started in Holuhraun, NE Iceland, on 31 August 2014, producing the Nornahraun lava flow field which had, by the beginning of 2015, covered over 83 km2. Throughout this event, various satellite images have been analyzed to monitor the development, active areas and map the lava extent in close collaboration with the field group, which involved regular exchange of direct observations and satellite based data for ground truthing and suggesting possible sites for lava sampling. From the beginning, satellite images in low geometric but high temporal resolution (NOAA AVHRR, MODIS) were used to monitor main regions of activity and position new vents to within 1km accuracy. As they became available, multispectral images in higher resolution (LANDSAT 8, LANDSAT 7, ASTER, EO-1 ALI) were used to map the lava channels, study lava structures and classify regions of varying activity. Hyper spectral sensors (EO-1 HYPERION), though with limited area coverage, have given a good indication of vent and lava temperature and effusion rates. All available radar imagery (SENTINEL-1, RADARSAT, COSMO SKYMED, TERRASAR X) have been used for studying lava extent, landscape and roughness. The Icelandic Coast Guard has, on a number of occasions, provided high resolution radar and thermal images from reconnaissance flights. These data sources compliment each other well and have improved analysis of events. Whilst classical TIR channels were utilized to map the temperature history of the lava, SWIR and NIR channels caught regions of highest temperature, allowing an estimate of the most active lava channels and even indicating potential changes in channel structure. Combining thermal images and radar images took this prediction a step further, improving interpretation of both image types and studying the difference between open and closed lava channels. Efforts are underway of comparing different methods of estimating magma discharge and improving the process for use in real

  10. Cooling of a channeled lava flow with non-Newtonian rheology: crust formation and surface radiance

    Directory of Open Access Journals (Sweden)

    Stefano Santini

    2011-12-01

    Full Text Available We present here the results from dynamical and thermal models that describe a channeled lava flow as it cools by radiation. In particular, the effects of power-law rheology and of the presence of bends in the flow are considered, as well as the formation of surface crust and lava tubes. On the basis of the thermal models, we analyze the assumptions implicit in the currently used formulae for evaluation of lava flow rates from satellite thermal imagery. Assuming a steady flow down an inclined rectangular channel, we solve numerically the equation of motion by the finite-volume method and a classical iterative solution. Our results show that the use of power-law rheology results in relevant differences in the average velocity and volume flow rate with respect to Newtonian rheology. Crust formation is strongly influenced by power-law rheology; in particular, the growth rate and the velocity profile inside the channel are strongly modified. In addition, channel curvature affects the flow dynamics and surface morphology. The size and shape of surface solid plates are controlled by competition between the shear stress and the crust yield strength: the degree of crust cover of the channel is studied as a function of the curvature. Simple formulae are currently used to relate the lava flow rate to the energy radiated by the lava flow as inferred from satellite thermal imagery. Such formulae are based on a specific model, and consequently, their validity is subject to the model assumptions. An analysis of these assumptions reveals that the current use of such formulae is not consistent with the model.

  11. Physical properties of lava flows on the southwest flank of Tyrrhena Patera, Mars

    Science.gov (United States)

    Crown, David A.; Porter, Tracy K.; Greeley, Ronald

    1991-01-01

    Tyrrhena Patera (TP) (22 degrees S, 253.5 degrees W), a large, low-relief volcano located in the ancient southern highlands of Mars, is one of four highland paterae thought to be structurally associated with the Hellas basin. The highland paterae are Hesperian in age and among the oldest central vent volcanoes on Mars. The morphology and distribution of units in the eroded shield of TP are consistent with the emplacement of pyroclastic flows. A large flank unit extending from TP to the SW contains well-defined lava flow lobes and leveed channels. This flank unit is the first definitive evidence of effusive volcanic activity associated with the highland paterae and may include the best preserved lava flows observed in the Southern Hemisphere of Mars. Flank flow unit averages, channelized flow, flow thickness, and yield strength estimates are discussed. Analysis suggests the temporal evolution of Martian magmas.

  12. Perception of Lava Flow Hazards and Risk at Mauna Loa and Hualalai Volcanoes, Kona, Hawaii

    Science.gov (United States)

    Gregg, C. E.; Houghton, B. F.; Johnston, D. M.; Paton, D.; Swanson, D. A.

    2001-12-01

    The island of Hawaii is composed of five sub-aerially exposed volcanoes, three of which have been active since 1801 (Kilauea, Mauna Loa, Hualalai). Hawaii has the fastest population growth in the state and the local economy in the Kona districts (i.e., western portion of the island) is driven by tourism. Kona is directly vulnerable to future lava flows from Mauna Loa and Hualalai volcanoes, as well as indirectly from the effects of lava flows elsewhere that may sever the few roads that connect Kona to other vital areas on the island. A number of factors such as steep slopes, high volume eruptions, and high effusion rates, combine to mean that lava flows from Hualalai and Mauna Loa can be fast-moving and hence unusually hazardous. The proximity of lifelines and structures to potential eruptive sources exacerbates societies' risk to future lava flows. Approximately \\$2.3 billion has been invested on the flanks of Mauna Loa since its last eruption in 1984 (Trusdell 1995). An equivalent figure has not yet been determined for Hualalai, but an international airport, several large resort complexes, and Kailua-Kona, the second largest town on the island, are down-slope and within 15km of potential eruptive Hualalai vents. Public and perhaps official understanding of specific lava flow hazards and the perceptions of risk from renewed volcanism at each volcano are proportional to the time lapsed since the most recent eruption that impacted Kona, rather than a quantitative assessment of risk that takes into account recent growth patterns. Lava flows from Mauna Loa and Hualalai last directly impacted upon Kona during the notorious 1950 and circa 1801 eruptions, respectively. Various non-profit organizations; local, state and federal government entities; and academic institutions have disseminated natural hazard information in Kona but despite the intuitive appeal that increased hazard understanding and risk perception results in increased hazard adjustment adoption, this

  13. Tracking lava flow emplacement on the east rift zone of Kilauea, Hawai’i with synthetic aperture radar (SAR) coherence

    Science.gov (United States)

    Dietterich, Hannah R.; Poland, Michael P.; Schmidt, David; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia

    2012-01-01

    Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu‘u ‘Ō‘ō-Kupaianaha eruption at Kīlauea, Hawai‘i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

  14. Communicating Science to Officials and People at Risk During a Slow-Motion Lava Flow Crisis

    Science.gov (United States)

    Neal, C. A.; Babb, J.; Brantley, S.; Kauahikaua, J. P.

    2015-12-01

    From June 2014 through March 2015, Kīlauea Volcano's Púu ´Ō´ō vent on the East Rift Zone produced a tube-fed pāhoehoe lava flow -the "June 27th flow" - that extended 20 km downslope. Within 2 months of onset, flow trajectory towards populated areas in the Puna District caused much concern. The USGS Hawaiian Volcano Observatory (HVO) issued a news release of increased hazard on August 22 and began participating in public meetings organized by Hawai`i County Mayor and Civil Defense two days later. On September 4, HVO upgraded the volcano alert level to WARNING based on an increased potential for lava to reach homes and infrastructure. Ultimately, direct impacts were modest: lava destroyed one unoccupied home and one utility pole, crossed a rural roadway, and partially inundated a waste transfer station, a cemetery, and agricultural land. Anticipation that lava could reach Pāhoa Village and cross the only major access highway, however, caused significant disruption. HVO scientists employed numerous methods to communicate science and hazard information to officials and the at-risk public: daily (or more frequent) written updates of the lava activity, flow front locations and advance rates; frequent updates of web-hosted maps and images; use of the 'lines of steepest descent' method to indicate likely lava flow paths; consistent participation in well-attended community meetings; bi-weekly briefings to County, State, and Federal officials; correspondence with the public via email and recorded phone messages; participation in press conferences and congressional briefings; and weekly newspaper articles (Volcano Watch). Communication lessons both learned and reinforced include: (1) direct, frequent interaction between scientists and officials and at-risk public builds critical trust and understanding; (2) images, maps, and presentations must be tailored to audience needs; (3) many people are unfamiliar with maps (oblique aerial photographs were more effective); (4

  15. Inflation Features of the Distal Pahoehoe Portion of the 1859 Mauna Loa Flow, Hawaii; Implications for Evaluating Planetary Lava Flows

    Science.gov (United States)

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

    2011-01-01

    The 1859 eruption of Mauna Loa, Hawaii, resulted in the longest subaerial lava flow on the Big Island. Detailed descriptions were made of the eruption both from ships and following hikes by groups of observers; the first three weeks of the eruption produced an `a`a flow that reached the ocean, and the following 10 months produced a pahoehoe flow that also eventually reached the ocean. The distal portion of the 1859 pahoehoe flow component includes many distinctive features indicative of flow inflation. Field work was conducted on the distal 1859 pahoehoe flow during 2/09 and 3/10, which allowed us to document several inflation features, in or-der evaluate how well inflated landforms might be detected in remote sensing data of lava flows on other planets.

  16. Silicon isotope systematics of acidic weathering of fresh basalts, Kilauea Volcano, Hawai’i

    OpenAIRE

    Chemtob, Steven M.; Rossman, George R.; Young, Edward D.; Ziegler, Karen; Moynier, Fréderic; Eiler, John M.; Hurowitz, Joel A.

    2015-01-01

    Silicon stable isotopes are fractionated by a host of low-temperature aqueous processes, making them potentially useful as a weathering proxy. Here we characterize the silicon isotope signature of surficial chemical weathering of glassy basaltic lava flows at Kilauea Volcano, Hawaii. Fresh basalt flow surfaces (

  17. Explosive lava-water interactions II: self-organization processes among volcanic rootless eruption sites in the 1783-1784 Laki lava flow, Iceland

    Science.gov (United States)

    Hamilton, Christopher W.; Fagents, Sarah A.; Thordarson, Thorvaldur

    2010-05-01

    We have applied quantitative geospatial analyses to rootless eruption sites in the Hnúta and Hrossatungur groups of the 1783-1784 Laki lava flow to establish how patterns of spatial distribution can be used to obtain information about rootless cone emplacement processes and paleo-environments. This study utilizes sample-size-dependent nearest neighbor (NN) statistics and Voronoi tessellations to quantify the spatial distribution of rootless eruption sites and validate the use of statistical NN analysis as a remote sensing tool. Our results show that rootless eruption sites cluster in environments with abundant lava and water resources, but competition for limited groundwater in these clusters can cause rootless eruption sites to develop repelled distributions. This pattern of self-organization can be interpreted within the context of resource availability and depletion. Topography tends to concentrate lava (fuel) and water (coolant) within topographic lows, thereby promoting explosive lava-water interactions in these regions. Given an excess supply of lava within broad sheet lobes, rootless eruption sites withdraw groundwater from their surroundings until there is insufficient water to maintain analogs to explosive molten fuel-coolant interactions. Rootless eruption sites may be modeled as a network of water extraction wells that draw down the water table in their vicinity. Rootless eruptions at locations with insufficient groundwater may either fail to initiate or terminate before explosive activity has ceased at nearby locations with a greater supply of water, thus imparting a repelled distribution to observed rootless eruption sites.

  18. The eruption in Holuhraun, NE Iceland 2014-2015: Real-time monitoring and influence of landscape on lava flow

    Science.gov (United States)

    Jónsdóttir, Ingibjörg; Höskuldsson, Ármann; Thordarson, Thor; Bartolini, Stefania; Becerril, Laura; Marti Molist, Joan; Þorvaldsson, Skúli; Björnsson, Daði; Höskuldsson, Friðrik

    2016-04-01

    The largest eruption in Iceland since the Laki 1783-84 event began in Holuhraun, NE Iceland, on 31 August 2014, producing a lava flow field which, by the end of the eruption on February 27th 2015, covered 84,5 km2 with volume of 1,44 km3. Throughout the event, various satellite images (NOAA AVHRR, MODIS, SUOMI NPP VIIRS, ASTER, LANDSAT7&8, EO-1 ALI & HYPERION, RADARSAT-2, SENTINEL-1, COSMO SKYMED, TERRASAR X) were analysed to monitor the development of activity, identify active flow fronts and channels, and map the lava extent in close collaboration with the on-site field group. Aerial photographs and radar images from the Icelandic Coast Guard Dash 8 aircraft supported this effort. By the end of 2015, Loftmyndir ehf had produced a detailed 3D model of the lava using aerial photographs from 2013 and 2015. The importance of carrying out real-time monitoring of a volcanic eruption is: i) to locate sites of elevated temperature that may be registering new areas of activity within the lava or opening of vents or fissures. ii) To establish and verify timing of events at the vents and within the lava. iii) To identify potential volcanic hazard that can be caused by lava movements, eruption-induced flash flooding, tephra fallout or gas pollution. iv) to provide up-to-date regional information to field groups concerning safety as well as to locate sites for sampling lava, tephra and polluted water. v) to produce quantitative information on magma discharge and lava flow advance, map the lava extent, document the flow morphology and plume/tephra dispersal. During the eruption, these efforts supported mapping of the extent of the lava every 3-4 days on average underpinning the time series of magma discharge calculations. Digitial elevation models from before and after the event, combined with the real-time data series, supports detailed analysis of how landscape affects lava flow in a flat terrain (<0,4°), and provides important input to further developing lava flow models

  19. A new tree-ring date for the "floating island" lava flow, Mount St. Helens, Washington

    Science.gov (United States)

    Yamaguchi, D.K.; Hoblitt, R.P.; Lawrence, D.B.

    1990-01-01

    Anomalously narrow and missing rings in trees 12 m from Mount St. Helens' "floating island" lava flow, and synchronous growth increases in trees farther from the flow margin, are evidence that this andesitic flow was extruded between late summer 1799 and spring 1800 a.d., within a few months after the eruption of Mount St. Helens' dacitic layer T tephra. For ease of reference, we assign here an 1800 a.d. date to this flow. The new date shows that the start of Mount St. Helens' Goat Rocks eruptive period (1800-1857 a.d.) resembled the recent (1980-1986) activity in both petrochemical trends and timing. In both cases, an initial explosive eruption of dacite was quickly succeeded by the eruption of more mafic lavas; dacite lavas then reappeared during an extended concluding phase of activity. This behavior is consistent with a recently proposed fluid-dynamic model of magma withdrawal from a compositionally zoned magma chamber. ?? 1990 Springer-Verlag.

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

    Directory of Open Access Journals (Sweden)

    Phisit Limtrakun

    2013-08-01

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

  1. Basaltic cannibalism at Thrihnukagigur volcano, Iceland

    Science.gov (United States)

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

    2014-12-01

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

  2. Structural and temporal requirements for geomagnetic field reversal deduced from lava flows.

    Science.gov (United States)

    Singer, Brad S; Hoffman, Kenneth A; Coe, Robert S; Brown, Laurie L; Jicha, Brian R; Pringle, Malcolm S; Chauvin, Annick

    2005-03-31

    Reversals of the Earth's magnetic field reflect changes in the geodynamo--flow within the outer core--that generates the field. Constraining core processes or mantle properties that induce or modulate reversals requires knowing the timing and morphology of field changes that precede and accompany these reversals. But the short duration of transitional field states and fragmentary nature of even the best palaeomagnetic records make it difficult to provide a timeline for the reversal process. 40Ar/39Ar dating of lavas on Tahiti, long thought to record the primary part of the most recent 'Matuyama-Brunhes' reversal, gives an age of 795 +/- 7 kyr, indistinguishable from that of lavas in Chile and La Palma that record a transition in the Earth's magnetic field, but older than the accepted age for the reversal. Only the 'transitional' lavas on Maui and one from La Palma (dated at 776 +/- 2 kyr), agree with the astronomical age for the reversal. Here we propose that the older lavas record the onset of a geodynamo process, which only on occasion would result in polarity change. This initial instability, associated with the first of two decreases in field intensity, began approximately 18 kyr before the actual polarity switch. These data support the claim that complete reversals require a significant period for magnetic flux to escape from the solid inner core and sufficiently weaken its stabilizing effect. PMID:15800621

  3. Channel, Lava Tube, and Edifice Flow Models: Developments and Recent Applications for Mars

    Science.gov (United States)

    Sakimoto, S. E.; Gregg, T. K.; Riedel, S. J.

    2001-12-01

    Recent advances in modeling of lava channels, lava tubes, and small edifice construction allow us to put more physically realistic constraints on effusion rates and rheologies. For this study, we combine these models with the new precise altimetry for Mars from the Mars Global Surveyor mission. The model suite includes solutions for Newtonian and Bingham rectangular channel flow, Newtonian and Bingham sheet flow, Newtonian and Bingham tube flow, and a percolation model for shield emplacement. We find that the new data and model accuracy allows us to apply these models for different flow regimes and regions to reveal probable differences in eruption rates or rheologies across Mars. Our estimations of effusions rates (for example) improve from a range of five to six orders of magnitude to a few, which allow possible discrimination of flow rate differences between regions of several orders of magnitude. Some, but not all, of the largest flow rates are found on the steepest slopes, but much of the variation is directly attributable to either effusion rate variations or rheology differences. We suggest that some of the differences are revealing characteristic eruption styles for specific martian regions, such as lower flow rates (after correction for different slopes) in Tyrrhena's flow field than are seen on the major shield volcanoes. However, some differences simply seem to reveal natural scatter within any given eruption style and model application. We will discuss results of models for several martian regions, and implications for regional and temporal changes in flow and effusion rate properties.

  4. Recent advances in the GPUSPH model for the thermal and rheological evolution of lava flows

    Science.gov (United States)

    Zago, Vito; Bilotta, Giuseppe; Cappello, Annalisa; Dalrymple, Robert A.; Fortuna, Luigi; Ganci, Gaetana; Herault, Alexis; Del Negro, Ciro

    2016-04-01

    GPUSPH is a fully three-dimensional model for the simulation of the thermal and rheological evolution of lava flows that relies on the Smoothed Particle Hydrodynamics (SPH) numerical method. Thanks to the Lagrangian, meshless nature of SPH, the model incorporates a more complete physical description of the emplacement process and rheology of lava that considers the free surface, the irregular boundaries represented by the topography, the solidification fronts and the non-Newtonian rheology. Because of the very high degree of parallelism, GPUSPH is implemented very efficiently on high-performance graphics processing units (GPUs) employing the Compute Unified Device Architecture (CUDA), a parallel programming language developed by NVIDIA for GPU computing. GPUSPH follows the very general Herschel-Bulkley rheological model, which encompasses Newtonian, power-law and Bingham flow behaviour and can thus be used to explore in detail the impact of rheology on the behaviour of lava flows and on their emplacement. We present here the first validation tests of the GPUSPH model against well known analytical problems, considering the different rheological models, heat exchanges by thermal conduction and radiation, and providing the relative error estimates.

  5. Evaluation of basalt flows as a waste isolation medium

    International Nuclear Information System (INIS)

    The Basalt Waste Isolation Program within Rockwell Hanford Operations has the responsibility of conducting studies to determine the feasibility of using the basalt formations, which are in the Pacific Northwest and the Hanford Site, as a site for terminal storage of commercial nuclear waste. This program is divided into systems integration, geology, hydrology, engineered barrier studies, engineering testing, and the construction of a near-surface test facility. Brief descriptions of each task are presented

  6. Dendritic lava flows, landslides and terraces around the central Azores islands

    Science.gov (United States)

    Tempera, F.; Mitchell, N. C.; Schmitt, T.; Isidro, E.; Cardigos, F.; Figueiredo, J.; Nunes, J.

    2004-12-01

    Surveying around volcanic ocean islands with sonars has recovered important information on giant landslides, faults and primary volcanic features, but efforts so far have largely been unable to image shallow water coastal areas because of vessel safety. Here we report surveying with a Reson 8160 multibeam sonar aboard a shallow draft research vessel, R/V Arquipelago, which enabled us to survey to less than 10 m water depth around the coasts of Faial, Pico and Sao Jorge islands of the Azores. The data cover coasts that have been growing volcanically, some during historical times. Where the coast has a finite abrasion shelf, the new data show that lava reaching the shore can breach the surf zone and develop a variety of submarine lava structures on the shelf. Many are dendritic in plan-view and some with transverse ribbing similar to pahoehoe flows on land but much larger scale. A variety of divergent flow paths are clearly indicated in the data. Some flows cross the shelf and descend the upper slope beyond the shelf break, providing evidence that a component of growth of the submarine island can include subaerially-originating lava as inferred from sulphur contents in submarine lava dredged from around Hawai'i. Where the abrasion shelf is very narrow or absent, the upper slope of the island contains abundant shallow landslides in the new unstable and steep volcanic material. The data show a variety of other interesting features, such as terraces, volcanic cones, collapse structures, tumuli, faults associated with the Azores plate boundary and sedimentary bedforms produced by interaction of oceanic currents with the island topography and from turbidity currents descending island slopes.

  7. Nature and extent of lava-flow aquifers beneath Pahute Mesa, Nevada Test Site

    Energy Technology Data Exchange (ETDEWEB)

    Prothro, L.B.; Drellack, S.L. Jr.

    1997-09-01

    Work is currently underway within the Underground Test Area subproject of the US Department of Energy/Nevada Operations Office Environmental Restoration Program to develop corrective action plans in support of the overall corrective action strategy for the Nevada Test Site as established in the Federal Facility Agreement and Consent Order (FFACO, 1996). A closure plan is currently being developed for Pahute Mesa, which has been identified in the FFACO as consisting of the Western and Central Pahute Mesa Corrective Action Units. Part of this effort requires that hydrogeologic data be compiled for inclusion in a regional model that will be used to predict a contaminant boundary for these Corrective Action Units. Hydrogeologic maps have been prepared for use in the model to define the nature and extent of aquifers and confining units that might influence the flow of contaminated groundwater from underground nuclear tests conducted at Pahute Mesa. Much of the groundwater flow beneath Pahute Mesa occurs within lava-flow aquifers. An understanding of the distribution and hydraulic character of these important hydrogeologic units is necessary to accurately model groundwater flow beneath Pahute Mesa. This report summarizes the results of a study by Bechtel Nevada geologists to better define the hydrogeology of lava-flow aquifers at Pahute Mesa. The purpose of this study was twofold: (1) aid in the development of the hydrostratigraphic framework for Pahute Mesa, and (2) provide information on the distribution and hydraulic character of lava-flow aquifers beneath Pahute Mesa for more accurate computer modeling of the Western and Central Pahute Mesa Corrective Action Units.

  8. Simulation of substrate erosion and sulphate assimilation by Martian low-viscosity lava flows: implications for the genesis of precious metal-rich sulphide mineralisation on Mars

    Science.gov (United States)

    Baumgartner, Raphael; Baratoux, David; Gaillard, Fabrice; Fiorentini, Marco

    2016-04-01

    On Earth, high temperature mafic to ultramafic lava flows, such as komatiites and ferropicrites of the Archean and Proterozic eons, can be hosts to Ni-Cu-PGE sulphide mineralisation. Mechanical/thermo-mechanical erosion and assimilation of sulphur-rich crustal rocks is ascribed as the principal mechanism that leads to sulphide supersaturation, batch segregation and subsequent accumulation of metal-enriched magmatic sulphides (e.g., Bekker et al., Science, 2009). In order to investigate the likelihood of the occurrence of similar sulphide mineralisation in extraterrestrial magmatic systems, we numerically modelled erosion and assimilation during the turbulent emplacement of Martian lavas, some of which display chemical and rheological analogies with terrestrial komatiites and ferropicrites, on a variety of consolidated sedimentary sulphate-rich substrates. The modelling approach relies on the integration of i) mathematical lava erosion models for turbulent flows (Williams et al., J. Geophys. Res., 1998), ii) thermodynamic volatile degassing models (Gaillard et al., Space Sci. Rev., 2013), and iii) formulations on the stability of sulphides (Fortin et al., Geochim. Cosmochim. Acta, 2015). A series of scenarios are examined in which various Martian mafic to ultramafic mantle-derived melts emplace over, and assimilate consolidated sulphate-rich substrates, such as the sedimentary lithologies (i.e., conglomerates, sandstones and mudstones) recently discovered at the Gale Crater landing site. Our modellings show that lavas emplacing over consolidated sedimentary substrate rather than stiff basaltic crust, are governed by relatively high cooling and substrate erosion rates. The rapid assimilation of sulphate, which serves as a strongly oxidising agent, could result in dramatic sulphur loss due to increased volatile degassing rates at fO2 ≳QFM-1. This effect is further enhanced with increased temperature. Nevertheless, sulphide supersaturation in the way of sulphate

  9. The Highway Flow in the Craters of the Moon Lava Field; A New Interpretation of Eruption History

    Science.gov (United States)

    Caress, M. E.; Owen, D. E.

    2005-12-01

    The Highway flow is a trachyandesitic lava flow that lies west of Sunset Cone in the Craters of the Moon lava field, and is part of a complex series of eruptive events that took place in the vicinity of North Crater during the most recent eruptive episode of the field (2,500-2,000 years ago). The trachyandesitic Devil's Orchard and Serrate flows originated from the same vicinity during this period, and carried large masses of rafted cinder cone blocks and disaggregated cinder cone material up to 12 km to the east. The rafted blocks have long been thought to be the remnants of a disintegrating North Crater cinder cone. However, recent work has established that the flows carry a cumulative volume of rafted blocks too large to have come from the existing breach in North Crater. Previous studies had postulated the Highway flow vent to be on the north side of North Crater, and suggested the lava had flowed north, and later drained back to the south when the Highway fault downdropped the vent area. This study examined lava flow characteristics and flow direction indicators based on flow fold patterns interpreted from aerial photographs and field mapping to provide new insight into the complicated history of the Highway flow. We found two vents on the northern side of the flow, and evidence that the lava flowed to the south and ponded against a formerly present cinder cone, which we have named "South Highway Cone". The following sequence of events for eruption of the Highway flow is hypothesized: 1) eruption from two linear vent systems in the northern part of the present day flow 2) flow from the second vent southward, down the valley between Sunset and Grassy Cones 3) ponding of the lava flow at the base of the South Highway Cone and 4) downdrop to the south along the Highway fault due to collapse into a lava chamber beneath South Highway Cone. The rafted blocks in the Devil's Orchard and Serrate flows represent pieces of North Crater and the now hypothesized South

  10. The Taylor Creek Rhyolite of New Mexico: a rapidly emplaced field of lava domes and flows

    Science.gov (United States)

    Duffield, Wendell A.; Dalrymple, G. Brent

    1990-08-01

    The Tertiary Taylor Creek Rhyolite of southwest New Mexico comprises at least 20 lava domes and flows. Each of the lavas was erupted from its own vent, and the vents are distributed throughout a 20 km by 50 km area. The volume of the rhyolite and genetically associated pyroclastic deposits is at least 100 km3 (denserock equivalent). The rhyolite contains 15% 35% quartz, sanidine, plagioclase, ±biotite, ±hornblende phenocrysts. Quartz and sanidine account for about 98% of the phenocrysts and are present in roughly equal amounts. With rare exceptions, the groundmass consists of intergrowths of fine-grained silica and alkali feldspar. Whole-rock major-element composition varies little, and the rhyolite is metaluminous to weakly peraluminous; mean SiO2 content is about 77.5±0.3%. Similarly, major-element compositions of the two feldsparphenocryst species also are nearly constant. However, whole-rock concentrations of some trace-elements vary as much as several hundred percent. Initial radiometric age determinations, all K-Ar and fission track, suggest that the rhyolite lava field grew during a period of at least 2 m.y. Subsequent 40Ar/39Ar ages indicate that the period of growth was no more than 100 000 years. The time-space-composition relations thus suggest that the Taylor Creek Rhyolite was erupted from a single magma reservoir whose average width was at least 30 km, comparable in size to several penecontemporaneous nearby calderas. However, this rhyolite apparently is not related to a caldera structure. Possibly, the Taylor Creek Phyolite magma body never became sufficiently volatile rich to produce a large-volume pyroclastic eruption and associated caldera collapse, but instead leaked repeatedly to feed many relatively small domes and flows. The new 40Ar/39Ar ages do not resolve preexisting unknown relative-age relations among the domes and flows of the lava field. Nonetheless, the indicated geologically brief period during which Taylor Creek Rhyolite magma was

  11. Distribution, 14C chronology, and paleomagnetism of latest Pleistocene and Holocene lava flows at Haleakala volcano, Island of Maui, Hawai'i: a revision of lava flow hazard zones

    Science.gov (United States)

    Sherrod, David R.; Hagstrum, Jonathan T.; McGeehin, John P.; Champion, Duane E.; Trusdell, Frank A.

    2006-01-01

    New mapping and 60 new radiocarbon ages define the age and distribution of latest Pleistocene and Holocene (past 13,000 years) lava flows at Haleakalā volcano, Island of Maui. Paleomagnetic directions were determined for 118 sites, of which 89 are in lava flows younger than 13,000 years. The paleomagnetic data, in conjunction with a reference paleosecular variation (PSV) curve for the Hawaiian Islands, are combined with our knowledge of age limitations based on stratigraphic control to refine age estimates for some of the undated lava flows. The resulting volumetric rate calculations indicate that within analytical error, the extrusion rate has remained nearly constant during the past 13,000 years, in the range 0.05–0.15 km3/kyr, only about half the long-term rate required to produce the postshield strata emplaced in the past ∼1 Myr. Haleakalā's eruptive frequency is similar to that of Hualālai volcano on the Island of Hawai‘i, but its lava flows cover substantially less area per unit time. The reduced rates of lava coverage indicate a lower volcanic hazard than in similar zones at Hualālai.

  12. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    Science.gov (United States)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  13. High-resolution AUV mapping and lava flow ages at Axial Seamount

    Science.gov (United States)

    Clague, D. A.; Paduan, J. B.; Dreyer, B. M.; Caress, D. W.; Martin, J.

    2011-12-01

    Mapping along mid-ocean ridges, as on land, requires identification of flow boundaries and sequence, and ages of some flows to understand eruption history. Multibeam sonars on autonomous underwater vehicles (AUV) now generate 1-m resolution maps that resolve lava pillars, internal flow structures and boundaries, and lava flow emplacement sequences using crosscutting relations and abundance of fissures. MBARI has now mapped the summit caldera floor and rims and the upper south rift zone on Axial Seamount on the Juan de Fuca Ridge. With the advent of the high-resolution bathymetry and the ability to observe flow contacts to determine superposition using ROVs and submersibles, the missing component has been determining absolute ages of the flows. We used the MBARI ROV Doc Ricketts to collect short push cores (summit of Axial Seamount and for 6 from the lowermost south rift. Ages of nearby samples commonly yield statistically identical ages, and 2 cores near the center of the caldera had multiple layers dated. These ages systematically increase with depth, indicating that redistribution of sediment by bottom currents does not significantly affect the stratigraphy. We will expand these collections in summer 2011. The coring is accompanied by collection of flow samples for chemistry and video observations to confirm contact locations and flow superposition inferred from the mapping data. Six ages from the lowermost part of the south rift of Axial Seamount include samples on a cone with deep summit crater that is ~16,580 aBP and on 5 flows between 950 and 1510 aBP. Two additional flows from the southeast rim of the caldera are 905 and 2005 aBP. An age of 6910 aBP from 15 cm depth in a 2-m volcaniclastic unit on top of a pre-caldera flow on the eastern rim of the caldera suggests formation of the caldera several tens of thousands aBP. Seven ages on at least 5 flows on the floor of Axial caldera range from 620 to 1145 aBP, whereas 10 extensive mapped flows are all inferred

  14. Modeling Recent Subsidence of Mars' Olympus Mons Using Lava Flows as Paleo-Slope Indicators

    Science.gov (United States)

    Simpson, M.; Reeves, A.; Chadwick, J.; McGovern, P. J.

    2013-12-01

    Olympus Mons is an enormous volcanic edifice on Mars with a basal diameter over 600 km and a height of 23 km. In spite of this size, no indications of subsidence, such as an obvious topographic moat, have previously been detected around the volcano. In this study, we mapped the orientations of long, thin lava flows on the plains to the south and southeast of Olympus Mons using 100m-resolution imagery from the Thermal Emission Imaging System (THEMIS) on Mars Odyssey, and topography using Mars Orbiter Laser Altimeter (MOLA) data from Mars Global Surveyor. The results show that the flows are no longer oriented in a downhill direction, consistently deviating from modern slope vectors in a counterclockwise direction by 21.4 × 10.8 degrees (n = 65). The configuration of this misalignment between modern and paleo-topography is consistent with subsidence centered on the volcano in the time since the flows were emplaced. Our preliminary geophysical modeling used a range of load volumes, load radii, and lithospheric thicknesses to identify the scenario required to best restore modern topography to match the paleo-topography present when the lava flows were emplaced (i.e. 'uplift' Olympus Mons until the lava flows on the surrounding plains are restored to a downhill direction). The results show that lithospheric subsidence of about 1.2 km due to the magmatic addition of 3.8x10^5 km^3 best fits the observed topographic changes. Load center heights of 1 to 8 km were considered, with best fits generally in the 3-5 km range. Best-fit elastic lithosphere thickness (Te) values were generally 100 km or greater, consistent with estimates for Te from loading models [1,2] and gravity-topography relationships [3,4,5]. Our new crater size-density measurements of the plains in the study area show that the observed subsidence occurred within the past 229 × 26 my. Previous crater counts for Olympus Mons calderas and lower flank flows [6] reveal volcanic activity clustered around 100

  15. Explosive lava-water interactions I: architecture and emplacement chronology of volcanic rootless cone groups in the 1783-1784 Laki lava flow, Iceland

    Science.gov (United States)

    Hamilton, Christopher W.; Thordarson, Thorvaldur; Fagents, Sarah A.

    2010-05-01

    To determine the relationships between rootless cone emplacement mechanisms, morphology, and spatial distribution, we mapped the Hnúta and Hrossatungur groups of the 1783-1784 Laki lava flow in Iceland. We based our facies maps on Differential Global Positioning System (DGPS) measurements, photogeological interpretations, and supporting field observations. The study area covers 2.77 km2 and includes 2216 explosion sites. To establish the timing of rootless cone formation we incorporated tephrochronological constraints from eighty-eight stratigraphic sections and determined that the Hnúta and Hrossatungur groups are composite structures formed by the emplacement of six geographically and chronologically discrete domains. Rootless eruptions initiated in domain 1 on the first day of the Laki eruption (June 8, 1783) and lasted 1-2 days. The second episode of rootless activity began in domain 2 on June 11 and lasted 1-3 days. The four domains of the Hrossatungur group dominantly formed after June 14 and exhibit a complex emplacement sequence that reflects interactions between the Laki lava, contemporaneously emplaced rootless cones, and an existing topographic ridge. In the study area, we identify three distinct rootless cone archetypes (i.e., recurring morphological forms) that are related to tube-, channel-, and broad sheet lobe-fed eruptions. We assert that emplacement of lava above compressible substrates (e.g ., unconsolidated sediments) may trigger rootless eruptions by causing subsidence-induced flexure and failure of the basal crust, thereby allowing molten lava (fuel) to come into direct contact with groundwater (coolant) and initiating analogs to explosive molten fuel-coolant interactions (MFCIs).

  16. Lava Flow Ages and Geologic Mapping on Mid-ocean Ridges

    Science.gov (United States)

    Clague, D. A.; Paduan, J. B.; Dreyer, B. M.; Caress, D. W.

    2010-12-01

    Geologic mapping of mid-ocean ridges has been hindered by a lack of high-resolution bathymetry and age data. Autonomous underwater vehicles (AUV) with multibeam sonars now produce maps with 1-m resolution. MBARI has collected data since 2006 along the Juan de Fuca and Gorda Ridges, including the 1998 eruptions in summit caldera and upper south rift zone on Axial Seamount, the 1993 and 1982-1991 eruptions on the CoAxial segment, the 1986 pillow mounds and “young sheet flow” on the north Cleft segment, the 1996 eruption on the North Gorda segment, and part of the Endeavour Ridge. The 1-m data allows identification of flow internal structure, boundaries, and emplacement sequences using superposition and abundance of fissures. Geologic maps of young volcanoes on land are constructed using the same principles, constrained by observations of flow contacts and 14C age dates on charcoal from beneath flow margins. In the deep sea, we collect sediment on top of the flows that contains planktic and benthic foraminifera that can be dated using AMS 14C dating. We sampled sediment on flows from the Axial, CoAxial, and North Cleft areas using 30-cm long pushcores deployed from remotely operated vehicles (ROVs). The coring is done with collection of flow samples for chemistry and video observations to confirm contact locations and flow superposition. Cores are inserted until they hit the underlying lava and can be recovered between pillow lobes when the sediment is >~10 cm thick. We recover the basal 1 cm of sediment, sieve to recover foraminifera, and hand-pick for 14C dating. The North Gorda neovolcanic zone at ~3150 m lacks carbonate sediment and therefore ages. Ages of planktic foraminifera are marine calibrated in years before present (aBP). Benthic foraminifera are calibrated against planktic foraminifera from 5 samples. 14C ages obtained from basal sediment from over 40 sites represent minimum ages as there is probably a small amount of unrecovered basal sediment. Ages

  17. Palaeomagnetic study of the Xitle-Pedregal de San Angel lava flow, southern Basin of Mexico

    Science.gov (United States)

    Urrutia-Fucugauchi, J.

    1996-10-01

    A detailed study of the ˜ 2000 years old Xitle-Pedregal de San Angel volcanic field in the southern Basin of Mexico was undertaken to assess the reliability of the palaeomagnetic record as derived from fresh well-preserved and exposed lava flows. The Xitle vent is on the slope of the Ajusco volcano, which results in a topographic difference of over 800 m in less than 12 km of horizontal distance. Most sites present a mean direction, with a small within-site dispersion, around the dipolar direction for the locality, but some sites, particularly in the basin sector of flat relief away from the vent, show shallow inclinations. Anisotropy of magnetic susceptibility (AMS) shows normal 'flow' fabrics with horizontal foliation planes and small anisotropy degree. AMS lineations correlate with observed flow directions. The magnetic properties vary systematically across flow units, but directions do not show a consistent pattern. Secular variation effects do not apparently contribute to the shallow inclinations or directional scatter. Some lava structures like pressure crests and blocky fronts give shallow inclinations and scattered directions, respectively. The resulting overall mean direction is well defined and close to the dipolar direction ( B = 26, Dec = 359.8°, Inc = 32.8°, k = 167, α95 = 2.2°), but this excludes two apparent directional groups. The mean direction for one group, with B = 19, Dec = 359.0°, Inc = 35.1°, k = 247, α95 = 2.1°, may be the representative estimate for the field. Shallow inclinations are considered anomalous and associated to a characteristic specific to given sectors of lava flows. Palaeointensity determinations have been obtained for six samples from five sites by using the Thellier and Shaw methods. Results agree well with previous studies, however, the standard deviation calculated for the mean value remains high after incorporation of the new data. Mean palaeointensity based on five new determinations and eight early data is N

  18. Thermal infrared observations of lava flows during the 1984 Mauna Loa eruption

    Science.gov (United States)

    Pieri, D. C.; Gillespie, R.; Kahle, A. B.; Kahle, J.; Baloga, S. M.

    1985-04-01

    Thermal infrared videotape images of the flowing lava streams and the vent areas at 10.6 microns were made, as well as some broadband images in the 8 to 12 micron range (for gas plume detection). These data were calibrated with on-site hand-held radiometer measurements, in-flow thermocouple measurements, and with later laboratory kiln measurements. Infrared video data are useful in quantitatively assessing the pattern and mode of flow thermal losses, particularly with regard to radiative losses from established/incipient floating crust. The general cooling of the flows downstream was readily apparent. Upper reaches of the active flow exhibited nearly crust-free main channels, radiating at about 700 to 800 degrees C. Below about the 7500 foot level (about 8 km from the vent) the flows formed nearly continuous crust and tended to spread, become less well-defined and founder due to a reduction in slope. Nevertheless, in thermal IR observations, the surface trace of the active subsurface channel was visible, radiating at about 500 to 700 degrees C. At the active flow front, most solid crust radiated at temperatures less than 500 to 600 degrees C, however bright high temperature interiors (approximately 900 to 1000 degrees C) were clearly visible though evolving fissures.

  19. Vertical variation of AMS along selected basalt flow profiles, Xitle volcano, Mexico. Zone-layer recognition by magnetic fabric

    International Nuclear Information System (INIS)

    Complete text of publication follows. Three selected basalt flow units from the Xitle volcano (2000-year-old, Basin of Mexico) are used to study the vertical variation of anisotropy of magnetic susceptibility (AMS) to examine their possible relationship with magnetic mineralogy, flow strain and general dynamic flow behavior of lava flows. Selected profiles are 4.8, 5.0 and 6.6 m thick and are located at different positions inside the flows; the thickest one is at the flow border. Sampling was performed at intervals from 12 to 20 cm. Number of specimens was 42, 75 and 36, respectively. Measurements were performed with a KLY2 and a Minisep instruments, a comparative analysis with selected specimens was performed with both instruments. Jelinek statistic was applied, as well as density distribution analysis for determining maximum distribution areas of principal directions. Hysteresis curves, Curie temperatures and some ore microscopy analysis indicate that magnetic mineralogy is dominated by Ti-poor titanomagnetite and that large ilmenite grains are also present, their sizes increasing towards the flow center. The k1 (maximum AMS axis) means broadly parallel the local geologically inferred flow direction, their inclinations point toward flow source. The respective k3 (minimum AMS axis) means reveal near horizontal main foliations (at least in 2 sites) defining dominant AMS ellipsoids dipping against flow. The density distribution analysis show that k3 individual directions have two maximums peaks; one of these peaks corresponding to a foliation dipping against the flow direction and the other one towards it, lying the k3 means among the two maximum peaks. A detailed analysis of the vertical variations of the AMS ellipsoids allowed identifying several zone-layers in the flow units, each one characterized with a particular AMS pattern. The lower layer in all cases shows ellipsoids dipping against flow; meanwhile the upper layer usually presents AMS ellipsoids dipping in

  20. Bringing the Volcano to the Students: The Syracuse University LAVA Project

    Science.gov (United States)

    Karson, J.; Wysocki, B.; Kissane, M. T.

    2011-12-01

    A collaborative effort between the Department of Earth Sciences and Sculpture Department at Syracuse University has resulted in the facility to make natural-scale lava flows in a laboratory environment for K-university students and the general public. Using a large, gas-fired, furnace with a tilting crucible, basaltic gravel is heated at temperatures of 1100° to 1300°C resulting in up to 800 lbs of homogeneous, basaltic lava. Lava is poured over a variety of surfaces including rock slab, wet or dry sand, ice and dry ice. A ceramic funnel permits pouring into and under water. Differing set-ups provide analogs for a wide range of terrestrial, marine, and extraterrestrial lava flows. Composition is held constant, but varying key parameters such as temperature, pouring (effusion) rate, and slope result in different flow morphologies including ropey to toey pahoehoe, inflated flows, channelized flows with levees, and hyaloclastites. Typical flows are 2-4 m long and hair and tears. Experiments are underway to quantify the variables associated with different morphologies, but the spectacular lava flows are also being integrated into class experiences. Students and instructors from K-12 classes as well as university classes are spectators and active participants in the lava flow events, commonly proposing experiments before or during flows. Lava flows are incorporated into labs for Earth Science classes and also used for artistic creations in the Sculpture program. Although students have access to still images and video of natural lava flows from active volcanoes, there is no substitute for "being there" and experiencing the spectacle of viscous, incandescent orange, lava flowing over the surface in a blast of heat. Grabbing student attention in this environment opens the door to discussions ranging from the nature of Earth materials (solid vs. liquid, rock vs glass, viscous vs brittle, etc.) to major planetary processes.

  1. Parallel Genetic Algorithms for calibrating Cellular Automata models: Application to lava flows

    International Nuclear Information System (INIS)

    Cellular Automata are highly nonlinear dynamical systems which are suitable far simulating natural phenomena whose behaviour may be specified in terms of local interactions. The Cellular Automata model SCIARA, developed far the simulation of lava flows, demonstrated to be able to reproduce the behaviour of Etnean events. However, in order to apply the model far the prediction of future scenarios, a thorough calibrating phase is required. This work presents the application of Genetic Algorithms, general-purpose search algorithms inspired to natural selection and genetics, far the parameters optimisation of the model SCIARA. Difficulties due to the elevated computational time suggested the adoption a Master-Slave Parallel Genetic Algorithm far the calibration of the model with respect to the 2001 Mt. Etna eruption. Results demonstrated the usefulness of the approach, both in terms of computing time and quality of performed simulations

  2. Using Lava Tube Skylights To Derive Lava Eruption Temperatures on Io

    Science.gov (United States)

    Davies, Ashley Gerard; Keszthelyi, Laszlo P.; McEwen, Alfred S.

    2015-11-01

    The eruption temperature of Io’s silicate lavas constrains Io’s interior state and composition [1]. We have examined the theoretical thermal emission from lava tube skylights above basaltic and ultramafic lava channels. Assuming that tube-fed lava flows are common on Io, skylights could also be common. Skylights present steady thermal emission on a scale of days to months. We find that the thermal emission from such a target, measured at multiple visible and NIR wavelengths, can provide a highly accurate diagnostic of eruption temperature. However, the small size of skylights means that close flybys of Io are necessary, requiring a dedicated Io mission [2]. Observations would ideally be at night or in eclipse. We have modelled the thermal emission spectrum for different skylight sizes, lava flow stream velocities, end-member lava compositions, and skylight radiation shape factors, determining the resulting flow surface cooling rates. We calculate the resulting thermal emission spectrum as a function of viewing geometry. From the resulting 0.7:0.9 μm ratios, we see a clear distinction between basaltic and ultramafic compositions for skylights smaller than 20 m across, even if sub-pixel. Our analysis will be further refined as accurate high-temperature short-wavelength emissivity values become available [3]. This work was performed at the Jet Propulsion Laboratory-California Institute of Technology, under contract to NASA. We thank the NASA OPR Program for support. References: [1] Keszthelyi et al. (2007) Icarus 192, 491-502 [2] McEwen et al. (2015) The Io Volcano Observer (IVO) LPSC-46 abstract 1627 [3] Ramsey and Harris (2015) IAVCEI-2015, Prague, Cz. Rep., abstract IUGG-3519.

  3. Field-based description of rhyolite lava flows of the Calico Hills Formation, Nevada National Security Site, Nevada

    Science.gov (United States)

    Sweetkind, Donald S.; Bova, Shiera C.

    2015-01-01

    Contaminants introduced into the subsurface of Pahute Mesa, Nevada National Security Site, by underground nuclear testing are of concern to the U.S. Department of Energy and regulators responsible for protecting human health and safety. The potential for contaminant movement away from the underground test areas at Pahute Mesa and into the accessible environment is greatest by groundwater transport through fractured volcanic rocks. The 12.9 Ma (mega-annums, million years) Calico Hills Formation, which consists of a mixture of rhyolite lava flows and intercalated nonwelded and bedded tuff and pyroclastic flow deposits, occurs in two areas of the Nevada National Security Site. One area is north of the Rainier Mesa caldera, buried beneath Pahute Mesa, and serves as a heterogeneous volcanic-rock aquifer but is only available to study through drilling and is not described in this report. A second accumulation of the formation is south of the Rainier Mesa caldera and is exposed in outcrop along the western boundary of the Nevada National Security Site at the Calico Hills near Yucca Mountain. These outcrops expose in three dimensions an interlayered sequence of tuff and lava flows similar to those intercepted in the subsurface beneath Pahute Mesa. Field description and geologic mapping of these exposures described lithostratigraphic variations within lava flows and assisted in, or at least corroborated, conceptualization of the rhyolite lava-bearing parts of the formation.

  4. Applications of MGS MOC and MOLA Data to Lava Flows: Investigations of Rheology, Topographic Influences and Tectonic Effects

    Science.gov (United States)

    Glaze, Lori S.

    2004-01-01

    Proxemy Research had a grant from NASA to perform scientific research using Mars Global Surveyor (MGS) data to study lava flows on Mars. Here we summarize the scientific progress and accomplishments of this grant. Scientific publications and abstracts of presentations are indicated in the final section.

  5. Mono Lake or Laschamp geomagnetic event recorded from lava flows in Amsterdam Island (southeastern Indian Ocean)

    CERN Document Server

    Carvallo, C; Ruffet, G; Henry, B I; Poidras, T; Carvallo, Claire; Camps, Pierre; Ruffet, Gilles; Henry, Bernard; Proxy, Thierry Poidras

    2003-01-01

    We report a survey carried out on basalt flows from Amsterdam Island in order to check the presence of intermediate directions interpreted to belong to a geomagnetic field excursion within the Brunhes epoch, completing this paleomagnetic record with paleointensity determinations and radiometric dating. The directional results corroborate the findings by Watkins and Nougier (1973) : normal polarity is found for two units and an intermediate direction, with associated VGPs close to the equator, for the other two units. A notable result is that these volcanic rocks are well suited for absolute paleointensity determinations. Fifty percent of the samples yields reliable intensity values with high quality factors. An original element of this study is that we made use of the PTRM-tail test of Shcherbakova et al. (2000) to help in the interpretation of the paleointensity measurements. Doing thus, only the high temperature intervals, beyond 400 degres C, were retained to obtain the most reliable estimate of the streng...

  6. Paleomagnetism of some Precambrian basaltic flows and red beds, Eastern Grand Canyon, Arizona

    Science.gov (United States)

    Elston, D.P.; Robert, Scott G.

    1973-01-01

    Lava flows and red sandstone beds near the middle of the Upper Precambrian Grand Canyon Series exhibit stable remanent magnetization. The beds are about 1000 m stratigraphically above rocks of the Grand Canyon Series for which paleomagnetic poles have been reported. All specimens were subjected to stepwise thermal (200??-700??C) or alternating field (25-5000 Oe) demagnetization for the determination of characteristic magnetization. The pole for two flows and an intercalated sandstone bed of the Cardenas Lavas of Ford, Breed and Mitchell (upper Unkar Group), is at 174.6W, 0.4N (N = 10, K = 50, ??95 = 6.9??). The pole for a weathered zone developed across the Cardenas Lavas is at 167.8W, 49.4N (N = 5, K = 79, ??95 = 8.6??). The pole for directly overlying sandstone of the Nankoweap Formation of Maxson is at 174.4E, 12.5N (N = 6, K = 105, ??95 = 6.6??). These poles lie on or near, and appear to follow, part of an apparent polar wandering path recently proposed for the Precambrian of North America by Spall. If the fit is not accidental, little or no rotation has occurred between north-central Arizona and parts of the North American continent used to define the proposed path. ?? 1973.

  7. Solidification of basaltic magma during flow in a dike.

    Science.gov (United States)

    Delaney, P.T.; Pollard, D.D.

    1982-01-01

    A model for time-dependent unsteady heat transfer from magma flowing in a dyke is developed. The ratio of solidification T to magma T is the most important parameter. Observations of volcanic fissure eruptions and study of dykes near Ship Rock, New Mexico, show that the low T at dyke margins and the rapidly advancing solidification front predicted by the model are qualitatively correct.-M.S.

  8. Gusev Rocks Solidified from Lava (False Color)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  9. Gusev Rocks Solidified from Lava (3-D)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  10. The 2014-2015 Pāhoa lava flow crisis at Kīlauea Volcano, Hawai‘i: Disaster avoided and lessons learned

    Science.gov (United States)

    Poland, Michael; Orr, Tim; Kauahikaua, James P.; Brantley, Steven R.; Babb, Janet; Patrick, Matthew R.; Neal, Christina; Anderson, Kyle R.; Antolik, Loren; Burgess, Matthew K.; Elias, Tamar; Fuke, Steven; Fukunaga, Pauline; Johanson, Ingrid; Kagimoto, Marian; Kamibayashi, Kevan P.; Lee, Lopaka; Miklius, Asta; Million, William; Moniz, Cyril J.; Okubo, Paul G.; Sutton, Andrew; Takahashi, T. Jane; Thelen, Weston A.; Tollett, Willam; Trusdell, Frank A.

    2016-01-01

    Lava flow crises are nothing new on the Island of Hawai‘i, where their destructive force has been demonstrated repeatedly over the past several hundred years. The 2014–2015 Pāhoa lava flow crisis, however, was unique in terms of its societal impact and volcanological characteristics. Despite low effusion rates, a long-lived lava flow whose extent reached 20 km (the longest at Kīlauea Volcano in the past several hundred years) was poised for months to impact thousands of people, although direct impacts were ultimately minor (thus far). Careful observation of the flow reaffirmed and expanded knowledge of the processes associated with pāhoehoe emplacement, including the direct correlation between summit pressurization and flow advance, the influence of existing geologic structures on flow pathways, and the possible relationship between effusion rate and flow length. Communicating uncertainty associated with lava flow hazards was a challenge throughout the crisis, but online distribution of information and direct contact with residents proved to be effective strategies for keeping the public informed and educated about flow progress and how lava flows work (including forecasting limitations). Volcanological and sociological lessons will be important for inevitable future lava flow crises in Hawai‘i and, potentially, elsewhere in the world.

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

    Science.gov (United States)

    Ward, P. L.

