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Sample records for central volcanic complex

  1. Temporal evolution of the Roccamonfina volcanic complex (Pleistocene), Central Italy

    Science.gov (United States)

    Rouchon, V.; Gillot, P. Y.; Quidelleur, X.; Chiesa, S.; Floris, B.

    2008-10-01

    The Roccamonfina volcanic complex (RVC), in southern Italy, is an Early to Middle Pleistocene stratovolcano sharing temporal and morphological characteristics with the Somma-Vesuvius and the Alban Hills; both being associated with high volcanic hazard for the cities of Naples and Rome, respectively. The RVC is important for the understanding of volcanic evolution in the Roman and Campanian volcanic provinces. We report a comprehensive study of its evolution based on morphological, geochemical and K-Ar geochronological data. The RVC was active from c.a. 550 ka to 150 ka. Its evolution is divided into five stages, defining a volcanic pulse recurrence time of c.a. 90-100 kyr. The two initial stages, consisted in the construction of two successive stratovolcanoes of the tephrite-phonolite, namely "High-K series". The first stage was terminated by a major plinian eruption emplacing the trachytic Rio Rava pumices at 439 ± 9 ka. At the end of the second stage, the last High-K series stratovolcano was destroyed by a large sector collapse and the emplacement of the Brown Leucitic Tuff (BLT) at 353 ± 5 ka. The central caldera of the RVC is the result of the overlapping of the Rio Rava and of the BLT explosions. The plinian eruption of the BLT is related to the emptying of a stratified, deep-seated HKS magma chamber during the upwelling of K series (KS) magma, marking a major geochemical transition and plumbing system re-organization. The following stage was responsible for the emplacement of the Lower White Trachytic Tuff at 331 ± 2 ka, and of basaltic-trachytic effusive products erupted through the main vent. The subsequent activity was mainly restricted to the emplacement of basaltic-shoshonitic parasitic cones and lava flows, and of minor subplinian deposits of the Upper White Trachytic Tuff between 275 and 230 ka. The northern crater is most probably a maar that formed by the phreatomagmatic explosion of the Yellow Trachytic Tuff at 230 ka. The latest stage of

  2. Pucarilla-Cerro Tipillas volcanic complex: the oldest recognized caldera in the southeastern portion of central volcanic zone of Central Andes?

    Energy Technology Data Exchange (ETDEWEB)

    Guzman, Silvina; Petrinovic, Ivan [CONICET -IBIGEO. Museo de Cs. Naturales, Universidad de Salta, Mendoza 2 (4400), Salta (Argentina)], E-mail: guzmansilvina@gmail.com

    2008-10-01

    We recognize the most eastern and oldest collapse caldera structure in the southern portion of the Central Volcanic Zone of the Andes. A description of Middle-Upper Miocene successions related to explosive- effusive events is presented. The location of this centre close to Cerro Galn Caldera attests a recurrence in the volcanism between 12 and 2 Ma in this portion of the Altiplano - Puna Plateau.

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

    Science.gov (United States)

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

    2014-05-01

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

  4. Structural control on arc volcanism: The Caviahue Copahue complex, Central to Patagonian Andes transition (38°S)

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    Melnick, Daniel; Folguera, Andrés; Ramos, Victor A.

    2006-11-01

    This paper describes the volcanostratigraphy, structure, and tectonic implications of an arc volcanic complex in an oblique subduction setting: the Caviahue caldera Copahue volcano (CAC) of the Andean margin. The CAC is located in a first-order morphotectonic transitional zone, between the low and narrow Patagonian and the high and broad Central Andes. The evolution of the CAC started at approximately 4-3 Ma with the opening of the 20 × 15 km Caviahue pull-apart caldera; Las Mellizas volcano formed inside the caldera and collapsed at approximately 2.6 Ma; and the Copahue volcano evolved in three stages: (1) 1.2-0.7 Ma formed the approximately 1 km thick andesitic edifice, (2) 0.7-0.01 Ma erupted andesitic-dacitic subglacial pillow lavas, and (3) 0.01-0 Ma erupted basaltic-andesites and pyroclastic flows from fissures, aligned cones, and summit craters. Magma ascent has occurred along planes perpendicular to the least principal horizontal stress, whereas hydrothermal activity and hot springs also occur along parallel planes. At a regional scale, Quaternary volcanism concentrates along the NE-trending, 90 km long Callaqui-Copahue-Mandolegüe lineament, the longest of the southern volcanic zone, which is here interpreted as an inherited crustal-scale transfer zone from a Miocene rift basin. At a local scale within the CAC, effusions are controlled by local structures that formed at the intersection of regional fault systems. The Central to Patagonian Andes transition occurs at the Callaqui-Copahue-Mandolegüe lineament, which decouples active deformation from the intra-arc strike-slip Liquiñe-Ofqui fault zone to the south and the backarc Copahue-Antiñir thrust system.

  5. Evolution of Icelandic Central Volcanoes: Evidence from the Austurhorn Plutonic and Vestmannaeyjar Volcanic Complexes

    Science.gov (United States)

    1989-09-01

    complex (figure 3.2; Blake, 1964, 1970). They consist of basic, intermediate and acid lavas as well as pyroclastic deposits. Early propylitic ...hypothesis because dikes are heavily fractured and commonly show incipient propylitization along fracture surfaces. Mafic dikes exhibit a sharp maximum in

  6. Volcanic hazards in Central America

    Science.gov (United States)

    Rose, William I.; Bluth, Gregg J.S.; Carr, Michael J.; Ewert, John W.; Patino, Lina C.; Vallance, James W.

    2006-01-01

    This volume is a sampling of current scientific work about volcanoes in Central America with specific application to hazards. The papers reflect a variety of international and interdisciplinary collaborations and employ new methods. The book will be of interest to a broad cross section of scientists, especially volcanologists. The volume also will interest students who aspire to work in the field of volcano hazards mitigation or who may want to work in one of Earth’s most volcanically active areas.

  7. Subvolcanic contact metasomatism at El Laco Volcanic Complex, Central Andes Metasomatismo de contacto subvolcánico en el Complejo Volcánico El Laco, Andes centrales

    Directory of Open Access Journals (Sweden)

    José A Naranjo

    2010-01-01

    Full Text Available Studies of drill cores from the Pasos Blancos area at El Laco in the central Andes, northern Chile, give evidence of an intense and extensive subvolcanic contact-metasomatic process. This process resulted from shallow-level emplacement of very volatile-rich iron-oxide magma, with discharge of volatiles that resulted in extensive fracturing of overlying volcanic rocks. The brecciated rocks were altered (mainly extensive scapolitization and formation of pyroxene by hot magmatic fluids emitted from the cooling intrusion , and accompanied by magnetite deposition. With time and decreasing temperature, the metasomatic fluids evolved to fluids of hydrothermal character, and a final recent geothermal event took place that deposited superficial gypsum over a large part of the El Laco Volcanic Complex.Estudios realizados en testigos de sondajes en el area de Pasos Blancos en El Laco, en los Andes Centrales del norte de Chile, dan evidencias de un intenso y extenso proceso subvolcánico de metasomatismo de contacto. Este proceso es el resultado de un emplazamiento a poca profundidad de un magma de óxido de fierro muy rico en volátiles y cuya descarga de gases produjo un intenso fracturamiento de las rocas sobrepuestas. Las rocas brechizadas fueron alteradas (principalmente una extensa escapolitización y formación de piroxeno, junto con la depositación de magnetita, por los fluidos magmáticos calientes emitidos por la intrusión durante su enfriamiento. Los fluidos metasomáticos evolucionaron en el tiempo y con la disminución de temperatura, a fluidos de carácter hidrotermal y finalmente tuvo lugar un evento geotérmico reciente, el cual depositó yeso superficial en gran parte del Complejo Volcánico El Laco.

  8. Shallow sub-surface structure of the central volcanic complex of Tenerife, Canary Islands: implications for the evolution and the recent reactivation of the Las Canadas caldera

    Energy Technology Data Exchange (ETDEWEB)

    Gottsmann, J [Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, Bristol BS8 1RJ (United Kingdom); Camacho, A G; Fernandez, J [Instituto de Astronomia y Geodesia (CSIC-UCM), Ciudad Universitaria, Pza. de Ciencias, 3, 28040 Madrid (Spain); MartI, J [Institute of Earth Sciences ' Jaume Almera' , CSIC, Lluis Sole SabarIs s/n, Barcelona 08028 (Spain); Wooller, L; Rymer, H [Department of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes, MK7 6AA (United Kingdom); GarcIa, A [Department of Volcanology, Museo Nacional de Ciencias Naturales, CSIC, C/ Jose Gutierrez Abascal, 2, 28006 Madrid (Spain)], E-mail: j.gottsmann@bristol.ac.uk

    2008-10-01

    We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain. The high-density core of the CVC and the pronounced gravity low centred in the Las Canadas caldera (LCC) in greater detail than previously available. Mathematical construction of a subsurface model from the local anomaly data, employing a 3-D inversion enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture of the complex, and shedding light on its evolution.

  9. Monitoring unrest in a large silicic caldera, the long Valley-inyo craters volcanic complex in east-central California

    Science.gov (United States)

    Hill, D. P.

    1984-06-01

    Recent patterns of geologic unrest in long Valley caldera in east-central California emphasize that this large, silicic volcanic system and the adjacent, geologically youthful Inyo-Mono Craters volcanic chain are still active and capable of producing locally hazardous volcanic eruptions. A series of four magnitude -6 earthquakes in May 1980 called attention to this current episode of unrest, and subsequent activity has included numerous earthquake swarms in the south moat of the caldera accompanied by inflation of the resurgent dome by more than 50 cm over the last five years. The seismicity associated with this unrest is currently monitored by a network of 31 telemetered seismic stations with an automatic processing system that yelds hypocentral locations and earthquake magnitudes in near-real time. Deformation of the ground is monitored by a) a series of overlapping trilateration networks that provide coverage ranging from annual measurements of regional deformation to daily measurements of deformation local to the active, southern section of the caldera, b) a regional network of level lines surveyed annually, c) a regional network of precise gravity stations occupied annually, d) local, L-shaped level figures surveyed every few months, and e) a network of fourteen borehole tiltmeter clusters (two instruments in each cluster) and a borehole dilatometer, the telemetered signals from which provide continuous data on deformation rates. Additional telemetered data provide continuous information on fluctuations in the local magnetic field, hydrogen gas emission rates at three sites, and water level and temperatures in three wells. Continuous data on disharge rates and temperatures from hot springs and fumaroles are collected by several on-site recorders within the caldera, and samples for liquid and gas chemistry are collected several times per year from selected hot springs and fumaroles.

  10. Secular Variations of Soil CO2 Efflux at Santa Ana-Izalco-Coatepeque Volcanic Complex, El Salvador, Central America

    Science.gov (United States)

    Olmos, R.; Barahona, F.; Cartagena, R.; Soriano, T.; Salazar, J.; Hernandez, P.; Perez, N.; Lopez, D.

    2002-12-01

    The Santa Ana-Izalco-Coatepeque volcanic complex (2,365 m elevation), located 40 Km west of San Salvador, consists of the Coatepeque collapse caldera (a 6.5 x 10.5 Km elliptical depression), the Santa Ana and Izalco stratovolcanoes, as well as numerous cinder cones and explosion craters. The summit of the Santa Ana volcano contains an acid lake where hot springs, gas bubbling and intense fumarolic emissions occur. A volcanic plume, usually driven by the NE trades, may be seen rising up to 500 m from the summit crater of the Santa Ana volcano. The goal of this study is to provide a multidisciplinary approach for the volcanic surveillance by means of performing geochemical continuous monitoring of diffuse CO2 emission rate in addition to seismic monitoring. Temporal variations of soil CO2 efflux measured at Cerro Pacho dome, Coatepeque caldera, by means of the accumulation chamber method and using a CO2 efflux continuous monitoring station developed by WEST Systems (Italy). From May 2001 till May 2002, CO2 efflux ranged from 4.3 to 327 gm-2d-1, with a median value of 98 and a quartile range of 26 gm-2d-1. Two distinct diffuse CO2 degassing periods have been observed: (1) an increasing trend from May to July 2001, and (2) a stationary period from November 2001 to May 2002. The increasing-trend period may be due to the anomalous plume degassing at the Santa Ana volcano during 2001 and soon after the January and February 2001 earthquakes. Temporal variations of CO2 efllux during the second period seem to be coupled with those of barometric pressure and wind speed at different time scales, though most of the variance is contained at diurnal and semi-diurnal frequencies. These observations can help to explain the existence of a persistent behavior (Hurst exponent, H=0.934 +/- 0.0039) within the diffuse CO2 degassing phenomena. However, further observations are in progress to understand the long-term memory of diffuse CO2 degassing at the Santa Ana volcanic complex.

  11. Upper pliocene-lower pleistocene 40Ar/39Ar ages of Pudahuel ignimbrite (Diamante-Maipo volcanic complex), Central Chile (33.50S)

    International Nuclear Information System (INIS)

    Wall, R.M.; Lara, L.E.; Perez de Arce, C

    2001-01-01

    brittle deformation, the age of N-S compressive event recognized by Lavenu and Cembrano (1999) toward the south in the Central Depression is constrained. Thus, the Pudahuel Ignimbrite (Diamante-Maipo Volcanic Complex) is part of a Plio-Quaternary silicic magmatic belt formed by the NNW alignment of volcanic centres and complexes like the Calabozos Caldera (35.5 o S ), with pleistocene pyroclastic flow deposits (Hildreth et al., 1984; Grunder and Mahood, 1988); the Puelche Volcanic Field (35.7 o S ), with rhyolitic lavas of Early Pleistocene age (Hildreth et al., 1999); the Laguna del Maule Volcanic Field (36 o S ) with plio-pleistocene lavas and ignimbrites (Hildreth et al., 1999) and Domuyo volcano (36.7 o S ) in Argentina. This belt is superimposed on rocks which are deformed by the Tertiary Malargue fold and thrust belt. To the south of 38 o S , and with the same orientation, another coeval magmatic belt is formed by alkaline basaltic centres (Munoz y Stern, 1989) (au)

  12. Central San Juan caldera cluster: Regional volcanic framework

    Science.gov (United States)

    Lipman, Peter W.

    2000-01-01

    Eruption of at least 8800 km3 of dacitic-rhyolitic magma as 9 major ash-slow sheets (individually 150-5000 km3) was accompanied by recurrent caldera subsidence between 28.3 and about 26.5 Ma in the central San Juan Mountains, Colorado. Voluminous andesitic-decitic lavas and breccias were erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of explosive volcanism, making the central San Juan caldera cluster an exceptional site for study of caldera-related volcanic processes. Exposed calderas vary in size from 10 to 75 km in maximum diameter, the largest calderas being associated with the most voluminous eruptions. After collapse of the giant La Garita caldera during eruption if the Fish Canyon Tuff at 17.6 Ma, seven additional explosive eruptions and calderas formed inside the La Garita depression within about 1 m.y. Because of the nested geometry, maximum loci of recurrently overlapping collapse events are inferred to have subsided as much as 10-17 km, far deeper than the roof of the composite subvolcanic batholith defined by gravity data, which represents solidified caldera-related magma bodies. Erosional dissection to depths of as much as 1.5 km, although insufficient to reach the subvolcanic batholith, has exposed diverse features of intracaldera ash-flow tuff and interleaved caldera-collapse landslide deposits that accumulated to multikilometer thickness within concurrently subsiding caldera structures. The calderas display a variety of postcollapse resurgent uplift structures, and caldera-forming events produced complex fault geometries that localized late mineralization, including the epithermal base- and precious-metal veins of the well-known Creede mining district. Most of the central San Juan calderas have been deeply eroded, and their identification is dependent on detailed geologic mapping. In contrast, the primary volcanic morphology of the

  13. Carbonatite ring-complexes explained by caldera-style volcanism.

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    Andersson, Magnus; Malehmir, Alireza; Troll, Valentin R; Dehghannejad, Mahdieh; Juhlin, Christopher; Ask, Maria

    2013-01-01

    Carbonatites are rare, carbonate-rich magmatic rocks that make up a minute portion of the crust only, yet they are of great relevance for our understanding of crustal and mantle processes. Although they occur in all continents and from Archaean to present, the deeper plumbing system of carbonatite ring-complexes is usually poorly constrained. Here, we show that carbonatite ring-complexes can be explained by caldera-style volcanism. Our geophysical investigation of the Alnö carbonatite ring-complex in central Sweden identifies a solidified saucer-shaped magma chamber at ~3 km depth that links to surface exposures through a ring fault system. Caldera subsidence during final stages of activity caused carbonatite eruptions north of the main complex, providing the crucial element to connect plutonic and eruptive features of carbonatite magmatism. The way carbonatite magmas are stored, transported and erupt at the surface is thus comparable to known emplacement styles from silicic calderas.

  14. Le volcanisme cambrien du Maroc central : implications géodynamiquesThe Central Morocco Cambrian volcanism: geodynamic implications

    Science.gov (United States)

    Ouali, Houssa; Briand, Bernard; Bouchardon, Jean-Luc; Capiez, Paul

    2003-05-01

    In southeastern Central Morocco, the Bou-Acila volcanic complex is considered of Cambrian age. In spite of low-grade metamorphic effect, initial volcanic texture and mineralogy can be recognized and volcanic rocks are dominated by dolerites and porphyric dolerites. The initial mineralogy is composed of plagioclases, pyroxenes and dark minerals. A secondary mineral assemblage is composed of albite, epidote, chlorite and calcite. According to their immobile elements compositions, the southeastern central Morocco metavolcanites are of within-plate continental tholeiites. This volcanism and those recognized in many other areas in Morocco confirm a Cambrian extensive episode within the Gondwana supercontinent. To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).To cite this article: H. Ouali et al., C. R. Geoscience 335 (2003).

  15. The Valle de Bravo Volcanic Field. A monogenetic field in the central front of the Mexican Volcanic Belt

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Jaimes-Viera, M. D.; Nieto-Obreg¢n, J.; Lozano-Santacruz, R.

    2003-12-01

    The Valle de Bravo volcanic field, VBVF, is located in the central-southern front of the Mexican Volcanic Belt just to the southwest of Nevado de Toluca volcano. The VBVF covers 3,703 square Km and includes at least 122 cinder cones, 1 shield volcano, several domes, and the 2 volcanic complexes of Zitacuaro and Villa de Allende. Morphometric parameters calibrated with isotopic ages of the volcanic products indicate four groups or units for the VBVF, Pliocene domes and lava flows, undifferentiated Pleistocene lava flows,> 40 Ka cones and lavas, 40 to 25 Ka cones and lavas, 25 to 10 Ka cones and lavas, and < 10 Ka cones and lavas. Whole-rock chemistry shows that all products of the VBVF range from basaltic andesites to dacites. No basalts were found, in spite of many units are olivine-rich and large some with large weight percent contents of MgO, 1 to 9. There is the possibility that some or all of the olivines in some samples could be xenocrysts. Some andesites are high in Sr, 1000 to 1800 ppm, that correlates with relatively high values of Ba, Cr, Ni, Cu, CaO and MgO. Y and Nb have the typical low values for orogenic rocks. The only shield volcano of the VBVF has a base of 9 Km, and its composition is practically the average composition of the whole field. Stratigraphycally, it is one of the earlier events of the VBVF. Compared with other volcanic fields of the Mexican Volcanic Belt, it lacks basalts and alkalic rocks. All volcanism of this field is calcalkaline

  16. Holocene volcanism of the upper McKenzie River catchment, central Oregon Cascades, USA

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    Deligne, Natalia I.; Conrey, Richard M.; Cashman, Katharine V.; Champion, Duane E.; Amidon, William H.

    2016-01-01

    To assess the complexity of eruptive activity within mafic volcanic fields, we present a detailed geologic investigation of Holocene volcanism in the upper McKenzie River catchment in the central Oregon Cascades, United States. We focus on the Sand Mountain volcanic field, which covers 76 km2 and consists of 23 vents, associated tephra deposits, and lava fields. We find that the Sand Mountain volcanic field was active for a few decades around 3 ka and involved at least 13 eruptive units. Despite the small total volume erupted (∼1 km3 dense rock equivalent [DRE]), Sand Mountain volcanic field lava geochemistry indicates that erupted magmas were derived from at least two, and likely three, different magma sources. Single units erupted from one or more vents, and field data provide evidence of both vent migration and reoccupation. Overall, our study shows that mafic volcanism was clustered in space and time, involved both explosive and effusive behavior, and tapped several magma sources. These observations provide important insights on possible future hazards from mafic volcanism in the central Oregon Cascades.

  17. U-series in zircon and 40Ar/39Ar geochronology reveal the most recent stage of a supervolcanic cycle in the Altiplano-Puna Volcanic Complex, Central Andes

    Science.gov (United States)

    Tierney, C.; de Silva, S. L.; Schmitt, A. K.; Jicha, B.; Singer, B. S.

    2010-12-01

    The ignimbrite flare up that produced the Altiplano-Puna Volcanic Complex of the Central Andes is characterized by episodic supervolcanism over a ~10 Ma time-span that climaxed about 4Ma. Since peak activity, the temporal and spatial record of volcanism suggests a waning of the system with only one other supervolcanic eruption at 2.6Ma. The most recent phase of volcanism from the APVC comprises a series of late Pleistocene domes that share a general petrochemical resemblance to the ignimbrites. New U-series data on zircons and high precision 40Ar/39Ar age determinations reveal that these effusive eruptions represent a temporally coherent magmatic episode. The five largest domes (Chao, Chillahuita, Chanka, Chascon-Runtu Jarita, and Tocopuri) have a combined volume >40 km3, and are distributed over an elliptical area of over 3000km2 centered at 22°S 68°W. They are crystal rich (>50%) dacites to rhyolites. New 40Ar/39Ar age determinations on biotite for the domes range range from 108±6 to 190±50 ka. However, 40Ar/39Ar ages from sanidine for some of the domes are more precise and span from 87±4 to 97±2 ka. We therefore interpret the eruption age of all these domes to be ~90 - 100 ka. This is consistent with SIMS U-series crystallization ages from the rims of 66 zircon crystals from four of the domes that reveal a fairly continuous spread of ages from ~90 ka to >300 ka with potentially common peaks in zircon ages at 100 ka and ~200 ka. U-Pb dating on the interiors of some of these zircon crystals indicates crystallization ages of up to 1.5 Ma. The common peaks of zircon crystallization between domes suggest that magma that fed these domes shared a larger regional source. Furthermore, the large volume of this potential source and the crystal-rich nature of the lava imply that this source was likely a large body of crystal-mush. The continuous nature of the zircon rim age population indicates that the residence time of this magma body was likely >200kyr. Potential

  18. The onset of the volcanism in the Ciomadul Volcanic Dome Complex (Eastern Carpathians): Eruption chronology and magma type variation

    Science.gov (United States)

    Molnár, Kata; Harangi, Szabolcs; Lukács, Réka; Dunkl, István; Schmitt, Axel K.; Kiss, Balázs; Garamhegyi, Tamás; Seghedi, Ioan

    2018-04-01

    Combined zircon U-Th-Pb and (U-Th)/He dating was applied to refine the eruption chronology of the last 2 Myr for the andesitic and dacitic Pilişca volcano and Ciomadul Volcanic Dome Complex (CVDC), the youngest volcanic area of the Carpathian-Pannonian region, located in the southernmost Harghita, eastern-central Europe. The proposed eruption ages, which are supported also by the youngest zircon crystallization ages, are much younger than the previously determined K/Ar ages. By dating every known eruption center in the CVDC, repose times between eruptive events were also accurately determined. Eruption of the andesite at Murgul Mare (1865 ± 87 ka) and dacite of the Pilişca volcanic complex (1640 ± 37 ka) terminated an earlier pulse of volcanic activity within the southernmost Harghita region, west of the Olt valley. This was followed by the onset of the volcanism in the CVDC, which occurred after several 100s kyr of eruptive quiescence. At ca. 1 Ma a significant change in the composition of erupted magma occurred from medium-K calc-alkaline compositions to high-K dacitic (Baba-Laposa dome at 942 ± 65 ka) and shoshonitic magmas (Malnaş and Bixad domes; 964 ± 46 ka and 907 ± 66 ka, respectively). Noteworthy, eruptions of magmas with distinct chemical compositions occurred within a restricted area, a few km from one another. These oldest lava domes of the CVDC form a NNE-SSW striking tectonic lineament along the Olt valley. Following a brief (ca. 100 kyr) hiatus, extrusion of high-K andesitic magma continued at Dealul Mare (842 ± 53 ka). After another ca. 200 kyr period of quiescence two high-K dacitic lava domes extruded (Puturosul: 642 ± 44 ka and Balvanyos: 583 ± 30 ka). The Turnul Apor lava extrusion occurred after a ca. 200 kyr repose time (at 344 ± 33 ka), whereas formation of the Haramul Mic lava dome (154 ± 16 ka) represents the onset of the development of the prominent Ciomadul volcano. The accurate determination of eruption dates shows that the

  19. Relationships between mineralization and silicic volcanism in the central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Francis, P.W.; Halls, C.; Baker, M.C.W.

    1983-10-01

    Studies of late Tertiary silicic volcanic centers in the Western and Eastern Cordilleras of the Central Andes show that three volcanic environments are appropriate sites for mineralization: (1) ring-fracture extrusions post-dating large calderas; (2) similar extrusions within ignimbrite shields; and (3) isolated, small silicic volcanoes. Subvolcanic tin mineralization in the Eastern Cordillera is located in silicic stocks and associated breccias of Miocene age. The Cerro Rico stock, Potosi, Bolivia, contains tin and silver mineralization and has an intrusion age apparently millions of years younger than that of the associated Kari Kari caldera. Similar age relationships between mineralization and caldera formation have been described from the San Juan province, Colorado. The vein deposits of Chocaya, southern Bolivia, were emplaced in the lower part of an ignimbrite shield, a type of volcanic edifice as yet unrecognized in comparable areas of silicic volcanism. The El Salvador porphyry copper deposit, Chile, is related to silicic stocks which may have been intruded along a caldera ring fracture. Existing models for the genesis of porphyry copper deposits suggest that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. The dome of La Soufriere, Guadeloupe is proposed as a modern analog for the surface expression of subvolcanic mineralization processes, the phreatic eruptions there suggesting the formation of hydrothermal breccia bodies in depth.

  20. Glacial evolution of the Ampato Volcanic Complex (Peru)

    Science.gov (United States)

    Alcalá, J.; Palacios, D.; Zamorano, J. J.; Vázquez, L.

    2009-04-01

    Ice masses on the Western range of the Central Andes are a main source of water resources and act as a geoindicator of variations in the climate of the tropics (Mark, 2008). The study of their evolution is of particular interest since they are situated in the transition zone between the tropical and mid-latitude circulation areas of the atmosphere (Zech et al., 2007). The function of this transition area is currently under debate, and understanding it is essential for the development of global climate models (Kull et al, 2008; Mark, 2008). However our understanding of the evolution of glaciers and their paleoclimatic factors for this sector of the Central Andes is still at a very basic level. This paper presents initial results of a study on the glacial evolution of the Ampato volcanic complex (15°24´- 15° 51´ S, 71° 51´ - 73° W; 6288 m a.s.l.) located in the Western Range of the Central Andes in Southern Peru, 70 km NW of the city of Arequipa. The main objectives are to identify the number of glacial phases the complex has undergone using geomorphological criteria to define a time frame for each phase, based on cosmogenic 36Cl dating of a sequence of moraine deposits; and to estimate the glacier Equilibrium Line Altitude (ELA) of each phase. The Ampato volcanic complex is formed by 3 great andesitic stratovolcanoes, the Nevados HualcaHualca-Sabancaya-Ampato, which started forming between the late Miocene and early Quaternary (Bulmer et al., 1999), aligned N-S and with summits covered with glaciers. The Sabancaya volcano is fully active, with its latest eruption occurring in 2001. Glacial landforms were identified and mapped using photointerpretation of vertical aerial photographs from 1955 (1:35,000 scale, National Geographic Institute of Peru), oblique photographs from 1943 (Aerophotographical Service of Peru), and a geo-referenced high-resolution Mrsid satellite image from 2000 (NASA). This cartography was corrected and improved through fieldwork. It was

  1. Petrology and geochronology of metamorphosed volcanic rocks and a middle Cretaceous volcanic neck in the east-central Sierra Nevada, California.

    Science.gov (United States)

    Kistler, R.W.; Swanson, S.E.

    1981-01-01

    Metamorphosed Mesozoic volcanic rocks from the E-central Sierra Nevada range in composition from basalt to rhyolite and have ages, based on whole rock Rb-Sr and U-Pb zircon dating, of about 237- 224, 185, 163, 134, and 100Ma. The major plutons of the batholith in this area are of Triassic (215-200Ma) and Cretaceous (94-80Ma) ages. Initial 87Sr/86Sr values for the metamorphosed volcanic rocks of the area are in the range from 0.7042 to 0.7058 and are generally different from the values for the surrounding batholithic rocks (0.7056-0.7066). A circular, zoned granitic pluton, with an outcrop area of 2.5km2, similar in appearance to a ring dike complex, was apparently a conduit for some or possibly all of the middle-Cretaceous metamorphosed volcanic rocks exposed about 5km to the S in the western part of the Ritter Range. Samples from the metamorphosed volcanic rocks and the pluton yield a Rb/Sr whole rock isochron age of 99.9+ or -2.2Ma with an intitial 87Sr/86Sr of 0.7048+ or -0.00001. Major element variation diagrams of the pluton and volcanic rocks define coincident compositional trends. The ages of volcanic events relative to the ages of the major intrusive epochs and the major element and isotopic compositions of the volcanic rocks relative to the major plutons indicate that the volcanic rocks are not simply or directly related to the major plutons in the Sierra Nevada. -from Authors

  2. Exploring the Rookwood volcanics at Gogango, Central Queensland

    International Nuclear Information System (INIS)

    Jones, M.

    2000-01-01

    Airborne radiometric surveys measure the potassium, thorium and uranium concentrations in the topmost 20-30cm of the earth. These datasets are now routinely used for geological interpretations and for defining exploration targets. The survey results are commonly presented as colour composite images of potassium-thorium-uranium distribution, and large copies of these colourful posters are commonplace on the walls of geological offices. However, in many cases, the data are not interpreted to their full potential. Further options exist for their evaluation. including determining potassium-thorium trends and the distribution of residuals across a prospective geological unit. This study of radiometric data over the Rookwood Volcanics near Gogango in central Queensland has detected areas of radio-element concentration and depletion. Comparison with known mineral occurrences suggests that some of these areas may be associated with copper mineralisation

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

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

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

  4. Hafnium Isotopic Variations in Central Atlantic Intraplate Volcanism

    Science.gov (United States)

    Geldmacher, J.; Hanan, B. B.; Hoernle, K.; Blichert-Toft, J.

    2008-12-01

    Although one of the geochemically best investigated volcanic regions on Earth, almost no Hf isotopic data have been published from the broad belt of intraplate seamounts and islands in the East Atlantic between 25° and 36° N. This study presents 176Hf/177Hf ratios from 61 representative samples from the Canary, Selvagen and Madeira Islands and nearby large seamounts, encompassing the full range of different evolutionary stages and geochemical endmembers. The majority of samples have mafic, mainly basaltic compositions with Mg-numbers within or near the range of magmas in equilibrium with mantle olivine (68-75). No correlation was found between Mg-number and 176Hf/177Hf ratios in the data set. In comparison to observed Nd isotope variations published for this volcanic province (6 ɛNd units), 176Hf/177Hf ratios span a larger range (14 ɛHf units). Samples from the Madeira archipelago have the most radiogenic compositions (176Hf/177Hfm= 0.283132-0.283335), widely overlapping the field for central Atlantic N-MORB. They form a relatively narrow, elongated trend (stretching over >6 ɛHf units) between a radiogenic MORB-like endmember and a composition located on the Nd-Hf mantle array. In contrast, all Canary Islands samples plot below the mantle array (176Hf/177Hfm = 0.282943-0.283067) and, despite being from an archipelago that stretches over a much larger geographic area, form a much denser cluster with less compositional variation (~4 ɛHf units). All samples from the seamounts NE of the Canaries, proposed to belong to the same Canary hotspot track (e.g. Geldmacher et al., 2001, JVGR 111; Geldmacher et al., 2005, EPSL 237), fall within the Hf isotopic range of this cluster. The cluster largely overlaps the composition of the proposed common mantle endmember 'C' (Hanan and Graham, 1996, Science 272) but spans a space between a more radiogenic (depleted) composition and a HIMU-type endmember. Although samples of Seine and Unicorn seamounts, attributed to the Madeira

  5. Immature intra-oceanic arc-type volcanism on the Izanagi Plate revealed by the geochemistry of the Daimaruyama greenstones in the Hiroo Complex, southern Hidaka Belt, central Hokkaido, Japan

    Science.gov (United States)

    Yamasaki, Toru; Nanayama, Futoshi

    2018-03-01

    The Izanagi Plate is assumed to have underlain the western Panthalassa Ocean to the east of Eurasia, and to have been subducting under the Eurasian continent. Although the Izanagi Plate has been lost to subduction, the subduction complexes of the circum-Panthalassa continental margins provide evidence that subduction-related volcanism occurred within the Panthalassa Ocean, and not just along its margins. The Daimaruyama mass is a kilometer-sized allochthonous greenstone body in the Hiroo Complex in the southeastern part of the Nakanogawa Group in the southern Hidaka Belt, northern Japan. The Hiroo Complex is a subduction complex that formed within the Paleo-Kuril arc-trench system at 57-48 Ma. The Daimaruyama greenstones consist mainly of coarse volcaniclastic rocks with lesser amount of lava. Red bedded chert, red shale, and micritic limestone are also observed as blocks associated with the greenstones. The presence of Early Cretaceous (Aptian-Albian) radiolaria in red bedded cherts within the greenstones indicates that the Daimaruyama greenstones formed after this time. An integrated major and trace element geochemical dataset for whole-rocks and clinopyroxenes of the greenstones indicates a calc-alkaline magmatic trend with low TiO2 contents and increases in SiO2 and decreases in FeO* with increasing differentiation. Negative anomalies of Nb, Ta, and Ti in normal mid-ocean-ridge basalt type normalized patterns are interpreted as "arc-signatures". Using "rhyolite-MELTS", we conducted a numerical simulation of magmatic differentiation under conditions of 1.5 kbar and H2O = 3 wt% to reproduce the liquid line of descent of the Daimaruyama greenstones. Back-calculations of the equilibrium melt compositions from the trace element chemistry of the clinopyroxenes generally agree with the whole-rock rare earth element compositions of the Daimaruyama greenstones, therefore providing support for the conditions used for the rhyolite-MELTS calculations as well as the actual

  6. Volcanic complexes in the eastern ridge of the Canary Islands: the Miocene activity of the island of Fuerteventura

    Science.gov (United States)

    Ancochea, E.; Brändle, J. L.; Cubas, C. R.; Hernán, F.; Huertas, M. J.

    1996-03-01

    Fuerteventura has been since early stages of its growth the result of three different adjacent large volcanic complexes: Southern, Central and Northern. The definition of these volcanic complexes and their respective growing episodes is based on volcano-stratigraphic, morphological and structural criteria, particularly radial dyke swarms. Each complex has its own prolonged history that might be longer than 10 m.y. During that time, several periods of activity alternating with gaps accompanied by important erosion took place. The evolution of each volcanic complex has been partially independent but all the three are affected by at least three Miocene tectonic phases that controlled considerably their activity. The volcanic complexes are deeply eroded and partially submerged. In the core of the Northern and the Central volcanic complexes there is a set of submarine and plutonic rocks intensely traversed by a dyke swarm, known as the Basal Complex. The Basal Complex has been interpreted in different ways but all previous authors have considered it to be prior to the subaerial shield stage of the island. Here we advance the idea that the Basal Complex represent the submarine growing stage of the volcanic complexes and the hypabyssal roots (plutons and dykes) of their successive subaerial growing episodes. Two seamounts situated nearby, southwest of the island, might be interpreted as remains of two other major volcanoes. These two volcanoes, together with those forming the present emerged island of Fuerteventura, and finally those of Famara and Los Ajaches situated further north on Lanzarote constitute a chain of volcanoes located along a lineation which is subparallel to the northwestern African coastline and which may relate to early Atlantic spreading trends in the area.

  7. Some aspects of volcanic ash layers in the Central Indian Basin.

    Digital Repository Service at National Institute of Oceanography (India)

    Sukumaran, N.P.; Banerjee, R.; Borole, D.V.; Gupta, S.M.

    Intercalated volcanic ash layers in two deep-sea sediment cores from the Central Indian Basin (CIB) are examined for the possibility of an in situ source of suboceanic volcanism. An in situ source has been predicated based on the bottom...

  8. 129I in volcanic fluids: Testing for the presence of marine sediments in the Central American volcanic arc

    International Nuclear Information System (INIS)

    Snyder, Glen; Fehn, Udo

    2000-01-01

    The long half-life and the geochemical behavior of the 129 I system suggest that this cosmogenic radioisotope can contribute significantly to the understanding of processes associated with subduction zones and volcanic arc systems. Because iodine is not incorporated into igneous rocks, the age-signal associated with 129 I permits the determination of the origin of volatiles within arc volcanic systems. We report here results of a study to test the application of 129 I in fluids collected from hotsprings, crater lakes, fumaroles and geothermal wells from the Central American volcanic arc. Both the Momotombo geothermal field in Nicaragua and the Miravalles geothermal field in Costa Rica show 129 I/I ratios consistent with magmatic contributions from subducted marine pelagic sediments (minimum iodine ages of 25-30 Ma). In addition, several wells provide iodine isotopic ratios indicative of an older end-member, presumably located in the shallow crust (minimum iodine age = 65 Ma)

  9. First volcanic CO2 budget estimate for three actively degassing volcanoes in the Central American Volcanic Arc

    Science.gov (United States)

    Robidoux, Philippe; Aiuppa, Alessandro; Conde, Vladimir; Galle, Bo; Giudice, Gaetano; Avard, Geoffroy; Muñoz, Angélica

    2014-05-01

    CO2 is a key chemical tracer for exploring volcanic degassing mechanisms of basaltic magmatic systems (1). The rate of CO2 release from sub-aerial volcanism is monitored via studies on volcanic plumes and fumaroles, but information is still sparse and incomplete for many regions of the globe, including the majority of the volcanoes in the Central American Volcanic Arc (2). Here, we use a combination of remote sensing techniques and in-situ measurements of volcanic gas plumes to provide a first estimate of the CO2 output from three degassing volcanoes in Central America: Turrialba, in Costa Rica, and Telica and San Cristobal, in Nicaragua. During a field campaign in March-April 2013, we obtained (for the three volcanoes) a simultaneous record of SO2 fluxes (from the NOVAC network (3)) and CO2 vs. SO2 concentrations in the near-vent plumes (obtained via a temporary installed fully-automated Multi-GAS instrument (4)). The Multi-GAS time-series allowed to calculate the plume CO2/SO2 ratios for different intervals of time, showing relatively stable gas compositions. Distinct CO2 - SO2 - H2O proportions were observed at the three volcanoes, but still within the range of volcanic arc gas (5). The CO2/SO2 ratios were then multiplied by the SO2 flux in order to derive the CO2 output. At Turrialba, CO2/SO2 ratios fluctuated, between March 12 and 19, between 1.1 and 5.7, and the CO2flux was evaluated at ~1000-1350 t/d (6). At Telica, between March 23 and April 8, a somewhat higher CO2/SO2 ratio was observed (3.3 ± 1.0), although the CO2 flux was evaluated at only ~100-500 t/d (6). At San Cristobal, where observations were taken between April 11 and 15, the CO2/SO2 ratio ranged between 1.8 and 7.4, with a mean CO2 flux of 753 t/d. These measurements contribute refining the current estimates of the total CO2 output from the Central American Volcanic Arc (7). Symonds, R.B. et al., (2001). J. Volcanol. Geotherm. Res., 108, 303-341 Burton, M. R. et al. (2013). Reviews in

  10. Scientific Drilling in a Central Italian Volcanic District

    Directory of Open Access Journals (Sweden)

    Paola Montone

    2007-09-01

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

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

    Science.gov (United States)

    Hildreth, Wes; Fierstein, Judy

    2015-01-01

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

  12. Satellite-based detection of volcanic sulphur dioxide from recent eruptions in Central and South America

    Directory of Open Access Journals (Sweden)

    D. Loyola

    2008-01-01

    Full Text Available Volcanic eruptions can emit large amounts of rock fragments and fine particles (ash into the atmosphere, as well as several gases, including sulphur dioxide (SO2. These ejecta and emissions are a major natural hazard, not only to the local population, but also to the infrastructure in the vicinity of volcanoes and to aviation. Here, we describe a methodology to retrieve quantitative information about volcanic SO2 plumes from satellite-borne measurements in the UV/Visible spectral range. The combination of a satellite-based SO2 detection scheme and a state-of-the-art 3D trajectory model enables us to confirm the volcanic origin of trace gas signals and to estimate the plume height and the effective emission height. This is demonstrated by case-studies for four selected volcanic eruptions in South and Central America, using the GOME, SCIAMACHY and GOME-2 instruments.

  13. Paleomagnetism of the Neoproterozoic Mount Harper Volcanic Complex, Canada

    Science.gov (United States)

    Eyster, A. E.; Macdonald, F. A.; O'Connell, R. J.

