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Sample records for active volcanic arcs

  1. Crustal structure along the active Costa Rican volcanic arc

    NASA Astrophysics Data System (ADS)

    Lizarralde, D.; Holbrook, W. S.; van Avendonk, H. J.; Mora Fernandez, M.; Alvarado, G. E.; Harder, S. H.

    2010-12-01

    We present results from an explosion-source seismic refraction transect along the entire active Costa Rican volcanic arc. The seismic data were acquired in 2005 as part of the TICO-CAVA experiment with the goals of delineating the basic crustal architecture of this relatively young volcanic arc, understanding magmatic emplacement processes, and estimating the bulk composition and growth rates of arc crust. The seismic transect extends ~280 km along the axis of the arc and consists of 16 shots (200 - 1200 kg) recorded by 710 seismometers. The active Costa Rican arc consists of two segments with distinct morphologies, the Guanacaste Cordillera (GC) in the north and Central Cordillera (CC) in the south. This segmentation is linked to the subducting Cocos ridge, which occurs beneath the CC and has a northern boundary roughly coincident with the arc segment boundary. Volcanoes of the GC rise from a plateau of ~500 m elevation to maximum heights of ~1500 m, while the CC volcanoes rise from ~1500 m to heights of 3500 m. The crustal structure beneath these segments is distinctly different. The entire arc is covered by a ~5-km-thick carapace with velocities of 4.5-5.8 km/s that probably represent volcaniclastics, flows and small plutons. Beneath the GC, a 1- to 2-km-thick “grainitic” layer (6.0-6.1 km/s) lies beneath the carapace. Velocities below this granitic layer suggest a somewhat more mafic composition, but they increase slowly with depth from 6.2-6.3 km/s between 6-15 km depth. Total crustal thickness beneath the GC is ~40 km, but analysis of crustal thickness is ongoing. The crust beneath Guanacaste thus has a velocity structure very similar to average continental crust, though with slightly slower velocities, perhaps due to high temperatures beneath the arc. As the arc has only been active in this location for <5 m.y., this suggests that either the earlier Neogene arc to the west substantially modified the oceanic-plateau crustal foundation here or that the

  2. Volcanic activity recorded in deep-sea sediments and the geodynamic evolution of western Pacific island arcs

    NASA Astrophysics Data System (ADS)

    Cambray, Hervé; Pubellier, Manuel; Jolivet, Laurent; Pouclet, André

    A compilation of volcanic ashes interbedded in deep-sea sediments was carried out from DSDP-IPOD and ODP data collected along the western Pacific margin. Using a tephrochronological method, we attempted to reconstruct the Cenozoic and Quaternary volcanic activity of major western Pacific arcs. For every arc, established volcanic episodes and volcanic-tectonic evolution recorded on land were compared. This study reveals close connections between tectonic events and volcanic activity of arcs, as well a temporal relationship between the opening of marginal basins and arc volcanism. In the Tohoku (NE Japan) and Bonin arcs (SE Japan), arc volcanic activity clearly vanishes during backarc spreading. In contrast, intense volcanism occurs during both arc rifting and intervals of no spreading. Detailed comparisons show that the maximum volcanic output is closely connected with the stress field evolution recorded on land. The case of Seinan arc (SW Japan) shows a good fit between volcanic episodes and periods of release of the compressional stress field after major orogenic events. Furthermore, in the marine sediments off Japan, a systematic late Miocene volcanic hiatus interpreted as a quiescence of volcanic activity corresponds to a changing stress field on the Tohoku and Bonin arcs. These correlations between volcanic episodicity and tectonic evolution of island arcs allow us to discuss the influence of subduction process on arc volcanism. In the Philippines, the volcanic signal in marine sediments is compromised by rapid alteration and diagenesis of ashes. Nonetheless, only the main events of arc volcanic activity are preserved. A comparison with on land volcanism shows that this filtered volcanic signal in different places corresponds to incipient subduction (transition from passive to active margins) or to the final stages of basin closure.

  3. Discovery of Active Hydrothermal Sites Along the Mariana Volcanic Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Embley, R. W.; Resing, J. A.; Lupton, J. E.; Massoth, G. J.; de Ronde, C. E.; Nakamura, K.; Walker, S. L.

    2003-12-01

    Some 20,000 km of volcanic arcs, roughly one-third the total length of the global midocean ridge (MOR) system, rim the western Pacific Ocean. But compared to 25 years of hydrothermal investigations along MORs, exploration of similar activity on the estimated 600 submarine arc volcanoes is only beginning. In February 2003, as part of the Submarine Ring of Fire project funded by NOAA's Ocean Exploration Program, we made the first systematic survey of hydrothermal activity along the 1270-km-long Mariana intraoceanic volcanic arc, which lies almost entirely within the US EEZ. Prior fieldwork had documented active (but low-temperature) hydrothermal discharge on only three volcanoes: Kasuga 2, Kasuga 3, and Esmeralda Bank. During the cruise, we conducted 70 CTD operations over more than 50 individual volcanoes from 13° N to 23° N, plus a continuous CTD survey along 75 km of the back-arc spreading center (13° 15'N to 13° 41'N) adjacent to the southern end of the arc. We found evidence for active hydrothermal venting at 11 submarine volcanoes with summit (or caldera floor) depths ranging from 50 to 1550 m. Two additional sites were identified on the back-arc spreading center. Ongoing analyses of collected water samples could increase these totals. Our results confirmed continuing hydrothermal activity at Kasuga 2 (but not Kasuga 3) and Esmeralda Bank, in addition to newly discovered sites on nine other volcanoes. Many of these sites produce intense and widely dispersed plumes indicative of vigorous, high-temperature discharge. The volcanoes with active hydrothermal systems are about equally divided between those with and without summit calderas. The addition of the Marianas data greatly improves our view of hydrothermal sources along arcs. The 20,000 km of Pacific arcs can be divided between 6380 km of intraoceanic (i.e., mostly submarine) arcs and 13,880 km of island (i.e., mostly subaerial) arcs. At present, ˜15% of the total length of Pacific arcs has been surveyed

  4. Interactions between active faulting, volcanism, and sedimentary processes at an island arc: Insights from Les Saintes channel, Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Feuillet, N.; Deplus, C.

    2016-07-01

    New high-resolution marine geophysical data allow to characterize a large normal fault system in the Lesser Antilles arc, and to investigate the interactions between active faulting, volcanism, sedimentary, and mass-wasting processes. Les Saintes fault system is composed of several normal faults that form a 30 km wide half-graben accommodating NE-SW extension. It is bounded by the Roseau fault, responsible for the destructive Mw 6.3 21 November 2004 earthquake. The Roseau fault has been identified from the island of Basse-Terre to Dominica. It is thus 40 km long, and it could generate Mw 7 earthquakes in the future. Several submarine volcanoes are also recognized. We show that the fault system initiated after the main volcanic construction and subsequently controls the emission of volcanic products. The system propagates southward through damage zones. At the tip of the damage zones, several volcanic cones were recently emplaced probably due to fissures opening in an area of stress increase. A two-way interaction is observed between active faulting and sedimentary processes. The faults control the development of the main turbiditic system made of kilometer-wide canyons, as well as the location of sediment ponding. In turn, erosion and sedimentation prevent scarp growth at the seafloor. Faulting also enhances mass-wasting processes. Since its initiation, the fault system has consequently modified the morphologic evolution of the arc through perturbation of the sedimentary processes and localization of the more recent volcanic activity.

  5. Significance of an Active Volcanic Front in the Far Western Aleutian Arc

    NASA Astrophysics Data System (ADS)

    Yogodzinski, G. M.; Kelemen, P. B.; Hoernle, K.

    2015-12-01

    Discovery of a volcanic front west of Buldir Volcano, the western-most emergent Aleutian volcano, demonstrates that the surface expression of Aleutian volcanism falls below sea level just west of 175.9° E longitude, but is otherwise continuous from mainland Alaska to Kamchatka. The newly discovered sites of western Aleutian seafloor volcanism are the Ingenstrem Depression, a 60 km-long structural depression just west of Buldir, and an unnamed area 300 km further west, referred to as the Western Cones. These locations fall along a volcanic front that stretches from Buldir to Piip Seamount near the Komandorsky Islands. Western Aleutian seafloor volcanic rocks include large quantities of high-silica andesite and dacite, which define a highly calc-alkaline igneous series and carry trace element signatures that are unmistakably subduction-related. This indicates that subducting oceanic lithosphere is present beneath the westernmost Aleutian arc. The rarity of earthquakes below depths of 200 km indicates that the subducting plate is unusually hot. Some seafloor volcanoes are 6-8 km wide at the base, and so are as large as many emergent Aleutian volcanoes. The seafloor volcanoes are submerged in water depths >3000 m because they sit on oceanic lithosphere of the Bering Sea. The volcanic front is thus displaced to the north of the ridge of arc crust that underlies the western Aleutian Islands. This displacement, which developed since approximately 6 Ma when volcanism was last active on the islands, must be a consequence of oblique convergence in a system where the subducting plate and large blocks of arc crust are both moving primarily in an arc-parallel sense. The result is a hot-slab system where low subduction rates probably limit advection of hot mantle to the subarc, and produce a relatively cool and perhaps stagnant mantle wedge. The oceanic setting and highly oblique subduction geometry also severely limit rates of sediment subduction, so the volcanic rocks, which

  6. Ultra-long-range hydroacoustic observations of submarine volcanic activity at Monowai, Kermadec Arc

    NASA Astrophysics Data System (ADS)

    Metz, D.; Watts, A. B.; Grevemeyer, I.; Rodgers, M.; Paulatto, M.

    2016-02-01

    Monowai is an active submarine volcanic center in the Kermadec Arc, Southwest Pacific Ocean. During May 2011, it erupted over a period of 5 days, with explosive activity directly linked to the generation of seismoacoustic T phases. We show, using cross-correlation and time-difference-of-arrival techniques, that the eruption is detected as far as Ascension Island, equatorial South Atlantic Ocean, where a bottom moored hydrophone array is operated as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization. Hydroacoustic phases from the volcanic center must therefore have propagated through the Sound Fixing and Ranging channel in the South Pacific and South Atlantic Oceans, a source-receiver distance of ~15,800 km. We believe this to be the furthest documented range of a naturally occurring underwater signal above 1 Hz. Our findings, which are consistent with observations at regional broadband stations and long-range, acoustic parabolic equation modeling, have implications for submarine volcano monitoring.

  7. Initial development of the Banda Volcanic Arc

    SciTech Connect

    Hartono, H.M.S. )

    1990-06-01

    The initial development of the Banda Volcanic Arc can be determined by obtaining absolute ages of granites or volcanics, stratigraphy of the Eocene Metan Volcanics of Timor as the oldest formation containing Banda Volcanic Arc extrusives, and tectonic analysis. Banda Arc volcanism is the result of subduction of oceanic crust under the volcanic arc. The time of initial subduction is related to initial seafloor spreading between Australia and Antarctica, which is identical to geomagnetic polarity time 34 (82 mybp). Therefore, 82 mybp can be used as one of the criteria to determine the birth of the Banda Volcanic Arc. With present available time data for determining the birth of the Banda Volcanic Arc, the minimum age coincides with the age of the Metan Volcanics (Eocene, 39-56 mybp) and the maximum age coincides with initial seafloor spreading between Australia and Antarctica (82 mybp). This time span is too long. With the assumption that it needs some time to develop from transcurrent faulting to subduction and volcanism, it is proposed that the initial development of Banda Arc volcanism was during early Tertiary.

  8. Using IMS hydrophone data for detecting submarine volcanic activity: Insights from Monowai, 26°S Kermadec Arc

    NASA Astrophysics Data System (ADS)

    Metz, Dirk; Watts, Anthony B.; Grevemeyer, Ingo; Rodgers, Mel; Paulatto, Michele

    2016-04-01

    Only little is known on active volcanism in the ocean. As eruptions are attenuated by seawater and fallout does not regularly reach the sea surface, eruption rates and mechanisms are poorly understood. Estimations on the number of active volcanoes across the modern seas range from hundreds to thousands, but only very few active sites are known. Monowai is a submarine volcanic centre in the northern Kermadec Arc, Southwest Pacific Ocean. During May 2011, it erupted over a period of five days, with explosive activity directly linked to the generation of seismoacoustic tertiary waves ('T-phases'), recorded at three broadband seismic stations in the region. We show, using windowed cross-correlation and time-difference-of-arrival techniques, that T-phases associated with this eruption are detected as far as Ascension Island, South Atlantic Ocean, where two bottom-moored hydrophone arrays are operated as part of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). We observe a high incidence of T-phase arrivals during the time of the eruption, with the angle of arrival stabilizing at the geodesic azimuth between the IMS arrays and Monowai. T-phases from the volcanic centre must therefore have propagated through the Sound Fixing And Ranging (SOFAR) channel in the South Pacific and South Atlantic Oceans and over a total geodesic range of approximately 15,800 km, one of the longest source-receiver distances of any naturally occurring underwater signal ever observed. Our findings, which are consistent with observations at regional broadband stations and two dimensional, long-range, parabolic equation modelling, highlight the exceptional capabilities of the hydroacoustic waveform component of the IMS for remotely detecting episodes of submarine volcanic activity. Using Monowai and the hydrophone arrays at Ascension Island as a natural laboratory, we investigate the long-term eruptive record of a submarine volcano from

  9. Shrimp Populations on Northwest Rota, an Active Volcano of the Mariana Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Tunnicliffe, V.; Juniper, S. K.; Limén, H.; Jones, W. J.; Vrijenhoek, R.; Webber, R.; Eerkes-Medrano, D.

    2004-12-01

    NW Rota-1 is a submarine volcano that manifested active volcanic and hydrothermal activity during submersible surveys in March 2004 (see Embley et al.). Substratum on the volcano summit (520 m depth) was entirely basalt outcrop or variously-sized ejecta lying near the angle of repose. While no fauna inhabited the rim of the volcanic pit, patches of shrimp were located within 25 m and on the nearby summit. Two species are present. Opaepele cf. loihi shows few morphological differences from either a nearby population on Eifuku Volcano (see Chadwick et al.) at 1700 m depth or from the type locality in Hawaii. A molecular comparison of COI sequences of 13 specimens found little difference from two Hawaiian sequences. Video observations detail frequent feeding activity using spatulate chelipeds to trim microbial filaments as the cephalothorax sways across the substratum. The second species is an undescribed Alvinocaris. Juveniles of this species appear to form clusters distinct from Opaepele where they also graze on filaments. Sparse adults of Alvinocaris range up to 5.5 cm long and display aggressive behaviour moving through patches of smaller shrimp. Densities of Opaepele were highest on sloping rock walls (over 500 per sq.m.) whereas adult Alvinocaris were more abundant on rubble. This division may reflect food preference: microbial filaments versus polychaetes and meiofauna. Characterization of particulates from these substrata was conducted using visual sorting and stable isotope composition. As Alvinocaris matures, the chelipeds enlarge, enabling a greater predatory capacity. Measurements of Opaepele from digital in situ images reveal a population structure suggesting a recent recruitment. Average size is significantly smaller than the Eifuku population and no egg-bearing females were collected. The disjunct range of this species where it occurs on active volcanoes 6000 km apart is puzzling. Further work on intermediate sites and into the reproductive strategy of

  10. Numerical modeling of volcanic arc development

    NASA Astrophysics Data System (ADS)

    Gerya, T.; Gorczyk, W.; Nikolaeva, K.

    2007-05-01

    We have created a new coupled geochemical-petrological-thermomechanical numerical model of subduction associated with volcanic arc development. The model includes spontaneous slab bending, subducted crust dehydration, aqueous fluid transport, mantle wedge melting and melt extraction resulting in crustal growth. Two major volcanic arc settings are modeled so far: active continental margins, and intraoceanic subduction. In case of Pacific-type continental margin two fundamentally different regimes of melt productivity are observed in numerical experiments which are in line with natural observations: (1) During continuous convergence with coupled plates highest amounts of melts are formed immediately after the initiation of subduction and then decrease rapidly with time due to the steepening of the slab inclination angle precluding formation of partially molten mantle wedge plumes; (2) During subduction associated with slab delamination and trench retreat resulting in the formation of a pronounced back arc basin with a spreading center in the middle melt production increases with time due to shallowing/stabilization of slab inclination associated with upward asthenospheric mantle flow toward the extension region facilitating propagation of hydrous partially molten plumes from the slab. In case of spontaneous nucleation of retreating oceanic subduction two scenarios of tecono-magmatic evolution are distinguished: (1) decay and, ultimately, the cessation of subduction and related magmatic activity, (2) increase in subduction rate (to up to ~12 cm/yr) and stabilization of subduction and magmatic arc growth. In the first case the duration of subduction correlates positively with the intensity of melt extraction: the period of continued subduction increases from 15,4 Myrs to 47,6 Myrs with the increase of melt extraction threshold from 1% to 9%. In scenario (1) the magmatic arc crust includes large amounts of rocks formed by melting of subducted crust atop the thermally

  11. Magma genesis of the acidic volcanism in the intra-arc rift zone of the Izu volcanic arc, Japan

    NASA Astrophysics Data System (ADS)

    Haraguchi, S.; Tokuyama, H.; Ishii, T.

    2010-12-01

    The Izu volcanic arc extends over 550 km from the Izu Peninsula, Japan, to the Nishinoshima Trough or Sofugan tectonic line. It is the northernmost segment of the Izu-Bonin-Mariana arc system, which is located at the eastern side of the Philippine Sea Plate. The recent magmatism of the Izu arc is bimodal and characterized by basalt and rhyolite (e.g. Tamura and Tatsumi 2002). In the southern Izu arc, volcanic front from the Aogashima to the Torishima islands is characterized by submarine calderas and acidic volcanisms. The intra-arc rifting, characterized by back-arc depressions, small volcanic knolls and ridges, is active in this region. Volcanic rocks were obtained in 1995 during a research cruise of the R/V MOANA WAVE (Hawaii University, cruise MW9507). Geochemical variation of volcanic rocks and magma genesis was studied by Hochstaedter et al. (2000, 2001), Machida et al (2008), etc. These studies focused magma and mantle dynamics of basaltic volcanism in the wedge mantle. Acidic volcanic rocks were also dredged during the curies MW9507. However, studies of these acidic volcanics were rare. Herein, we present petrographical and chemical analyses of these acidic rocks, and compare these results with those of other acidic rocks in the Izu arc and lab experiments, and propose a model of magma genesis in a context of acidic volcanism. Dredge sites by the cruise MW9507 are 120, and about 50 sites are in the rift zone. Recovered rocks are dominated by the bimodal assemblage of basalt-basaltic andesite and dacite-rhyolite. The most abundant phase is olivine basalt, less than 50 wt% SiO2. Andesites are minor in volume and compositional gap from 56 to 65 wt% SiO2 exists. The across-arc variation of the HFSE contents and ratios, such as Zr/Y and Nb/Zr of rhyolites exhibit depleted in the volcanic front side and enriched in reararc side. This characteristic is similar to basaltic volcanism pointed out by Hochstaedter et al (2000). The petrographical features of rhyolites

  12. Geothermal resource potential of Cascade volcanic arc

    SciTech Connect

    Priest, G.R.

    1987-08-01

    The central and southern cascade volcanic arc has the following features that suggest a high potential for geothermal resources: (1) extensive Quaternary volcanism with some silicic to intermediate volcanoes, (2) hundreds of square kilometers with regional background heat flow in excess of 100 mW/m/sup 2/, (3) shallow (4-9 km) calculated depth to Curie point in the same areas that have heat flow in excess of 100 mW/m/sup 2/, (4) a thick pile of volcanic rock with moderate to low thermal conductivity, (5) hot springs with minimum reservoir temperatures of 174/sup 0/-186/sup 0/C (from the anhydrite geothermometer of Mariner, 1985), and (6) fault zones for fracture permeability. These features are the result of interactions between the North American plate (NAP), the Pacific plate (PP), and the subducted Gorda, Juan de Fuca, and Explorer plates (GJEP). Interactions between the NAP and the PP produce north-south compression and east-west extension, causing extensive development of north-south normal faults and partial melting episodes in upper mantle. Northeast-southwest convergence between the NAP and the GJEP produce subduction-related magmas and crustal deformation from northeast-southwest compression. NAP-GJEP interactions dominate in the northern part of the arc, whereas NAP-PP and NAP-GJEP interactions have combined in the central and southern part of the arc to produce rates of magmatism and heat flow higher than in the north.

  13. Magnesium isotope geochemistry in arc volcanism.

    PubMed

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-28

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ(26)Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ(26)Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  14. Magnesium isotope geochemistry in arc volcanism

    NASA Astrophysics Data System (ADS)

    Teng, Fang-Zhen; Hu, Yan; Chauvel, Catherine

    2016-06-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from -0.25 to -0.10, in contrast to the narrow range that characterizes the mantle (-0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid-mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration.

  15. Magnesium isotope geochemistry in arc volcanism

    PubMed Central

    Teng, Fang-Zhen; Hu, Yan

    2016-01-01

    Incorporation of subducted slab in arc volcanism plays an important role in producing the geochemical and isotopic variations in arc lavas. The mechanism and process by which the slab materials are incorporated, however, are still uncertain. Here, we report, to our knowledge, the first set of Mg isotopic data for a suite of arc lava samples from Martinique Island in the Lesser Antilles arc, which displays one of the most extreme geochemical and isotopic ranges, although the origin of this variability is still highly debated. We find the δ26Mg of the Martinique Island lavas varies from −0.25 to −0.10, in contrast to the narrow range that characterizes the mantle (−0.25 ± 0.04, 2 SD). These high δ26Mg values suggest the incorporation of isotopically heavy Mg from the subducted slab. The large contrast in MgO content between peridotite, basalt, and sediment makes direct mixing between sediment and peridotite, or assimilation by arc crust sediment, unlikely to be the main mechanism to modify Mg isotopes. Instead, the heavy Mg isotopic signature of the Martinique arc lavas requires that the overall composition of the mantle wedge is buffered and modified by the preferential addition of heavy Mg isotopes from fluids released from the altered subducted slab during fluid−mantle interaction. This, in turn, suggests transfer of a large amount of fluid-mobile elements from the subducting slab to the mantle wedge and makes Mg isotopes an excellent tracer of deep fluid migration. PMID:27303032

  16. Linear volcanic segments in the Sunda Arc, Indonesia: Implications for arc lithosphere control upon volcano distribution

    NASA Astrophysics Data System (ADS)

    Macpherson, C. G.; Pacey, A.; McCaffrey, K. J.

    2012-12-01

    The overall curvature of many subduction zones is immediately apparent and the term island arc betrays the common assumption that subduction zone magmatism occurs in curved zones. This assumption can be expressed by approximating island arcs as segments of small circles on the surface of a sphere. Such treatments predict that the location of arc volcanoes is related to their vertical separation from the slab (in fact, the depth to seismicity in the slab) and require that the primary control on the locus of magmatism lies either within the subducted slab or the mantle wedge that separates the subducted and overriding lithospheric plates. The concept of curved arcs ignores longstanding observations that magmatism in many subduction systems occurs as segments of linearly arranged volcanic centres. Further evidence for this distribution comes from the close relationship between magmatism and large scale, arc-parallel fabrics in some arcs. Similarly, exposures of deep arc crust or mantle often reveal elongation of magmatic intrusions sub-parallel to the inferred trend of the arc. The Sunda Arc forms the Indonesian islands from Sumatra to Alor and provides an important test for models of volcano distribution for several reasons. First, Sunda has hosted abundant historic volcanic activity. Second, with the notable exception of Krakatau, every volcano in the arc is subaerial from base to cone and, therefore, can be readily identified where there is a suitable extent of local mapping that can be used to ground-truth satellite imagery. Third, there are significant changes in the stress regime along the length of the arc, allowing the influence of the upper plate to be evaluated by comparison of different arc segments. Finally, much of the Sunda Arc has proved difficult to accommodate in models that try to relate volcano distribution to the depth to the subducted slab. We apply an objective line-fitting protocol; the Hough Transform, to explore the distribution of volcanoes

  17. Postcaldera volcanism and hydrothermal activity revealed by autonomous underwater vehicle surveys in Myojin Knoll caldera, Izu-Ogasawara arc

    NASA Astrophysics Data System (ADS)

    Honsho, Chie; Ura, Tamaki; Kim, Kangsoo; Asada, Akira

    2016-06-01

    Myojin Knoll caldera, one of the submarine silicic calderas lying on the volcanic front of the northern Izu-Ogasawara arc, has attracted increasing attention since the discovery of a large hydrothermal field called the Sunrise deposit. Although numerous submersible surveys have been conducted in Myojin Knoll caldera, they have not sufficiently explored areas to produce a complete picture of the caldera and understand the origin of the Sunrise deposit. We conducted comprehensive deep-sea surveys using an autonomous underwater vehicle and obtained high-resolution bathymetric and magnetic data and sonar images from ~70% of the caldera. The detailed bathymetric map revealed that faulting and magma eruptions, possibly associated with an inflation-deflation cycle of the magma reservoir during postcaldera volcanism, had generally occurred in the caldera wall. The main dome of the central cone was covered with lava flows and exhibits exogenous growth, which is unusual for rhyolitic domes. The magnetization distribution in the central cone indicates preferential magma intrusion along a NW-SE direction. It is presumed that magma migrated along this direction and formed a rhyolite dome at the foot of the southeastern caldera wall, where the Sunrise deposit occurs. The Sunrise deposit is composed mainly of three ridges extending in slope directions and covers ~400 × ~400 m. Magnetization reduction in the deposit area is small, indicating that the alteration zone beneath the Sunrise deposit is slanting rather than vertical. It is presumed that several slanting and near-vertical volcanic vents serve as pathways of hydrothermal fluid in Myojin Knoll caldera.

  18. Early Jurassic Volcanism in the South Lhasa Terrane, Southern Tibet: Record of Back-arc Extension in the Active Continental Margin

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Zhao, Z.; Zhu, D. C.; Wang, Z.; Liu, D.; Mo, X.

    2015-12-01

    Indus-Yarlung Zangbo Suture Zone (IYZSZ) represents the Mesozoic remnants of the Neo-Tethyan Ocean lithosphere after its northward subduction beneath the Lhasa Terrane. The evolution of the Neo-Tethyan Ocean prior to India-Asia collision remains unclear. To explore this period of history, we investigate zircon U-Pb geochronology, geochemistry and Nd-Hf isotopes of the Early Jurassic bimodal-like volcanic sequence around Dagze area, south Tibet. The volcanic sequence comprises calc-alkaline basalts to rhyolites whereas intermediate components are volumetrically restricted. Zircons from a basaltic andesite yielded crystallization age of 178Ma whereas those from 5 silicic rocks were dated at 183-174Ma, which suggest that both the basaltic and the silicic rocks are coeval. The basaltic rocks are enriched in LREE and LILE, and depleted in HFSE, with Epsilon Nd(t) of 1.6-4.0 and zircon Epsilon Hf(t) of 0.7-11.8, which implies that they were derived from a heterogenetic mantle source metasomatized by subduction components. Trace element geochemistry shows that the basaltic rocks are compositionally transitional from normal mid-ocean ridge basalts (N-MORB) to island arc basalts (IAB, e.g. Zedong arc basalts of ~160-155Ma in the south margin of Lhasa Terrane), with the signature of immature back-arc basin basalts. The silicic rocks display similar Nd-Hf isotopic features of the Gangdese batholith with Epsilon Nd(t) of 0.9-3.4 and zircon Epsilon Hf(t) of 2.4-17.7, indicating that they were possibly generated by anatexis of basaltic juvenile lower crust, instead of derived from the basaltic magma. These results support an Early to Middle Jurassic (183-155Ma) model that the back-arc extension tectonic setting were existing in the active continental margin in the south Lhasa Terrane.

  19. Volcanic Supply Rate and Evolving of the Izu-Bonin Arc

    NASA Astrophysics Data System (ADS)

    Fujioka, K.; Kido, M.

    2001-12-01

    The Izu-Bonin Arc-Trench system is one of the oceanic arc-trench system which is crucial for understanding how to evolve island arc and continental crust during Archean. We estimated total volume of the volcanic materials accreted to IB arc since 48 Ma by the model crustal structure and bathymetric map available through IB arc which is divided into three segments by two tectonic lines. ODP Leg 125 and 126 have revealed the volcanic history of the IB arc. We took into account the spatial distribution and isotopic ages of the volcanic rocks and elucidated the arc evolution by the division of events occurred during 48-43, 43-34, 34-27, 27-15, 15-6, 6-2, and < 2Ma, respectively. Boninitic rocks pored out on the deep sea environment during 48-43 Ma. After the change of the Pacific plate motion strong boninitic and calc-alkalic volcanism took place along the paleo-IB arc during 43-34 Ma. The arc grew quickly to the shallow level and yielded explosive volcanic materials and debris flow deposits until 34 Ma. Paleo-IB arc split into to halves, present-day IB arc and Palau-Kyushu remnant arc to form Shikoku and Parece Vela backarc basins at 30-27 Ma. Volcanic activity during the 27-15 Ma was quiescent compared to the other stage because of the backarc spreading consumed a large amount of volcanic materials. Explosive and bimodal volcanism were dominated to form backarc depressions in the backarc area and strata-volcanoes on the volcanic front during 15-6 Ma. Finally, strato-volcanoes and catastrophic explosion of the caldera forming acidic volcanics were predominating on the volcanic front since 2 Ma. Through the volcanic history the IB arc was formed most part during initial 10 my to build a paleo-IB arc and volcanic supply rate during initial 10 my was very high, almost compatible to that of super plume.

  20. Propagation of back-arc extension into the arc lithosphere in the southern New Hebrides volcanic arc

    NASA Astrophysics Data System (ADS)

    Patriat, M.; Collot, J.; Danyushevsky, L.; Fabre, M.; Meffre, S.; Falloon, T.; Rouillard, P.; Pelletier, B.; Roach, M.; Fournier, M.

    2015-09-01

    New geophysical data acquired during three expeditions of the R/V Southern Surveyor in the southern part of the North Fiji Basin allow us to characterize the deformation of the upper plate at the southern termination of the New Hebrides subduction zone, where it bends eastward along the Hunter Ridge. Unlike the northern end of the Tonga subduction zone, on the other side of the North Fiji Basin, the 90° bend does not correspond to the transition from a subduction zone to a transform fault, but it is due to the progressive retreat of the New Hebrides trench. The subduction trench retreat is accommodated in the upper plate by the migration toward the southwest of the New Hebrides arc and toward the south of the Hunter Ridge, so that the direction of convergence remains everywhere orthogonal to the trench. In the back-arc domain, the active deformation is characterized by propagation of the back-arc spreading ridge into the Hunter volcanic arc. The N-S spreading axis propagates southward and penetrates in the arc, where it connects to a sinistral strike-slip zone via an oblique rift. The collision of the Loyalty Ridge with the New Hebrides arc, less than two million years ago, likely initiated this deformation pattern and the fragmentation of the upper plate. In this particular geodynamic setting, with an oceanic lithosphere subducting beneath a highly sheared volcanic arc, a wide range of primitive subduction-related magmas has been produced including adakites, island arc tholeiites, back-arc basin basalts, and medium-K subduction-related lavas.

  1. Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

    NASA Astrophysics Data System (ADS)

    Ruch, J.; Vezzoli, L.; De Rosa, R.; Di Lorenzo, R.; Acocella, V.

    2016-02-01

    The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive. To better understand these relationships, we collected stratigraphic, volcanic, and structural field data along the strike-slip central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures, and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activities steadily migrated eastward and currently focus on a 10 km long × 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter term, days to months), rather than from steady longer-term regional tectonics (102-104 years). More in general, the central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface.

  2. Eastern Aleutian volcanic arc digital model - version 1.0

    USGS Publications Warehouse

    Saltus, R.W.; Barnett, Adrienne

    2000-01-01

    A 3-dimensional model (Figure 1) of the interaction of oceanic and continental tectonic plates along the eastern portion of the Aleutian volcanic arc helps in the visualization of basic tectonic, geodetic, and geophysical data in this active plate boundary region. The model is constrained by topographic, bathymetric, and seismic data and by the principle of isostasy. Examination of free-air gravity anomalies over the region indicates where the flexural strength of the down-going oceanic slab disturbs local isostatic balance and where low-density sediments have accumulated in the trench and forearc regions.

  3. Unraveling the diversity in arc volcanic eruption styles: Examples from the Aleutian volcanic arc, Alaska

    NASA Astrophysics Data System (ADS)

    Larsen, Jessica F.

    2016-11-01

    The magmatic systems feeding arc volcanoes are complex, leading to a rich diversity in eruptive products and eruption styles. This review focuses on examples from the Aleutian subduction zone, encompassed within the state of Alaska, USA because it exhibits a rich diversity in arc structure and tectonics, sediment and volatile influx feeding primary magma generation, crustal magma differentiation processes, with the resulting outcome the production of a complete range in eruption styles from its diverse volcanic centers. Recent and ongoing investigations along the arc reveal controls on magma production that result in diversity of eruptive products, from crystal-rich intermediate andesites to phenocryst-poor, melt-rich silicic and mafic magmas and a spectrum in between. Thus, deep to shallow crustal "processing" of arc magmas likely greatly influences the physical and chemical character of the magmas as they accumulate in the shallow crust, the flow physics of the magmas as they rise in the conduit, and eruption style through differences in degassing kinetics of the bubbly magmas. The broad spectrum of resulting eruption styles thus depends on the bulk magma composition, melt phase composition, and the bubble and crystal content (phenocrysts and/or microlites) of the magma. Those fundamental magma characteristics are in turn largely determined by the crustal differentiation pathway traversed by the magma as a function of tectonic location in the arc, and/or the water content and composition of the primary magmas. The physical and chemical character of the magma, set by the arc differentiation pathway, as it ascends towards eruption determines the kinetic efficiency of degassing versus the increasing internal gas bubble overpressure. The balance between degassing rate and the rate at which gas bubble overpressure builds then determines the conditions of fragmentation, and ultimately eruption intensity.

  4. The geochemistry of lithium-bearing geothermal water, Taupo Volcanic Zone, and shallow fluid processes in a very active silicic volcanic arc

    NASA Astrophysics Data System (ADS)

    Dean, A. S.; Hoskin, P. W.; Rudnick, R. L.; Liu, X.; Boseley, C.

    2011-12-01

    The Li abundances and isotopic systematics of Taupo Volcanic Zone (TVZ) geothermal fluids preserves a record of processes occurring within shallow portions of geothermal reservoirs as well as deeper portions of the arc crust. Understanding Li cycling and isotopic fractionation in TVZ geothermal systems contributes to a more refined understanding of physicochemical processes affecting New Zealand's geothermal resources. A comprehensive dataset of 73 samples was compiled, with samples collected from geothermal surface features (springs, spouters, geysers, etc.) and electric-power industry production wells, collectively representing18 geothermal fields across the breadth and width the TVZ. No comparable dataset of fluid analyses exists. Ion chromatography, AAS, and quadrupole ICP-MS analyses were done for Li, Cl-, SiO2, SO42- K, Na, Ca, Mg, B, Sr and Pb concentrations. Lithium abundance in geothermal fluids from the TVZ have a dataset-wide average of 5.9 mg/L and range 4 μg/L to 29 mg/L. The Li abundance and Li/Cl ratios for geothermal water and steam condensates vary systematically as a result of boiling, mixing, and water/rock reaction. Lithium abundance and Li/Cl ratios are, therefore, indicators of shallow (above 2.5 km) and locally variable reservoir processes. δ7Li analysis of 63 samples was performed at the University of Maryland, College Park. Data quality was controlled by measurement of L-SVEC as a calibration standard and by multiple analysis of selected samples. The average δ7Li value for TVZ geothermal fluids is -0.8%. Most δ7Li values for geothermal water fall within a small range of about -3% to+2% indicating similar processes are causing similar isotopic fractionation throughout the region. Considered together, Li aundances and δ7Li values, in combination with numerical models, indicate possible evolution pathways and water/rock reactions in TVZ geothermal systems. Models based on rocks and surface water analysis indicate that Li cycles and

  5. Petrographic and Geochemical Investigation of Andesitic Arc Volcanism: Mount Kerinci, Sunda Arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Tully, M.; Saunders, K.; Troll, V. R.; Jolis, E.; Muir, D. D.; Deegan, F. M.; Budd, D. A.; Astbury, R.; Bromiley, G. D.

    2014-12-01

    Present knowledge of the chain of dominantly andesitic volcanoes, which span the Sumatran portion of the Sunda Arc is extremely limited. Previous studies have focused on Toba and Krakatau, although over 13 further volcanic edifices are known. Several recent explosive eruptions in Sumatra such as that of Mt. Sinabung, 2014, have highlighted the potential hazard that these volcanoes pose to the local and regional communities. Mount Kerinci, is one of the most active of the volcanoes in this region, yet little is known about the petrogenesis of the magma by which it is fed. Kerinci is located approximately mid-way between Toba in the North and Krakatau in the south. Along arc variations are observed in the major, minor and trace elements of whole rock analyses. However, bulk rock approaches produce an average chemical composition for a sample, potentially masking important chemical signatures. In-situ micro-analytical analysis of individual components of samples such as melt inclusions, crystals and groundmass provides chemical signatures of individual components allowing the evolution of volcanic centres to be deciphered in considerably more detail. Examination of whole rock chemistry indicates its location may be key to unravelling the petrogenesis of the arc as significant chemical changes occur between Kerinci and Kaba, 250 km to the south. Kerinci samples are dominantly porphyritic with large crystals of plagioclase, pyroxene and Fe-Ti oxides, rare olivine crystals are observed. Plagioclase and pyroxene crystals are chemically zoned and host melt inclusions. Multiple plagioclase populations are observed. A combination of in-situ micro-analysis techniques will be used to characterise the chemical composition of melt inclusions and crystals. These data can be used along with extant geothermobarometric models to help determine the magma source, storage conditions and composition of the evolving melt. Integration of the findings from this study with existing data for

  6. A Finite Element Model for the Active Extension in the Central Part of the Trans Mexican Volcanic Belt: Control of Subduction on Intra-arc Deformation

    NASA Astrophysics Data System (ADS)

    Contreras, J.

    2005-12-01

    An extensional strain field of normal faults with a preferred E-W orientation dominates the central part of the Trans-Mexican Volcanic Belt (TMVB). Faults lay west of 99 W meridian. These faults tend to form tectonic depressions filled with lake sediments and volcanic rocks. Typically these faults have lengths < 50 km, are disconnected, and are seismically active. The origin of the extension is enigmatic and has been attributed to collapse of the volcanic belt (Suter, 2001), partition of deformation induced by subduction (Alanis et al., 1998), end recently to mantle plumes and rift dynamics (Marquez et al, 1999; Verma, 2002). This work uses a finite element model to explain the origin of the extension based on the dynamical subduction model proposed by Scholz and Campos (1995). These authors demonstrated that resistive forces in the mantle as well as slab pull control the coupling of the plates. They also showed that in some arcs these forces put in tension the interior of the overriding plate leading to back-arc extension. The model used here incorporates an iso-viscous mantle whose flow is forced by subduction of the Rivera and Cocos plates; deformation in North America plate (central Mexico) is modeled by an elastic plate; weakening of the elastic plate by heat flow is also considered. Boundary conditions and geometries in the model are constrained by geological observations like convergence rates, geometry of the Wadati-Benioff zone, heat-flow measurements, and gravity modeling in central-south Mexico. Two 2D-models are presented: one cutting through the Mexican state of Michoacan, characterized by a high subduction angle, and a second one through Guerrero, in southern Mexico, which has a sub-horizontal angle. Hypocenters of earthquakes, however, indicate that the subducted plate bends under the TMVB, increasing its subduction angle. Results from the model show that mantle corner flow under Michoacan drags downwards the edge of North America, inducing upward

  7. Continental arc volcanism as the principal driver of icehouse-greenhouse variability

    NASA Astrophysics Data System (ADS)

    McKenzie, N. Ryan; Horton, Brian K.; Loomis, Shannon E.; Stockli, Daniel F.; Planavsky, Noah J.; Lee, Cin-Ty A.

    2016-04-01

    Variations in continental volcanic arc emissions have the potential to control atmospheric carbon dioxide (CO2) levels and climate change on multimillion-year time scales. Here we present a compilation of ~120,000 detrital zircon uranium-lead (U-Pb) ages from global sedimentary deposits as a proxy to track the spatial distribution of continental magmatic arc systems from the Cryogenian period to the present. These data demonstrate a direct relationship between global arc activity and major climate shifts: Widespread continental arcs correspond with prominent early Paleozoic and Mesozoic greenhouse climates, whereas reduced continental arc activity corresponds with icehouse climates of the Cryogenian, Late Ordovician, late Paleozoic, and Cenozoic. This persistent coupled behavior provides evidence that continental volcanic outgassing drove long-term shifts in atmospheric CO2 levels over the past ~720 million years.

  8. Continental arc volcanism as the principal driver of icehouse-greenhouse variability.

    PubMed

    McKenzie, N Ryan; Horton, Brian K; Loomis, Shannon E; Stockli, Daniel F; Planavsky, Noah J; Lee, Cin-Ty A

    2016-04-22

    Variations in continental volcanic arc emissions have the potential to control atmospheric carbon dioxide (CO2) levels and climate change on multimillion-year time scales. Here we present a compilation of ~120,000 detrital zircon uranium-lead (U-Pb) ages from global sedimentary deposits as a proxy to track the spatial distribution of continental magmatic arc systems from the Cryogenian period to the present. These data demonstrate a direct relationship between global arc activity and major climate shifts: Widespread continental arcs correspond with prominent early Paleozoic and Mesozoic greenhouse climates, whereas reduced continental arc activity corresponds with icehouse climates of the Cryogenian, Late Ordovician, late Paleozoic, and Cenozoic. This persistent coupled behavior provides evidence that continental volcanic outgassing drove long-term shifts in atmospheric CO2 levels over the past ~720 million years.

  9. Geochemical differences between along-arc and across-arc volcanics in west-central Nicaragua

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Freundt, Armin; Wörner, Gerhard; Kutterolf, Steffen

    2012-04-01

    The La Paz Centro - Malpaisillo Lineament (LPML) in west-central Nicaragua is a north-south striking, 20 km long chain of maars and cinder cones, which intersects the northwest-southeast striking main volcanic front. A tectonic control of LPML volcanism is likely but only evident for the Malpaisillo fissure at the northern end of the LPML. Previous work demonstrated geochemical variations implying changes in mantle-source composition (i.e., added slab components) along the Central American Volcanic Arc at spatial scales of some 10's of kilometers. Our study of the LPML shows that minor but systematic changes also occur across the arc within 20 km distance. Variations in trace element ratios such as Zr/Nb, Ba/Th, Ba/La, Th/Zr, U/La and La/Yb along the LPML, i.e. across the volcanic front indicate little change in the degree of partial melting but an increase particularly in the hemipelagic sediment component in the mantle source from the fore arc towards the arc front, followed by a decrease behind the arc. Interestingly, the slab component is most prominent just in front of the arc. About 60 km southeast of the LPML, the Nejapa-Miraflores volcanic and tectonic lineament, which marks a 20 km north-south offset in the arc, differs substantially from the LPML. There is a wide scatter in incompatible trace element ratios indicating a heterogeneous mantle source at small spatial scales (c. 1 km). This mantle heterogeneity may represent vertical rather than across-arc variations and is probably related to the arc offset, because in the absence of such offset at the LPML mantle source conditions vary much less but more systematically.

  10. Tertiary volcanic rocks from the Halmahera arc, Eastern Indonesia

    NASA Astrophysics Data System (ADS)

    Sufni Hakim, A.; Hall, Robert

    Halmahera is a K-shaped volcanic island arc situated near the junction of the Australian, Eurasian and Philippine Sea Plates. Recent work on Halmahera has identified two important pre-Quaternary intervals of volcanism in western Halmahera. Neogene andesites were produced in the Halmahera Arc during subduction of the Molucca Sea Plate at the western boundary of the Philippine Sea Plate. Pre-Neogene basalts of the Oha Formation are probably the equivalent of volcanic basement rocks found elsewhere in the Philippine Sea region and are interpreted to represent the products of Late Mesozoic or Early Tertiary subduction within the Pacific. Neogene andesites and subordinate basalts contain abundant phenocrysts; plaioclase feldspars, orthopyroxene, clinopyroxene, hornblende and titanomagnetic are common. Like the products of Quaternary volcanism andesitic bulk rock compositions reflect high proportions of acid glass. The Neogene volcanic rocks have evolved by plagioclase, pyroxene, hornblende and magnetite fractionation. They are medium-K to high-K rocks of the calcalkaline series, REE patterns are sloping, typical of arc volcanic rocks, and MORB-normalized element plots show strong depletion of Nb, similar to other West Pacific arc volcanic rocks. Most samples are very fresh. A single zeolite (mordenite) is rarely present and chlorites, smectites and chalcedony occur in a few samples. The local, very low-grade, alteration is typical of geothermal environments. Volcanic rocks of the Oha Formation, which forms the basement of the western arms, are aphyric and phyric basalts, typically with textures which reflect rapid cooling. Plagioclase feldspar, olivine and clinopyroxene phenocrysts are common, orthopyroxene is rare and phenocrysts of hornblende and magnetite are absent. The Oha Formation basalts evolved by olivine, plagioclase and clinopyroxene fractionation. They are depleted in HFS elements, and enrichment in LIL elements is partly due to extensive sub

  11. Investigation of the deep crustal structure and magmatic activity at the NW Hellenic Volcanic Arc with 3-D aeromagnetic inversion and seimotectonic analysis.

    NASA Astrophysics Data System (ADS)

    Efstathiou, Angeliki; Tzanis, Andreas; Chailas, Stylianos; Stamatakis, Michael

    2013-04-01

    We report the results of a joint analysis of geophysical (aeromagnetic) and seismotectonic data, applied to the investigation of the deep structure, magmatic activity and geothermal potential of the north-western stretches of the Hellenic Volcanic Arc (HVA). The HVA is usually considered to be a single arcuate entity stretching from Sousaki (near Corinth) at the NW, to Nisyros Island at the SE. However, different types of and their ages indicate the presence of two different volcanic groups. Our study focuses on the northern part of the west (older) volcanic group and includes the Crommyonian (Sousaki) volcanic field at the west end of Megaris peninsula (east margin on the contemporary Corinth Rift), the Aegina and Methana volcanic complex at the Saronic Gulf, where typical Quaternary calc-alkaline volcanics predominate, and the Argolid peninsula to the south and south-west. In addition to the rocks associated with Quaternary volcanism, the study area includes a series of Mesozoic ultramafic (ophiolitic) outcrops at the Megaris peninsula, to the north and north-east of the Crommyonian volcanic field, as well as throughout the Argolid. A major deep structural and tectonic feature of the study area, and one with profound influence on crustal deformation and the evolution of rapidly deforming extensional structures like the Corinth Rift and the Saronic Gulf, is the local geometry and dynamics of the African oceanic crust subducting beneath the Aegean plate. Locally, the subducting slab has a NNW strike and ENE plunge, with the dip angle changing rapidly (steepening) approx. beneath the Argolid. The aeromagnetic data was extracted from the recently (re)compiled aeromagnetic map of Greece (Chailas et al, 2010) and was inverted with the UBC-GIF magnetic inversion suite (Li and Oldenburg, 1996). The inversion included rigorous geological constraints introduced by means of numerous in-situ magnetic susceptibility measurements. The inversion has imaged several isolated

  12. Geology and geochemistry characteristics of the Chiapanecan Volcanic Arc (Central Area), Chiapas Mexico

    NASA Astrophysics Data System (ADS)

    Mora, J. C.; Jaimes-Viera, M. C.; Garduño-Monroy, V. H.; Layer, P. W.; Pompa-Mera, V.; Godinez, M. L.

    2007-04-01

    The Chiapanecan Volcanic Arc (CVA), located in the central portion of the State of Chiapas, is a 150 km stretch of volcanoes irregularly aligned in the northwest direction between two great volcanic features: the Trans-Mexican Volcanic Belt to the northwest and the Central American Volcanic Arc to the southeast. The CVA is located in a complex zone marking the interaction of the North American, Caribbean and Cocos plates, near the Motagua-Polochic fault system, the boundary between North American and Caribbean plates. The central part of the CVA is composed of an irregular northwest alignment of at least 10 volcanic structures generally lying along NNW-SSE-trending faults splayed from the Motagua-Polochic system. Among the structures there are seven volcanic domes (Huitepec, Amahuitz, La Iglesia, Mispía, La Lanza, Venustiano Carranza and Santotón), one explosion crater (Navenchauc), one collapse structure (Apas), and one dome complex (Tzontehuitz). In the majority of the structures there is a clear resurgence with the formation of several domes in the same structure, with the destruction of previous domes (Navenchauc) or with the formation of new explosion craters or collapse structures (Apas). The volcanic activity in the CVA was mainly effusive accompanied by explosive and phreatomagmatic events and is characterized by volcanic domes accompanied by block-and-ash-flows, ash flows with accretionary lapilli, falls, and pumice flows. The volcanic structures and deposits are calcalkaline in composition with a medium to high content of potassium. CVA volcanic rocks vary from andesite to dacite with SiO 2 between 57 and 66 wt.%, show low concentrations of Ti, P, Nb and Ta, are enriched in Light Rare Earths, depleted in Heavy Rare Earths, and show a small Eu anomaly; all indicative of arc-related volcanism associated with subduction of the Cocos plate under the North American plate, but complicated by the geometry of the plate boundary fault system.

  13. Geothermal systems in volcanic arcs: Volcanic characteristics and surface manifestations as indicators of geothermal potential and favorability worldwide

    NASA Astrophysics Data System (ADS)

    Stelling, P.; Shevenell, L.; Hinz, N.; Coolbaugh, M.; Melosh, G.; Cumming, W.

    2016-09-01

    This paper brings a global perspective to volcanic arc geothermal assessments by evaluating trends and correlations of volcanic characteristic and surface manifestation data from world power production sites in subduction zone volcanic settings. The focus of the work was to evaluate volcanic centers individually and as a group in these arcs by correlating various geologic characteristics with known potential to host electricity grade geothermal systems at the volcanic centers. A database was developed that describes key geologic factors expected to be indicative of productive geothermal systems in a global training set, which includes all 74 subduction zone volcanic centers world-wide with current or proven power production capability. Importantly, this data set only contains data from subduction zone volcanoes and contains no negative cases, limiting the populations of any statistical groups. Regardless, this is the most robust geothermal benchmark training set for magmatic-heated systems to date that has been made public. The work reported here is part of a larger project that included data collection, evaluation, correlations and weightings, fairway and favorability modeling and mapping, prediction of blind systems, and uncertainty analysis to estimate errors associated with model predictions. This first paper describes volcano characteristics, compositions and eruption ages and trends along with surface manifestation observations and temperatures as they relate to known power producing systems. Our findings show a strong correlation between the presence and size of active flank fumarole areas and installed power production. Additionally, the majority of volcanic characteristics, including long-held anecdotal correlations related to magmatic composition or size, have limited to no correlation with power production potential. Notable exceptions are correlations between greater power yield from geothermal systems associated with older (Pleistocene) caldera systems

  14. Slip partitioning in the Lesser Antilles arc: implications for seismic and volcanic hazards

    NASA Astrophysics Data System (ADS)

    Feuillet, N.; Leclerc, F.; Deplus, C.; Tapponnier, P.; Beauducel, F.; Jacques, E.; Beck, C.; Le Friant, A.; Boudon, G.; LeBrun, J.; Bazin, S.

    2012-12-01

    The Lesser Antilles arc is a region of high seismic and volcanic hazards exposed to large megathrust earthquakes along the subduction zone, to more local events within the arc and to destructive eruptions as in 1902 at Mount Pelee or in 1995 at Soufriere Hills of Montserrat. On November 21, 2004, the Guadeloupe archipelago was struck by a magnitude 6.3 superficial and very damaging earthquake. To better constrain the mechanisms of the recent deformation within the arc and its link with volcanic activity, several marine cruises were conducted since 1998 (AGUADOMAR, GWADASEIS and BATHYSAINTES). A lot of high-resolution data were acquired: Bathymetry, back-scatter images, Küllenberg cores, seismic reflection and chirp profiles. By combining them with onshore data, observations and measurements in the field, we have documented at several scales the active faulting between St Lucia and Saba, the northernmost emerged volcano of the arc. We have shown that the Lesser Antilles arc is crosscut by two main fault sets: arc perpendicular graben in the outer arc and a large en echelon system along the inner active arc. Volcanic complexes are crosscut by or emplaced within fault systems implying that faulting controls the emission of volcanic products. The Nevis volcano is growing on the hanging-wall of a large NE-dipping offshore normal fault probably responsible for the M6+ 1961 earthquake. Montserrat volcanic domes are aligned along a fissure set, parallel to large normal faults and Soufriere of Guadeloupe lies at the western tip of the Marie-Galante graben. At plate scale, the arc perpendicular fore arc graben and inner arc en echelon system are connected, forming a sinistral horsetail, east of the tip of the left lateral Puerto Rico fault zone that takes up the trench parallel component of convergence between the North American and Caribbean plates, west of the Anegada passage. Considering the newly published Caribbean North American Euler vector, the trench parallel

  15. The volcanic response to deglaciation: Evidence from glaciated arcs and a reassessment of global eruption records

    NASA Astrophysics Data System (ADS)

    Watt, Sebastian F. L.; Pyle, David M.; Mather, Tamsin A.

    Several lines of evidence have previously been used to suggest that ice retreat after the last glacial maximum (LGM) resulted in regionally-increased levels of volcanic activity. It has been proposed that this increase in volcanism was globally significant, forming a substantial component of the post-glacial rise in atmospheric CO2, and thereby contributing to climatic warming. However, as yet there has been no detailed investigation of activity in glaciated volcanic arcs following the LGM. Arc volcanism accounts for 90% of present-day subaerial volcanic eruptions. It is therefore important to constrain the impact of deglaciation on arc volcanoes, to understand fully the nature and magnitude of global-scale relationships between volcanism and glaciation. The first part of this paper examines the post-glacial explosive eruption history of the Andean southern volcanic zone (SVZ), a typical arc system, with additional data from the Kamchatka and Cascade arcs. In all cases, eruption rates in the early post-glacial period do not exceed those at later times at a statistically significant level. In part, the recognition and quantification of what may be small (i.e. less than a factor of two) increases in eruption rate is hindered by the size of our datasets. These datasets are limited to eruptions larger than 0.1 km3, because deviations from power-law magnitude-frequency relationships indicate strong relative under-sampling at smaller eruption volumes. In the southern SVZ, where ice unloading was greatest, eruption frequency in the early post-glacial period is approximately twice that of the mid post-glacial period (although frequency increases again in the late post-glacial). A comparable pattern occurs in Kamchatka, but is not observed in the Cascade arc. The early post-glacial period also coincides with a small number of very large explosive eruptions from the most active volcanoes in the southern and central SVZ, consistent with enhanced ponding of magma during

  16. The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

    NASA Astrophysics Data System (ADS)

    Brounce, Maryjo; Kelley, Katherine A.; Stern, Robert; Martinez, Fernando; Cottrell, Elizabeth

    2016-10-01

    In the Mariana convergent margin, large arc volcanoes disappear south of Guam even though the Pacific plate continues to subduct and instead, small cones scatter on the seafloor. These small cones could form either due to decompression melting accompanying back-arc extension or flux melting, as expected for arc volcanoes, or as a result of both processes. Here, we report the major, trace, and volatile element compositions, as well as the oxidation state of Fe, in recently dredged, fresh pillow lavas from the Fina Nagu volcanic chain, an unusual alignment of small, closely spaced submarine calderas and cones southwest of Guam. We show that Fina Nagu magmas are the consequence of mantle melting due to infiltrating aqueous fluids and sediment melts sourced from the subducting Pacific plate into a depleted mantle wedge, similar in extent of melting to accepted models for arc melts. Fina Nagu magmas are not as oxidized as magmas elsewhere along the Mariana arc, suggesting that the subduction component responsible for producing arc magmas is either different or not present in the zone of melt generation for Fina Nagu, and that amphibole or serpentine mineral destabilization reactions are key in producing oxidized arc magmas. Individual Fina Nagu volcanic structures are smaller in volume than Mariana arc volcanoes, although the estimated cumulative volume of the volcanic chain is similar to nearby submarine arc volcanoes. We conclude that melt generation under the Fina Nagu chain occurs by similar mechanisms as under Mariana arc volcanoes, but that complex lithospheric deformation in the region distributes the melts among several small edifices that get younger to the northeast.

  17. Effect of Aseismic Ridge Subduction on Volcanism in the NE Lesser Antilles Arc

    NASA Astrophysics Data System (ADS)

    Stinton, A. J.; Hatfield, R. G.; McCanta, M. C.

    2014-12-01

    The interaction of aseismic ridges or buoyant crust in subduction zones can affect the volcanism occurring on the overriding plate. Here we describe the affect of the subduction of an aseismic ridge on volcanism in the NE Lesser Antilles. The Lesser Antilles island arc is a result of westward subduction of the North American plate beneath the Caribbean plate and stretches 800 km from Saba in the north to Grenada in the south. From Guadeloupe northwards, the arc bifurcates into an eastern, inactive arc (known as the Limestone Caribees) and a western, active arc (Volcanic Caribees). It has been suggested that this bifurcation is the result of the subduction of buoyant crust in the form of at least two aseismic ridges, in the North American plate. In 2012, IODP Expedition 340 recovered 130 m of core from site U1396, located 55 km SW of Montserrat, Lesser Antilles. The core contains a detailed record of volcanism, in the form of more than 180 tephra layers, that stretches back nearly 4.5 Ma. This is the longest and most complete record of volcanism for the NE Lesser Antilles and provides insight into the evolution and development of the island arc in this region. A variety of techniques are being applied to the tephra layers from U1396 to determine their age, chemistry, components and origin. Here we present preliminary results from paeleomagnetic age determinations for each tephra layer to show how the subduction of aseismic ridges on the North American plate has affected the rate of volcanism and development of the island arc in the NE Lesser Antilles over the last 4.5 Ma.

  18. Submarine Arc Volcanism in the Southern Mariana Arc: Results of Recent ROV studies

    NASA Astrophysics Data System (ADS)

    Nichols, A. R.; Tamura, Y.; Stern, R. J.; Embley, R. W.; Hein, J. R.; Jordan, E.; Ribeiro, J. M.; Sica, N.; Kohut, E. J.; Whattam, S. A.; Hirahara, Y.; Senda, R.; Nunokawa, A.

    2009-12-01

    The submarine Diamante cross-arc volcanoes (~16°N) and the Sarigan-Zealandia Bank Multi-Volcano Complex (SZBMVC; ~16°45’N), north and south, respectively, of Anatahan Island in the southern Mariana Arc, were studied during several dives in June 2009 using the ROV Hyper-Dolphin, cruise NT09-08 (R/V Natsushima); neither has been studied in detail before. The data collected provide a new perspective on how the subduction factory operates to complement previous studies on other cross-arc volcanic chains in the Izu-Bonin-Mariana Arc. The Diamante complex consists of three major edifices, two cones (West and Central Diamante) and a more complex caldera-like edifice at the volcanic front (East Diamante). West and Central Diamante are basaltic volcanoes but East Diamante has a more complex history. Our studies indicate initial construction of a basaltic volcano. Magmatic evolution led to a violent caldera-forming and quieter dome-building events. Post-caldera quiescence allowed a carbonate platform to grow, now preserved on the eastern caldera wall. Felsic magma or hot rock provides a heat source for an active hydrothermal field associated with felsic domes in the caldera, which NOAA investigators discovered in 2004. A new type of hydrothermal deposit was discovered in the hydrothermal field, consisting of large sulfide-sulfate mounds topped by bulbous constructions of low-temperature Fe and Mn oxides. Vents on the mounds were observed to emit shimmering water. The SZBMVC consists of six closely spaced edifices whose loci are aligned along two parallel trends, one along the volcanic front (Zealandia Bank, Sarigan and South Sarigan), and one about 15 km west towards the rear-arc (Northwest Zealandia, West Zealandia and West Sarigan). Zealandia Bank dives revealed that, as with East Diamante, initial activity was basaltic and became more evolved with time. The western half of Zealandia Bank is dominated by felsic lavas centered on a small (~2 km diameter) caldera and

  19. Rapid extension in an Eocene volcanic arc: Structure and paleogeography of an intra-arc half graben in central Idaho

    USGS Publications Warehouse

    Janecke, S.U.; Hammond, B.F.; Snee, L.W.; Geissman, J.W.

    1997-01-01

    tectonism during conglomerate deposition. Provenance data from the sedimentary rocks imply that the highland in the footwall of the Panther Creek half graben was never thickly blanketed by synex-tension volcanic rocks, despite intense volcanic activity. Analysis of the Panther Creek half graben and other intra-arc rift basins supports previous interpretations that relative rates of volcanism and subsidence control the proportion of volcanic rocks deposited in intra-arc rifts.

  20. Discovery of an active shallow submarine silicic volcano in the northern Izu-Bonin Arc: volcanic structure and potential hazards of Oomurodashi Volcano (Invited)

    NASA Astrophysics Data System (ADS)

    Tani, K.; Ishizuka, O.; Nichols, A. R.; Hirahara, Y.; Carey, R.; McIntosh, I. M.; Masaki, Y.; Kondo, R.; Miyairi, Y.

    2013-12-01

    Oomurodashi is a bathymetric high located ~20 km south of Izu-Oshima, an active volcanic island of the northern Izu-Bonin Arc. Using the 200 m bathymetric contour to define its summit dimensions, the diameter of Oomurodashi is ~20 km. Oomurodashi has been regarded as inactive, largely because it has a vast flat-topped summit at 100 - 150 meters below sea level (mbsl). During cruise NT07-15 of R/V Natsushima in 2007, we conducted a dive survey in a small crater, Oomuro Hole, located in the center of the flat-topped summit, using the remotely-operated vehicle (ROV) Hyper-Dolphin. The only heat flow measurement conducted on the floor of Oomuro Hole during the dive recorded an extremely high value of 4,200 mW/m2. Furthermore, ROV observations revealed that the southwestern wall of Oomuro Hole consists of fresh rhyolitic lavas. These findings suggest that Oomurodashi is in fact an active silicic submarine volcano. To confirm this hypothesis, we conducted detailed geological and geophysical ROV Hyper-Dolphin (cruise NT12-19). In addition to further ROV surveys, we carried out single-channel seismic (SCS) surveys across Oomurodashi in order to examine the shallow structures beneath the current edifice. The ROV surveys revealed numerous active hydrothermal vents on the floor of Oomuro Hole, at ~200 mbsl, with maximum water temperature measured at the hydrothermal vents reaching 194°C. We also conducted a much more detailed set of heat flow measurements across the floor of Oomuro Hole, detecting very high heat flows of up to 29,000 mW/m2. ROV observations revealed that the area surrounding Oomuro Hole on the flat-topped summit of Oomurodashi is covered by extensive fresh rhyolitic lava and pumice clasts with minimum biogenetic or manganese cover, suggesting recent eruption(s). These findings strongly indicate that Oomurodashi is an active silicic submarine volcano, with recent eruption(s) occurring from Oomuro Hole. Since the summit of Oomurodashi is in shallow water, it

  1. Hot, shallow mantle melting under the Cascades volcanic arc

    USGS Publications Warehouse

    Elkins Tanton, Linda T.; Grove, Timothy L.; Donnelly-Nolan, Julie

    2001-01-01

    Melting occurs at progressively greater depths and higher temperatures from west to east across the Cascades volcanic arc in northern California, as demonstrated by compositional variations observed in high-alumina olivine tholeiites. The lavas studied erupted from seven vents defining a 75-km-long, east-west transect across the arc, from near Mount Shasta to east of Medicine Lake volcano. The increase in melting depth across the arc parallels modeled isotherms in the mantle wedge and does not parallel the inferred dip of the slab. The depth of mantle melting at which the high-alumina olivine tholeiites were created is ∼36 km at the western end of the transect and 66 km at the eastern end. The very high temperatures of dry melting so close to the crust indicate a transitory condition of the mantle.

  2. Hot, shallow mantle melting under the Cascades volcanic arc

    NASA Astrophysics Data System (ADS)

    Elkins Tanton, Linda T.; Grove, Timothy L.; Donnelly-Nolan, Julie

    2001-07-01

    Melting occurs at progressively greater depths and higher temperatures from west to east across the Cascades volcanic arc in northern California, as demonstrated by compositional variations observed in high-alumina olivine tholeiites. The lavas studied erupted from seven vents defining a 75-km-long, east-west transect across the arc, from near Mount Shasta to east of Medicine Lake volcano. The increase in melting depth across the arc parallels modeled isotherms in the mantle wedge and does not parallel the inferred dip of the slab. The depth of mantle melting at which the high-alumina olivine tholeiites were created is ˜36 km at the western end of the transect and 66 km at the eastern end. The very high temperatures of dry melting so close to the crust indicate a transitory condition of the mantle.

  3. Mercury and Iodine systematics of volcanic arc fluids

    NASA Astrophysics Data System (ADS)

    Varekamp, J. C.; Kading, T.; Fehn, U.; Lu, Z.

    2008-12-01

    The mantle has low Mercury and Iodine concentrations, but these elements occur in volcanic gases and hydrothermal fluids at ppb (Hg) and ppm (Iodine) levels. Possibly, the Hg and Iodine concentrations in volcanic fluids reflect subducted sediment sources in arc magmas. Iodine is a biophilic element, and I129/I values indicate that subducted sediment (especially organic matter) is an important Iodine source for arc magmas. It is uncertain if this is true for Hg as well, although in the surface environment Hg is commonly associated with organic matter. We present 60 new analyses of Hg and I in fluids from volcanoes in Central America, New Zealand, Japan, and the Cascades. A first assessment suggests that Iodine is released to some degree in the early stage of subduction in the forearc, whereas Hg may be released largely below the main volcanic arc. Isotope and trace element signatures of volcanic rocks of the investigated volcanoes show no simple correlation with Hg or Iodine abundances. The acid hot spring fluids of Copahue volcano (Argentina) carried ~ 200 ppt Hg in January 1999, ~80 ppt Hg in March 2008, and 90 ppt Hg in the crater lake in March 1997. The dissolved Hg fluxes from the Copahue hydrothermal system are ~300 gr Hg/year in 1999 and ~130 gr Hg/year in 2008. The bulk hydrothermal Hg flux (particle bound+dissolved) in 2008 was ~ 350 gr Hg/year. The potential Mercury evasion from these hydrothermal spring fluids into the air has not yet been incorporated in these estimates.

  4. Volcanic Tsunami Generation in the Aleutian Arc of Alaska

    NASA Astrophysics Data System (ADS)

    Waythomas, C. F.; Watts, P.

    2003-12-01

    Many of the worlds active volcanoes are situated on or near coastlines, and during eruptions the transfer of mass from volcano to sea is a potential source mechanism for tsunamis. Flows of granular material off of volcanoes, such as pyroclastic flow, debris avalanche, and lahar, often deliver large volumes of unconsolidated debris to the ocean that have a large potential tsunami hazard. The deposits of both hot and cold volcanic grain flows produced by eruptions of Aleutian arc volcanoes are exposed at many locations along the coastlines of the Bering Sea, North Pacific Ocean, and Cook Inlet indicating that the flows entered the sea and in some cases may have initiated tsunamis. We evaluate the process of tsunami generation by granular subaerial volcanic flows using examples from Aniakchak volcano in southwestern Alaska, and Augustine volcano in southern Cook Inlet. Evidence for far-field tsunami inundation coincident with a major caldera-forming eruption of Aniakchak volcano ca. 3.5 ka has been described and is the basis for one of our case studies. We perform a numerical simulation of the tsunami using a large volume pyroclastic flow as the source mechanism and compare our results to field measurements of tsunami deposits preserved along the north shore of Bristol Bay. Several attributes of the tsunami simulation, such as water flux and wave amplitude, are reasonable predictors of tsunami deposit thickness and generally agree with the field evidence for tsunami inundation. At Augustine volcano, geological investigations suggest that as many as 14 large volcanic-rock avalanches have reached the sea in the last 2000 years, and a debris avalanche emplaced during the 1883 eruption may have initiated a tsunami observed about 80 km east of the volcano at the village of English Bay (Nanwalek) on the coast of the southern Kenai Peninsula. By analogy with the 1883 event, previous studies concluded that tsunamis could have been generated many times in the past. If so

  5. The Chahnaly low sulfidation epithermal gold deposit, western Makran volcanic arc, southeastern Iran

    USGS Publications Warehouse

    Sholeh, Ali; Rastad, Ebrahim; Huston, David L.; Gemmell, J. Bruce; Taylor, Ryan D.

    2016-01-01

    The Chahnaly Au deposit formed during the early stages of magmatism. LA-ICP-MS zircon U-Pb geochronology of host andesite and 40Ar/39Ar dating of two samples of gold-associated adularia show that the ore-stage adularia (19.83 ± 0.10 and 19.2 ± 0.5 Ma) is younger, by as much as 1.5 million years, than the volcanic host rock (20.32 ± 0.4 Ma). Therefore, either hydrothermal activity continued well after volcanism or a second magmatic event rejuvenated hydrothermal activity. This second magmatic event may be related to eruption of porphyritic andesite at ~20.32 ± 0.40 Ma, which is within error of ~19.83 ± 0.10 Ma adularia. The new LA-ICP-MS zircon U-Pb host rock and vein adularia 40Ar/39Ar ages suggest that early Miocene magmatism and mineralization in the Bazman area is of a similar age to that of the Saindak porphyry and Tanjeel porphyry center of the giant Reko Diq deposit. This confirms the existence of early Miocene arc magmatism and mineralization along the Iranian part of the Makran volcanic arc. Ore, alteration mineralogy, and alteration patterns indicate that the Chahnaly deposit is a typical low-sulfidation epithermal Au deposit, located in a poorly explored part of the Makran volcanic arc in Iran.                   

  6. Geology and Geochronology of the Central Part of Chiapanecan Volcanic Arc, Mexico.

    NASA Astrophysics Data System (ADS)

    Layer, P. W.