    2015-12-01

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

  12. Studies of vesicle distribution patterns in Hawaiian lavas

    International Nuclear Information System (INIS)

    Basaltic lava flows are generally vesicular, and the broader facts relating to vesicle distribution have long been established; few studies have yet been made with a view to determining how and when vesicles form in the cooling history of the lava, explaining vesicle shape and size distribution, and gaining enough understanding to employ vesicles as a geological tool. Various avenues of approach exist by which one may seek to gain a better understanding of these ubiquitous structures and make a start towards developing a general theory, and three such avenues have recently been explored. One avenue involves the study of pipe vesicles; these are a well known feature of lava flows and are narrow pipes which occur near the base of many pahoehoe flow units. Another avenue of approach is that presented by the distinctive spongy pahoehoe facies of lava that is common in distal locations on Hawaiian volcanoes. A third avenue of approach is that of the study of gas blisters in lava. Gas blisters are voids, which can be as much as tens of meters wide, where the lava split along a vesicle-rich layer and the roof up-arched by gas pressure. These three avenues are briefly discussed

  13. Early Silurian (~ 440 Ma) adakitic, andesitic and Nb-enriched basaltic lavas in the southern Altay Range, Northern Xinjiang (western China): Slab melting and implications for crustal growth in the Central Asian Orogenic Belt

    Science.gov (United States)

    Shen, Xiao-Ming; Zhang, Hai-Xiang; Wang, Qiang; Ma, Lin; Yang, Yue-Heng

    2014-10-01

    As an important part of the Central Asian Orogenic Belt (CAOB), the Altay Range contains large-scale Paleozoic magmatic rocks. However, owing to the lack of precise age constraints, the tectonic setting and petrogenesis of the magmatic rocks in this area have been controversial, which has led to the debate on Phanerozoic crustal growth mechanisms and accretionary orogenic processes in the CAOB. Herein, we report geochronological and geochemical data of the Suoerkuduke adakitic, andesitic and Nb-enriched basaltic (NEB) lavas in the southern margin of the southern Altay Range. LA-ICP-MS zircon U-Pb analyses for five adakitic, andesitic and NEB samples indicate that they were coevally generated in the Early Silurian (~ 440 Ma). The adakites and basaltic andesites are geochemically characterized by high Na2O/K2O, Sr/Y, Al2O3, Sr, εNd(t) and zircon εHf(t) values and relatively low (87Sr/86Sr)i ratios. The NEBs are sodium-rich and have higher TiO2, P2O5, Zr, Nb, and Nb/U values than those of typical arc basalts. They also have positive εNd(t) values and positive and variable zircon εHf(t) values. We suggest that the Suoerkuduke adakites were derived by a partial melting of the subducted oceanic crust with minor overlying sediments, and the continuous compositional variations between adakites and basaltic andesites confirm that the interaction between slab melts and mantle peridotite played an important role in the formation of basaltic andesites. The associated NEBs were possibly generated by a partial melting of mantle wedge peridotites metasomatized by slab-derived adakitic melts and minor fluids. In combination with the occurrence of voluminous Silurian-Devonian granitoids, coeval ophiolite mélanges, and a series of intra-arc basins, a slab window model triggered by slab tearing is proposed to account for the formation of the Suoerkuduke adakite-basaltic andesite-NEB suites. The upwelling of the asthenospheric mantle through the slab window probably caused

  14. Effusion rate, length, and area relationships for some lava flows on Hawaii and Mount Etna with planetary implications

    Science.gov (United States)

    Pieri, D.; Baloga, S.

    1984-01-01

    A model for the radiative cooling of thermally well mixed lava flows is presented and the relationship between effusion rate and length and area is analyzed. If radiative cooling is the prime mode of heat loss for a lava flow, one should expect to see a stronger correlation between the effusion rate and the plan area of the flow, than between effusion rate and just flow length. Different flows on a single volcano with differing initial temperatures, volatile content, and gross compositions should yield different areas for a given effusion rate. Likewise, a range of slopes for the relationship between effusion rate and flow area should result from comparisons between different volcanoes. As a test of these ideas, available data on the effusion rates, lengths, and areas of Hawaiian and Etnean flow is studied. It was found that: (1) the effusion rate/area correlation was statistically more significant than the correlation between effusion rate and length for four out of the five eruption episodes which met the necessary criteria of more than three individual flows with area, length, and effusion rate independently measured; (2) that there exists a minimum length and area for a given effusion rate, reflecting competition between overall characteristic proportionality between effusion rate and flow length, width, and area.

  15. Morphology and structure of the 1999 lava flows at Mount Cameroon Volcano (West Africa) and their bearings on the emplacement dynamics of volume-limited flows

    OpenAIRE

    Suh, C Emmanuel; Stansfield, SA; Sparks, RSJ; Njome, MS; Wantim, Mabel Nechia; Ernst, Gerald

    2011-01-01

    The morphology and structure of the 1999 lava flows at Mount Cameroon volcano are documented and discussed in relation to local and source dynamics. Structures are analysed qualitatively and more detailed arguments are developed on the processes of levee formation and systematic links between flow dynamics and levee-channel interface geometry. The flows have clear channels bordered by four main types of levees: initial, accretionary, rubble and overflow levees. Thermally immature pahoehoe lav...

  16. Lead isotopic systematics for native copper-chalcocite mineralization in basaltic lavas of the Emeishan large igneous province, SW China:Implications for the source of copper

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qian; WANG Dapeng; ZHU Xiaoqing; ZHANG Zhengwei; ZHU Chaohui

    2009-01-01

    The Emeishan continental flood basalt, which is widespread in Yunnan, Guizhou and Sichuan provinces of Southwest China, is the volcanic product of a Permian mantle plume, and native copper-chalcocite mineralization associated with the basalt is very common in the border area of Yunnan and Guizhou provinces. The mineralization occurred in the tuff intercalation and terrestrial sedimentary rock intercalation which were formed during the main period of basalt eruption. The orebodies are controlled by the stratigraphic position and faults. Metal ore minerals in the ores are mainly native copper, chalcocite and tenorite, with small amounts of chalcopyrite, bomite, pyrite and malachite, and sometimes with large amounts of bitumen, carbon and plant debris. Several decades of ore deposits are distributed in the neighboring areas of the two provinces, while most of them are small-scale deposits or only ore occurrences. By comparing the lead isotopic composition of the ores with that of the wall-rocks, cover and basement rocks of various periods, the source of copper in this type of ore deposits was studied in this paper. The results showed that: (1) The Pb isotopic composition of the ores from ten deposits is absolutely different from that of sili-ceous-argillaceus rocks of the Upper Permian Xuanwei Formation, limestones of the Lower Permian Series and Carboniferous, Cambrian sandstone-shale and recta-sedimentary rock and dolomite from the upper part of the Meso-Proterozoic Kunyang Group, This indicates that ore lead was derived neither from the cover rock nor from the basement rocks; (2) Although the Neo-Proterozoic Siman dolomite and silicalite, and dolomite in the lower part of the Kunyang Group are similar in Pb isotopic composition to the ores, lead and copper contents in these rocks are very low and they have not made great contributions to copper mineralization; (3) The ores have the same Pb iso-topic composition as the basalt, the latter being enriched in copper

  17. Reconstructing lava flow emplacement processes at the hot spot-affected Galápagos Spreading Center, 95°W and 92°W

    Science.gov (United States)

    McClinton, Tim; White, Scott M.; Colman, Alice; Sinton, John M.

    2013-08-01

    Volcanic eruptions at mid-ocean ridges (MORs) control the permeability, internal structure, and architecture of oceanic crust, thus establishing the foundation for the evolution of the ocean basins. To better understand the emplacement of submarine lava flows at MORs, we have integrated submersible-based geologic mapping with remote sensing techniques to characterize the lava flow morphology within previously mapped lava flow fields produced during single eruptive episodes at the Galápagos Spreading Center (GSC). Detailed attributes describing the surface geometry and texture of the lava flows have been extracted from high-resolution sonar data and combined with georeferenced visual observations from submersible dives and camera tows; based on signatures contained in these data, a fuzzy logic-based classification algorithm categorized lava flow morphology as pillows, lobates, or sheets. The resulting digital thematic maps offer an unprecedented view of GSC lava morphology, collectively covering 77 km2 of ridge axis terrain at a resolution of 2 m × 2 m. Error assessments with independent visual reference data indicate approximately 90% agreement, comparable to subaerial classification studies. The digital lava morphology maps enable quantitative, spatially comprehensive measurements of the abundance and distribution of lava morphologies over large areas of seafloor and within individual eruptive units. A comparison of lava flow fields mapped at lower- and higher-magma-supply settings (95° and 92°W, respectively) indicates that effusion rates increase along with magma supply and independent of spreading rate at the GSC, although a complete range of eruptive behavior exists at each setting.

  18. Reliability of rock magnetic properties and paleointensity along vertical basalt flow profiles: identification of best part for sampling?

    Science.gov (United States)

    Alva-Valdivia, L. M.; Caballero, C. M.; Bohnel, H.

    2013-12-01

    A review of the rock magnetic properties, AMS, opaque microscopy and paleointensity (PI) of two vertical single lava flows (RM and PC) and its comparison with the CU profile of Xitle volcano are presented. The emplacement dynamics of the RM and PC lava flows indicates that possibly was via inflation in its internal structure. We search for the possible explanation (emplacement physics, mineralogical, magnetic anomalies) to the variability of magnetic properties and PI along the lava flows, and at the same time look for the best part to get the paleomagnetic samples. Considerable intra- and inter-flow differences in both the characteristic directions and paleointensities are observed both in one of the new profiles (RM) and previous studies of sites distributed across the lava field. These variations do not correlate with any of the measured physical or magnetic properties of the flows. At any one site the mean directions are well defined and it is only when considered collectively that the inconsistencies are recognized. Intra-flow and inter-site PI variations are large: a total of 117 determinations yield between 36.6 and 139.7 μT. Within this range it is difficult to recognize a best estimate on the basis of rock magnetic criteria. These results raise questions about the reliability of lavas as paleomagnetic recorders and highlight the importance of sampling strategy in obtaining representative flow-mean parameters. Thellier-type PI data from Mexico are related to global records, which could indicate that non-dipole features might be responsible for the higher than expected results. However, the scarcity of available data obscures the significance of this observation and the balance of evidence rather suggest an artificial biasing of most measurements towards high values. This is in contrasts to the AMS results, which suggests that in the Xitle lava flows their (almost) lower part are the best to give reliable PI studies results.

  19. Insights on the 2010 Lava Flows of Piton de la Fournaise Using Cosmo-SkyMed and TanDEM-X Data: Lava Displacement Rates, Thicknesses, and Volume Estimates

    Science.gov (United States)

    Bato, M. G.; Froger, J. L.; Harris, A. J. L.; Villeneuve, N.

    2014-12-01

    Characterization of lava flow after its emplacement provides volume and constraints for lava flow emplacement simulations that help assess pending volcanic hazards. Additionally, it gives us better insights in understanding the dynamics of the underlying magmatic plumbing system and the possible mechanism of the eruption. In this work, we developed a technique using monostatic Cosmo-SkyMed and bistatic TanDEM-X data to calculate the volume, measure the thickness, and the horizontal and vertical displacements immediately after the emplacement of the October 2010 lava flow at Piton de la Fournaise. Results show that the thickest part of the October 2010 lava flow is about 13 to 16 m and the DRE volume is estimated to fall within the range of 1.71 to 3.00 x 106 m3 (±1σ), depending on which InSAR database was used. We also observe that the October 2010 lava flow is subsiding at a maximum rate of 14 cm yr-1. Apart from the vertical displacement, joint sliding and centripetal displacement were also identified with a maximum rate of 4.0 cm yr-1. We cross-validated our InSAR results with the mixed-pixel technique of Harris [1997] in terms of the estimated volumes. Our analysis shows that the volume derived using a few TanDEM-X interferograms fitted well within the range of volume given by the mixed-pixel technique as compared to the huge monostatic Cosmo-SkyMed database. In addition to the October 2010 lava flow, we also characterized the thin lava flow deposit of the December 2010 eruption, however using only bistatic TanDEM-X data. In this case of thin lava deposits, we expect that TanDEM-X are best to use in deriving the thickness and estimating the volume as these type of data are more sensitive to topographic change. Reference: Harris AJL, Blake S, Rothery DA, Stevens NF., 1997. A chronology of the 1991 to 1993 Mount Etna eruption using advanced very high resolution radiometer data: implications for real-time thermal volcano monitoring. Geophys. Res. Lett. 102:7985-8003.

  20. Flow-by-flow chemical stratigraphy and evolution of thirteen Serra Geral Group basalt flows from Vista Alegre, southernmost Brazil

    Directory of Open Access Journals (Sweden)

    Viter M Pinto

    2011-06-01

    Full Text Available The geochemical characterization of thirteen Serra Geral Group flows in the Vista Alegre region (RS-SC, southern Brazil, displays the homogeneous basaltic composition near 50 wt.% SiO2. Each of the five basal flows (Pitanga-type, high-Ti/Y ~600, TiO2 > 3 wt.% and eight upper flows (Paranapanema-type, medium Ti/Y ~400, TiO2 > 2 wt.% can be identified from their chemical composition; sets of flows have parallel variation in chemical composition. The flow-by-flowcorrelation in four sections shows the horizontal position of the flows in three profiles and an approximately 200-m downdrop of the Itapiranga block with respect to the Frederico Westphalen block. The world-class amethyst geode mineralization and the systematic presence of native copper in the basalts make the correlation of great geological and economic significance.A caracterização geoquímica de treze derrames do Grupo Serra Geral na região de Vista Alegre (RS e SC, sul do Brasil, exibe uma composição basáltica homogênea próxima a 50% de SiO2. Os cinco derrames basais são classificados quimicamente como tipo Pitanga (alto Ti/Y ~600 e TiO2 > 3 em peso percentual, os demais oito derrames possuem médio Ti/Y ~400 com TiO2 ~2.5 em peso percentual, sendo classificados como magma tipo Paranapanema. Cada derrame pode ser identificado através de sua composição química e correlacionado, com variação paralela entre os perfis estudados. A correlação derrame a derrame nos quatro perfis demonstra uma posição horizontal em três perfis e um rejeito vertical de aproximadamente 200 m do bloco Itapiranga em relação ao bloco Frederico Westphalen. A presença de jazidas de ametista em geodos e a sistemática ocorrência de cobre nativo nos basaltos da região tornam a correlação de grande significado geológico e econômico.

  1. Satellite Measurements of Lava Extrusion Rate at Volcán Reventador, Ecuador

    Science.gov (United States)

    Arnold, D. W. D.; Biggs, J.; Ebmeier, S. K.; Vallejo Vargas, S.; Naranjo, M. F.

    2015-12-01

    The extrusion rate of lava at active volcanoes provides a principle control on the style of eruptive behavior and the extent of lava flows, while also providing information about magma supply to the volcano. Measurements of extrusion rate at active volcanoes are therefore important for assessing hazard, and improving understanding of volcanic systems. Volcán Reventador is an asymmetric stratovolcano in the Cordillera Real of Ecuador. The largest historically observed eruption at Reventador in 2002 has been followed by several periods of eruptive activity. Eruptions are characterised by effusion of andesitic to basaltic-andesitic lava flows, and Vulcanian explosions. The ongoing eruption at Reventador therefor provides an excellent target for investigating the link between effusion rate, explosivity, and lava flow behaviour. Satellite InSAR provides regular observations of the volcano, even during night or periods of cloud cover. We use a dataset of Radarsat-2 and TanDEM-X imagery, with intervals of 11 to 192 days, over the period 2011 to 2014 to measure the extent, thickness and volume of new lava flows at Reventador. We use radar amplitude and inteferometric coherence to map 25 individual lava flows, as well as pyroclastic deposits and changes in lava dome morphology. We observe 43 Mm3 of deposits over a three year period, giving an average effusion rate of 0.5 m3s-1. We do not observe any ground deformation due to magmatic sources at Reventador, therefore variations in lava effusion rate can be interpreted as changes in the magma supply to the volcano. We investigate the link between variations in effusion rate and the length, area, thickness, and aspect ratio of lava flows, and the explosive-effusive transition. We also characterise the relationship between lava flow age, thickness, and subsidence rate.

  2. Preliminary assessment for the use of VORIS as a tool for rapid lava flow simulation at Goma Volcano Observatory, Democratic Republic of the Congo

    Science.gov (United States)

    Syavulisembo, A. M.; Havenith, H.-B.; Smets, B.; d'Oreye, N.; Marti, J.

    2015-10-01

    Assessment and management of volcanic risk are important scientific, economic, and political issues, especially in densely populated areas threatened by volcanoes. The Virunga volcanic province in the Democratic Republic of the Congo, with over 1 million inhabitants, has to cope permanently with the threat posed by the active Nyamulagira and Nyiragongo volcanoes. During the past century, Nyamulagira erupted at intervals of 1-4 years - mostly in the form of lava flows - at least 30 times. Its summit and flank eruptions lasted for periods of a few days up to more than 2 years, and produced lava flows sometimes reaching distances of over 20 km from the volcano. Though most of the lava flows did not reach urban areas, only impacting the forests of the endangered Virunga National Park, some of them related to distal flank eruptions affected villages and roads. In order to identify a useful tool for lava flow hazard assessment at Goma Volcano Observatory (GVO), we tested VORIS 2.0.1 (Felpeto et al., 2007), a freely available software (http://www.gvb-csic.es) based on a probabilistic model that considers topography as the main parameter controlling the lava flow propagation. We tested different parameters and digital elevation models (DEM) - SRTM1, SRTM3, and ASTER GDEM - to evaluate the sensitivity of the models to changes in input parameters of VORIS 2.0.1. Simulations were tested against the known lava flows and topography from the 2010 Nyamulagira eruption. The results obtained show that VORIS 2.0.1 is a quick, easy-to-use tool for simulating lava-flow eruptions and replicates to a high degree of accuracy the eruptions tested when input parameters are appropriately chosen. In practice, these results will be used by GVO to calibrate VORIS for lava flow path forecasting during new eruptions, hence contributing to a better volcanic crisis management.

  3. Rate of deformation in the Pasco Basin during the Miocene as determined by distribution of Columbia River basalt flows

    International Nuclear Information System (INIS)

    Detailed mapping of over 8000 square kilometers and logs from 20 core holes were used to determine the distribution and thickness of basalt flows and interbeds in the Pasco Basin. The data indicate the high-MgO Grande Ronde Basalt and Wanapum Basalt thicken from the northeast to the southwest. Deformation began in late Frenchman Springs time in the Saddle Mountains along a northwest-southeast trend and in Roza time along an east-west trend. By late Wanapum time, basalt flows were more restricted on the east side. Saddle Mountains Basalt flows spread out in the basin from narrow channels to the east. The Umatilla Member entered from the southeast and is confined to the south-central basin, while the Wilbur Creek, Asotin, Esquatzel, Pomona, and Elephant Mountain Members entered from the east and northeast. The distribution of these members is controlled by flow volume, boundaries of other flows, and developing ridges. The Wilbur Creek, Asotin, and Esquatzel flows exited from the basin in a channel along the northern margin of the Umatilla flow, while the Pomona and Elephant Mountain flows exited between Umtanum Ridge and Wallula Gap. The thickness of sedimentary interbeds and basalt flows indicated subsidence and/or uplift began in post-Grande Ronde time (14.5 million years before present) and continued through Saddle Mountains time (10.5 million years before present). Maximum subsidence occurred 40 kilometers (24 miles) north of Richland, Washington with an approximate rate of 25 meters (81 feet) per million years during the eruption of the basalt. Maximum uplift along the developing ridges was 70 meters (230 feet) per million years

  4. Emplacement of Basaltic Flow Fields: New Insights Using MODIS/ASTER Airborne Simulator (MASTER) Data

    Science.gov (United States)

    Byrnes, J. M.; Ramsey, M. S.; Crown, D. A.

    2001-12-01

    Surface units that reflect local emplacement conditions within the 1969-1974 Mauna Ulu lava flow field (Kilauea Volcano, Hawaii) have been identified and are being mapped using field observations and remote sensing analyses. Investigation of a preliminary study site on and below Holei Pali utilized high-resolution color aerial photographs [Byrnes and Crown, 2000. J Geophys Res 106, 2139-2151] and TIMS (Thermal Infrared Multispectral Scanner) airborne data. Four surface units were identified that are related to the state of the lava during emplacement and were found to be correlated with the pre-eruption topography but not to the major lava tube segments mapped previously. These units show variations at visible wavelengths related to color, the presence of a glassy surface crust, and unit (dm- to m-scale) morphology. Variations at thermal wavelengths are presumably related to surface variations in phenocryst abundance, vesicles/micron-scale roughness, and glass. Interpretations based on the TIMS data are significantly limited by noise in available data covering the flow field. The present study uses MASTER (MODIS/ASTER airborne simulator) data to extend the spatial and spectral coverage of the Mauna Ulu flow field. Preliminary analyses of the data (corrected for atmospheric effects) indicate that: (1) additional classes of surface units (such as shelly pahoehoe) can be identified within the flow field, and (2) systematic changes in emplacement occurred from the proximal to the medial and distal portions of the flow field. Comparison with ASTER images indicates that similar classes of surface units may be discriminated in both datasets, though MASTER is preferable for this study because it provides: (1) higher spatial resolution (especially in thermal bands), and (2) constant pixel size for all wavelengths. These factors allow for discrimination of smaller flow units and more accurate correlation of visible- and thermal-wavelength spectral signatures. The higher

  5. Identification of Columbia River basalt flows from deep cores in the Pasco Basin based on trace element abundances

    Energy Technology Data Exchange (ETDEWEB)

    Fruchter, J.S.; Rancitelli, L.A.

    1976-03-31

    Samples of basalt from three deep core holes drilled in the Pasco Basin, Washington (DDH-3, DH-4, DH-5) were analyzed by instrumental neutron activation (INAA) for up to fifteen trace and major elements. These analyses were used to assign each basalt flow to one of a series of previously defined chemical types of the Columbia River Basalt Group. All of the flows except the two flows at the bottom of well DDH-3 were clearly assignable to one of the defined chemical types. These two flows apparently represent new, as yet undefined chemical types. Average values and standard deviations for compositions of each of the chemical types found in the three wells are presented along with two-element variation diagrams for the geochemically important pair La-Cr, La-Fe, La-Th and La-Sc. The assignment of the flows to known chemical types accomplished in this study was very helpful in relating the basalts in the core holes to stratigraphically defined basalt flows in surface sections. A correlation diagram relating the flows in the core holes to one another on the basis of chemical type is presented.

  6. Hawaii Volcanism: Lava Forms

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Over the last several million years the Hawaiian Islands have been built of successive lava flows. They are the most recent additions in a long line of volcanoes...

  7. The eruptive history of the Trous Blancs pit craters, La Réunion Island: The origin of a 24 km long lava flow

    Science.gov (United States)

    Walther, Georg; Frese, Ingmar; Di Muro, Andrea; Kueppers, Ulrich; Michon, Laurent; Métrich, Nicole

    2015-04-01

    The assessment of volcanic hazards is strongly based on the past eruptive behaviour of volcanoes and its morphological parameters. Since past eruption characteristics and their frequency provide the best probabilities of such eruptions for the future, understanding the complete eruptive history of a volcano is one of the most powerful tools in assessing the potential hazards or eruptions. At Piton de la Fournaise (PdF) volcano (La Réunion, Indian Ocean), the most frequent style of activity is the effusion of lava flows, which pose the greatest hazard by invasion of inhabited areas and destruction of human property. Here we examined the eruptive history of a previously uninvestigated area, believed to be the origin of a 24 km long lava flow. The eruptions recurrence time of PdF is about one eruption every 9 months in the central caldera. Besides this central activity, eruptive vents have been built along three main rift zones cutting the edifice during the last 50 kyrs. In this study we focused on the largest rift zone of about 15 km width and 20 km length, which extends in a north westerly direction between PdF and the nearby Piton des Neiges volcanic complex. This rift zone is typified by deep seismicity (up to 30 km), emitting mostly primitive magmas, indicative of high fluid pressures (up to 5 kbar) and large volume eruptions. Our area of investigation focused on four consecutively aligned pit craters called the Trous Blancs. These have been identified [1] as the source area of one of the youngest (ca. 6 kyrs) and largest lava field, which extends for 24 km from a height of 1800m asl, passing Le Tampon and Saint Pierre city, until it reaches the coast. To gain insight into the development of this eruption and possible future similar activity, we collected new field data (including stratigraphic logs, a geological map of the area, C-14 dating and geochemical analyses of the eruptive products). Fieldwork revealed that the eruption initiated with intense

  8. Asthenosphere–lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah

    Science.gov (United States)

    Konrad, Kevin;; Graham, David W; Thornber, Carl; Duncan, Robert A; Kent, Adam J.R.; Al-Amri, Abdulla

    2016-01-01

    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (< 850 ka) and the northeasternmost of the volcanic fields. There is a remarkable homogeneity of 3He/4He trapped within most xenoliths, with a weighted mean of 7.54 ± 0.03 RA (2σ, n = 20). This homogeneity occurs over at least eight different xenolith types (including spinel lherzolite, amphibole clinopyroxenite, olivine websterite, clinopyroxenite and garnet websterite), and encompasses ten different volcanic centers within an area of ~ 2500 km2. The homogeneity is caused by volatile equilibration between the xenoliths and fluids derived from their host magma, as fluid inclusions are annealed during the infiltration of vapor-saturated magmas along crystalline grain boundaries. The notable exceptions are the anhydrous spinel lherzolites, which have a lower weighted mean 3He/4He of 6.8 ± 0.3 RA (2σ, n = 2), contain lower concentrations of trapped He, and have a distinctly depleted light rare earth element signature. 3He/4He values of ~ 6.8 RA are also commonly found in spinel lherzolites from harrats Ithnayn, Al Birk, and from Zabargad Island in the Red Sea. Olivine from non-xenolith-bearing lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting.

  9. Asthenosphere-lithosphere interactions in Western Saudi Arabia: Inferences from 3He/4He in xenoliths and lava flows from Harrat Hutaymah

    Science.gov (United States)

    Konrad, Kevin; Graham, David W.; Thornber, Carl R.; Duncan, Robert A.; Kent, Adam J. R.; Al-Amri, Abdullah M.

    2016-04-01

    Extensive volcanic fields on the western Arabian Plate have erupted intermittently over the last 30 Ma following emplacement of the Afar flood basalts in Ethiopia. In an effort to better understand the origin of this volcanism in western Saudi Arabia, we analyzed 3He/4He, and He, CO2 and trace element concentrations in minerals separated from xenoliths and lava flows from Harrat Hutaymah, supplemented with reconnaissance He isotope data from several other volcanic fields (Harrat Al Birk, Harrat Al Kishb and Harrat Ithnayn). Harrat Hutaymah is young (caused by volatile equilibration between the xenoliths and fluids derived from their host magma, as fluid inclusions are annealed during the infiltration of vapor-saturated magmas along crystalline grain boundaries. The notable exceptions are the anhydrous spinel lherzolites, which have a lower weighted mean 3He/4He of 6.8 ± 0.3 RA (2σ, n = 2), contain lower concentrations of trapped He, and have a distinctly depleted light rare earth element signature. 3He/4He values of ~ 6.8 RA are also commonly found in spinel lherzolites from harrats Ithnayn, Al Birk, and from Zabargad Island in the Red Sea. Olivine from non-xenolith-bearing lava flows at Hutaymah spans the He isotope range of the xenoliths. The lower 3He/4He in the anhydrous spinel lherzolites appears to be tied to remnant Proterozoic lithosphere prior to metasomatic fluid overprinting. Elevated 3He/4He in the western harrats has been observed only at Rahat (up to 11.8 RA; Murcia et al., 2013), a volcanic field situated above thinned lithosphere beneath the Makkah-Medinah-Nafud volcanic lineament. Previous work established that spinel lherzolites at Hutaymah are sourced near the lithosphere-asthenosphere boundary (LAB), while other xenolith types there are derived from shallower depths within the lithosphere itself (Thornber, 1992). Helium isotopes are consistent with melts originating near the LAB beneath many of the Arabian harrats, and any magma derived from

  10. Differences in Landsat TM derived lava flow thermal structures during summit and flank eruption at Mount Etna

    Science.gov (United States)

    Lombardo, V.; Buongiorno, M. F.; Pieri, D.; Merucci, L.

    2004-06-01

    The simultaneous solution of the Planck equation (the so-called "dual-band" technique) for two shortwave infrared Landsat Thematic Mapper (TM) bands allows an estimate of the fractional area of the hottest part of an active flow and the temperature of the cooler crust. Here, the dual-band method has been applied to a time series of Mount Etna eruptions. The frequency distribution of the fractional area of the hottest component reveals specific differences between summit and flank lava flows. The shape of the density function shows a trend consistent with a Gaussian distribution and suggests a relationship between the moments of the distribution and the emplacement environment. Because flow composition of Etnean lavas generally remains constant during the duration of their emplacement, it appears that the shape of any particular frequency distribution is probably related to fluid mechanical aspects of flow emplacement that affect flow velocity and flow heat loss and thus the rate of formation of the surface crust. These factors include the influence of topographical features such as changes in slope gradient, changes in volume effusion rate, and progressive downflow increases in bulk or effective viscosity. A form of the general theoretical solution for the 'dual-band' system, which illustrates the relationship between radiance in TM bands 5 and 7, corresponding to hot fractional area and crust temperature, is presented. Generally speaking, it appears that for a given flow at any point in time, larger fractional areas of exposed hot material are correlated with higher temperatures and that, while the overall shape of that distribution is common for the flows studied, its amplitude and slope reflect individual flow rheological regimes.

  11. Uses of anisotropy of magnetic susceptibility in the study of emplacement processes of lava flows and dykes

    International Nuclear Information System (INIS)

    Complete text of publication follows. The anisotropy of magnetic susceptibility (AMS) is a powerful technique that can be used to explore in detail the mineral fabric of many types of rocks. In particular, it is well suited to determine mineral fabric of massive, otherwise featureless rocks, like for example the internal parts of many lava flows and dykes. Like most other mineral fabric indicators, the AMS is mainly acquired at a stage when flow-related deformation promotes a mineral array within the melted rock. Unlike is the case with other petrofabric methods, however, the effort required to obtain three-dimensional information of such mineral array using AMS is much reduced, although due to differences in the shape of various minerals involved in the process of fabric acquisition it is possible to find some differences between magnetic and optically determined mineral fabrics. When attention is given to the systematic variations of the AMS within a lava flow or dyke, however, the AMS method allows us to infer aspects of lava (magma) emplacement that are not easy to study through other traditional petrofabric techniques. Such detailed information can be used to obtain a detailed record of the internal deformation of one flow unit with relative ease and little effort. Despite of these advantages, the abundant information obtained from one single unit through AMS methods might not be interpreted in a simple form. The main complications arise from two contrasting premises. On the one hand it can be assumed that mineral fabric remains constant along one single unit, and therefore departures from an expected value are considered indicative of post-emplacement alteration. Alternatively, it can be considered that changes in the mineral fabric are to be expected due to changing conditions of emplacement. For this reason, a more thoroughly investigation that takes into consideration independent lines of information is always advisable. Nevertheless, AMS remains as the

  12. A glassy lava flow from Toconce volcano and its relation with the Altiplano-Puna Magma Body in Central Andes

    Science.gov (United States)

    Godoy, B.; Rodriguez, I.; Aguilera, F.

    2012-12-01

    Toconce is a composite stratovolcano located at the San Pedro - Linzor volcanic chain (SPLVC). This volcanic chain distributes within the Altiplano-Puna region (Central Andes) which is characterized by extensive rhyodacitic-to-rhyolitic ignimbritic fields, and voluminous domes of dacitic-to-rhyolitic composition (de Silva, 1989). The felsic melts that gave origin to ignimbrites and domes at this area were generated by mixing of mantle-derived magmas and anatectic melts assimilated during their ascent through the thick crust. Thus, partially molten layers exist in the upper crust below the APVC (de Silva et al., 2006). Evidence of large volumes of such melts has been also proposed by geophysical methods (i.e. the Altiplano-Puna Magma Body; Chmielowsky et al., 1999) In this work, petrography and whole rock, mineralogical and melt inclusions geochemistry of a glassy lava flow of Toconce volcano are presented. Petrographically, this lava flow shows a porphyric texture, with euhdral to subhedral plagioclase, ortho- and clino-pyroxene phenocrysts immersed in a glassy groundmass. Geochemically, the lava flow has 64.7% wt. SiO2. The glassy groundmass (~70% wt. SiO2) is more felsic than all the lavas in the volcanic chain (47-68% wt., Godoy et al., 2011). Analyzed orthopyroxene-hosted melt inclusions show an even higher SiO2 content (72-75% wt.), and a decreasing on Al2O3, Na2O, and CaO content with differentiation. Crystallization pressures of this lava flow, obtained using Putirka's two-pyroxene and clinopyroxene-liquid models (Putirka, 2008), range between 6 and 9 kbar. According to crystallization pressures, and major element composition, a felsic source located at shallow crustal pressures - where plagioclase is a stable mineralogical phase - originated the inclusions. This could be related to the presence of the Altiplano-Puna Magma Body (APMB) located below SPLVC. On the other hand, glassy groundmass, and disequilibrium textures in minerals of this lava flow could

  13. Geologic mapping on the deep seafloor: Reconstructing lava flow emplacement and eruptive history at the Galápagos Spreading Center

    Science.gov (United States)

    McClinton, J. T.; White, S.; Colman, A.; Sinton, J. M.; Bowles, J. A.

    2012-12-01

    The deep seafloor imposes significant difficulties on data collection that require the integration of multiple data sets and the implementation of unconventional geologic mapping techniques. We combine visual mapping of geological contacts by submersible with lava flow morphology maps and relative and absolute age constraints to create a spatiotemporal framework for examining submarine lava flow emplacement at the intermediate-spreading, hotspot-affected Galápagos Spreading Center (GSC). We mapped 18 lava flow fields, interpreted to be separate eruptive episodes, within two study areas at the GSC using visual observations of superposition, surface preservation and sediment cover from submersible and towed camera surveys, augmented by high-resolution sonar surveys and sample petrology [Colman et al., Effects of variable magma supply on mid-ocean ridge eruptions: Constraints from mapped lava flow fields along the Galápagos Spreading Center; 2012 G3]. We also mapped the lava flow morphology within the majority of these eruptive units using an automated, machine-learning classification method [McClinton et al., Neuro-fuzzy classification of submarine lava flow morphology; 2012 PE&RS]. The method combines detailed geometric, acoustic, and textural attributes derived from high-resolution sonar data with visual observations and a machine-learning algorithm to classify submarine lava flow morphology as pillows, lobates, or sheets. The resulting lava morphology maps are a valuable tool for interpreting patterns in the emplacement of submarine lava flows at a mid-ocean ridge (MOR). Within our study area at 92°W, where the GSC has a relatively high magma supply, high effusion rate sheet and lobate lavas are more abundant in the oldest mapped eruptive units, while the most recent eruptions mostly consist of low effusion rate pillow lavas. The older eruptions (roughly 400yrs BP by paleomagnetic intensity) extend up to 1km off axis via prominent channels and tubes, while the

  14. Subsidence of Puna, Hawaii inferred from sulfur content of drilled lava flows

    Science.gov (United States)

    Moore, J.G.; Thomas, D.M.

    1988-01-01

    Sulfur was analyzed in more than 200 lava samples from five drill holes located on the east rift zone of Kilauea volcano on the island of Hawaii. The sulfur content is a gage of whether lava was erupted subaerially (low sulfur) or erupted subaqueously (high sulfur). Despite considerable variation, sulfur is generally low (less than 0.025%) in the upper part of the holes, begins to increase at a depth of 250-320 m below sea level, and generally reaches a high level (greater than 0.1%) indicative of steady submarine eruption at 330-450 m below sea level. Assuming that the island is subsiding at 2.4 mm/yr, an analysis of these data indicates that part of the variation in sulfur concentration results from past eustatic oscillation of sea level, and that the volcano (at the drill hole site) finally emerged for the last time about 98 ka. The long-term average rate of lava accumulation is roughly 4.4 mm/yr, and upward growth of the volcano at the drill hole area is about 2 mm/yr in excess of subsidence. ?? 1988.

  15. Mapping the vegetation colonization on recent lava flows using spectral unmixing of moderate spatial resolution satellite images: Nyamuragira volcano, D. R. Congo

    Science.gov (United States)

    Li, Long; Kervyn, Matthieu; Canters, Frank

    2014-05-01

    In volcanic areas, vegetation colonizes recently erupted lava flows and expands over time. The fraction of vegetation is therefore likely to provide information on lava flows' age. Individual lava flows are usually not well resolved on satellite imagery due to the coarse spatial resolution: one pixel on the imagery is a mixture of mainly lava and vegetation. In order to solve the mixed pixel problem, many different methods have been proposed among which linear spectral unmixing is the most widely-used. It assumes that the reflectance of the mixed pixel is the sum of the reflectance of each pure end members multiplied by their proportion in the pixel. It has been frequently used in urban area studies, but no efforts have yet been made to apply it to volcanic areas. Here, we demonstrate the application of linear spectral unmixing for the lava flows of Nyamuragira volcano, in the Virunga Volcanic province. Nyamuragira is an active volcano, emitting over 30 lava flows in the last 100 years. The limited access to the volcano due to social unrest in D. R. Congo justifies the value of remote sensing techniques. This shield volcano is exposed to tropical climate and thus vegetation colonizes lava flows rapidly. An EO-1 ALI image (Advanced land imager mounted on Earth Observing -1 Satellite) acquired over Nyamuragira on January 3, 2012 at spatial resolution of 30 m was processed with minimum noise fraction transform and end member extraction, and spectrally unmixed by linear mixture modelling technique into two types of lava, and one or two types of vegetation. The three end member model is better in terms of the RMSE and the expected spatial distribution of end members. A 2 m resolution Pleiades image acquired on January 21, 2013 and partly overlapping with the ALI image was taken as the reference image for validation. It was first classified using a supervised pixel-based classification technique and then compared to the proportion image derived from the ALI image

  16. Permeameter studies of water flow through cement and clay borehole seals in granite, basalt and tuff

    International Nuclear Information System (INIS)

    Boreholes near a repository must be sealed to prevent rapid migration of radionuclide-contaminated water to the accessible environment. The objective of this research is to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. Flow through a sealed borehole is compared with flow through intact rock. Cement or bentonite seals have been tested in granite, basalt, and welded tuff. The main conclusion is that under laboratory conditions, existing commercial materials can form high quality seals. Triaxial stress changes about a borehole do not significantly affect seal performance if the rock is stiffer than the seal. Temperature but especially moisture variations (drying) significantly degrade the quality of cement seals. Performance partially recovers upon resaturation. A skillfully sealed borehole may be as impermeable as the host rock. Analysis of the influence of relative seal-rock permeabilities shows that a plug with permeability one order of magnitude greater than that of the rock results in a flow increase through the hole and surrounding rock of only 1-1/2 times compared to the undisturbed rock. Since a borehole is only a small part of the total rock mass, the total effect is even less pronounced. The simplest and most effective way to decrease flow through a rock-seal system is to increase the seal length, assuming it can be guaranteed that no dominant by-pass flowpath through the rock exists

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

    Science.gov (United States)

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

    2014-05-01

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

  18. The 2011 El Hierro submarine eruption: estimation of erupted lava flow volume on the basis of helicopter thermal surveys

    Science.gov (United States)

    Hernández, P. A.; Calvari, S.; Calvo, D.; Marquez, A.; Padron, E.; Pérez, N.; Melian, G.; Padilla, G.; Barrancos, J.; Dionis, S.; Rodríguez, F.; Nolasco, D.; Hernández, I.

    2012-04-01

    been collected each time in order to compare the temperature distribution with the features observed on the sea surface. Calculation of lava flow volume and effusion rate from thermal images collected by helicopter surveys has been largely used during the last decade for monitoring effusive eruptions at Etna, Stromboli, Kilauea, and other volcanoes. In this study, lava flow volume is calculated on the basis of temperature difference between the seawater contained within the dark patch, and the temperature of the seawater surface away from the eruption. These values have to be considered as minimum values, because they do not take into account the volume of lava isolated from the seawater by a thick crust that did not contribute to seawater warming. To calculate the lava volume we have used the model proposed by Harris et al. (1998) for the portion of the lava flow field spreading below sea level. Preliminary results indicate that during the period of study, about 5Mm3 of magma have been needed to heat the observed surface heated sea water at the submarine eruption site.

  19. Variations of magnetic properties in thin lava flow profiles: Implications for the recording of the Laschamp Excursion

    Science.gov (United States)

    Vérard, Christian; Leonhardt, Roman; Winklhofer, Michael; Fabian, Karl

    2012-06-01

    Two blocks have been cut in two lava flows from the Skalamaelifell Hill (Iceland) known to have recorded the Laschamp magnetic excursion (40.4 ± 2.0 ka). Detailed sampling and analyses have revealed multiple magnetic components. The high temperature/coercivity component corresponds to the primary magnetisation, with corresponding pole position close to the equator in the Pacific Ocean (φ = 251.90°/λ = -06.49°; dp = 0.74°/dm = 2.12°) and palaeo-intensity determinations below 5 μT. The different VGPs, however, vary in relation with the position of samples in the profiles. It could not be firmly established whether this distribution is associated with a change in the Earth magnetic field during lava cooling. In any case, variations are related with zones in the profiles marked, in particular, by the presence of vesicles. Moreover, the other components are interpreted to be linked with alteration inside the rocks, caused by interactions between vesicles content and the surrounding matrix. Secondary component, however, is interpreted as recording an excursional magnetic field, and should be of greater consideration in studies of Earth magnetic field excursions or reversals.

  20. Circulation patterns in active lava lakes

    Science.gov (United States)

    Redmond, T. C.; Lev, E.

    2014-12-01

    Active lava lakes provide a unique window into magmatic conduit processes. We investigated circulation patterns of 4 active lava lakes: Kilauea's Halemaumau crater, Mount Erebus, Erta Ale and Nyiragongo, and in an artificial "lava lake" constructed at the Syracuse University Lava Lab. We employed visual and thermal video recordings collected at these volcanoes and use computer vision techniques to extract time-dependent, two-dimensional surface velocity maps. The large amount of data available from Halemaumau enabled us to identify several characteristic circulation patterns. One such pattern is a rapid acceleration followed by rapid deceleration, often to a level lower than the pre-acceleration level, and then a slow recovery. Another pattern is periodic asymmetric peaks of gradual acceleration and rapid deceleration, or vice versa, previously explained by gas pistoning. Using spectral analysis, we find that the dominant period of circulation cycles at approximately 30 minutes, 3 times longer than the dominant period identified previously for Mount Erebus. Measuring a complete surface velocity field allowed us to map and follow locations of divergence and convergence, therefore upwelling and downwelling, thus connecting the surface flow with that at depth. At Nyiragongo, the location of main upwelling shifts gradually, yet is usually at the interior of the lake, for Erebus it is usually along the perimeter yet often there is catastrophic downwelling at the interior; For Halemaumau upwelling/downwelling position is almost always on the perimeter. In addition to velocity fields, we developed an automated tool for counting crustal plates at the surface of the lava lakes, and found a correlation, and a lag time, between changes if circulation vigor and the average size of crustal plates. Circulation in the artificial basaltic lava "lake" was limited by its size and degree of foaming, yet we measured surface velocities and identify patterns. Maximum surface velocity

  1. Gusev Rocks Solidified from Lava (Approximate True Color)

    Science.gov (United States)

    2006-01-01

    In recent weeks, as NASA's Mars Exploration Rover Spirit has driven through the basin south of 'Husband Hill,' it has been traversing mainly sand and dune deposits. This week, though, Spirit has been maneuvering along the edge of an arc-shaped feature called 'Lorre Ridge' and has encountered some spectacular examples of basaltic rocks with striking textures. This panoramic camera (Pancam) image shows a group of boulders informally named 'FuYi.' These basaltic rocks were formed by volcanic processes and may be a primary constituent of Lorre Ridge and other interesting landforms in the basin. Spirit first encountered basalts at its landing site two years ago, on a vast plain covered with solidified lava that appeared to have flowed across Gusev Crater. Later, basaltic rocks became rare as Spirit climbed Husband Hill. The basaltic rocks that Spirit is now seeing are interesting because they exhibit many small holes or vesicles, similar to some kinds of volcanic rocks on Earth. Vesicular rocks form when gas bubbles are trapped in lava flows and the rock solidifies around the bubbles. When the gas escapes, it leaves holes in the rock. The quantity of gas bubbles in rocks on Husband Hill varies considerably; some rocks have none and some, such as several here at FuYi, are downright frothy. The change in textures and the location of the basalts may be signs that Spirit is driving along the edge of a lava flow. This lava may be the same as the basalt blanketing the plains of Spirit's landing site, or it may be different. The large size and frothy nature of the boulders around Lorre Ridge might indicate that eruptions once took place at the edge of the lava flow, where the lava interacted with the rocks of the basin floor. Scientists hope to learn more as Spirit continues to investigate these rocks. As Earth approaches the Chinese New Year (The Year of the Dog), the Athena science team decided to use nicknames representing Chinese culture and geography to identify rocks and

  2. Lava tubes and aquifer vulnerability in the upper Actopan River basin, Veracruz, México

    Science.gov (United States)

    Espinasa-Pereña, R.; Delgado Granados, H.

    2011-12-01

    Rapid infiltration leads to very dry conditions on the surface of some volcanic terrains, with large allogenic streams sometimes sinking underground upon reaching a lava flow. Aquifers in lava flows tend to be heterogeneous and discontinuous, generally unconfined and fissured, and have high transmissivity. Springs associated with basalts may be very large but are typically restricted to lava-flow margins. Concern has been expressed regarding the potential for lava-tube caves to facilitate groundwater contamination similar to that afflicting some karst aquifers (Kempe et al., 2003; Kiernan et al., 2002; Halliday 2003). The upper Actopan River basin is a series of narrow valleys excavated in Tertiary volcanic brechias. Several extensive Holocene basaltic tube-fed lava flows have partially filled these valleys. The youngest and longest flow originates at El Volcancillo, a 780 ybP monogenetic volcano. It is over 50 km long, and was fed through a major master tube, the remains of which form several lava-tube caves (Gassos and Espinasa-Pereña, 2008). Another tube-fed flow initiates at a vent at the bottom of Barranca Huichila and can be followed for 7 km to where it is covered by the Volcancillo flow. The Huichila River is captured by this system of lava tubes and can be followed through several underground sections. In dry weather the stream disappears at a sump in one of these caves, although during hurricanes it overflows the tube, floods the Tengonapa plain, and finally sinks through a series of skylights into the master tube of the Volcancillo flow. Near villages, the cave entrances are used as trash dumps, which are mobilized during floods. These include household garbage, organic materials associated with agriculture and even medical supplies. This is a relatively recent phenomenon, caused by population growth and the building of houses above the lava flows. The water resurges at El Descabezadero, gushing from fractures in the lava above the underlying brechias

  3. K-Ar dating of lavas from Zao volcano, North-eastern Japan

    International Nuclear Information System (INIS)

    The K-Ar age was determined for the lava samples collected in North Zao, Central Zao and South Zao Volcanoes, and compared with the volcano stratigraphy and rock magnetism. Except a few cases, the K-Ar age was compatible with the stratigraphic and magnetic data. From the K-Ar age and geological data, the growth history of the Zao Volcano group was deduced as follows. In Central Zao Volcano, the first stage of volcanism started about 1 Ma ago. In the second stage of activity, there were many lava flows distinguished both in the K-Ar age ranging from 0.32 to 0.12 Ma and in the geological succession. The voluminous effusion of andesitic lavas in this stage formed most part of the volcanoes. This is in contrast to Ryuzan Volcano which was action from 0.94 to 1.13 Ma ago, accompanied by the effusion of tholeititic basalt and andesite lavas, and has been dormant since then. The age of 0.01 Ma of Furikosawa lava indicates that the third stage of volcanism involved a lava flow. The K-Ar age which was corrected for the mass fractionation was in agreement with the volcano stratigraphic data. The peak comparison method enables to measure the age and to check the mass fractionation by analyzing Ar with only one sample, and the error of determining radiogenic Ar in a young rock with large atomospheric Ar contamination is small. (Kako, I.)

  4. 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

  5. Results of hydrologic testing of the Cold Creek interbed and Umatilla basalt flow top at Borehole DC-15

    International Nuclear Information System (INIS)

    Results and a description of hydrologic testing of the Cold Creek interbed and Umatilla basalt flow top are presented in this report. The isolated test interval is from 713 to 787 ft below land surface. Hydrologic test results are assigned to the Cold Creek interbed (721 to 769 ft) and Umatilla basalt flow top (769 to 787 ft). Hydrologic tests conducted between March 21 and March 26, 1980 included a constant discharge airlift pumping tests and a constant discharge submersible pumping test. An observed hydraulic head for the interval was about 359 ft above mean sea level. Transmissivity values determined from tests performed range from 28 to 29 ft2/day, with an assigned best estimate of 29 ft2/day. The best estimate of equivalent hydraulic conductivity, based on an effective test thickness of 66 ft, is 0.4 ft/day. 3 refs., 6 figs., 4 tabs

  6. Geochemical aspects of some Japanese lavas.

    Science.gov (United States)

    Philpotts, J. A.; Martin, W.; Schnetzler, C. C.

    1971-01-01

    K, Rb, Sr, Ba and rare-earth concentrations in some Japanese lavas have been determined by mass-spectrometric stable-isotope dilution. The samples fall into three rare-earth groups corresponding to tholeiitic, high alumina and alkali basalts. Japanese tholeiites have trace element characteristics similar to those of oceanic ridge tholeiites except for distinctly higher relative concentrations of Ba. Japanese lavas may result from various degrees of partial fusion of amphibole eclogite.

  7. Recovery of datable charcoal beneath young lavas: lessons from Hawaii.

    Science.gov (United States)

    Lockwood, J.P.; Lipman, P.W.

    1980-01-01

    Field studies in Hawaii aimed at providing a radiocarbon-based chronology of prehistoric eruptive activity have led to a good understanding of the processes that govern the formation and preservation of charcoal beneath basaltic lava flows. Charcoal formation is a rate-dependent process controlled primarily by temperature and duration of heating, as well as by moisture content, density, and size of original woody material. Charcoal will form wherever wood buried by lava is raised to sufficiently high temperatures, but owing to the availability of oxygen it is commonly burned to ash soon after formation. Wherever oxygen circulation is sufficiently restricted, charcoal will be preserved, but where atmospheric oxygen circulates freely, charcoal will only be preserved at a lower temperature, below that required for charcoal ignition or catalytic oxidation. These factors cause carbonized wood, especially that derived from living roots, to be commonly preserved beneath all parts of pahoehoe flows (where oxygen circulation is restricted), but only under margins of aa. Practical guidelines are given for the recovery of datable charcoal beneath pahoehoe and aa. Although based on Hawaiian basaltic flows, the guidelines should be applicable to other areas. -Authors

  8. Experimental constraints on the rheology and mechanical properties of lava erupted in the Holuhraun area during the 2014 rifting event at Bárðarbunga, Iceland

    Science.gov (United States)

    Lavallee, Yan; Kendrick, Jackie; Wall, Richard; von Aulock, Felix; Kennedy, Ben; Sigmundsson, Freysteinn

    2015-04-01

    A fissure eruption began at Holuhraun on 16 August 2014, following magma drainage from the Bárðarbunga volcanic system (Iceland). Extrusion initiated as fire fountaining along a segment of the fracture and rapidly localised to a series of small, aligned cones containing a lava lake that over spilled at both ends, feeding a large lava field. The lava composition and flow behaviour put some constraints on its rheology and mechanical properties. The lava erupted is a nearly aphyric basalt containing approximately 2-3% plagioclase with traces of olivine and pyroxene in a quenched groundmass composed of glass and 20-25% microlites. The transition from fire fountaining to lava flow leads to lava with variable vesicularities; pyroclasts expelled during fire fountaining reach up to 80% vesicles whilst the lava contain up to 45% vesicles. Textures in the lava vary from a'a to slabby pahoehoe, and flow thicknesses from several meters to few centimetres. Tension gashes, crease structures and shear zones in the upper lava carapace reveal the importance of both compressive and tensional stresses. In addition, occasional frictional marks at the base of the lava flow as well as bulldozing of sediments along the flow hint at the importance of frictional properties of the rocks during lava flow. Flow properties, textures and failure modes are strongly dependent on the material properties as well as the local conditions of stress and temperature. Here we expand our field observation with preliminary high-temperature experimental data on the rheological and mechanical properties of the erupted lava. Dilatometric measurements are used to constrain the thermal expansion coefficient of the lava important to constrain the dynamics of cooling of the flow. Micropenetration is further employed to determine the viscosity of the melt at super-liquidus temperature, which is compared to the temperature-dependence of viscosity as constrained by geochemistry. Lastly, uniaxial compression and

  9. Evidence for a new geomagnetic reversal from lava flows in Idaho: discussion of short polarity reversals in the Brunhes and late Matuyama Polarity Chrons

    Science.gov (United States)

    Champion, D.E.; Lanphere, M.A.; Kuntz, M.A.