    2012-12-01

    Paleomagnetism can be used to identify apparent polar wander, which involves contributions from plate tectonics and true polar wander. True polar wander events have been suggested to have played an important role throughout Earth's history. The Neoproterozoic Mount Harper Volcanic Complex (MHVC) provides paleomagnetic data that bears on this issue. The MHVC is located in the southern Ogilvie Mountains in the Yukon Territory, on the north-west corner of the Laurentian craton. The MHVC involves up to 1200 m of basaltic and andesitic flows. The MHVC reflects the propagating rifting event involved in the breakup of the supercontinent Rodinia. The MHVC is well dated with an age of 717.43± 0.14Ma from the top (Macdonald et al., Science, 2010). Below the MHVC are alluvial fan conglomerate and sandstone from Proterozoic normal faulting. Above the MHVC is a glacial diamictite dated to 716.47± 0.24 Ma and related to Snowball Earth glaciation (Macdonald et al., Science, 2010). Both block and core samples were collected from different members of the MHVC for paleomagnetic study. Included in the sampling were several stratigraphic sections. Alternating field and thermal stepwise demagnetization methods were used to analyze specimens. Magnetic components were determined using principal component analysis and Fisher statistical procedures were used to calculate mean directions. The stratigraphically sampled basalt flows yielded two components. One was a common secondary overprint, and the other was a high stability component which yielded two different directions. One pole is the same as the accepted Neoproterozoic Laurentian grand mean pole and the other is ˜50 degrees away from this grand mean pole. Several possible interpretations are explored- tectonic rotation, true polar wander or the presence of a non-dipolar geomagnetic field.

  14. Ponderosa pine growth response to soil strength in the volcanic ash soils of central Oregon.

    Science.gov (United States)

    R.T. Parker; D.A. Maguire; D.D. Marshall; P. Cochran

    2007-01-01

    Mechanical harvesting and associated logging activities have the capacity to compact soil across large portions of harvest units. Two thinning treatments (felled only versus felled and skidded) in 70- to 80-year-old ponderosa pine stands were replicated at three sites with volcanic soils in central Oregon. Growth in diameter, height, and volume of residual trees were...

  15. Relationships between mineralization and silicic volcanism in the central Andes

    Science.gov (United States)

    Francis, P. W.; Halls, C.; Baker, M. C. W.

    1983-01-01

    Existing models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.

  16. Controlling centrality in complex networks

    Science.gov (United States)

    Nicosia, V.; Criado, R.; Romance, M.; Russo, G.; Latora, V.

    2012-01-01

    Spectral centrality measures allow to identify influential individuals in social groups, to rank Web pages by popularity, and even to determine the impact of scientific researches. The centrality score of a node within a network crucially depends on the entire pattern of connections, so that the usual approach is to compute node centralities once the network structure is assigned. We face here with the inverse problem, that is, we study how to modify the centrality scores of the nodes by acting on the structure of a given network. We show that there exist particular subsets of nodes, called controlling sets, which can assign any prescribed set of centrality values to all the nodes of a graph, by cooperatively tuning the weights of their out-going links. We found that many large networks from the real world have surprisingly small controlling sets, containing even less than 5 – 10% of the nodes. PMID:22355732

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

    Science.gov (United States)

    Matthews, Zoe; Manning, Christina J.

    2017-04-01

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

  18. The effects of subduction termination on the continental lithosphere: Linking volcanism, deformation, surface uplift, and slab tearing in central Anatolia

    Science.gov (United States)

    Delph, Jonathan R.; Abgarmi, Bijan; Ward, Kevin M.; Beck, Susan L.; Arda Ozacar, A.; Zandt, George; Sandvol, Eric; Turkelli, Niyazi; Kalafat, Dogan

    2017-04-01

    The lithospheric evolution of Anatolia is largely defined by processes associated with the terminal stages of subduction along its southern margin. Central Anatolia represents the transition from the subduction of oceanic lithosphere at the Aegean trench in the west to the Arabian - Eurasian continental collision in the east. In the overriding plate, this complicated transition is contemporaneous with uplift along the southern margin of central Anatolia (2 km in 6 Myr), voluminous felsic-intermediate ignimbrite eruptions (>1000 km3), extension, and tectonic deformation reflected by abundant low-magnitude seismic activity. The addition of 72 seismic stations as part of the Continental Dynamics - Central Anatolian Tectonics project, along with development of a new approach to the joint inversion of receiver functions and dispersion data, enables us obtain a high-resolution 3D shear wave velocity model of central Anatolia down to 150 km. This new velocity model has important implications for the complex interactions between the downgoing, segmenting African lithosphere and the overriding Anatolian Plate. These results reveal that the lithosphere of central Anatolia and the northern Arabian Plate is thin (4.5 km/s), indicating the presence of the Cyprean slab beneath central Anatolia. Thus, uplift of the Central Taurus Mountains may be due to slab rebound after the detachment of the oceanic portion of the Cyprean slab beneath Anatolia rather than the presence of shallow asthenospheric material. These fast velocities extend to the northern margin of the Central Taurus Mountains, giving way to a NE-SW trend of very slow upper mantle shear wave velocities (interpreted to be shallow, warm asthenosphere in which melt is present. The combination of a shallow asthenosphere and lithospheric-scale weaknesses associated with relict tectonic structures formed during the assembly of Anatolia are responsible for the spatial distribution of volcanism in the Central Anatolian

  19. Patterns of seismicity in a complex volcanic crisis at Brava, Cabo Verde

    Science.gov (United States)

    Faria, B. V. E.; Day, S. J.

    2017-12-01

    Brava is the smallest inhabited island of the Cape Verde archipelago, with an area of 62.5 km2 and a population of 6000. Geologically recent volcanism on Brava has produced lava (including carbonatite) flows, phonolite lava domes, pyroclastic density current deposits, and many phreatomagmatic craters in central Brava (where most of the population lives). Recent geological studies indicate that last eruptive period is about 1000 years old. Brava has experienced recurrent seismic swarms and felt earthquakes. The first permanent seismic station was installed in 1999, and a small network in 2011. From then until 2015 the seismic rate was near constant with sporadic peaks. Most seismic events were located offshore and associated with submarine volcanoes. However, the pattern of activity has been very different since 25th September 2015, when a M4 earthquake occurred in the submarine slopes of Brava. Subsequently, the seismicity became very complex with frequent volcano-tectonic (VT) earthquake swarms beneath Brava itself, with a few offshore events in some months. In addition, long-period, hybrid and hydrothermal events and likely very weak volcanic tremor episodes have been recorded. These non-VT events support the hypothesis that magma emplacement beneath Brava is at the origin of the abnormal seismic activity. The VT swarms indicate deformation around the magma body and possible dike intrusions, and there are indications of perturbation of a shallow hydrothermal system. The largest swarm occurred on the 1st and 2nd August 2016, with almost 1000 shallow events, including a M3.7 VT earthquake, medium-frequency events and weak volcanic tremor. An alert for a possible eruption was issued and a village (about 300 people) was evacuated as a precaution. Distributions of the cumulative number of events with depth in the main swarms suggest that the hypocenters are becoming shallower with time. Thus a possible eruption in the near future cannot be ruled out.

  20. Microstructures of the Kirsehir Complex, Central Turkey

    Science.gov (United States)

    ISIK, V.; Caglayan, A.; Uysal, T.; Bolhar, R.

    2011-12-01

    Turkey is positioned on the boundary between the Eurasian and African/Arabian plates, providing an ideal natural laboratory for learning passive and active earth processes such as deformation, metamorphism, earthquakes and volcanism. Central Turkey historically has played an important role in evolution of the Alpine orogeny. The Kirsehir Complex is one of three Mesozoic-Early Tertiary metamorphic and plutonic mid-crustal basement units exposed in central Turkey. The most common lithology of the metamorphites are the banded gneisses, which are intercalated with layers of schists, amphibolites and quartzite, and marbles representing the structurally the highest metamorphites of the study area. The metamorphites are characterized by multiple folding episodes and overprinting faults (thrust, normal and strike-slip). These metamorphites reached peak metamorphic conditions of upper amphibolite facies, as indicated by local presence of clinopyroxene, sillimanite, hornblende, andalusite and garnet. Later, retrograde greenschist facies conditions were attained characterized by the alteration of feldspar and mafic minerals to muscovite and chlorite/actinolite, respectively. The microstructures of selected minerals can be used to bracket the metamorphic grade during which microstructure formed. Quartz displays undulose extinction, deformation bands, subgrains and deformation lamellae, and recrystallisation. The presence of lobate grain boundaries of quartz indicates that GBM recrystallisation occurred. Undulose extinction and recrystallisation are common in micas. Recrystallisation, core-mantle structures in feldspar, myrmekites in K-feldspars within the gneisses suggest that deformation occurred within the amphibolite facies. Garnet occurs as slightly elliptical porphroclats. Sillimanite is present as fibrolite growing near biotite and microboudinaged. Andalusite porphyroblast/porphroclats are elongate and microboudinaged. Kinematic indicators (asymmetric mantled grains, S

  1. Within-plate Cenozoic Volcanism and Mantle Sources Within The Western-central Mediterranean Area

    Science.gov (United States)

    Beccaluva, L.; Bianchini, G.; Bonadiman, C.; Coltorti, M.; Siena, F.

    An integrated study of anorogenic basic magmas and entrained mantle xenoliths rep- resents a promising approach for a comprehension of the magmatogenic events occur- ring within the lithospheric mantle in the western-central Mediterranean area. In this contribution we review the geochemical characteristics of mafic lavas and associated peridotite xenoliths from three anorogenic volcanic districts: Pliocene-Quaternary vol- canism of Sardinia; Pliocene-Quaternary volcanism of the Iblean area (eastern Sicily); Paleocene-Oligocene Veneto Volcanic Province. Investigations have been focused on 1) petrological features of parental magmas, which may contribute to infer the com- positional characteristics of mantle sources and to constrain the modes of partial melt- ing; 2) modelling the depletion events and metasomatic enrichments in mantle xeno- liths of the three volcanic districts, as well as the nature of their causative agents. Petrological features and Sr-Nd-Pb isotopic data, both of lava and xenoliths, indicate that DM+HIMU components distinguish the lithospheric mantle sections of Iblean and Veneto Volcanic Provinces. On the other hand, lavas and xenoliths from Sardinia display a significant different isotopic signature characterised by DM+EM1. Similar geochemical fingerprints, i.e. the significant presence of EM components are gener- ally recorded by mafic lavas and mantle xenoliths from the European Plate, whereas they are not observed in the stable African lithospheric domain.

  2. Hydrothermal uranium deposits containing molybdenum and fluorite in the Marysvale volcanic field, west-central Utah

    Science.gov (United States)

    Cunningham, C.G.; Rasmussen, J.D.; Steven, T.A.; Rye, R.O.; Rowley, P.D.; Romberger, S.B.; Selverstone, J.

    1998-01-01

    Uranium deposits containing molybdenum and fluorite occur in the Central Mining Area, near Marysvale, Utah, and formed in an epithermal vein system that is part of a volcanic/hypabyssal complex. They represent a known, but uncommon, type of deposit; relative to other commonly described volcanic-related uranium deposits, they are young, well-exposed and well-documented. Hydrothermal uranium-bearing quartz and fluorite veins are exposed over a 300 m vertical range in the mines. Molybdenum, as jordisite (amorphous MoS2, together with fluorite and pyrite, increase with depth, and uranium decreases with depth. The veins cut 23-Ma quartz monzonite, 20-Ma granite, and 19-Ma rhyolite ash-flow tuff. The veins formed at 19-18 Ma in a 1 km2 area, above a cupola of a composite, recurrent, magma chamber at least 24 ?? 5 km across that fed a sequence of 21- to 14-Ma hypabyssal granitic stocks, rhyolite lava flows, ash-flow tuffs, and volcanic domes. Formation of the Central Mining Area began when the intrusion of a rhyolite stock, and related molybdenite-bearing, uranium-rich, glassy rhyolite dikes, lifted the fractured roof above the stock. A breccia pipe formed and relieved magmatic pressures, and as blocks of the fractured roof began to settle back in place, flat-lying, concave-downward, 'pull-apart' fractures were formed. Uranium-bearing, quartz and fluorite veins were deposited by a shallow hydrothermal system in the disarticulated carapace. The veins, which filled open spaces along the high-angle fault zones and flat-lying fractures, were deposited within 115 m of the ground surface above the concealed rhyolite stock. Hydrothermal fluids with temperatures near 200??C, ??18OH2O ~ -1.5, ?? -1.5, ??DH2O ~ -130, log fO2 about -47 to -50, and pH about 6 to 7, permeated the fractured rocks; these fluids were rich in fluorine, molybdenum, potassium, and hydrogen sulfide, and contained uranium as fluoride complexes. The hydrothermal fluids reacted with the wallrock resulting in

  3. Timing the evolution of a monogenetic volcanic field: Sierra Chichinautzin, Central Mexico

    Science.gov (United States)

    Jaimes-Viera, M. C.; Martin Del Pozzo, A. L.; Layer, P. W.; Benowitz, J. A.; Nieto-Torres, A.

    2018-05-01

    The unique nature of monogenetic volcanism has always raised questions about its origin, longevity and spatial distribution. Detailed temporal and spatial boundaries resulted from a morphometric study, mapping, relative dating, twenty-four new 40Ar/39Ar dates, and chemical analyses for the Sierra Chichinautzin, Central Mexico. Based on these results the monogenetic cones were divided into four groups: (1) Peñón Monogenetic Volcanic Group (PMVG); (2) Older Chichinautzin Monogenetic Volcanic Group (Older CMVG); (3) Younger Chichinautzin Monogenetic Volcanic Group (Younger CMVG) and (4) Sierra Santa Catarina Monogenetic Volcanic Group (SSC). The PMVG cover the largest area and marks the northern and southern boundaries of this field. The oldest monogenetic volcanism (PMVG; 1294 ± 36 to 765 ± 30 ka) started in the northern part of the area and the last eruption of this group occurred in the south. These basaltic-andesite cones are widely spaced and are aligned NE-SW (N60°E). After this activity, monogenetic volcanism stopped for 527 ka. Monogenetic volcanism was reactivated with the birth of the Tezoyuca 1 Volcano, marking the beginning of the second volcanic group (Older CMVG; 238 ± 51 to 95 ± 12 ka) in the southern part of the area. These andesitic to basaltic andesite cones plot into two groups, one with high MgO and Nb, and the other with low MgO and Nb, suggesting diverse magma sources. The eruption of the Older CMVG ended with the eruption of Malacatepec volcano and then monogenetic volcanism stopped again for 60 ka. At 35 ka, monogenetic volcanism started again, this time in the eastern part of the area, close to Popocatépetl volcano, forming the Younger CMVG (<35 ± 4 ka). These cones are aligned in an E-W direction. Geochemical composition of eruptive products of measured samples varies from basalts to dacites with low and high MgO. The Younger CMVG is considered still active since the last eruptions took place <2 ka. The SSC (132 ± 70 to 2 ± 56 ka

  4. Cretaceous alkaline volcanism in south Marzanabad, northern central Alborz, Iran: Geochemistry and petrogenesis

    Directory of Open Access Journals (Sweden)

    Roghieh Doroozi

    2016-11-01

    Full Text Available The alkali-basalt and basaltic trachy-andesites volcanic rocks of south Marzanabad were erupted during Cretaceous in central Alborz, which is regarded as the northern part of the Alpine-Himalayan orogenic belt. Based on petrography and geochemistry, en route fractional crystallization of ascending magma was an important process in the evolution of the volcanic rocks. Geochemical characteristics imply that the south Marzanabad alkaline basaltic magma was originated from the asthenospheric mantle source, whereas the high ratios of (La/YbN and (Dy/YbN are related to the low degree of partial melting from the garnet bearing mantle source. Enrichment pattern of Nb and depletion of Rb, K and Y, are similar to the OIB pattern and intraplate alkaline magmatic rocks. The K/Nb and Zr/Nb ratios of volcanic rocks range from 62 to 588 and from 4.27 to 9 respectively, that are some higher in more evolved samples which may reflect minor crustal contamination. The isotopic ratios of Sr and Nd respectively vary from 0.70370 to 0.704387 and from 0.51266 to 0.51281 that suggest the depleted mantle as a magma source. The development of south Marzanabad volcanic rocks could be related to the presence of extensional phase, upwelling and decompressional melting of asthenospheric mantle in the rift basin which made the alkaline magmatism in Cretaceous, in northern central Alborz of Iran.

  5. Volcanism and Tectonics of the Central Deep Basin, Sea of Japan

    Science.gov (United States)

    Lelikov, E. P.; Emelyanova, T. A.; Pugachev, A. A.

    2018-01-01

    The paper presents the results of a study on the geomorphic structure, tectonic setting, and volcanism of the volcanoes and volcanic ridges in the deep Central Basin of the Sea of Japan. The ridges rise 500-600 m above the acoustic basement of the basin. These ridges were formed on fragments of thinned continental crust along deep faults submeridionally crossing the Central Basin and the adjacent continental part of the Primorye. The morphostructures of the basin began to submerge below sea level in the Middle Miocene and reached their contemporary positions in the Pliocene. Volcanism in the Central Basin occurred mostly in the Middle Miocene-Pliocene and formed marginal-sea basaltoids with OIB (ocean island basalt) geochemical signatures indicating the lower-mantle plume origin of these rocks. The OIB signatures of basaltoids tend to be expressed better in the eastern part of the Central Basin, where juvenile oceanic crust has developed. The genesis of this crust is probably related to rising and melting of the Pacific superplume apophyse.

  6. Calderas and mineralization: volcanic geology and mineralization in the Chianti caldera complex, Trans-Pecos Texas

    Energy Technology Data Exchange (ETDEWEB)

    Duex, T.W.; Henry, C.D.

    1981-01-01

    This report describes preliminary results of an ongoing study of the volcanic stratigraphy, caldera activity, and known and potential mineralization of the Chinati Mountains area of Trans-Pecos Texas. Many ore deposits are spatially associated with calderas and other volcanic centers. A genetic relationship between calderas and base and precious metal mineralization has been proposed by some and denied by others. Steven and others have demonstrated that calderas provide an important setting for mineralization in the San Juan volcanic field of Colorado. Mineralization is not found in all calderas but is apparently restricted to calderas that had complex, postsubsidence igneous activity. A comparison of volcanic setting, volcanic history, caldera evolution, and evidence of mineralization in Trans-Pecos to those of the San Juan volcanic field, a major mineral producer, indicates that Trans-Pecos Texas also could be an important mineralized region. The Chianti caldera complex in Trans-Pecos Texas contains at least two calderas that have had considerable postsubsidence activity and that display large areas of hydrothermal alteration and mineralization. Abundant prospects in Trans-Pecos and numerous producing mines immediately south of the Trans-Pecos volcanic field in Mexico are additional evidence that ore-grade deposits could occur in Texas.

  7. Unravelling the magmatic system beneath a monogenetic volcanic complex (Jagged Rocks Complex, Hopi Buttes, AZ, USA)

    Science.gov (United States)

    Re, G.; Palin, J. M.; White, J. D. L.; Parolari, M.

    2017-12-01

    The Jagged Rocks complex is the eroded remnant of the plumbing systems of closely spaced monogenetic alkaline volcanic centres in the southern Hopi Buttes Volcanic Field (AZ, USA). It contains different clinopyroxene populations with distinctive textures and geochemical patterns. In the Northwestern part of the complex, which exposes the best developed system of conduits, most of the clinopyroxenes consist of large- to medium-sized resorbed cores overgrown by euhedral rims (type 1), small moderately resorbed greenish cores with the same overgrown rims (type 2), and phlogopite as an accessory phase. By contrast, in the Southern part of the complex the majority of clinopyroxenes are euhedral with oscillatory zonation (type 3) and are accompanied by minor euhedral olivine. The differences between these mineral assemblages indicate a composite history of crystallization and magmatic evolution for the two parts of the complex, governed by different mechanisms and ascent patterns from a single source at 50 km depth (16 kbar). The Northwest system preserves a high-pressure assemblage that cooled rapidly from near-liquidus conditions, suggesting direct ascent from the source to the surface at high-to-moderate transport rates (average 1.25 m/s). By contrast, the Southern system represents magma that advanced upward at much lower overall ascent rates, stalling at times to form small-volume mid-crustal storage zones (e.g., sills or a network of sheeted intrusions); this allowed the re-equilibration of the magma at lower pressure ( 30 km; 8 kbar), and led to nucleation and growth of euhedral clinopyroxene and olivine phenocrysts.

  8. Volcanic tremor and local earthquakes at Copahue volcanic complex, Southern Andes, Argentina

    Science.gov (United States)

    Ibáñez, J. M.; Del Pezzo, E.; Bengoa, C.; Caselli, A.; Badi, G.; Almendros, J.

    2008-07-01

    In the present paper we describe the results of a seismic field survey carried out at Copahue Volcano, Southern Andes, Argentina, using a small-aperture, dense seismic antenna. Copahue Volcano is an active volcano that exhibited a few phreatic eruptions in the last 20 years. The aim of this experiment was to record and classify the background seismic activity of this volcanic area, and locate the sources of local earthquakes and volcanic tremor. Data consist of several volcano-tectonic (VT) earthquakes, and many samples of back-ground seismic noise. We use both ordinary spectral, and multi-spectral techniques to measure the spectral content, and an array technique [Zero Lag Cross Correlation technique] to measure the back-azimuth and apparent slowness of the signals propagating across the array. We locate VT earthquakes using a procedure based on the estimate of slowness vector components and S-P time. VT events are located mainly along the border of the Caviahue caldera lake, positioned at the South-East of Copahue volcano, in a depth interval of 1-3 km below the surface. The background noise shows the presence of many transients with high correlation among the array stations in the frequency band centered at 2.5 Hz. These transients are superimposed to an uncorrelated background seismic signal. Array solutions for these transients show a predominant slowness vector pointing to the exploited geothermal field of "Las Maquinitas" and "Copahue Village", located about 6 km north of the array site. We interpret this coherent signal as a tremor generated by the activity of the geothermal field.

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

    Science.gov (United States)

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

    2017-08-16

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

  10. The eruptive chronology of the Ampato-Sabancaya volcanic complex (Southern Peru)

    Science.gov (United States)

    Samaniego, Pablo; Rivera, Marco; Mariño, Jersy; Guillou, Hervé; Liorzou, Céline; Zerathe, Swann; Delgado, Rosmery; Valderrama, Patricio; Scao, Vincent

    2016-09-01

    We have reconstructed the eruptive chronology of the Ampato-Sabancaya volcanic complex (Southern Peru) on the basis of extensive fieldwork, and a large dataset of geochronological (40K-40Ar, 14C and 3He) and geochemical (major and trace element) data. This volcanic complex is composed of two successive edifices that have experienced discontinuous volcanic activity from Middle Pleistocene to Holocene times. The Ampato compound volcano consists of a basal edifice constructed over at least two cone-building stages dated at 450-400 ka and 230-200 ka. After a period of quiescence, the Ampato Upper edifice was constructed firstly during an effusive stage (80-70 ka), and then by the formation of three successive peaks: the Northern, Southern (40-20 ka) and Central cones (20-10 ka). The Southern peak, which is the biggest, experienced large explosive phases, resulting in deposits such as the Corinta plinian fallout. During the Holocene, eruptive activity migrated to the NE and constructed the mostly effusive Sabancaya edifice. This cone comprised many andesitic and dacitic blocky lava flows and a young terminal cone, mostly composed of pyroclastic material. Most samples from the Ampato-Sabancaya define a broad high-K magmatic trend composed of andesites and dacites with a mineral assemblage of plagioclase, amphibole, biotite, ortho- and clino-pyroxene, and Fe-Ti oxides. A secondary trend also exists, corresponding to rare dacitic explosive eruptions (i.e. Corinta fallout and flow deposits). Both magmatic trends are derived by fractional crystallisation involving an amphibole-rich cumulate with variable amounts of upper crustal assimilation. A marked change in the overall eruptive rate has been identified between Ampato ( 0.1 km3/ka) and Sabancaya (0.6-1.7 km3/ka). This abrupt change demonstrates that eruptive rates have not been homogeneous throughout the volcano's history. Based on tephrochronologic studies, the Late Holocene Sabancaya activity is characterised by strong

  11. Widespread Neogene and Quaternary Volcanism on Central Kerguelen Plateau, Southern Indian Ocean

    Science.gov (United States)

    Duncan, R. A.; Falloon, T.; Quilty, P. G.; Coffin, M. F.

    2016-12-01

    We report new age determinations and compositions for rocks from 18 dredge hauls collected from eight submarine areas across Central Kerguelen Plateau (CKP). Sea knolls and volcanic fields with multiple small cones were targeted over a 125,000 km2 region that includes Heard and McDonald islands. Large early Miocene (16-22 Ma) sea knolls rise from the western margin of the CKP and are part of a NNW-SSE line of volcanic centers that lie between Îles Kerguelen and Heard and McDonald islands. A second group of large sea knolls is aligned E-W across the center of this region. We see evidence of much younger activity (5 Ma to present) in volcanic fields to the north of, and up to 300 km NE of Heard Island. Compositions include basanite, basalt, and trachybasalt, that are broadly similar to plateau lava flows from nearby Ocean Drilling Program (ODP) Site 1138, lower Miocene lavas at Îles Kerguelen, dredged rocks from the early Miocene sea knolls, and Big Ben lavas from Heard Island. Geochemical data indicate decreasing fractions of mantle source melting with time. The western line of sea knolls has been related to hotspot activity now underlying the Heard Island area. In view of the now recognized much larger area of young volcanic activity, we propose that a broad region of CKP became volcanically active in Neogene time due to incubation of plume material at the base of the relatively stationary overlying plateau. The presence of pre-existing crustal faults promotes access for melts from the Heard mantle plume to rise to the surface.

  12. The Quaternary history of effusive volcanism of the Nevado de Toluca area, Central Mexico

    Science.gov (United States)

    Torres-Orozco, R.; Arce, J. L.; Layer, P. W.; Benowitz, J. A.

    2017-11-01

    Andesite and dacite lava flows and domes, and intermediate-mafic cones from the Nevado de Toluca area were classified into five groups using field data and 40Ar/39Ar geochronology constraints. Thirty-four lava units of diverse mineralogy and whole-rock major-element geochemistry, distributed between the groups, were identified. These effusive products were produced between ∼1.5 and ∼0.05 Ma, indicating a mid-Pleistocene older-age for Nevado de Toluca volcano, coexisting with explosive products that suggest a complex history for this volcano. A ∼0.96 Ma pyroclastic deposit attests for the co-existence of effusive and explosive episodes in the mid-Pleistocene history. Nevado de Toluca initiated as a composite volcano with multiple vents until ∼1.0 Ma, when the activity began to centralize in an area close to the present-day crater. The modern main edifice reached its maximum height at ca. 50 ka after bulky, spiny domes erupted in the current summit of the crater. Distribution and geochemical behavior in major elements of lavas indicate a co-magmatic relationship between different andesite and dacite domes and flows, although unrelated to the magmatism of the monogenetic volcanism. Mafic-intermediate magma likely replenished the system at Nevado de Toluca since ca. ∼1.0 Ma and contributed to the eruption of new domes, cones, as well as effusive-explosive activity. Altogether, field and laboratory data suggest that a large volume of magma was ejected around 1 Ma in and around the Nevado de Toluca.

  13. Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA

    Science.gov (United States)

    Wicks, Charles W.; Dzurisin, Daniel; Ingebritsen, Steven; Thatcher, Wayne; Lu, Zhong; Iverson, Justin

    2002-04-01

    Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ~10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ~130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ~1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ~100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ~6.5 km.

  14. Aeromagnetic Study of the Nortern Acambay Graben and Amealco Caldera, Central Mexican Volcanic Belt

    Science.gov (United States)

    Gonzalez, T.

    2011-12-01

    The Mexican Volcanic Belt (MVB) is characterized by E-W striking faults which form a series of en echelon graben along its length. In the central region of the MVB is located the Acambay graben an intra-arc tectonic depression structure, of apparent Quaternary age, which gives rise to pronounced scarps over a distance of about 80 Km. and 15 to 35 Km wide. The general arrangement of the faults that constitute the Acambay graben shows E-W trend which defines the fronts of the graben exhibits a major fault discontinuity. The graben is limited of the north by the Acambay- Tixmadeje and Epitafio Huerta faults and in the south by the Pastores and Venta de Bravo faults.. In the northern wall in the graben is located the Amealco caldera. This volcanic center (approximately 10 km in diameter) was formed by several discrete volcanic events, which produced an ignimbrite which covers the area. It is partially cut by a regional fault and the southern portion of the Amealco Caldera was displaced by a normal faulting along a segment of the Epitafio Huerta system. Continued tectonic activity in the Acambay area is confirmed by recent seismic episodes The Amealco tuff is the most important volcanic unit because of its volume and distribution. Aeromagnetic data was obtained and analyzed the anomalies. The anomaly map was compared with the surface geology and larger anomalies were correlated with major volcanic features. Since our main interest was in mapping the subsurface intrusive and volcanic bodies, the total field magnetic anomalies were reduced to the pole by using the double integral Fourier method. The reduced to the pole anomaly map results in a simplified pattern of isolated positive and negative anomalies, which show an improved correlation with all major volcanic structures. For the analysis and interpretation of the anomalies, the reduced to the pole anomalies were continued upward at various reference levels. These operations result in smoothing of the anomaly field by

  15. Crustal structure, evolution, and volcanic unrest of the Alban Hills, Central Italy

    Science.gov (United States)

    Chiarabba, C.; Amato, A.; Delaney, P.T.

    1997-01-01

    The Alban Hills, a Quaternary volcanic center lying west of the central Apennines, 15-25 km southeast of Rome, last erupted 19ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka. Earthquakes of moderate intensity have been generated there at least since the Roman age. Modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features, the phreatomagmatic craters on the west side of the volcano. Results from seismic tomography allow identification of a low-velocity region, perhaps still hot or partially molten, more than 6 km beneath the youngest craters and a high-velocity region, probably a solidified magma body, beneath the older central volcanic construct. Thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters. The volume of magma accumulation and the amount of maximum uplift was probably at least 40 ?? 106 m3 and 40 cm, respectively. Comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift. The magma chamber beneath the western Alban Hills is probably responsible for much of the past 200 ka of eruptive activity, is still receiving intermittent batches of magma, and is, therefore, continuing to generate modest levels of volcanic unrest. Bending of overburden is the most likely cause of the persistent earthquakes, which generally have hypocenters above the 6-km-deep top of the magma reservoir. In this view, the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity.

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

    Science.gov (United States)

    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.

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

    KAUST Repository

    Ruch, Joel

    2016-01-23

    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 activity steadily migrated eastward and currently focus on a 10 km long x 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.

  18. Nature, source and composition of volcanic ash in sediments from a fracture zone trace of Rodriguez Triple Junction in the Central Indian Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Mascarenhas-Pereira, M.B.L.; Nath, B.N.; Borole, D.V.; Gupta, S.M.

    Volcanic glasses associated with pumice, micro nodules and palagonite like lithic fragments were recovered from a volcanic terrain in a fracture zone defined as Rodriguez Triple Junction trace in the Central Indian Basin. Morphologically, the tephra...

  19. Recent geophysical investigation at Somma-Vesuvio volcanic complex

    Science.gov (United States)

    Berrino, Giovanna; Coppa, Ugo; De Natale, Giuseppe; Pingue, Folco

    1993-11-01

    Activity at Somma-Vesuvio volcanic area in southern Italy is monitored by seismic stations and periodic geodetic and gravity surveys. The seismic network, which consists at present of four vertical stations and one three-component station, recorded an increase in earthquake activity in 1978 and between November 1988 and March 1989. During the later activity, earthquakes were located in a cluster about 3 km beneath the summit of the volcano. Two tide gauges, two tiltmeters and a recording gravimeter are also operating at Somma-Vesuvio. Yearly levelling surveys are conducted along several closed routes that extend from as much as 6 km from the base of the volcano to the summit area. Survey results reveal no significant ground movement since 1959, except for a slight subsidence around the rim of the summit crater. Gravity changes have been larger than the expected 10 μGal uncertainty of the measurements. The lack of contemporary elevation changes implies that the observed gravity changes are the result of a slight change in density structure. The cone of Somma-Vesuvio has been very stable for the last few decades, showing no indications of a buildup to activity. The lack of surface movement should rule out a magma-supply rate to this volcano at the historic eruptive rate of 0.002 km 3/yr.

  20. The Middlesex Fells Volcanic Complex: A Revised Tectonic Model based on Geochronology, Geochemistry, and Field Data

    Science.gov (United States)

    Hampton, R.

    2017-12-01

    The Boston Bay area is composed of several terranes originating on the paleocontinent of Avalonia, an arc terrane that accreted onto the continent of Laurentia during the Devonian. Included in these terranes is the Middlesex Fells Volcanic Complex, a bimodal complex composed of both intrusive and extrusive igneous rocks. Initial studies suggested that this volcanic complex formed during a rift event as the Avalonian continent separated from its parent continent 700-900 Ma. New geochemical and geochronological data and field relationships observed in this study establishes a new tectonic model. U-Pb laser ablation zircon data on four samples from different units within the complex reveal that the complex erupted 600 Ma. ICP-MS geochemical analysis of the metabasalt member of the complex yield a trace element signature enriched in Rb, Pb, and Sr and depleted in Th, indicating a subduction component to the melt and interpreted as an eruption into a back-arc basin. The felsic units similarly have an arc related signature when plotted on trace element spider diagrams and tectonic discrimination diagrams. Combined with the field relationships, including an erosional unconformity, stratigraphic and intrusional relationships and large faults from episodic extension events, this data suggests that the Middlesex Fells Volcanic Complex was erupted as part of the arc-sequence of Avalonia and as part of the formation of a back-arc basin well after Avalonia separated from its parent continent. This model presents a significantly younger eruption scenario for the Middlesex Fells Volcanics than previously hypothesized and may be used to study and compare to other volcanics from Avalon terranes in localities such as Newfoundland and the greater Boston area.

  1. A possible cause of the Miocene uplift and volcanism in the central Anatolian plateau

    Science.gov (United States)

    Bartol, J.; Govers, R. M.; Wortel, M. J.

    2010-12-01

    During the middle and late Miocene (13-5Ma) several seemingly unrelated events occurred in central Anatolia, Turkey; (1) a new epoch of widespread volcanic activity with a mantle signature, (2) sudden uplift and disruption of a Oligocene-lower Miocene palaeo drainage system in the Western Taurus (southwest Turkey) and (3) a regional regression across southern Turkey (Antalya, Adana, Mut) coeval with volcanic activity. These observations suggest an uplift (>1000 meters) of the central Anatolian plateau by a mechanism which also triggered widespread volcanic activity. In eastern Anatolia, similar events are attributed to delamination of the lithospheric mantle [e.g. Keskin et al., 2003]. Results from tomography [W.Spakman, pers. com]) suggest that the (deeper) Bitlis slab was laterally continuous below the eastern and central Anatolian plateau. We therefore propose that the scenario developed for eastern Anatolian plateau also applies to the central Anatolian plateau. In this scenario, delamination started along the Izmir-Ankara-Erzincan suture zone and was possibly induced by remnants of a northern Neotethys slab or continental collision between Arabia and Eurasia. As the lithospheric mantle separated from the crust it sank into the asthenosphere and was replaced by hot mantle material. If true, delamination is expected to have had a thermal and isostatic imprint. Using a three-dimensional thermal-flexural model and taking changes of the effective elastic thickness due to thermal perturbation into account, we aim to quantify the possible imprints in the geological record of the central and eastern Anatolian plateau. Our model results show that delamination of the lithospheric mantle can explain the present day elevation (1500 m) of the central Anatolian plateau. For the eastern Anatolian plateau, however, delamination of the lithospheric mantle alone can only explain half (1000 m) of the present day elevation. Thickening of the eastern Anatolia crust by 1-5 km (β=1

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

    Science.gov (United States)

    Motuza, Gediminas; Šliaupa, Saulius

    2017-10-01

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

  3. Late Pleistocene and Holocene activity of the Atacazo-Ninahuilca Volcanic Complex (Ecuador)

    NARCIS (Netherlands)

    Hidalgo, Silvana; Monzier, Michel; Almeida, Eduardo; Chazot, Gilles; Eissen, Jean-Philippe; van der Plicht, Johannes; Hall, Minard L.

    2008-01-01

    The Atacazo-Ninahuilca Volcanic Complex (ANVC) is located in the Western Cordillera of Ecuador, 10 km southwest of Quito. At least six periods of Pleistocene to Holocene activity (N1 to N6) have been preserved in the geologic record as tephra fallouts and pyroclastic flow deposits. New field data,

  4. Shallow crustal structure of eastern-central Trans-Mexican Volcanic Belt.

    Science.gov (United States)

    Campos-Enriquez, J. O.; Ramón, V. M.; Lermo-Samaniego, J.

    2015-12-01

    Central-eastern Trans-Mexican Volcanic Belt (TMVB) is featured by large basins (i.e., Toluca, Mexico, Puebla-Tlaxcala, Libres-Oriental). It has been supposed that major crustal faults limit these basins. Sierra de Las Cruces range separates the Toluca and Mexico basins. The Sierra Nevada range separates Mexico basin from the Puebla-Tlaxcala basin. Based in gravity and seismic data we inferred the Toluca basin is constituted by the Ixtlahuaca sub-basin, to the north, and the Toluca sub-basin to the south, which are separated by a relative structural high. The Toluca depression is more symmetric and bounded by sub-vertical faults. In particular its eastern master fault controlled the emplacement of Sierra de Las Cruces range. Easternmost Acambay graben constitutes the northern and deepest part of the Ixtlahuaca depression. The Toluca-Ixtlahuaca basin is inside the Taxco-San Miguel de Allende fault system, and limited to the west by the Guerrero terrane which continues beneath the TMVB up to the Acambay graben. Mexico basin basement occupies an intermediate position and featured by a relative structural high to the north-east, as established by previous studies. This relative structural high is limited to the west by the north-south Mixhuca trough, while to the south it is bounded by the east-west Copilco-Xochimilco-Chalco sub-basin. The Puebla-Tlaxcala basin basement is the shallowest of these 3 tectonic depressions. In general, features (i.e., depth) and relationship between these basins, from west to east, are controlled by the regional behavior of the Sierra Madre Oriental fold and thrust belt basement (i.e., Oaxaca Complex?). This study indicates that an active east-west regional fault system limits to the south the TMVB (from the Nevado de Toluca volcano through the Popocatepetl volcano and eastward along southern Puebla-Tlaxcala basin). The Tenango and La Pera fault systems constituting the western part of this regional fault system coincide with northern

  5. Volcanic gas emissions and degassing dynamics at Ubinas and Sabancaya volcanoes; implications for the volatile budget of the central volcanic zone

    Science.gov (United States)

    Moussallam, Yves; Tamburello, Giancarlo; Peters, Nial; Apaza, Fredy; Schipper, C. Ian; Curtis, Aaron; Aiuppa, Alessandro; Masias, Pablo; Boichu, Marie; Bauduin, Sophie; Barnie, Talfan; Bani, Philipson; Giudice, Gaetano; Moussallam, Manuel

    2017-09-01

    Emission of volcanic gas is thought to be the dominant process by which volatiles transit from the deep earth to the atmosphere. Volcanic gas emissions, remain poorly constrained, and volcanoes of Peru are entirely absent from the current global dataset. In Peru, Sabancaya and Ubinas volcanoes are by far the largest sources of volcanic gas. Here, we report the first measurements of the compositions and fluxes of volcanic gases emitted from these volcanoes. The measurements were acquired in November 2015. We determined an average SO2 flux of 15.3 ± 2.3 kg s- 1 (1325-ton day- 1) at Sabancaya and of 11.4 ± 3.9 kg s- 1 (988-ton day- 1) at Ubinas using scanning ultraviolet spectroscopy and dual UV camera systems. In-situ Multi-GAS analyses yield molar proportions of H2O, CO2, SO2, H2S and H2 gases of 73, 15, 10 1.15 and 0.15 mol% at Sabancaya and of 96, 2.2, 1.2 and 0.05 mol% for H2O, CO2, SO2 and H2S at Ubinas. Together, these data imply cumulative fluxes for both volcanoes of 282, 30, 27, 1.2 and 0.01 kg s- 1 of H2O, CO2, SO2, H2S and H2 respectively. Sabancaya and Ubinas volcanoes together contribute about 60% of the total CO2 emissions from the Central Volcanic zone, and dominate by far the total revised volatile budget of the entire Central Volcanic Zone of the Andes.

  6. Origin of silicic magmas along the Central American volcanic front: Genetic relationship to mafic melts

    Science.gov (United States)

    Vogel, Thomas A.; Patino, Lina C.; Eaton, Jonathon K.; Valley, John W.; Rose, William I.; Alvarado, Guillermo E.; Viray, Ela L.