    2006-12-01

    The Chiapanecan Volcanic Arc (CVA) is a 150 km stretch of volcanoes irregularly aligned in a northwest direction, including El Chichón volcano located in the central portion of the State of Chiapas, southern Mexico. It lies between two great volcanic features: the Trans-Mexican Volcanic Arc to the northwest, and the Central American Volcanic Arc to the southeast, in a complex zone of the interaction of the North American, Caribbean and Cocos Plates. The central part of the CVA is composed of an irregular northwest alignment of at least 12 volcanic structures located 80 km to the southeast of El Chichón (the only currently active volcano in the CVA). These structures include one explosion crater (Navenchauc), one collapse structure (Apas), one dome complex (Tzontehuitz) and nine volcanic domes (Navenchauc, Huitepec, Amahuitz, La Iglesia, Mispía, La Lanza, Venustiano Carranza, Miguel Hidalgo and Santotón) with associated pyroclastic flow deposits. The juvenile lithics from these deposits have a porphyritic texture with phenocrysts of plagioclase (±), amphibole (±), clinopyroxene (±), orthopyroxene (±) and Fe-Ti oxides surrounded by a matrix composed by microlites of plagioclase and glass. The chemical results obtained from representative samples from the deposits and structures indicate that these belong to the series of subalkaline rocks, and fall into the calcalkaline field with medium to high contents of potassium. They vary in their composition from andesite to dacite with an interval of silica between a 56 to a 66% (wt.). The ages reported in the literature and obtained in this study by means of the K-Ar and the 40Ar/39Ar methods, respectively, indicated that volcanism was episodic and spanned a time from 2100 ky ago (Tzontehuitz) to 225 ky ago (Venustiano Carranza).

  7. Spatial distribution of helium isotopes in volcanic gases and thermal waters along the Vanuatu (New Hebrides) volcanic arc

    NASA Astrophysics Data System (ADS)

    Jean-Baptiste, P.; Allard, P.; Fourré, E.; Bani, P.; Calabrese, S.; Aiuppa, A.; Gauthier, P. J.; Parello, F.; Pelletier, B.; Garaebiti, E.

    2016-08-01

    We report the first helium isotope survey of volcanic gases, hot springs and some olivine phenocrysts along the Vanuatu island arc, from Tanna in the south to Vanua Lava in the north. Low CO2 content and low 3He/4He ratios in thermal fluids of Epi (4.0 ± 0.1 Ra), Efate (4.5 ± 0.1 Ra) and Pentecost (5.3 ± 0.5 Ra) islands coherently indicate reduced mantle gas leakage and crustal contamination by radiogenic helium on these extinct volcanic systems of the former (Pliocene) arc. Instead, presently active Vanuatu volcanoes display 3He/4He and C/3He ratios typical of subduction-related volcanic arcs: 3He/4He ratios range from 6.4 ± 0.5 Ra in southernmost Tanna and 7.23 ± 0.09 Ra in northernmost Vanua Lava to typical MORB values in the central islands of Gaua (7.68 ± 0.06 Ra), Ambrym (7.6 ± 0.8 Ra) and Ambae (7 ± 2 Ra in groundwaters, 7.9 ± 1.4 Ra in olivine phenocrysts, and 8.0 ± 0.1 Ra in summit fumaroles of Aoba volcano). On Ambrym, however, we discover that hydrothermal manifestations separated by only 10-15 km on both sides of a major E-W transverse fault zone crossing the island are fed by two distinct helium sources, with different 3He/4He signatures: while fluids in southwest Ambrym (Baiap and Sesivi areas) have typical arc ratios (7.6 ± 0.8 Ra), fluids on the northwest coast (Buama Bay area) display both higher 3He/4He ratios (9.8 ± 0.2 Ra in waters to 10.21 ± 0.08 Ra in bubbling gases) and lower C/3He ratios that evidence a hotspot influence. We thus infer that the influx of Indian MORB mantle beneath the central Vanuatu arc, from which Ambrym magmas originate, also involves a 3He-rich hotspot component, possibly linked to a westward influx of Samoan hotspot material or another yet unknown local source. This duality in magmatic He source at Ambrym fits with the bimodal composition and geochemistry of the erupted basalts, implying two distinct magma sources and feeding systems. More broadly, the wide He isotopic variations detected along the Vanuatu

  8. The Lesser Antilles volcanic chain: a study in arc magmatism

    NASA Astrophysics Data System (ADS)

    Macdonald, R.; Hawkesworth, C. J.; Heath, E.

    2000-03-01

    The Lesser Antilles volcanic arc is related to subduction of the American plate under the Caribbean plate. The rate of subduction is low, 2-4 cm a -1, and this has been reflected, at least over the past 0.1 Ma, in relatively low magma production rates (3-5 km 3 Ma -1 km -1 of arc). The arc is segmented; a northern segment trends 330° and the Benioff zone dips at 50-60°, whilst the southern segment trends 020° and the dip varies from 45° to 50° in the north to vertical in the south. Pleistocene-Recent volcanism (<2 Ma) occurs in narrow zones less than 10 km wide and seems to define three segments, the break between the central and southern segments being in the same location as the kink in the Benioff zone. Magma production over the past 0.1 Ma has been higher in islands of the central segment (8-40 km 3) than in the northern and southern segments (0-5 km 3); the variations may be related to the degree of obliquity of subduction along the arc. Cenozoic volcanic rocks of the arc are divided into low-K and medium-K series, each of which contains basaltic (MgO>6%) members ranging from hypersthene- to nepheline-normative. It is likely that all the Lesser Antilles eruptives had picritic (or, more rarely, ankaramitic), possibly silica-undersaturated, primary magmas. The medium-K rocks show wide variations in trace-element and isotopic characteristics. A generalised sequence of phenocryst assemblages, applicable to both groups, is: olivine+spinel±clinopyroxene→olivine+spinel+clinopyroxene+plagioclase→plagioclase+clinopyroxene+titanomagnetite+orthopyroxene±amphibole±quartz. Phenocryst crystallisation temperatures were: basalts 1180-1130°C; basaltic andesites 1060-1050°C; and andesites-dacites 960-740°C. Magmas inferred to be primary to the eruptive suites equilibrated within the spinel peridotite facies in the mantle wedge at pressures between 1.5 and 3 GPa. fO 2 conditions of magma crystallisation were rather oxidising (NNO +0.5 to NNO +3). Estimates of

  9. Detailed bathymetry and magnetic anomaly inthe Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after ~2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, T.; Oda, H.; Ishizuka, O.; Arai, K.

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed ~20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least ~2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  10. Detailed bathymetry and magnetic anomaly in the Central Ryukyu Arc, Japan: implications for a westward shift of the volcanic front after approximately 2.1 Ma

    NASA Astrophysics Data System (ADS)

    Sato, Taichi; Oda, Hirokuni; Ishizuka, Osamu; Arai, Kohsaku

    2014-12-01

    Detailed bathymetry and magnetic anomalies in the southern part of the Central Ryukyu Arc reveal recent volcanic structures in a southwestward extension of the active volcanic front of the Ryukyu Arc. A line of bathymetric highs running subparallel to this recent volcanic front was observed approximately 20 km to the east. A set of small, sharply defined magnetic anomalies extends southward from this line of bathymetric highs to the islands Kume-jima and Aguni-jima, suggesting the former existence of an ancient volcanic front. The ages of volcanic rocks from these islands indicate that magmatic activity along the ancient volcanic front continued until at least approximately 2.1 Ma. The presence of magnetic anomalies between the two volcanic fronts suggests that the volcanic front has moved gradually westward. This shift can be explained by the termination of asthenospheric upwelling and/or the rapid retreat of the Ryukyu Trench after its change in subduction direction.

  11. Seismological evidence for a sub-volcanic arc mantle wedge beneath the Denali volcanic gap, Alaska

    USGS Publications Warehouse

    McNamara, D.E.; Pasyanos, M.E.

    2002-01-01

    Arc volcanism in Alaska is strongly correlated with the 100 km depth contour of the western Aluetian Wadati-Benioff zone. Above the eastern portion of the Wadati-Benioff zone however, there is a distinct lack of volcanism (the Denali volcanic gap). We observe high Poisson's ratio values (0.29-0.33) over the entire length of the Alaskan subduction zone mantle wedge based on regional variations of Pn and Sn velocities. High Poisson's ratios at this depth (40-70 km), adjacent to the subducting slab, are attributed to melting of mantle-wedge peridotites, caused by fluids liberated from the subducting oceanic crust and sediments. Observations of high values of Poisson's ratio, beneath the Denali volcanic gap suggest that the mantle wedge contains melted material that is unable to reach the surface. We suggest that its inability to migrate through the overlying crust is due to increased compression in the crust at the northern apex of the curved Denali fault.

  12. Natural gamma-radiation in the Aeolian volcanic arc.

    PubMed

    Chiozzi, P; Pasquale, V; Verdoya, M; Minato, S

    2001-11-01

    Pulse-height distributions of gamma-rays, obtained with a field NaI(Tl) scintillation spectrometer in numerous sites of the Lipari and Vulcano islands (Aeolian volcanic arc, Italy), were measured to determine the U, Th and K concentrations of the bedrock and the relative values of the air absorbed dose rate. U is spatially related to both Th and K and the Th/U ratio is on average 3.1-3.5. The magmatic evolution is reflected by the concentration of the three radioelements, as they are more abundant within the more felsic units of the volcanic series. The higher values of U (15.7-20.0 ppm) coincide with higher Th (48.3-65.9 ppm) and K (4.9-6.1%) concentrations associated with rhyolitic rocks of the third cycle (< 50 ky). The air absorbed dose rate varies from 20 to 470 nGy h(-1). The highest values (> 350 nGy h(-1)) are observed on outcrops of rhyolitic obsidian lava flows. The cosmic-ray contribution is also evaluated to estimate the total background radiation dose rate.

  13. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter

    2015-03-01

    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  14. The arc arises: The links between volcanic output, arc evolution and melt composition

    NASA Astrophysics Data System (ADS)

    Brandl, Philipp A.; Hamada, Morihisa; Arculus, Richard J.; Johnson, Kyle; Marsaglia, Kathleen M.; Savov, Ivan P.; Ishizuka, Osamu; Li, He

    2017-03-01

    Subduction initiation is a key process for global plate tectonics. Individual lithologies developed during subduction initiation and arc inception have been identified in the trench wall of the Izu-Bonin-Mariana (IBM) island arc but a continuous record of this process has not previously been described. Here, we present results from International Ocean Discovery Program Expedition 351 that drilled a single site west of the Kyushu-Palau Ridge (KPR), a chain of extinct stratovolcanoes that represents the proto-IBM island arc, active for ∼25 Ma following subduction initiation. Site U1438 recovered 150 m of oceanic igneous basement and ∼1450 m of overlying sediments. The lower 1300 m of these sediments comprise volcaniclastic gravity-flow deposits shed from the evolving KPR arc front. We separated fresh magmatic minerals from Site U1438 sediments, and analyzed 304 glass (formerly melt) inclusions, hosted by clinopyroxene and plagioclase. Compositions of glass inclusions preserve a temporal magmatic record of the juvenile island arc, complementary to the predominant mid-Miocene to recent activity determined from tephra layers recovered by drilling in the IBM forearc. The glass inclusions record the progressive transition of melt compositions dominated by an early 'calc-alkalic', high-Mg andesitic stage to a younger tholeiitic stage over a time period of 11 Ma. High-precision trace element analytical data record a simultaneously increasing influence of a deep subduction component (e.g., increase in Th vs. Nb, light rare earth element enrichment) and a more fertile mantle source (reflected in increased high field strength element abundances). This compositional change is accompanied by increased deposition rates of volcaniclastic sediments reflecting magmatic output and maturity of the arc. We conclude the 'calc-alkalic' stage of arc evolution may endure as long as mantle wedge sources are not mostly advected away from the zones of arc magma generation, or the rate of

  15. Episodic continental arc volcanism, tectonism and erosion recorded in stratigraphy and detrital zircon geochronology

    NASA Astrophysics Data System (ADS)

    Cao, W.; Paterson, S. R.

    2015-12-01

    Stratigraphic studies and detrital zircon geochronology of metamorphic host rock pendants of the Mesozoic Sierra Nevada arc in California show temporal correlations with episodic arc volcanism and tectonism, and have implications for our understanding of sources and sinks of recycled volcanic and sedimentary materials, as well as the paleo-geography and erosion history of an ancient continental arc. The Middle Triassic to Early Cretaceous stratigraphy of the metamorphic pendants shows alternating volcanic and sedimentary beds. The latter varies from rocks formed in high-energy terrestrial to low-energy shallow marine environments. Sedimentary textures also vary from poorly sorted volcanic-clast/breccia-rich to well-sorted fine-grained rocks and carbonates. We interpret these variations in stratigraphic records to reflect the waning and waxing of arc volcanism and tectonism, which controls erosion of source rocks, as well as elevation changes through isostastic balance. These in turn control the paleo-geography and depositional environments. Detrital zircon geochronology confirms our hypothesis. Detrital zircon ages of sedimentary rocks closely track the ages of volcanic/plutonic rocks formed immediately earlier and also include age signals of older igneous rocks and pre-arc basement, suggesting the erosion of igneous rocks of higher elevation during the magmatic flare-ups and deposition of these clasts afterwards. We conclude that episodic arc volcanism and tectonism play important roles on processes of surface erosion and sedimentation.

  16. Late Cretaceous infant intra-oceanic arc volcanism, the Central Pontides, Turkey: Petrogenetic and tectonic implications

    NASA Astrophysics Data System (ADS)

    Aygül, Mesut; Okay, Aral I.; Oberhänsli, Roland; Schmidt, Alexander; Sudo, Masafumi

    2015-11-01

    A tectonic slice of an arc sequence consisting of low-grade metavolcanic rocks and overlying metasedimentary succession is exposed in the Central Pontides north of the İzmir-Ankara-Erzincan suture separating Laurasia from Gondwana-derived terranes. The metavolcanic rocks mainly consist of basaltic andesite/andesite and mafic cognate xenolith-bearing rhyolite with their pyroclastic equivalents, which are interbedded with recrystallized pelagic limestone and chert. The metasedimentary succession comprises recrystallized micritic limestone with rare volcanogenic metaclastic rocks and stratigraphically overlies the metavolcanic rocks. The geochemistry of the metavolcanic rocks indicates an arc setting evidenced by depletion of HFSE (Ti, P and Nb) and enrichment of fluid mobile LILE. Identical trace and rare earth elements compositions of basaltic andesites/andesites and rhyolites suggest that they are cogenetic and derived from a common parental magma. The arc sequence crops out between an Albian-Turonian subduction-accretionary complex representing the Laurasian active margin and an ophiolitic mélange. Absence of continent derived detritus in the arc sequence and its tectonic setting in a wide Cretaceous accretionary complex suggest that the Kösdağ Arc was intra-oceanic. Zircons from two metarhyolite samples give Late Cretaceous (93.8 ± 1.9 and 94.4 ± 1.9 Ma) U/Pb ages. These ages are the same as the age of the supra-subduction ophiolites in western Turkey, which implies that that the Kösdağ Arc may represent part of the incipient arc formed during the generation of the supra-subduction ophiolites. The low-grade regional metamorphism in the Kösdağ Arc is constrained to 69.9 ± 0.4 Ma by 40Ar/39Ar muscovite dating indicating that the arc sequence became part of a wide Tethyan Cretaceous accretionary complex by the latest Cretaceous. Non-collisional cessation of the arc volcanism is possibly associated with southward migration of the magmatism as in the Izu

  17. Activities and source mechanisms of volcanic deep low-frequency earthquakes and its implication for deep crustal process in magmatic arc (Invited)

    NASA Astrophysics Data System (ADS)

    Nakamichi, H.

    2013-12-01

    Rocks under upper mantle and lower crustal temperatures and pressures typically deform in a ductile manner, therefore it is difficult to accumulate enough deviatoric stress in rocks to generate brittle failure under this condition. However earthquakes occur at upper mantle and lower crust beneath active volcanoes, and are recognized as volcanic deep low-frequency earthquakes (VDLFs). VDLFs are characterized by mostly low-frequency energy (<5 Hz), emergent arrivals and long-duration codas. VDLF activity observed at depths of 10-50 km in Japan, the Philippines, Alaska and the Western US (Power et al., 2004; Ukawa, 2005; Nichols et al. 20011), has generally been attributed to magma transport in the mid-to-lower crustal and uppermost mantle regions. However because VDLF seismicity is infrequent, with relatively weak and emergent signals, the relationship between deep magma transport and seismic radiation remains poorly understood. Borehole dense seismic observation systems, such as the high-sensitivity seismograph network 'Hi-net' in Japan (Obara et al. 2005), are effective for detecting not only non-VDLFs (Obara, 2002) but also VDLFs. Since 1997 the Japan Meteorological Agency has routinely detected and located DLFs using the Hi-net dataset, and have identified DLFs in and around most quaternary volcanoes in Japan (Takahashi and Miyamura, 2009). Several studies have attempted to estimate source mechanisms of VDLFs in Japan. The first attempt by Ukawa and Ohtake (1987), obtained a single force as the source mechanism of a VDLF beneath Izu-Ohshima by using particle motions of S-waves. Following that work strike-slip type and non-double-couple source mechanisms were obtained using waveform inversions for VDLFs in Northeast Japan (Nishidomi and Takeo 1996; Okada and Hasegawa, 2000). Nakamichi et al. (2003; 2004) estimated the source mechanisms of Mts. Iwate and Fuji through the moment tensor inversion of spectral ratios of body waves from using data from a dense seismic

  18. Structure and petrology of newly discovered volcanic centers in the northern Kermadec-southern Tofua arc, South Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Graham, Ian J.; Reyes, Agnes G.; Wright, Ian C.; Peckett, Kimberley M.; Smith, Ian E. M.; Arculus, Richard J.

    2008-08-01

    The NZAPLUME III expedition of September-October 2004 to the northern Kermadec-southern Tofua (NKST) arc, between 28°52'S and 25°07'S, resulted in the discovery of at least seven new submarine volcanic centers and a substantial caldera complex adjacent to the previously known Monowai Seamount. The volcanic centers form a sublinear chain that coincides with the Kermadec Ridge crest in the south (Hinetapeka) and diverges ˜45 km westward of the ridge crest in the north ("V") just to the south of where the Louisville Ridge intersects with the arc. All of the centers contain calderas or caldera-like structures, as well as multiple cones, domes, fissure ridges, and vent fields. All show signs of recent eruptive and current hydrothermal activity. There are strong structural controls on edifice location, with cones and fissure ridges typically associated with faulting parallel to the regional ˜12° strike of the arc front. Several of the calderas are ellipsoidal, orientated northwest-southeast in the general direction of least compressive stress. Sampled volcanic rocks, representing the most recently erupted lavas, are all low-K tholeiites. Two of the centers, Gamble and Rakahore, yielded only high-silica dacite to rhyolite (69-74 wt% silica), whereas two others, Monowai and "V," yielded only basalt to andesite (48-63 wt% silica). Mineral assemblages are plagioclase-pyroxene dominated, with accessory Fe-Ti oxides, apatite, olivine, and quartz/tridymite/cristobalite, typical of dry volcanic arc systems. Hornblende occurs only in a felsitic rhyolite from Hinepuia volcanic center, and zircon is absent. Glass contents range to 57% in basalts-andesites (mean 20%), and 97% in andesites-rhyolites (mean 59%) and other quench textures, including swallow-tailed, plumose, or dendritic crystal forms and crystallites, are common. Most lavas are highly vesicular (≤63%; mean 28%) and have low volatile contents (mostly <2 wt%) which, together with the occurrence of tridymite or

  19. Space-geodetic evidence of shallow magma reservoirs in the West-Sunda arc; Insights from global data compilation on what controls magma ascent in volcanic arcs

    NASA Astrophysics Data System (ADS)

    Chaussard, E.; Amelung, F.

    2011-12-01

    A large proportion of the world's population lives on or near active volcanoes. Ground deformation measurements are key observations for volcano monitoring not only because they allow identification of precursory uplift caused by ascent of new magma towards the surface but also because volcanic hazard assessment relies on interpretations of geodetic data in terms of depth of magma accumulation. Here we conducted a global survey of the West-Sunda volcanic arc using differential InSAR combined with SBAS-time series analysis covering an area of about 500 000 km2 on the islands of Sumatra, Java and Bali. The compiled ground velocity map reveals the background level of activity of the 84 volcanic centers of the West-Sunda arc. We identified uplift at 6 volcanic centers and subsidence at 2 edifices. Interestingly, 3 of the 6 uplifting centers erupted after the time period of our survey, suggesting that edifice inflation is a precursor of eruptions. Elastic half-space models of the measured deformation give quantitative estimates of the depths of the magmatic sources and reveal that the sources of inflation are located at shallow depths, less than 3km under the sea level. To interpret these results from a global point of view we compiled data of magma chamber depths in volcanic arcs. Because magma primarily rises by buoyancy forces, in the absence of exterior stress, magma chambers are expected to develop at the level of neutral buoyancy, where magma first encounters a crustal density similar to its density, typically between 5 and 10km for Andesitic volcanoes [Ryan, 1987]. Magma chambers around these depths are found in most volcanic arcs, such as the Central Andes [Pritchard, 2004; Pritchard and Simons, 2004]. However, some volcanic arcs present in addition to magma chambers at these levels, shallower reservoirs, above 4km depth. It is the case in the Aleutian arc, the Costa-Rican arc and, from our survey, the West-Sunda arc [Lu et al., 2002; Lu, 2007; Alvarado et al

  20. Impact of subduction geometry on high-productivity arc volcanism of the Klyuchevskoy volcanic group (Kamchatka, Russia)

    NASA Astrophysics Data System (ADS)

    Dunham, B.; Levin, V. L.; Droznina, S.; Gavrilenko, M.

    2013-12-01

    Klyuchevskoy volcanic group is located at the northern termination of the Kamchatka volcanic arc. It is a typical island-arc volcanic center, its lava chemistry is consistent with the subduction fluid induced melting in the mantle wedge. It is however significantly larger than any other arc volcano or volcanic group. With a volume of~7500 km3 it is similar to shield volcanoes associated with rifts and hot spots. The causes of such high rates of volcanism are not clear, and likely reflect the unusual geodynamic setting of the Klyuchevskoy volcanic group. Subduction of the Pacific plate forms a convergent margin along the eastern coast of Kamchatka that terminates at the junction with the Aleutian Arc. Along most of its strike the subducting slab descends at ~45 degrees, is nearly planar, and reaches transition zone depths, with its deepest earthquakes at ~400 km. Near its northern termination the geometry of the subducting slab changes, seismicity is limited to 200 km, and the angle of subduction is likely more shallow. Determining the exact configuration of the Pacific slab beneath Kamchatka is complicated by the lack of large earthquakes within it in the last 30 years. Consequently, all global compilations of slab depth based on seismicity above M~5.5 do not extend into the region of the northern termination of the Kamchatka subduction zone. A study of the slab geometry using regional seismicity carried out by Gorbatov et al. (1997) was based on a regional earthquake catalog compiled by the seismic monitoring network of Kamchatka prior to its conversion to modern digital data acquisition. It suggests an abrupt change in slab dip close to the location of the Klyuchevskoy volcanic group. In this study we use a new digital catalog compiled over years 2000 - 2013. The new catalog contains data for over 28,000 earthquakes, most of which are below M~5. With the new catalog, we created a contour map and 3-D image of the slab surface using 2-D profiles of the earthquakes

  1. Along-arc geochemical and isotopic variations in Javanese volcanic rocks: 'crustal' versus 'source' contamination at the Sunda arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Handley, H.; Blichert-Toft, J.; Turner, S.; Macpherson, C. G.

    2012-12-01

    Understanding the genesis of volcanic rocks in subduction zone settings is complicated by the multitude of differentiation processes and source components that exert control on lava geochemistry. Magma genesis and evolution at the Sunda arc is controlled and influenced by 1) along arc changes in the composition and thickness of the overriding Eurasian plate, 2) the variable age of the subducting oceanic crust and, 3) changes in the type and amount of sediment deposited on the subducting plate. Along-arc changes in geochemistry have long been recognised in the Sunda arc (Whitford, 1975), but debate still prevails over the cause of such variations and the relative importance of shallow (crustal) versus deep (subduction) contamination at the Sunda arc, Indonesia. Detailed study of individual Sunda arc volcanic centres is, therefore, a prerequisite in order to establish the relative importance and contributions of various potential source components and composition modifying differentiation processes at individual volcanoes, prior to an along arc comparative petrogenetic investigation. We present new radiogenic isotope data for Javanese volcanoes, which is combined with our recently published (Handley et al., 2007; Handley et al., 2008, Handley et al., 2010; Handley et al., 2011) geochemical and isotopic data of Javanese volcanic rocks along with data from other detailed geochemical studies to establish whether variable contributions from the subducting slab, or a change in crustal architecture of the overriding plate, best explain along-arc variations in isotope ratios and trace element characteristics. In West and Central Java Sr isotope ratios of the volcanic rocks broadly correlate with inferred lithospheric thickness implicating a shallow level control on isotopic composition. However, key trace element ratios combined with Hf isotope data indicate that the subducted slab and slab thermal regime also exert major control on the composition of the erupted Javanese

  2. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand

    PubMed Central

    Hamling, Ian J.; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

    2016-01-01

    Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system. PMID:27386580

  3. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand.

    PubMed

    Hamling, Ian J; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

    2016-06-01

    Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system.

  4. Late cenozoic vertical movements of non-volcanic islands in the Banda Arc area

    NASA Astrophysics Data System (ADS)

    De Smet, M. E. M.; Fortuin, A. R.; Tjokrosapoetro, S.; Van Hinte, J. E.

    During onshore campaigns of the Snellius-II Expedition late Cenozoic sections were recorded and systematically sampled on the non-volcanic outer Banda Arc Islands of Timor, Buton, Buru, Seram and Kai. Microfaunal studies provided age and palaeobathymetric data to construct geohistory diagrams. Geohistory analysis of field and laboratory data allows to calculate rates of vertical movements of the island basements. The vertical movements were intermittent and differed widely from place to place in the arc; short periods of uplift alternated with longer periods of tectonic rest or subsidence and lateral variations in timing and magnitude seem to be more the rule than the exception. Movements affected larger segments of the arc at about the same time, especially since the late Pliocene, when widespread vertical movements started, which led to the present configuration of the arc. Rates of uplift or subsidence differed within each segment. On an intermediate scale, deformation has the character of tilting or doming of whole islands or parts of islands. On a local scale, various types of deformation occur. Calculated duration of uplift pulses is in the order of a million years where less than 50 cm·ka -1 of vertical movements are involved. Sections, however, with a high time stratigraphic resolutions show pulses of uplift with a duration of only some hundreds of thousands of years and rates of more than 500 cm·ka -1. The duration of such pulses therefore is comparable to that of eustatic third order sea level changes. But because their amplitude is an order of magnitude larger, this implies that in tectonically active areas eustatic signals, preserved in the sedimentary record, will be overprinted by tectonics, i.e. will be difficult to disentangle from the tectonic signal.

  5. Seismotectonic pattern and the source region of volcanism in the central part of Sunda Arc

    NASA Astrophysics Data System (ADS)

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

    2005-07-01

    The seismotectonic pattern in the central part of the Sunda Arc (Java, Nusa Tenggara) was studied in relation to the distribution of active calc-alkaline volcanoes, using global seismological data. Hypocentral determinations of the International Seismological Centre from the period 1964-1999, as relocated by Engdahl, and Harvard Centroid Moment Tensor Solutions from the period 1976-2003 were used. The following phenomena, which could assist the location of the source region of primary magma for island arc calc-alkaline volcanism, were observed: (1) An aseismic gap without any strong teleseismically recorded earthquakes was found in the Wadati-Benioff zone of the subducting slab along the whole investigated region of the Sunda Arc, forming a continuous strip of laterally variable depth and shape, at depths between 100 and 200 km. The absence of strong earthquakes (with mb>4.0) indicates a significant change in the mechanical properties of the subducting slab at intermediate depths. All active calc-alkaline volcanoes in the Sunda Arc are located above this gap. (2) The majority of earthquakes occurring in the lithospheric wedge of the Eurasian Plate above the subducted slab could be attributed to several deep-rooted seismically active fracture zones of regional extent. All delineated active fracture zones display a thrust tectonic regime as shown by the available fault plane solutions. (3) Clusters of earthquakes were found beneath active volcanoes of western Java, Bali and Nusa Tenggara in the lithospheric wedge above the slab and identified as seismically active columns. These clusters occur only beneath the volcanoes that are located at the outcrops of seismically active fracture zones. We interpret the earthquakes in these clusters beneath volcanoes as events induced by magma transport through the medium of the lithospheric wedge that has been subcritically pre-stressed by the process of plate convergence. (4) Beneath the volcanoes of central Java no seismically

  6. Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States

    USGS Publications Warehouse

    Ingebritsen, S.E.; Randolph-Flagg, N. G.; Gelwick, K.D.; Lundstrom, E.A.; Crankshaw, I.M.; Murveit, A.M.; Schmidt, M.E.; Bergfeld, D.; Spicer, K.R.; Tucker, D.S.; Mariner, R.H.; Evans, William C.

    2014-01-01

    Ongoing (1996–present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the US Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade volcanic arc, from Mount Baker near the Canadian border to Lassen Peak in northern California. A concerted effort was made to develop hourly, multiyear records of temperature and/or hydrothermal solute flux, suitable for retrospective comparison with other continuous geophysical monitoring data. Targets included summit fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and/or anomalous fluxes of magmatic CO2 or heat. As of 2009–2012, summit fumarole temperatures in the Cascade Range were generally near or below the local pure water boiling point; the maximum observed superheat was 3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multidecadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in response to the 1980–present eruptive cycle, there is no clear evidence of ongoing long-term trends in hydrothermal activity at other Cascade Range volcanoes that have been active or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range hydrothermal-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more active but generally less accessible volcanoes such as those in the Aleutian arc.

  7. The Relationship Between the Signature of Subducted Sediments in Volcanic Gases and Volatile Flux along the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Fischer, T. P.; Zimmer, M. M.; Hilton, D. R.; Shaw, A. M.; Cameron, B. I.; Walker, J. A.; Molina C., E.

    2002-05-01

    Volcanic arcs are locations where elements are recycled from the Earth's surface into the mantle. Fluxes of volcanic volatile emissions can vary significantly along a single arc and a fundamental aim of arc-related studies is to quantify these variations and compare them to subduction zone parameters. As part of the Central American arc study, we report N2, He and Ar abundance relationships and N-isotope ratios for 7 volcanic centers in Guatemala to complement on-going studies in Costa Rica. In Guatemala, the arc crust is thicker and older than in Costa Rica and the entire sediment sequence on the down-going plate is likely to contribute to the slab flux. Sulfur dioxide fluxes vary significantly along the arc (2001 measurements): in the Guatemala segment, Fuego and Pacaya emit a total of ~1500 t/day whereas in Costa Rica, Arenal and Poas are emitting only ~190 t/day. The Guatemalan volcanic centers of Amatitlan-Pacaya, Fuego, Moyuta, Tecuamburro, Amatitlan, Zunil and San Marcos have N2/He ratios ranging from 2200 - 8100, typical for arc-related fluids. N2/Ar ratios (40-500) and the high N2/He indicate addition of N2 from subducted sediments or arc crust to a mantle derived component (N2/He < 200). The high N2/He ratios of Guatemala are in contrast to typical mantle-derived N2/He ratios (160 - 600) measured at Poas and Turialba, Costa Rica. Nitrogen isotope ratios for the Guatemalan volcanic centers range from δ 15N = + 1.0‰ for San Marcos to + 5.8‰ for Fuego (δ 15N air = 0.0‰ ), indicating a sedimentary nitrogen component. The mantle-derived N2/He ratios for Poas (- 3.0‰ ) are consistent with a more mantle-like δ 15N. In Guatemala, the highest 3He/4He ratios (7.6 for Pacaya and 7.3 Ra for Fuego) correlate with the lowest N2/He ratios (1500 and 2100) and high δ 15N values (+3.8‰ and +5.8‰ ). Mixing relationships (3He/4He and δ 15N) suggest that at Fuego and Pacaya up to 20% of the nitrogen is of subducted sedimentary origin, contrary to Poas and

  8. Feedback between deglaciation and volcanism in arc settings: the example of the Mount Mazama volcanic system, Crater Lake, Oregon

    NASA Astrophysics Data System (ADS)

    Branecky, C.; Farner, M. J.; Keller, T.; Lanza, F.; Siravo, G.; Gonnermann, H. M.; Huybers, P. J.; Manga, M.; van der Wal, W.

    2015-12-01

    Previous studies have found correlations between glacial cycles and volcanism. Any such feedback mechanisms could have important implications for climate through variations in volcanic outgassing. Although decompression melting has been established as a cause for increased volcanism during deglaciation at mid-ocean ridge systems (Jull and McKenzie, 1996), it has not been determined how changes in glacial loading affect other settings such as volcanic arcs. We examine the Mount Mazama volcanic system, Oregon, where pulses of volcanism have been suggested to follow major deglaciations (Bacon et al. 2006). A statistical test regarding the timing of eruptions is first developed, and its application to eruption dates demonstrates statistically significant clustering of eruptions following deglaciation. To explore potential causes for the identified changes in probability of eruptions, the effects of glacial unloading on melt production are computed using a 1D mantle melting model, and the effect of ice unloading on shallow crustal stress conditions is tested with a viscoelastic stress model. Combining these effects into a simple eruption model, we propose that variations in melt supply rates from the mantle and changing stress conditions around a shallow crustal magma reservoir modulate eruption probability during glacial cycles. This model illustrates the physical plausibility of glacial variability causing the identified changes in eruption rates at Mt Mazama.

  9. Characteristics of Mineralized Volcanic Centers in Javanese Sunda Island Arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Setijadji, L. D.; Imai, A.; Watanabe, K.

    2007-05-01

    The subduction-related arc magmatism in Java island, Sunda Arc, Indonesia might have started in earliest Tertiary period, but the distinctively recognizable volcanic belts related with Java trench subduction occurred since the Oligocene. We compiled geoinformation on volcanic centers of different epochs, distribution of metallic mineral deposits, petrochemistry of volcanic rocks, geologic structures, and regional gravity image in order to elucidate characteristics of the known mineralized volcanic centers. Metallic deposits are present in various styles from porphyry-related, high-sulfidation, and low-sulfidation epithermal systems; all related with subaerial volcanism and subvolcanic plutonism. Only few and small occurrences of volcanigenic massive sulfides deposits suggest that some mineralization also occurred in a submarine environment. Most locations of mineral deposits can be related with location of Tertiary volcanic centers along the volcanic arcs (i.e. volcanoes whose genetic link with subduction is clear). On the other side there is no mineralization has been identified to occur associated with backarc magmatism whose genetic link with subduction is under debate. There is strong evidence that major metallic deposit districts are located within compressive tectonic regime and bound by coupling major, deep, and old crustal structures (strike-slip faults) that are recognizable from regional gravity anomaly map. So far the most economical deposits and the only existing mines at major industry scale are high-grade epithermal gold deposits which are young (Upper Miocene to Upper Pliocene), concentrated in Bayah dome complex in west Java, and are associated with alkalic magmatism-volcanism. On the other hand, known porphyry Cu-Au deposits are associated with old (Oligocene to Upper Miocene) stocks, and except for one case, all deposits are located in east Java. Petrochemical data suggest a genetic relationship between porphyry mineralization with low- to

  10. Halogen content in Lesser Antilles arc volcanic rocks : exploring subduction recycling

    NASA Astrophysics Data System (ADS)

    Thierry, Pauline; Villemant, Benoit; Caron, Benoit

    2016-04-01

    Halogens (F, Cl, Br and I) are strongly reactive volatile elements which can be used as tracers of igneous processes, through mantle melting, magma differentiation and degassing or crustal material recycling into mantle at subduction zones. Cl, Br and I are higly incompatible during partial melting or fractional cristallization and strongly depleted in melts by H2O degassing, which means that no Cl-Br-I fractionation is expected through magmatic differenciation [current thesis]. Thus, Cl/Br/I ratios in lavas reflect the halogen content of their mantle sources. Whereas these ratios seemed quite constant (e.g. Cl/Br =300 as seawater), recent works suggest significant variations in arc volcanism [1,2]. In this work we provide high-precision halogen measurements in volcanic rocks from the recent activity of the Lesser Antilles arc (Montserrat, Martinique, Guadeloupe, Dominique). Halogen contents of powdered samples were determined through extraction in solution by pyrohydrolysis and analysed by Ion Chromatography for F and Cl and high performance ICP-MS (Agilent 8800 Tripe Quad) for Cl, Br and I [3,4]. We show that lavas - and mantle sources - display significant vraiations in Cl/Br/I ratios along the Lesser Antilles arc. These variations are compared with Pb, Nd and Sr isotopes and fluid-mobile elements (Ba, U, Sr, Pb etc.) compositions which vary along the arc from a nothern ordinary arc compositions to a southern 'crustal-like' composition [5,6]. These characteristics are attributed to subducted sediments recycling into the mantle wedge, whose contribution vary along the arc from north to south [7,8]. The proportion of added sediments is also related to the distance to the trench as sediment melting and slab dehydration may occur depending on the slab depth [9]. Further Cl-Br-I in situ measurements by LA-ICP-MS in Lesser Antilles arc lavas melt inclusions will be performed, in order to provide better constraints on the deep halogen recycling cycle from crust to

  11. Sediment dynamics and the changing nature of the subduction component beneath the Kurile volcanic Arc

    NASA Astrophysics Data System (ADS)

    Dreyer, B.; Morris, J.; Tera, F.; Gill, J.

    2006-12-01

    Strong slab signatures in the lavas of the of the Kurile volcanic arc and their systematic changes across this unusually wide (~120-200km above the downgoing slab) arc provide excellent leverage for investigating the changing nature of subduction components and mixing processes across volcanic arcs. Results of new and published geochemical transects of the Kurile arc indicate a waning fluid subduction component across the arc (Bailey et al., Contrib. Mineral. Petrol., 1987; Zhuralev et al., Chem. Geol., 1987; Ryan et al., Science, 1995; Noll, et al., Geochimica et Cosmochimica Acta, 1996; Ishikawa and Tera, Earth Planet. Sci. Lett., 1997; Morris and Ryan, Treatise on Geochemistry, 2003); little geochemical change is observed along the arc. Boron, Sb, As, Pb, Cs, Ba, and Be, are progressively distilled from the slab in approximately decreasing efficiency. When the effects of decreasing degree of partial melting towards the rear-arc are minimized, Cs, Ba, and Be do not return to Pacific MORB values, indicating that they are still being added to the mantle wedge beneath the rear-arc. Despite the longer transit times, and hence additional decay of cosmogenic 10Be (t1/2=1.5Ma), 10Be/9Be ratios in the rear arc are frequently greater than or comparable to those measured at the front and requires (young, <10Ma) sediment contribution across the width of the arc, which likely reflects a greater proportion of sediment Be in rear-arc lavas, possibly as a melt or supercritical fluid (Johnson and Plank, G3, 1999). To characterize the incoming sediment and clarify the sediment dynamics beneath the Kurile arc and, new trace element, radiogenic isotope, and 10Be concentration data have been measured for a 250 meter section of marine sediments from ODP Site 1179 ~550 km outboard of the trench; these data are integrated with those of the Kurile arc lavas. Initial calculations suggest a maximum 10Be inventory of ~1.5x1013 atoms/cm2 in the incoming sediment column, which translates to

  12. Distribution of Late Cenozoic volcanic vents in the Cascade range: Volcanic arc segmentation and regional tectonic considerations

    NASA Astrophysics Data System (ADS)

    Guffanti, Marianne; Weaver, Craig S.

    1988-06-01

    Spatial, temporal, and compositional distributions of approximately 4000 volcanic vents formed since 16 Ma in Washington, Oregon, northern California, and northwestern Nevada illustrate the evolution of volcanism related to subduction of the Juan de Fuca plate system and extension of the Basin and Range province. Vent data were obtained from published map compilations and include monogenetic and small polygenetic volcanoes in addition to major composite centers. On the basis of the distribution of 2821 vents formed since 5 Ma, the Cascade Range is divided into five segments, with vents of the High Lava Plains along the northern margin of the Basin and Range province in Oregon forming a sixth segment. Some aspects of the Cascade Range segmentation can be related to gross structural features of the subducting Juan de Fuca plate. The orientation of the volcanic front of segments one and two changes from NW in northern Washington to NE in southern Washington, paralleling the strike of the subducting Juan de Fuca plate. Segments one and two are separated by a 90-km volcanic gap between Mount Rainier and Glacier Peak that is landward of the portion of the subducting plate having the least average dip to a depth of 60 km. A narrow, N-S trending belt of predominantly andesitic vents in Oregon constitutes a third segment, which is landward of the seismically quiet portion of the subduction zone. The narrowness of this segment may indicate steep dip of the subducting plate beneath the Cascade arc in Oregon. Vents are sparse between segment four (containing the Mount Shasta and Medicine Lake centers) and segment five (containing Lassen Peak), where the Juan de Fuca and Gorda North plates are characterized by differing age, amounts of subcrustal seismicity, and probably geometry. From the relation between seismicity at depth of 60 km and the position of the volcanic front of vents formed since 5 Ma, transitions between subducting-plate segments of varying geometry likely occur

  13. Lithospheric-folding-based understanding on the origin of the back-arc basaltic magmatism beneath Jeju volcanic island, Korea

    NASA Astrophysics Data System (ADS)

    Yun, S.; Shin, Y.; CHOI, K.; Koh, J.; Nakamura, E.; Na, S.

    2012-12-01

    Jeju Island is an intraplate volcanic island located at the eastern margin on the East Asia behind the Ryukyu Trench, the collisional/subduction boundary between the Eurasian plate and Philippine Sea plate. It is a symmetrical shield volcano, having numerous monogenetic cinder cones, over 365, on the Mt. Halla volcanic edifice. The basement rock mainly consists of Precambrian gneiss, Mesozoic granite and volcanic rocks. Unconsolidated sedimentary rock is found between basement rock and surface lava. The lava plateau is composed of voluminous basaltic lava flows, which extend to the coast region with a gentle slope. Based on the evidence obtained from volcanic stratigraphy, paleontology, and geochronology, the age of the Jeju basalts ranges from the early Pleistocene to Holocene(Historic). The alkaline and tholeiitic basalts exhibits OIB composition from intraplate volcanism which is not associated with plate subduction, while the basement xenolith contained in the volcanic rock indicates that there were volcanic activities associated with the Mesozoic plate subduction. The Geochemical characteristics have been explained with the plume model, lithospheric mantle origin, and melting of shallow asthenosphere by the rapid change of stress regimes between the collision of the India-Eurasia plates and subduction of the Pacific plate, while there has not been any geophysical investigation to disclose it. Compression near collisional plate boundaries causes lithospheric folding which results in the decrease of pressure beneath the ridge of the fold while the pressure increases beneath trough. The decompression beneath lithosphere is likely to accelerate basaltic magmatism along and below the ridge. We investigate the subsurface structure beneath Jeju volcanic island, South Korea and its vicinity and propose an alternative hypothesis that the basaltic magma beneath the island could be caused by episodic lithospheric folding. Unlike the prevailing hypothesis of the

  14. The Central Sierra Nevada Volcanic Field: A Geochemical Study of a Transitional Arc

    NASA Astrophysics Data System (ADS)

    Jean, M. M.; Putirka, K.; Busby, C.; Hagan, J.

    2006-12-01

    The Central Sierra Nevada (CSN) offers evidence about the effects of an arc/post-arc transition, which occurred in the middle to late Miocene. With passage of the Mendocino Triple Junction (MTJ), there should be a reflection of this new tectonic regime in the geochemistry of the resulting volcanic rocks. We conducted a search for systematic changes in magma chemistry, with regard to time and/or geography that may yield clues regarding tectonic origin, post 6 M.a. Major oxide and trace element analysis of 42 volcanic rock samples from the Sierra Nevada have been collected to assess the characteristics of ancestral Cascade volcanism. Major oxide element variation of 35 samples displayed high total alkalis (Na2O + K2O), medium to high K calc-alkaline compositions, and lavas that range from 50-75 wt% SiO2; all key signatures for Cascade volcanism. The remaining 7 samples displayed tholeiitic affinities. We looked for distinct chemical signatures to examine whether CSN volcanism was indicative of arcs. Spider-diagrams assisted in illustrating that the CSN suite is enriched in large ion lithophile elements (LILE) and depleted in high field strength elements (HFSE). Arcs contain Ba/Nb between 52 and 151 (Lange et. al., 1996), low Zr/Ba ratios, Y + Nb from 10 to 100 ppm, and high Sr/P2O5 ratios. The CSN volcanic field has geochemical characteristics that agree with each of these criteria that define subduction-related lavas. Two models were tested to explain the evolution of the CSN suite: fractional crystallization (FC) and combined assimilation-fractional crystallization (AFC). FC better explains both major oxide and trace element variations, compared to AFC. Our initial magma crystallized along the following liquid line of descent: ol+cpx, ol+cpx+plag, ol+cpx+plag+opx+hbl, ol+cpx+plag+opx+hbl+mag+ap.

  15. Transtension controlling volcanic morphology: Insights from oblique-to-the-arc tectonic domains

    NASA Astrophysics Data System (ADS)

    Sielfeld, G.; Cembrano, J. M.; Lara, L. E.

    2014-12-01

    Long and short-term tectonic activity plays an essential role in the segregation, transport and emplacement of fluids and magmas within the continental crust. Magma ascent and emplacement mechanisms within volcanic arcs are largely controlled by the interplay between pre-existing structural anisotropies, regional stress field, magmatic driving pressure, and the viscous resistance to magma flow. For the upper crust, many authors have stated that the orientation of principal tectonic stresses may determine the spatial distribution and geometry of eruptive vents and related feeder dykes Thus, regional and/or local tectonics (differential stresses) may exert a fundamental control in volcanic morphology and produce linear eruptive arrays of Andean-type strato-volcanoes, as a result of stability on long-lived structural system of sub-parallel dyke swarms and aligned minor eruptive centers along volcano flanks. In South-central Chile, the Callaqui Volcano consists of tens of aligned Pleisto-Holocene eruptive vents and hundreds of sub-parallel dykes, preserved along the ENE-WSW Callaqui volcano ridge. Morpho-structural field mapping and remote sensing analysis yields that Pleistocene eruptive vents are aligned into a N60°E-trending en echelon array, whereas its elliptical craters maximum diameter trend N66°E. Post-glacial eruptive vents also are organized into a N60°E trend, observed in both, isolated talweg scoria cone and flank fissural eruption. In addition, sub-parallel, underlying dyke swarms strike N60°E in it central portion of the volcanic system, becoming nearly E-W on distal zones. Examination of morphometrical and structural data yields that emplacement of magma occurs within a dextral transtensional regime, along a major regional discontinuity recognized previously by other authors. The strain field obtained within this study is consistent with the regional ENE shortening derived by the oblique convergence between Nazca and South-American plates.

  16. Generation of porphyry copper deposits by gas-brine reaction in volcanic arcs

    NASA Astrophysics Data System (ADS)

    Blundy, Jon; Mavrogenes, John; Tattitch, Brian; Sparks, Steve; Gilmer, Amy

    2014-05-01

    Porphyry copper deposits (PCDs) are characterised by a close spatial and temporal association with small, hypabyssal intrusions of silicic magmas in volcanic arcs. PCD formation requires elevated chlorine and water to concentrate copper in magmatic hypersaline liquids (or brines), and elevated sulphur to precipitate copper-rich sulphides. These twin requirements are hard to reconcile with experimental and petrological evidence that voluminous chlorine-rich, hydrous silicic magmas, of the variety favourable to copper enrichment, lack sufficient sulphur to precipitate directly the requisite quantities of sulphides. These features are, however, consistent with observations of active volcanic arcs whereby PCDs can be viewed as roots of dome volcanoes above shallow reservoirs where silicic magmas accumulate over long time spans. During protracted periods of dormancy metal-enriched dense brines accumulate in and above the silicic reservoir through slow, low-pressure degassing. Meanwhile cogenetic volatile-rich mafic magmas and their exsolved, sulphur and CO2-rich fluids accumulate in deeper reservoirs. Periodic destabilisation of these reservoirs leads to short-lived bursts of volcanism liberating sulphurous gases, which react with the shallow-stored brines to form copper-rich sulphides and acidic vapours. We test this hypothesis with a novel set of 'porphyry in a capsule' experiments designed to simulate low-pressure (1-2 kbar) interaction of basalt-derived, sulphur-rich gases with brine-saturated, copper-bearing, but sulphur-free, granite. Experiments were run at 720-850 ° C in cold-seal apparatus with basaltic andesite, loaded with H2O and S, situated below dacite, loaded with H2O, Cl and Cu. At run conditions both compositions are substantially degassed and crystallized. S-rich gas from the basaltic andesite ascends to react with Cu-rich brines exsolved from the dacite, Our experiments reveal the direct precipitation of copper-sulphide minerals, in vugs and veins

  17. Systematic Osmium Isotope Binary Mixing Arrays in Arc Volcanism

    NASA Astrophysics Data System (ADS)

    Alves, S.; Alves, S.; Schiano, P.; Capmas, F.; Allegre, C. J.

    2001-12-01

    Isotopic and geochemical studies on subduction-related lavas aim at constraining the nature of their mantle sources and the respective roles of source heterogeneity and petrogenetic processes in their compositions. Many components are potentially involved in producing the geochemical signatures of arc lavas: depleted mantle, subducted oceanic crust and sediments, and the overlying continental or oceanic crust. A further complication in characterizing mantle sources of arc lavas is complex mixing of some component parts via derivative fluids or melts released from the slab. Os isotope ratios are potential tracers of slab contribution in arc lavas because 1) subducted sediments are very radiogenic in Os compared to the upper mantle, and 2) Re behaves as a moderately incompatible element during mantle partial melting, whereas Os is highly compatible. Therefore, MORB have much higher Re/Os ratios than peridotites. Consequently, old oceanic crust is likely to be extremely more radiogenic than the depleted upper mantle so that recycled basaltic components should be identified by their elevated 187Os/188Os ratios. Os isotope ratios and Os and Re concentrations have been measured in 55 lavas coming from 10 different subduction zones. Samples span a large range of major element concentrations (from basalts to dacites) and Mg# (from 0.32 to 0.81). The 10 subduction zones, namely the Lesser Antilles, Java, Papua-New Guinea, the Philippines, Izu-Bonin, Kamchatka, the Aleutians, Mexico, Colombia and Peru-Chile, have a range of basement nature and thickness, as well as a range of age and sediment cover of the subducting plate. Measured 187Os/188Os ratios range from 0.130 to 1.524 and Os concentrations range from 0.048 to 46 ppt. Re concentrations range from 37 to 915 ppt. Os initial isotope ratios are systematically positively and linearly correlated with the inverse of Os concentrations in arc lavas from a given volcano, indicating that the Os isotopic compositions always

  18. Subaerial records of large-scale explosive volcanism and tsunami along an oceanic arc, Tonga, SW Pacific

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We present a new chronology of major terrestrial eruptions and tsunami events for the central Tongan Arc. The active Tonga-Kermadec oceanic arc extends 2500 km northward of New Zealand and hosts many tens of submarine volcanoes with around a dozen forming islands. Despite its obious volcanic setting, the impacts of explosive volcanism and volcano-tectonic related tsunami are an often overlooked in archaeological and paleo-botanical histories, mainly due the lack of good Holocene subaerial exposures. The inhabited small uplifted coral platform islands east of the volcanic arc in Tonga collectively cover only <550 km2. Inspired by local mythology of gods flying overhead with baskets of ash, and an analysis of the high-level wind distribution patterns, lake and wetland sites were investigated along the Tongan chain. In most cases former lagoon basins lifted above sea-level by a combination of tectonic rise and the lowering of mean sea levels by around 2 m since the Mid-Holocene form closed lake or swampy depressions. Coring reveaed between 6 and 20 mineral layers at each site, withn humic sediment or peat. Over thirty new radiocarbon dates were collected to develop a chronology for the sequences and the mineral layers were examined mineralogically and geochemically. These sites reveal mainly tephra fall layers of <6500 cal. years B.P., including several very large and regionally significant tephras. Erupted compositions range from basaltic to dacitic, with some showing compositional change during eruption. In addition, some large eruptions appear to have generated regionally significant tsunami, represented by characteristically mixed sandy layers with lithologies including shell fragment, foraminifera and volcanic particles.

  19. Volcanic and tectonic evolution of the Cascade volcanic arc, central Oregon

    SciTech Connect

    Priest, G.R. )

    1990-11-10

    From 22 to 0 Ma, {sigma}{sub 1} and {sigma}{sub 3} was likely a response to decreasing influence of ENE to NE compression at the Juan de Fuca plate-North American plate (JDFP-NAP) boundary relative to N-S compression and attendant continental extension produced at the Pacific plate (PP)-North American plate boundary. Decreases in orthogonal convergence rate, convergence angle, and length of the convergent margin relative to the NAP-PP transform Ma to 16.9-7.4 Ma, probably reflecting a decrease in convergence rate. Volcanic production increased at 7.4-0 Ma even though convergence rate continued to decrease. The extensional stress regime at 7-0 Ma promoted mafic volcanism that caused the increased volcanic production. Volcanic production is therefore a function of convergence rate and upper plate stress regime. The volcanic front migrated progressively eastward from 35 to 0 Ma as the volcanic belt narrowed. The narrowing was caused primarily by steepening slab dip at depths greater than 100 km. Eastward migration was likely caused by decreasing shallow (0-100 km) slab dip resulting from thinning of the NAP. Uplift of the Western Cascades province in the early Pliocene may have been caused by vigorous flow into the mantle wedge accommodating an increase of free rollback rate of the subducted plate at 4 Ma.

  20. Arc-transform magmatism in the Wrangell volcanic belt

    SciTech Connect

    Skulski, T.; Francis, D. ); Ludden, J. )

    1991-01-01

    The late Cenozoic Wrangell volcanic belt records a transition in magma supply and geochemistry from a subduction to transform margin between the northeastern Pacific and North American plates. The northwestern volcanic belt comprises calc-alkaline lavas that are above the Wrangell-Wadati Benioff zone, whereas the southeastern belt comprises transitional lavas with minor alkaline and calc-alkaline lavas that overlie a leaky transform fault. The subduction-transform transition is marked by an increase in Fe/Mg and Nb/La ratios and a decrease in Ba/La ratios. Thus, the lavas of the transform regime display a geochemical signature that is intermediate to that of calc-alkaline and intraplate alkaline lavas. Whereas the effects of crustal contamination can be recognized in the evolved lavas of all suites, all primitive lavas in the transform regime are mantle derived and reflect the variable melting and mixing depleted (mid-ocean ridge basalt) upper mantle, enriched mantle (ocean island basalt), and slab-derived components.

  1. Three dimensional modeling of mantle melt underneath the Lau Back-Arc spreading center and Tofua Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Tarlow, Scott

    Valu Fa and Eastern Lau's (two regions along Lau's back-arc spreading center) observed axial morphology suggest that Valu Fa is more magmatically robust than Eastern Lau despite Eastern Lau's spreading rate nearly doubling Valu Fa's. Early geochemical [Pearce et al., 1994] and geophysical [Martinez and Taylor, 2002] studies predict a gradational decrease in melting moving north from Valu Fa to Eastern Lau, but more recent geochemical and seismic observations ([Escrig, .et al 2009]; [Dunn and Martinez, 2011]; [Dunn et al., 2011]) show a sharper stepwise decrease in melting as the spreading center's ridge axis sweeps away from the Tofua Volcanic-Arc. As the ridge sweeps away from the volcanic-arc, the influence of the slab hydrated mantle in the melting structure of the ridge decreases. Furthermore, Eastern Lau produces a thinner crust than expected for a robust spreading center. 2-D numerical studies [Harmon and Blackmon, 2010] show a gradational decrease in melting from Valu Fa to Eastern Lau but with no corresponding thinning of Eastern Lau's crust. To understand the melting dynamics underneath Lau's back-arc spreading center and the Tofua Volcanic-Arc implementing the effects of 3-D mantle flow and slab hydration appears to be required. To explain the observed geochemical and seismic observations, three 3-D numerical were performed, using a community developed mantle convection solver (CitcomS). The first model shows that observed geometric and surface kinematic boundary conditions cause a steep gradational increase in relative melting area (anhydrous) moving northward with increasing spreading rate along the ridge axis from Valu Fa to Eastern Lau caused by a northwestern along axis mantle flow. A peak in the relative melting area appears particularly close to Eastern Lau where crust is thinnest. These predictions run in opposition to the observations. The second model shows including a viscosity reduction in the mantle wedge due to slab hydration causes a more

  2. Magma generation process beneath volcanic front of Kyushu arc, southwest Japan

    NASA Astrophysics Data System (ADS)

    Tamura, T.; Hasenaka, T.; Wallace, P. J.; Yasuda, A.; Mori, Y.

    2015-12-01

    We presents data for major and volatile (H2O, CO2, S, Cl) elements in olivine-hosted melt inclusions from Quaternary volcanoes (Aso, Kuju, Kirishima and Kaimon) along volcanic front of Kyushu arc, southwest Japan. Melt inclusion data are corrected for post-entrapment modifications including diffusive Fe-loss, H2O loss and post-entrapment crystallization. The primitive magma compositions calculated from corrected melt inclusion data are used to estimate the degree of partial melting and compositions of slab-derived fluids beneath Kyushu volcanic front. The result show that magmatism of four volcanoes in Kyushu arc is divided into two groups (Group A and B). Group A indicates high K2O contents in primitive magmas and in fluids at Aso and Kuju volcanoes, northern Kyushu arc. Group B indicates low K2O contents in primitive magmas and in fluids at Kirishima and Kaimon volcanoes, southern Kyushu arc. K2O contents of Group A and B are impossible of explaining by degree of partial melting and the origin of hydrous mantle. High K2O content in fluids is attributed to dehydration of phengite-bearing slab at deep depth (about 140 km) in Group A compared with shallow depth (about 100 km) in Group B. Phengite is dehydrated from submerging plate beneath 110 km depth. This study suggests that compositions of primitive magmas beneath Kyushu arc are reflected by the depth of slab and the kind of dehydrating hydrous minerals.

  3. Hydrothermal Monitoring in a Quiescent Volcanic Arc: Cascade Range, Northwestern United States

    NASA Astrophysics Data System (ADS)

    Gelwick, K.; Randolph-Flagg, N. G.; Crankshaw, I. M.; McCulloch, C. L.; Lundstrom, E. A.; Murveit, A. M.; Bergfeld, D.; Spicer, K.; Tucker, D.; Schmidt, M. E.; Mariner, R. H.; Evans, W.; Ingebritsen, S.

    2013-12-01

    Ongoing (1996-present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major-ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the U.S. Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade Range volcanic arc, from Mount Baker near the Canadian border to Mount Lassen in northern California. A concerted effort was made to develop hourly records of temperature and (or) hydrothermal solute flux spanning multiple years, suitable for comparison with other continuous geophysical monitoring data. Monitored sites included summit-fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and (or) large fluxes of magmatic CO2 or heat. As of 2009-2012 measured summit-fumarole temperatures in the Cascade Range were generally near or below the local pure-water boiling point; the maximum observed superheat was <+2.5°C at Mount Baker. Temporal variability in ground-temperature records from the summit-fumarole sites is temperature-dependent, with the hottest sites tending to show less variability. Seasonal variability in the flux of hydrothermally sourced major anions from the springs varied from essentially undetectable to a factor of 5-10. This range of observed behavior owes mainly to the local climate regime, with strongly snowmelt-influenced springs and streams exhibiting more variability. As of the end of the 2012 field season, there had been 87 occurrences of local seismic energy densities ~>0.001 J/m3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multi-decadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in

  4. A new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin

    USGS Publications Warehouse

    Parsons, T.; Trehu, A.M.; Luetgert, J.H.; Miller, K.; Kilbride, F.; Wells, R.E.; Fisher, M.A.; Flueh, E.; ten Brink, U.S.; Christensen, N.I.

    1998-01-01

    In light of suggestions that the Cascadia subduction margin may pose a significant seismic hazard for the highly populated Pacific Northwest region of the United States, the U.S. Geological Survey (USGS), the Research Center for Marine Geosciences (GEOMAR), and university collaborators collected and interpreted a 530-km-long wide-angle onshore-offshore seismic transect across the subduction zone and volcanic arc to study the major structures that contribute to seismogenic deformation. We observed (1) an increase in the dip of the Juan de Fuca slab from 2??-7?? to 12?? where it encounters a 20-km-thick block of the Siletz terrane or other accreted oceanic crust, (2) a distinct transition from Siletz crust into Cascade arc crust that coincides with the Mount St. Helens seismic zone, supporting the idea that the mafic Siletz block focuses seismic deformation at its edges, and (3) a crustal root (35-45 km deep) beneath the Cascade Range, with thinner crust (30-35 km) east of the volcanic arc beneath the Columbia Plateau flood basalt province. From the measured crustal structure and subduction geometry, we identify two zones that may concentrate future seismic activity: (1) a broad (because of the shallow dip), possibly locked part of the interplate contact that extends from ???25 km depth beneath the coastline to perhaps as far west as the deformation front ???120 km offshore and (2) a crustal zone at the eastern boundary between the Siletz terrane and the Cascade Range.

  5. From northern Gondwana passive margin to arc dismantling: a geochemical discrimination of Ordovician volcanisms (Sardinia, Italy)

    NASA Astrophysics Data System (ADS)

    Gaggero, L.; Oggiano, G.; Buzzi, L.; Funedda, A.

    2009-04-01

    In Sardinia, one of the southernmost remain of the European Variscan belt, a crustal section through northern Gondwanan paleodomains is largely preserved. It bears significant evidence of igneous activity, recently detailed in field relationships and radiometric dating (Oggiano et al., submitted). A Cambro - Ordovician (491.7 ± 3.5 Ma ÷ 479.9 ± 2.1 Ma, LA-ICP-MS U-Pb zircon age) bimodal volcanic suite occurs with continuity in external and inner Variscan nappes of Sardinia below the so-called Sardic unconformity. The igneous suite represents an intraplate volcanic activity developed through subsequent episodes: i) an intermediate explosive and effusive volcanism, i.e. pyroclastic fall deposits and lava flows, embedded into epicontinental clastic sediments, culminating in silicic ignimbrite eruptions, and ii) mafic effusives. Geochemical data document a transitional, within-plate signature, e.g. the average Th/Ta (4.5) and La/Nb (2.7) overlap the upper continental crust values. The volcanites are characterized by slight fractionation of LREEs, nearly flat HREE abundance. The negative Eu anomaly increases towards evolved compositions. Some prominent HREE depletion (GdCN/YbCN = 13.8), and the high Nb/Y suggest a garnet-bearing source. The high 87Sr radiogenic content (87Sr/86Sr 490 Ma = 0.71169) and the epsilon Nd 490 Ma value of -6.54 for one dacite sample, imply a time integrated LREE-enriched source with a high Rb/Sr, such as a metasedimentary source. The stratigraphy of the succession and the geochemical composition of igneous members suggest a volcanic passive margin along the northern Gondwana at the early Ordovician. The bimodal Mid-Ordovician arc volcanism (465.4 ± 1.4 Ma, U-Pb zircon age; Oggiano et al., submitted) is developed in the external nappes (e.g. in Sarrabus and Sarcidano) and in the foreland occurs as clasts at the base of the Hirnantian succession (Leone et al. 1991). The Mid Ordovician sub-alkalic volcanic suite has reliable stratigraphic and

  6. Late Cretaceous infant intra-oceanic arc volcanism, the Central Pontides, Turkey

    NASA Astrophysics Data System (ADS)

    Aygül, Mesut; Okay, Aral; Oberhänsli, Roland; Schmidt, Alexander; Sudo, Masafumi

    2015-04-01

    Low-grade bimodal metavolcanic rocks overlain by recrystallized micritic limestone with volcanogenic metasediments are exposed along the central part of the İzmir-Ankara-Erzincan suture separating Laurasia from Gondwana-derived terranes. Metavolcanic rocks mainly consist of rhyolite and basaltic andesite with pyroclastic equivalents that are interbedded with pelagic limestone and chert. Two groups can be identified based on rare and trace element characteristics. The first group consists of basaltic andesite/andesite and rhyolite with abundant cognate gabbroic xenoliths. It is characterized by relative enrichment of LREE with respect to HREE. The rocks are enriched in fluid mobile LILE, and strongly depleted in Ti and P reflecting fractionation of Fe-Ti oxides and apatite, which are found in the mafic cognate xenoliths. We infer that this group is cogenetic and felsic rocks are derived from a common mafic parental magma. The second group consists only of basaltic andesites with flat REE pattern resembling island arc tholeiites. Although enriched in LILE, this group is not depleted in Ti or P. Geochemistry of the bimodal volcanic rocks indicates supra-subduction volcanism. The tectonic setting and absence of continent derived detritus in the arc sequence suggest an intra-oceanic setting. Zircons from two metarhyolite samples give 93.8 ± 1.9 and 94.4 ± 1.9 Ma U/Pb ages, respectively. Low-grade regional metamorphism is constrained to 69.86 ± 0.4 Ma by 40Ar/39Ar dating on metamorphic muscovite. The zircon age data shows that the intra-oceanic arc is coeval with the ophiolite obduction in NW Turkey, Armenia and Oman suggesting that it formed during an initial subduction leading to the regional ophiolite obduction. Reduced thickness of the arc sequence and its short age span depicts the infancy of the arc. Non-collisional cessation of the young volcanism was probably associated with southward migration of the arc volcanism as in the Izu-Bonin-Mariana arc system.

  7. Intraplate volcanism controlled by back-arc and continental structures in NE Asia inferred from transdimensional Bayesian ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Kim, Seongryong; Tkalčić, Hrvoje; Rhie, Junkee; Chen, Youlin

    2016-08-01

    Intraplate volcanism adjacent to active continental margins is not simply explained by plate tectonics or plume interaction. Recent volcanoes in northeast (NE) Asia, including NE China and the Korean Peninsula, are characterized by heterogeneous tectonic structures and geochemical compositions. Here we apply a transdimensional Bayesian tomography to estimate high-resolution images of group and phase velocity variations (with periods between 8 and 70 s). The method provides robust estimations of velocity maps, and the reliability of results is tested through carefully designed synthetic recovery experiments. Our maps reveal two sublithospheric low-velocity anomalies that connect back-arc regions (in Japan and Ryukyu Trench) with current margins of continental lithosphere where the volcanoes are distributed. Combined with evidences from previous geochemical and geophysical studies, we argue that the volcanoes are related to the low-velocity structures associated with back-arc processes and preexisting continental lithosphere.

  8. Long-term eruptive activity at a submarine arc volcano

    USGS Publications Warehouse

    Embley, R.W.; Chadwick, W.W.; Baker, E.T.; Butterfield, D.A.; Resing, J.A.; De Ronde, C. E. J.; Tunnicliffe, V.; Lupton, J.E.; Juniper, S.K.; Rubin, K.H.; Stern, R.J.; Lebon, G.T.; Nakamura, K.-I.; Merle, S.G.; Hein, J.R.; Wiens, D.A.; Tamura, Y.

    2006-01-01

    Three-quarters of the Earth's volcanic activity is submarine, located mostly along the mid-ocean ridges, with the remainder along intraoceanic arcs and hotspots at depths varying from greater than 4,000 m to near the sea surface. Most observations and sampling of submarine eruptions have been indirect, made from surface vessels or made after the fact. We describe here direct observations and sampling of an eruption at a submarine arc volcano named NW Rota-1, located 60 km northwest of the island of Rota (Commonwealth of the Northern Mariana Islands). We observed a pulsating plume permeated with droplets of molten sulphur disgorging volcanic ash and lapilli from a 15-m diameter pit in March 2004 and again in October 2005 near the summit of the volcano at a water depth of 555 m (depth in 2004). A turbid layer found on the flanks of the volcano (in 2004) at depths from 700 m to more than 1,400 m was probably formed by mass-wasting events related to the eruption. Long-term eruptive activity has produced an unusual chemical environment and a very unstable benthic habitat exploited by only a few mobile decapod species. Such conditions are perhaps distinctive of active arc and hotspot volcanoes. ?? 2006 Nature Publishing Group.

  9. Sedimentary, volcanic, and tectonic processes of the central Mariana Arc: Mariana Trough back-arc basin formation and the West Mariana Ridge

    NASA Astrophysics Data System (ADS)

    Oakley, A. J.; Taylor, B.; Moore, G. F.; Goodliffe, A.

    2009-08-01

    We present new multichannel seismic profiles and bathymetric data from the central Marianas that image the West Mariana Ridge (WMR) remnant arc, both margins of the Mariana Trough back-arc basin, the modern arc, and Eocene frontal-arc high. These data reveal structure and stratigraphy related to three periods of arc volcanism and two periods of arc rifting. We interpret the boundary between accreted back-arc basin and rifted arc crust along the Mariana Trough and support these findings with drilling results and recent seismic refraction and gravity studies. We show that with the exception of a few volcanoes behind the volcanic front that straddle the boundary between crustal types, the modern Mariana Arc is built entirely on rifted arc crust between 14 and 19°N. Our data indicate that there is more accreted back-arc seafloor to the west of the Mariana Trough spreading axis than to the east, confirming previous evidence for an asymmetric basin. The rifted margin of the WMR remnant arc forms a stepped pattern along the western boundary of the Mariana Trough, between 15°30' and 19°N. In this region, linear volcanic cross chains behind the WMR are aligned with the trend of Mariana Trough spreading segments, and the WMR ridges extend into the back-arc basin along the same strike. These ridges are magmatic accommodation zones which, to the north along the Izu-Bonin Arc, punctuate tectonic extension. For the WMR we hypothesize that rift basins are more commonly the sites where spreading segment offsets nucleate, whereas magmatic centers of spreading segments are sites where magmatism continues from arc volcanism, through rifting to back-arc spreading. The Mariana Trough is opening nonrigidly and is characterized by two predominant abyssal hill trends, NNW-SSE in the north and N-S in the south. Between the only two basin-crossing fracture zones at ˜15.5 and 17.5°, N-S axes propagated north at the expense of NNW axes.

  10. Active Volcanic Plumes on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon (see inset at upper right), erupting over a caldera (volcanic depression) named Pillan Patera after a South American god of thunder, fire and volcanoes. The plume seen by Galileo is 140 kilometers (86 miles) high and was also detected by the Hubble Space Telescope. The Galileo spacecraft will pass almost directly over Pillan Patera in 1999 at a range of only 600 kilometers (373 miles).

    The second plume, seen near the terminator (boundary between day and night), is called Prometheus after the Greek fire god (see inset at lower right). The shadow of the 75-kilometer (45- mile) high airborne plume can be seen extending to the right of the eruption vent. The vent is near the center of the bright and dark rings. Plumes on Io have a blue color, so the plume shadow is reddish. The Prometheus plume can be seen in every Galileo image with the appropriate geometry, as well as every such Voyager image acquired in 1979. It is possible that this plume has been continuously active for more than 18 years. In contrast, a plume has never been seen at Pillan Patera prior to the recent Galileo and Hubble Space Telescope images.

    North is toward the top of the picture. The resolution is about 6 kilometers (3.7 miles) per picture element. This composite uses images taken with the green, violet and near infrared filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The images were obtained on June 28, 1997, at a range of more than 600,000 kilometers (372,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page

  11. GPS-derived coupling estimates for the Central America subduction zone and volcanic arc faults: El Salvador, Honduras and Nicaragua

    NASA Astrophysics Data System (ADS)

    Correa-Mora, F.; DeMets, C.; Alvarado, D.; Turner, H. L.; Mattioli, G.; Hernandez, D.; Pullinger, C.; Rodriguez, M.; Tenorio, C.