    1988-01-01

    K-Ar ages and paleomagnetic data for basalt samples from a new core hole (site E) at the Idaho National Engineering Laboratory (INEL) indicate that the age of the reversed polarity event recorded in Snake River Plain lavas is older than 465 ?? 50 ka (1000 years before present) reported previously by Champion et al. (1981). A review of data documenting short reversal records from volcanic and sedimentary rocks shows that there is evidence for eight polarity subchrons in the Brunhes and two besides the Jaramillo in the late Matuyama. These 10 short subchrons begin to indicate the many short events that Cox (1968) hypothesized must exist if polarity interval lengths have a Poisson distribution. The mean sustained polarity interval length since late Matuyama Chron time is 90 000 years. The similarity of this number with the 105-year period of the Earth's orbital eccentricity suggests anew that linkage between geomagnetic, paleoclimatic, and possible underlying Earth orbital parameters should be evaluated. -from Authors

  10. Rodingitization and carbonization processes in Triassic ultramafic cumulates and lavas, Othris Mt, Central Greece

    Science.gov (United States)

    Koutsovitis, Petros; Magganas, Andreas; Economou, Georgios

    2016-04-01

    A Triassic magmatic sequence from the south Othris region is comprised of early stage basaltic pillow lavas, as well as late stage ultramafic rocks, lava flows, high-Mg doleritic dykes and pyroclastic tuffs. The ultramafic rocks include slightly serpentinized wehrlites and lavas consisting of cumulate olivine, variably textured clinopyroxene (cumulate, quench, hollow, skeletal or blade shaped), magnesiohornblende, tremolite, phlogopite, spinel, chlorite, garnet, serpentine, calcite and devitrified glass[1]. Part of their secondary mineralogy developed due to percolation of metasomatic fluids during rodingitization and carbonization processes. In ultramafic rocks from Agia Marina and Mili, rodingitization was rather penetratively and expressed with crystallization of hydrogarnets, accompanied by secondary diopside and chlorite. Hydrogarnets are characterized by their low Ti-contents (recycling thermal carbonated seawater, leached from the rifted Triassic platform carbonates. References. [1] Koutsovitis, Magganas, Ntaflos 2012: Lithos 144-145, 177-193; [2] Koutsovitis, Magganas, Pomonis, Ntaflos 2013: Lithos 172-173, 139-157.

  11. Littoral hydrovolcanic explosions: a case study of lava seawater interaction at Kilauea Volcano

    Science.gov (United States)

    Mattox, Tari N.; Mangan, Margaret T.

    1997-01-01

    A variety of hydrovolcanic explosions may occur as basaltic lava flows into the ocean. Observations and measurements were made during a two-year span of unusually explosive littoral activity as tube-fed pahoehoe from Kilauea Volcano inundated the southeast coastline of the island of Hawai`i. Our observations suggest that explosive interactions require high entrance fluxes (≥4 m 3/s) and are most often initiated by collapse of a developing lava delta. Two types of interactions were observed. "Open mixing" of lava and seawater occurred when delta collapse exposed the mouth of a severed lava tube or incandescent fault scarp to wave action. The ensuing explosions produced unconsolidated deposits of glassy lava fragments or lithic debris. Interactions under "confined mixing" conditions occurred when a lava tube situated at or below sea level fractured. Explosions ruptured the roof of the tube and produced circular mounds of welded spatter. We estimate a water/rock mass ratio of 0.15 for the most common type of littoral explosion and a kinetic energy release of 0.07-1.3 kJ/kg for the range of events witnessed.

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

    Science.gov (United States)

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

    2005-06-01

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

  13. 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

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

    Science.gov (United States)

    Kestay, Laszlo P.; Jaeger, Windy L.

    2015-01-01

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

  15. Inverse modeling of Central American lavas: old lithospheric and young asthenospheric heterogeneities

    Science.gov (United States)

    Feigenson, M.; Gazel, E.; Carr, M. J.

    2009-12-01

    In recent years, there have been a number of models proposed to account for the OIB-like geochemical characteristics of lavas from central Costa Rica. The source for most basalts of the Central American volcanic front (ranging from Guatemala to northern Costa Rica) is dominantly DM (depleted MORB-source mantle) fluxed by subduction-derived fluids. In contrast, central Costa Rican basalts display striking isotopic similarities to the Galapagos hotspot. How the Galapagos signature is introduced into the Central American source is at the heart of the conflicting theories. Several models incorporate asthenospheric flow of this enriched mantle, either around the Central American arc via South America, or through a slab window, which may have opened about 5 my ago beneath central Costa Rica. Alternatively, passage of the Caribbean plate over the Galapagos hotspot may have left veins of unerupted melt within the sub-Caribbean lithosphere. These veins may be preferentially tapped during later superimposed arc volcanism. Although these models yield identical isotopic systematics, it may be possible to distinguish between them by a geochemical technique that can indicate the presence of garnet in the source region. This method, developed by Hofmann and coworkers in the 1980s, is termed inverse modeling, and uses the variation of REEs in lavas to assess the relative importance of garnet vs. clinopyroxene during partial melting. We have applied this method to new REE data from back arc lavas throughout Central America, and preliminary results indicate that garnet is not present in their sources. In contrast, direct slab melts (adakites) from Central America, as well as volcanic front lavas and alkaline basalt (with minimal slab signature) from central Costa Rica and Panama, require a source with garnet. Therefore, enriched mantle in the back arc is likely stored in the shallow lithosphere rather than introduced through asthenospheric flow. Enriched material in the volcanic

  16. Satellite-Based Thermophysical Analysis of Volcaniclastic Deposits: A Terrestrial Analog for Mantled Lava Flows on Mars

    Directory of Open Access Journals (Sweden)

    Mark A. Price

    2016-02-01

    example. Accurate identification of non-mantled lava surfaces within an apparently well-mantled flow field on either planet provides locations to extract important mineralogical constraints on the individual flows using TIR data.

  17. Structural and Temporal Requirements for Geomagnetic Field Reversal Deduced From 40Ar/39Ar Dated Lava Flows

    Science.gov (United States)

    Singer, B. S.; Hoffman, K. A.; Coe, R. S.; Brown, L. L.; Jicha, B. R.; Pringle, M. S.; Chauvin, A.

    2004-12-01

    40Ar/39Ar dating of lavas on Tahiti, long thought to record the primary part of the Matuyama-Bruhnes (M-B) reversa1, gives an age of 795+/- 7 ka, indistinguishable from that of transitional lavas in Chile and La Palma, but older than the accepted age for the reversal. Only the transitional lavas on Maui and one from La Palma (dated at 776 +/- 2 ka), agree with the astronomical age for the M-B reversal. Virtual geomagnetic poles (VGPs) associated with the Tahitian and Chilean lavas cluster near Australia, as do VGPs recorded on Tahiti during the Big Lost and Punaruu events, two apparently unsuccessful reversals. These findings, suggestive of a recurring, mantle-held flux pattern at the outer core surface during reversal attempts, are also theoretically equivalent to the situation that would arise today if the axial dipole were to continue to weaken and vanish. Hence, we propose that the 795 ka lavas record the onset of a dynamo process--one which only on occasion would result in polarity change. This initial instability, associated with the first of two decreases in field intensity, began 18 kyrs prior to the actual polarity switch. These data may provide the first observational support to the claim that complete reversals require a significant interval of time for magnetic flux to escape from the solid inner core and sufficiently weaken its stabilizing effect.

  18. Influence of Geological and Geomorphological Characteristics on Groundwater Occurrence in Deccan Basalt Hard Rock Area of Tawarja river Sub-Basin Latur, Maharashtra, India

    Directory of Open Access Journals (Sweden)

    Babar

    2012-04-01

    Full Text Available The entire study area is covered by Deccan basalt formations comprising nearly horizontal lava flows of late Cretaceous to early Eocene. There are eight flows of lava found in the area and these flows have been considered to be a result of fissure type lava eruption. The types of basaltic flows occurring in the area are simple basalt (aa type and vesicular-amygdaloidal (Compound pahoehoe type basalt flow and also red bole beds (Tachylitic bands are observed in the exposures, quarries and well sections. The drainage pattern varies from dendritic to sub-dendritic and sub-parallel. The bifurcation ratio is moderate (3.00 to 4.67 and the lower values of drainage density (1.77 km/km2 and stream frequency (1.74 streams/km2 indicates the region is of permeable subsoil strata of the basin. Morphometric attributes like form factor (0.85, circularity ratio (0.37 and elongation ratio (0.63 reflects the early mature stage of erosional development. The groundwater occurrence with reference to hydrogeological and geomorphological characters of the sub-basin is discussed. The groundwater occurrence is good productive in the geomorphic surfaces like moderately dissected plateau and pediplains, moderate in highly dissected plateau and lateritic uplands and poor in denudational hills.

  19. Understanding heat and groundwater flow through continental flood basalt provinces: insights gained from alternative models of permeability/depth relationships for the Columbia Plateau, USA

    Energy Technology Data Exchange (ETDEWEB)

    Burns, Erick R.; Williams, Colin F.; Ingebritsen, Steven E.; Voss, Clifford I.; Spane, Frank A.; DeAngelo, Jacob

    2015-02-01

    Heat-flow mapping of the western USA has identified an apparent low-heat-flow anomaly coincident with the Columbia Plateau Regional Aquifer System, a thick sequence of basalt aquifers within the Columbia River Basalt Group (CRBG). A heat and mass transport model (SUTRA) was used to evaluate the potential impact of groundwater flow on heat flow along two different regional groundwater flow paths. Limited in situ permeability (k) data from the CRBG are compatible with a steep permeability decrease (approximately 3.5 orders of magnitude) at 600–900 m depth and approximately 40°C. Numerical simulations incorporating this permeability decrease demonstrate that regional groundwater flow can explain lower-than-expected heat flow in these highly anisotropic (kx/kz ~ 104) continental flood basalts. Simulation results indicate that the abrupt reduction in permeability at approximately 600 m depth results in an equivalently abrupt transition from a shallow region where heat flow is affected by groundwater flow to a deeper region of conduction-dominated heat flow. Most existing heat-flow measurements within the CRBG are from shallower than 600 m depth or near regional groundwater discharge zones, so that heat-flow maps generated using these data are likely influenced by groundwater flow. Substantial k decreases at similar temperatures have also been observed in the volcanic rocks of the adjacent Cascade Range volcanic arc and at Kilauea Volcano, Hawaii, where they result from low-temperature hydrothermal alteration.

  20. Age and petrology of alkalic postshield and rejuvenated-stage lava from Kauai, Hawaii

    Science.gov (United States)

    Clague, D.A.; Dalrymple, G.B.

    1988-01-01

    At the top of the Waimea Canyon Basalt on the island of Kauai, rare flows of alkalic postshield-stage hawaiite and mugearite overlie tholeiitic flows of the shield stage. These postshield-stage flows are 3.92 Ma and provide a younger limit for the age of the tholeiitic shield stage. The younger Koloa Volcanics consist of widespread alkalic rejuvenated-stage flows and vents of alkalic basalt, basanite, nephelinite, and nepheline melilitite that erupted between 3.65 and 0.52 Ma. All the flows older than 1.7 Ma occur in the west-northwestern half of the island and all the flows younger than 1.5 Ma occur in the east-southeastern half. The lithologies have no spatial or chronological pattern. The flows of the Koloa Volcanics are near-primary magmas generated by variable small degrees of partial melting of a compositionally heterogeneous garnet-bearing source that has about two-thirds the concentration of P2O5, rare-earth elements, and Sr of the source of the Honolulu Volcanics on the island of Oahu. The same lithology in the Koloa and Honolulu Volcanics is generated by similar degrees of partial melting of distinct source compositions. The lavas of the Koloa Volcanics can be generated by as little as 3 percent to as much as 17 percent partial melting for nepheline melilitite through alkalic basalt, respectively. Phases that remain in the residue of the Honolulu Volcanics, such as rutile and phlogopite, are exhausted during formation of the Koloa Volcanics at all but the smallest degrees of partial melting. The mantle source for Kauai lava becomes systematically more depleted in 87Sr/86Sr as the volcano evolves from the tholeiitic shield stage to the alkalic postshield stage to the alkalic rejuvenated stage: at the same time, the lavas become systematically more enriched in incompatible trace elements. On a shorter timescale, the lavas of the Koloa Volcanics display the same compositional trends, but at a lower rate of change. The source characteristics of the Koloa

  1. High-resolution TanDEM-X DEM: An accurate method to estimate lava flow volumes at Nyamulagira Volcano (D. R. Congo)

    Science.gov (United States)

    Albino, F.; Smets, B.; d'Oreye, N.; Kervyn, F.

    2015-06-01

    Nyamulagira and Nyiragongo are two of the most active volcanoes in Africa, but their eruptive histories are poorly known. Assessing lava flow volumes in the region remains difficult, as field surveys are often impossible and available Digital Elevation Models (DEMs) do not have adequate spatial or temporal resolutions. We therefore use TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X) interferometry to produce a series of 0.15 arc sec (˜5 m) DEMs from between 2011 and 2012 over these volcanoes. TanDEM-X DEMs have an absolute vertical accuracy of 1.6 m, resulting from the comparison of elevation with GPS measurements acquired around Nyiragongo. The difference between TanDEM-X-derived DEMs from before and after the 2011-2012 eruption of Nyamulagira provides an accurate thickness map of the lava flow emplaced during that activity. Values range from 3 m along the margins to 35 m in the middle, with a mean of 12.7 m. The erupted volume is 305.2 ± 36.0 × 106 m3. Height errors on thickness depend on the land covered by the flow and range from 0.4 m in old lavas to 5.5 m in dense vegetation. We also reevaluate the volume of historical eruptions at Nyamulagira since 2001 from the difference between TanDEM-X and SRTM 1 arc sec DEMs and compare them to previous work. Planimetric methods used in literature are consistent with our results for short-duration eruptions but largely underestimate the volume of the long-lived 2011-2012 eruption. Our new estimates of erupted volumes suggest that the mean eruption rate and the magma supply rate were relatively constant at Nyamulagira during 2001-2012, respectively, 23.1 m3 s-1 and 0.9 m3 s-1.

  2. Lava Lakes in Io's Paterae

    Science.gov (United States)

    Radebaugh, J.; McEwen, A. S.; Milazzo, M.; Davies, A. G.; Keszthelyi, L. P.; Geissler, P.

    2002-05-01

    lava lakes. The presence of giant lava lakes within these large paterae (up to 200 km diameter) has implications for the transfer of internal heat to the surface, as the paterae require direct links to comparably large, well supplied magma chambers (Harris et al., 1999, JGR, 104, 7117-7136) in order to maintain their vigorous activity over the observed timescales of tens of years. In addition, if much of Io's heat flow is restricted to these large lava lakes, then Io's resurfacing may be extremely spatially confined.

  3. Effets thermique et hydrothermal de la coulée de basalte triasico-liasique sur les argiles du bassin d'Argana (Maroc)Thermal and hydrothermal effects of Triassic Liassic basalt flow deposition on clays (Agana Basin, Morocco)

    Science.gov (United States)

    Daoudi, Lahcen; Pot de Vin, Jean-Luc

    Thermal and hydrothermal effects of Triassic-Liassic basalt flow deposition on sedimentary series of the Argana Basin are responsible for major modifications in detrital clays, until 20 m in depth. It expressed by transformation of detrital smectite to corrensite and moreover to chlorite, and by increasing illite crystallinity. On the 2 m of sediments located immediately under the flow, magnesium-rich hydrothermal fluids have caused precipitation of new mineral phases. To cite this article: L. Daoudi, J.-L. Pot de Vin, C. R. Geoscience 334 (2002) 463-468.

  4. Aspects of a conceptual groundwater flow model of the Serra Geral basalt aquifer (Sao Paulo, Brazil) from physical and structural geology data

    Science.gov (United States)

    Fernandes, Amélia J.; Maldaner, Carlos H.; Negri, Francisco; Rouleau, Alain; Wahnfried, Ingo D.

    2016-08-01

    A preliminary conceptual model of groundwater flow was developed for the Serra Geral fractured basalt aquifer in order to assess the recharge to the underlying sandstone Guarani Aquifer System, one of the main aquifer systems in Brazil, which supplies water to millions of people. Detailed geological investigations included macroscopic description of the basalt flow units and the underlying sandstone. Petrographic and chemical analyzes were conducted on rock samples from outcrops and from five drilled boreholes. Detailed fracture surveys were accomplished at outcrops to characterize fracture sets and their potential to transmit water in the current tectonic context. Four basalt flows were identified in the Ribeirao Preto area and were named B1, B2, B3 and B4 (from oldest to youngest). The cooling process in flow B3 led to the generation of large sub-horizontal fractures at the contacts B2/B3 and B3-C/B3-E, which are the most transmissive structures. Groundwater flow in the basalt appears to be of the stratabound type because fractures, in general, do not propagate through the basalt vesicular layers, which behave as a regional hydraulic barrier for the vertical groundwater flow. However, it is proposed that the localized, continuous and closely spaced subvertical tectonic fractures, the only features that have the potential to crosscut the vesicular layers and the intertrappe sediments, can vertically connect the sub-horizontal transmissive fractures. Weathering and water seepage, observed in rock exposures, indicate that subvertical NE-trending fractures would be the most transmissive in the Ribeirao Preto area.

  5. Aspects of a conceptual groundwater flow model of the Serra Geral basalt aquifer (Sao Paulo, Brazil) from physical and structural geology data

    Science.gov (United States)

    Fernandes, Amélia J.; Maldaner, Carlos H.; Negri, Francisco; Rouleau, Alain; Wahnfried, Ingo D.

    2016-02-01

    A preliminary conceptual model of groundwater flow was developed for the Serra Geral fractured basalt aquifer in order to assess the recharge to the underlying sandstone Guarani Aquifer System, one of the main aquifer systems in Brazil, which supplies water to millions of people. Detailed geological investigations included macroscopic description of the basalt flow units and the underlying sandstone. Petrographic and chemical analyzes were conducted on rock samples from outcrops and from five drilled boreholes. Detailed fracture surveys were accomplished at outcrops to characterize fracture sets and their potential to transmit water in the current tectonic context. Four basalt flows were identified in the Ribeirao Preto area and were named B1, B2, B3 and B4 (from oldest to youngest). The cooling process in flow B3 led to the generation of large sub-horizontal fractures at the contacts B2/B3 and B3-C/B3-E, which are the most transmissive structures. Groundwater flow in the basalt appears to be of the stratabound type because fractures, in general, do not propagate through the basalt vesicular layers, which behave as a regional hydraulic barrier for the vertical groundwater flow. However, it is proposed that the localized, continuous and closely spaced subvertical tectonic fractures, the only features that have the potential to crosscut the vesicular layers and the intertrappe sediments, can vertically connect the sub-horizontal transmissive fractures. Weathering and water seepage, observed in rock exposures, indicate that subvertical NE-trending fractures would be the most transmissive in the Ribeirao Preto area.

  6. A frozen record of density-driven crustal overturn in lava lakes: The example of Kilauea Iki 1959

    Science.gov (United States)

    Stovall, W.K.; Houghton, B.F.; Harris, A.J.L.; Swanson, D.A.

    2009-01-01

    Lava lakes are found at basaltic volcanoes on Earth and other planetary bodies. Density-driven crustal foundering leading to surface renewal occurs repeatedly throughout the life of a lava lake. This process has been observed and described in a qualitative sense, but due to dangerous conditions, no data has been acquired to evaluate the densities of the units involved. Kilauea Iki pit crater in Hawai'i houses a lava lake erupted during a 2 month period in 1959. Part of the surface of the Kilauea Iki lake now preserves the frozen record of a final, incomplete, crustal-overturn cycle. We mapped this region and sampled portions of the foundering crust, as well as overriding and underlying lava, to constrain the density of the units involved in the overturn process. Overturn is driven by the advance of a flow front of fresh, low-density lava over an older, higher density surface crust. The advance of the front causes the older crust to break up, founder, and dive downwards into the lake to expose new, hot, low-density lava. We find density differences of 200 to 740 kg/m3 between the foundering crust and over-riding and under-lying lava respectively. In this case, crustal overturn is driven by large density differences between the foundering and resurfacing units. These differences lead, inevitably, to frequent crustal renewal: simple density differences between the surface crust and underlying lake lava make the upper layers of the lake highly unstable. ?? Springer-Verlag 2008.

  7. The effect of particle size on the rheology of liquid-solid mixtures with application to lava flows: Results from analogue experiments

    OpenAIRE

    Del Gaudio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Taddeucci, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia

    2013-01-01

    We investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size (from 63 to 0.5 mm) and volume fraction fi (from 0.03 to 0.6). At constant fi, finer suspensions display higher viscosities than coarser ones. Shear thinning (flow index n 0.1–0.2 and is more pronounced (stronger departure from the Newtonian behavior) in finer suspensions. Maximum pac...

  8. New argon-argon (40Ar/39Ar) radiometric age dates from selected subsurface basalt flows at the Idaho National Laboratory, Idaho

    Science.gov (United States)

    Hodges, Mary K.; Turrin, Brent D.; Champion, Duane E.; Swisher, Carl C., III

    2015-01-01

    In 2011, the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, collected samples for 12 new argon-argon radiometric ages from eastern Snake River Plain olivine tholeiite basalt flows in the subsurface at the Idaho National Laboratory. The core samples were collected from flows that had previously published paleomagnetic data. Samples were sent to Rutgers University for argon-argon radiometric dating analyses.

  9. Formation of Hematite fine crystals by hydrothermal alteration of synthetic Martian basalt, static and fluid flow experiments

    Science.gov (United States)

    Kobayashi, K.; Isobe, H.

    2011-12-01

    Exploration made by Martian rovers and probes provided enormous information on the composition of the Martian surface materials. Origin and formation processes of the Martian surface materials should be various depending on topography and history of the Martian crust. Especially, iron minerals in the Martian soil should have essential role to characterize surface environment of the "red planet". In the present study, experimental reproduction of the Martian soil was carried out by hydrothermal alteration of the synthetic iron-rich basaltic rock. Experimental conditions for temperature and fluid composition followed Isobe and Yoshizawa (2010). Static alteration experiments are carried out at 100 °C and 150 °C, and mass ratio of the starting material to the pH1.0 sulfuric acid solution is 1:50. Run durations are 1, 2, 4 or 8 weeks. Appropriate mass of dry ice was sealed in the experimental vessels to expel atmospheric oxygen with CO2. For the static experiments, powdered starting materials were charged in PFA vial to keep textures of the run products. For the fluid flow experiments, we constructed closed loop with Teflon tube inclined approximately 45°. One of the vertical tube is charged with crushed synthetic basalt and heated approximately 150°C by aluminum block with ribbon heater. Surlfuric acid solution flows through the tube from bottom to top and cooled at the end of the aluminum block. Cooled solution returns to the bottom of the heated tube through another vertical tube without heating block. In the static condition run products, characteristic iron mineral particles are formed for 100°C and 150°C concordant with Isobe and Yoshizawa (2010). These iron minerals distributed not only inside the starting material powder but also on the surface of the reaction vessel and the PFA vial in the reactive solution. The surface of the reaction vessel shows orange and reddish color on 100°C and 150°C run products, respectively. By SEM observation, dissolution of

  10. Petrophysical properties of the Deccan basalts exposed in the Western Ghats escarpment around Mahabaleshwar and Koyna, India

    Science.gov (United States)

    Prasanna Lakshmi, K. J.; Senthil Kumar, P.; Vijayakumar, K.; Ravinder, S.; Seshunarayana, T.; Sen, Mrinal K.

    2014-04-01

    We present petrophysical properties (density, P and S wave velocity, porosity and Poisson's ratio) of the Deccan basalts from the Western Ghats escarpment around Mahabaleshwar and Koyna and characterize the Dhawar basement rocks around Goa. The petrophysical properties of basaltic lava flows show significant variation in the Bushe, Poladpur, Ambenali and Mahabaleshwar Formations that are widespread in the Deccan volcanic province. The Bushe Formation stands out distinctly from other formations because of its lower density, and P and S wave velocity. The porosity (vesicles and amygdales) plays a major role in controlling the variation of the petrophysical properties of the basalts. The Poisson's ratio of the Deccan basalts is largely affected by the vesicular porosity, aspect ratio of the amygdales, and zeolite content. The Dharwar basement rocks (greywackes and granites) are found to be lower in density, P and S wave velocity, and Poisson's ratio than the basaltic rocks. The variation of the petrophysical properties with elevation in the Western Ghats sections roughly follows the geochemical stratigraphy. High porosity of the Bushe and Mahabaleshwar Formations constitute a multi-layered aquifer system in the Deccan volcanic province. In the Koyna earthquake zone, these formations may provide an effective groundwater connectivity between the reservoir and earthquake focal areas. The new petrophysical data of the Deccan basalts and Dharwar basement rocks will help to refine the geophysical models of the southwestern Deccan basalt province.

  11. Absolute paleointensity determinations by using of conventional double-heating and multispecimen approaches on a Pliocene lava flow sequence from the Lesser Caucasus

    Science.gov (United States)

    Goguitchaichvili, Avto; Caccavari, Ana; Calvo-Rathert, Manuel; Morales, Juan; Solano, Miguel Cervantes; Vashakidze, Goga; Huaiyu, He; Vegas, Néstor

    2016-08-01

    We report 28 successful Thellier type absolute geomagnetic paleointensity determinations from a Pleistocene lava sequence composed of 39 successive flows in the Djavakheti Highland (Lesser Caucasus, Georgia). Additionally, multispecimen technique provided the estimation of geomagnetic field strength for 12 independent cooling units. Paleointensity studies were performed using both Thellier type double heating and multispecimen techniques. Samples selection was mainly based on uni-vectorial remanent magnetization, thermal stability and domain size of the samples. Flow-mean Thellier paleointensity values range from 16.3 ± 5.2 to 71.0 ± 0.3 μT, while intensities obtained using multispecimen approach vary from17.2 ± 2.3 to 69.3 ± 7.9 μT. One of the flows is located near a possible discontinuity in the sequence and yields a rather low Thellier absolute intensity (16.3 ± 5.2) suggesting a transitional regime and the onset of the Matuyama-Olduvai polarity transition, which does not appear on the directional record. Multispecimen paleointensities from the same flow, however, yield higher, close to present day values which makes untenable the hypothesis of occurrence of transitional field. Thus the whole sequence was emplaced in a short time between the Olduvai chron and 1.73 ± 0.03 Ma, as suggested by available radiometric and paleomagnetic data (Caccavari et al., 2014).

  12. Geochemistry and petrogenetic history of lavas from Sumaco Volcano, Northern Volcanic Zone, Ecuador

    Science.gov (United States)

    Escobar, R. D.; Garrison, J. M.; Sims, K. W.; Matthews, T. P.; Yogodzinski, G. M.

    2012-12-01

    Sumaco Volcano is located in the rear arc of the Northern Volcanic Zone (NVZ) of Ecuador, 105 km from the capital city of Quito. It is one of several volcanoes in the rear arc of the NVZ and is located south of El Reventador volcano. On the basis of summit morphology, Sumaco is believed to have erupted most recently in 1933, however there are few constraints on the timing of past eruptions and it is currently inactive. Lava flows on the steep, jungle-covered flanks are largely inaccessible and therefore few studies have been published for this volcano, and most representative samples are from the volcano summit. The goals of this research are 1) to use major and trace element data to obtain a better understanding of the petrogenetic history of Sumaco Volcano and 2) to use U-series isotopes to constrain the eruption ages and, if possible get information about magma storage times. We collected and sent 23 rock samples to Washington State University for analysis of major and trace elements using XRF and ICP, including six lavas from the summit and 17 from the southern flanks, including bread-crust bombs. A subgroup of samples was chosen for U-series disequilibrium measurements on whole rocks and minerals. Based on hand-sample observations and electron microprobe analyses, the primary mineral phases found in the Sumaco lavas include titanaugite, hauyne, olivine and plagioclase, with accessory apatite and hercynite. The plagioclase and apatite have seive textures consistent with magma mixing or recharge, and the titanaugite crystals are euhedral with oscillatory zoning that records repeated recharge events. On the basis of major and trace element data, the lavas are alkaline and range in composition from picro-basalt to tephri-phonolite; the picro basalt has MgO of 10 wt % and the summit samples are the most evolved with MgO of 2 wt %. The summit lavas (also presumed to be the youngest lavas) have the highest concentration of alkali elements with K2O content (> 4 wt

  13. Multiphase Alkaline Basalts of Central Al-Haruj Al-Abyad of Libya: Petrological and Geochemical Aspects

    Directory of Open Access Journals (Sweden)

    Abdel-Aal M. Abdel-Karim

    2013-01-01

    Full Text Available Al-Haruj basalts that represent the largest volcanic province in Libya consist of four lava flow phases of varying thicknesses, extensions, and dating. Their eruption is generally controlled by the larger Afro-Arabian rift system. The flow phases range from olivine rich and/or olivine dolerites to olivine and/or normal basalts that consist mainly of variable olivine, clinopyroxene, plagioclase, and glass. Olivine, plagioclase, and clinopyroxene form abundant porphyritic crystals. In olivine-rich basalt and olivine basalt, these minerals occur as glomerophyric or seriate clusters of an individual mineral or group of minerals. Groundmass textures are variably intergranular, intersertal, vitrophyric, and flow. The pyroclastic, clastogenic flows and/or ejecta of the volcanic cones show porphyritic, vitrophric, pilotaxitic, and vesicular textures. They are classified into tholeiite, alkaline, and olivine basalts. Three main groups are recorded. Basalts of phase 1 are generated from tholeiitic to alkaline magma, while those of phases 3 and 4 are derived from alkaline magma. It is proposed that the tholeiitic basalts represent prerift stage magma generated by higher degree of partial melting (2.0–3.5% of garnet-peridotite asthenospheric mantle source, at shallow depth, whereas the dominant alkaline basalts may represent the rift stage magma formed by low degree of partial melting (0.7–1.5% and high fractionation of the same source, at greater depth in an intra-continental plate with OIB affinity. The melt generation could be also attributed to lithosphere extension associated with passive rise of variable enriched mantle.

  14. Siderophile and chalcophile metal variations in Tertiary picrites and basalts from West Greenland with implications for the sulphide saturation history of continental flood basalt magmas

    Science.gov (United States)

    Keays, Reid R.; Lightfoot, Peter C.

    2007-04-01

    much more severe than that of the West Greenland contaminated basalts. Moreover, the volumes of the contaminated and metal-depleted volcanic rocks in West Greenland pale is significant when compared to the Nadezhdinsky Formation; local centers rarely contain more than 15 thin flows with a combined thickness of <50 m and more typically 10-20 m, so the volume of the eruptive portions of each system is probably two orders of magnitude smaller than the Nadezhdinsky edifice. The West Greenland centres are juxtaposed along fault zones that appear to be linked to the subsidence of the Tertiary delta, and so emplacement along N-S structures appears to be a principal control on the distribution of lavas and feeder intrusions. This leads us to suggest that the Greenland system is small and segregation of sulphide took place at high levels in the crust, whereas at Noril’sk, the saturation event took place at depth with subsequent emplacement of sulphide-bearing magmas into high levels of the crust. As a consequence, it may be unreasonable to expect that the West Greenland flood basalts experienced mineralizing processes on the scale of the Noril’sk system.

  15. An analysis of Apollo lunar soil samples 12070,889, 12030,187, and 12070,891: Basaltic diversity at the Apollo 12 landing site and implications for classification of small-sized lunar samples

    Science.gov (United States)

    Alexander, Louise; Snape, Joshua F.; Joy, Katherine H.; Downes, Hilary; Crawford, Ian A.

    2016-07-01

    Lunar mare basalts provide insights into the compositional diversity of the Moon's interior. Basalt fragments from the lunar regolith can potentially sample lava flows from regions of the Moon not previously visited, thus, increasing our understanding of lunar geological evolution. As part of a study of basaltic diversity at the Apollo 12 landing site, detailed petrological and geochemical data are provided here for 13 basaltic chips. In addition to bulk chemistry, we have analyzed the major, minor, and trace element chemistry of mineral phases which highlight differences between basalt groups. Where samples contain olivine, the equilibrium parent melt magnesium number (Mg#; atomic Mg/[Mg + Fe]) can be calculated to estimate parent melt composition. Ilmenite and plagioclase chemistry can also determine differences between basalt groups. We conclude that samples of approximately 1-2 mm in size can be categorized provided that appropriate mineral phases (olivine, plagioclase, and ilmenite) are present. Where samples are fine-grained (grain size fines) from future sample return missions to investigate lava flow diversity and petrological significance.

  16. 基性熔岩火山地层单元类型、特征及其储层意义%Types, characteristics and reservoir significance of basic lava flow units

    Institute of Scientific and Technical Information of China (English)

    衣健; 唐华风; 王璞珺; 高有峰; 赵然磊

    2016-01-01

    Based on profile measurements, the observation of the core samples, the interpretation of detection logging and seismic profiles, three typical fields and wells in Songliao Basin were chosen, and the types, the characteristics and the stacking patterns of the volcanic units were studied. The results show that the basic lava volcanic units can be formed by the diagenesis of solidification with cooling, and can be divided into four types according to their external morphology:the braid lava flow units, the fan-like lava flow units, the tabular lava flow units, and the tube lava flow units. The first three of these lava flow units are formed by the lava effusion on the ground, and the tube lava flow units are formed by the lava flowing along the buried tube underground. The internal structure of the lava flow units can be characterized by the vesicular zones. The braid lava flow units are divided into three parts:the rich vesicular zone on the tope, the spare vesicular zone in the middle, and the base vesicular zone at the base. The fan-like lava flow units have an autoclastic breccia zone on the rich vesicular zone, and a thin dense zone under the spare vesicular zone. The tabular lava flow units have a thick dense zone under the spare vesicular zone. The tube lava flow consists of a loop columnar zone in the outer ring and an autoclastic breccia core. The volcanostratigraphy is built by the stacking of volcanic units, and the spatial and temporal distribution of the lithology, and facies and reservoir are directly controlled by the shape and stacking patterns of lava flow units, and make up three distribution modes of reservoirs: the layered, the quasi layered and the mixed-lenticular. Thus this study may provide theoretic foundation for the final target attempt to define the fine characterization of the volcanostratigraphy using outcrop, well and seismic data.%为了探索基性熔岩的火山地层单元类型、特征与叠置关系,精选中国东北3个具

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

    Science.gov (United States)

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

    2008-12-01

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

  18. Stratigraphy of the Basalt Flows of the Formação Serra Geral (Ribeirão Preto - SP Based on Physical Geology, Petrography and Geochemistry

    Directory of Open Access Journals (Sweden)

    Amélia João Fernandes

    2010-07-01

    Full Text Available The study of the physical geology and geochemistry of the basalts of Ribeirão Preto was part of a hydrogeologicalresearch that aimed at investigating the recharge of the Guarani Aquifer System (SAG through the basalts of the SerraGeral Aquifer (ASG, a project shortly named FRATASG. In addition to hydrogeological methods, the research demandeda detailed geological investigation, which is essential for the elaboration of conceptual models of groundwater circulationin complex aquifers, as is the case of the fractured basalts of the ASG. Thus, the study encompassed field work for thedescription of the macroscopic aspects and relationships among the basalts and the underlying sandstones, as well as, rocksampling and petrographic and chemical analysis. Furthermore, the use of lithologic logs of five wells drilled in FRATASG project was essential for the establishment of the subsurface basalt stratigraphy. The study concluded that, in Bonfim Paulista region,there are four basalt floods, namely B1, B2, B3 and B4. The B4 occurrence is very restricted as it was largely eroded. B1 and B2average thicknesses are 45 and 60 m, respectively. All four basalts are of sheet-like lobe types and were probably emplaced by inflation,B1 being the one that presents more evidence in that respect. B1 presents a thick vesicular top and, as well as B2, can show more thanone vesicular layer at the top. Columnar joints were observed in B2 and B3 and are more remarkable in B3, where a lower colonnadetier (B3-C is overlain by an entablature layer (B3-E. B3 is the thickest flow (75 to 105 m and contains irregular and roughly roundpatches of hydraulic breccia in B3-C or along sub-horizontal fractures that allow the circulation of fluids (groundwater at the present. The chemical composition of B3 is homogeneous and very different from B1 and B2 with regard to several oxides (Al2O3, P2O5, Fe2O3, TiO2 e MgO and trace elements (Ni, Zn, Cu, Y. B1 is very different from B2 with regard

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

    Science.gov (United States)

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

    2013-12-01

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

  20. A preliminary assessment of the regional dispersivity of selected basalt flows at the Hanford Site, Washington, U.S.A.

    Science.gov (United States)

    Lavenue, A. M.; Domenico, P. A.

    1986-06-01

    Dispersivity is one of the hydraulic parameters that controls the distribution in groundwater of chemical constituents migrating from a source region. Therefore, knowledge of the range of dispersivity values along likely flow paths from proposed high-level nuclear waste repositories is important for assessing how well a site will perform in limiting releases of radionuclides to the environment. A primary reason why dispersivity has not been analyzed with regional-scale data is the general lack of suitable environmental tracers that have been in the hydrologic environment for long periods of time. Such tracers could normally result from some natural event, perhaps disruptive, that may have transpired in the geologic past. Such an event may have occurred at the U.S. Department of Energy Hanford Site in the State of Washington, resulting in a chemical enclave of regional proportions. A preliminary interpretation is that the enclave occurs immediately down-gradient from a hydraulic barrier, possibly a fault, which may have placed deeper formations in hydraulic connection with the upper basalts. With this hypothesized source for constituents making up the enclave, the observed concentrations are employed in a preliminary attempt to assess the regional dispersivity. This is the single conceptual model being tested in this paper. The mathematical method employed assumes that the concentration data conform to what would be expected of a perfectly symmetrical enclave, and part of the problem deals with identifying that symmetry. The results obtained are quite reasonable when compared to the range in dispersivities determined in laboratory, tracer, and model-scale studies.

  1. An analysis of Apollo lunar soil samples 12070,889, 12030,187, and 12070,891: Basaltic diversity at the Apollo 12 landing site and implications for classification of small-sized lunar samples

    Science.gov (United States)

    Alexander, Louise; Snape, Joshua F.; Joy, Katherine H.; Downes, Hilary; Crawford, Ian A.

    2016-09-01

    Lunar mare basalts provide insights into the compositional diversity of the Moon's interior. Basalt fragments from the lunar regolith can potentially sample lava flows from regions of the Moon not previously visited, thus, increasing our understanding of lunar geological evolution. As part of a study of basaltic diversity at the Apollo 12 landing site, detailed petrological and geochemical data are provided here for 13 basaltic chips. In addition to bulk chemistry, we have analyzed the major, minor, and trace element chemistry of mineral phases which highlight differences between basalt groups. Where samples contain olivine, the equilibrium parent melt magnesium number (Mg#; atomic Mg/[Mg + Fe]) can be calculated to estimate parent melt composition. Ilmenite and plagioclase chemistry can also determine differences between basalt groups. We conclude that samples of approximately 1-2 mm in size can be categorized provided that appropriate mineral phases (olivine, plagioclase, and ilmenite) are present. Where samples are fine-grained (grain size <0.3 mm), a "paired samples t-test" can provide a statistical comparison between a particular sample and known lunar basalts. Of the fragments analyzed here, three are found to belong to each of the previously identified olivine and ilmenite basalt suites, four to the pigeonite basalt suite, one is an olivine cumulate, and two could not be categorized because of their coarse grain sizes and lack of appropriate mineral phases. Our approach introduces methods that can be used to investigate small sample sizes (i.e., fines) from future sample return missions to investigate lava flow diversity and petrological significance.

  2. Trace elemental and Nd-Sr-Pb isotopic compositional variation in 37 lava flows of the Mandla lobe and their chemical relation to the western Deccan stratigraphic succession, India

    Science.gov (United States)

    Shrivastava, J. P.; Mahoney, J. J.; Kashyap, M. R.

    2014-12-01

    The Mandla lobe is a 900 m thick lava pile that forms a 29,400 km2 northeastern extension of the Deccan Traps. Earlier, combined field, petrographic, and major element studies have shown that this lobe comprises 37 lava flows. Using a combination of trace elements (Ba, Ti, Zr, Rb, Sr) and Nb/Zr values, we group the flows into six chemical types (A-F) that are separated stratigraphically. Combined trace element and Nd-Pb-Sr isotopic data, document the presence of lavas resembling those of the Poladpur Formation and less abundantly, the Ambenali Formation of the southwestern Deccan are in conformity with the earlier reconnaissance work. In addition, our data reveal several flows similar to those of the Mahabaleshwar Formation, the type sections of which are located ~ 900 km to the southwest. Based on the isotopic data the superposition of Mahabaleshwar-like flows over flows with Ambenali- and Poladpur-like characteristics is in the same stratigraphic order seen in the southwestern Deccan type section. However, from the stratigraphy indicated by the Discriminant Function Analysis (DFA) results and the serious discrepancy between the DFA and isotopic data, it seems that few Mandla lobe flows are different and not in the same stratigraphic order as in the southwestern part of the province. To some extent the differences may be explained by faulting along four large post-Deccan normal faults near Nagapahar, Kundam, Deori, and Dindori areas across which offsets of ~150 m have been measured. This post-emplacement faulting accounts for the presence of several chemically Mahabaleshwar-like lavas at the base of the ~900 m thick Mandla lobe pile, at a lower elevation than a thick sequence dominated by chemically Poladpur-like flows. However, presence of common signature lavas (similar to that in the northeastern Deccan) cannot be ruled out in this area. They are similar to Poladpur-type lavas both chemically and isotopically. They appear in different formations and erupted at

  3. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

    Science.gov (United States)

    Clague, David A.; Dreyer, Brian M; Paduan, Jennifer B; Martin, Julie F; Caress, David W; Gillespie, James B.; Kelley, Deborah S; Thomas, Hans; Portner, Ryan A; Delaney, John R; Guilderson, Thomas P.; McGann, Mary L.

    2016-01-01

    High-resolution bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ~4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ~4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ~4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ~2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620–1760 yr BP and within the axial graben since ~1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ~2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  4. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages

    Science.gov (United States)

    Clague, David. A.; Dreyer, Brian M.; Paduan, Jennifer B.; Martin, Julie F.; Caress, David W.; Gill, James B.; Kelley, Deborah S.; Thomas, Hans; Portner, Ryan A.; Delaney, John R.; Guilderson, Thomas P.; McGann, Mary L.

    2014-08-01

    bathymetric surveys from autonomous underwater vehicles ABE and D. Allan B. were merged to create a coregistered map of 71.7 km2 of the Endeavour Segment of the Juan de Fuca Ridge. Radiocarbon dating of foraminifera in cores from three dives of remotely operated vehicle Doc Ricketts provide minimum eruption ages for 40 lava flows that are combined with the bathymetric data to outline the eruptive and tectonic history. The ages range from Modern to 10,700 marine-calibrated years before present (yr BP). During a robust magmatic phase from >10,700 yr BP to ˜4300 yr BP, flows erupted from an axial high and many flowed >5 km down the flanks; some partly buried adjacent valleys. Axial magma chambers (AMCs) may have been wider than today to supply dike intrusions over a 2 km wide axial zone. Summit Seamount formed by ˜4770 yr BP and was subsequently dismembered during a period of extension with little volcanism starting ˜4300 yr BP. This tectonic phase with only rare volcanic eruptions lasted until ˜2300 yr BP and may have resulted in near-solidification of the AMCs. The axial graben formed by crustal extension during this period of low magmatic activity. Infrequent eruptions occurred on the flanks between 2620-1760 yr BP and within the axial graben since ˜1750 yr BP. This most recent phase of limited volcanic and intense hydrothermal activity that began ˜2300 yr BP defines a hydrothermal phase of ridge development that coincides with the present-day 1 km wide AMCs and overlying hydrothermal vent fields.

  5. Paleomagnetism of Midway Atoll lavas and northward movement of the Pacific plate

    Science.gov (United States)

    Gromme, S.; Vine, F.J.

    1972-01-01

    Two deep drill holes through the reef limestones of Midway Atoll penetrated 120 m and 19 m of basaltic lavas that were dated by the KAr method at 18 my. Inclinations of natural remanent magnetization have been measured in 173 specimens cut from 57 core samples from 13 of the lava flows. The mean paleomagnetic inclination is 27.6?? ?? 6.8??, corresponding to a paleolatitude of 14.7?? ?? 4.2??. The present latitude of Midway is 28??, suggesting a northward component of motion of the Pacific plate of approximately 13?? or 1400 km in the last 18 my. The paleolatitude of Midway is thus not significantly different from the present latitude (19??) of the active volcanic island of Hawaii. The paleomagnetic data from the Midway basalts thus support the hypothesis of Wilson and Morgan that volcanic heat sources are fixed with respect to the Earth's mantle below the asthenosphere and their apparent migration with time is due to plate motion. ?? 1972.

  6. Mapping Planetary Volcanic Deposits: Identifying Vents and Distingushing between Effects of Eruption Conditions and Local Lava Storage and Release on Flow Field Morphology

    Science.gov (United States)

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

    2014-01-01

    Terrestrial geologic mapping techniques are regularly used for "photogeologic" mapping of other planets, but these approaches are complicated by the diverse type, areal coverage, and spatial resolution of available data sets. When available, spatially-limited in-situ human and/or robotic surface observations can sometimes introduce a level of detail that is difficult to integrate with regional or global interpretations. To assess best practices for utilizing observations acquired from orbit and on the surface, our team conducted a comparative study of geologic mapping and interpretation techniques. We compared maps generated for the same area in the San Francisco Volcanic Field (SFVF) in northern Arizona using 1) data collected for reconnaissance before and during the 2010 Desert Research And Technology Studies campaign, and 2) during a traditional, terrestrial field geology study. The operations, related results, and direct mapping comparisons are discussed in companion LPSC abstracts [1-3]. Here we present new geologic interpretations for a volcanic cone and related lava flows as derived from all approaches involved in this study. Mapping results indicate a need for caution when interpreting past eruption conditions on other planetary surfaces from orbital data alone.

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

    Science.gov (United States)

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

    1997-01-01

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

  8. Submarine lava flow emplacement and faulting in the axial valley of two morphologically distinct spreading segments of the Mariana back-arc basin from Wadatsumi side-scan sonar images

    OpenAIRE

    Asada, Miho; Deschamps, Anne; FUJIWARA, Toshiya; Nakamura, Yasuyuki

    2007-01-01

    International audience High-resolution, deep-tow side-scan sonar data were collected over two distinct spreading segments in the central part of the Mariana back-arc basin. These data allow mapping of small fissures and faults and the distinguishing of hummocky from smooth lava flows. Using these data, we observe spatial variations in seafloor deformation and volcanic activity within each segment, and also significant differences in the degree of tectonic deformation between the two segmen...

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

    Science.gov (United States)

    Clague, D.A.

    1982-01-01

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

  10. Shallow outgassing changes disrupt steady lava lake activity, Kilauea Volcano

    Science.gov (United States)

    Patrick, M. R.; Orr, T. R.; Swanson, D. A.; Lev, E.

    2015-12-01

    Persistent lava lakes are a testament to sustained magma supply and outgassing in basaltic systems, and the surface activity of lava lakes has been used to infer processes in the underlying magmatic system. At Kilauea Volcano, Hawai`i, the lava lake in Halema`uma`u Crater has been closely studied for several years with webcam imagery, geophysical, petrological and gas emission techniques. The lava lake in Halema`uma`u is now the second largest on Earth, and provides an unprecedented opportunity for detailed observations of lava lake outgassing processes. We observe that steady activity is characterized by continuous southward motion of the lake's surface and slow changes in lava level, seismic tremor and gas emissions. This normal, steady activity can be abruptly interrupted by the appearance of spattering - sometimes triggered by rockfalls - on the lake surface, which abruptly shifts the lake surface motion, lava level and gas emissions to a more variable, unstable regime. The lake commonly alternates between this a) normal, steady activity and b) unstable behavior several times per day. The spattering represents outgassing of shallowly accumulated gas in the lake. Therefore, although steady lava lake behavior at Halema`uma`u may be deeply driven by upwelling of magma, we argue that the sporadic interruptions to this behavior are the result of shallow processes occurring near the lake surface. These observations provide a cautionary note that some lava lake behavior is not representative of deep-seated processes. This behavior also highlights the complex and dynamic nature of lava lake activity.

  11. Paleomagnetism and dating of a thick lava pile in the Permian Bakaly formation of eastern Kazakhstan: Regularities and singularities of the paleomagnetic record in thick lava series

    Science.gov (United States)

    Bazhenov, Mikhail L.; Van der Voo, Rob; Menzo, Zachary; Dominguez, Ada R.; Meert, Joseph G.; Levashova, Natalia M.

    2016-04-01

    Paleomagnetic results on thick lava series are among the most important sources of information on the characteristics of ancient geomagnetic fields. Most paleo-secular variation data from lavas (PSVL) are of late Cenozoic age. There are far fewer results from lavas older than 5 Ma. The Central Asia Orogenic Belt that occupies several million square kilometers in Asia is probably the world's largest area of Paleozoic volcanism and is thus an attractive target for PSVL studies. We studied a ca. 1700 m thick lava pile in eastern Kazakhstan of Early Permian age. Magmatic zircons, successfully separated from an acid flow in this predominantly basaltic sequence, yielded an Early Permian age of 286.3 ± 3.5 Ma. Oriented samples were collected from 125 flows, resulting in 88 acceptable quality flow-means (n ⩾ 4 samples, radius of confidence circle α95 ⩽ 15°) of the high-temperature magnetization component. The uniformly reversed component is pre-tilting and arguably of a primary origin. The overall mean direction has a declination = 242.0° and an inclination = -56.2° (k = 71.5, α95 = 1.8°; N = 88 sites; pole at 44.1°N, 160.6°E, A95 = 2.2°). Our pole agrees well with the Early Permian reference data for Baltica, in accord with the radiometric age of the lava pile and geological views on evolution of the western part of the Central Asia Orogenic Belt. The new Early Permian result indicates a comparatively low level of secular variation especially when compared to PSVL data from intervals with frequent reversals. Still, the overall scatter of dispersion estimates that are used as proxies for SV magnitudes, elongation values and elongation orientations for PSVL data is high and cannot be fitted into any particular field model with fixed parameters. Both observed values and numerical simulations indicate that the main cause for the scatter of form parameters (elongation values and elongation orientations) is the too small size of collections. Dispersion estimates

  12. Bunbury Basalt: Gondwana breakup products or earliest vestiges of the Kerguelen mantle plume?

    Science.gov (United States)

    Olierook, Hugo K. H.; Jourdan, Fred; Merle, Renaud E.; Timms, Nicholas E.; Kusznir, Nick; Muhling, Janet R.

    2016-04-01

    In this contribution, we investigate the role of a mantle plume in the genesis of the Bunbury Basalt using high-precision 40Ar/39Ar geochronology and whole-rock geochemistry, and by using crustal basement thickness of the eastern Indian Ocean and the western Australian continent. The Bunbury Basalt is a series of lava flows and deep intrusive rocks in southwestern Australia thought to be the earliest igneous products from the proto-Kerguelen mantle plume. Nine new plateau ages indicate that the Bunbury Basalt erupted in three distinct phases, at 136.96 ± 0.43 Ma, 132.71 ± 0.43 Ma and 130.45 ± 0.82 Ma. All Bunbury Basalt samples are enriched tholeiitic basalts with varying contributions from the continental lithosphere that are similar to other Kerguelen plume-products. Based on plate reconstructions and the present geochronological constraints, the eruption of the oldest Bunbury Basalt preceded the emplacement of the Kerguelen large igneous province by at least 10-20 m.y. Such age differences between a precursor and the main magmatic event are not uncommon but do require additional explanation. Low crustal stretching factors beneath the Bunbury Basalt (β ≈ 1.4) indicate that decompression melting could not have been generated from asthenospheric mantle with a normal chemistry and geotherm. An elevated geotherm from the mantle plume coupled with the geochemical similarity between the Bunbury Basalt and other Kerguelen plume-products suggests a shared origin exists. However, new age constraints of the oldest Bunbury Basalt are synchronous with the breakup of eastern Gondwana and the initial opening of the Indian Ocean at ca. 137-136 Ma, which may mean an alternative explanation is possible. The enriched geochemistry can equally be explained by a patch of shallow mantle beneath the southern Perth Basin. The patch may have been enriched during Gondwana suturing at ca. 550-500 Ma, during early rifting events by magmatic underplating or by intruded melts into the

  13. Paleomagnetism and the compositions of highly-oxidised iron-titanium oxides in basalts

    Science.gov (United States)

    Smith, P.J.

    1968-01-01

    As a preliminary step towards determination of the source of the natural remanence in highly-oxidised basalt lava flows, electron probe microanalysis has been carried out on the two main phases in each of two types of highly-oxidised iron-titanium oxide. The discovery of the source of NRM in these basalts is important because the correlations obtained recently by several workers between high oxidation and reversed polarity in basalts appear to support the possibility of self-reversal, even though some of the rocks studied give independent indications that the reversed magnetizations are due to field reversal. In one type of grain analysed the probe data are consistent with a titanohematite phase and a pseudobrookite phase. This agrees with previous petrographic data. In the other type of grain the probe data are consistent with one phase of titanohematite but contradict petrographic data by showing that the other phase cannot be titanomagnetite. It is concluded that significant contributions to the NRM could possibly arise from the titanohematite (whose magnetic properties in basalts are little known) or the unindentified phase (unless subsequent work rules this phase out), but not in the pseudobrookite phase. However, the NRM may not lie in the analysed grains at all; and other workers are at present investigating this possibility. ?? 1968.