    2006-09-01

    Silicic pyroclastic flows and related deposits are abundant along the Central American volcanic front. These silicic magmas erupted through both the non-continental Chorotega block to the southeast and the Paleozoic continental Chortis block to the northwest. The along-arc variations of the silicic deposits with respect to diagnostic trace element ratios (Ba/La, U/Th, Ce/Pb), oxygen isotopes, Nd and Sr isotope ratios mimic the along-arc variation in the basaltic and andesitic lavas. This variation in the lavas has been interpreted to indicate relative contributions from the slab and asthenosphere to the basaltic magmas [Carr, M.J., Feigenson, M.D., Bennett, E.A., 1990. Incompatible element and isotopic evidence for tectonic control of source mixing and melt extraction along the Central American arc. Contributions to Mineralogy and Petrology, 105, 369-380.; Patino, L.C., Carr, M.J. and Feigenson, M.D., 2000. Local and regional variations in Central American arc lavas controlled by variations in subducted sediment input. Contributions to Mineralogy and Petrology, 138 (3), 265-283.]. With respect to along-arc trends in basaltic lavas the largest contribution of slab fluids is in Nicaragua and the smallest input from the slab is in central Costa Rica — similar trends are observed in the silicic pyroclastic deposits. Data from melting experiments of primitive basalts and basaltic andesites demonstrate that it is difficult to produce high K 2O/Na 2O silicic magmas by fractional crystallization or partial melting of low-K 2O/Na 2O sources. However fractional crystallization or partial melting of medium- to high-K basalts can produce these silicic magmas. We interpret that the high-silica magmas associated Central America volcanic front are partial melts of penecontemporaneous, mantle-derived, evolved magmas that have ponded and crystallized in the mid-crust — or are melts extracted from these nearly completely crystallized magmas.

  7. Central waste complex interim safety basis

    International Nuclear Information System (INIS)

    Cain, F.G.

    1995-01-01

    This interim safety basis provides the necessary information to conclude that hazards at the Central Waste Complex are controlled and that current and planned activities at the CWC can be conducted safely. CWC is a multi-facility complex within the Solid Waste Management Complex that receives and stores most of the solid wastes generated and received at the Hanford Site. The solid wastes that will be handled at CWC include both currently stored and newly generated low-level waste, low-level mixed waste, contact-handled transuranic, and contact-handled TRU mixed waste

  8. Change with time in extrusion and chemical composition of volcanic rock in geothermal areas in central Kyushu

    Energy Technology Data Exchange (ETDEWEB)

    Kamata, Hiroki

    1986-10-01

    Changes with time in extrusion and chemical composition of volcanic rocks in central Kyushu are studied to provide basic data required for evaluation of geothermal resources. Distribution of volcanic rocks in successive 1Ma (10/sup 6/ year) periods and the average thickness of volcanic rock layers in each period are determined, from which the volume of volcanic rocks in each 1Ma period is calculated. Results indicate that volcanos in central Kyushu extruded about 3,000 km/sup 3//Ma of volcanic rocks during the early periods (about 5Ma), followed by a series of declining periods up to the present. Comparison of volcanic extrusive rocks of each 1Ma period shows that lava of hornblende andesite and pyroxenic andesite has been extruded in great quantities in every period. Chemical composition is studied based on diagrams showing changes in SiO/sub 2/ content. The K/sub 2/O content is relatively high in most volcanos younger than 1.6Ma, compared to those older than 1.6Ma. the K/sub 2/O content in extruded rocks has been high during the latest 0.4Ma in the Aso volcanic area, unlike other island arc conjunction areas. (4 figs, 5 tabs, 28 refs)

  9. Geochemical constraints on the link between volcanism and plutonism at the Yunshan caldera complex, SE China

    Science.gov (United States)

    Yan, Lili; He, Zhenyu; Beier, Christoph; Klemd, Reiner

    2018-01-01

    The Yunshan caldera complex is part of a larger scale, ca. 2000-km-long volcanic-plutonic complex belt in the coastal region of SE China. The volcanic rocks in the caldera complex are characterized by high-silica peraluminous and peralkaline rhyolites associated with an intracaldera porphyritic quartz monzonite pluton. In this study, we present zircon U-Pb, Hf and stable O isotopes along with geochemical data of both volcanic and plutonic rocks to evaluate the potential petrogenetic link between volcanism and plutonism in the Yunshan caldera complex. SHRIMP zircon U-Pb geochronology of both volcanic and plutonic rocks yields almost identical ages ranging from 95.6 to 93.1 Ma. The peraluminous and peralkaline rhyolites show negative anomalies of Sr, P, Ti and Ba and to a lesser extent negative Nb and Ta anomalies, along with positive Rb anomalies and `seagull-like' rare earth element (REE) patterns with negative Eu anomalies and low (La/Yb)N ratios. The intracaldera porphyritic quartz monzonite displays minor negative Rb, Nb, Ta, Sr, P and Ti anomalies and a positive Ba anomaly with REE patterns characterized by relatively high (La/Yb)N ratios and lack significant Eu anomalies. The peraluminous and peralkaline rhyolites and the porphyritic quartz monzonite exhibit consistent ɛ Nd( t) of - 3.7 to - 2.2 and display zircon ɛ Hf( t) values of - 2.1 to 3.7. They further have similar, mantle-like, zircon oxygen isotopic compositions (δ18OVSMOW mainly = 4.63 to 5.76‰). We interpret these observations to be in agreement with a crystal mush model in which the parental magma of the volcanic and plutonic rocks of the Yunshan caldera complex was likely produced by interaction of asthenosphere melts with subduction-influenced enriched mantle wedge. The peralkaline rhyolites are interpreted to represent the most differentiated magma that has subsequently experienced significant fluid-melt interactions, whereas the porphyritic quartz monzonite may be representative of the

  10. Fault propagation folds induced by gravitational failure and slumping of the Central Costa Rica volcanic range: Implications for large terrestrial and Martian volcanic edifices

    International Nuclear Information System (INIS)

    Borgia, A.; Burr, J.; Montero, W.; Morales, L.D.; Alvarado, G.E.

    1990-01-01

    Long sublinear ridges and related scarps located at the base of large volcanic structures are frequently interpreted as normal faults associated with extensional regional stress. In contrast, the ridges bordering the Central Costa Rica volcanic range (CCRVR) are the topographic expression of hanging wall asymmetric angular anticlines overlying low-angle thrust faults at the base of the range. These faults formed by gravitational failure and slumping of the flanks of the range due to the weight of the volcanic edifices and were perhaps triggered by the intrusion of magma over the past 20,000 years. These anticlines are hypothesized to occur along the base of the volcano, where the thrust faults ramp up toward the sea bottom. Ridges and scarps between 2,000 and 5,000 m below sea level are interpreted as the topographic expression of these folds. The authors further suggest that the scarps of the CCRVR and valid scaled terrestrial analogs of the perimeter scarp of the Martian volcano Olympus Mons. They suggest that the crust below Olympus Mons has failed under the load of the volcano, triggering the radial slumping of the flanks of the volcano on basal thrusts. The thrusting would have, in turn, formed the anticlinal ridges and scarps that surround the edifice. The thrust faults may extend all the way to the base of the Martian crust (about 40 km), and they may have been active until almost the end of the volcanic activity. They suggest that gravitational failure and slumping of the flanks of volcanoes is a process common to most large volcanic edifices. In the CCRVR this slumping of the flanks is a slow intermittent process, but it could evolve to rapid massive avalanching leading to catastrophic eruptions. Thus monitoring of uplift and displacement of the folds related to the slump tectonics could become an additional effective method for mitigating volcanic hazards

  11. Drilling into Rhyolitic Magma at Shallow depth at Krafla Volcanic Complex, NE-Iceland

    Science.gov (United States)

    Mortensen, A. K.; Markússon, S. H.; Gudmundsson, Á.; Pálsson, B.

    2017-12-01

    Krafla volcanic complex in NE-Iceland is an active volcano but the latest eruption was the Krafla Fires in 1975-1984. Though recent volcanic activity has consisted of basaltic fissure eruptions, then it is rhyolitic magma that has been intercepted on at least two occasions while drilling geothermal production wells in the geothermal field suggesting a layered magma plumbing system beneath the Krafla volcanic complex. In 2008 quenched rhyolitic glass was retrieved from the bottom of well KJ-39, which is 2865 m deep ( 2571 m true vertical depth). In 2009 magma was again encountered at an even shallower depth and in more than 2,5 km distance from the bottom of well KJ-39, but in 2009 well IDDP-1 was drilled into magma three times just below 2100 m depth. Only on the last occasion was quenched glass retrieved to confirm that magma had been encountered. In well KJ-39 the quenched glass was rhyolitic in composition. The glass contained resorbed minerals of plagioclase, clinopyroxene and titanomagnetite, but the composition of the glass resembles magma that has formed by partial melting of hydrated basalt. The melt was encountered among cuttings from impermeable, coarse basaltic intrusives at a depth, where the well was anticipated to penetrate the Hólseldar volcanic fissure. In IDDP-1 the quenched glass was also rhyolitic in composition. The glass contained less than 5% of phenocrysts, but the phenocryst assemblage included andesine plagioclase, augite, pigeonite, and titanomagnetite. At IDDP-1 the melt was encountered below a permeable zone composed of fine to coarse grained felsite and granophyre. The disclosure of magma in two wells at Krafla volcanic complex verify that rhyolitic magma can be encountered at shallow depth across a larger area within the caldera. The encounter of magma at shallow depth conforms with that superheated conditions have been found at >2000 m depth in large parts of Krafla geothermal field.

  12. Multi-scale seismic tomography of the Merapi-Merbabu volcanic complex, Indonesia

    Science.gov (United States)

    Mujid Abdullah, Nur; Valette, Bernard; Potin, Bertrand; Ramdhan, Mohamad

    2017-04-01

    Merapi-Merbabu volcanic complex is the most active volcano located on Java Island, Indonesia, where the Indian plate subducts beneath Eurasian plate. We present a preliminary study of a multi-scale seismic tomography of the substructures of the volcanic complex. The main objective of our study is to image the feeding paths of the volcanic complex at an intermediate scale by using the data from the dense network (about 5 km spacing) constituted by 53 stations of the French-Indonesian DOMERAPI experiment complemented by the data of the German-Indonesian MERAMEX project (134 stations) and of the Indonesia Tsunami Early Warning System (InaTEWS) located in the vicinity of the complex. The inversion was performed using the INSIGHT algorithm, which follows a non-linear least squares approach based on a stochastic description of data and model. In total, 1883 events and 41846 phases (26647 P and 15199 S) have been processed, and a two-scale approach was adopted. The model obtained at regional scale is consistent with the previous studies. We selected the most reliable regional model as a prior model for the local tomography performed with a variant of the INSIGHT code. The algorithm of this code is based on the fact that inverting differences of data when transporting the errors in probability is equivalent to inverting initial data while introducing specific correlation terms in the data covariance matrix. The local tomography provides images of the substructure of the volcanic complex with a sufficiently good resolution to allow identification of a probable magma chamber at about 20 km.

  13. Formation and uranium explorating prospect of sub-volcanic granitic complex and rich uranium ore deposit in South China

    International Nuclear Information System (INIS)

    Wang Yusheng

    1997-01-01

    The rich uranium ore deposits are all closely related to tecto-magmatism of late-magmatic cycle whether volcanic types or granitic types in south China. Volcanic type rich uranium deposit has closely relationship with sub-volcanic activity, and granitic type rich uranium deposit is also closely related to mid-fine, unequal particle small massif in late main invasion stage. Based on characteristics of magmatism, we name the rock sub-volcanic granite complex, which is a unique style and closely related to the formation of rich uranium ore deposit

  14. Temporal evolution of the Western and Central volcanism of the Aeolian Island Arc (Italy, southern Tyrhhenian Sea)

    Science.gov (United States)

    Leocat, E.; Gillot, P.-Y.; Peccerillo, A.

    2009-04-01

    4 ka. Then the activity was followed by the construction of the Mte Terrione at 168±4 ka (Gillot 1987), which is matched by High K-Ca andesites emplaced in the Chiumento crater. Therefore, two different magmatic series took place in only 15 ka. The last eruption of Filicudi built the High K-CA dacite lava dome of Mte Montagnola. For Lipari island, the same event is observed around 120-100 ka. In fact, the emitted products evolved from CA andesitic basalts, that emplaced from 256±8 ka (Monte Chirica) to 119±7 ka (Monterosa), to High K-CA andesite after 100 ka. The rocks becam more and more differentiated to achieve High K-CA rhyolite composition during the last 40 ka. At the same time, the Monte Fossa delle Felci of Salina island shows a geochemical "excursion" around 100 ka, characterised by High K-CA dacite. The lower limit of Pollara explosive eruption, that emitted High K-CA rhyolite products, is constrain by a Monte dei Porri lava flow affected by Pollara crater and dated at 13±2 ka. Thus, all these magmatic changes correlate with morphological and volcanic variations. Finally, our first results confirm that the Aeolian arc volcanism is generated in a complex source, with important roles of both arc-type and anorogenic-type compositions. Datings on key samples show that role of different mantle sources change within a very short time span, especially in the central portion of the arc, along the TL lithosheric fault system. This work also gives new geochronological constrains on the duration of magmatic evolution and eruptive phases.

  15. Volcanic stratigraphy of a high-altitude Mammuthus columbi (Tlacotenco, Sierra Chichinautzin), Central México

    Science.gov (United States)

    Guilbaud, Marie-Noelle; Arana-Salinas, Lilia; Siebe, Claus; Barba-Pingarrón, Luis Alberto; Ortiz, Agustín

    2015-03-01

    The discovery of a near complete skeleton of Mammuthus columbi in a cornfield located on the northern slopes of the Sierra Chichinautzin volcanic field south of Mexico City sparked the interest of the scientific and public community. Although remains of this species of mammoth are frequently discovered in central Mexico, this new find is at the southernmost and highest (ca. 2770 m asl) location yet within the Mexico Basin. In addition, the bones were found embedded in dark volcanic ash, raising the possibility of a relationship between the death of the animal and explosive activity at a neighboring scoria cone, as the site is located <10 km from several young volcanoes. Stratigraphic, sedimentological, geochemical, and geochronological studies were conducted at the discovery site and within a 5-km radius to determine the tephra stratigraphy in the area and constrain the source of the " mammoth ash" and the age and taphonomy of the fossil remains. Results show that the mammoth was buried after death by stream-flows (dilute lahars) that were triggered by torrential rain that remobilized loose scoriaceous ash ejected by the San Miguel cone some time after its eruption ca. 17,000 BP.

  16. Volcanic avalanche fault zone with pseudotachylite and gouge in French Massif Central

    Science.gov (United States)

    Bernard, Karine; van Wyk de Vries, Benjamin

    2017-11-01

    Structures and textures with sedimentological variations at different scales of the lithofacies assemblage help us to constrain the basal kinematic transition from non-depositional to depositional conditions during volcanic avalanche emplacement. In the well-exposed impact-sheared contact along volcanic avalanche fault zone in the French Massif Central, we observe how the granular textures of the pseudotachylite and fault gouge have recorded the propagation of shock wave with granular oscillatory stress. Sequential events of basal aggradation along avalanche fault zone have been established related to fractal D-values, temperature pressure regime and oscillatory stress during slow wave velocity. A typical lithofacies assemblage with a reverse grading shows the pseudotachylite and fault gouge. A cataclastic gradient is characterised by the fractal D-values from 2.7 in jigsaw breccias with pseudotachylite partial melt, to 2.6 in the polymodal gouge. Shock, brecciation and comminution produce cataclastic shear bands in the pseudotachylite and quartz microstructures along the basal contact of the volcanic debris-avalanche deposit. Gouge microstructures show granular segregation, cataclasis with antithetic rotational Riedel shear, and an arching effect between the Riedel shear bands. X-ray microtomography provided 3D microfabrics along the clastic vein in the sandy-gouge. From the available statistical dataset, a few equations have been developed implicating the same cataclastic origin with a co-genetic evolution of lithofacies. An impact wave during primary shear propagation may contribute to produce hydroclastic matrix, pseudotachylite partial melt and proximal gouge thixotropy with v 50m/s and a T < 654 °C. The interseismic period with oscillatory stress is related to crushed clasts and basaltic melt around 800 °C, Riedel shear bands with granular segregation along the fault gouge. The secondary shock by matrix-rich avalanche (ΔP = 10GPa, T ≥ 1000-1500

  17. Hydrothermal alteration, fumarolic deposits and fluids from Lastarria Volcanic Complex: A multidisciplinary study

    OpenAIRE

    Aguilera, Felipe; Layana, Susana; Rodríguez-Díaz, Augusto; González, Cristóbal; Cortés, Julio; Inostroza, Manuel

    2016-01-01

    A multidisciplinary study that includes processing of Landsat ETM+ satellite images, chemistry of gas condensed, mineralogy and chemistry of fumarolic deposits, and fluid inclusion data from native sulphur deposits, has been carried out in the Lastarria Volcanic Complex (LVC) with the objective to determine the distribution and characteristics of hydrothermal alteration zones and to establish the relations between gas chemistry and fumarolic deposits. Satellite image processing shows the pres...

  18. The occurrence of pycnogonids associated with the volcanic structures of Bransfield Strait central basin (Antarctica

    Directory of Open Access Journals (Sweden)

    Tomás Munilla

    2007-12-01

    Full Text Available Fifty-four specimens of pycnogonids belonging to twenty-two species, eight genera and six families were collected with a rocky dredge during the cruise Gebrap-96 in the central basin of Bransfield Strait, from depths between 647 and 1592 m. The richest station in terms of abundance and biomass was DR6 (south of Livingston Island, which was also the shallowest one; at this relatively shallow depth food is more available than in deeper waters. The families Nymphonidae and Colossendeidae had the same number of specimens (21 specimens; 39% abundance each. The most abundant species were Nymphon villosum and N. proximum. Pallenopsis buphthalmus was collected for only the third time. The collections increased the geographical distribution of three species and the depth range of six species. The volcanic structures sampled were inactive during 1996, since none of the specimens showed signs of hydrothermal phenomena. This collection was typically representative of the west Antarctic benthic zone.

  19. Investigating Crustal Scale Fault Systems Controlling Volcanic and Hydrothermal Fluid Processes in the South-Central Andes, First Results from a Magnetotelluric Survey

    Science.gov (United States)

    Pearce, R.; Mitchell, T. M.; Moorkamp, M.; Araya, J.; Cembrano, J. M.; Yanez, G. A.; Hammond, J. O. S.

    2017-12-01

    At convergent plate boundaries, volcanic orogeny is largely controlled by major thrust fault systems that act as magmatic and hydrothermal fluid conduits through the crust. In the south-central Andes, the volcanically and seismically active Tinguiririca and Planchon-Peteroa volcanoes are considered to be tectonically related to the major El Fierro thrust fault system. These large scale reverse faults are characterized by 500 - 1000m wide hydrothermally altered fault cores, which possess a distinct conductive signature relative to surrounding lithology. In order to establish the subsurface architecture of these fault systems, such conductivity contrasts can be detected using the magnetotelluric method. In this study, LEMI fluxgate-magnetometer long-period and Metronix broadband MT data were collected at 21 sites in a 40km2 survey grid that surrounds this fault system and associated volcanic complexes. Multi-remote referencing techniques is used together with robust processing to obtain reliable impedance estimates between 100 Hz and 1,000s. Our preliminary inversion results provide evidence of structures within the 10 - 20 km depth range that are attributed to this fault system. Further inversions will be conducted to determine the approximate depth extent of these features, and ultimately provide constraints for future geophysical studies aimed to deduce the role of these faults in volcanic orogeny and hydrothermal fluid migration processes in this region of the Andes.

  20. Intra-Arc extension in Central America: Links between plate motions, tectonics, volcanism, and geochemistry

    Science.gov (United States)

    Phipps Morgan, Jason; Ranero, Cesar; Vannucchi, Paola

    2010-05-01

    This study revisits the kinematics and tectonics of Central America subduction, synthesizing observations of marine bathymetry, high-resolution land topography, current plate motions, and the recent seismotectonic and magmatic history in this region. The inferred tectonic history implies that the Guatemala-El Salvador and Nicaraguan segments of this volcanic arc have been a region of significant arc tectonic extension; extension arising from the interplay between subduction roll-back of the Cocos Plate and the ~10-15 mm/yr slower westward drift of the Caribbean plate relative to the North American Plate. The ages of belts of magmatic rocks paralleling both sides of the current Nicaraguan arc are consistent with long-term arc-normal extension in Nicaragua at the rate of ~5-10 mm/yr, in agreement with rates predicted by plate kinematics. Significant arc-normal extension can ‘hide' a very large intrusive arc-magma flux; we suggest that Nicaragua is, in fact, the most magmatically robust section of the Central American arc, and that the volume of intrusive volcanism here has been previously greatly underestimated. Yet, this flux is hidden by the persistent extension and sediment infill of the rifting basin in which the current arc sits. Observed geochemical differences between the Nicaraguan arc and its neighbors which suggest that Nicaragua has a higher rate of arc-magmatism are consistent with this interpretation. Smaller-amplitude, but similar systematic geochemical correlations between arc-chemistry and arc-extension in Guatemala show the same pattern as the even larger variations between the Nicaragua arc and its neighbors. We are also exploring the potential implications of intra-arc extension for deformation processes along the subducting plate boundary and within the forearc ‘microplate'.

  1. Gravity in extensional regimes: A case study in the Central Volcanic Region, New Zealand

    Science.gov (United States)

    Greve, A.; Stern, T. A.

    2017-12-01

    Using the interpretation of a large crustal seismic experiment conducted in 2009 as boundary model, we produced a sequence of new 2D gravity models for the central North Island in New Zealand. The Bouguer gravity field in the region ranges from -100 to 60 mGal and is dominated by the long wavelength signals of the subduction of the Pacific beneath the Australian plate along the Hikurangi margin and the transition from continental to oceanic lithosphere about the Bay of Plenty coast (NE New Zealand). Removal of these broad regional trends reveals the presence of a triangular shaped area, within the lines Taranaki-Coromandel and Taranaki - White Island, with negative anomalies between -30 and 60 mGal and positive anomalies around 10 mGal along the margins. This area, commonly referred to as the Central Volcanic Region (CVR) represents the continental continuation of the Lau-Havre, oceanic, back-arc rift basin. The Taupo Volcanic Zone forms the active eastern half of the CVR, where anomalously high heat output, geothermal activity and active volcanism occur. The new gravity model includes the presence of a 90km wide, ca. 10 km thick rift pillow of new underplated, lower crust between the depths of 15 and 25 km. A positive density contrast of 300 kg/m3 for this body is consistent with the observed seismic velocities (6.8 ≤ Vp ≤ 7.1 km/s). A ca. 2.5 km deep basin dominates the upper crustal structure and is about 50 km wide, infilled by low density volcaniclastics, with adopted average negative densities of -425 kg/m3. In the mid-crustal region, between 2.5 and 15 km depth, isostatic compensation requires a small density contrast of -110 kg/m3. This density contrast, with respect to a standard crustal model, can be ascribed to the presence of low density intrusives, within the old and now stretched crust. On the basis of this new crustal structure model we estimate a stretching factor (ß) for the old crust of 2-2.4. The intruded mid crust and the underplated new

  2. A 150-ka-long record for the volcano-tectonic deformation of Central Anatolian Volcanic Province

    Science.gov (United States)

    Karabacak, Volkan; Tonguç Uysal, I.; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin

    2017-04-01

    The Anatolian Block represents one of the most outstanding examples of intra-plate deformation related to continental collision. Deformation related to the convergence of the Afro-Arabian continent toward north gives rise to widespread and intense arc volcanism in the Central Anatolia. All the usual studies on dating the volcano-tectonic deformation of the region are performed entirely on volcanic events of the geological record resulted in eruptions. However, without volcanic eruption, magma migration and related fluid pressurization also generate crustal deformation. In the current study has been funded by the Scientific and Technological Research Council of Turkey with the project no. 115Y497, we focused on fracture systems and their carbonate veins around the Ihlara Valley (Cappadocia) surrounded by well-known volcanic centers with latest activities of the southern Central Anatolian Volcanic Province. We dated 37 samples using the Uranium-series technique and analyzed their isotope systematics from fissure veins, which are thought to be controlled by the young volcanism in the region. Our detailed fracture analyses in the field show that there is a regional dilatation as a result of a NW-SE striking extension which is consistent with the results of recent GPS studies. The Uranium-series results indicate that fracture development and associated carbonate vein deposition occurred in the last 150 ka. Carbon and oxygen isotope systematics have almost remained unchanged in the studied time interval. Although veins in the region were precipitated from fluids primarily of meteoric origin, fluids originating from water-rock interaction also contribute for the deposition of carbonate veins. The age distribution indicates that the crustal deformation intensified during 7 different period at about 4.7, 34, 44, 52, 83, 91, 149 ka BP. Four of these periods (4.7, 34, 91, 149 ka BP) correspond to the volcanic activities suggested in the previous studies. The three crustal

  3. Complex conductivity of volcanic rocks and the geophysical mapping of alteration in volcanoes

    Science.gov (United States)

    Ghorbani, A.; Revil, A.; Coperey, A.; Soueid Ahmed, A.; Roque, S.; Heap, M. J.; Grandis, H.; Viveiros, F.

    2018-05-01

    Induced polarization measurements can be used to image alteration at the scale of volcanic edifices to a depth of few kilometers. Such a goal cannot be achieved with electrical conductivity alone, because too many textural and environmental parameters influence the electrical conductivity of volcanic rocks. We investigate the spectral induced polarization measurements (complex conductivity) in the frequency band 10 mHz-45 kHz of 85 core samples from five volcanoes: Merapi and Papandayan in Indonesia (32 samples), Furnas in Portugal (5 samples), Yellowstone in the USA (26 samples), and Whakaari (White Island) in New Zealand (22 samples). This collection of samples covers not only different rock compositions (basaltic andesite, andesite, trachyte and rhyolite), but also various degrees of alteration. The specific surface area is found to be correlated to the cation exchange capacity (CEC) of the samples measured by the cobalthexamine method, both serving as rough proxies of the hydrothermal alteration experienced by these materials. The in-phase (real) conductivity of the samples is the sum of a bulk contribution associated with conduction in the pore network and a surface conductivity that increases with alteration. The quadrature conductivity and the normalized chargeability are two parameters related to the polarization of the electrical double layer coating the minerals of the volcanic rocks. Both parameters increase with the degree of alteration. The surface conductivity, the quadrature conductivity, and the normalized chargeability (defined as the difference between the in-phase conductivity at high and low frequencies) are linearly correlated to the CEC normalized by the bulk tortuosity of the pore space. The effects of temperature and pyrite-content are also investigated and can be understood in terms of a physics-based model. Finally, we performed a numerical study of the use of induced polarization to image the normalized chargeability of a volcanic edifice

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

    Science.gov (United States)

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

    2014-08-01

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

  5. Spreading of Somma-Vesuvio Volcanic Complex: is the Hazard for Plinian Eruptions being reduced?

    Science.gov (United States)

    Borgia, A.; Tizzani, P.; Solaro, G.; Luongo, G.; Fusi, N.

    2003-12-01

    Contrary to what is the common knowledge, a detailed structural study of active faulting and rifting of the summit area of Somma-Vesuvio volcanic complex, combined with INSAR, levelling data and seismic profiling at sea suggests that the present-day long-term dynamic behaviour of the complex and of its summit caldera is characterized by volcanic spreading. The structural evolution is controlled by a number of asymmetric, intersecting leaf-grabens. The boundary faults of these grabens intersect at different angles the Somma caldera walls generating a set of wedge-horsts. While normal faulting characterizes the Somma caldera walls, the lavas of the past 150 years, infilling the caldera, have been rifted all around the southern, eastern and northern base of Vesuvio's cone, which, in turn, is being displaced seaward. Associated to the subsidence and extension of the summit area, relative uplift occurs along the coast; in addition, deformation of recent sediments 6-18 km offshore also indicate compression and uplift, which appears to be unrelated to regional tectonics. A preliminary evaluation indicates that rifting of the lavas is in the order of 1-2 mm/a with a southwestward average direction of displacement. Based on these data, we suggest that a wide sector of Somma-Vesuvio is spreading on its plastic sedimentary substratum, which have been identified by drilling. Volcanic spreading appears to have controlled the magmatic evolution and the energy decrease of major historic explosive eruptions since 79 AD. If our interpretation is correct, major plinian eruptions should not occur in the near future. On the other hand, rifting around the caldera suggests that volcanic activity could soon be renewed.

  6. Tectonic Constraints on the Evolution of Geothermal Systems in the Central Andean Volcanic Zone (CAVZ)

    Science.gov (United States)

    Veloso, E. E.; Tardani, D.; Aron, F.; Elizalde, J. D.; Sanchez-Alfaro, P.; Godoy, B.

    2017-12-01

    South of 19°S, geothermal fields and Pliocene-to-Holocene volcanic centers of the Central Andean Volcanic Zone are spatially associated with distinct, large-scale fault systems disrupting the volcanic arc, which control the architecture and dynamics of the fluids reservoirs at shallow crustal levels. Based on an extensive compilation of structural, lithological and isotopic data, and satellite imagery band-ratio analyses, we produced detailed maps of 13 areas comprising 19 identified and/or potential geothermal fields, to examine if particular local-scale tectonic configurations are associated to fluids migrating from different crustal levels. We defined three main tectonic environments according to the specific, kilometer-scale structural arrangement and its spatial relation to the geothermal surface manifestations. T1, dominated by left-lateral, pure strike-slip motion on a NW-trending duplex-like geometry with geothermal fields located along the faults - in turn distributed into five major subparallel zones cutting across the orogenic belt between ca. 20° and 27°S. T2, dominated by shortening on a series of N-trending thrust faults and fault-propagated folds, cut and displaced by the above mentioned NW-trending faults, with geothermal fields hosted at fault intersections and at fold hinges. And T3, characterized by transtension accommodated by NW-to-WNW-trending left-lateral/normal faults, with hot-springs lying along the fault traces. Interestingly, each of the independently defined tectonic environments has distinctive helium (in fluids) and strontium (in lavas) isotopic signatures and estimated geothermal reservoir temperatures. T1 shows a large 4He contribution, low 87Sr/86Sr ratio and temperatures varying between ca. 220°-310°C; T3 low 4He and high 87Sr/86Sr ratio and temperature (260°-320°C); T2 isotopic values fall between T1 and T3, yet showing the lowest (130°-250°C) temperatures. We suggest that these particular isotopic signatures are due to

  7. Transient magmatic control in a tectonic domain: the central Aeolian volcanic arc (South Italy)

    KAUST Repository

    Ruch, Joel; Vezzoli, Luigina; Di Lorenzo, Riccardo; De Rosa, Rosanna; Acocella, Valerio

    2015-01-01

    The background stress field in volcanic areas may be overprinted by that produced by transient magmatic intrusions, generating local faulting. These events are rarely monitored and thus not fully understood, generating debate about the role of magma and tectonics in any geodynamic setting. Here we carried out a field structural analysis on the NNW-SSE strike-slip system of the central Aeolian Arc, Italy (Lipari and Vulcano islands) with ages constrained by stratigraphy to better capture the tectonic and magmatic evolution at the local and regional scales. We consider both islands as a single magmatic system and define 5 principal stratigraphic units based on magmatic and tectonic activity. We collected >500 measurements of faults, extension fractures and dikes at 40 sites, mostly NNE-SSW to NNW-SSE oriented with a dominant NS orientation. These structures are governed quasi exclusively by pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral slip, the latter being mostly related to old deposits (>50 ka). We further reconstructed the evolution of the Vulcano-Lipari system during the last ~20 ka and find that it consists of an overall half-graben-like structure, with faults with predominant eastward dips. Field evidence suggests that faulting occurs often in temporal and spatial relation with magmatic events, suggesting that most of the observable deformation derived from transient magmatic activity, rather than from steady regional tectonics. To explain the dominant magmatic and episodic extension in a tectonic dominant domain, we propose a model where the regional N-S trending maximum horizontal stress, responsible for strike-slip activity, locally rotates to vertical in response to transient pressurization of the magmatic system and magma rise below Lipari and Vulcano. This has possibly generated the propagation of N-S trending dikes in the past 1 ka along a 10 km long by 1 km wide crustal corridor, with important

  8. Transient magmatic control in a tectonic domain: the central Aeolian volcanic arc (South Italy)

    KAUST Repository

    Ruch, Joel

    2015-04-01

    The background stress field in volcanic areas may be overprinted by that produced by transient magmatic intrusions, generating local faulting. These events are rarely monitored and thus not fully understood, generating debate about the role of magma and tectonics in any geodynamic setting. Here we carried out a field structural analysis on the NNW-SSE strike-slip system of the central Aeolian Arc, Italy (Lipari and Vulcano islands) with ages constrained by stratigraphy to better capture the tectonic and magmatic evolution at the local and regional scales. We consider both islands as a single magmatic system and define 5 principal stratigraphic units based on magmatic and tectonic activity. We collected >500 measurements of faults, extension fractures and dikes at 40 sites, mostly NNE-SSW to NNW-SSE oriented with a dominant NS orientation. These structures are governed quasi exclusively by pure dip-slip motion, consistent with an E-W extension direction, with minor dextral and sinistral slip, the latter being mostly related to old deposits (>50 ka). We further reconstructed the evolution of the Vulcano-Lipari system during the last ~20 ka and find that it consists of an overall half-graben-like structure, with faults with predominant eastward dips. Field evidence suggests that faulting occurs often in temporal and spatial relation with magmatic events, suggesting that most of the observable deformation derived from transient magmatic activity, rather than from steady regional tectonics. To explain the dominant magmatic and episodic extension in a tectonic dominant domain, we propose a model where the regional N-S trending maximum horizontal stress, responsible for strike-slip activity, locally rotates to vertical in response to transient pressurization of the magmatic system and magma rise below Lipari and Vulcano. This has possibly generated the propagation of N-S trending dikes in the past 1 ka along a 10 km long by 1 km wide crustal corridor, with important

  9. Crustal seismicity associated to rpid surface uplift at Laguna del Maule Volcanic Complex, Southern Volcanic Zone of the Andes

    Science.gov (United States)

    Cardona, Carlos; Tassara, Andrés; Gil-Cruz, Fernando; Lara, Luis; Morales, Sergio; Kohler, Paulina; Franco, Luis

    2018-03-01

    Laguna del Maule Volcanic Complex (LMVC, Southern Andes of Chile) has been experiencing large rates (ca. 30 cm/yr) of surface uplift as detected since 2008 by satellite geodetic measurements. Previous works have modeled the source of this deformation as an inflating rectangular sub-horizontal sill underlying LMVC at 5 km depth, which is supposedly related to an active process of magmatic replenishment of a shallow silicic reservoir. However little is known about the tectonic context on which this activity is taking place, particularly its relation with crustal seismicity that could help understanding and monitoring the current deformation process. Here we present the first detailed characterization of the seismic activity taking place at LMVC and integrate it with structural data acquired in the field in order to illuminate the possible connection between the ongoing process of surface uplift and the activation of crustal faults. Our main finding is the recognition of repetitive volcano-tectonic (VT) seismic swarms that occur periodically between 2011 and 2014 near the SW corner of the sill modeled by InSAR studies. A cross-correlation analysis of the waveforms recorded for these VT events allows identifying three different seismic families. Families F1 and F3 share some common features in the stacked waveform and its locations, which markedly differ from those of family F2. Swarms belonging to this later family are more energetic and its energy was increasing since 2011 to a peak in January 2013, which coincide with maximum vertical velocities detected by local GPS stations. This points to a common process relating both phenomena. The location of VT seismic swarms roughly coincides with the intersection of a NE-SW lineament with a WNW-ESE lineament. The former shows clear field evidences of dextral strike-slip that are fully consistent with one nodal plane of focal mechanism for well-recorded F2 events. The conjugate nodal plane of these focal mechanisms could

  10. K-Ar Geochronology and isotopic composition of the late oligocene- early miocene Ancud volcanic complex, Chiloe

    International Nuclear Information System (INIS)

    Munoz B, Jorge; Duhart O, Paul; Farmer, G. Lang; Stern, Charles R

    2001-01-01

    The Ancud Volcanic Complex (Gally and Sanchez , 1960) forms a portion of the Mid-Tertiary Coastal Magmatic Belt which outcrops in the area of northern Chiloe island. Main exposures occur at Ancud, Punta Polocue, Punihuil, Pumillahue, Tetas de Teguaco and Bahia Cocotue. The Ancud Volcanic Complex consists of basaltic to basaltic andesites lava flows and volcanic necks and rhyolitic pyroclastic flows and vitric domes. Previous studies indicate a Late Oligocene-Early Miocene age (Garcia et al., 1988; Stern and Vergara, 1992; Munoz et al., 2000). The Ancud Volcanic Complex covers and intrudes Palaeozoic-Triassic metamorphic rocks and is partially covered by an early to middle Miocene marine sedimentary sequence known as Lacui Formation (Valenzuela, 1982) and by Pleistocene glacial deposits (Heusser, 1990). At Punihuil locality, lava flows are interbedded with the lower part of the marine sedimentary sequence, which includes significant amounts of redeposited pyroclastic components. Locally, the presence of hyaloclastic breccias suggests interaction of magma with marine water (au)

  11. Attack robustness and centrality of complex networks.

    Directory of Open Access Journals (Sweden)

    Swami Iyer

    Full Text Available Many complex systems can be described by networks, in which the constituent components are represented by vertices and the connections between the components are represented by edges between the corresponding vertices. A fundamental issue concerning complex networked systems is the robustness of the overall system to the failure of its constituent parts. Since the degree to which a networked system continues to function, as its component parts are degraded, typically depends on the integrity of the underlying network, the question of system robustness can be addressed by analyzing how the network structure changes as vertices are removed. Previous work has considered how the structure of complex networks change as vertices are removed uniformly at random, in decreasing order of their degree, or in decreasing order of their betweenness centrality. Here we extend these studies by investigating the effect on network structure of targeting vertices for removal based on a wider range of non-local measures of potential importance than simply degree or betweenness. We consider the effect of such targeted vertex removal on model networks with different degree distributions, clustering coefficients and assortativity coefficients, and for a variety of empirical networks.

  12. Central Waste Complex (CWC) Waste Analysis Plan

    International Nuclear Information System (INIS)

    ELLEFSON, M.D.

    2000-01-01

    The purpose of this waste analysis plan (WAP) is to document the waste acceptance process, sampling methodologies, analytical techniques, and overall processes that are undertaken for waste accepted for storage at the Central Waste Complex (CWC), which is located in the 200 West Area of the Hanford Facility, Richland, Washington. Because dangerous waste does not include the source special nuclear and by-product material components of mixed waste, radionuclides are not within the scope of this document. The information on radionuclides is provided only for general knowledge. This document has been revised to meet the interim status waste analysis plan requirements of Washington Administrative Code (WAC) 173 303-300(5). When the final status permit is issued, permit conditions will be incorporated and this document will be revised accordingly

  13. Link between the granitic and volcanic rocks of the Bushveld Complex, South Africa

    Science.gov (United States)

    Schweitzer, J. K.; Hatton, C. J.; De Waal, S. A.

    1997-02-01

    Until recently, it was proposed that the Bushveld Complex, consisting of the extrusive Rooiberg Group and the intrusive Rashoop Granophyre, Rustenburg Layered and Lebowa Granite Suites, evolved over a long period of time, possibly exceeding 100 Ma. Most workers therefore considered that the various intrusive and extrusive episodes were unrelated. Recent findings suggest that the intrusive, mafic Rustenburg Layered Suite, siliceous Rashoop Granophyre Suite and the volcanic Rooiberg Group were synchronous, implying that the Bushveld igneous event was short-lived. Accepting the short-lived nature of the complex, the hypothesis that the granites are genetically unrelated to the other events of the Bushveld Complex can be reconsidered. Re-examination of the potential Rooiberg Group/Lebowa Granite Suite relationship suggests that the granites form part of the Bushveld event. Rhyolite lava, granite and granophyre melts originated from a source similar in composition to upper crustal rocks. This source is interpreted to have been melted by a thermal input associated with a mantle plume. Granite intruded after extrusion of the last Rooiberg rhyolite, or possibly overlapped in time with the formation of the youngest volcanic flows.

  14. A shallow crustal earthquake doublet from the Trans-Mexican volcanic belt (Central Mexico)

    Science.gov (United States)

    Quintanar, L.; Rodríguez-González, M.; Campos-Enríquez, O.

    2003-04-01

    The trans-Mexican volcanic belt is an active volcanic arc related to subduction along the Middle America trench and characterized by shallow seismicity and synvolcanic to postvolcanic extensional arc-parallel faulting. The Mezquital graben is a major intra-arc basin of the central trans-Mexican volcanic belt. A doublet of moderate shallow shocks occurred in March and October 1976 in the region of this graben. These earthquakes were recorded by the Mexican National Seismological network, in particular by the Bosch-Omori seismograph (T_0 = 18 s) at the Tacubaya Observatory in Mexico City. We have carefully relocated the two main shocks and their major aftershocks by reading the original records and using a modified crustal velocity model for this region. A difference of ˜50 km is observed between the locations reported by the Mexican Seismological Service and those obtained in this study, which are additionally supported by the damage distribution of these earthquakes. A first motion analysis, based on regional and teleseismic records, defines for the March and October shocks normal fault mechanisms, characterized by E-W striking fault planes, which coincides with the orientation of the master faults of the Mezquital graben. After calculating the instrumental response, the source parameters were obtained from the Bosch-Omori seismograph records by body-wave modeling. For the March earthquake, we estimate a seismic moment of 4.5×1023 dyne-cm (equivalent to M_w=5.0) and a stress drop of 0.7 MPa assuming a circular rupture model (radius = 3 km). Given the poor quality of the Bosch-Omori record for the October earthquake, we used the comparison, between both events, of long-period (T=20 sec) teleseismic records at 2 stations to obtain its corresponding source parameters. By assuming a similar stress drop as for the March event, we obtain a M_0 of 5.6×1023 dyne-cm and M_w = 5.1 with a rupture length of 6.5 km. According to gravity data, the regional E-W faults are

  15. The Complex Refractive Index of Volcanic Ash Aerosol Retrieved From Spectral Mass Extinction

    Science.gov (United States)

    Reed, Benjamin E.; Peters, Daniel M.; McPheat, Robert; Grainger, R. G.