    2009-12-01

    We invert GPS velocities from 32 sites in El Salvador, Honduras and Nicaragua to estimate the rate of long-term forearc motion and distributions of interseismic coupling across the Middle America subduction zone offshore from these countries and faults in the Salvadoran and Nicaraguan volcanic arcs. A 3-D finite element model is used to approximate the geometries of the subduction interface and strike-slip faults in the volcanic arc and determine the elastic response to coupling across these faults. The GPS velocities are best fit by a model in which the forearc moves 14-16 mmyr-1 and has coupling of 85-100 per cent across faults in the volcanic arc, in agreement with the high level of historic and recent earthquake activity in the volcanic arc. Our velocity inversion indicates that coupling across the potentially seismogenic areas of the subduction interface is remarkably weak, averaging no more than 3 per cent of the plate convergence rate and with only two poorly resolved patches where coupling might be higher along the 550-km-long segment we modelled. Our geodetic evidence for weak subduction coupling disagrees with a seismically derived coupling estimate of 60 +/- 10 per cent from a published analysis of earthquake damage back to 1690, but agrees with three other seismologic studies that infer weak subduction coupling from 20th century earthquakes. Most large historical earthquakes offshore from El Salvador and western Nicaragua may therefore have been intraslab normal faulting events similar to the Mw 7.3 1982 and Mw 7.7 2001 earthquakes offshore from El Salvador. Alternatively, the degree of coupling might vary with time. The evidence for weak coupling indirectly supports a recently published hypothesis that much of the Middle American forearc is escaping to the west or northwest away from the Cocos Ridge collision zone in Costa Rica. Such a hypothesis is particularly attractive for El Salvador, where there is little or no convergence obliquity to drive the

  12. Geochemistry of selected lavas of the Panarea volcanic group, Aeolian Arc, Italy

    NASA Astrophysics Data System (ADS)

    Doherty, A. L.; Cannatelli, C.; Raia, F.; Belkin, H. E.; Albanese, S.; Lima, A.; De Vivo, B.

    2015-10-01

    The Panarea Volcanic Group (PVG) is a group of emergent islands rising from the truncated cone of an underwater edifice in the eastern sector of the Aeolian Island Arc in the Tyrrhenian Sea, Italy. Selected lava units from the main island of Panarea and some of the nearby islets were analysed for their major and trace element compositions to the dataset available in the literature. Major mineral phases were identified as plagioclase ± clinopyroxene ± orthopyroxene ± olivine ± amphibole ± mica. The lavas of this study range from andesite to rhyolite with major element compositions equivalent to previously published data. Pyroxene geobarometry suggests a polybaric distribution to crystal fractionation, beginning at the Moho, and continuing to a shallow magma reservoir, at approximately 0.8 km depth. A plot of Nd143/Nd144 vs. Sr87/Sr86 show the compositions of Panarea overlap with the compositions of the eastern and central Aeolian Arc, while Pb208/Pb204 vs. Pb206/Pb204 do not overlap, but fall between the central and eastern arc values. As major and trace element concentrations, and isotope compositions of the lavas of this study overlap most consistently with lava compositions from the central and eastern Aeolian Arc, indicating Panarea should be considered an "intermediate" volcano in the arc.

  13. Isotopic compositions of volcanic arc rocks in the Southern Volcanic Zone (33°-43°S), Chile: along- and across-arc variations

    NASA Astrophysics Data System (ADS)

    Jacques, Guillaume; Hoernle, Kaj; Gill, Jim; Wehrmann, Heidi

    2014-05-01

    We investigate young, olivine-bearing volcanic arc (VA) rocks from the Southern Volcanic Zone (33-43°S; SVZ) in Chile, and from the backarc (BA) in Argentina for their major and trace element, and Sr-Nd-Hf-Pb-O isotope geochemistry. The compositional data are processed to identify the source components contributing to the arc magmas and to estimate their proportions, with the aim to better understand the effects of the large-scale along-arc tectonic variations onto melt generation and erupted compositions. The Transitional (T) SVZ (34.5-38°S; Jacques et al., 2013) samples overlap the BA samples in Sr and Nd isotopes, whereas the Central (C) SVZ (38-43°S; Jacques et al., submitted, Chemical Geology) samples are shifted to slightly higher Sr and/or Nd isotope ratios. All samples form a tight correlation on the Pb isotope diagrams. The VA samples plot at the radiogenic end of the positive BA array and overlap trench sediment, indicating mixing between a South Atlantic MORB-type source and a slab component derived from subducted trench sediments and altered oceanic crust. On the Nd versus Hf isotope diagram, the VA and BA form two sub parallel linear trends, neither pointing to subducting sediment. The VA may display an asthenospheric mantle array, whereas enriched Proterozoic lithospheric mantle may be involved in the BA. The CSVZ samples have higher fluid-mobile to fluid-immobile element ratios and lower more- to less-incompatible fluid-immobile element ratios than the TSVZ samples, consistent with higher hydrous melt flux and higher degrees of melting resulting in higher magma production and eruption rates in the CSVZ. Low δ18O(melt) of CSVZ lavas suggests that the source of the enhanced water flux is likely to be hydrated lower crust and serpentinized upper mantle of the incoming plate, resulting from the multiple large fracture zones in this part of the SVZ. The δ18O(melt) values of the NSVZ, TSVZ and BA, on the other hand, largely overlap the MORB mantle

  14. Arc-rift transition volcanism in the Volcanic Hills, Jacumba and Coyote Mountains, San Diego and Imperial Counties, california

    NASA Astrophysics Data System (ADS)

    Fisch, Gregory Zane

    Neogene volcanism associated with the subduction of the Farallon-Pacific spreading center and the transition from a subduction zone to a rift zone has been studied extensively in Baja, California, Mexico. One of the main goals of these studies was to find a geochemical correlation with slab windows that may have formed during that complicated transition. While workers have been able to find distinct geochemical signatures in samples from Baja California, none have shown statistically significant correlation with samples from southern California that are thought to be related to the same arc-rift transition events. All of the basaltic samples from this study of southern California rocks have prominent Nb depletions typical of island-arc subduction-related volcanism, in contrast to the chemistry of Baja California volcanics that have trace element patterns typical of synrift related volcanism. The work done by previous investigators has been additionally complicated due to each investigator's choice of important ratios or patterns, which bears little, if any, correlation with work done by others working in the same area. For example, Martin-Barajas et al. (1995) use K/Rb ratios in their study of the Puertocitos Volcanic Province, while Castillo (2008) argues that Sr/Y vs. Y is a better indicator of petrogenetic processes. Little petrologic work has been done on Neogene volcanic rocks in the Imperial Valley and eastern San Diego County region of Southern California. This thesis combines new research with that of previous workers and attempts to establish a better understanding of the processes involved with the transition volcanism. Prior work documents significant differences in the geochemistry between some of these areas, especially those in close proximity to each other (e.g. the Volcanic Hills and Coyote Mountains). These differences were thought to be largely the result different magmatic sources. The potential of finding two differing magma types in close

  15. The Galapagos-OIB signature of the central Costa Rican volcanic front: arc-hotspot interaction

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Carr, M. J.; Hoernle, K.; Feigenson, M. D.; Hauff, F.; Szymanski, D.; van den Bogaard, P.

    2008-12-01

    Although most Central American magmas have a typical arc geochemical signature, magmas in southern Central America have isotopic and trace element compositions with an OIB affinity, similar to the Galapagos hotspot lavas. Our new data for Costa Rica suggest that this signature, unusual for a convergent margin, has a relatively recent origin (Late Miocene-Pliocene ca. 6 Ma). We also show that there was a transition from typical arc magmas (analogous to the modern Nicaraguan volcanic front) to OIB-like magmas. The geographic distribution of the Galapagos signature in recent lavas from southern Central America is present landward from the subduction of the Galapagos hotspot tracks (the Seamount Province and the Cocos/Coiba Ridges) at the Middle American Trench. The higher Pb isotopic ratios, relatively low Nd isotopic ratios and enriched geochemical signature of central Costa Rican magmas can be explained by arc-hotspot interaction. The isotopic ratios of central Costa Rican lavas require the subducting Seamount Province (Northern Galapagos Domain) component, whereas the isotopic ratios of the adakites and alkaline basalts from southern Costa Rica and Panama are in the geochemical range of the subducting Cocos/Coiba Ridges (Central Galapagos Domain). Geological, geochemical, and isotopic evidence collectively indicate that the relatively recent Galapagos-OIB signature in southern Central America represents a geochemical signal from subducting Galapagos hotspot tracks, which started to collide with the margin ~8 Ma ago. The Galapagos hotspot contribution decreases systematically along the volcanic front from central Costa Rica to NW Nicaragua.

  16. Melting above the anhydrous solidus controls the location of volcanic arcs.

    PubMed

    England, Philip C; Katz, Richard F

    2010-10-07

    Segregation of magma from the mantle in subduction zones is one of the principal mechanisms for chemical differentiation of the Earth. Fundamental aspects of this system, in particular the processes by which melt forms and travels to the Earth's surface, remain obscure. Systematics in the location of volcanic arcs, the surface expression of this melting, are widely considered to be a clue to processes taking place at depth, but many mutually incompatible interpretations of this clue exist (for example, see refs 1-6). We discriminate between those interpretations by the use of a simple scaling argument derived from a realistic mathematical model of heat transfer in subduction zones. The locations of the arcs cannot be explained by the release of fluids in reactions taking place near the top of the slab. Instead, the sharpness of the volcanic fronts, together with the systematics of their locations, requires that arcs must be located above the place where the boundary defined by the anhydrous solidus makes its closest approach to the trench. We show that heat carried by magma rising from this region is sufficient to modify the thermal structure of the wedge and determine the pathway through which both wet and dry melts reach the surface.

  17. Rate of lateral magma transport in the Earth's crust beneath submarine volcanic arcs derived from earthquake swarm analysis

    NASA Astrophysics Data System (ADS)

    Spicak, A.; Vanek, J.

    2015-12-01

    This contribution deals with subduction-related submarine magmatism. We are offering a tool to contribute to delimitation of domains of current magma unrest at convergent plate margins and to understand better the behavior of magma in the lithospheric wedge above the subducting slab: a detailed analysis of teleseismic earthquake occurrence. A specific seismicity pattern has been observed beneath submarine portions of several volcanic arcs at convergent plate margins (Andaman Sea region, southern Ryukyu area). We have found three arguments that allowed us to interpret such a seismicity pattern as a magma-driven process: (i) clustering of medium-size earthquakes (M~5) in space and time in shallow earthquake swarms; (ii) rapid migration of seismic activity during the swarms (comparison of epicentral maps of individual stages of the swarm development showed consistently that earthquake epicenters migrate laterally at a rate of several hundred meters per hour); (iii) correlation of epicentral zones of the swarms with distinct seamounts and submarine ridges (current seismically active intrusions probably propagate along plumbing systems that served as conduits of magma to the surface in the past). The repeated occurrence of relatively strong, teleseismically recorded earthquake swarms thus probably reflects fluid and/or magma ascent through the plumbing system of the volcanic arc, points to brittle character of the lithospheric wedge at respective depths and favors the studied areas - the Andaman Sea region and the southern Ryukyu area - to be potential sites of submarine volcanic activity.. The study documents high accuracy of hypocenter parameter determinations published by data centers such as ISC and NEIC USGS, and the usefulness of the EHB relocation procedure.

  18. Petrogenesis of Gympie Group volcanics: evidence for remnants of an early Permian volcanic arc in eastern Australia

    NASA Astrophysics Data System (ADS)

    Sivell, W. J.; Waterhouse, J. B.

    1988-02-01

    Mafic ohenocryst-rich basalt to basaltic andesite tuff-breccias, agglomerates and subordinate lavas, together with sparsely quartz- and plagiophyric dacitic tuffs and glassy flows, comprise the tectonomorphically anomalous lower Permian submarine volcanic sequence of the Gympie Group, southeast Queensland. Geochemical data imply three distinct crystallisation stages for the main volcanic series. These are (1) initial olivine ( ± Cr-spinel) + clinopyroxene removal that caused rapid MgO, CaO, Ni and Cr depletion in the ascending mantle-derived magma; (2) extensive clinopyroxene-dominated olivine+clinopyroxene+plagioclase fractionation that gave rise to tholeiitic FeO 1, TiO 2, Al 2O 3, P 2O 5, Zr and Y enrichment in the basalt-basaltic andesite range; and (3) plagioclase (dominant)+augite+magnetite+apatite crystallisation that resulted in decreasing Al 2O 3, TiO 2, FeO 1, P 2O 5, V, Nb and Sr levels in the dacites. Identical degrees of rare-earth element (REE) fractionation for the basalts and dacites suggest their comagmatic origin and preclude significant amphibole involvement in their petrogenesis. Low Mg-numbers (Mg 1), Ni, Cr, REE and high-field-strength cation (HFSC) abundances in the Gympie basalts, along with low {Zr}/{Y}, {Ti}/{Y} and {Nb}/{Zr} ratios, are features typical of island arc tholeiites. The Gympie suite represents an immature submarine tholeiitic stage of development of a portion of a major intra-oceanic arc that bordered Gondwana, but was fragmented by opening of the Tasman Sea. The presence of coarse clinopyroxene-phyric ankaramites, together with highly differentiated dacites, may relate to a phase of strike-slip tectonics that exerted important control on magma supply and volumetric eruptive rates during the early Permian evolution of the Gondwana margin.

  19. Volcanic eruptions and solar activity

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

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

  20. Tracking Sediment Subduction Along the Sangihe Volcanic Arc, Indonesia Using Volatile Chemistry and N-isotopes

    NASA Astrophysics Data System (ADS)

    Clor, L. E.; Fischer, T. P.; Hilton, D. R.; Sharp, Z.; Hartono, U.

    2002-12-01

    We report the first data on volatile emissions from the Sangihe Volcanic Arc to trace sediment subduction. The Sangihe Arc is part of an unusual tectonic setting where the Molucca Sea Plate subducts beneath both the Sangihe and Halmahera Arcs, resulting in oblique arc-arc collision. The northern parts of Sangihe and Halmahera are fused, while the south has not yet collided. Collision has resulted in sediment obduction onto the facing arcs, decoupling it from the oceanic plate below. To study the geochemical effects of collision, we collected gases at eight locations along Sangihe Arc at fumaroles and hot springs. Our results complement CO2-He systematics of the same samples (Jaffe et al., this volume). Gas samples were analyzed for major volatiles and N isotopes. Typical N2/He for subduction zones are 1000-25,000, while MORB and OIB are lower (10-100) due to the lack of sediment-derived N input. Most Sangihe samples have N2/He that deviate from the subduction signature (330-2825). The N isotopic (δ15N) value of air is 0‰ by definition, -3 to -5‰ in the upper mantle, and +7‰ in marine sediments. δ15N values for Sangihe samples range from -7 to +2‰ . Variations in N2/He ratios and δ15N data (tracers of hemipelagic sediment) correlate with latitude, with values decreasing to the north suggesting that subduction of hemipelagic sediment is less significant in the north than the south. The N2-He systematics suggest that arc-arc collision, more advanced in the north (where N2/He=537 and δ15N=-7‰ at Ruang Volcano), has caused the sediment package to become less coupled to the underlying ocean crust. The higher values in the south (N2/He=1977 and δ15N=+2‰ at Ambang Volcano) suggest that sediment is still subducting there, as the collision is less developed. Alternatively, sediment composition may vary along strike of the arc, with hemipelagic and carbonate-rich sediments subducted in the south and north, respectively.

  1. Data on Holocene Tephra (Volcanic Ash) Deposits in the Alaska Peninsula and Lower Cook Inlet Region of the Aleutian Volcanic Arc, Alaska

    USGS Publications Warehouse

    Riehle, J.R.; Meyer, C.E.; Miyaoka, Ronny T.

    1999-01-01

    Introduction This site provides information about the number, thickness, and grainsize of Holocene volcanic ash deposits at 50 localities in the eastern Aleutian volcanic arc. In addition, the major-element compositions of the glasses separated from more than 350 samples of tephra from these localities, determined by electron microprobe, are presented as a basis for correlating samples. Where known with reasonable certainty, the source of an analyzed sample is also identified for use in comparative studies of magma chemistry.

  2. Active Volcanic Eruptions on Io

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Six views of the volcanic plume named Prometheus, as seen against Io's disk and near the bright limb (edge) of the satellite by the SSI camera on the Galileo spacecraft during its second (G2) orbit of Jupiter. North is to the top of each frame. To the south-southeast of Prometheus is another bright spot that appears to be an active plume erupting from a feature named Culann Patera. Prometheus was active 17 years ago during both Voyager flybys, but no activity was detected by Voyager at Culann. Both of these plumes were seen to glow in the dark in an eclipse image acquired by the imaging camera during Galileo's first (G1) orbit, and hot spots at these locations were detected by Galileo's Near-Infrared Mapping Spectrometer.

    The plumes are thought to be driven by heating sulfur dioxide in Io's subsurface into an expanding fluid or 'geyser'. The long-lived nature of these eruptions requires that a substantial supply of sulfur dioxide must be available in Io's subsurface, similar to groundwater. Sulfur dioxide gas condenses into small particles of 'snow' in the expanding plume, and the small particles scatter light and appear bright at short wavelengths. The images shown here were acquired through the shortest-wavelength filter (violet) of the Galileo camera. Prometheus is about 300 km wide and 75 km high and Culann is about 150 km wide and less than 50 km high. The images were acquired on September 4, 1996 at a range of 2,000,000 km (20 km/pixel resolution). Prometheus is named after the Greek fire god and Culann is named after the Celtic smith god.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the

  3. The temporal evolution of back-arc magmas from the Auca Mahuida shield volcano (Payenia Volcanic Province, Argentina)

    NASA Astrophysics Data System (ADS)

    Pallares, Carlos; Quidelleur, Xavier; Gillot, Pierre-Yves; Kluska, Jean-Michel; Tchilinguirian, Paul; Sarda, Philippe

    2016-09-01

    In order to better constrain the temporal volcanic activity of the back-arc context in Payenia Volcanic Province (PVP, Argentina), we present new K-Ar dating, petrographic data, major and trace elements from 23 samples collected on the Auca Mahuida shield volcano. Our new data, coupled with published data, show that this volcano was built from about 1.8 to 1.0 Ma during five volcanic phases, and that Auca Mahuida magmas were extracted from, at least, two slightly different OIB-type mantle sources with a low partial melting rate. The first one, containing more garnet, was located deeper in the mantle, while the second contains more spinel and was thus shallower. The high-MgO basalts (or primitive basalts) and the low-MgO basalts (or evolved basalts), produced from the deeper and shallower lherzolite mantle sources, respectively, are found within each volcanic phase, suggesting that both magmatic reservoirs were sampled during the 1 Myr lifetime of the Auca Mahuida volcano. However, a slight increase of the proportion of low-MgO basalts, as well as of magmas sampled from the shallowest source, can be observed through time. Similar overall petrological characteristics found in the Pleistocene-Holocene basaltic rocks from Los Volcanes and Auca Mahuida volcano suggest that they originated from the same magmatic source. Consequently, it can be proposed that the thermal asthenospheric anomaly is probably still present beneath the PVP. Finally, our data further support the hypothesis that the injection of hot asthenosphere with an OIB mantle source signature, which was triggered by the steepening of the Nazca subducting plate, induced the production of a large volume of lavas within the PVP since 2 Ma.

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

    PubMed

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

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

    PubMed Central

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

    2016-01-01

    Abstract This study reports the first detailed geochemical characterization of Kolumbo submarine volcano in order to investigate the role of source heterogeneity in controlling geochemical variability within the Santorini volcanic field in the central Aegean arc. Kolumbo, situated 15 km to the northeast of Santorini, last erupted in 1650 AD and is thus closely associated with the Santorini volcanic system in space and time. Samples taken by remotely‐operated vehicle that were analyzed for major element, trace element and Sr‐Nd‐Hf‐Pb isotope composition include the 1650 AD and underlying K2 rhyolitic, enclave‐bearing pumices that are nearly identical in composition (73 wt.% SiO2, 4.2 wt.% K2O). Lava bodies exposed in the crater and enclaves are basalts to andesites (52–60 wt.% SiO2). Biotite and amphibole are common phenocryst phases, in contrast with the typically anhydrous mineral assemblages of Santorini. The strong geochemical signature of amphibole fractionation and the assimilation of lower crustal basement in the petrogenesis of the Kolumbo magmas indicates that Kolumbo and Santorini underwent different crustal differentiation histories and that their crustal magmatic systems are unrelated. Moreover, the Kolumbo samples are derived from a distinct, more enriched mantle source that is characterized by high Nb/Yb (>3) and low 206Pb/204Pb (<18.82) that has not been recognized in the Santorini volcanic products. The strong dissimilarity in both petrogenesis and inferred mantle sources between Kolumbo and Santorini suggests that pronounced source variations can be manifested in arc magmas that are closely associated in space and time within a single volcanic field. PMID:27917071

  7. Mount St. Helens' volcanic ash: hemolytic activity.

    PubMed

    Vallyathan, V; Mentnech, M S; Stettler, L E; Dollberg, D D; Green, F H

    1983-04-01

    Volcanic ash samples from four Mount St. Helens' volcanic eruptions were subjected to mineralogical, analytical, and hemolytic studies in order to evaluate their potential for cytotoxicity and fibrogenicity. Plagioclase minerals constituted the major component of the ash with free crystalline silica concentrations ranging from 1.5 to 7.2%. The in vitro hemolytic activity of the volcanic ash was compared to similar concentrations of cytotoxic and inert minerals. The ash was markedly hemolytic, exhibiting an activity similar to chrysotile asbestos, a known fibrogenic agent. The hemolysis of the different ash samples varied with particle size but not with crystalline silica concentration. The results of these studies taken in conjunction with the results of our animal studies indicate a fibrogenic potential of volcanic ash in heavily exposed humans.

  8. Stratigraphy, petrology, and geochemistry of the Spurr Volcanic Complex, eastern Aleutian Arc, Alaska. [(Appendix for geothermal fluid chemistry)

    SciTech Connect

    Nye, C.J.

    1987-12-01

    The Spurr Volcanic Complex (SVC) is a calcalkaline, medium-K, sequence of andesites erupted over the last quarter of a million years by the easternmost currently active volcanic center in the Aleutian Arc. The ancestral Mt. Spurr was built mostly of andesites of uniform composition (58 to 60% SiO/sub 2/), although andesite production was episodically interrupted by the introduction of new batches of more mafic magma. Near the end of the Pleistocene the ancestral Mt. Spurr underwent Bezyianny-type avalanche caldera formation, resulting in the production of a volcanic debris avalanche with overlying ashflows. Immediately afterward, a large dome (the present Mt. Spurr) was emplaced in the caldera. Both the ashflows and dome are made of acid andesite more silicic than any analyzed lavas from the ancestral Mt. Spurr (60 to 63% SiO/sub 2/), yet contain olivine and amphibole xenocrysts derived from more mafic magma. The mafic magma (53 to 57% SiO/sub 2/) erupted during and after dome emplacement, forming proto-Crater Peak and Crater Peak. Hybrid pyroclastic flows and lavas were also produced. Proto-Crater Peak underwent glacial dissection prior to the formation of Crater Peak in approximately the same location. Appendices II through VIII contain a summary of mineral compositions; Appendix I contains geochemical data. Appendix IX by R.J. Motyka and C.J. Nye describes the chemistry of geothermal fluids. 78 refs., 16 figs., 3 tabs.

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

    NASA Astrophysics Data System (ADS)

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

    2000-03-01

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

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

    USGS Publications Warehouse

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

    1997-01-01

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

  11. A New Hygrometer based on the Europium Anomaly in Clinopyroxene Phenocrysts in Arc Volcanic Rocks

    NASA Astrophysics Data System (ADS)

    Plank, T.; Benjamin, E.; Wade, J.; Grove, T.

    2004-12-01

    Water is arguably the most important chemical component in arc magmas, affecting everything from liquidus temperatures to crystal fractionation trends to melt rheology. Water concentrations in arc magmas provide a first-order constraint on water contents in the mantle wedge, and the mechanisms of wet mantle melting. However, measuring the water content of primary arc magmas has been difficult, or in some cases impossible, due to the near complete degassing of volcanic rocks, and the scarcity of olivine-hosted melt inclusions in many arc volcanoes. We have thus developed a new hygrometer using the composition of clinopyroxene phenocrysts, which are common in arc basalts and andesites. The hygrometer is based on the well-known suppression of plagioclase by water dissolved in the melt, and the effect on the rare earth element (REE) pattern of coexisting phases, such as clinopyroxene. Dry melts saturate in plagioclase early, and the preferential partitioning of Eu2+ in plagioclase causes a negative Eu anomaly to develop in coexisting melts and clinopyroxene. In wet magmas, clinopyroxene crystallizes before plagioclase, and so initially appears with a negligible Eu anomaly. Clinopyroxenes then record water content in the delayed development of their negative Eu anomaly, caused by the delayed appearance of plagioclase along the cotectic with increasing water. We have tested this model using tephras from the 1723 eruption of Irazu, the ET3 unit of Arenal and the 1995 eruption of Cerro Negro volcanoes in Central America, with known water contents of ˜ 3, 4 and 5 wt%, respectively, based on olivine-hosted melt inclusions. Clinopyroxene phenocrysts separated from these samples vary in Mg# from 86-72, and in some cases span the entire liquid line of descent of the volcano. REE patterns were determined by laser ablation ICPMS on 150 micron spots. A marked increase in the magnitude of the negative Eu anomaly occurs in clinopyroxenes with Mg# < 84 in Irazu, < 82 in Arenal and

  12. Variation of the Earth tide-seismicity compliance parameter the last 50 years for the west site of the Aegean Volcanic Arc, Greece

    NASA Astrophysics Data System (ADS)

    Contadakis, M. E.; Arabelos, D. N.; Vergos, G.; Spatalas, S.

    2015-07-01

    Based on the results of our studies for the tidal triggering effect on the seismicity of the Hellenic area, we consider the confidence level of earthquake occurrence - tidal period accordance as an index of tectonic stress criticality for earthquake occurrence and we check if the recent increase in the seismic activity at the west site of the Aegean Volcanic Arc indicate faulting maturity for a stronger earthquake. In this paper we present the results of this test which are positive.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  15. Metagenomic investigation of the geologically unique Hellenic Volcanic Arc reveals a distinctive ecosystem with unexpected physiology.

    PubMed

    Oulas, Anastasis; Polymenakou, Paraskevi N; Seshadri, Rekha; Tripp, H James; Mandalakis, Manolis; Paez-Espino, A David; Pati, Amrita; Chain, Patrick; Nomikou, Paraskevi; Carey, Steven; Kilias, Stephanos; Christakis, Christos; Kotoulas, Georgios; Magoulas, Antonios; Ivanova, Natalia N; Kyrpides, Nikos C

    2016-04-01

    Hydrothermal vents represent a deep, hot, aphotic biosphere where chemosynthetic primary producers, fuelled by chemicals from Earth's subsurface, form the basis of life. In this study, we examined microbial mats from two distinct volcanic sites within the Hellenic Volcanic Arc (HVA). The HVA is geologically and ecologically unique, with reported emissions of CO2 -saturated fluids at temperatures up to 220°C and a notable absence of macrofauna. Metagenomic data reveals highly complex prokaryotic communities composed of chemolithoautotrophs, some methanotrophs, and to our surprise, heterotrophs capable of anaerobic degradation of aromatic hydrocarbons. Our data suggest that aromatic hydrocarbons may indeed be a significant source of carbon in these sites, and instigate additional research into the nature and origin of these compounds in the HVA. Novel physiology was assigned to several uncultured prokaryotic lineages; most notably, a SAR406 representative is attributed with a role in anaerobic hydrocarbon degradation. This dataset, the largest to date from submarine volcanic ecosystems, constitutes a significant resource of novel genes and pathways with potential biotechnological applications.

  16. Open-Vent Degassing of CO2 from Typical Andesitic Volcanoes in the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Robidoux, P.; Aiuppa, A.; Rotolo, S.; Giudice, G.; Moretti, R.; Conde, V.; Galle, B.; Tamburello, G.

    2014-12-01

    The collection of H2O-CO2-SO2 volcanic gas datasets at open-vent basaltic volcanoes has increased since the introduction of electrochemical/NDIR (Multi-GAS) instruments in the field. An open problem remains to understand the degassing regime of volcanoes of intermediate compositions, which is complicated by wide range of eruption styles. We propose here to initiate the study of the degassing regime of Telica and San Cristobal (Nicaragua), two constantly monitored volcanoes in the Central American Volcanic Arc (CAVA). We calculated the CO2 flux sustained by summit plume degassing at Telica and San Cristobal as the product of the CO2/SO2 ratio of Multi-GAS technique with parallel SO2 flux measurements, made by using scanning UV-DOAS instruments in 2013. At Telica, the CO2 flux was evaluated at 166±76 t/d and at San Cristobal we measured 520±260 t/d. Degassing activity at Telica volcano consists in surface gas discharges dominated by H2O (70-98 mol%; mean of 92 mol%), and by CO2 (1-23 mol%; mean of 6 mol%) and SO2 (0.5-7.4 mol%; mean of 2.9 mol%). San Cristobal gas is dominated by H2O (85-97 mol%; mean of 92 mol%), and by CO2 (2-12 mol%; mean of 6 mol%) and SO2 (3-5 mol%; mean of 3.8 mol%). These values are typical of volcanic arc regions and the volcanoes were in a stage of quiescent degassing without excess of CO2 output relatively to the other major gases. By interpreting our recent gas measurements in tandem with preliminary melt inclusion records of pre-eruptive dissolved volatile abundances, we hope to build a conceptual degassing model taking into account the active degassing regimes during past volcanic eruptions. Finally, we hope to refine the CO2 budget estimates along the CAVA.

  17. The 10 April 2014 Nicaraguan Crustal Earthquake: Evidence of Complex Deformation of the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Suárez, Gerardo; Muñoz, Angélica; Farraz, Isaac A.; Talavera, Emilio; Tenorio, Virginia; Novelo-Casanova, David A.; Sánchez, Antonio

    2016-10-01

    On 10 April 2014, an M w 6.1 earthquake struck central Nicaragua. The main event and the aftershocks were clearly recorded by the Nicaraguan national seismic network and other regional seismic stations. These crustal earthquakes were strongly felt in central Nicaragua but caused relatively little damage. This is in sharp contrast to the destructive effects of the 1972 earthquake in the capital city of Managua. The differences in damage stem from the fact that the 1972 earthquake occurred on a fault beneath the city; in contrast, the 2014 event lies offshore, under Lake Managua. The distribution of aftershocks of the 2014 event shows two clusters of seismic activity. In the northwestern part of Lake Managua, an alignment of aftershocks suggests a northwest to southeast striking fault, parallel to the volcanic arc. The source mechanism agrees with this right-lateral, strike-slip motion on a plane with the same orientation as the aftershock sequence. For an earthquake of this magnitude, seismic scaling relations between fault length and magnitude predict a sub-surface fault length of approximately 16 km. This length is in good agreement with the extent of the fault defined by the aftershock sequence. A second cluster of aftershocks beneath Apoyeque volcano occurred simultaneously, but spatially separated from the first. There is no clear alignment of the epicenters in this cluster. Nevertheless, the decay of the number of earthquakes beneath Apoyeque as a function of time shows the typical behavior of an aftershock sequence and not of a volcanic swarm. The northeast-southwest striking Tiscapa/Ciudad Jardín and Estadio faults that broke during the 1972 and 1931 Managua earthquakes are orthogonal to the fault where the 10 April earthquake occurred. These orthogonal faults in close geographic proximity show that Central Nicaragua is being deformed in a complex tectonic setting. The Nicaraguan forearc sliver, between the trench and the volcanic arc, moves to the

  18. Andesite petrogenesis in a hybrid arc-rift setting: the Western Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Gómez-Tuena, A.; Vázquez-Duarte, A.; Díaz-Bravo, B.; Mori, L.

    2011-12-01

    The western sector of the Mexican subduction zone is characterized by the steep subduction of one of the youngest slabs on the planet (Rivera plate), and by the existence of a continental rift at ~230 km to the north from the trench (the so-called Tepic-Zacoalco rift, TZR), under which the subducted slab is either extremely deep or even absent (>250 km). The volcanic front is located at ~170 km from the trench and contains abundant potassic-alkaline lamprophyres with strong subduction (Ba/Ta= 1600-6000) and garnet signatures (Gd/Yb= 2-8), that have been recently interpreted as influenced by deep K2O-rich slab melts or supercritical fluids (Gómez-Tuena et al., 2011, GCA). In contrast, the most mafic rocks within the TZR are high-Nb, intraplate-like basalts that appear to derive from low extents of melting of a dryer (Ba/Ta= 800-60) and shallower (Gd/Yb= 2-2.5) mantle source. Even though a simple transition from an arc environment to an extensional tectonic regime is apparent when only the most primitive volcanic rocks are taken into account, the scenario becomes more complicated since at least five stratovolcanoes have been erupting typical arc andesites within the TZR over the last million years (San Juan, Sanganguey, Tepetiltic, Ceboruco and Tequila). Surprisingly, true calc-alkaline basalts that could be parental to andesites have not been found, indicating that andesites may have a direct mantle origin. Indeed, mayor and trace element compositions of volcanic rocks from western Mexico arrange in discrete suites with linear trends that are indicative of mixing, but they form sub-parallel arrays that do not converge to a common primitive basaltic melt, and often follow diverging trends in trace element-ratio plots. Melt-crust interactions likely occurred during magma ascent, since the volcanic rocks frequently include xenoliths and disequilibrium textures, but correlations among isotopic compositions and indexes of fractionation are not clearly observed in the

  19. Deep diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Murray, N.; McManus, J.; Haley, B. A.; Palmer, M. R.

    2015-12-01

    We measured dithionite extractable iron and manganese along with a variety of bulk sedimentary solid and dissolved phases to constrain the diagenetic reactions occurring within the sediment package of the Grenada Basin, which resides within the southern Lesser Antilles volcanic arc region. Core material was obtained during IODP Expedition 340, and for this presentation we focus primarily on two sites (U1399 and U1400) located off the island of Martinique. Sediments in this region include tephra-rich volcanic sands, hemipelagic mud sequences, and carbonate-rich sequences, and vary widely in their proportions over short time and distance intervals. Regardless of the main sediment type, organic carbon contents are uniformly low with average values of 0.28 ± 0.08% for U1399 and 0.23 ± 0.15% for U1400. Carbonate contents are more variable ranging between 1 and 40% in both cores and these variations likely reflect variable dilution with volcanogenic sediment. Pore fluids in U1399 exhibit a decrease in Ca, Mg, and Sr with depth, indicative of carbonate precipitation, and a decrease in total dissolved S to values less than 10 mM by 160 meters. A reaction zone is present at ~70 meters in core U1400, with a slight increase in ammonium and alkalinity but a small decrease in total dissolved S. Ca, Mg, and Sr show little to no change with depth. Pore fluid Sr isotope data show a surprisingly narrow range of values suggesting minimal reaction of pore fluid with volcanic material. Reactive Fe ranges from 0.15 to 1.5% in both cores whereas reactive Mn ranges from 0 to 0.3%. For this presentation we assess the relationships among reactive iron, manganese, organic carbon and other constituents with an emphasis on how the presence of volcanic material might influence the cycling of these components during diagenesis.

  20. Modeling Central American Volcanic Front Primitive Lavas with the Arc Basalt Simulator (abs 4.0)

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We have used the Arc Basalt Simulator (ABS), developed by J-I Kimura, to explore the conditions and components of melting beneath the Central American volcanic front. ABS is a comprehensive forward model that incorporates slab dehydration and melting and mantle wedge fluxing and melting using realistic P-T conditions and experimentally determined phase relations and partition coefficients. We have applied ABS version 4.00, which includes melting/dehydration relations in eight distinct subducting layers, to model representative magma types along the Central American volcanic front. These magmas are first projected to primary melt compositions by the addition of olivine until they reach Fo90. Then, using a wide range of input parameters including variations in slab components, extent of peridotite depletion, depth of slab dehydration and wedge fluxing and degree of peridotite melting, successful model fits are generated (based on trace element and isotope matching). The solution space is probed using a Monte Carlo technique to cover the enormous range of parameter values. Nicaragua and Costa Rica represent geochemical and geophysical end members of the volcanic front, differing greatly in volcano volume, slab dip beneath the volcano, isotopic composition and incompatible element enrichment. Using appropriate input compositions for ABS 4.0, we find through millions of simulations that the Cerro Negro primary magma (Nicaragua) requires high degrees of source melting (22-27%) and large amounts of slab-derived water (3-5%). In contrast, the Irazu primary magma (central Costa Rica) is generated from more enriched sources with only a small amount of water (less than 0.5%) and at low degrees of partial melting (less than 5%). Other Central American lavas with intermediate geochemical characteristics are produced from conditions within the Nicaragua-Costa Rica range. By reproducing the lava geochemistry with ABS 4.0, it becomes possible to extract constraints on source input

  1. A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d'Arc Cave (Ardèche, France)?

    PubMed

    Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean-François; Geneste, Jean-Michel

    2016-01-01

    Among the paintings and engravings found in the Chauvet-Pont d'Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d'Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey.

  2. A 36,000-Year-Old Volcanic Eruption Depicted in the Chauvet-Pont d’Arc Cave (Ardèche, France)?

    PubMed Central

    Nomade, Sébastien; Genty, Dominique; Sasco, Romain; Scao, Vincent; Féruglio, Valérie; Baffier, Dominique; Guillou, Hervé; Bourdier, Camille; Valladas, Hélène; Reigner, Edouard; Debard, Evelyne; Pastre, Jean–François; Geneste, Jean-Michel

    2016-01-01

    Among the paintings and engravings found in the Chauvet-Pont d’Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d’Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey. PMID:26745626

  3. Volcanic activity: a review for health professionals.

    PubMed Central

    Newhall, C G; Fruchter, J S

    1986-01-01

    Volcanoes erupt magma (molten rock containing variable amounts of solid crystals, dissolved volatiles, and gas bubbles) along with pulverized pre-existing rock (ripped from the walls of the vent and conduit). The resulting volcanic rocks vary in their physical and chemical characteristics, e.g., degree of fragmentation, sizes and shapes of fragments, minerals present, ratio of crystals to glass, and major and trace elements composition. Variability in the properties of magma, and in the relative roles of magmatic volatiles and groundwater in driving an eruption, determine to a great extent the type of an eruption; variability in the type of an eruption in turn influences the physical characteristics and distribution of the eruption products. The principal volcanic hazards are: ash and larger fragments that rain down from an explosion cloud (airfall tephra and ballistic fragments); flows of hot ash, blocks, and gases down the slopes of a volcano (pyroclastic flows); "mudflows" (debris flows); lava flows; and concentrations of volcanic gases in topographic depressions. Progress in volcanology is bringing improved long- and short-range forecasts of volcanic activity, and thus more options for mitigation of hazards. Collaboration between health professionals and volcanologists helps to mitigate health hazards of volcanic activity. Images FIGURE 1 FIGURE 2 FIGURE 6a-6e FIGURE 6a-6e FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 PMID:3946726

  4. Volcanic activity: a review for health professionals.

    PubMed

    Newhall, C G; Fruchter, J S

    1986-03-01

    Volcanoes erupt magma (molten rock containing variable amounts of solid crystals, dissolved volatiles, and gas bubbles) along with pulverized pre-existing rock (ripped from the walls of the vent and conduit). The resulting volcanic rocks vary in their physical and chemical characteristics, e.g., degree of fragmentation, sizes and shapes of fragments, minerals present, ratio of crystals to glass, and major and trace elements composition. Variability in the properties of magma, and in the relative roles of magmatic volatiles and groundwater in driving an eruption, determine to a great extent the type of an eruption; variability in the type of an eruption in turn influences the physical characteristics and distribution of the eruption products. The principal volcanic hazards are: ash and larger fragments that rain down from an explosion cloud (airfall tephra and ballistic fragments); flows of hot ash, blocks, and gases down the slopes of a volcano (pyroclastic flows); "mudflows" (debris flows); lava flows; and concentrations of volcanic gases in topographic depressions. Progress in volcanology is bringing improved long- and short-range forecasts of volcanic activity, and thus more options for mitigation of hazards. Collaboration between health professionals and volcanologists helps to mitigate health hazards of volcanic activity.

  5. Miocene to Recent geological evolution of the Lazufre segment in the Andean volcanic arc

    NASA Astrophysics Data System (ADS)

    Naranjo, J. A.; Villa, V.; Ramírez, C.; Pérez de Arce, C.

    2014-12-01

    The volcano-tectonic setting in which the InSAR-detected Lazufre deformation is developing is particularly relevant in the evolution of this Andean volcanic arc segment (25-26°S). Through regional mapping techniques, a comprehensive field control in addition to geochronological sampling, various volcanic units comprising stratovolcanoes, volcanic complexes, ignimbrites and caldera structures are distinguished. The Lazufre intumescence is located above the overlying block of the NE trending Middle Miocene, Pedernales-Arizaro overthrust. This area comprises an Upper Miocene (8-4 Ma) basal unit of andesitic-dacitic volcanoes and lava fields, upon which nine volcanic complexes of similar composition, including Caletones de Cori Ignimbrite and Escorial Volcano, Lastarria, Cordón del Azufre and Bayo volcanic complexes, were emplaced in several pulses between 3.5 Ma and Holocene times. Coalescing Lazufre structure, immediately to the SE, we have discovered the Miocene (9.8 Ma) Los Colorados caldera. This caldera is 30 km in diameter and sourced the homonymous dacitic ignimbrite of about 500 km3. The caldera scarp was formed in Paleozoic rocks, Miocene dacitic-rhyolitic ignimbrites and ~16 and 10 Ma volcanoes. A 6.9-6.8 Ma andesitic-dacitic volcano ridge formed by Abra Grande, Río Grande and Aguas Calientes stratovolcanoes, from NE to SW, is nested on the caldera floor. Lavas of early stages of Cordón del Azufre and Bayo complexes were shed into the NW part of the caldera. The coalescing structure formed by the Lazufre intumescence and Los Colorados caldera is conjugate at about 30° to the Pedernales-Arizaro overthrust, and has a NW-SE orientation, parallel to the Archibarca lineament. A SE to NW migration of volcanism is observed along this structure at least since the Middle Miocene. We proposed that, since Miocene, tectonic spaces with no surficial fault displacements and conjugated to the main compressive structures within the upper crust, have been created as a

  6. Depth to Curie temperature or magnetic sources bottom in the Lesser Antilles Arc volcanic area

    NASA Astrophysics Data System (ADS)

    Gailler, Lydie-Sarah; Martelet, Guillaume; Thinon, Isabelle; Münch, Philippe; Arcay, Diane

    2015-04-01

    In the continuation of the innovative study carried out at the scale of La Réunion Island to generalize Curie Point Depth (CPD) determinations at the scale of oceanic volcanic islands, we present here a similar work at the scale of the Lesser Antilles Arc. Assuming that magnetic anomalies are concentrated within the oceanic crust and using the growing assumption of a magnetized upper mantle, the Curie depth should become deeper as the oceanic lithosphere becomes older (i.e. thicker). We use the magnetic anomaly map computed by Gailler et al. (2013), completed and extended with the global Earth Magnetic Anomaly Grid (EMAG2) (Maus et al., 2007). The calculated magnetic sources bottom lies at depths between 18 and 32 km and exhibits a complex topography, presumably caused by the combination of various magmatic and tectonic crustal structures in this complex subduction context. The correlations between our depth to magnetic sources bottom and the large scale bathymetric and geophysical studies provide an interesting overview of the Lesser Antilles Arc structuring. The Inner Arc is mainly associated with a deepening of the depth to magnetic sources bottom. On the contrary, a huge doming appears along the central Lesser Antilles Arc, consistent with the seismic imaging (Kopp et al., 2011). This uprise of our calculated magnetic surface extents southeastern to the Guadeloupe Island in the direction of the Tiburon Ridge following the abnormal transverse component of the subduction in the N130°E direction defined by Gailler et al. (2013). A strong lateral narrowing of this doming is evidenced southern of Dominique Island where the two arcs converge. In this central area, the averaged depth of the magnetic sources bottom is also larger than expected in the case of classical oceanic crust. This is in agreement with previous interpretation of an original oceanic crust thickened by deep magmatic processes and underplating prior to the evolution of the Lesser Antilles Arc

  7. Tracing the evolution of island-arc volcanism in the Tanna-Futuna transect (New Hebrides)

    NASA Astrophysics Data System (ADS)

    Lima, S. M.; Haase, K. M.; Beier, C.

    2014-12-01

    The New Hebrides island arc, located in the southwestern Pacific, is associated with the fast subduction of the Australian Plate under the North Fiji Basin. It extends over 1500 km including the entire Vanuatu archipelago. Several studies dealing with the geochemistry of the most important islands interpret the chemical variability to originate from the heterogeneities in the sub-arc mantle wedge1 and variable addition of the subduction component along the arc2. In order to trace the differences between the source(s) of New Hebrides volcanic arc and back-arc magmatism, five submarine cones (4 of them aligned NE-SW), located in the Futuna Through, were sampled. The lavas range from basalt to andesite with fractionation of olivine being the main magma evolution mechanism until MgO ≈ 6 wt.%. The most primitive lavas have similar fractionation-corrected TiO2 (0.90-1.18 wt.%) and Na2O (2.89-3.41 wt.%) contents suggesting comparable degrees of partial melting. The comparison with published data from adjacent islands shows a more important contribution of the slab closer to the trench (Tanna) where the erupted basalts, basaltic trachyandesites and trachyandesites have considerably higher U/Nb and Ba/Nb ratios. Yet, these lavas display significant negative Sr anomalies (PM-normalized). This could provide evidence of input of continental derived sediments or could reflect the role of plagioclase in the source / evolution of these magmas. The first hypothesis is not supported by published data from the Vanuatu trench3 and the second is not supported by the decoupled behavior of Sr and Eu in normalized-diagrams. On the other hand, island crust samples collected along the northern flank of Futuna Island display strong positive anomalies of Sr and, although more modest, the submarine cones show a similar behavior. Based on source chemical tracers, an increasing depletion of the source is observed from east to west, consistent with progressive mantle flow towards the arc front

  8. Deep long-period earthquakes west of the volcanic arc in Oregon: evidence of serpentine dehydration in the fore-arc mantle wedge

    USGS Publications Warehouse

    Vidale, John E.; Schmidt, David A.; Malone, Stephen D.; Hotovec-Ellis, Alicia J.; Moran, Seth C.; Creager, Kenneth C.; Houston, Heidi

    2014-01-01

    Here we report on deep long-period earthquakes (DLPs) newly observed in four places in western Oregon. The DLPs are noteworthy for their location within the subduction fore arc: 40–80 km west of the volcanic arc, well above the slab, and near the Moho. These “offset DLPs” occur near the top of the inferred stagnant mantle wedge, which is likely to be serpentinized and cold. The lack of fore-arc DLPs elsewhere along the arc suggests that localized heating may be dehydrating the serpentinized mantle wedge at these latitudes and causing DLPs by dehydration embrittlement. Higher heat flow in this region could be introduced by anomalously hot mantle, associated with the western migration of volcanism across the High Lava Plains of eastern Oregon, entrained in the corner flow proximal to the mantle wedge. Alternatively, fluids rising from the subducting slab through the mantle wedge may be the source of offset DLPs. As far as we know, these are among the first DLPs to be observed in the fore arc of a subduction-zone system.

  9. Precursory deformation and depths of magma storage revealed by regional InSAR time series surveys: example of the Indonesian and Mexican volcanic arcs

    NASA Astrophysics Data System (ADS)

    Chaussard, E.; Amelung, F.; Aoki, Y.

    2012-12-01

    Despite the threat posed to millions of people living in the vicinity of volcanoes, only a fraction of the worldwide ~800 potentially active arc volcanoes have geodetic monitoring. Indonesian and Mexican volcanoes are sparsely monitored with ground-based methods but especially dangerous, emphasizing the need for remote sensing monitoring. In this study we take advantage of over 1200 ALOS InSAR images to survey the entire west Sunda and Mexican volcanic arcs, covering a total of 500 000 km2. We use 2 years of data to monitor the background activity of the Indonesian arc, and 4 years of data at four volcanic edifices (Sinabung, Kerinci, Merapi, and Agung), as well as 4 years of data to survey the Mexican arc. We derive time-dependent ground deformation data using the Small Baseline technique with DEM error correction. We detect seven volcanoes with significant deformation in the west-Sunda arc: six inflating volcanoes (Sinabung, Kerinci, Slamet, Lawu, Lamongan, and Agung) and one deflating volcano (Anak Krakatau). Three of the six inflating centers erupted during or after the observation period. We detect inflation prior to Sinabung's first Holocene eruption in September 2010, followed by a small deflation of the summit area. A similar signal is observed at Kerinci before and after its April 2009 eruption. We also detect uplift prior to Slamet's eruption in April 2009. Agung, in Bali, whose last eruption was in 1964, has been inflating steadily between mid 2007 and early 2009, followed by a period with little deformation until mid-2011. Inflation not followed by eruption is also observed at Lamongan and Lawu, both historically active centers. The close relation between periods of activity and observed deformation suggests that edifice inflation is of magmatic origin and represents the pressurization of reservoirs caused by ascent of new magma. We model the observed deformation and show that the seven deforming Indonesian volcanoes have shallow magma reservoirs at ~1

  10. Oligocene and Miocene arc volcanism in northeastern California: evidence for post-Eocene segmentation of the subducting Farallon plate

    USGS Publications Warehouse

    Colgan, J.P.; Egger, A.E.; John, D.A.; Cousens, B.; Fleck, R.J.; Henry, C.D.

    2011-01-01

    The Warner Range in northeastern California exposes a section of Tertiary rocks over 3 km thick, offering a unique opportunity to study the long-term history of Cascade arc volcanism in an area otherwise covered by younger volcanic rocks. The oldest locally sourced volcanic rocks in the Warner Range are Oligocene (28–24 Ma) and include a sequence of basalt and basaltic andesite lava flows overlain by hornblende and pyroxene andesite pyroclastic flows and minor lava flows. Both sequences vary in thickness (0–2 km) along strike and are inferred to be the erosional remnants of one or more large, partly overlapping composite volcanoes. No volcanic rocks were erupted in the Warner Range between ca. 24 and 16 Ma, although minor distally sourced silicic tuffs were deposited during this time. Arc volcanism resumed ca. 16 Ma with eruption of basalt and basaltic andesite lavas sourced from eruptive centers 5–10 km south of the relict Oligocene centers. Post–16 Ma arc volcanism continued until ca. 8 Ma, forming numerous eroded but well-preserved shield volcanoes to the south of the Warner Range. Oligocene to Late Miocene volcanic rocks in and around the Warner Range are calc-alkaline basalts to andesites (48%–61% SiO2) that display negative Ti, Nb, and Ta anomalies in trace element spider diagrams, consistent with an arc setting. Middle Miocene lavas in the Warner Range are distinctly different in age, composition, and eruptive style from the nearby Steens Basalt, with which they were previously correlated. Middle to Late Miocene shield volcanoes south of the Warner Range consist of homogeneous basaltic andesites (53%–57% SiO2) that are compositionally similar to Oligocene rocks in the Warner Range. They are distinctly different from younger (Late Miocene to Pliocene) high-Al, low-K olivine tholeiites, which are more mafic (46%–49% SiO2), did not build large edifices, and are thought to be related to backarc extension. The Warner Range is ∼100 km east of the

  11. High-resolution magnetics reveal the deep structure of a volcanic-arc-related basalt-hosted hydrothermal site (Palinuro, Tyrrhenian Sea)

    NASA Astrophysics Data System (ADS)

    Szitkar, Florent; Petersen, Sven; Caratori Tontini, Fabio; Cocchi, Luca

    2015-06-01

    High-resolution magnetic surveys have been acquired over the partially sedimented Palinuro massive sulfide deposits in the Aeolian volcanic arc, Tyrrhenian Sea. Surveys flown close to the seafloor using an autonomous underwater vehicle (AUV) show that the volcanic-arc-related basalt-hosted hydrothermal site is associated with zones of lower magnetization. This observation reflects the alteration of basalt affected by hydrothermal circulation and/or the progressive accumulation of a nonmagnetic deposit made of hydrothermal and volcaniclastic material and/or a thermal demagnetization of titanomagnetite due to the upwelling of hot fluids. To discriminate among these inferences, estimate the shape of the nonmagnetic deposit and the characteristics of the underlying altered area—the stockwork—we use high-resolution vector magnetic data acquired by the AUV Abyss (GEOMAR) above a crater-shaped depression hosting a weakly active hydrothermal site. Our study unveils a relatively small nonmagnetic deposit accumulated at the bottom of the depression and locked between the surrounding volcanic cones. Thermal demagnetization is unlikely but the stockwork extends beyond the limits of the nonmagnetic deposit, forming lobe-shaped zones believed to be a consequence of older volcanic episodes having contributed in generating the cones.

  12. Different sources involved in generation of continental arc volcanism: The Carboniferous-Permian volcanic rocks in the northern margin of the North China block

    NASA Astrophysics Data System (ADS)

    Zhang, Shuan-Hong; Zhao, Yue; Liu, Jian-Min; Hu, Zhao-Chu

    2016-01-01

    New zircon U-Pb dating results on the Carboniferous-Permian volcanic rocks in the northern margin of the North China block (NCB) indicate their eruption during the Early Carboniferous to Late Permian from 347 ± 3 Ma to 258 ± 1 Ma and a slight decrease of the upper limits of the volcanic sequences from west to east. They have a main rock association of basalt, basaltic andesite, andesite, dacite, rhyolite, tuff, and tufaceous sandstone. Most of them have calc-alkaline compositions and exhibit variable SiO2 contents from 48.2 wt.% to 77.1 wt.%. There is no significant gap between the mafic and felsic volcanic rocks in major and trace element classification diagrams, indicating that they are not bimodal in composition. The Carboniferous-Permian volcanic rocks exhibit subduction-related geochemical features such as negative Nb and Ta anomalies of mafic to intermediate rocks on primitive mantle-normalized diagrams, indicating they were formed in an Andean-type continental arc during southward subduction of the Paleo-Asian oceanic plate beneath the northern NCB. However, their wide range of whole-rock Sr-Nd and zircon Hf isotopic compositions indicate that their source areas are very complex and different sources were involved in generation of these volcanic rocks. Geochemical and Sr-Nd-Hf isotopic results show that the basalt and some andesite were produced by fractional crystallization of mafic magma derived from partial melting of mantle wedge and subducted oceanic crust; however, most of the intermediate to felsic volcanic rocks were derived from partial melting of lower continental crust. There is an increasing input of crustal materials from the Carboniferous to Permian as indicated by increasing volumes of felsic volcanic rocks in the volcanic sequences. The results show that origin of the continental arc volcanism is very complex and both materials from the subducted oceanic crust and sediments, mantle wedge and arc continental crust could be involved in their

  13. A new radiative forcing data set comprising the major volcanic eruptions from the Central American Volcanic Arc for paleo climate studies

    NASA Astrophysics Data System (ADS)

    Metzner, D.; Krüger, K.; Timmreck, C.; Kutterolf, S.; Freundt, A.

    2009-04-01

    Of all the natural causes of climate change, major volcanic eruptions are most important as they have a significant impact on Earth's global climate system, especially on the stratosphere and troposphere, the atmospheric circulation and chemical composition. The direct injection of gases, aerosols and volcanic ash into the stratosphere has a strong and long lasting radiative influence, which leads to a global cooling of surface temperatures for several years, probably decades. In this study we will investigate the climate feedbacks of large Plinian eruptions from volcanoes at the Central American Arc within the last 200ka with the help of state of the art climate models. To evaluate the radiative forcing of the climate system, we need reliable estimates of the paleo volcanic stratospheric aerosol loading. Here we use a newly derived volcanic data set for Central America based on a) new eruptive mass estimations that are based on compositional land-sea correlations of widespread tephra layers and b) incoporation of measured degassed volatile fractions (S, Cl, F, Br, I) derived from those tephras by the "petrological method" into the mass calculations (Kutterolf et al. 2008a,b). This facilitates the consideration of large eruptions of the past for climate modelling. Using information about strength and height of the volcanic sulphur injection we create a new data set of aerosol optical depth comprising the major volcanic eruptions of Central American Volcanic Arc over the last 200ka. The poster will introduce the underlying steps to derive an aerosol optical depth set from the petrologic derived sulfate aerosol loading in more detail and discuss possible uncertainties. As soon as possible climate sensitivity studies will follow, in which different SO2 scenarios will be applied, for low, medium and large size SO2 eruptions. To assess the climate impact of past CAVA eruptions on a paleo time scale an earth system climate model of intermediate complexity will be

  14. Tellurium in active volcanic environments: Preliminary results

    NASA Astrophysics Data System (ADS)

    Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco

    2014-05-01

    Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

  15. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    USGS Publications Warehouse

    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

  16. Age and chemical constraints of Volcán Tunupa: Implications for behind arc volcanism in the Bolivian central Andes

    NASA Astrophysics Data System (ADS)

    salisbury, M. J.; Kent, A. J.; Jiménez, N.; Jicha, B. R.

    2011-12-01

    New 40Ar/39Ar age determinations of groundmass separates and whole-rock geochemical data constrain the Pleistocene eruptive history of Volcán Tunupa, a glacially-dissected composite volcano (~50 km3) situated between the Salar de Uyuni and Salar de Coipasa. Tunupa erupted ~110 km east of the arc front of the Western Cordillera of the central Andes near the eastern edge of the Intersalar Volcanic Field, an arc-perpendicular expression of volcanism that extends to the central Altiplano basin of Bolivia. 40Ar/39Ar age determinations indicate that the edifice was constructed between ~1.40 and 1.55 Ma, whereas nearby Cerro Huayrana lavas erupted ~ 11 Ma. Published ages from the Western Cordillera that are concordant with both Tunupa and Huayrana lavas demonstrate that the central Altiplano lavas are a long-lived expression of behind arc volcanism. The Tunupa lavas define a calc-alkaline trend from trachyandesite to trachydacite (wt.% SiO2 = 60.6 - 63.6; wt.% K2O + Na2O = 7.5 - 8.3) and are overlain by younger, more silicic (wt.% SiO2 = 66) trachydacitic domes. Major element compositions of Tunupa and Huayrana are enriched in FeO and TiO2 compared to the arc front. These lavas are also enriched in high field strength elements, notably Nb and Ta, and are characterized by considerably lower Ba/Nb and La/Ta ratios than arc front lavas in northern Chile. The geochemical and spatiotemporal patterns of the behind arc Tunupa and Huayrana lavas suggest different petrogenetic histories from typical central Andean arc lavas.

  17. Nitrogen Isotopes in Olivine Separates from Volcanic Arcs, Hot Spots and Continental Mantle Xenoliths

    NASA Astrophysics Data System (ADS)

    Fischer, T. P.; Takahata, N.; Sano, Y.; Hilton, D. R.

    2004-12-01

    We report the first nitrogen isotopic data of olivine separates from volcanic arcs (Cerro Negro, Nicaragua; Izalco, El Salvador; Turrialba, Costa Rica; Ichinomegata, Japan). In addition, we report nitrogen isotopic data of olivine separates from ocean islands (Hawaii, Reunion, Iceland) and continental mantle xenoliths (San Carlos, Arizona). Samples were processed by crushing and analyzed using a modified noble gas mass spectrometer (VG3400). N concentrations range from 0.6 to 22 micro ccSTP/g olivine. The 15N/14N ratios (expressed in the δ 15N notation where δ 15N sample = {[(15N/14N)sample/(15N/14N)Air]-1} X 1000) of olivine separates are distinctly different from air (0.0‰ ) and range from lower than mean MORB (- 5 ‰ ) to values characteristic of (subducted) oceanic sediments (+ 7 ‰ ). Positive δ 15N values are found in olivines from volcanic arcs: Cerro Negro 1992 ash (+ 6.2 ± 1.6‰ ), Izalco lava flow (+ 5.1 ± 0.7‰ ), Ichinomengata spinel lherzolite (+ 1.1 ± 0.5 ‰ ) with the exception of Turrialba lava (- 1.7 ± 2.5‰ ). Olivines from hot spots have both positive and negative δ 15N signatures: Iceland, Theistareykir - northern rift zone (- 8± 1.6 ‰ ), Hawaii, dunite from 1801 Kaupulehu flow of Hualuai volcano (+ 3.1 ± 0.3 ‰ ) and Reunion dunite (+ 0.2 ± 0.5‰ ). The San Carlos mantle xenolith has a value of - 1.5 ± 2.5‰ . 40Ar/36Ar ratios of the samples as determined in this study or reported in the literature are significantly higher than air (295.5) in olivines from Ichinomegata, San Carlos, Iceland, Reunion and Hawaii. The olivines from Cerro Negro have a 40Ar/36Ar ratio of 306, close to that of air. The 3He/4He ratios of the samples are higher than the MORB value of 8.0 RA (RA is the 3He/4He of air), the exception being Cerro Negro (6.1 RA). Hawaii, Reunion and Iceland have 3He/4He of 10.3, 12.9 and 12.3 RA, respectively. δ 15N signatures of fumarole gas samples collected at Cerro Negro (+ 4.9 ±0.1 ‰ ), Turrialba (- 1.0 ±0

  18. Sr, Nd, Pb and Os Isotopic Compositions of Lavas From the Mount Baker Volcanic Field, Cascade Arc

    NASA Astrophysics Data System (ADS)

    Mullen, E. K.; McCallum, I.; Brandon, A. D.

    2008-12-01

    We present the results of a trace element and Sr, Nd, Pb and Os isotopic study of the Mt. Baker volcanic field (MBVF), part of the northern segment of the Cascade magmatic arc known as the Garibaldi Belt. To date, only 4 Sr isotopic ratios (all from the Sulphur Creek flow) have been published. The Mount Baker volcanic field extends to 3.72 Ma and a case can be made for continuous magmatic activity in this region extending from 34 Ma to present. Our goal is to use isotope ratios to characterize the mantle source regions that underlie the Garibaldi Belt, to document the chemical inputs of slab fluid/melt, sediment, and lower crust, and to assess temporal and spatial variations in these factors. We measured 29 Sr and Nd isotopic ratios, 8 Pb isotopic ratios, and 9 Os isotopic ratios, representing the full age range and compositional diversity (calc- alkaline basalt through rhyolite) of the MBVF, including all known MBVF basalts. A 22.86-Ma gabbronorite from the adjacent Chilliwack batholith was analyzed as an analog for the modern mafic lower crust. All Mt. Baker lavas are calc-alkaline with the arc-characteristic signatures of HFSE depletion and LILE enrichment. MBVF 87Sr/86Sr values (0.703932 to 0.703057) and ɛNd (+4.71 to +7.79) are well correlated and lie within the mantle array. Mt. Baker Sr and Nd data are indistinguishable from other Garibaldi belt lavas (Green & Harry 1999, Green & Sinha 2005), and also overlap data from the neighboring Chilliwack batholith (Tepper 1996; Tepper et al. 1993). In contrast, central and southern Cascade arc lavas with similar Sr ratios have corresponding ɛNd values that are lower by ~2 epsilon units. The Garibaldi Belt and Chilliwack magmas are tapping a mantle source distinct from that of the rest of the Cascade arc. 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of MBVF basalts plot close to the NHRL, in a linear trend between Juan de Fuca MORB and Pacific sediment, indicating a sediment contribution to the MBVF magmas. With

  19. Late-Pleistocene to precolumbian behind-the-arc mafic volcanism in the eastern Mexican Volcanic Belt; implications for future hazards

    NASA Astrophysics Data System (ADS)

    Siebert, Lee; Carrasco-Núñez, Gerardo

    2002-06-01

    An area of widespread alkaline-to-subalkaline volcanism lies at the northern end of the Cofre de Perote-Citlaltépetl (Pico de Orizaba) volcanic chain in the eastern Mexican Volcanic Belt (MVB). Two principal areas were active. About a dozen latest-Pleistocene to precolumbian vents form the 11-km-wide, E-W-trending Cofre de Perote vent cluster (CPVC) at 2300-2800 m elevation on the flank of the largely Pleistocene Cofre de Perote shield volcano and produced an extensive lava field that covers >100 km 2. More widely dispersed vents form the Naolinco volcanic field (NVF) in the Sierra de Chiconquiaco north of the city of Jalapa (Xalapa). Three generations of flows are delineated by cone and lava-flow morphology, degree of vegetation and cultivation, and radiocarbon dating. The flows lie in the behind-the-arc portion of the northeastern part of the MVB and show major- and trace-element chemical patterns transitional between intraplate and subduction zone environments. Flows of the oldest group originated from La Joya cinder cone (radiocarbon ages ˜42 000 yr BP) at the eastern end of the CPVC. This cone fed an olivine-basaltic flow field of ˜20 km 2 that extends about 14 km southeast to underlie the heavily populated northern outskirts of Jalapa, the capital city of the state of Veracruz. The Central Cone Group (CCG), of intermediate age, consists of four morphologically youthful cinder cones and associated vents that were the source of a lava field>27 km 2 of late-Pleistocene or Holocene age. The youngest group includes the westernmost flow, from Cerro Colorado, and a lava flow ˜2980 BP from the Rincón de Chapultepec scoria cone of the NVF. The latest eruption, from the compound El Volcancillo scoria cone, occurred about 870 radiocarbon years ago and produced two chemically and rheologically diverse lava flows that are among the youngest precolumbian flows in México and resemble paired aa-pahoehoe flows from Mauna Loa volcano. The El Volcancillo eruption

  20. Impact of Volcanic Activity on AMC Channel Operations

    DTIC Science & Technology

    2014-06-13

    IMPACT OF VOLCANIC ACTIVITY ON AMC CHANNEL OPERATIONS GRADUATE RESEARCH PROJECT Matthew D... VOLCANIC ACTIVITY ON AMC CHANNEL OPERATIONS GRADUATE RESEARCH PROJECT Presented to the Faculty Department of Operational Sciences...AFIT-ENS-GRP-14-J-11 IMPACT OF VOLCANIC ACTIVITY ON AMC CHANNEL OPERATIONS Matthew D. Meshanko, BS, MA Major, USAF

  1. Late Triassic island-arc--back-arc basin development along the Bangong-Nujiang suture zone (central Tibet): Geological, geochemical and chronological evidence from volcanic rocks

    NASA Astrophysics Data System (ADS)

    Chen, S. S.; Shi, R.; Zou, H.

    2015-12-01

    A major debate related to the evolution of the Tibetan Plateau is centered on whether or not an island arc-back-arc basin system occurred along the Bangong-Nujiang suture zone, central Tibet. Here we present new zircon U-Pb geochronology, rare earth elements (REE) and bulk-rock geochemistry of these magmatic rocks in the Amdo area, the middle Bangong-Nujiang suture zone, central Tibet, to identify significant and new records of Mesozoic tectonomagmatic processes. Zircon U-Pb dating using LA-ICP-MS techniques yields a concordant age with a weighted mean 206Pb/238U age of 228.6 ± 1.6 Ma (n = 7, MSWD = 1.19) for the Quehala basalts, and a mean ages of 220.0 ± 2.1 (n = 8, MSWD = 1.5) for the Amdo pillow lavas. On the normalized REE patterns of zircon, significant Ce enrichment indicates the magma sources of these magmatic rocks have been subjected to modification of slab-derived fluid. Geochemical features suggest that the Quehala basalts (ca. 228 Ma), displaying an island arc tholeiites (IAT) affinity, resulted from partial melting of an enriched mantle wedge in the subduction zone, whereas the Amdo pillow lavas (ca. 220 Ma) characterized by both arc-like and N-MORB-like geochemical characteristics occurred as associated back-arc basin basalts (BABB) at the spreading center of back-arc basin after the formation of island arc tholeiites. In conclusion, the volcanic rocks in the Amdo area have documented the magmatic processes from early-stage subduction to development of associated back-arc basin, confirming the occurrence of intra-oceanic subduction within the Bangong-Nujiang Tethys during the late Triassic. Furthermore, the spatial relationships among the Quehala formation, Tumengela formation and Amdo pillow lavas indicate northward subduction of the Bangong-Nujiang Tethyan Ocean during the Late Triassic to middle Jurassic.

  2. Late Triassic island-arc-back-arc basin development along the Bangong-Nujiang suture zone (central Tibet): Geological, geochemical and chronological evidence from volcanic rocks

    NASA Astrophysics Data System (ADS)

    Chen, Sheng-Sheng; Shi, Ren-Deng; Zou, Hai-Bo; Huang, Qi-Shuai; Liu, De-Liang; Gong, Xiao-Han; Yi, Guo-Ding; Wu, Kang

    2015-08-01

    A major debate related to the evolution of the Tibetan Plateau is centered on whether or not an island arc-back-arc basin system occurred along the Bangong-Nujiang suture zone, central Tibet. Here we present new zircon U-Pb geochronology, rare earth elements (REEs) and bulk-rock geochemistry of these magmatic rocks in the Amdo area, the middle Bangong-Nujiang suture zone, central Tibet, to identify significant and new records of Mesozoic tectonomagmatic processes. Zircon U-Pb dating using LA-ICP-MS techniques yields a concordant age with a weighted mean 206Pb/238U age of 228.6 ± 1.6 Ma (n = 7, MSWD = 1.19) for the Quehala basalts, and a mean age of 220.0 ± 2.1 (n = 8, MSWD = 1.5) for the Amdo pillow lavas. On the normalized REE patterns of zircon, significant Ce enrichment indicates that the magma sources of these magmatic rocks have been subjected to modification of slab-derived fluid. Geochemical features suggest that the Quehala basalts (ca. 228 Ma), displaying an island arc tholeiites (IATs) affinity, resulted from partial melting of an relatively enriched mantle wedge in the subduction zone, whereas the Amdo pillow lavas (ca. 220 Ma) characterized by both arc-like and N-MORB-like geochemical characteristics occurred as associated back-arc basin basalts (BABBs) at the spreading center of back-arc basin after the formation of island arc tholeiites. In conclusion, the volcanic rocks in the Amdo area have documented the magmatic processes from early-stage subduction to development of associated back-arc basin, confirming the occurrence of intra-oceanic subduction within the Bangong-Nujiang Tethys during the late Triassic. Furthermore, the spatial relationships among the Quehala formation, Tumengela formation and Amdo pillow lavas indicate likely northward subduction of the Bangong-Nujiang Tethyan Ocean during the Late Triassic to middle Jurassic.