  14. SMALL-VOLUME BASALTIC VOLCANOES: ERUPTIVE PRODUCTS AND PROCESSES, AND POST-ERUPTIVE GEOMORPHIC EVOLUTION IN CRATER FLAT (PLEISTOCENE), SOUTHERN NEVADA

    Energy Technology Data Exchange (ETDEWEB)

    G.A. Valentine; F.V. Perry; D. Krier; G.N. Keating; R.E. Kelley; A.H. Cogbill

    2006-04-04

    Five Pleistocene basaltic volcanoes in Crater Flat (southern Nevada) demonstrate the complexity of eruption processes associated with small-volume basalts and the effects of initial emplacement characteristics on post-eruptive geomorphic evolution of the volcanic surfaces. The volcanoes record eruptive processes in their pyroclastic facies ranging from ''classical'' Strombolian mechanisms to, potentially, violent Strombolian mechanisms. Cone growth was accompanied, and sometimes disrupted, by effusion of lavas from the bases of cones. Pyroclastic cones were built upon a gently southward-sloping surface and were prone to failure of their down-slope (southern) flanks. Early lavas flowed primarily southward and, at Red and Black Cone volcanoes, carried abundant rafts of cone material on the tops of the flows. These resulting early lava fields eventually built platforms such that later flows erupted from the eastern (at Red Cone) and northern (at Black Cone) bases of the cones. Three major surface features--scoria cones, lava fields with abundant rafts of pyroclastic material, and lava fields with little or no pyroclastic material--experienced different post-eruptive surficial processes. Contrary to previous interpretations, we argue that the Pleistocene Crater Flat volcanoes are monogenetic, each having formed in a single eruptive episode lasting months to a few years, and with all eruptive products having emanated from the area of the volcanoes main cones rather than from scattered vents. Geochemical variations within the volcanoes must be interpreted within a monogenetic framework, which implies preservation of magma source heterogeneities through ascent and eruption of the magmas.

  15. Secondary Sulfate Mineralization and Basaltic Chemistry of Craters of the Moon National Monument, Idaho: Potential Martian Analog

    Energy Technology Data Exchange (ETDEWEB)

    C. Doc Richardson; Nancy W. Hinman; Lindsay J. McHenry; J. Michelle Kotler; Jill R. Scott

    2012-05-01

    Secondary deposits associated with the basaltic caves of Craters of the Moon National Monument (COM) in southern Idaho were examined using X-ray powder diffraction, X-ray fluorescence spectrometry, Fourier transform infrared spectrometry, and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The secondary mineral assemblages are dominated by Na-sulfate minerals (thenardite, mirabilite) with a small fraction of the deposits containing minor concentrations of Na-carbonate minerals. The assemblages are found as white, efflorescent deposits in small cavities along the cave walls and ceilings and as localized mounds on the cave floors. Formation of the deposits is likely due to direct and indirect physiochemical leaching of meteoritic water through the overlying basalts. Whole rock data from the overlying basaltic flows are characterized by their extremely high iron concentrations, making them good analogs for martian basalts. Understanding the physiochemical pathways leading to secondary mineralization at COM is also important because lava tubes and basaltic caves are present on Mars. The ability of FTICR-MS to consistently and accurately identify mineral species within these heterogeneous mineral assemblages proves its validity as a valuable technique for the direct fingerprinting of mineral species by deductive reasoning or by comparison with reference spectra.

  16. Hydrogen isotope systematics of submarine basalts

    International Nuclear Information System (INIS)

    The D/H ratios and water contents in fresh submarine basalts from the Mid-Atlantic Ridge, the East Pacific Rise, and Hawaii indicate that the primary D/H ratios of many submarine lavas have been altered by processes including (1) outgassing, (2) addition of seawater at magmatic temperature, and (3) low-temperature hydration of glass. Decreases in deltaD and H2O+ from exteriors to interiors of pillows are explained by outgassing of water whereas inverse relations between deltaD and H2O+ in basalts from the Galapagos Rise and the FAMOUS Area are attributed to outgassing of CH4 and H2. A good correlation between deltaD values and H2O is observed in a suite of submarine tholeiites dredged from the Kilauea East Rift Zone where seawater (added directly to the magma), affected only the isotopic compositions of hydrogen and argon. Analyses of some glassy rims indicate that the outer millimeter of the glass can undergo low-temperature hydration by hydroxyl groups having deltaD values as low as -100. deltaD values vary with H2O contents of subaerial transitional basalts from Molokai, Hawaii, and subaerial alkali basalts from the Society Islands, indicating that the primary deltaD values were similar to those of submarine lavas. The results are discussed. (author)

  17. Deep-ocean basalts: inert gas content and uncertainties in age dating.

    Science.gov (United States)

    Noble, C S; Naughton, J J

    1968-10-11

    The radiogenic argon and helium contents of three basalts erupted into the deep ocean from an active volcano (Kilauea) have been measured. Ages calculated from these measurements increase with sample depth up to 22 million years for lavas deduced to be recent. Caution is urged in applying dates from deep-ocean basalts in studies on ocean-floor spreading. PMID:17779379

  18. Hydrothermal conditions and resaturation times in underground openings for a nuclear waste repository in the Umtanum flow at the Basalt Waste Isolation Project

    International Nuclear Information System (INIS)

    Numerical simulation techniques have been used to study heat flow and pore fluid migration in the near field of storage tunnels and canister storage holes in a proposed high-level nuclear waste repository in the Umtanum Basalt at the Basalt Waste Isolation Project site at Hanford, Washington. Particular emphasis was placed on evaluating boiling conditions in the host rock. Sensitivity studies were performed to determine the influence of variations in critical site-specific parameters which are not presently accurately known. The results indicate that, even when rather extreme values are assumed for key hydrothermal parameters, the volume of rock dried by boiling of pore fluids is negligible compared to the volume of excavated openings. The time required for saturation of backfilling materials is thus controlled by the volume of the mined excavations. When realistic values for the parameters of the natural and man-made systems are used resaturation is predicted to occur within less than two years after backfilling is placed. The approximations used in the analyses, and their limitations, are discussed in the body of the report. Recommendations are made for additional studies of the thermohydrological behavior of a high-level nuclear waste repository. 31 references, 76 figures, 7 tables

  19. A comparative Study of Circulation Patterns at Active Lava Lakes

    Science.gov (United States)

    Lev, Einat; Oppenheimer, Clive; Spampinato, Letizia; Hernandez, Pedro; Unglert, Kathi

    2016-04-01

    Lava lakes present a rare opportunity to study magma dynamics in a large scaled-up "crucible" and provide a unique natural laboratory to ground-truth dynamic models of magma circulation. The persistence of lava lakes allows for long-term observations of flow dynamics and of lava properties, especially compared to surface lava flows. There are currently five persistent lava lakes in the world: Halemaumau in Kilauea (Hawaii, USA), Erta Ale (Ethiopia), Nyiragongo (Congo), Erebus (Antarctica), and Villarica (Chile). Marum and Benbow craters of Ambrym volcano (Vanuatu) and Masaya (Nicaragua) have often hosted lava lakes as well. We use visible-light and thermal infrared time-lapse and video footage collected at all above lakes (except Villarica, where the lake is difficult to observe), and compare the circulation patterns recorded. We calculate lake surface motion from the footage using the optical flow method (Lev et al., 2012) to produce 2D velocity fields. We mined both the surface temperature field and the surface velocity field for patterns using machine learning techniques such as "self-organizing maps (SOMs)" and "principle component analysis (PCA)". We use automatic detection technique to study the configuration of crustal plates at the lakes' surface. We find striking differences among the lakes, in flow direction, flow speed, frequency of changes in flow direction and speed, location and consistency of upwelling and downwelling, and crustal plate configuration. We relate the differences to lake size, shallow conduit geometry, lava viscosity, crystal and gas content, and crust integrity.

  20. 3-D reconstructions of subsurface Pleistocene basalt flows from paleomagnetic inclination data and 40Ar/39Ar ages in the southern part of the Idaho National Laboratory (INL), Idaho (USA)

    Science.gov (United States)

    Hodges, Mary K.; Champion, Duane E.; Turrin, B.D.; Swisher, C. C., III

    2012-01-01

    The U. S. Geological Survey, in cooperation with the U.S. Department of Energy, is mapping the distribution of basalt flows and sedimentary interbeds at the Idaho National Laboratory in three dimensions to provide data for refining numerical models of groundwater flow and contaminant transport in the eastern Snake River Plain aquifer. Paleomagnetic inclination and polarity data from basalt samples from 47 coreholes are being used to create a three-dimensional (3-D) model of the subsurface of the southern part of the INL. Surface and sub-surface basalt flows can be identified in individual cores and traced in three dimensions on the surface and in the subsurface for distances of more than 20 km using a combination of paleomagnetic, stratigraphic, and 40Ar/39Ar data. Eastern Snake River Plain olivine tholeiite basalts have K2O contents of 0.2 to 1.0 weight per cent. In spite of the low-K content, high-precision 40Ar/39Ar ages were obtained by applying a protocol that employs short irradiation times (minimizing interferences from Ca derived 36Ar), frequent measurement of various size atmospheric Ar pipettes to monitor and correct for temporal variation, and signal size dependent nonlinearity in spectrometer mass bias, resulting in age dates with resolution generally between 2 to 10% of the age. 3-D models of subsurface basalt flows are being used to: (1) Estimate eruption volumes; (2) locate the approximate vent areas and extent of sub-surface flows; and (3) Help locate high and low transmissivity zones. Results indicate that large basalt eruptions (>3 km3) occurred at and near the Central Facilities Area between 637 ka and 360 ka; at and near the Radioactive Waste Management Complex before 540 ka; and north of the Naval Reactors Facility at about 580 ka. Since about 360 ka, large basalt flows have erupted along the Arco-Big Southern Butte Volcanic Rift Zone and the Axial Volcanic Zone, and flowed northerly towards the Central Facilities Area. Basalt eruptions shifted

  1. Origins and implications of zigzag rift patterns on lava lakes

    Science.gov (United States)

    Karlstrom, Leif; Manga, Michael

    2006-06-01

    The distinctive rift patterns observed on newly formed lava lakes are very likely a product of interaction between heat transfer (cooling of lava) and deformation of the solid crust in response to applied stresses. One common pattern consists of symmetric "zigzag" rifts separating spreading plates. Zigzags can be characterized by two measurable parameters: an amplitude A, and an angle θ between segments that make up the zigzags. Similar patterns are observed in analog wax experiments in which molten wax acts as cooling and solidifying lava. We perform a series of these wax experiments to find the relationship between θ, A, and the cooling rate. We develop a model to explain the observed relationships: θ is determined by a balance of spreading and solidification speeds; the amplitude A is limited by the thickness of the solid wax crust. Theoretical predictions agree well with experimental data; this enables us to scale the model to basaltic lava lakes. If zigzag rifts are observed on the surface of lava lakes, and if physical properties of the lava crust can be measured or inferred by other means, measurements of θ and A make it possible to calculate crust-spreading velocity and crust thickness.

  2. The foaming of lavas

    Science.gov (United States)

    Okeefe, J. A.; Walton, W.

    1976-01-01

    Foaming is of great practical and theoretical significance for volcanic processes on the earth, the moon, and perhaps the meteorite parent bodies. The theory of foams agrees with steelmaking experience to indicate that their presence depends on the existence of solutes in the lavas which reduce the surface tension, and are not saturated. These solutes concentrate at the surface, and are called surfactants. The surfactant responsible for the formation of volcanic ash was not identified; it appears to be related to the oxygen partial pressure above the lava. This fact may explain why lunar and meteoritic melts are not observed to foam. Experimental studies are needed to clarify the process.

  3. Orthopyroxene fractionation in the Grande Ronde Basalt--Columbia River Basalt group

    International Nuclear Information System (INIS)

    Six orthopyroxenes were microprobed; five orthopyroxenes were from the Grande Ronde Basalt, and one was from the Buford flow of the Saddle Mountains Basalt. The orthopyroxenes are primarily bronzite in composition, but some analyses show that hypersthene is present. The reaction rims of all analyzed orthopyroxene crystals are pigeonite, while the groundmass pyroxene is both augite and pigeonite. Preliminary results from the least-squares linear modeling of the Grande Ronde Basalt indicate orthopyroxene is a necessary phase for mass balancing between flow compositions. Three models were tried in order to determine if selected mineral phases could be used to model the chemical compositions of the flows. These models suggest that orthopyroxene and plagioclase are phases common to the Grande Ronde Basalt. The similarity of orthopyroxene and plagioclase occurrences suggests that they are important intratelluric phases of the Grande Ronde Basalt which reacted out when the basaltic liquids were erupted at the surface

  4. Preliminary results of hydrologic testing the composite middle sentinel bluffs basalt flow bottom at Borehole RRL-2 (3,247--3,344 feet)

    International Nuclear Information System (INIS)

    This report presents preliminary results and description of hydrologic test activities for the composite Middle Sentinel Bluffs basalt flow bottom (3,247-3,344 feet) at Borehole RRL-2. Hydrologic tests conducted include one constant discharge air-lift and two slug tests. Preliminary results indicate an observed hydraulic head for the test interval of 405.5 feet above mean sea level. Transmissivity values determined from hydrologic tests performed range between 203 and 847 ft2/day, with an assigned best estimate of 770 ft2 day. The best estimate of equivalent hydraulic conductivity, based on an effective test thickness of 77.5 feet, is 9.9 ft/day

  5. Preliminary results of hydrologic testing: The composite Umtanum basalt flow top at borehole RRL-2 (3,568 - 3,781 feet)

    International Nuclear Information System (INIS)

    This report presents preliminary results and description of hydrologic test activities for the composite Umtanum basalt flow top (3,568--3,781 feet) at Borehole RRL-2. Hydrologic tests conducted include two constant discharge air-lift and four slug tests. Preliminary results indicate an observed hydraulic head for the test interval of 405.7 feet above mean sea level. Transmissivity values determined from hydrologic tests performed, range between 244 to 481 ft2/day, with an assigned best estimate of 480 ft2/day. The best estimate of equivalent hydraulic conductivity, based on an effective test thickness of 157 feet, is 3.1 ft/day. 7 refs., 9 figs., 3 tabs

  6. LAVA Applications to Open Rotors

    Science.gov (United States)

    Kiris, Cetin C.; Housman, Jeff; Barad, Mike; Brehm, Christoph

    2015-01-01

    Outline: LAVA (Launch Ascent Vehicle Aerodynamics); Introduction; Acoustics Related Applications; LAVA Applications to Open Rotor; Structured Overset Grids; Cartesian Grid with Immersed Boundary; High Speed Case; High Speed Case with Plate Low Speed Case.

  7. Sharing geographic databases via the world wide web: applications to the whole Italian territory and a focus on lava flow hazard at Mount Etna

    Science.gov (United States)

    Tarquini, S.; Favalli, M.; Nannipieri, L.

    2009-04-01

    DAR survey of the Vesuvius volcano (1 m resolution). Additionally, the GE-based system can be effectively used to present the simulation results from numerical models within a geographic context, to support the assessment and communication of the impact associated to geophysical mass flow on a volcanic area. Finally, we are currently developing a system to interactively navigate a large database of lava flow simulations at Mount Etna (including more than 80,000 simulated vents). The simulations database has been derived using the DEM-driven DOWNFLOW probabilistic code. By elaborating this database a 10m-resolution hazard map has been derived and can be loaded via Web using GE. Upon a click on any location on a map of the volcano, this system is expected to convert on the fly the requested simulation from the database to an image format that can be loaded and visualized by GE.

  8. Silicon isotope systematics of acidic weathering of fresh basalts, Kilauea Volcano, Hawai'i

    Science.gov (United States)

    Chemtob, Steven M.; Rossman, George R.; Young, Edward D.; Ziegler, Karen; Moynier, Fréderic; Eiler, John M.; Hurowitz, Joel A.

    2015-11-01

    Silicon stable isotopes are fractionated by a host of low-temperature aqueous processes, making them potentially useful as a weathering proxy. Here we characterize the silicon isotope signature of surficial chemical weathering of glassy basaltic lava flows at Kilauea Volcano, Hawaii. Fresh basalt flow surfaces (silica surface coatings up to 80 μm thick. These silica coatings and associated silica cements are enriched in the heavier isotopes of Si (δ30SiNBS-28 = +0.92‰ to +1.36‰) relative to their basaltic substrate (δ30SiNBS-28 = -0.3‰ to -0.2‰). Secondary clays and opals are typically depleted in 30Si relative to the dissolved reservoirs from which they precipitated, so this sense of isotopic fractionation is unusual. Mechanisms capable of producing isotopically heavy secondary minerals were explored by conducting batch alteration experiments on fresh basaltic glass. Batch acidic alteration of basalt glass in HCl, H2SO4, and HF produced silica-rich surface layers resembling the Hawaiian surface coatings. Differences in fluid chemical composition affected the direction and magnitude of Si isotope fractionation. Basalt leaching in HCl or H2SO4 produced 30Si-enriched fluids (1000 ln αprecip-Si(aq) ≅ -0.8‰) and 30Si-depleted secondary silica layers. In contrast, HF-bearing experiments produced highly 30Si-depleted fluid compositions (1000 ln αprecip-Si(aq) up to +8‰). Larger isotopic fractionations were observed in experiments with lower fluid-rock ratios. In Hawaii, where altering fluids contain H2SO4 and HCl but minimal HF, high δ30Si values for the silica coatings were likely achieved by Rayleigh fractionation. Aqueous 30Si-enriched silica was released during incongruent basalt dissolution then subsequently transported and deposited from an evaporating solution at the flow surface. Our results indicate that (1) altering fluid chemistry and fluid-rock ratio impact the Si isotope signature of chemical weathering and (2) δ30Si of solids produced

  9. The First Paleomagnetic data from the Cambrian basalts of Henrietta Island (De Long Archipelago, Arctic Ocean)

    Science.gov (United States)

    Metelkin, D. V.; Zhdanova, A.; Vernikovskiy, V. A.; Matushkin, N. Y.

    2015-12-01

    Henrietta Island in De Long archipelago (East-Siberian sea) still remains poorly studied geologically but last investigations show that its volcano-sedimentary sequences can help reconstruct tectonic evolution of East Russian Arctic in Early Paleozoic stage. The deposits lying on Precambrian basements are deformed to varying degrees and intruded by mafic dykes.The study was carried out on two basaltic lava flows whose 40Ar/39Ar age is 520.6±9.5 Ma. Previously the age of these basalts was assumed Cretaceous. According to available data the underlaying sediments contain zircons with Cambrian and Ordovician ages but all boundaries between these basalts and other strata are tectonic. So we suppose the age of basalts as Middle Cambrian but more precise geochronological data are required. All magnetic measurements were performed at the Laboratory of Geodynamics and Paleomagnetism of Institute of Petroleum Geology and Geophysics (Novosibirsk). Basalt samples has relatively high magnetic susceptibility values varying from 5x10-4 to 180x10-4SI units. NRM values range is from 3 to 170 mA/m. Petromagnetic parameters including also coercive characteristics point at the good potentially preserving primary magnetization. Stepwise thermal demagnetization permits to isolate characteristic components of magnetization and calculate mean directions in two lava flows: 1. Ds=294.3°, Is=29.1°, K=81.1, α95=5.1; 2. Ds=301.0°, Is=28.3°, K=34.4, α95=7.9). The mean paleomagnetic pole has coordinates: Plat=20.9°, Plong = 42.6°, dp/dm=14.3/7.9. Paleolatitude was defined as 15.3° but the question of the hemisphere for De Long Islands is open yet. In case of south hemisphere in Middle Cambrian according to available paleomagnetic data De Long islands could be placed close to Taimyr margin of Siberia and in case of northern hemisphere they may be located near south (in present-day coordinates) margin of Siberia. The work was supported by grant RFBR 14-05-31399 and Russian Research Fund

  10. A large submarine sand-rubble flow on kilauea volcano, hawaii

    Science.gov (United States)

    Fornari, D.J.; Moore, J.G.; Calk, L.

    1979-01-01

    Papa'u seamount on the south submarine slope of Kilauea volcano is a large landslide about 19 km long, 6 km wide, and up to 1 km thick with a volume of about 39 km3. Dredge hauls, remote camera photographs, and submersible observations indicate that it is composed primarily of unconsolidated angular glassy basalt sand with scattered basalt blocks up to 1 m in size; no lava flows were seen. Sulfur contents of basalt glass from several places on the sand-rubble flow and nearby areas are low (volcano disintegrated when they entered the sea. The current eruptive output of the volcano suggests that the material in the submarine sand-rubble flow represents about 6000 years of accumulation, and that the flow event occurred several thousand years ago. ?? 1979.

  11. The scarcity of mappable flow lobes on the lunar maria - Unique morphology of the Imbrium flows

    Science.gov (United States)

    Schaber, G. G.; Boyce, J. M.; Moore, H. J.

    1976-01-01

    Unique features of Imbrium lava flows are their thickness (10-30 + m) and lengths (up to 400 km for phase-III, and up to 600 km for phase-II) when compared along later Imbrium and Eratosthenian units. They are distinct by virtue of their inferred short-lived (on the order of days) and extremely rapid rates of effusion. It is shown that there are numerous other basalt eruptives within the young blue western maria. The emplacement of these flows was by complex multilayering and intertonguing of individual flow units with thicknesses less than 10 m. They are generally restricted to the near vicinity of multiple vent sources.

  12. Characteristics of terrestrial basaltic rock populations: Implications for Mars lander and rover science and safety

    Science.gov (United States)

    Craddock, Robert A.; Golombek, Matthew P.

    2016-08-01

    We analyzed the morphometry of basaltic rock populations that have been emplaced or affected by a variety of geologic processes, including explosive volcanic eruptions (as a proxy for impact cratering), catastrophic flooding, frost shattering, salt weathering, alluvial deposition, and chemical weathering. Morphometric indices for these rock populations were compared to an unmodified population of rocks that had broken off a solidified lava flow to understand how different geologic processes change rock shape. We found that a majority of rocks have an sphericity described as either a disc or sphere in the Zingg classification system and posit that this is a function of cooling fractures in the basalt (Zingg [1935] Schweiz. Miner. Petrogr. Mitt., 15, 39-140). Angularity (roundness) is the most diagnostic morphometric index, but the Corey Shape Factor (CSF), Oblate-Prolate Index (OPI) and deviation from compactness (D) also sometimes distinguished weathering processes. Comparison of our results to prior analyses of rock populations found at the Mars Pathfinder, Spirit, and Curiosity landing sites support previous conclusions. The observation that the size-frequency distribution of terrestrial rock populations follow exponential functions similar to lander and orbital measurements of rocks on Mars, which is expected from fracture and fragmentation theory, indicates that these distributions are being dominantly controlled by the initial fracture and fragmentation of the basalt.

  13. Bubble Growth in Lunar Basalts

    Science.gov (United States)

    Zhang, Y.

    2009-05-01

    Although Moon is usually said to be volatile-"free", lunar basalts are often vesicular with mm-size bubbles. The vesicular nature of the lunar basalts suggests that they contained some initial gas concentration. A recent publication estimated volatile concentrations in lunar basalts (Saal et al. 2008). This report investigates bubble growth on Moon and compares with that on Earth. Under conditions relevant to lunar basalts, bubble growth in a finite melt shell (i.e., growth of multiple regularly-spaced bubbles) is calculated following Proussevitch and Sahagian (1998) and Liu and Zhang (2000). Initial H2O content of 700 ppm (Saal et al. 2008) or lower is used and the effect of other volatiles (such as carbon dioxide, halogens, and sulfur) is ignored. H2O solubility at low pressures (Liu et al. 2005), concentration-dependent diffusivity in basalt (Zhang and Stolper 1991), and lunar basalt viscosity (Murase and McBirney 1970) are used. Because lunar atmospheric pressure is essentially zero, the confining pressure on bubbles is completely supplied by the overlying magma. Due to low H2O content in lunar basaltic melt (700 ppm H2O corresponds to a saturation pressure of 75 kPa), H2O bubbles only grow in the upper 16 m of a basalt flow or lake. A depth of 20 mm corresponds to a confining pressure of 100 Pa. Hence, vesicular lunar rocks come from very shallow depth. Some findings from the modeling are as follows. (a) Due to low confining pressure as well as low viscosity, even though volatile concentration is very low, bubble growth rate is extremely high, much higher than typical bubble growth rates in terrestrial melts. Hence, mm-size bubbles in lunar basalts are not strange. (b) Because the pertinent pressures are so low, bubble pressure due to surface tension plays a main role in lunar bubble growth, contrary to terrestrial cases. (c) Time scale to reach equilibrium bubble size increases as the confining pressure increases. References: (1) Liu Y, Zhang YX (2000) Earth

  14. High-Ti type N-MORB parentage of basalts from the south Andaman ophiolite suite, India

    Indian Academy of Sciences (India)

    Rajesh K Srivastava; R Chandra; Anant Shastry

    2004-12-01

    A complete dismembered sequence of ophiolite is well exposed in the south Andaman region that mainly comprises ultramafic cumulates, serpentinite mafic plutonic and dyke rocks, pillow lava, radiolarian chert, and plagiogranite. Pillow lavas of basaltic composition occupy a major part of the Andaman ophiolite suite (AOS). These basalts are well exposed all along the east coast of southern part of the south AOS. Although these basalts are altered due to low-grade metamorphism and late hydrothermal processes, their igneous textures are still preserved. These basalts are mostly either aphyric or phyric in nature. Aphyric type exhibits intersertal or variolitic textures, whereas phyric variety shows porphyritic or sub-ophitic textures. The content of alkalies and silica classify these basalts as sub-alkaline basalts and alkaline basalts. A few samples show basaltic andesite, trachybasalt, or basanitic chemical composition. High-field strength element (HFSE) geochemistry suggests that studied basalt samples are probably derived from similar parental magmas. Al2O3/TiO2 and CaO/TiO2 ratios classify these basalts as high-Ti type basalt. On the basis of these ratios and many discriminant functions and diagrams, it is suggested that the studied basalts, associated with Andaman ophiolite suite, were derived from magma similar to N-MORB and emplaced in the mid-oceanic ridge tectonic setting.

  15. The microwave palaeointensity technique and its application to lava

    CERN Document Server

    Hill, M J

    2000-01-01

    application is required at each power step thus removing the need for accurate reproducibility of absorbed microwave power and also reducing experimental time. This method as well as a previous method developed for use with ceramic samples are described and discussed. The microwave palaeointensity technique has been used successfully in three palaeomagnetic studies (that include rock magnetic and directional analyses). These are a study of historic lava from Mt. Etna, Sicily, a detailed through the flow study of the 1960 Kilauea lava flow, Hawaii and a study of Tertiary Australian lava. Palaeointensity results are compared to observatory records and / or results of previous studies using conventional techniques. The research undertaken, described in this thesis, demonstrates that the microwave palaeointensity technique is a viable technique for use with lava. This enables greater confidence that any palaeointensity results obtained are not affected by sample alteration during experimentation. The suitability ...

  16. Interpretation of trace element and isotope features of basalts: relevance of field relations, petrology, major element data, phase equilibria, and magma chamber modeling in basalt petrogenesis

    Science.gov (United States)

    O'Hara, M. J.; Herzberg, C.

    2002-06-01

    explain the chemical variation between fertile and residual peridotite in natural ultramafic rock suites. The subtleties of magma chamber partial crystallization processes can produce an astounding array of "pseudospidergrams," a small selection of which have been explored here. Major modification of the trace element geochemistry and trace element ratios, even those of the highly incompatible elements, must always be entertained whenever the evidence suggests the possibility of partial crystallization. At one extreme, periodically recharged, periodically tapped magma chambers might undergo partial crystallization by ˜95% consolidation of a succession of small packets of the magma. Refluxing of the 5% residual melts from such a process into the main body of melt would lead to eventual discrimination between highly incompatible elements in that residual liquid comparable with that otherwise achieved by 0.1 to 0.3% liquid extraction in equilibrium partial melting. Great caution needs to be exercised in attempting the reconstruction of more primitive compositions by addition of troctolite, gabbro, and olivine to apparently primitive lava compositions. Special attention is focussed on the phase equilibria involving olivine, plagioclase (i.e., troctolite), and liquid because a high proportion of erupted basalts carry these two phases as phenocrysts, yet the equilibria are restricted to crustal pressures and are only encountered by wide ranges of basaltic compositions at pressures less than 0.5 GPa. The mere presence of plagioclase phenocrysts may be sufficient to disqualify candidate primitive magmas. Determination of the actual contributions of crustal processes to petrogenesis requires a return to detailed field, experimental, and forensic petrologic studies of individual erupted basalt flows; of a multitude of cumulate gabbros and their contacts; and of upper-mantle outcrops.

  17. Diversion of lava during the 1983 eruption of Mount Etna

    Science.gov (United States)

    Lockwood, J.P.; Romano, R.

    1985-01-01

    Mankind's first known attempt to divert a lava flow was in 1669, when a flow from Mount Etna volcano threatened the Sicilian city of Catania. This attempt was largely unsuccessful, in part due to opposition by citizens of another town, Paterno. Attempts to divert lava flows from Mauna Loa Volcano on the island of Hawaii by aerial bombing were made in 1935 and 1942, with no signifcant effects. Earthen bariers were hurriedly constructed in attempts to divert flows from Kilauea Volcano, Hawaii in 1955 and 1960, again with little success.

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

    International Nuclear Information System (INIS)

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

  19. Petrology and Geochemistry of Jinlongdingzi Active Volcano—the Most Recent Basaltic Explosive Volcano at Longgang

    Institute of Scientific and Technical Information of China (English)

    樊祺诚; 随建立; 等

    2000-01-01

    The Jinlongdingzi active volcano erupted before 1600a,and it is the latest basaltic explosive volcano at Longgang Volcano.Its volcanic products include the Jinlongdingzi Volcanic cone(elevation 999.4m),the lava flow and the widely-spread volcanic pyroclastic sheet(sihai Pyroclastic Sheet),Jinlongdingzi volcanic rocks are trachybasalts with very similar REE patterns and incompatible element patterns,and their 87Sr/86Sr and 143Nd/144Nd ratios range from 0.704846 ot 0.704921 and from 0.512619 to 0.512646,respectively.It is revealed that the trachybasalt has the character of primary magma derived directly from mantle sources with very little evolution and crust contamination during its ascending.The younger mantle xenoliths demonstrate that the mantle source of the Jinlongdingzi Volcao is hydrous,with relatively low temperature.

  20. Juxtaposition of adakite, boninite, high-TiO 2 and low-TiO 2 basalts in the Devonian southern Altay, Xinjiang, NW China

    Science.gov (United States)

    Niu, Hecai; Sato, Hiroaki; Zhang, Haixiang; Ito, Jun'ichi; Yu, Xueyuan; Nagao, Takashi; Terada, Kentaro; Zhang, Qi

    2006-12-01

    We present petrographic and geochemical data on representative samples of the Devonian adakite, boninite, low-TiO 2 and high-TiO 2 basalts and associated rocks in the southern Altay areas, Xinjiang, NW China. These volcanic rocks mostly occur as tectonic blocks within suture zones between the Siberian and Junggar plates. Adakite occurs in the Suoerkuduke area ca. 40 km south of Fuyun, and actually represents a poorly-sorted massive volcaniclastic deposit, mostly consisting of a suite of hornblende andesite to pyroxene andesite. The geochemical features of the adakite suggest its generation by melting of subducted oceanic crust. Boninite occurs in the Saerbulake area ca. 20 km southwest of Fuyun, as pillowed lava or pillowed breccia. It is associated with high-TiO 2 basalt/gabbro and low-TiO 2 basalt. The boninites are metamorphosed, but contain relict clinopyroxene with Mg# (=100*Mg/(Mg+Fe)) of 90-92, and Cr 2O 3 contents of 0.5-0.7 wt% and chromian spinel with Cr/(Cr+Al) ratio of 0.84. The bulk rock compositions of the boninites are characterized by low and U-shaped REE with variable La/Yb ratios. They are classified as high-Ca boninite. The Cr-rich cpx phenocryst and Chromian spinel suggests that the boninites were formed by melting of mildly refractory mantle peridotite fluxed by a slab-derived fluid component under normal mantle potential temperature conditions. Basaltic rocks occur as massive flows, pillowed lavas, tuff breccia, lapilli tuff and blocks in tectonic mélanges. Together with gabbros, the basaltic rocks are classified into high-TiO 2 (>1.7 wt%) and low-TiO 2 (<1.5 wt%) types. They show variable trace element compositions, from MORB-type through transitional back-arc basin basalt to arc tholeiite, or within plate alkalic basalt. A notable feature of the Devonian formations in the southern Altay is the juxtaposition of volcanic rocks of various origins even within a limited area; i.e. the adakite and the boninites are associated with high-TiO 2 and

  1. Dissolution of Olivine, Siderite, and Basalt at 80 Deg C in 0.1 M H2SO4 in a Flow Through Process: Insights into Acidic Weathering on Mars

    Science.gov (United States)

    Golden, D. C.; Ming, D. W.; Hausrath, E. M.; Morris, R. V.; Niles, P. B.; Achilles, C. N.; Ross, D. K.; Cooper, B. L.; Gonzalex, C. P.; Mertzman, S. A.

    2012-01-01

    The occurrence of jarosite, other sulfates (e.g., Mg-and Ca-sulfates), and hematite along with silicic-lastic materials in outcrops of sedimentary materials at Meridiani Planum (MP) and detection of silica rich deposits in Gusev crater, Mars, are strong indicators of local acidic aqueous processes [1,2,3,4,5]. The formation of sediments at Meridiani Planum may have involved the evaporation of fluids derived from acid weathering of Martian basalts and subsequent diagenesis [6,7]. Also, our previous work on acid weathering of basaltic materials in a closed hydro-thermal system was focused on the mineralogy of the acid weathering products including the formation of jarosite and gray hematite spherules [8,9,10]. The object of this re-search is to extend our earlier qualitative work on acidic weathering of rocks to determine acidic dissolution rates of Mars analog basaltic materials at 80 C using a flow-thru reactor. We also characterized residual phases, including poorly crystalline or amorphous phases and precipitates, that remained after the treatments of olivine, siderite, and basalt which represent likely MP source rocks. This study is a stepping stone for a future simulation of the formation of MP rocks under a range of T and P.

  2. Vapor segregation and loss in basaltic melts

    Science.gov (United States)

    Edmonds, M.; Gerlach, T.M.

    2007-01-01

    Measurements of volcanic gases at Pu'u'O??'o??, Kilauea Volcano, Hawai'i, reveal distinct degassing regimes with respect to vapor segregation and loss during effusive activity in 2004-2005. Three styles of vapor loss are distinguished by the chemical character of the emitted volcanic gases, measured by open path Fourier transform infrared spectroscopy: 1 persistent continuous gas emission, 2 gas piston events, and 3 lava spattering. Persistent continuous gas emission is associated with magma ascent and degassing beneath the crater vents, then eruption of the degassed magma from flank vents. Gas piston events are the result of static gas accumulation at depths of 400-900 m beneath Pu'u'O??'o??. A CO2-rich gas slug travels up the conduit at a few meters per second, displacing magma as it expands. Lava spattering occurs due to dynamic bubble coalescence in a column of relatively stagnant magma. The Large gas bubbles are H2O rich and are generated by open-system degassing at depths of segregation in basaltic melts, but their implications differ. Accumulation and segregation of CO2-rich vapor at depth does not deplete the melt of H2O (required to drive lava fountains near to the surface) and therefore gas piston events can occur interspersed with lava fountaining activity. Lava spattering, however, efficiently strips H2O-rich vapor from magma beneath the crater vents; the magma must then erupt effusively from vents on the flank of the cone. ?? 2007 The Geological Society of America.

  3. 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

  4. Genetic aspects of basalts from the Carlsberg Ridge

    Digital Repository Service at National Institute of Oceanography (India)

    Banerjee, R.; Iyer, S.D.

    of the plagioclase from a basaltic magma at a slower rate than the co - precipitating olivine and/or pyroxenes, due to the high - pressure effect 33 or density dif - ferences between plagiocl ase and the basaltic magma 34 . Plagioclase phenocrysts with An - rich... show no zoned mineral, while those that ascend slowly are more likely to cool extensively and have zoned phenocrysts. Further, the size of the magma chambers could also have an effect in th ose lavas that originated from a large, thermally he...

  5. Basaltic rocks analyzed by the Spirit Rover in Gusev Crater

    Science.gov (United States)

    McSween, H. Y.; Arvidson, R. E.; Bell, J. F., III; Blaney, D.; Cabrol, N. A.; Christensen, P. R.; Clark, B. C.; Crisp, J. A.; Crumpler, L. S.; DesMarais, D. J.; Farmer, J. D.; Gellert, R.; Ghosh, A.; Gorevan, S.; Graff, T.; Grant, J.; Haskin, L. A.; Herkenhoff, K. E.; Johnson, J. R.; Jolliff, B. L.; Klingelhoefer, G.; Morris, R. V.; Yen, A.

    2004-01-01

    The Spirit landing site in Gusev Crater on Mars contains dark, fine-grained, vesicular rocks interpreted as lavas. Pancam and Mini-Thermal Emission Spectrometer (Mini-TES) spectra suggest that all of these rocks are similar but have variable coatings and dust mantles. Magnified images of brushed and abraded rock surfaces show alteration rinds and veins. Rock interiors contain Particle X-ray Spectrometer are consistent with picritic basalts, containing normative olivine, pyroxenes, plagioclase, and accessory FeTi oxides. Mossbauer, Pancam, and Mini-TES spectra confirm the presence of olivine, magnetite, and probably pyroxene. These basalts extend the known range of rock compositions composing the martian crust.

  6. Birth of a lava lake: Nyamulagira volcano 2011-2015

    Science.gov (United States)

    Coppola, D.; Campion, R.; Laiolo, M.; Cuoco, E.; Balagizi, C.; Ripepe, M.; Cigolini, C.; Tedesco, D.

    2016-03-01

    Since 1938, Nyamulagira volcano (Democratic Republic of Congo) has operated as a classic pressurized basaltic closed system, characterized by frequent dike-fed flank eruptions. However, on June 24, 2014, an active lava lake was observed in its summit, after a period of 76 years. The small lava lake is now exposed at the bottom of a pit-crater and is rising and growing. Based on satellite-derived infrared (IR) data, SO2 fluxes and periodic field surveys, we provide evidence that the development of the lava lake was gradual and occurred more than 2 years before it was first observed in the field. Notably, this process followed the voluminous 2011-2012 distal flank eruption and was coeval with weakening of the central rock column below the summit. Hence, the opening and development of the pit-crater favoured the continuous rise of fresh magma through the central conduit and promoted the gradual "re-birth" of the Nyamulagira lava lake. Budgeted volumes of magma erupted, and magma degassed at depth indicate that the formation of the lava lake is due to the draining and refilling of a shallow plumbing system (1-2 km depth), probably in response to the rift-parallel 2011-2012 distal eruption. We thus suggest that the transition from lateral to central activity did not result from a substantial change in the magma supply rate but, more likely, from the perturbation of the plumbing system (and related stress field) associated with the distal eruption. The processes observed at Nyamulagira are not unique and suggest that rift-fissure eruptions, in addition to triggering caldera collapses or lava lake drainages, may also induce a progressive resumption of central vent activity. Current activity at Nyamulagira represents a tangible and major hazard for the population living at the base of its southern flank.

  7. Reconstruction of lava fields based on 3D and conventional images. Arenal volcano, Costa Rica.

    Science.gov (United States)

    Horvath, S.; Duarte, E.; Fernandez, E.

    2007-05-01

    Conventional air photographs, multi-spectral images and a map scale 1:10 000 were used to upgrade Arenal volcano's lava field. Arenal volcano located in NW Costa Rica has been active for 39 years. Fifty two days after the initial explosive events that opened three craters on the west flank, lava flows were erupted from crater A (1050 m) in September, 1968 and continued flowing until November, 1973. These lavas were the most voluminous of the eruption and the effusion rate of lava was relatively high in this period. In April, 1974 lava flows were erupted from crater C (1460 m) and continue to present time. Younger lava flows extended over uncovered ground to the south and southwest in the 1980s and early 1990s and onto the northern slopes in the 1990s and 2000s. Lava flows are becoming shorter and narrower with time. Therefore, the centre of mass of the whole lava flow-field has migrated closer to the vent. Above crater C a cone has been growing steadily, reaching a height of 1670 m, 36 m higher than the prehistoric Arenal cone by 2004. After 39 years of continuous emission of lava flows, the profile of Arenal volcano consists of a duplet of cones whose summits are separated by less than 500 meters. Most of the build up around the new cone comes from varied lava flows. For near 30 years volcano monitoring staff (from OVSICORI-UNA) has recorded field observations of regular and extraordinary events, in paper. Several drafts maps have been used for teaching, academic presentations and for graphic explanations to specific audiences and to the general public. An upgraded version was needed. The purpose of this work is to present the most recent lava flows giving a visual presentation of them by computer methods. Combined SIG techniques (Arc View 3.3) and ERDAS produced a base map in which layers containing the recorded lava flows from the recent 16 years, were depicted. Each lava flow has its own characteristics: direction, year of origin, width, length, surface texture

  8. Reactive transport modeling of CO2 mineral sequestration in basaltic rocks

    Science.gov (United States)

    Aradottir, E. S.; Sonnenthal, E. L.; Bjornsson, G.; Jonsson, H.

    2011-12-01

    CO2 mineral sequestration in basalt may provide a long lasting, thermodynamically stable, and environmentally benign solution to reduce greenhouse gases in the atmosphere. Multi-dimensional, field scale, reactive transport models of this process have been developed with a focus on the CarbFix pilot CO2 injection in Iceland. An extensive natural analog literature review was conducted in order to identify the primary and secondary minerals associated with water-basalt interaction at low and elevated CO2 conditions. Based on these findings, an internally consistent thermodynamic database describing the mineral reactions of interest was developed and validated. Hydrological properties of field scale mass transport models were properly defined by calibration to field data using iTOUGH2. Reactive chemistry was coupled to the models and TOUGHREACT used for running predictive simulations carried out with the objective of optimizing long-term management of injection sites, to quantify the amount of CO2 that can be mineralized, and to identify secondary minerals that compete with carbonates for cations leached from the primary rock. Calibration of field data from the CarbFix reservoir resulted in a horizontal permeability for lava flows of 300 mD and a vertical permeability of 1700 mD. Active matrix porosity was estimated to be 8.5%. The CarbFix numerical models were a valuable engineering tool for designing optimal injection and production schemes aimed at increasing groundwater flow. Reactive transport simulations confirm dissolution of primary basaltic minerals as well as carbonate formation, and thus indicate in situ CO2 mineral sequestration in basalts to be a viable option. Furthermore, the simulations imply that clay minerals are most likely to compete with magnesite-siderite solid solutions for Mg and Fe leached from primary minerals, whereas zeolites compete with calcite for dissolved Ca. In the case of the CarbFix pilot injection, which involves a continuous

  9. Impeller flow-meter logging of vertical cross flow between basalt aquifers through wells at the Idaho National Engineering Laboratory, Eastern Snake River Plain, Idaho

    International Nuclear Information System (INIS)

    An impeller flowmeter was used with a COLOG digital acquisition system to determine existing borehole flows, to compare with previous logging results, and to acquire flow measurements of vertical cross-flow of water in the wells between permeable zones in the open-hole intervals. The direction of flow found was predominantly downward with velocities ranging from 0-30 ft/min. Some flow reversals were noted and attributed to nearby pumping wells. USGS wells 44 and 46 were studied in September, 1991 near the Idaho Chemical Processing Plant (ICPP). The results showed a usual overall flow direction downward with flow entering the wells at around 510 to 600 ft. below the land surface. Water exited these wells at lower levels around 550 to 580 ft. Flow velocities ranged up to 24 ft/min. Using published aquifer parameters, the rate of propagation of a pressure change in an aquifer was calculated for the well CPP-2 turning on and off, at 3100 gpm

  10. Ascent and eruption of basaltic magma on the earth and moon

    International Nuclear Information System (INIS)

    Geological and physical observations and constraints are applied to the development of a model of the ascent and emplacement of basaltic magma on the earth and moon. Mathematical models of the nature and motion of gas/liquid mixtures are developed and show that gas exsolution from terrestrial and lunar magmas commonly only occurs at shallow depths (less than 2 km); thus the ascent of bubble-free magma at depth can be treated separately from the complex motions caused by gas exsolution near the surface. Magma ascent is related to dike or conduit width. For terestrial basalts with negligible yield strengths and viscosities greater than 102 Ps s, widths in the range 0.2--0.6 m are needed to allow eruptions from between depths of 0.5--20 km. Fissure widths of about 4 m would be needed to account for output rates estimated for the Columbia River flood basalt eruptions. As the magma nears the surface, bubble coalescence will tend to occur, leading to intermittent explosive strombolian-style activity. For commonly occuring lunar and terrestrial basalts the magma rise speed must be greater than 0.5-1 m/s if strombolian activity is to be avoided and relatively steady fire fountaining is to take place. Terrestrial fire fountain heights are dictated by the vertical velocity of the magma/gas dispersion emerging through the vent, increasing with increasing magma gas content and mass eruption rate, and decreasing with increasing magma viscosity. Terrestrial fire fountain heights up to 500 m imply the release of up to 0.4 wt % water from the magma, corresponding to initial water contents up to 0.6 wt %. The presence of extremely long lava flows and sinuous rilles on the moon has often been cited as evidence for very high extrusion rates and thus a basic difference between terrestrial and lunar magmas and crustal environments

  11. Thermophysical properties of the Lipari lavas (Southern Tyrrhenian Sea

    Directory of Open Access Journals (Sweden)

    D. Russo

    1997-06-01

    Full Text Available Results of thermophysical investigations into the lavas of the island of Lipari (Southern Tyrrhenian Sea are presented. Samples selected for laboratory measurements belong to four main magmatic cycles, which produced basaltic-andesitic, andesitic and rhyolitic lavas. The wet-bulk density and the thermal conductivity measured on 69 specimens range from 1900 to 2760 kg m-3 and from 1.02 to 2.88 W m-1 K-1, respectively. Porosity is never negligible and its influence on density is maximum in rhyolites of the third cycle. The thermal conductivity is also influenced by the amount of glass. Rhyolitic obsidians show values lower than other rhyolites, although the latter rocks have a larger average porosity. The radioactive heat production determined on 36 specimens varies with the rock type, depending on the amount of U, Th and K. In basic lavas of the first cycle its value is 0.95°± 0.30 mW m-3, while in rhyolites of the fourth cycle it attains 6.68°±0.61 mW m-3. A comparison between results of g-ray spectrometry and X-ray fluorescence points out that the assumption of equilibrium in the decay series of the isotopic elements seems fulfilled. The information obtained is useful not only for the interpretation of geophysical surveys but also for the understanding of the geochemical characteristics of lavas.

  12. Permeability within basaltic oceanic crust

    Science.gov (United States)

    Fisher, Andrew T.

    1998-05-01

    Water-rock interactions within the seafloor are responsible for significant energy and solute fluxes between basaltic oceanic crust and the overlying ocean. Permeability is the primary hydrologic property controlling the form, intensity, and duration of seafloor fluid circulation, but after several decades of characterizing shallow oceanic basement, we are still learning how permeability is created and distributed and how it changes as the crust ages. Core-scale measurements of basaltic oceanic crust yield permeabilities that are quite low (generally 10-22 to 10-17 m²), while in situ measurements in boreholes suggest an overlapping range of values extending several orders of magnitude higher (10-18 to 10-13 m²). Additional indirect estimates include calculations made from borehole temperature and flow meter logs (10-16 to 10-11 m²), numerical models of coupled heat and fluid flow at the ridge crest and within ridge flanks (10-16 to 10-9 m²), and several other methods. Qualitative indications of permeability within the basaltic oceanic crust come from an improved understanding of crustal stratigraphy and patterns of alteration and tectonic modification seen in ophiolites, seafloor samples and boreholes. Difficulties in reconciling the wide range of estimated permeabilities arise from differences in experimental scale and critical assumptions regarding the nature and distribution of fluid flow. Many observations and experimental and modeling results are consistent with permeability varying with depth into basement and with primary basement lithology. Permeability also seems to be highly heterogeneous and anisotropic throughout much of the basaltic crust, as within crystalline rocks in general. A series of focused experiments is required to resolve permeability in shallow oceanic basement and to directly couple upper crustal hydrogeology to magmatic, tectonic, and geochemical crustal evolution.

  13. Isotopic and trace element constraints on the genesis of the Faeroe lava pile

    International Nuclear Information System (INIS)

    Basaltic lavas from the Faeroe Islands form three stratigraphic series which define two geochemical groups. Both the lower and middle series are LREE enriched ((La/Yb)sub(e.f.): 2-3) and are characterized by convex LREE profiles; in contrast, the upper series comprises both depleted ((La/Yb)sub(e.f.): 0.45-0.6) and enriched lavas. This twofold geochemical division is also evident from the incompatible trace elements such as Zr, Nb, Hf and Ta and the compatible trace elements Cr, Ni, Sr and Y. Nd-Sr-Pb isotopic measurements show that the basalts are contaminated by crustal materials, implying the presence of Precambrian sialic basement underneath the Faeroes block, a conclusion supported by geophysical data. The uncontaminated end-members, for the LREE-depleted basalts (87Sr/86Sr)0 approx.= 0.7026 and epsilonNd0 + 10 and for the LREE-enriched basalts (87Sr/86Sr)0 approx.= 0.7034 and epsilonNd0 + 9, require two different mantle source regions thus posing serious problems for petrogenetic models such as dynamic partial melting which have been proposed for the Faeroes. We interpret the LREE-depleted basalts as partial melts of the oceanic asthenosphere whilst the LREE-enriched basalts may result either from the partial melting of deep mantle blobs or of the subcontinental lithosphere during upwelling of the asthenosphere. (orig.)

  14. Complex Formation History of Highly Evolved Basaltic Shergottite, Zagami

    Science.gov (United States)

    Niihara, T.; Misawa, K.; Mikouchi, T.; Nyquist, L. E.; Park, J.; Hirata, D.

    2012-01-01

    Zagami, a basaltic shergottite, contains several kinds of lithologies such as Normal Zagami consisting of Fine-grained (FG) and Coarse-grained (CG), Dark Mottled lithology (DML), and Olivine-rich late-stage melt pocket (DN). Treiman and Sutton concluded that Zagami (Normal Zagami) is a fractional crystallization product from a single magma. It has been suggested that there were two igneous stages (deep magma chamber and shallow magma chamber or surface lava flow) on the basis of chemical zoning features of pyroxenes which have homogeneous Mg-rich cores and FeO, CaO zoning at the rims. Nyquist et al. reported that FG has a different initial Sr isotopic ratio than CG and DML, and suggested the possibility of magma mixing on Mars. Here we report new results of petrology and mineralogy for DML and the Olivine-rich lithology (we do not use DN here), the most evolved lithology in this rock, to understand the relationship among lithologies and reveal Zagami s formation history

  15. Reactive transport models for mineral CO2 storage in basaltic rocks

    Science.gov (United States)

    Aradottir, E. S.; Sonnenthal, E. L.; Bjornsson, G.; Jonsson, H.

    2010-12-01

    CO2 mineral storage in basalts may provide a long lasting, thermodynamically stable and environmentally benign solution to reduce anthropogenic CO2 in the atmosphere. We present here development of reactive transport models of this process with focus on the CarbFix experiment at Hellisheidi geothermal power plant in Iceland. There, up to 2.2 tons/year of purified CO2 of volcanic origin will be dissolved in water and injected at intermediate depths (400-800 m) into relatively fresh basaltic lava. Plans call for a full-scale injection if the experiment is successful. Reactive transport modeling is an important factor in the CarbFix project, providing tools to predict and optimize long-term management of the injection site as well as to quantify the amount of CO2 that has the potential of being mineralized. TOUGHREACT and iTOUGH2 are used to develop reactive fluid flow models that simulate hydrology and mineral alteration associated with injecting dissolved CO2 into basalts. The mineral reactions database in TOUGHREACT has been revised and extended, providing an internally consistent database suitable for mineral reactions of interest for this study. A multiple interacting continua (MINC) dissolution model was developed to simulate the long and short-term dissolution of basaltic glass taking into account dissolution kinetics, leached layer formation and diffusion-limited dissolution rates. Our main focus has been on developing a three dimensional field model of the injection site at Hellisheidi. Hydrological parameters of the model were calibrated using iTOUGH2 to simulate tracer tests that have been ongoing since 2007. Modeling results indicate groundwater velocity in the reservoir to be significantly lower than expected. The slow groundwater velocity may necessitate increasing groundwater flow by producing downstream wells at low rates after CO2 injection has started. The three dimensional numerical model has proven to be a valuable tool in simulating different

  16. Late Permian basalts in the northwestern margin of the Emeishan Large Igneous Province: Implications for the origin of the Songpan-Ganzi terrane

    Science.gov (United States)

    Li, Hongbo; Zhang, Zhaochong; Santosh, M.; LÜ, Linsu; Han, Liu; Liu, Wei; Cheng, Zhiguo

    2016-07-01

    SHRIMP zircon U-Pb ages, geochemical and Sr-Nd isotopic data are reported for two types of basalts (Type I and Type II) from a Permian volcanic-pyroclastic succession in the Tubagou section, Baoxing area along the southeastern margin of the Songpan-Ganzi terrane (SGT) in the Sichuan province of SW China. Zircons from the uppermost basaltic flows yield crystallization age of 257.3 ± 2.0 Ma, which may represent the time of culmination the basaltic eruption. Type I shows alkaline affinity with εNd(t) values of + 2.4 to + 2.9, and is characterized by oceanic island basalt (OIB)-type light rare earth element (LREE) and trace-element patterns. In contrast, Type II rocks are tholeiitic, and close to initial rift tholeiite (IRT)-like REE and trace element patterns, and are relatively depleted in highly incompatible elements with slightly negative Nb-Ta anomaly. The εNd(t) values of Type II are between + 1.8 to + 2.2. The geochemical characteristics suggest the Type I has not been significantly crustally contaminated, whereas Type II maybe have experienced minor crustal contamination. Clinopyroxene crystallization temperature is ~ 80-120°C higher than that of the normal asthenospheric mantle, implying anomalous thermal input from mantle source and a possible plume-head origin for the Tubagou lava. The geochemical and isotopic fes, reflecting progressive lithosphere thinning probably through plume-lithosphere interaction. The spatial and temporal coincidence between the Dashibao basalt eruptions, reflecting progressive lithosphere thinning probably through plume-lithosphere interaction. The spatial and temporal coincidence between the Dashibao basalt eruption and continental rifting suggest that continental break-up and the opening of an extensional basin was probably related to the Late Permian Emeishan plume, which triggered the breakup between the SGT and the Yangtze craton.