    2018-01-01

    The complex refractive indices of eight volcanic ash samples, chosen to have a representative range of SiO2 contents, were retrieved from simultaneous measurements of their spectral mass extinction coefficient and size distribution. The mass extinction coefficients, at 0.33-19 μm, were measured using two optical systems: a Fourier transform spectrometer in the infrared and two diffraction grating spectrometers covering visible and ultraviolet wavelengths. The particle size distribution was measured using a scanning mobility particle sizer and an optical particle counter; values for the effective radius of ash particles measured in this study varied from 0.574 to 1.16 μm. Verification retrievals on high-purity silica aerosol demonstrated that the Rayleigh continuous distribution of ellipsoids (CDEs) scattering model significantly outperformed Mie theory in retrieving the complex refractive index, when compared to literature values. Assuming the silica particles provided a good analogue of volcanic ash, the CDE scattering model was applied to retrieve the complex refractive index of the eight ash samples. The Lorentz formulation of the complex refractive index was used within the retrievals as a convenient way to ensure consistency with the Kramers-Kronig relation. The short-wavelength limit of the electric susceptibility was constrained by using independently measured reference values of the complex refractive index of the ash samples at a visible wavelength. The retrieved values of the complex refractive indices of the ash samples showed considerable variation, highlighting the importance of using accurate refractive index data in ash cloud radiative transfer models.

  16. Time Series Analysis OF SAR Image Fractal Maps: The Somma-Vesuvio Volcanic Complex Case Study

    Science.gov (United States)

    Pepe, Antonio; De Luca, Claudio; Di Martino, Gerardo; Iodice, Antonio; Manzo, Mariarosaria; Pepe, Susi; Riccio, Daniele; Ruello, Giuseppe; Sansosti, Eugenio; Zinno, Ivana

    2016-04-01

    The fractal dimension is a significant geophysical parameter describing natural surfaces representing the distribution of the roughness over different spatial scale; in case of volcanic structures, it has been related to the specific nature of materials and to the effects of active geodynamic processes. In this work, we present the analysis of the temporal behavior of the fractal dimension estimates generated from multi-pass SAR images relevant to the Somma-Vesuvio volcanic complex (South Italy). To this aim, we consider a Cosmo-SkyMed data-set of 42 stripmap images acquired from ascending orbits between October 2009 and December 2012. Starting from these images, we generate a three-dimensional stack composed by the corresponding fractal maps (ordered according to the acquisition dates), after a proper co-registration. The time-series of the pixel-by-pixel estimated fractal dimension values show that, over invariant natural areas, the fractal dimension values do not reveal significant changes; on the contrary, over urban areas, it correctly assumes values outside the natural surfaces fractality range and show strong fluctuations. As a final result of our analysis, we generate a fractal map that includes only the areas where the fractal dimension is considered reliable and stable (i.e., whose standard deviation computed over the time series is reasonably small). The so-obtained fractal dimension map is then used to identify areas that are homogeneous from a fractal viewpoint. Indeed, the analysis of this map reveals the presence of two distinctive landscape units corresponding to the Mt. Vesuvio and Gran Cono. The comparison with the (simplified) geological map clearly shows the presence in these two areas of volcanic products of different age. The presented fractal dimension map analysis demonstrates the ability to get a figure about the evolution degree of the monitored volcanic edifice and can be profitably extended in the future to other volcanic systems with

  17. An InSAR-based survey of volcanic deformation in the central Andes

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2004-02-01

    We extend an earlier interferometric synthetic aperture radar (InSAR) survey covering about 900 remote volcanos of the central Andes (14°-27°S) between the years 1992 and 2002. Our survey reveals broad (10s of km), roughly axisymmetric deformation at 4 volcanic centers: two stratovolcanoes are inflating (Uturuncu, Bolivia, and Hualca Hualca, Peru); another source of inflation on the border between Chile and Argentina is not obviously associated with a volcanic edifice (here called Lazufre); and a caldera (Cerro Blanco, also called Robledo) in northwest Argentina is subsiding. We explore the range of source depths and volumes allowed by our observations, using spherical, ellipsoidal and crack-like source geometries. We further examine the effects of local topography upon the deformation field and invert for a spherical point-source in both elastic half-space and layered-space crustal models. We use a global search algorithm, with gradient search methods used to further constrain best-fitting models. Inferred source depths are model-dependent, with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure. Source depths relative to sea level are: 8-18 km at Hualca Hualca; 12-25 km for Uturuncu; 5-13 km for Lazufre, and 5-10 km at Cerro Blanco. Deformation at all four volcanoes seems to be time-dependent, and only Uturuncu and Cerro Blanco were deforming during the entire time period of observation. Inflation at Hualca Hualca stopped in 1997, perhaps related to a large eruption of nearby Sabancaya volcano in May 1997, although there is no obvious relation between the rate of deformation and the eruptions of Sabancaya. We do not observe any deformation associated with eruptions of Lascar, Chile, at 16 other volcanoes that had recent small eruptions or fumarolic activity, or associated with a short-lived thermal anomaly at Chiliques volcano. We posit a hydrothermal system at Cerro Blanco to explain the

  18. Late Hercynian volcanic and hypovolcanic phenomena in South of the French Massif Central. Associated mineralization: U, F, Ba, Pb, Zn, Sn, W

    International Nuclear Information System (INIS)

    Badia; Fuchs

    1983-01-01

    Volcanism of the Stephanian period produced lava rich in potassium and fluorine with mineralization of U, F, Sn, W without Mo in the French Massif Central. Permian volcanism and associated magmatism are reviewed. Studied elements allow the characterization of their thermalism. These mineralizations are important for prospection [fr

  19. Origin and Development of El Bajío Basin in the Central Sector of Trans-Mexican Volcanic Belt

    Science.gov (United States)

    Botero, P. A.; Alaniz Álvarez, S. A.; Nieto Samaniego, Á. F.; Lopez-Martinez, M.; Levresse, G.; Xu, S.; Ortega Obregón, C.

    2015-12-01

    Volcanism of the Trans-Mexican Volcanic Belt has been placed on pre-existing tectonic basins; one of them is El Bajío Basin. We present the origin and evolution of this basin through the study of its deformation events occurring mainly on the El Bajío fault, at the boundary between the Trans-Mexican Volcanic Belt and the Mesa Central. Detailed stratigraphy, and structural analysis suggest 4 deformation events in the northwest of the Sierra de Guanajuato. The first event (D1) with E-W shortening is characterized by the development of axial plane foliation (S1) with N-S direction, this event occurred between the Tithonian and Aptian age. In the second event (D2), occurred between the Albian and the early Eocene, foliations NW-SE (S2) were generated with a NE-SW shortening trend dated between the Albian and early Eocene, this deformation is related to the Laramide Orogeny. The Granito Comanja was emplaced during the third event (D3) and generated foliation (S3) in sediments of the complejo vulcanosedimentario Sierra de Guanajuato that circumscribes the Granito Comanja in response to its intrusion. After its emplacement, NW-SE normal faults were generated along the S-SE contact of the Granito Comanja, at that time El Bajío fault began. The fourth event (D4) has three phases that affected the sedimentary and volcanic Cenozoic rocks. D4F1 is marked by continental conglomerates deposition with variable thickness along of the main trace of the El Bajío fault. D4F2 affected the Oligocene volcanic rocks showing an important fault activity at that time, as evidenced the tilting above 45o in the Oligocene rocks, temporarily coincides with the triaxial extension to the Mesa Central. The direction of elongation of D4F3 is ESE-WNW, El Bajío fault had little movement. Since the Miocene the deformation was concentrated along the southern central sector of the Trans-mexican Volcanic Belt and there were few deformation in the Mesa central. During the three phases of deformation

  20. Classification of the ecological status of volcanic lakes in Central Italy

    Directory of Open Access Journals (Sweden)

    Daria VAGAGGINI

    2003-09-01

    Full Text Available A synthesis is made of biological data collected in the last three decades on five volcanic lakes in Central Italy with the aim of evaluating their environmental status by means of biological parameters related to zooplankton, littoral and profundal zoobenthos frequently used to detect water quality changes in lakes. A number of bioindicators and bioindices were selected for this purpose, as far as possible following an integrated approach using information drawn from physical and chemical variables. Our results allowed the lakes to be classified according to their biological quality level, which proved to be in good agreement with physical and chemical diagnoses. Lake Bracciano exhibited the best environmental quality, due to the presence of a ring waste water collecting system, to its large size and depth, and to its strong hydrodynamism. Lake Martignano followed, with some symptoms of stress in the hypolimnion due to a marked summer deoxygenation. Oxygen depletion in the profundal characterized also Lake Vico, which showed a mesotrophic condition in the sixties, and 20 years later now shows clear signs of increased trophy (meso-eutrophy. Lake Albano seemed meso-eutrophic with total absence of fauna below a depth of 120 m due to a meromictic status. Finally Lake Nemi, exposed to domestic wastes in the 70s, suffered a heavy eutrophication with dramatic algal blooms and fish kills. Following the diversion of discharges that occurred in the early 90s, today this lake is characterized by the partial improvement of many ecological features. The need for integration between physical and chemical analyses and biological data in order to obtain a reliable evaluation of lake environmental quality is stressed, especially as far as routine implementation in managing and recovery procedures is concerned.

  1. Pre-eruptive conditions of the ~31 ka rhyolitic magma of Tlaloc volcano, Sierra Nevada Volcanic Range, Central Mexico

    Science.gov (United States)

    Macias, J.; Arce, J.; Rueda, H.; Gardner, J.

    2008-12-01

    Tlaloc volcano is located at the northern tip of the Sierra Nevada Volcanic Range in Central Mexico. This Pleistocene to Recent volcanic range consists from north to south of Tlaloc-Telapón-Teyotl-Iztaccíhuatl-and- Popocatépetl volcanoes. While andesitic to barely dacitic volcanism dominates the southern part of the range (i.e. Popocatépetl and Iztaccíhuatl); dacitic and rare rhyolithic volcanism (i.e. Telapón, Tlaloc) dominates the northern end. The known locus of rhyolitic magmatism took place at Tlaloc volcano with a Plinian-Subplinian eruption that occurred 31 ka ago. The eruption emplaced the so-called multilayered fallout and pumiceous pyroclastic flows (~2 km3 DRE). The deposit consists of 95% vol. of juvenile particles (pumice + crystals) and minor altered lithics 5% vol. The mineral association of the pumice fragments (74-76 % wt. SiO2) consists of quartz + plagioclase + sanidine + biotite and rare oxides set in a glassy groundmass with voids. Melt inclusions in quartz phenocrysts suggest that prior to the eruption the rhyolitic contain ~7% of H2O and Nevado de Toluca volcano (~6 km) some 50 km to the southwest.

  2. Unrest of Chiles - Cerro Negro volcanic complex: A binational Ecuador - Colombia effort

    Science.gov (United States)

    Ruiz, M. C.; Gomez, D.; Torres, R.; Cadena, O.; Mothes, P. A.; Anzieta, J. C.; Pacheco, D. A.; Bernard, B.; Acero, W.; Hidalgo, S.; Enriquez, W.; Cordova, A.

    2014-12-01

    The increasing seismic activity at the area of Chiles - Cerro Negro volcanic complex, located at the Ecuador-Colombian border, has been jointly monitored by the Instituto Geofisico - Ecuador and the Observatorio Vulcanologico y Sismologico de Pasto OVSP, a division of the Servicio Geologico Colombiano. Since April 2013, three seismic swarms have been detected in this area and more than 100.000 events are recorded since November 2013. The largest and more recent swarm has a daily average of 676 events between March and June 2014. Currently a seismic network of 8 seismic stations (5 in the Colombian and 3 in Ecuadorean side) are deployed in this area. Epicenters of more than 315 seismic events with magnitudes Ml>2.0 and 10 or more phases are located in an area 1-4 km south of Chiles volcano with shallow depths (up to 14 km). Most of events have magnitudes between 1.0 to 4.0. Nine events have magnitudes larger than 4.0 and the largest event occurred on April 30. 2014 with a local magnitude of 4.7 and inverse-transcurrent component focal mechanism. Waveforms and spectral patterns define these events as volcano-tectonic. Events with large magnitudes (above 3.0) show a very long-period component. Hot spring and deformation measurements also show signals of volcanic unrest.

  3. The Riscos Bayos Ignimbrites of the Caviahue-Copahue volcanic caldera complex, southern Andes, Argentina

    Science.gov (United States)

    Colvin, A.; Merrill, M.; Demoor, M.; Goss, A.; Varekamp, J. C.

    2004-05-01

    The Caviahue-Copahue volcanic complex (38 S, 70 W) is located on the eastern margin of the active arc in the southern Andes, Argentina. Volcán Copahue, an active stratovolcano which hosts an active hydrothermal system, sits on the southwestern rim of the elliptical Caviahue megacaldera (17 x 15 km). The caldera wall sequences are up to 0.6 km thick and consist of lavas with 51 -69 percent SiO2 and 0.2 - 5 percent MgO as well as breccias, dikes, sills, domes and minor ignimbrites. Andesitic lava flows also occur within the caldera, and are overlain by a chaotic complex of silicic lava and intracaldera pyroclastic flow deposits. The eastern wall sequence is capped by several extracaldera ignimbrites (Riscos Bayos formation) of about 50 m maximum thickness which extend 30 km east-southeast of the caldera. Young back-arc alkali basalt scoria cones occur east of the Caviahue-Copahue volcanic complex. The eruption of the Riscos Bayos formation at about 1.1 Ma (12 km cubed) may be related to the Caviahue caldera formation, though the Riscos Bayos account for only about 7 percent of the caldera volume. The Riscos Bayos consists of three lithic-bearing flow units: a grey basal flow, a tan middle flow and a bright-white, highly indurated uppermost flow. The basal unit consists of white and grey pumice fragments, black scoria clasts, black obsidian clasts (which give it the grey color), and accidental volcanic lithics set in a matrix of ash and crystals. The middle unit is composed of large mauve pumice fragments and accidental lithics set in a fine tan ash groundmass. The uppermost unit is composed of small pink and white pumice fragments set in a matrix of fine white ash. These pumices carry quartz and biotite crystals, whereas the lower two units are orthopyroxene-bearing trachy-dacites. The Caviahue-Copahue magmas all bear arc signatures, but possibly some magma mixing between the andesitic arc magmas and basaltic back-arc magmas may have occurred. The evolved top layer

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

    Science.gov (United States)

    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 discharged 700 kilotons of Br. On average, each of the remaining 21 CAVA eruptions studied have discharged c.100 kilotons of bromine. During the past 200 ka, CAVA volcanoes have emitted a cumulative mass of 3.2 Mt of Br through highly explosive eruptions. There are six periods in the past (c. 2ka, 6ka, 25ka, 40ka, 60ka, 75

  5. Origin of Holocene trachyte lavas of the Quetrupillán volcanic complex, Chile: Examples of residual melts in a rejuvenated crystalline mush reservoir

    Science.gov (United States)

    Brahm, Raimundo; Parada, Miguel Angel; Morgado, Eduardo; Contreras, Claudio; McGee, Lucy Emma

    2018-05-01

    The Quetrupillán Volcanic Complex (QVC) is a stratovolcano placed in the center of a NW-SE volcanic chain, between Villarrica volcano and Lanín volcano, in the Central Southern Volcanic Zone of the Andes. Its youngest effusive products are dominated by crystal-poor (most samples with differentiation at shallow depth (<1 kbar) and NNO-QFM oxidation conditions were obtained from initial melt compositions equivalent to the Huililco basalts, a small eruptive centre located ca. 12 km NE of the QVC main vent. Pyroxene-bearing crystal clots, locally abundant in the trachytes, were formed at 900-960 °C (±55 °C) and represent a dismembered crystal mush from which interstitial trachytic melts were extracted and transported upward before eruption. Heating of the crystal mush by a hotter magma recharge is inferred from complex zoned plagioclases formed at higher crystallization temperatures (50-90 °C) than those obtained from pyroxene. Ca-rich plagioclase overgrowths around more albitic cores, followed by an external rim of similar composition to the core are interpreted as restoration to the initial conditions of plagioclase crystallization after the mentioned heating event. Additionally, a late heating of up to 150 °C just prior to eruption is recorded by Fe-Ti oxide thermometry.

  6. Various origins of clinopyroxene megacrysts from basanites from the eastern part of Central European Volcanic Province

    Science.gov (United States)

    Lipa, Danuta; Puziewicz, Jacek; Ntaflos, Theodoros; Matusiak-Małek, Magdalena; Kukuła, Anna

    2014-05-01

    Clinopyroxene megacrysts up to few centimetres in size occur in Cenozoic alkaline lavas forming the north-eastern part of Central European Volcanic Province in Lower Silesia (SW Poland). The megacrysts occur, among other, in the Miocene basanite from Ostrzyca Proboszczowicka (bulk rock mg# 0.65-0.66) and in that from Lutynia (Pliocene, K-Ar age: 4.56 +/- 0.2 Ma; Birkenmajer et al. 2002; bulk rock mg# 0.64). The megacrysts typically consist of homogeneous core surrounded by patchy and spongy mantle, which is covered by a thin outermost rim of composition similar to that of the groundmass clinopyroxene occurring in the host basanite. The mantles of the megacrysts have been affected by melting, whereas the cores preserve their primary composition. We compare the core parts of megacrysts in the following. The Ostrzyca clinopyroxene megacrysts contain euhedral apatite intergrowths. The clinopyroxene has the composition of Fe-rich diopside (mg# = 0.61 - 0.70), contain significant sodium (to 0.12 a pfu) and are calcium rich (0.89-0.92 a pfu). The Lutynia megacrysts have the composition of augite and diopside (mg# 0.80-0.83). The sodium content is also high (to 0.12 a pfu), but calcium varies from 0.68 to 0.77 a pfu. The REE concentrations for Lutynia (1-10 x PM) are lower relative to Ostrzyca, enriched 10-100 times relative to PM. In both sites the megacrysts are strongly enriched in LREE relative to HREE and TE are characterized by positive Th, La and Ce anomalies, slight negative Sr and Y anomalies and strong Pb anomaly in the PM normalised patterns. The megacrysts from Ostrzyca reveal slight negative Ti and strong positive Zr and Hf anomalies, whereas those Lutynia have negative Zr anomaly and Ti anomaly is absent. Major and trace element composition shows that the megacrysts from Ostrzyca formed as coarse-grained cumulate at significant depth (lower crust?) from the LREE enriched alkaline melt. That melt was very rich in phosphorous which enabled its saturation in

  7. Numerical modeling perspectives on zircon crystallization and magma reservoir growth at the Laguna del Maule volcanic field, central Chile

    Science.gov (United States)

    Andersen, N. L.; Dufek, J.; Singer, B. S.

    2017-12-01

    Magma reservoirs in the middle to upper crust are though to accumulate incrementally over 104 -105 years. Coupled crystallization ages and compositions of zircon are a potentially powerful tracer of reservoir growth and magma evolution. However, complex age distributions and disequilibrium trace element partitioning complicate the interpretation of the zircon record in terms of magmatic processes. In order to make quantitative predictions of the effects of magmatic processes that contribute reservoir growth and evolution—such as cooling and crystallization, magma recharge and mixing, and rejuvenation and remelting of cumulate-rich reservoir margins—we develop a model of zircon saturation and growth within a numerical framework of coupled thermal transfer, phase equilibrium, and magma dynamics. We apply this model to the Laguna del Maule volcanic field (LdM), located in central Chile. LdM has erupted at least 40 km3 of rhyolite from 36 vents distributed within a 250 km2 lake basin. Ongoing unrest demonstrates the large, silicic magma system beneath LdM remains active to this day. Zircon from rhyolite erupted between c. 23 and 1.8 ka produce a continuous distribution of 230Th-238U ages ranging from eruption to 40 ka, as well as less common crystal domains up to 165 ka and rare xenocrysts. Zircon trace element compositions fingerprint compositionally distinct reservoirs that grew within the larger magma system. Despite the dominantly continuous distributions of ages, many crystals are characterized by volumetrically substantial, trace element enriched domains consistent with rapid crystal growth. We utilize numerical simulations to assess the magmatic conditions required to catalyze these "blooms" of crystallization and the magma dynamics that contributed to the assembly of the LdM magma system.

  8. Post-Eocene volcanics of the Abazar district, Qazvin, Iran: Mineralogical and geochemical evidence for a complex magmatic evolution

    Science.gov (United States)

    Asiabanha, A.; Bardintzeff, J. M.; Kananian, A.; Rahimi, G.

    2012-02-01

    The style of volcanism of post-Eocene volcanism in the Alborz zone of northern Iran is different to that of Eocene volcanism (Karaj Formation). Indeed, the volcanic succession of the Abazar district, located in a narrow volcanic strip within the Alborz magmatic assemblage, is characterized by distinct mineralogical and chemical compositions linked to a complex magmatic evolution. The succession was produced by explosive eruptions followed by effusive eruptions. Two main volcanic events are recognized: (1) a thin rhyolitic ignimbritic sheet underlain by a thicker lithic breccia, and (2) lava flows including shoshonite, latite, and andesite that overlie the first event across a reddish soil horizon. Plagioclase in shoshonite (An 48-92) shows normal zoning, whereas plagioclase in latite and andesite (An 48-75) has a similar composition but shows reverse and oscillatory zoning. QUILF temperature calculations for shoshonites and andesites yield temperatures of 1035 °C and 1029 °C, respectively. The geothermometers proposed by Ridolfi et al. (2010) and Holland and Blundy (1994) yield temperatures of 960 °C and 944 °C for latitic lava, respectively. The samples of volcanic rock show a typical geochemical signature of the continental arc regime, but the andesites clearly differ from the shoshonites, the latites and the rhyolites. The mineralogical and chemical characteristics of these rocks are explained by the following petrogenesis: (1) intrusion of a hot, mantle-depth mafic (shoshonitic) magma, which differentiated in the magma chamber to produce a latitic and then a rhyolitic liquid; (2) rhyolitic ignimbritic eruptions from the top of the magma chamber, following by shoshonitic and then latitic extrusions; (3) magma mingling between the latitic and andesitic magmas, as indicated by the occurrence of andesite clasts within the latite; and (4) andesitic effusions. The youngest volcanic events in the Alborz zone show a close chemical relationship with continental arc

  9. U-Th age evidence from carbonate veins for episodic crustal deformation of Central Anatolian Volcanic Province

    Science.gov (United States)

    Karabacak, Volkan; Uysal, I. Tonguç; Ünal-İmer, Ezgi; Mutlu, Halim; Zhao, Jian-xin

    2017-12-01

    Central Anatolia represents one of the most outstanding examples of intraplate deformation related to both continental collision and back-arc extension generating non-uniformly distributed stress fields. In this study, we provide direct field evidence of various stress directions and investigate carbonate-filled fracture systems in the Central Anatolian Volcanic Province using U/Th geochronology and isotope geochemistry for evaluating the episodes of latest volcanic activity under regional stress. Field data reveal two independent fracture systems in the region. Successive fracture development has been controlled by two different volcanic eruption centers (Hasandağ Composite Volcano and Acıgöl Caldera). Trace element, and stable (C and O) and radiogenic (Sr) isotope compositions of carbonate veins indicate different fluid migration pathways for two different fracture systems. The U/Th age data for carbonate veins of two independent fracture systems indicate that the crustal deformation intensified during 7 episodic periods in the last 150 ka. The NNE-trending first fracture system was formed as a result of strain cycles in a period from 149 ± 2.5, through 91 ± 1.5 to 83 ± 2.5 ka BP. Subsequent deformation events represented by the ENE-trending second fracture zone have been triggered during the period of 53 ± 3.5, 44 ± 0.6 and 34 ± 1 ka BP before the first fracture zone resumed the activity at about 4.7 ± 0.15 ka BP. Although further studies are needed to evaluate statistical significance of age correlations, the periods of carbonate precipitation inferred from U-Th age distributions in this study are comparable with the previous dating results of surrounding volcanic eruption events.

  10. Transition of neogene arc volcanism in central-western Hokkaido, viewed from K-Ar ages, style of volcanic activity, and bulk rock chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, Wataru; Iwasaki, Miyuki; Nakagawa, Mitsuhiro [Hokkaido Univ., Sapporo (Japan)

    2000-02-01

    Spatial and temporal variations in late Cenozoic volcanism of southwestern Hokkaido at the northern end of NE-Japan arc have been clarified by 261 K-Ar and 76 FT ages including 49 newly determined K-Ar ages, volcanic stratigraphy, physical volcanology and whole-rock geochemistry. Arc volcanism characterized by rocks with low-Ti and Nb, and by across-arc increase in K{sub 2}O content in these rocks has continued at least since 12 Ma. Based on volcanic stratigraphy, physical volcanology and whole-rock geochemistry, volcanism after 12 Ma can be subdivided into 4 stages, 12-5, 5-1.7, and 1.7-0 Ma. The volcanism from 12 Ma to 5 Ma extended northward widely compared with distribution of Quaternary arc volcanism (1.7-0 Ma). This suggests that the arc trench junction between Kuril and NE-Japan arc's trenches was located about 100 km northward from the present position. Since around 5 Ma until 1.7 Ma, different type of volcanism under local extension field, characterized by a group of monogenetic volcanoes of alkali basalt and shield volcanoes of calc-alkaline andesite, had occurred at northern end of the volcanic region (Takikawa-Mashike region). During and after this volcanism, the northern edge of arc volcanism in the area has migrated southward. This suggests that the trench junction has migrated about 100 km southward since {approx}5 Ma. The quaternary arc volcanism (1.7-0 Ma) has been restricted at the southern part of the region. The volcanism since 12 Ma might be influenced by oblique subduction of Pacific plate beneath Kuril arc, resulting in the formation of local back arc basin at the junction and to southward migration of the trench junction. (author)

  11. Seismic Model and Geological Interpretation of the Basement Beneath the Doupovske Hory Volcanic Complex (NW Czech Republic)

    Czech Academy of Sciences Publication Activity Database

    Valenta, Jan; Brož, Milan; Málek, Jiří; Mlčoch, B.; Rapprich, V.; Skácelová, Z.

    2011-01-01

    Roč. 59, č. 3 (2011), s. 597-617 ISSN 1895-6572 R&D Projects: GA AV ČR IAA300460602 Institutional research plan: CEZ:AV0Z30460519 Keywords : seismic refraction * seismic tomography * Doupovske Hory Volcanic Complex Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.617, year: 2011

  12. Synthesis of morphotectonics and volcanics of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Mukherjee, A.D.; Iyer, S.D.

    to the hydrothermal effect on the pre-existing subalkaline basalts. Besides these rocks, there is a wide occurrence of pumice of probably in situ origin. A distinct relation occurs between the morpho-tectonic forms and the volcanics. For example, in and around...

  13. San Miguel Volcanic Seismic and Structure in Central America: Insight into the Physical Processes of Volcanoes

    Science.gov (United States)

    Patlan, E.; Velasco, A.; Konter, J. G.

    2010-12-01

    The San Miguel volcano lies near the city of San Miguel, El Salvador (13.43N and - 88.26W). San Miguel volcano, an active stratovolcano, presents a significant natural hazard for the city of San Miguel. In general, the internal state and activity of volcanoes remains an important component to understanding volcanic hazard. The main technology for addressing volcanic hazards and processes is through the analysis of data collected from the deployment of seismic sensors that record ground motion. Six UTEP seismic stations were deployed around San Miguel volcano from 2007-2008 to define the magma chamber and assess the seismic and volcanic hazard. We utilize these data to develop images of the earth structure beneath the volcano, studying the volcanic processes by identifying different sources, and investigating the role of earthquakes and faults in controlling the volcanic processes. We initially locate events using automated routines and focus on analyzing local events. We then relocate each seismic event by hand-picking P-wave arrivals, and later refine these picks using waveform cross correlation. Using a double difference earthquake location algorithm (HypoDD), we identify a set of earthquakes that vertically align beneath the edifice of the volcano, suggesting that we have identified a magma conduit feeding the volcano. We also apply a double-difference earthquake tomography approach (tomoDD) to investigate the volcano’s plumbing system. Our preliminary results show the extent of the magma chamber that also aligns with some horizontal seismicity. Overall, this volcano is very active and presents a significant hazard to the region.

  14. An investigation of thermal anomalies in the Central American volcanic chain and evaluation of the utility of thermal anomaly monitoring in the prediction of volcanic eruptions. [Central America

    Science.gov (United States)

    Stoiber, R. E. (Principal Investigator); Rose, W. I., Jr.

    1975-01-01

    The author has identified the following significant results. Ground truth data collection proves that significant anomalies exist at 13 volcanoes within the test site of Central America. The dimensions and temperature contrast of these ten anomalies are large enough to be detected by the Skylab 192 instrument. The dimensions and intensity of thermal anomalies have changed at most of these volcanoes during the Skylab mission.

  15. Temporal node centrality in complex networks

    Science.gov (United States)

    Kim, Hyoungshick; Anderson, Ross

    2012-02-01

    Many networks are dynamic in that their topology changes rapidly—on the same time scale as the communications of interest between network nodes. Examples are the human contact networks involved in the transmission of disease, ad hoc radio networks between moving vehicles, and the transactions between principals in a market. While we have good models of static networks, so far these have been lacking for the dynamic case. In this paper we present a simple but powerful model, the time-ordered graph, which reduces a dynamic network to a static network with directed flows. This enables us to extend network properties such as vertex degree, closeness, and betweenness centrality metrics in a very natural way to the dynamic case. We then demonstrate how our model applies to a number of interesting edge cases, such as where the network connectivity depends on a small number of highly mobile vertices or edges, and show that our centrality definition allows us to track the evolution of connectivity. Finally we apply our model and techniques to two real-world dynamic graphs of human contact networks and then discuss the implication of temporal centrality metrics in the real world.

  16. Volcaniclastic and sedimentary deposits in Late Oligocene/Early Miocene Smrekovec Volcanic Complex, northern Slovenia

    Science.gov (United States)

    Kralj, Polona

    2010-05-01

    Late Oligocene/Early Miocene volcanic activity in northern Slovenia is related to post-collisional accommodation of continental Apulian and oceanic European plates (von Blanckenburg and Davis, 1996). It occurred in one of small south-western marginal depressions of the Pannonian basin system, locally termed the Smrekovec Basin (Hanfland et al., 2004). Contemporaneous clastic sedimentation is evidenced by several hundred metres thick succession composed mainly of mudstone, siltstone and sand. Smrekovec Volcanic Complex (SVC) is an eroded and tectonically uplifted remain of a larger submarine stratovolcano edifice, built of lavas, shallow or subsurface intrusive bodies, and pyroclastic, hyaloclastic, syn-eruptively resedimented volcaniclastic and reworked volcaniclastic-sedimentary deposits (Kralj, 1996). The development of lithofacies of syn-eruptively resedimented deposits is controlled by the proximity to the ancient volcano summit and the volcano sloping. Moreover, close to the rising volcano edifice, distinct shallow-water environments with siliciclastic sedimentation developed. Syn-eruptively resedimented deposits are the most widespread and are related to volcaniclastic debris flows and volcaniclastic tubidity flows. Volcaniclastic debris flow deposits are subdivided into lithofacies Bx - polymict volcaniclastic breccia, and Bt - volcaniclastic tuff-breccia. Bx occurs as tabular, up to some ten metres thick bodies with abundant up to 5 dm large angular lava clasts and angular or rounded clasts of fine-grained tuff, and tuffaceous matrix. Bt forms basal, massive layers in fining-upward sequences. The main constituent is tuffaceous matrix; up to 1.5 dm large clasts of lavas and tuffs are subordinate. In a distance up to 2 km from the former volcano summit (proximal area), Bt predominates in the sequence lithofacies composition (~75 %), and attains a thickness of up to 4 m. At a distance of 2-4 km (distal area), a maximum Bt thickness rarely exceeds 5 dm, an

  17. Chemistry of ash-leachates to monitor volcanic activity: An application to Popocatepetl volcano, central Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Armienta, M.A., E-mail: victoria@geofisica.unam.mx [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico); De la Cruz-Reyna, S. [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico); Soler, A. [Grup de Mineralogia Aplicada i Medi Ambient, Dep. Cristal.lografia, Mineralogia i Diposits Minerals, Fac. Geologia, Universidad de Barcelona (Spain); Cruz, O.; Ceniceros, N.; Aguayo, A. [Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, Circuito Exterior, C.U., Mexico 04510 D.F. (Mexico)

    2010-08-15

    Monitoring volcanic activity and assessing volcanic risk in an on-going eruption is a problem that requires the maximum possible independent data to reduce uncertainty. A quick, relatively simple and inexpensive method to follow the development of an eruption and to complement other monitoring parameters is the chemical analysis of ash leachates, particularly in the case of eruptions related to dome emplacement. Here, the systematic analysis of SO{sub 4}{sup 2-}, Cl{sup -} and F{sup -} concentrations in ash leachates is proposed as a valuable tool for volcanic activity monitoring. However, some results must be carefully assessed, as is the case for S/Cl ratios, since eruption of hydrothermally altered material may be confused with degassing of incoming magma. Sulfur isotopes help to identify SO{sub 4} produced by hydrothermal processes from magmatic SO{sub 2}. Lower S isotopic values correlated with higher F{sup -} percentages represent a better indicator of fresh magmatic influence that may lead to stronger eruptions and emplacement of new lava domes. Additionally, multivariate statistical analysis helps to identify different eruption characteristics, provided that the analyses are made over a long enough time to sample different stages of an eruption.

  18. Volcanic risk perception in rural communities along the slopes of mount Cameroon, West-Central Africa

    Science.gov (United States)

    Njome, Manga S.; Suh, Cheo E.; Chuyong, George; de Wit, Maarten J.

    2010-11-01

    A study of volcanic risk perception was carried out in rural communities around the Mount Cameroon volcano between August and December 2008. The results indicate that risk perception reflects the levels of threat to which a resident population has been exposed to previously. Results of 70 responses to questionnaires show that local knowledge of hazards is high. Most respondents correctly indicated that earthquake and lava flow activities would affect resident population most in the future. By contrast, respondent's ability to adapt and protect themselves from the effects of future eruptions is poor, and inhabitants would likely shift responsibility for their protection to the requisite experts. This study confirms that there is little knowledge of any existing emergency plan, little or no educational outreach activities, but a high perceived need for information about and implementation of such actions. Knowledge about natural threats is found to be directly related to past exposure to volcanic hazard, and is significantly higher for people living along the southern than those along the northern slopes of Mt. Cameroon. The data also show that the media remains the most accessible channel for hazard communication, and that the internet is a growing information source that should be used to reach out to the younger generation. It is clear from the results of this study that major education and information efforts are required to improve the public's knowledge, confidence in the government, and growing self-reliance, in order to improve both collective and individual capacity to face future volcanic emergencies.

  19. Chemistry of ash-leachates to monitor volcanic activity: An application to Popocatepetl volcano, central Mexico

    International Nuclear Information System (INIS)

    Armienta, M.A.; De la Cruz-Reyna, S.; Soler, A.; Cruz, O.; Ceniceros, N.; Aguayo, A.

    2010-01-01

    Monitoring volcanic activity and assessing volcanic risk in an on-going eruption is a problem that requires the maximum possible independent data to reduce uncertainty. A quick, relatively simple and inexpensive method to follow the development of an eruption and to complement other monitoring parameters is the chemical analysis of ash leachates, particularly in the case of eruptions related to dome emplacement. Here, the systematic analysis of SO 4 2- , Cl - and F - concentrations in ash leachates is proposed as a valuable tool for volcanic activity monitoring. However, some results must be carefully assessed, as is the case for S/Cl ratios, since eruption of hydrothermally altered material may be confused with degassing of incoming magma. Sulfur isotopes help to identify SO 4 produced by hydrothermal processes from magmatic SO 2 . Lower S isotopic values correlated with higher F - percentages represent a better indicator of fresh magmatic influence that may lead to stronger eruptions and emplacement of new lava domes. Additionally, multivariate statistical analysis helps to identify different eruption characteristics, provided that the analyses are made over a long enough time to sample different stages of an eruption.

  20. GFT centrality: A new node importance measure for complex networks

    Science.gov (United States)

    Singh, Rahul; Chakraborty, Abhishek; Manoj, B. S.

    2017-12-01

    Identifying central nodes is very crucial to design efficient communication networks or to recognize key individuals of a social network. In this paper, we introduce Graph Fourier Transform Centrality (GFT-C), a metric that incorporates local as well as global characteristics of a node, to quantify the importance of a node in a complex network. GFT-C of a reference node in a network is estimated from the GFT coefficients derived from the importance signal of the reference node. Our study reveals the superiority of GFT-C over traditional centralities such as degree centrality, betweenness centrality, closeness centrality, eigenvector centrality, and Google PageRank centrality, in the context of various arbitrary and real-world networks with different degree-degree correlations.

  1. Paleointensity Variation of The Earth's Magnetic Field Obtained from Neogene and Quaternary Volcanic Rocks in Central Anatolian Plateau

    Science.gov (United States)

    Kaya, Nurcan; Makaroǧlu, Özlem; Hisarlı, Z. Mümtaz

    2017-04-01

    We present the variation of the earth magnetic field intensity obtained from Neogene and Quaternary volcanic rocks located in the Central Anatolian plateau. Total of four hundred and fifty volcanic rocks were sub-sampled in eighteen different sites around the study region. A modified Thellier method including the Leonhardt protocol was used to determine paleointensity values. Paleointensity results from ten sites were accepted according to the confidence criteria . According to first results the average total paleointensity field values, indicated by F, are 51.797±5.044 μT for site NK8,NK17,NK18,NK15 with age of 4.4-10.7 my, 51.91±4.651 for site NK4, NK3, NK12, NK6, NK11, NK14 with age of 0.1-2.6 m.y. The average VDMs (Virtual Dipol Moments) correspond to 8.39x1022 , 8.92x1022 Am2 for the four Neogene and six Quaternary rocks sites respectively. Our data were correlated with IAGA database that were obtained from the surrounding area. The correlation showed that the paleointensity data from the Central Anatolia plateau considerably agree with the IAGA data.

  2. Diffuse Carbon Dioxide Degassing Monitoring at Santa Ana-Izalco-Coatepeque Volcanic System, El Salvador, Central America

    Science.gov (United States)

    Olmos, R.; Barahona, F.; Cartagena, R.; Soriano, T.; Salazar, J.; Hernandez, P.; Perez, N.; Notsu, K.; Lopez, D.

    2001-12-01

    Santa Ana volcanic complex (0.22 Ma), located 40 Km west of San Salvador, comprises Santa Ana, Izalco, and Cerro Verde stratovolcanoes, the Coatepeque collapse caldera, as well as several cinder cones and explosion craters. Most recent activity has occurred at Izalco (1966) and Santa Ana which shows a permanent acidic crater lake with an intense fumarolic activity. In addition, Santa Ana exhibits a SO2-rich rising plume though no local seismicity has been reported. Weak fumarolic activity is also present at two locations within the Santa Ana volcanic complex: the summit crater of Izalco and Cerro Pacho at Coatepeque caldera. Other important structural features of this volcanic complex are two fault/fissure systems running NNW-SSE that can be identified by the alignment of the stratovolcanoes and numerous cinder cones and explosion craters. In January 2001, a 7.6 magnitude earthquake occurred about 150 Km SE of Santa Ana volcano. A soil gas and CO2 efflux survey was performed to evaluate the impact of this seismic event upon the diffuse degassing rates in Santa Ana volcanic complex in March 2001. A total of 450 soil gas and diffuse CO2 efflux measurements were carried out covering an area of 209.5 Km2. CO2 efflux ranged from non-detectable values to 293 gm-2d-1, with a median of 8.9 gm-2d-1 and an upper quartile of 5.2 gm-2d-1. The CO2 efflux spatial distribution reveals the existence of areas with CO2 efflux higher than 60 gm-2d-1 associated to the fault/fissure systems of NNW-SSE orientation. One of these areas, Cerro Pacho, was selected for the continuous monitoring of diffuse CO2 efflux in late May 2001. Secular variations of diffuse CO2 efflux ranged from 27.4 to 329 gm-2d-1 with a median of 130 gm-2d-1 and a quartile range of 59.3 gm-2d-1. An increasing trend of 43 gm-2d-1 was observed between May and August 2001 overlapped to high-frequency minor fluctuations related to meteorological variables' changes. However, a larger observation time-span is needed to

  3. Complex explosive volcanic activity on the Moon within Oppenheimer crater, Icarus

    Science.gov (United States)

    Bennett, Kristen A; Horgan, Briony H N; Gaddis, Lisa R.; Greenhagen, Benjamin T; Allen, Carlton C.; Hayne, Paul O; Bell, James F III; Paige, David A.