  3. Probabilities of future VEI ≥ 2 eruptions at the Central American Volcanic Arc: a statistical perspective based on the past centuries' eruption record

    NASA Astrophysics Data System (ADS)

    Dzierma, Yvonne; Wehrmann, Heidi

    2014-10-01

    A probabilistic eruption forecast is provided for seven historically active volcanoes along the Central American Volcanic Arc (CAVA), as a pivotal empirical contribution to multi-disciplinary volcanic hazards assessment. The eruption probabilities are determined with a Kaplan-Meier estimator of survival functions, and parametric time series models are applied to describe the historical eruption records. Aside from the volcanoes that are currently in a state of eruptive activity (Santa María, Fuego, and Arenal), the highest probabilities for eruptions of VEI ≥ 2 occur at Concepción and Cerro Negro in Nicaragua, which are likely to erupt to 70-85 % within the next 10 years. Poás and Irazú in Costa Rica show a medium to high eruption probability, followed by San Miguel (El Salvador), Rincón de la Vieja (Costa Rica), and Izalco (El Salvador; 24 % within the next 10 years).

  4. Insights from Pb and O isotopes into along-arc variations in subduction inputs and crustal assimilation for volcanic rocks in Java, Sunda arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Handley, Heather K.; Blichert-Toft, Janne; Gertisser, Ralf; Macpherson, Colin G.; Turner, Simon P.; Zaennudin, Akhmad; Abdurrachman, Mirzam

    2014-08-01

    New Pb isotope data are presented for Gede Volcanic Complex, Salak and Galunggung volcanoes in West Java, Merbabu and Merapi volcanoes in Central Java and Ijen Volcanic Complex in East Java of the Sunda arc, Indonesia. New O isotope data for Merbabu and new geochemical and radiogenic isotope data (Sr-Nd-Hf-Pb) for three West Javanese, upper crustal, Tertiary sedimentary rocks are also presented. The data are combined with published geochemical and isotopic data to constrain the relative importance of crustal assimilation and subducted input of crustal material in petrogenesis in Java. Also discussed are the significance of limestone assimilation in controlling the geochemical and isotopic characteristics of erupted Javanese rocks and the geochemical impact upon central and eastern Javanese arc rocks due to the subduction of Roo Rise between 105 and 109°E. The negative correlation between Pb isotopes and SiO2, combined with mantle-like δ18O values in Gede Volcanic Complex rocks, West Java, are most likely explained by assimilation of more isotopically-primitive arc rocks and/or ophiolitic crust known to outcrop in West Java. The negative Pb isotope-SiO2 trend cannot be explained by assimilation of the known compositions of the upper crustal rocks. A peak in δ18O whole-rock and mineral values in Central Javanese volcanic rocks (Merbabu and Merapi) combined with along-arc trends in Sr isotope ratios suggest that a different or additional crustal assimilant exerts control on the isotopic composition of Central Javanese volcanic rocks. This assimilant (likely carbonate material) is characterised by high δ18O and high Sr isotope ratio but is not particularly elevated in its Pb isotopic ratio. Once the effects of crustal assimilation are accounted for, strong East to West Java regional variations in Ba concentration, Ba/Hf ratio and Pb isotopic composition are evident. These differences are attributed to heterogeneity in the subducted source input component along the

  5. Shallow marine event sedimentation in a volcanic arc-related setting: The Ordovician Suri Formation, Famatina range, northwest Argentina

    USGS Publications Warehouse

    Mangano, M.G.; Buatois, L.A.

    1996-01-01

    The Loma del Kilome??tro Member of the Lower Ordovician Suri Formation records arc-related shelf sedimentation in the Famatina Basin of northwest Argentina. Nine facies, grouped into three facies assemblages, are recognized. Facies assemblage 1 [massive and parallel-laminated mudstones (facies A) locally punctuated by normally graded or parallel-laminated silty sandstones (facies B] records deposition from suspension fall-out and episodic storm-induced turbidity currents in an outer shelf setting. Facies assemblage 2 [massive and parallel-laminated mudstones (facies A) interbedded with rippled-top very fine-grained sandstones (facies D)] is interpreted as the product of background sedimentation alternating with distal storm events in a middle shelf environment. Facies assemblage 3 [normally graded coarse to fine-grained sandstones (facies C); parallel-laminated to low angle cross-stratified sandstones (facies E); hummocky cross-stratified sandstones and siltstones (facies F); interstratified fine-grained sandstones and mudstones (facies G); massive muddy siltstones and sandstones (facies H); tuffaceous sandstones (facies I); and interbedded thin units of massive and parallel-laminated mudstones (facies A)] is thought to represent volcaniclastic mass flow and storm deposition coupled with subordinated suspension fall-out in an inner-shelf to lower-shoreface setting. The Loma del Kilo??metro Member records regressive-transgressive sedimentation in a storm- and mass flow-dominated high-gradient shelf. Volcano-tectonic activity was the important control on shelf morphology, while relative sea-level change influenced sedimentation. The lower part of the succession is attributed to mud blanketing during high stand and volcanic quiescence. Progradation of the inner shelf to lower shoreface facies assemblage in the middle part represents an abrupt basinward shoreline migration. An erosive-based, non-volcaniclastic, turbidite unit at the base of this package suggests a sea

  6. Adakitic volcanism in the eastern Aleutian arc: Petrology and geochemistry of Hayes volcano, Cook Inlet, Alaska

    NASA Astrophysics Data System (ADS)

    McHugh, K.; Hart, W. K.; Coombs, M. L.

    2012-12-01

    are the result of partial melting of this slab where thermal erosion and weakening of the crust occurs along the Pacific plate-Yakutat terrane transition. Additionally, flat slab subduction may be responsible for producing adakitic magmas by equilibration of the hydrous slab with ambient mantle temperatures. In contrast, it is possible that the adakitic signature at Hayes is from underplated mafic lower crust that melted as the result of pooling mantle melt at depth. Two volcanoes within the WVF, Mt. Drum and Mt. Churchill, are adakitic with an abundance of biotite and amphibole similar to Hayes volcano and have been suggested to have slab melt origins. Mt. Drum lavas have less radiogenic 87Sr/86Sr but overlapping 206Pb/204Pb signatures while Mt. Churchill, which approximately overlies the eastern edge of the Yakutat terrane, has similar 87Sr/86Sr compositions, but more radiogenic 206Pb/204Pb than Hayes. Mt. Spurr, the nearest CIV to Hayes volcano (90 km south), does not share its adakitic signature but exhibits overlapping, more heterogeneous isotopic compositions. Thus, understanding the petrogenetic history of Hayes volcano is essential not only to explain the development of an adakitic volcanic system but how this relates to regional, arc-wide volcanism.

  7. Paleoproterozoic arc basalt-boninite-high magnesian andesite-Nb enriched basalt association from the Malangtoli volcanic suite, Singhbhum Craton, eastern India: Geochemical record for subduction initiation to arc maturation continuum

    NASA Astrophysics Data System (ADS)

    Rajanikanta Singh, M.; Manikyamba, C.; Ganguly, Sohini; Ray, Jyotisankar; Santosh, M.; Dhanakumar Singh, Th.; Chandan Kumar, B.

    2017-02-01

    -boninite-HMA-NEB association from Malangtoli volcanic suite in Singhbhum Craton preserves the signature of a complete spectrum of Paleoproterozoic active convergent margin processes spanning from subduction initiation to arc maturation.

  8. Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 1. Tephra ages and provenance

    NASA Astrophysics Data System (ADS)

    Schindlbeck, J. C.; Kutterolf, S.; Freundt, A.; Alvarado, G. E.; Wang, K.-L.; Straub, S. M.; Hemming, S. R.; Frische, M.; Woodhead, J. D.

    2016-11-01

    We studied the tephra inventory of 18 deep-sea drill sites from six DSDP/ODP legs (Legs 84, 138, 170, 202, 205, and 206) and two IODP legs (Legs 334 and 344) offshore the southern Central American Volcanic Arc (CAVA). Eight drill sites are located on the incoming Cocos plate and 10 drill sites on the continental slope of the Caribbean plate. In total, we examined ˜840 ash-bearing horizons and identified ˜650 of these as primary ash beds of which 430 originated from the CAVA. Correlations of ash beds were established between marine cores and with terrestrial tephra deposits, using major and trace element glass compositions with respect to relative stratigraphic order. As a prerequisite for marine-terrestrial correlations, we present a new geochemical data set for significant Neogene and Quaternary Costa Rican tephras. Moreover, new Ar/Ar ages for marine tephras have been determined and marine ash beds are also dated using the pelagic sedimentation rates. The resulting correlations and provenance analyses build a tephrochronostratigraphic framework for Costa Rica and Nicaragua that covers the last <15 Myr. We define 39 correlations of marine ash beds to specific tephra formations in Costa Rica and Nicaragua; from the 4.15 Ma Lower Sandillal Ignimbrite to the 3.5 ka Rincón de la Vieja Tephra from Costa Rica, as well as another 32 widely distributed tephra layers for which their specific region of origin along Costa Rica and Nicaragua can be constrained.

  9. Timing of Volcanism on Yunaska Island, Central Aleutian arc, Alaska: an Investigation Applying Multi-temporal Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Brown, M. E.; Nicolaysen, K. P.; Dehn, J.; Myers, J. D.

    2003-12-01

    The volcanoes of the central Aleutian arc remain largely uninstrumented and unstudied despite numerous eruptions within the last century. Many of these eruptions are not documented and others may not have been observed. Previous synthetic aperture radar (SAR) studies at Westdahl volcano show that radar can be used to relatively date a'a lava flows and to suggest whether some flows are "historic" though not recorded. This is accomplished through comparison of semi-quantitative measurements of surface roughness for young, unvegetated lavas. Because a'a lavas typically become smoother as they weather, they produce less radar backscatter. Thus, lavas that exhibit higher radar backscatter intensities are younger than those with lower backscatter intensities for regions of similar relief and aspect. Located 305 km west of Dutch Harbor, Yunaska has six volcanic centers, of which three have probably been active in the Quaternary. Based on field observations, recent volcanism on Yunaska is associated with the younger of two nested calderas and several smaller vents and cones on the eastern half of the island. Although there is a reported 1937 eruption, it is not clear if this came from fissures north of the caldera or created the intracaldera cinder cone and lava flows. Using a twenty-year composite of SAR data, we establish relative ages for five basaltic andesite lavas from these fissures and from within the young caldera. Clear stratigraphic relationships among three lavas within the caldera provide a check on the accuracy of this technique. The use of SAR to differentiate between young lavas allows us to better document the eruption history of remote volcanoes and to mitigate their hazards.

  10. Small-scale lithospheric foundering beneath the Peruvian Altiplano: evidence from back arc potassic volcanic rocks and lower crustal and mantle xenoliths

    NASA Astrophysics Data System (ADS)

    Chapman, A. D.; Ducea, M. N.

    2013-12-01

    Small-volume, Pliocene to Quaternary back arc high-K calc-alkaline to shoshonitic volcanic rocks and entrained xenoliths of southeastern Peru permit evaluation of models for the removal of crustal and mantle lithosphere beneath the northwestern Altiplano. Two distinct subsets of volcanic samples are apparent based on sample location, eruption age, geochemistry, and xenolith types. Suite 1 Quaternary mafic extrusives show: high K2O (1.3-8.4%), steep rare earth element patterns with La/Yb ranging from 17 to 161 and lacking Eu anomalies, and Sr-Nd isotope decoupling with 143Nd/144Nd from 0.5124 to 0.5129 at 87Sr/86Sr of 0.7095 to 0.7038. A second Plio-Quaternary suite shows small Eu anomalies, lower K2O (2.3-3.4%), a lower and narrower range of La/Yb (from 28 to 50), and Nd and Sr isotopic data follow an array from 143Nd/144Nd = 0.5125 to 0.5123 with corresponding range in 87Sr/86Sr from 0.7059 to 0.7072. Xenoliths from suite 2 lavas consist almost exclusively of clinopyroxene and plagioclase, whereas suite 1 inclusions are more diverse, containing clinopyroxenite (× garnet × plagioclase), garnet-bearing gabbro and diorite, aluminous garnet granulite gneiss; and rare spinel harzburgite. Thermobarometric, geochronologic, and Sr-Nd isotopic relations suggest a melting link between suite 1 xenoliths and volcanic rocks. Geochemical differences between back arc suites and frontal arc volcanic rocks strongly suggest that each was derived from a different source. Most notably, higher Nd isotopic values, younger depleted mantle model ages, and higher La/Yb in suite 1 vs. suite 2 lavas suggest an increased contribution of asthenospheric material and an increase in the depth to melting in the back arc region from Pliocene to Quaternary time. Variations in transition element ratios from the back arc to the frontal arc suggest a larger contribution of pyroxenitic material in the source of the former. Interactions between a downgoing lower crustal drip structure and upwelling

  11. Active Volcanism on Io: Global Distribution and Variations in Activity

    USGS Publications Warehouse

    Lopes-Gautier, R.; McEwen, A.S.; Smythe, W.B.; Geissler, P.E.; Kamp, L.; Davies, A.G.; Spencer, J.R.; Keszthelyi, L.; Carlson, R.; Leader, F.E.; Mehlman, R.; Soderblom, L.

    1999-01-01

    Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the near-infrared mapping spectrometer (NIMS) for the first 10 orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI) and from groundbased observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager flybys in 1979. A total of 61 active volcanic centers have been identified from Voyager, groundbased, and Galileo observations. Of these, 41 are hot spots detected by NIMS and/or SSI. Another 25 locations were identified as possible active volcanic centers, mostly on the basis of observed surface changes. Hot spots are correlated with surface colors, particularly dark and red deposits, and generally anti-correlated with white, SO2-rich areas. Surface features corresponding to the hot spots, mostly calderas or flows, were identified from Galileo and Voyager images. Hot spot temperatures obtained from both NIMS and SSI are consistent with silicate volcanism, which appears to be widespread on Io. Two types of hot spot activity are present: persistent-type activity, lasting from months to years, and sporadic events, which may represent either short-lived activity or low-level activity that occasionally flares up. Sporadic events are not often detected, but may make an important contribution to Io's heat flow and resurfacing. The distribution of active volcanic centers on the surface does not show any clear correlation with latitude, longitude, Voyager-derived global topography, or heat flow patterns predicted by the asthenosphere and deep mantle tidal dissipation models. However, persistent hot spots and active plumes are concentrated toward lower latitudes, and this distribution favors the asthenosphere rather than the deep mantle tidal dissipation model. ?? 1999 Academic Press.

  12. Petrology of Early Miocene volcanic rocks from Okushiri Island, Japan: geochemical characteristics of lithospheric mantle beneath the back-arc side of the NE Japan arc.

    NASA Astrophysics Data System (ADS)

    Sato, M.; Shuto, K.; Ishimoto, H.; Yagi, M.; Takazawa, E.

    2004-12-01

    The Sr and Nd isotopic studies on Tertiary to Quaternary basaltic rocks of the NE Japan arc have shown that isotopic characteristics of basaltic rocks found on the back-arc side of the NE Japan arc changed drastically from an undepleted isotopic signature (initial 87Sr/86Sr (SrI)=0.7040-0.7060 and initial 143Nd/144Nd (NdI)=0.51260-0.51284) to a depleted isotopic signature (SrI=0.7030-0.7040 and NdI=0.70284-0.51308) at around 15 Ma (Shuto et., 2004). This feature may have resulted from changes around 15 Ma in the isotopic compositions of the magma source beneath the back-arc side in the NE Japan arc due to the thinning of the undepleted subcontinental lithospheric mantle by upwelling of depleted asthenospheric mantle material during the opening of Japan Sea. Based on major and trace element data as well as SrI and NdI values for Early Miocene basaltic rocks from the back-arc side of the NE Japan arc, we examined geochemical characterization of the magma source (lithospheric mantle) for these basaltic rocks. Early Miocene (23-18 Ma) basalts and associated more felsic volcanic rocks form seven volcanic fields (Okushiri Is., Matsumae Pen., Fukaura, Oga Pen., Honjo, Atsumi and Sado Is.) delineating a 500 km-long array in the back-arc side of the NE Japan arc. In terms of major, trace element and Nd isotopic compositions, two groups of Early Miocene basalts can be distinguished. Group 1 is composed of tholeiitic basalts and alkali basalts, and is characterized by high TiO2 contents (1.5-2.5 %) and high (La/Yb)n ratios (>5.5), and high Zr/Y ratios (>6). These samples show the chondrite-normalized LREE-enriched patterns and have NdI values ranging from 0.51259 to 0.51282. Group 2 is composed of tholeiitic basalts, and is different from Group 1 by lower TiO2 contents (<1.5 %), lower (La/Yb)n ratios (<5) and lower Zr/Y ratios (<5.5). These samples show modelately LREE-enriched patterns and have NdI values ranging from 0.51250 to 0.51278. In contrast, Middle Miocene (after 15

  13. The role of crystallization-driven exsolution on the sulfur mass balance in volcanic arc magmas

    NASA Astrophysics Data System (ADS)

    Su, Y.; Huber, Christian; Bachmann, Olivier; Zajacz, Zoltán.; Wright, Heather; Vazquez, Jorge

    2016-08-01

    The release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur-rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur-rich phases can all be considered as closed-system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous "excess sulfur" problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the "petrologic estimate"), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed- and open-system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization-induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal-rich arc magmas. This result does not negate the important role of vapor

  14. Diverse Primitive Basalts from an Extensional Back-arc Setting, Fort Rock Volcanic Field, Oregon.

    NASA Astrophysics Data System (ADS)

    Popoli, F. M., Jr.; Schmidt, M. E.

    2014-12-01

    The Pleistocene to Pliocene Fort Rock Volcanic Field (FRVF), situated in a back-arc extensional setting ~65 km east of the Central Oregon High Cascades has erupted a diverse array of basaltic magmas, including some primitive compositions with an Mg#>60. Major and trace element concentrations have been determined for 80 mafic bulk lava samples by X-ray Fluorescence (XRF) and selected minerals by electron microprobe. Petrological and geochemical data suggest three primitive basalt end-members similar to basalts in the nearby Oregon Cascade arc and High Lava Plains: high-alumina olivine tholeiite or low-K tholeiites (LKT), calc-alkaline basalts (CAB), ocean island basalts (OIB). Primitive Mg# (61-68) HAOTs are aphyric to phenocryst-poor (~2-5 %) olivine and plagioclase bearing and diktytaxitic. HAOTs are distinguished by low K2O (0.22-0.44 wt%), high Al2O3 (17.19-18.67 wt%) and CaO contents. CABs are the most dominant basalt type in the area with higher large ion lithophile element (LILE) concentrations (e.g., 170-426 ppm Ba) relative to high field strength elements (HFSE; 4.6-10.4 ppm Nb) and lower Mg#s (60-64) than HAOTs. CABs have more abundant (~5-15 %) and larger phenocrysts (~2-4 mm) of olivine and plagioclase than in HAOTs. OIBs contain higher Nb contents ranging from 11.7-18.6 ppm (vs. 3.0-7.2 ppm in HAOTs). OIBs are similar to both HAOTs and CABs, ranging from aphyric to porphyritic and diktytaxitic and may include amphibole phenocrysts. Tectonic extension associated with the Basin and Range in this area likely facilitated eruptions of primitive magmas. A comparison of the most primitive magmas (HAOTs with Mg#>65) found in eastern and western FRVF indicates that the western HAOTs contain higher incompatible element concentrations relative to eastern HAOT (Ba, Sc, Sr, Zr, Nb), which may reflect lower degrees of melting of a more enriched mantle source to the west.

  15. The role of crystallization-driven exsolution on the sulfur mass balance in volcanic arc magmas

    USGS Publications Warehouse

    Su, Yanqing; Huber, Christian; Bachmann, Olivier; Zajacz, Zoltán; Wright, Heather M.; Vazquez, Jorge A.

    2016-01-01

    The release of large amounts of sulfur to the stratosphere during explosive eruptions affects the radiative balance in the atmosphere and consequentially impacts climate for up to several years after the event. Quantitative estimations of the processes that control the mass balance of sulfur between melt, crystals, and vapor bubbles is needed to better understand the potential sulfur yield of individual eruption events and the conditions that favor large sulfur outputs to the atmosphere. The processes that control sulfur partitioning in magmas are (1) exsolution of volatiles (dominantly H2O) during decompression (first boiling) and during isobaric crystallization (second boiling), (2) the crystallization and breakdown of sulfide or sulfate phases in the magma, and (3) the transport of sulfur-rich vapor (gas influx) from deeper unerupted regions of the magma reservoir. Vapor exsolution and the formation/breakdown of sulfur-rich phases can all be considered as closed-system processes where mass balance arguments are generally easier to constrain, whereas the contribution of sulfur by vapor transport (open system process) is more difficult to quantify. The ubiquitous “excess sulfur” problem, which refers to the much higher sulfur mass released during eruptions than what can be accounted for by amount of sulfur originally dissolved in erupted melt, as estimated from melt inclusion sulfur concentrations (the “petrologic estimate”), reflects the challenges in closing the sulfur mass balance between crystals, melt, and vapor before and during a volcanic eruption. In this work, we try to quantify the relative importance of closed- and open-system processes for silicic arc volcanoes using kinetic models of sulfur partitioning during exsolution. Our calculations show that crystallization-induced exsolution (second boiling) can generate a significant fraction of the excess sulfur observed in crystal-rich arc magmas. This result does not negate the important role of

  16. Late Cenozoic tephrostratigraphy offshore the southern Central American Volcanic Arc: 2. Implications for magma production rates and subduction erosion

    NASA Astrophysics Data System (ADS)

    Schindlbeck, J. C.; Kutterolf, S.; Freundt, A.; Straub, S. M.; Vannucchi, P.; Alvarado, G. E.

    2016-11-01

    Pacific drill sites offshore Central America provide the unique opportunity to study the evolution of large explosive volcanism and the geotectonic evolution of the continental margin back into the Neogene. The temporal distribution of tephra layers established by tephrochonostratigraphy in Part 1 indicates a nearly continuous highly explosive eruption record for the Costa Rican and the Nicaraguan volcanic arc within the last 8 Myr. The widely distributed marine tephra layers comprise the major fraction of the respective erupted tephra volumes and masses thus providing insights into regional and temporal variations of large-magnitude explosive eruptions along the southern Central American Volcanic Arc (CAVA). We observe three pulses of enhanced explosive volcanism between 0 and 1 Ma at the Cordillera Central, between 1 and 2 Ma at the Guanacaste and at >3 Ma at the Western Nicaragua segments. Averaged over the long-term the minimum erupted magma flux (per unit arc length) is ˜0.017 g/ms. Tephra ages, constrained by Ar-Ar dating and by correlation with dated terrestrial tephras, yield time-variable accumulation rates of the intercalated pelagic sediments with four prominent phases of peak sedimentation rates that relate to tectonic processes of subduction erosion. The peak rate at >2.3 Ma near Osa particularly relates to initial Cocos Ridge subduction which began at 2.91 ± 0.23 Ma as inferred by the 1.5 Myr delayed appearance of the OIB geochemical signal in tephras from Barva volcano at 1.42 Ma. Subsequent tectonic re-arrangements probably involved crustal extension on the Guanacaste segment that favored the 2-1 Ma period of unusually massive rhyolite production.

  17. Sr and Nd isotopic compositions of mafic xenoliths and volcanic rocks from the Oga Peninsula, Northeast Japan Arc: Genetic relationship between lower crust and arc magmas

    NASA Astrophysics Data System (ADS)

    Yamamoto, Masatsugu; Kagami, Hiroo; Narita, Akiyuki; Maruyama, Takahiko; Kondo, Azusa; Abe, Shiho; Takeda, Rika

    2013-03-01

    one end-member of a mixing curve, is assumed to have a 87Sr/86Sr ratio of 0.705250 and a 143Nd/144Nd ratio of 0.512570, whereas the Oga parental magma, forming the other end-member on the mixing curve, has a 87Sr/86Sr ratio of 0.702958 and a 143Nd/144Nd ratio of 0.512933, as represented by Oga volcanic rocks with the lowest 87Sr/86Sr and highest 143Nd/144Nd ratios (stage 3 lavas from Kampu volcano near Ichinomegata maar). The isotopic compositions of other Oga volcanic rocks vary from the most contaminated Toga rhyolitic pumices (87Sr/86Sr of 0.703723-0.703885 and 143Nd/144Nd of 0.512906-0.512847) through to the Ichinomegata host pumice (87Sr/86Sr of 0.703398 and 143Nd/144Nd of 0.512895). This research indicates that both the Ichinomegata mafic xenoliths and the Oga volcanic rocks have undergone isotopic changes, creating an overlap in compositions caused by metasomatism and contamination, respectively. This relationship between lower crustal and volcanic rocks can be also be applied to trench-side volcanic rocks. If the Ichinomegata lower crustal material extends to the trench side of the NE Japan Arc, the island-arc tholeiites typically found within the volcanic front probably also contain a similar, if not identical, lower crustal component.

  18. The structure and morphology of the Basse Terre Island, Lesser Antilles volcanic arc

    NASA Astrophysics Data System (ADS)

    Mathieu, Lucie; van Wyk de Vries, Benjamin; Mannessiez, Claire; Mazzoni, Nelly; Savry, Cécile; Troll, Valentin R.

    2013-03-01

    Basse Terre Island is made up of a cluster of composite volcanoes that are part of the Lesser Antilles volcanic arc. The morphology of these volcanoes and the onshore continuation of the grabens and strike-slip faults that surround the island are poorly documented due to erosion and rainforest cover. Therefore, we conducted a morphological analysis of the island using Digital Elevation Model (DEM) data integrated with field observations to document erosional, constructional, and deformational processes. A DEM-based analysis of 1,249 lineaments and field structural measurements of 16 normal faults, 3,741 veins and fractures, and 46 dykes was also carried to document the structures that predominate in sub-surface rocks. The results indicate that the over 1-My-old and elongated Northern Chain volcano, which makes up the northern half of the island, was built by high eruption rates and/or a low viscosity magma injected along the N-S to NNW-SSE-striking extensional structures formed by the flexure of the lithosphere by the overall subduction regime. After 1 Ma, the southern half of the island was shaped by an alignment of conical volcanoes, likely built by a more viscous magma type that was guided by the NW-SE-striking Montserrat-Bouillante strike-slip fault system. These N to NNW and NW structural directions are however poorly expressed onshore, possibly due to slow slip motion. The sub-surface rocks mostly contain E-W-striking structures, which have likely guided the many flank instabilities documented in the studied area, and guide hydrothermal fluids and shallow magmatic intrusions. These structures are possibly part of the E-W-striking Marie-Gallante offshore graben.

  19. Segmentation of the Cascade Arc Based on Compositional and Sr and Nd Isotopic Variations in Primitive Volcanic Rocks

    NASA Astrophysics Data System (ADS)

    Schmidt, M. E.; Grunder, A. L.

    2006-12-01

    We define four segments in the Cascade Volcanic Arc based on 87Sr/86Sr and 143Nd/144Nd of primitive volcanic rocks: 1) The North segment extends 450 km from Mt. Meager to Glacier Peak; 2) the 350-km Columbia segment includes volcanoes from Mt. Rainier to Mt. Jefferson; 3) the 250 km Central segment comprises the portion of the arc between the Three Sisters and Crater Lake; and 4) the 350-km South segment includes Mt. Shasta to Mt. Lassen. Isotopic data were compiled for primitive bulk composition (MgO concentrations >8 wt.% MgO) as a fingerprint mantle sources. The North segment has a range in 87Sr/86Sr of 0.7030-0.7037 and is distinguished by the predominance of calcalkaline basalts (CAB) and few low K tholeiites (LKT). The North segment lies on the North Cascade craton where convergence is near orthogonal. Oblique subduction occurs beneath the Columbia, Central, and South segments. The Columbia segment (87Sr/86Sr of 0.7028-0.7037) has both LKT and CABs as well as enriched ocean island-like basalts (OIB) that are found both on the arc axis and, especially at the Simcoe Volcanic Field, behind the arc. This segment lies primarily on the accreted Tertiary oceanic plateau terrane of the Columbia Embayment. The Central segment is dominated by LKT with lesser CAB and has the most restricted Sr isotopic range (0.7034- 0.7038). Like the South segment, the Central segment mainly overlies accreted terranes stitched by Mesozoic plutons and has Basin and Range (B&R) extension behind as well as locally within the arc. Medicine Lake Volcano, on the margin of the B&R behind Mt. Shasta is also dominated by LKT and has a narrow isotopic range like the Central segment. This suggests that the LKT's are related to extension in the arc. The South segment is distinguished by the widest Sr isotopic range (0.7028-0.7042) and the presence of high Mg basaltic andesite and andesite compositions in addition to LKT and CABs. These arc segments broadly correspond to physical segments that were

  20. Middle Cambrian to Late Ordovician evolution of the Appalachian margin: Foundering of a passive margin to form a subduction zone and volcanic arc

    SciTech Connect

    Washington, P.A. , Southern Pines, NC )

    1994-03-01

    From late Middle Cambrian to early Late Ordovician time, the Appalachian passive margin experienced a series of orogenic events culminating in the Taconic orogeny. Most of these events are generally viewed as enigmatic and isolated, but they can be viewed as a coherent tectonic sequence of events. The early stages involved broad uplifts and localized extension, especially of internal shelf and adjacent continental interiors. Later stages involved increased subsidence rates of the outer shelf, resulting in retreat of the outer margin of the carbonate platform.The beginning of volcanic activity coincides with, or immediately follows, the rapid subsidence. Onset of compressional orogenesis is often temporally separated from the initial rapid subsidence. These events can be integrated into a tectonic model in which the passive margin is converted into an active Andean margin. Early uplift and extension events represented the surface expression of the beginning of deep-seated downward mantle convection. Subsequent rapid subsidence events represented the mechanical failure of the lithosphere as the convection reaches maturity. Failure of the lithosphere resulted in a subduction zone that quickly created arc volcanism. The compressive Taconic orogenesis occurred when the arc was thrust back onto the shelf margin as the subduction zone migrated continentward in response to progressively channeled convective flow.

  1. Mantle dynamics beneath the Pacific Northwest and the generation of voluminous back-arc volcanism

    NASA Astrophysics Data System (ADS)

    Long, Maureen D.; Till, Christy B.; Druken, Kelsey A.; Carlson, Richard W.; Wagner, Lara S.; Fouch, Matthew J.; James, David E.; Grove, Timothy L.; Schmerr, Nicholas; Kincaid, Chris

    2012-08-01

    The Pacific Northwest (PNW) has a complex tectonic history and over the past ˜17 Ma has played host to several major episodes of intraplate volcanism. These events include the Steens/Columbia River flood basalts (CRB) and the striking spatiotemporal trends of the Yellowstone/Snake River Plain (Y/SRP) and High Lava Plains (HLP) regions. Several different models have been proposed to explain these features, which variously invoke the putative Yellowstone plume, rollback and steepening of the Cascadia slab, extensional processes in the lithosphere, or a combination of these. Here we integrate seismologic, geodynamic, geochemical, and petrologic results from the multidisciplinary HLP project and associated analyses of EarthScope USArray seismic data to propose a conceptual model for post-20 Ma mantle dynamics beneath the PNW and the relationships between mantle flow and surface tectonomagmatic activity. This model invokes rollback subduction as the main driver for mantle flow beneath the PNW beginning at ˜20 Ma. A major pulse of upwelling due to slab rollback and upper plate extension and consequent melting produced the Steens/CRB volcanism, and continuing trench migration enabled mantle upwelling and hot, shallow melting beneath the HLP. An additional buoyant mantle upwelling is required to explain the Y/SRP volcanism, but subduction-related processes may well have played a primary role in controlling its timing and location, and this upwelling likely continues today in some form. This conceptual model makes predictions that are broadly consistent with seismic observations, geodynamic modeling experiments, and petrologic and geochemical constraints.

  2. Submarine record of volcanic island construction and collapse in the Lesser Antilles arc: First scientific drilling of submarine volcanic island landslides by IODP Expedition 340

    NASA Astrophysics Data System (ADS)

    Le Friant, A.; Ishizuka, O.; Boudon, G.; Palmer, M. R.; Talling, P. J.; Villemant, B.; Adachi, T.; Aljahdali, M.; Breitkreuz, C.; Brunet, M.; Caron, B.; Coussens, M.; Deplus, C.; Endo, D.; Feuillet, N.; Fraas, A. J.; Fujinawa, A.; Hart, M. B.; Hatfield, R. G.; Hornbach, M.; Jutzeler, M.; Kataoka, K. S.; Komorowski, J.-C.; Lebas, E.; Lafuerza, S.; Maeno, F.; Manga, M.; Martínez-Colón, M.; McCanta, M.; Morgan, S.; Saito, T.; Slagle, A.; Sparks, S.; Stinton, A.; Stroncik, N.; Subramanyam, K. S. V.; Tamura, Y.; Trofimovs, J.; Voight, B.; Wall-Palmer, D.; Wang, F.; Watt, S. F. L.

    2015-02-01

    IODP Expedition 340 successfully drilled a series of sites offshore Montserrat, Martinique and Dominica in the Lesser Antilles from March to April 2012. These are among the few drill sites gathered around volcanic islands, and the first scientific drilling of large and likely tsunamigenic volcanic island-arc landslide deposits. These cores provide evidence and tests of previous hypotheses for the composition and origin of those deposits. Sites U1394, U1399, and U1400 that penetrated landslide deposits recovered exclusively seafloor sediment, comprising mainly turbidites and hemipelagic deposits, and lacked debris avalanche deposits. This supports the concepts that i/ volcanic debris avalanches tend to stop at the slope break, and ii/ widespread and voluminous failures of preexisting low-gradient seafloor sediment can be triggered by initial emplacement of material from the volcano. Offshore Martinique (U1399 and 1400), the landslide deposits comprised blocks of parallel strata that were tilted or microfaulted, sometimes separated by intervals of homogenized sediment (intense shearing), while Site U1394 offshore Montserrat penetrated a flat-lying block of intact strata. The most likely mechanism for generating these large-scale seafloor sediment failures appears to be propagation of a decollement from proximal areas loaded and incised by a volcanic debris avalanche. These results have implications for the magnitude of tsunami generation. Under some conditions, volcanic island landslide deposits composed of mainly seafloor sediment will tend to form smaller magnitude tsunamis than equivalent volumes of subaerial block-rich mass flows rapidly entering water. Expedition 340 also successfully drilled sites to access the undisturbed record of eruption fallout layers intercalated with marine sediment which provide an outstanding high-resolution data set to analyze eruption and landslides cycles, improve understanding of magmatic evolution as well as offshore sedimentation

  3. Volcanic Activity at Tvashtar Catena, Io

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    Tvashtar Catena (63 N, 120 W) is one of the most interesting features on Io. This chain of large paterae (caldera-like depressions) has exhibited highly variable volcanic activity in a series of observations. Tvashtar is the type example of a style of volcanism seen only at high latitudes, with short-lived Pele-type plumes and short-lived by intense thermal events. Evidence for a hot spot at Tvashtar was first detected in an eclipse observation in April 1997 (orbit G7) by the Solid State Imager (SSI) on the Galileo Spacecraft. Tvashtar was originally targeted for observation at higher resolution in the close flyby in November 1999 (I25) because of its interesting large-scale topography. There are relatively few but generally larger paterae at high latitudes on Io. I25 images revealed a 25 km long, 1-2 km high lava curtain via a pattern of saturation and bleeding in the CCD image, which requires very high temperatures.

  4. Distribution of late Cenozoic volcanic vents in the Cascade Range: volcanic arc segmentation and regional tectonic considerations ( USA).

    USGS Publications Warehouse

    Guffanti, M.; Weaver, C.S.

    1988-01-01

    Spatial, temporal, and compositional distributions of c4000 volcanic vents formed since 16 Ma in Washington, Oregon, N California, and NW Nevada illustrate the evolution of volcanism related to subduction of the Juan de Fuca plate system and extension of the Basin and Range province. Vent data were obtained from published map compilations and include monogenetic and small polygenetic volcanoes in addition to major composite centers. On the basis of the distribution of 2821 vents formed since 5 Ma, the Cascade Range is divided into 5 segments, with vents of the High Lava Plains along the northern margin of the Basin and Range province in Oregon forming a sixth segment. Some aspects of the Cascade Range segmentation can be related to gross structural features of the subducting Juan de Fuca plate.-from Authors

  5. A structural outline of the Yenkahe volcanic resurgent dome (Tanna Island, Vanuatu Arc, South Pacific)

    NASA Astrophysics Data System (ADS)

    Merle, O.; Brothelande, E.; Lénat, J.-F.; Bachèlery, P.; Garaébiti, E.

    2013-12-01

    A structural study has been conducted on the resurgent Yenkahe dome (5 km long by 3 km wide) located in the heart of the Siwi caldera of Tanna Island (Vanuatu arc, south Pacific). This spectacular resurgent dome hosts a small caldera and a very active strombolian cinder cone - the Yasur volcano - in the west and exhibits an intriguing graben in its central part. Detailed mapping and structural observations make it possible to unravel the volcano-tectonic history of the dome. It is shown that, following the early formation of a resurgent dome in the west, a complex collapse (caldera plus graben) occurred and this was associated with the recent uplift of the eastern part of the present dome. Eastward migration of the underlying magma related to regional tectonics is proposed to explain this evolution.

  6. Bromine release during Plinian eruptions along the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Hansteen, T. H.; Kutterolf, S.; Appel, K.; Freundt, A.; Perez-Fernandez, W.; Wehrmann, H.

    2010-12-01

    Volcanoes of the Central American Volcanic Arc (CAVA) have produced at least 72 highly explosive eruptions within the last 200 ka. The eruption columns of all these “Plinian” eruptions reached well into the stratosphere such that their released volatiles may have influenced atmospheric chemistry and climate. While previous research has focussed on the sulfur and chlorine emissions during such large eruptions, we here present measurements of the heavy halogen bromine by means of synchrotron radiation induced micro-XRF microanalysis (SR-XRF) with typical detection limits at 0.3 ppm (in Fe rich standard basalt ML3B glass). Spot analyses of pre-eruptive glass inclusions trapped in minerals formed in magma reservoirs were compared with those in matrix glasses of the tephras, which represent the post-eruptive, degassed concentrations. The concentration difference between inclusions and matrix glasses, multiplied by erupted magma mass determined by extensive field mapping, yields estimates of the degassed mass of bromine. Br is probably hundreds of times more effective in destroying ozone than Cl, and can accumulate in the stratosphere over significant time scales. Melt inclusions representing deposits of 22 large eruptions along the CAVA have Br contents between 0.5 and 13 ppm. Br concentrations in matrix glasses are nearly constant at 0.4 to 1.5 ppm. However, Br concentrations and Cl/Br ratios vary along the CAVA. The highest values of Br contents (>8 ppm) and lowest Cl/Br ratios (170 to 600) in melt inclusions occur across central Nicaragua and southern El Salvador, and correlate with bulk-rock compositions of high Ba/La > 85 as well as low La/Yb <5. Thus we observe the maximum magmatic Br-concentrations in the segements of the arc. where the input of sediment and water into the subduction system is largest and the melting column is longest. The largest eruptive emissions of Br into the atmosphere, however, occurred in Guatemala due to the large magnitude of

  7. Structure of the Volcanic Vent Distribution of the Cascades Arc from a New Database of Holocene and Pleistocene Volcanism, with Focus on Pre-Caldera Monogenetic Volcanism at Mount Mazana, Oregon

    NASA Astrophysics Data System (ADS)

    Loh, L.; Karlstrom, L.; Ramsey, D. W.; Wright, H. M.

    2013-12-01

    The spatial and temporal distribution of volcanoes in the Cascades Arc, USA,reflects modulation of time-varying mantle melt influx by crustal magmatic plumbing and tectonic forces. The relative contribution of spatio-temporal source variations versus crustal focusing in generating the observed distribution of vents is poorly constrained. To identify patterns in preserved eruptive products and validate models for crustal magma transport we have assembled the most complete database of Cascades volcanism to date. Our database contains >2900 volcanic vent locations from the Holocene and Pleistocene, and includes vent types, ages, and major element geochemistry of eruptive products from the Holocene and Pleistocene. Bulk geochemistry is obtained from USGS Professional Papers and the American Volcanic and Intrusive Rock Database (NAVDAT). We also include arc-wide heat flow data, modeled ambient noise crustal seismic tomography and crust thickness interpolated to each vent. We perform spectral clustering on vent locations to define volcanic centers for the Holocene and Pleistocene. Centers found through Spectral Clustering reproduce the major loci of volcanism in the Cascades, and show time-varying structure in the number, type and distribution eruptions. There is significant North-South variation in vent type and distribution that correlates with variations in heat flow, bulk silica content and average crustal shear velocity. Although precise eruption ages for the complete dataset are not yet available, Mount Mazama, OR, has a well-resolved time/composition/volume/location history of eruptions <400 ka that allow for further analysis. The spatial distribution of Mazamaeruptive units does not follow a Poisson distribution when well resolved in time, but rather clusters around an evolved center that exhibits progressively more evolved eruptive products in time. Monogenetic eruptions preceding the 7.8 ka Crater Lake eruption define a spatial and temporal pattern that is

  8. Integrating Multiple Space Ground Sensors to Track Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Chien, Steve; Davies, Ashley; Doubleday, Joshua; Tran, Daniel; Jones, Samuel; Kjartansson, Einar; Thorsteinsson, Hrobjartur; Vogfjord, Kristin; Guomundsson, Magnus; Thordarson, Thor; Mandl, Daniel

    2011-01-01

    Volcanic activity can occur with little or no warning. Increasing numbers of space borne assets can enable coordinated measurements of volcanic events to enhance both scientific study and hazard response. We describe the use of space and ground measurements to target further measurements as part of a worldwide volcano monitoring system. We utilize a number of alert systems including the MODVOLC, GOESVOLC, US Air Force Weather Advisory, and Volcanic Ash Advisory Center (VAAC) alert systems. Additionally we use in-situ data from ground instrumentation at a number of volcanic sites, including Iceland.

  9. Crustal rifting and magmatic underplating in the Izu-Ogasawara (Bonin) intra-oceanic arc detected by active source seismic studies

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Kodaira, S.; Yamashita, M.; Miura, S.; Sato, T.; No, T.; Tatsumi, Y.; Kaneda, Y.

    2009-12-01

    Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic experiments using a multichannel reflection system and ocean bottom seismographs (OBSs) in the Izu-Ogasawara (Bonin)-Mariana (IBM) arc region since 2002 to understand growth process of continental crust. The source was an airgun array with a total capacity of 12,000 cubic inches and the OBSs as the receiver were deployed with an interval of 5 km for all seismic refraction experiments. As the results, we obtained crustal structures across the whole IBM arc with an interval of 50 km and detected the structural characteristics showing the crustal growth process. The IBM arc is one of typical oceanic island arc, which crustal growth started from subduction of an oceanic crust beneath the other oceanic crust. The arc crust has developed through repeatedly magmatic accretion from subduction slab and backarc opening. The volcanism has activated in Eocene, Oligocene, Miocene and Quaternary (e.g., Taylor, 1992), however, these detailed locations of past volcanic arc has been remained as one of unknown issues. In addition, a role of crustal rifting for the crustal growth has also been still unknown issue yet. Our seismic structures show three rows of past volcanic arc crusts except current arc. A rear arc and a forearc side have one and two, respectively. The first one, which was already reported by Kodaira et al. (2008), distributes in northern side from 27 N of the rear arc region. The second one, which develops in the forearc region next to the recent volcanic front, distributes in whole of the Izu-Ogasawara arc having crustal variation along arc direction. Ones of them sometimes have thicker crust than that beneath current volcanic front and no clear topographic high. Last one in the forearc connects to the Ogasawara Ridge. However, thickest crust is not always located beneath these volcanic arcs. The initial rifting region like the northern end of the Mariana Trough and the Sumisu

  10. Geothermal Potential of the Cascade and Aleutian Arcs, with Ranking of Individual Volcanic Centers for their Potential to Host Electricity-Grade Reservoirs

    SciTech Connect

    Shevenell, Lisa; Coolbaugh, Mark; Hinz, Nick; Stelling, Pete; Melosh, Glenn; Cumming, William

    2015-10-16

    This project brings a global perspective to volcanic arc geothermal play fairway analysis by developing statistics for the occurrence of geothermal reservoirs and their geoscience context worldwide in order to rank U.S. prospects. The focus of the work was to develop play fairways for the Cascade and Aleutian arcs to rank the individual volcanic centers in these arcs by their potential to host electricity grade geothermal systems. The Fairway models were developed by describing key geologic factors expected to be indicative of productive geothermal systems in a global training set, which includes 74 volcanic centers world-wide with current power production. To our knowledge, this is the most robust geothermal benchmark training set for magmatic systems to date that will be made public.

  11. Volcanic activity at Tvashtar Catena, Io

    USGS Publications Warehouse

    Milazzo, M.P.; Keszthelyi, L.P.; Radebaugh, J.; Davies, A.G.; Turtle, E.P.; Geissler, P.; Klaasen, K.P.; Rathbun, J.A.; McEwen, A.S.

    2005-01-01

    Galileo's Solid State Imager (SSI) observed Tvashtar Catena four times between November 1999 and October 2001, providing a unique look at a distinctive high latitude volcanic complex on Io. The first observation (orbit I25, November 1999) resolved, for the first time, an active extraterrestrial fissure eruption; the brightness temperature was at least 1300 K. The second observation (orbit I27, February 2000) showed a large (??? 500 km 2) region with many, small, hot, regions of active lava. The third observation was taken in conjunction with Cassini imaging in December 2000 and showed a Pele-like, annular plume deposit. The Cassini images revealed an ???400 km high Pele-type plume above Tvashtar Catena. The final Galileo SSI observation of Tvashtar (orbit I32, October 2001), revealed that obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. In this paper, we primarily analyze the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of simple advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping eruptions. The highest reliable color temperature is ???1300 K. Although higher temperatures cannot be ruled out, they do not need to be invoked to fit the observed data. The total power output from the active lavas in February 2000 was at least 1011 W. ?? 2005 Elsevier Inc. All rights reserved.

  12. Petrology and age of volcanic-arc rocks from the continental margin of the Bering Sea: implications for Early Eocene relocation of plate boundaries

    USGS Publications Warehouse

    Davis, A.S.; Pickthorn, L.-B.G.; Vallier, T.L.; Marlow, M. S.

    1989-01-01

    Eocene volcanic flow and dike rocks from the Beringian margin have arc characteristics, implying a convergent history for this region during the early Tertiary. Chemical and mineralogical compositions are similar to those of modern Aleutian-arc lavas. They also resemble volcanic-arc compositions from western mainland Alaska, although greater chemical diversity and a stronger continental influence are observed in the Alaskan mainland rocks. Early Eocene ages of 54.4-50.2 Ma for the Beringian samples are well constrained by conventional K-Ar ages of nine plagioclase separates and by concordant 40Ar/39Ar incremental heating and total-fusion experiments. A concordant U-Pb zircon age of 53 Ma for the quartz-diorite dike is in good agreement with the K-Ar data. Plate motion studies of the North Pacific Ocean indicate more northerly directed subduction prior to the Tertiary and a continuous belt of arc-type volcanism extending from Siberia, along the Beringian margin, into mainland Alaska. Around 56 Ma (chron 25-24), subduction changed to a more westerly direction and subduction-related volcanism ceased for most of mainland Alaska. The increasingly oblique angle of convergence should have ended subduction along the Beringian margin as well. However, consistent ages of 54-50 Ma indicate a final pulse in arc-type magmatism during this period of plate adjustment. -from Authors

  13. Rhyolitic calderas of the Yukon-Tanana Terrane, east central Alaska: volcanic remnants of a mid-Cretaceous magmatic arc

    USGS Publications Warehouse

    Bacon, C.R.; Foster, H.L.; Smith, James G.

    1990-01-01

    Four large but poorly exposed rhyolitic calderas are present in the Yukon-Tanana terrane (YTT) in east central Alaska. At least two are mid-Cretaceous in age (~93 Ma). Similar volcanic rocks, the South Fork Volcanics, occur northeast of the Tintina fault in Yukon Territory. Evidence for the calderas consists of thick deposits of devitrified crystal- and lithic-rich densely welded tuff, interpreted as caldera fill, associated with lava domes or shallow intrusive rocks. Coeval outflow sheets have been largely stripped by erosion. The calderas are preserved within a northeast trending depression extending across the axis of the elongate mid-Cretaceous plutonic province. Trace element abundances in andesites and rhyolites associated with the caldera structures are similar to those of volcanic and plutonic rocks of subduction-related magmatic arcs developed on continental crust and thus are suggestive of formation in such an environment. Late Cretaceous and early Tertiary igneous rocks in the YTT near the calderas are interpreted to have been emplaced in a more extensional setting when the subduction-related magmatic front was farther oceanward. -Authors

  14. High resolution seismic data coupled to Multibeam bathymetry of Stromboli island collected in the frame of the Stromboli geophysical experiment: implications with the marine geophysics and volcanology of the Aeolian Arc volcanic complex (Sicily, Southern Tyrrhenian sea, Italy).

    PubMed

    Aiello, Gemma; Di Fiore, Vincenzo; Marsella, Ennio; Passaro, Salvatore

    2014-01-01

    New high resolution seismic data (Subbottom Chirp) coupled to high resolution Multibeam bathymetry collected in the frame of the Stromboli geophysical experiment aimed at recording active seismic data and tomography of the Stromboli Island are here presented. The Stromboli geophysical experiment has been already carried out based on onshore and offshore data acquisition in order to investigate the deep structure and the location of the magma chambers of the Stromboli volcano. A new detailed swath bathymetry of Stromboli Island is here shown and discussed to reconstruct an up-to-date morpho-bathymetry and marine geology of the area compared to the volcanologic setting of the Aeolian Arc volcanic complex. Due to its high resolution the new Digital Terrain Model of the Stromboli Island gives interesting information about the submerged structure of the volcano, particularly about the volcano-tectonic and gravitational processes involving the submarine flanks of the edifice. Several seismic units have been identified based on the geologic interpretation of Subbottom Chirp profiles recorded around the volcanic edifice and interpreted as volcanic acoustic basement pertaining to the volcano and overlying slide chaotic bodies emplaced during its complex volcano-tectonic evolution. They are related to the eruptive activity of Stromboli, mainly poliphasic and to regional geological processes involving the intriguing geology of the Aeolian Arc, a volcanic area still in activity and needing improved research interest.

  15. Geologic Map of the Bodie Hills Volcanic Field, California and Nevada: Anatomy of Miocene Cascade Arc Magmatism in the Western Great Basin

    NASA Astrophysics Data System (ADS)

    John, D. A.; du Bray, E. A.; Blakely, R. J.; Box, S.; Fleck, R. J.; Vikre, P. G.; Rytuba, J. J.; Moring, B. C.

    2011-12-01

    The Bodie Hills Volcanic Field (BHVF) is a >700 km2, long-lived (~9 Ma) but episodic, Miocene eruptive center in the southern part of the ancestral Cascade magmatic arc. A 1:50,000-scale geologic map based on extensive new mapping, combined with 40Ar/39Ar dates, geochemical data, and detailed gravity and aeromagnetic surveys, defines late Miocene magmatic and hydrothermal evolution of the BHVF and contrasts the subduction-related BHVF with the overlying, post-subduction, bimodal Plio-Pleistocene Aurora Volcanic Field (AVF). Important features of the BHVF include: Eruptions occurred during 3 major eruptive stages: dominantly trachyandesite stratovolcanoes (~14.7 to 12.9 Ma), mixed silicic trachyandesite, dacite, and rhyolite (~11.3 to 9.6 Ma), and dominantly silicic trachyandesite to dacite domes (~9.2 to 8.0 Ma). Small rhyolite domes were emplaced at ~6 Ma. Trachyandesitic stratovolcanoes with extensive debris flow aprons form the outer part of BHVF, whereas silicic trachyandesite to rhyolite domes are more centrally located. Geophysical data suggest that many BHVF volcanoes have shallow plutonic roots that extend to depths ≥1-2 km below the surface, and much of the Bodie Hills may be underlain by low density plutons presumably related to BHVF volcanism. BHVF rocks contain ~50 to 78% SiO2 (though few rocks have <55% SiO2), have high-K calc-alkaline compositions, and have negative Ti-P-Nb-Ta anomalies and high Ba/Nb, Ba/Ta, and La/Nb typical of subduction-related continental margin arcs. BHVF rocks include mafic trachyandesite/basaltic andesite (50%), silicic trachyandesite-dacite (40%), and rhyolite (10%). Approximately circular, polygenetic volcanoes and scarcity of dikes suggest a low differential horizontal stress field during formation of BHVF. Subduction ceased beneath the Bodie Hills at ~10 Ma, but the composition and eruptive style of volcanism continued unchanged for 2 Ma. However, kinematic data for veins and faults in mining districts suggest a change

  16. Petrology and geochemistry of Ordovician K-bentonites in New York State: Constraints on the nature of a volcanic arc

    SciTech Connect

    Delano, J.W.; Schirnick, C.; Bock, B.; Kidd, W.S.F.; Heizler, M.T.; Putman, G.W.; De Long, S.E.; Ohr, M. )

    1990-03-01

    Altered volcanic ashes (K-bentonites) in the late Ordovician (Caradocian) Utica shale of New York State are the product of explosive arc volcanism. Most of the 30 K-bentonites examined in this investigation contain fragmental crystals and rock fragments (microliths) up to 600 {mu}m in diameter that generally are neither detrital contamination from the surrounding black shale nor igneous phenocrysts. The dominant phases are garnet (two groups; Gr{sub 15-20}Alm{sub 45-75}Py{sub 35-0}Sp{sub 2-5}; Gr{sub 2-5}Alm{sub 55-85}Py{sub 10-40}Sp{sub 1}), plagioclase feldspar (An{sub 80-10}), alkali feldspar (Or{sub 99-0}), clinopyroxene (Wo{sub 50-40}En{sub 50-30}Fs{sub 0-30}), and orthopyroxene (Wo{sub 1-2}En{sub 77-32}Fs{sub 32-66}), accompanied by lesser quantities of hornblende, aluminosilicate, quartz, sphene, Fe-Ti oxides, apatite, and zircon. Most of the fragmental crystals appear to be derived from the same source as the metamorphic microliths, which possess minerals with similar compositions. Both crystals and microliths are interpreted as xenocrysts and xenoliths from the ancient continental crust on which the Ordovician arc was constructed. They became entrained in the volcanic plume during explosive eruptions. A Precambrian age acquired on K-feldspars from one K-bentonite using the {sup 40}Ar/{sub 39}Ar method shows that these xenocrysts were derived from depths of less than 5-10 km in the microcontinent at the time of late Ordovician volcanism. The occurrence of xenocrysts and xenoliths in these K-bentonites underscores the importance of performing detailed petrology on ash layers prior to the onset of more sophisticated tasks (e.g., isotopic age determinations; regional stratigraphic correlations of K-bentonites based upon chemical compositions).

  17. Using Volcanic Lightning Measurements to Discern Variations in Explosive Volcanic Activity

    NASA Astrophysics Data System (ADS)

    Behnke, S. A.; Thomas, R. J.; McNutt, S. R.; Edens, H. E.; Krehbiel, P. R.; Rison, W.

    2013-12-01

    VHF observations of volcanic lightning have been made during the recent eruptions of Augustine Volcano (2006, Alaska, USA), Redoubt Volcano (2009, Alaska, USA), and Eyjafjallajökull (2010, Iceland). These show that electrical activity occurs both on small scales at the vent of the volcano, concurrent with an eruptive event and on large scales throughout the eruption column during and subsequent to an eruptive event. The small-scale discharges at the vent of the volcano are often referred to as 'vent discharges' and are on the order of 10-100 meters in length and occur at rates on the order of 1000 per second. The high rate of vent discharges produces a distinct VHF signature that is sometimes referred to as 'continuous RF' radiation. VHF radiation from vent discharges has been observed at sensors placed as far as 100 km from the volcano. VHF and infrasound measurements have shown that vent discharges occur simultaneously with the onset of eruption, making their detection an unambiguous indicator of explosive volcanic activity. The fact that vent discharges are observed concurrent with explosive volcanic activity indicates that volcanic ejecta are charged upon eruption. VHF observations have shown that the intensity of vent discharges varies between eruptive events, suggesting that fluctuations in eruptive processes affect the electrification processes giving rise to vent discharges. These fluctuations may be variations in eruptive vigor or variations in the type of eruption; however, the data obtained so far do not show a clear relationship between eruption parameters and the intensity or occurrence of vent discharges. Further study is needed to clarify the link between vent discharges and eruptive behavior, such as more detailed lightning observations concurrent with tephra measurements and other measures of eruptive strength. Observations of vent discharges, and volcanic lightning observations in general, are a valuable tool for volcano monitoring, providing a

  18. Recording the transition from flare-up to steady-state arc magmatism at the Purico-Chascon volcanic complex, northern Chile

    NASA Astrophysics Data System (ADS)

    Burns, Dale H.; de Silva, Shanaka L.; Tepley, Frank; Schmitt, Axel K.; Loewen, Matthew W.

    2015-07-01

    The long-term evolution of continental magmatic arcs is episodic, where a few transient events of high magmatic flux or flare-ups punctuate the low-flux magmatism or "steady state" that makes up most of the arc history. How this duality manifests in terms of differences in crustal architecture, magma dynamics and chemistry, and the time scale over which transitions occur is poorly known. Herein we use multiscale geochemical and isotopic characteristics coupled with geothermobarometry at the Purico-Chascon Volcanic Complex (PCVC) in the Central Andes to identify a transition from flare-up to steady state arc magmatism over ∼800 kyr during which significant changes in upper crustal magmatic dynamics are recorded. The PCVC is one of the youngest volcanic centers related to a 10-1 Ma ignimbrite flare-up in the Altiplano-Puna Volcanic Complex of the Central Andes. Activity at the PCVC initiated 0.98 ± 0.03 Ma with the eruption of a large 80-100 km3 crystal-rich dacite ignimbrite. High, restricted 87Sr/86Sr isotope ratios between 0.7085 and 0.7090 in the bulk rock and plagioclase crystals from the Purico ignimbrite, combined with mineral chemistry and phase relationships indicate the dacite magma accumulated and evolved at relatively low temperatures around 800-850 °C in the upper crust at 4-8 km depth. Minor andesite pumice erupted late in the ignimbrite sequence records a second higher temperature (965 °C), higher pressure environment (17-20 km), but with similar restricted radiogenic bulk rock 87Sr/86Sr = 0.7089-0.7091 to the dacites. The compositional and isotopic characteristics of the Purico ignimbrite implicate an extensive zone of upper crustal mixing, assimilation, storage and homogenization (MASH) between ∼30 and 4 km beneath the PCVC ∼1 Ma. The final eruptions at the PCVC < 0.18 ± 0.02 Ma suggest a change in the magmatic architecture beneath the PCVC. These eruptions produced three small <6 km3 crystal-rich dacite lava domes with radiogenic bulk rock

  19. High-Sr Volcanic Domes from the Lassen Volcanic Region, Southernmost Cascade Arc, Northern California: Implications for Andesite and Dacite Magma Generation

    NASA Astrophysics Data System (ADS)

    Stout, C.; DeBari, S. M.; Clynne, M. A.

    2015-12-01

    The Onion Butte (OB) and Barkley Mountain (BM) groups comprise two linear arrays of volcanic domes at a high angle to the Cascade arc axis (40 km SW of Lassen Volcanic Center). These groups have atypical petrographic and geochemical characteristics compared to other lithologies in the Lassen area. Petrographically, both groups are sparsely phyric containing hornblende and pyroxene, but lacking plagioclase; disequilibrium textures are not observed. The OB group is composed of dacite (64.0-65.2wt. % SiO2) characterized by high Sr (> 1000ppm), with low 87Sr/86Sr (<0.7040), high (Sr/P)N (2.8-3.5), no Eu anomaly, and moderate (La/Yb)N (11-23). The BM group is composed of basaltic andesite to andesite (53.6-62.3wt. % SiO2) characterized by lower Sr (354-611ppm), but higher 87Sr/86Sr (>0.7040), low (Sr/P)N (1.1-2.1), no Eu anomaly, and moderate (La/Yb)N (4.6-11.8). The distinctive characteristics of these two groups mirror those of the two end members of calc-alkaline primitive basalts recognized in the Lassen region (high Sr/P vs. low Sr/P). We invoke different sources and processes to explain the origin and evolution of these groups. The BM basaltic andesites are likely derived from fractionation of low Sr/P basalts and the BM andesites are successfully modeled by fractional crystallization of BM basaltic andesites with a fractionating assemblage that contains <10% plagioclase. In contrast, the OB dacites share geochemical characteristics with some adakites, suggesting an origin by partial melting of the subducting slab. However, partial melting models of the subducting Gorda plate at eclogite facies conditions failed to reproduce the observed trends of the OB dacites. Partial melting of an amphibolitic lower arc crust with a source composition similar to high Sr/P calc-alkaline basalts successfully reproduces observed trends. Geochemical characteristics and results from modeling suggest Sr concentrations may be a useful source indicator in the Lassen region.

  20. Recent volcanic activity on Venus - Evidence from radiothermal emissivity measurements

    NASA Astrophysics Data System (ADS)

    Robinson, C. A.; Wood, J. A.

    1993-03-01

    Radiothermal emissivity measurements are analyzed in order to study large volcanic constructs on Venus and to correlate details of the reflectivity/emissivity patterns with geological landforms and stratigraphy visible in corresponding SAR images. There appears to be a correlation between locations on Venus where high emissivity at high altitudes and low emissivity at low altitudes are observed. These phenomena are attributed here to relatively recent volcanic activity: the former to summit eruptions that have not had time to weather to the low-emissivity state, the latter to continuing emission of volcanic gases from neighboring small plains volcanoes. The pattern of reflectivity and emissivity on Maat Mons is examined in the light of these findings. It is concluded that Maat Mons has undergone the most recent episode of volcanic activity of all the volcanoes studied here.

  1. Recent volcanic activity on Venus - Evidence from radiothermal emissivity measurements

    NASA Technical Reports Server (NTRS)

    Robinson, Cordula A.; Wood, John A.

    1993-01-01

    Radiothermal emissivity measurements are analyzed in order to study large volcanic constructs on Venus and to correlate details of the reflectivity/emissivity patterns with geological landforms and stratigraphy visible in corresponding SAR images. There appears to be a correlation between locations on Venus where high emissivity at high altitudes and low emissivity at low altitudes are observed. These phenomena are attributed here to relatively recent volcanic activity: the former to summit eruptions that have not had time to weather to the low-emissivity state, the latter to continuing emission of volcanic gases from neighboring small plains volcanoes. The pattern of reflectivity and emissivity on Maat Mons is examined in the light of these findings. It is concluded that Maat Mons has undergone the most recent episode of volcanic activity of all the volcanoes studied here.

  2. Localised magmatic constraints on continental back-arc volcanism in southern Mendoza, Argentina: the Santa Maria Volcano

    NASA Astrophysics Data System (ADS)

    Espanon, Venera R.; Chivas, Allan R.; Turner, Simon P.; Kinsley, Leslie P. J.; Dosseto, Anthony

    2016-11-01

    The Payún Matrú Volcanic Field constitutes part of the continental back-arc in Argentina. This volcanic field has been the focus of several regional investigations; however, geochemical analysis of recent volcanoes (<8 ka) at the scale of an individual volcano has not been conducted. We present a morphological description for the Santa Maria Volcano in addition to results from major and trace element analysis and 238U-230Th-226Ra disequilibria. The trace element evidence suggests that the Santa Maria magmatic source has a composition similar to that of the local intraplate end member (resembling an ocean island basalt-like source), with a slight contribution from subduction-related material. The U-series analyses suggest a high 226Ra excess over 230Th for this volcano, which is not derived from a shallow process such as hydrothermal alteration or upper crustal contamination. Furthermore, intermediate-depth processes such as fractional crystallisation have been inferred for the Santa Maria Volcano, but they are not capable of producing the 226Ra excess measured. The 226Ra excess is explained by deep processes like partial melting of mantle lithologies with some influence from subducted Chilean trench sediments. Due to the short half-life of 226Ra (1600 years), we infer that fast magma ascent rates are required to preserve the high 226Ra excess.

  3. Upper plate deformation induced by subduction of a volcanic arc: the Snellius Plateau (Molucca Sea, Indonesia and Mindanao, Philippines)

    NASA Astrophysics Data System (ADS)

    Pubellier, Manuel; Bader, Anne Gaelle; Rangin, Claude; Deffontaines, Benoit; Quebral, Ray

    1999-04-01

    The northern Molucca Sea shows the incipient subduction of a composite oceanic and arc volcanic block, the Snellius-Halmahera block (SHB). Multi-beam, reflectivity, seismic and gravity data obtained during the MODEC marine survey showed that the SHB disappears beneath the accretionary wedge and the outer ridge of the Sangihe Arc. To the north in Mindanao Island, ongoing convergence generated shortening of the forearc basin and the backthrusting of the SHB; meanwhile a classical system of paired subduction (Philippine Trench) and strike-slip fault (Philippine Fault) was installed. The transition from lithospheric subduction to crustal overthrusting is located where the Philippine Trench sensu stricto begins, and also coincides with the off-shore extension of the Philippine Fault. We observe a reversal of the thrusts from an eastward vergence in the Molucca Sea to a westward vergence in Mindanao Island. This reversal takes place at the latitude where the forearc area emerges by uplift, and the downgoing crust (SHB) deepens, resulting in a strong gravity low centered above the accretionary wedge. The Philippine Fault initiated in a place where the crust was sliced off by a transfer zone which marked the northern termination of the Molucca Sea, and drags northward a sliver of the previously accreted SHB. The northward drifting of this sliver created an extension, which, however, cannot account for the gravity low. We propose that the shortening and the uplift of the upper plate were induced by the buoyancy of the subducted unit (SHB), and triggered the thrust reversal.

  4. Hydrothermal nontronite formation at Eolo Seamount (Aeolian volcanic arc, Tyrrhenian Sea)

    USGS Publications Warehouse

    Dekov, V.M.; Kamenov, George D.; Stummeyer, Jens; Thiry, M.; Savelli, C.; Shanks, Wayne C.; Fortin, D.; Kuzmann, E.; Vertes, A.

    2007-01-01

    A sediment core containing a yellowish-green clay bed was recovered from an area of extensive hydrothermal deposition at the SE slope of the Eolo Seamount, Tyrrhenian Sea. The clay bed is composed of pure nontronite (described for the first time in the Tyrrhenian Sea), which appears to be the most aluminous nontronite ever found among the seafloor hydrothermal deposits. The high Al content suggests precipitation from Al-containing hydrothermal solutions. The REE distribution of the Eolo nontronite has a V-shape pattern. The heavy REE enrichment is in part due to their preferential partitioning in the nontronite structure. This enrichment was possibly further enhanced by the HREE preferential sorption on bacterial cell walls. The light REE enrichment is the result of scavenging uptake by one of the nontronite precursors, i.e., poorly-ordered Fe-oxyhydroxides, from the hydrothermal fluids. Oxygen isotopic composition of the nontronite yields a formation temperature of 30????C, consistent with a low-temperature hydrothermal origin. The relatively radiogenic Nd isotopic signature of the nontronite compared to the present-day Mediterranean seawater indicates that approximately half of Nd, and presumably the rest of the LREE, are derived from local volcanic sources. On the other hand, 87Sr/86Sr is dominated by present-day seawater Sr. Scanning electron microscopy investigation revealed that the nontronite is composed of aggregates of lepispheres and tube-like filaments, which are indicative of bacteria assisted precipitation. Bacteria inhabiting this hydrothermal site likely acted as reactive geochemical surfaces on which poorly-ordered hydrothermal Fe-oxyhydroxides and silica precipitated. Upon aging, the interactions of these primary hydrothermal precipitates coating bacterial filaments and cell walls likely led to the formation of nontronite. Finally, the well-balanced interlayer and layer charges of the crystal lattice of seafloor hydrothermal nontronite decrease its

  5. Mantle and Crustal Sources of Carbon, Nitrogen, and Noble gases in Cascade-Range and Aleutian-Arc Volcanic gases

    USGS Publications Warehouse

    Symonds, Robert B.; Poreda, Robert J.; Evans, William C.; Janik, Cathy J.; Ritchie, Beatrice E.

    2003-01-01

    Here we report anhydrous chemical (CO2, H2S, N2, H2, CH4, O2, Ar, He, Ne) and isotopic (3He/4He, 40Ar/36Ar, δ13C of CO2, δ13C of CH4, δ15N) compositions of virtually airfree gas samples collected between 1994 and 1998 from 12 quiescent but potentially restless volcanoes in the Cascade Range and Aleutian Arc (CRAA). Sample sites include ≤173°C fumaroles and springs at Mount Shasta, Mount Hood, Mount St. Helens, Mount Rainier, Mount Baker, Augustine Volcano, Mount Griggs, Trident, Mount Mageik, Aniakchak Crater, Akutan, and Makushin. The chemical and isotopic data generally point to magmatic (CO2, Ar, He), shallow crustal sedimentary (hereafter, SCS) (CO2, N2, CH4), crustal (He), and meteoric (N2, Ar) sources of volatiles. CH4 clearly comes from SCS rocks in the subvolcanic systems because CH4 cannot survive the higher temperatures of deeper potential sources. Further evidence for a SCS source for CH4 as well as for non-mantle CO2 and non-meteoric N2 comes from isotopic data that show wide variations between volcanoes that are spatially very close and similar isotopic signatures from volcanoes from very disparate areas. Our results are in direct opposition to many recent studies on other volcanic arcs (Kita and others, 1993; Sano and Marty, 1995; Fischer and others, 1998), in that they point to a dearth of subducted components of CO2 and N2 in the CRAA discharges. Either the CRAA volcanoes are fundamentally different from volcanoes in other arcs or we need to reevaluate the significance of subducted C and N recycling in convergent-plate volcanoes.

  6. Contributions of poroelastic rebound and a weak volcanic arc to the postseismic deformation of the 2011 Tohoku earthquake

    NASA Astrophysics Data System (ADS)

    Hu, Yan; Bürgmann, Roland; Freymueller, Jeffrey T.; Banerjee, Paramesh; Wang, Kelin

    2014-12-01

    A better understanding of fluid-related processes such as poroelastic rebound of the upper crust and weakening of the lower crust beneath the volcanic arc helps better understand and correctly interpret the heterogeneity of postseismic deformation following great subduction zone earthquakes. The postseismic deformation following the 2011 M w 9.0 Tohoku earthquake, recorded with unprecedented high resolution in space and time, provides a unique opportunity to study these `second-order' subduction zone processes. We use a three-dimensional viscoelastic finite element model to study the effects of fluid-related processes on the postseismic deformation. A poroelastic rebound (PE) model alone with fluid flow in response to coseismic pressure changes down to 6 and 16 km in the continental and oceanic crusts, respectively, predicts 0 to 6 cm uplift on land, up to approximately 20 cm uplift above the peak rupture area, and up to approximately 15 cm subsidence elsewhere offshore. PE produces up to approximately 30 cm of horizontal motions in the rupture area but less than 2 cm horizontal displacements on land. Effects of a weak zone beneath the arc depend on its plan-view width and vertical viscosity profile. Our preferred model of the weak sub-arc zone indicates that in the first 2 years after the 2011 earthquake, the weak zone contributes to the surface deformation on land on the order of up to 20 cm in both horizontal and vertical directions. The weak-zone model helps eliminate the remaining systematic misfit of the viscoelastic model of upper mantle relaxation and afterslip of the megathrust.