  17. New Petrologic and Geochemical Insights into Differentiation Processes Required to Produce the Lower Steens Basalt, Columbia River Basalt Province, SE Oregon

    Science.gov (United States)

    Moore, N. E.; Lytle, K.; Bohrson, W. A.; Grunder, A.

    2015-12-01

    The Steens Basalt (~16.7 Ma) of SE Oregon is the oldest member and contains the most mafic compositions of the Columbia River Flood Basalt (CRB) event. The lower Steens lavas are more mafic and incompatible element poor than upper Steens flows, which are less magnesian, mildly alkalic, richer in incompatible elements, and mainly basaltic andesites, much like the CRB proper. At Steens Mountain, the lower Steens are thickest and comprise 35-40 mainly compound flows with modest soil development between, suggesting a period of slower effusion rate transitioning to high effusion rates as represented by stratigraphically higher flows that make up the prominent cliffs of the range. Stronger soil development between the uppermost flows implies a waning effusion rate. Whole rock major element data define two distinct trends in the lower Steens; the first has increasing Al2O3 with decreasing MgO at relatively low FeO, whereas the second exhibits increasing Al2O3 with decreasing MgO until an inflection point (~8 wt.% MgO), at which both Al2O3 and MgO decrease. Plagioclase mode is not coupled with Al2O3. MELTS closed system fractionation models across a range of pressures cannot reproduce these trends, suggesting open-system processes were at work. Olivine is homogeneous in some flows (~Fo80-78), but heterogeneous in others (~Fo84-62). Fo range does not correlate with whole rock MgO; two different flows with >10 wt.% MgO have Fo85-70 and Fo84-82. Plagioclase composition is restricted within and between flows (~An75-60). All these data suggest lower Steens magmas underwent large amounts of crystal fractionation and recharge with modest assimilation. Some assimilation requires an aluminous contaminant other than simple plagioclase accumulation. During other periods, magma mixing must have been efficient. Magma Chamber Simulator modeling will provide quantitative estimates for the roles of fractionation, recharge and assimilation in the lower Steens magma system.

  18. Eruptive Process, Geochemical Variation, and Weathering Controls on the Hyperspectral Reflectance Properties of the Blue Dragon Lava Flow, Craters of the Moon National Monument

    Science.gov (United States)

    Poplawski, J.; Chadwick, D. J.

    2010-12-01

    About 60 eruptive events have occurred at the Craters of the Moon volcanic field (Idaho, US), ranging in age from 15 to 2 ka. The Blue Dragon flow is one of the youngest, a large (280 sq. km) hawaiite flow which erupted from a dike-fed central rift zone, the Great Rift. Airborne Visible Infrared Imaging Spectrometer (AVIRIS) hyperspectral imagery (224-bands, 0.4 to 2.5 micron spectral range, and 15.3 m spatial resolution) shows at least five distinct regions within the Blue Dragon flow that exhibit different spectral reflectance properties. Field observations show these regions to be associated with different eruptive phases of the flow, and in some cases, different flow morphologies (e.g. aa, and ropey, sheet, and hummocky pahoehoe). Airborne Synthetic Aperture Radar (AIRSAR) imagery of the study area also shows average roughness variability among the different spectral regions. We performed petrographic and laboratory spectral analyses on samples from each spectral region to investigate variation in primary surface properties and the effects of weathering and lichen growth on surface reflectance. We also analyzed bulk major elements for several samples from each spectral region to investigate a possible connection between the observed spectral variability and chemical variability in the Blue Dragon eruption over time. Analyses using hydrologic flow accumulation and solar irradiance models provide further information about the effects of post-eruptive processes on spectral reflectance of the flow.

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

    Energy Technology Data Exchange (ETDEWEB)

    ,

    1976-11-01

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

  20. Long term low latitude and high elevation cosmogenic 3He production rate inferred from a 107 ka-old lava flow in northern Chile; 22°S-3400 m a.s.l.

    Science.gov (United States)

    Delunel, Romain; Blard, Pierre-Henri; Martin, Léo C. P.; Nomade, Sébastien; Schlunegger, Fritz

    2016-07-01

    Available geological calibration sites used to estimate the rate at which cosmogenic 3He is produced at the Earth's surface are mostly clustered in medium to high latitudes. Moreover, most of them have exposure histories shorter than tens of thousands of years. This lack of sites prevents a qualitative assessment of available production models used to convert cosmogenic 3He concentrations into exposure ages and/or denudation rates. It thus limits our ability to take into account the atmospheric, geomagnetic and solar modulation conditions that might have affected the production of cosmogenic nuclides in the past for longer exposure histories and in low latitude regions. We present the cosmogenic 3He production rate inferred from a new geological calibration site located in northern Chile. Five samples were collected on the surface of the largest and best-preserved lava flow of the San Pedro volcano (21.934°S-68.510°W-3390 m a.s.l.), which displays pristine crease-structure features. 40Ar/39Ar dating yields a reliable plateau age of 107 ± 12 ka for the eruption of this lava flow. Eight pyroxene aliquots separated from the surface samples yield a weighted average cosmogenic 3He concentration of 99.3 ± 1.2 Mat g-1 from which a local cosmogenic 3He production rate of 928 ± 101 at g-1 yr-1 is calculated. The local production rate is then scaled to a sea level high latitude (SLHL) reference position using different combinations of geographic spatialization schemes, atmosphere models and geomagnetic field reconstructions, yielding SLHL production rates between 103 ± 11 and 130 ± 14 at g-1 yr-1 consistent with the most recent estimates available from the literature. Finally, we use the same scaling frameworks to re-evaluate the mean global-scale cosmogenic 3He production rate in olivine and pyroxene minerals at 120 ± 16 at g-1 yr-1 from the compilation of previously published calibration datasets.

  1. Radionuclide reactions with groundwater and basalts from Columbia River basalt formations

    International Nuclear Information System (INIS)

    Chemical reactions of radionuclides with geologic materials found in Columbia River basalt formations were studied. The objective was to determine the ability of these formations to retard radionuclide migration from a radioactive waste repository located in deep basalt. Reactions that can influence migration are precipitation, ion-exchange, complexation, and oxidation-reduction. These reactions were studied by measuring the effects of groundwater composition and redox potential (Eh) on radionuclide sorption on fresh basalt surfaces, a naturally altered basalt, and a sample of secondary minerals associated with a Columbia River basalt flow. In addition, radionuclide sorption isotherms were measured for these materials and reaction kinetics were determined. The radionuclides studied were 137Cs, 85Sr, 75Se, /sup 95m/Tc, 237Np, 241Am, 226Ra and 237Pu. The Freundlich equation accurately describes the isotherms when precipitation of radionuclides does not occur. In general, sorption increased in the order: basalt < altered basalt < secondary minerals. This increase in sorption corresponds to increasing surface area and cation exchange capacity. The Eh of the system had a large effect on technetium, plutonium, and neptunium sorption. Technetium(VII), Pu(VI), and Np(V) are reduced to Tc(IV), Pu(IV), and Np(IV), respectively, under Eh conditions expected in deep basalt formations. The kinetics of radionuclide sorption and basalt-groundwater reactions were observed over a period of 18 weeks. Most sorption reactions stabilized after about four weeks. Groundwater composition changed the least in contact with altered basalt. Contact with secondary minerals greatly increased Ca, K, and Mg concentrations in the groundwater

  2. Lava and Life: New investigations into the Carson Volcanics, lower Kimberley Basin, north Western Australia

    Science.gov (United States)

    Orth, Karin; Phillips, Chris; Hollis, Julie

    2014-05-01

    The Carson Volcanics are the only volcanic unit in the Paleoproterozoic Kimberley Basin and are part of a poorly studied Large Igneous Province (LIP) that was active at 1790 Ma. New work focussing on this LIP in 2012 and 2013 involved helicopter-supported traverses and sampling of the Carson Volcanics in remote areas near Kalumburu in far north Western Australia's Kimberley region. The succession is widespread and flat lying to gently dipping. It consists of three to six basalt units with intercalated sandstone and siltstone. The basalts are 20-40 m thick, but can be traced up to 60 km along strike. The basalt can be massive or amygdaloidal and commonly display polygonal to subhorizontal and rare vertical columnar jointing. Features of the basalt include ropy lava tops and basal pipe vesicles consistent with pahoehoe lavas. The intercalated cross-bedded quartzofeldspathic sandstone and siltstone vary in thickness up to 40 m and can be traced up to 40 km along strike. Peperite is common and indicates interaction between wet, unconsolidated sediment and hot lava. Stromatolitic chert at the top of the formation represents the oldest life found within the Kimberley region. Mud cracks evident in the sedimentary rocks, and stromatolites suggest an emergent broad tidal flat environment. The volcanics were extruded onto a wide marginal margin setting subject to frequent flooding events. Thickening of the volcanic succession south and the palaeocurrents in the underlying King Leopold Sandstone and the overlying Warton Sandstone suggest that this shelf sloped to the south. The type of basalt and the basalt morphology indicate a low slope gradient of about 1°.

  3. Glass and mineral chemistry of northern central Indian ridge basalts: Compositional diversity and petrogenetic significance

    Digital Repository Service at National Institute of Oceanography (India)

    Ray; Banerjee, R.; Iyer, S.D.; Basavalingu, B.; Mukhopadhyay, S.

    seamount shows more fractionated characters (Mg: 0.56-0.57) compared to the outer ridge flank lava of the VT area (Mg: 0.63-0.65). This study concludes that present basalts experienced low-pressure crystallization at a relatively shallow depth...

  4. Paleointensity and Rock Magnetic Study of Lavas From the Galapagos Islands: Preliminary Results

    Science.gov (United States)

    Fucugauchi, J. U.; Perez-Cruz, L.

    2009-05-01

    Initial results of paleomagnetic studies of basaltic lava flows from three islands, Isabela, Santa Cruz and Bartra, Galapagos archipielago, focusing on the rock magnetic analyses and preliminary paleointensity determinations, are presented. Remanent magnetizations are well defined and stable to thermal and AF demagnetization. Magnetic susceptibility, remanent magnetization, thermomagnetic curves and coercivity and unblocking temperature spectra are used to analyze magnetic mineralogy and sample selection for paleointensities. Relatively complex mineralogy shown in k-T curves appear correlated to quality in the Thellier- Thellier experiments. Galapagos Islands have formed from intense volcanic activity in the past few million years above the Galapagos hot spot in the Nazca plate, south of Galapagos spreading center. The archipielago consists of 15 islands and numerous islets and seamounts built on a large platform. Active volcanism occurs towards the west and islands get older to the east due to east-southeast Nazca plate motion. Sampling in Isabela concentrated in east and south flanks of Sierra Negra volcano, a structurally complex large caldera that represents the largest Galapagos volcano. Sampling sites are distributed along the shore west of Port Villamil and the east caldera flank with historic activity. Records show eleven eruptions from 1813 to 2005, which translates into intervals roughly from 4-37 yr with eruptions in 1963, 1979, and 2005. Lavas reaching Isabela coast are Late Pleistocene-Holocene. Sampling in Santa Cruz was done along NS transect from Las Bachas beach to Darwin Station and Punta Raton, including the Gemelos craters. Sampling in Bartra is in the southwest part of Salinas beach.

  5. Enriched component of the proto-Icelandic mantle plume revealed in alkaline Tertiary lavas from East Greenland

    DEFF Research Database (Denmark)

    Bernstein, Stefan; Brooks, Charles Kent; Stecher, Ole

    2001-01-01

    similar to those of the alkaline lavas. These features are not caused by fractional crystallization or crustal contamination and are thus regarded as inherited from the mantle source. The trace element profiles and Sr and Nd isotopic compositions of the flood basalts are shown to be consistent with a...

  6. A preliminary analysis of lunar extra-mare basalts - Distribution, compositions, ages, volumes, and eruption styles

    Science.gov (United States)

    Whitford-Stark, J. L.

    1982-01-01

    Extra-mare basalts occupy 8.5% of the lunar basalt area and comprise 1% of the total mare basalt volume. They are preferentially located where the crust is thin and topographically low. In terms of age, eruption style, and composition they are as variable as the mare basalts. In some instances extrusion in extra-mare craters was preceded by floor-fracturing whereas in other cases it apparently was not. The volume of lava erupted may have been controlled more by the volume of magma produced than by hydrostatic effects. A minimum of nearly 1300 separate basalt eruptions is indicated; the true value could be nearer 30,000 separate eruptions.

  7. Recent flood lavas in the Elysium region of Mars

    International Nuclear Information System (INIS)

    A volcanic origin is presently suggested for the Cerberus Formation region of smooth plains in the southeastern Elysium region of Mars, on the basis of its surface morphology, lobate edges, vents, and an embayment relation of the unit with adjacent, older units. The low viscosity lavas that filled a topographic depression in southeastern Elysium subsequently flowed into western Amazonic Planitia via channels formed by an earlier fluvial episode. A young, upper Amazonian dating is indicated by crater frequencies and stratigraphic relations, implying that large-scale eruptions of low-viscosity lava were still possible late in Martian history. 34 refs

  8. Magma crystallization and viscosity : a study of molten basalts from the Piton de la Fournaise volcano (La Reunion island)

    OpenAIRE

    Villeneuve, Nicolas; D. R. Neuville; Boivin, P.; Bacheery, P.; Richet, P.

    2008-01-01

    The viscosity of three molten basalts produced by fusion of lavas issued from different eruptions of the Piton de la Fournaise (La Reunion island) has been investigated above the liquidus and at high degrees of supercooling. For all basalts. crystallization took place rapidly above the glass transition range, which made static measurements problematic because of time-dependent, non-Newtonian rheology. By contrast, reproducible results were obtained in dynamic measurements made at a constant h...

  9. 塔里木溢流玄武岩的喷发特征%The eruption characteristics of the Tarim flood basalt

    Institute of Scientific and Technical Information of China (English)

    上官时迈; 田伟; 徐义刚; 关平; 潘路

    2012-01-01

    通过对柯坪地区二叠系野外火山岩露头剖面和英买力、哈拉哈塘井区二叠系火山岩钻井剖面的对比,将塔里木早二叠世溢流玄武岩划分为三个旋回,从老到新依次是:库普库兹满溢流玄武岩旋回(KP),长英质火山碎屑岩旋回(FP)和开派兹雷克溢流玄武岩旋回(KZ).KP旋回以巨厚溢流玄武岩夹凝灰岩为特征,在柯坪露头区和英买力井区均可划分出三层巨厚玄武质熔岩流,至哈拉哈塘井区减少为一层玄武岩流,但长英质火山碎屑岩和熔岩厚度增加.FP旋回在柯坪露头区自下而上包括空落相凝灰岩,熔结凝灰岩,再沉积火山碎屑岩和正常碎屑岩夹火山灰层,该层可与英买力及哈拉哈塘井区的凝灰岩层对比,表明在塔北存在一期面积广泛的长英质火山喷发.KZ旋回以溢流玄武岩为主,在开派兹雷克剖面识别出四期喷发共8层溢流玄武岩和一期安山质玄武岩,每期喷发之间夹少量碎屑岩,但未见长英质火山碎屑岩夹层,该特征与英买力和哈拉哈塘井区的火山层序组合不同,而与塔中溢流玄武岩类似.三个火山旋回的划分表明塔里木大火成岩省经历了“基性溢流玄武岩-酸性火山碎屑岩-基性溢流玄武岩”的演变过程,与Afro-Arabian溢流玄武岩省相似,可进行对比研究.%Integration of field investigation, regional stran'graphic comparison, remote sensing and image interpretation allow us to divide the Tarim Permian flood basalt province into three eruptive cycles listed by decreasing age: Kupukuziman flood basalt ( KP), Felsic pyroclastic rocks (FP), Kaipaizileike flood basalt ( KZ). KP features flood basalt and tuff; in the outcrop in Keping and Yingmaili areas, it can be differentiated into two units containing three thick layers of basaltic lava flows. These three layers decrease to one layer of basaltic lava flow in the Halahatang area; however, felsic pyroclastic rocks and lava layer thicknesses

  10. Geochemistry of basalts from the Dumisseau formation, southern Haiti: Implications for the origin of the Caribbean Sea crust

    International Nuclear Information System (INIS)

    Basalt and diabase from the Cretaceous Dumisseau Formation, southern Haiti have Mg-numbers of 43-63, TiO2 contents of 1.6-3.9% and La abundances of 3.6-15.3 ppm. La/Ta ratios average 10, and indicate that the basalts are oceanic in character, distinct from the arc associations forming the northern part of Haiti. Oldest lavas have low TiO2, (1.6%) and are LREE-depleted, similar to N-MORBs, whereas overlying lavas have higher TiO2 (2-3.9%) and are LREE-enriched, similar to E-MORBs or hotspot basalts. 87Sr/86Sr ratios vary from 0.70280 to 0.70316, 143Nd/144Nd from 0.512929 to 0.513121, and 206Pb/204Pb from 19.00 to 19.27 LREE-depleted lavas have high 143Nd/144Nd (0.51309-0.51310) typical of MORBs, whereas 143Nd/144Nd in the LREE-enriched lavas varies widely (0.512929-0.513121). Chemical features of the Dumisseau basalts are equivalent to those of Caribbean seafloor basalts recovered on DSDP Leg 15, and support the contention that the Dumisseau is an uplifted section of Caribbean Sea crust. Oldest lavas are analogous to MORB-like basalts cored at Leg 15 Sites 146, 150, 152 and 153, and the overlying lavas are analogous to incompatible-element-enriched basalts cored at Site 151 on the Beata Ridge. Isotopic compositions of the Dumisseau basalts overlap with those of the eastern Pacific Galapagos and Easter Island hotspots. However, the presence of N-MORB basalts in the lower part of the Dumisseau and at the majority of Leg 15 Sites indicates that the anomalously thick Caribbean crust probably did not originate as a hotspot-related basaltic-plateau, but may have been generated by on-ridge or near-ridge hotspot magmatism. (orig.)

  11. The origin of tubular lava stalactites and other related forms

    OpenAIRE

    Kevin Allred; Carlene Allred

    1998-01-01

    Tubular lava stalactites are often found in lava tubes. Field observations, sample analysis, and comparative studies indicate that these are segregations extruded during cooling from partially crystallized lava al about 1,070 - 1,000 °C. Retrograde boiling (gas pressure) within the lava provides a mechanism to expel the interstitial liquid. In addition to tubular lava stalactites, a variety of other lava features can also result, such as lava helictites, lava coralloids, barnacle-like stretch...

  12. A network of lava tubes as the origin of Labyrinthus Noctis and Valles Marineris on Mars

    Science.gov (United States)

    Leone, Giovanni

    2014-05-01

    The role of lava tube networks and lava channels is reassessed as the primordial stage of the volcano-erosional processes that formed the Labyrinthus Noctis-Valles Marineris system instead of a tectonic origin. The combined use of CTX, CRISM, HiRISE imagery, and MOLA profiles has provided valuable insight in the evolution of pit chains into fossae first and then chasmata later due to mass wasting processes caused by the erosional effect of the lava flows that draped Valles Marineris and other outflow channels. Although a quantitative evaluation of eruption rates is difficult even with digital terrain models (DTMs) because of the mixing between new flows and paleoflows, a comparison with Elysium and other Tharsis outflow channels suggests that the availability of lava supply is correlated to their widths. The images of ubiquitous lava flows rather than sporadic light-toned deposits strengthen the role of lava over that of water in the erosional processes that formed Labyrinthus Noctis and carved Valles Marineris like many other outflow channel on Mars. The erosional evolution of the outflow channels shows an increasing trend of age and a decreasing trend of depth from the sources on Tharsis to the mouths at Chryse Planitia. This finding, coupled with the observation of lava flows mantling Chryse Planitia, may have profound implications for the water inventories thought to have filled the lowlands with an ocean.

  13. Petrogenesis of intraplate lavas from isolated volcanoes in the Pacific : implications for the origin of the enriched mantle source of OIB

    OpenAIRE

    Tian, Liyan

    2011-01-01

    Years of studies show that most of the ocean island basalts (OIB) that comprise the bulk of prominent linear volcanic chains are geochemically different from mid-ocean ridge basalts (MORB). However, the cause of the geochemical differences between OIB and MORB as well as the origin of geochemical enrichment and heterogeneity in OIB are highly controversial. Volcanic glasses and lavas with OIB-like composition from isolated intraplate volcanoes in the northern Lau Basin in the southwestern Pac...

  14. Helium isotope characteristics of Andean geothermal fluids and lavas

    Science.gov (United States)

    Hilton, D. R.; Hammerschmidt, K.; Teufel, S.; Friedrichsen, H.

    1993-12-01

    The first comprehensive helium isotope survey of the Andes is reported here. We have sampled geothermal fluids and phyric lava flows from the Southern (svz) and Central (cvz) Volcanic Zones, the volcanically active Puna region and the Precordillera, Salta Basin, Longitudinal Valley and the aseismic region between the two volcanic zones. Although the active areas are characterized by significant differences in crustal age and thickness, the svz, cvz and Puna are characterized by a wide and overlapping range in He-3/He-4 ratios (for fluids and phenocrysts) from predominantly radiogenic values to close to the Mid-Ocean Ridge Basalt (MORB) ratio. The measured ranges in He-3/He-4 ratios (R) (reported normalised to the air He-3/He-4 -- R(sub A)) are: svz (0.18 less than R/R(sub A) less than 6.9); cvz (0.82 less than R/R(sub A) less than 6.0); and Puna (1.8 less than R/R(sub A) less than 5.4). Modification of magmatic He-3/He-4 ratios by water/rock interactions (fluids) or post-eruptive grow-in of radiogenic He-4 or preferential diffusive loss of He-3 (phenocrysts) is considered unlikely; this means that the wide range reflects the helium isotope characteristics of magma bodies in the Andean crust. The mechanism controlling the He-3/He-4 ratios appears to be a mixing between mantle (MORB-like) helium and a radiogenic helium component derived from radioactive decay within the magma (magma aging) and/or interaction with He-4-rich country rock: a process expected to be influenced by pre-eruptive degassing of the mantle component. Assimilation of lower crust is also capable of modifying He-3/He-4 ratios, albeit to a much lesser extent. However, it is possible that the highest measured values in each zone were established by the addition of lower crustal radiogenic helium to MORB helium. In this case, the higher 'base level' ratios of the svz would reflect the younger crustal structure of this region. In contrast to helium, there is no overlap in the Sr or Pb isotope

  15. Primitive off-rift basalts from Iceland and Jan Mayen

    DEFF Research Database (Denmark)

    Debaille, Vinciane; Trønnes, Reidar G.; Brandon, Alan D.;

    2009-01-01

    appear to be contaminated at a shallow level. The 187Os/188Os ratios in the remaining lavas with >30 ppt Os (n = 17) range between 0.12117 and 0.13324. These values are surprisingly low for oceanic island basalts and include some samples that are less than putative present-day primitive upper mantle (PUM...... with 187Os/188Os of 0.1296). These low 187Os/188Os preclude significant shallow-level contamination from oceanic crust. The 187Os/188Os ratios for Jan Mayen lavas are less than PUM, severely limiting the presence of any continental crust in their mantle source. A positive correlation between 143Nd/144...

  16. Palaeointensities from Pliocene lava sequences in Iceland: emphasis on the problem of Arai plot with two linear segments

    Science.gov (United States)

    Tanaka, Hidefumi; Yamamoto, Yuhji

    2016-05-01

    Palaeointensity experiments were carried out to a sample collection from two sections of basalt lava flow sequences of Pliocene age in north central Iceland (Chron C2An) to further refine the knowledge of the behaviour of the palaeomagnetic field. Selection of samples was mainly based on their stability of remanence to thermal demagnetization as well as good reversibility in variations of magnetic susceptibility and saturation magnetization with temperature, which would indicate the presence of magnetite as a product of deuteric oxidation of titanomagnetite. Among 167 lava flows from two sections, 44 flows were selected for the Königsberger-Thellier-Thellier experiment in vacuum. In spite of careful pre-selection of samples, an Arai plot with two linear segments, or a concave-up appearance, was often encountered during the experiments. This non-ideal behaviour was probably caused by an irreversible change in the domain state of the magnetic grains of the pseudo-single-domain (PSD) range. This is assumed because an ideal linear plot was obtained in the second run of the palaeointensity experiment in which a laboratory thermoremanence acquired after the final step of the first run was used as a natural remanence. This experiment was conducted on six selected samples, and no clear difference between the magnetic grains of the experimented and pristine sister samples was found by scanning electron microscope and hysteresis measurements, that is, no occurrence of notable chemical/mineralogical alteration, suggesting that no change in the grain size distribution had occurred. Hence, the two-segment Arai plot was not caused by the reversible multidomain/PSD effect in which the curvature of the Arai plot is dependent on the grain size. Considering that the irreversible change in domain state must have affected data points at not only high temperatures but also low temperatures, fv ≥ 0.5 was adopted as one of the acceptance criteria where fv is a vectorially defined

  17. Stability of Basalt plus Anhydrite plus Calcite at HP-HT: Implications for Venus, the Earth and Mars

    Science.gov (United States)

    Martin, A. M.; Righter, K.; Treiman, A. H.

    2010-01-01

    "Canali" observed at Venus surface by Magellan are evidence for very long melt flows, but their composition and origin remain uncertain. The hypothesis of water-rich flow is not reasonable regarding the temperature at Venus surface. The length of these channels could not be explained by a silicate melt composition but more likely, by a carbonate-sulfate melt which has a much lower viscosity (Kargel et al 1994). One hypothesis is that calcite CaCO3 and anhydrite CaSO4 which are alteration products of basalts melted during meteorite impacts. A famous example recorded on the Earth (Chicxulub) produced melt and gas rich in carbon and sulfur. Calcite and sulfate evaporites are also present on Mars surface, associated with basalts. An impact on these materials might release C- and S-rich melt or fluid. Another type of planetary phenomenon (affecting only the Earth) might provoke a high pressure destabilization of basalt+anhydrite+calcite. Very high contents of C and S are measured in some Earth s magmas, either dissolved or in the form of crystals (Luhr 2008). As shown by the high H content and high fO2 of primary igneous anhydrite-bearing lavas, the high S content in their source may be explained by subduction of an anhydrite-bearing oceanic crust, either directly (by melting followed by eruption) or indirectly (by release of S-rich melt or fluid that metasomatize the mantle) . Calcite is a major product of oceanic sedimentation and alteration of the crust. Therefore, sulfate- and calcite-rich material may be subducted to high pressures and high temperatures (HP-HT) and release S- and C-rich melts or fluids which could influence the composition of subduction zone lavas or gases. Both phenomena - meteorite impact and subduction - imply HP-HT conditions - although the P-T-time paths are different. Some HP experimental/theoretical studies have been performed on basalt/eclogite, calcite and anhydrite separately or on a combination of two. In this study we performed piston

  18. Topographic and Stochastic Influences on Pahoehoe Lava Lobe Emplacement

    Science.gov (United States)

    Hamilton, Christopher W.; Glaze, Lori S.; James, Mike R.; Baloga, Stephen M.

    2013-01-01

    A detailed understanding of pahoehoe emplacement is necessary for developing accurate models of flow field development, assessing hazards, and interpreting the significance of lava morphology on Earth and other planetary surfaces. Active pahoehoe lobes on Kilauea Volcano, Hawaii, were examined on 21-26 February 2006 using oblique time-series stereo-photogrammetry and differential global positioning system (DGPS) measurements. During this time, the local discharge rate for peripheral lava lobes was generally constant at 0.0061 +/- 0.0019 m3/s, but the areal coverage rate of the lobes exhibited a periodic increase every 4.13 +/- 0.64 minutes. This periodicity is attributed to the time required for the pressure within the liquid lava core to exceed the cooling induced strength of its margins. The pahoehoe flow advanced through a series of down slope and cross-slope breakouts, which began as approximately 0.2 m-thick units (i.e., toes) that coalesced and inflated to become approximately meter-thick lobes. The lobes were thickest above the lowest points of the initial topography and above shallow to reverse facing slopes, defined relative to the local flow direction. The flow path was typically controlled by high-standing topography, with the zone directly adjacent to the final lobe margin having an average relief that was a few centimeters higher than the lava inundated region. This suggests that toe-scale topography can, at least temporarily, exert strong controls on pahoehoe flow paths by impeding the lateral spreading of the lobe. Observed cycles of enhanced areal spreading and inflated lobe morphology are also explored using a model that considers the statistical likelihood of sequential breakouts from active flow margins and the effects of topographic barriers.

  19. Comparison of Inflation Processes at the 1859 Mauna Loa Flow, HI, and the McCartys Flow Field, NM

    Science.gov (United States)

    Bleacher, Jacob E.; Garry, W. Brent; Zimbelman, James R.; Crumpler, Larry S.

    2012-01-01

    Basaltic lavas typically form channels or tubes during flow emplacement. However, the importance of sheet flow in the development of basalt ic terrains received recognition over the last 15 years. George Walke r?s research on the 1859 Mauna Loa Flow was published posthumously in 2009. In this paper he discusses the concept of endogenous growth, or inflation, for the distal portion of this otherwise channeldominated lava flow. We used this work as a guide when visiting the 1859 flow to help us better interpret the inflation history of the McCartys flow field in NM. Both well preserved flows display similar clues about the process of inflation. The McCartys lava flow field is among the you ngest (approx.3000 yrs) basaltic lava flows in the continental United States. It was emplaced over slopes of <1 degree, which is similar to the location within the 1859 flow where inflation occurred. Although older than the 1859 flow, the McCartys is located in an arid environ ment and is among the most pristine examples of sheet flow morphologies. At the meter scale the flow surface typically forms smooth, undula ting swales that create a polygonal terrain. The literature for simil ar features includes multiple explanatory hypotheses, original breakouts from adjacent lobes, or inflation related upwarping of crust or sa gging along fractures that enable gas release. It is not clear which of these processes is responsible for polygonal terrains, and it is po ssible that one explanation is not the sole cause of this morphology between all inflated flows. Often, these smooth surfaces within an inflated sheet display lineated surfaces and occasional squeeze-ups alon g swale contacts. We interpret the lineations to preserve original fl ow direction and have begun mapping these orientations to better interpret the emplacement history. At the scale of 10s to 100s of meters t he flow comprises multiple topographic plateaus and depressions. Some depressions display level floors with

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

    Science.gov (United States)

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

    2015-12-01

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

  1. Insights into the dynamics of the Nyiragongo lava lake level

    Science.gov (United States)

    Smets, Benoît; d'Oreye, Nicolas; Geirsson, Halldor; Kervyn, Matthieu; Kervyn, François

    2016-04-01

    Nyiragongo volcano, in North Kivu, Democratic Republic of Congo, is among the most active volcanoes in Africa and on Earth. Since the first European observations in the late 19th Century, its eruptive activity mostly concentrated into its main crater, with the presence of a persistent lava lake from at least 1928 to 1977 and since 2002. The size, shape and elevation of this lava lake have evolved through time, modifying the topography of the main crater. In January 1977 and 2002, the uppermost magmatic system of Nyiragongo, including the lava lake, was drained during flank eruptions. These flank events caused major disasters, mostly due to the exceptionally fast-moving lava flows and the presence of a dense population living at foot of this volcano. Despite a large scientific interest and societal concern, the study of the eruptive activity of Nyiragongo remains limited by climate and vegetation conditions that, most of the time, limit use of satellite remote sensing techniques, and recurrent armed conflicts in the Kivu region, which sometimes prevent field access to the main crater. Here we focus on the dynamics of the Nyiragongo lava lake level and its relationship with the volcanic plumbing system by describing the historical and recent lava lake activity and presenting new quantitative observations using close-range photogrammetry, a Stereographic Time-Lapse Camera (STLC) system and high-resolution satellite SAR and InSAR remote sensing. Results highlight that, contrary to the interpretation found in some recent publications, the lava lake drainages appear to be the consequence and not the cause of the 1977 and 2002 flank eruptions. Two types of short-term lava lake level variations are observed. The first one corresponds to cyclic metre-scale variations attributed to gas piston activity. The STLC data recorded in September 2011 show hour-scale gas piston cycles reaching up to 3.8 m, which are interpreted to be related to gas accumulation and release in the

  2. Dating transitionally magnetized lavas of the late Matuyama Chron: Toward a new 40Ar/39Ar timescale of reversals and events

    Science.gov (United States)

    Singer, Bradley S.; Hoffman, Kenneth A.; Chauvin, Annick; Coe, Robert S.; Pringle, Malcolm S.

    1999-01-01

    The K-Ar based geomagnetic polarity timescale was constructed using data from lavas and tuffs that bracketed, but rarely dated, the transitions between polarity intervals. Subsequent 40Ar/39Ar dating indicated that the ages of some polarity transitions had been underestimated by about 6%. Although the accepted ages of the polarity chron boundaries have increased, their precise temporal definition remained uncertain. We have taken a different approach and used incremental-heating techniques to obtain 18 new 40Ar/39Ar ages from basaltic lavas within flow sequences at Punaruu Valley, Tahiti, and Haleakala volcano, Hawaii. These lavas record transitional paleomagnetic directions corresponding to four mid-Pleistocene polarity reversals or events. Three lavas from Punaruu Valley previously thought to record the Cobb Mountain Normal Polarity Subchron (CMNS) gave a mean age of 1.105+/-0.005Ma, indicating that they were erupted about 76 kyr after the CMNS; this period of transitional field behavior is designated the Punaruu event. In addition, seven new 40Ar/39Ar ages from the Punaruu Valley indicate that the Jaramillo Normal Polarity Subchron (JNS) lasted about 67 kyr, starting at 1.053+/-0.006Ma and ending 0.986+/-0.005Ma. This agrees with astronomical estimates but conflicts with JNS ages proposed by Spell and McDougall [1992] and Izett and Obradovich [1994] on the basis of 40Ar/39Ar dating of rhyolite domes in the Valles Caldera. Indistinguishable 40Ar/39Ar ages of seven lavas, including one from Punaruu Valley and six from Haleakala that record broadly similar intermediate paleodirections, suggest that the Kamikatsura event occurred at 0.886+/-0.003Ma. Moreover, these data indicate that the Kamikatsura event occurred 20-40 kyr after another geomagnetic event, most probably taking place at 0.92 Ma. We designate this earlier field behavior the Santa Rosa event, adopting its name from that of a transitionally magnetized rhyolite dome which happened to figure prominently

  3. The microwave palaeointensity technique and its application to lava

    Energy Technology Data Exchange (ETDEWEB)

    Hill, M.J

    2000-05-01

    the flow study of the 1960 Kilauea lava flow, Hawaii and a study of Tertiary Australian lava. Palaeointensity results are compared to observatory records and / or results of previous studies using conventional techniques. The research undertaken, described in this thesis, demonstrates that the microwave palaeointensity technique is a viable technique for use with lava. This enables greater confidence that any palaeointensity results obtained are not affected by sample alteration during experimentation. The suitability and reliability of lava as a recorder of magnetic field intensity can therefore be investigated more readily with the ultimate aim of producing a record of the intensity of the Earth's magnetic field through time. (author)

  4. The microwave palaeointensity technique and its application to lava

    International Nuclear Information System (INIS)

    flow study of the 1960 Kilauea lava flow, Hawaii and a study of Tertiary Australian lava. Palaeointensity results are compared to observatory records and / or results of previous studies using conventional techniques. The research undertaken, described in this thesis, demonstrates that the microwave palaeointensity technique is a viable technique for use with lava. This enables greater confidence that any palaeointensity results obtained are not affected by sample alteration during experimentation. The suitability and reliability of lava as a recorder of magnetic field intensity can therefore be investigated more readily with the ultimate aim of producing a record of the intensity of the Earth's magnetic field through time. (author)

  5. Lavas Las Pataguas: volcanismo alcalino en el antearco andino del Mioceno Inferior, Chile central Lavas Las Pataguas: alkaline volcanism in the Early Miocene Andean forearc of central Chile

    Directory of Open Access Journals (Sweden)

    Renate M Wall

    2001-12-01

    alcalinas de Las Pataguas representan un episodio volcánico singular, intermedio entre dos regímenes tectonomagmáticos característicosThe presence of Lower Miocene volcanic rocks in the Coastal Range of central Chile is unique in that the westernmost outcrops of the Oligocene-Miocene volcanic arc occur 80 km to the east. The Las Pataguas Lavas (LLP; 33,8°S consists of a total exposed area of 1.15 km² without evidence of feeder conduits nor the construction of a volcanic edifice. The presence of east-west aligned and elongated flow-lobe tumuli suggests a flow from the west, over a gently sloping surface. This suggests a fissure-type eruptive system. The proposed age of the LLP, of ca. 18 Ma is intermediate between Abanico Formation (34-20 Ma and Farellones Formation (20-10 Ma, and is coeval with littoral facies of the Navidad Formation, exposed 20 km to the west. LLP consists of basaltic trachiandesites with 52.8-54.5 weight % silica, however their high total alkali contents (6.21-6.26 weight % K2O + Na2O place these rocks in the alkaline series of differentiation. This is a clear difference with the tholeiitic products of the Abanico Formation, and those typical calc-alkaline of the Farellones Formation. The rare earth element patterns are significantly enriched in light rare earth elements, with a La/Sm ratio of 3.4 and the heavy rare earth elements, present a flat pattern. The silica and MgO contents indicate an advanced differentiation state dominated by fractional crystallization of olivine, clinopiroxene and magnetite. The content of Ba and Nb indicate a significant contribution from the lithospheric mantle. Th and the Ta-Nb trough show a crustal signal as well. The particular petrogenesis and isolated westward forearc setting of the LLP can be explained as a response to the slowing of convergence acceleration at the end of the extensional regime in place until the late Early Miocene, related to the Abanico Formation volcanism. Therefore, the alkaline basaltic

  6. The diversity and abundance of bacteria inhabiting seafloor lavas positively correlate with rock alteration.

    Science.gov (United States)

    Santelli, Cara M; Edgcomb, Virginia P; Bach, Wolfgang; Edwards, Katrina J

    2009-01-01

    Young, basaltic ocean crust exposed near mid-ocean ridge spreading centers present a spatially extensive environment that may be exploited by epi- and endolithic microbes in the deep sea. Geochemical energy released during basalt alteration reactions can theoretically support chemosynthesis, contributing to a trophic base for the ocean crust biome. To examine associations between endolithic microorganisms and basalt alteration processes, we compare the phylogenetic diversity, abundance and community structure of bacteria existing in several young, seafloor lavas from the East Pacific Rise at approximately 9 degrees N that are variably affected by oxidative seawater alteration. The results of 16S rRNA gene analyses and real-time, quantitative polymerase chain reaction measurements show that the abundance of prokaryotic communities, dominated by the bacterial domain, positively correlates with the extent of rock alteration--the oldest, most altered basalt harbours the greatest microbial biomass. The bacterial community overlap, structure and species richness relative to alteration state is less explicit, but broadly corresponds to sample characteristics (type of alteration products and general alteration state). Phylogenetic analyses suggest that the basalt biome may contribute to the geochemical cycling of Fe, S, Mn, C and N in the deep sea. PMID:18783382

  7. Basalt-radionuclide distribution coefficient determinations. FY-1979 annual report

    International Nuclear Information System (INIS)

    Experimental radionuclide distribution coefficients (Kd') were determined for Pomona, Flow E, Umtanum basalts, and secondary mineralization associated with Pomona basalt at 230, 600 and 1500C. Radionuclides used were 75Se, 85Sr, 99Tc, 125I, 135Cs, 226Ra, 237Np, 238U, 241Am, and 241Pu. Solution oxygen contents were controlled by the basalt/groundwater system (Eh = 600 to 700 mV), and were high (8.2 to 8.4 mg/l) at 230C. Oxygen contents and pH changed little in contact with basalt. The effects of temperature changes on radionuclide Kd' results varied depending upon the radionuclide involved, solution-solid reactions, and the relationship of the radionuclide to these reactions. For example, cesium Kd' values decreased from 3100 ml/g for Umtanum basalt at 230C to 120 ml/g at 1500C. At the same time, strontium Kd' values increased for Umtanum basalt from 105 ml/g at 230C to complete removal at 1500C and 40 days. Radionuclide adsorption coefficient measurements at higher temperatures and pressures were made in addition to the 230C, solution-solid contact time-conditional Kd (Kd') measurements. These include Kd' measurements with Umtanum basalt, Pomona basalt, Flow E basalt and secondary mineralization and radioisotopes of americium, cesium, iodine, neptunium, plutonium, radium, selenium, strontium, technetium and uranium. The additional temperatures involved were 600C, 1500C, and 3000C. At 1500C, argon pressures of 6.9, 13.8, 20.7, and 27.6 MPa will be used to ascertain the effects of pressure changes on Kd' values. So far only the 6.9 MPa argon pressure has been investigated. The upper temperature of 2500C is where thermal breakdown of dioctahedral smectites (secondary mineralization) begins

  8. Geochemistry of Ua Huka basalts (Marquesas): partial melting variations and mantle source heterogeneity

    International Nuclear Information System (INIS)

    The main shield volcano of Ua Huka Island (Marquesas Archipelago) was emplaced between 2.2 and 2.4 Ma, and then affected by two caldera collapse events. After a 0.9 Ma-long gap, volcanic activity resumed with the emplacement of two smaller volcanoes in the southwest part of the island, between 1.5 and 0.75 Ma. The geochemical characteristics of Ua Huka mafic lavas, which range from olivine tholeiites to alkali basalts and basanites, are consistent with a temporal decrease in partial melting degrees of a heterogeneous mantle source. The associated temporal variation of the isotopic signatures of Ua Huka basalts implies a more important contribution of a Depleted MORB Mantle (DMM) end-member during the genesis of the youngest basanitic lavas. Such a variation was not previously documented in the Marquesas Archipelago. (authors)

  9. Permo-Triassic hypabyssal mafic intrusions and associated tholeiitic basalts of the Kolyuchinskaya Guba, Chukotka (NE Russia): Significance for interregional correlations

    Science.gov (United States)

    Ledneva, G. V.; Pease, V. L.; Sokolov, S. D.

    2008-12-01

    In order to test tectonic hypotheses regarding the evolution of the Arctic Alaska-Chukotka microplate prior to the opening of the Amerasian basin, we investigated rocks exposed near Kolyuchinskaya Guba, eastern Chukotka. Hypabyssal mafic rocks and associated basaltic flows enclose terrigenous sediments, minor cherts and limestones in pillow interstices. The hypabyssal mafic rock yields a U-Pb zircon age of 252+/-4 Ma and indicates intrusion of basic magma at the Permo-Triassic boundary, contemporaneous with voluminous magmatism of the Siberian large igneous province (LIP). The lava flows and hypabyssal mafic rocks of the Kolyuchinskaya Guba region have major and trace element compositions identical the tholeiitic flood basalts of the main plateau stage of the Siberian LIP. They are strongly differentiated, the result of high-pressure equilibrium crystallization of a low-Ti/Y tholeiitic melt, and contaminated. The compositional variations in these rocks, however, neither proves nor disproves a correlation between the Permo-Triassic tholeiitic flood basalts of eastern Chukotka and the Siberian LIP. Thus, two alternative geodynamic interpretations are possible: 1) The hypabyssal mafic rocks and associated tholeiitic flows crystallized from a plume-derived melt; 2) The rocks are not related to plume activity, consequently eastern Chukotka was probably part of a passive rifted or extensional continental margin in the Permo-Triassic. Nonetheless, we prefer the first of these two possibilities. Funding for this work is gratefully acknowledged from the Swedish Polar Research Secretariat ("Beringia-2005"), the Swedish Research Council, the Russian Foundation for Basic Research (grant No 08-05-00547), Leading Scientific School (NSH-3172.2008.5) and ONZ RAS. Thanks are also extended to M.J. Whitehouse and the Nordsim facility - the Nordsim facility is funded by the research councils of Denmark, Norway, Sweden, the Geological Survey of Finland, and the Swedish Museum of

  10. Re-examination of crystal ages in recent Mount St. Helens lavas: implications for magma reservoir processes

    Science.gov (United States)

    Cooper, Kari M.; Reid, Mary R.

    2003-08-01

    U-series data for recent Mount St. Helens lavas suggest that crystallization preceded eruption by more than 0.5 ka but are complicated by possible evidence of crystal recycling and/or addition of radium to the liquid after crystallization. We report new ion and electron microprobe trace- and major-element data for plagioclase and pyroxene in these recent Mount St. Helens lavas and use these data to reassess 226Ra-230Th crystal ages by taking into account differences in the partitioning behavior of radium and barium and the effects of impurities in mineral separates. Revised 226Ra-230Th model crystallization ages are ∼2-4 ka for plagioclase (with the exception of the 1982 dacite) and ∼0.15-5.7 ka for pyroxene. In contrast to previous interpretations, no late-stage addition of Ra to the liquid after precipitation of the minerals is required. The variability of Ba concentrations measured in plagioclase is too large to be consistent with progressive crystallization from the same liquid or with diffusive re-equilibration of xenocrysts with a new host liquid. Ba heterogeneity limits the residence time of the crystals in a magma at high temperatures and also suggests that in most cases Ra-Th ages have not been significantly modified by Ra diffusion into or out of the crystals. High (226Ra)/Ba in plagioclase in the 1982 dacite relative to the host liquid likely reflects crystallization processes that precluded bulk crystal-liquid chemical equilibrium. One possibility is that of growth entrapment of surface enrichments during rapid crystallization, which could lead to less discrimination between Ra and Ba than predicted by calculated bulk partition coefficients. 226Ra-230Th crystal ages for the Castle Creek andesite and basalt that are younger than 230Th-238U ages of the same crystals could be explained by mixing of crystals into melts with different 230Th/232Th ratios, by combinations of older and younger crystal growth within the same magma, or, for the basalt, by

  11. Biological Alteration of Basaltic Glass With Altered Composition and Oxidation States

    Science.gov (United States)

    Bailey, B. E.; Staudigel, H.; Templeton, A.; Tebo, B. M.; Ryerson, F.; Plank, T.; Schroder, C.; Klingelhoefer, G.

    2004-12-01

    The ocean crust is an extreme and oligotrophic environment and yet recent studies have shown that reactions between oceanic crust and seawater are capable of supporting microbial life. We are specifically targeting volcanic glass as a source of energy and nutrients necessary to support endolithic microbial communities. A significant amount of chemical energy is available from the process of iron oxidation and our goal is to determine the ability of microorganisms to use Fe(II) as an energy source as well as liberate other essential nutrients from the host rock. In addition, microbes may oxidize Mn or use phosphate from glass. To explore the dependency of microbial life on these nutrients and energy sources, we produce basaltic glasses with varying Fe oxidation states and relative abundance of iron, manganese and phosphate and introduce them to microbial isolates and consortia both in the laboratory and in deep-ocean environments. The natural exposure experiments occur in a variety of settings including hydrothermal vents and cold deep seawater (Loihi Seamount), brines (Mediterranean), and basaltic flows at spreading ridges (EPR), when possible on submarine lava flows of recent and known age. Upon collection of the exposure experiments, we compare basalt colonizing microbial communities on our synthetic glasses with the in situ glass communities through a large culturing effort and molecular (t-RFLP) studies. So far we have produced a number of enrichment cultures and isolated several iron-oxidizing and manganese-oxidizing bacteria that were used to inoculate glasses in the laboratory. Laboratory experiments concentrate on biofilm formation and dissolution of the colonized glasses. Continued collection of exposure experiments on a yearly time-scale provides valuable information regarding spatial and temporal variations in microbial community diversity and structure. We have also analyzed the authigenic reaction products of seafloor, microbially mediated alteration

  12. Open-path FTIR spectroscopy of magma degassing processes during eight lava fountains on Mount Etna

    Science.gov (United States)

    La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

    2016-04-01

    In June-July 2001 a series of 16 discrete lava fountain paroxysms occurred at the Southeast summit crater (SEC) of Mount Etna, preceding a 28-day long violent flank eruption. Each paroxysm was preceded by lava effusion, growing seismic tremor and a crescendo of Strombolian explosive activity culminating into powerful lava fountaining up to 500m in height. During 8 of these 16 events we could measure the chemical composition of the magmatic gas phase (H2O, CO2, SO2, HCl, HF and CO), using open-path Fourier transform infrared (OP-FTIR) spectrometry at ˜1-2km distance from SEC and absorption spectra of the radiation emitted by hot lava fragments. We show that each fountaining episode was characterized by increasingly CO2-rich gas release, with CO2/SO2and CO2/HCl ratios peaking in coincidence with maxima in seismic tremor and fountain height, whilst the SO2/HCl ratio showed a weak inverse relationship with respect to eruption intensity. Moreover, peak values in both CO2/SO2ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval (2-6 days) between lava fountains. These observations, together with a model of volatile degassing at Etna, support the following driving process. Prior to and during the June-July 2001 lava fountain sequence, the shallow (˜2km) magma reservoir feeding SEC received an increasing influx of deeply derived carbon dioxide, likely promoted by the deep ascent of volatile-rich primitive basalt that produced the subsequent flank eruption. This CO2-rich gas supply led to gas accumulation and overpressure in SEC reservoir, generating a bubble foam layer whose periodical collapse powered the successive fountaining events. The anti-correlation between SO2/HCl and eruption intensity is best explained by enhanced syn-eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation.

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

    Energy Technology Data Exchange (ETDEWEB)

    G.A> Valentine; F.V. Perry

    2006-06-06

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

  14. Eruption style and flow emplacement in the Submarine North Arch Volcanic Field, Hawaii

    Science.gov (United States)

    Clague, David A.; Uto, Kozo; Satake, Kenji; Davis, Alicé S.

    The North Arch Volcanic Field covers about 24,000 km2 of seafloor north of Oahu and has an estimated volume between 1,000 and 1,250 km3. The field straddles the Hawaiian flexural arch about 250 km north of the axis of the island chain and surrounds numerous Cretaceous volcanic ridges, circular flat-topped volcanoes, and low-relief regions of sediment-covered seafloor. New SeaBeam bathymetric maps that cover about 1/3 of the flow field reveal nearly 100 volcanic structures ranging from low shields to steep cones. One shield is modified by a pit crater, approximately 1.1×1.25 km and 300 m deep. A lava flow in the SE part of the volcanic field covers about 3,600 km2, has an estimated volume of 36-72 km3, and apparently erupted from a 75-km-long NNW-trending fissure system. A 108-km-long flow advanced north in a graben parallel to the Cretaceous mid-ocean ridge that formed the crust; its surface gradient is 1.9 m/km (slope of 0.1°). Shinkai 6500 submersible dive 502 explored one of the composite volcanoes and observed and collected dense alkalic basalt sheet flows erupted after vesicular basanite pillow basalts and fragmental hyaloclastite that make up the steep-sided cone. Dive 503 collected alkalic basalt sheet flows and pillow basalt from the top 122 m of the southern wall of a pit crater that formed by collapse caused by a decrease in magma volume from a shallow storage chamber located 1-2 km below the surface. The volume change may have been caused by loss of gas bubbles from the stored magma when replenishment ceased at the end of the eruption. The surficial drapery-folded sheet flow is covered by only a few cm of sediment, indicating that it is younger than the 0.5-1.5 Ma ages previously estimated for North Arch flows and vents. The near-vent constructs and flow characteristics indicate that vigorous eruption of highly vesicular lava constructed steep-sided cones of pillow basalt and hyaloclastite whereas steady eruption of dense lava that had lost its bubbles

  15. Partial pressures of oxygen, phosphorus and fluorine in some lunar lavas

    Science.gov (United States)

    Nash, W. P.; Hausel, W. D.

    1973-01-01

    Lunar sample 14310 is a feldspar-rich basalt which shows no evidence of shock deformation or recrystallization. Pyroxenes include Mg-rich orthopyroxene, pigeonite and augite; pyroxferroite occurs in the interstitial residuum. Plagioclase feldspars are zoned from An(96) to An(67), and variations in feldspar compositions do not necessarily indicate loss of Na during eruption of the lava. Opaque phases include ilmenite, ulvospinel, metallic iron, troilite, and schreibersite. Both whitlockite and apatite are present, and the interstitial residua contain baddeleyite, tranquillityite and barium-rich sanidine. Theoretical calculations provide estimates of partial pressures of oxygen, phosphorus, and fluorine in lunar magmas. In general, partial pressures of oxygen are restricted by the limiting assemblages of iron-wuestite and ilmenite-iron-rutile; phosphorus partial pressures are higher in lunar magmas than in terrestrial lavas. The occurrence of whitlockite indicates significantly lower fugacities of fluorine in lunar magmas than in terrestrial magmas.