    2016-01-01

    Oppenheimer Crater is a floor-fractured crater located within the South Pole-Aitken basin on the Moon, and exhibits more than a dozen localized pyroclastic deposits associated with the fractures. Localized pyroclastic volcanism on the Moon is thought to form as a result of intermittently explosive Vulcanian eruptions under low effusion rates, in contrast to the higher-effusion rate, Hawaiian-style fire fountaining inferred to form larger regional deposits. We use Lunar Reconnaissance Orbiter Camera images and Diviner Radiometer mid-infrared data, Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra, and Clementine orbiter Ultraviolet/Visible camera images to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. Mineralogically, we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor, juvenile clinopyroxene, and juvenile iron-rich glass, and that the mineralogy of the pyroclastics varies both across the Oppenheimer deposits as a whole and within individual deposits. We observe similar variability in the inferred iron content of pyroclastic glasses, and note in particular that the northwest deposit, associated with Oppenheimer U crater, contains the most iron-rich volcanic glass thus far identified on the Moon, which could be a useful future resource. We propose that this variability in mineralogy indicates variability in eruption style, and that it cannot be explained by a simple Vulcanian eruption. A Vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit; however, large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material. Thus, we propose that at least the most recent portion of these deposits must have erupted via a Strombolian or more continuous fire

  4. Petrogenesis of Cretaceous volcanic-intrusive complex from the giant Yanbei tin deposit, South China: Implication for multiple magma sources, tin mineralization, and geodynamic setting

    Science.gov (United States)

    Li, Qian; Zhao, Kui-Dong; Lai, Pan-Chen; Jiang, Shao-Yong; Chen, Wei

    2018-01-01

    The giant Yanbei tin ore deposit is the largest porphyry-type tin deposit in South China. The orebodies are hosted by the granite porphyry in the central part of the Yanbei volcanic basin in southern Jiangxi Province. The Yanbei volcanic-intrusive complex mainly consists of dacitic-rhyolitic volcanic rocks, granite, granite porphyry and diabase dikes. In previous papers, the granite porphyry was considered as subvolcanic rocks, which came from the same single magma chamber with the volcanic rocks. In this study, zircon U-Pb ages and Hf isotope data, as well as whole-rock geochemical and Sr-Nd isotopic compositions of different magmatic units in the Yanbei complex are reported. Geochronologic results show that various magmatic units have different formation ages. The dacite yielded a zircon U-Pb age of 143 ± 1 Ma, and the granite porphyry has the emplacement age of 138 ± 1 Ma. Diabase dikes which represented the final stage of magmatism, yielded a zircon U-Pb age of 128 ± 1 Ma. Distinctive whole rock Sr-Nd and zircon Hf isotopic compositions suggest that these magmatic units were derived from different magma sources. The volcanic rocks were mainly derived from the partial melting of Paleoproterozoic metasedimentary rocks without additions of mantle-derived magma. The granite porphyry has an A-type geochemical affinity, and was derived from remelting of Paleo-Mesoproterozoic crustal source with involvement of a subordinate mantle-derived magma. The granite porphyry is also a typical stanniferous granite with high F (4070-6090 ppm) and Sn (7-39 ppm) contents. It underwent strongly crystal fractionation of plagioclase, K-feldspar, and accessory minerals (like apatite, Fe-Ti oxides), which may contribute to the tin mineralization. The diabase was derived by partial melting of enriched lithospheric mantle which had been metasomatised by slab-derived fluids. The change of magmatic sources reflected an increasing extensional tectonic environment, perhaps induced by slab

  5. Late Cretaceous transition from subduction to collision along the Bangong-Nujiang Tethys: New volcanic constraints from central Tibet

    Science.gov (United States)

    Liu, De-Liang; Shi, Ren-Deng; Ding, Lin; Zou, Hai-Bo

    2018-01-01

    This study deals with arc-type and subsequent bimodal volcanic rocks interbedded with (late) Cretaceous sedimentary formations near Gaize, central Tibet that shed new light on the Tethyan evolution along the Bangong-Nujiang suture. Unit I consists of trachyandesites interbedded with fine-grained sandstone, slate, and limestone. Zircon dating on a trachyandesite sample yields a 206Pb/238U age of 99 ± 1 Ma. The trachyandesites are characterized by strong enrichment in LILE but depletion in HFSE, low zircon saturation temperatures (TZr = 642-727 °C), and high oxygen fugacity (Δ FMQ = - 0.67-0.73), indicating their arc affinities. Unit II comprises a bimodal basalt-rhyolite suite interbedded with coarse-grained sandstone and conglomerate. Zircon dating on two rhyolitic samples yield 206Pb/238U ages of 97.1-87.0 Ma. In contrast with Unit I trachyandesites, Unit II basalts and rhyolites exhibit OIB-like trace element patterns, high temperatures (T = 1298-1379 °C for basalts, TZr = 855-930 °C for rhyolites), and low oxygen fugacity (Δ FMQ = - 3.37 - 0.43), suggesting that Unit II bimodal volcanic rocks probably formed in an extensional setting. The Sr-Nd isotopes of both Unit I (87Sr/86Sri = 0.7052-0.7074, εNd(t) = - 2.21-1.02) and Unit II (87Sr/86Sri = 0.7057-0.7098, εNd(t) = - 3.22-0.88) rocks are similar to mantle-wedge-derived volcanic rocks within the southern Qiangtang block. The parental magma of Unit I trachyandesites was formed by fluid induced melting of the mantle wedge above the subducted Bangong-Nujiang Tethyan slab, and contaminated by crustal materials during MASH process within a deep crustal hot zone; and Unit II bimodal volcanic rocks were derived by melting of upwelling asthenosphere and a mildly metasomatized mantle wedge during the Lhasa-Qiangtang collision. We propose that the transition from the Bangong-Nujiang Tethyan subduction to the Lhasa-Qiangtang collision occurred during the Late Cretaceous in central Tibet.

  6. Contemporaneous alkaline and calc-alkaline series in Central Anatolia (Turkey): Spatio-temporal evolution of a post-collisional Quaternary basaltic volcanism

    Science.gov (United States)

    Dogan-Kulahci, Gullu Deniz; Temel, Abidin; Gourgaud, Alain; Varol, Elif; Guillou, Hervé; Deniel, Catherine

    2018-05-01

    strength elements (HFSE; Y, Yb) and the La/Nb >1 favor a shallow lithospheric source for ES, HS, OZ and KA basaltic volcanic rocks, whereas some samples bear the trace element signature of an asthenospheric mantle source. The lithospheric mantle beneath Central Anatolia may have not been affected from asthenospheric mantle directly. Negative Nb-Ta-Ti anomalies and a positive Pb spike of ES, HS, OZ and KA may be ascribed to crustal contamination or as the imprints of the previous subduction processes. According to this study, and previous studies, the effect of subduction and/or crustal contamination in Central Anatolia decreased from the Miocene to the Quaternary, and the origin of the Quaternary basaltic rocks mainly derived from subduction-related magmas enriched with sediment input rather than to slab-derived fluids. Our calculated eruption ages for the four basaltic complexes show that spatial differences predominate, whereas temporal trends are difficult to discern due to limited age resolution. According to the available geochronological, petrological and geochemical data, alkaline and calc-alkaline volcanism occurred simultaneously from distinct parental magmas.

  7. Tectonic evolution of the central-eastern sector of Trans Mexican Volcanic Belt and its influence on the eruptive history of the Nevado de Toluca volcano (Mexico)

    Science.gov (United States)

    Bellotti, F.; Capra, L.; Groppelli, G.; Norini, G.

    2006-11-01

    The Nevado de Toluca is an andesitic to dacitic stratovolcano of Late Pliocene-Holocene age located within the central and eastern sectors of the Trans Mexican Volcanic Belt. Morphostructural analysis, aerial photograph and satellite image interpretation, structural analysis and geological fieldwork were methods used to investigate the relationship between the evolution of the volcano and the tectonic framework of its basement. The study revealed that the area of Nevado de Toluca is affected by three main fault systems that intersect close to the volcanic edifice. These are from oldest to youngest, the Taxco-Querétaro, San Antonio and Tenango fault systems. The NNW-SSE Taxco-Querétaro fault system was active in the area since Early Miocene, and is characterized by right-lateral transtensive movement. Its reactivation during Early to Middle Pleistocene was responsible for the emplacement of andesitic to dacitic lava flows and domes of La Cieneguilla Supersynthem. The NE-SW San Antonio fault system was active during Late Pliocene, before the reactivation of the Taxco-Querétaro fault system, and is characterized by extensional left-lateral oblique-slip kinematics. The youngest is the E-W Tenango fault system that has been active since Late Pleistocene. This fault system is characterized by transtensive left-lateral strike-slip movement, and partly coeval with the youngest eruptive phase, the Nevado Supersynthem, which formed the present summit cone of the Nevado de Toluca volcano. The stress re-orientation from the Taxco-Querétaro to the Tenango fault system during Late Pleistocene is responsible for the ˜ 1 Ma hiatus in the magmatic activity between 1.15 Ma and 42 ka. After this period of repose, the eruptive style drastically changed from effusive to explosive with the emission of dacitic products. The methodology presented here furnish new data that can be used to better assess the complex structural evolution of this sector of the Trans Mexican Volcanic Belt

  8. Trace elements release from volcanic ash to seawater. Natural concentrations in Central Mediterranean sea

    Science.gov (United States)

    Randazzo, L. A.; Censi, P.; Saiano, F.; Zuddas, P.; Aricò, P.; Mazzola, S.

    2009-04-01

    Distributions and concentrations of many minor and trace elements in epicontinental basins, as Mediterranean Sea, are mainly driven to atmospheric fallout from surroundings. This mechanism supplies an estimated yearly flux of about 1000 kg km-2 of terrigenous matter of different nature on the whole Mediterranean basin. Dissolution of these materials and processes occurring at solid-liquid interface along the water column drive the distributions of many trace elements as V, Cr, Mn, Co, Cu, and Pb with contents ranging from pmol l-1 (Co, Cd, Pb) to nmol l-1 scale in Mediterranean seawater, with some local differences in the basin. The unwinding of an oceanographic cruise in the coastal waters of Ionian Sea during the Etna's eruptive activity in summer 2001 led to the almost unique chance to test the effects of large delivery of volcanic ash to a coastal sea water system through the analyses of distribution of selected trace elements along several seawater columns. The collection of these waters and their analyses about V, Cr, Mn, Co, Cu, and Pb contents evidenced trace element concentrations were always higher (about 1 order of magnitude at least) than those measured concentrations in the recent past in Mediterranean seawater, apart from Pb. Progressive increase of concentrations of some elements with depth, sometimes changing in a "conservative" behaviour without any clear reason and the observed higher concentrations required an investigation about interaction processes occurring at solid-liquid interface between volcanic ash and seawater along water columns. This investigation involving kinetic evaluation of trace element leaching to seawater, was carried out during a 6 months time period under laboratory conditions. X-ray investigations, SEM-EDS observations and analyses on freshly-erupted volcanic ash evidenced formation of alteration clay minerals onto glass fraction surfaces. Chemical analyses carried out on coexisting liquid phase demonstrated that trace

  9. Geochemical and visual indicators of hydrothermal fluid flow through a sediment-hosted volcanic ridge in the Central Bransfield Basin (Antarctica.

    Directory of Open Access Journals (Sweden)

    Alfred Aquilina

    Full Text Available In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (E(h were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition ((87Sr/(86Sr = 0.708776 at core base compared with modern seawater ((87Sr/(86Sr ≈ 0.70918, indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column E(h anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in E(h, temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.

  10. Melt zones beneath five volcanic complexes in California: an assessment of shallow magma occurrences

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, N.E.; Flexser, S.

    1984-12-01

    Recent geological and geophysical data for five magma-hydrothermal systems were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area. The areas studied were: (1) Salton Trough, (2) The Geysers-Clear Lake, (3) Long Valley caldera, (4) Coso volcanic field, and (5) Medicine Lake volcano, all located in California and all selected on the basis of recent volcanic activity and published indications of crustal melt zones. 23 figs.

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

    Science.gov (United States)

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

    2017-08-01

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

  12. Magmatic Activity Beneath the Quiescent Three Sisters Volcanic Center, Central Oregon Cascade Range, USA, Inferred from Satellite InSAR

    Science.gov (United States)

    Wicks, C. W.; Dzurisin, D.; Ingebritsen, S.; Thatcher, W.; Lu, Z.; Iverson, J.

    2001-12-01

    Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ~10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ~130 km south of Mt. St. Helens. The uplift is centered ~5 km west of South Sister volcano, the youngest stratovolcano in the volcanic center. The center has been volcanically inactive since the last eruption ~1500 years ago. Multiple European Space Agency ERS-1 and 2 satellite images from 1992 through 2000, used in this study, were selected based on orbital separation and time of year. Summer and early autumn scenes were necessary to avoid decorrelation from snow cover. Interferograms generated from these images indicate that most if not all of ~100 mm of observed uplift occurred between September 1998 and October 2000. We interpret the uplift as inflation caused by an apparently ongoing episode of magma intrusion at a depth of ~6.5 km. Geochemical (water chemistry) anomalies, first noted ~1990, coincide with the area of uplift and suggest the existence of a magma reservoir prior to the uplift. High chloride and sulfate concentrations, and a positive correlation between chloride concentration and spring temperature were found within the uplift area, with larger SO4/Cl ratios in springs at higher elevations. These findings are indicative of a high-temperature hydrothermal system driven by magma intrusions. The current inflation episode observed with InSAR may lead to an eruption, but the more persistent geochemical evidence suggests that the episode is likely the latest in a series of hitherto undetected magma intrusions. We do not yet know if the inflation has abated, is continuing, or has accelerated since October 2000--we only know that the highest rate of uplift occurred in the last year for which ERS-2 data was available (1999- 2000). In May of 2001, a continuous GPS receiver and seismometer were installed by the USGS within the Three Sisters Wilderness to monitor the

  13. Water and gas geochemistry of the Calatrava Volcanic Province (CVP) hydrothermal system (Ciudad Real, central Spain)

    Science.gov (United States)

    Vaselli, Orlando; Nisi, Barbara; Tassi, Franco; Giannini, Luciano; Grandia, Fidel; Darrah, Tom; Capecchiacci, Francesco; del Villar, Pèrez

    2013-04-01

    An extensive geochemical and isotopic investigation was carried out in the water and gas discharges of the Late Miocene-Quaternary Calatrava Volcanic Province (CVP) (Ciudad Real, Spain) with the aim reconstruct the fluid circulation in the area. CVP consists of a series of scattered (monogenetic) vents from where alkaline lava flows and pyroclastic deposits formed in two different periods. The first stage (8.7-6.4 Ma) mainly included ultra-potassic mafic extrusives, whilst the second stage (4.7-1.75 Ma) prevalently originated alkaline and ultra-alkaline volcanics. Both stages were followed by a volcanic activity that extended up to 1.3 and 0.7 Ma, respectively. This area can likely be regarded as one of the most important emitting zones of CO2 in the whole Peninsular Spain along with that of Selva-Emporda in northeastern Spain (Cataluña) and it can be assumed as one of the best examples of natural analogues of CO2 leakages in Spain. This latter aspect is further evidenced by the relatively common water-gas blast events that characterize the CCVF. In the last few years the presence of a CO2-pressurized reservoir at a relatively shallow level as indeed caused several small-sized explosion particularly during the drilling of domestic wells. The fluid discharging sites are apparently aligned along well-defined directions: NW-SE and NNW-SSE and subordinately, ENE-WSW, indicating a clear relationship between the thermal discharges and the volcanic centers that also distribute along these lineaments. The CVP waters are mostly hypothermal (up to 33 °C) and are generally Mg(Ca)-HCO3 in composition and occasionally show relatively high concentrations of Fe and Mn, with pH and electrical conductivity down to 5.5 and up to 6.5 mS/cm, respectively. The oxygen and hydrogen isotopes suggest a meteoric origin for these waters. The mantle source of these volcanic products is apparently preserved in the many CO2-rich (up to 990,000 mmol/mol) gas discharges that characterize CVP

  14. Asthenospheric counterflows beneath the moving lithosphere of Central and East Asia in the past 90 Ma: volcanic and tomographic evidence

    Science.gov (United States)

    Rasskazov, Sergei; Chuvashova, Irina; Kozhevnikov, Vladimir

    2015-04-01

    Asthenospheric counterflows, accompanied motions of the lithosphere in Central and East Asia, are defined on basis of spatial-temporal activity of mantle sources [Rasskazov et al., 2012; Rasskazov, Chuvashova, 2013; Chuvashova, Rasskazov, 2014] and the tomographic model of the Rayleigh wave group velocities [Kozhevnikov et al., 2014]. The opposite fluxes are defined relative to centers of convective instability (low-velocity anomalies), expressed by thinning of the mantle transition layer under Southwestern Gobi (44 °N, 95 °E) and Northern Baikal (52 °N, 108 °E). Cretaceous-Paleogene volcanic fields in Southern Gobi are shifted eastwards relative to the former anomaly over 600 km with the opposite sub-lithospheric flux at depths of 150-300 km. Likewise, the Late Tertiary Vitim volcanic field is shifted relative to the latter anomaly over 100-200 km. We suggest that the Gobi and Baikal asthenospheric counterflows contributed to the rollback mechanism of downgoing slab material from the Pacific under the eastern margin of Asia in the Cretaceous-Paleogene and Early-Middle Miocene. The east-west Gobi reverse flux, caused by differential block motions in front of the Indo-Asian convergence, resulted in the oblique Honshu-Korean flexure of the Pacific slab that propagated beneath the continental margin, while the Japan Sea was quickly opening at about 15 Ma. The Baikal N60°W reverse flux, originated due to oncoming traffic between Eurasia and the Pacific plate, entailed the formation of the Baikal Rift Zone and direct Hokkaido Amur slab flexure [Rasskazov et al., 2004]. The study is supported by the Russian Foundation for Basic Research (Grant 14-05-31328). References Chuvashova I.S., Rasskazov S.V. Magmatic sources in the mantle of the evolving Earth. Irkutsk: Publishing House of the Irkutsk State University, 2014. 310 p. (in Russian) Kozhevnikov V.M., Seredkina A.I., Solovei O.A. 3D mantle structure of Central Asia from Rayleigh wave group velocity dispersion

  15. Introduction to the LaRC central scientific computing complex

    Science.gov (United States)

    Shoosmith, John N.

    1993-01-01

    The computers and associated equipment that make up the Central Scientific Computing Complex of the Langley Research Center are briefly described. The electronic networks that provide access to the various components of the complex and a number of areas that can be used by Langley and contractors staff for special applications (scientific visualization, image processing, software engineering, and grid generation) are also described. Flight simulation facilities that use the central computers are described. Management of the complex, procedures for its use, and available services and resources are discussed. This document is intended for new users of the complex, for current users who wish to keep appraised of changes, and for visitors who need to understand the role of central scientific computers at Langley.

  16. Low-pressure evolution of arc magmas in thickened crust: The San Pedro-Linzor volcanic chain, Central Andes, Northern Chile

    Science.gov (United States)

    Godoy, Benigno; Wörner, Gerhard; Kojima, Shoji; Aguilera, Felipe; Simon, Klaus; Hartmann, Gerald

    2014-07-01

    Magmatism at Andean Central Volcanic Zone (CVZ), or Central Andes, is strongly influenced by differentiation and assimilation at high pressures that occurred at lower levels of the thick continental crust. This is typically shown by high light to heavy rare earth element ratios (LREE/HREE) of the erupted lavas at this volcanic zone. Increase of these ratios with time is interpreted as a change to magma evolution in the presence of garnet during evolution of Central Andes. Such geochemical signals could be introduced into the magmas be high-pressure fractionation with garnet on the liquidus and/or assimilation from crustal rocks with a garnet-bearing residue. However, lavas erupted at San Pedro-Linzor volcanic chain show no evidence of garnet fractionation in their trace element patterns. This volcanic chain is located in the active volcanic arc, between 22°00‧S and 22°30‧S, over a continental crust ˜70 km thick. Sampled lavas show Sr/Y and Sm/Yb ratios Chile. We relate our geochemical observations to shallow crustal evolution of primitive magmas involving a high degree of assimilation of upper continental crust. We emphasize that low pressure AFC- (Assimilation Fractional Crystallization) type evolution of the San Pedro-Linzor volcanic chain reflects storage, fractionation, and contamination of mantle-derived magmas at the upper felsic crust (<40 km depth). The ascent of mantle-derived magmas to mid-crustal levels is related with the extensional regime that has existed in this zone of arc-front offset since Late-Miocene age, and the relatively thin portion of mafic lower crust observed below the volcanic chain.

  17. Glacial recession in the Tropical Andes from the Little Ice Age: the case of Ampato Volcanic Complex (Southern Peru

    Science.gov (United States)

    Alcalá, J.; Palacios, D.; Zamorano, J. J.

    2010-03-01

    Data published over the last decade reveal substantial glacial recession in the tropical Andes since the Little Ice Age (LIA), (Ramirez, et al., 2001; Rabatel, et al., 2005; Rabatel, et al., 2008; Vuille, et al., 2008; Hastenrath, 2009; Jomelli, et al., 2009), and a growing rate of recession since the 1980’s caused by global warming (Ramirez, et al., 2001; Vuille, et al., 2008). Today there is great interest in the evolution of these ice masses due to heightened awareness of climate change and of the strategic importance that glaciers have as a hydrologic resource for communities in arid climate zones in the tropical Andes (Mark, 2008; Vuille et al., 2008). Cordillera Blanca forms part of the Andes Mountains of northern Peru, and is a chosen site for many studies on glacier evolution. Vuille et al. 2008 determined that a considerable area of ice mass was lost at Huascarán-Chopicalqui glacier (18% from 1920-1970) and Astesonraju glacier (20% from 1962-2003). Studies at Coropuna volcano, which has the most extensive glacier field in the western range of southern Peru, also report a strong melting trend that began with only minimal recession from 1955-1986 (4%), but increased to 14% from 1986-2007 (Úbeda et al., 2009). Only a few of the Andes glaciers are consistently monitored, and the most comprehensive data are for Chacaltaya and Zongo glaciers (16º S) in Bolivia. Since the maximum LIA, Chacaltaya has lost 89% of its surface area, particularly in recent years. By 1983, the totaled loss was five times the shrinkage for the period 1940-1963 (Ramirez, et al., 2001). Zongo glacier maintained equilibrium from 1956-1975, but later experienced a period dominated by continuous recession (Soruco, et al., 2009). This study expands current knowledge of glacier evolution since the LIA in the Central Volcanic Zone (CVZ; 14º - 27º S) (Stern, 2004) of the Andes. The study site was chosen in an area that had never been used for preliminary research of this type, concretely

  18. The Lepanto Cu–Au deposit, Philippines: A fossil hyperacidic volcanic lake complex

    Science.gov (United States)

    Berger, Byron R.; Henley, Richard W.; Lowers, Heather; Pribil, Michael

    2014-01-01

    Hyperacidic lakes and associated solfatara in active volcanoes are the expression of magmatic gas expansion from source to surface. Here we show for the first time, that the vein system that comprises the ~ 2 Ma high-sulfidation, Lepanto copper–gold deposit in the Mankayan district (Philippines) was associated with a contemporary hyperacidic volcanic lake complex—possibly the first such lake recognized in the geological record. A 15–20‰ difference in sulfur isotopic composition between barite and sulfides and sulfosalts in the vent fumarole encrustations supports the interpretation that SO2-rich volcanic gas vented into the base of the lake and marginal to it and ties the mineralization directly to magmatic gas expansion, fracture propagation, and mineralization that occurred through a series of decompression steps within the feeder fracture network. These data confirm that crater lake environments such as Kawah Ijen (Java, Indonesia) provide modern day analogs of the Lepanto and other high sulfidation Cu–Au depositing environments.We also provide extensive analysis of sulfosalt–sulfide reactions during vein formation within the hyperacidic lake complex. Pyrite ±  silica deposited first at high temperature followed by enargite that preserves the vapor–solid diffusion of, for example, antimony, tin, and tellurium into the vapor from the crystallizing solid. Subsolidus, intra-crystalline diffusion continued as temperature declined. Pyrite and enargite are replaced by Fe-tennantite in the lodes which initially has low Sb/(Sb + As) atomic ratios around 13.5% close to the ideal tennantite formula, but evolves to higher ratios as crystallization proceeds. Fumarole encrustation clasts and sulfosalts in the lake sediment are more highly evolved with a larger range of trace element substitutions, including antimony. Substitution of especially Zn, Te, Ag, and Sn into tennantite records metal and semi-metal fractionation between the expanding magmatic

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

    Science.gov (United States)

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

    2015-08-01

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

  20. Analyzing complex networks through correlations in centrality measurements

    International Nuclear Information System (INIS)

    Ricardo Furlan Ronqui, José; Travieso, Gonzalo

    2015-01-01

    Many real world systems can be expressed as complex networks of interconnected nodes. It is frequently important to be able to quantify the relative importance of the various nodes in the network, a task accomplished by defining some centrality measures, with different centrality definitions stressing different aspects of the network. It is interesting to know to what extent these different centrality definitions are related for different networks. In this work, we study the correlation between pairs of a set of centrality measures for different real world networks and two network models. We show that the centralities are in general correlated, but with stronger correlations for network models than for real networks. We also show that the strength of the correlation of each pair of centralities varies from network to network. Taking this fact into account, we propose the use of a centrality correlation profile, consisting of the values of the correlation coefficients between all pairs of centralities of interest, as a way to characterize networks. Using the yeast protein interaction network as an example we show also that the centrality correlation profile can be used to assess the adequacy of a network model as a representation of a given real network. (paper)

  1. Neotectonics of Graciosa island (Azores: a contribution to seismic hazard assessment of a volcanic area in a complex geodynamic setting

    Directory of Open Access Journals (Sweden)

    Ana Hipólito

    2014-02-01

    Full Text Available Graciosa is a mid-Pleistocene to Holocene volcanic island that lies in a complex plate boundary between the North American, Eurasian, and Nubian plates. Large fault scarps displace the oldest (Middle Pleistocene volcanic units, but in the younger areas recent volcanism (Holocene to Upper Pleistocene conceals the surface expression of faulting, limiting neotectonic observations. The large displacement accumulated by the older volcanic units when compared with the younger formations suggests a variability of deformation rates and the possibility of alternating periods of higher and lower tectonic deformation rates; this would increase the recurrence interval of surface rupturing earthquakes. Nevertheless, in historical times a few destructive earthquakes affected the island attesting for its seismic hazard. Regarding the structural data, two main fault systems, incompatible with a single stress field, were identified at Graciosa Island. Thus, it is proposed that the region is affected by two alternating stress fields. The stress field #1 corresponds to the regional stress regime proposed by several authors for the interplate shear zone that constitutes the Azorean segment of the Eurasia-Nubia plate boundary. It is suggested that the stress field #2 will act when the area under the influence of the regional stress field #1 narrows as a result of variations in the differential spreading rates north and south of Azores. The islands closer to the edge of the sheared region will temporarily come under the influence of a different (external stress field (stress field #2. Such data support the concept that, in the Azores, the Eurasia-Nubia boundary corresponds to a complex and wide deformation zone, variable in time.

  2. Las comunidades vegetales del Zacatonal Alpino de los volcanes Popocatépetl y Nevado de Toluca, Región Central de México.

    NARCIS (Netherlands)

    Almeida-Lenero, L.; Gimenez de Azcarate, J.; Cleef, A.M.; Gonzales Trapaga, A.

    2004-01-01

    This study of the zacatonal alpino zone of the volcanoes Popocatepetl (5452 in) and Nevado de Toluca (4690 m) in the central region of the Transmexican Volcanic Belt, is a follow-up of the study of ALMEIDA et al. (1994). This tropical alpine zacatonal represents the potential vegetation of the

  3. REE behavior during weathering of basaltic rocks from the Lisbon Volcanic Complex (Portugal)

    International Nuclear Information System (INIS)

    Prudencio, M.I.; Cabral, J.M.P.; Sequeira Braga, M.A.

    1991-01-01

    Two weathering profiles developed in alkali basalts from the Lisbon Volcanic Complex were chosen for a REE behavior study. Profile 1 consists of a lava flow with porphyritic texture. Olivine and clinopyroxene are set in a groundmass which mainly comprises plagioclase, clinopyroxene, olivine, biotite, glass and Fe-Ti oxides. X-ray diffraction analysis of the 0 < 2μm fraction revealed: 45-95% smectites and 5-40% halloysite (7.3 angstrom), and Fe and/or Ti oxides. Profile 2 consists of a lava flow with an intergranular texture, where olivine, clinopyroxene and spinel grains are surrounded by large feldspars laths. The 0 < 2μ fraction consists of 80-100% halloysite (7.3 angstrom), < 20% micas and < 10% palygorskite and Fe and/or Ti oxides. The REE were determined by instrumental neutron activation analysis. The clay-sized fractions of the more weathered samples were separated and analyzed too. For the whole samples it was observed that: (1) when halloysites are the dominant clay-minerals (profile 2), REE are more retained in the profile and (2) in general the light REE are less concentrated in the profiles than the intermediate or even the heavy REE. In most weathered samples of profile 1 a significant loss of Ce was found. The REE in the 0 < 2μm fractions are in general enriched relative to the whole samples. In profile 1, where smectites dominate, a significant negative Ce anomaly is also present except for one sample collected at an intermediate level. Among the REE analyzed, Nd is the most enriched compared to the whole samples. In profile 2, where halloysites dominate and micas are present mainly at the bottom of the profile, it was observed that: (a) REE are less fractionated than in profile 1, (b) Ce is depleted at the bottom of the profile but increases upwards, so that at the top the 0 < 2μm fraction reveals a small positive anomaly relative to whole sample

  4. Central Waste Complex (CWC) essential/support drawing list

    International Nuclear Information System (INIS)

    WHITLOCK, R.W.

    1999-01-01

    Essential and supporting engineering drawings for the Central Waste Complex (CWC) are identified in this document. The purpose of the document is to describe the criteria used to identify drawings and the plan for updating and maintaining their accuracy. This document supports HNF-PRO-242 and HNF-PRO-440

  5. Volcanic ash and its enigma: A case study from the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Pattan, J.N.

    An ash layer occurs between 10-35 cm depth in sediment cores from the Central Indian Ocean basin. Morphology, major, trace and rare earth element composition of glass shards from the ash layer suggest that the Youngest Toba Tuff of ~74 ka from...

  6. Volcanic evolution of central Basse-Terre Island revisited on the basis of new geochronology and geomorphology data

    Science.gov (United States)

    Ricci, J.; Quidelleur, X.; Lahitte, P.

    2015-10-01

    Twenty-six new and seven previous K-Ar ages obtained on groundmass separates for samples from the Axial Chain massif (Guadeloupe, F.W.I.), associated with geomorphological investigations, allow us to propose a new model of the volcanic evolution of the central part of Basse-Terre Island. The Axial Chain is composed of four edifices, Moustique, Matéliane, Capesterre, and Icaque mounts, showing coeval activity from 681 ± 12 to 509 ± 10 ka, which contradicts a previous hypothesis that flank collapse affected them successively. Our geomorphological reconstruction shows that the Axial Chain can be considered as a single large volcano, named the Southern Axial Chain volcano (SCA), rather than a succession of several smaller volcanoes. It raises questions regarding the formation of a large depression within the SCA volcano, prior to the construction of the Sans-Toucher volcano between 451 ± 13 and 412 ± 8 ka. Given presently available evidence, a slump affecting the western part of the SCA volcano is the most probable scenario to reconcile the complete age dataset and the present-day morphology of central Basse-Terre. Finally, our study shows that the SCA volcano had a post-activity volume of 90 km3, implying a construction rate of 0.5 km3/kyr. This value strongly constrains interpretations of magma generation processes throughout the Lesser Antilles arc.

  7. Economic potential of the Rooiberg Group: volcanic rocks in the floor and roof of the Bushveld Complex

    Science.gov (United States)

    Schweitzer, J. K.; Hatton, C. J.; de Waal, S. A.

    1995-04-01

    Volcanic rocks of the Rooiberg Group are preserved in the floor and roof of the mafic Rustenburg Layered Suite of the Bushveld Complex. Field and geochemical characteristics of these volcanic rocks imply that they are genetically related to the Rustenburg Layered Suite. Four major ore-forming events are identified in the Rooiberg Group. The first phase was accompanied by volcanic hosted, fault controlled, hydrothermal copper mineralisation, which is found in the lowermost portion of the Rooiberg Group, underlying the Rustenburg Layered Suite. This type of mineralisation is tentatively linked to initial Rustenburg Layered Suite intrusions. Stratabound arsenic mineralisation that possibly formed in response to contact metamorphism, characterises the second phase, and occurred after extrusion of the Damwal Formation, possibly due to shallow granophyric intrusion. The third mineralising event occurred in response to contact metamorphism during the final stages of the Rustenburg Layered Suite, where especially Pb and Zn were introduced into the felsite roof rocks. This type of mineralisation affected the majority of the Rooiberg Group, but is most pronounced towards the contact with the Rustenburg Layered Suite. The fourth phase is restricted to the Rooiberg Group in the Nylstroom area and is linked to the granite intrusions of the Lebowa Granite Suite, from which Sn and F were introduced into the uppermost felsite succession. Mineralisation in the Rooiberg Group appears to be controlled by the character and intrusion level of the associated Bushveld magmas. Different styles of mineralisation in Rooiberg Group volcanic rocks are encountered at various stratigraphic levels. Major primary volcanogenic ore deposits appear to be absent.

  8. Source region of volcanism and seismicity pattern beneath Central American volcanoes

    Czech Academy of Sciences Publication Activity Database

    Špičák, Aleš; Hanuš, Václav; Vaněk, Jiří

    2005-01-01

    Roč. 236, 1/2 (2005), s. 149-172 ISSN 0077-7749 R&D Projects: GA ČR GA205/03/1203; GA AV ČR IAA3012303 Institutional research plan: CEZ:AV0Z30120515 Keywords : Central America * subduction * convergent plate margins Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 0.721, year: 2005

  9. Fluid escape structures in the Graham Bank region (Sicily Channel, Central Mediterranean) revealing volcanic and neotectonic activity.

    Science.gov (United States)

    Spatola, Daniele; Pennino, Valentina; Basilone, Luca; Interbartolo, Francesco; Micallef, Aaron; Sulli, Attilio; Basilone, Walter

    2016-04-01

    In the Sicily Channel, (Central Mediterranean), two geodynamic processes overlap each other, the Maghrebides-Apennines accretionary prism and the Sicily Channel rift. Moreover, the northwestern sector (Banks sector) is characterised by an irregular seafloor morphology linked to the recent volcanic and tectonic activity.In order to discriminate the role exerted by both the processes in the morphostructural setting of the area we used a dataset of both high and very high resolution single-channel and multi-channel profiles, acquired in the frame of the RITMARE project respectively with CHIRP and sparker, and airgun sources, and high resolution (5 m cell) morpho-bathymetric data. The data allowed us to identify and characterise two areas where different geological features (sedimentary and volcanic) are prevailing. They present fluid escaping evidence, which often appears to be active and generating different types of morphologies (both positive and negative). In the western sector we recognised pockmarks at water depths of 195 to 317 m, with diameters from 25 to 580 m, depths from 1.3 to 15 m, and slope up to 23°. They show sub-circular shape in plan-view and reflectors with upward concavity in cross section, and are oriented along a NW-SE trend.The CHIRP and multichannel profiles highlight fluids that affect the Plio-Quaternary succession, especially in areas where the top surface of the Messinian succession is shallower. Conversely, wipe-out acoustic facies were recognised in proximity of: i) extensional faults of Mesozoic age with NW-SE trend; ii) dip/strike slip faults of Cenozoic age with NW-SE, N-S and about NNE-SSW trends, and iii) extensional neo-tectonic faults with NW-SE and NNW-SSE trends. We cannot exclude that they could feed the shallower reservoir producing a mixing between the two. In the eastern sector we recognised a cluster of volcanoes composed of seven cone-shaped structures (SCV1-7), pertaining to a wide area known as Graham Bank. A detailed

  10. Centrality Robustness and Link Prediction in Complex Social Networks

    DEFF Research Database (Denmark)

    Davidsen, Søren Atmakuri; Ortiz-Arroyo, Daniel

    2012-01-01

    . Secondly, we present a method to predict edges in dynamic social networks. Our experimental results indicate that the robustness of the centrality measures applied to more realistic social networks follows a predictable pattern and that the use of temporal statistics could improve the accuracy achieved......This chapter addresses two important issues in social network analysis that involve uncertainty. Firstly, we present am analysis on the robustness of centrality measures that extend the work presented in Borgati et al. using three types of complex network structures and one real social network...

  11. Neogene Tiporco Volcanic Complex, San Luis, Argentina: An explosive event in a regional transpressive - local transtensive setting in the pampean flat slab

    Science.gov (United States)

    Ibañes, Oscar Damián; Sruoga, Patricia; Japas, María Silvia; Urbina, y. Nilda Esther

    2017-07-01

    The Neogene Tiporco Volcanic Complex (TVC) is located in the Sierras Pampeanas of San Luis, Argentina, at the southeast of the Pampean flat-slab segment. Based on the comprehensive study of lithofacies and structures, the reconstruction of the volcanic architecture has been carried out. The TVC has been modeled in three subsequent stages: 1) initial updoming, 2) ignimbritic eruptive activity and 3) lava dome emplacement. Interplay of magma injection and transtensional tectonic deformation has been invoked to reproduce TVC evolution.

  12. Petrology and deformation style of lithospheric mantle beneath the Heldburg Dike swarm (Central Germany) subset of Central European Volcanic Province

    Science.gov (United States)

    Kukuła, Anna; Puziewicz, Jacek; Hidas, Károly; Ntaflos, Theodoros; Matusiak-Małek, Magdalena; Milke, Ralf

    2017-04-01

    The Heldburg Dike swarm is a set of Cenozoic alkali basalt dikes occurring in the central part of Germany at the border between Thuringia and Bavaria. We studied xenoliths from Strauf, Feldstein, Bramberg and from the active quarry in Zeilberg. The peridotites from Strauf, Feldstein and Bramberg have the composition of spinel lherzolite (15), spinel harzburgite (9) and dunite (3). They vary in size from 1.5 cm (Strauf) up to 20 cm (Zeilberg). We distinguish groups (A, A- and B) of peridotites based on different forsterite content in olivine. Group A consists of olivine (89.6 - 91.8 Fo), orthopyroxene (Mg# 0.90-0.93, Al 0.05-0.18 a pfu), clinopyroxene (Mg# 0.87-0.95, Al 0.06-0.26 a pfu) and spinel (Cr# 0.13-0.65, Mg# 0.54-0.78). Clinopyroxene rare earth elements (REE) patterns are S-shaped (Feldstein, Bramberg) or U-shaped (Strauf); spoon-shaped patterns occur occasionally. Trace element (TE) patterns show negative Nb, Ta, Zr, Hf, Ti and positive Th, U anomalies. The most magnesian clinopyroxene (xenolith 3140, Feldstein) is strongly aluminous and LREE depletedwith weak anomalies in TE patterns. Group A- is contains olivine (88.9-89.5 Fo), orthopyroxene (Mg# 0.89-0.90, Al 0.10-0.13 a pfu) and clinopyroxene (Mg# 0.90-0.92, Al 0.10-0.17 a pfu). Clinopyroxene is increasingly enriched in REEs from Lu to La. TE patterns are similar to those of group A but with less pronounced anomalies. Group B (3 xenoliths only) consists of olivine Fo 86.7-88.9, orthopyroxene (Mg# 0.88-0.89, Al 0.07-0.19 a pfu), clinopyroxene (Mg# 0.88-0.90, Al 0.10-0.26 a pfu). Clinopyroxene is enriched in LREE, concave upward in Pr. TE patterns are similar to those in group A. One of group B harzburgites contains grains (up to 0.5 mm) of Ca-Mg carbonate located in interstices. The clinopyroxene chemical composition plots away from the melting trend in the MgO-Al2O3 diagram of Upton et al. (2011), suggesting a later addition of the clinopyroxene. The composition of orthopyroxene corresponds to ca. 15

  13. Solid Waste Burial Grounds/Central Waste Complex hazards assessment

    International Nuclear Information System (INIS)

    Broz, R.E.

    1994-01-01

    This document establishes the technical basis in support of Emergency Planning Activities for Solid Waste Burial Grounds/Central Waste Complex on the Hanford Site. The document represents an acceptable interpretation of the implementing guidance document for DOE Order 5500.3A. Through this document, the technical basis for the development of facility specific Emergency Action Levels and the Emergency Planning Zone is documented

  14. High-resolution 40Ar/39Ar geochronology of volcanic rocks from the Siebengebirge (Central Germany)—Implications for eruption timescales and petrogenetic evolution of intraplate volcanic fields

    Science.gov (United States)

    Przybyla, Thomas; Pfänder, Jörg A.; Münker, Carsten; Kolb, Melanie; Becker, Maike; Hamacher, Uli

    2017-11-01

    A key parameter in understanding mantle dynamics beneath continents is the temporal evolution of intraplate volcanism in response to lithospheric thinning and asthenospheric uplift. To contribute to a better understanding of how intraplate volcanic fields evolve through time, we present a high precision 40Ar/39Ar age dataset for volcanic rocks from the Siebengebirge volcanic field (SVF) from central Germany, one of the best studied and compositionally most diverse intraplate volcanic fields of the Cenozoic Central European Volcanic Province (CEVP). Petrological and geochemical investigations suggest that the formation of the different rock types that occur in the SVF can be explained by a combination of assimilation and fractional crystallisation processes, starting from at least two different parental magmas with different levels of silica saturation (alkali basaltic and basanitic), and originating from different mantle sources. These evolved along two differentiation trends to latites and trachytes, and to tephrites and tephriphonolites, respectively. In contrast to their petrogenesis, the temporal evolution of the different SVF suites is poorly constrained. Previous K/Ar ages suggested a time of formation between about 28 and 19 Ma for the mafic rocks, and of about 27 to 24 Ma for the differentiated rocks. Our results confirm at high precision that the differentiated lithologies of both alkaline suites (40Ar/39Ar ages from 25.3 ± 0.2 Ma to 25.9 ± 0.3 Ma) erupted contemporaneously within a very short time period of 0.6 Ma, whereas the eruption of mafic rocks (basanites) lasted at least 8 Ma (40Ar/39Ar ages from 22.2 ± 0.2 Ma to 29.5 ± 0.3 Ma). This implies that felsic magmatism in the central SVF was likely a single event, possibly triggered by an intense phase of rifting, and that ongoing melting and eruption of mostly undifferentiated mafic lavas dominate the > 8 Ma long magmatic history of this region. Among the mafic lavas, most basanites and tephrites

  15. Volcanic Structures Within Niger and Dao Valles, Mars, and Implications for Outflow Channel Evolution and Hellas Basin Rim Development

    Science.gov (United States)

    Korteniemi, J.; Kukkonen, S.