  7. Lead isotopes in volcanic rocks and possible ocean-floor thrusting beneath island arcs

    USGS Publications Warehouse

    Tatsumoto, M.

    1969-01-01

    The isotopic composition of lead in the Japanese primary basalts gradually decreases in radiogenic character in a transverse from the Pacific Ocean side to the Japan Sea side, whereas the observed 238U 204Pb and 232Th 204Pb ratios in the basalts increase in the same direction. The isotopic composition of lead suggests that tholeiite (Pacific side) is generated at a shallower depth than alkali basalt (Japan Sea side) as postulated by Kuno. The inverse correlation of the 238U 204Pb with the 206Pb 204Pb ratios could be due to preferential Pb extraction with respect to uranium at shallow depths. Alternatively, these geochemical results can be interpreted in terms of the Pacific oceanic rigid plate being underthurst beneath the island arc. The isotopic variation in basalts across the Japanese island arc would result from different proportions of the plate material and the upper mantle of continental side in the partial melt. ?? 1969.

  8. Crustal deformation and volcanic earthquakes associated with the recent volcanic activity of Iwojima Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, H.; Fujita, E.; Tanada, T.

    2013-12-01

    Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The seismometer and GPS network of National Research Institute for Earth Science and Disaster Prevention (NIED) in Iwojima has observed a repeating island wide uplift more than 1 m associated with large number of volcanic earthquakes every several years. During 2006-2012, we observed more than 20000 volcanic earthquakes and an uplift of about 3 m, and precursory volcanic earthquakes and rapid crustal deformation just before the small submarine eruption near the northern coast of Iwojima in April 2012. In a restless volcano such as Iwojima, it is important issue to distinguish whether rapid crustal deformation and intense earthquake activity lead to an eruption or not. According to a long period geodetic observation by Ukawa et al. (2006), the crustal deformation of Iwojima can be classify into 2 phases. The first is an island wide large uplift centering on Motoyama area (the eastern part of the island, the center of the caldera), and the second is contraction and subsidence at local area centering on Motoyama and uplift around that area. They are interpreted by superposition of crustal deformations by a shallow contraction source and a deep seated inflation source beneath Motoyama. The earthquake activity of Iwojima highly correlates with the island wide large uplift, suggesting the earthquakes are almost controlled by a magma accumulation into a deep seated magma chamber. In contrast to the activity, the precursory activity of the eruption in 2012 is deviated from the correlation. The rapid crustal deformation just before and after the eruption in 2012 can be interpreted by rapid inflation and deflation of a shallow sill source about 1km deep, respectively, suggesting that it was caused by a shallow hydrothermal activity. The result shows that we can probably distinguish an abnormal activity related with a volcanic eruption when we observe

  9. International Collaboration on Building Local Technical Capacities for Monitoring Volcanic Activity at Pacaya Volcano, Guatemala.

    NASA Astrophysics Data System (ADS)

    Escobar-Wolf, R. P.; Chigna, G.; Morales, H.; Waite, G. P.; Oommen, T.; Lechner, H. N.

    2015-12-01

    Pacaya volcano is a frequently active and potentially dangerous volcano situated in the Guatemalan volcanic arc. It is also a National Park and a major touristic attraction, constituting an important economic resource for local municipality and the nearby communities. Recent eruptions have caused fatalities and extensive damage to nearby communities, highlighting the need for risk management and loss reduction from the volcanic activity. Volcanic monitoring at Pacaya is done by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), instrumentally through one short period seismic station, and visually by the Parque Nacional Volcan de Pacaya y Laguna de Calderas (PNVPLC) personnel. We carry out a project to increase the local technical capacities for monitoring volcanic activity at Pacaya. Funding for the project comes from the Society of Exploration Geophysicists through the Geoscientists Without Borders program. Three seismic and continuous GPS stations will be installed at locations within 5 km from the main vent at Pacaya, and one webcam will aid in the visual monitoring tasks. Local educational and outreach components of the project include technical workshops on data monitoring use, and short thesis projects with the San Carlos University in Guatemala. A small permanent exhibit at the PNVPLC museum or visitor center, focusing on the volcano's history, hazards and resources, will also be established as part of the project. The strategy to involve a diverse group of local collaborators in Guatemala aims to increase the chances for long term sustainability of the project, and relies not only on transferring technology but also the "know-how" to make that technology useful. Although not a primary research project, it builds on a relationship of years of joint research projects at Pacaya between the participants, and could be a model of how to increase the broader impacts of such long term collaboration partnerships.

  10. Basalt-Limestone and Andesite-Limestone Interaction in the Arc Crust - Implications for Volcanic Degassing of CO2

    NASA Astrophysics Data System (ADS)

    Carter, L. B.; Dasgupta, R.

    2014-12-01

    Volcanically emitted CO2 is generally mantle-derived, but high degassing rates at some arcs (e.g. Merapi [1] and Colli Albani Volcanic District [2]) are thought to be affected by magma-carbonate interaction in the upper plate. However, the effects of depth, temperature, and composition on this process are poorly known. We experimentally simulated magma (50%)-limestone (50%) wallrock interactions at 0.5-1.0 GPa, 1100-1200 °C using pure calcite and a hydrous (~3-5 wt.% H2O) melt (basalt, andesite, or dacite). At 1.0 GPa, 1200 °C starting melts are superliquidus, whereas in the presence of calcite, Ca-rich cpx ± Ca-scapolite are produced. With increasing T, basalt-calcite interaction causes the melt, on a volatile-free basis, to become silica-poor and Ca-rich with alumina decreasing as cpx becomes more CaTs-rich. The same trend is seen with all starting melt compositions as P decreases at a constant T (1200 °C), producing melts similar to ultracalcic (CaO/Al2O3>>1) melt inclusions found in arc settings. Shifting from basalt to andesite has little effect on SiO2 and CaO of the reacted melt (e.g. 37 wt.% SiO2, 42 wt.% CaO at 0.5 GPa, 1200 °C), whereas Al2O3 of andesite-derived reacted melt is lower, likely a result of lower alumina in the starting andesite. Wall-rock calcite consumption is observed to increase with increasing T, decreasing P, and increasing melt XSiO2. At 0.5 GPa between 1100 and 1200 °C, our basalt experiments yield carbonate assimilation from 22 to 48 wt.%. This decreases to 20 wt.% at 1.0 GPa, 1200 °C, whereas an andesitic composition assimilates 59 to 52 wt.% from 0.5 to 1.0 GPa at 1200 °C. The higher assimilation in andesite-added runs at high-T is because of lower silicate liquidus as evidenced by lower modal proportion or absence of cpx ± scapolite. Using a magma flux rate estimated for Mt. Vesuvius [3], we obtain a CO2 outflux for a single such volcano experiencing arc magma-calcite reaction [4] of at least 2-4% of the present

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

    USGS Publications Warehouse

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

    2004-01-01

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

  12. Exploring Links Between Global Climate and Explosive Arc Volcanism in Tephra-Rich Quaternary Sediments: A Pilot Study from IODP Expedition 350 Site 1437B, Izu Bonin Rear-Arc Region

    NASA Astrophysics Data System (ADS)

    Corry-Saavedra, K.; Straub, S. M.; Bolge, L.; Schindlbeck, J. C.; Kutterolf, S.; Woodhead, J. D.

    2015-12-01

    Fallout tephra in marine sediment provide an excellent archive of explosive arc volcanism that can be directly related to the other parameters of climate change, such as ice volume data, IRD (ice-rafted debris) input, etc. Current studies are based on 'discrete' tephra beds, which are produced by major eruptions and visible with the naked eye. Yet the more common, but less explosive arc eruptions that are more continuous through time produce 'disperse' tephra, which is concealed by the non-volcanic host sediment and invisible to the eye. The proportion of disperse tephra in marine sediments is known to be significant and may be critical in elucidating potential synchronicity between arc volcanism and glacial cycles. We conducted a pilot study in young sediments of IODP Hole 1437B drilled at 31°47.3911'N and 139°01.5788'E at the rear-arc of the Izu Bonin volcanic arc. By means of δ18O (Vautravers, in revision), eleven climatic cycles are recorded in uppermost 120 meter of carbonate mud that is interspersed by cm-thick tephra fallout layers. We selected six tephra layers, ranging from 0.2 to 1.16 million years in age, and sampled those vertically, starting from carbonate mud below the basal contact throughout the typical gradational top into the carbonate mud above. From each tephra bed, volcanic particles (>125 micrometer) were handpicked. All other samples were powdered and leached in buffered acetic acid and hydroxylamine hydrochloride to remove the carbonate and authigenous fraction, respectively. Major and trace element abundances (except for SiO2) from all samples were determined by ICP-MS and ICP-OES methods. Strong binary mixing trends are revealed between the pure tephra end member, and detrital sediment component. The tephra is derived from the Izu Bonin volcanic front and rear-arc, while the sediment component is presumably transported by ocean surface currents from the East China Sea. Our data show that mixing proportions change systematically with

  13. The Physics of a Volcanic System: What is the Actual Role Played by Tectonic Setting in Controlling Volcanic Activity?

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2005-12-01

    Modern text-books commonly explain volcanic activity as a direct consequence of plate tectonics, overlooking the different scales characteristic of both types of processes. By acknowledging such differences, however, it is possible to envisage a model of a volcanic system that is based in the same principles of hydrostatics established by Blaise Pascal over 300 yrs ago. Such principles allow us to estimate the local conditions required for the occurrence of volcanism at a given location highlighting the importance of the rock strength and the density difference between melt and its surroundings. This model shows that the minimum thickness of the zone of partial melting in the mantle (or seismically defined Low Velocity Zone) that is required to feed volcanic activity might range from 5 to over 100 km, but also that under certain circumstances a rock strength < 200 MPa may suffice to keep magma trapped at depth whereas in other cases a strength > 600 MPa will not suffice to stop magma ascent resulting in volcanic activity at the surface. Consequently, the model of volcanism developed here explains why is that a given LVZ may lead to volcanic activity in some places whereas a completely identical LVZ may not result in volcanic activity in a different location. Consequently, this model provides a general framework that allows us to better understand the actual role played by tectonic setting in controlling volcanism at a planetary scale.

  14. Assessing the state of our knowledge of continental arc volcanism: The Tatara-San Pedro Complex, 36°S, Andean Southern Volcanic Zone: Talca and Tatara-San Pedro, Chile 4-12 February 2007

    USGS Publications Warehouse

    Jaupart, Claude; Sisson, Thomas W.; Blundy, Jon; Arculus, Richard

    2007-01-01

    Tatara-San Pedro Volcanic Complex in Chile is one of the best studied continental arc volcanic centers in the world. In connection to this, a field forum was conducted to discuss the processes involved in the construction of such volcanoes and the origins of its magmas. With 40 international participants from diverse scientific backgrounds, the forum opened in the Talca municipal library with two days of presentation, fieldworks and a hike to the trailhead. The key issues that were tackled include information on the compositions, ages, and distributions of preserved eruptive products.

  15. Oxygen isotope geochemistry of the lassen volcanic center, California: Resolving crustal and mantle contributions to continental Arc magmatism

    USGS Publications Warehouse

    Feeley, T.C.; Clynne, M.A.; Winer, G.S.; Grice, W.C.

    2008-01-01

    This study reports oxygen isotope ratios determined by laser fluorination of mineral separates (mainly plagioclase) from basaltic andesitic to rhyolitic composition volcanic rocks erupted from the Lassen Volcanic Center (LVC), northern California. Plagioclase separates from nearly all rocks have ??18O values (6.1-8.4%) higher than expected for production of the magmas by partial melting of little evolved basaltic lavas erupted in the arc front and back-arc regions of the southernmost Cascades during the late Cenozoic. Most LVC magmas must therefore contain high 18O crustal material. In this regard, the ??18O values of the volcanic rocks show strong spatial patterns, particularly for young rhyodacitic rocks that best represent unmodified partial melts of the continental crust. Rhyodacitic magmas erupted from vents located within 3.5 km of the inferred center of the LVC have consistently lower ??18 O values (average 6.3% ?? 0.1%) at given SiO2 contents relative to rocks erupted from distal vents (>7.0 km; average 7.1% ?? 0.1%). Further, magmas erupted from vents situated at transitional distances have intermediate values and span a larger range (average 6.8% ?? 0.2%). Basaltic andesitic to andesitic composition rocks show similar spatial variations, although as a group the ??18O values of these rocks are more variable and extend to higher values than the rhyodacitic rocks. These features are interpreted to reflect assimilation of heterogeneous lower continental crust by mafic magmas, followed by mixing or mingling with silicic magmas formed by partial melting of initially high 18O continental crust (??? 9.0%) increasingly hybridized by lower ??18O (???6.0%) mantle-derived basaltic magmas toward the center of the system. Mixing calculations using estimated endmember source ??18O values imply that LVC magmas contain on a molar oxygen basis approximately 42 to 4% isotopically heavy continental crust, with proportions declining in a broadly regular fashion toward the

  16. The recent seismo-volcanic activity at Deception Island volcano

    NASA Astrophysics Data System (ADS)

    Ibáñez, Jesús M.; Almendros, Javier; Carmona, Enrique; Martínez-Arévalo, Carmen; Abril, Miguel

    2003-06-01

    This paper reviews the recent seismic studies carried out at Deception Island, South Shetland Islands, Antarctica, which was monitored by the Argentinean and Spanish Antarctic Programs since 1986. Several types of seismic network have been deployed temporarily during each Antarctic summer. These networks have consisted of a variety of instruments, including radio-telemetered stations, autonomous digital seismic stations, broadband seismometers, and seismic arrays. We have identified two main types of seismic signals generated by the volcano, namely pure seismo-volcanic signals, such as volcanic tremor and long-period (LP) events, and volcano-tectonic (VT) earthquakes. Their temporal distributions are far from homogeneous. Volcanic tremors and LP events usually occur in seismic swarms lasting from a few hours to some days. The number of LP events in these swarms is highly variable, from a background level of less than 30/day to a peak activity of about 100 events/h. The occurrence of VT earthquakes is even more irregular. Most VT earthquakes at Deception Island have been recorded during two intense seismic crises, in 1992 and 1999, respectively. Some of these VT earthquakes were large enough to be felt by researchers working on the island. Analyses of both types of seismic events have allowed us to derive source locations, establish seismic source models, analyze seismic attenuation, calculate the energy and stress drop of the seismic sources, and relate the occurrence of seismicity to the volcanic activity. Pure seismo-volcanic signals are modelled as the consequence of hydrothermal interactions between a shallow aquifer and deeper hot materials, resulting in the resonance of fluid-filled fractures. VT earthquakes constitute the brittle response to changes in the distribution of stress in the volcanic edifice. The two VT seismic series are probably related to uplift episodes due to deep injections of magma that did not reach the surface. This evidence, however

  17. Arc magmatism at the incipient stage of formation of subduction zone: geochemistry of Eocene volcanic rocks from the Bonin Islands

    NASA Astrophysics Data System (ADS)

    Kanayama, K.; Umino, S.; Ishizuka, O.

    2009-12-01

    Bonin Islands are known for the occurrence of boninite series and high-Mg arc tholeiite and calk-alkaline rock series generated at the incipient stage of formation of subduction zone. We present new analysis of major and trace elements and petrogenetic processes of volcanic rocks of the Bonin Islands. Boninite series rocks in Chichijima and Mukojima Island Group represent the primitive arc magmatism in middle Eocene time, which gave way to arc tholeiite and calk-alkaline rocks are in Hahajima Island Groups. Boninite series of the Maruberiwan and Asahiyama Formations indicates a differentiation trend that sharply increases in FeO*/MgO (0.47-32) with increasing SiO2 contents (53.8-78.2 wt %). FeO*/MgO ratios (0.74-4.19) of arc tholeiite and calk-alkaline rocks of the Hahajima Island Group are slightly lower than those of the Izu-Bonin Quaternary volcanic front lavas. Boninite series samples of the Mikazukiyama Formation show a similar trend to the Maruberiwan-Asahiyama boninite series samples. However, the former has lower SiO2 contents (55.7-58.2 wt %), and higher FeO*/MgO ratios (1.05-1.98) than the latter. Most of the Maruberiwan and Mikazukiyama boninites belong to low-Ca type, while only a small number of Maruberiwan boninite samples belong to high-Ca type. Maruberiwan boninites (MgO>8 wt%) are the most depleted in REEs (Yb=0.36-1.01 ppm), which is only about 1/10 of N-MORBs, and the most enriched in LILEs (Rb=6-23, Ba=6-58 ppm) in the Bonin Islands. Low-Ca boninites indicate a distinct positive anomaly of Zr and negative anomalies of Sm and Ti ((Sm/Zr)n=0.45-0.78, (Ti/Zr)n=0.25-0.64), while high-Ca boninites indicate moderate anomalies of these elements ((Sm/Zr)n=0.79-1.29, (Ti/Zr)n=0.57-1.02). Basalts of the Hahajima Island Group are the most enriched in REEs (Yb=1.2-2.4 ppm) and HFSEs (Nb=0.47-1.75 ppm) in the Bonin Islands. Compared to the Hahajima basalts, the present Izu-Bonin front lavas are more depleted in LREEs and HFSE, and enriched in LILEs

  18. Geochemistry of the Bonin Fore-arc Volcanic Sequence: Results from IODP Expedition 352

    NASA Astrophysics Data System (ADS)

    Godard, M.; Ryan, J. G.; Shervais, J. W.; Whattam, S. A.; Sakuyama, T.; Kirchenbaur, M.; Li, H.; Nelson, W. R.; Prytulak, J.; Pearce, J. A.; Reagan, M. K.

    2015-12-01

    The Izu-Bonin-Mariana intraoceanic arc system, in the western Pacific, results from ~52 My of subduction of the Pacific plate beneath the eastern margin of the Philippine Sea plate. Four sites were drilled south of the Bonin Islands during IODP Expedition 352 and 1.22 km of igneous basement was cored upslope to the west of the trough. These stratigraphically controlled igneous suites allow study of the earliest stages of arc development from seafloor spreading to convergence. We present the preliminary results of a detailed major and trace element (ICPMS) study on 128 igneous rocks drilled during Expedition 352. Mainly basalts and basaltic andesites were recovered at the two deeper water sites (U1440 and U1441) and boninites at the two westernmost sites (U1439 and U1442). Sites U1440 and U1441 basaltic suites are trace element depleted (e.g. Yb 4-6 x PM); they have fractionated REE patterns (LREE/HREE = 0.2-0.4 x C1-chondrites) compared to mid-ocean ridge basalts. They have compositions overlapping that of previously sampled Fore-Arc Basalts (FAB) series. They are characterized also by an increase in LILE contents relative to neighboring elements up-section (e.g. Rb/La ranging from <1 to 3-7 x PM at Site U1440) suggesting a progressive contamination of their source by fluids. This process in turn may have favored melting and efficient melt extraction from the source and thus its extreme depletion. Boninites are depleted in moderately incompatible elements with a decrease in their contents up-section (e.g. Yb = ~6.2 to 2.8 x C1-chondrite at Site U1439). These changes in trace element contents are associated with the development of a positive Zr-Hf anomaly relative to neighboring elements and a strong increase in LILE (e.g., Zr/Sm=~1 to 2.6 x PM and Rb/La=1-2 to 10-18). The progressive upward depletion of boninitic lavas could reveal the incorporation of harzburgitic residues from FAB generation into their mantle source.

  19. The Extremes of Volcanic Activity: Earth and Jupiter's Moon Io

    NASA Astrophysics Data System (ADS)

    Lowes, L. L.; Lopes, R.

    2004-12-01

    Jupiter's moon Io is the solar system's most volcanically active body, and the only place that magmatic volcanic eruptions have been observed beyond Earth. One of the first images of Io obtained by NASA's Voyager 1 spacecraft in 1979 shows a plume above one of its volcanoes. The NASA Voyager and Galileo spacecraft imaged many explosive eruptions of plumes and deposits - which travel hundreds of kilometers (farther than on the Earth or the Moon). Very hot lavas that are erupting from volcanic vents on Io may be similar to lavas that erupted on Earth billions of years ago. Understanding the physical processes driving volcanic eruptions is important for the understanding of terrestrial volcanoes, not only because of their potential hazards, but also as geologic resources, biologic environments, and for their role in shaping the surface of Earth and other planets. Volcanic eruptions are perhaps the most dramatic events on Earth, and are of intrinsic interest to students, youth, and adults. Topics involving volcanoes are a part of the national science education benchmarks for understanding the Earth's composition and structure for grades 6-8 (the process of creating landforms) and grades 9-12 (the effects of movement of crustal plates). Natural events on Earth coupled with exciting discoveries in space can serve to heighten the awareness of these phenomena and provide learning opportunities for real world applications of science. Educational applications for youth to compare volcanic activity on Io and Earth have been done through NASA-sponsored field trip workshops to places such as Yellowstone National Park (allowing educators to experience environments similar to those on other worlds), targeted classroom and hands-on activities, special interest books, and other resources. A sampling of such activities will be presented, and discussion invited on other related developmentally appropriate resources and activities.

  20. Textural and chemical variation in phenocrysts from the early eruptions of Lutao volcanic island, the northern Luzon arc

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Iizuka, Y.; Huang, K.

    2012-12-01

    The Lutao volcanic island at the northern end of Luzon arc was formed by the subduction of South China Sea Plate beneath the Philippine Sea plate. Three edifices on the island were built up by pyroclastic deposits from different eruption stages. In this study, the textural and chemical zonings in phenocrysts are used to characterize the subvolcanic magma chamber for the earliest eruption stage (1.4-2.0 Ma). The high 143Nd/144Nd and 176Hf/177Hf ratios of six volcanic breccias collected from the lowermost layer indicate that they were derived from a common depleted mantle source. However, their compositional variations cannot be explained by simple fractional crystallization. The textures and compositions of the phenocrysts reveal the complication in the magma chamber processes. Compared to the average primitive arc basalts, two basaltic andesites have similar major element compositions with higher incompatible trace element abundances. The un-zoned or normally zoned olivine, plagioclase, and pyroxenes indicate the relatively undisturbed processes (961-1011°C and 2.8-5.5 kb) at the earlier crystallization stage. The peritectic olivine and abundance melt inclusions accompanied by abrupt XAn increase at the rims of plagioclase inferred recharge of H2O-rich mafic melt at later stage, which also triggered rapid eruption. The cryptic magma mixing had limited effect on isotopic signatures and major element variations, but had great chance to modify the bulk trace element abundances. In contrast, plagioclase phenocrysts in four low-mg# basaltic samples contain An-rich dissolved or resorbed cores with abundant melt inclusions, which were formed from rapid decompression of volatile-rich magma at H2O-undersaturated conditions. The calcic plagioclase and minor Mg-rich olivine formed at greater depth were rapidly brought to magma chamber to crystallized sodic plagioclase rim, clinopyroxene, and minor orthopyroxene (954-994°C and 2.1-4.1 kb). The normally zoned clinopyroxene

  1. On-and offshore tephrostratigraphy and -chronology of the southern Central American Volcanic Arc (CAVA)

    NASA Astrophysics Data System (ADS)

    Schindlbeck, J. C.; Kutterolf, S.; Hemming, S. R.; Wang, K. L.

    2015-12-01

    Including the recently drilled CRISP sites (IODP Exp. 334&344) the deep sea drilling programs have produced 69 drill holes at 29 Sites during 9 Legs at the Central American convergent margin, where the Cocos plate subducts beneath the Caribbean plate. The CAVA produced numerous plinian eruptions in the past. Although abundant in the marine sediments, information and data regarding large late Cenozoic explosive eruptions from Costa Rica, Nicaragua, Honduras, El Salvador, and Guatemala remain very sparse and discontinuous on land. We have established a tephrostratigraphy from recent through Miocene times from the unique archive of ODP/IODP sites offshore Central America in which we identify tephra source regions by geochemical fingerprinting using major and trace element glass shard compositions. Here we present first order correlations of ­~500 tephra layers between multiple holes at a single site as well as between multiple sites. We identified ashes supporting Costa Rican (~130), Nicaraguan (17) and Guatemalan (27) sources as well as ~150 tephra layers from the Galápagos hotspot. Within our marine record we also identified well-known marker beds such as the Los Chocoyos tephra from Atitlán Caldera in Guatemala and the Tiribi Tuff from Costa Rica but also correlations to 15 distinct deposits from known Costa Rican and Nicaraguan eruptions within the last 4.1 Ma. These correlations, together with new radiometric age dates, provide the base for an improved tephrochronostratigraphy in this region. Finally, the new marine record of explosive volcanism offshore southern CAVA provides insights into the eruptive history of long-living volcanic complexes (e.g., Barva, Costa Rica) and into the distribution and frequency of large explosive eruptions from the Galápagos hotspot. The integrated approach of Ar/Ar age dating, correlations with on land deposits from CAVA, biostratigraphic ages and sediment accumulation rates improved the age models for the drilling sites.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  3. Investigation of the thermal regime and geologic history of the Cascade volcanic arc: First phase of a program for scientific drilling in the Cascade Range

    SciTech Connect

    Priest, G.R.

    1987-01-01

    A phased, multihole drilling program with associated science is proposed as a means of furthering our understanding of the thermal regime and geologic history of the Cascade Range of Washington, Oregon, and northern California. The information obtained from drilling and ancillary geological and geophysical investigations will contribute to our knowledge in the following general areas: (1) the magnitude of the regional background heat flow of parts of the Quaternary volcanic belt dominated by the most abundant volcanic rock types, basalt and basaltic andesite; (2) the nature of the heat source responsible for the regional heat-flow anomaly; (3) the characteristics of the regional hydrothermal and cold-water circulation; the rates of volcanism for comparison with models for the rate and direction of plate convergence of the Cascades; (5) the history of deformation and volcanism in the volcanic arc that can be related to subduction; (6) the present-day stress regime of the volcanic arc and the relation of these stresses to plate interactions and possible large earthquakes; and the current geometry of the subducted oceanic plate below the Cascade Range and the relationship of the plate to the distribution of heat flow, Quaternary volcanism, and Quaternary deformation. Phase I research will be directed toward a detailed investigation of the Santiam Pass segment. In concert with the Santiam Pass research, a detailed study of the nearby Breitenbush Hot Springs area is also recommended as a component of Phase I. The object of the Breitenbush research is to study one of the hottest known Cascade hydrothermal systems, which coincidentally also has a good geological and geophysical data base. A coordinated program of drilling, sampling, subsurface measurements, and surface surveys will be associated with the drilling of several holes.

  4. Middle Jurassic Topawa group, Baboquivari Mountains, south-central Arizona: Volcanic and sedimentary record of deep basins within the Jurassic magmatic arc

    USGS Publications Warehouse

    Haxel, G.B.; Wright, J.E.; Riggs, N.R.; Tosdal, R.M.; May, D.J.

    2005-01-01

    Among supracrustal sequences of the Jurassic magmatic arc of the southwestern Cordillera, the Middle Jurassic Topawa Group, Baboquivari Mountains, south-central Arizona, is remarkable for its lithologic diversity and substantial stratigraphic thickness, ???8 km. The Topawa Group comprises four units (in order of decreasing age): (1) Ali Molina Formation-largely pyroclastic rhyolite with interlayered eolian and fluvial arenite, and overlying conglomerate and sandstone; (2) Pitoikam Formation-conglomerate, sedimentary breccia, and sandstone overlain by interbedded silt- stone and sandstone; (3) Mulberry Wash Formation-rhyolite lava flows, flow breccias, and mass-flow breccias, with intercalated intraformational conglomerate, sedimentary breccia, and sandstone, plus sparse within-plate alkali basalt and comendite in the upper part; and (4) Tinaja Spring Porphyry-intrusive rhyolite. The Mulberry Wash alkali basalt and comendite are genetically unrelated to the dominant calcalkaline rhyolite. U-Pb isotopic analyses of zircon from volcanic and intrusive rocks indicate the Topawa Group, despite its considerable thickness, represents only several million years of Middle Jurassic time, between approximately 170 and 165 Ma. Sedimentary rocks of the Topawa Group record mixing of detritus from a minimum of three sources: a dominant local source of porphyritic silicic volcanic and subvolcanic rocks, identical or similar to those of the Topawa Group itself; Meso- proterozoic or Cambrian conglomerates in central or southeast Arizona, which contributed well-rounded, highly durable, polycyclic quartzite pebbles; and eolian sand fields, related to Middle Jurassic ergs that lay to the north of the magmatic arc and are now preserved on the Colorado Plateau. As the Topawa Group evidently represents only a relatively short interval of time, it does not record long-term evolution of the Jurassic magmatic arc, but rather represents a Middle Jurassic "stratigraphic snapshot" of the arc

  5. The petrology, phase relations and tectonic setting of basalts from the taupo volcanic zone, New Zealand and the Kermadec Island arc - havre trough, SW Pacific

    NASA Astrophysics Data System (ADS)

    Gamble, John A.; Smith, Ian E. M.; Graham, Ian J.; Peter Kokelaar, B.; Cole, James W.; Houghton, Bruce F.; Wilson, Colin J. N.

    1990-10-01

    Volcanism in the Taupo Volcanic Zone (TVZ) and the Kermadec arc-Havre Trough (KAHT) is related to westward subduction of the Pacific Plate beneath the Indo-Australian Plate. The tectonic setting of the TVZ is continental whereas in KAHT it is oceanic and in these two settings the relative volumes of basalt differ markedly. In TVZ, basalts form a minor proportion (< 1%) of a dominant rhyolite (97%)-andesite association while in KAHT, basalts and basaltic andesites are the major rock types. Neither the convergence rate between the Pacific and Indo-Australian Plates nor the extension rates in the back-arc region or the dip of the Pacific Plate Wadati-Benioff zone differ appreciably between the oceanic and continental segments. The distance between the volcanic front and the axis of the back-arc basin decreases from the Kermadec arc to TVZ and the distance between trench and volcanic front increases from around 200 km in the Kermadec arc to 280 km in TVZ. These factors may prove significant in determining the extent to which arc and backarc volcanism in subduction settings are coupled. All basalts from the Kermadec arc are porphyritic (up to 60% phenocrysts) with assemblages generally dominated by plagioclase but with olivine, clinopyroxene and orthopyroxene. A single dredge sample from the Havre Trough back arc contains olivine and plagioclase microphenocrysts in glassy pillow rind and is mildly alkaline (< 1% normative nepheline) contrasting with the tholeiitic nature of the other basalts. Basalts from the TVZ contain phenocryst assemblages of olivine + plagioclase ± clinopyroxene; orthopyroxene phenocrysts occur only in the most evolved basalts and basaltic andesites from both TVZ and the Kermadec Arc. Sparsely porphyritic primitive compositions (Mg/(Mg+Fe 2) > 70) are high in Al 2O 3 (>16.5%), and project in the olivine volume of the basalt tetrahedron. They contain olivine (Fo 87) phenocrysts and plagioclase (> An 60) microphenocrysts. These magmas have ratios of

  6. Control of the location of the volcanic front in island arcs by aqueous fluid connectivity in the mantle wedge

    NASA Astrophysics Data System (ADS)

    Mibe, Kenji; Fujii, Toshitsugu; Yasuda, Atsushi

    1999-09-01

    The water released from descending oceanic lithosphere is thought to have an important role in subduction-zone magmatism, as this water might trigger partial melting of the mantle wedge above the subducting plate. If, however, there is incomplete wetting of mineral grain boundaries in the mantle (that is, the dihedral angle at the triple junctions between grains is more than 60°), then the water would not form an interconnected network and might instead be trapped as interstitial fluid in the mantle peridotite. The water would then be transported to deeper parts of the mantle rather than triggering partial melting. Here we use dihedral-angle data to estimate the connectivity of an aqueous fluid phase in a model upper-mantle mineral assemblage (forsterite) at pressures from 3 to 5GPa (corresponding to depths of ~80-150km). By combining these data with previous results, we find that the dihedral angle is greater than 60° at low pressure and temperature (<1,000°C at 2GPa and <800°C at 4GPa) and lower than 60° at higher pressures and temperatures, suggesting that wetting is incomplete below these conditions. This indicates that the connectivity of water in hydrous upper-mantle peridotite at convergent plate boundaries might control the position of the volcanic front in island arcs.

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

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

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

  8. Generation of porphyry copper deposits by gas-brine reaction in volcanic arcs

    NASA Astrophysics Data System (ADS)

    Blundy, J.; Mavrogenes, J.; Tattitch, B.; Sparks, S.; Gilmer, A.

    2015-03-01

    Porphyry copper deposits, that is, copper ore associated with hydrothermal fluids rising from a magma chamber, supply 75% of the world's copper. They are typically associated with intrusions of magma in the crust above subduction zones, indicating a primary role for magmatism in driving mineralization. However, it is not clear that a single, copper-rich magmatic fluid could trigger both copper enrichment and the subsequent precipitation of sulphide ore minerals within a zone of hydrothermally altered rock. Here we draw on observations of modern subduction zone volcanism to propose an alternative process for porphyry copper formation. We suggest that copper enrichment initially involves metalliferous, magmatic hyper-saline liquids, or brines, that exsolve from large, magmatic intrusions assembled in the shallow crust over tens to hundreds of thousands of years. In a subsequent step, sulphide ore precipitation is triggered by the interaction of the accumulated brines with sulphur-rich gases, liberated in short-lived bursts from the underlying mafic magmas. We use high-temperature and high-pressure laboratory experiments to simulate such gas-brine interactions. The experiments yield copper-iron sulphide minerals and hydrogen chloride gas at magmatic temperatures of 700-800 °C, with textural and chemical characteristics that resemble those in porphyry copper deposits. We therefore conclude that porphyry copper ore forms in a two-stage process of brine enrichment followed by gas-induced precipitation.

  9. Geomicrobiological exploration and characterization of a novel deep-sea hydrothermal system at the TOTO caldera in the Mariana Volcanic Arc.

    PubMed

    Nakagawa, Tatsunori; Takai, Ken; Suzuki, Yohey; Hirayama, Hisako; Konno, Uta; Tsunogai, Urumu; Horikoshi, Koki

    2006-01-01

    Novel hydrothermal activities accompanying effluent white smokers and elemental sulfur chimney structures at the north-east lava dome of the TOTO caldera depression in the Mariana Volcanic Arc have been explored and characterized by geochemical and microbiological surveys. White smoker hydrothermal fluids were observed in the potential hydrothermal activity centre of the field and represented the maximal temperature of 170 degrees C and the lowest pH of 1.6. The chimney structures, all consisting of elemental sulfur (sulfur chimney), were also unique to the TOTO caldera hydrothermal field. Microbial community structures in a sulfur chimney and its formation hydrothermal fluid with a high concentration of hydrogen sulfide (15 mM) have been investigated by culture-dependent and -independent analyses. 16S rRNA gene clone analysis and fluorescence in situ hybridization (FISH) analysis revealed that epsilon-Proteobacteria dominated the microbial communities in the sulfur chimney structure and formed a dense microbial mat covering the sulfur chimney surface. Archaeal phylotypes were consistently minor components in the communities and related to the genera Thermococcus, Pyrodictium, Aeropyrum, and the uncultivated archaeal group of 'deep-sea hydrothermal vent euryarchaeotal group'. Cultivation analysis suggested that the chemolithoautotrophs might play a significant ecological role as primary producers utilizing gas and sulfur compounds provided from hydrothermal fluids.

  10. Warm storage for arc magmas

    NASA Astrophysics Data System (ADS)

    Barboni, Mélanie; Boehnke, Patrick; Schmitt, Axel K.; Harrison, T. Mark; Shane, Phil; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2016-12-01

    Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the “cold storage” model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.

  11. Warm storage for arc magmas.

    PubMed

    Barboni, Mélanie; Boehnke, Patrick; Schmitt, Axel K; Harrison, T Mark; Shane, Phil; Bouvier, Anne-Sophie; Baumgartner, Lukas

    2016-12-06

    Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the "cold storage" model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.

  12. 1997 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Wallace, Kristi L.

    1999-01-01

    The Alaska Volcano Observatory (AVO) monitors over 40 historically active volcanoes along the Aleutian Arc. Twenty are seismically monitored and for the rest, the AVO monitoring program relies mainly on pilot reports, observations of local residents and ship crews, and daily analysis of satellite images. In 1997, AVO responded to eruptive activity or suspect volcanic activity at 11 volcanic centers: Wrangell, Sanford, Shrub mud volcano, Iliamna, the Katmai group (Martin, Mageik, Snowy, and Kukak volcanoes), Chiginagak, Pavlof, Shishaldin, Okmok, Cleveland, and Amukta. Of these, AVO has real-time, continuously recording seismic networks at Iliamna, the Katmai group, and Pavlof. The phrase “suspect volcanic activity” (SVA), used to characterize several responses, is an eruption report or report of unusual activity that is subsequently determined to be normal or enhanced fumarolic activity, weather-related phenomena, or a non-volcanic event. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team (KVERT) about the 1997 activity of 5 Russian volcanoes--Sheveluch, Klyuchevskoy, Bezymianny, Karymsky, and Alaid (SVA). This report summarizes volcanic activity and SVA in Alaska during 1997 and the AVO response, as well as information on the reported activity at the Russian volcanoes. Only those reports or inquiries that resulted in a “significant” investment of staff time and energy (here defined as several hours or more for reaction, tracking, and follow-up) are included. AVO typically receives dozens of reports throughout the year of steaming, unusual cloud sightings, or eruption rumors. Most of these are resolved quickly and are not tabulated here as part of the 1997 response record.

  13. Acoustic stratigraphy and hydrothermal activity within Epi Submarine Caldera, Vanuatu, New Hebrides Arc

    USGS Publications Warehouse

    Greene, H. Gary; Exon, N.F.

    1988-01-01

    Geological and geophysical surveys of active submarine volcanoes offshore and southeast of Epi Island, Vanuatu, New Hebrides Arc, have delineated details of the structure and acoustic stratigraphy of three volcanic cones. These submarine cones, named Epia, Epib, and Epic, are aligned east-west and spaced 3.5 km apart on the rim of a submerged caldera. At least three acoustic sequences, of presumed Quaternary age, can be identified on single-channel seismic-reflection profiles. Rocks dredged from these cones include basalt, dacite, and cognate gabbroic inclusions with magmatic affinities similar to those of the Karua (an active submarine volcano off the southeastern tip of Epi) lavas. ?? 1988 Springer-Verlag New York Inc.

  14. Chlorine isotopes of thermal springs in arc volcanoes for tracing shallow magmatic activity

    NASA Astrophysics Data System (ADS)

    Li, Long; Bonifacie, Magali; Aubaud, Cyril; Crispi, Olivier; Dessert, Céline; Agrinier, Pierre

    2015-03-01

    The evaluation of the status of shallow magma body (i.e., from the final intrusion stage, to quiescence, and back to activity), one of the key parameters that trigger and sustain volcanic eruptions, has been challenging in modern volcanology. Among volatile tracers, chlorine (Cl) uniquely exsolves at shallow depths and is highly hydrophilic. Consequently, Cl enrichment in volcanic gases and thermal springs has been proposed as a sign for shallow magmatic activities. However, such enrichment could also result from numerous other processes (e.g., water evaporation, dissolution of old chloride mineral deposits, seawater contamination) that are unrelated to magmatic activity. Here, based on stable isotope compositions of chloride and dissolved inorganic carbon, as well as previous published 3He/4He data obtained in thermal springs from two recently erupted volcanoes (La Soufrière in Guadeloupe and Montagne Pelée in Martinique) in the Lesser Antilles Arc, we show that the magmatic Cl efficiently trapped in thermal springs displays negative δ37Cl values (≤ - 0.65 ‰), consistent with a slab-derived origin but distinct from the isotope compositions of chloride in surface reservoirs (e.g. seawater, local meteoric waters, rivers and cold springs) displaying common δ37Cl values of around 0‰. Using this δ37Cl difference as an index of magmatic Cl, we further examined thermal spring samples including a 30-year archive from two thermal springs in Guadeloupe covering samples from its last eruption in 1976-1977 to 2008 and an island-wide sampling event in Martinique in 2008 to trace the evolution of magmatic Cl in the volcanic hydrothermal systems over time. The results show that magmatic Cl can be rapidly flushed out of the hydrothermal systems within <30 to 80 years after the eruption, much quicker than other volatile tracers such as CO2 and noble gases, which can exsolve at greater depths and constantly migrate to the surface. Because arc volcanoes often have well

  15. Age, geochemical and isotopic variations in volcanic rocks from the Coastal Range of Taiwan: Implications for magma generation in the Northern Luzon Arc

    NASA Astrophysics Data System (ADS)

    Lai, Yu-Ming; Song, Sheng-Rong; Lo, Ching-Hua; Lin, Te-Hsien; Chu, Mei-Fei; Chung, Sun-Lin

    2017-02-01

    This paper reports the first systematic analysis of age and geochemical variations in volcanic rocks from the Coastal Range of Taiwan, the Northern Luzon Arc. The rocks, recovered from four main volcanoes, vary from low-K tholeiitic to medium-K calc-alkaline basalts to dacites. The rocks are typical of arc magmatic products, exhibiting enrichment in the large ion lithophile elements and depletion in the high field strength elements. Our new 40Ar/39Ar age data constrain the youngest eruption time in each of the four volcanoes, i.e., from north to south, at 7.2 Ma (Yuemei), 4.2 Ma (Chimei), 6.2 Ma (Chengkuang'ao) and 8.5 Ma (Tuluanshan), respectively. These data indicate that volcanism in the Northern Luzon Arc did not cease progressively from north to south, as previously alleged. The high and broadly uniform Nd isotope ratios [εNd = + 10.1 to + 8.8] and trace element characteristics of the rocks suggest a principal magma source from the depleted mantle wedge. Their overall geochemical variations are ascribed to magma chamber processes. The effects of magmatic differentiation and crustal contamination differ among each volcano, most likely owing to the discrepancy of residence time in individual magma chambers. Consequently, we propose a binary mixing model for the magma generation that involves arc magmas sourced from the depleted mantle wedge and up to 5% crustal contamination with a continental fragment split off from the Eurasian margin.

  16. Mafic dike swarms in the South Shetland Islands volcanic arc: Unravelling multiepisodic magmatism related to subduction and continental rifting

    NASA Astrophysics Data System (ADS)

    Willan, Robert C. R.; Kelley, Simon P.

    1999-10-01

    Eight groups of mafic dikes and related high-level stocks cut Triassic accretionary complex and Mesozoic magmatic arc formations on Livingston Island. Some are affected by silicic/sericitic alteration, related to Cretaceous hydrothermal activity, and propylitic/epidosite alteration, analogous to that in ocean floor sheeted dikes. Alteration was accompanied by major and trace element metasomatism. Ar-Ar analysis of the freshest rocks indicates five intrusive events, some of which are unexpectedly young. Groups 1-3 were intruded in the mid to late Cretaceous (˜108-74 Ma) and were coeval with the calc-alkaline arc. Between 70 and 50 Ma, relatively rapid and oblique plate convergence led to strike-slip tectonism and a pause in magmatism. At ˜52 Ma, orthogonal, slow convergence resulted in extensional faulting and emplacement of calc-alkaline (group 2) and primitive tholeiitic dikes (groups 4-6) between 51 and 45 Ma. Extension of Antarctic Peninsula-southern South American crust culminated in emplacement of mafic to intermediate, medium-grained plutons and group C porphyries between 44 and 36 Ma. Localized hydrothermal flow along fault zones resulted in partial to complete argon loss from nearby Cretaceous lavas and Ar-Ar reset ages of ˜40 Ma in mid-Cretaceous hydrothermal K-feldspar. Primitive olivine basalts (group D) and epithermal carbonate veins (31-29 Ma) were emplaced during along-arc extension accompanying the opening of Drake Passage and Powell Basin. Excess argon occurs in two forms: strongly held in melt? inclusions in the primitive tholeiites and weakly held in some secondary alteration. There is no radiometric evidence, in the area studied, for magmatism related to late Cenozoic subduction, nor to the Pleistocene-Recent opening of the back arc Bransfield rift.

  17. Episodic Volcanism and Geochemistry in Western Nicaragua

    NASA Astrophysics Data System (ADS)

    Saginor, I.; Carr, M. J.; Gazel, E.; Swisher, C.; Turrin, B.

    2007-12-01

    The active volcanic arc in western Nicaragua is separated from the Miocene arc by a temporal gap in the volcanic record, during which little volcanic material was erupted. Previous work suggested that this gap lasted from 7 to 1.6 Ma, during which volcanic production in Nicaragua was limited or nonexistent. Because the precise timing and duration of this gap has been poorly constrained, recent fieldwork has focused on locating samples that may have erupted close to or even during this apparent hiatus in activity. Recent 40Ar/39Ar dates reveal pulses of low- level episodic volcanism at 7 Ma and 1 Ma between the active and Miocene arcs with current volcanism beginning ~350 ka. In addition, sampling from an inactive area between Coseguina and San Cristobal yielded two distinct groupings of ages; one of Tamarindo age (13 Ma) and the other around 3.5 Ma-the only samples of that age collected on-strike with the active arc. This raises the possibility the bases of the other active volcanoes contain lavas that are older than expected, but have been covered by subsequent eruptions. The Miocene arc differs from the active arc in Central America in several ways, with the latter having higher Ba/La and U/Th values due to increased slab input and changes in subducted sediment composition. Analysis of sample C-51 and others taken from the same area may shed light on the timing of this shift from high to low Ba/La and U/Th values. More importantly, it may help explain why the arc experienced such a dramatic downturn in volcanic production during this time. We also report 25 new major and trace element analyses that shed some light on the origins of these minor episodes of Nicaraguan volcanism. These samples are currently awaiting Sr and Nd isotopic analyses.

  18. Frequency Based Volcanic Activity Detection through Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

    Worden, A. K.; Dehn, J.; Webley, P. W.

    2015-12-01

    Satellite remote sensing has proved to offer a useful and relatively inexpensive method for monitoring large areas where field work is logistically unrealistic, and potentially dangerous. Current sensors are able to detect the majority of explosive volcanic activity; those that tend to effect and represent larger scale changes in the volcanic systems, eventually relating to ash producing periods of extended eruptive activity, and effusive activity. As new spaceborne sensors are developed, the ability to detect activity improves so that a system to gauge the frequency of volcanic activity can be used as a useful monitoring tool. Four volcanoes were chosen for development and testing of a method to monitor explosive activity: Stromboli (Italy); Shishaldin and Cleveland (Alaska, USA); and Karymsky (Kamchatka, Russia). Each volcano studied had similar but unique signatures of pre-cursory and eruptive activity. This study has shown that this monitoring tool could be applied to a wide range of volcanoes and still produce useful and robust data. Our method deals specifically with the detection of small scale explosive activity. The method described here could be useful in an operational setting, especially at remote volcanoes that have the potential to impact populations, infrastructure, and the aviation community. A number of important factors will affect the validity of application of this method. They are: (1) the availability of a continuous and continually populated dataset; (2) appropriate and reasonable sensor resolutions; (3) a recorded history of the volcano's previous activity; and, if available, (4) some ground-based monitoring system. We aim to develop the method further to be able to capture and evaluate the frequency of other volcanic processes such as lava flows, phreatomagmatic eruptions and dome growth and collapse. The work shown here has served to illustrate the capability of this method and monitoring tool for use at remote, un-instrumented volcanoes.

  19. Too much slab waving in South America? Wet plumes as an alternative to flat slab steepening as the cause of back arc large volcanic provinces

    NASA Astrophysics Data System (ADS)

    Booker, J. R.; Burd, A. I.

    2013-12-01

    A widely held view is that the Nazca Slab under western S. America acts like a tattered flag waving in the wind: It is segmented and the dip angle of segments flap up and down with time. There are presently two flat segments - one under Peru and the other, the "Pampean" flat slab (centered around 31S) under central Chile and Argentina. Both are correlated with subduction of buoyant crust of oceanic aseismic ridges, complete cessation of Andean arc volcanism and very thick crust. It has been argued that the waxing and waning of flat subduction is responsible for much of the time variations in tectonics and volcanism up to 800 km east of the S. American coast for at least 100 MA. For instance, the back arc Payenia igneous plateau (35-38S) and the Somuncura igneous plateau (40.5-43S) are both thought to follow from the steepening of flat slabs at about 2 and 27 MA. Each flat slab existed for more than 5 MA. However, the case for the existence of these flat slabs rests heavily on volcanism with "arc signature" hundreds of km east of the modern volcanic arc at a time when an asthenospheric wedge would be in its final stages of being squeezed out of the space between the slab and the lithosphere. Arc signature can be summarized as the geochemical consequence of mantle melting in the presence of water. If there is a source of water in the mantle other than a shallow slab, the strongest argument for a flat slab dissolves. We have found two electrically conductive plumes rising from below 350 km near the top of the Mantle Transition Zone (MTZ). One passes through a window in the Pampean flat slab but does not penetrate the lithosphere. The other rises under Payenia. The maximum resistivity at the core of these plumes is less than 10 Ohm-m. Partial melt can explain such low resistivity, but will not be buoyant and rise from below 350 km. We propose that the low resistivity is more likely due to water and that we are seeing "wet plumes" that have been proposed to explain

  20. Active Volcanism on Io as Seen by Galileo SSI

    USGS Publications Warehouse

    McEwen, A.S.; Keszthelyi, L.; Geissler, P.; Simonelli, D.P.; Carr, M.H.; Johnson, T.V.; Klaasen, K.P.; Breneman, H.H.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Senske, D.A.; Belton, M.J.S.; Schubert, G.

    1998-01-01

    Active volcanism on Io has been monitored during the nominal Galileo satellite tour from mid 1996 through late 1997. The Solid State Imaging (SSI) experiment was able to observe many manifestations of this active volcanism, including (1) changes in the color and albedo of the surface, (2) active airborne plumes, and (3) glowing vents seen in eclipse. About 30 large-scale (tens of kilometers) surface changes are obvious from comparison of the SSI images to those acquired by Voyager in 1979. These include new pyroclastic deposits of several colors, bright and dark flows, and caldera-floor materials. There have also been significant surface changes on Io during the Galileo mission itself, such as a new 400-km-diameter dark pyroclastic deposit around Pillan Patera. While these surface changes are impressive, the number of large-scale changes observed in the four months between the Voyager 1 and Voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive. There are two reasons why this was not actually the case. First, it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years. Second, it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of Io's surface. The plume monitoring has revealed 10 active plumes, comparable to the 9 plumes observed by Voyager. One of these plumes was visible only in the first orbit and three became active in the later orbits. Only the Prometheus plume has been consistently active and easy to detect. Observations of the Pele plume have been particularly intriguing since it was detected only once by SSI, despite repeated attempts, but has been detected several times by the Hubble Space Telescope at 255 nm. Pele's plume is much taller (460 km) than during Voyager 1 (300 km) and much fainter at visible wavelengths. Prometheus-type plumes (50

  1. Chlorine Stable Isotopes to reveal contribution of magmatic chlorine in subduction zones: the case of the Kamchatka-Kuril and the Lesser Antilles Volcanic Arcs

    NASA Astrophysics Data System (ADS)

    Agrinier, Pierre; Shilobreeva, Svetlana; Bardoux, Gerard; Michel, Agnes; Maximov, Alexandr; Kalatcheva, Elena; Ryabinin, Gennady; Bonifacie, Magali

    2015-04-01

    By using the stable isotopes of chlorine (δ 37Cl), we have shown that magmatic chlorine (δ 37Cl ≤ -0.6 ‰ [1]) is different from surface chlorine (δ 37Cl ≈ 0 ‰ [1]) in hydrothermal system of Soufrière and Montagne Pelé from the young arc volcanic system of Lesser Antilles. First measurements on condensed chlorides from volcanic gases (e.g. [2], [3]) did not permitted to get sensible δ 37Cl values on degassed chlorine likely because chlorine isotopes are fractionated during the HClgas - chloride equilibrium in the fumaroles or during sampling artifacts. Therefore we have developed an alternative strategy based on the analysis of chloride in thermal springs, streams, sout{f}lowing on the flanks of the volcanoes. Due to the highly hydrophilic behavior of Cl, we hypothesize that thermal springs incorporate chlorine without fractionation of chlorine isotopes and might reflect the chlorine isotopic composition degassed by magmas [1]. Indeed Thermal spring with low δ 37Cl chlorides (≤ -0.6 perthousand{}) are linked with magmatic volatiles characters (3He ratio at 5 Ra at and δ 13C CO2 quad ≈ -3 perthousand{}). To go further in the potentiality of using the Chlorine isotopes to reveal contribution of magmatic chlorine in volcanic systems, we have started the survey of thermal springs and wells waters in the Kamchatka-Kuril volcanic mature Arc (on sites Mutnovsky, Paratunka, Nalychevsky, Khodutkinsky, Paramushir Island, identified by Taran, 2009 [4] for concentrations of chloride). Preliminary results show δ 37Cl values ranging from 0.5 to -0.2 ‰ and generally higher chloride concentrations. The δ 37Cl values are higher than the value recorded for the young arc volcanic system of lesser Antilles. At present moment very few negative δ 37Cl have been measured in the Kamchatka-Kuril volcanic mature Arc. [1] Li et al., 2015 EPSL in press. [2] Sharp et al. 2010 GCA. [3] Rizzo et al., 2013, EPSL, 371, 134. [4] Taran, 2009, GCA, 73, 1067

  2. Using VHF Lightning Observations to Monitor Explosive Volcanic Activity

    NASA Astrophysics Data System (ADS)

    Behnke, S. A.; Thomas, R. J.; McNutt, S. R.; Krehbiel, P. R.; Rison, W.; Edens, H. E.

    2011-12-01

    Lightning is an integral part of explosive volcanic eruptions and volcanic lightning measurements are a useful tool for volcano monitoring. VHF measurements of volcanic lightning can be made remotely, at distances of up to 100 km. A strategically placed network of 6 or more VHF ground stations could locate lightning in eruption columns from several regional volcanoes, and a minimum of two stations could be used to monitor a single volcano. Such a network would be particularly useful for detection or confirmation of explosive activity in situations where volcanoes are remotely located, and thus lack visual observations, or are not well instrumented with seismic networks. Furthermore, clouds are fully transparent to VHF signals, making lightning detection possible even when weather obscures visual observations. Recent VHF observations of volcanic lightning at Augustine Volcano (Alaska, USA, 2006), Redoubt Volcano (Alaska, USA, 2009) and Eyjafjallajökull (Iceland, 2010) have shown that two basic types of VHF signals are observed during volcanic eruptions, one of which is unique to volcanic activity. The unique signal, referred to as a 'continual RF' signal, was caused by very high rates of small 'vent discharges' occurring directly above the vent in the eruption column and was unlike any observations of lightning in meteorological thunderstorms. Vent discharges were observed to begin immediately following an explosive eruption. The second type of signal is from conventional lightning discharges, such as upward directed 'near-vent lightning' and isolated 'plume lightning.' Near-vent lightning was observed to begin 1-2 minutes following the onset of an explosive eruption while plume lightning began 4 or more minutes after the onset. At Redoubt the plume lightning occurred at such high rates that it rivaled lightning rates of supercell thunderstorms on the Great Plains of the United States. While both types of lightning signals can be used as indicators that explosive

  3. Fluid-melt partitioning of sulfur in differentiated arc magmas and the sulfur yield of explosive volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Masotta, M.; Keppler, H.; Chaudhari, A.

    2016-03-01

    The fluid-melt partitioning of sulfur (DSfluid/melt) in differentiated arc magmas has been experimentally investigated under oxidizing conditions (Re-ReO2 buffer) from 800 to 950 °C at 200 MPa. The starting glasses ranged in composition from trachyte to rhyolite and were synthesized targeting the composition of the residual melt formed after 10-60% crystallization of originally trachy-andesitic, dacitic and rhyodacitic magmas (Masotta and Keppler, 2015). Fluid compositions were determined both by mass balance and by Raman spectroscopy of fluid inclusions. DSfluid/melt increases exponentially with increasing melt differentiation, ranging from 2 to 15 in the trachytic melt, from 20 to 100 in the dacitic and rhyodacitic melts and from 100 to 120 in the rhyolitic melt. The variation of the DSfluid/melt is entirely controlled by the compositional variation of the silicate melt, with temperature having at most a minor effect within the range investigated. Experiments from this study were used together with data from the literature to calibrate the following model that allows predicting DSfluid/melt for oxidized arc magmas: where nbo/t is the non-bridging oxygen atoms per tetrahedron, ASI is the alumina saturation index, Al# and Ca# are two empirical compositional parameters calculated in molar units (Al # = XAl2O3/XSiO2 +XTiO2 +XAl2O3 and Ca # = XCaO/XNa2O +XK2O). The interplay between fluid-melt partitioning and anhydrite solubility determines the sulfur distribution among anhydrite, melt and fluid. At increasing melt polymerization, the exponential increase of the partition coefficient and the decrease of anhydrite solubility favor the accumulation of sulfur either in the fluid phase or as anhydrite. On the other hand, the higher anhydrite solubility and lower partition coefficient for less polymerized melts favor the retention of sulfur in the melt. At equilibrium conditions, these effects yield a maximum of the sulfur fraction in the fluid phase for slightly

  4. Sensor web enables rapid response to volcanic activity

    USGS Publications Warehouse

    Davies, Ashley G.; Chien, Steve; Wright, Robert; Miklius, Asta; Kyle, Philip R.; Welsh, Matt; Johnson, Jeffrey B.; Tran, Daniel; Schaffer, Steven R.; Sherwood, Robert

    2006-01-01

    Rapid response to the onset of volcanic activity allows for the early assessment of hazard and risk [Tilling, 1989]. Data from remote volcanoes and volcanoes in countries with poor communication infrastructure can only be obtained via remote sensing [Harris et al., 2000]. By linking notifications of activity from ground-based and spacebased systems, these volcanoes can be monitored when they erupt.Over the last 18 months, NASA's Jet Propulsion Laboratory (JPL) has implemented a Volcano Sensor Web (VSW) in which data from ground-based and space-based sensors that detect current volcanic activity are used to automatically trigger the NASA Earth Observing 1 (EO-1) spacecraft to make highspatial-resolution observations of these volcanoes.

  5. Numerical Tsunami Hazard Assessment of the Only Active Lesser Antilles Arc Submarine Volcano: Kick 'em Jenny.

    NASA Astrophysics Data System (ADS)

    Dondin, F. J. Y.; Dorville, J. F. M.; Robertson, R. E. A.

    2015-12-01

    The Lesser Antilles Volcanic Arc has potentially been hit by prehistorical regional tsunamis generated by voluminous volcanic landslides (volume > 1 km3) among the 53 events recognized so far. No field evidence of these tsunamis are found in the vincity of the sources. Such a scenario taking place nowadays would trigger hazardous tsunami waves bearing potentially catastrophic consequences for the closest islands and regional offshore oil platforms.Here we applied a complete hazard assessment method on the only active submarine volcano of the arc Kick 'em Jenny (KeJ). KeJ is the southernmost edifice with recognized associated volcanic landslide deposits. From the three identified landslide episodes one is associated with a collapse volume ca. 4.4 km3. Numerical simulations considering a single pulse collapse revealed that this episode would have produced a regional tsunami. An edifice current volume estimate is ca. 1.5 km3.Previous study exists in relationship to assessment of regional tsunami hazard related to shoreline surface elevation (run-up) in the case of a potential flank collapse scenario at KeJ. However this assessment was based on inferred volume of collapse material. We aim to firstly quantify potential initial volumes of collapse material using relative slope instability analysis (RSIA); secondly to assess first order run-ups and maximum inland inundation distance for Barbados and Trinidad and Tobago, i.e. two important economic centers of the Lesser Antilles. In this framework we present for seven geomechanical models tested in the RSIA step maps of critical failure surface associated with factor of stability (Fs) for twelve sectors of 30° each; then we introduce maps of expected potential run-ups (run-up × the probability of failure at a sector) at the shoreline.The RSIA evaluates critical potential failure surface associated with Fs <1 as compared to areas of deficit/surplus of mass/volume identified on the volcanic edifice using (VolcanoFit 2

  6. Active faulting induced by the slip partitioning in the Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, Frédérique; Feuillet, Nathalie

    2010-05-01

    AGUADOMAR marine cruise data acquired 11 years ago allowed us to identified and map two main sets of active faults within the Lesser Antilles arc (Feuillet et al., 2002; 2004). The faults belonging to the first set, such as Morne-Piton in Guadeloupe, bound up to 100km-long and 50km-wide arc-perpendicular graben or half graben that disrupt the fore-arc reef platforms. The faults of the second set form right-stepping en echelon arrays, accommodating left-lateral slip along the inner, volcanic islands. The two fault systems form a sinistral horsetail east of the tip of the left-lateral Puerto Rico fault zone that takes up the trench-parallel component of convergence between the North-American and Caribbean plates west of the Anegada passage. In other words, they together accommodate large-scale slip partitioning along the northeastern arc, consistent with recent GPS measurements (Lopez et al., 2006). These intraplate faults are responsible for a part of the shallow seismicity in the arc and have produce damaging historical earthquakes. Two magnitude 6.3 events occurred in the last 25 years along the inner en echelon faults, the last one on November 21 2004 in Les Saintes in the Guadeloupe archipelago. To better constrain the seismic hazard related to the inner arc faults and image the ruptures and effects on the seafloor of Les Saintes 2004 earthquake, we acquired new marine data between 23 February and 25 March 2009 aboard the French R/V le Suroît during the GWADASEIS cruise. We present here the data (high-resolution 72 channel and very high-resolution chirp 3.5 khz seismic reflection profiles, EM300 multibeam bathymetry, Küllenberg coring and SAR imagery) and the first results. We identified, mapped and characterized in detail several normal to oblique fault systems between Martinique and Saba. They offset the seafloor by several hundred meters and crosscut all active volcanoes, among them Nevis Peak, Soufriere Hills, Soufriere de Guadeloupe and Montagne Pel

  7. Stratospheric ozone, solar activity and volcanism

    NASA Astrophysics Data System (ADS)

    Komitov, Boris; Stoychev, Konstantin

    The aim of this study is to investigate the long-term (multiannual) variations of the total ozone content (TOC) on the base of TOMS instrument measurements on the board of Nimbus-7 satellite for the period 1979 -- 1993 AD. The total effects of the solar activity influence over stratosphere ozone has been investigated by using multiple regression analysis. The monthly radio-index F10.7, the cosmic rays neutron flux, the geomagnetic index Ap and the number of GOES x-ray X-class flares have been used as solar or solar-modulated parameters as predictors in the model. The global mean-monthly TOC-parameter has been used as a predictant. It has been found that the coefficient of correlation of the model between TOC and above-mentioned solar and geomagnetic factors is about 0.544. Thus the corresponding factor variance is about 37%. The results calculated by the model have been removed from the original TOC data. It has been found out that during the first 12 years since 1979 the downward trend is predominantly caused by the solar and solar-modulated processes. However during the remaining 3 years after 1990 the slope of the negative trend has been essentially increased. This phenomenon could only be explained by some catastrophic event. Most probably such one is the Pinatubo volcano eruption in June, 1991. An evidence for the possibility that the last one is caused by trigger effect from the extremely high solar flare activity in May -- June 1991, is given.

  8. Is uplift of volcano clusters in the Tohoku Volcanic Arc, Japan, driven by magma accumulation in hot zones? A geodynamic modeling study

    NASA Astrophysics Data System (ADS)

    George, Ophelia A.; Malservisi, Rocco; Govers, Rob; Connor, Charles B.; Connor, Laura J.

    2016-06-01

    In many volcanic arcs, the rate of tectonic uplift cannot be explained by lithospheric plate motion alone but may be associated with dynamic uplift. Buoyant forces associated with underplated magma bodies lift the upper crust and leads to relatively high rates of topographic change. One such region is northern Honshu, Japan, where Quaternary volcano clusters are spatially associated with uplifted crust and isostatic gravity anomalies. Axisymmetric inversion of Bouguer gravity data for the Sengan volcano cluster shows that these gravity anomalies can be modeled by 30 km radius bodies emplaced at ˜15 km depth. Axisymmetric, finite element models, generated using GTECTON, of a layered Earth representative of the Tohoku crust indicate that the deformation of these midcrustal intrusions produces elevated topography on the surface directly above the intrusion that is bounded by a shallow peripheral trough. The wavelengths of vertical deformation produced by these bodies are sensitive to the thickness of the models' elastic layer and relatively insensitive to the models' rheology. This suggests that the amplitude of the vertical deformation represents a trade-off between the size of the intrusion and the thickness of the elastic layer and is less strongly influenced by the rheology of the lithosphere into which the bodies are emplaced. Our results are consistent with hot zone and hot finger models for the arc and indicate that Tohoku Volcanic Arc features such as gravity anomalies and uplifted basement are related to crustal magma intrusions and hot zones rather than directly related to mantle processes.

  9. Esmeralda Bank: Geochemistry of an active submarine volcano in the Mariana Island Arc

    NASA Astrophysics Data System (ADS)

    Stern, Robert J.; Bibee, L. D.

    1984-05-01

    Esmeralda Bank is the southernmost active volcano in the Izu-Volcano-Mariana Arc. This submarine volcano is one of the most active vents in the western Pacific. It has a total volume of about 27 km3, rising to within 30 m of sea level. Two dredge hauls from Esmeralda recovered fresh, nearly aphyric, vesicular basalts and basaltic andesites and minor basaltic vitrophyre. These samples reflect uniform yet unusual major and trace element chemistries. Mean abundances of TiO2 (1.3%) and FeO* (12.6%) are higher and CaO (9.2%) and Al2O3 (15.1%) are lower than rocks of similar silica content from other active Mariana Arc volcanoes. Mean incompatible element ratios K/Rb (488) and K/Ba (29) of Esmeralda rocks are indistinguishable from those of other Mariana Arc volcanoes. On a Ti-Zr plot, Esmeralda samples plot in the field of oceanic basalts while other Mariana Arc volcanic rocks plot in the field for island arcs. Incompatible element ratios K/Rb and K/Ba and isotopic compositions of Sr (87Sr/86Sr=0.70342 0.70348), Nd (ɛND=+7.6 to +8.1), and O(δ18O=+5.8 to +5.9) are incompatible with models calling for the Esmeralda source to include appreciable contributions from pelagic sediments or fresh or altered abyssal tholeiite from subduction zone melting. Instead, incompatible element and isotopic ratios of Esmeralda rocks are similar to those of intra-plate oceanic islands or “hot-spot” volcanoes in general and Kilauean tholeiites in particular. The conclusion that the source for Esmeralda lavas is an ocean-island type mantle reservoir is preferred. Esmeralda Bank rare earth element patterns are inconsistent with models calling for residual garnet in the source region, but are adequately modelled by 7 10% equilibrium partial melting of spinel lherzolite. This is supported by consideration of the results of melting experiments at 20 kbars, 1,150° C with CO2 and H2O as important volatile components. These experiments further indicate that low MgO (4.1%), MgO/FeO*(0.25) and

  10. Recognizing subtle evidence for silicic magma derivation from petrochemically-similar arc crust: Isotopic and chemical evidence for the bimodal volcanic series of Gorely Volcanic Center, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Seligman, A. N.; Bindeman, I. N.; Ellis, B. S.; Ponomareva, V.; Leonov, V.

    2012-12-01

    The Kamchatka Peninsula is home to some of the most prolific subduction related volcanic activity in the world. Gorely caldera and its central volcano are located in the rear of its currently active Eastern Volcanic Front. Recent work determined the presence of explosive ignimbrite eruptions sourced from Gorely volcano during the Pleistocene. We studied 32 eruptive units, including tephrochronologically-dated Holocene tephra, stratigraphically-arranged ignimbrites, as well as pre- and post-caldera lavas. We analyzed oxygen isotope ratios of pyroxene and plagioclase grains by laser fluorination, and major and trace element compositions of whole rocks. In addition, we determined 87Sr/86Sr and 143Nd/144Nd ratios of caldera-forming ignimbrite eruptions. Chemical compositions show that Gorely eruptive units range from basalt to basaltic andesite in the "Pra-Gorely" stages prior to caldera formation and the modern Gorely stages forming its current edifice. In contrast, eruptive material from earlier ignimbrites exposed at Opasny Ravine consists primarily of dacite. Whole rock analyses for Gorely indicate that silicic rocks and ignimbrites volumetrically dominate all other products, forming separate bimodal peaks in our SiO2-frequency diagram. In addition, trace element concentrations and ratios define two trends, one for more silicic and another for more mafic material. δ18Omelt values range from a low of 4.85 up to 6.22‰, where the lowest value was found in the last caldera forming eruption, suggesting incorporation of hydrothermally-altered material from earlier eruptions. 87Sr/86Sr and 143Nd/144Nd ratios range from 0.70328 to 0.70351 and from 0.51303 to 0.51309 respectively, with higher and more diverse values being characteristic of earlier ignimbrite units; again suggesting incorporation of surrounding crustal material. In contrast to these results, MELTS modeling using a variety of likely primitive basalts from Gorely shows it is possible to obtain silicic

  11. Active fault systems and tectono-topographic configuration of the central Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Szynkaruk, Ewa; Graduño-Monroy, Víctor Hugo; Bocco, Gerardo

    2004-07-01

    The central Trans-Mexican Volcanic Belt (TMVB) reflects the interplay between three regional fault systems: the NNW-SSE to NW-SE striking Taxco-Querétaro fault system, the NE-SW striking system, and the E-W striking Morelia-Acambay fault system. The latter is the youngest and consists of fault scarps up to 500 m high, whose formation caused structural and morphological reorganization of the region. In this paper, we investigate possible activity of the three systems within the central TMVB, and assess the role that they play in controlling the tectono-topographic configuration of the area. Our study is based on DEM-derived morphometric maps, longitudinal river profiles, geomorphologic mapping, and structural field data concerning recent faulting. We find that all three regional fault systems are active within the central TMVB, possibly with different displacement rates and/or type of motion; and that NNW-SSE and NE-SW striking faults control the major tectono-topographic elements that build up the region, which are being re-shaped by E-W striking faults. We also find that tectonic information can be deciphered from the topography of the youthful volcanic arc in question, regardless its complexity.