  16. Compositional evolution of lava plains in the Syria-Thaumasia Block, Mars

    Science.gov (United States)

    Huang, Jun; Xiao, Long

    2014-05-01

    Tharsis is the most prominent volcanic province on Mars, yet the compositions of lava flows and how composition relates to the development of Tharsis are poorly known. Most of Tharsis is covered with air-fall dust, which inhibits spectroscopic determination of lava mineralogy. The Syria-Thaumasia Block (STB) is a complex tectono-volcanic province closely related to the Tharsis bulge. The lava plains of STB have different emplacement ages, which provide an opportunity to examine whether magma composition changed with the evolution of Tharsis. In this study, we assessed the lava plains using Thermal Emission Spectrometer (TES) data. Using derived physical properties, we targeted dust-free regions from four different-aged geological units' surfaces and determined the mineralogical composition by modeling the average TES surface spectrum from each of the four surfaces. All units have similar mineralogy but the younger two units have elevated abundance of high-SiO2 phases. The spatial distribution of wrinkle ridges indicates lava plains of unit HNr (older ridged plains material) and Hr (younger ridged plains material) were emplaced before the rise of Tharsis, whereas Hsl (flows of lower member) and Hsu (upper member) were emplaced after Tharsis uplift was initiated. We show that the magma composition differed in the lava plains of STB after the uplift of Tharsis. This study further characterizes early martian magma composition and evolution.

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

    Science.gov (United States)

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

    2015-12-01

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

  18. Geochemistry of Paraná-Etendeka basalts from Misiones, Argentina: Some new insights into the petrogenesis of high-Ti continental flood basalts

    Science.gov (United States)

    Rämö, O. Tapani; Heikkilä, Pasi A.; Pulkkinen, Arto H.

    2016-04-01

    The Early Cretaceous (˜135-131 Ma) Paraná-Etendeka continental flood basalts, preserved in bulk in the Paraná basin of southern Brazil and vicinity, have been divided into low-Ti and high-Ti types that govern the southern and northern halves of the basin, respectively. We have examined a new sample set from the southern margin of the northern high-Ti segment of Paraná basalts in Misiones, northeastern Argentina. These basalts are strongly to moderately enriched in TiO2 (2-4 wt.%), have relatively high Ti/Y (300-500), low MgO (3.5-6.5 wt.%), and high Fe (FeO(tot) 12-14 wt.%) and belong to the Pitanga and Paranapanema magma types of Peate et al. (1992). Nd and Sr isotope compositions are quite unvarying with ɛNd (at 133 Ma) values of -4.6 to -3.6 and initial 87Sr/86Sr of 0.7054-0.7059 and show no variation with fractionation. Compared to high-Ti lavas in the central and northern parts of the Paraná high-Ti basalt segment, the lavas from Misiones are similar to those in the northeastern magin of the basin but less radiogenic in initial Nd isotope composition than those in the central part. This variation probably reflects mixed EM1-EM2 source components in the sublithospheric mantle. A polybaric melt model of a sublithospheric mantle source at the garnet lherzolite-spinel lherzolite transition is compatible with the observed Ti budget of the Pitanga and Paranapanema lavas, regardless of the Nd isotope composition of their purported source.

  19. East Mariana Basin tholeiites: Cretaceous intraplate basalts or rift basalts related to the Ontong Java plume?

    Science.gov (United States)

    Castillo, P.R.; Pringle, M.S.; Carlson, R.W.

    1994-01-01

    Studies of seafloor magnetic anomaly patterns suggest the presence of Jurassic oceanic crust in a large area in the western Pacific that includes the East Mariana, Nauru and Pigafetta Basins. Sampling of the igneous crust in this area by the Deep Sea Drilling Program (DSDP) and the Ocean Drilling Program (ODP) allows direct evaluation of the age and petrogenesis of this crust. ODP Leg 129 drilled a 51 m sequence of basalt pillows and massive flows in the central East Mariana Basin. 40Ar 39Ar ages determined in this study for two Leg 129 basalts average 114.6 ?? 3.2 Ma. This age is in agreement with the Albian-late Aptian paleontologic age of the overlying sediments, but is distinctively younger than the Jurassic age predicted by magnetic anomaly patterns in the basin. Compositionally, the East Mariana Basin basalts are uniformly low-K tholeiites that are depleted in highly incompatible elements compared to moderately incompatible ones, which is typical of mid-ocean ridge basalts (MORB) erupted near hotspots. The Sr, Nd and Pb isotopic compositions of the tholeiites ( 87Sr 86Srinit = 0.70360-0.70374; 143Nd 144Ndinit = 0.512769-0.512790; 206Pb 204Pbmeas = 18.355-18.386) also overlap with some Indian Ocean Ridge MORB, although they are distinct from the isotopic compositions of Jurassic basalts drilled in the Pigafetta Basin, the oldest Pacific MORB. The isotopic compositions of the East Mariana Basin tholeiites are also similar to those of intraplate basalts, and in particular, to the isotopic signature of basalts from the nearby Ontong Java and Manihiki Plateaus. The East Mariana Basin tholeiites also share many petrologic and isotopic characteristics with the oceanic basement drilled in the Nauru Basin at DSDP Site 462. In addition, the new 110.8 ?? 1.0 Ma 40Ar 39Ar age for two flows from the bottom of Site 462 in the Nauru Basin is indistinguishable from the age of the East Mariana Basin flows. Thus, while magnetic anomaly patterns predict that the igneous

  20. Influence of pre-existing topography on downflow lava discharge rates estimated from thermal infrared airborne data

    Science.gov (United States)

    Lombardo, V.

    2016-04-01

    Remote sensing thermal data of active lava flows allow the evaluation of effusion rates. This is made possible by a simple formula relating the lava effusion rate to the heat flux radiated per unit time from the surface of the flow. Due to the assumptions of the model, this formula implies that heat flux, surface temperature and lava temperature vary as a function of the flow thickness. These relationships, never verified or validated before, have been used by several authors as a proof of the weakness of the model. Here, multispectral infrared and visible imaging spectrometer (MIVIS) high spatial resolution (5-10 m) thermal data acquired during Etna's 2001 eruption were used to investigate downflow heat flux variations in the lava flow emitted from a vent located at 2100 m a.s.l. A high correlation between the downflow heat flux and the lava flow thickness (measured from a pre-existing digital elevation model) was found. Topography beneath the flow appears to play an important role both in lava emplacement mechanisms and flow dynamics. MIVIS-derived downflow effusion rates are consistent with the law of conservation of mass assessing the reliability of remote sensing techniques.

  1. Petrochemistry and tectonic significance of Lower Cretaceous Barros Arana Formation basalts, southernmost Chilean Andes

    Science.gov (United States)

    Stern, C. R.; Mohseni, P. P.; Fuenzalida, P. R.

    The Lower Cretaceous Barros Arana Formation (Albian, hornblende KAr age of 104 Ma), in the Magallanes region of Chile, consists of a sequence of spilitized clinopyroxene- and amphibole-bearing mafic dikes and lavas, and volcaniclastic breccias, occurring within the sedimentary infill of the Rocas Verdes marginal basin and its eastward extension onto the Cretaceous continental platform. Although the original alkali and alkaline earth element concentrations of the basaltic lavas and dikes have been altered by spilitization, the presence of relict pargasitic amphibole phenocrysts, the absence of orthopyroxene, and high LREE contents and LREE/HREE ratios imply mildly alkaline affinities for these basalts. Their low TiO 2 and HFSE (Zr, Nb, Ta, and Hf) contents and high LREE/HFSE ratios suggest affinities with convergent plate boundary arc magmas. The Barros Arana basalts are interpreted as mafic members of the mildly alkaline shoshonitic rock suite of subduction-related arcs. They may have formed as subduction geometry began to undergo the changes (flattening) that ultimately led to the initiation of the closure, deformation, and uplift of the Rocas Verdes basin by the late or post-Albian. The low initial 87Sr/ 86Sr (0.7031) and high initial 143Nd/ 144Nd (0.51277) of the basalts indicate that a generally extensional tectonic regime east of the main calc-alkaline arc allowed eruption of these mafic shoshonites without interaction with continental crust (in contrast to the contemporaneous plutons of the Patagonian batholith).

  2. Immense vent complex marks flood-basalt eruption in a wet, failed rift: Coombs Hills, Antarctica

    Science.gov (United States)

    White, J. D. L.; McClintock, M. K.

    2001-10-01

    Large lava effusions can have impressive explosive antecedents. Although our picture of flood basalt is overwhelmingly effusive, phreatomagmatic eruptions have preceded quiet effusion of some flood basalts and reflect the same influence of vent architecture and hydrology on eruptive style as seen for small-volume eruptions. The scale of phreatomagmatic deposits associated with flood basalts can be huge. At Coombs Hills a vast, but otherwise typical, phreatomagmatic vent complex is exposed over more than 25 km2, and its features are interpreted to reflect processes of tephra-jet eruptions with diatreme development. Similar vent complexes are probably the source of laharic deposits reported elsewhere in the Transantarctic Mountains and in the Karoo province of South Africa.

  3. Petrogenesis of high-CaO lavas from Mauna Kea, Hawaii: Constraints from trace element abundances

    Science.gov (United States)

    Huang, Shichun; Humayun, Munir

    2016-07-01

    The role of a mafic component in the petrogenesis of Oceanic Island Basalts (OIBs) is highly debated. As the best studied OIB, Hawaiian lavas provide critical insights into OIB genesis. At a given MgO content, the CaO content in the melt has been used to distinguish between partial melts of peridotite and garnet pyroxenite/eclogite. However, calculations using the BATCH program show that CaO contents in volatile-free melts saturated with all four phases, garnet, clinopyroxene, orthopyroxene and olivine, are controlled by both degrees of partial melting and source compositions, and low melt CaO content is not diagnostic of partial melts from garnet pyroxenite/eclogite. This is an important consideration in understanding the origin of high-CaO lavas recovered from the Hawaii Scientific Drilling Project (HSDP). Detailed geochemical and isotopic studies have been focused on the HSDP high- and low-SiO2 group lavas, and high-CaO lavas were not well studied because they were not included in the original reference suite samples. Here, we report trace element abundances obtained on a suite of high-CaO glasses and compared the trace element abundances of high-CaO lavas to those in high- and low-SiO2 lavas. When normalized to the average composition of low-SiO2 lavas, high-CaO lavas form a U-shaped trace element pattern, enriched in both the most incompatible (Nb, Th) and the least incompatible (Sc, V) elements. This compositional distinction is best explained if high-CaO parental magma represents a mixture of a low degree partial melt of the low-SiO2 mantle source with a high degree (>80%) partial melt derived from a mafic cumulate component. This mafic cumulate must be clinopyroxene-rich, and it could be delaminated mafic cumulate formed under arcs during continent formation, lower continental crust, recycled lower oceanic crust, or high pressure cumulates from a magma chamber.

  4. Statistical evaluation of some Columbia River basalt chemical analyses

    International Nuclear Information System (INIS)

    This study had a threefold purpose: to examine the atomic absorption gamma spectroscopy, emission spectroscopy, and neutron activation data accumulated by Atlantic Richfield Hanford Company through 1976 (predecessor company to Rockwell Hanford Operations), and evaluate the precision of the data and their calibration reliability; to determine from these chemical data those elements that were best for characterizing basalt flows for correlation purposes; and, to use these chemical data to establish statistical correlations among type locality reference groups and the basalt flows penetrated by deep core holes in the Pasco Basin or exposed on the surface at certain field section locations

  5. Changing compositions in the Iceland plume; Isotopic and elemental constraints from the Paleogene Faroe flood basalts

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin

    Elemental and Sr, Nd, Hf and high precision Pb isotopic data are presented from 59 low-Ti and high-Ti lavas from the syn-break up part of the Faroe Flood Basalt Province. The depleted MORB-like low-Ti lavas erupted in the rift zone between the Faroe Islands and central East Greenland around the...... enriched EM-type component similar in geochemistry to the Icelandic Öræfajökull lavas. This component is believed to be recycled pelagic sediments in the plume but it can alternatively be a local crustal or lithospheric mantle component. The enriched Faroe high-Ti lavas erupted inland from the rift have...... isotopic compositions very similar to the enriched Icelandic neo-volcanics and these lava suites apparently share the two enriched plume end-members IE1 and IE2 (Geochim. Cosmochim. Acta 68, 2, 2004). The lack of mixing between high and low-Ti melts at the time of break up, is explained by a zoned plume...

  6. The Lava sequence of the East African Rift escarpment in the Oldoinyo Lengai - Lake Natron sector, Tanzania

    Science.gov (United States)

    Neukirchen, Florian; Finkenbein, Thomas; Keller, Jörg

    2010-12-01

    A 500 m sequence of horizontal lava flows forms the Gregory rift escarpment of the western rift shoulder between Lake Natron and Oldoinyo Lengai. A detailed volcanic stratigraphy of this >1.2 Ma evolution of the EAR in Northern Tanzania is presented. The sequence is formed by several distinct rock suites, with increasing alkalinity from base to top. Alkali olivine basalts of the Waterfall Sequence at the base are followed by a basanite series, and by a range of evolved nephelinites forming the upper part of the escarpment. Numerous dykes and Strombolian scoria deposits indicate local fissure eruptions as opposed to or in addition to more distant sources. Primitive compositions within each of the series indicate variable candidates for primary magmas. The composition of the basanite suite ranges from primitive mantle melts (high Mg#, Cr, Ni) to more evolved rocks, in particular hawaiites, generated by fractionation of olivine, pyroxene and magnetite. Inter-bedded within the basanite suite, one single olivine melilitite flow with high Mg# and abundant olivine and pyroxene megacrysts is the only primitive candidate for the nephelinite suite. However, in view of the large compositional gap and marked differences in incompatible element ratios, a relation between this flow and the nephelinites remains hypothetical. The variation within the evolved nephelinite series can be partly explained by fractionation of pyroxene, apatite, perovskite (and some nepheline), while magma mixing is indicated by zonation patterns of pyroxene. The most evolved nephelinite, however, differs significantly from all other nephelinites in major and trace elements. Thus the entire sequence is petrologically not a coherent evolution, rather the result of different mantle melts fractionating under variable conditions. Carved into the rift scarp of the study area west of Engare Sero is a young explosion crater, the Sekenge Crater. Sekenge Tuffs are olivine melilitites, similar to other craters and

  7. Lava Tube Exploration Robot and Payload Development

    Science.gov (United States)

    Kelly, H. S.; Parness, A. J.; Boston, P. J.

    2015-10-01

    Merging science and engineering from the ground up to co-develop a comprehensive instrument/robot package for exploration of and scientific data collection within lava tubes that target analog sites on the Moon and Mars.

  8. Mysterious Lava Mineral on Mars

    Science.gov (United States)

    2004-01-01

    This graph or spectrum captured by the Moessbauer spectrometer onboard the Mars Exploration Rover Spirit shows the presence of three different iron-bearing minerals in the soil at the rover's landing site. One of these minerals has been identified as olivine, a shiny green rock commonly found in lava on Earth. The other two have yet to be pinned down. Scientists were puzzled by the discovery of olivine because it implies the soil consists at least partially of ground up rocks that have not been weathered or chemically altered. The black line in this graph represents the original data; the three colored regions denote individual minerals and add up to equal the black line.The Moessbauer spectrometer uses two pieces of radioactive cobalt-57, each about the size of pencil erasers, to determine with a high degree of accuracy the composition and abundance of iron-bearing minerals in martian rocks and soil. It is located on the rover's instrument deployment device, or 'arm.'

  9. Olivine and chromian spinel in primitive calc-alkaline and tholeiitic lavas from the southernmost cascade range, California: A reflection of relative fertility of the source

    Science.gov (United States)

    Clynne, M.A.; Borg, L.E.

    1997-01-01

    Chromian spinel and coexisting olivine phenocrysts from a geochemically diverse suite of primitive tholeiitic and calc-alkaline basalts and magnesian andesites from the Lassen region, in the southernmost Cascade Range, in California, show that the sub-arc mantle is zoned. Depleted calc-alkaline basalts and magnesian andesites erupt in the forearc region, and calc-alkaline basalts contain increasing abundances of incompatible elements toward the backarc. High-alumina olivine tholeiites erupt from the arc and backarc areas. Olivine from all these lavas displays a limited compositional range, from Fo86 to Fo91, and crystallized at high temperature, generally 1225-1275??C. Chromian spinel trapped in the olivine phenocrysts displays a large range of composition: Cr# values span the range 9-76. Excess Al in the spinel relative to that in 1-atm spinel suggests that it crystallized at elevated pressure. The phenocrysts in these lavas are in equilibrium with their host liquids. The full range of Cr# of the spinel compositions cannot be explained by differentiation or variable pressure, variations in f(O2), subsolidus equilibration or variations in degree of partial melting of a single peridotitic source. Rather, the systematic compositional differences among phenocrysts in these primitive lavas result from bulk chemical variability in their mantle sources. Correlations between spinel and host-rock compositions support the assertion that the geochemical diversity of Lassen basalts reflects the relative fertility of their mantle sources.

  10. Preliminary Hydrogeologic Characterization Results from the Wallula Basalt Pilot Study

    Energy Technology Data Exchange (ETDEWEB)

    B.P. McGrail; E. C. Sullivan; F. A. Spane; D. H. Bacon; G. Hund; P. D. Thorne; C. J. Thompson; S. P. Reidel; F. S. Colwell

    2009-12-01

    The DOE's Big Sky Regional Carbon Sequestration Partnership has completed drilling the first continental flood basalt sequestration pilot borehole to a total depth (TD) of 4,110 feet on the Boise White Paper Mill property at Wallula, Washington. Site suitability was assessed prior to drilling by the 2007-2008 acquisition, processing and analysis of a four-mile, five-line three component seismic swath, which was processed as a single data-dense line. Analysis of the seismic survey data indicated a composite basalt formation thickness of {approx}8,000 feet and absence of major geologic structures (i.e., faults) along the line imaged by the seismic swath. Drilling of Wallula pilot borehole was initiated on January 13, 2009 and reached TD on April 6, 2009. Based on characterization results obtained during drilling, three basalt breccia zones were identified between the depth interval of 2,716 and 2,910 feet, as being suitable injection reservoir for a subsequent CO2 injection pilot study. The targeted injection reservoir lies stratigraphically below the massive Umtanum Member of the Grande Ronde Basalt, whose flow-interior section possesses regionally recognized low-permeability characteristics. The identified composite injection zone reservoir provides a unique and attractive opportunity to scientifically study the reservoir behavior of three inter-connected reservoir intervals below primary and secondary caprock confining zones. Drill cuttings, wireline geophysical logs, and 31one-inch diameter rotary sidewall cores provided geologic data for characterization of rock properties. XRF analyses of selected rock samples provided geochemical characterizations of the rocks and stratigraphic control for the basalt flows encountered by the Wallula pilot borehole. Based on the geochemical results, the pilot borehole was terminated in the Wapshilla Ridge 1 flow of the Grande Ronde Basalt Formation. Detailed hydrologic test characterizations of 12 basalt interflow

  11. Lava heating and loading of ice sheets on early Mars: Predictions for meltwater generation, groundwater recharge, and resulting landforms

    Science.gov (United States)

    Cassanelli, James P.; Head, James W.

    2016-06-01

    Recent modeling studies of the early Mars climate predict a predominantly cold climate, characterized by the formation of regional ice sheets across the highland areas of Mars. Formation of the predicted "icy highlands" ice sheets is coincident with a peak in the volcanic flux of Mars involving the emplacement of the Late Noachian - Early Hesperian ridged plains unit. We explore the relationship between the predicted early Mars "icy highlands" ice sheets, and the extensive early flood volcanism to gain insight into the surface conditions prevalent during the Late Noachian to Early Hesperian transition period. Using Hesperia Planum as a type area, we develop an ice sheet lava heating and loading model. We quantitatively assess the thermal and melting processes involved in the lava heating and loading process following the chronological sequence of lava emplacement. We test a broad range of parameters to thoroughly constrain the lava heating and loading process and outline predictions for the formation of resulting geological features. We apply the theoretical model to a study area within the Hesperia Planum region and assess the observed geology against predictions derived from the ice sheet lava heating and loading model. Due to the highly cratered nature of the Noachian highlands terrain onto which the volcanic plains were emplaced, we predict highly asymmetrical lava loading conditions. Crater interiors are predicted to accumulate greater thicknesses of lava over more rapid timescales, while in the intercrater plains, lava accumulation occurs over longer timescales and does not reach great thicknesses. We find that top-down melting due to conductive heat transfer from supraglacial lava flows is generally limited when the emplaced lava flows are less than ∼10 m thick, but is very significant at lava flow thicknesses of ∼100 m or greater. We find that bottom-up cryosphere and ice sheet melting is most likely to occur within crater interiors where lavas

  12. Melting processes and mantle sources of lavas on Mercury

    Science.gov (United States)

    Namur, Olivier; Collinet, Max; Charlier, Bernard; Grove, Timothy L.; Holtz, Francois; McCammon, Catherine

    2016-04-01

    The MESSENGER spacecraft provided geochemical data for surface rocks on Mercury. In this study, we use the major element composition of these lavas to constrain melting conditions and residual mantle sources on Mercury. We combine modelling and high-temperature (1320-1580 °C), low- to high-pressure (0.1 to 3 GPa) experiments on average compositions for the Northern Volcanic Plains (NVP) and the high-Mg region of the Intercrater Plains and Heavily Cratered Terrains (High-Mg IcP-HCT). Near-liquidus phase relations show that the S-free NVP and High-Mg IcP-HCT compositions are multiply saturated with forsterite and enstatite at 1450 °C - 1.3 GPa and 1570 °C - 1.7 GPa, respectively. For S-saturated melts (1.5-3 wt.% S), the multiple saturation point (MSP) is shifted to 1380 °C - 0.75 GPa for NVP and 1480 °C - 0.8 GPa for High-Mg IcP-HCT. To expand our experimental results to the range of surface compositions, we used and calibrated the pMELTS thermodynamic calculator and estimated phase equilibria of ∼5800 compositions from the Mercurian surface and determined the P-T conditions of liquid-forsterite-enstatite MSP (1300-1600 °C; 0.25-1.25 GPa). Surface basalts were produced by 10 to 50% partial melting of variably enriched lherzolitic mantle sources. The relatively low pressure of the olivine-enstatite-liquid MSP seems most consistent with decompression batch melting and melts being segregated from their residues near the base of Mercury's ancient lithosphere. The average melting degree is lower for the young NVP (0.27 ± 0.04) than for the older IcP-HCT (0.46 ± 0.02), indicating that melt productivity decreased with time. The mantle potential temperature required to form Mercurian lavas and the initial depth of melting also decreased from the older High-Mg IcP-HCT terrane (1650 °C and 360 km) to the younger lavas covering the NVP regions (1410 °C and 160 km). This evolution supports strong secular cooling of Mercury's mantle between 4.2 and 3.7 Ga and

  13. Single and Multi-Date Landsat Classifications of Basalt to Support Soil Survey Efforts

    Directory of Open Access Journals (Sweden)

    Jessica J. Mitchell

    2013-10-01

    Full Text Available Basalt outcrops are significant features in the Western United States and consistently present challenges to Natural Resources Conservation Service (NRCS soil mapping efforts. Current soil survey methods to estimate basalt outcrops involve field transects and are impractical for mapping regionally extensive areas. The purpose of this research was to investigate remote sensing methods to effectively determine the presence of basalt rock outcrops. Five Landsat 5 TM scenes (path 39, row 29 over the year 2007 growing season were processed and analyzed to detect and quantify basalt outcrops across the Clark Area Soil Survey, ID, USA (4,570 km2. The Robust Classification Method (RCM using the Spectral Angle Mapper (SAM method and Random Forest (RF classifications was applied to individual scenes and to a multitemporal stack of the five images. The highest performing RCM basalt classification was obtained using the 18 July scene, which yielded an overall accuracy of 60.45%. The RF classifications applied to the same datasets yielded slightly better overall classification rates when using the multitemporal stack (72.35% than when using the 18 July scene (71.13% and the same rate of successfully predicting basalt (61.76% using out-of-bag sampling. For optimal RCM and RF classifications, uncertainty tended to be lowest in irrigated areas; however, the RCM uncertainty map included more extensive areas of low uncertainty that also encompassed forested hillslopes and riparian areas. RCM uncertainty was sensitive to the influence of bright soil reflectance, while RF uncertainty was sensitive to the influence of shadows. Quantification of basalt requires continued investigation to reduce the influence of vegetation, lichen and loess on basalt detection. With further development, remote sensing tools have the potential to support soil survey mapping of lava fields covering expansive areas in the Western United States and other regions of the world with similar

  14. Limited role for thermal erosion by turbulent lava in proximal Athabasca Valles, Mars

    Science.gov (United States)

    Cataldo, Vincenzo; Williams, David A.; Dundas, Colin M.; Keszthelyi, Laszlo P.

    2015-11-01

    The Athabasca Valles flood lava is among the most recent (factor of ~2.2. If flow viscosity increases with increasing bubble content in the lava, the presence of 30-50 vol % bubbles leads to erosion depths lower than those relative to bubble-free lava by a factor of ~2.4. The presence of 25 vol % ice in the substrate increases erosion depths by a factor of 1.3. Nevertheless, modeled erosion depths, consistent with the emplacement volume and flow duration constraints, are far less than the depth of the channel (~35-100 m). We conclude that thermal erosion does not appear to have had a major role in excavating Athabasca Valles.

  15. Key variables influencing patterns of lava dome growth and collapse

    Science.gov (United States)

    Husain, T.; Elsworth, D.; Voight, B.; Mattioli, G. S.; Jansma, P. E.

    2013-12-01

    Lava domes are conical structures that grow by the infusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Dome growth can be characterized by repeated cycles of growth punctuated by collapse, as the structure becomes oversized for its composite strength. Within these cycles, deformation ranges from slow long term deformation to sudden deep-seated collapses. Collapses may range from small raveling failures to voluminous and fast-moving pyroclastic flows with rapid and long-downslope-reach from the edifice. Infusion rate and magma rheology together with crystallization temperature and volatile content govern the spatial distribution of strength in the structure. Solidification, driven by degassing-induced crystallization of magma leads to the formation of a continuously evolving frictional talus as a hard outer shell. This shell encapsulates the cohesion-dominated soft ductile core. Here we explore the mechanics of lava dome growth and failure using a two-dimensional particle-dynamics model. This meshless model follows the natural evolution of a brittle carapace formed by loss of volatiles and rheological stiffening and avoids difficulties of hour-glassing and mesh-entangelment typical in meshed models. We test the fidelity of the model against existing experimental and observational models of lava dome growth. The particle-dynamics model follows the natural development of dome growth and collapse which is infeasible using simple analytical models. The model provides insight into the triggers that lead to the transition in collapse mechasnism from shallow flank collapse to deep seated sector collapse. Increase in material stiffness due to decrease in infusion rate results in the transition of growth pattern from endogenous to exogenous. The material stiffness and strength are strongly controlled by the magma infusion rate. Increase in infusion rate decreases the time available for degassing induced crystallization leading to a

  16. Tectonic focusing of voluminous basaltic eruptions in magma-deficient backarc rifts

    Science.gov (United States)

    Anderson, Melissa O.; Hannington, Mark D.; Haase, Karsten; Schwarz-Schampera, Ulrich; Augustin, Nico; McConachy, Timothy F.; Allen, Katie

    2016-04-01

    The Coriolis Troughs of the New Hebrides subduction zone are among the youngest backarc rifts in the world. They reach depths of >3 km, despite their small size (morphology is characteristic of magma-deficient arc rifts in the early stages of backarc extension, where the rate of extension and subsidence exceeds the magmatic input. Unexpectedly, the youngest graben, the Vate Trough, contains a centrally-located 1000-m tall and 14-km wide shield volcano with a large, 5 × 8 km breached summit caldera. The Nifonea axial volcano has a volume of ∼126 km3, reflecting unusually high extrusion rates, given its young age (lake, the first described from a submarine backarc setting. Extensive diffuse hydrothermal venting and several clusters of black smoker chimneys, with the highest recorded fluid temperatures (368 °C) in the SW Pacific, occur on the youngest lava flows. Comparison with similar axial volcanoes on the mid-ocean ridges suggests that the 46 ×106 m3 of sheet flows in the caldera could have been erupted in <30 hours. The focusing of voluminous basaltic eruptions into an otherwise magma-deficient backarc has been linked to strong left-lateral transtension caused by clockwise rotation and segmentation of the southern portion of the arc after collision with d'Entrecasteaux ridge. This study shows that the upper plate stresses can result in dramatic variability in magma supply and hydrothermal activity at the earliest stages of arc rifting and could explain the wide range of melt compositions, volcanic styles and mineral deposit types found in nascent backarc rifts.

  17. Conceptual model for regional radionuclide transport from a basalt repository site. Final draft, technical memorandum

    International Nuclear Information System (INIS)

    This technical memorandum was prepared to: (1) describe a typical basalt radionuclide repository site, (2) describe geologic and hydrologic processes associated with regional radionuclide transport in basalts, (3) define the parameters required to model regional radionuclide transport from a basalt repository site, and (4) develop a ''conceptual model'' of radionuclide transport from a basalt repository site. In a general hydrological sense, basalts may be described as layered sequences of aquifers and aquitards. The Columbia River Basalt, centered near the semi-arid Pasco Basin, is considered by many to be typical basalt repository host rock. Detailed description of the flow system including flow velocities with high-low hydraulic conductivity sequences are not possible with existing data. However, according to theory, waste-transport routes are ultimately towards the Columbia River and the lengths of flow paths from the repository to the biosphere may be relatively short. There are many physical, chemical, thermal, and nuclear processes with associated parameters that together determine the possible pattern of radionuclide migration in basalts and surrounding formations. Brief process descriptions and associated parameter lists are provided. Emphasis has been placed on the use of the distribution coefficient in simulating ion exchange. The use of the distribution coefficient approach is limited because it takes into account only relatively fast mass transfer processes. In general, knowledge of hydrogeochemical processes is primitive

  18. Selective environmental stress from sulphur emitted by continental flood basalt eruptions

    Science.gov (United States)

    Schmidt, Anja; Skeffington, Richard A.; Thordarson, Thorvaldur; Self, Stephen; Forster, Piers M.; Rap, Alexandru; Ridgwell, Andy; Fowler, David; Wilson, Marjorie; Mann, Graham W.; Wignall, Paul B.; Carslaw, Kenneth S.

    2016-01-01

    Several biotic crises during the past 300 million years have been linked to episodes of continental flood basalt volcanism, and in particular to the release of massive quantities of magmatic sulphur gas species. Flood basalt provinces were typically formed by numerous individual eruptions, each lasting years to decades. However, the environmental impact of these eruptions may have been limited by the occurrence of quiescent periods that lasted hundreds to thousands of years. Here we use a global aerosol model to quantify the sulphur-induced environmental effects of individual, decade-long flood basalt eruptions representative of the Columbia River Basalt Group, 16.5-14.5 million years ago, and the Deccan Traps, 65 million years ago. For a decade-long eruption of Deccan scale, we calculate a decadal-mean reduction in global surface temperature of 4.5 K, which would recover within 50 years after an eruption ceased unless climate feedbacks were very different in deep-time climates. Acid mists and fogs could have caused immediate damage to vegetation in some regions, but acid-sensitive land and marine ecosystems were well-buffered against volcanic sulphur deposition effects even during century-long eruptions. We conclude that magmatic sulphur from flood basalt eruptions would have caused a biotic crisis only if eruption frequencies and lava discharge rates had been high and sustained for several centuries at a time.

  19. Hydrogeological and quantitative groundwater assessment of the Basaltic Aquifer, Northern Harrat Rahat, Saudi Arabia

    International Nuclear Information System (INIS)

    The Northern Harrat Rahat consists of 300m basalt lavas covering some 2000 km2 to the south-east of Al-Madinah in western Saudi Arabia. Like many basalt sequences, the Rahat basalts form an important aquifer and groundwater resource. The aquifer has a saturated thickness of up to 60m and made up of the weathered upper part of underlying basement, pre-basalt sands and gravels and the fractured basalts. Since 1992, groundwater has been abstracted from the aquifer as part of the Al-Madinah water supply. To assess the potential of the aquifer an assessment has been made based on pumping tests of 70 wells. The hydraulic parameters have been shown to be highly variable typical of the fractured domain. The aquifer contains good-quality water in storage, but receives limited recharge. Groundwater temperature anomalies indicate remnant volcanic activity locally. A numerical groundwater model has been constructed, which has been calibrated using limited groundwater head measurements, but with good abstraction records. Prediction of groundwater heads and the examination of several abstraction scenarios indicate that the aquifer can continue to support part of the Al-Madinah demand for the next several years, if certain well distributions are adopted. The predictions also show that the aquifer can only support the total demand of the city for a few days as a contingency resource. (author)

  20. Geochemistry of pillow lavas and their clinopyroxene: ophiolitic mélanges of Nain and Ashin, northeastern Isfahan province

    Directory of Open Access Journals (Sweden)

    Nargess Shirdashtzadeh

    2016-04-01

    Full Text Available The Nain and Ashin ophiolites are located in northeastern Isfahan province, in western Central-East Iranian Microplate. Pillow lavas are one of the most significant Cretaceous rock units. The lower partial melting degree in mantle peridotites of Ashin ophiolite, and the derived melt by melting their clinopyroxene caused a more basic (basalt and enriched nature for the Ashin pillow lavas, whereas higher partial melting degree and consequently incongruent melting of orthopyroxene and increment of silica in the ascending melt, together with aqueous fluids led to formation of more acidic (andesite – basaltic andesite and depleted melts (in trace elements in Nain ophiolite. The REE content of Nain samples have IAT chemical affinity, but the samples from Ashin show MORB characteristics. Based on petrograhic observations, lower Eu/Eu* of clinopyroxene phenocrystals of Ashin, calculated Kd of clinopyroxene together with HREE enrichment in the melt in equilibrium with clinopyroxene (especially in Ashin when compared with Nain, the plagioclase crystallization was primer and higher in comparison with clinopyroxene, especially in Ashin compared with Nain. The melt in equilibrium with clinopyroxene in Ashin was similar to MORB composition, whereas it is similar to IAT in Nain. Thus, despite the proximity of these two ophiolitic series and some field and petrographic similarities, pillow lavas from them are different from each other in both primary melt composition and the processes of differentiation and the tectonic setting.

  1. Flood basalt volcanism on the Moon and Mars

    International Nuclear Information System (INIS)

    Comparative studies of the surfaces of the terrestrial planets reveal that processes of flood basalt volcanism were common to all of them, irrespective of their stages of evolution either primitive, intermediate or progressive. On the Moon manifestations of flood basalt volcanism have been recognized in basins (maria); on the planet Mars both in basins (planitiae) and in higher topographic (continental) levels. The mare-epoch of the less developed planets led to significant changes in their relief and in the crustal structure. Examples of volcanic flows from the lunar and martian surface are introduced. Some crustal uplifts on Mars can be interpreted in terms of Van Bemmelen's undations. (Auth.)

  2. Surface oxidization-reduction reactions in Columbia Plateau basalts

    International Nuclear Information System (INIS)

    Results are presented which define principal oxidation-reduction reactions expected between ground water and iron in the Umtanum and Cohassett basalt flows of south central Washington. Data include kinetics of aqueous iron speciation, rates of O2 uptake and nature of oxyhydroxide precipitates. Such data are important in predicting behavior of radionuclides in basalt aquifers including determination of valence states, speciation, solubility, sorption, and coprecipitation on iron oxyhydroxide substrates and colloids. Analyses of the basalt by XPS indicates that ferrous iron is oxidized to ferric iron on the surface and that the total iron decreases as a function of pH during experimental weathering. Iron oxyhydroxide phases did not form surface coating on basalt surfaces but rather nucleated as separate plases in solution. No significant increases in Cs or Sr sorption were observed with increased weathering of the basalt. Concurrent increases in Fe(II) and decreases in Fe(III) in slightly to moderately acid solutions indicated continued oxidization of ferrous iron in the basalt. At neutral to basic pH, Fe(II) was strongly sorbed onto the basalt surface (Kd = 6.5 x 10-3 1 x m2) resulting in low dissolved concentrations even under anoxic conditions. The rate of O2 uptake increased with decreasing pH. Diffusion rates (-- 10-14 cm2 x s-1), calculated using a one-dimensional analytical model, indicate grain boundary diffusion. Comparisons of Eh values calculated by Pt electrode, dissolved O2 and Fe(II)/Fe(III) measurements showed considerable divergence, with the ferric-ferrous couple being the preferred method of estimating Eh

  3. Elastic laboratory measurements and modeling of saturated basalts

    Science.gov (United States)

    Adam, Ludmila; Otheim, Thomas

    2013-03-01

    Understanding the elastic behavior of basalt is important to seismically monitor volcanoes, subsea basalts, and carbon sequestration in basalt. We estimate the elastic properties of basalt samples from the Snake River Plain, Idaho, at ultrasonic (0.8 MHz) and seismic (2-300 Hz) frequencies. To test the sensitivity of seismic waves to the fluid content in the pore structure, measurements are performed at three saturation conditions: saturated with liquid CO2, water, and dry. When CO2 replaces water, the P-wave velocity drops, on average, by 10%. Vesicles and cracks, observed in the rock microstructure, control the relaxation of pore-fluid pressures in the rock as a wave propagates. The bulk and shear moduli of basalts saturated with liquid CO2 are not frequency dependent, suggesting that fluid pore pressures are in equilibrium between 2 Hz and 0.8 MHz. However, when samples are water saturated, the bulk modulus of the rock is frequency dependent. Modeling with Gassmann's equations predicts the measured saturated rock bulk modulus for all fluids for frequencies below 20 Hz but underpredicts the water-saturated basalt bulk modulus for frequencies greater than 20 Hz. The most likely reason is that the pore-fluid pressures are unrelaxed. Instead, the ultrasonic frequency rock moduli are modeled with high-frequency elastic theories of squirt flow and Kuster-Toksöz (KT). Although KT's model is based on idealized pore shapes, a combination of spheres (vesicles) and penny-shaped cracks (fractures) interpreted and quantified from petrographical data predicts the ultrasonic dry and saturated rock moduli for the measured basalts.

  4. Strength of Concrete Containing Basalt Fibre

    Directory of Open Access Journals (Sweden)

    Parvez Imraan Ansari

    2015-04-01

    Full Text Available This paper presents the comparative study of effect of basalt fibre on compressive and split tensile strength of M40 grade concrete. The basalt fibre was mixed in concrete by (0.5%, 1%, and 1.5% of its total weight of cement in concrete. Results indicated that the strength increases with increase of basalt fibre content up to 1.0% beyond that there is a reduction in strength on increasing basalt fibre. The results show that the concrete specimen with 1.0% of basalt fibre gives better performance when it compared with 0.5%and 1.5% basalt fibre mix in concrete specimens.

  5. Late Holocene hydrous mafic magmatism at the Paint Pot Crater and Callahan flows, Medicine Lake Volcano, N. California and the influence of H2O in the generation of silicic magmas

    Science.gov (United States)

    Kinzler, R.J.; Donnelly-Nolan, J. M.; Grove, T.L.

    2000-01-01

    This paper characterizes late Holocene basalts and basaltic andesites at Medicine Lake volcano that contain high pre-eruptive H2O contents inherited from a subduction related hydrous component in the mantle. The basaltic andesite of Paint Pot Crater and the compositionally zoned basaltic to andesitic lavas of the Callahan flow erupted approximately 1000 14C years Before Present (14C years B.P.). Petrologic, geochemical and isotopic evidence indicates that this late Holocene mafic magmatism was characterized by H2O contents of 3 to 6 wt% H2O and elevated abundances of large ion lithophile elements (LILE). These hydrous mafic inputs contrast with the preceding episodes of mafic magmatism (from 10,600 to ~3000 14C years B.P.) that was characterized by the eruption of primitive high alumina olivine tholeiite (HAOT) with low H2O (magmatic inclusions similar in character to the mafic lavas at Callahan and Paint Pot Crater. The influence of H2O on fractional crystallization of hydrous mafic magma and melting of pre-existing granite crust beneath the volcano combined to produce the rhyolite. Fractionation under hydrous conditions at upper crustal pressures leads to the early crystallization of Fe-Mg silicates and the suppression of plagioclase as an early crystallizing phase. In addition, H2O lowers the saturation temperature of Fe and Mg silicates, and brings the temperature of oxide crystallization closer to the liquidus. These combined effects generate SiO2-enrichment that leads to rhyodacitic differentiated lavas. In contrast, low H2O HAOT magmas at Medicine Lake differentiate to iron-rich basaltic liquids. When these Fe-enriched basalts mix with melted granitic crust, the result is an andesitic magma. Since mid-Holocene time, mafic volcanism has been dominated primarily by hydrous basaltic andesite and andesite at Medicine Lake Volcano. However, during the late Holocene, H2O-poor mafic magmas continued to be erupted along with hydrous mafic magmas, although in

  6. Absolute paleointensity from Hawaiian lavas younger than 35 ka

    Science.gov (United States)

    Valet, J.-P.; Tric, E.; Herrero-Bervera, E.; Meynadier, L.; Lockwood, J.P.

    1998-01-01

    Paleointensity studies have been conducted in air and in argon atmosphere on nine lava flows with radiocarbon ages distributed between 3.3 and 28.2 ka from the Mauna Loa volcano in the big island of Hawaii. Determinations of paleointensity obtained at eight sites depict the same overall pattern as the previous results for the same period in Hawaii, although the overall average field intensity appears to be lower. Since the present results were determined at higher temperatures than in the previous studies, this discrepancy raises questions regarding the selection of low versus high-temperature segments that are usually made for absolute paleointensity. The virtual dipole moments are similar to those displayed by the worldwide data set obtained from dated lava flows. When averaged within finite time intervals, the worldwide values match nicely the variations of the Sint-200 synthetic record of relative paleointensity and confirm the overall decrease of the dipole field intensity during most of this period. The convergence between the existing records at Hawaii and the rest of the world does not favour the presence of persistent strong non-dipole components beneath Hawaii for this period.

  7. Experimental determination of phase equilibria of a basalt from Piton de la Fournaise (La Réunion island): 1 atm data and high pressure results in presence of volatiles

    OpenAIRE

    Brugier, Yann-Aurélien; Pichavant, Michel; Di Muro, Andréa

    2015-01-01

    To understand the petrogenetic relations between the 4 groups of lavas erupted at Piton de la Fournaise (PdF), constrain the structure of the feeding system and the magma storage conditions, experimental phase equilibria have been determined, both at 1 atm and high pressures (HP), on a lava representative of Steady State Basalts (SSB). The lava (SiO 2 =49.2 wt%, MgO=7.8 wt%, CaO/Al2O 3 = 0.81) was fused at 1400 • C, 1 atm in air. The resulting glass was crushed and the powder directly used as...

  8. Distribution of "Compound" and "Simple" Flows in the Deccan Traps (India)

    Science.gov (United States)

    Vanderkluysen, L.; Self, S.; Jay, A. E.; Sheth, H. C.; Clarke, A. B.

    2014-12-01

    The Deccan Traps are a dominantly mafic large igneous province (LIP) that, prior to erosion, covered ~1 million km2 of west-central India with lava flows. The type sections of the Western Ghats escarpment, where the Deccan lava pile reaches a maximum reconstructed stratigraphic thickness of ~3400 m, are subdivided into eleven formations defined on chemo-stratigraphic grounds. Earlier work recognized that emplacement of Deccan basalt flows primarily occurs following two main modes: as a stack of meter-sized pāhoehoe toes and lobes, termed "compound" flows; or as inflated sheet lobes tens to hundreds of meters in width and meters to tens of meters in height, previously termed "simple" flows. Initially, the distribution of small lobes and sheet lobes in the Deccan was thought to be controlled by distance from source, but later work suggested the distribution to be mainly controlled along stratigraphic, formational boundaries, with six of the lower formations being composed exclusively of compound flows, and the upper 4-5 formations being wholly built of sheet lobes. This simple stratigraphic subdivision of lava flow morphologies has also been documented in the volcanic architecture of other LIPs, e.g., the Etendeka, the Ethiopian Traps, and in the Faeroe Islands (North Atlantic LIP). Upon examination of eight sections carefully logged along the Western Ghats, this traditional view must be challenged. Where the lower Deccan formations crop out, we found that as much as 65% of the exposed thickness (below the Khandala Formation) is made up of sheet lobes, from 40% in the Bhimashankar Formation to 75% in the Thakurvadi Formation. Near the bottom of the sequence, 25% of the Neral Formation is composed of sheet lobes ≥15 m in thickness. This distribution in lava flow morphology does not seem to be noticeably affected by the inferred distance to the source (based on the location of similar-composition dikes for each formation). Several mechanisms have been proposed to

  9. The basalts of Mare Frigoris

    Science.gov (United States)

    Kramer, G. Y.; Jaiswal, B.; Hawke, B. R.; Öhman, T.; Giguere, T. A.; Johnson, K.

    2015-10-01

    This paper discusses the methodology and results of a detailed investigation of Mare Frigoris using remote sensing data from Clementine, Lunar Prospector, and Lunar Reconnaissance Orbiter, with the objective of mapping and characterizing the compositions and eruptive history of its volcanic units. With the exception of two units in the west, Mare Frigoris and Lacus Mortis are filled with basalts having low-TiO2 to very low TiO2, low-FeO, and high-Al2O3 abundances. These compositions indicate that most of the basalts in Frigoris are high-Al basalts—a potentially undersampled, yet important group in the lunar sample collection for its clues about the heterogeneity of the lunar mantle. Thorium abundances of most of the mare basalts in Frigoris are also low, although much of the mare surface appears elevated due to contamination from impact gardening with the surrounding high-Th Imbrium ejecta. There are, however, a few regional thorium anomalies that are coincident with cryptomare units in the east, the two youngest mare basalt units, and some of the scattered pyroclastic deposits and volcanic constructs. In addition, Mare Frigoris lies directly over the northern extent of the major conduit for a magma plumbing system that fed many of the basalts that filled Oceanus Procellarum, as interpreted by Andrews-Hanna et al. (2014) using data from the Gravity Recovery and Interior Laboratory mission. The relationship between this deep-reaching magma conduit and the largest extent of high-Al basalts on the Moon makes Mare Frigoris an intriguing location for further investigation of the lunar mantle.

  10. Geomorphological characteristics of recent debris flows in the monogenic basaltic volcan of Red Mountain (Tenerife, Canary Islands, Spain); Caracteristicas geomorfologicas de los debris flows recientes del volcan basaltico monogenico de Montana Roja (Tenerife, Canarias, Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Doniz Paez, F. J.; Romero Ruiz, C.; Coello de la Plaza, E.; Criado, C.

    2009-07-01

    Debris flows are some of the remodelling processes that highly affect cinder cones. the formation of debris flows in Montana Roja volcano during an episode of heavy rain permitted us to evaluate the features characterising these forms. they present a diverse morphology, from simple linear debris, with only one channel and a lentil-shaped lobe, to complex debris of sinuous layouts, with several channels that bifurcate, and multi-lobular fronts. (Author) 4 refs.

  11. Lava channel formation during the 2001 eruption on Mount Etna: evidence for mechanical erosion

    CERN Document Server

    Ferlito, C; Ferlito, Carmelo; Siewert, Jens

    2005-01-01

    We report the direct observation of a peculiar lava channel that was formed near the base of a parasitic cone during the 2001 eruption on Mount Etna. Erosive processes by flowing lava are commonly attributed to thermal erosion. However, field evidence strongly suggests that models of thermal erosion cannot explain the formation of this channel. Here, we put forward the idea that the essential erosion mechanism was abrasive wear. By applying a simple model from tribology we demonstrate that the available data agree favorably with our hypothesis. Consequently, we propose that erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment.

  12. Seismic wave propagation through surface basalts - implications for coal seismic surveys

    Science.gov (United States)

    Sun, Weijia; Zhou, Binzhong; Hatherly, Peter; Fu, Li-Yun

    2010-02-01

    Seismic reflection surveying is one of the most widely used and effective techniques for coal seam structure delineation and risk mitigation for underground longwall mining. However, the ability of the method can be compromised by the presence of volcanic cover. This problem arises within parts of the Bowen and Sydney Basins of Australia and seismic surveying can be unsuccessful. As a consequence, such areas are less attractive for coal mining. Techniques to improve the success of seismic surveying over basalt flows are needed. In this paper, we use elastic wave-equation-based forward modelling techniques to investigate the effects and characteristics of seismic wave propagation under different settings involving changes in basalt properties, its thickness, lateral extent, relative position to the shot position and various forms of inhomogeneity. The modelling results suggests that: 1) basalts with high impedance contrasts and multiple flows generate strong multiples and weak reflectors; 2) thin basalts have less effect than thick basalts; 3) partial basalt cover has less effect than full basalt cover; 4) low frequency seismic waves (especially at large offsets) have better penetration through the basalt than high frequency waves; and 5) the deeper the coal seams are below basalts of limited extent, the less influence the basalts will have on the wave propagation. In addition to providing insights into the issues that arise when seismic surveying under basalts, these observations suggest that careful management of seismic noise and the acquisition of long-offset seismic data with low-frequency geophones have the potential to improve the seismic results.

  13. Probability encoding of hydrologic parameters for basalt. Elicitation of expert opinions from a panel of three basalt waste isolation project staff hydrologists

    International Nuclear Information System (INIS)

    The present study implemented a probability encoding method to estimate the probability distributions of selected hydrologic variables for the Cohassett basalt flow top and flow interior, and the anisotropy ratio of the interior of the Cohassett basalt flow beneath the Hanford Site. Site-speciic data for these hydrologic parameters are currently inadequate for the purpose of preliminary assessment of candidate repository performance. However, this information is required to complete preliminary performance assessment studies. Rockwell chose a probability encoding method developed by SRI International to generate credible and auditable estimates of the probability distributions of effective porosity and hydraulic conductivity anisotropy. The results indicate significant differences of opinion among the experts. This was especially true of the values of the effective porosity of the Cohassett basalt flow interior for which estimates differ by more than five orders of magnitude. The experts are in greater agreement about the values of effective porosity of the Cohassett basalt flow top; their estimates for this variable are generally within one to two orders of magnitiude of each other. For anisotropy ratio, the expert estimates are generally within two or three orders of magnitude of each other. Based on this study, the Rockwell hydrologists estimate the effective porosity of the Cohassett basalt flow top to be generally higher than do the independent experts. For the effective porosity of the Cohassett basalt flow top, the estimates of the Rockwell hydrologists indicate a smaller uncertainty than do the estimates of the independent experts. On the other hand, for the effective porosity and anisotropy ratio of the Cohassett basalt flow interior, the estimates of the Rockwell hydrologists indicate a larger uncertainty than do the estimates of the independent experts

  14. Probability encoding of hydrologic parameters for basalt. Elicitation of expert opinions from a panel of three basalt waste isolation project staff hydrologists

    Energy Technology Data Exchange (ETDEWEB)

    Runchal, A.K.; Merkhofer, M.W.; Olmsted, E.; Davis, J.D.

    1984-11-01

    The present study implemented a probability encoding method to estimate the probability distributions of selected hydrologic variables for the Cohassett basalt flow top and flow interior, and the anisotropy ratio of the interior of the Cohassett basalt flow beneath the Hanford Site. Site-speciic data for these hydrologic parameters are currently inadequate for the purpose of preliminary assessment of candidate repository performance. However, this information is required to complete preliminary performance assessment studies. Rockwell chose a probability encoding method developed by SRI International to generate credible and auditable estimates of the probability distributions of effective porosity and hydraulic conductivity anisotropy. The results indicate significant differences of opinion among the experts. This was especially true of the values of the effective porosity of the Cohassett basalt flow interior for which estimates differ by more than five orders of magnitude. The experts are in greater agreement about the values of effective porosity of the Cohassett basalt flow top; their estimates for this variable are generally within one to two orders of magnitiude of each other. For anisotropy ratio, the expert estimates are generally within two or three orders of magnitude of each other. Based on this study, the Rockwell hydrologists estimate the effective porosity of the Cohassett basalt flow top to be generally higher than do the independent experts. For the effective porosity of the Cohassett basalt flow top, the estimates of the Rockwell hydrologists indicate a smaller uncertainty than do the estimates of the independent experts. On the other hand, for the effective porosity and anisotropy ratio of the Cohassett basalt flow interior, the estimates of the Rockwell hydrologists indicate a larger uncertainty than do the estimates of the independent experts.

  15. Concentric cylinder viscometry at subliquidus conditions on Mauna Ulu lavas, Kilauea Volcano, Hawaii

    Science.gov (United States)

    Sehlke, A.; Robert, B.; Harris, A. J.; gurioli, L.; Whittington, A. G.