    2018-04-01

    Outflow channel formation on the eastern Hellas rim region is traditionally thought to have been triggered by activity phases of the nearby volcanoes Hadriacus and Tyrrhenus Montes: As a result of volcanic heating subsurface volatiles were mobilized. It is, however, under debate, whether eastern Hellas volcanism was in fact more extensive, and if there were volcanic centers separate from the identified central volcanoes. This work describes previously unrecognized structures in the Niger-Dao Valles outflow channel complex. We interpret them as volcanic edifices: cones, a shield, and a caldera. The structures provide evidence of an additional volcanic center within the valles and indicate volcanic activity both prior to and following the formation of the outflow events. They expand the extent, type, and duration of volcanic activity in the Circum-Hellas Volcanic Province and provide new information on interaction between volcanism and fluvial activity.

  16. Geological evolution of the Boset-Bericha Volcanic Complex, Main Ethiopian Rift: 40Ar/39Ar evidence for episodic Pleistocene to Holocene volcanism

    Science.gov (United States)

    Siegburg, Melanie; Gernon, Thomas M.; Bull, Jonathan M.; Keir, Derek; Barfod, Dan N.; Taylor, Rex N.; Abebe, Bekele; Ayele, Atalay

    2018-02-01

    The Boset-Bericha Volcanic Complex (BBVC) is one of the largest stratovolcanoes of the northern Main Ethiopian Rift (MER). However, very little is known about its eruptive history, despite the fact that approximately 4 million people live within 100 km of the complex. Here, we combine field observations, morphometric analysis using high-resolution LiDAR data, geochemistry and 40Ar/39Ar geochronology to report the first detailed account of the geological evolution of the BBVC, with a focus on extensive young lava flows covering the two edifices, Gudda and Bericha. These lavas exhibit a bimodal composition ranging dominantly from basaltic rift floor lavas and scoria cones, to pantelleritic trachytes and rhyolite flows at Gudda, and comenditic rhyolites at Bericha. Further, several intermediate compositions are associated with fissure vents along the Boset-Kone segment that also appear to link the silicic centres. We divide the BBVC broadly into four main eruptive stages, comprising: (1) early rift floor emplacement, (2) formation of Gudda Volcano within two main cycles, separated by caldera formation, (3) formation of the Bericha Volcano, and (4) sporadic fissure eruptions. Our new 40Ar/39Ar geochronology, targeting a representative array of these flows, provides evidence for episodic activity at the BBVC from 120 ka to the present-day. We find that low-volume mafic episodes are more frequent ( 10 ka cyclicity) than felsic episodes ( 100 ka cyclicity), but the latter are more voluminous. Over the last 30 ka, mafic to intermediate fissure activity might have reinvigorated felsic activity (over the last 16 ka), manifested as peralkaline lava flows and pyroclastic deposits at Gudda and Bericha. Felsic episodes have on average a higher eruption rate (2-5/1000 years) and productivity at Gudda compared to Bericha (1-2/1000 years). The young age of lavas and current fumarolic activity along the fault system, suggest that the BBVC is still potentially active. Coincident

  17. Spectral analysis of geological materials in the Central Volcanic Range of Costa Rica and its relationship to the remote detection of anomalies

    OpenAIRE

    Rejas, J. G.; Martínez-Frías, J.; Martínez, R.; Bonatti, J.

    2014-01-01

    The aim of this work is the comparative study of methods for calculating spectral anomalies from imaging spectrometry in several test areas of the Central Volcanic Range (CVR) of Costa Rica. In the detection of anomalous responses it is assumed no prior knowledge of the targets, so that the pixels are automatically separated according to their spectral information significantly differentiated with respect to a background to be estimated, either globally for the full scene, either locally by i...

  18. Multi-elemental characterization of volcanic and vulcano-sedimentary rocks from Pina petroleum ore, central Cuba

    International Nuclear Information System (INIS)

    Montero-Cabrera, M.E.; Herrera-Peraza, E.; Betancourt-Tanda, L.; Campa-Menendez, R.; Diaz-Rizo, O.; Rodriguez-Martinez, N.; Segura-Soto, R.; Hernandez-Lopez, B.; Valdes-Lopez, S.

    1994-01-01

    Concentrations of 32 elements in 22 clay, limestone, tuff and volcanic rock samples from the Pina ore have been obtained by neutron activation and X-ray fluorescence analyses. Several LILE (large ion lithofile elements) and REE (rare earth element) concentration diagrams showed the calc-alkaline character of the volcanic rocks corresponding to the Greater Antilles Island, Arc. The basaltic andesite behavior of the rocks studied was confirmed by comparing the average concentrations obtained from tuffs and volcanic rocks with proper mean values of rock elemental compositions of the earth's crust. (Author)

  19. Multi-elemental characterization of volcanic and vulcano-sedimentary rocks from Pina petroleum ore, central Cuba

    Energy Technology Data Exchange (ETDEWEB)

    Montero-Cabrera, M.E.; Herrera-Peraza, E.; Betancourt-Tanda, L.; Campa-Menendez, R.; Diaz-Rizo, O. (Instituto Superior de Ciencia y Tecnologia Nuclear (ISCTN), La Habana (Cuba)); Rodriguez-Martinez, N.; Segura-Soto, R.; Hernandez-Lopez, B.; Valdes-Lopez, S. (Centro de Investigaciones y Desarrollo del Petroleo, La Habana (Cuba))

    1994-08-01

    Concentrations of 32 elements in 22 clay, limestone, tuff and volcanic rock samples from the Pina ore have been obtained by neutron activation and X-ray fluorescence analyses. Several LILE (large ion lithofile elements) and REE (rare earth element) concentration diagrams showed the calc-alkaline character of the volcanic rocks corresponding to the Greater Antilles Island, Arc. The basaltic andesite behavior of the rocks studied was confirmed by comparing the average concentrations obtained from tuffs and volcanic rocks with proper mean values of rock elemental compositions of the earth's crust. (Author).

  20. Earth Girl Volcano: An Interactive Casual Game about Complex Volcanic Hazards

    Science.gov (United States)

    Kerlow, I.

    2017-12-01

    Earth Girl Volcano is an interactive casual strategy game for disaster preparedness. The project is designed for mainstream audiences, particularly for children, as an engaging and fun way to learn about volcano hazards, monitoring, and mitigation strategies. The game is deceptively simple but it provides a toolbox to address practically all volcanic hazards ranging from gas and ash fall to pyroclastic flows, lava and lahars. This presentation shows the basic dynamic to explore the area, assess the risk, choose the best-suited tools and execute a mitigation strategy within the available budget. This game is a real-time simulation of a crowd evacuation that allows players to intervene before and during the disaster.

  1. Petrogenesis and depositional history of felsic pyroclastic rocks from the Melka Wakena archaeological site-complex in South central Ethiopia

    Science.gov (United States)

    Resom, Angesom; Asrat, Asfawossen; Gossa, Tegenu; Hovers, Erella

    2018-06-01

    The Melka Wakena archaeological site-complex is located at the eastern rift margin of the central sector of the Main Ethiopian Rift (MER), in south central Ethiopia. This wide, gently sloping rift shoulder, locally called the "Gadeb plain" is underlain by a succession of primary pyroclastic deposits and intercalated fluvial sediments as well as reworked volcaniclastic rocks, the top part of which is exposed by the Wabe River in the Melka Wakena area. Recent archaeological survey and excavations at this site revealed important paleoanthropological records. An integrated stratigraphic, petrological, and major and trace element geochemical study has been conducted to constrain the petrogenesis of the primary pyroclastic deposits and the depositional history of the sequence. The results revealed that the Melka Wakena pyroclastic deposits are a suite of mildly alkaline, rhyolitic pantellerites (ash falls, pumiceous ash falls and ignimbrites) and slightly dacitic ash flows. These rocks were deposited by episodic volcanic eruptions during early to middle Pleistocene from large calderas along the Wonji Fault Belt (WFB) in the central sector of the MER and from large silicic volcanic centers at the eastern rift shoulder. The rhyolitic ash falls, pumiceous ash falls and ignimbrites have been generated by fractional crystallization of a differentiating basaltic magma while the petrogenesis of the slightly dacitic ash flows involved some crustal contamination and assimilation during fractionation. Contemporaneous fluvial activities in the geomorphologically active Gadeb plain deposited overbank sedimentary sequences (archaeology bearing conglomerates and sands) along meandering river courses while a dense network of channels and streams have subsequently down-cut through the older volcanic and sedimentary sequences, redepositing the reworked volcaniclastic sediments further downstream.

  2. Event recognition by detrended fluctuation analysis: An application to Teide-Pico Viejo volcanic complex, Tenerife, Spain

    International Nuclear Information System (INIS)

    Del Pin, Enrico; Carniel, Roberto; Tarraga, Marta

    2008-01-01

    In this work we investigate the application of the detrended fluctuation analysis (DFA) to seismic data recorded in the island of Tenerife (Canary Islands, Spain) during the month of July 2004, in a phase of possible unrest of the Teide-Pico Viejo volcanic complex. Tectonic events recorded in the area are recognized and located by the Spanish national agency Instituto Geografico Nacional (IGN) and their catalogue is the only currently available dataset, whose completeness unfortunately suffers from the strong presence of anthropogenic noise. In this paper we propose the use of DFA to help to automatically identify events. The evaluation of this case study proves DFA to be a promising tool to be used for rapidly screening large seismic datasets and highlighting time windows with the potential presence of discrete events

  3. Carboniferous continental arc in the Hegenshan accretionary belt: Constrains from plutonic complex in central Inner Mongolia

    Science.gov (United States)

    Wei, Ruihua; Gao, Yongfeng; Xu, Shengchuan; Santosh, M.; Xin, Houtian; Zhang, Zhenmin; Li, Weilong; Liu, Yafang

    2018-05-01

    The architecture and tectonic evolution of the Hegenshan accretionary belt in the Central Asian Orogenic Belt (CAOB) remains debated. Here we present an integrated study of zircon U-Pb isotopic ages, whole rock major-trace elements, and Sr-Nd-Pb isotopic data from the Hegenshan volcanic-plutonic belt in central Inner Mongolia. Field observations and zircon U-Pb ages allow us to divide the intrusive complex into an early phase at 329-306 Ma and a late phase at 304 to 299 Ma. The intrusive bodies belong to two magma series: calc-alkaline rocks with I-type affinity and A-type granites. The early intrusions are composed of granodiorite, monzogranite and porphyritic granite, and the late calc-alkaline intrusions include gabbro though diorite to granodiorite. The calc-alkaline intrusive rocks exhibit a well-defined compositional trend from gabbro to granite, reflecting continuous fractional crystallization. These rocks show obvious enrichment in LILEs and LREEs and relative depletion of HFSEs, typical of subduction-related magma. They also exhibit isotopic characteristics of mantle-derived magmas such as low initial 87Sr/86Sr (0.7029-0.7053), positive ɛNd(t) values (0.06-4.76) and low radiogenic Pb isotopic compositions ((206Pb/204Pb)I = 17.907-19.198, (207Pb/204Pb)I = 15.474-15.555, (208Pb/204Pb)I = 37.408-38.893). The marked consistency in geochemical and isotopic compositions between the intrusive rocks and the coeval Baoligaomiao volcanic rocks define a Carboniferous continental arc. Together with available regional data, we infer that this east-west trending continental arc was generated by northward subduction of the Hegenshan ocean during Carboniferous. The late alkali-feldspar granites and the high-Si rhyolites of the Baoligaomiao volcanic succession show similar geochemical compositions with high SiO2 and variable total alkali contents, and low TiO2, MgO and CaO. These rocks are characterized by unusually low Sr and Ba, and high abundances of Zr, Th, Nb, HREEs

  4. Preliminary study of the uranium favorability of Mesozoic intrusive and Tertiary volcanic and sedimentary rocks of the Central Mojave Desert, Kern and San Bernardino counties, California

    International Nuclear Information System (INIS)

    Leedom, S.H.; Kiloh, K.D.

    1978-02-01

    Numerous, small, low-grade, supergene uranium deposits are found in Tertiary volcanic and sedimentary rocks in the central Mojave Desert of southern California. Large thorium-to-uranium ratios in samples of Mesozoic intrusive rocks exposed in the area indicate that these rocks have been extensively weathered, eroded, and subsequently leached by ground waters, and that they may have been the primary source of uranium for the deposits. The uranium content of samples of volcanic intrusive and extrusive rocks is average for intermediate to silicic rocks, but samples of basalt flows in the area contain six times the average uranium content of mafic igneous rocks. Devitrified tuffs and tuffaceous sedimentary rocks, interbedded with calcareous units, are additional sources of uranium for supergene uranium deposits found in calcareous units. Uranium is also found in accessory minerals in a few Mesozoic quartz-rich pegmatite dikes. Uranium deposits in the central Mojave Desert have been formed by enrichment during diagenetic replacement of Tertiary carbonate rocks; by supergene enrichment along fractures, joints, and bedding planes in Tertiary volcanic and sedimentary rocks; during formation of Holocene caliche; and by deposition within hydrothermally altered shear zones. Within the area, the diagenetic replacement type of deposit has the greatest potential for large, low-grade uranium occurrences. The other type of uranium deposits are small, erratically distributed, and extensively covered by alluvium

  5. Evidences of Episodic Crustal Magmatic Diapir and Shallow Volcanic Activity at Uturuncu, Central Andes, from Geodetic Observations between 2014 - 2017

    Science.gov (United States)

    Lau, H. N.; Tymofyeyeva, E.; Fialko, Y. A.

    2017-12-01

    Previous space geodetic studies using ERS-1/2 and Envisat Interferometric Synthetic Aperture Radar (InSAR) data revealed a broad uplift of 10 mm/yr within the Altiplano-Puna Volcanic Complex (APVC), centered at the Uturuncu volcano, surrounded by a ring of subsidence at a rate of a few millimeters per year. This pattern was attributed to formation of a diapir in the middle of the Altiplano-Puna Magma Body (APMB), at depth of 15-19 km. We use new data from the Sentinel-1 InSAR mission, collected between 2014-2017, to produce high-resolution maps of surface displacements in the satellite's line of sight (LOS) from 4 satellite tracks. We estimated random propagation effects (e.g. due to atmospheric turbulence) using a common-point stacking method by Tymofyeyeva and Fialko [2015] and estimated temporally-correlated propagation effects (e.g. due to seasonal variations in atmospheric moisture) using a regression of the residual phase against topography. The estimated atmospheric artifacts were removed from the interferograms prior to computing the time series of the LOS displacements. The data indicate that the uplift above the APMB has considerably slowed down compared to the 1992-2010 epoch. The observed variations in the uplift rate suggest that the "ballooning" of the mid-crustal diapir is episodic on time scales of year to decades, possibly due to variations in melt supply from the partially molten APMB to the incipient diapir. We also find a previously undiscovered localized uplift 11 km south of Uturuncu's peak with maximum LOS velocities of 10 - 15 mm/yr. Joint inversions of data from different satellite tracks for a point source of inflation in an elastic half space constrain the source depth to be at 2 km, suggestive of a shallow magma chamber or a hydrothermal system.

  6. Complex Indigenous Organic Matter Embedded in Apollo 17 Volcanic Black Glass Surface Deposits

    Science.gov (United States)

    Thomas-Keprta, Kathie L.; Clemett, S. J.; Ross, D. K.; Le, L.; Rahman, Z.; Gonzalez, C.; McKay, D. S.; Gibson, E. K.

    2013-01-01

    Papers presented at the first Lunar Science Conference [1] and those published in the subsequent Science Moon Issue [2] reported the C content of Apollo II soils, breccias, and igneous rocks as rang-ing from approx.50 to 250 parts per million (ppm). Later Fegley & Swindle [3] summarized the C content of bulk soils from all the Apollo missions as ranging from 2.5 (Apollo 15) to 280 ppm (Apollo 16) with an overall average of 124+/- 45 ppm. These values are unexpectedly low given that multiple processes should have contributed (and in some cases continue to contribute) to the lunar C inventory. These include exogenous accretion of cometary and asteroidal dust, solar wind implantation, and synthesis of C-bearing species during early lunar volcanism. We estimate the contribution of C from exogenous sources alone is approx.500 ppm, which is approx.4x greater than the reported average. While the assessm ent of indigenous organic matter (OM) in returned lunar samples was one of the primary scientific goals of the Apollo program, extensive analysis of Apollo samples yielded no evidence of any significant indigenous organic species. Furthermore, with such low concentrations of OM reported, the importance of discriminating indigenous OM from terrestrial contamination (e.g., lunar module exhaust, sample processing and handling) became a formidable task. After more than 40 years, with the exception of CH4 [5-7], the presence of indigenous lunar organics still remains a subject of considerable debate. We report for the first time the identification of arguably indigenous OM present within surface deposits of black glass grains collected on the rim of Shorty crater during the Apollo 17 mission by astronauts Eugene Cernan and Harrison Schmitt.

  7. Contrasting sodic and mildly potassic magma differentiation lineages at The Pleaides volcanic complex, northern Victoria Land, Antarctica

    Science.gov (United States)

    Kim, J.; Park, J. W.; Lee, J.; Kyle, P. R.; Lee, M. J.

    2017-12-01

    The magma evolution of The Pleiades, a Quaternary alkaline volcanic complex in northern Victoria Land, Antarctica, is investigated using major and trace elements, and Sr, Nd and Pb isotopic data. The volcanic rocks can be subdivided into two distinct magmatic lineages based on petrography and whole-rock compositions: (1) a sodic silica-undersaturated alkaline lineage with abundant kaersutite phenocrysts, and (2) a mildly-potassic and mildly-alkaline, nearly silica-saturated lineage containing olivine but not kaersutite. The basanite and trachybasalt of both lineages exhibit similar degrees of negative K anomalies, moderately steep rare earth element patterns, and elevated trace element ratios such as Ce/Pb (> 20) and Nb/U (> 38), suggesting their primary magmas were generated by low degree (≤3%) of partial melting of amphibole and garnet-bearing mantle sources. The sodic lineage is characterized by elevated 206Pb/204Pb (>19.5) ratios and narrow ranges of 87Sr/86Sr (0.70313-0.70327) and 143Nd/144Nd (0.51289-0.51290) ratios consistent with a significant HIMU component typical of Neogene volcanic rocks in Antarctica. The mafic rocks of the potassic lineage have isotopic compositions similar to those of the sodic lineage, however the evolved lavas in the lineage have higher 87Sr/86Sr (> 0.7035) and lower 143Nd/144Nd (< 0.51285) and 206Pb/204Pb (< 19.3) ratios than the mafic rocks, suggesting significant amounts of crustal contamination. The pressure-temperature paths estimated by clinopyroxene-liquid thermobarometry are similar in each lineage. The mafic magmas were emplaced at Moho depths ( 1.2 GPa) and the evolved magmas pooled at middle-crustal depths ( 0.7 GPa). Mass-balance calculations based on whole-rock and mineral compositions show that kaersutite fractionation has played a major role in magma differentiation of the sodic lineage whereas the compositional variations of the potassic lineage can be ascribed to fractionation of a kaersutite-free mineral

  8. Cyanobacteria biennal dynamic in a volcanic mesotrophic lake in central Italy: Strategies to prevent dangerous human exposures to cyanotoxins.

    Science.gov (United States)

    Manganelli, Maura; Stefanelli, Mara; Vichi, Susanna; Andreani, Paolo; Nascetti, Giuseppe; Scialanca, Fabrizio; Scardala, Simona; Testai, Emanuela; Funari, Enzo

    2016-06-01

    Vico Lake, a volcanic meso-eutrophic lake in Central Italy, whose water is used for drinking and recreational activities, experienced the presence of the microcystins (MC) producing cyanobacterium Planktothrix rubescens. In order to assess the human health risks and to provide the local health authorities with a scientific basis for planning tailored monitoring activities, we studied P. rubescens ecology and toxicity for two years. P. rubescens generally dominated the phytoplankton community, alternating with Limnothrix redekei, potentially toxic. P. rubescens was distributed throughout the water column during winter; in summer it produced intense blooms where drinking water is collected (-20 m); here MC were detected all year round (0.5-5 μg/L), with implications for drinking water quality. In surface waters, MC posed no risk for recreational activities in summer, while in winter surface blooms and foams (containing up to 56 μg MC/L) can represent a risk for people and children practicing water sports and for animals consuming raw water. Total phosphorus, phosphate and inorganic nitrogen were not relevant to predict densities nor toxicity; however, a strong correlation between P. rubescens density and aminopeptidase ectoenzymatic activity, an enzyme involved in protein degradation, suggested a role of organic nitrogen for this species. The fraction of potentially toxic population, determined both as mcyB(+)/16SrDNA (10-100%) and as the MC/mcyB(+) cells (0.03-0.79 pg MC/cell), was much more variable than usually observed for P. rubescens. Differently from other Italian and European lakes, the correlation between cell density or the mcyB(+) cells and MC explained only ∼50 and 30% of MC variability, respectively: for Vico Lake, monitoring only cell or the mcyB(+) cell density is not sufficient to predict MC concentrations, and consequently to protect population health. Finally, during a winter bloom one site has been sampled weekly, showing that

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

    Science.gov (United States)

    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 engine". High magmatic fluxes during the flare-up would lead to elevated geothermal gradients and efficient crustal processing leading to a dominantly "crustal" magmatism feeding the

  10. Volcanic settings and their reservoir potential: An outcrop analog study on the Miocene Tepoztlán Formation, Central Mexico

    Science.gov (United States)

    Lenhardt, Nils; Götz, Annette E.

    2011-07-01

    The reservoir potential of volcanic and associated sedimentary rocks is less documented in regard to groundwater resources, and oil and gas storage compared to siliciclastic and carbonate systems. Outcrop analog studies within a volcanic setting enable to identify spatio-temporal architectural elements and geometric features of different rock units and their petrophysical properties such as porosity and permeability, which are important information for reservoir characterization. Despite the wide distribution of volcanic rocks in Mexico, their reservoir potential has been little studied in the past. In the Valley of Mexico, situated 4000 m above the Neogene volcanic rocks, groundwater is a matter of major importance as more than 20 million people and 42% of the industrial capacity of the Mexican nation depend on it for most of their water supply. Here, we present porosity and permeability data of 108 rock samples representing five different lithofacies types of the Miocene Tepoztlán Formation. This 800 m thick formation mainly consists of pyroclastic rocks, mass flow and fluvial deposits and is part of the southern Transmexican Volcanic Belt, cropping out south of the Valley of Mexico and within the two states of Morelos and Mexico State. Porosities range from 1.4% to 56.7%; average porosity is 24.8%. Generally, permeabilities are low to median (0.2-933.3 mD) with an average permeability of 88.5 mD. The lavas are characterized by the highest porosity values followed by tuffs, conglomerates, sandstones and tuffaceous breccias. On the contrary, the highest permeabilities can be found in the conglomerates, followed by tuffs, tuffaceous breccias, sandstones and lavas. The knowledge of these petrophysical rock properties provides important information on the reservoir potential of volcanic settings to be integrated to 3D subsurface models.

  11. Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden.

    Science.gov (United States)

    Andersson, Magnus; Almqvist, Bjarne S G; Burchardt, Steffi; Troll, Valentin R; Malehmir, Alireza; Snowball, Ian; Kübler, Lutz

    2016-06-10

    Magma transport through the Earth's crust occurs dominantly via sheet intrusions, such as dykes and cone-sheets, and is fundamental to crustal evolution, volcanic eruptions and geochemical element cycling. However, reliable methods to reconstruct flow direction in solidified sheet intrusions have proved elusive. Anisotropy of magnetic susceptibility (AMS) in magmatic sheets is often interpreted as primary magma flow, but magnetic fabrics can be modified by post-emplacement processes, making interpretation of AMS data ambiguous. Here we present AMS data from cone-sheets in the Alnö carbonatite complex, central Sweden. We discuss six scenarios of syn- and post-emplacement processes that can modify AMS fabrics and offer a conceptual framework for systematic interpretation of magma movements in sheet intrusions. The AMS fabrics in the Alnö cone-sheets are dominantly oblate with magnetic foliations parallel to sheet orientations. These fabrics may result from primary lateral flow or from sheet closure at the terminal stage of magma transport. As the cone-sheets are discontinuous along their strike direction, sheet closure is the most probable process to explain the observed AMS fabrics. We argue that these fabrics may be common to cone-sheets and an integrated geology, petrology and AMS approach can be used to distinguish them from primary flow fabrics.

  12. Petrogenesis of the Cenozoic alkaline volcanic rock series of the České Středohoří Complex (Bohemian Massif), Czech Republic: A case for two lineages

    Czech Academy of Sciences Publication Activity Database

    Dostal, J.; Schellnutt, J. G.; Ulrych, Jaromír

    2017-01-01

    Roč. 317, June (2017), s. 677-706 ISSN 0002-9599 Institutional support: RVO:67985831 Keywords : Bohemian Massif * Central European volcanic province * continental alcaline volcanism * fractional crystallization * magmatic fluids Subject RIV: DB - Geology ; Mineralogy OBOR OECD: Geology Impact factor: 4.099, year: 2016

  13. C-14 dating of volcanic eruptions. Application to the dating of a volcano of the french Massif Central

    International Nuclear Information System (INIS)

    Delibrias, G.; Labeyrie, J.; Pelletier, H.; Perquis, M.Th.

    1960-01-01

    The volcanic eruption of Puy-de-la-Vache (Puy-de-Dome) has been dated by means of age measurements carried out on charcoal fragments found under a flow of lava; the result is 7650 ± 350 years. (author) [fr

  14. Geochronology and petrology of OIB-type lavas from the central part of the Mexican Volcanic Belt

    International Nuclear Information System (INIS)

    Hasenaka, Toshiaki; Yoshida, Takeyoshi; Uto, Kozo; Uchiumi, Shigeru

    1995-01-01

    In Mexican Volcanic Belt, typical continental margin arc volcanic activities have occurred accompanying the subduction of Rivera Plate and Cocos Plate into North American Plate. It has been known by recent geochemical research that the oceanic island type magma which does not show the characteristic chemical composition of subduction zone has extruded. In order to investigate the relation of the development of volcanic belt in continental margin are with the change of wide area tectonics, and to impose important limit on magma formation models, it is important to know the state of production of oceanic island type magma in continental margin arc and the age of its activities. In this report, the results of the K-Ar age measurement for the oceanic island type lava produced in the middle of Mexican Volcanic Belt are shown, and the geochemical features of those samples are clarified. The state of production and the petrography of oceanic island type igneous rock samples are explained. The K-Ar age measurement experiment and the results are reported. The chemical composition of oceanic island type lava determined by photon activation process and fluorescent X-ray analysis is shown. (K.I.)

  15. Evidence for sub-lacustrine volcanic activity in Lake Bolsena (central Italy) revealed by high resolution seismic data sets

    Science.gov (United States)

    Lindhorst, Katja; Krastel, Sebastian; Wagner, Bernd; Schuerer, Anke

    2017-06-01

    The Bolsena caldera that formed between 0.6 and 0.2 Ma has a well preserved structural rim, which makes it an ideal site to study the tectonic and volcanic evolution of calderas. However, the main area is covered by a 150 m deep lake which makes it rather difficult to investigate the subsurface structure directly. To overcome this problem new high resolution hydro-acoustic surveys using a multichannel reflection seismic system and a sediment echo-sounder system were conducted in September 2012. As space was limited we used a rowing boat towed by a rubber boat to handle a 36 m long and 24 channel streamer to receive seismic reflections produced using a Mini GI-Gun (0.25 l). The subsurface structure of Lake Bolsena was imaged up to a sediment depth of 190 m, which is estimated to have filled over a period of 333 kyrs. However, massive pyroclastic flow deposits found in the deeper parts of the basin indicate an initial infill of volcanic deposits from two adjacent younger calderas, the Latera (W) and Montefiascone (SE) calderas. Our data suggest that the caldera has a long history of active volcanism, because the lacustrine sediments show post-sedimentary influences of geothermal fluids. We mapped several mound structures at various stratigraphic depths. Two volcanic structures outcrop at the modern lake surface implying recent activity. One of these structures is hardly covered by sediments and has a crater-like feature in its summit. The other structure shows a pockmark-like depression on top. Another observable feature is a partially sediment filled crater located in the western part of the lake which further implies the existence of a magma chamber located beneath the Bolsena caldera. Since the late Pleistocene and Holocene, the sedimentation was mainly hemipelagic evidenced by a sediment drape of up to 10 m thick sediment drape on the uppermost sediments. Beneath the drape we found evidence for a distal tephra layer likely related to an explosive eruption from

  16. Centralization and Decentralization of Public Policy in a Complex Framework

    Directory of Open Access Journals (Sweden)

    Maria ROSARIA ALFANO

    2009-05-01

    Full Text Available The public economic literature of the past century is characterized by a traditional paradigm that ascribes little attention to the spatial dimension. However, contemporary globalization requires that researchers and economists expand their perspectives to consider space conceptualization. What is required in the 21st century is a richer and more realistic framework that broadens existing concepts of socio-economic analysis while overcoming narrow national borders. Although national governments will remain prominent performers in the global market, regional and local governments cannot be ignored because citizens worldwide are exerting greater self-determination in influencing governmental decisions. This paper is focused on the opportunity to analyze the governance of decentralization by the new optimizing procedures provided by complex system theory. The first section of the paper explores the positive and normative issues related to centralization and decentralization in a globalized framework as well as the increased interdependence in power sharing among different jurisdictional level. In the second section, Kauffman’s (1993 contributions are examined as a means of determining if the fitness landscape allows combining the institutional evolution. Finally, this paper concludes highlighting that complex system theory is one of the possible tools useful to redesign the map of institutional sharing power in an era of globalization, considering that it allows catching Pareto improving in the level of welfare.

  17. Volcanic risk

    International Nuclear Information System (INIS)

    Rancon, J.P.; Baubron, J.C.

    1995-01-01

    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles' volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO 2 , H 2 O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs

  18. C-14 dating of volcanic eruptions. Application to the dating of a volcano of the french Massif Central

    Energy Technology Data Exchange (ETDEWEB)

    Delibrias, G; Labeyrie, J; Pelletier, H; Perquis, M Th [Commissariat a l' Energie Atomique, Saclay (France).Centre d' Etudes Nucleaires

    1960-07-01

    The volcanic eruption of Puy-de-la-Vache (Puy-de-Dome) has been dated by means of age measurements carried out on charcoal fragments found under a flow of lava; the result is 7650 {+-} 350 years. (author) [French] Une mesure d'age effectuee sur des fragments de charbons de bois trouves sous une coulee de lave, au Puy-de-la-Vache (Puy-de-Dome) a permis de dater cette eruption; le resultat est de 7650 {+-} 350 ans. (auteur)

  19. Application of ASAR-ENVISAT Data for Monitoring Andean Volcanic Activity : Results From Lastarria-Azufre Volcanic Complex (Chile-Argentina)

    Science.gov (United States)

    Froger, J.; Remy, D.; Bonvalot, S.; Franco Guerra, M.

    2005-12-01

    Since the pioneer study on Mount Etna by Massonnet et al., in 1995, several works have illustrated the promising potentiality of Synthetic Aperture Radar Interferometry (INSAR) for the monitoring of volcanoes. In the case of wide, remote or hazardous volcanic areas, in particular, INSAR represents a safer and more economic way to acquire measurements than from ground based geodetic networks. Here we present the preliminary results of an interferometric survey made with ASAR-ENVISAT data on a selection of South American volcanoes where deformation signals had been previously evidenced or are expected. An interesting result is the detection of a present-day active ground deformation on the Azufre-Lastarria area (Chile-Argentina) indicating that process, identified during 1998-2000 by Pritchard and Simmons (2004) from ERS data, is still active. The phase signal visible on ASAR interferograms (03/2003-06/2005) is roughly elliptical with a 45 km NNE-SSW major axis. Its amplitude increases as a function of time and is compatible with ground uplift in the line of sight of the satellite. The ASAR time series (up to 840 days, 7 ASAR images) indicates variable deformation rate that might confirm the hypothesis of a non uniform deformation process. We investigated the origin and the significance of the deformation using various source modelling strategies (analytical and numerical). The observed deformation can be explained by the infilling of an elliptical magmatic reservoir lying between 7 and 10 km depth. The deformation could represent the first stage of a new caldera forming as it is correlated with a large, although subtle, topographic depression surrounded by a crown of monogenetic centers. A short wavelength inflation has also been detected on Lastaria volcano. It could result from the on-going infilling of a small subsurface magmatic reservoir, eventually supplied by the deeper one. All these observations point out the need of a closer monitoring of this area in

  20. Origins and exploration significance of replacement and vein-type alunite deposits in the Marysvale volcanic field, west central Utah.

    Science.gov (United States)

    Cunningham, C.G.; Rye, R.O.; Steven, T.A.; Mehnert, H.H.

    1984-01-01

    Alunite in the Marysvale volcanic field forms two (three are described) different types of deposits which contrast in appearance and conditions of origin: 1) Replacement deposits are generally fine-grained and formed by near-surface replacement of intermediate-composition volcanic rocks. The deposits form a bead necklace around a monzonite stock. Each deposit is zoned horizontally from alunitic cores to kaolinitic and propylitic envelopes and zoned vertically from pyrite/propylite upward through alunite/jarosite/hematite to a silica cap. Alunite does not extend below 100 m. Sulphur isotope ratios agree with derivation from underlying Mesozoic evaporites. 2) Natroalunite of 14-m.y. age crosscuts replacement-type alunite deposits. Its S-isotope ratios are comparable with those of pyrite in the volcanics. The Na may be from underlying Mesozoic halites. 3) Veins of coarse-grained alunite of 14-m.y. age filled extension fractures above a postulated stock. S-isotope ratios indicate a probable magmatic source. The contrasting properties of the Marysvale alunite deposits preclude any simple relation to ore deposits, but serve to refine interpretations based on other geological considerations. The replacement deposits are a logical near-surface result of skarn forming processes at depth around the monzonite stock. The vein- type deposits are a logical near-surface result of porphyry metallization in an underlying stock. -G.J.N.

  1. Imaging the Laguna del Maule Volcanic Field, central Chile using magnetotellurics: Evidence for crustal melt regions laterally-offset from surface vents and lava flows

    Science.gov (United States)

    Cordell, Darcy; Unsworth, Martyn J.; Díaz, Daniel

    2018-04-01

    Magnetotelluric (MT) data were collected at the Laguna del Maule volcanic field (LdMVF), located in central Chile (36°S, 70.5°W), which has been experiencing unprecedented upward ground deformation since 2007. These data were used to create the first detailed three-dimensional electrical resistivity model of the LdMVF and surrounding area. The resulting model was spatially complex with several major conductive features imaged at different depths and locations around Laguna del Maule (LdM). A near-surface conductor (C1; 0.5 Ωm) approximately 100 m beneath the lake is interpreted as a conductive smectite clay cap related to a shallow hydrothermal reservoir. At 4 km depth, a strong conductor (C3; 0.3 Ωm) is located beneath the western edge of LdM. The proximity of C3 to the recent Pleistocene-to-Holocene vents in the northwest LdMVF and nearby hot springs suggests that C3 is a hydrous (>5 wt% H2O), rhyolitic partial melt with melt fraction >35% and a free-water hydrothermal component. C3 dips towards, and is connected to, a deeper conductor (C4; 1 Ωm). C4 is located to the north of LdM at >8 km depth below surface and is interpreted as a long-lived, rhyolitic-to-andesitic magma reservoir with melt fractions less than 35%. It is hypothesized that the deeper magma reservoir (C4) is providing melt and hydrothermal fluids to the shallower magma reservoir (C3). A large conductor directly beneath the LdMVF is not imaged with MT suggesting that any mush volume beneath LdM must be anhydrous (10 km) as it moves from the deep magma reservoir (C4) to create small, ephemeral volumes of eruptible melt (C3). It is hypothesized that there may be a north-south contrast in physical processes affecting the growth of melt-rich zones since major conductors are imaged in the northern LdMVF while no major conductors are detected beneath the southern vents. The analysis and interpretation of features directly beneath the lake is complicated by the surface conductor C1 which attenuates

  2. Analysis on the Capacity Building Efforts for Mitigating Volcanic Risks during 2010 Eruption of Mount Merapi, Central Java, Indonesia

    Directory of Open Access Journals (Sweden)

    SARI BAHAGIARTI KUSUMAYUDHA

    2012-12-01

    Full Text Available Mount Merapi is one of the most active volcanoes on the World erupted again during October to November 2010. Its climax activities happened on 5th November at 00.10 pm, with different type of eruption from Mount Merapi of last 50 years. Ordinary, Mount Merapi activity starts from lava dome development, followed by dome collapse to create pyroclastic flow. This specific character of eruption is called Merapi type. The pyroclastic flows at that time killed 341 people and buried many villages on the southeastern slope, while the secondary hazard of lahar destroyed many other human settlements and infrastructures on the western slope of the volcano. Actually, capacity building program in the areas of around Mount Merapi has been established since more than 15 years ago. In most villages, there are community associations that well trained on volcanic hazard mitigation and early warning system. The association name is Association of Mountains Belt of Merapi. Map of Mount Merapi hazards was also already set by the Center of Volcanology and Geologic Disaster Mitigation. Unfortunately, human are not able to order the nature. The character of Mount Merapi eruption in the year 2010 was inconsistent. There was much higher gas pressure, much longer distant of pyroclastic flow, and much greater volume of volcanic material poured from the crater. This made people and stake holders very astonished in handling the evacuation. However, a socio-cultural factor in this respect is that the local people and agriculturists view Mount Merapi as a God which gives them fertile soil and water for agriculture and are reluctant to move away even under an impending threat of a volcanic hazard. This mind-set of people is a challenge in capacity building as the people prefer in-situ protective measures rather than moving away.

  3. Miocene shoshonite volcanism in Sardinia: Implications for magma sources and geodynamic evolution of the central-western Mediterranean

    Science.gov (United States)

    Beccaluva, Luigi; Bianchini, Gianluca; Mameli, Paola; Natali, Claudio

    2013-11-01

    In this paper we document the existence of a Miocene shoshonite (SHO) volcanism in Northern Sardinia (Anglona). This occurrence completes the spectrum of orogenic magmas related to the subduction process which developed from the Eocene along the Palaeo-European continental margin, in concert with the opening of the Ligurian-Balearic back-arc basin and southeastward drift/rotation of the Sardinia-Corsica continental block. K-Ar ages show that the oldest volcanics of the area are calcalkaline (CA) basalts and andesites (~ 21 Ma), overlain by 19.7-18.4 Ma-old more potassic products such as high-potassium calcalkaline (HK-CA) and SHO lavas. CA, HK-CA and SHO suites include basalts and differentiated lavas of andesite and latite composition, respectively, that (according to the PELE software modelling) represent ~ 40-45% residual liquid fraction after shallow fractional crystallization. Application of the "Arc Magma Simulator" software suggests that the generation of primary melts of the distinct suites may occur at similar degrees of partial melting (5-8%) and melting pressures (2-2.2 GPa, ~ 60-70 km depth) in the mantle wedge. By contrast, the potassic character of parental melts of CA, HK-CA and SHO suites is controlled by 1) the amount of subducted continental components (possibly terrigenous sediments) and 2) the pressure (depth) at which these metasomatic agents are released from the slab. Results suggest that the slab depth beneath the volcanic district increased from ~ 80-100 to 100-120 km for CA and SHO magmas, respectively. Accordingly, the evolution from CA to SHO magmatism in the same plumbing system could be related to slab deepening and increase of the subduction angle of ~ 5-10° in the time span of 2-3 Ma. This tectono-magmatic scenario conforms to the major anticlockwise rotation (~ 30°) event of the Sardinia block (between 20.5 and 18 Ma). This geodynamic evolution preludes the development of the volcanism in the Apennine-Tyrrhenian domains, where the

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2013-01-01

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

  6. Chemostratigraphy and evolution of the Paraná Igneous Province volcanism in the central portion of the state of Paraná, Southern Brazil

    Science.gov (United States)

    Gomes, Allan Silva; Licht, Otavio Augusto Boni; Vasconcellos, Eleonora Maria Gouvêa; Soares, Jan Savaris

    2018-04-01

    Analysis of borehole samples offers the potential to investigate the chemostratigraphic variations of a large igneous province in subsurface. New geochemical data based on multielement analyses of 829 chip samples that were obtained during the drilling of seven deep boreholes is presented for the central area of the Paraná Igneous Province (PIP). In order to detail the compositional variations found within the two main types from the Central-Northern Subprovince (CNSP), simple statistical treatment was carried out for part this database. Thus, the combination of low (L) and high (H) contents of Th, Nb, La and Yb was used as a means to create 16 geochemical subtypes for the Type 4 (LSi-LZr-HTi-HP) sequence. Likewise, other four elements (Cr, Ni, Cu and Pd) were selected with the same intention for the Type 1 (Central-Northern) (LSi-LZr-LTi-LP) sequence. When subtypes are plotted in the cross section, it is possible to observe that those with similar characteristics tend to be associated in groups (cycles). This analysis showed that the volcanic pile can be divided into at least eleven different cycles and also that they are laterally continuous throughout the section. The compositional changes observed in these volcanic cycles also display correlations with Mg#, Zr, Ti/Y and La/SmN ratios, for example. Therefore, since the reservoir is marked by periods of injection of more differentiated or more mafic magmas, it could be suggested that it was periodically recharged with batches of magma from the parental source.