  12. Silicic volcanism in Iceland: Composition and distribution within the active volcanic zones

    NASA Astrophysics Data System (ADS)

    Jónasson, Kristján

    2007-01-01

    Silicic volcanic rocks within the active volcanic zones of Iceland are mainly confined to central volcanoes. The volcanic zones of Iceland can be divided into rift zones and flank zones. Each of these zones contains several central volcanoes, most of which have produced minor amounts of silicic rocks. The silicic rocks occur as lavas and domes or as tephra layers, welded tuffs and ignimbrites, formed both in effusive and explosive eruptions. They tend to be glassy or very fine-grained, containing small amounts of phenocrysts. Plagioclase (andesine-oligoclase), anorthoclase or occasionally sanidine coexist with minerals such as augite, fayalite, pigeonite, orthopyroxene and magnetite. Quartz phenocrysts are exceedingly rare. Zoning of phenocrysts is limited and the pattern is variable. A set of 90 samples representing all active central volcanoes that have erupted silicic rocks was analysed for major- and trace-elements. The silicic rocks can be classified as dacites, trachytes, low-alkali rhyolites and alkalic rhyolites. Some of the trachytes and alkalic rhyolites are peralkaline (mostly comenditic). Trachytes and alkalic rhyolites are only found within the flank zones, while dacites and low-alkali rhyolites are mostly confined to the rift zones. The Icelandic rhyolites plot close to the thermal minimum in the "granite" system, while dacites and trachytes plot within the plagioclase field and towards the alkali feldspar temperature minimum. The silicic rocks are relatively Fe-rich and Ca-poor indicating low water pressure in the source. Trace element concentrations follow similar patterns in most central volcanoes. Exceptions are Torfajökull where silicic rocks display a negative correlation of Ba to Th and unusually high Th-contents, and the western flank zone where Ba-concentrations are highly variable. The ratios of different high field-strength elements are generally similar within each central volcano or region, which probably reflects different ratios in the

  13. Nitrogen-Helium-Argon and Nitrogen Isotope Relationships in Geothermal Fluids from the Central American Volcanic Arc: Mapping Subducted and Crustal Contributions to Volatile Output

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Sharp, Z.; Hilton, D. R.

    2001-12-01

    Volcanic arcs are locations where elements are recycled from the subducted slab, the mantle wedge and the overlying arc crust to the atmosphere and hydrosphere. A fundamental aim of arc-related studies and the MARGINS initiative is to quantify this flux and compare it with subduction zone parameters, such as sediment compositions and subduction rates. As part of the Central American arc study, we report N2, He, and Ar abundance relationships and N-isotope ratios for 7 volcanic centers in Guatemala to complement on-going studies in Costa Rica (see previous abstract). In Guatemala, the arc crust is thicker and older than in Costa Rica and the entire sedimentary sequence on the down-going plate is likely to contribute to the slab flux. The Guatemalan volcanic centers of Amatitlan-Pacaya, Fuego, Moyuta, Tecuamburro, Amatitlan, Zunil and San Marcos have N2/He ratios ranging from 2200 to 8100, typical for arc-related fluids. N2/Ar ratios (40 - 500) and the high N2/He indicate addition of N2 from subducted sediments or arc crust to a mantle derived component (N2/He < 200). The high N2/He ratios of Guatemala, are in contrast to the mantle-derived N2/He ratios measured at Poas, Costa Rica. Nitrogen isotope ratios for the Guatemalan volcanic centers range from δ 15N = +1.0‰ for San Marcos to +5.8‰ for Fuego (δ 15Nair = 0.0‰ ), indicating a sedimentary nitrogen signature. The mantle-derived N2/He ratio for Poas is consistent with a more mantle-like δ 15N of - 1.0‰ . In Guatemala, the highest 3He/4He ratios (7.6 for Pacaya and 7.3 RA for Fuego) correlate with the lowest N2/He ratios (1500 and 2100) and high δ 15N values (+3.8‰ and +5.8‰ ). Lower 3He/4He ratios for Zunil (4.7 RA) and San Marcos (2.2 RA) correlate with N2/He of 5000 and 6600, and lower δ 15N values of +2.3‰ and +1.0‰ , respectively. These N-He relationships suggest that the nitrogen at Pacaya and Fuego is primarily of subducted organic sedimentary origin, with only minor crustal

  14. Across-arc variations of isotope and trace element compositions from Quaternary basaltic volcanic rocks in northeastern Japan: Implications for interaction between subducted oceanic slab and mantle wedge

    NASA Astrophysics Data System (ADS)

    Shibata, Tomoyuki; Nakamura, Eizo

    1997-04-01

    Isotopic compositions of Pb, Sr, and Nd and concentrations of trace elements were determined for Quaternary island arc basaltic rocks from northeastern Japan. Sr and Pb isotopic ratios decrease, and Nd isotopic ratios increase from the volcanic front toward the back arc. The isotopic compositions nearest the back arc side are nearly identical to those of mid-ocean ridge basalt (MORB). The high field strength elements and heavy rare earth elements show homogeneous and MORB-like characteristics. These observations indicate that the mantle wedge beneath northeastern Japan originally had a MORB-type mantle composition that was homogeneous across the arc. Pb isotope compositions show a mixing relationship between mantle wedge and oceanic sediments reflecting the introduction of subduction component into the mantle wedge, Across-arc isotopic variations were caused by interaction between MORB-type mantle wedge and the subducting slab, and the amount of subduction component correlates with the depth to the slab. The isotopic compositions of subduction component are expressed by bulk mixing of 15 wt % of oceanic sediment and 85 wt % of altered MORB. Inversion analyses of isotopic compositions using two-component mixing relationships show that the Sr/Nd and Pb/Nd ratios in subduction component decrease with increasing depth to the slab, while the Sr/Pb ratio is nearly constant. These changes can be explained only by a preferential discharge of the elements into the wedge mantle associated with continuous dehydration of the subducting slab. The present study further demonstrates that a very wide range of isotopic and elemental compositions in island arc magmas is a consequence of the interaction between subducting slab and mantle wedge without the involvement of an oceanic island basalts component, and the slab can carry water and supply a subduction component as a fluid to the overlying mantle wedge to depths exceeding 150 km.

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

    NASA Astrophysics Data System (ADS)

    Carter, Laura B.; Dasgupta, Rajdeep

    2015-10-01

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

  16. Jovian dust streams: A monitor of Io's volcanic plume activity

    USGS Publications Warehouse

    Kruger, H.; Geissler, P.; Horanyi, M.; Graps, A.L.; Kempf, S.; Srama, R.; Moragas-Klostermeyer, G.; Moissl, R.; Johnson, T.V.; Grun, E.

    2003-01-01

    Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s-1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10-3 and 10 kg s-1, and is typically in the range of 0.1 to 1 kg s-1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes. Copyright 2003 by the American Geophysical Union.

  17. Relationship between Jovian Hectometric Attenuation Lanes And Io Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Spencer, J. R.; Stansberry, J. A.

    2001-01-01

    Within the Galileo plasma wave instrument data a narrow (in frequency) attenuation band is seen in the hectometric (HOM) emission that varies in frequency with system III longitude. This attenuation lane is believed to be the result of near-grazing incidence or coherent scattering of radio emission near the outer edge of the Io torus, i.e., when the ray path is nearly tangent to an L shell containing the Io flux tube. Such a process should, therefore, be enhanced when the Io volcanic activity is increased and the Io flux tube has enhanced density. We have performed a systematic study of the existing Galileo radio emission data in an effort to determine the phenomenology and frequency of occurrence of the attenuation lanes and the association, if any, with published volcanic activity of Io. Our results indicate that the attenuation lanes are present almost all of the time but are enhanced on occasion. The best examples of attenuation lanes occur when Galileo is within approximately 65 R(sub J) of Jupiter and thus are probably more apparent because of the increased signal-to-noise ratio of the radio receivers. The lack of continuous monitoring of Io activity and the lack of known activity on the anti-Earthward side of Io are problematic and make detailed correlation with radio emission very difficult at this time. Nevertheless, if the data are displayed for periods when the spacecraft is within 65 R(sub J) (i.e., for each perijove pass), then the highest-contrast lanes occur on most passes when the Io volcanic activity is also high for that pass. These results support our current understanding of attenuation lane formation and suggest that future efforts can be made to better understand the interaction of HOM emission with the Io flux tube.

  18. The search for active release of volcanic gases on Mars

    NASA Astrophysics Data System (ADS)

    Khayat, Alain; Villanueva, Geronimo; Mumma, Michael; Tokunaga, Alan

    2015-11-01

    The study of planetary atmospheres by means of spectroscopy is important for understanding their origin and evolution. The presence of short-lived trace gases in the martian atmosphere would imply recent production, for example, by ongoing geologic activity. On Earth, sulfur dioxide (SO2), sulfur monoxide (SO) and hydrogen sulfide (H2S) are the main sulfur-bearing gases released during volcanic outgassing. Carbonyl sulfide (OCS), also released from some volcanoes on Earth (e.g., Erebus and Nyiragongo), could be formed by reactions involving SO2 or H2S inside magma chambers. We carried out the first ground-based, semi-simultaneous, multi-band and multi-species search for such gases above the Tharsis and Syrtis volcanic regions on Mars. The submillimeter search extended between 23 November 2011 and 13 May 2012 which corresponded to Mars’ mid Northern Spring and early Northern Summer seasons (Ls = 34-110°). The strong submillimeter rotational transitions of SO2, SO and H2S were targeted using the high-resolution heterodyne receiver (aka Barney) on the Caltech Submillimeter Observatory. We reached sensitivities sufficient to detect a volcanic release on Mars that is 4% of the SO2 released continuously from Kilauea volcano in Hawaii, or 5% that of the Masaya volcano in Nicaragua. The infrared search covered OCS in its combination band (ν2+ν3) at 3.42 μm at two successive Mars years, during Mars’ late Northern Spring and mid Northern Summer seasons, spanning Ls= 43º and Ls= 147º. The targeted volcanic districts were observed during the two intervals, 14 Dec. 2011 to 6 Jan. 2012 in the first year, and 30 May 2014 to 16 June 2014 in the second year, using the high resolution infrared spectrometer (CSHELL) on NASA’s Infrared Telescope Facility (NASA/IRTF). We will present our results and discuss their implications for current volcanic outgassing activity on the red planet. We gratefully acknowledge support from the NASA Planetary Astronomy Program under NASA

  19. Observations on Multi-Slug Activity - Implications for Volcanic Processes

    NASA Astrophysics Data System (ADS)

    Pering, T. D.; McGonigle, A. J. S.; James, M. R.; Lane, S. J.; Capponi, A.; Tamburello, G.; Aiuppa, A.

    2014-12-01

    The study of single gas slugs in volcanic conduits has received a large amount of focus within the literature. However, the more complex behaviour associated with the rise and burst of multiple slugs has yet to be considered in detail in a volcanic context. Here we combine observations and analyses of such activity using a three-pronged approach consisting of existing gas mass data collected during rapid slug driven activity at Mt. Etna, scaled laboratory analogue experiments, and computer simulations using the Ansys Fluent® fluid dynamics software. Particular focus was applied to the process of coalescence and wake capture during slug expansion and rise. The results indicate a variety of potential features and relationships, including: promotion of coalescence at distances further than predicted wake lengths, approximate maximum gas volume fraction and minimum magma viscosity values for the occurrence of stable multi-slug activity, and in the laboratory regimes a series of linear trends are associated with overall gas volume fraction and burst volume. A previously observed phenomenon at Mt. Etna, whereby larger slug bursting events are subject to a longer repose period prior to the following event, than smaller events, is also evident in the lab setting. By combining all acquired and modelled data, we derive an approximate relation, using existing formulae for slug base rise speed (Viana et al. 2003) and wake length (Campos and Guedes de Carvalho, 1988), to describe a minimum repose period which is likely to follow the burst of a slug at the surface. The outlined work has significant fluid dynamic implications for possible magma and conduit properties which can allow multi-slug activity at volcanic targets.

  20. Temporal and geochemical constraints on active volcanism in southeastern Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Catalano, J. P.; Baldwin, S.; Fitzgerald, P. G.; Webb, L. E.; Hollocher, K.

    2010-12-01

    Active volcanism in southeastern Papua New Guinea occurs on the Papuan Peninsula (Mt. Lamington and Mt. Victory), in the Woodlark Rift (Dobu Island, SE Goodenough Island, and Western Fergusson Island), and in the Woodlark Basin. In the Woodlark Basin seafloor spreading is active and decompression melting of the mantle produces basalts. However, the cause of volcanism on the Papuan Peninsula and immediately west of active seafloor spreading rift tip in the Woodlark Basin is controversial. Previous studies have suggested active volcanism there results from 1) southward subduction of Solomon Sea lithosphere at the Trobriand Trough or 2) decompression melting as the lithosphere is extended and eventually ruptures. To evaluate these possibilities 20 samples were collected from a bimodal basalt-rhyolite suite in the D’Entrecasteaux Islands approximately 80 km west of the sea floor spreading rift tip. Siliceous ash flow tuffs on Dobu Island, Sanaroa Island, and Eastern Fergusson Island consist of sanidine/anorthoclase + Fe/Ti oxides (illmenite/ magnetite) ± quartz ± nepheline ± clinopyroxene ± xenocrystic olivine. Sanidine and K-feldspar from these ash flow tuffs yielded flat age spectra with 40Ar/39Ar isochron ages of 0.008 ± 0.002 Ma and 0.553 ± 0.001 Ma. ICP-MS trace and REE geochemistry on felsic rocks from Dobu Island and Eastern Fergusson Island yielded multi-element diagrams with enriched incompatible elements, and corresponding negative Nb, Sr, Eu, and Ti anomalies. In contrast, mafic volcanics from SE Goodenough Island are comprised of plagioclase + olivine + Fe/Ti oxides ± orthopyroxene ± clinopyroxene ± hornblende ± biotite. Biotite yielded a 40Ar/39Ar isochron age of 0.376 ± 0.05 Ma. MORB-normalized multi-element diagrams of mafic rocks from SE Goodenough Island are LREE-enriched patterns with negative Nb and positive Sr anomalies. In comparison, multi-element diagrams from previous work on mafic rocks from the New Britain arc to the north also

  1. Thyroid cancer incidence in relation to volcanic activity

    SciTech Connect

    Arnbjoernsson, E.A.; Arnbjoernsson, A.O.; Olafsson, A.

    1986-01-01

    Environmental or genetic factors are sought to explain the high incidence of thyroid cancer in Iceland. At present, it is impossible to cite any environmental factor, particularly one related to the volcanic activity in the country, which could explain the high incidence of thyroid cancer in Iceland. However, the thyroid gland in Icelanders is very small due to the high intake of iodine from seafood. It is, therefore, easier for physicians to find thyroid tumors. Furthermore, genetic factors are very likely to be of great importance in the small, isolated island of Iceland.

  2. The relationship between eruptive activity, flank collapse, and sea level at volcanic islands: A long-term (>1 Ma) record offshore Montserrat, Lesser Antilles

    NASA Astrophysics Data System (ADS)

    Coussens, Maya; Wall-Palmer, Deborah; Talling, Peter. J.; Watt, Sebastian. F. L.; Cassidy, Michael; Jutzeler, Martin; Clare, Michael A.; Hunt, James. E.; Manga, Michael; Gernon, Thomas. M.; Palmer, Martin. R.; Hatter, Stuart. J.; Boudon, Georges; Endo, Daisuke; Fujinawa, Akihiko; Hatfield, Robert; Hornbach, Matthew. J.; Ishizuka, Osamu; Kataoka, Kyoko; Le Friant, Anne; Maeno, Fukashi; McCanta, Molly; Stinton, Adam. J.

    2016-07-01

    Hole U1395B, drilled southeast of Montserrat during Integrated Ocean Drilling Program Expedition 340, provides a long (>1 Ma) and detailed record of eruptive and mass-wasting events (>130 discrete events). This record can be used to explore the temporal evolution in volcanic activity and landslides at an arc volcano. Analysis of tephra fall and volcaniclastic turbidite deposits in the drill cores reveals three heightened periods of volcanic activity on the island of Montserrat (˜930 to ˜900 ka, ˜810 to ˜760 ka, and ˜190 to ˜120 ka) that coincide with periods of increased volcano instability and mass-wasting. The youngest of these periods marks the peak in activity at the Soufrière Hills volcano. The largest flank collapse of this volcano (˜130 ka) occurred toward the end of this period, and two younger landslides also occurred during a period of relatively elevated volcanism. These three landslides represent the only large (>0.3 km3) flank collapses of the Soufrière Hills edifice, and their timing also coincides with periods of rapid sea level rise (>5 m/ka). Available age data from other island arc volcanoes suggest a general correlation between the timing of large landslides and periods of rapid sea level rise, but this is not observed for volcanoes in intraplate ocean settings. We thus infer that rapid sea level rise may modulate the timing of collapse at island arc volcanoes, but not in larger ocean-island settings.

  3. Seismicity and active tectonics at Coloumbo Reef (Aegean Sea, Greece): Monitoring an active volcano at Santorini Volcanic Center using a temporary seismic network

    NASA Astrophysics Data System (ADS)

    Dimitriadis, I.; Karagianni, E.; Panagiotopoulos, D.; Papazachos, C.; Hatzidimitriou, P.; Bohnhoff, M.; Rische, M.; Meier, T.

    2009-02-01

    The volcanic center of Santorini Island is the most active volcano of the southern Aegean volcanic arc. Α dense seismic array consisting of fourteen portable broadband seismological stations has been deployed in order to monitor and study the seismo-volcanic activity at the broader area of the Santorini volcanic center between March 2003 and September 2003. Additional recordings from a neighbouring larger scale temporary network (CYCNET) were also used for the relocation of more than 240 earthquakes recorded by both arrays. A double-difference relocation technique was used, in order to obtain optimal focal parameters for the best-constrained earthquakes. The results indicate that the seismic activity of the Santorini volcanic center is strongly associated with the tectonic regime of the broader Southern Aegean Sea area as well as with the volcanic processes. The main cluster of the epicenters is located at the Coloumbo Reef, a submarine volcano of the volcanic system of Santorini Islands. A smaller cluster of events is located near the Anydros Islet, aligned in a NE-SW direction, running almost along the main tectonic feature of the area under study, the Santorini-Amorgos Fault Zone. In contrast, the main Santorini Island caldera is characterized by the almost complete absence of seismicity. This contrast is in very good agreement with recent volcanological and marine studies, with the Coloumbo volcanic center showing an intense high-temperature hydrothermal activity, in comparison to the corresponding low-level activity of the Santorini caldera. The high-resolution hypocentral relocations present a clear view of the volcanic submarine structure at the Coloumbo Reef, showing that the main seismic activity is located within a very narrow vertical column, mainly at depths between 6 and 9 km. The focal mechanisms of the best-located events show that the cluster at the Coloumbo Reef is associated with the "Kameni-Coloumbo Fracture Zone", which corresponds to the

  4. Comparative Study of Subduction Zone Thermal Structure: Implications for Slab Dehydration and Fluid Supply for Mantle Wedge Serpentinization and Arc Volcanism

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; He, J.; Hyndman, R. D.

    2007-12-01

    Aqueous fluid from the dehydrating slab is critical to the processes of forearc mantle wedge serpentinization and arc volcanism. Its availability depends mainly on the thermal structure of the subducting slab, which is strongly controlled by the age of the slab and mantle wedge flow. In this study, we develop 2-D steady state numerical thermal models for a number of subduction zones to investigate how the thermal structure affects the fluid supply. Subduction zones investigated in this comparative study include Cascadia, Chile, Colombia-Ecuador, Costa Rica, Hikurangi, Kermadec, Mariana, Mexico, Nankai, NE Japan, and Sumatra. Geophysical and geological observations indicate that the shallow part of the forearc mantle wedge is decoupled from the subducting slab and does not participate in the wedge flow. The maximum depth of the slab-mantle wedge decoupling is one of the most important parameters controlling the subduction zone thermal structure. In our models, the depth of downdip transition from decoupling to coupling is constrained by surface heat flow and the location of the arc, beneath which the mantle wedge temperature is required to be greater than 1200°C. We find that the optimal transition depth for most subduction zones is in the range of 70 to 90 km; too shallow a transition will over-predict the forearc heat flow, and too deep a transition will under-predict the mantle temperature beneath the arc. The model results show that, for all subduction zones, the stagnant part of the forearc mantle wedge is sufficiently cold to allow serpentine to be stable, but the actual degree of its serpentinization should differ between different subduction zones depending on the availability of fluids. For subduction zones with a young and warm slab such as Cascadia and Nankai, dehydration of the subducting crust peaks at depths shallower than the decoupling-coupling transition depth and therefore provides ample fluid to serpentinize the overlying stagnant mantle wedge

  5. Comparative Study of Subduction Zone Thermal Structure: Implications for Slab Dehydration and Fluid Supply for Mantle Wedge Serpentinization and Arc Volcanism

    NASA Astrophysics Data System (ADS)

    Wada, I.; Wang, K.; He, J.; Hyndman, R. D.

    2004-12-01

    Aqueous fluid from the dehydrating slab is critical to the processes of forearc mantle wedge serpentinization and arc volcanism. Its availability depends mainly on the thermal structure of the subducting slab, which is strongly controlled by the age of the slab and mantle wedge flow. In this study, we develop 2-D steady state numerical thermal models for a number of subduction zones to investigate how the thermal structure affects the fluid supply. Subduction zones investigated in this comparative study include Cascadia, Chile, Colombia-Ecuador, Costa Rica, Hikurangi, Kermadec, Mariana, Mexico, Nankai, NE Japan, and Sumatra. Geophysical and geological observations indicate that the shallow part of the forearc mantle wedge is decoupled from the subducting slab and does not participate in the wedge flow. The maximum depth of the slab-mantle wedge decoupling is one of the most important parameters controlling the subduction zone thermal structure. In our models, the depth of downdip transition from decoupling to coupling is constrained by surface heat flow and the location of the arc, beneath which the mantle wedge temperature is required to be greater than 1200°C. We find that the optimal transition depth for most subduction zones is in the range of 70 to 90 km; too shallow a transition will over-predict the forearc heat flow, and too deep a transition will under-predict the mantle temperature beneath the arc. The model results show that, for all subduction zones, the stagnant part of the forearc mantle wedge is sufficiently cold to allow serpentine to be stable, but the actual degree of its serpentinization should differ between different subduction zones depending on the availability of fluids. For subduction zones with a young and warm slab such as Cascadia and Nankai, dehydration of the subducting crust peaks at depths shallower than the decoupling-coupling transition depth and therefore provides ample fluid to serpentinize the overlying stagnant mantle wedge

  6. Microgravity change as a precursor to volcanic activity

    NASA Astrophysics Data System (ADS)

    Rymer, Hazel

    1994-07-01

    In recent decades, systematic microgravity studies over some 20 active volcanoes in Central America, Iceland, Italy, Japan, Papua New Guinea and the USA have provided valuable data on sub-surface mass redistribution associated with volcanic activity. Concurrent data on ground deformation are essential to the unambiguous interpretation of gravity changes. In some instances, gravity and elevation vary along the free-air or Bouguer gradients, implying that there has been no sub-surface mass or density change, respectively. Where there are residual gravity changes after correction for elevation changes, magma movements in sub-surface chambers, feeder systems, vents and fissures (dykes) or water table variations are proposed. Although detailed interpretations depend on local circumstances and the calculations depend on source geometry, in general, the smallest residual gravity changes are associated with eruptions from volatile-poor basaltic vents and at extensional rift zones, whereas the highest residual values occur at explosive, subduction-related stratocones built from volatile-rich andesitic magma. The most intriguing, yet difficult, data to interpret derive from large-volume, infrequently erupting volcanic systems where caldera unrest is now becoming well documented and the ultimate hazards are most severe. Mass increases during inflation followed by limited mass loss during subsequent deflation typify these structures.

  7. Temporal Geochemical Variations in Glass and Minerals from Early Oligocene to Miocene Volcanic Sediments, DSDP Site 296, Kyushu Palau Ridge: Is There a Geochemical Signal for Arc Rifting?

    NASA Astrophysics Data System (ADS)

    Hickey-Vargas, R.; Samajpati, E.

    2015-12-01

    Volcaniclastic sediments and sedimentary rocks from DSDP Site 296, located within a basin at the crest of the northern Kyushu Palau ridge (KPR), record the latter part of the first stage of Izu Bonin Mariana (IBM) arc evolution, up to the cessation of volcanism caused by arc rifting and opening of the Shikoku basin. The lower section consists of early to late Oligocene coarse volcaniclastic sedimentary rocks, and is overlain by late Oligocene to Pleistocene nannofossil chalks and oozes with volcanic sand and ash-rich layers. We have studied the chemical composition of pyroxene, feldspar and glass grains separated from the coarse volcaniclastic rocks at depths from 435 to 1082 meters below sea floor, and of glass shards in layers in the overlying sediments of late Oligocene to early Miocene age. Overall, pyroxene and feldspar compositions show little systematic variation with depth in the core, although for pyroxene, highest En and highest Al2O3 contents are found in the interval from 600-900 meters bsf. An contents in feldspars show a bimodal distribution throughout the core, with most values > 90 or in the range 60-70, with more abundant intermediate compositions in the 600-900 meter interval. Compositions of glass shards vary widely, from basalt to rhyolite, and from low K, light rare earth (LREE)-depleted to high K, strongly LREE-enriched character, without systematic variation with depth in the core. However, all cores sampled from early Oligocene to early Miocene contain relatively low K basalt and basaltic andesite glass. Like the pyroxenes, a wider range of compositions is found in glass from the 600 to 900 mbsf interval. The Site 296 sequence overlaps in age with the uppermost sedimentary section of recently drilled IODP Site 1438, located 230 km to the southwest in the Amami Sankaku basin, thus the two sites may contain volcanic debris shed from contemporaneous sections of the KPR.

  8. Role of the Alboran Sea volcanic arc choking the Mediterranean to the Messinian salinity crisis and foundering biota diversification in North Africa and Southeast Iberia

    NASA Astrophysics Data System (ADS)

    Booth-Rea, Guillermo; Ranero, Cesar R.; Grevemer, Ingo

    2016-04-01

    The Mediterranean Sea desiccated ~5.96 million years ago when it became isolated from the world oceans during the Messinian salinity crisis. This event permitted the exchange of terrestrial biota between Africa and Iberia contributing to the present rich biodiversity of the Mediterranean region. The cause chocking the Mediterranean has been proposed to be tectonic uplift and dynamic topography but the driving mechanism still remains debated. We present a new wide-angle seismic profile that provides a detailed image of the thickness and seismic velocity distribution of the crust in the eastern Alboran basin. The velocity model shows a characteristic structure of a subduction-related volcanic arc with a high-velocity lower crust and a 16-18 km total-thickness igneous crust that magmatic accreted mostly between ~10-6 Ma across the eastern Alboran basin. Estimation of the isostatically corrected depth of the arc crust taking into account the original thermal structure and sediment-loading subsidence since 6 Ma places a large area of the eastern Alboran basin above sea level at the time. This estimation is supported by geophysical data showing subaereal erosional unconformities for that time. This model may explain several up-to-now-disputed features of the Messinian salinity crisis, including: the progressive isolation of the Mediterranean since 7.1 Ma with the disappearance of open marine taxa, the existence of evaporites mostly to the east of the volcanic arc, the evidence that the Gibraltar straits were not a land bridge offered by continuous Messinian open marine sediments at ODP site 976 in the western Alboran basin, the importance of southeastern Iberia and North Africa as centres of biota diversification since before the salinity crisis, and patterns of speciation irradiating from SE Iberia and the eastern Rif in some taxons.

  9. Monitoring active volcanism using ASTER satellite remote sensing: Volcan de Colima, Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Silvertooth, Maggie Lin

    Scope and Method of Study. ASTER satellite data was collected and analyzed in order to quantify changes in temperature, vesicularity, and morphology of the dome and crater that support evidence of constructive and destructive phases of lava dome growth and destruction cycles. These cycles are characterized by sporadic growth of a lava dome that is subsequently destroyed by a Vulcanian or Pelean style eruption. Activity reports were compared with ASTER images and new deposits were mapped along the flanks of the volcano. There is no way to distinguish between pyroclastic material, rockfall deposits, lahar deposits or lava flows therefore all new flows were mapped. Findings and Conclusions. During a constructive phase, magma that is low in volatiles rises and forms a new dome. The low amount of volatiles leads to a decrease in vesicularity. Therefore during a destructive phase vesicularity is increased. Examining changes in temperature on the dome, it appears that temperatures are at a maximum before an eruptive event, such as incandescent material being extruded at the edge of the dome. Immediately after the lava dome is removed by an explosive event, a decrease in temperature is observed. Once activity resumes, increase in temperature is seen. Morphological changes on the dome can be due to explosive events, gravitational collapse, and factors affecting the endogenous and exogenous growth of the dome. Satellite data provides a synoptic view allowing for observation of new activity to be observed earlier than ground based data may allow. In the case of the Volcan de Colima, satellite remote sensing provided insight to the constructive and destructive phases of the lava dome and current activity.

  10. The preliminary results of new submarine caldera on the west of Kume-jima island, Central Ryukyu Arc, Japan

    NASA Astrophysics Data System (ADS)

    Harigane, Y.; Ishizuka, O.; Shimoda, G.; Sato, T.

    2014-12-01

    The Ryukyu Arc occurs between the islands of Kyushu and Taiwan with approximately 1200 km in the full length. This volcanic arc is caused by subduction of the Philippine Sea plate beneath the Eurasia Plate along the Ryukyu trench, and is composed of forearc islands, chains of arc volcanoes, and a back-arc rift called Okinawa Trough. The Ryukyu Arc is commonly divided into three segments (northern, central and southern) that bounded by the Tokara Strait and the Kerama Gap, respectively (e.g., Konishi 1965; Kato et al., 1982). Sato et al. (2014) mentioned that there is no active subaerial volcano in the southwest of Iotori-shima in the Central Ryukyu Arc whereas the Northern Ryukyu Arc (i.e., the Tokara Islands) has active frontal arc volcanoes. Therefore, the existence of volcanoes and volcanotectonic history of active volcanic front in the southwestern part of the Central Ryukyu Arc are still ambiguous. Detailed geophysical and geological survey was mainly conducted using R/V Kaiyou-maru No.7 during GK12 cruise operated by the Geological Survey of Japan/National Institute of Advanced Industrial Science and Technology, Japan. As a result, we have found a new submarine volcanic caldera on the west of Kume-jima island, where located the southwestern part of Central Ryukyu Arc. Here, we present (1) the bathymetrical feature of this new submarine caldera for the first time and (2) the microstructural and petrological observations of volcanic rocks (20 volcanic samples in 13 dredge sites) sampled from the small volcanic cones of this caldera volcano. The dredged samples from the caldera consist of mainly rhyolite pumice with minor andesites, Mn oxides-crust and hydrothermally altered rocks. Andesite has plagioclase, olivine and pyroxene phenocrysts. Key words: volcanic rock, caldera, arc volcanism, active volcanic front, Kume-jima island, Ryukyu Arc

  11. Galileo SSI Observations of Volcanic Activity at Tvashtar Catena, Io

    NASA Technical Reports Server (NTRS)

    Milazzo, M. P.; Keszthely, L. P.; Radebaugh, J.; Davies, A. G.; Turtle, E. P.; Geissler, P.; Klaasen, K. P.; McEwen, A. S.

    2005-01-01

    Introduction: We report on the analysis of the Galileo SSI's observations of the volcanic activity at Tvashtar Catena, Io as discussed by Milazzo et al. Galileo's Solid State Imager (SSI) observed Tvashtar Catena (63 deg N, 120 deg W) four times between November 1999 and October 2001, providing a unique look at the distinctive high latitude volcanism on Io. The November 1999 observation spatially resolved, for the first time, an active extraterrestrial fissure eruption. The brightness temperature of the lavas at the November 1999 fissure eruption was 1300 K. The second observation (orbit I27, February 2000) showed a large (approx. 500 sq km) region with many, small spots of hot, active lava. The third observation was taken in conjunction with a Cassini observation in December 2000 and showed a Pele-like plume deposition ring, while the Cassini images revealed a 400 km high Pele-type plume above the Catena. The final Galileo SSI observation of Tvashtar was acquired in October 2001, and all obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. We have concentrated on analyzing the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of "simple" advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping (in time and space) eruptions.

  12. Nondestructive neutron activation analysis of volcanic samples: Hawaii

    SciTech Connect

    Zoller, W.H.; Finnegan, D.L.; Crowe, B.

    1986-01-01

    Samples of volcanic emissions have been collected between and during eruptions of both Kilauea and Mauna Loa volcanoes during the last three years. Airborne particles have been collected on Teflon filters and acidic gases on base-impregnated cellulose filters. Chemically neutral gas-phase species are collected on charcoal-coated cellulose filters. The primary analytical technique used is nondestructive neutron activation analysis, which has been used to determine the quantities of up to 35 elements on the different filters. The use of neutron activation analysis makes it possible to analyze for a wide range of elements in the different matrices used for the collection and to learn about the distribution between particles and gas phases for each of the elements.

  13. Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1980-February 28, 1981

    SciTech Connect

    Jacob, K.H.; Davies, J.N.; House, L.

    1981-01-01

    Refined hypocenter locations beneath the Shumagin Islands seismic network of the eastern Aleutian arc, Alaska, provide for the first time conclusive evidence for a double-sheeted dipping seismic (Benioff) zone in this arc. This refined seismicity structure was obtained in the arc section centered on the Shumagin seismic gap. A thorough review of three seismic gaps in the eastern Aleutian arc shows a high potential for great earthquakes within the next one to two decades in the Shumagin and Yakataga seismic gaps, and a less certain potential for a large or great earthquake in the possible Unalaska gap. A tilt reversal was geodetically observed to have occurred in 1978/79 in the forearc region of the Shumagin gap and could indicate the onset of a precursory strain relief episode prior to a great quake. A comparative study of the Pavlof volcano seismicity with that of other recently active volcanoes (i.e., Mt. St. Helens) indicates that island-arc (explosive-type) volcanoes respond to small ambient, periodic stress changes (i.e., tides). Stress drop measurements from earthquakes on the main thrust zone indicate high stress drops within the seismic gap regions of the Aleutian arc and low stress drops outside the gap region.

  14. Geochemistry of Volcanic Rocks from International Ocean Discovery Program (IODP) Site 1438, Amami Sankaku Basin: Implications for Izu-Bonin-Mariana (IBM) Arc Initiation

    NASA Astrophysics Data System (ADS)

    Hickey-Vargas, R.; Ishizuka, O.; Yogodzinski, G. M.; Bizimis, M.; Savov, I. P.; McCarthy, A. J.; Arculus, R. J.; Bogus, K.

    2015-12-01

    IODP Expedition 351 drilled 150 m of volcanic basement overlain by 1461 m of sedimentary material at Site 1438 in the Amami Sankaku basin, just west of the Kyushu Palau Ridge, the locus of IBM arc initiation. Age interpretations based on biostratigraphy (Arculus et al., Nat. Geosci., in-press) determined that the age of the basement section is between 64 and 51 Ma, encompassing the age of the earliest volcanic products of the IBM arc. The Site 1438 volcanic basement consists of multiple flows of aphyric microcrystalline to finely crystalline basalts containing plagioclase and clinopyroxene with rare olivine pseudomorphs. New XRF major and ICPMS trace element data confirm findings of shipboard analysis that the basalts are moderately differentiated (6-14 % MgO; Mg# = 51-83; 73-490 ppm Cr and 58-350 ppm Ni) with downcore variations related to flow units. Ti/V and Ti/Sc ratios are 16-27 and 75-152, respectively, with lowest values at the base of the core. One prominent characteristic of the basalts is their depletion of immobile highly incompatible elements compared with MORB. Basalts have MORB-normalized La/Nd of 0.5 to 0.9, and most have Th/La < 0.05. Although all basalts are LREE-depleted, La/Nd ratios increase slightly upcore, and Th enrichment compared with LREE occurs in the uppermost 5 meters. Cs, Rb, K, Ba and U are concomitantly enriched relative to LREE in several intervals as a probable result of seawater alteration, but ratios less than those of MORB are found in other areas. In contrast to basement, andesites from three sills in the lowermost sedimentary unit have arc-like trace element patterns with La/Nb > 3 and primitive mantle normalized La/Yb > 1. Our results suggest that mantle melting at the onset of subduction involved exceptionally depleted sources. Enrichment over time may be related to increasing subduction inputs and/or other processes, such as entrainment of fertile asthenosphere during extension of the overriding plate.

  15. Sedimentation rate curves as a key to understand the evolution of arc and backarc basin -Arc type and Basin type-

    NASA Astrophysics Data System (ADS)

    Fujioka, K.; Matsuoka, H.

    2003-12-01

    The deepsea cores recovered from about 50 drilling sites in the Philippine Sea, equally distributed in marginal basins, remnant arcs, present arcs and other tectonic settings, during the DSDP/IPOD/ODP offer significant geotectonic information. Sediment accumulation rates, lithologic changes and frequency of tephras were examined in the light of the recent advanced nannofossil biostratigraphy of the sediment on these cores. Sediment accumulation rate curves of these drill sites were classified into two major types, A and B types, respectively. A type has rapid accumulation rates just above the arc basement and then shows a decreasing pattern. In contrast, B type has rather constant accumulation rate throughout the cores. Sediments from the rapid sediment accumulation rates imply volcanogenic debris flow and volcaniclastic turbidite sequences derived which were derived from arcs that represent an activity of magmatic arc consisting of tholeiitic and calc-alkalic volcanic rocks. On the contrary, sediments from the low sediment accumulation rates imply mostly biogenic materials instead of volcaniclastic materials. This may mean the termination of intense arc volcanism. Frequency of volcanic ash layers deduced from these cores has maxima just after the rapid sediment accumulation stage of A type curves. As for the remnant arcs such as the Kyushu-Palau and the Daito Ridge, tephra maxima exist at both late Eocene to early Oligocene time and the present arc such as the Izu-Bonin Arc, there are two major maxima at Eocene-Oligocene and Pliocene-Pleistocene time, respectively. Explosive volcanism may take place when oceanic arc develops as shallow as the pressure compensation level (PCL). If this is the case, we may draw the volcanic history of oceanic island arc. At the incipient stage of arc evolution the style of volcanism is quiet resultant formation of pillow lavas and hyaloclastite. On the contrary, the intense volcanism takes place with formation of marine tephra

  16. Evidence of sub-vent biosphere: enzymatic activities in 308 °C deep-sea hydrothermal systems at Suiyo seamount, Izu Bonin Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Takano, Yoshinori; Edazawa, Yae; Kobayashi, Kensei; Urabe, Tetsuro; Marumo, Katsumi

    2005-01-01

    A high-temperature deep-sea hydrothermal system related to dacitic arc-volcanism was drilled using a tethered, submarine rock-drill system as a part of the Archaean Park Project. The benthic multi-coring system (BMS) employed allowed for direct sampling of microorganisms, rocks and fluids beneath hydrothermal vents. The samples examined in this study were from sites APSK 05 and APSK 07 on the Suiyo Seamount of the Izu-Bonin Arc in the Pacific Ocean. Based on the vertical distribution of samples derived from this vigorous sub-vent environment, a model of deep-sea subterranean chemistry and biology was determined detailing optimal microbial activities. Deep-sea hydrothermal sub-vent core samples of dacitic arc-volcanism obtained at the Suiyo Seamount, Izu-Bonin Arc, Western Pacific Ocean were analyzed for acid and alkaline phosphatase enzymatic activities. Useful biomarkers of acid phosphatase (ACP) and alkaline phosphatase (ALP) enzymatic activities were positively correlated against each other and was greatest at the partial middle core sequences; ACP and ALP activities determined were as high as 5.10 and 6.80 nmol/min/g rock, respectively. Biochemical indicators of ACP and ALP were consistent with the origin of biogenic amino acids occupied in the sub-vent region and microbial cell number in the fluid. The significant enzymatic activities demonstrated in this study provides crucial evidence that sub-vent regions represent part of the previously unknown extreme-environment biosphere, extending the known subterranean habitable spaces of, for example, extremophilic microbes. This boring trial was first example of discharging high temperature hydrothermal activities at the frontal arc volcanoes.

  17. GRID based Thermal Images Processing for volcanic activity monitoring

    NASA Astrophysics Data System (ADS)

    Mangiagli, S.; Coco, S.; Drago, L.; Laudani, A.,; Lodato, L.; Pollicino, G.; Torrisi, O.

    2009-04-01

    Since 2001, the Catania Section of the National Institute of Geophysics and Volcanology (INGV) has been running the video stations recording the volcanic activity of Mount Etna, Stromboli and the Fossa Crater of Vulcano island. The video signals of 11 video cameras (seven operating in the visible band and four in infrared) are sent in real time to INGV Control Centre where they are visualized on monitors and archived on a dedicated NAS storage. The video surveillance of the Sicilian volcanoes, situated near to densely populated areas, helps the volcanologists providing the Civil Protection authorities with updates in real time on the on-going volcanic activity. In particular, five video cameras are operating on Mt. Etna and they record the volcano from the south and east sides 24 hours a day. During emergencies, mobile video stations may also be used to better film the most important phases of the activity. Single shots are published on the Catania Section intranet and internet websites. On June 2006 a A 40 thermal camera was installed in Vulcano La Fossa Crater. The location was in the internal and opposite crater flank (S1), 400 m distant from the fumarole field. The first two-year of data on temperature distribution frequency were recorded with this new methodology of acquisition, and automatically elaborated by software at INGV Catania Section. In fact a dedicated software developed in IDL, denominated Volcano Thermo Analysis (VTA), was appositely developed in order to extract a set of important features, able to characterize with a good approssimation the volcanic activity. In particular the program first load and opportunely convert the thermal images, then according to the Region Of Interest (ROI) and the temperature ranges defined by the user provide to automatic spatial and statistic analysis. In addition the VTA is able to analysis all the temporal series of images available in order to achieve the time-event analysis and the dynamic of the volcanic

  18. Tectonomagmatic activity and ice dynamics in the Bransfield Strait back-arc basin, Antarctica

    NASA Astrophysics Data System (ADS)

    Dziak, Robert P.; Park, Minkyu; Lee, Won Sang; Matsumoto, Haru; Bohnenstiehl, Delwayne R.; Haxel, Joseph H.

    2010-01-01

    An array of moored hydrophones was used to monitor the spatiotemporal distribution of small- to moderate-sized earthquakes and ice-generated sounds within the Bransfield Strait, Antarctica. During a 2 year period, a total of 3900 earthquakes, 5925 icequakes and numerous ice tremor events were located throughout the region. The seismic activity included eight space-time earthquake clusters, positioned along the central neovolcanic rift zone of the young Bransfield back-arc basin. These sequences of small magnitude earthquakes, or swarms, suggest ongoing magmatic activity that becomes localized along isolated volcanic features and fissure-like ridges in the southwest portion of the basin. A total of 122 earthquakes were located along the South Shetland trench, indicating continued deformation and possibly ongoing subduction along this margin. The large number of icequakes observed show a temporal pattern related to seasonal freeze-thaw cycles and a spatial distribution consistent with channeling of sea ice along submarine canyons from glacier fronts. Several harmonic tremor episodes were sourced from a large (˜30 km2) iceberg that entered northeast portion of the basin. The spectral character of these signals suggests they were produced by either resonance of a small chamber of fluid within the iceberg, or more likely, due to periodicity of discrete stick-slip events caused by contact of the moving iceberg with the seafloor. These pressure waves appear to have been excited by abrasion of the iceberg along the seafloor as it passed Clarence and Elephant Islands.

  19. New Insights Into Volcanic Hazards in Western Mexico: Multiple Cone-Building Episodes at Arc Stratovolcanoes Revealed by 40Ar/39Ar Geochronology

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

    The detailed eruptive histories of two andesitic stratocones, Volcáns Ceboruco and Tequila, in the western Mexican arc have been documented using 40Ar/39Ar geochronology. The volumes of these volcanoes were obtained with mapping, airphotos, and digital elevation models. The age and volume data constrain the rate and duration of major cone-building events, which bears on the longevity of the underlying upper-crustal magma chambers that fed the eruptions. The results indicate that at each stratovolcano there were two discrete cone-building events, separated by a hiatus. At V. Tequila, six samples from the edifice yielded dates (196 +/- 8, 196 +/- 19, 178 +/- 8, 191 +/- 13, 216 +/- 11, and 198 +/- 11 ka; errors are 1 sigma) with a mean eruption age of 196 +/- 12 ka. Thus the bulk of the main edifice ( ˜31 km3) erupted within 24 kyrs (at the 2 sigma level), leading to a cone-building rate of > 1.3 km3/kyr. After a hiatus of ˜110 kyrs, ˜14 km3 of andesite erupted along the NW and SE flanks of V. Tequila at 90 +/- 19 ka. The last activity at V. Tequila produced a ˜2 km3 parasitic cone at ˜60 ka. Since an eruption has not occurred in the last 60 kyrs, V. Tequila is often considered an extinct volcano. This may be the view held by the > 75,000 inhabitants of the town of Tequila located on the northern flanks. A similar history of two discrete cone-building events is found at V. Ceboruco, ˜75 km to the NW. Seven samples taken from various parts of the edifice, including the inner caldera wall, indicate an initial cone-building event at ˜45 ka in which ˜37 km3 of andesite erupted. After a hiatus of nearly 44 kyrs, a second eruptive period began ˜1000 years ago. The first eruption to occur after the hiatus was Plinian and released 3-4 km3 of dacite. In the last 1 kyr, 9.5 km3 of andesite and dacite erupted effusively, culminating in the historic 1870 flow. The sobering conclusion, in terms of volcanic hazards assessment, is that the only Plinian eruption to occur

  20. Tectonic evolution and volcanism of Okinawa Trough

    SciTech Connect

    Sibuet, J.C.; Letouzey, J.; Marsset, B.; Davagnier, M.; Foucher, J.P.; Bougault, H.; Dosso, L.; Maury, R.; Joron, J.L.

    1986-07-01

    The Okinawa Trough is a back-arc basin formed by extension of the east China continental lithosphere behind the Ryukyu Trench system. The age of marine deposits drilled in the northern Okinawa Trough indicates a Miocene age for the splitting of the volcanic arc and the first tensional movements. The POP 1 cruise of the R/V Jean-Charcot (September-October 1984) provided new evidence concerning the two main periods of extension as recognized by Kimura (Marine and Petroleum Geology, 1985). Tilted fault blocks in the northern Okinawa Trough trend north 40/sup 0/-60/sup 0/ and belong to the early Pleistocene phase (2-0.5 Ma). The present-day phase is characterized over the entire basin by normal faults oriented 80/sup 0/N in the north and 90/sup 0/N in the south. In the southern Okinawa Trough, most of the deformation occurs along linear, subparallel, en echelon depressions intruded by volcanic ridges associated with positive magnetic anomalies. The system of volcanic ridges ends northeast of Okinawa Island in a series of parallel volcanic ridges named the VAMP (Volcanic arc-rift migration processes) area, which merges into an active volcanic chain extending north to Japan. Chemical analyses of the vesicular basalts dredged on the back-arc basin display flat to enriched rare-earth patterns. The niobium-tantalum negative anomalies reflect a subduction signature. A good positive correlation between strontium isotopic compositions and concentrations suggests a contamination effect.

  1. The Influence of Crystal Mush on Magmatism Under Arc Volcanoes Recorded in Zircon from the Lassen Volcanic Center, California and Mount Hood, Oregon

    NASA Astrophysics Data System (ADS)

    Klemetti, E. W.; Clynne, M. A.; Kent, A. J.; Bertolett, E. M.; Hernandez, L. D.; Coble, M. A.

    2015-12-01

    Many arc volcanoes are constructed by repeated tapping of complex subvolcanic magmatic plumbing containing new and inherited crystals and liquids that interact in the hours to millennia prior to an eruption. This process is often modulated by long-lived (10-100 k.y.) shallow (<5 km) silicic crystal mush. Constraining the development and growth of mush zones is therefore essential in predicting a volcano's future behavior. The Lassen Volcanic Center (LVC) in California and Mount Hood (MH) in Oregon are two of the most recently active Cascade volcanoes, with last major eruptions in 1915 and ~1780-81 respectively. We performed U-Th/U-Pb dating of LVC and MH zircon from lavas and tephras erupted between 0.1-825 ka. In the LVC, the Rockland Tephra (611 ka; Ar/Ar) contains zircon from 800-520 ka, spanning the age of the Rockland caldera complex (825-611 ka eruption ages). During the Lassen Domefield (315-0.1 ka eruption ages), zircon ages vary from secular equilibrium to 15 ka, overlapping with the Bumpass Sequence (315-190 ka eruption ages) and an eruptive hiatus (190-90 ka eruption ages). Nine of 116 Lassen Domefield zircon are in secular equilibrium (>350 ka). These data support a model of long-lived zircon-saturated silicic mushes existing under the LVC during the Rockland caldera complex stage and since the end of the Brokeoff Volcano stage (590-385 ka eruption ages). Preliminary zircon data from the Old Maid stage (~0.2 ka eruption age) at MH indicate two broad age groups. Younger zircon (<10 ka) suggest reactivation and/or expansion of mush following Polallie phase (20-12 ka eruption ages), Timberline (~1.5 ka eruption age), and Old Maid eruptions. Older zircon (>100 ka) are generally consistent with U-Th ages from plagioclase (~120 ka U-Th), indicating a long-lived zircon-saturated crystal mush tapped by Timberline and Old Maid lavas. At both of these volcanoes, silicic crystal mushes interact with intruding mafic magma, producing monotonous mixed andesite

  2. Early Cretaceous arc volcanic suite in Cebu Island, Central Philippines and its implications on paleo-Pacific plate subduction: Constraints from geochemistry, zircon U-Pb geochronology and Lu-Hf isotopes

    NASA Astrophysics Data System (ADS)

    Deng, Jianghong; Yang, Xiaoyong; Zhang, Zhao-Feng; Santosh, M.

    2015-08-01

    The Philippine island arc system is a collage of amalgamated terranes of oceanic, continental and island arc affinities. Here we investigate a volcanic suite in Cebu Island of central Philippines, including basalt, diabase dike, basaltic pyroclastic rock and porphyritic andesite. LA-ICP-MS U-Pb geochronology of zircon grains from the porphyritic andesite and pyroclastic rock yielded ages of 126 ± 3 Ma and 119 ± 2 Ma, respectively, indicating an Early Cretaceous age. The age distribution of the detrital zircons from river sand in the area displays a peak at ca. 118 Ma, close to the age of the pyroclastic rock. The early Cretaceous volcanic rocks in the central Philippines were previously regarded as parts of ophiolite complexes by most investigators, whereas the Cebu volcanics are distinct from these, and display calc-alkaline affinity and island arc setting, characterized by high LREE/HREE ratios and low HFSE contents. These features are similar to the Early Cretaceous arc basalts in the Amami Plateau and east Halmahera in the northernmost and southernmost West Philippine Basin respectively. Zircon Hf isotopes of the pyroclastic rocks show depleted nature similar to those of the Amami Plateau basalts, implying the subducted Pacific-type MORB as probable source. Zircon Hf isotopes of the porphyritic andesite show slight enrichment relative to that of the pyroclastic rocks and MORB, indicating subducted sediments as a minor end-member in the source. The Hf isotopic compositions of the volcanic rocks are also reflected in the detrital zircons from the river sands. We propose that the volcanic rocks of Cebu Island were derived from partial melting of sub-arc mantle wedge which was metasomatized by dehydration of subducted oceanic crust together with minor pelagic sediments. Within the tectonic environment of Southeast Asia during Early Cretaceous, the volcanic rocks in Cebu Island can be correlated to the subduction of paleo-Pacific plate. The Early Cretaceous

  3. Geochemical Interpretation of Collision Volcanism

    NASA Astrophysics Data System (ADS)

    Pearce, Julian

    2014-05-01

    Collision volcanism can be defined as volcanism that takes place during an orogeny from the moment that continental subduction starts to the end of orogenic collapse. Its importance in the Geological Record is greatly underestimated as collision volcanics are easily misinterpreted as being of volcanic arc, extensional or mantle plume origin. There are many types of collision volcanic province: continent-island arc collision (e.g. Banda arc); continent-active margin collision (e.g. Tibet, Turkey-Iran); continent-rear-arc collision (e.g. Bolivia); continent-continent collision (e.g. Tuscany); and island arc-island arc collision (e.g. Taiwan). Superimposed on this variability is the fact that every orogeny is different in detail. Nonetheless, there is a general theme of cyclicity on different time scales. This starts with syn-collision volcanism resulting from the subduction of an ocean-continent transition and continental lithosphere, and continues through post-collision volcanism. The latter can be subdivided into orogenic volcanism, which is related to thickened crust, and post-orogenic, which is related to orogenic collapse. Typically, but not always, collision volcanism is preceded by normal arc volcanism and followed by normal intraplate volcanism. Identification and interpretation of collision volcanism in the Geologic Record is greatly facilitated if a dated stratigraphic sequence is present so that the petrogenic evolution can be traced. In any case, the basis of fingerprinting collision terranes is to use geochemical proxies for mantle and subduction fluxes, slab temperatures, and depths and degrees of melting. For example, syn-collision volcanism is characterized by a high subduction flux relative to mantle flux because of the high input flux of fusible sediment and crust coupled with limited mantle flow, and because of high slab temperatures resulting from the decrease in subduction rate. The resulting geochemical patterns are similar regardless of

  4. Geochemistry and zircon U-Pb-Hf isotopes of Early Paleozoic arc-related volcanic rocks in Sonid Zuoqi, Inner Mongolia: Implications for the tectonic evolution of the southeastern Central Asian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Zhang, Zhicheng; Li, Ke; Yu, Haifei; Wu, Tairan

    2016-11-01

    An Early Paleozoic acid volcanic sequence has been recently detected southeast of Sonid Zuoqi in central Inner Mongolia to constrain the tectonic evolution of the Central Asian Orogenic Belt in this area. First, the volcanic rocks have zircon U-Pb ages of 439-445 Ma. They are characterized by (a) a high silica content, moderate alkali content and low iron content; (b) enrichment in light rare earth elements, depletion of heavy rare earth elements, and negative Eu anomalies; and (c) negative Nb, Ta, and Ti anomalies. Finally, the volcanic samples yield εHf(t) values of - 4.7 to + 9.2 with TDM2 ages of 835-1724 Ma. For petrogenesis, they were possibly arc derived, from predominant juvenile materials with subordinate ancient continental crust. Combined with previous studies, the Early Paleozoic Sonid Zuoqi arc magmatism can be divided into three stages: a primitive arc stage represented by 464-490 Ma low-K, calcic granitoids; a normal continental arc stage represented by 439-445 Ma medium-K, calcic to calcic-alkalic plutons and volcanic rocks and a syn-collisional stage represented by 423-424 Ma high-K granites. Furthermore, the timing and tectonic settings of the above magmatic rocks show similarities to those in Xilinhot and other areas of the northern Early to Mid-Paleozoic orogenic belt (NOB), although the rock assemblies and their proportions vary more or less in different areas. Accordingly, the NOB that formed on this arc was probably attributed to the northward subduction of the Paleo-Asian Ocean beginning at 500 Ma, which experienced this type of arc development and was terminated by a soft collision before the Late Devonian.

  5. Rifting process of the Izu-Ogasawara-Mariana arc-backarc system inferred from active source seismic studies

    NASA Astrophysics Data System (ADS)

    Takahashi, N.; Kodaira, S.; Miura, S.; Sato, T.; Yamashita, M.; No, T.; Takizawa, K.; Kaiho, Y.; Kaneda, Y.

    2008-12-01

    The Izu-Ogasawara-Mariana (IBM) arc-backarc system has continued the crustal growth through crustal thickening by magmatic activities and crustal thinning by backarc opening. Tatsumi et al (2008) proposed petrological crustal growth model started from basaltic magmas rising from the slab, and showed the consistency with the seismic velocity model. Although crustal growth by the crustal thickening are modeled, crustal structural change by the backarc opening are not still unknown yet. The Shikoku Basin and Parece Vela Basin were formed by the backarc opening during approximately 15-30 Ma. Since 6 Ma, the Mariana Trough has opened and the stage already moved to spreading process from rifting process. In the northern Izu-Ogasawara arc, the Sumisu rift is in the initial rifting stage. Therefore, understanding of the crustal change by the backarc opening from rifting to spreading is indispensable to know the crustal growth of whole Izu-Ogasawara-Mariana island arc. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has carried out seismic studies using a multichannel reflection survey system and ocean bottom seismographs (OBSs) around the IBM arc since 2003 (Takahashi et al., 2007; Kodaira et al., 2007; Takahashi et al., 2008; Kodaira et al., 2008). We already obtained eight P-wave velocity models across the IBM arc and these structures record the crustal structural change during the backarc opening process from the rifting stage to the spreading stage. As the results, we identified characteristics of the crustal structural change accompanied with backarc opening as follows. (1) Beneath the initial rifting stage without normal faults, for example, in the northern tip of the Mariana Trough, crustal thickening are identified. (2) Beneath the initial rifting stage with normal faults, for example, in the Sumisu Rift, the crustal thickness is almost similar to that beneath the volcanic front. Although an existence of the crust-mantle transition layer with

  6. Occurrence rate of SAR arcs during the 23nd solar activity cycle

    NASA Astrophysics Data System (ADS)

    Ievenko, Igor

    By data of photometric observations at the Maimaga station (57° N, 200° E, geomagnetic coordinates) at the Yakutsk meridian the occurrence rate of subauroral red (SAR) arcs for the 1997 to 2006 period has been analysed. The observations were carried out during winterspring periods at moonless nights under favorable atmospheric conditions. For˜370 nights of observations (total duration is˜3170 hours) 114 cases of SAR arcs occurrence (˜500 hours) have been registered. The occurrence rate of SAR arcs have been determined as a ratio of the number of registration hour intervals of SAR arcs to the summary observation time in hours for particular months. Subauroral red arcs have been registered every year both in the maximum and in the minimum of the solar activity cycle. The most observation occurrence of red arcs is registered on the rise (˜27%) and decay of the maximum of the solar activity cycle (˜36%). The average occurrence rate of SAR arcs during these years was less than in the 22nd solar activity cycle and is equal to ˜16% of the total observation time. The occurrence rate of SAR arcs observations corresponds to the changes of geomagnetic activity during the 23nd solar activity cycle.

  7. Remote OP-FTIR sensing of magmatic gases driving Yasur trachyandesitic explosive activity, Vanuatu island arc

    NASA Astrophysics Data System (ADS)

    Allard, P.; Burton, M.; Sawyer, G.

    2012-04-01

    Yasur volcano, located in the southern part of the Vanuatu island arc (Tanna island), is a small trachyandesitic cone that has grown in the resurgent (17 cm y-1) Siwi caldera. Since about 1,400 years Yasur has displayed almost continuous Strombolian-Vulcanian explosive activity and is one of the most actively erupting volcanoes worldwide. Using open-path Fourier transform infrared (OP-FTIR) spectroscopy from the crater rim (260-300 m slanting distance) and molten lava as the radiation source, we measured during several days the high frequency compositional variations of magmatic gases driving this explosive activity. Our results expand previous observations from a first FTIR measurement in 2005 [1] and complement in-situ gas measurements made in 2007 [2] within our same research framework (French ANR 'VOLGASPEC' project). FTIR absorption spectra allowed simultaneous retrieval of the molar path amounts of volcanic H2O, CO2, SO2, HCl and CO, corrected for air background in case of H2O, CO2 and CO. We observe a rather steady composition of the crater gas release between the explosions (~one every 1-3 mn) and sharp compositional variations (increases of SO2/HCl, CO2/SO2 and CO/CO2 ratios, decrease of H2O/SO2) associated with the explosions, which demonstrate the ascent and bursting of deeper-derived, CO2-SO2-CO-enriched gas slugs. Such abrupt compositional changes of magmatic gases driving explosive activity at Yasur do resemble those recorded at Stromboli volcano [3]. However, in contrast to Stromboli, Yasur explosions generate dense ash clouds whose fast expansion significantly affects the measured column gas amounts at the onset of each event (an effect considered in our data elaboration). When referred to the pressure-related behaviour of dissolved volatiles in the trachyandesitic magma feeding Yasur (melt inclusions [2]), our results provide new constraints on the source depth(s) of the explosions and the magma degassing processes controlling the volcanic activity

  8. Nitrite Reductase and Nitric-oxide Synthase Activity of the Mitochondrial Molybdopterin Enzymes mARC1 and mARC2*

    PubMed Central

    Sparacino-Watkins, Courtney E.; Tejero, Jesús; Sun, Bin; Gauthier, Marc C.; Thomas, John; Ragireddy, Venkata; Merchant, Bonnie A.; Wang, Jun; Azarov, Ivan; Basu, Partha; Gladwin, Mark T.

    2014-01-01

    Mitochondrial amidoxime reducing component (mARC) proteins are molybdopterin-containing enzymes of unclear physiological function. Both human isoforms mARC-1 and mARC-2 are able to catalyze the reduction of nitrite when they are in the reduced form. Moreover, our results indicate that mARC can generate nitric oxide (NO) from nitrite when forming an electron transfer chain with NADH, cytochrome b5, and NADH-dependent cytochrome b5 reductase. The rate of NO formation increases almost 3-fold when pH was lowered from 7.5 to 6.5. To determine if nitrite reduction is catalyzed by molybdenum in the active site of mARC-1, we mutated the putative active site cysteine residue (Cys-273), known to coordinate molybdenum binding. NO formation was abolished by the C273A mutation in mARC-1. Supplementation of transformed Escherichia coli with tungsten facilitated the replacement of molybdenum in recombinant mARC-1 and abolished NO formation. Therefore, we conclude that human mARC-1 and mARC-2 are capable of catalyzing reduction of nitrite to NO through reaction with its molybdenum cofactor. Finally, expression of mARC-1 in HEK cells using a lentivirus vector was used to confirm cellular nitrite reduction to NO. A comparison of NO formation profiles between mARC and xanthine oxidase reveals similar Kcat and Vmax values but more sustained NO formation from mARC, possibly because it is not vulnerable to autoinhibition via molybdenum desulfuration. The reduction of nitrite by mARC in the mitochondria may represent a new signaling pathway for NADH-dependent hypoxic NO production. PMID:24500710

  9. Gish Bar Patera, Io: Geology and Volcanic Activity, 1996-2001

    NASA Technical Reports Server (NTRS)

    Perry, Jason; Radebaugh, Jani; Lopes, Rosaly; McEwen, Alfred; Keszthelyi, Laszlo

    2003-01-01

    Since the two Voyagers passed by Jupiter in 1979, it has been known that volcanic activity is ubiquitous on the surface of Io. With over 400 volcanic centers, Io is even more volcanically active than the earth with massive flood basalt-style eruptions and komatitite lavas a common occurrence. Additionally, some volcanoes appear to be giant lava lakes, with violent activity churning the crust of the lake for periods of 20 years or more. Finally, sulfur is believed to play a large role in Io's volcanism, be it as a primary lava or as a secondary product of large, high-temperature eruptions. By studying one volcano in particular, Gish Bar Patera, one can observe many of these characteristics in one volcanic center.

  10. 2011 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Maharrey, J. Zebulon; Neal, Christina A.

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest at or near three separate volcanic centers in Alaska during 2011. The year was highlighted by the unrest and eruption of Cleveland Volcano in the central Aleutian Islands. AVO annual summaries no longer report on activity at Russian volcanoes.

  11. Multi-stage volcanic activities and geodynamic evolution of the Lhasa terrane during the Cretaceous: Insights from the Xigaze forearc basin

    NASA Astrophysics Data System (ADS)

    Dai, Jingen; Wang, Chengshan; Zhu, Dicheng; Li, Yalin; Zhong, Hanting; Ge, Yukui

    2015-03-01

    The history of volcanic activity of the Gangdese arc in southern Tibet during the Cretaceous remains poorly known due to the intense erosion of the arc. Here we present zircon U-Pb ages, trace element and Hf isotopic data of tuffs and volcanic conglomerates from the Chongdoi and the Ngamring Formation in the Xigaze forearc basin. Three tuff samples from the Chongdoi Formation yield zircon U-Pb ages around 112 Ma. Such ages could be taken as their depositional ages, indicating that detrital clasts of the Chongdoi Formation were deposited at that time. One andesitic conglomerate sample from the Ngamring Formation was dated at ca. 105 Ma, the other rhyolitic conglomerate sample and one tuff sample were dated to be ca. 95 Ma and 91 Ma, respectively, suggesting that this formation was formed during the late Albian-late Turonian. All zircons illustrate I-type granitoid characteristics and possess low Ti-in-zircon temperatures (< 800 °C). Zircon εHf(t) values of tuffs from the Chongdoi Formation define two groups: (1) the first group of 117-110 Ma displays large positive εHf(t) values (+ 12.1 to + 17.1), larger than those of the tuff from the Ngamring Formation (+ 6.0 to + 10.2); (2) the second group of 119-111 Ma yields negative to small positive εHf(t) values (- 4.5 to + 1.1). All above observations indicate that their host rocks were derived from the juvenile materials with significant input of fluids. Combined with extant data, the first group and the tuff, volcanic conglomerates from the Ngamring Formation are mostly likely derived from the eroded Cretaceous volcanic rocks in the Gangdese arc, while the second group is likely sourced from the late Early Cretaceous volcanic rocks in the central Lhasa terrane. Our data confirm the presence of Cretaceous volcanism in the Gangdese arc, suggesting that the Neo-Tethyan Ocean lithosphere was most likely subducted northerly in a normal angle rather than in a manner of low-angle subduction.

  12. Io's Diverse Styles of Volcanic Activity: Results from Galileo NIMS

    NASA Technical Reports Server (NTRS)

    Lopes, R. M. C.; Smythe, W. D.; Kamp, L. W.; Doute, S.; Carlson, R.; McEwen, A.; Geissler, P.

    2001-01-01

    Observations by Galileo's Near-Infrared Mapping Spectrometer were used to map the thermal structure of several of Io's hot spots, revealing different styles of volcanism Additional information is contained in the original extended abstract..

  13. Catastrophic volcanism

    NASA Technical Reports Server (NTRS)

    Lipman, Peter W.

    1988-01-01

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

  14. Episodic nature of continental arc activity since 750 Ma: A global compilation

    NASA Astrophysics Data System (ADS)

    Cao, Wenrong; Lee, Cin-Ty A.; Lackey, Jade Star

    2017-03-01

    Continental arcs have been recently hypothesized to outflux large amounts of CO2 compared to island arcs so that global flare-ups in continental arc magmatism might drive long-term greenhouse events. Quantitative testing of this hypothesis, however, has been limited by the lack of detailed studies on the spatial distribution of continental arcs through time. Here, we compile a worldwide database of geological maps and associated literature to delineate the surface exposure of granitoid plutons, allowing reconstruction of how the surface area addition rate of granitoids and the length of continental arcs have varied since 750 Ma. These results were integrated into an ArcGIS framework and plate reconstruction models. We find that the spatial extent of continental arcs is episodic with time and broadly matches the detrital zircon age record. Most vigorous arc magmatism occurred during the 670-480 Ma and the 250-50 Ma when major greenhouse events are recognized. Low continental arc activity characterized most of the Cryogenian, middle-late Paleozoic, and Cenozoic when climate was cold. Our results indicate that plate tectonics is not steady, with fluctuations in the nature of subduction zones possibly related in time to the assembly and dispersal of continents. Our results corroborate the hypothesis that variations in continental arc activity may play a first order role in driving long-term climate change. The dataset presented here provides a quantitative basis for upscaling continental arc processes to explore their effects on mountain building, climate, and crustal growth on a global scale.

  15. 1996 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Neal, Christina A.; McGimsey, Robert G.

    1997-01-01

    During 1996, the Alaska Volcano Observatory (AVO) responded to eruptive activity, anomalous seismicity, or suspected volcanic activity at 10 of the approximately 40 active volcanic centers in the state of Alaska. As part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also disseminated information about eruptions and other volcanic unrest at six volcanic centers on the Kamchatka Peninsula and in the Kurile Islands, Russia.

  16. Seismic velocity variation along the Izu-Bonin arc estaimated from traveltime tomography using OBS data

    NASA Astrophysics Data System (ADS)

    Obana, K.; Tamura, Y.; Takahashi, T.; Kodaira, S.

    2014-12-01

    The Izu-Bonin (Ogasawara) arc is an intra-oceanic island arc along the convergent plate boundary between the subducting Pacific and overriding Philippine Sea plates. Recent active seismic studies in the Izu-Bonin arc reveal significant along-arc variations in crustal structure [Kodaira et al., 2007]. The thickness of the arc crust shows a remarkable change between thicker Izu (~30 km) and thinner Bonin (~10 km) arcs. In addition to this, several geological and geophysical contrasts, such as seafloor topography and chemical composition of volcanic rocks, between Izu and Bonin arc have been reported [e.g., Yuasa 1992]. We have conducted earthquake observations using ocean bottom seismographs (OBSs) to reveal seismic velocity structure of the crust and mantle wedge in the Izu-Bonin arc and to investigate origin of the along-arc structure variations. We deployed 40 short-period OBSs in Izu and Bonin area in 2006 and 2009, respectively. The OBS data were processed with seismic data recorded at routine seismic stations on Hachijo-jima, Aoga-shima, and Chichi-jima operated by National Research Institute for Earth Science and Disaster Prevention (NIED). More than 5000 earthquakes were observed during about three-months observation period in each experiment. We conducted three-dimensional seismic tomography using manually picked P- and S-wave arrival time data. The obtained image shows a different seismic velocity structures in the mantle beneath the volcanic front between Izu and Bonin arcs. Low P-wave velocity anomalies in the mantle beneath the volcanic front in the Izu arc are limited at depths deeper than those in the Bonin arc. On the other hand, P-wave velocity in the low velocity anomalies beneath volcanic front in the Bonin arc is slower than that in the Izu arc. These large-scale along-arc structure variations in the mantle could relate to the geological and geophysical contrasts between Izu and Bonin arcs.

  17. Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

    USGS Publications Warehouse

    Pearson, S.C.P.; Connor, C.B.; Sanford, W.E.

    2008-01-01

    Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

  18. Sedimentary processes in modern and ancient oceanic arc settings: evidence from the Jurassic Talkeetna Formation of Alaska and the Mariana and Tonga Arcs, western Pacific

    USGS Publications Warehouse

    Draut, Amy E.; Clift, Peter D.

    2006-01-01

    Sediment deposited around oceanic volcanic ares potentially provides the most complete record of the tectonic and geochemical evolution of active margins. The use of such tectonic and geochemical records requires an accurate understanding of sedimentary dynamics in an arc setting: processes of deposition and reworking that affect the degree to which sediments represent the contemporaneous volcanism at the time of their deposition. We review evidence from the modern Mariana and Tonga arcs and the ancient arc crustal section in the Lower Jurassic Talkeetna Formation of south-central Alaska, and introduce new data from the Mariana Arc, to produce a conceptual model of volcaniclastic sedimentation processes in oceanic arc settings. All three arcs are interpreted to have formed in tectonically erosive margin settings, resulting in long-term extension and subsidence. Debris aprons composed of turbidites and debris flow deposits occur in the immediate vicinity of arc volcanoes, forming relatively continuous mass-wasted volcaniclastic records in abundant accommodation space. There is little erosion or reworking of old volcanic materials near the arc volcanic front. Tectonically generated topography in the forearc effectively blocks sediment flow from the volcanic front to the trench; although some canyons deliver sediment to the trench slope, most volcaniclastic sedimentation is limited to the area immediately around volcanic centers. Arc sedimentary sections in erosive plate margins can provide comprehensive records of volcanism and tectonism spanning < 10 My. The chemical evolution of a limited section of an oceanic arc may be best reconstructed from sediments of the debris aprons for intervals up to ~ 20 My but no longer, because subduction erosion causes migration of the forearc basin crust and its sedimentary cover toward the trench, where there is little volcaniclastic sedimentation and where older sediments are dissected and reworked along the trench slope.