    2013-12-01

    The morphology of lava flows is controlled by the physical properties of the lava and its effusion rates, as well as environmental influences such as surface medium, slope and ambient temperature and pressure conditions. The important physical properties of lavas include viscosity (η), yield strength (σy), thermal diffusivity (κ) and heat capacity (CP), all of which strongly depend on temperature (T), composition (Χ), crystal fraction (φc) and vesicularity (φb). The crystal fraction (φc) typically increase as temperature decreases, and therefore is temperature dependent itself and influences the residual liquid composition (Χ). The rheological behavior of multi-phase lavas in lava flows is expressed as different flow types, forced from a smooth pahoehoe to a blocky ';a'a within a transition zone. Recent field studies of overflow units at the Muliwai a Pele lava flow erupted from Mauna Ulu in 1974 on Kilauea volcano (Hawaii) reveal a transition zone in a distance approximately 4.5 km from the vent as a result of a cooling gradient of 6 °C/km, crystallization rates of 0.05/km and a density increase from 1010 × 150 kg/m3 near to 1410 × 120 kg/m3 6 km distant from the vent due to degassing. Concentric cylinder viscometry under atmospheric conditions has been conducted in order to investigate the rheological response of crystal-liquid lava suspensions at different equilibrium temperatures for Mauna Ulu lavas. We detect first solid phases around 1230 °C being clinopyroxene, olivine and spinel, followed by plagioclase appearing as microlites as observed in natural rock samples. Measured apparent viscosities (ηapp) with applied strain rates between 50 s-1 and 0.3 s-1 at 1201 °C, 1192 °C and 1181 °C show a strong stress-strain rate dependency, classifying our 2-phase suspensions as Herschel-Bulkey fluids with an extrapolated apparent yield strength (τ0) around 200 to 150 Pa in presence of different crystal fractions, resulting in a 2.5 fold increase of

  16. Investigation of magnesium isotope fractionation during basalt differentiation: Implications for a chondritic composition of the terrestrial mantle

    Science.gov (United States)

    Teng, F.-Z.; Wadhwa, M.; Helz, R.T.

    2007-01-01

    To investigate whether magnesium isotopes are fractionated during basalt differentiation, we have performed high-precision Mg isotopic analyses by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) on a set of well-characterized samples from Kilauea Iki lava lake, Hawaii, USA. Samples from the Kilauea Iki lava lake, produced by closed-system crystal-melt fractionation, range from olivine-rich cumulates to highly differentiated basalts with MgO content ranging from 2.37 to 26.87??wt.%. Our results demonstrate that although these basalts have diverse chemical compositions, mineralogies, crystallization temperatures and degrees of differentiation, their Mg isotopic compositions display no measurable variation within the limits of our external precision (average ??26Mg = - 0.36 ?? 0.10 and ??25Mg = - 0.20 ?? 0.07; uncertainties are 2SD). This indicates that Mg isotopic fractionation during crystal-melt fractionation at temperatures of ??? 1055????C is undetectable at the level of precision of the current investigation. Calculations based on our data suggest that at near-magmatic temperatures the maximum fractionation in the 26Mg/24Mg ratio between olivine and melt is 0.07???. Two additional oceanic basalts, two continental basalts (BCR-1 and BCR-2), and two primitive carbonaceous chondrites (Allende and Murchison) analyzed in this study have Mg isotopic compositions similar to the Kilauea Iki lava lake samples. In contrast to a recent report [U. Wiechert, A.N. Halliday, Non-chondritic magnesium and the origins of the inner terrestrial planets, Earth and Planetary Science Letters 256 (2007) 360-371], the results presented here suggest that the Bulk Silicate Earth has a chondritic Mg isotopic composition. ?? 2007.

  17. Pyroxenite-derived Early Cretaceous lavas in the Liaodong Peninsula: Implication for metasomatism and thinning of the lithospheric mantle beneath North China Craton

    Science.gov (United States)

    Pang, Chong-Jin; Wang, Xuan-Ce; Xu, Yi-Gang; Wen, Shu-Nv; Kuang, Yong-Sheng; Hong, Lu-Bing

    2015-06-01

    The Xiaoling lavas, erupted at ca. 110 Ma in the Liaodong Peninsula, North China, provide vital constraints on the thermochemical state of subcontinental lithospheric mantle (SCLM) during the destruction of the craton. The Xiaoling lavas comprise basalt, andesite and dacite. They are characterized by depletion of high field strength elements (HFSE), enrichment of large ion lithophile elements (LILE) and EM1-like Sr-Nd isotopic compositions (εNd(t) = - 8.7--16.0; 87Sr/86Sri = 0.7046-0.7054), consistent with a derivation from the SCLM. With the exception of TiO2, the studied samples have major element compositions similar to those of experimentally determined partial melts of volatile-free Mid-Ocean-Ridge Basalt (MORB)-like eclogite at 3-5 GPa, but differ from anhydrous peridotite-derived melts. The olivine phenocrysts of the basaltic samples have high Ni and Fe/Mn, and low Ca contents, which are typical of the olivines crystallized from melts derived from a garnet pyroxenitic mantle source. This suggests that the Xiaoling lavas were derived from a pyroxenitic mantle source, which may have been formed by the solid-state reaction between recycled crustal materials and their surrounding peridotites. The presence of abundant amphibole phenocrysts in the Xiaoling lavas suggests a highly hydrated SCLM in this region. The high Rb/Sr but low initial 87Sr/86Sr ratios of the Xiaoling samples require a recent metasomatism in the mantle source, which is most likely related to the Pacific subduction. The genesis of the Xiaoling lavas therefore highlights the important role of water and Pacific subduction in the destruction of the North China Craton.

  18. Radiometric dating of bioalteration textures in Archean basaltic metaglasses

    International Nuclear Information System (INIS)

    Full text: Direct in-situ U-Pb dating of titanite which infills tubular bioalteration textures in pillow basalt rims from the ∼ 3.35 Ga Euro basalt of the Pilbara craton, W. Australia (PWA) confirms their Archean age. A novel in situ laser ablation multi-collector-ICP-MS technique is here reported that has enabled the first radiometric age determination of an Archean biosignature. Multiple lines of evidence suggest that these tubular bioalteration textures formed by microbial etching of formerly glassy Archean lavas that were subsequently mineralized by titanite. Firstly, there are striking morphological similarities between tubular structures from both the Pilbara and Barberton (BGB) cratons and bioalteration textures in modern glasses. Secondly, x-ray mapping indicates C enriched along the margins of the tubular structures from both the BGB and PWA. Thirdly, disseminated carbonates in the BGB pillow rims have C-isotopes depleted by as much as -16 %o, which is consistent with microbial oxidation of organic matter. A pre-metamorphic age for these microtubes is indicated by their segmentation caused by metamorphic chlorite overgrowths. A laser ablation spot size of ∼ 40 μm was used to analyze titanite in the 'root zones' at the centre of microtube clusters. Thirteen analyzes upon three thin sections gave a weighted average 206Pb/238U age of 2921 ± 110 Ma. This corresponds to the oldest metamorphic episode that has affected the PWA rocks and gives a minimum, late Archean age estimate for the bioalteration. (author)

  19. Basalt fiber reinforced polymer composites: Processing and properties

    Science.gov (United States)

    Liu, Qiang

    A high efficiency rig was designed and built for in-plane permeability measurement of fabric materials. A new data derivation procedure to acquire the flow fluid pattern in the experiment was developed. The measurement results of the in-plane permeability for basalt twill 31 fabric material showed that a high correlation exists between the two principal permeability values for this fabric at 35% fiber volume fraction. This may be the most important scientific contribution made in this thesis. The results from radial measurements corresponded quite well with those from Unidirectional (UD) measurements, which is a well-established technique. No significant differences in mechanical properties were found between basalt fabric reinforced polymer composites and glass composites reinforced by a fabric of similar weave pattern. Aging results indicate that the interfacial region in basalt composites may be more vulnerable to environmental damage than that in glass composites. However, the basalt/epoxy interface may have been more durable than the glass/epoxy interface in tension-tension fatigue because the basalt composites have significantly longer fatigue life. In this thesis, chapter I reviews the literature on fiber reinforced polymer composites, with concentration on permeability measurement, mechanical properties and durability. Chapter II discusses the design of the new rig for in-plane permeability measurement, the new derivation procedure for monitoring of the fluid flow pattern, and the permeability measurement results. Chapter III compares the mechanical properties and durability between basalt fiber and glass fiber reinforced polymer composites. Lastly, chapter IV gives some suggestions and recommendations for future work.

  20. 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.

  1. The paleointensity record of Icelandic subglacial volcanic glasses and recent lavas

    Science.gov (United States)

    Cromwell, G.; Tauxe, L.; Halldorsson, S. A.

    2013-05-01

    The Earth's ancient magnetic field can be approximated by a geocentric axial dipole (GAD) where the average field intensity is twice as strong at the poles than at the equator. The present day geomagnetic field, and some global paleointensity datasets, support the GAD hypothesis with a virtual axial dipole moment (VADM) of about 80 ZAm2 , which corresponds to surface field intensities of ~30 μT and 60 μT at the equator and poles, respectively. An astounding departure from the GAD hypothesis is found in Antarctica where the average field strength for 0-5 Ma (31.5 ± 2.4 μT, 78° S (1)) is equivalent to predictions at the Earth's equator. Proposed explanations for this decidedly non-GAD behavior at high southern latitudes include incomplete temporal sampling, effects from the tangent cylinder, and hemispheric asymmetry (especially at high latitudes). A comparison of Arctic and Antarctic paleointensity data over similar timescales might offer insights into the GAD field, however northern high latitude data comparable to the Antarctic collection are sparse due to the lack of young (0-5 Ma) and accessible lava flows. One exception is Iceland, a volcanic island on the Mid-Atlantic Ridge with continuous volcanism for the last ~15 Ma. Many of the paleointensity studies from Iceland target very young lavas (Holocene age) or transitional geomagnetic field states, both of which offer limited analysis of the long-term geomagnetic field. Additionally, some studies employ experimental methods that do not provide tests for alteration or other irreversible magnetic behaviors that can occur during multiple high temperature heating steps. We present a detailed collection of Icelandic paleointensity records from 85 volcanic units ranging in age from 1783 C.E. to ~4 Ma. We sample volcanic glass from flow tops and subglacially erupted volcanic units in order to collect single-domain magnetic material, which has been shown to accurately record magnetic field strength (2). Preliminary

  2. Origin of phenocrysts and compositional diversity in pre-Mazama rhyodacite lavas, Crater Lake, Oregon

    Science.gov (United States)

    Nakada, S.; Bacon, C.R.; Gartner, A.E.

    1994-01-01

    Phenocrysts in porphyritic volcanic rocks may originate in a variety of ways in addition to nucleation and growth in the matrix in which they are found. Porphyritic rhyodacite lavas that underlie the eastern half of Mount Mazama, the High Cascade andesite/dacite volcano that contains Crater Lake caldera, contain evidence that bears on the general problem of phenocryst origin. Phenocrysts in these lavas apparently formed by crystallization near the margins of a magma chamber and were admixed into convecting magma before eruption. About 20 km3 of pre-Mazama rhyodacite magma erupted during a relatively short period between ~400 and 500 ka; exposed pre-Mazama dacites are older and less voluminous. The rhyodacites formed as many as 40 lava domes and flows that can be assigned to three eruptive groups on the basis of composition and phenocryst content. -from Authors

  3. A detailed palaeomagnetic study of the oldest lava sequences in Northwest Iceland

    Energy Technology Data Exchange (ETDEWEB)

    Leo Kristjansson; Bjoern S. Hardarson; Haraldur Audunsson [University of Iceland, Reykjavik (Iceland). Science Institute

    2003-12-01

    We have determined the directions of primary remanence in over 400 lava flows in the northwestern peninsula of Iceland (near 66.1{sup o}N, 23.3{sup o}W). These lavas were sampled in 16 profiles spread across 75 km, at the stratigraphic level of the oldest (approximately 15 Myr in age) of several distinctive lignite-bearing sediments in the peninsula. We find that the pattern of polarity reversals in the lava pile is broadly similar in these profiles but it is generally not possible to trace short polarity zones and excursions over more than a few kilometres laterally. Our results, which also include measurements on the lignite sediments at three sites, are consistent with previous suggestions that these sediment beds represent a time gap of the order of 0.2 Myr between the lavas above and below. The mean virtual geomagnetic pole of this collection is 'far-sided' by approximately 7{sup o}, and the scatter of individual poles is greater than that in palaeomagnetic surveys on younger lava series in Iceland.

  4. Extended correlation of the Paleogene Faroe Islands and East Greenland plateau basalts

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin

    /204Pb = 17.59-18.30 while the High-Ti3 group has 206Pb/204Pb = 18.88-19.12. The three Faroese lava groups can be correlated with the East Greenland syn-breakup basalt formations using their geochemistry, lava morphology and phenocryst contents. The High-Ti1 group correlates with the Milne Land......-Ti1 and Milne Land Formation lavas have a higher content of most incompatible elements compared to High-Ti2 and Geikie Plateau Formation. This is unexpected because the Zr/Nb ratio indicates that the High-Ti2 and Geikie Plateau Formation lavas are formed by lower degrees of melting. An explanation may...... be that High-Ti1 and Milne Land Formation magmas fractionated significant amounts of clinopyroxene at the bottom of the crust before rising to higher crustal levels, whereas High-Ti2 and Geikie Plateau Formation magmas initially fractionated olivine at lower pressures....

  5. Verification and Validation Studies for the LAVA CFD Solver

    Science.gov (United States)

    Moini-Yekta, Shayan; Barad, Michael F; Sozer, Emre; Brehm, Christoph; Housman, Jeffrey A.; Kiris, Cetin C.

    2013-01-01

    The verification and validation of the Launch Ascent and Vehicle Aerodynamics (LAVA) computational fluid dynamics (CFD) solver is presented. A modern strategy for verification and validation is described incorporating verification tests, validation benchmarks, continuous integration and version control methods for automated testing in a collaborative development environment. The purpose of the approach is to integrate the verification and validation process into the development of the solver and improve productivity. This paper uses the Method of Manufactured Solutions (MMS) for the verification of 2D Euler equations, 3D Navier-Stokes equations as well as turbulence models. A method for systematic refinement of unstructured grids is also presented. Verification using inviscid vortex propagation and flow over a flat plate is highlighted. Simulation results using laminar and turbulent flow past a NACA 0012 airfoil and ONERA M6 wing are validated against experimental and numerical data.

  6. Intercomparison of gas emissions from the lava lakes of Nyiragongo and Nyamulagira, DR Congo

    Science.gov (United States)

    Bobrowski, Nicole; Calabrese, Sergio; Giuffrida, Giovanni; Scaglione, Sarah; Pandolfo, Francesco; Minani, Abel; Shamavu Mulumeoderhwa, Patient; Liotta, Marcello; Brusca, Lorenzo; D'Alessandro, Walter; Yalire, Mathiew; Arellano, Santiago; Galle, Bo; Tedesco, Dario

    2015-04-01

    From 25th of October to 5th of November 2014 field surveys were carried out at Nyiragongo and Nyamulagira volcanoes, DR Congo. These two volcanoes belong to the eight volcanoes in the Virunga volcanic chain. They have an altitude of about 3470 m.a.s.l. and 3060 m.a.s.l., respectively. The craters of the two volcanoes lie within a distance of less than 15 km and both have a diameter of about 1000 m and 2000 m, respectively showing a similar inner geometry containing several terraces inside. The lava lake of Nyamulagira is still under formation while Nyiragongo's lava lake is known since more than 100 years with short interruptions after the eruptions in 1977 and 2002. However, also Nyamulagira had a long period of lava lake activity, at least from 1912 to 1938. Both volcanoes are characterized by low SiO2 content of their lava, but Nyiragongo being exceptionally low in SiO2 and with significantly higher alkali content than Nyamulagira. There is a clear distinction between both lavas; a basaltic to tephritic one in the case of Nyamulagira and an often foidite one in the case of Nyiragongo. Also their volcanic activity has differed significantly during the last decades from each other. While Nyiragongo is famous for its permanent lava lake, Nyamulagira is characterized by frequent eruptions, which sum up to more than 40 since 1865. During our field survey we investigated and compared the gas composition and fluxes of both volcanoes in autumn 2014. The ground - based remote sensing technique - Multi Axis Differential Optical Absorption spectroscopy (MAX-DOAS) using scattered sunlight, the in-situ Multi-GAS-instrument, as well as active alkaline and particle traps have been simultaneously applied at each crater of the two volcanoes during the field trip. Downwind installed DOAS instruments (appendant to NOVAC (Network of Observation of Volcanic and Atmospheric Change)) were used to determine SO2 emission fluxes. Among others, bromine monoxide/sulphur dioxide (BrO/SO2

  7. Temperature dependence of basalt weathering

    Science.gov (United States)

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

    2016-06-01

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

  8. Ultramafic parent magmas for mare basalts

    International Nuclear Information System (INIS)

    Solidification products of basaltic magmas (fine grained basalts and ultramafic glasses) at the Apollo 15 site were examined. Consideration of simple MgO-6IO2-Al2O3 systematics plus results of calculations of fractional crystallization was reviewed. Suggestions are presented to account for the lack of correlation between the ultramafic glasses and basalts

  9. Re-Os isotopic systematics of primitive lavas from the Lassen region of the Cascade arc, California

    Science.gov (United States)

    Borg, L.E.; Brandon, A.D.; Clynne, M.A.; Walker, R.J.

    2000-01-01

    Rhenium-osmium isotopic systematics of primitive calc-alkaline lavas from the Lassen region appear to be controlled by mantle wedge processes. Lavas with a large proportion of slab component have relatively low Re and Os abundances, and have radiogenic Os and mid ocean ridge basalt-like Sr and Pb isotopic compositions. Lavas with a small proportion of slab component have higher Re and Os elemental abundances and display mantle-like Os, Sr, Nd, and Pb isotopic compositions. Assimilation with fractional crystallization can only generate the Re-Os systematics of the Lassen lavas from a common parent if the distribution coefficient for Re in sulfide is ~40-1100 times higher than most published estimates and if most incompatible element abundances decrease during differentiation. High Re/Os ratios in mid ocean ridge basalts makes subducted oceanic crust a potential source of radiogenic Os in volcanic arcs. The slab beneath the southernmost Cascades is estimated to have 187Os/188Os ratios as high as 1.4. Mixing between a slab component and mantle wedge peridotite can generate the Os isotopic systematics of the Lassen lavas provided the slab component has a Sr/Os ratio of ~7.5X105 and Os abundances that are 100-600 times higher than mid ocean ridge basalts. For this model to be correct, Os must be readily mobilized and concentrated in the slab component, perhaps as a result of high water and HCl fugacities in this subduction environment. Another possible mechanism to account for the correlation between the magnitude of the subduction geochemical signature and Os isotopic composition involves increasing the stability of an Os-bearing phase in mantle wedge peridotites as a result of fluxing with the slab component. Melting of such a source could yield low Os magmas that are more susceptible to crustal contamination, and hence have more radiogenic Os isotopic compositions, than magmas derived from sources with a smaller contribution from the slab. Thus, the addition of the

  10. Low-Ti basalts from the Faroe Islands constrain the early Iceland depleted plume component

    DEFF Research Database (Denmark)

    Søager, Nina; Holm, Paul Martin

    be an early version of the ID1 component but it could also be explained as a product of crustal contamination of the ID1 or DM components. The fact that NAEM seems to be a common component in lavas from all of the early NAIP (North Atlantic Igneous Province) and that it is also a mixing end...... magmas. However, 5 of the samples show signs of mixing with high-Ti melts. Although highly sensitive to crustal contamination, only little is detected in the low-Ti basalts. Isotopically the low-Ti basalts can be explained by mixing of the two end-members DM (the local depleted mantle as defined by the...

  11. Petrogenesis of Late Cenozoic basalts from North Hainan Island: Constraints from melt inclusions and their host olivines

    Science.gov (United States)

    Liu, Jian-Qiang; Ren, Zhong-Yuan; Nichols, Alexander R. L.; Song, Mao-Shuang; Qian, Sheng-Ping; Zhang, Yan; Zhao, Pei-Pei

    2015-03-01

    Melt inclusions and their host olivines in basaltic lavas provide important information about the nature of their mantle source. We present the first analyzed chemical data of olivine-hosted melt inclusions in Cenozoic basalts from the North Hainan Island and report the discovery of both tholeiitic and alkalic melt inclusions in a single rock sample. Cenozoic basalts from the Hainan Island are predominantly tholeiites with only small amounts of alkali basalts. There is a much broader compositional variation in melt inclusions than whole rocks. Compared to partial melts of mantle peridotite, the Hainan basalts have lower CaO, Na2O/TiO2, CaO/Al2O3 and Co/Fe, and higher TiO2, FeO∗, Fe/Mn, Zn/Fe and Zn/Mn. The olivine phenocrysts from the Hainan basalts contain lower Ca and Mn, and higher Ni and Fe/Mn than those of olivines crystallized from partial melts of peridotite. Projections from or towards olivine into the plane CS-MS-A for melt inclusions and whole rocks with MgO >7.5 wt% imply that the residual minerals in the source of the tholeiites are mainly clinopyroxene and garnet, possibly with some orthopyroxene, while in the source of the alkali basalts they are dominated by clinopyroxene and garnet. This indicates that a pyroxenite component could serve as the source lithology of the Hainan basalts. The OIB-like trace element compositions, with Ba, Sr, Nb and Ta positive anomalies, and Th and U negative anomalies, of the Hainan basalts suggest that a recycled oceanic crust component was involved in the source of the Hainan basalts. Based on a CMAS projection of primary magma compositions of the whole rocks and melt inclusions, we infer that a stage-2 silica-deficient pyroxenite derived from melt-peridotite reaction or mechanical mixing between recycled oceanic crust and peridotite can serve as the source lithology. Partial melts derived from such a source can match the overall compositions of the Hainan basalts better than those of MORB-eclogite and fertile

  12. Palaeomagnetism of the Upper Miocene- Lower Pliocene lavas from the East Carpathians: contribution to the paleosecular variation of geomagnetic field

    Science.gov (United States)

    Vişan, Mădălina; Panaiotu, Cristian G.; Necula, Cristian; Dumitru, Anca

    2016-03-01

    Investigations of the paleosecular variation of the geomagnetic field on geological timescales depend on globally distributed data sets from lava flows. We report new paleomagnetic results from lava flows of the East Carpathian Mountains (23.6°E, 46.4°N) erupted between 4 and 6 Ma. The average virtual geomagnetic pole position (76 sites) includes the North Geographic Pole and the dispersion of virtual geomagnetic poles is in general agreement with the data of the Time Averaged geomagnetic Field Initiative. Based on this study and previous results from the East Carpathians obtained from 0.04–4 Ma old lava flows, we show that high value of dispersion are characteristic only for 1.5–2.8 Ma old lava flows. High values of dispersion during the Matuyama chron are also reported around 50°N, in the global paleosecular variation data set. More data are needed at a global level to determine if these high dispersions reflect the behaviour of the geomagnetic field or an artefact of inadequate number of sites. This study of the East Carpathians volcanic rocks brings new data from southeastern Europe and which can contribute to the databases for time averaged field and paleosecular variation from lavas in the last 6 Ma.

  13. Palaeomagnetism of the Upper Miocene- Lower Pliocene lavas from the East Carpathians: contribution to the paleosecular variation of geomagnetic field.

    Science.gov (United States)

    Vişan, Mădălina; Panaiotu, Cristian G; Necula, Cristian; Dumitru, Anca

    2016-01-01

    Investigations of the paleosecular variation of the geomagnetic field on geological timescales depend on globally distributed data sets from lava flows. We report new paleomagnetic results from lava flows of the East Carpathian Mountains (23.6°E, 46.4°N) erupted between 4 and 6 Ma. The average virtual geomagnetic pole position (76 sites) includes the North Geographic Pole and the dispersion of virtual geomagnetic poles is in general agreement with the data of the Time Averaged geomagnetic Field Initiative. Based on this study and previous results from the East Carpathians obtained from 0.04-4 Ma old lava flows, we show that high value of dispersion are characteristic only for 1.5-2.8 Ma old lava flows. High values of dispersion during the Matuyama chron are also reported around 50°N, in the global paleosecular variation data set. More data are needed at a global level to determine if these high dispersions reflect the behaviour of the geomagnetic field or an artefact of inadequate number of sites. This study of the East Carpathians volcanic rocks brings new data from southeastern Europe and which can contribute to the databases for time averaged field and paleosecular variation from lavas in the last 6 Ma. PMID:26997549

  14. Os isotopes in hornblende-bearing intra-plate alkaline lavas (Central European Volcanic Province; CEVP)

    Science.gov (United States)

    Mayer, B.; Jung, S.; Brauns, M.; Pfänder, J.

    2013-12-01

    Previous Os isotope studies on CEVP lavas have shown that samples with the lowest Os isotopic composition (init. 187Os/188Os: 0.132-0.135) have the highest Os concentrations (70-93 ppt). These isotope ratios are higher than those usually proposed for the lithospheric upper mantle with inferred subchondritic 187Os/188Os ratios but are similar to 187Os/188Os ratios found in lithospheric peridotite xenoliths from the CEVP. Lower Os concentrations of other lavas from the CEVP (6-43 ppt) are correlated with radiogenic init. 187Os/188Os ratios up to 0.469 and are best explained by AFC processes involving lower crustal rocks. Fairly primitive samples of high-TiO2 alkaline hornblende-bearing lavas from the Rhön area (CEVP) with MgO up to 10.4 wt% have a large range in their Os isotopic composition (init. 187Os/188Os: 0.268-0.552; 15-30 ppt Os) exceeding the range observed in other intraplate basalts including OIB. Fractionated samples have distinctly more radiogenic Os (init. 187Os/188Os: up to 0.890; 3-10 ppt Os) isotopic compositions. For most samples, uniform Nd, Sr, and Pb isotope data are not consistent with AFC processes, hence, the radiogenic Os isotopic composition is also unlikely to result from assimilation processes alone. Some samples with radiogenic Os isotopic compositions and low Os concentrations have radiogenic 87Sr/86Sr, unradiogenic 143Nd/144Nd, and unradiogenic Pb isotope ratios suggesting contamination with crustal material in this case. Energy-constrained AFC calculations involving previously used hypothetical crustal endmembers show that for the majority of the hornblende-bearing lavas crustal contamination is unlikely. An alternative view would be that the mantle source of the hornblende-bearing lavas contains significant portions of non-peridoditic (i.e. pyroxenitic) material. Pyroxenites can have elevated Re/Os ratios and may evolve towards radiogenic Os isotopic compositions over time. New high-precision 40Ar-39Ar ages on hornblende from these

  15. Magmatic differentiation evidences of the basaltic floods of the Arapey formation:(Uruguay). Brief discussion obtained from the interpretation about some chemical analysis of mayor element

    International Nuclear Information System (INIS)

    Studying the data obtained from some chemical of mayor element, it is possible to define a general trend of magmatic differentiation of the basaltic floods of the Arapey Formation due to crystal-liquid fractionation in the magmatic chamber. The apparent chaos of the chemical composition of the lavas from the point of view of the chronostratigrafic position is explained using a petrogenetic model that tales in account the trends of variation diagrams. It is also demonstrated the inconsistency of the hypothesis of assimilation of eolic sandstone by the lavas as the process responsible for the variation in the chonostratigrafic sequence mentioned above. (author)

  16. Long term dismantling of a basaltic volcano (Piton des Neiges, La Réunion hotspot).

    Science.gov (United States)

    Chaput, Marie; Famin, Vincent; Michon, Laurent; Catry, Thibault

    2010-05-01

    We present a structural investigation of destabilization processes at the Piton des Neiges, the extinct volcano of La Reunion Island. We focus on the Cirque of Cilaos (a large erosional depression south of the volcano summit), where the exposed internal structure of Piton des Neiges is made of pahoehoe lava flows of the shield building stage (unknown thickness) and breccias (~1 km thick), covered by volcanic products of the differentiated stage (~1 km thick). The breccias contain only basic elements and consist in debris flows and debris avalanches deposits. Beddings in the debris flows and shear structures in the avalanche deposits indicate a runout in the direction 300°. We suggest that these breccias may represent the upper part of the Cap La Houssaye mass wasting events observed onshore and offshore on the western side of la Réunion (Bachèlery et al., 2003). The breccias display many indicators of brittle deformation, such as faults (normal and strike slip) and intrusions (dykes and sills). Fault data inversion allows to recognize two episodes of deformation. The first, older step of deformation is consistent with a minimum principal stress oriented N120. Intrusions related to this deformation are basic magmas of the shield building stage. The second, later stage of extension oriented N-S crosscuts the N120 deformation with intrusion compositions of the differentiated stage. These results show that the dismantling of Piton des Neiges proceeded in two ways: catastrophic episodic destabilization and slow internal deformation. During the shield-building stage, slow and rapid dismantling was occurring in the 300° direction in the studied area, whereas it evolved toward a N-S slow collapse during the differentiated stage of magmatic activity. This result fully agrees with a recent study carried out within debris avalanches deposits in the cirque of Salazie (north of Piton des Neiges summit) which attests that the northern flank of the Piton des Neiges has also

  17. LAVA (Los Alamos Vulnerability and Risk Assessment Methodology): A conceptual framework for automated risk analysis

    Energy Technology Data Exchange (ETDEWEB)

    Smith, S.T.; Lim, J.J.; Phillips, J.R.; Tisinger, R.M.; Brown, D.C.; FitzGerald, P.D.

    1986-01-01

    At Los Alamos National Laboratory, we have developed an original methodology for performing risk analyses on subject systems characterized by a general set of asset categories, a general spectrum of threats, a definable system-specific set of safeguards protecting the assets from the threats, and a general set of outcomes resulting from threats exploiting weaknesses in the safeguards system. The Los Alamos Vulnerability and Risk Assessment Methodology (LAVA) models complex systems having large amounts of ''soft'' information about both the system itself and occurrences related to the system. Its structure lends itself well to automation on a portable computer, making it possible to analyze numerous similar but geographically separated installations consistently and in as much depth as the subject system warrants. LAVA is based on hierarchical systems theory, event trees, fuzzy sets, natural-language processing, decision theory, and utility theory. LAVA's framework is a hierarchical set of fuzzy event trees that relate the results of several embedded (or sub-) analyses: a vulnerability assessment providing information about the presence and efficacy of system safeguards, a threat analysis providing information about static (background) and dynamic (changing) threat components coupled with an analysis of asset ''attractiveness'' to the dynamic threat, and a consequence analysis providing information about the outcome spectrum's severity measures and impact values. By using LAVA, we have modeled our widely used computer security application as well as LAVA/CS systems for physical protection, transborder data flow, contract awards, and property management. It is presently being applied for modeling risk management in embedded systems, survivability systems, and weapons systems security. LAVA is especially effective in modeling subject systems that include a large human component.

  18. Thermoluminescence dating of Hawaiian basalt

    Science.gov (United States)

    May, Rodd James

    1979-01-01

    The thermoluminescence (TL) properties of plagioclase separates from 11 independently dated alkalic basalts 4,500 years to 3.3 million years old and 17 tholeiitic basalts 16 years to 450,000 years old from the Hawaiian Islands were investigated for the purpose of developing a TL dating method for young volcanic rocks. Ratios of natural to artificial TL intensity, when normalized for natural radiation dose rates, were used to quantify the thermoluminescence response of individual samples for age-determination purposes. The TL ratios for the alkalic basalt plagioclase were found to increase with age at a predictable exponential rate that permits the use of the equation for the best-fit line through a plot of the TL ratios relative to known age as a TL age equation. The equation is applicable to rocks ranging in composition from basaltic andesite to trachyte over the age range from about 2,000 to at least 250,000 years before present (B.P.). The TL ages for samples older than 50,000 years have a calculated precision of less than :t 10 percent and a potential estimated accuracy relative to potassium-argon ages of approximately :t 10 percent. An attempt to develop a similar dating curve for the tholeiitic basalts was not as successful, primarily because the dose rates are on the average lower than those for the alkalic basalts by a factor of 6, resulting in lower TL intensities in the tholeiitic basalts for samples of equivalent age, and also because the age distribution of dated material is inadequate. The basic TL properties of the plagioclase from the two rock types are similar, however, and TL dating of tholeiitic basalts should eventually be feasible over the age range 10,000 to at least 200,000 years B.P. The average composition of the plagioclase separates from the alkalic basalts ranges from oligoclase to andesine; compositional variations within this range have no apparent effect on the TL ratios. The average composition of the plagioclase from the tholeiitic

  19. Guano mining in Kenyan lava tunnel caves

    OpenAIRE

    Jim W. Simons

    1998-01-01

    Commercial mining of bat guano for agricultural fertilizer only became possible in Kenya through discovery of major deposits in the lava tunnel caves of Mt. Suswa and the North Chyulu Hills in the early 1960’s. This paper provides historical information leading up to the guano mining, describes the cave deposits, outlines the mining under-takings, and provides information on the guano producing bats and insect faunas. The results of guano analyses, details of the tonnages extracted and sold t...

  20. Kilauea Iki lava lake experiment plans

    Energy Technology Data Exchange (ETDEWEB)

    Dunn, J.C.; Hills, R.G.

    1981-01-01

    Twelve experimental studies are proposed to complete field laboratory work at Kilauea Iki lava lake. Of these twelve experiments, eleven do not require the presence of melt. Some studies are designed to use proven techniques in order to expand our existing knowledge, while others are designed to test new concepts. Experiments are grouped into three main categories: geophysics, energy extraction, and drilling technology. Each experiment is described in terms of its location, purpose, background, configuration, operation, and feasibility.

  1. Petrology of gabbroic xenoliths in 1960 Kilauea basalt: crystalline remnants of prior (1955) magmatism

    Science.gov (United States)

    Fodor, R.V.; Moore, R.B.

    1994-01-01

    The 1960 Kapoho lavas of Kilauea's east rift zone contain 1-10 cm xenoliths of olivine gabbro, olivine gabbro-norite, and gabbro norite. Textures are poikilitic (ol+sp+cpx in pl) and intergranular (cpx+pl??ol??opx). Poikilitic xenoliths, which we interpret as cumulates, have the most primitive mineral compositions, Fo82.5, cpx Mg# 86.5, and An80.5. Many granular xenoliths (ol and noritic gabbro) contain abundant vesicular glass that gives them intersertal, hyaloophitic, and overall 'open' textures to suggest that they represent 'mush' and 'crust' of a magma crystallization environment. Their phase compositions are more evolved (Fo80-70, cpx Mg# 82-75, and An73-63) than those of the poikilitic xenoliths. Associated glass is basaltic, but evolved (MgO 5 wt%; TiO2 3.7-5.8 wt%). The gabbroic xenolith mineral compositions fit existing fractional crystallization models that relate the origins of various Kilauea lavas to one another. FeO/MgO crystal-liquid partitioning is consistent with the poikilitic ol-gabbro assemblage forming as a crystallization product from Kilauea summit magma with ???8 wt% MgO that was parental to evolved lavas on the east rift zone. For example, least squares calculations link summit magmas to early 1955 rift-zone lavas (???5 wt% MgO) through ???28-34% crystallization of the ol+sp+cpx+pl that comprise the poikilitic ol-gabbros. The other ol-gabbro assemblages and the olivine gabbro-norite assemblages crystallized from evolved liquids, such as represented by the early 1955 and late 1955 lavas (???6.5 wt% MgO) of the east rift zone. The eruption of 1960 Kapoho magmas, then, scoured the rift-zone reservoir system to entrain portions of cumulate and solidification zones that had coated reservoir margins during crystallization of prior east rift-zone magmas. ?? 1994 Springer-Verlag.

  2. Terrestrial analogs to lunar sinuous rilles - Kauhako Crater and channel, Kalaupapa, Molokai, and other Hawaiian lava conduit systems

    International Nuclear Information System (INIS)

    Two source vents, one explosive and one effusive erupted to form a cinder cone and low lava shield that together compose the Kalaupapa peninsula of Molokai, Hawaii, A 50-100-m-wide channel/tube system extends 2.3 km northward from kauhako crater in the center of the shield. Based on modeling, a volume of up to about 0.2 cu km of lava erupted at a rate of 260 cu m/sec to flow through the Kauhako conduit system in one of the last eruptive episodes on the peninsula. Channel downcutting by thermal erosion occurred at a rate of about 10 micron/sec to help form the 30-m-deep conduit. Two smaller, secondary tube systems formed east of the main lava channel/tube. Several other lava conduit systems on the islands of Oahu and Hawaii were also compared to the Kauhako and lunar sinuous rille systems. These other lava conduits include Whittington, Kupaianaha, and Mauna Ulu lava tubes. Morphologically, the Hawaiian tube systems studied are very similar to lunar sinuous rilles in that they have deep head craters, sinuous channels, and gentle slopes. Thermal erosion is postulated to be an important factor in the formation of these terrestrial channel systems and by analogy is inferred to be an important process involved in the formation of lunar sinuous rilles. 28 refs

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

    Science.gov (United States)

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

    1983-01-01

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

  4. Iron isotope fractionation during magmatic differentiation in Kilauea Iki lava lake

    Science.gov (United States)

    Teng, F.-Z.; Dauphas, N.; Helz, R.T.

    2008-01-01

    Magmatic differentiation helps produce the chemical and petrographic diversity of terrestrial rocks. The extent to which magmatic differentiation fractionates nonradiogenic isotopes is uncertain for some elements. We report analyses of iron isotopes in basalts from Kilauea Iki lava lake, Hawaii. The iron isotopic compositions (56Fe/54Fe) of late-stage melt veins are 0.2 per mil (???) greater than values for olivine cumulates. Olivine phenocrysts are up to 1.2??? lighter than those of whole rocks. These results demonstrate that iron isotopes fractionate during magmatic differentiation at both whole-rock and crystal scales. This characteristic of iron relative to the characteristics of magnesium and lithium, for which no fractionation has been found, may be related to its complex redox chemistry in magmatic systems and makes iron a potential tool for studying planetary differentiation.

  5. Comments on "Deccan flood basalts at the Cretaceous/Tertiary boundary?" by V. Courtillot, J. Besse, D. Vandamme, R. Montigny, J.-J. Jaeger and H. Cappetta

    OpenAIRE

    Wensink, H.

    1987-01-01

    The age of the flood basalts of the Deccan area and the length of the interval during which the outpourings took place are not known precisely. The authors have tried to date those basalts and estimate how long the volcanic activity lasted: on the basis of new paleomagnetic, paleontological and geochronological data of the Deccan effusives they came to the preliminary conclusion that the volcanic activity may have lasted less than 1 Ma and that the majority of the lavas poured out during chro...

  6. Plume composition changes during the birth of a new lava lake - Nyamulagira volcano, DR Congo

    Science.gov (United States)

    Bobrowski, Nicole; Giuffrida, Giovanni Bruno; Calabrese, Sergio; Scaglione, Sarah; Yalire, Mathieu; Liotta, Marcello; Brusca, Lorenzo; Arellano, Santiago; Rüdiger, Julian; Galle, Bo; Castro, Jonathan; Tedesco, Dario

    2016-04-01

    Nyamulagira, in the Virunga Volcanic Province (VVP), Democratic Republic of Congo, is one of the most active volcanoes in Africa. The volcano is located about 25 km north-northwest of Lake Kivu in the Western Branch of the East African Rift System (EARS) with a distance of only 15 km to Nyiragongo, which is well known for its decades-old active lava lake. Nyamulagira is a shield volcano with a 3058 m high and ~2000 m wide summit caldera. The volcano is characterized by frequent eruptions, which occur both from the summit crater and from the flanks (31 flank eruptions over the last 110 years). Due to the low viscosity lava, although significantly higher than the one of Nyiragongo, wide lava fields cover over 1100 km2 and lava flows often reach > 20 km length. More than 100 flank cones can be counted around the summit crater. A part from its frequent eruptions Nyamulagira had a long period of lava lake activity in the past, at least from 1912 to 1938. During the past decades, gas emissions from Nyamulagira have been only reported during eruptions. This changed in 2012, however, when Nyamulagira began emitting a persistent gas plume above its crater. By the end of 2014, and beginning in 2015, a lava lake was born, a feature that - as of the time of this writing - is still growing. To date, very little is known about gas emissions of Nyamulagira volcano with the only exception for SO2. Very few studies have been conducted regarding the volatile chemistry of Nyamulagira. We try to fill this gap by reporting gas composition measurements of Nyamulagira's volcanic plume during the birth of the lava lake, and in the first year of the lake's activity. Two field surveys have been carried out, the first one on November 1st, 2014 and the second one October 13th - 15th, 2015. Applying the broad toolbox of volcanic gas composition measurement techniques offered us the opportunity to characterize Nyamulagira's plume in excruciating detail. Nyamulagira is known to be a significant

  7. A mantle plume beneath California? The mid-Miocene Lovejoy Flood Basalt, northern California

    Science.gov (United States)

    Garrison, N.J.; Busby, C.J.; Gans, P.B.; Putirka, K.; Wagner, D.L.

    2008-01-01

    The Lovejoy basalt represents the largest eruptive unit identified in California, and its age, volume, and chemistry indicate a genetic affinity with the Columbia River Basalt Group and its associated mantle-plume activity. Recent field mapping, geochemical analyses, and radiometric dating suggest that the Lovejoy basalt erupted during the mid-Miocene from a fissure at Thompson Peak, south of Susanville, California. The Lovejoy flowed through a paleovalley across the northern end of the Sierra Nevada to the Sacramento Valley, a distance of 240 km. Approximately 150 km3 of basalt were erupted over a span of only a few centuries. Our age dates for the Lovejoy basalt cluster are near 15.4 Ma and suggest that it is coeval with the 16.1-15.0 Ma Imnaha and Grande Ronde flows of the Columbia River Basalt Group. Our new mapping and age dating support the interpretation that the Lovejoy basalt erupted in a forearc position relative to the ancestral Cascades arc, in contrast with the Columbia River Basalt Group, which erupted in a backarc position. The arc front shifted trenchward into the Sierran block after 15.4 Ma. However, the Lovejoy basalt appears to be unrelated to volcanism of the predominantly calc-alkaline Cascade arc; instead, the Lovejoy is broadly tholeiitic, with trace-element characteristics similar to the Columbia River Basalt Group. Association of the Lovejoy basalt with mid-Miocene flood basalt volcanism has considerable implications for North American plume dynamics and strengthens the thermal "point source" explanation, as provided by the mantle-plume hypothesis. Alternatives to the plume hypothesis usually call upon lithosphere-scale cracks to control magmatic migrations in the Yellowstone-Columbia River basalt region. However, it is difficult to imagine a lithosphere-scale flaw that crosses Precambrian basement and accreted terranes to reach the Sierra microplate, where the Lovejoy is located. Therefore, we propose that the Lovejoy represents a rapid

  8. Further Constraints for the Pliocene Geomagnetic Field Strength: Case Study of Los Tuxtlas Basalts (Mexico)

    Science.gov (United States)

    Alva-Valdivia, L.; Goguitchaichvili, A.; Urrutia-Fucugauchi, J.

    2001-05-01

    A rock-magnetic, paleomagnetic and paleointensity study was carried out on Pliocene volcanic formations from Los Tuxtlas (Trans Mexicain Volcanic Belt) in order to obtain some decisive constraints for the geomagnetic field strength during Pliocene time. Age of the volcanic units lies between 3.1 and 0.8 Ma according to available radiometric data. Thermomagnetic investigations reveal that remanence is carried in most cases by Ti-poor titanomagnetite, resulting of oxy-exsolution, which probably occurred during the initial flow cooling. Unblocking temperature spectra and relatively high coercivity, point to 'small' pseudo-single domain magnetic grains for these (titano)magnetites. Single-component, linear demagnetization plots were observed in most cases. Six sites yield reverse polarity magnetization, 5 are normally magnetized and one unit shows intermediate polarity magnetization. An evidence of strong lightning-produced magnetization overprint was detected for one site. The mean paleodirection obtained in this study is I=31.3?, D=352?, k=36, a95=8.2, N=10, which is not significantly different from the expected direction estimated from the North American apparent polar wander path. 39 samples were pre-selected for Thellier palaeointensity experiments because of their stable remanent magnetization. Only 21 samples, coming from 4 individual basaltic lava flows, yielded reliable paleointensity estimates with the flow-mean virtual dipole moments (VDM) ranging from 6.4 to 9.1 x1022 Am2. Although our results are not numerous, some credit should be given because of good technical quality determination, attested by the reasonably high Coe et al's quality factors. Combination of Mexican data with the available comparable quality Pliocene paleointensity results yield a mean VDM of 6.2 x 1022 Am2, which is 79 percent of the present geomagnetic axial dipole (7.8 x 1022 Am2 after Barton et al., 1996). Reliable paleointensity results for the last 5 My is still very scarce and

  9. A deterministic methodology for prediction of fracture distribution in basaltic multiflows

    Science.gov (United States)

    Lore, Jason; Aydin, Atilla; Goodson, Kenneth

    2001-04-01

    The fracture distribution in basalt flows is a direct result of thermal processes. Thus basalt flows present a unique opportunity to characterize a nearly perfect deterministic system with its fundamental physical parameters. Fracture distribution data collected on cliff exposures of basalt flows near the Idaho National Engineering and Environmental Laboratory (INEEL) are combined with calculations of cooling rate and temperature distribution from a finite element model to construct a predictive methodology for fracture spacing. The methodology is based on an empirical power law relationship between inverse cooling rate and fracture spacing. The methodology may be applied to unexposed basalt flows of approximately elliptical cross section whose thickness and width are constrained only by geophysical or borehole data if sufficient fracture data on nearby exposed flows are available. The methodology aids waste remediation efforts at sites involving contaminant transport through fractured basalt, such as the INEEL and the Hanford site in Washington, as well as involving transport and fluid flow through volcanic or intrusive rocks where thermal processes are responsible for fracturing.

  10. Petrogenesis of mafic magmatism in Arabia-Eurasia collision zone: valley filling flows in Armenia

    Science.gov (United States)

    Meliksetian, Khachatur; Neill, Iain; Allen, Mark; Navasardyan, Gevorg

    2015-04-01

    The Turkish- Armenian-Iranian orogenic plateau grew after the Middle Miocene following the initial Paleogene Arabia- Eurasia collision. It is widely accepted, that uplift of the plateau is related to break-off of the southern Neo-Tethys slab beneath the Bitlis-Zagros Suture at ~15-10 Ma, coupled with continued plate convergence and regional crustal shortening. Since this time there has also been a widespread mantle-derived collision magmatism over large parts of NW Iran, Eastern Anatolia and the Lesser Caucasus, potentially hundreds of kilometres from the site of southern Neo-Tethys slab break-off, >10 Myr after the proposed break-off event. Detailed wholer rock geochemistry and Sr-Nd-Pb-Hf isotope data are presented for ~2.5 Ma trachy-basalt to trachy-basaltic andesite lavas erupted in Armenia in the South Caucasus. These thick (up to 400 m) mafic flows generated several plateaux within the Lesser Caucasus: the Javakheti Plateau (S Georgia and NW Armenia), and the Lori and Kotayk Plateaux (Armenia). These basalts sequences also extend to the NE Kars-Erzurum Plateau in eastern Turkey. It is demonstrated that studied series formed by Iranian Plateau, have Th/La ratios ≤ 0.2, much lower than the value of ~0.3 for continental crust, so infra-crustal recycling and/or lower crustal delamination are certainly required to produce andesitic high-Th/La bulk continental crust.

  11. Compositional variation within thick (>10 m) flow units of Mauna Kea Volcano cored by the Hawaii Scientific Drilling Project

    Science.gov (United States)

    Huang, Shichun; Vollinger, Michael J.; Frey, Frederick A.; Rhodes, J. Michael; Zhang, Qun

    2016-07-01

    Geochemical analyses of stratigraphic sequences of lava flows are necessary to understand how a volcano works. Typically one sample from each lava flow is collected and studied with the assumption that this sample is representative of the flow composition. This assumption may not be valid. The thickness of flows ranges from 100 m. Geochemical heterogeneity in thin flows may be created by interaction with the surficial environment whereas magmatic processes occurring during emplacement may create geochemical heterogeneities in thick flows. The Hawaii Scientific Drilling Project (HSDP) cored ∼3.3 km of basalt erupted at Mauna Kea Volcano. In order to determine geochemical heterogeneities in a flow, multiple samples from four thick (9.3-98.4 m) HSDP flow units were analyzed for major and trace elements. We found that major element abundances in three submarine flow units are controlled by the varying proportion of olivine, the primary phenocryst phase in these samples. Post-magmatic alteration of a subaerial flow led to loss of SiO2, CaO, Na2O, K2O and P2O5, and as a consequence, contents of immobile elements, such as Fe2O3 and Al2O3, increase. The mobility of SiO2 is important because Mauma Kea shield lavas divide into two groups that differ in SiO2 content. Post-magmatic mobility of SiO2 adds complexity to determining if these groups reflect differences in source or process. The most mobile elements during post-magmatic subaerial and submarine alteration are K and Rb, and Ba, Sr and U were also mobile, but their abundances are not highly correlated with K and Rb. The Ba/Th ratio has been used to document an important role for a plagioclase-rich source component for basalt from the Galapagos, Iceland and Hawaii. Although Ba/Th is anomalously high in Hawaiian basalt, variation in Ba abundance within a single flow shows that it is not a reliable indicator of a deep source component. In contrast, ratios involving elements that are typically immobile, such as La/Nb, La

  12. The emplacement of pahoehoe lavas on Kilauea and in the Deccan Traps

    Indian Academy of Sciences (India)

    H C Sheth

    2006-12-01

    There is a growing interest in deciphering the emplacement and environmental impact of flood basalt provinces such as the Deccan, India. Observations of active volcanism lead to meaningful interpretations of now-extinct volcanic systems. Here, I illustrate and discuss the morphology and emplacement of the modern and active lava flows of Kilauea volcano in Hawaii, and based on them, interpret the compound pahoehoe lavas of the Deccan Traps. The latter are vastly larger (areally extensive and voluminous) than Kilauea flows, and yet, their internal architecture is the same as that of Kilauea flows, and even the sizes of individual flow units often identical. Many or most compound flows of the Deccan Traps were emplaced in a gentle, effusive, Kilauea-like fashion. Bulk eruption rates for the Deccan province are unknown, and were probably high, but the local eruption rates of the compound flows were no larger than Kilauea’s. Large (≥ 1000 km3) individual compound pahoehoe flows in the Deccan could have been emplaced at Kilauea-like local eruption rates (1 m3/sec per metre length of fissure) in a decade or less, given fissures of sufficient length (tens of kilometres), now exposed as dyke swarms in the province.

  13. Mantle amphibole control on arc and within-plate chemical signatures: Quaternary lavas from Kurdistan Province, Iran

    Science.gov (United States)

    Kheirkhah, M.; Allen, M. B.; Neill, I.; Emami, M. H.; McLeod, C.

    2012-04-01

    New analyses of Quaternary lavas from Kurdistan Province in west Iran shed light on the nature of collision zone magmatism. The rocks are from the Turkish-Iranian plateau within the Arabia-Eurasia collision. Compositions are typically basanite, hawaiite and alkali basalt. Sr-Nd isotope values are close to BSE, which is similar to Quaternary alkali basalts of NW Iran, but distinct from a depleted source melting under Mount Ararat. The chemical signatures suggests variable melting of two distinct sources. One inferred source produced melts with La/Nb from~3.5 to~1.2, which we model as the result of depletion of amphibole during ≤1% melting in the garnet stability field. We infer phlogopite in the source of potassic lavas from Takab. Lithosphere delamination or slab break-off mechanisms for triggering melting are problematic, as the lithosphere is~150-200km thick. It is possible that the negative dT/dP section of the amphibole peridotite solidus was crossed as a result of lithospheric thickening in the collision zone. This explanation is conditional upon the mantle source being weakly hydrated and so only containing a small proportion of amphibole, which can be exhausted during small degrees of partial melting. Our model maybe viable for other magmatic areas within orogenic plateaux, e.g. northern Tibet. Depletion of mantle amphibole may also help explain larger scale transitions from arc to within-plate chemistry in orogens, such as the Palaeogene Arabia-Eurasia system.

  14. Experimental Melting Study of Basalt-Peridotite Hybrid Source: Melting model of Hawaiian plume

    Science.gov (United States)

    Takahashi, E.; Gao, S.