  7. An InSAR survey of the central Andes: Constraints on magma chamber geometry and mass balance in a volcanic arc

    Science.gov (United States)

    Pritchard, M. E.; Simons, M.

    2002-12-01

    The central Andes (14-28o S) has a high density of volcanoes, but a sparse human population, such that the activity of most volcanoes is poorly constrained. We use InSAR to conduct the first systematic observations of deformation at nearly 900 volcanoes (about 50 of which are classified ``potentially active'') during the 1992-2002 time interval. We find volcanic deformation in four locations. Subsidence is seen at Robledo (or Cerro Blanco) caldera, Argentina. We observe inflation at the stratovolcano Uturuncu, Bolivia, near stratovolcano Hualca Hualca, Peru, and in a region not associated with any known edifice on the border between Chile and Argentina that we call ``Lazufre'' because it lies between volcanoes Lastarria and Cordon del Azufre. The deformation pattern can be well explained by a uniform point-source source of inflation or deflation, but we compare these model results with those from a tri-axial point-source ellipsoid to test the robustness of estimated source depth and source strength (inferred here to be volume change). We further explore the sensitivity of these parameters to elastic half-space and layered-space models of crustal structure, and the influence of local topography. Because only one satellite look direction is available for most time periods, a variety of models are consistent with our observations. If we assume that inflation is due solely to magmatic intrusion, we can compare the rate of magma intrusion to volcanic extrusion during the decade for which data is available and the longer-term geologic rate. For the last decade, the ratio of volume intruded to extruded is between about 1-10, which agrees with previous geologic estimates in this and other volcanic arcs. The combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate.

  8. Hydrothermal activity in the Tulancingo-Acoculco Caldera Complex, central Mexico. Exploratory studies

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Hernandez, Aida [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico); Garcia-Estrada, Gerardo; Palma-Guzman, Hugo; Quijano-Leon, Jose L. [Gerencia de Proyectos Geotermoelectricos, CFE, Alejandro Volta 655, 58290 Morelia, Michoacan (Mexico); Aguirre-Diaz, Gerardo; Gonzalez-Partida, Eduardo [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico)

    2009-09-15

    Mineral alteration and fluid inclusion studies of drill cuttings and core samples indicate that the sedimentary basement rocks and the volcanic rocks associated with Tulancingo-Acoculco Caldera Complex have been the site of two distinct and major hydrothermal events. The complex, located in the eastern portion of the Trans-Mexican Volcanic Belt, is formed by the Pliocene Tulancingo Caldera and the younger (Pleistocene) Acoculco Caldera, which developed within the older depression. The volcanic rocks are underlain by Cretaceous sedimentary rocks of the Sierra Madre Oriental. The earliest important hydrothermal event occurred during the emplacement of Mid-Tertiary granitic intrusions that metamorphosed the sedimentary rocks; these intrusives are not exposed at the surface. However, granitic rocks were encountered at the bottom of exploratory borehole EAC-1, drilled within the Caldera Complex. The second main event occurred during the formation of the Tulancingo and Acoculco Calderas. Both episodes lead to secondary mineralization that reduced the permeability of the reservoir rocks. A possible third hydrothermal event may be associated with the recent magmatic activity within the Acoculco Caldera.Thermal logs from well EAC-1 display a conductive thermal gradient with maximum temperatures exceeding 300 C at 2000 m depth. Although there are no active thermal springs in the area, there is extensive fossil surface hydrothermal alteration and cold gas discharges with high He{sup 3}/He{sup 4} ratios. (author)

  9. Insights from gas and water chemistry on the geothermal system of the Domuyo volcanic complex (Patagonia, Argentina)

    Science.gov (United States)

    Tassi, F.; Liccioli, C.; Chiodini, G.; Agusto, M.; Caselli, A. T.; Caliro, S.; Vaselli, O.; Pecoraino, G.

    2015-12-01

    This study focuses on the geochemistry of geothermal fluids discharging from the western flank of the Domuyo volcanic complex (Argentina), which is hosted within an extensional basins that interrupts the Andes at latitudes comprises between 35° and 39°S. The analytical results of gas and water samples collected during three sampling campaigns (2013, 2014 and 2015) are presented and discussed in order to: i) evaluate the equilibrium temperature(s) of the main fluid reservoir, ii) provide information on the origin of the fluid discharges and the secondary processes controlling their chemistry. Geothermometry based on the chemical composition of thermal waters indicates a maximum equilibrium temperature of 220 °C. This temperature, coupled with the measured amount of discharged Cl, suggest that the total energy released from this system is 1.1±0.2 GW. Atmospheric gases from a thick shallow aquifer contaminate most gas emissions, masking the chemical features of the deep fluid component, with the only exception of a jet fumarole located at 3,000 m a.s.l. (Bramadora). The H2O-CO2-CH4-H2-CO-C3H6-C3H8 composition of this gas emission was used to construct a geochemical conceptual model showing that the hydrothermal reservoir is liquid-dominated and thermally stratified, with temperatures ranging from 180 to 270 °C. The helium isotopic ratios (up to 6.8 Ra) and the δ13C-CO2 values (from -7.05 to -7.75 ‰ V-PDB) indicate that mantle degassing represents the dominant primary source for this dormant volcano. These results highlight the huge potential of this system as energy resource for the region. Accordingly, the regional authorities have recently planned and approved an investigation project aimed to provide further insights into the fluid geochemistry and the geostructural assessment in this promising area.

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

    Science.gov (United States)

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

    2010-01-01

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

  11. The Triassic-Liassic volcanic sequence and rift evolution in the Saharan Atlas basins (Algeria). Eastward vanishing of the Central Atlantic magmatic province

    International Nuclear Information System (INIS)

    Meddah, A.; Bertrand, H.; Seddiki, A.; Tabeliouna, M.

    2017-01-01

    We investigate the Triassic-Liassic sequence in ten diapirs from the Saharan Atlas (Algeria). Based on detailed mapping, two episodes are identified. The first one consists of a volcano-sedimentary sequence in which three volcanic units were identified (lower, intermediate and upper units). They are interlayered and sometimes imbricated with siliciclastic to evaporitic levels which record syn-sedimentary tectonics. This sequence was deposited in a lagoonal-continental environment and is assigned to the Triassic magmatic rifting stage. The second episode, lacking lava flows (post magmatic rifting stage), consists of carbonate levels deposited in a lagoonal to marine environment during the Rhaetian-Hettangian. The volcanic units consist of several thin basaltic flows, each 0.5 to 1m thick, with a total thickness of 10–15m. The basalts are low-Ti continental tholeiites, displaying enrichment in large ion lithophile elements and light rare earth elements [(La/Yb)n= 2.5-6] with a negative Nb anomaly. Upwards decrease of light-rare-earth-elements enrichment (e.g. La/Yb) is modelled through increasing melting rate of a spinel-bearing lherzolite source from the lower (6–10wt.%) to the upper (15–20wt.%) unit. The lava flows from the Saharan Atlas share the same geochemical characteristics and evolution as those from the Moroccan Atlas assigned to the Central Atlantic magmatic province. They represent the easternmost witness of this large igneous province so far known.

  12. The Triassic-Liassic volcanic sequence and rift evolution in the Saharan Atlas basins (Algeria). Eastward vanishing of the Central Atlantic magmatic province

    Energy Technology Data Exchange (ETDEWEB)

    Meddah, A.; Bertrand, H.; Seddiki, A.; Tabeliouna, M.

    2017-11-01

    We investigate the Triassic-Liassic sequence in ten diapirs from the Saharan Atlas (Algeria). Based on detailed mapping, two episodes are identified. The first one consists of a volcano-sedimentary sequence in which three volcanic units were identified (lower, intermediate and upper units). They are interlayered and sometimes imbricated with siliciclastic to evaporitic levels which record syn-sedimentary tectonics. This sequence was deposited in a lagoonal-continental environment and is assigned to the Triassic magmatic rifting stage. The second episode, lacking lava flows (post magmatic rifting stage), consists of carbonate levels deposited in a lagoonal to marine environment during the Rhaetian-Hettangian. The volcanic units consist of several thin basaltic flows, each 0.5 to 1m thick, with a total thickness of 10–15m. The basalts are low-Ti continental tholeiites, displaying enrichment in large ion lithophile elements and light rare earth elements [(La/Yb)n= 2.5-6] with a negative Nb anomaly. Upwards decrease of light-rare-earth-elements enrichment (e.g. La/Yb) is modelled through increasing melting rate of a spinel-bearing lherzolite source from the lower (6–10wt.%) to the upper (15–20wt.%) unit. The lava flows from the Saharan Atlas share the same geochemical characteristics and evolution as those from the Moroccan Atlas assigned to the Central Atlantic magmatic province. They represent the easternmost witness of this large igneous province so far known.

  13. New evidence of effusive and explosive volcanism in the Lower Carboniferous formations of the Moroccan Central Hercynian Massif: Geochemical data and geodynamic significance

    Science.gov (United States)

    Ntarmouchant, A.; Smaili, H.; Bento dos Santos, T.; Dahire, M.; Sabri, K.; Ribeiro, M. L.; Driouch, Y.; Santos, R.; Calvo, R.

    2016-03-01

    The Azrou-Khénifra basin, located in the SE sector of the Moroccan Central Hercynian Massif of the Western Meseta of Morocco comprises volcanic and volcanoclastic rocks where two magmatic sequences can be distinguished: i) the Dhar Lahmar Sequence, composed of Upper Visean basaltic lava flows and pyroclastic deposits; and ii) the Kef Al Asri Sequence, composed of Visean - Serpukhovian intermediate to acid rocks. A continuous spatial and temporal evolution between the two volcano-sedimentary sequences was observed during the detailed geological work performed in the studied area. Petrography and geochemical studies additionally suggest a continuous compositional evolution from the more basic magmatic rocks to the intermediate/acid rocks, which implies a cogenetic magmatic differentiation controlled by crystal fractionation (with minor crustal assimilation) of a calc-alkaline trend magmatic suite. The inferred magmatic evolution is consistent with a geodynamic environment of an orogenic zone within an active continental margin setting. This partly explosive Visean - Serpukhovian volcanism, identified for the first time in the Western Meseta of Morocco, displays very similar petrographic and geochemical characteristics to its Eastern Meseta analogues, which implies that the emplacement of these magmatic rocks must have occurred in similar collisional geodynamic settings for both major geological domains, further constraining the evolution of this major crustal segment within the Carboniferous events that shaped the Hercynian Orogeny.

  14. A new estimate for present-day Cocos-Caribbean Plate motion: Implications for slip along the Central American Volcanic Arc

    Science.gov (United States)

    DeMets, Charles

    Velocities from 153 continuously-operating GPS sites on the Caribbean, North American, and Pacific plates are combined with 61 newly estimated Pacific-Cocos seafloor spreading rates and additional marine geophysical data to derive a new estimate of present-day Cocos-Caribbean plate motion. A comparison of the predicted Cocos-Caribbean direction to slip directions of numerous shallow-thrust subduction earthquakes from the Middle America trench between Costa Rica and Guatemala shows the slip directions to be deflected 10° clockwise from the plate convergence direction, supporting the hypothesis that frequent dextral strike-slip earthquakes along the Central American volcanic arc result from partitioning of oblique Cocos-Caribbean plate convergence. Linear velocity analysis for forearc locations in Nicaragua and Guatemala predicts 14±2 mm yr-1 of northwestward trench-parallel slip of the forearc relative to the Caribbean plate, possibly decreasing in magnitude in El Salvador and Guatemala, where extension east of the volcanic arc complicates the tectonic setting.

  15. Unravelling the Volcanological Complexities of a Flood Basalt Province: Volcanology, Paleomagnetism and Geochemistry, From the Deccan Volcanic Province

    Science.gov (United States)

    Jay, A. E.; Widdowson, M.; Self, S.; Mac Niocaill, C.

    2006-12-01

    The lavas of the Deccan Volcanic Province (DVP), India, were erupted across the Cretaceous-Tertiary boundary (KTB) and, as such, have been suggested as a candidate for causing the KTB mass extinction event. Understanding the development of such large outpourings of lava is essential to deducing their environmental impact. Detailed flow-by-flow logging was undertaken along four roads up the Mahabaleshwar Plateau, and a further three road sections to the north and south were investigated in order to study the volcanological style of this area of the DVP. Logging along the four roads which ascend the Mahabaleshwar Plateau was combined with detailed geochemical and paleomagnetic sampling and provides the first integrated study of its kind in the DVP. The logging demonstrated that almost all the lavas encountered were inflated pahoehoe sheet lobes. No `a'a flows were encountered and one rubbly pahoehoe flow may have been observed. Statistical analyses of XRF trace element data, and the occurrence of differing thicknesses and numbers of lava units between the paleomagnetic reversal horizon (Chron 29r/29n) and the top of the Ambenali Formation, suggest that individual sheet lobes are not greater than the width of the Plateau c. 20 km. This provides an explanation for the topography, up to 95 m in our study area, on the surface of the DVP at the time when the lavas were being erupted. As the sheet lobes were emplaced and inflated they left areas uncovered by lava, the topographic difference between these two areas could be many 10s of metres, and as this process occurred over the whole DVP the topographic differences could increase. As well as topography, this leads to other complexities. When later lavas in-fill these depressions it causes them to occur physically lower in the sequence than older lavas. This demonstrates that the previously held concept of large, flat-lying sheets lobes covering vast tracts of the province is not probable, as on the local scale tracing

  16. Palaeomagnetism of the Cappadocian Volcanic Succession, Central Turkey: Major ignimbrite emplacement during two short (Miocene) episodes and Neogene tectonics of the Anatolian collage

    Science.gov (United States)

    Piper, J. D. A.; Koçbulut, F.; Gürsoy, H.; Tatar, O.; Viereck, L.; Lepetit, P.; Roberts, A. P.; Akpınar, Z.

    2013-07-01

    The Central Anatolian Volcanic Province in Cappadocia includes 13 high volume calc-alkaline ignimbrite sheets emplaced by plinian eruptions within a succession (the Ürgüp Formation) after ~ 10 Ma recording the last phase of Neotethyan subduction and accompanying emplacement of the Tauride orogen in southern Turkey. To evaluate magnetostratigraphy in the context of recent revisions of the chronostratigraphy we have extended palaeomagnetic investigation to 32 new sites yielding significant ChRM directions. Integrated rock magnetic and palaeomagnetic investigations identify magnetic remanence residing predominantly in Ti-poor titanomagnetites although secondary processes within the ignimbrite sheets, notably post-emplacement oxidation, have locally produced hematisation expressed by composite IRM spectra and variable reduction in intensity of magnetisation. The ignimbrite sheets possess weak anisotropies of magnetic susceptibility (AMS, mostly < 5%) describing tensors with axial distributions close to bedding and minimum axes predominantly perpendicular to this plane; collectively directions show weak imbrication correlating with palaeoflow during emplacement predominantly towards the north and east away from the Erdas Dağ, an inferred topographic palaeohigh at the southern margin of the basin. The precise control provided by magnetostratigraphy and radiometric age dating now shows that the bulk of Cappadocian ignimbrite magmatism was concentrated into two short episodes. An older Cardak Centre (Kavak Group and Zelve ignimbrites) produced in excess of 200 km3 of pyroclastic deposits during polarity chron C4r.1n between 9.31 and 9.43 Ma. Subsequent activity from the Acıgöl Centre further to the south west (Cemilköy, Gelveri, Gördeles, and Kızılkaya) produced in excess of 620 km3 of pyroclastic deposits during polarity chrons between 5.3 and 7.1 Ma. The younger İncesu ignimbrite was sourced in the Sultansazlığı pull-apart basin to the east during the Gauss

  17. Volcanic hotspots of the central and southern Andes as seen from space by ASTER and MODVOLC between the years 2000-2011

    Science.gov (United States)

    Jay, J.; Pritchard, M. E.; Mares, P. J.; Mnich, M. E.; Welch, M. D.; Melkonian, A. K.; Aguilera, F.; Naranjo, J.; Sunagua, M.; Clavero, J. E.

    2011-12-01

    We examine 153 volcanoes and geothermal areas in the central, southern, and austral Andes for temperature anomalies between 2000-2011 from two different spacebourne sensors: 1) those automatically detected by the MODVOLC algorithm (Wright et al., 2004) from MODIS and 2) manually identified hotspots in nighttime images from ASTER. Based on previous work, we expected to find 8 thermal anomalies (volcanoes: Ubinas, Villarrica, Copahue, Láscar, Llaima, Chaitén, Puyehue-Cordón Caulle, Chiliques). We document 31 volcanic areas with pixel integrated temperatures of 4 to more than 100 K above background in at least two images, and another 29 areas that have questionable hotspots with either smaller anomalies or a hotspot in only one image. Most of the thermal anomalies are related to known activity (lava and pyroclastic flows, growing lava domes, fumaroles, and lakes) while others are of unknown origin or reflect activity at volcanoes that were not thought to be active. A handful of volcanoes exhibit temporal variations in the magnitude and location of their temperature anomaly that can be related to both documented and undocumented pulses of activity. Our survey reveals that low amplitude volcanic hotspots detectable from space are more common than expected (based on lower resolution data) and that these features could be more widely used to monitor changes in the activity of remote volcanoes. We find that the shape, size, magnitude, and location on the volcano of the thermal anomaly vary significantly from volcano to volcano, and these variations should be considered when developing algorithms for hotspot identification and detection. We compare our thermal results to satellite InSAR measurements of volcanic deformation and find that there is no simple relationship between deformation and thermal anomalies - while 31 volcanoes have continuous hotspots, at least 17 volcanoes in the same area have exhibited deformation, and these lists do not completely overlap. In

  18. About the use of radon in the surveillance of volcanoes from Central America; De l`utilisation du radon dans la surveillance des volcans d`amerique centrale

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, E [Obviscori, Heridia (Costa Rica); Garcia Vindas, R; Monnin, M; Seidel, J L [Centre National de la Recherche Scientifique (CNRS), 34 -Montpellier (France). Centre d` Etudes Phytosociologiques et Ecologiques Louis-Emberger; Segovia, N [ININ, Mexico (Mexico)

    1997-12-31

    Anomalous fluctuations of radon content in soil gases, fumaroles or thermal sources associated with volcanic systems are considered as precursors of deep degassing phenomena. Radon measurements in soil gases were performed for several years on three active volcanoes of Costa-Rica (Arenal, Irazu, Poas), also on El Chichon and Colima volcanoes in Mexico and more recently on the Popocatepetl since its reactivation in December 1994. Data acquisition was initially performed using plastic detectors with a 15 days integration. Since 1993, autonomous automatic probes are used and give hourly measurements. A nine stations network for ground measurements is installed on the Poas since 1982. Radon and Cl{sup -}, F{sup -} and SO{sub 4}{sup 2-} variations of the main crater lake are examined and correlated with the volcanic activity which led to the decay and disappearing of the lake in April 1989. On the Irazu, five stations were installed in 1982 and 3 automatic ones were added in November 1993. Results obtained so far are discussed according to the phreatic eruption of December 1994. The Popocatepetl measurements obtained since December 1994 are presented too. Abstract only. (J.S.).

  19. About the use of radon in the surveillance of volcanoes from Central America; De l`utilisation du radon dans la surveillance des volcans d`amerique centrale

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, E. [Obviscori, Heridia (Costa Rica); Garcia Vindas, R.; Monnin, M.; Seidel, J.L. [Centre National de la Recherche Scientifique (CNRS), 34 -Montpellier (France). Centre d`Etudes Phytosociologiques et Ecologiques Louis-Emberger; Segovia, N. [ININ, Mexico (Mexico)

    1996-12-31

    Anomalous fluctuations of radon content in soil gases, fumaroles or thermal sources associated with volcanic systems are considered as precursors of deep degassing phenomena. Radon measurements in soil gases were performed for several years on three active volcanoes of Costa-Rica (Arenal, Irazu, Poas), also on El Chichon and Colima volcanoes in Mexico and more recently on the Popocatepetl since its reactivation in December 1994. Data acquisition was initially performed using plastic detectors with a 15 days integration. Since 1993, autonomous automatic probes are used and give hourly measurements. A nine stations network for ground measurements is installed on the Poas since 1982. Radon and Cl{sup -}, F{sup -} and SO{sub 4}{sup 2-} variations of the main crater lake are examined and correlated with the volcanic activity which led to the decay and disappearing of the lake in April 1989. On the Irazu, five stations were installed in 1982 and 3 automatic ones were added in November 1993. Results obtained so far are discussed according to the phreatic eruption of December 1994. The Popocatepetl measurements obtained since December 1994 are presented too. Abstract only. (J.S.).

  20. Gas geochemistry of the magmatic-hydrothermal fluid reservoir in the Copahue-Caviahue Volcanic Complex (Argentina)

    Science.gov (United States)

    Agusto, M.; Tassi, F.; Caselli, A. T.; Vaselli, O.; Rouwet, D.; Capaccioni, B.; Caliro, S.; Chiodini, G.; Darrah, T.

    2013-05-01

    Copahue volcano is part of the Caviahue-Copahue Volcanic Complex (CCVC), which is located in the southwestern sector of the Caviahue volcano-tectonic depression (Argentina-Chile). This depression is a pull-apart basin accommodating stresses between the southern Liquiñe-Ofqui strike slip and the northern Copahue-Antiñir compressive fault systems, in a back-arc setting with respect to the Southern Andean Volcanic Zone. In this study, we present chemical (inorganic and organic) and isotope compositions (δ13C-CO2, δ15N, 3He/4He, 40Ar/36Ar, δ13C-CH4, δD-CH4, and δD-H2O and δ18O-H2O) of fumaroles and bubbling gases of thermal springs located at the foot of Copahue volcano sampled in 2006, 2007 and 2012. Helium isotope ratios, the highest observed for a Southern American volcano (R/Ra up to 7.94), indicate a non-classic arc-like setting, but rather an extensional regime subdued to asthenospheric thinning. δ13C-CO2 values (from - 8.8‰ to - 6.8‰ vs. V-PDB), δ15N values (+ 5.3‰ to + 5.5‰ vs. Air) and CO2/3He ratios (from 1.4 to 8.8 × 109) suggest that the magmatic source is significantly affected by contamination of subducted sediments. Gases discharged from the northern sector of the CCVC show contribution of 3He-poor fluids likely permeating through local fault systems. Despite the clear mantle isotope signature in the CCVC gases, the acidic gas species have suffered scrubbing processes by a hydrothermal system mainly recharged by meteoric water. Gas geothermometry in the H2O-CO2-CH4-CO-H2 system suggests that CO and H2 re-equilibrate in a separated vapor phase at 200°-220 °C. On the contrary, rock-fluid interactions controlling CO2, CH4 production from Sabatier reaction and C3H8 dehydrogenation seem to occur within the hydrothermal reservoir at temperatures ranging from 250° to 300 °C. Fumarole gases sampled in 2006-2007 show relatively low N2/He and N2/Ar ratios and high R/Ra values with respect to those measured in 2012. Such compositional and

  1. Reconstructing the eruption magnitude and energy budgets for the pre-historic eruption of the monogenetic ˜5 ka Mt. Gambier Volcanic Complex, south-eastern Australia

    Science.gov (United States)

    van Otterloo, Jozua; Cas, Raymond A. F.

    2013-12-01

    Understanding explosive volcanic eruptions, especially phreatomagmatic eruptions, their intensities and energy budgets is of major importance when it comes to risk and hazard studies. With only a few historic occurrences of phreatomagmatic activity, a large amount of our understanding comes from the study of pre-historic volcanic centres, which causes issues when it comes to preservation and vegetation. In this research, we show that using 3D geometrical modelling it is possible to obtain volume estimates for different deposits of a pre-historic, complex, monogenetic centre, the Mt. Gambier Volcanic Complex, south-eastern Australia. Using these volumes, we further explore the energy budgets and the magnitude of this eruption (VEI 4), including dispersal patterns (eruption columns varying between 5 and 10 km, dispersed towards north-east to south), to further our understanding of intraplate, monogenetic eruptions involving phreatomagmatic activity. We also compare which thermodynamic model fits best in the creation of the maar crater of Mt. Gambier: the major-explosion-dominated model or the incremental growth model. In this case, the formation of most of the craters can best be explained by the latter model.

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

    Science.gov (United States)

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

    2017-09-01

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

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

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D.; Sudhakar, M.

    Volcanologlst Association, Napoh, 128 pp. PAUTOT G and M HOFFERT (1984) Les nodules du Pactfique Central darts leur environment geologtque Campagne CopantT--1979 Publication du CNEXO, 26, 202 pp PATRIAT P and J SECOUFIN (1988) Reconstruction of the Central...

  4. Volcanic deformation in the Andes

    Science.gov (United States)

    Riddick, S.; Fournier, T.; Pritchard, M.

    2009-05-01

    We present the results from an InSAR survey of volcanic activity in South America. We use data from the Japanese Space Agency's ALOS L-band radar satellite from 2006-2009. The L-band instrument provides better coherence in densely vegetated regions, compared to the shorter wave length C-band data. The survey reveals volcano related deformation in regions, north, central and southern, of the Andes volcanic arc. Since observations are limited to the austral summer, comprehensive coverage of all volcanoes is not possible. Yet, our combined observations reveal volcanic/hydrothermal deformation at Lonquimay, Llaima, Laguna del Maule, and Chaitén volcanoes, extend deformation measurements at Copahue, and illustrate temporal complexity to the previously described deformation at Cerro Hudson and Cordón Caulle. No precursory deformation is apparent before the large Chaitén eruption (VEI_5) of 2 May 2008, (at least before 16 April) suggesting rapid magma movement from depth at this long dormant volcano. Subsidence at Ticsani Volcano occurred coincident with an earthquake swarm in the same region.

  5. Correlation and stratigraphic eruption age of the pyroclastic flow deposits and wide spread volcanic ashes intercalated in the Pliocene-Pleistocene strata, central Japan

    International Nuclear Information System (INIS)

    Nagahashi, Yoshitaka; Satoguchi, Yasufumi; Yoshikawa, Shusaku

    2000-01-01

    Three pyroclastic flow deposits in the Takayama and Omine area, central Honshu, are correlated to the distal widespread volcanic ashes intercalated in the Plio-Pleistocene boundary strata in central Japan. The correlation is based on these stratigraphic relationships, facies, magnetostratigraphy, petrographic properties such as mineral assemblage, refractive index and chemical composition of the volcanic glasses and orthopyroxene. As the result of these correlation, the eruption age of the proximal pyroclastic flow deposits have become clear. And precise correlation between proximal eruption units and distal depositional units is now possible. Ho-Kd 39 Tephra erupted at about 1.76 Ma, forming a co-ignimbrite ash, which deposited in the Kanto sedimentary basin. Eb-Fukuda Tephra erupted at about 1.75 Ma, and distal volcaniclastic deposit sedimented in the Kinki, Niigata and Kanto sedimentary basins. The eruptional and depositional phase are divided into the stage 1, stage 2 (early), stage 2 (late) and stage 3. Stage 1 is phreato-plinian type eruption phase, forming distal ash fall deposit. Stage 2 (early) is plinian pumice fall, intra-plinian pyroclastic flow and plinian pumice fall eruption phase, forming distal ash fall. Stage 2 (late) is final eruptional phase of the biggest pyroclastic flow of the Eb-Fukuda Tephra, forming a co-ignimbrite ash fall. Stage 3 is resedimented stage after the end of the explosive eruption. It is notable that resedimented volcaniclastic deposit reached Osaka sedimentary basin 300 km away from the eruption center. Om-SK110 Tephra erupted at about 1.65 Ma, divided into the stage 1, stage 2 and stage 3. Stage 1 is eruption phase of the plinian pumice fall and first pyroclastic flow. Stage 2 is pauses in eruption activity. Stage 3 is second pyroclastic flow phase, it is inferred that the pyroclastic flow of the stage 3 directly entered the Niigata sedimentary basin and simultaneously formed a co-ignimbrite ash. (author)

  6. A geochemical approach for assessing the possible uses of the geothermal resource in the eastern sector of the Sabatini Volcanic District (Central Italy)

    Science.gov (United States)

    Cinti, Daniele; Tassi, Franco; Procesi, Monia; Brusca, Lorenzo; Cabassi, Jacopo; Capecchiacci, Francesco; Delgado Huertas, Antonio; Galli, Gianfranco; Grassa, Fausto; Vaselli, Orlando; Voltattorni, Nunzia

    2017-04-01

    The Sabatini Volcanic District (SVD) hosts a hydrothermal reservoir heated by the post-magmatic activity that affected the peri-Tyrrhenian sector of central Italy, giving rise to a number of thermal and mineral discharges. In this study, a complete geochemical and isotopic dataset based on the composition of 215 water and 9 bubbling gases, collected from the eastern sector of this huge hydrothermal system, is reported. The main aims are to (i) investigate the fluid sources and the main chemical-physical processes controlling the fluid chemistry and (ii) construct a conceptual fluid circulation model to provide insights into the possible use(s) of the geothermal resource. The fluid discharges are fed by two main aquifers, characterized by: (1) a Ca-HCO3 to Ca(Na)-HCO3 composition, typical of a shallow hydrological circuit within volcanic and sedimentary formations, and (2) a Ca-HCO3(SO4) to Na(Ca)-HCO3(Cl) composition, produced by the interaction of CO2-rich fluids with Mesozoic and Triassic carbonate-evaporite rocks. A thick sequence of low-permeability volcanic products represents a physical barrier between the two fluid reservoirs. As commonly occurring in central-southern Italy, CO2 is mainly produced by thermo-metamorphic decarbonation within the carbonate-evaporite reservoir, with minor contribution of mantle CO2. A dominant crustal source is also indicated by the relatively low R/Ra values (0.07-1.04). Methane and light hydrocarbons are mostly thermogenic, whereas H2S derives from thermogenic reduction of the Triassic anhydrites. Slightly positive 15N/14N values suggest minor N2 contribution from deep sedimentary sources. On the whole, a comparison of these geochemical features with those of the thermal fluids from the western portion of SVD highlights an eastward increasing influence of the shallow aquifer on the deep-originated fluids, likely caused by the proximity of the Apennine range from where the meteoric water, recharging the hydrothermal system

  7. The Mons Rümker volcanic complex of the Moon: A candidate landing site for the Chang'E-5 mission

    Science.gov (United States)

    Zhao, Jiannan; Xiao, Long; Qiao, Le; Glotch, Timothy D.; Huang, Qian

    2017-07-01

    Mons Rümker is a large volcanic complex in Oceanus Procellarum on the Moon and is a candidate landing site for China's Chang'E-5 sample return mission. We conducted a comprehensive study of the topography, geomorphology, composition, and stratigraphy of the Mons Rümker region with multisource remote sensing data in order to better understand the geology of the region and provide further support for the Chang'E-5 mission. The results show that the Rümker plateau stands 200-1300 m above the surrounding mare surface and 75% of the plateau has a slope of less than 3° at a baseline length of 30 m. Domes are the most prominent volcanic landforms in Mons Rümker and a total of 22 domes were identified and divided into two types that may represent different stages of volcanic activity. Spectral analyses indicated that Mons Rümker is covered by low-Ti basalt and the dominant mafic mineral is high-calcium pyroxene, though signs of mixing of highland materials and basalt have been found. Mons Rümker has three main basalt units, and their absolute model ages are 3.71 Ga, 3.58 Ga, and 3.51 Ga, respectively. Steep-sided domes could be the youngest volcanic features on the plateau with indications that they were active until the Eratosthenian. A new geologic map of the study region was produced and used to interpret and discuss the geologic evolution of the region. Finally, we propose two candidate landing sites for the Chang'E-5 mission.

  8. Constraining Silicate Weathering Processes in an Active Volcanic Complex: Implications for the Long-term Carbon Cycle

    Science.gov (United States)

    Washington, K.; West, A. J.; Hartmann, J.; Amann, T.; Hosono, T.; Ide, K.

    2017-12-01

    While analyzing geochemical archives and carbon cycle modelling can further our understanding of the role of silicate weathering as a sink in the long-term carbon cycle, it is necessary to study modern weathering processes to inform these efforts. A recent compilation of data from rivers draining basaltic catchments estimates that rock weathering in active volcanic fields (AVFs) consumes atmospheric CO2 approximately three times faster than in inactive volcanic fields (IVFs), suggesting that the eruption and subsequent weathering of large igneous provinces likely played a major role in the carbon cycle in the geologic past [1]. The study demonstrates a significant correlation between catchment mean annual temperature (MAT) and atmospheric CO2 consumption rate for IVFs. However CO2 consumption due to weathering of AVFs is not correlated with MAT as the relationship is complicated by variability in hydrothermal fluxes, reactive surface area, and groundwater flow paths. To investigate the controls on weathering processes in AVFs, we present data for dissolved and solid weathering products from Mount Aso Caldera, Japan. Aso Caldera is an ideal site for studying the how the chemistry of rivers draining an AVF is impacted by high-temperature water/rock interactions, volcanic ash weathering, and varied groundwater flow paths and residence times. Samples were collected over five field seasons from two rivers and their tributaries, cold groundwater springs, and thermal springs. These samples capture the region's temperature and precipitation seasonality. Solid samples of unaltered volcanic rocks, hydrothermally-altered materials, volcanic ash, a soil profile, and suspended and bedload river sediments were also collected. The hydrochemistry of dissolved phases were analyzed at the University of Hamburg, while the mineralogy and geochemical compositions of solid phases were analyzed at the Natural History Museum of Los Angeles. This work will be discussed in the context of

  9. Centrality measures and thermodynamic formalism for complex networks.

    Science.gov (United States)

    Delvenne, Jean-Charles; Libert, Anne-Sophie

    2011-04-01

    In the study of small and large networks it is customary to perform a simple random walk where the random walker jumps from one node to one of its neighbors with uniform probability. The properties of this random walk are intimately related to the combinatorial properties of the network. In this paper we propose to use the Ruelle-Bowens random walk instead, whose probability transitions are chosen in order to maximize the entropy rate of the walk on an unweighted graph. If the graph is weighted, then a free energy is optimized instead of the entropy rate. Specifically, we introduce a centrality measure for large networks, which is the stationary distribution attained by the Ruelle-Bowens random walk; we name it entropy rank. We introduce a more general version, which is able to deal with disconnected networks, under the name of free-energy rank. We compare the properties of those centrality measures with the classic PageRank and hyperlink-induced topic search (HITS) on both toy and real-life examples, in particular their robustness to small modifications of the network. We show that our centrality measures are more discriminating than PageRank, since they are able to distinguish clearly pages that PageRank regards as almost equally interesting, and are more sensitive to the medium-scale details of the graph.

  10. Post-Laramide and pre-Basin and Range deformation and implications for Paleogene (55-25 Ma) volcanism in central Mexico: A geological basis for a volcano-tectonic stress model

    Science.gov (United States)

    Tristán-González, Margarito; Aguirre-Díaz, Gerardo J.; Labarthe-Hernández, Guillermo; Torres-Hernández, José Ramón; Bellon, Hervé

    2009-06-01

    At central-eastern Mexico, in the Mesa Central province, there are several ranges that were formed after the K/T Laramide compression but before the Basin and Range peak extensional episodes at middle-late Oligocene. Two important volcano-tectonic events happened during this time interval, 1) uplift of crustal blocks exhuming the Triassic-Jurassic metamorphic sequence and formation of basins that were filled with red beds and volcanic sequences, and 2) normal faulting and tilting to the NE of these blocks and fanglomerate filling of graben and half-graben structures. The first event, from late Paleocene to early Eocene, was related to NNE and NNW oriented dextral strike-slip faults. These faults were combined with NW-SE en echelon faulting in these blocks through which plutonism and volcanism occurred. The second event lasted from early Oligocene to early Miocene and coincided with Basin and Range extension. Intense volcanic activity occurred synchronously with the newly-formed or reactivated old fault systems, producing thick sequences of silicic pyroclastic rocks and large domes. Volcano-tectonic peaks occurred in three main episodes during the middle-late Oligocene in this part of Mexico, at about 32-30 Ma, 30-28 Ma, and 26-25 Ma. The objectives of this work is to summarize the volcano-tectonic events that occurred after the end of the Laramide orogeny and before the peak episodes of Basin and Range faulting and Sierra Madre Occidental Oligocene volcanism, and to discuss the influence of these events on the following Oligocene-Miocene volcano-tectonic peak episodes that formed the voluminous silicic volcanism in the Mesa Central, and hence, in the Sierra Madre Occidental. A model based upon geological observations summarizes the volcanic-tectonic evolution of this part of Mexico from the late Paleocene to the Early Miocene.

  11. Magma-Tectonic Interactions along the Central America Volcanic Arc: Insights from the August 1999 Magmatic and Tectonic Event at Cerro Negro, Nicaragua

    Science.gov (United States)

    La Femina, P.; Connor, C.; Strauch, W.

    2002-12-01

    Volcanic vent alignments form parallel to the direction of maximum horizontal stress, accommodating extensional strain via dike injection. Roughly east-west extension within the Central America Volcanic Arc is accommodated along north-northwest-trending basaltic vent alignments. In Nicaragua, these alignments are located in a northwest-trending zone of dextral shear, with shear accommodated along northeast trending bookshelf faults. The recent eruption of Cerro Negro volcano, Nicaragua and Marabios Range seismic swarm revealed the interaction of these fault systems. A low energy (VEI 1), small volume (0.001 km3 DRE) eruption of highly crystalline basalt occurred at Cerro Negro volcano, Nicaragua, August 5-7, 1999. This eruption followed three tectonic earthquakes (each Mw 5.2) in the vicinity of Cerro Negro hours before the onset of eruptive activity. The temporal and spatial pattern of microseismicity and focal mechanisms of the Mw 5.2 earthquakes suggests the activation of northeast-trending faults northwest and southeast of Cerro Negro within the Marabios Range. The eruption was confined to three new vents formed on the southern flank of Cerro Negro along a preexisting north-northwest trending alignment; the El Hoyo alignment of cinder cones, maars and explosion craters. Surface ruptures formed > 1 km south and southeast of the new vents suggest dike injection. Numerical simulations of conduit flow illustrate that the observed effusion rates (up to 65 ms-1) and fountain heights (50-300 m) can be achieved by eruption of magma with little or no excess fluid pressure, in response to tectonic strain. These observations and models suggest that 1999 Cerro Negro activity is an excellent example of tectonically induced small-volume eruptions in an arc setting.

  12. Discovery of modern (post-1850 CE) lavas in south-central British Columbia, Canada: Origin from coal fires or intraplate volcanism?

    Science.gov (United States)

    Canil, Dante; Mihalynuk, Mitch; Lacourse, Terri

    2018-01-01

    We describe three unusual lavas in the Northern Cordillera in south-central British Columbia, Canada, occurring as spatter, scoria and blocks over small 400 m2 areas. The lavas coat and weld cobbles and pebbles in glacial till and are vesicular and glassy with microlites of clinopyroxene and plagioclase, and xenocrysts of quartz, feldspar or clinopyroxene. Chemically the lavas are basaltic trachyandesite (55-61 wt% SiO2) with trace element patterns similar to average British Columbia upper crust, except for having higher V and lower Zr, Hf, Nb, Th and U. Melting experiments and plagioclase-melt thermometry on the glasses, and phase equilibrium in simple systems, require liquidus temperatures of 1150-1300 °C. Interaction of the liquids with carbonaceous matter at low pressure formed Fe metal spherules and SiC. Radiocarbon ages of charcoal and dendrochronology show the lavas are modern, emplaced in the last 120 years. The similar bulk composition of these lavas to several other Quaternary-aged volcanic centers in the North American Cordillera, some of which show recent seismic activity, could suggest a possible tectonic origin, but the deposits are unusually small and show no central vent for emplacement. Conversely, the balance of evidence would suggest an origin from coal fires or hot gas venting, but is less consistent with the observed calc- and per-alkaline lava compositions, and the lack of known local coal-bearing strata as a heat source. Other anthropogenic origins for the lavas are considered less plausible.

  13. The "Escarot" gas seep, French Massif Central: CO2 discharge from a quiescent volcanic system - Characterization and quantification of gas emissions

    Science.gov (United States)

    Gal, F.; Leconte, S.; Gadalia, A.