  19. Arc - arc collisional tectonics within the Central Mobile Belt of the Newfoundland Appalachians

    NASA Astrophysics Data System (ADS)

    Zagorevski, A.; Rogers, N.; van Staal, C. R.; McNicoll, V. J.; Valverde-Vaquero, P.

    2007-12-01

    The Central Mobile Belt of Newfoundland Appalachians records the Ordovician arc - arc collision between the peri-Laurentian Red Indian Lake Arc of the Annieopsquotch accretionary tract (c. 480-460 Ma), and the peri- Gondwanan Victoria - Popelogan Arc (c. 473-453 Ma), which marks the closure of the Cambro-Ordovician Iapetus Ocean. Although the arc systems are in part coeval, they are distinguishable by the preservation of distinct structural histories and stratigraphies, unique basement characteristics as demonstrated by lead isotopic values of volcanic massive sulphide deposits and faunal differences. A modern analogue of such an arc - arc collision is observed in the Molucca and Solomon seas of the southwest Pacific. From such modern analogues it is evident that the Victoria - Popelogan Arc occupied a lower-plate setting during collision. This tectonic setting is demonstrated by subsidence of the Victoria - Popelogan Arc similar to the collision induced subsidence that is developed on the Australian active margin and Halmahera arcs of the Southwest Pacific. The timing of Victoria - Popelogan Arc subsidence is constrained by three age dates that form the last vestiges of arc volcanism (457 ± 2; 456.8 ± 3.1; 457 ± 3.6 Ma). These volcanic rocks are immediately overlain by Caradocian black shale of the Point Leamington Formation that marks the base of the Badger Group and the initiation of a successor basin. Caradocian black shale is noticeably absent from the top of the Red Indian Lake Arc with this time interval instead represented by a sub-Silurian unconformity, formed in response to collisional uplift. Emergence of the peri- Laurentian margin is demonstrated by detritus from it preserved in the Badger Group, which as it stratigraphically overlies the peri-Gondwanan Victoria - Popelogan Arc, requires that Iapetus was closed by this time. Following this collision, subduction stepped back into the outboard Tetagouche - Exploits back-arc basin. Whereas correlative

  20. Mantle Heterogeneities and Crustal Processes of the Cascade Arc Represented by Basalts of the Poison Lake Chain, Lassen Volcanic Center, California

    NASA Astrophysics Data System (ADS)

    Wenner, J. M.; Teasdale, R.; Hiebing, M. S.; Lenz, Q. A.; Kroeninger, K.

    2013-12-01

    Basalts in the Poison Lake chain (PLC) include eight chemically distinct groups of primitive calc-alkaline basalts (defined by major element geochemistry and mineralogy). Located east of the Lassen Volcanic Center, PLC primitive basalts span the range of basalt compositions exposed throughout the entire Cascade arc (e.g. Ba: 100-1000 ppm; (Sr/P)n: 1.3 - 3.8; La/Yb: 4-26). PLC groups have trace-element and isotope ratios that show little evidence of direct genetic relationships among groups or a common source. Major, trace element and isotope ratios show evidence of contributions from multiple mantle sources including MORB, fluid rich subduction component and subduction-related sediment. Some groups record compositional variations from multiple mantle sources with minimal crustal processing. Similarly, preliminary probe data for olivine-spinel pairs suggest that some PLC groups are derived from heterogeneous mantle sources. Geochemical evidence indicates that other groups have petrogenetic histories that include crustal processes such as fractional crystallization, mixing or crustal contamination. Isotope ratios, major and trace element compositions and crystal compositions provide insights into the extent of source heterogeneities versus the degree of crustal processing. The broad range of compositional variations in basalts of PLC provides the opportunity to examine the extent of mantle heterogeneities and crustal processing in a small geographic area (50km2) for rocks that are nearly the same age (100-110 ka). The diverse primitive compositions erupted in the constrained time and space of the Poison Lake chain and the lack of genetic relationship among groups make it the ideal place to investigate the small scale nature of mantle domains and the roles of subduction and modification processes in the generation of basaltic compositions in arcs such as the Cascades, Mexico, Japan.

  1. 2010 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Neal, Christina A.; Herrick, Julie; Girina, O.A.; Chibisova, Marina; Rybin, Alexander; McGimsey, Robert G.; Dixon, Jim

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest at 12 volcanic centers in Alaska during 2010. The most notable volcanic activity consisted of intermittent ash emissions from long-active Cleveland volcano in the Aleutian Islands. AVO staff also participated in hazard communication regarding eruptions or unrest at seven volcanoes in Russia as part of an ongoing collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  2. A continuous 770-year record of volcanic activity from east Antarctica

    NASA Astrophysics Data System (ADS)

    Moore, John C.; Narita, Hideki; Maeno, Norikazu

    1991-09-01

    A 100-m ice core from east Antarctica has been analyzed for volcanic activity using dielectric profiling. Reasonably accurate dates are given for the eruptions of Tambora (1815), Agung (1963), Krakatoa (1883), and the well-known eruption of 1259.

  3. G-EVER Activities and the Next-generation Volcanic Hazard Assessment System

    NASA Astrophysics Data System (ADS)

    Takarada, S.

    2013-12-01

    The Asia-Pacific Region Global Earthquake and Volcanic Eruption Risk Management (G-EVER) is a consortium of Asia-Pacific geohazard research institutes that was established in 2012. G-EVER aims to formulate strategies to reduce the risks of disasters worldwide caused by the occurrence of earthquakes, tsunamis and volcanic eruptions. G-EVER is working on enhancing collaboration, sharing of resources, and making information on the risks of earthquakes and volcanic eruptions freely available and understandable. The 1st G-EVER International Symposium was held in Tsukuba, Japan in March 11, 2013. The 2nd Symposium is scheduled in Sendai, Tohoku Japan, in Oct. 19-20, 2013. Currently, 4 working groups were proposed in the G-EVER Consortium. The next-generation volcano hazard assessment WG is developing a useful system for volcanic eruption prediction, risk assessment, and evacuation at various eruption stages. The assessment system is based on volcanic eruption history datasets, volcanic eruption database, and numerical simulations. Volcanic eruption histories including precursor phenomena leading to major eruptions of active volcanoes are very important for future prediction of volcanic eruptions. A high quality volcanic eruption database, which contains compilations of eruption dates, volumes, and types, is important for the next-generation volcano hazard assessment system. Proposing international standards on how to estimate the volume of volcanic products is important to make a high quality volcanic eruption database. Spatial distribution database of volcanic products (e.g. tephra and pyroclastic flow distributions), encoded into a GIS based database is necessary for more precise area and volume estimation and risk assessments. The volcanic eruption database is developed based on past eruption results, which only represents a subset of possible future scenarios. Therefore, numerical simulations with controlled parameters are needed for more precise volcanic eruption

  4. Attaining high-resolution eruptive histories for active arc volcanoes with argon geochronology

    NASA Astrophysics Data System (ADS)

    Calvert, A. T.

    2012-04-01

    Geochronology of active arc volcanoes commonly illuminates eruptive behavior over tens to hundreds of thousands of years, lengthy periods of repose punctuated by short eruptive episodes, and spatial and compositional changes with time. Despite the >1 Gyr half-life of 40K, argon geochronology is an exceptional tool for characterizing Pleistocene to Holocene eruptive histories and for placing constraints on models of eruptive behavior. Reliable 40Ar/39Ar ages of calc-alkaline arc rocks with rigorously derived errors small enough (± 500 to 3,000 years) to constrain eruptive histories are attainable using careful procedures. Sample selection and analytical work in concert with geologic mapping and stratigraphic studies are essential for determining reliable eruptive histories. Preparation, irradiation and spectrometric techniques have all been optimized to produce reliable, high-precision results. Examples of Cascade and Alaska/Aleutian eruptive histories illustrating duration of activity from single centers, eruptive episodicity, and spatial and compositional changes with time will be presented: (1) Mt. Shasta, the largest Cascade stratovolcano, has a 700,000-year history (Calvert and Christiansen, 2011 Fall AGU). A similar sized and composition volcano (Rainbow Mountain) on the Cascade axis was active 1200-950 ka. The eruptive center then jumped west 15 km to the south flank of the present Mt. Shasta and produced a stratovolcano from 700-450 ka likely rivaling today's Mt. Shasta. The NW portion of that edifice failed in an enormous (>30 km3) debris avalanche. Vents near today's active summit erupted 300-135 ka, then 60-15 ka. A voluminous, but short-lived eruptive sequence occurred at 11 ka, including a summit explosion producing a subplinian plume, followed by >60 km3 andesite-dacite Shastina domes and flows, then by the flank dacite Black Butte dome. Holocene domes and flows subsequently rebuilt the summit and flowed to the north and east. (2) Mt. Veniaminof on

  5. Volcanism and associated hazards: the Andean perspective

    NASA Astrophysics Data System (ADS)

    Tilling, R. I.

    2009-12-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene. The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia, Ecuador, and

  6. Volcanism and associated hazards: The Andean perspective

    USGS Publications Warehouse

    Tilling, R.I.

    2009-01-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene.

    The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km 3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia

  7. Assessment of the atmospheric impact of volcanic eruptions

    NASA Technical Reports Server (NTRS)

    Sigurdsson, H.

    1988-01-01

    The dominant global impact of volcanic activity is likely to be related to the effects of volcanic gases on the Earth's atmosphere. Volcanic gas emissions from individual volcanic arc eruptions are likely to cause increases in the stratospheric optical depth that result in surface landmass temperature decline of 2 to 3 K for less than a decade. Trachytic and intermediate magmas are much more effective in this regard than high-silica magmas, and may also lead to extensive ozone depletion due to effect of halogens and magmatic water. Given the assumed relationship between arc volcanism and subduction rate, and the relatively small variation in global spreading rates in the geologic record, it is unlikely that the rates of arc volcanism have varied greatly during the Cenozoic. Hotspot related basaltic fissure eruptions in the subaerial environment have a higher mass yield of sulfur, but lofting of the valcanic aerosol to levels above the tropopause is required for a climate impact. High-latitude events, such as the Laki 1783 eruption can easily penetrate the tropopause and enter the stratosphere, but formation of a stratospheric volcanic aerosol form low-latitude effusive basaltic eruptions is problematical, due to the elevated low-latitude tropopause. Due to the high sulfur content of hotspot-derived basaltic magmas, their very high mass eruption rates and the episodic behavior, hotspots must be regarded as potentially major modifiers of Earth's climate through the action of their volcanic volatiles on the chemistry and physics of the atmosphere.

  8. 10 Ma of Igneous Activity in the Transmexican Volcanic Belt: Tectonic and Geomagnetic Implications.

    NASA Astrophysics Data System (ADS)

    Ruiz-Martinez, V. C.; Osete, M. L.; Urrutia-Fucugauchi, J.

    2007-05-01

    A total of 51 sites with geochronological control were sampled in the central and western segments of the Transmexican Volcanic Belt (TMVB). Together with other previously published 69 sites from the eastern segment, they span the spatial and temporal activity of the TMVB. Using now the same reference directions and methodologies, they are analyzed in order (i) to determine the possible occurrence and significance (spatially and temporally) of vertical axis crustal block rotations that have been reported in this region; and (ii) to study the geomagnetic Paleo Secular Variation during the last 10 Ma; to check the previously suggested existence of a "Pacific Dipole Window" extending to Mexico. Paleomagnetic results, backed by statistical tests performed according to their geographical distribution (3 structural segments) or according to their ages (Late Miocene, Pliocene or Quaternary), do not support the notion that large vertical axis block rotations (paleomagnetically detectable) occurred in this arc after Late Miocene times. They suggest that the TMVB could be considered paleomagnetically as an unique tectonic domain under a transtensional regime, where its extension component prevails over its left-lateral component. The mean paleomagnetic directions, obtained in the age ranges 10-5 Ma and 5-0 Ma, do not differ from their respective reference directions. In both datasets, VGPs have been selected using quality Fisher's precision parameters and optimum cutoff angles. This results in a circularly symmetrical data distribution with statistically indistinguishable antipodal normal and reverse polarities. VGP dispersions are consistent with those from globally distributed observations at Mexican latitudes for the Miocene and the Plio- Quaternary. An analysis of all the published paleomagnetic data from the TMVB, when combined all together and selected in the same terms, do not support neither the existence of large crustal block rotations nor the persistence of a

  9. Volcanism, isostatic residual gravity, and regional tectonic setting of the Cascade volcanic province

    SciTech Connect

    Blakely, R.J.; Jachens, R.C. )

    1990-11-10

    A technique to locate automatically boundaries between crustal blocks of disparate densities was applied to upward continued isostatic residual gravity data. The boundary analysis delineates a narrow gravitational trough that extends the length of the Pliocene and Quaternary volcanic arc from Mount Baker in northern Washington to Lassen Peak in California. Gravitational highs interrupt the trough at two localities: A northwest trending high in southern Washington and a northeast trending high between Mount Shasta and Lassen Peak. The latter anomaly is one of a set of northeast trending anomalies that, within the Quaternary arc, appear related to volcanic segmentation proposed previously on the basis of spatial compositional distributions of volcanoes. These northeast trending anomalies extend hundreds of kilometers northeast of the arc, are caused by sources in the upper crust, and in some cases are related to exposed pre-Tertiary rocks. Segmentation models invoke geometric characteristics of the subducting plate as the primary factor controlling location and chemistry of volcanism, and these northeast trending gravity sources also may be a product of disturbance of the upper crust by the subduction process. More likely, the gravity sources may reflect upper crustal structures older than the High Cascades, possibly relicts from earlier accretionary events or more recent crustal deformation, that have actively influenced the spatial location of more recent volcanism. Much of the Pliocene and Quaternary volcanism of the Cascade arc has concentrated on or near contacts between crustal blocks of disparate density. These contacts may promote the ascension of magma to the Earth's surface.

  10. Volcanism, isostatic residual gravity, and regional tectonic setting of the Cascade Volcanic Province

    NASA Astrophysics Data System (ADS)

    Blakely, Richard J.; Jachens, Robert C.

    1990-11-01

    A technique to locate automatically boundaries between crustal blocks of disparate densities was applied to upward continued isostatic residual gravity data. The boundary analysis delineates a narrow gravitational trough that extends the length of the Pliocene and Quaternary volcanic arc from Mount Baker in northern Washington to Lassen Peak in California. Gravitational highs interrupt the trough at two localities: a northwest trending high in southern Washington and a northeast trending high between Mount Shasta and Lassen Peak. The latter anomaly is one of a set of northeast trending anomalies that, within the Quaternary arc, appear related to volcanic segmentation proposed previously on the basis of spatial and compositional distributions of volcanoes. These northeast trending anomalies extend hundreds of kilometers northeast of the arc, are caused by sources in the upper crust, and in some cases are related to exposed pre-Tertiary rocks. Segmentation models invoke geometric characteristics of the subducting plate as the primary factor controlling location and chemistry of volcanism, and these northeast trending gravity sources also may be a product of disturbance of the upper crust by the subduction process. More likely, the gravity sources may reflect upper crustal structures older than the High Cascades, possibly relicts from earlier accretionary events or more recent crustal deformation, that have actively influenced the spatial location of more recent volcanism. Much of the Pliocene and Quaternary volcanism of the Cascade arc has concentrated on or near contacts between crustal blocks of disparate density. These contacts may promote the ascension of magma to the Earth's surface.

  11. Characterization of volcanic activity using observations of infrasound, volcanic emissions, and thermal imagery at Karymsky Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Lopez, T.; Fee, D.; Prata, F.

    2012-04-01

    Karymsky Volcano is one of the most active and dynamic volcanoes in Kamchatka, with activity ranging from vigorous degassing, frequent ash emissions, and apparent vent sealing, all punctuated by daily to weekly explosive magmatic eruptions. Recent studies have highlighted the strengths in using complementary infrasound measurements and remote volcanic emission measurements to characterize volcanic activity, with the potential to discriminate emission-type, approximate ash-cloud height, and estimate SO2 emission mass. Here we use coincident measurements of infrasound, SO2, ash, and thermal radiation collected over a ten day period at Karymsky Volcano in August 2011 to characterize the observed activity and elucidate vent processes. The ultimate goal of this project is to enable different types of volcanic activity to be identified using only infrasound data, which would significantly improve our ability to continuously monitor remote volcanoes. Four types of activity were observed. Type 1 activity is characterized by discrete ash emissions occurring every 1 - 5 minutes that either jet or roil out of the vent, by plumes from 500 - 1500 m (above vent) altitudes, and by impulsive infrasonic onsets. Type 2 activity is characterized by periodic pulses of gas emission, little or no ash, low altitude (100 - 200 m) plumes, and strong audible jetting or roaring. Type 3 activity is characterized by sustained emissions of ash and gas, with multiple pulses lasting from ~1 - 3 minutes, and by plumes from 300 - 1500 m. Type 4 activity is characterized by periods of relatively long duration (~30 minutes to >1 hour) quiescence, no visible plume and weak SO2 emissions at or near the detection limit, followed by an explosive, magmatic eruption, producing ash-rich plumes to >2000 m, and centimeter to meter (or greater) sized pyroclastic bombs that roll down the flanks of the edifice. Eruption onset is accompanied by high-amplitude infrasound and occasionally visible shock

  12. Consolidation state of marine sediments west of Martinique, Lesser Antilles volcanic arc: preliminary geotechnical analyses from IODP Expedition 340

    NASA Astrophysics Data System (ADS)

    Lafuerza, S.; Le Friant, A.; Manga, M.; Hornbach, M. J.; Jutzeler, M.; Breitkreuz, C. F.

    2012-12-01

    From shipboard measurements of undrained shear strength performed in hemipelagic sediments during the IODP Expedition 340 in the Lesser Antilles arc we infer the consolidation state of the upper 200 meters of marine successions in the Grenada Basin, west of Martinique. Results from consolidation tests and hydraulic conductivity measurements on sediment samples from site U1400 are used to verify observations based on undrained shear strength measurements. The selected sites (U1397, U1398, U1399 and U1400) contain stacked mass transport deposits made of volcaniclastic and hemipelagic sediments. The ratio of the undrained shear strength to the effective stress of normally consolidated hemipelagic sediments at the upper slope west of Montserrat (site U1396) is used as a reference. The drilled mass transport deposit at site U1400 comprises an upper package (˜80 metres below sea floor: mbsf) of deformed hemipelagic sediments with some layers of overconsolidated sediments. At greater depths (> 80 mbsf), layers with underconsolidated sediments suggest that pore fluid pressures exist in excess of hydrostatic. Values of excess pore pressure range from 30 and 60 % of the vertical effective stress at 84 m and 159 mbsf, respectively. Hydraulic conductivity ranges around 10-9 m/s in normally consolidated sediments and decreases to values of less than 10-10 m/s in overconsolidated sediments. At sites U1397, U1398 and U1399, hemipelagic layers interbedded within coarse volcaniclastic sediments are underconsolidated, which implies increased pore fluid pressures. We propose that shear-induced compaction during transport leads to overconsolidation and hydraulic conductivity reduction. The low hydraulic conductivity that characterises these hemipelagic sediments may reduce rates of dewatering and allow pore fluid overpressure to persist. These results suggest that excess pore fluid pressures, which reduce slope stability, may have been involved in the destabilisation and

  13. Short-term spasmodic switching of volcanic tremor source activation in a conduit of the 2011 Kirishima eruption

    NASA Astrophysics Data System (ADS)

    Matsumoto, S.; Shimizu, H.; Matsushima, T.; Uehira, K.; Yamashita, Y.; Nakamoto, M.; Miyazaki, M.; Chikura, H.

    2012-04-01

    Volcanic tremors are seismic indicators providing clues for magma behavior, which is related to volcanic eruptions and activity. Detection of spatial and temporal variations of volcanic tremors is important for understanding the mechanism of volcanic eruptions. However, temporal variations of tremor activity in short-term than a minute have not been previously detected by seismological observations around volcanoes. Here, we show that volcanic tremor sources were activated at the top of the conduit (i.e. the crater) and at its lower end by analyzing seismograms from a dense seismic array during the 2011 Kirishima eruption. We observed spasmodic switching in the seismic ray direction during a volcanic tremor sequence. Such fine volcanic tremor structure suggests an interaction between tremor sources located in both deep and shallow depths. Our result suggests that seismic array observations can monitor the magma behavior and contribute to the evaluation of the activity's transition.

  14. Volcanic features of Io

    USGS Publications Warehouse

    Carr, M.H.; Masursky, H.; Strom, R.G.; Terrile, R.J.

    1979-01-01

    Volcanic activity is apparently higher on Io than on any other body in the Solar System. Its volcanic landforms can be compared with features on Earth to indicate the type of volcanism present on Io. ?? 1979 Nature Publishing Group.

  15. Volcanic eruption source parameters from active and passive microwave sensors

    NASA Astrophysics Data System (ADS)

    Montopoli, Mario; Marzano, Frank S.; Cimini, Domenico; Mereu, Luigi

    2016-04-01

    It is well known, in the volcanology community, that precise information of the source parameters characterising an eruption are of predominant interest for the initialization of the Volcanic Transport and Dispersion Models (VTDM). Source parameters of main interest would be the top altitude of the volcanic plume, the flux of the mass ejected at the emission source, which is strictly related to the cloud top altitude, the distribution of volcanic mass concentration along the vertical column as well as the duration of the eruption and the erupted volume. Usually, the combination of a-posteriori field and numerical studies allow constraining the eruption source parameters for a given volcanic event thus making possible the forecast of ash dispersion and deposition from future volcanic eruptions. So far, remote sensors working at visible and infrared channels (cameras and radiometers) have been mainly used to detect, track and provide estimates of the concentration content and the prevailing size of the particles propagating within the ash clouds up to several thousand of kilometres far from the source as well as track back, a-posteriori, the accuracy of the VATDM outputs thus testing the initial choice made for the source parameters. Acoustic wave (infrasound) and microwave fixed scan radar (voldorad) were also used to infer source parameters. In this work we want to put our attention on the role of sensors operating at microwave wavelengths as complementary tools for the real time estimations of source parameters. Microwaves can benefit of the operability during night and day and a relatively negligible sensitivity to the presence of clouds (non precipitating weather clouds) at the cost of a limited coverage and larger spatial resolution when compared with infrared sensors. Thanks to the aforementioned advantages, the products from microwaves sensors are expected to be sensible mostly to the whole path traversed along the tephra cloud making microwaves particularly

  16. Origin of Late Paleogene to Neogene basalts and associated coeval felsic volcanic rocks in Southwest Hokkaido, northern NE Japan arc: Constraints from Sr and Nd isotopes and major- and trace-element chemistry

    NASA Astrophysics Data System (ADS)

    Takanashi, Koshiro; Shuto, Kenji; Sato, Makoto

    2011-07-01

    Basalts and felsic volcanic rocks (mainly dacite and rhyolite) found in southwest Hokkaido, northern part of the NE Japan arc, result from protracted volcanism during the Oligocene (34-30 Ma), Early Miocene (25-17 Ma), Middle Miocene (16-12 Ma), Late Miocene (10-5 Ma), Pliocene (4 Ma) and Quaternary (2 Ma), thus spanning the pre-Japan Sea opening to post-opening stages. The majority of basaltic rocks after about 16 Ma show depleted Sr (SrI) and Nd (NdI) isotopic signatures compared with some Middle to Early Miocene basalts, which strongly resemble, in terms of both timing and extent, the change in SrI and NdI values for back-arc basaltic rocks of the central NE Japan arc. However, significant differences exist for younger basaltic rocks, in that basaltic rocks with depleted SrI and NdI signatures are found from the Middle Miocene onwards throughout the eastern-, transitional- and western-volcanic zones in SW Hokkaido, whereas in the central NE Japan arc, basaltic rocks with similar isotopic signatures are confined to the back-arc side. Felsic volcanic rocks in southwest Hokkaido have SrI and NdI values, which overlap with coeval southwest Hokkaido basaltic rocks. Although the relationship between mafic and felsic rocks could be attributed to fractional crystallization, this process is inconsistent with REE chemistry, as total REE do not increase systematically from basaltic rocks to felsic volcanic rocks. Alternatively, lower crustal mafic rocks, represented by gabbroic and amphibolitic xenoliths found in basaltic rocks at Itinome-gata (Oga Peninsula), are a possible source for Late Paleogene to Quaternary felsic magmas, as both felsic volcanic rocks and xenoliths have similar SrI and NdI. A possible tectono-magmatic model for the production of post-Late Paleogene volcanic rocks from SW Hokkaido commences in the Oligocene (34 Ma) with asthenospheric mantle upwelling followed by partial melting to generate basalt magma (Matsue basalt) with depleted SrI and Nd

  17. Geologic evolution of the Jemez Mountains and their potential for future volcanic activity

    SciTech Connect

    Burton, B.W.

    1982-01-01

    Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10/sup -9//km/sup 2//y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10/sup -7//y.

  18. Felsic Magmatism through Intracrustal Melting of Previously Formed Volcanic-Arc Crust: Implications for Differentiation and Secular Evolution of the Continental Crust

    NASA Astrophysics Data System (ADS)

    G R, R. K.; C, S.

    2015-12-01

    The fundamental challenge in understanding the origin and evolution of the continental crust is to recognize how primary mantle source, and oceanic crust, which are essentially mafic to ultramafic in composition, could differentiate into a more or less felsic compositions. It is possible to understand growth and differentiation of the continental crust by constraining the interplay of magmatism, deformation, and high-grade metamorphism in the lower crust. Here, we apply this knowledge on the lower crustal granitoids of southern India and speculate on the variations in geochemistry as a consequence of differentiation and secular evolution of the continental crust.The major groups of granitoids of southern India are classified as metatonalites, comparable to typical Archaean TTGs with pronounced calc-alkaline affinity, and metagranites which are magmatic fractionation produced by reworking of early crust. Metatonalites are sodic-trondhjemites with slightly magnesian, moderate LREE (average LaN = 103) and low HREE (average YbN = 2) characerestics, where as metagranites are calc-alkaline ferroan types with enriched LREE (average LaN = 427) and HREE (average YbN = 23). Petrogenetic characteristics of granitoids illustrate continuous evolution of a primary crust into diverse magmatic units by multiple stages of intracrustal differentiation processes attributed to following tectonic scenarios: (1) formation of tonalitic magma by low- to moderate-degree partial melting of hydrated basaltic crust at pressures high enough to stabilize garnet-amphibole residue and (2) genesis of granite in a continental arc-accretion setting by an episode of crustal remelting of the tonalitic crust, within plagioclase stability field. The first-stage formed in a flat-subduction setting of an volcanic-arc, leading to the formation of tonalites. The heat budget required is ascribed to the upwelling of the mantle and/or basaltic underplating. Progressive decline in mantle potential temperature

  19. Contrasting sedimentary processes along a convergent margin: the Lesser Antilles arc system

    NASA Astrophysics Data System (ADS)

    Picard, Michel; Schneider, Jean-Luc; Boudon, Georges

    2006-12-01

    Sedimentation processes occurring in an active convergent setting are well illustrated in the Lesser Antilles island arc. The margin is related to westward subduction of the North and/or the South America plates beneath the Caribbean plate. From east to west, the arc can be subdivided into several tectono-sedimentary depositional domains: the accretionary prism, the fore-arc basin, the arc platform and inter-arc basin, and the Grenada back-arc basin. The Grenada back-arc basin, the fore-arc basin (Tobago Trough) and the accretionary prism on the east side of the volcanic arc constitute traps for particles derived from the arc platform and the South American continent. The arc is volcanically active, and provides large volumes of volcaniclastic sediments which accumulate mainly in the Grenada basin by volcaniclastic gravity flows (volcanic debris avalanches, debris flows, turbiditic flows) and minor amounts by fallout. By contrast, the eastern side of the margin is fed by ash fallout and minor volcaniclastic turbidites. In this area, the dominant component of the sediments is pelagic in origin, or derived from South America (siliciclastic turbidites). Insular shelves are the locations of carbonate sedimentation, such as large platforms which develop in the Limestone Caribbees in the northern part of the margin. Reworking of carbonate material by turbidity currents also delivers lesser amounts to eastern basins of the margin. This contrasting sedimentation on both sides of the arc platform along the margin is controlled by several interacting factors including basin morphology, volcanic productivity, wind and deep-sea current patterns, and sea-level changes. Basin morphology appears to be the most dominant factor. The western slopes of the arc platform are steeper than the eastern ones, thus favouring gravity flow processes.

  20. Seismic Activity at tres Virgenes Volcanic and Geothermal Field

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  1. The He-CO 2 isotope and relative abundance characteristics of geothermal fluids in El Salvador and Honduras: New constraints on volatile mass balance of the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    de Leeuw, G. A. M.; Hilton, D. R.; Fischer, T. P.; Walker, J. A.

    2007-06-01

    We report helium and carbon isotope and relative abundance data of fumaroles, hot springs, water springs, mud-pots and geothermal wells from El Salvador and Honduras to investigate both along and across-arc controls on the release of CO 2 from the subducted slab. El Salvador localities show typical volcanic front volcanic gas signatures, with 3He/ 4He ratios of 5.2-7.6 RA, δ13C values of - 3.6‰ to - 1.3‰ and CO 2/ 3He ratios of 8-25 × 10 9. In Honduras, we find similar values only for volatiles collected in the Sula Graben region located ˜ 200 km behind the volcanic front. All other areas in Honduras show significantly lower 3He/ 4He ratios (0.7-3.5 RA), lower δ13C values (< - 7.3‰) and more variable CO 2/ 3He ratios (6.2 × 10 7-2.0 × 10 11): characteristics consistent with degassing-induced fractionation of CO 2 and He and/or interaction with crustal rocks. The provenance of CO 2 released along the volcanic front is dominated by subducted marine carbonates (L = 76 ± 4%) and organic sediments (S = 14 ± 3%), with the mantle wedge (M) contributing 10 ± 3% to the total carbon flux. The L/S ratio of the El Salvador volatiles (average = 5.6) is comparable to volcanic front localities in Costa Rica and Nicaragua [A.M. Shaw, D.R. Hilton, T.P. Fischer, L.A. Walker, G.E. Alvarado, Contrasting He-C relationships in Nicaragua and Costa Rica: insights into C cycling through subduction zones. Earth Planet. Sci. Lett. 214 (2003) 499-513] but is approximately one-half the input value of sediments at the trench (L. Li, G.E. Bebout, Carbon and nitrogen geochemistry of sediments in the Central American convergent margin: Insights regarding subduction input fluxes, diagenesis, and paleoproductivity, J. Geophys. Res. 110 (2005), doi: 10.1029/2004JB003276). We use the L/S ratio of El Salvador geothermal fluids, together with estimates of the CO 2 output flux from the arc, to constrain the amount and composition of subducted sediments involved in the supply of CO 2 to the

  2. Magmatically Greedy Reararc Volcanoes of the N. Tofua Segment of the Tonga Arc

    NASA Astrophysics Data System (ADS)

    Rubin, K. H.; Embley, R. W.; Arculus, R. J.; Lupton, J. E.

    2013-12-01

    Volcanism along the northernmost Tofua Arc is enigmatic because edifices of the arc's volcanic front are mostly, magmatically relatively anemic, despite the very high convergence rate of the Pacific Plate with this section of Tonga Arc. However, just westward of the arc front, in terrain generally thought of as part of the adjacent NE Lau Backarc Basin, lie a series of very active volcanoes and volcanic features, including the large submarine caldera Niuatahi (aka volcano 'O'), a large composite dacite lava flow terrain not obviously associated with any particular volcanic edifice, and the Mata volcano group, a series of 9 small elongate volcanoes in an extensional basin at the extreme NE corner of the Lau Basin. These three volcanic terrains do not sit on arc-perpendicular cross chains. Collectively, these volcanic features appear to be receiving a large proportion of the magma flux from the sub-Tonga/Lau mantle wedge, in effect 'stealing' this magma flux from the arc front. A second occurrence of such magma 'capture' from the arc front occurs in an area just to the south, on southernmost portion of the Fonualei Spreading Center. Erupted compositions at these 'magmatically greedy' volcanoes are consistent with high slab-derived fluid input into the wedge (particularly trace element abundances and volatile contents, e.g., see Lupton abstract this session). It is unclear how long-lived a feature this is, but the very presence of such hyperactive and areally-dispersed volcanism behind the arc front implies these volcanoes are not in fact part of any focused spreading/rifting in the Lau Backarc Basin, and should be thought of as 'reararc volcanoes'. Possible tectonic factors contributing to this unusually productive reararc environment are the high rate of convergence, the cold slab, the highly disorganized extension in the adjacent backarc, and the tear in the subducting plate just north of the Tofua Arc.

  3. Sulfur dioxide - Episodic injection shows evidence for active Venus volcanism

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.

    1984-03-01

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  4. Sulfur dioxide - Episodic injection shows evidence for active Venus volcanism

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.

    1984-01-01

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  5. Age and progression of volcanism, Wrangell volcanic field, Alaska

    USGS Publications Warehouse

    Richter, D.H.; Smith, James G.; Lanphere, M.A.; Dalrymple, G.B.; Reed, B.L.; Shew, N.

    1990-01-01

    The Wrangell volcanic field covers more than 10 000 km2 in southern Alaska and extends uninterrupted into northwest. Yukon Territory. Lavas in the field exhibit medium-K, calc-alkaline affinities, typical of continental volcanic arcs along convergent plate margins. Eleven major eruptive centers are recognized in the Alaskan part of the field. More than 90 K-Ar age determinations in the field show a northwesterly progression of eruptive activity from 26 Ma, near the Alaska-Yukon border, to about 0.2 Ma at the northwest end of the field. A few age determinations in the southeast extension of the field in Yukon Territory, Canada, range from 11 to 25 Ma. The ages indicate that the progression of volcanism in the Alaska part of the field increased from about 0.8 km/Ma, at 25 Ma, to more than 20 km/MA during the past 2 Ma. The progression of volcanic activity and its increased rate of migration with time is attributed to changes in the rate and angle of Pacific plate convergence and the progressive decoupling of the Yakutat terrane from North America. Subduction of Yakutat terrane-Pacific plate and Wrangell volcanic activity ceased about 200 000 years age when Pacific plate motion was taken up by strike-slip faulting and thrusting. ?? 1990 Springer-Verlag.

  6. U.S. Geological Survey's Alert Notification System for Volcanic Activity

    USGS Publications Warehouse

    Gardner, Cynthia A.; Guffanti, Marianne C.

    2006-01-01

    The United States and its territories have about 170 volcanoes that have been active during the past 10,000 years, and most could erupt again in the future. In the past 500 years, 80 U.S. volcanoes have erupted one or more times. About 50 of these recently active volcanoes are monitored, although not all to the same degree. Through its five volcano observatories, the U.S. Geological Survey (USGS) issues information and warnings to the public about volcanic activity. For clarity of warnings during volcanic crises, the USGS has now standardized the alert-notification system used at its observatories.

  7. Nurture Versus Nature: Accounting for the Differences Between the Taiwan and Timor active arc-continent collisions

    NASA Astrophysics Data System (ADS)

    Harris, R. A.

    2011-12-01

    The active Banda arc/continent collision of the Timor region provides many important contrasts to what is observed in Taiwan, which is mostly a function of differences in the nature of the subducting plate. One of the most important differences is the thermal state of the respective continental margins: 30 Ma China passive margin versus 160 Ma NW Australian continental margin. The subduction of the cold and strong NW Australian passive margin beneath the Banda trench provides many new constraints for resolving longstanding issues about the formative stages of collision and accretion of continental crust. Some of these issues include evidence for slab rollback and subduction erosion, deep continental subduction, emplacement or demise of forearc basement, relative amounts of uplift from crustal vs. lithospheric processes, influence of inherited structure, partitioning of strain away from the thrust front, extent of mélange development, metamorphic conditions and exhumation mechanisms, continental contamination and accretion of volcanic arcs, does the slab tear, and does subduction polarity reverse? Most of these issues link to the profound control of lower plate crustal heterogeneity, thermal state and inherited structure. The thermomechanical characteristics of subducting an old continental margin allow for extensive underthrusting of lower plate cover units beneath the forearc and emplacement and uplift of extensive nappes of forearc basement. It also promotes subduction of continental crust to deep enough levels to experience high pressure metamorphism (not found in Taiwan) and extensive contamination of the volcanic arc. Seismic tomography confirms subduction of continental lithosphere beneath the Banda Arc to at least 400 km with no evidence for slab tear. Slab rollback during this process results in massive subduction erosion and extension of the upper plate. Other differences in the nature of the subducting plates in Taiwan in Timor are differences in the

  8. Evidence for Slab Melt Contributions to the Mexican Volcanic Belt and Other Young Hot Slab Arcs from Lu-Hf Isotopes

    NASA Astrophysics Data System (ADS)

    Goldstein, S. L.; Cai, Y. M.; Langmuir, C. H.; Lagatta, A.; Straub, S. M.; Gomez-Tuena, A.; Martin Del Pozzo, A.

    2007-12-01

    Despite major advances in delineating the processes that govern magma generation at convergent margins, the problem persists of distinguishing slab, mantle wedge, and crustal contributions. A corrollary question is whether there is significant melting of subducted ocean crust. Especially in thick crust regions, the importance of crustal versus mantle contributions to lavas represents a long-standing fundamental issue in arc magma geochemistry. We show that frontal arc magmas from the Central Mexican Volcanic Belt (CMVB), including the large andesitic stratovolcanoes Popocatepetl and Nevado de Toluca, display negligible crustal contamination, and contain substantial contributions from melting of subducted Pacific ocean crust. Despite ca. 50 km thick continental crust, the CMVB erupts near primitive lavas including "high-Nb" alkaline basalts that show negligible "subduction signatures" in their trace element patterns. These "high-Nb" basalts define the regional mantle wedge composition in isotope-trace element space. The "normal" calcalkaline lavas form a negative correlation between Hf isotopes and Lu/Hf. One endmember is like the high Nb basalts representing the regional mantle wedge. The other endmember has higher Hf isotopes (approaching values of Pacific MORB) and very low Lu/Hf of less than 0.04 (e.g. compared to typical values of ca. 0.2 in Pacific MORB). The low Lu/Hf values require low degree partial melting of a source rich in garnet. The high Hf isotopes require a depleted mantle source with isotopes like Pacific MORB. Together the Lu-Hf data indicate a substantial component derived from melting of eclogitic Pacific ocean crust. A key feature of the data is that the stratovolcano lavas showing the largest slab melt signature also show the highest Hf isotope ratios and thus are more "depleted mantle-like" than the regional mantle wedge. Thus, the integrated data allow us to clearly distinguish between mantle and crustal sources in the CMVB and point to

  9. Crustal thickening drives arc front migration

    NASA Astrophysics Data System (ADS)

    Karlstrom, Leif; Lee, Cin-Ty; Manga, Michael

    2014-05-01

    The location of volcanic arcs, relative to the trench evolves over time. Arc front migration has been observed in relic (Sierra Nevada, Andes) as well as active (Cascades) arcs, sometimes with cycles of retreat and return of the front towards the trench over millions of years. Other arcs, particularly where back-arc extension dominates, migrate more slowly, if at all. Coupled with arc migration there are systematic changes in the geochemistry of magmas such as the ratio of trace elements La/Yb and 87Sr/86Sr isotopes (e.g., Haschke et al., 2002). The position of active volcanic arcs relative to the trench is controlled by the location where melt is generated in the mantle wedge, in turn controlled by the geometry of subduction, and the processes that focus rising melt. Arc front migration is commonly attributed to variation in dip angle of the downgoing slab, delamination of overthickened crust, or to subduction erosion. Here we present an alternative hypothesis. Assuming mantle wedge melting is a largely temperature-dependant process, the maximum isotherm in the wedge sets arc front location. Isotherm location depends on slab angle, subduction velocity and wedge thermal diffusivity (England and Katz, 2010). It also depends on crustal thickness, which evolves as melt is transferred from the wedge to the crust. Arc front migration can thus occur purely through magmatic thickening of crust and lithosphere. Thickening rate is determined by the mantle melt flux into the crust, modulated by tectonics and surface erosion. It is not steady in time, as crustal thickening progressively truncates the mantle melt column and eventually shuts it off. Thus slab angle need not change, and in the absence of other contribution processes front location and crustal thickness have long-time steady state values. We develop a quantitative model for arc front migration that is consistent with published arc front data, and explains why arc fronts do not move when there is extension, such

  10. Characterization of Io's Volcanic Activity by Infrared Polarimetry.

    PubMed

    Goguen, J D; Sinton, W M

    1985-10-04

    The thermal emission from Io's volcanic hot spots is linearly polarized. Infrared measurements at 4.76 micrometers show disk-integrated polarization as large as 1.6 percent. The degree and position angle of linear polarization vary with Io's rotation in a manner characteristic of emission from a small number of hot spots. A model incorporating three hot spots best fits the data. The largest of these hot spots lies to the northeast of Loki Patera, as mapped from Voyager, and the other spot on the trailing hemisphere is near Ra Patera. The hot spot on the leading hemisphere corresponds to no named feature on the Voyager maps. The value determined for the index of refraction of the emitting surface is a lower bound; it is similar to that of terrestrial basalts and is somewhat less than that of sulfur.

  11. Characterization of Io's volcanic activity by infrared polarimetry

    SciTech Connect

    Goguen, J.D.; Sinton, W.M.

    1985-10-01

    The thermal emission from Io's volcanic hot spots is linearly polarized.Infrared measurements at 4.76 micrometers show disk-integrated polarization as large as 1.6 percent. The degree and position angle of linear polarization vary with Io's rotation in a manner characteristic of emission from a small number of hot spots. A model incorporating three hot spots best fits the data. The largest of these hot spots lies to the northeast of Loki Patera, as mapped from Voyager, and the other spot on the trailing hemisphere is near Ra Patera. The hot spot on the leading hemisphere corresponds to no named feature on the Voyager maps. The value determined for the index of refraction of the emitting surface is a lower bound; it is similar to that of terrestrial basalts and is somewhat less than that of sulfur. 25 references.

  12. Evolution of Eocene to Oligocene arc-related volcanism in the North Patagonian Andes (39-41°S), prior to the break-up of the Farallon plate

    NASA Astrophysics Data System (ADS)

    Iannelli, Sofía B.; Litvak, Vanesa D.; Fernández Paz, Lucía; Folguera, Andrés; Ramos, Miguel E.; Ramos, Víctor A.

    2017-01-01

    Voluminous Paleogene magmatic rocks (44 to 29 Ma) are found in a retroarc position in the Northern Patagonian to Southern Central Andes ( 39-42°S), whose origin remains controversial. Geochemical data in these Eocene to Oligocene volcanic associations are herein used to unravel their origin and understand changes in subduction parameters. Geochemical signatures indicate arc-related associations and reflect changing geodynamic boundary conditions of the Andean margin through time. In particular, Eocene magmatism ( 44 Ma; Pilcaniyeu Belt) shows an alkaline-like signature and limited slab influence. Reported contemporaneous within-plate magmatism ( 47-43 Ma) in an easternmost position reflects a more typical enriched source. Oligocene arc-like volcanism ( 29 Ma; El Maitén Belt), which developed in an extensional retroarc setting, shows a higher contribution from slab-derived fluids and a calc-alkaline source. A comparison with younger arc-related magmas from the region ( 26-20 Ma), emplaced in an intra- to retroarc position (Cura Mallín and Abanico basins), indicates a progressive increase in slab-signature, associated with a tholeiitic magma source. We propose that these compositional variations could be directly related to changes in plate configuration before and after the Farallon plate break-up and the initiation of a more orthogonal convergence typical of the present Andean-type subduction zone.

  13. Short Term Forecasts of Volcanic Activity Using An Event Tree Analysis System and Logistic Regression

    NASA Astrophysics Data System (ADS)

    Junek, W. N.; Jones, W. L.; Woods, M. T.

    2011-12-01

    An automated event tree analysis system for estimating the probability of short term volcanic activity is presented. The algorithm is driven by a suite of empirical statistical models that are derived through logistic regression. Each model is constructed from a multidisciplinary dataset that was assembled from a collection of historic volcanic unrest episodes. The dataset consists of monitoring measurements (e.g. InSAR, seismic), source modeling results, and historic eruption activity. This provides a simple mechanism for simultaneously accounting for the geophysical changes occurring within the volcano and the historic behavior of analog volcanoes. The algorithm is extensible and can be easily recalibrated to include new or additional monitoring, modeling, or historic information. Standard cross validation techniques are employed to optimize its forecasting capabilities. Analysis results from several recent volcanic unrest episodes are presented.

  14. 2013 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Dixon, James P.; Cameron, Cheryl; McGimsey, Robert G.; Neal, Christina A.; Waythomas, Chris

    2015-08-14

    The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2013. Beginning with the 2013 AVO Summary of Events, the annual description of the AVO seismograph network and activity, once a stand-alone publication, is now part of this report. Because of this change, the annual summary now contains an expanded description of seismic activity at Alaskan volcanoes. Eruptions occurred at three volcanic centers in 2013: Pavlof Volcano in May and June, Mount Veniaminof Volcano in June through December, and Cleveland Volcano throughout the year. None of these three eruptive events resulted in 24-hour staffing at AVO facilities in Anchorage or Fairbanks.

  15. Steady rotation of the Cascade arc

    USGS Publications Warehouse

    Wells, Ray E.; McCaffrey, Robert

    2013-01-01

    Displacement of the Miocene Cascade volcanic arc (northwestern North America) from the active arc is in the same sense and at nearly the same rate as the present clockwise block motions calculated from GPS velocities in a North American reference frame. Migration of the ancestral arc over the past 16 m.y. can be explained by clockwise rotation of upper-plate blocks at 1.0°/m.y. over a linear melting source moving westward 1–4.5 km/m.y. due to slab rollback. Block motion and slab rollback are in opposite directions in the northern arc, but both are westerly in the southern extensional arc, where rollback may be enhanced by proximity to the edge of the Juan de Fuca slab. Similarities between post–16 Ma arc migration, paleomagnetic rotation, and modern GPS block motions indicate that the secular block motions from decadal GPS can be used to calculate long-term strain rates and earthquake hazards. Northwest-directed Basin and Range extension of 140 km is predicted behind the southern arc since 16 Ma, and 70 km of shortening is predicted in the northern arc. The GPS rotation poles overlie a high-velocity slab of the Siletzia terrane dangling into the mantle beneath Idaho (United States), which may provide an anchor for the rotations.

  16. "Explosive volcanic activity at Mt. Yasur: A characterization of the acoustic events (9-12th July 2011)"

    NASA Astrophysics Data System (ADS)

    Spina, Laura; Taddeucci, Jacopo; Cannata, Andrea; Gresta, Stefano; Lodato, Luigi; Privitera, Eugenio; Scarlato, Piergiorgio; Gaeta, Mario; Gaudin, Damien; Palladino, Danilo Mauro

    2016-08-01

    Volcanic processes occur in a wide range of temporal and spatial scales. However, a key step of magma ascent is recognizable in the dynamics of gas and magma in the shallow plumbing system, where volatiles play a fundamental role in controlling the eruptive style. With the aim of investigating shallow degassing processes, an experimental setup was deployed at Mt. Yasur, an active volcano located in Tanna Island (Vanuatu arc), from 9th to 12th July 2011. The setup comprised high-speed and thermal cameras, as well as a microphone, capable of recording both in the infrasonic and audible range. The analysis of acoustic signals, validated by observing images from the high-speed and thermal cameras, has enabled characterizing the explosive activity during the investigated period. Two types of explosions, distinct for spectral features and waveforms, were observed: (i) minor events, corresponding to small overpressurized bursts, occurring almost continuously; (ii) major events, characterizing the Strombolian activity at Mt. Yasur. By investigating variation in the occurrence rate of the minor events, we found that, on a short timescale, the dynamics responsible for the two types of explosions are decoupled. These results, together with previous literature data, bring additional evidence of the existence of distinct sources of degassing. Finally, major events can be distinguished as emergent events, i.e. long-lasting signals, corresponding to ash-rich explosions, and impulsive events, featuring shorter duration and larger amplitude.

  17. The impact of a volcanic edifice on intrusive and eruptive activity

    NASA Astrophysics Data System (ADS)

    Roman, Alberto; Jaupart, Claude

    2014-12-01

    In a volcanic area, the orientation and composition of dikes record the development of the magmatic system that feeds intrusive and eruptive activity. At Spanish Peaks, Colorado, curved dike trajectories issuing from a single focal area have been attributed to horizontal propagation from a pressurized central reservoir in a deviatoric tectonic stress field. These dikes, however, are nowhere in contact with the central intrusion, are younger than it by about 1 My and are not filled with the same magma. They were emplaced at shallow depths (≈ 1 km), where the local stress field is very sensitive to surface loads. Here, we show that their trajectories can be set by the load of a volcanic edifice in a tectonic stress field. The orientation and distribution of the Spanish Peaks dikes have changed in the course of two million years as magmas were evolving chemically. Early dikes that were parallel to each another and filled with primitive melts document ascent in the regional tectonic stress field. They were replaced by curved dikes carrying evolved melts, which record the influence of a sizable volcanic edifice. Beneath this edifice, the induced compression prevented dense primitive magmas from erupting in the focal area and diverted intermediate magmas sideways. The growth of this large volcanic cone was probably responsible for the formation of a magma reservoir. The mechanisms that have shaped the Spanish Peaks dike swarm may control the spatial distribution and migration of eruptive centers in many active volcanic areas.

  18. Volcanism, isostatic residual gravity and regional tectonic setting of the Cascade volcanic province

    USGS Publications Warehouse

    Blakely, R.J.; Jachens, R.C.

    1990-01-01

    A technique to locate automatically boundaries between crustal blocks of disparate densities was applied to upward continued isostatic residual gravity data. The boundary analysis delineates a narrow gravitational trough that extends the length of the Pliocene and Quaternary volcanic arc from Mount Baker in northern Washington to Lassen Peak in California. Gravitational highs interrupt the trough at two localities: a northwest trending high in southern Washington and a northeast trending high between Mount Shasta and Lassen Peak. The gravity sources may reflect upper crustal structures older than the High Cascades, possibly relicts from earlier accretionary events or more recent crustal deformation, that have actively influenced the spatial location of more recent volcanism. Much of the Pliocene and Quaternary volcanism of the Cascade arc has concentrated on or near contacts between crustal blocks of disparate density. These contacts may promote the ascension of magma to the Earth's surface. -from Authors

  19. Propagation of back-arc extension in the arc of the southern New Hebrides Subduction Zone (South West Pacific) and possible relation to subduction initiation.

    NASA Astrophysics Data System (ADS)

    Fabre, M.; Patriat, M.; Collot, J.; Danyushevsky, L. V.; Meffre, S.; Falloon, T.; Rouillard, P.; Pelletier, B.; Roach, M. J.; Fournier, M.

    2015-12-01

    Geophysical data acquired during three expeditions of the R/V Southern Surveyor allows us to characterize the deformation of the upper plate at the southern termination of the New Hebrides subduction zone where it bends 90° eastward along the Hunter Ridge. As shown by GPS measurements and earthquake slip vectors systematically orthogonal to the trench, this 90° bend does not mark a transition from subduction to strike slip as usually observed at subduction termination. Here the convergence direction remains continuously orthogonal to the trench notwithstanding its bend. Multibeam bathymetric data acquired in the North Fiji Basin reveals active deformation and fragmentation of the upper plate. It shows the southward propagation of a N-S back-arc spreading ridge into the pre-existing volcanic arc, and the connection of the southern end of the spreading axis with an oblique active rift in the active arc. Ultimately the active arc lithosphere is sheared as spreading progressively supersedes rifting. Consequently to such incursion of back-arc basin extension into the arc, peeled off and drifted pieces of arc crust are progressively isolated into the back-arc basin. Another consequence is that the New Hebrides arc is split in two distinct microplates, which move independently relative to the lower plate, and thereby define two different subduction systems. We suggest arc fragmentation could be a consequence of the incipient collision of the Loyalty Ridge with the New Hebrides Arc. We further speculate that this kinematic change could have resulted, less than two million year ago, in the initiation of a new subduction orthogonal to the New Hebrides Subduction possibly along the paleo STEP fault. In this geodynamic setting, with an oceanic lithosphere subducting beneath a sheared volcanic arc, a particularly wide range of primitive subduction-related magmas have been produced including adakites, island arc tholeiites, back-arc basin basalts, and medium-K subduction

  20. Active tectonics and mud diapirism in the Gulf of Squillace (Crotone Basin, Calabrian Arc, Italy)

    NASA Astrophysics Data System (ADS)

    Artoni, A.; Capozzi, R.; Lorenzini, S.; Oppo, D.; Polonia, A.; Torelli, L.

    2009-04-01

    The Calabrian arc is a prominent accretionary prism in the Mediterranean sea that contains alpine metamorphic rocks and connects the southern Apennine chain of Calabria, to the north, with the Maghrebian chain of Sicily, to the southwest. Recent active deformation inside the prism is testified by the earthquakes records and by submarine mud volcanism. The latter, not yet well defined within the accretionary prism, is generally associated to deeper active tectonic structures. In order to unravel the relationships between mud volcanoes and deeper deformations a study has been carried out in the Gulf of Squillace, located in the central portion of the backstop zone of the Calabrian arc and inside the Crotone basin. The deeper tectono-stratigraphic frame has been defined by using 10 well logs, 330 kms of public seismic reflection lines and three CROP seismic lines (the project for deep crust of Italy) recently processed with prestack depth migration. The study has been carried out within the Italian PRIN 2006 Project: "Tectonic and Sedimentation in the Accretionary Complex at the Front of the Calabrian Arc (Ionian Sea)". Three major tectonic units could be distinguished; from the top to the bottom, they are: 1) a metamorphic basement nappe (Alpine/Calabrian units); 2) a complex and east-verging Apenninic-Maghrebian prism, that can be subdivided in an outer prism sealed by middle Eocene(?)/Oligocene deposits and an inner prism sealed by middle/late Miocene deposits; 3) a deeper Mesozoic to Neogene relatively undeformed block interpreted as a thinned block of continental crust that preserves Mesozoic extensional fault. Subsurface mapping of Alpine/Calabrian and Apenninic-Maghrebian units show that their leading edges are oriented NNE-SSW and their tectonic stack was completed at least in the late Miocene; since then, WNW-ESE trending Catanzaro-Squillace transcurrent faults system and out-of-sequence thrusting started to locally reshape the backstop. The Cantanzaro

  1. The influence of volcanic activity on suspended sediment yield of rivers (Kamchatka, Russia)

    NASA Astrophysics Data System (ADS)

    Kuksina, Ludmila

    2014-05-01

    Kamchatka is specific region of suspended sediment yield formation. This fact is particularly connected with active volcanism in the territory. The influence of volcanism on suspended sediment yield characteristics was studied in various time scales - into-diurnal, seasonal and long-term ones. The study of spatial variability of these characteristics reveals the maximum values characterize river basins in zones of strong impact of volcanic eruptions, especially, rivers draining slopes and flanks of active volcanoes. Into-diurnal fluctuations were studied for rivers in volcanic areas. They are characterized by synchronous changes of water flow and turbidity. It's determined by weak erosion-preventive capacity of friable volcanic deposits and big slopes of channels (2.5 - 6.0 %). The maximum of water flow and turbidity is observed at the period between 12 and 6 pm. The air temperature reaches its maximum by that time, and consequently, the intensity of snow melting is also maximum one. The maximum of turbidity advances diurnal maximum of water flow a little, and it's connected with the features of flood wave moving and consecutive maximums of slopes, turbidity, velocity, water flow, and capacity of stream during flush. Into-diurnal fluctuations are determined by complicated and little-studied processes of mass transfer between stream and channel deposits. These processes are connected with into-diurnal changes of stream capacity and water transfer between channel and underflow. As the result water regime is pulsating. Rivers under the influence of volcanic eruptions transport the main amount of sediments during floods which usually occur in summer-autumn period (in the absence of extreme floods in winter-spring period during volcanic eruptions). Combination of maximum snow supply, significant precipitation in warm part of the year and weak erosion-preventive capacity of friable volcanic deposits on volcanoes slopes is the reason of the most intense erosion in this

  2. Rebalancing risk management--Part 2: The Active Risk Control (ARC) Toolkit.

    PubMed

    Card, Alan J; Ward, James R; Clarkson, P John

    2015-01-01

    The adoption of systems-focused risk assessment techniques has not led to measurable improvement in the rate of patient harm. Why? In part, because these tools focus solely on understanding problems and provide no direct support for designing and managing solutions (ie, risk control). This second installment of a 2-part series on rebalancing risk management describes a structured approach to bridging this gap: The Active Risk Control (ARC) Toolkit. A pilot study is presented to show how the ARC Toolkit can improve the quality of risk management practice.

  3. Eruptive stratigraphy of the Tatara-San Pedro complex, 36°S, sourthern volcanic zone, Chilean Andes: reconstruction method and implications for magma evolution at long-lived arc volcanic centers

    USGS Publications Warehouse

    Dungan, M.A.; Wulff, A.; Thompson, R.

    2001-01-01

    The Quaternary Tatara-San Pedro volcanic complex (36°S, Chilean Andes) comprises eight or more unconformity-bound volcanic sequences, representing variably preserved erosional remnants of volcanic centers generated during 930 ky of activity. The internal eruptive histories of several dominantly mafic to intermediate sequences have been reconstructed, on the basis of correlations of whole-rock major and trace element chemistry of flows between multiple sampled sections, but with critical contributions from photogrammetric, geochronologic, and paleomagnetic data. Many groups of flows representing discrete eruptive events define internal variation trends that reflect extrusion of heterogeneous or rapidly evolving magna batches from conduit-reservoir systems in which open-system processes typically played a large role. Long-term progressive evolution trends are extremely rare and the magma compositions of successive eruptive events rarely lie on precisely the same differentiation trend, even where they have evolved from similar parent magmas by similar processes. These observations are not consistent with magma differentiation in large long-lived reservoirs, but they may be accommodated by diverse interactions between newly arrived magma inputs and multiple resident pockets of evolved magma and / or crystal mush residing in conduit-dominated subvolcanic reservoirs. Without constraints provided by the reconstructed stratigraphic relations, the framework for petrologic modeling would be far different. A well-established eruptive stratigraphy may provide independent constraints on the petrologic processes involved in magma evolution-simply on the basis of the specific order in which diverse, broadly cogenetic magmas have been erupted. The Tatara-San Pedro complex includes lavas ranging from primitive basalt to high-SiO2 rhyolite, and although the dominant erupted magma type was basaltic andesite ( 52-55 wt % SiO2) each sequence is characterized by unique proportions of

  4. Degassing-Induced Crystallization of Plagioclase in Hydrous Rhyolite Liquids: Evidence from Obsidian Samples from the Mexican and Cascades Volcanic Arcs

    NASA Astrophysics Data System (ADS)

    Waters, L.; Lange, R. A.

    2010-12-01

    Rhyolites are among the most differentiated magmatic liquids on Earth, and in order to understand their origin, it is necessary to constrain temperatures and melt water concentrations during phenocryst growth. In this study, we present a detailed petrologic study of obsidian samples (71-75 wt% SiO2) from the Mexican and Cascades volcanic arcs. Despite low phenocryst abundances (2-10%), the samples are each multiply saturated with plagioclase + titanomagnetite + ilmenite ± orthopyroxene ± clinopyroxene ± hornblende ± biotite ± sanidine ± quartz. Pre-eruptive temperatures have been calculated from equilibrium pairs of titanomagnetite and ilmenite using the thermometer of Ghiorso and Evans (2008); values range from ~797-837°C. The plagioclase hygrometer (Lange et al., 2009) was applied to the sparse plagioclase crystals in each sample using these temperatures, leading to maximum melt water concentrations (based on the most calcic plagioclase in each sample) that range from 7.3 to 6.0 wt% H2O. These results require that all of these magmas were fluid-saturated at depths ≥ 9.5 km, respectively, and that during adiabatic ascent to the surface they would have degassed and lost water from the melt phase. In many of the rhyolites, we document a wide and continuous range of plagioclase compositions (e.g., 52-27 mol% An), despite low crystal (phenocryst + microphenocryst) abundances (< 3%), which can be attributed to crystallization under variable melt water concentrations, owing to degassing upon ascent. Analyzed Sr and Ba concentrations in these plagioclases lead to partition coefficients that are consistent with a phenocryst origin. The lowest recorded melt water concentrations in the glassy rhyolites, based on their most sodic plagioclases, are also relatively high and range from ~5.0-6.4 wt%. These results suggest that there may have been a kinetic barrier to plagioclase crystallization as the ascending magmas degassed and lost water, leading to a rapid increase

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

    USGS Publications Warehouse

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

    2009-01-01

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

  6. Search for possible relationship between volcanic ash particles and thunderstorm lightning activity

    NASA Astrophysics Data System (ADS)

    Várai, A.; Vincze, M.; Lichtenberger, J.; Jánosi, I. M.

    2011-12-01

    Explosive volcanic eruptions that eject columns of ash from the crater often generate lightning discharges strong enough to be remotely located by very low frequency radio waves. A fraction of volcanic ash particles can stay and disperse long enough to have an effect on weather phenomena days later such as thunderstorms and lightnings. In this work we report on lightning activity analysis over Europe following two recent series of volcanic eruptions in order to identify possible correlations between ash release and subsequent thunderstorm flash frequency. Our attempts gave negative results which can be related to the fact that we have limited information on local atmospheric variables of high enough resolution, however lightning frequency is apparently determined by very local circumstances.

  7. Soil radon measurements as a potential tracer of tectonic and volcanic activity.

    PubMed

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-15

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

  8. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    PubMed Central

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  9. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    NASA Astrophysics Data System (ADS)

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

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

    SciTech Connect

    Weiss, S.I.; Noble, D.C.; Jackson, M.C.

    1994-12-31

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

  11. Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): part 2--morphological and mineralogical features.

    PubMed

    Calabrese, S; D'Alessandro, W

    2015-01-01

    Volcanic emissions were studied at Mount Etna (Italy) by using moss-bags technique. Mosses were exposed around the volcano at different distances from the active vents to evaluate the impact of volcanic emissions in the atmosphere. Morphology and mineralogy of volcanic particulate intercepted by mosses were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Particles emitted during passive degassing activity from the two active vents, Bocca Nuova and North East Crater (BNC and NEC), were identified as silicates, sulfates and halide compounds. In addition to volcanic particles, we found evidences also of geogenic, anthropogenic and marine spray input. The study has shown the robustness of this active biomonitoring technique to collect particles, very useful in active volcanic areas characterized by continuous degassing and often not easily accessible to apply conventional sampling techniques.

  12. Submarine explosive activity and ocean noise generation at Monowai Volcano, Kermadec Arc: constraints from hydroacoustic T-waves

    NASA Astrophysics Data System (ADS)

    Grevemeyer, Ingo; Metz, Dirk; Watts, Anthony

    2016-04-01

    Submarine volcanic activity is difficult to detect, because eruptions at depth are strongly attenuated by seawater. With increasing depth the ambient water pressure increases and limits the expansion of gas and steam such that volcanic eruptions tend to be less violent and less explosive with depth. Furthermore, the thermal conductivity and heat capacity of water causes rapid cooling of ejected products and hence erupted magma cools much more quickly than during subaerial eruptions. Therefore, reports on submarine volcanism are restricted to those sites where erupted products - like the presence of pumice rafts, gas bubbling on the sea surface, and local seawater colour changes - reach the sea surface. However, eruptions cause sound waves that travel over far distances through the Sound-Fixing-And-Ranging (SOFAR) channel, so called T-waves. Seismic networks in French Polynesia recorded T-waves since the 1980's that originated at Monowai Volcano, Kermadec Arc, and were attributed to episodic growth and collapse events. Repeated swath-mapping campaigns conducted between 1998 and 2011 confirm that Monowai volcano is a highly dynamic volcano. In July of 2007 a network of ocean-bottom-seismometers (OBS) and hydrophones was deployed and recovered at the end of January 2008. The instruments were located just to the east of Monowai between latitude 25°45'S and 27°30'S. The 23 OBS were placed over the fore-arc and on the incoming subducting plate to obtain local seismicity associated with plate bending and coupling of the subduction megathrust. However, we recognized additional non-seismic sleuths in the recordings. Events were best seen in 1 Hz high-pass filtered hydrophone records and were identified as T-waves. The term T-wave is generally used for waves travelling through the SOFAR channel over large distances. In our case, however, they were also detected on station down to ~8000 m, suggesting that waves on the sea-bed station were direct waves caused by explosive

  13. Crustal deformation induced by volcanic activity measured by InSAR time series analysis (Volcan de Colima-Mexico)

    NASA Astrophysics Data System (ADS)

    Brunori, Carlo Alberto; Norini, Gianluca; Stramondo, Salvatore; Capra, Lucia; Zucca, Francesco; Groppelli, Gianluca; Bignami, Christian; Chini, Marco; Manea, Marina; Manea, Vlad

    2010-05-01

    The Volcán de Colima (CV) is currently the most active Mexican volcano. After the 1913 plinian activity the volcano presented several eruptive phases that lasted few years, but since 1991 its activity became more persistent with vulcanian eruptions, lava and dome extrusions. During the last 15 years the volcano suffered several eruptive episodes as in 1991, 1994, 1998-1999, 2001-2003, 2004 and 2005 with the emplacement of pyroclastic flows. During rain seasons lahars are frequent affecting several infrastructures such as bridges and electric towers. This work is focused on the detection of surface deformation with centimetre or sub-centimeter accuracy of the Volcán de Colima and surrounding areas. We try to assess the amount and the spatial extension of surface movements of the CV and to get insights into the causes of the surface deformation by using Interferometric Synthetic Aperture Radar (InSAR), a powerful tool ensuring measurements at high-accuracy over large areas. The image dataset acquired by ESA ENVISAT ASAR (C band) sensor, has been processed using Advanced interferometric techniques (A-InSAR) to overcome the really challenging sources of decorrelation related to the setting context, mainly vegetation and atmosphere, in order to give us the opportunity to detect also very low rates of deformations. The main objectives of the interferometric analysis is the measurement of deformations in the CV in relation with active tectonics and gravity induced spreading, the identification of magma migration below the surface in the last decade, the detection of the incipient movements of volcanic landslides and large scale volcano instability, and the kinematics of the Colima rift. We present preliminary results of the A-InSAR processing, in the framework of the interdisciplinary Colima Deformation project (ColDef).

  14. Feedback Between Volcanism and Milankovitch Cycles

    NASA Astrophysics Data System (ADS)

    Langmuir, C. H.; Huybers, P.

    2008-12-01

    Deglaciation is known to induce volcanism in many regions, notably Iceland. Since volcanism contributes CO2 to the atmosphere, we have investigated the global extent of glacially induced magmatism, and whether such volcanism may contribute to the co-variation between atmospheric CO2 and glacial cycles over the course of the late Pleistocene. Investigation of two combined global data sets on dated eruptions shows that global frequency of subaerial volcanic events increases substantially between 12Ka and 7Ka. An important aspect of the data is the temporal bias. While the record extends to 40,000 years, 80% of dated eruptions occur in the last 1000 years. The observation appears robust despite the temporal bias because it is apparent when comparing the 12-7Ka data with both older and younger time intervals. Application of a correction for the temporal bias indicates that global volcanic activity increases by a factor of 3-5 during this time interval. Increased volcanism can be confidently linked to deglaciation both in terms of location and mechanism. All of the increase occurs in regions thought to have experienced significant deglaciation, that is, predominantly high latitude or high elevation regions with significant precipitation. We show that two possible mechanisms may be important. As previously known from Iceland, deglaciation leads to decompression melting of the underlying mantle, yielding more magmatic input to volcanoes beneath ablating ice. In addition, pacing of volcanic eruptions reflects a balance between the forces generated by melt production and degassing, and the confining pressure and integrity of the surrounding rocks. A simple pacing model based on an eruption threshold and observed power law behavior of eruption frequency with number of volcanoes shows that ice volumes changes (estimated from oceanic δ18O) could also cluster the timing of volcanic eruptions near times of deglaciation. The influence of deglaciation upon volcanism is thus

  15. Exploratory Data Analysis Using a Dedicated Visualization App: Looking for Patterns in Volcanic Activity

    NASA Astrophysics Data System (ADS)

    van Manen, S. M.; Chen, S.

    2015-12-01

    Here we present an App designed to visualize and identify patterns in volcanic activity during the last ten years. It visualizes VEI (volcanic explosivity index) levels, population size, frequency of activity, and geographic region, and is designed to address the issue of oversampling of data. Often times, it is difficult to access a large set of data that can be scattered at first glance and hard to digest without visual aid. This App serves as a model that solves this issue and can be applied to other data. To enable users to quickly assess the large data set it breaks down the apparently chaotic abundance of information into categories and graphic indicators: color is used to indicate the VEI level, size for population size within 5 km of a volcano, line thickness for frequency of activity, and a grid to pinpoint a volcano's latitude. The categories and layers within them can be turned on and off by the user, enabling them to scroll through and compare different layers of data. By visualising the data this way, patterns began to emerge. For example, certain geographic regions had more explosive eruptions than others. Another good example was that low frequency larger impact volcanic eruptions occurred more irregularly than smaller impact volcanic eruptions, which had a more stable frequencies. Although these findings are not unexpected, the easy to navigate App does showcase the potential of data visualization for the rapid appraisal of complex and abundant multi-dimensional geoscience data.

  16. Planetary Volcanism

    NASA Technical Reports Server (NTRS)

    Antonenko, I.; Head, J. W.; Pieters, C. W.

    1998-01-01

    The final report consists of 10 journal articles concerning Planetary Volcanism. The articles discuss the following topics: (1) lunar stratigraphy; (2) cryptomare thickness measurements; (3) spherical harmonic spectra; (4) late stage activity of volcanoes on Venus; (5) stresses and calderas on Mars; (6) magma reservoir failure; (7) lunar mare basalt volcanism; (8) impact and volcanic glasses in the 79001/2 Core; (9) geology of the lunar regional dark mantle deposits; and (10) factors controlling the depths and sizes of magma reservoirs in Martian volcanoes.