    2015-12-01

    Eclogite component entrained in ascending plume is considered to be essentially important in producing flood basalts (e.g., Columbia River basalt, Takahashi et al., 1998 EPSL), alkalic OIBs (e.g., Kogiso et al.,2003), ferro-picrites (Tuff et al.,2005) and Hawaiian shield lavas (e.g., Hauri, 1996; Takahashi & Nakajima, 2002, Sobolev et al.,2005). Size of the entrained eclogite, which controls the reaction rates with ambient peridotite, however, is very difficult to constrain using geophysical observation. Among Hawaiian shield volcanoes, Koolau is the most enriched end-member in eclogite component (Frey et al, 1994). Reconstruction of Koolau volcano based on submarine study on Nuuanu landslide (AGU Monograph vol.128, 2002, Takahashi Garcia Lipman eds.) revealed that silica-rich tholeiite appeared only at the last stage (Makapuu stage) of Koolau volcano. Chemical compositions of lavas as well as isotopes change abruptly and coherently across a horizon (Shinozaki et al. and Tanaka et al. ibid.). Based on these observation, Takahashi & Nakajima (2002 ibid) proposed that the Makapuu stage lava in Koolau volcano was supplied from a single large eclogite block. In order to study melting process in Hawaiian plume, high-pressure melting experiments were carried out under dry and hydrous conditions with layered eclogite/peridotite starting materials. Detail of our experiments will be given by Gao et al (2015 AGU). Combined previous field observation with new set of experiments, we propose that variation in SiO2 among Hawaiian tholeiites represent varying degree of wall-rock interaction between eclogite and ambient peridotite. Makapuu stage lavas in Koolau volcano represents eclogite partial melts formed at ~3 GPa with various amount of xenocrystic olivines derived from Pacific plate. In other words, we propose that "primary magma" in the melting column of Hawaiian plume ranges from basaltic andesite to ferro-picrite depending on the lithology of the source. Solidus of

  15. Petrology and geochronology of lavas from Ka'ula Volcano: Implications for rejuvenated volcanism of the Hawaiian mantle plume

    Science.gov (United States)

    Garcia, Michael O.; Weis, Dominique; Jicha, Brian R.; Ito, Garrett; Hanano, Diane

    2016-07-01

    Marine surveying and submersible sampling of Ka'ula Volcano, located 100 km off the axis of the Hawaiian chain, revealed widespread areas of young volcanism. New 40Ar/39Ar and geochemical analyses of the olivine-phyric submarine and subaerial volcanic rocks show that Ka'ula is shrouded with 1.9-0.5 Ma alkalic basalts. The ages and chemistry of these rocks overlap with rejuvenated lavas on nearby, northern Hawaiian Island shields (Ni'ihau, Kaua'i and South Kaua'i Swell). Collectively, these rejuvenated lavas cover a vast area (∼7000 km2), much more extensive than any other area of rejuvenated volcanism worldwide. Ka'ula rejuvenated lavas range widely in alkalinity and incompatible element abundances (e.g., up to 10× P2O5 at a given MgO value) and ratios indicating variable degrees of melting of a heterogeneous source. Heavy REE elements in Ka'ula lavas are pinned at a mantle normalized Yb value of 10 ± 1, reflecting the presence of garnet in the source. Trace element ratios indicate the source also contained phlogopite and an Fe-Ti oxide. The new Ka'ula ages show that rejuvenated volcanism was nearly coeval from ∼0.3 to 0.6 Ma along a 450 km segment of the Hawaiian Islands (from West Maui to north of Ka'ula). The ages and volumes for rejuvenated volcanism are inconsistent with all but one geodynamic melting model proposed to date. This model advocates a significant contribution of pyroxenite to rejuvenated magmas. Analyses of olivine phenocryst compositions suggest a major (33-69%) pyroxenite component in Ka'ula rejuvenated lavas, which correlates positively with radiogenic Pb isotope ratios for Ka'ula. This correlation is also observed in lavas from nearby South Kaua'i lavas, as was reported for Atlantic oceanic islands. The presence of pyroxenite in the source may have extended the duration and volume of Hawaiian rejuvenated volcanism.

  16. Inventario y clasificación de manifestaciones basálticas de Patagonia mediante imágenes satelitales y SIG, Provincia de Santa Cruz Inventory and classification of basaltic occurrences of Patagonia based on satellite images and G.I.S, province of Santa Cruz

    Directory of Open Access Journals (Sweden)

    Elizabeth Mazzoni

    2010-06-01

    Full Text Available Las mesetas basálticas constituyen un rasgo típico del paisaje patagónico. Su génesis está vinculada a derrames de lavas máficas que se produjeron en distintos períodos efusivos durante el Terciario y Cuaternario. De acuerdo a su edad, la morfología de los mantos lávicos ha sido modificada por diferentes procesos erosivos. Las coladas más antiguas han quedado sobreelevadas decenas a centenas de metros por procesos de inversión del relieve. En la zona de contacto entre el manto basáltico y la roca subyacente se originan manantiales que brindan un aporte de agua extra al ambiente patagónico extracordillerano, favoreciendo el desarrollo de pastizales húmedos (mallines que constituyen un recurso natural de alto valor económico, ecológico y escénico. Con el fin de contar con una herramienta que permita evaluar su importancia hidrológica, se llevó a cabo un inventario de estas formas volcánicas en la provincia de Santa Cruz, Argentina. Para ello se aplicaron técnicas de procesamiento digital e interpretación visual de imágenes satelitales de mediana resolución espacial. Los resultados se expresaron cartográficamente y mediante bases de datos, integrándose la información en un entorno S.I.G. Los datos obtenidos para cada campo volcánico, referidos a aspectos topográficos, geológicos y geomorfológicos, superficie del campo lávico y presencia de mallines en sus laderas y áreas próximas, fueron analizados estadísticamente. La información así generada permitió obtener una caracterización general de estas formas del paisaje y diseñar un sistema de clasificación, además de corroborar su importancia en la localización y desarrollo de los mallines.Basaltic plateaus are a typical feature of the Patagonian landscape. Their origin is associated with basaltic flows that took place in different effusive periods of the Tertiary and Quaternary. According to the age, morphology of the different lava fields has been modified

  17. Fracture Analysis of the Ribeirao Preto Basalts, SP: Application for Developing a Conceptual Hydrogeological Model

    Directory of Open Access Journals (Sweden)

    Amélia João Fernandes

    2011-12-01

    Full Text Available The study of the physical geology and geochemistry of the Ribeirão Preto basalts was part of a hydrogeologicalresearch, which aimed to investigate the recharge of the Guarani Aquifer System (SAG through the basalts of the SerraGeral Aquifer (ASG, a project shortly named FRATASG. In addition to the hydrogeological research, a detailed geologicalinvestigation was conducted to develop a conceptual model of groundwater fl ow in complex aquifers, as is the case ofthe fractured basalts of the ASG. Therefore, this study included a thorough structural survey and analysis of horizontaland subvertical fractures, which resulted in the identifi cation of four tectonic events. It was concluded that the verticalgroundwater flow is important up to 10 m in depth and, secondarily, up to 25 m. Horizontal fl ow, more evident up to thedepth of 50 m, predominates and occurs along sub-horizontal fractures, which occur mainly at the contact between basalts2 and 3 and in its vicinity. Because the great majority of subvertical fractures do not propagate into the vesicular layers,which occur at the basalt contacts, it is suggested that these layers act as regional hydraulic barriers, and greatly hamperthe recharge of the SAG through the ASG. As a consequence, groundwater flow in the basalt stack is of stratabound type,as it occurs mainly along the basalt contacts. Based on diagnostic features of the fl ow, it is proposed in this study that the vertical flow,which crosses the basalt stack reaching the SAG, is local and probably occurs along NE structures.

  18. Recent Radar Imaging Observations of the Moon: New Views of Pyrocastics, Mare Basalts, Impact Crater Deposits, and the Lunar Subsurface

    Science.gov (United States)

    Carter, L. M.; Campbell, B. A.; Morgan, G. A.; Ghent, R. R.; Neish, C. D.

    2016-05-01

    In the last decade, radars with different wavelengths have provided polarimetric imaging of the lunar surface. These data sets have yielded new information about topics such as pyroclastics, mare basalts, cryptomare, and impact ejecta and melt flows.

  19. Pressure Analysis for LAVA-OVEN

    Science.gov (United States)

    Cendana, Donna Q.

    2014-01-01

    The Lunar Advanced Volatiles Analysis (LAVA) and the Oxygen Volatiles Extraction Node (OVEN) are subsystems included in the Regolith Environment Science, and Oxygen Lunar Volatiles Extraction (RESOLVE) payload bound for the Moon in 2019. This Resource Prospector Mission (RPM) has the objective of landing on a shadowed region of the Moons South Pole to collect data and determine whether the resources could be effectively used for space exploration systems. The quantification of the resources will help understand if it can adequately minimize materials carried from Earth by: providing life support, propellants, construction materials or energy supply to the payload or crew. This paper outlines the procedures done for the pressure analysis of the LAVA-OVEN (LOVEN) Integration Testing. The pressure analysis quantifies how much gases and water are present in the sample tested during the Engineering Testing Unit (ETU) phase of instrument development. Ultimately the purpose of these tests is to improve the estimate of the amount of water in each Lunar sample and reduce the time necessary for this estimate. The governing principle that was used for the analysis is the Ideal Gas Law, PV=nRT where P stands for pressure, V for volume, n for number of moles, R being the gas constant and T for temperature. We also estimate the errors involved in these measured and derived quantities since a key objective of the mission is to estimate the quantity of volatiles present in the lunar samples introduced into OVEN.

  20. Gem-bearing basaltic volcanism, Barrington, New South Wales: Cenozoic evolution, based on basalt K-Ar ages and zircon fission track and U-Pb isotope dating

    International Nuclear Information System (INIS)

    Based on basalt K-Ar and zircon fission track dating, Barrington shield volcano was active for 55 million years. Activity in the northeast, at 59 Ma, preceded more substantial activity between 55 and 51 Ma and more limited activity on western and southern flanks after 45 Ma. Eruptions brought up megacrystic gemstones (ruby, sapphire and zircon) throughout the volcanism, particularly during quieter eruptive periods. Zircon fission track dating (thermal reset ages) indicates gem-bearing eruptions at 57, 43, 38, 28 and 4-5 Ma, while U-Pb isotope SHRIMP dating suggests two main periods of zircon crystallisation between 60 and 50 Ma and 46-45 Ma. Zircons show growth and sector twinning typical of magmatic crystallisation and include low-U, moderate-U and high-U types. The 46 Ma high-U zircons exhibit trace and rare-earth element patterns that approach those of zircon inclusions in sapphires and may mark a sapphire formation time at Barrington. Two Barrington basaltic episodes include primary lavas with trace-element signatures suggesting amphibole/apatite-enriched lithospheric mantle sources. Other basalts less-enriched in Th, Sr, P and light rare-earth elements have trace-element ratios that overlap those of HIMU-related South Tasman basalts. Zircon and sapphire formation is attributed to crystallisation from minor felsic melts derived by incipient melting of amphibole-enriched mantle during lesser thermal activity. Ruby from Barrington volcano is a metamorphic type, and a metamorphic/metasomatic origin associated with basement ultramafic bodies is favoured. Migratory plate/plume paths constructed through Barrington basaltic episodes intersect approximately 80% of dated Palaeogene basaltic activity (65-30 Ma) along the Tasman margin (27-37 deg S) supporting a migratory plume-linked origin. Neogene Barrington activity dwindled to sporadic gem-bearing eruptions, the last possibly marking a minor plume trace. The present subdued thermal profile in northeastern New South

  1. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    Science.gov (United States)

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

    2009-01-01

    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain

  2. Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc

    Energy Technology Data Exchange (ETDEWEB)

    Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler; Gerseny, Megan

    2010-08-29

    The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the Hf in Aleutian lavas is derived from subducted sediment, indicating that Hf is mobilized out of the subducted sediment with an efficiency that is similar to that of Sr, Pb and Nd. Low published solubility for Hf and Nd in aqueous subduction fluids lead us to conclude that these elements are mobilized out of the subducted component and transferred to the mantle wedge as bulk sediment or as a silicate melt. Neodymium isotopes also generally increase from east to west, but the pattern is absent in the eastern third of the arc, where the sediment flux is high and increases from east to west, due to the presence of abundant terrigenous sediment in the

  3. The petrogenesis of high-calcium boninite lavas dredged from the northern Tonga ridge

    Energy Technology Data Exchange (ETDEWEB)

    Falloon, T.J.; Crawford, A.J. (Dept. of Geology, Univ. of Tasmania, Sandy Bay (Australia))

    1991-03-01

    In 1984 the research vessel 'Natsushima' dredged a fresh suite of MgO- and SiO{sub 2}-rich lavas from the northern termination of the northern Tonga ridge. These lavas are high-Ca boninites and are characterized by the presence of magnesian olivine (up to Fo{sub 94}), orthopyroxene, clinopyroxene, Cr-rich spinel and calcic plagioclase (>An{sub 90}) phenocrysts. Boninite lavas from one dredge site, station 21, range in MgO contents from 3-15 wt% and their major element chemistry appears to be consistent with production of this suite via crystal fractionation. However, large variations in incompatible trace element ratios plus petrographic and mineral chemical evidence demonstrate that magma mixing has been an important process. The isotopic (Sr, Nd) composition of the Tongan high-Ca boninites suggest that their mantle sources are part of a regional OIB mantle domain upwelling beneath the Fiji-Lau Tonga subduction zone system. The OIB mantle source to the Tongan boninites was of refractory lherzolite composition, depleted in 'basaltic' components by prior generation of Lau Basin back arc crust. The mantle sources of the Tongan high-Ca boninites have been enriched in incompatible elements by one or more metasomatic phases, suggested to be a hydrous fluid from the subducting lithospheric slab, a carbonatite melt and a small-degree silicate partial melt both derived from OIB mantle sources. There is no evidence for the involvement of sediment in the source of the Tonga boninites. The presence of the high-Ca boninite lavas at the northern end of the Tonga ridge can be explained by the presence of a northeast-directed spreading ridge in the northern part of the Lau Basin which is propagating into the north Tonga arc. Upwelling asthenospheric mantle beneath the spreading ridge may cause partial melting of refractory peridotite located in the mantle wedge above the subducting Pacific plate at shallow depths (<25 km). (orig.).

  4. Origins and Implications of Zigzag Rift atterns on the surface of lava lakes

    Science.gov (United States)

    Karlstrom, L.; Manga, M.

    2005-12-01

    The distinctive rift patterns observed on newly formed lava lakes are very likely a product of interaction between heat transfer (cooling of lava) and the ability of the solid crust to deform in response to applied stresses. Ragnarsson et al. ( Phys Rev Lett. 1996) observed similar features in analog wax experiments. The experimental setup consisted of a layer of liquid wax heated from below and cooled from above to create a solid crust, which is then pulled apart to form a rift filled with liquid wax. Of particular interest for lava lakes is a regime in which "zigzag" shaped rifts form. We performed a similar series of analog wax experiments designed to characterize the symmetric zigzag rift patterns associated with the cooling and deformation of a newly formed crust layer. The experimental setup is similar to that in Manga and Sinton ( JGR 2004). We vary the wind speed, which controls the cooling rate, and pulling speed. The rifts are characterized by two quantities: the angle between rifts and a line perpendicular to the pulling direction Φ, and the amplitude of the zigzags A. We find experimentally the relationship between Φ, A and cooling rate. We also develop a model to explain the observed relationships: Φ is determined by a balance of pulling and solidification speeds, the latter being governed by wind speed (the primary control on cooling rate); the amplitude A is limited by the thickness of the solid wax crust. The theoretical model is based on a local energy balance in which the conductive heat flux through solidifying crust is balanced by convective and radiative heat loss to the overlying air. Model predictions agree well with experimental results. We can scale this model to basaltic lava lakes. Observed angles are consistent with model predictions. The critical thickness of the solid crust, limiting the amplitude of zigzags (and rift propagation) is a few centimeters, consistent with other estimates (Harris et al., JVGR 2005). The model enables us

  5. High-alumina basalts from the Bogda Mountains suggest an arc setting for Chinese Northern Tianshan during the Late Carboniferous

    Science.gov (United States)

    Xie, Wei; Xu, Yi-Gang; Chen, Yi-Bing; Luo, Zhen-Yu; Hong, Lu-Bing; Ma, Liang; Liu, Hai-Quan

    2016-07-01

    Considerable debate persists as to the tectonic setting of the Tianshan Orogen during the Late Paleozoic, with active subduction system and intraplate large igneous provinces as two dominant schools. With aims of providing constraints on this issue, geochronological and geochemical analyses have been carried out on the Late Carboniferous high-Al basaltic lava (HAB) from the Bogda Mountains. These lavas, in conformable contact with the felsic rocks, belong to the Upper Carboniferous Liushugou Group. Zircon SHRIMP U-Pb dating of two felsic ignimbrites further suggest that they were mainly erupted during 315-319 Ma. The Bogda basaltic lava is classified as HAB given their high Al contents > 16% and their chemical resemblance to those from modern arcs such as Aleutian and Kamchatka. They are characterized by strong enrichment in large ion lithophile elements (LILE), strong negative Nb-Ta and Ti anomalies, and distinct positive Pb anomalies. Hence, they are significantly different from the mantle plume-related basalts, as exemplified by those from Siberian, Emeishan, and Tarim large igneous provinces. Instead, their MORB-like Nd-Hf-Pb isotopes and arc-like trace elements indicate that the Bogda HABs may have been generated from a mantle wedge metasomatized by sediment-derived melts. The sector and oscillatory zoning in clinopyroxene phenocrysts in the Bogda HABs is attributable to rapid dynamic crystallization during magma ascent. High Al content is due to delayed plagioclase nucleation likely by the high crystallization pressure rather than water content. Collectively, our data lend support to an island arc environment during the Late Paleozoic, probably related to southward subduction of the Paleo-Tianshan Ocean.

  6. Distinctly different parental magmas for calc-alkaline plutons and tholeiitic lavas in the central and eastern Aleutian arc

    Science.gov (United States)

    Cai, Yue; Rioux, Matthew; Kelemen, Peter B.; Goldstein, Steven L.; Bolge, Louise; Kylander-Clark, Andrew R. C.

    2015-12-01

    Cenozoic calc-alkaline plutons that comprise the middle crust of the central and eastern Aleutians have distinct isotopic and elemental compositions compared to Holocene tholeiitic lavas in the same region, including those from the same islands. Therefore the Holocene lavas are not representative of the net magmatic transfer from the mantle into the arc crust. Compared to the lavas, the Eocene to Miocene (9-39 Ma) intermediate to felsic plutonic rocks show higher SiO2 at a given Fe/Mg ratio, and have higher εNd-εHf values and lower Pb-Sr isotope ratios. However, the plutonic rocks strongly resemble calc-alkaline Holocene volcanics with more "depleted" isotope ratios in the western Aleutians, whose composition has been attributed to significant contributions from partial melting of subducted basaltic oceanic crust. These data could reflect a temporal variation of central and eastern Aleutian magma source compositions, from predominantly calc-alkaline compositions with more "depleted" isotope ratios in the Paleogene, to tholeiitic compositions with more "enriched" isotopes more recently. Alternatively, the differences between central Aleutian plutonic and volcanic rocks may reflect different transport and emplacement processes for the magmas that form plutons versus lavas. Calc-alkaline parental magmas, with higher SiO2 and high viscosity, are likely to form plutons after extensive mid-crustal degassing of initially high water contents. This conclusion has overarching importance because the plutonic rocks are chemically similar to bulk continental crust. Formation of similar plutonic rocks worldwide may play a key role in the genesis and evolution of continental crust.

  7. Characteristics and genesis of porphyroclastic lava rock in Xiangshan

    International Nuclear Information System (INIS)

    Due to the transitional characteristics of porphyroclastic lava rock in Xiangshan of Jiangxi province, there are a variety of views on its genesis, petrographic attribution. This is because the marginal facies of the porphyroclastic lava is with ignimbrite and tuff characteristics, its transition phase has the characteristics of lava, and its intermediate phase has the feature of sub-volcanic rocks, further more, different texture of the rocks bears transition relationship. By the study of mineral composition, REE pattern, trace elements, isotopes, we put forward that the porphyroclastic lava is formed by the remelting of basement metamorphic rocks. The rocks was believed to be formed in the environment similar to volcanics and subvolcanics, and quite different to plutonic rocks due to the features of low-structure of potassium feldspar phenocrysts and solution mechanism, because the porphyroclastic lava phenocrysts occurs as fragments and maybe related to cryptoexplosion. Therefore the rocks was believed to belong to the volcano extrusive facies. (authors)

  8. Toward continuous quantification of lava extrusion rate: Results from the multidisciplinary analysis of the 2 January 2010 eruption of Piton de la Fournaise volcano, La Réunion

    Science.gov (United States)

    Hibert, C.; Mangeney, A.; Polacci, M.; Muro, A. Di; Vergniolle, S.; Ferrazzini, V.; Peltier, A.; Taisne, B.; Burton, M.; Dewez, T.; Grandjean, G.; Dupont, A.; Staudacher, T.; Brenguier, F.; Kowalski, P.; Boissier, P.; Catherine, P.; Lauret, F.

    2015-05-01

    The dynamics of the 2-12 January 2010 effusive eruption at Piton de la Fournaise volcano were examined through seismic and infrasound records, time-lapse photography, SO2 flux measurements, deformation data, and direct observations. Digital elevation models were constructed for four periods of the eruption, thus providing an assessment of the temporal evolution of the morphology, the volume and the extrusion rate of the lava flow. These data were compared to the continuous recording of the seismic and infrasonic waves, and a linear relationship was found between the seismic energy of the tremor and the lava extrusion rate. This relationship is supported by data from three other summit eruptions of Piton de la Fournaise and gives total volume and average lava extrusion rate in good agreement with previous studies. We can therefore provide an estimate of the lava extrusion rate for the January 2010 eruption with a very high temporal resolution. We found an average lava extrusion rate of 2.4 m3s-1 with a peak of 106.6 m3s-1 during the initial lava fountaining phase. We use the inferred average lava extrusion rate during the lava fountaining phase (30.23 m3s-1) to estimate the value of the initial overpressure in the magma reservoir, which we found to range from 3.7×106 Pa to 5.9×106 Pa. Finally, based on the estimated initial overpressure, the volume of magma expelled during the lava fountaining phase and geodetic data, we inferred the volume of the magma reservoir using a simple Mogi model, between 0.25 km3 and 0.54 km3, which is in good agreement with previous studies.

  9. Dissolution-precipitation reactions and permeability evolution from reactions of CO2-rich aqueous solutions with fractured basalt

    Science.gov (United States)

    Wells, R. K.; Xiong, W.; Bae, Y.; Sesti, E.; Skemer, P. A.; Giammar, D.; Conradi, M.; Ellis, B. R.; Hayes, S. E.

    2015-12-01

    The injection of CO2 into fractured basalts is one of several possible solutions to mitigate global climate change; however, research on carbonation in natural basalts in relation to carbon sequestration is limited, which impedes our understanding of the processes that may influence the viability of this strategy. We are conducting bench-scale experiments to characterize the mineral dissolution and precipitation and the evolution of permeability in synthetic and natural basalts exposed to CO2-rich fluids. Analytical methods include optical and electron microscopy, electron microprobe, Raman spectroscopy, nuclear magnetic resonance (NMR), and micro X-ray computed tomography (μCT) with variable flow rates. Reactive rock and mineral samples consist of 1) packed powders of olivine or natural basalt, and 2) sintered cores of olivine or a synthetic basalt mixture. Each sample was reacted in a batch reactor at 100 °C, and 100 bars CO2. Magnesite is detected within one day in olivine packed beds, and within 15 days in olivine sintered cores. Forsterite and synthetic basalt sinters were also reacted in an NMR apparatus at 102 °C and 65 bars CO2. Carbonate signatures are observed within 72 days of reaction. Longer reaction times are needed for carbonate precipitation in natural basalt samples. Cores from the Columbia River flood basalt flows that contain Mg-rich olivine and a serpentinized basalt from Colorado were cut lengthwise, the interface mechanically roughened or milled, and edges sealed with epoxy to simulate a fractured interface. The cores were reacted in a batch reactor at 50-150 °C and 100 bars CO2. At lower temperatures, calcite precipitation is rare within the fracture after 4 weeks. At higher temperatures, numerous calcite and aragonite crystals are observed within 1 mm of the fracture entrance along the roughened fracture surface. In flow-through experiments, permeability decreased along the fracture paths within a few hours to several days of flow.

  10. The Longevity of Lava Dome Eruptions

    CERN Document Server

    Wolpert, Robert L; Calder, Eliza S

    2015-01-01

    Understanding the duration of past, on-going and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of on-going and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding we show that probability distributions for dome eruption durations are both heavy-tailed and composition-dependent. We construct Objective Bayes statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and on-going eruptions that depend on both eruption duration-to-date and composition. Our Bayesian predictive distributions reflect both uncertainty about mode...

  11. Isotope geochemistry of lavas of central Java, Indonesia and Heard Island, Indian ocean - evidence for sedimentary and mantle plume source components

    International Nuclear Information System (INIS)

    Trace element and Sr-Nd-Pb isotopic data for Slamet basalt-andesites indicate that their parental magmas are affected by small degrees of crustal contamination. The geochemistry of their mantle sources, rich in LILE and LREE has been influenced by a sedimentary component of the underlying subducted lithosphere. This contribution presents some of the elemental and isotopic data (including new Pb- isotope data) upon which this interpretation is based, and compares the isotopic compositions of the Slamet lavas of north-central Java, Indonesia, with estimates of Heard Island (an oceanic island volcano, in the southern Indian Ocean ) low 87Sr/86Sr end-members and also lavas of Muriah and Ringgit-Beser, Java

  12. The longevity of lava dome eruptions

    Science.gov (United States)

    Wolpert, Robert L.; Ogburn, Sarah E.; Calder, Eliza S.

    2016-02-01

    Understanding the duration of past, ongoing, and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of ongoing and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding, we show that probability distributions for dome eruption durations are both heavy tailed and composition dependent. We construct objective Bayesian statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and ongoing eruptions that depend on both eruption duration to date and composition. Our Bayesian predictive distributions reflect both uncertainty about model parameter values (epistemic uncertainty) and the natural variability of the geologic processes (aleatoric uncertainty). The results are illustrated by presenting likely trajectories for 14 dome-building eruptions ongoing in 2015. Full representation of the uncertainty is presented for two key eruptions, Soufriére Hills Volcano in Montserrat (10-139 years, median 35 years) and Sinabung, Indonesia (1-17 years, median 4 years). Uncertainties are high but, importantly, quantifiable. This work provides for the first time a quantitative and transferable method and rationale on which to base long-term planning decisions for lava dome-forming volcanoes, with wide potential use and transferability to forecasts of other types of eruptions and other adverse events across the geohazard spectrum.

  13. The consanguinity of the oldest Apollo 11 mare basalts

    Science.gov (United States)

    Gamble, R. P.; Coish, R. A.; Taylor, L. A.

    1978-01-01

    The textural, mineralogical, and chemical relationships between three of the oldest dates lunar mare basalt samples returned by Apollo 11 (10003, 10029 and 10062) were investigated. Very strong resemblances were noted between the modal minerologies of 10003 and 10029. Significantly more modal olivine and cristobalite was observed in 10062 than in the other basalt samples. A detailed examination of mineral-chemical relationships among the samples revealed similarities between 10003 and 10062 and differences between these two rocks and 10029, the most significant of which is the presence of akaganeite in 10029, implying that lawrencite was present in the pristine sample of 10029 but not in 10003 and 10062. Results of a Wright-Doherty mixing program used to test various fractional crystallization schemes show that 10062 can be derived from a liquid with the composition of either 10003 or 10029 by removing 2-5% ilmenite and 5% olivine. By removing about 6% plagioclase, 10003 can be derived from a liquid with the bulk composition of 10062. It is concluded that 10003 and 10029 may have come from different basaltic flows, whereas it is possible that 10003 and 10062 were derived from the same parental magma by near-surface fractionation of olivine plus ilmenite or of plagioclase plus or minus olivine.

  14. Paleomagnetism of Jurassic-Cretaceous basalts from the Franz Josef Land Archipelago: tectonic implications

    Science.gov (United States)

    Abashev, Victor; Mikhaltsov, Nikolay; Vernikovsky, Valery

    2015-04-01

    New paleomagnetic data were obtained from a total of 158 oriented samples collected from the Jurassic magmatic complexes exposed on the Franz Joseph Land Archipelago (FJL). The field work was conducted during 2011 field season. Present study was focused on the tholeiitic basaltic lava flows that crop out on the Hooker Island. The samples were subjected to a detailed step-wise thermal demagnetization in temperatures up to 600 deg C or alternating field demagnetization with maximum filed up to 140 mT. Natural remanent magnetization (NRM) was measured with a 2G cryogenic magnetometer or a JR-6A spin-magnetometer housed in a magnetically shielded room at the Institute of Petroleum Geology and Geophysics, Siberian Branch of Russian Academy of Sciences. The main NRM carriers in the FJL samples are titanomagnetites with varying Ti-content. Magnetic remanence was unblocked in temperatures of 350-400 deg C. Some samples are characterized by unblocking temperatures of 560 deg C. The new paleomagnetic data were combined with those previously obtained from the early Cretaceous volcanics exposed on the FJL. A new mean paleomagnetic direction for the Jurassic rocks was calculated as D=78.3 deg, I=74.7 deg, a95=3.1 deg, k=194.3, N=13. A corresponding paleomagnetic pole is now located at Plat=62.1 deg; Plon=136.5 deg, A95=5.5 deg, K=63.6. New results suggest that the JFL occupied a significantly different position from that of the present day. However, in early Cretaceous the JFL was already located close to its present day position. We propose a rifting event between the North Barentz terrane (FJL and possibly Svalbard) and the counterpart of European tectonic domain. The rifting occurred during Early-Middle Jurassic. This event was accompanied by a significant shift of the FJL to the north-east for approximately 500 km. New results are in good agreement with a hypothesis that the FJL was passing over the Icelandic-Siberian hot spot during the Jurassic-Cretaceous time

  15. Experimental research on continuous basalt fiber and basalt-fibers-reinforced polymers

    Science.gov (United States)

    Zhang, Xueyi; Zou, Guangping; Shen, Zhiqiang

    2008-11-01

    The interest for continuous basalt fibers and reinforced polymers has recently grown because of its low price and rich natural resource. Basalt fiber was one type of high performance inorganic fibers which were made from natural basalt by the method of melt extraction. This paper discusses basic mechanical properties of basalt fiber. The other work in this paper was to conduct tensile testing of continuous basalt fiber-reinforced polymer rod. Tensile strength and stress-strain curve were obtained in this testing. The strength of rod was fairly equal to rod of E-glass fibers and weaker than rod of carbon fibers. Surface of crack of rod was studied. An investigation of fracture mechanism between matrix and fiber was analyzed by SEM (Scanning electron microscopy) method. A poor adhesion between the matrix and fibers was also shown for composites analyzing SEM photos. The promising tensile properties of the presented basalt fibers composites have shown their great potential as alternative classical composites.

  16. Dinitrogen Gas Production From Epi- and Endolithic Basalt Communities at Loihi Seamount: A New Challenge for the Marine Nitrogen Budget

    Science.gov (United States)

    Horn, G.; Kroeger, K. D.; Kartal, B.; Jetten, M. S.; Edwards, K. J.

    2007-12-01

    Current knowledge of the nitrogen cycle in the oceans indicates a net loss of biologically available nitrogen from the oceans. One marine habitat that is conspicuously absent from current nitrogen budget estimations is seafloor-exposed lavas, such as occur at young ridge flanks around mid-ocean ridge systems and seamounts. Basalt from two locations on Loihi Seamount, an actively venting volcano southeast of the island of Hawai'i, were incubated shipboard with 15N labelled nitrate and ammonium additions to determine the rate of nitrogen loss mediated by epi- and endolithic microbial communities. In all incubations a net production of dinitrogen gas occurred with concurrent consumption of oxidized nitrogen species (nitrate plus nitrite) and ammonium. The availability of reduced iron and manganese from the basalts could serve as potential electron donors for microbial metabolisms, including denitrification and anaerobic ammonia oxidizing (anammox) bacteria. The presence of 16S rRNA gene sequences that align with the anammox clade of Planctomycetes and ongoing anammox enrichment cultures inoculated with Loihi basalt suggest a role for anammox bacteria as well. This initial study indicates an active and significant role for basalt associated microbial communities in the nitrogen budget of the oceans.

  17. Basaltic Soil of Gale Crater: Crystalline Component Compared to Martian Basalts and Meteorites

    Science.gov (United States)

    Treiman, A. H.; Bish, D. L.; Ming, D. W.; Morris, R. V.; Schmidt, M.; Downs, R. T.; Stolper, E. M.; Blake, D. F.; Vaniman, D. T.; Achilles, C. N.; Chipera, S. J.; Bristow, T. F.; Crisp, J. A.; Farmer, J. A.; Morookian, J. M.; Morrison, S. M.; Rampe, E. B.; Sarrazin, P.; Yen, A. S.; Anderosn, R. C.; DesMarais, D. J.; Spanovich, N.

    2013-01-01

    A significant portion of the soil of the Rocknest dune is crystalline and is consistent with derivation from unweathered basalt. Minerals and their compositions are identified by X-ray diffraction (XRD) data from the CheMin instrument on MSL Curiosity. Basalt minerals in the soil include plagioclase, olivine, low- and high-calcium pyroxenes, magnetite, ilmenite, and quartz. The only minerals unlikely to have formed in an unaltered basalt are hematite and anhydrite. The mineral proportions and compositions of the Rocknest soil are nearly identical to those of the Adirondack-class basalts of Gusev Crater, Mars, inferred from their bulk composition as analyzed by the MER Spirit rover.

  18. Noble Gases and Halogens in Icelandic Basalts

    OpenAIRE

    Weston, Bridget

    2013-01-01

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

  19. The significance of PGE variations with Sr-Nd isotopes and lithophile elements in the Emeishan flood basalt province from SW China to northern Vietnam

    Science.gov (United States)

    Li, Chusi; Ripley, Edward M.; Tao, Yan; Hu, Ruizhong

    2016-04-01

    New analyses of siderophile-lithophile elements and Sr-Nd isotopes in the Permian basalts and picrites from northern Vietnam, the southernmost occurrence of the Emeishan flood basalt province, together with previously published data, are used to address the question of whether any meaningful correlation between these elements and isotopes exists at a province scale. The available data show that negative correlations between εNd, (87Sr/86Sr)i and mantle-normalized (Nb/Th)n are present in the basalts but not in the associated picrites. This indicates that crustal contamination is negligible in the picrites but significant in some of the basalts. The picrites and basalts from the entire province show negative correlations between (Rh/Ru)n, (Pt/Ru)n, (Pd/Ru)n and Mg-number. This indicates that Ru behaves compatibly whereas Rh, Pt and Pd behave incompatibly during magma differentiation. The incompatible behavior of Rh in natural basaltic systems is also supported by the fact that (Pt/Rh)n remains constant with decreasing Mg-number in the lavas. Depletions of Pd and Pt, and to a lesser degree Cu, in some basaltic samples characterized by relatively low εNd and (Nb/Th)n support the notion that sulfide saturation in the magmas was triggered by a combination of siliceous crustal contamination and addition of external sulfur. Within the entire flood basalt province only the picrites from Song Da, northern Vietnam show clear depletion in Ir relative to Ru. These picrites are also characterized higher Al2O3/TiO2 and lower mantle-normalized La/Yb (0.2-2.4) than those from elsewhere in the province, possibly due to the involvement of an Ir-depleted, fertile mantle component in magma generation at this location.

  20. Hydrothermal evolution of repository groundwaters in basalt

    International Nuclear Information System (INIS)

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

  1. Petrophysical and geochemical properties of Columbia River flood basalt: Implications for carbon sequestration

    Science.gov (United States)

    Zakharova, Natalia V.; Goldberg, David S.; Sullivan, E. Charlotte; Herron, Michael M.; Grau, James A.

    2012-11-01

    This study presents borehole geophysical data and sidewall core chemistry from the Wallula Pilot Sequestration Project in the Columbia River flood basalt. The wireline logging data were reprocessed, core-calibrated and interpreted in the framework of reservoir and seal characterization for carbon dioxide storage. Particular attention is paid to the capabilities and limitations of borehole spectroscopy for chemical characterization of basalt. Neutron capture spectroscopy logging is shown to provide accurate concentrations for up to 8 major and minor elements but has limited sensitivity to natural alteration in fresh-water basaltic reservoirs. The Wallula borehole intersected 26 flows from 7 members of the Grande Ronde formation. The logging data demonstrate a cyclic pattern of sequential basalt flows with alternating porous flow tops (potential reservoirs) and massive flow interiors (potential caprock). The log-derived apparent porosity is extremely high in the flow tops (20-45%), and considerably overestimates effective porosity obtained from hydraulic testing. The flow interiors are characterized by low apparent porosity (0-8%) but appear pervasively fractured in borehole images. Electrical resistivity images show diverse volcanic textures and provide an excellent tool for fracture analysis, but neither fracture density nor log-derived porosity uniquely correlate with hydraulic properties of the Grande Ronde formation. While porous flow tops in these deep flood basalts may offer reservoirs with high mineralization rates, long leakage migration paths, and thick sections of caprock for CO2 storage, a more extensive multiwell characterization would be necessary to assess lateral variations and establish sequestration capacity in this reservoir.

  2. Petrophysical and Geochemical Properties of Columbia River Flood Basalt: Implications for Carbon Sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Zakharova, Natalia V.; Goldberg, David S.; Sullivan, E. C.; Herron, Michael M.; Grau, Jim A.

    2012-11-02

    Abstract This study presents borehole geophysical data and sidewall core chemistry from the Wallula Pilot Sequestration Project in the Columbia River flood basalt. The wireline logging data were reprocessed, core-calibrated and interpreted in the framework of reservoir and seal characterization for carbon dioxide storage. Particular attention is paid to the capabilities and limitations of borehole spectroscopy for chemical characterization of basalt. Neutron capture spectroscopy logging is shown to provide accurate concentrations for up to 8 major and minor elements but has limited sensitivity to natural alteration in fresh-water basaltic reservoirs. The Wallula borehole intersected 26 flows from 7 members of the Grande Ronde formation. The logging data demonstrate a cyclic pattern of sequential basalt flows with alternating porous flow tops (potential reservoirs) and massive flow interiors (potential caprock). The log-derived apparent porosity is extremely high in the flow tops (20%-45%), and considerably overestimates effective porosity obtained from hydraulic testing. The flow interiors are characterized by low apparent porosity (0-8%) but appear pervasively fractured in borehole images. Electrical resistivity images show diverse volcanic textures and provide an excellent tool for fracture analysis, but neither fracture density nor log-derived porosity uniquely correlate with hydraulic properties of the Grande Ronde formation. While porous flow tops in these deep flood basalts may offer reservoirs with high mineralization rates, long leakage migration paths, and thick sections of caprock for CO2 storage, a more extensive multi- well characterization would be necessary to assess lateral variations and establish sequestration capacity in this reservoir.

  3. DISCRIMINATION OF ALTERED BASALTIC ROCKS IN THE SOUTHWESTERN UNITED STATES BY ANALYSIS OF LANDSAT THEMATIC MAPPER DATA.

    Science.gov (United States)

    Davis, Philip A.; Berlin, Graydon L.; Chavez, Pat S.

    1987-01-01

    Landsat Thematic Mapper image data were analyzed to determine their ability to discriminate red cone basalts from gray flow basalts and sedimentary country rocks for three volcanic fields in the southwestern United States. Analyses of all of the possible three-band combinations of the six nonthermal bands indicate that the combination of bands 1, 4, and 5 best discriminates among these materials. The color-composite image of these three bands unambiguously discriminates 89 percent of the mapped red volcanic cones in the three volcanic fields. Mineralogic and chemical analyses of collected samples indicate that discrimination is facilitated by the presence of hematite as a major mineral phase in the red cone basalts (hematite is only a minor mineral phase in the gray flow basalts and red sedimentary rocks).

  4. Old Shield Basalts from Savai'i Island, Samoa: Validation of A Plume-Hotspot Model for the Samoan Chain

    Science.gov (United States)

    Jackson, M.; Hart, S.; Koppers, A.; Staudigel, H.

    2006-12-01

    The standard model for the generation of an oceanic hotspot track maintains that a deep-seated mantle plume impinges on, and generates melts that escape through, the overriding tectonic plate, thereby generating an age-progressive series of volcanic islands and seamounts. The Samoan hotspot track exhibits several characteristics that are consistent with this model, including an active submarine volcano—Vailulu'u—that anchors the eastern extremity of the chain. The older, submarine portions of the 1700 km chain display a reasonable fit to Pacific plate velocity. However, Savai'i, the westernmost island, has been almost completely re-surfaced with recent, rejuvenated volcanism and there are no subaerial shield basalts with ages (~5 my) predicted by the plume-hotspot model. This lack of a clear age-progression has been taken as evidence that the Samoan hotspot chain is not plume-driven, but is simply a tectono-magmatic manifestation of the nearby Tonga subduction zone. We report geochemical analyses of old basalts recovered from the deep flanks of Savai'i during the 2005 Samoan ALIA cruise. In Samoa, Pb-isotopes provide a good discriminant between shield and rejuvenated basalts, as basalts mapped as rejuvenated in the field have an isotopic signature that is distinct from basalts mapped as shield. Basalts from four separate dredges on the submarine flanks Savai'i exhibit Pb-isotope pedigrees previously observed only in the young, shield-building province of the eastern Samoan islands and seamounts: Dredge 114 has two samples similar in chemistry to Ta'u island, dredge 128 samples are similar to lavas from Tutuila Island, dredge 115 lavas plot either within or very near the Samoan shield basalt field, and dredge 118 reveals surprising heterogeneity, with samples that lie well outside the field for published Samoan basalt data. A fifth dredge (116) on the west rift zone of Savai'i yielded a basalt with clear post-erosional affinities. Dredges 115, 118 and 128 also

  5. Petrological and tectono-magmatic significance of ophiolitic basalts from the Elba Island within the Alpine Corsica-Northern Apennine system

    Science.gov (United States)

    Saccani, Emilio; Principi, G.

    2016-05-01

    Two distinct ophiolitic units, which represent remnants of the Jurassic Ligurian-Piedmont Ocean, crop out in the Elba Island. They are the Monte Strega unit in central-eastern Elba and the Punta Polveraia-Fetovaia unit in western Elba. Ophiolitic rocks from the Monte Strega unit are commonly affected by ocean floor metamorphism, whereas those from the Punta Polveraia-Fetovaia unit are affected to various extent by thermal metamorphism associated with the Late Miocene Monte Capanne monzogranitic intrusion. Both ophiolitic units include pillow lavas and dykes with compositions ranging from basalt to basaltic andesite, Fe-basalt, and Fe-basaltic andesite. Basaltic rocks from these distinct ophiolitic units show no chemical differences, apart those due to fractional crystallization processes. They display a clear tholeiitic nature with low Nb/Y ratios and relatively high TiO2, P2O5, Zr, and Y contents. They generally display flat N-MORB normalized high field strength element patterns, which are similar to those of N-MORB. Chondrite-normalized rare earth element patterns show light REE / middle REE (LREE/MREE) depletion and marked heavy (H-) REE fractionation with respect to MREE. This HREE/MREE depletion indicates a garnet signature of their mantle sources. Accordingly, they can be classified as garnet-influenced MORB (G-MORB), based on Th, Nb, Ce, Dy, and Yb systematics. We suggest that the Elba Island ophiolitic basalts were generated at a magma starved, slow-spreading mid-ocean ridge. REE, Th, and Nb partial melting modelling shows that the compositions of the relatively primitive Elba Island ophiolitic basalts are compatible with partial melting of a depleted MORB mantle (DMM) source bearing garnet-pyroxenite relics. Hygromagmatophile element ratios suggest that basalts from both ophiolitic units were originated from chemically very similar mantle sources. A comparison with basalts and metabasalts from Alpine Corsica and northern Apennine ophiolitic units shows

  6. Subglacial to emergent basaltic volcanism at Hlöðufell, south-west Iceland: A history of ice-confinement

    Science.gov (United States)

    Skilling, I. P.

    2009-09-01

    Hlöðufell is a familiar 1186 m high landmark, located about 80 km northeast of Reykjavík, and 9 km south of the Langkjökull ice-cap in south-west Iceland. This is the first detailed study of this well-exposed and easily accessible subglacial to emergent basaltic volcano. Eight coherent and eleven volcaniclastic lithofacies are described and interpreted, and its evolution subdivided into four growth stages (I-IV) on the basis of facies architecture. Vents for stages I, II, and IV lie along the same fissure zone, which trends parallel to the dominant NNE-SSW volcano-tectonic axis of the Western Volcanic Zone in this part of Iceland, but the stage III vent lies to the north, and is probably responsible for the present N-S elongation of the volcano. The basal stage (I) is dominated by subglacially erupted lava mounds and ridges, which are of 240 m maximum thickness, were fed from short fissures and locally display lava tubes. Some of the stage I lavas preserve laterally extensive flat to bulbous, steep, glassy surfaces that are interpreted to have formed by direct contact with surrounding ice, and are termed ice-contact lava confinement surfaces. These surfaces preserve several distinctive structures, such as lava shelves, pillows that have one flat surface and mini-pillow (vault), and was also transported to the south by sub-ice meltwater traction currents. This cone is onlapped by a subaerial pahoehoe lava-fed delta sequence, formed during stage III, and which was most likely fed from a now buried vent(s), located somewhere in the north-central part of the mountain. A 150 m rise in lake level submerged the capping lavas, and was associated with progradation of a new pahoehoe lava-fed delta sequence, produced during stage IV, and which was fed from the present summit cone vent. The water level rise and onset of stage IV eruptions were not associated with any obviously exposed phreatomagmatic deposits, but they are most likely buried beneath stage IV delta deposits

  7. Repository site definition in basalt: Pasco Basin, Washington

    Energy Technology Data Exchange (ETDEWEB)

    Guzowski, R.V.; Nimick, F.B.; Muller, A.B.

    1982-03-01

    Discussion of the regional setting, geology, hydrology, and geochemistry of the Pasco Basin are included in this report. Pasco basin is a structural and topographic basin of approximately 2000 mi/sup 2/ (5180 km/sup 2/) located within the Yakima Fold Belt Subprovince of the Columbia Plateau. The stratigraphic sequence within the basin consists of an undetermined thickness of lower Miocene and younger flood basalts with interbedded and overlying sedimentary units. This sequence rests upon a basement of probably diverse rock types that may range in age from precambrian through early Tertiary. Although a large amount of information is available on the hydrology of the unconfined aquifer system, ground-water flow within the basin is, in general, poorly understood. Recharge areas for the Mabton interbed and the Saddle Mountains Formation are the highlands surrounding the basin with the flow for these units toward Gable Butte - Gable Mountain and Lake Wallula. Gable Butte - Gable Mountain probably is a ground-water sink, although the vertical flow direction in this zone is uncertain. The amount of upward vertical leakage from the Saddle Mountains Formation into the overlying sediments or to the Columbia River is unknown. Units underlying the Mabton interbed may have a flow scheme similar to those higher units or a flow scheme dominated by interbasin flow. Upward vertical leakage either throughout the basin, dominantly to the Columbia River, or dominantly to Lake Wallula has been proposed for the discharge of the lower units. None of these proposals is verified. The lateral and vertical distribution of major and minor ions in solution, Eh and pH, and ion exchange between basalt and ground-water are not well defined for the basin. Changes in the redox potential from the level of the subsurface facility to the higher stratigraphic levels along with the numerous other factors influencing K/sub d/, result in a poor understanding of the retardation process.

  8. Repository site definition in basalt: Pasco Basin, Washington

    International Nuclear Information System (INIS)

    Discussion of the regional setting, geology, hydrology, and geochemistry of the Pasco Basin are included in this report. Pasco basin is a structural and topographic basin of approximately 2000 mi2 (5180 km2) located within the Yakima Fold Belt Subprovince of the Columbia Plateau. The stratigraphic sequence within the basin consists of an undetermined thickness of lower Miocene and younger flood basalts with interbedded and overlying sedimentary units. This sequence rests upon a basement of probably diverse rock types that may range in age from precambrian through early Tertiary. Although a large amount of information is available on the hydrology of the unconfined aquifer system, ground-water flow within the basin is, in general, poorly understood. Recharge areas for the Mabton interbed and the Saddle Mountains Formation are the highlands surrounding the basin with the flow for these units toward Gable Butte - Gable Mountain and Lake Wallula. Gable Butte - Gable Mountain probably is a ground-water sink, although the vertical flow direction in this zone is uncertain. The amount of upward vertical leakage from the Saddle Mountains Formation into the overlying sediments or to the Columbia River is unknown. Units underlying the Mabton interbed may have a flow scheme similar to those higher units or a flow scheme dominated by interbasin flow. Upward vertical leakage either throughout the basin, dominantly to the Columbia River, or dominantly to Lake Wallula has been proposed for the discharge of the lower units. None of these proposals is verified. The lateral and vertical distribution of major and minor ions in solution, Eh and pH, and ion exchange between basalt and ground-water are not well defined for the basin. Changes in the redox potential from the level of the subsurface facility to the higher stratigraphic levels along with the numerous other factors influencing K/sub d/, result in a poor understanding of the retardation process

  9. Lunar Lava Tubes as Potential Human Settlements and Refuge Sites

    Science.gov (United States)

    Lemke, K. A.; Mardon, A. A.

    2015-10-01

    Lava tubes have been detected on the surface of Earth's moon via satellite images. Upon further exploration of these caves through robotic technology and other means, a refuge place for astronauts may be installed.

  10. Catastrophic lava dome failure at Soufrière Hills Volcano, Montserrat, 12-13 July 2003

    Science.gov (United States)

    Herd, Richard A.; Edmonds, Marie; Bass, Venus A.

    2005-01-01

    The lava dome collapse of 12–13 July 2003 was the largest of the Soufrière Hills Volcano eruption thus far (1995–2005) and the largest recorded in historical times from any volcano; 210 million m3 of dome material collapsed over 18 h and formed large pyroclastic flows, which reached the sea. The evolution of the collapse can be interpreted with reference to the complex structure of the lava dome, which comprised discrete spines and shear lobes and an apron of talus. Progressive slumping of talus for 10 h at the beginning of the collapse generated low-volume pyroclastic flows. It undermined the massive part of the lava dome and eventually prompted catastrophic failure. From 02:00 to 04:40 13 July 2003 large pyroclastic flows were generated; these reached their largest magnitude at 03:35, when the volume flux of material lost from the lava dome probably approached 16 million m3 over two minutes. The high flux of pyroclastic flows into the sea caused a tsunami and a hydrovolcanic explosion with an associated pyroclastic surge, which flowed inland. A vulcanian explosion occurred during or immediately after the largest pyroclastic flows at 03:35 13 July and four further explosions occurred at progressively longer intervals during 13–15 July 2003. The dome collapse lasted approximately 18 h, but 170 of the total 210 million m3 was removed in only 2.6 h during the most intense stage of the collapse.

  11. BWIP data package for reference chemistry of and procedures for preparation of synthetic Grande Ronde basalt and Mabton Interbed groundwaters

    International Nuclear Information System (INIS)

    Synthetic groundwater compositions have been specified which represent the groundwater solutions found in the proposed repository site (the Grande Ronde Basalt) and in an interbed above the Grande Ronde Basalt (the Mabton Interbed). These compositions are based on analyses of Grande Ronde groundwater and Mabton Interbed groundwater and will be used in hydrothermal and sorption experiments designed to simulate the repository environment independent of characteristics of individual flows. Procedures for making these groundwaters are included. 5 tabs

  12. Chemical evolution, petrogenesis, and regional chemical correlations of the flood basalt sequence in the central Deccan Traps, India

    Indian Academy of Sciences (India)

    Leone Melluso; Mario Barbieri; Luigi Beccaluva

    2004-12-01

    The lava sequence of the central-western Deccan Traps (from Jalgaon towards Mumbai) is formed by basalts and basaltic andesites having a significant variation in TiO2 (from 1.2 to 3.3 wt%), Zr (from 84 to 253 ppm), Nb (from 5 to 16 ppm) and Ba (from 63 to 407 ppm), at MgO ranging from 10 to 4.2 wt%. Most of these basalts follow a liquid line of descent dominated by low pressure fractionation of clinopyroxene, plagioclase and olivine, starting from the most mafic compositions, in a temperature range from 1220° to 1125°C. These rocks resemble those belonging to the lowermost formations of the Deccan Traps in the Western Ghats (Jawhar, Igatpuri and Thakurvadi) as well as those of the Poladpur formation. Samples analyzed for 87Sr/86Sr give a range of initial ratios from 0.70558 to 0.70621. A group of flows of the Dhule area has low TiO2 (1.2–1.5 wt%) and Zr (84–105 ppm) at moderate MgO (5.2–6.2 wt%), matching the composition of low-Ti basalts of Gujarat, low-Ti dykes of the Tapti swarm and Toranmal basalts, just north of the study area. This allows chemical correlations between the lavas of central Deccan, the Tapti dykes and the northwestern outcrops. The mildly enriched high field strength element contents of the samples with TiO2 < 1.5 wt% make them products of mantle sources broadly similar to those which generated the Ambenali basalts, but their high La/Nb and Ba/Nb, negative Nb anomalies in the mantle normalized diagrams, and relatively high 87Sr/86Sr, make evident a crustal input with crustally derived materials at less differentiated stages than those represented in this sample set, or even within the sub-Indian lithospheric mantle.

  13. Mapping lava morphology of the Galapagos Spreading Center at 92°W: fuzzy logic provides a classification of high-resolution bathymetry and backscatter

    Science.gov (United States)

    McClinton, J. T.; White, S. M.; Sinton, J. M.; Rubin, K. H.; Bowles, J. A.

    2010-12-01

    Differences in axial lava morphology along the Galapagos Spreading Center (GSC) can indicate variations in magma supply and emplacement dynamics due to the influence of the adjacent Galapagos hot spot. Unfortunately, the ability to discriminate fine-scale lava morphology has historically been limited to observations of the small coverage areas of towed camera surveys and submersible operations. This research presents a neuro-fuzzy approach to automated seafloor classification using spatially coincident, high-resolution bathymetry and backscatter data. The classification method implements a Sugeno-type fuzzy inference system trained by a multi-layered adaptive neural network and is capable of rapidly classifying seafloor morphology based on attributes of surface geometry and texture. The system has been applied to the 92°W segment of the western GSC in order to quantify coverage areas and distributions of pillow, lobate, and sheet lava morphology. An accuracy assessment has been performed on the classification results. The resulting classified maps provide a high-resolution view of GSC axial morphology and indicate the study area terrain is approximately 40% pillow flows, 40% lobate and sheet flows, and 10% fissured or faulted area, with about 10% of the study area unclassifiable. Fine-scale features such as eruptive fissures, tumuli, and individual pillowed lava flow fronts are also visible. Although this system has been applied to lava