  17. Variation in the Source Mantle of the Northern Izu arc with Time and Space -Constraints from High-precision Pb Isotopes -

    NASA Astrophysics Data System (ADS)

    Ishizuka, O.; Taylor, R. N.; Milton, J. A.; Nesbitt, R. W.; Uto, K.; Yuasa, M.; Sakamoto, I.

    2002-12-01

    We present new isotopic and trace element data for back-arc lavas from the northern Izu arc (33-36oN) including high-precision double-spike Pb isotope measurements. The northern part of the Izu arc is distinct from the rest of the arc in the lack of active rifting and presence of Quaternary volcanoes behind the front (e.g. Niijima). Common features with the rest of the arc include the presence of the back-arc seamounts chains and NE-SW volcanic ridges. 40Ar/39Ar dating of volcanic rocks has revealed that Quaternary volcanism is limited to within 40 km of the volcanic front. Active volcanism occurred from Miocene and Pliocene in the back-arc seamounts and ridges as far as 120km west of the current volcanic front. Chemical characteristics of the Quaternary behind-the-front volcanism and Tertiary volcanism in the back-arc seamounts are significantly different. Opx-cpx andesite and hornblende andesite are dominant in the back-arc seamounts, while Quaternary behind-the-front volcanism is characterized by basalt and rhyolite. In terms of the trace element and isotopic characteristics, Tertiary back-arc seamount lavas show a marked correlation between Th/Ce and Pb and Nd isotopes. Generally these lavas have higher Δ7/4 and lower 143Nd/144Nd with increasing Th/Ce. In contrast, the Quaternary lavas show little, if any, Th enrichment relative to potential mantle sources and no correlation with isotopes. These correlations suggest that sediment melt from the subducting slab is an important component in the Tertiary back-arc seamounts, whereas, the Quaternary volcanism behind the front shows little indication of sediment melt and is restricted to a contribution of fluid from altered oceanic crust. Quaternary volcanoes at similar distances from the volcanic front are estimated to have similar compositions and amounts of slab-derived fluid in their sources. However, on Pb-Pb isotope plots, they lie closer to the NHRL towards south (i.e., Δ8/4 decreases towards south). Almost

  18. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matthew J.; Le Friant, Anne; Ishizuka, Osamu; Stroncik, Nicole; Adachi, Tatsuya; Aljahdali, Mohammed; Boudon, Georges; Breitkreuz, Christoph; Fraass, Andrew; Fujinawa, Akihiko; Hatfield, Robert; Jutzeler, Martin; Kataoka, Kyoko; Lafuerza, Sara; Maeno, Fukashi; Martinez-Colon, Michael; McCanta, Molly; Morgan, Sally; Palmer, Martin R.; Saito, Takeshi; Slagle, Angela; Stinton, Adam J.; Subramanyam, K. S. V.; Tamura, Yoshihiko; Talling, Peter J.; Villemant, Benoit; Wall-Palmer, Deborah; Wang, Fei

    2012-08-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to <0.07 W/m2 at distances >15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present-day volcanism is confined to the region with the highest heat flow.

  19. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, M.; Hornbach, M. J.; Le Friant, A.; Ishizuka, O.; Stroncik, N.

    2012-12-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  20. Heat flow in the Lesser Antilles island arc and adjacent back arc Grenada basin

    NASA Astrophysics Data System (ADS)

    Manga, Michael; Hornbach, Matt; Le Friant, Anne; Ishizuka, Osamu

    2014-05-01

    Using temperature gradients measured in 10 holes at 6 sites, we generate the first high fidelity heat flow measurements from Integrated Ocean Drilling Program drill holes across the northern and central Lesser Antilles arc and back arc Grenada basin. The implied heat flow, after correcting for bathymetry and sedimentation effects, ranges from about 0.1 W/m2 on the crest of the arc, midway between the volcanic islands of Montserrat and Guadeloupe, to < 0.07 W/m2 at distances > 15 km from the crest in the back arc direction. Combined with previous measurements, we find that the magnitude and spatial pattern of heat flow are similar to those at continental arcs. The heat flow in the Grenada basin to the west of the active arc is 0.06 W/m2, a factor of 2 lower than that found in the previous and most recent study. There is no thermal evidence for significant shallow fluid advection at any of these sites. Present day volcanism is confined to the region with the highest heat flow.

  1. The STRATegy COLUMN for Precollege Science Teachers: Volcanic Activity.

    ERIC Educational Resources Information Center

    Metzger, Ellen Pletcher

    1995-01-01

    Describes resources for information and activities involving volcanoes. Includes an activity that helps students become familiar with the principal types of volcanoes and explores how the viscosity of magma affects the way a volcano erupts. (MKR)

  2. High resolution DEM from Tandem-X interferometry: an accurate tool to characterize volcanic activity

    NASA Astrophysics Data System (ADS)

    Albino, Fabien; Kervyn, Francois

    2013-04-01

    Tandem-X mission was launched by the German agency (DLR) in June 2010. It is a new generation high resolution SAR sensor mainly dedicated to topographic applications. For the purpose of our researches focused on the study of the volcano-tectonic activity in the Kivu Rift area, a set of Tandem-X bistatic radar images were used to produce a high resolution InSAR DEM of the Virunga Volcanic Province (VVP). The VVP is part of the Western branch of the African rift, situated at the boundary between D.R. Congo, Rwanda and Uganda. It has two highly active volcanoes, Nyiragongo and Nyamulagira. A first task concerns the quantitative assessment of the vertical accuracy that can be achieved with these new data. The new DEMs are compared to other space borne datasets (SRTM, ASTER) but also to field measurements given by differential GPS. Multi-temporal radar acquisitions allow us to produce several DEM of the same area. This appeared to be very useful in the context of an active volcanic context where new geomorphological features (faults, fissures, volcanic cones and lava flows) appear continuously through time. For example, since the year 2000, time of the SRTM acquisition, we had one eruption at Nyiragongo (2002) and six eruptions at Nyamulagira (2001, 2002, 2004, 2006, 2010 and 2011) which all induce large changes in the landscape with the emplacement of new lava fields and scoria cones. From our repetitive Tandem-X DEM production, we have a tool to identify and also quantify in term of size and volume all the topographic changes relative to this past volcanic activity. These parameters are high value information to improve the understanding of the Virunga volcanoes; the accurate estimation of erupted volume and knowledge of structural features associated to past eruptions are key parameters to understand the volcanic system, to ameliorate the hazard assessment, and finally contribute to risk mitigation in a densely populated area.

  3. Io volcanism

    SciTech Connect

    Carr, M.H.

    1985-01-01

    Io is the most volcanically active body in the Solar System. The Voyage spacecraft observed nine active eruption plumes in 1979, and detected numerous thermal anomalies. Loki the most active volcanic region has been emitting 1.5 x 10/sup 13/ W over the last few years. Many of the volcanic features have been interpreted as the result of sulfur volcanism because 1) the spectral reflectance of the surface resembles sulfur, 2) SO/sub 2/ has been positively identified, 3) the satellite leaves a trail of sulfur atoms in its wake; and 4) many of the hot spots have surfaces temperatures less than 400/sup 0/K, compatible with low-temperature melts. The evidence for sulfur has led to suggestions of sulfur lava flows hundreds of kilometers long, and sulfur lava lakes as large as Lake Erie. The observations are, however, equally compatible with basaltic volcanism. Modeling of the cooling of basaltic lava flows indicates that regions of basaltic volcanism on Io should have temperatures similar to those detected by the Voyager spacecraft. High eruption rates are required. High rates of fumarolic activity accompanying the eruptions and expulsion of volatiles by the plumes give the surface its sulfur-like spectral reflectance.

  4. Evidence of recent deep magmatic activity at Cerro Bravo-Cerro Machín volcanic complex, central Colombia. Implications for future volcanic activity at Nevado del Ruiz, Cerro Machín and other volcanoes

    NASA Astrophysics Data System (ADS)

    Londono, John Makario

    2016-09-01

    In the last nine years (2007-2015), the Cerro Bravo-Cerro Machín volcanic complex (CBCMVC), located in central Colombia, has experienced many changes in volcanic activity. In particular at Nevado del Ruiz volcano (NRV), Cerro Machin volcano (CMV) and Cerro Bravo (CBV) volcano. The recent activity of NRV, as well as increasing seismic activity at other volcanic centers of the CBCMVC, were preceded by notable changes in various geophysical and geochemical parameters, that suggests renewed magmatic activity is occurring at the volcanic complex. The onset of this activity started with seismicity located west of the volcanic complex, followed by seismicity at CBV and CMV. Later in 2010, strong seismicity was observed at NRV, with two small eruptions in 2012. After that, seismicity has been observed intermittently at other volcanic centers such as Santa Isabel, Cerro España, Paramillo de Santa Rosa, Quindío and Tolima volcanoes, which persists until today. Local deformation was observed from 2007 at NRV, followed by possible regional deformation at various volcanic centers between 2011 and 2013. In 2008, an increase in CO2 and Radon in soil was observed at CBV, followed by a change in helium isotopes at CMV between 2009 and 2011. Moreover, SO2 showed an increase from 2010 at NRV, with values remaining high until the present. These observations suggest that renewed magmatic activity is currently occurring at CBCMVC. NRV shows changes in its activity that may be related to this new magmatic activity. NRV is currently exhibiting the most activity of any volcano in the CBCMVC, which may be due to it being the only open volcanic system at this time. This suggests that over the coming years, there is a high probability of new unrest or an increase in volcanic activity of other volcanoes of the CBCMVC.

  5. Volcanic activity before and after large tectonic earthquakes: Observations and statistical significance

    NASA Astrophysics Data System (ADS)

    Eggert, S.; Walter, T. R.

    2009-04-01

    The study of volcanic triggering and coupling to the tectonic surroundings has received special attention in recent years, using both direct field observations and historical descriptions of eruptions and earthquake activity. Repeated reports of volcano-earthquake interactions in, e.g., Europe and Japan, may imply that clustered occurrence is important in some regions. However, the regions likely to suffer clustered eruption-earthquake activity have not been systematically identified, and the processes responsible for the observed interaction are debated. We first review previous works about the correlation of volcanic eruptions and earthquakes, and describe selected local clustered events. Following an overview of previous statistical studies, we further elaborate the databases of correlated eruptions and earthquakes from a global perspective. Since we can confirm a relationship between volcanic eruptions and earthquakes on the global scale, we then perform a statistical study on the regional level, showing that time and distance between events follow a linear relationship. In the time before an earthquake, a period of volcanic silence often occurs, whereas in the time after, an increase in volcanic activity is evident. Our statistical tests imply that certain regions are especially predisposed to concurrent eruption-earthquake pairs, e.g., Japan, whereas such pairing is statistically less significant in other regions, such as Europe. Based on this study, we argue that individual and selected observations may bias the perceptible weight of coupling. Volcanoes located in the predisposed regions (e.g., Japan, Indonesia, Melanesia), however, indeed often have unexpectedly changed in association with either an imminent or a past earthquake.

  6. Cordon Caulle: an active volcanic-geothermal extensional system of Southern Andes of Chile

    NASA Astrophysics Data System (ADS)

    Sepulveda, F.

    2013-05-01

    Cordon Caulle (CC; 40.5° S) is an active volcanic-geothermal system of the Southern Volcanic Zone (SVZ; 37°-44°S). Morphologically, the CC system is a 6 km x 13 km volcanic plateau bordered by NW-trending structures, limited by Puyehue Volcano to the SE and by Caldera Nevada Caldera to the NW. While the SVZ is dominantly basaltic, CC is unique in that it has produced a wide compositional spectrum from basalt to rhyolite. The most recent volcanic activity of Puyehue-CC (last 70 ky) is dominantly silicic, including two historic fissure eruptions (1921-1922; 1960) and a recent central eruption from Puyehue Volcano (2011). Abnormally silicic volcanism was formerly attributed to a localized compression and long-term magma residence and differentiation, resulting from the NW orientation of underlying CC structures with respect to a NE-oriented σ1 (linked to regional strike-slip stress state). However, later studies, including examination of morpho-tectonic features; detailed structural analysis of the 1960 eruption (triggered by Mw 9.5 1960 Chilean Earthquake); InSAR deformation and gravity surveys, point to both historic and long-term extension at CC with σhmax oriented NNW to NW. The pre-2011 (i.e. Puyehue Volcano eruption) geothermal features of CC included boiling hot springs and geysers (Caldera Nevada) and fumaroles (CC and Puyehue Volcano). Both water and gas chemistry surveys were undertaken to assess the source fluid composition and equilibrium temperature. The combination of water and gas geothermometers led to a conceptual model of a stratified geothermal reservoir, with shallow, low-chloride, steam-heated aquifers equilibrated at temperatures between 150°-180°C, overlying a deeper, possibly dominated reservoir with temperatures in excess of 280°C. Gas chemistry also produced the highest He ratios of the SVZ, in agreement with a relatively pure, undiluted magmatic signature and heat source fueling the geothermal system. Other indicators such as N2/Ar

  7. Factors limiting microbial activity in volcanic tuff at Yucca Mountain

    SciTech Connect

    Kieft, T.L.; Kovacik, W.P.; Taylor, J.

    1996-09-01

    Samples of tuff aseptically collected from 10 locations in the Exploratory Shaft Facility at the site of the proposed high-level nuclear waste repository at Yucca Mountain, Nevada Test Site were analyzed for microbiological populations, activities, and factors limiting microbial activity. Radiotracer assays ({sup 14}C-labeled organic substrate mineralization), direct microscopic counts, and plate counts were used. Radiolabeled substrates were glucose, acetate, and glutamate. Radiotracer experiments were carried out with and without moisture and inorganic nutrient amendments to determine factors limiting to microbial activities. Nearly all samples showed the presence of microorganisms with the potential to mineralize organic substrates. Addition of inorganic nutrients stimulated activities in a small number of samples. The presence of viable microbial communities within the tuff has implications for transport of contaminants.

  8. Analysis of volcanic activity patterns using MODIS thermal alerts

    NASA Astrophysics Data System (ADS)

    Rothery, Dave A.; Coppola, Diego; Saunders, Charlotte

    2005-07-01

    We investigate eruptive activity by analysis of thermal-alert data from the MODIS (moderate resolution imaging spectrometer) thermal infrared satellite instrument, detected by the MODVOLC (MODIS Volcano alert) algorithm. These data are openly available on the Internet, and easy to use. We show how such data can plug major gaps in the conventional monitoring record of volcanoes in an otherwise generally poorly documented region (Melanesia), including: characterising the mechanism of lava effusion at Pago; demonstrating an earlier-than-realised onset of lava effusion at Lopevi; extending the known period of lava lake activity at Ambrym; and confirming ongoing activity at Bagana, Langila and Tinakula. We also add to the record of activity even at some generally better-monitored volcanoes in Indonesia, but point out that care must be taken to recognise and exclude fires.

  9. Compilation of Disruptions to Airports by Volcanic Activity (Version 1.0, 1944-2006)

    USGS Publications Warehouse

    Guffanti, Marianne; Mayberry, Gari C.; Casadevall, Thomas J.; Wunderman, Richard

    2008-01-01

    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. To more fully characterize the nature and scope of volcanic hazards to airports, we collected data on incidents of airports throughout the world that have been affected by volcanic activity, beginning in 1944 with the first documented instance of damage to modern aircraft and facilities in Naples, Italy, and extending through 2006. Information was gleaned from various sources, including news outlets, volcanological reports (particularly the Smithsonian Institution's Bulletin of the Global Volcanism Network), and previous publications on the topic. This report presents the full compilation of the data collected. For each incident, information about the affected airport and the volcanic source has been compiled as a record in a Microsoft Access database. The database is incomplete in so far as incidents may not have not been reported or documented, but it does present a good sample from diverse parts of the world. Not included are en-route diversions to avoid airborne ash clouds at cruise altitudes. The database has been converted to a Microsoft Excel spreadsheet. To make the PDF version of table 1 in this open-file report resemble the spreadsheet, order the PDF pages as 12, 17, 22; 13, 18, 23; 14, 19, 24; 15, 20, 25; and 16, 21, 26. Analysis of the database reveals that, at a minimum, 101 airports in 28 countries were impacted on 171 occasions from 1944 through 2006 by eruptions at 46 volcanoes. The number of affected airports (101) probably is better constrained than the number of incidents (171) because recurring disruptions at a given airport may have been lumped together or not reported by news agencies, whereas the initial disruption likely is noticed and reported and thus the airport correctly counted.

  10. Activity-regulated, cytoskeleton-associated protein (Arc) is essential for visceral endoderm organization during early embryogenesis.

    PubMed

    Liu, D; Bei, D; Parmar, H; Matus, A

    2000-04-01

    Activity-regulated, cytoskeleton-associated protein (Arc) was first identified as an immediate-early gene regulated by synaptic activity. We have studied its functional role in vivo using a gene-targeting approach. We found that Arc is encoded by a single exon, and Arc mRNA is ubiquitously expressed in early mouse embryos. Homozygous Arc mutants are severely growth-retarded, fail to gastrulate and subsequently die before day 8.5 of embryogenesis. Further analysis revealed severe disorganization of visceral endoderm formation, and total separation and ectopic location of embryonic and extraembryonic structure. These findings demonstrate that Arc function is essential for early embryo development and patterning in mice, and support the hypothesis that signaling from visceral endoderm is essential for normal patterning of the extraembryonic and embryonic structure.

  11. Stress-induced spatiotemporal variations in anisotropic structures beneath Hakone volcano, Japan, detected by S wave splitting: A tool for volcanic activity monitoring

    NASA Astrophysics Data System (ADS)

    Honda, Ryou; Yukutake, Yohei; Yoshida, Akio; Harada, Masatake; Miyaoka, Kazuki; Satomura, Mikio

    2014-09-01

    Hakone volcano, located at the northern tip of the Izu-Mariana volcanic arc, Japan, has a large caldera structure containing numerous volcanic hot springs. Earthquake swarms have occurred repeatedly within the caldera. The largest seismic swarm since the commencement of modern seismic observations (in 1968) occurred in 2001. We investigated the anisotropic structure of Hakone volcano based on S wave splitting analysis and found spatiotemporal changes in the splitting parameters accompanying the seismic swarm activity. Depth-dependent anisotropic structures are clearly observed. A highly anisotropic layer with a thickness of ~1.5 km is located beneath the Koziri (KZR) and Kozukayama (KZY) stations. The anisotropic intensity in the region reaches a maximum of 6-7% at a depth of 1 km and decreases markedly to less than 1% at a depth of 2 km. The anisotropic intensity beneath Komagatake station (KOM) decreases gradually from a maximum of 6% at the surface to 0% at a depth of 5 km but is still greater than 2.5% at a depth of 3 km. At KZY, the anisotropic intensity along a travel path of which the back azimuth was the south decreased noticeably after the 2001 seismic swarm activity. During the swarm activity, tilt meters and GPS recorded the crustal deformation. The observed decrease in anisotropic intensity is presumed to be caused by the closing of microcracks by stress changes accompanying crustal deformation near the travel path.

  12. Earthquake evidence for along-arc extension in the Mariana Islands

    NASA Astrophysics Data System (ADS)

    Heeszel, David S.; Wiens, Douglas A.; Shore, Patrick J.; Shiobara, Hajime; Sugioka, Hiroko

    2008-12-01

    Analysis of data from a deployment of ocean bottom and land seismographs in 2003-2004 detected four swarms of earthquakes in the overriding plate of the Mariana subduction system between the fore-arc and the back-arc spreading center. Two additional shallow swarms were identified by analyzing the teleseismic earthquake catalogs from 1967 to 2003. Focal mechanism solutions for these swarms, determined from regional waveform inversion for the 2003-2004 events or retrieved from the Centroid Moment Tensor catalog for previous years, suggest a complex system of deformation throughout the arc. We observe arc-parallel extension near volcanic cross chains, arc-perpendicular extension along the frontal arc, and arc-parallel compression farther into the back arc near the Mariana Trough. A swarm beneath the middle and eastern summits of the Diamante cross chain may have recorded magmatic activity. Volcanic cross chains showing evidence of adiabatic decompression melting from extensional upwelling are localized at regions of enhanced along-strike extension. The earthquake data are consistent with recent GPS results indicating 12 mm/a of extension between Guam and Agrihan. The along-arc extension may result from either increasing curvature of the Mariana system with time or from deformation induced by oblique subduction in the northernmost and southernmost regions of the arc.

  13. Electrical activity during the 2006 Mount St. Augustine volcanic eruptions

    USGS Publications Warehouse

    Thomas, Ronald J.; Krehbiel, Paul R.; Rison, William; Edens, H. E.; Aulich, G. D.; McNutt, S.R.; Tytgat, Guy; Clark, E.

    2007-01-01

    By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms.

  14. Explosive activity associated with the growth of volcanic domes

    USGS Publications Warehouse

    Newhall, C.G.; Melson, W.G.

    1983-01-01

    Domes offer unique opportunities to measure or infer the characteristics of magmas that, at domes and elsewhere, control explosive activity. A review of explosive activity associated with historical dome growth shows that: 1. (1) explosive activity has occurred in close association with nearly all historical dome growth; 2. (2) whole-rock SiO2 content, a crude but widely reported indicator of magma viscosity, shows no systematic relationship to the timing and character of explosions; 3. (3) the average rate of dome growth, a crude indicator of the rate of supply of magma and volatiles to the near-surface enviornment, shows no systematic relationship to the timing or character of explosions; and 4. (4) new studies at Arenal and Mount St. Helens suggest that water content is the dominant control on explosions from water-rich magmas, whereas the crystal content and composition of the interstitial melt (and hence magma viscosity) are equally or more important controls on explosions from water-poor magmas. New efforts should be made to improve current, rather limited techniques for monitoring pre-eruption volatile content and magma viscosity, and thus the explosive potential of magmas. ?? 1983.

  15. Long-term global temperature variations under total solar irradiance, cosmic rays, and volcanic activity.

    PubMed

    Biktash, Lilia

    2017-07-01

    The effects of total solar irradiance (TSI) and volcanic activity on long-term global temperature variations during solar cycles 19-23 were studied. It was shown that a large proportion of climate variations can be explained by the mechanism of action of TSI and cosmic rays (CRs) on the state of the lower atmosphere and other meteorological parameters. The role of volcanic signals in the 11-year variations of the Earth's climate can be expressed as several years of global temperature drop. Conversely, it was shown that the effects of solar, geophysical, and human activity on climate change interact. It was concluded that more detailed investigations of these very complicated relationships are required, in order to be able to understand issues that affect ecosystems on a global scale.

  16. Hawaiian oral tradition describes 400 years of volcanic activity at Kīlauea

    USGS Publications Warehouse

    Swanson, Donald A.

    2008-01-01

    Culturally significant oral tradition involving Pele, the Hawaiian volcano deity, and her youngest sister Hi'iaka may involve the two largest volcanic events to have taken place in Hawai'i since human settlement: the roughly 60-year-long ‘Ailā’au eruption during the 15th century and the following development of Kīlauea's caldera. In 1823, Rev. William Ellis and three others became the first Europeans to visit Kīlauea's summit and were told stories about Kīlauea's activity that are consistent with the Pele–Hi'iaka account and extend the oral tradition through the 18th century. Recent geologic studies confirm the essence of the oral traditions and illustrate the potential value of examining other Hawaiian chants and stories for more information about past volcanic activity in Hawai‘i.

  17. Quantifying unsteadiness and dynamics of pulsatory volcanic activity

    NASA Astrophysics Data System (ADS)

    Dominguez, L.; Pioli, L.; Bonadonna, C.; Connor, C. B.; Andronico, D.; Harris, A. J. L.; Ripepe, M.

    2016-06-01

    Pulsatory eruptions are marked by a sequence of explosions which can be separated by time intervals ranging from a few seconds to several hours. The quantification of the periodicities associated with these eruptions is essential not only for the comprehension of the mechanisms controlling explosivity, but also for classification purposes. We focus on the dynamics of pulsatory activity and quantify unsteadiness based on the distribution of the repose time intervals between single explosive events in relation to magma properties and eruptive styles. A broad range of pulsatory eruption styles are considered, including Strombolian, violent Strombolian and Vulcanian explosions. We find a general relationship between the median of the observed repose times in eruptive sequences and the viscosity of magma given by η ≈ 100 ṡtmedian. This relationship applies to the complete range of magma viscosities considered in our study (102 to 109 Pa s) regardless of the eruption length, eruptive style and associated plume heights, suggesting that viscosity is the main magma property controlling eruption periodicity. Furthermore, the analysis of the explosive sequences in terms of failure time through statistical survival analysis provides further information: dynamics of pulsatory activity can be successfully described in terms of frequency and regularity of the explosions, quantified based on the log-logistic distribution. A linear relationship is identified between the log-logistic parameters, μ and s. This relationship is useful for quantifying differences among eruptive styles from very frequent and regular mafic events (Strombolian activity) to more sporadic and irregular Vulcanian explosions in silicic systems. The time scale controlled by the parameter μ, as a function of the median of the distribution, can be therefore correlated with the viscosity of magmas; while the complexity of the erupting system, including magma rise rate, degassing and fragmentation efficiency

  18. Middle Miocene hiatus in volcanic activity in the Great Basin area of the Western United States

    USGS Publications Warehouse

    McKee, E.H.; Noble, D.C.; Silberman, M.L.

    1970-01-01

    A summary of potassium-argon dates shows that a high level of igneous activity in the Great Basin and adjacent regions during middle Tertiary time (40 to 20 my ago) was followed by a period of relative quiescence in middle Miocene time that lasted for several million years (from 20 to 17 my ago). Volcanism resumed 16 my ago mainly at the margins of the region and has continued to the present. ?? 1970.

  19. Permian evolution of sandstone composition in a complex back-arc extensional to foreland basin: The Bowen Basin, eastern Australia

    SciTech Connect

    Baker, J.C. . Centre for Microscopy and Microanalysis); Fielding, C.R. . Dept. of Earth Sciences); Caritat, P de . Dept. of Geology); Wilkinson, M.M. )

    1993-09-01

    The Bowen Basin is a Permo-Triassic, back-arc extensional to foreland basin that developed landward of an intermittently active continental volcanic arc associated with the eastern Australian convergent plate margin. The basin has a complex, polyphase tectonic history that began with limited back-arc crustal extension during the Early Permian. This created a series of north-trending grabens and half grabens which, in the west, accommodated quartz-rich sediment derived locally from surrounding, uplifted continental basement. In the east, coeval calc-alkaline, volcanolithic-rich, and volcaniclastic sediment was derived from the active volcanic arc. This early extensional episode was followed by a phase of passive thermal subsidence accompanied by episodic compression during the late Early Permian to early Late Permian, with little contemporaneous volcanism. In the west, quartzose sediment was shed from stable, polymictic, continental basement immediately to the west and south of the basin, whereas volcanolithic-rich sediment that entered the eastern side of the basin during this time was presumably derived from the inactive, and possibly partly submerged volcanic arc. During the late Late Permian, flexural loading and increased compression occurred along the eastern margin of the Bowen Basin, and renewed volcanism took place in the arc system to the east. Reactivation of this arc led to westward and southward spread of volcanolithic-rich sediment over the entire basin. Accordingly, areas in the west that were earlier receiving quartzose, craton-derived sediment from the west and south were overwhelmed by volcanolithic-rich, arc-derived sediment from the east and north. This transition from quartz-rich, craton-derived sediments to volcanolithic-rich, arc-derived sediments is consistent with the interpreted back-arc extensional to foreland basin origin for the Bowen Basin.

  20. Variation in the mantle sources of the northern Izu arc with time and space — Constraints from high-precision Pb isotopes

    NASA Astrophysics Data System (ADS)

    Ishizuka, Osamu; Taylor, Rex N.; Milton, J. Andy; Nesbitt, Robert W.; Yuasa, Makoto; Sakamoto, Izumi

    2006-09-01

    We present new ages and geochemical data for back-arc lavas from the northern Izu Bonin arc 33 35° N including high-precision double-spike Pb isotope measurements. The northern part of the Izu Bonin arc is distinct from the rest of the arc as it lacks active rifting behind the volcanic front but it does have Quaternary volcanoes (e.g. Niijima). However, in common with the rest of the arc the northern section has back-arc seamount chains and NE SW volcanic ridges. 40Ar/39Ar dating of volcanic rocks has revealed that Quaternary volcanism is limited to within 40 km of the volcanic front. Miocene and Pliocene volcanism extended as far as 120 km west of the current volcanic front along the back-arc seamounts and ridges. The chemical characteristics of back-arc volcanism are significantly different in the Pliocene Quaternary compared to the Miocene. Opx cpx andesite and hornblende andesite are dominant in Miocene volcanic centres, while Pliocene and Quaternary centres are characterized by basalt and rhyolite. Miocene volcanic centres show a marked correlation between Th/Ce and Pb and Nd isotopes. Generally, these lavas have higher Δ7/4 and lower 143Nd/144Nd with increasing Th/Ce. In contrast, the Pliocene and Quaternary lavas show little, if any, Th enrichment relative to potential mantle sources and no correlation with isotopes. These correlations suggest that partial melt of sediment from the subducting slab was an important component in the Miocene, whereas, the Pliocene Quaternary volcanic centres show little evidence of sediment melt and are restricted to a contribution of fluid from altered oceanic crust and fluid from sediment. Quaternary volcanoes at similar distances from the volcanic front are calculated to have similar compositions and amounts of slab-derived fluid in their sources. However, on Pb Pb isotope plots, they lie closer to the NHRL towards south (i.e., Δ8/4 decreases towards south). Almost parallel but distinct trends on Pb Pb plots imply

  1. Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

    NASA Astrophysics Data System (ADS)

    Martínez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.; HiRISE Team

    2011-04-01

    Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region. Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

  2. Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

    USGS Publications Warehouse

    Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

    2011-01-01

    Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

  3. Volcanic activity before and after large tectonic earthquakes: Observations and statistical significance

    NASA Astrophysics Data System (ADS)

    Eggert, Silke; Walter, Thomas R.

    2009-06-01

    The study of volcanic triggering and interaction with the tectonic surroundings has received special attention in recent years, using both direct field observations and historical descriptions of eruptions and earthquake activity. Repeated reports of clustered eruptions and earthquakes may imply that interaction is important in some subregions. However, the subregions likely to suffer such clusters have not been systematically identified, and the processes responsible for the observed interaction remain unclear. We first review previous works about the clustered occurrence of eruptions and earthquakes, and describe selected events. We further elaborate available databases and confirm a statistically significant relationship between volcanic eruptions and earthquakes on the global scale. Moreover, our study implies that closed volcanic systems in particular tend to be activated in association with a tectonic earthquake trigger. We then perform a statistical study at the subregional level, showing that certain subregions are especially predisposed to concurrent eruption-earthquake sequences, whereas such clustering is statistically less significant in other subregions. Based on this study, we argue that individual and selected observations may bias the perceptible weight of coupling. The activity at volcanoes located in the predisposed subregions (e.g., Japan, Indonesia, Melanesia), however, often unexpectedly changes in association with either an imminent or a past earthquake.

  4. Volcanic history of the Colorado River extensional corridor: Active or passive rifting

    SciTech Connect

    Howard, K.A. )

    1993-04-01

    Magmatism and extension began nearly simultaneously in the Colorado River extensional corridor (CREC) between 34 and 35[degree] N. Initial eruptions of basanite at 23--19.5 Ma were low-volume but spanned a region now twice as wide as the 100-km-wide corridor. Extensional tilting of this age was local. A large flux of calc-alkaline basalt, andesite, dacite, and rhyolite was erupted at 22--18.5 Ma. They accumulated to average thicknesses of [approximately]1 km in the early CREC basin, and were accompanied by extensional tilting. Dike swarms, necks, and plutons represent intrusive equivalents. Plutons concentrate in the central belt of metamorphic core complexes, the most highly extended areas. Massive eruption at 18.5 Ma of the rhyolitic Peach Springs Tuff marked an ensuing lowered rate of volcanic output, a change to bimodal volcanism, much tilting and extension, and deposition of thick (to [approximately]2 km) synextensional clastic sediments 18--14 Ms. By 14--12 Ma, extensional tilting had largely ceased, and eruptions were sparse and basaltic only, as they have been since. Basalt compositions reveal changing patterns of trace-element composition that bear on sources. The early basanites have OIB-like compositions on spidergram plots, suggesting origin from the asthenosphere as would be expected from initiation of rifting driven by hot mantle upwelling. Basalts 20--12 Ma show low concentrations of Nb and Ta as in subduction-related arc magmas. Post-extensional basalts erupted 15--10 Ma exhibit a transition back toward primitive compositions seen in Quaternary alkalic basalts.

  5. Relationship between the latest activity of mare volcanism and topographic features of the Moon

    NASA Astrophysics Data System (ADS)

    Kato, Shinsuke; Morota, Tomokatsu; Yamaguchi, Yasushi; Watanabe, Sei-ichiro; Otake, Hisashi; Ohtake, Makiko

    2016-04-01

    Lunar mare basalts provide insights into compositions and thermal history of lunar mantle. According to crater counting analysis with remote sensing data, the model ages of mare basalt units indicate a second peak of magma activity at the end of mare volcanism (~2 Ga), and the latest eruptions were limited in the Procellarum KREEP Terrane (PKT), which has high abundances of heat-producing elements. In order to understand the mechanism for causing the second peak and its magma source, we examined the correlation between the titanium contents and eruption ages of mare basalt units using compositional and chronological data updated by SELENE/Kaguya. Although no systematic relationship is observed globally, a rapid increase in mean titanium (Ti) content occurred at 2.3 Ga in the PKT, suggesting that the magma source of mare basalts changed at that time. The high-Ti basaltic eruption, which occurred at the late stage of mare volcanism, can be correlated with the second peak of volcanic activity at ~2 Ga. The latest volcanic activity can be explained by a high-Ti hot plume originated from the core-mantle boundary. If the hot plume was occurred, the topographic features formed by the hot plume may be remained. We calculated the difference between topography and selenoid and found the circular feature like a plateau in the center of the PKT, which scale is ~1000 km horizontal and ~500 m vertical. We investigated the timing of ridge formation in the PKT by using stratigraphic relationship between mare basalts and ridges. The ridges were formed before and after the high-Ti basaltic eruptions and seem to be along with the plateau. These results suggest that the plateau formation is connected with the high-Ti basaltic eruptions.

  6. 2009 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Neal, Christina A.; Girina, Olga A.; Chibisova, Marina; Rybin, Alexander

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest, and reports of unusual activity at or near eight separate volcanic centers in Alaska during 2009. The year was highlighted by the eruption of Redoubt Volcano, one of three active volcanoes on the western side of Cook Inlet and near south-central Alaska's population and commerce centers, which comprise about 62 percent of the State's population of 710,213 (2010 census). AVO staff also participated in hazard communication and monitoring of multiple eruptions at ten volcanoes in Russia as part of its collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  7. Adaptive tracking of weld joints using active contour model in arc-welding processes

    NASA Astrophysics Data System (ADS)

    Kim, Jaeseon; Koh, Kyoungchul; Cho, Hyungsuck

    2001-02-01

    12 This paper presents a vision processing scheme to automatic weld joint tracking in robotic arc welding process. Particular attention is concentrated on its robustness against various optical disturbances, such as arc glares and weld spatters radiating from the melted weld pool. Underlying the developed vision processing is a kind of model-based pattern searching, which is necessarily accompanied by two separate stages of modeling and tracking. In the modeling stage, a syntactic approach is adopted to identify unknown weld joint structure. The joint profile identified in the modeling stage is used as a starting point for successive tracking of variations in the geometry of weld joint during welding, which is automatically achieved by an active contour model technology following feature- based template matching. The performance of the developed scheme is investigated through a series of practical welding experiments.

  8. 1995 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Neal, Christina A.

    1996-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity (SVA) at 6 volcanic centers in 1995: Mount Martin (Katmai Group), Mount Veniaminof, Shishaldin, Makushin, Kliuchef/Korovin, and Kanaga. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team (KVERT) on the 1995 eruptions of 2 Russian volcanoes: Bezymianny and Karymsky. This report summarizes volcanic activity in Alaska during 1995 and the AVO response, as well as information on the 2 Kamchatkan eruptions. Only those reports or inquiries that resulted in a "significant" investment of staff time and energy (here defined as several hours or more for reaction, tracking, and follow-up) are included. AVO typically receives dozens of phone calls throughout the year reporting steaming, unusual cloud sightings, or eruption rumors. Most of these are resolved quickly and are not tabulated here as part of the 1995 response record.

  9. Multi-Source Autonomous Response for Targeting and Monitoring of Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Davies, Ashley G.; Doubleday, Joshua R.; Tran, Daniel Q.

    2014-01-01

    The study of volcanoes is important for both purely scientific and human survival reasons. From a scientific standpoint, volcanic gas and ash emissions contribute significantly to the terrestrial atmosphere. Ash depositions and lava flows can also greatly affect local environments. From a human survival standpoint, many people live within the reach of active volcanoes, and therefore can be endangered by both atmospheric (ash, debris) toxicity and lava flow. There are many potential information sources that can be used to determine how to best monitor volcanic activity worldwide. These are of varying temporal frequency, spatial regard, method of access, and reliability. The problem is how to incorporate all of these inputs in a general framework to assign/task/reconfigure assets to monitor events in a timely fashion. In situ sensing can provide a valuable range of complementary information such as seismographic, discharge, acoustic, and other data. However, many volcanoes are not instrumented with in situ sensors, and those that have sensor networks are restricted to a relatively small numbers of point sensors. Consequently, ideal volcanic study synergistically combines space and in situ measurements. This work demonstrates an effort to integrate spaceborne sensing from MODIS (Terra and Aqua), ALI (EO-1), Worldview-2, and in situ sensing in an automated scheme to improve global volcano monitoring. Specifically, it is a "sensor web" concept in which a number of volcano monitoring systems are linked together to monitor volcanic activity more accurately, and this activity measurement automatically tasks space assets to acquire further satellite imagery of ongoing volcanic activity. A general framework was developed for evidence combination that accounts for multiple information sources in a scientist-directed fashion to weigh inputs and allocate observations based on the confidence of an events occurrence, rarity of the event at that location, and other scientists

  10. The roar of Yasur: Handheld audio recorder monitoring of Vanuatu volcanic vent activity

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Turtle, Elizabeth P.; Howell, Robert; Radebaugh, Jani; Lopes, Rosaly M. C.

    2016-08-01

    We describe how near-field audio recording using a pocket digital sound recorder can usefully document volcanic activity, demonstrating the approach at Yasur, Vanuatu in May 2014. Prominent emissions peak at 263 Hz, interpreted as an organ-pipe mode. High-pass filtering was found to usefully discriminate volcano vent noise from wind noise, and autocorrelation of the high pass acoustic power reveals a prominent peak in exhalation intervals of 2.5, 4 and 8 s, with a number of larger explosive events at 200 s intervals. We suggest that this compact and inexpensive audio instrumentation can usefully supplement other field monitoring such as seismic or infrasound. A simple estimate of acoustic power interpreted with a dipole jet noise model yielded vent velocities too low to be compatible with pyroclast emission, suggesting difficulties with this approach at audio frequencies (perhaps due to acoustic absorption by volcanic gases).

  11. Acoustic waves in the atmosphere and ground generated by volcanic activity

    SciTech Connect

    Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru

    2012-09-04

    This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

  12. Acoustic waves in the atmosphere and ground generated by volcanic activity

    NASA Astrophysics Data System (ADS)

    Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru

    2012-09-01

    This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

  13. Volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory 1993

    USGS Publications Warehouse

    Neal, Christina A.; McGimsey, Robert G.; Doukas, Michael P.

    1996-01-01

    During 1993, the Alaska Volcano Observatory (AVO) responded to episodes of eruptive activity or false alarms at nine volcanic centers in the state of Alaska. Additionally, as part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also responded to eruptions on the Kamchatka Peninsula, details of which are summarized in Miller and Kurianov (1993). In 1993, AVO maintained seismic instrumentation networks on four volcanoes of the Cook Inlet region--Spurr, Redoubt, Iliamna, and Augustine--and two stations at Dutton Volcano near King Cove on the Alaska Peninsula. Other routine elements of AVO's volcano monitoring program in Alaska include periodic airborne measurement of volcanic SO2 and CO2 at Cook Inlet volcanoes (Doukas, 1995) and maintenance of a lightning detection system in Cook Inlet (Paskievitch and others, 1995).

  14. Active deformations of the Jura arc inferred by GPS and seismotectonics

    NASA Astrophysics Data System (ADS)

    Rabin, Mickael; Sue, Christian; Walpersdorf, Andrea

    2016-04-01

    The Jura Mountain is the most recent expression of the alpine orogeny. At the northern end of the western Alps, its recent deformation is still a matter of debates. GPS data available in the Jura bear witness of disagreement between studies, as interpretations vary from uplifted belt to arc-parallel extension (Walpersdorf, et al., 2006) and very slow horizontal movements. Moreover, the traditionally accepted model of an active collisional activity of the Jura, in the dynamic continuity of the Alps, rises up the matter of its geodynamic origin. Indeed, the European Alps are in a post-collisional regime characterized by isostatic-related extension and uplift driven by interaction between buoyancy forces and erosional dynamics (e.g. Sue et al. 2007; Champagnac, et al., 2007; Vernant, et al., 2013.). We present a reappraisal of published focal mechanisms combined with a new GPS solution over the entire arc and surrounding areas. Although the Jura presents a low seismic activity, 53 focal mechanisms over the Jura have been inverted in order to infer the current stress field. Anyhow, we tested several combinations of f.m. inversions, by structural zones, in order to test the regional stress stability. It appears that the current stress field is very stable all over the arc, and following our different sub-datasets. Indeed, the stress field shows a stable near horizontal NW-SE-oriented s1, associated to a NE-SW-oriented s3. Therefore, the structural arc of the Jura seems to have very low or no impact in terms of current stress. Complementarily, we present preliminary velocity and strain fields from a GPS network composed of 25 permanent stations implemented between 1998 and 2014 all around the Jura arc. Indeed, we also integrated the recent GPS-JURA station (OSU THETA Besançon), but they are still too young to accurately constrain the strain of the belt. Preliminary results exhibit very slow velocities across the arc in term of baselines evolution, with infra

  15. Understanding the Evolution of the Scotia Arc

    NASA Astrophysics Data System (ADS)

    Maldonado, Andrés.; Dalziel, Ian; Leat, Philip T.

    2013-07-01

    An international 3-day meeting in which participants discussed geodynamic and multidisciplinary topics related to the evolution of the Scotia Arc was held at the Andalucía Institute of Earth Sciences (Spanish Research Council (CSIC)/University of Granada (UGR)) in Granada, Spain. The Scotia Arc encompasses southern South America, the Antarctic Peninsula, and the intervening part of the Southern Ocean including the South Georgia and South Orkney crustal blocks and the volcanically active South Sandwich Arc. It is a region of critical importance because of its role as a developing ocean gateway during Eocene-Miocene times and because of its impact on global ocean circulation, with possible importance for Paleogene-Neogene paleoenvironmental change, early phases of development of Antarctic ice sheets, gene flow, and resulting biodiversity.

  16. Eruptions in space and time: durations, intervals, and comparison of world's active volcanic belts

    SciTech Connect

    Simkin, T.; McClelland, L.

    1986-07-01

    A computerized data bank, compiled over the last 12 years at the Smithsonian Institution, allows summaries to be made of Holocene volcanism. The Scientific Event Alert Network tracks current volcanic activity. However, the record of most volcanoes is poor before the last 100 years, and some eruptions still pass unreported. The time interval since the previous eruption can be calculated for 4835 of the 5564 compiled eruptions. The median interval is 5.0 years, but much longer intervals commonly precede unusually violent eruptions. For the 25 most violent eruptions in the file (with known preceding interval), the medium interval is 865 years. Of the historic eruptions in this group, 50% resulted in fatalities. The interval between an eruption's start and its most violent paroxysm may be measured in months or years, but it is usually short. Of the 205 larger eruptions for which data are available, 92 had the paroxysmal event within the first day of the eruption, allowing little time for emergency preparations after the eruption's opening phase. To compare the recent vigor of different volcanic belts, they calculated the number of years in which each volcano was active in the last 100 years, summed these for each belt, and divided by belt length. Another index of recent vigor is the number of recognized Holocene volcanoes divided by belt length. A third index is the number of large explosive eruptions (volcanic explosive index greater than or equal to 3) of the last 100 years, again normalized by belt length. These three measures correlate reasonably well, serving to contrast vigorous belts such as Kamchatka, Central America, and Java with relatively quiet belts such as the Cascades, South Sandwich Islands, Greece, and southern Chile.

  17. Ca(2+)-activated K current in the ARC muscle of Aplysia.

    PubMed

    Brezina, V; Weiss, K R

    1995-03-01

    1. This work continues our examination of the electrophysiology and contractions of single, functionally intact fibers dissociated from a widely studied molluscan muscle, the accessory radula closer (ARC) muscle of Aplysia californica, aimed at understanding its excitation-contraction mechanisms and their modulation. Extensive previous work has characterized a number of ion currents in the fibers. 2. Here we describe an additional major current that could not be studied earlier because, unlike all of the other currents in the ARC muscle fibers, it becomes prominent only during contraction of the fiber. It is a Ca(2+)-activated K current, associated with contraction most likely because both are activated by the same elevation in intracellular free Ca2+. 3. We used several manipulations to elicit the Ca(2+)-activated K current and contraction: depolarizing voltage steps in the presence of extracellular Ca2+, application of caffeine in the presence or absence of extracellular Ca2+ (and thus presumably working by releasing Ca2+ from intracellular stores), application of the Ca(2+)-ionophore A23187, and direct iontophoretic injection of Ca2+ into the fiber. 4. The Ca(2+)-activated K current reversed around -70 mV, not far from EK, and the reversal potential shifted substantially with elevated extracellular K+. Activation of the current was not only Ca2+ dependent, but also quite strongly voltage dependent, promoted by depolarization. The current was well blocked by tetraethylammonium (KD approximately 2 mM), but not blocked by even 10 mM 4-aminopyridine or low concentrations of the K-current blocking toxins charybdotoxin and apamin. 5. After a depolarizing voltage step in Ca(2+)-containing solution, the Ca(2+)-activated K current appeared, often with some delay, as a large peak of current that soon disintegrated into a prolonged period of individual oscillatory transients of Ca(2+)-activated K current, sometimes correlated with transient contractions. Similar transients

  18. Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

    USGS Publications Warehouse

    Hein, J.R.; Schulz, M.S.; Dunham, R.E.; Stern, R.J.; Bloomer, S.H.

    2008-01-01

    Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 ?? and 7 ?? manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean-8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of

  19. Crustal thickening drives arc front migration

    NASA Astrophysics Data System (ADS)

    Karlstrom, L.; Lee, C.; Manga, M.

    2012-12-01

    The position of active volcanism relative to the trench in arcs depends on melt focusing processes within the mantle wedge and the geometric parameters of subduction. Arc front migration has been observed in relic (Sierra Nevada, Andes) as well as active (Cascades) arcs, sometimes with cycles of retreat and return of the front towards the trench over millions of years. Other arcs, particularly where backarc extension dominates, exhibit a more stationary front in time relative to the trench. In addition, crustal indices of magmatism as measured by the ratio of trace elements La/Yb or isotopes 87}Sr/{86Sr covary with arc front migration (e.g., Haschke et al., 2002). Arc front migration is commonly attributed to variation in dip angle of the downgoing slab, delamination of overthickened crust, or to subduction erosion. Here we present an alternative hypothesis. Assuming mantle wedge melting is a largely temperature-dependant process, the maximum isotherm in the wedge sets arc front location. Isotherm location depends on slab angle, subduction velocity and wedge thermal diffusivity (England and Katz, 2010). It also depends on crustal thickness, which evolves as melt is transferred from the wedge to the crust. Arc front migration can thus occur purely through magmatic thickening of crust. Thickening proceeds through intrusive as well as extrusive volcanism, modulated by tectonics and surface erosion. Migration rate is set by the mantle melt flux into the crust, which decreases as thickening occurs. Thus slab angle need not change, and in the absence of other contribution processes front location and crustal thickness have long-time steady state values. We develop an analytic model of this process that produces migration rates consistent with published data and explains arc fronts that do not move (dominated by extension, such as in the case of intra-oceanic arcs). We present new geochemical and age data from the Peninsular Ranges Batholith that are also consistent with

  20. Coupled interactions between volatile activity and Fe oxidation state during arc crustal processes

    USGS Publications Warehouse

    Humphreys, Madeleine C.S.; Brooker, R; Fraser, D.C.; Burgisser, A; Mangan, Margaret T.; McCammon, C

    2015-01-01

    Arc magmas erupted at the Earth’s surface are commonly more oxidized than those produced at mid-ocean ridges. Possible explanations for this high oxidation state are that the transfer of fluids during the subduction process results in direct oxidation of the sub-arc mantle wedge, or that oxidation is caused by the effect of later crustal processes, including protracted fractionation and degassing of volatile-rich magmas. This study sets out to investigate the effect of disequilibrium crustal processes that may involve coupled changes in H2O content and Fe oxidation state, by examining the degassing and hydration of sulphur-free rhyolites. We show that experimentally hydrated melts record strong increases in Fe3+/∑Fe with increasing H2O concentration as a result of changes in water activity. This is relevant for the passage of H2O-undersaturated melts from the deep crust towards shallow crustal storage regions, and raises the possibility that vertical variations in fO2 might develop within arc crust. Conversely, degassing experiments produce an increase in Fe3+/∑Fe with decreasing H2O concentration. In this case the oxidation is explained by loss of H2 as well as H2O into bubbles during decompression, consistent with thermodynamic modelling, and is relevant for magmas undergoing shallow degassing en route to the surface. We discuss these results in the context of the possible controls on fO2 during the generation, storage and ascent of magmas in arc settings, in particular considering the timescales of equilibration relative to observation as this affects the quality of the petrological record of magmatic fO2.

  1. Infrasound Monitoring of the Volcanic Activities of Japanese Volcanoes in Korea

    NASA Astrophysics Data System (ADS)

    Lee, H. I.; Che, I. Y.; Shin, J. S.

    2015-12-01

    Since 1999 when our first infrasound array station(CHNAR) has been installed at Cheolwon, Korea Institute of Geoscience and Mineral Resources(KIGAM) is continuously observing infrasound signals with an infrasound array network, named KIN(Korean Infrasound Network). This network is comprised of eight seismo-acoustic array stations(BRDAR, YPDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR, TJIAR). The aperture size of the smallest array is 300m and the largest is about 1.4km. The number of infrasound sensors are between 4(TJIAR) and 18(YAGAR), and 1~5 seismometers are collocated with infrasound sensors. Many interesting infrasound signals associated with different type of sources, such as blasting, large earthquake, bolide, volcanic explosion are detected by KIN in the past 15 years. We have analyzed the infrasound signals possibly associated with the japanese volcanic explosions with reference to volcanic activity report published by Japanese Meteorological Agency. Analysis results of many events, for example, Asama volcano explosion in 2004 and Shinmoe volcano in 2011, are well matched with the official report. In some cases, however, corresponding infrasound signals are not identified. By comparison of the infrasound signals from different volcanoes, we also found that the characteristics of signals are distinguishing. It may imply that the specific volcano has its own unique fingerprint in terms of infrasound signal. It might be investigated by long-term infrasound monitoring for a specific volcano as a ground truth generating repetitive infrasound signal.

  2. 2005 Volcanic Activity in Alaska, Kamchatka, and the Kurile Islands: Summary of Events and Response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, R.G.; Neal, C.A.; Dixon, J.P.; Ushakov, Sergey

    2008-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity at or near 16 volcanoes in Alaska during 2005, including the high profile precursory activity associated with the 2005?06 eruption of Augustine Volcano. AVO continues to participate in distributing information about eruptive activity on the Kamchatka Peninsula, Russia, and in the Kurile Islands of the Russian Far East, in conjunction with the Kamchatkan Volcanic Eruption Response Team (KVERT) and the Sakhalin Volcanic Eruption Response Team (SVERT), respectively. In 2005, AVO helped broadcast alerts about activity at 8 Russian volcanoes. The most serious hazard posed from volcanic eruptions in Alaska, Kamchatka, or the Kurile Islands is the placement of ash into the atmosphere at altitudes traversed by jet aircraft along the North Pacific and Russian Trans East air routes. AVO, KVERT, and SVERT work collaboratively with the National Weather Service, Federal Aviation Administration, and the Volcanic Ash Advisory Centers to provide timely warnings of volcanic eruptions and the production and movement of ash clouds.

  3. Trace elements in scalp hair of children chronically exposed to volcanic activity (Mt. Etna, Italy).

    PubMed

    Varrica, D; Tamburo, E; Dongarrà, G; Sposito, F

    2014-02-01

    The aim of this survey was to use scalp hair as a biomonitor to evaluate the environmental exposure to metals and metalloids of schoolchildren living around the Mt. Etna area, and to verify whether the degree of human exposure to trace elements is subject to changes in local environmental factors. Twenty trace elements were determined in 376 samples of scalp hair from schoolboys (11-13 years old) of both genders, living in ten towns located around the volcanic area of Mt. Etna (Sicily). The results were compared with those (215 samples) from children living in areas of Sicily characterized by a different geological setting (reference site). As, U and V showed much higher concentrations at the volcanic site whereas Sr was particularly more abundant at the reference site. Linear Discriminant Analysis (LDA) indicated an Etna factor, made up of V, U and Mn, and a second factor, concerning the reference site, characterized by Ni and Sr, and to a lesser extent by Mo and Cd. Significant differences in element concentrations were also observed among three different sectors of Mt. Etna area. Young people living in the Mt. Etna area are naturally exposed to enhanced intakes of some metals (V, U, Mn) and non-metals (e.g., As) than individuals of the same age residing in other areas of Sicily, characterized by different lithologies and not influenced by volcanic activity. The petrographic nature of local rocks and the dispersion of the volcanic plume explain the differences, with ingestion of water and local food as the most probable exposure pathways.

  4. Assessing microbial activities in metal contaminated agricultural volcanic soils--An integrative approach.

    PubMed

    Parelho, C; Rodrigues, A S; Barreto, M C; Ferreira, N G C; Garcia, P

    2016-07-01

    Volcanic soils are unique naturally fertile resources, extensively used for agricultural purposes and with particular physicochemical properties that may result in accumulation of toxic substances, such as trace metals. Trace metal contaminated soils have significant effects on soil microbial activities and hence on soil quality. The aim of this study is to determine the soil microbial responses to metal contamination in volcanic soils under different agricultural land use practices (conventional, traditional and organic), based on a three-tier approach: Tier 1 - assess soil microbial activities, Tier 2 - link the microbial activity to soil trace metal contamination and, Tier 3 - integrate the microbial activity in an effect-based soil index (Integrative Biological Response) to score soil health status in metal contaminated agricultural soils. Our results showed that microbial biomass C levels and soil enzymes activities were decreased in all agricultural soils. Dehydrogenase and β-glucosidase activities, soil basal respiration and microbial biomass C were the most sensitive responses to trace metal soil contamination. The Integrative Biological Response value indicated that soil health was ranked as: organic>traditional>conventional, highlighting the importance of integrative biomarker-based strategies for the development of the trace metal "footprint" in Andosols.

  5. Potassium-argon geochronology of a basalt-andesite-dacite arc system: the Mount Adams volcanic field, Cascade Range of southern Washington

    USGS Publications Warehouse

    Hildreth, W.; Lanphere, M.A.

    1994-01-01

    High-precision K-Ar dating and detailed mapping have established an eruptive chronology for a Cascade stratovolcano and its surrounding array of coeval basaltic centers. The time-volume-composition data bear upon several fundamental questions concerning the long-term behavior of arc volcanoes. -from Authors

  6. Identifying glacial influences on sedimentation in tectonically-active, mass flow dominated arc basins with reference to the Neoproterozoic Gaskiers glaciation (c. 580 Ma) of the Avalonian-Cadomian Orogenic Belt

    NASA Astrophysics Data System (ADS)

    Carto, Shannon L.; Eyles, Nick

    2012-06-01

    Neoproterozoic 'Avalonian-Cadomian' volcanic arc basins once lay peripheral to Gondwana and are now found around the North Atlantic Ocean in New England, Atlantic Canada and northwestern Europe as 'peri-Gondwanan terranes.' Their thick (up to 9 km) marine fills are dominated by turbidites, debrites (diamictites and variably graded conglomerates), slumps and olistostromes recording the dominance of mass flow processes in arc basins oversupplied with volcaniclastic sediment. Several diamictite horizons in these basins were identified as glacial tillites more than one hundred years ago on the basis of poor textural sorting, and the lack of any understanding of mass flow processes. An association with thin-bedded turbidite facies, then interpreted as glaciolacustrine varvites, was seen as evidence for widespread glacial conditions which is still the basis today of a near global 'Gaskiers glaciation' at c. 580 Ma, despite classic sedimentological work which shows that the 'tillites' and 'varvites' of these basins are deep marine sediment gravity flow deposits. Only in two basins (Gaskiers Formation, Avalon Peninsula in Newfoundland, and the Konnarock Formation of Virginia) is a distal and regionally-restricted glacial influence on marine sedimentation identified from ice-rafted, striated dropstones in turbidites but terrestrial 'ice-contact' facies are absent. As revealed in this study, terrestrial glacial facies may not have survived frequent volcanic activity such as seen today on glaciated active plate margin volcanoes such as Mount Rainier in Washington USA, and Cotopaxi Volcano in Ecuador where primary glacial sediment is frequently reworked by lahars, pyroclastic flows, debris avalanches and outburst floods. The weight of evidence presented in this study indicates that ice covers during the Gaskiers glaciation were not widespread across the Avalonian-Cadomian back arc basins; the deep marine Grenada Basin (Caribbean Sea) filled with turbidites, debrites (lahars

  7. Scaling and extended scaling in sediment registers of a paleolake perturbed by volcanic activity

    NASA Astrophysics Data System (ADS)

    Ugalde, Edgardo; Martínez-Mekler, Gustavo; Vilaclara, Gloria

    2006-07-01

    We analyze a sequence of density variations of sedimentary material from an extinct paleolake of the state of Tlaxcala, Mexico, which we previously obtained by means of computer-aided tomography [J. Miranda, A. Oliver, G. Vilaclara, R. Rico-Montiel, V.M. Macias, J.L. Ruvalcava, M.A. Zenteno, Nucl. Instrum. Methods Phys. Res. B 85 (1994) 886]. In the stratified blocks chiselled out of mines at the lake bed, low-density sediments have a high concentration of diatomite, while high-density strata show a considerable amount of material external to the lake, mostly of volcanic origin. Two regions can be distinguished by visual inspection: a darker and older one which we attribute to a strongly externally perturbed regime, and a whiter more recent one which appears to have been subjected to less frequent volcanic perturbations. By means of a scaling analysis of the distribution function of density fluctuations, we show that for the most recent region there is a range of scales where these fluctuations present a self-similar behavior. We attribute this observation to a rare event response, namely, the onset of correlations in the lake relaxation processes to steady-state conditions following intense volcanic disturbances. Based on scaling properties of the structure function, we also show that the complete data series presents extended self-similarity as encountered in turbulence studies [R. Benzi, S. Ciliberto, R. Tripiccione, C. Baudet, F. Massoli, S. Succi, Phys. Rev. E 48 (1993) R29]. Our characterization of the statistical behavior of the density fluctuations contributes to our knowledge of the volcanic activity over a period of thousands of years, as well as aspects of ecological interest of the lake's response to these disturbances [G. Vilaclara, E. Ugalde, E. Cuna, G. Martinez-Mekler, Complex dynamics of the evolution of a Paleolake subjected to volcanic activity: geology meets ecology, submitted for publication]. Our approach can be implemented in general to other

  8. A new model for the development of the active Afar volcanic margin

    NASA Astrophysics Data System (ADS)

    Pik, Raphaël; Stab, Martin; Bellahsen, Nicolas; Leroy, Sylvie

    2016-04-01

    Volcanic passive margins, that represent more than the three quarters of continental margins worldwide, are privileged witnesses of the lithospheric extension processes thatform new oceanic basins. They are characterized by voluminous amounts of underplated, intruded and extruded magmas, under the form of massive lavas prisms (seaward-dipping reflectors, or SDR) during the course of thinning and stretching of the lithosphere, that eventually form the ocean-continent transition. The origin and mechanisms of formation of these objects are still largely debated today. We have focussed our attention in the last few years on the Afar volcanic province which represents an active analogue of such volcanic margins. We explored the structural and temporal relationships that exist between the development of the major thinning and stretching structures and the magmatic production in Central Afar. Conjugate precise fieldwork analysis along with lavas geochronology allowed us to revisit the timing and style of the rift formation, since the early syn-rift period of time in the W-Afar marginal area to present days. Extension is primarily accommodated over a wide area at the surface since the very initial periods of extension (~ 25 Ma) following the emplacement of Oligocene CFBs. We propose in our reconstruction of central Afar margin history that extension has been associated with important volumes of underplated mafic material that compensate crustal thinning. This has been facilitated by major crustal-scale detachments that help localize the thinning and underplating at depth. In line with this 'magmatic wide-rift' mode of extension, we demonstrate that episodic extension steps alternate with more protracted magmatic phases. The production of syn-rift massive flood basalts (~ 4 Ma) occurs after early thinning of both the crust and the lithosphere, which suggests that SDR formation, is controlled by previous tectonic event. We determined how the melting regime evolved in

  9. Volcanic activity in the Acambay Graben: a < 25 Ka subplinian eruption from the Temascalcingo volcano and implications for volcanic hazard.

    NASA Astrophysics Data System (ADS)

    Pedrazzi, Dario; Aguirre Díaz, Gerardo; Sunyé Puchol, Ivan; Bartolini, Stefania; Geyer, Adelina

    2016-04-01

    The Trans-Mexican Volcanic Belt (TMVB) contains a large number of stratovolcanoes, some well-known, as Popocatepetl, Iztaccihuatl, Nevado de Toluca, or Colima and many others of more modest dimensions that are not well known but constitute the majority in the TMVB. Such volcanoes are, for example, Tequila, San Juan, Sangangüey, Cerro Culiacán, Cerro Grande, El Zamorano, La Joya, Palo Huerfano, Jocotitlán, Altamirano and Temascalcingo, among many others. The Temascalcingo volcano (TV) is an andesitic-dacitic stratovolcano located in the Trans-Mexican Volcanic Belt (TMVB) at the eastern part of the Acambay Graben (northwest portion of Estado de México). The TV is composed mainly by dacitic, porphyritic lavas, block and ash deposits and subordinate pumice fall deposits and ignimbrites (Roldán-Quintana et al., 2011). The volcanic structure includes a summit caldera that has a rectangular shape, 2.5×3.5 km, with the largest side oriented E-W, parallel to major normal faults affecting the edifice. The San Mateo Pumice eruption is one of the greatest paroxysmal episodes of this volcano with pumice deposits mainly exposed at the scarp of the Acambay-Tixmadeje fault and at the northern and northeastern flanks of TV. It overlies a paleosol dated at 25 Ka. A NE-trending dispersion was obtained from field data covering an area of at least 80 km2. These deposits overlie older lava flows and mud flows and are discontinuously covered and eroded by younger reworked deposits of Temascalcingo volcano. This event represents a highly explosive phase that generated a relatively thick and widespread pumice fallout deposit that may occur again in future eruptions. A similar eruption today would have a significantly impact in the region, overall due to the fact that there has been no systematic assessment of the volcanic hazard in any of the studies that have been conducted so far in the area. So, this is a pending and urgent subject that must be tackled without delay. Financed by

  10. Treatment with activated water by GlidArc technology of bacteria producing Biofouling

    NASA Astrophysics Data System (ADS)

    Hnatiuc, B.; Ghita, S.; Sabau, A.; Hnatiuc, M.; Dumitrache, C. L.; Wartel, M.

    2015-02-01

    Corrosion in marine environment is an actual problem, being a complex dynamic process influenced mainly by physical, chemical, microbiological and mechanical parameters. Around 70% of the maintenance costs of a ship are associated with the corrosion protection. Times for maintenance related to this phenomenon are greater than 80% of the total repair. Reducing this cost would be a significant saving, and an effective treatment can reduce times related to ships repairing. Biofouling is a main cause of corrosion and for its reduction different methods could be applied, especially in the first part of its production. The atmospheric pressure non-thermal plasmas have been gaining an ever increasing interest for different biodecontamination applications and present potential utilisation in the control of biofouling and biodeterioration. They have a high efficiency of the antimicrobial treatment, including capacity to eradicate microbial biofilms. The adhesion microbial biofilm is mainly influenced by presence of bacteria from the liquid environment. That is why this work concerns the study of annihilation of maximum amount of bacteria from sea water, by using GlidArc technology that produces non-thermal plasma. Bacteria suspended in sea water are placed in contact with activated water. This water is activated by using GlidArc working in humid air. Experimental results refer to the number of different activated and inactivated marine organisms and their evolution, present in solution at certain time intervals after mixing different amounts of seawater with plasma activated water.

  11. Explorations of Mariana Arc Volcanoes Reveal New Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Embley, R. W.; Baker, E. T.; Chadwick, W. W., Jr.; Lupton, J. E.; Resing, J. A.; Massoth, G. J.; Nakamura, K.

    2004-01-01

    Some 20,000 km of volcanic arcs, roughly one-third the length of the global mid-ocean ridge (MOR) system, rim the western Pacific Ocean. Compared to 25 years of hydrothermal investigations along MORs, exploration of similar activity on the estimated ~600 submarine arc volcanoes is only beginning [Ishibashi and Urabe, 1995; De Ronde et al., 2003]. To help alleviate this under-sampling, the R/V T. G. Thompson was used in early 2003 (9 February to 5 March) to conduct the first complete survey of hydrothermal activity along 1200 km of the Mariana intra-oceanic volcanic arc. This region includes both the Territory of Guam and the Commonwealth of the Northern Mariana Islands. The expedition mapped over 50 submarine volcanoes with stunning new clarity (Figures 1 and 2) and found active hydrothermal discharge at 12 sites, including the southern back-arc site. This includes eight new sites along the arc (West Rota, Northwest Rota, E. Diamante, Zealandia Bank, Maug Caldera, Ahyi, Daikoku, and Northwest Eifuku) and four sites of previously known hydrothermal activity (Seamount X, Esmeralda, Kasuga 2, and Nikko) (Figures 1 and 2). The mapping also fortuitously provided a ``before'' image of the submarine flanks of Anatahan Island, which had its first historical eruption on 10 May 2003 (Figures 1 and 3).

  12. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input

    PubMed Central

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders. PMID:27999532

  13. Genetic Feedback Regulation of Frontal Cortical Neuronal Ensembles Through Activity-Dependent Arc Expression and Dopaminergic Input.

    PubMed

    Mastwal, Surjeet; Cao, Vania; Wang, Kuan Hong

    2016-01-01

    Mental functions involve coordinated activities of specific neuronal ensembles that are embedded in complex brain circuits. Aberrant neuronal ensemble dynamics is thought to form the neurobiological basis of mental disorders. A major challenge in mental health research is to identify these cellular ensembles and determine what molecular mechanisms constrain their emergence and consolidation during development and learning. Here, we provide a perspective based on recent studies that use activity-dependent gene Arc/Arg3.1 as a cellular marker to identify neuronal ensembles and a molecular probe to modulate circuit functions. These studies have demonstrated that the transcription of Arc is activated in selective groups of frontal cortical neurons in response to specific behavioral tasks. Arc expression regulates the persistent firing of individual neurons and predicts the consolidation of neuronal ensembles during repeated learning. Therefore, the Arc pathway represents a prototypical example of activity-dependent genetic feedback regulation of neuronal ensembles. The activation of this pathway in the frontal cortex starts during early postnatal development and requires dopaminergic (DA) input. Conversely, genetic disruption of Arc leads to a hypoactive mesofrontal dopamine circuit and its related cognitive deficit. This mutual interaction suggests an auto-regulatory mechanism to amplify the impact of neuromodulators and activity-regulated genes during postnatal development. Such a mechanism may contribute to the association of mutations in dopamine and Arc pathways with neurodevelopmental psychiatric disorders. As the mesofrontal dopamine circuit shows extensive activity-dependent developmental plasticity, activity-guided modulation of DA projections or Arc ensembles during development may help to repair circuit deficits related to neuropsychiatric disorders.

  14. Volcanic gas emissions during active dome growth at Mount Cleveland, Alaska, August 2015

    NASA Astrophysics Data System (ADS)

    Werner, Cynthia; Kern, Christoph; Lyons, John; Kelly, Peter; Schneider, David; Wallace, Kristi; Wessels, Rick

    2016-04-01

    Volcanic gas emissions and chemistry data were measured for the first time at Mount Cleveland (1730 m) in the Central Aleutian arc, Alaska, on August 14-15, 2015 as part of the NSF-GeoPRISMS initiative, and co-funded by the Deep Carbon Observatory (DCO) and the USGS Alaska Volcano Observatory. The measurements were made in the month following two explosive events (July 21 and August 7, 2015) that destroyed a small dome (˜50x85 m), which had experienced episodic growth in the crater since November, 2014. These explosions resulted in the elevation of the aviation color code and alert level from Yellow/Advisory to Orange/Watch on July 21, 2015. Between the November, 2014 and July, 2015 dome-destroying explosions, the volcano experienced: (1) frequent periods of elevated surface temperatures in the summit region (based on Mid-IR satellite observations), (2) limited volcano-seismic tremor, (3) visible degassing as recorded in webcam images with occasionally robust plumes, and (4) at least one aseismic volcanic event that deposited small amounts of ash on the upper flanks of the volcano (detected by infrasound, observed visually and in Landsat 8 images). Intermittent plumes were also sometimes detectable up to 60 km downwind in Mid-IR satellite images, but this was not typical. Lava extrusion resumed following the explosion as indicated in satellite data by highly elevated Mid-IR surface temperatures, but was not identifiable in seismic data. By early-mid August, 2015, a new dome growing in the summit crater had reached 80 m across with temperatures of 550-600 C as measured on August 4 with a helicopter-borne thermal IR camera. A semitransparent plume extended several kilometers downwind of the volcano during the field campaign. A helicopter instrumented with an upward-looking UV spectrometer (mini DOAS) and a Multi-GAS was used to measure SO2 emission rates and in situ mixing ratios of H2O, CO2, SO2, and H2S in the plume. On August 14 and 15, 2015, a total of 14

  15. The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions

    NASA Astrophysics Data System (ADS)

    Pouclet, A.; Bellon, H.; Bram, K.

    2016-09-01

    The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time. The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the

  16. A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-10

    USGS Publications Warehouse

    Patrick, Matthew R.; Smellie, John L.

    2015-01-01

    Of the more than twenty historically active volcanoes in Antarctica and the sub-Antarctic region only two, to our knowledge, host any ground-based monitoring instruments. Moreover, because of their remoteness, most of the volcanoes are seldom visited, thus relegating the monitoring of volcanism in this region almost entirely to satellites. In this study, high temporal resolution satellite data from the Hawaii Institute of Geophysics and