    2018-03-01

    Natural CO2 emissions from the volcanic rocks of the French Massif Central are poorly constrained. It is of interest better to assess the emission of such non-anthropogenic gases that may significantly contribute to the global carbon budget. We quantified the CO2 emissions to the atmosphere in a small area (0.052 km2) located in the Massif Central close to Lake Pavin, the most recent volcanic edifice in metropolitan France. The specific character of this area, known as the Escarot mofette, was earlier studied for soil-gas concentrations only. In June 2017, we used the accumulation chamber method for measuring CO2 flux and related O2 depletion in the gases emitted at the soil/atmosphere interface, resulting in 176 data acquisitions over four days. In addition, 44 soil-gas concentration measurements were made at selected locations. CO2 emission rates are estimated at 8100 ± 1800 tons/year of deep-seated CO2 and at 660 ± 440 tons/year of biologically produced CO2. The uncertainty on these evaluations comes from the high-frequency variability of CO2 efflux in the more emissive areas and from the occurrence of heavy precipitation events. Though unexpected, these events were used for quantifying the decreases in CO2 efflux, which were as high as 500% over a few hours or even days in some locations. However, repeat acquisitions performed under more favourable weather conditions showed errors of commonly accepted amplitude (±15%). The area showed several degassing centres aligned along a NNW-SSE direction that correlates well with known geological structures, proving the ability of soil-gas methods to map hidden faults. The whole area is characterized by strong CO2 enrichment and related O2 depletion, but it is nonetheless possible to detect areas influenced by the rise of deep-seated gases and a few peripheral areas where biological processes dominate (CO2 up to 10% vol.). This study of gas emissions in a non-urban area also provides complementary information that is

  14. The Mediator complex: a central integrator of transcription

    Science.gov (United States)

    Allen, Benjamin L.; Taatjes, Dylan J.

    2016-01-01

    The RNA polymerase II (pol II) enzyme transcribes all protein-coding and most non-coding RNA genes and is globally regulated by Mediator, a large, conformationally flexible protein complex with variable subunit composition (for example, a four-subunit CDK8 module can reversibly associate). These biochemical characteristics are fundamentally important for Mediator's ability to control various processes important for transcription, including organization of chromatin architecture and regulation of pol II pre-initiation, initiation, re-initiation, pausing, and elongation. Although Mediator exists in all eukaryotes, a variety of Mediator functions appear to be specific to metazoans, indicative of more diverse regulatory requirements. PMID:25693131

  15. Geodetic observations and modeling of magmatic inflation at the Three Sisters volcanic center, central Oregon Cascade Range, USA

    Science.gov (United States)

    Dzurisin, Daniel; Lisowski, Michael; Wicks, Charles W.; Poland, Michael P.; Endo, Elliot T.

    2006-02-01

    Tumescence at the Three Sisters volcanic center began sometime between summer 1996 and summer 1998 and was discovered in April 2001 using interferometric synthetic aperture radar (InSAR). Swelling is centered about 5 km west of the summit of South Sister, a composite basaltic-andesite to rhyolite volcano that last erupted between 2200 and 2000 yr ago, and it affects an area ˜20 km in diameter within the Three Sisters Wilderness. Yearly InSAR observations show that the average maximum displacement rate was 3-5 cm/yr through summer 2001, and the velocity of a continuous GPS station within the deforming area was essentially constant from June 2001 to June 2004. The background level of seismic activity has been low, suggesting that temperatures in the source region are high enough or the strain rate has been low enough to favor plastic deformation over brittle failure. A swarm of about 300 small earthquakes ( Mmax = 1.9) in the northeast quadrant of the deforming area on March 23-26, 2004, was the first notable seismicity in the area for at least two decades. The U.S. Geological Survey (USGS) established tilt-leveling and EDM networks at South Sister in 1985-1986, resurveyed them in 2001, the latter with GPS, and extended them to cover more of the deforming area. The 2001 tilt-leveling results are consistent with the inference drawn from InSAR that the current deformation episode did not start before 1996, i.e., the amount of deformation during 1995-2001 from InSAR fully accounts for the net tilt at South Sister during 1985-2001 from tilt-leveling. Subsequent InSAR, GPS, and leveling observations constrain the source location, geometry, and inflation rate as a function of time. A best-fit source model derived from simultaneous inversion of all three datasets is a dipping sill located 6.5 ± 2.5 km below the surface with a volume increase of 5.0 × 10 6 ± 1.5 × 10 6 m 3/yr (95% confidence limits). The most likely cause of tumescence is a pulse of basaltic magma

  16. Ten-a affects the fusion of central complex primordia in Drosophila.

    Directory of Open Access Journals (Sweden)

    Xuebo Cheng

    Full Text Available The central complex of Drosophila melanogaster plays important functions in various behaviors, such as visual and olfactory memory, visual orientation, sleep, and movement control. However little is known about the genes regulating the development of the central complex. Here we report that a mutant gene affecting central complex morphology, cbd (central brain defect, was mapped to ten-a, a type II trans-membrane protein coding gene. Down-regulation of ten-a in pan-neural cells contributed to abnormal morphology of central complex. Over-expression of ten-a by C767-Gal4 was able to partially restore the abnormal central complex morphology in the cbd mutant. Tracking the development of FB primordia revealed that C767-Gal4 labeled interhemispheric junction that separated fan-shaped body precursors at larval stage withdrew to allow the fusion of the precursors. While the C767-Gal4 labeled structure did not withdraw properly and detached from FB primordia, the two fan-shaped body precursors failed to fuse in the cbd mutant. We propose that the withdrawal of C767-Gal4 labeled structure is related to the formation of the fan-shaped body. Our result revealed the function of ten-a in central brain development, and possible cellular mechanism underlying Drosophila fan-shaped body formation.

  17. Assessing future vent opening locations at the Somma-Vesuvio volcanic complex: 1. A new information geodatabase with uncertainty characterizations

    Science.gov (United States)

    Tadini, A.; Bisson, M.; Neri, A.; Cioni, R.; Bevilacqua, A.; Aspinall, W. P.

    2017-06-01

    This study presents new and revised data sets about the spatial distribution of past volcanic vents, eruptive fissures, and regional/local structures of the Somma-Vesuvio volcanic system (Italy). The innovative features of the study are the identification and quantification of important sources of uncertainty affecting interpretations of the data sets. In this regard, the spatial uncertainty of each feature is modeled by an uncertainty area, i.e., a geometric element typically represented by a polygon drawn around points or lines. The new data sets have been assembled as an updatable geodatabase that integrates and complements existing databases for Somma-Vesuvio. The data are organized into 4 data sets and stored as 11 feature classes (points and lines for feature locations and polygons for the associated uncertainty areas), totaling more than 1700 elements. More specifically, volcanic vent and eruptive fissure elements are subdivided into feature classes according to their associated eruptive styles: (i) Plinian and sub-Plinian eruptions (i.e., large- or medium-scale explosive activity); (ii) violent Strombolian and continuous ash emission eruptions (i.e., small-scale explosive activity); and (iii) effusive eruptions (including eruptions from both parasitic vents and eruptive fissures). Regional and local structures (i.e., deep faults) are represented as linear feature classes. To support interpretation of the eruption data, additional data sets are provided for Somma-Vesuvio geological units and caldera morphological features. In the companion paper, the data presented here, and the associated uncertainties, are used to develop a first vent opening probability map for the Somma-Vesuvio caldera, with specific attention focused on large or medium explosive events.

  18. Intrusive hyaloclastite and peperitic breccias associated to sill and cryptodome emplacement on an Early Paleocene polymagmatic compound cone-dome volcanic complex from El Guanaco mine, Northern Chile

    Science.gov (United States)

    Páez, G. N.; Permuy Vidal, C.; Galina, M.; López, L.; Jovic, S. M.; Guido, D. M.

    2018-04-01

    This work explores the textural characteristics, morphology and facies architecture of well-preserved Paleocene hyaloclastic and peperitic breccias associated with subvolcanic intrusions at El Guanaco gold mine (Northern Chile). The El Guanaco mine volcanic sequence is part of a polymagmatic compound cone-dome volcanic complex grouping several dacitic domes and maar-diatremes, and subordinated subvolcanic intrusions of basaltic, andesitic and dacitic compositions. The Soledad-Peñafiel Fault System is a first order regional structure controlling the location and style of the volcanism in the region. Three different intrusive bodies (Basaltic sills, Dacitic cryptodomes and Andesitic cryptodomes) were found to intrude into a wet and poorly consolidated pyroclastic sequence representing the upper portions of a maar-diatreme. Consequently, extensive quench fragmentation and fluidization along their contacts occurred, leading to the formation of widespread breccia bodies enclosing a coherent nucleus. Differences in matrix composition allows to define two main breccias types: 1) poorly-sorted monomictic breccias (intrusive hyaloclastites) and 2) poorly-sorted tuff-matrix breccias (peperites). The observed facies architecture is interpreted as the result of the interplay of several factors, including: 1) magma viscosity, 2) the geometry of the intrusives, and 3) variations on the consolidation degree of the host rocks. Additionally, the overall geometry of each intrusive is interpreted to be controlled by the effective viscosity of the magmas along with the available magma volume at the time of the intrusions. The presence of three compositionally different subvolcanic bodies with intrusive hyaloclastite and peperite envelopes indicate, not only that all these intrusions occurred in a short period of time (probably less than 2-3 Ma), but also that the volcaniciclastic pile suffer little or none compaction nor consolidation during that time. The presence of three

  19. U-Pb SHRIMP and Sm-Nd geochronology of the Silvania Volcanics and Jurubatuba Granite: juvenile paleoproterozoic crust in the basement of the Neo proterozoic Brasilia Belt, Goias, central Brazil

    International Nuclear Information System (INIS)

    Fischel, Danielle P.; Pimentel, Marcio M.; Fuck, Reinhardt A.; Armstrong, Richard

    2001-01-01

    U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic meta volcanic rocks from the Silvania Sequence and Jurubatuba Granite in the central part of the Brasilia Belt. Zircon grains from a meta volcanic sample yielded 2115 ± 23 Ma and from the granite yielded 2089 ±14 Ma, interpreted as crystallization ages of these rocks. Six meta volcanic samples of the Silvania Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 ±110 Ma and positive ε Nd (T) = +3.0 interpreted as a juvenile magmatic event. Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T DM model ages between 2.30 and 2.42 Ga and ε Nd (T) values vary between -0.22 and -0.58. The oldest T DM value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvania volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasilia Belt that implies the presence of arc/suture hidden in reworked basement of the Brasilia Belt. (author)

  20. U-Pb SHRIMP and Sm-Nd geochronology of the Silvania Volcanics and Jurubatuba Granite: juvenile paleoproterozoic crust in the basement of the Neo proterozoic Brasilia Belt, Goias, central Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Fischel, Danielle P.; Pimentel, Marcio M.; Fuck, Reinhardt A. [Brasilia Univ., DF (Brazil). Inst. de Geociencias; Armstrong, Richard [Australian National Univ., Canberra (Australia). Research School of Earth Sciences

    2001-09-15

    U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic meta volcanic rocks from the Silvania Sequence and Jurubatuba Granite in the central part of the Brasilia Belt. Zircon grains from a meta volcanic sample yielded 2115 {+-} 23 Ma and from the granite yielded 2089 {+-}14 Ma, interpreted as crystallization ages of these rocks. Six meta volcanic samples of the Silvania Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 {+-}110 Ma and positive {epsilon}{sub Nd} (T) = +3.0 interpreted as a juvenile magmatic event. Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T{sub DM} model ages between 2.30 and 2.42 Ga and {epsilon}{sub Nd} (T) values vary between -0.22 and -0.58. The oldest T{sub DM} value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvania volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasilia Belt that implies the presence of arc/suture hidden in reworked basement of the Brasilia Belt. (author)

  1. Outline of tectonic geology of the cenozoic Pacific volcanic zone concerned with geothermal areas in the central America; Chubei ni okeru chinetsutai wo tomonau shinseidai Taiheiyo kazantai no chishitsu gaisetsu

    Energy Technology Data Exchange (ETDEWEB)

    Yamasaki, T [Kyushu University, Fukuoka (Japan); Matsumoto, Y [Yamaguchi University, Yamaguchi (Japan)

    1994-09-16

    For the purpose of technological cooperation on geothermal development, investigations and discussions have been given on the geological background in the geothermal areas in Central America where the Pacific volcanic zone stretches. The geology in Central America is divided largely into three geological structures distributed in a band form in the east-west direction. Among these structure, the Pacific Volcanic Province is a Caenozoic volcanic area ranging along the Pacific Ocean coast in the south-east direction, where young and active Quarternary volcanoes are lined straight over a distance of 1,400 km. The geological structure is such that continuously traceable rift valley or pit structure agrees with the array of volcanoes. The long and wide rift valley that governs this volcanic activity forms the base of the geothermal areas dotted in the above structure. Guatemala had been proceeding with a 24-MW power plant plan in Zunil, the most important point, but the construction has been delayed because of a landslide that caused impediment to the productive wells. The plant completion is now scheduled for 1995. El Salvador is the most advanced country in geothermal power generation, which operates three plants in the Ahuachapa geothermal area, with the output reaching 95 MW. The geothermal condition per production well is 110 tons per hour at 250{degree}C. Nicaragua had been successful in generating power of 70 KW with two plants in Momtombo by 1989. 22 refs., 8 figs., 4 tabs.

  2. Reappraisal of Los Humeros Volcanic Complex by New U/Th Zircon and 40Ar/39Ar Dating: Implications for Greater Geothermal Potential

    Science.gov (United States)

    Carrasco-Núñez, G.; Bernal, J. P.; Dávila, P.; Jicha, B.; Giordano, G.; Hernández, J.

    2018-01-01

    Longevity and size of magmatic systems are fundamental factors for assessing the potential of a geothermal field. At Los Humeros volcanic complex (LHVC), the first caldera-forming event was reported at 460 ± 40 ka. New zircon U/Th and plagioclase 40Ar/39Ar dates of pre-, syn- and postcaldera volcanics allow a reappraisal of the evolution of the geothermally active LHVC. The age of the voluminous Xaltipan ignimbrite (115 km3 dense rock equivalent [DRE]) associated with the formation of the Los Humeros caldera is now constrained by two geochronometers (zircon U/Th and plagioclase 40Ar/39Ar dating) to 164 ± 4.2 ka, which postdates a long episode of precaldera volcanism (rhyolitic domes), the oldest age of which is 693.0 ± 1.9 ka (40Ar/39Ar). The inferred short residence time (around 5 ka) for the paroxysmal Xaltipan ignimbrite is indicative of rapid assembly of a large magma body and rejuvenation of the system due to recurrent recharge magmas, as it has been occurred in some other large magmatic systems. Younger ages than previously believed have been obtained also for the other voluminous explosive phases of the Faby fall tuff at ˜70 ka and the second caldera-forming Zaragoza ignimbrite with 15 km3 DRE, which erupted immediately after. Thus, the time interval that separates the two caldera-forming episodes at Los Humeros is only 94 kyr, which is a much shorter interval than suggested by previous K-Ar dates (410 kyr). This temporal proximity allows us to propose a caldera stage encompassing the Xaltipan and the Zaragoza ignimbrites, followed by emplacement at 44.8 ± 1.7 ka of rhyolitic magmas interpreted to represent a postcaldera, resurgent stage. Rhyolitic eruptions have also occurred during the Holocene (˜1,200 km3) and these new ages indicating much younger caldera-forming volcanism than previously believed are fundamental factors in the application of classical conductive models of heat resource, enhancing the heat production capacity and favor a higher

  3. 2D resistivity survey in complex geological structure area. Application to the volcanic area; Fukuzatsuna chishitsu kozo chiiki ni okeru hiteiko nijigen tansa. Kazangan chiiki deno tekiorei

    Energy Technology Data Exchange (ETDEWEB)

    Asakawa, S; Ikuma, T; Tanifuji, R [DIA Consultants Co. Ltd., Tokyo (Japan)

    1996-05-01

    Introduced herein is an application of 2D resistivity survey to a volcanic rock area where the survey result is difficult to interpret because of its complex geological structure. In a dam site survey, main problems involve the permeability of water through faults and weathered, altered zones. At this site, a 2D resistivity survey was conducted, a 2D geological structure was deduced from the resistivity section, and the result was examined. It was found that resistivity distribution was closely related to hydrographic factors, but no obvious correlation was detected between rock classes and R, Q, and D. In conducting investigations into a section planned for a highway tunnel, it was learned that the problem was a volcanic ash layer to collapse instantly upon absorbing water, and the distribution of the ash layer, not to be disclosed by boring, was subjected to a 2D resistivity survey. The survey was conducted into the structure above where the tunnel would run, and further into the face, and studies were made about what layer was reflected by the resistivity distribution obtained by analysis. The result of the analysis agreed with the details of the layer that was disclosed afterward. 4 figs., 1 tab.

  4. Continuing Inflation at Three Sisters Volcanic Center, Central Oregon Cascade Range, USA, From GPS, InSAR, and Leveling Observations

    Science.gov (United States)

    Lisowski, M.; Dzurisin, D.; Wicks, C. W.

    2007-12-01

    Uplift of a broad area centered ~5 km west of South Sister volcano in central Oregon started sometime after fall 1996, accelerated after fall 1998, and was continuing when last surveyed with GPS and leveling in fall 2006. Surface displacements were measured whenever possible since 1992 with satellite radar interferometry (InSAR), annually since 2001 with GPS and leveling campaigns, and with a continuous GPS station since 2001. The average maximum displacement rate from InSAR was 3 to 5 cm/yr during 1998--2001 and ~1.4 cm/yr during 2004--2006. The other three datasets show a similar pattern, i.e., surface dilation and uplift rates decreased over time but deformation continued through 2006. Our best-fit model is a spherical point pressure (Mogi) source located 6.0--6.5 km below the surface and 4.5--5 km west-southwest of the summit of South Sister volcano. Any marginal improvement gained by using a more complicated source shape is not constrained by the data. This same model fits the deformation data for 2001--2003 and 2003--2006 equally well, so there is no indication that the location or shape of the source has changed. However, the source inflation rate has decreased exponentially since 2001 with a 1/e decay time of about 4 years. The net increase in source volume from the beginning of the episode (~1997) through 2006 was 60 × 106 m3 ± 10 × 106 m3. The only unusual seismicity near the deforming area was a swarm of about 300 small earthquakes on March 23- -26, 2004 ---the first notable seismicity for at least two decades. Timing of the swarm generally coincides with slowing of surface deformation, but any link between the two, if one exists, is not understood. Similar episodes in the past probably would have gone unnoticed if, as we suspect, most were small intrusions that do not culminate in eruptions.

  5. The volcaniclastic sequence of Aranzazu: Record of the impact of volcanism on Neogene fluvial system in the middle part of the Central Cordillera, Colombia

    International Nuclear Information System (INIS)

    Borrero Pena, Carlos Alberto; Rosero Cespedes, Juan Sebastian; Valencia M, Julian David; Pardo Trujillo, Andres

    2008-01-01

    The volcaniclastic sequence of Aranzazu (VSA, late Pliocene - early Pleistocene?) was sourced from the northernmost sector of the Machin - Cerro Bravo volcanic complex. The volcaniclastic accumulations filled the pre-existing fault-bend depressions in the surroundings of Aranzazu town (Caldas department, Colombia). A new classification of volcaniclastic deposits is proposed, in which the lahars are defined as volcaniclastic resedimented deposits, and differentiated from the primary volcaniclastic and epiclastic deposits. The updating the sedimentology and rheology of the deposits related with the laharic events is aimed. The VSA stratigraphy is based on the lithofacies identification and the definition of the architectural elements for syn- and inter-eruptive periods. The VSA lower member corresponds to the successive aggradation of syneruptive lahars (SV and SB elements) resulted from re-sedimentation of pumice-rich pyroclastic deposits and transported as debris and hyperconcentrated stream/flood flows. The VSA middle and upper members defined by coal contents were formed during the dominion of inter-eruptive (FF element) over the syn-eruptive (SV and SB elements) periods. They were formed during the reestablishment of the fluvial condition after the syn-eruptive laharic activity. Once the fluvial deposition was strengthened, the necessary conditions for the peat formation were propitious and the coal-bearing bed sets were developed.

  6. Contrasting styles of sedimentation and deformation in the Chugach Terrane accretionary complex, south-central Alaska

    Science.gov (United States)

    Amato, J. M.; Pavlis, T. L.; Worthman, C.; Kochelek, E.; Day, E. M.; Clift, P. D.; Hecker, J.

    2011-12-01

    In southeast Alaska the Chugach terrane represents an accretionary complex associated with several arcs active at 200-65 Ma. This lithostratigraphic unit consists of blueschists with Early Jurassic metamorphic ages and uncertain depositional ages; the Jurassic-Cretaceous McHugh Complex; and the Late Cretaceous Valdez Group. Detrital zircon ages from densely sampled transects reveals patterns in the assembly of the complex. Blueschists are almost totally barren of zircon, suggesting protoliths derived from mafic-intermediate volcanic protoliths far from a continental source. There is an age gap between the blueschists and the McHugh complex interpreted to be caused by an episode of tectonic erosion. The McHugh Complex is two separate units that are lithologically and geochronologically distinct. The older McHugh is a melange is dominated by stratally disrupted volcanic rocks, chert, and argillite. The oldest McHugh rocks have maximum depositional ages (MDA) of 177-150 Ma at Seldovia and 157-145 Ma at Turnagain Arm; the lack of older rocks at Turnagain Arm suggests removal of structural section by faulting. The MDAs of the older McHugh rocks do not decrease progressively away from the arc. There is a 45 m.y. gap in MDA between the older McHugh and the Late Cretaceous McHugh rocks. The younger McHugh rocks are dominated by volcanogenic sandstone and coarse conglomerate and MDA decreases from 100 Ma near the boundary with the older McHugh mesomelange to 85 Ma near the Valdez Group. The Valdez Group consists of coherently bedded turbidites with a MDA range of 85-60 Ma that decreases progressively outboard of the arc source. A sample from the Orca Group of the Prince William terrane is lithologically similar to the Valdez Group and there is no gap in MDA between Valdez and Orca Groups. 55 Ma dikes cut the McHugh and Valdez Groups in the western Chugach and Kenai Mountains. The oldest units of the Chugach terrane are the most deformed, with deformation and metamorphism

  7. The Geothermal Systems along the Watukosek fault system (East Java, Indonesia):The Arjuno-Welirang Volcanic Complex and the Lusi Mud-Eruption

    Science.gov (United States)

    Inguaggiato, Salvatore; Mazzini, Adriano; Vita, Fabio; Sciarra, Alessandra

    2016-04-01

    The Java Island is characterized by an intense volcanic activity with more then 100 active volcanoes. Moreover, this island is also known by the presence of many mud volcanoes and hydrothermal springs. In particular, in the 2006 several sudden hot mud eruptions, with fluids around 100° C, occurred in the NE side of the island resulting in a prominent eruption named Lusi (contraction of Lumpur Sidoarjo) located along the major Watukosek strike-slip fault zone. The Watukosek fault system, strikes from the Arjuno-Welirang volcanic complex, intersects Lusi and extends towards the NE of the Java island. Conversely of the normal mud eruptions (cold fluids emitted in a short time period of few days), the Lusi eruption was characterized by a persistent effusive hot fluids emissions for a long-time period of, so far, nearly a decade. Moreover, the isotopic composition of emitted gases like Helium showed a clear magmatic origin. For this reasons we decided to investigate the near Arjuno-Welirang complex located on the same strike-slip fault. Arjuno-Welirang is a twin strato-volcano system located in the East of Java along the Watukosek fault, at about 25 km SW respect to the Lusi volcano system. It features two main peaks: Arjuno (3339 masl) and Welirang (3156 masl). The last recorded eruptive activity took place in August 1950 from the flanks of Kawah Plupuh and in October 1950 from the NW part of the Gunung Welirang. This strato-volcano is characterized by a S-rich area, with high T-vent fumarole at least up to 220° C (and likely higher), located mainly in the Welirang crater. In addition, several hot springs vent from the flanks of the volcano, indicate the presence of a large hydrothermal system. During July 2015, in the framework of the Lusi Lab project (ERC grant n° 308126), we carried out a geochemical field campaign on the Arjuno-Welirang volcano hydrothermal system area, sampling water and dissolved gases from the thermal and cold springs located on the flanks of

  8. Complex remanent magnetization in the Kızılkaya ignimbrite (central Anatolia): Implication for paleomagnetic directions

    Science.gov (United States)

    Agrò, Alessandro; Zanella, Elena; Le Pennec, Jean-Luc; Temel, Abidin

    2017-04-01

    Pyroclastic flow deposits, known as ash-flow tuffs or ignimbrites, are invaluable materials for paleomagnetic studies, with many applications for geological and tectonic purposes. However, little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy. In this work we investigate this issue by concentrating on the Kızılkaya ignimbrite, the youngest large-volume unit of the Neogene ignimbrite sequence of the Central Anatolian Volcanic Province in Turkey, bringing evidence of significant magnetic heterogeneities in ignimbrite deposits (magnetic mineralogy, susceptibility, magnetic remanence, coercivity, etc.) and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data. Six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite. Isothermal remanence measurements point to low-Ti titanomagnetite as the main magnetic carrier at all sites; at some sites, the occurrence of oxidized Ti-magnetite and hematite is disclosed. The bulk susceptibility (km) decreases vertically at two out of six sections: its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base. In most cases, low km values relate to high coercivity of remanence (BCR) values, which range from 25 to > 400 mT, and to low S-ratios (measured at 0.3 T) between 0.28 and 0.99. These data point to the occurrence of oxidized magnetic phases. We therefore consider the km parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized Ti-magnetite and hematite within the deposit. The characteristic remanent magnetization is determined after stepwise thermal and AF demagnetization and clearly isolated by principal component analysis at most sites. For these sites, the

  9. Suppression of grasshopper sound production by nitric oxide-releasing neurons of the central complex

    Science.gov (United States)

    Weinrich, Anja; Kunst, Michael; Wirmer, Andrea; Holstein, Gay R.

    2008-01-01

    The central complex of acridid grasshoppers integrates sensory information pertinent to reproduction-related acoustic communication. Activation of nitric oxide (NO)/cyclic GMP-signaling by injection of NO donors into the central complex of restrained Chorthippus biguttulus females suppresses muscarine-stimulated sound production. In contrast, sound production is released by aminoguanidine (AG)-mediated inhibition of nitric oxide synthase (NOS) in the central body, suggesting a basal release of NO that suppresses singing in this situation. Using anti-citrulline immunocytochemistry to detect recent NO production, subtypes of columnar neurons with somata located in the pars intercerebralis and tangential neurons with somata in the ventro-median protocerebrum were distinctly labeled. Their arborizations in the central body upper division overlap with expression patterns for NOS and with the site of injection where NO donors suppress sound production. Systemic application of AG increases the responsiveness of unrestrained females to male calling songs. Identical treatment with the NOS inhibitor that increased male song-stimulated sound production in females induced a marked reduction of citrulline accumulation in central complex columnar and tangential neurons. We conclude that behavioral situations that are unfavorable for sound production (like being restrained) activate NOS-expressing central body neurons to release NO and elevate the behavioral threshold for sound production in female grasshoppers. PMID:18574586

  10. Carbon dioxide diffuse emission and thermal energy release from hydrothermal systems at Copahue-Caviahue Volcanic Complex (Argentina)

    Science.gov (United States)

    Chiodini, Giovanni; Cardellini, Carlo; Lamberti, María Clara; Agusto, Mariano; Caselli, Alberto; Liccioli, Caterina; Tamburello, Giancarlo; Tassi, Franco; Vaselli, Orlando; Caliro, Stefano

    2015-10-01

    The north-western sector of Caviahue caldera (Argentina), close to the active volcanic system of Copahue, is characterized by the presence of several hydrothermal sites that host numerous fumarolic emissions, anomalous soil diffuse degassing of CO2 and hot soils. In March 2014, measurements of soil CO2 fluxes in 5 of these sites (namely, Las Máquinas, Las Maquinitas I, Las Maquinitas II, Anfiteatro, and Termas de Copahue) allowed an estimation that 165 t of deeply derived CO2 is daily released. The gas source is likely related to a relatively shallow geothermal reservoir containing a single vapor phase as also suggested by both the geochemical data from the 3 deep wells drilled in the 1980s and gas geoindicators applied to the fumarolic discharges. Gas equilibria within the H-C-O gas system indicate the presence of a large, probably unique, single phase vapor zone at 200-210 °C feeding the hydrothermal manifestations of Las Máquinas, Las Maquinitas I and II and Termas de Copahue. A natural thermal release of 107 MW was computed by using CO2 as a tracer of the original vapor phase. The magmatic signature of the incondensable fumarolic gases, the wide expanse of the hydrothermal areas and the remarkable high amount of gas and heat released by fluid expulsion seem to be compatible with an active magmatic intrusion beneath this portion of the Caviahue caldera.

  11. Facies volcánicas del depósito de avalancha de detritos del volcán Tata Sabaya, Andes Centrales Volcanic facies of the debris avalanche deposit of Tata Sabaya Volcano, Central Andes

    Directory of Open Access Journals (Sweden)

    Benigno Godoy

    2012-09-01

    Full Text Available Las avalanchas de detritos, asociadas a colapsos parciales de edificios volcánicos, son fenómenos comunes en la evolución de un volcán. Este tipo de flujos son por inestabilidades, que pueden deberse a factores tales como la existencia de zonas afectadas por alteración hidrotermal, cambios climáticos, terremotos, intrusión de magmas en zonas superficiales (criptodomos y/o diques y/o movimiento de fallas bajo el edificio volcánico o cercanas a él. El producto final de estos flujos -denominado depósito de avalancha de detritos (DAD- presenta morfologías típicas de cerrillos y drenajes cerrados. En los Andes Centrales se han reconocido, al menos, 14 centros volcánicos con depósitos de avalancha asociados, entre los que está el volcán Tata Sabaya (Bolivia. El colapso que ha dado origen a este depósito podría haberse generado por una combinación de actividad sísmica y magmática en el volcán. El depósito asociado al colapso parcial de este volcán se distribuye sobre la parte baja del flanco sur del volcán y sobre la parte noroccidental de la cuenca del salar de Coipasa. Cubre una superficie de más de 230 km² y tiene un volumen estimado de 6±1 km³. Sobre la base de las composiciones litológicas, se ha establecido que el depósito está constituido por 6 tipos distintos de cerrillos, los cuales son: lávicos, piroclásticos, sedimentarios mixtos, brecha piroclástica y andesítico-basálticos. Considerando el tipo predominante de cerrillos y su distribución espacial dentro del depósito, se ha definido 6 facies diferentes (Facies de Bloques Toreva, Facies de Cerrillos Volcánicos, Facies Central, Facies de Cerrillos Sedimentarios, Facies Mixta y Facies de Cerrillos de Brecha Piroclástica. Tomando en cuenta la distribución espacial de estas facies, se propone la estructura del paleovolcán previa a su colapso parcial.Debris avalanches associated with partial sector collapse of volcanic edifices are common phenomena in the

  12. Complex Non-volcanic Tremor in Guerrero Mexico Triggered by the 2010 Mw 8.8 Chilean Earthquake

    Science.gov (United States)

    Zigone, D.; Campillo, M.; Husker, A. L.; Kostoglodov, V.; Payero, J. S.; Frank, W.; Shapiro, N. M.; Voisin, C.; Cougoulat, G.; Cotte, N.

    2010-12-01

    In this study we analyze the tremors triggered in Guerrero region (Mexico) by the 2010 magnitude 8.8 Chilean Earthquake using mini-seismic array data from the French-Mexican G-GAP project and broadband data from the Servicio Sismologico Nacional of Mexico. The strong dynamic shaking by the earthquake produced the first observed triggered non-volcanic tremors (NVT) in Mexico so far with at least 3 different types of tremors at different time scales. There was a slow slip event (SSE) occurring at the time of the earthquake, which may have increased the probability of tremor triggering in the region. The first type of observed triggered tremors occurred during the S waves, Love waves and Rayleigh waves as already reported in other subductions zones and continental faults (Miyazawa and Mori, 2005, 2006; Rubinstein et al., 2007; Gomberg et al., 2008; Peng et al, 2009…). The greatest amount of energy and duration accompanies the long-period Rayleigh waves, with smaller bursts during the S and Love waves. For this particular tremor we observed the dispersion of Rayleigh waves in the envelopes of triggered tremors, which indicates a very strong modulation of the source by the passing surface wave. An unexpected short-term tremor occurred approximately one hour later of the arrival of the surface waves on the coastal stations. The NVT has only been previously observed at distances > 100 km inland. It also has a shorter frequency range (3-6 Hz) than other NVT (1-10 Hz) observed in the region. Finally, we observed a significant increase of so-called ambient tremor activity with higher intensity than all triggered NVT during the days after the earthquake. This study adds new types of tremors to the lexicon of triggered NVT observed in the world.

  13. Geology and metallogeny of the volcanic complex of Rio Blanco Ullum. Province of San Juan. Republica Argentina

    International Nuclear Information System (INIS)

    Mendoza, N.; Weidmann, N.; Puigdomenech, H.; Weidmann, R.

    2007-01-01

    Preliminary results of a research carried out at the Complejo Rio Blanco de Ullum, San Juan. Argentina are summarized in the present paper. These studies are focused on geological and metallogenic features o f this unit. The study area is located 20 km. WNW of San Juan city with geographic coordinates of 31grades 30' South latitude and 68 grades 52' West longitude. The older rocks aotcroping in the area correspond to limestones of Ordovician San Juan Formation, the chronologic succession continues with sales and siltstones of Silurian Tambolar Formation, pelites and subgraywackes of Devonian Punta Negra Formation and finally a 1500 m thick package of piroclastics and sediments of Albarracin Formation of Tertiary age. Albarracin Formation is composed pf a Basal Member (sandstones and stilstones), a Tuffaceous Member (tuffs, tuffites and oligomictic breccia s with conglomerate interbed dings in the upper part) and a Conglomeratic Member (polimictic para conglomerates). According to piroclastics facies, relationships and spreading area of piroclastics deposits a c olapsed dome and avalanche model is proposed to be the main process for the piroclastics package outcropping in the area.Sedimentary and piroclastics rocks are intruded by five sub volcanic units as noted by Leveratto (1968) which are composed by different lithologies such as: Altered Da cite - Rhyolite, Ullum Da cite, Cerro Blanco de Zonda Andesite, Ullum Andesite and Hybrid Andesite.Detailed work on alteration assemblages and metallogenic features in the southwestern sector of the Complejo resulted in the identification of three alteration zones with characteric features of potassic, argillic and propyllitic signature. (author)

  14. Characterization of unsaturated zone hydrogeologic units using matrix properties and depositional history in a complex volcanic environment

    Science.gov (United States)

    Flint, Lorraine E.; Buesch, David C.; Flint, Alan L.

    2006-01-01

    Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture-retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (deep (500–1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture-retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and accurate

  15. Mio Pliocene volcaniclastic deposits in the Famatina Ranges, southern Central Andes: A case of volcanic controls on sedimentation in broken foreland basins

    Science.gov (United States)

    Martina, Federico; Dávila, Federico M.; Astini, Ricardo A.

    2006-04-01

    A well-constrained record of Miocene-Pliocene explosive volcanism is preserved within the broken foreland of Western Argentina along the Famatina Ranges. This paper focuses on the volcaniclastic record known as the Río Blanco member of the El Durazno Formation. Three facies can be recognized in the study area: (1) massive tuffs; (2) volcaniclastic conglomerates and (3) pumiceous sandstones. These facies are interpreted as primary pyroclastic flow deposits (ignimbrites) and reworked volcanogenic deposits within interacting volcanic-fluvial depositional systems. Alternation between ignimbrites and volcanogenic sandstones and conglomerates suggest a recurrent pattern of sedimentation related to recurrent volcanic activity. Considering the facies mosaic and relative thicknesses of facies, short periods of syn-eruption sedimentation (volcaniclastic deposits) seem to have been separated by longer inter-eruption periods, where normal stream-flow processes were dominant. The volcaniclastic component decreases up-section, suggesting a gradual reduction in volcanic activity. The mean sedimentation rate of the Río Blanco member is higher (0.44 mm/year) than those obtained for the underlying and overlying units. This increase cannot be fully explained by foreland basement deformation and tectonic loading. Hence, we propose subsidence associated with volcanic activity as the causal mechanism. Volcanism would have triggered additional accommodation space through coeval pyroclastic deposition, modification of the stream equilibrium profile, flexural loading of volcanoes, and thermal processes. These mechanisms may have favored the preservation of volcaniclastic beds in the high-gradient foreland system of Famatina during the Mio-Pliocene. Thus, the Río Blanco member records the response of fluvial systems to large, volcanism-induced sediment loads.

  16. Phase V storage (Project W-112) Central Waste Complex operational readiness review, final report

    International Nuclear Information System (INIS)

    Wight, R.H.

    1997-01-01

    This document is the final report for the RFSH conducted, Contractor Operational Readiness Review (ORR) for the Central Waste Complex (CWC) Project W-112 and Interim Safety Basis implementation. As appendices, all findings, observations, lines of inquiry and the implementation plan are included

  17. Ticks of the Hyalomma marginatum complex transported by migratory birds into Central Europe

    Czech Academy of Sciences Publication Activity Database

    Čapek, Miroslav; Literák, I.; Kocianová, E.; Sychra, O.; Najer, T.; Trnka, A.; Kverek, P.

    2014-01-01

    Roč. 5, č. 5 (2014), s. 489-493 ISSN 1877-959X R&D Projects: GA MŠk LC06073 Institutional support: RVO:68081766 Keywords : Ticks * Hyalomma marginatum complex * Vector * Passerines * Migration * Central Europe Subject RIV: EG - Zoology Impact factor: 2.718, year: 2014

  18. Phase 5 storage (Project W-112) Central Waste Complex operational readiness review, final report

    Energy Technology Data Exchange (ETDEWEB)

    Wight, R.H.

    1997-05-30

    This document is the final report for the RFSH conducted, Contractor Operational Readiness Review (ORR) for the Central Waste Complex (CWC) Project W-112 and Interim Safety Basis implementation. As appendices, all findings, observations, lines of inquiry and the implementation plan are included.

  19. Late Jurassic rifting in the southern central Graben -A complex story simplified

    NARCIS (Netherlands)

    Verreussel, R.M.C.H.; Munsterman, D.K.; Ten Veen, J.H.; Weerd, A. van de; Dybkjaer, K.; Johannessen, P.N.

    2014-01-01

    In order to be able to predict the distribution of reservoir sands and of grainsize and porosity trends in a hydrocarbon province, it is essential to understand the basin evolution in detail. In this study, an attempt is made to reconstruct the complex basin evolution of the southern Central Graben

  20. Structural control of monogenetic volcanism in the Garrotxa volcanic field (Northeastern Spain) from gravity and self-potential measurements

    Science.gov (United States)

    Barde-Cabusson, S.; Gottsmann, J.; Martí, J.; Bolós, X.; Camacho, A. G.; Geyer, A.; Planagumà, Ll.; Ronchin, E.; Sánchez, A.

    2014-01-01

    We report new geophysical observations on the distribution of subsurface structures associated with monogenetic volcanism in the Garrotxa volcanic field (Northern Spain). As part of the Catalan Volcanic Zone, this Quaternary volcanic field is associated with the European rifts system. It contains the most recent and best preserved volcanic edifices of the Catalan Volcanic Zone with 38 monogenetic volcanoes identified in the Garrotxa Natural Park. We conducted new gravimetric and self-potential surveys to enhance our understanding of the relationship between the local geology and the spatial distribution of the monogenetic volcanoes. The main finding of this study is that the central part of the volcanic field is dominated by a broad negative Bouguer anomaly of around -0.5 mGal, within which a series of gravity minima are found with amplitudes of up to -2.3 mGal. Inverse modelling of the Bouguer data suggests that surficial low-density material dominates the volcanic field, most likely associated with effusive and explosive surface deposits. In contrast, an arcuate cluster of gravity minima to the NW of the Croscat volcano, the youngest volcano of this zone, is modelled by vertically extended low-density bodies, which we interpret as a complex ensemble of fault damage zones and the roots of young scoria cones. A ground-water infiltration zone identified by a self-potential anomaly is associated with a steep horizontal Bouguer gravity gradient and interpreted as a fault zone and/or magmatic fissure, which fed the most recent volcanic activity in the Garrotxa. Gravimetric and self-potential data are well correlated and indicate a control on the locations of scoria cones by NNE-SSW and NNW-SSE striking tectonic features, which intersect the main structural boundaries of the study area to the north and south. Our interpretation of the data is that faults facilitated magma ascent to the surface. Our findings have major implications for understanding the relationship

  1. Eruptive history of the Elysium volcanic province of Mars

    International Nuclear Information System (INIS)

    Tanaka, K.L.; Scott, D.H.

    1987-01-01

    New geologic mapping of the Elysium volcanic province at 1:2,000,000 scale and crater counts provide a basis for describing its overall eruptive history. Four stages are listed and described in order of their relative age. They are also distinguished by eruption style and location. Stage 1: Central volcanism at Hecates and Albor Tholi. Stage 2: Shield and complex volcanism at Elysium Mons and Elysium Fossae. Stage 3: Rille volcanism at Elysium Fossae and Utopia Planitia. Stage 4: Flood lava and pyroclastic eruptions at Hecates Tholus and Elysium Mons. Tectonic and channeling activity in the Elysium region is intimately associated with volcanism. Recent work indicates that isostatic uplift of Tharsis, loading by Elysium Mons, and flexural uplift of the Elysium rise produced the stresses responsible for the fracturing and wrinkle-ridge formation in the region. Coeval faulting and channel formation almost certainly occurred in the pertinent areas in Stages 2 to 4. Older faults east of the lava flows and channels on Hecates Tholus may be coeval with Stage 1

  2. Hanford Central Waste Complex: Radioactive mixed waste storage facility dangerous waste permit application

    International Nuclear Information System (INIS)

    1991-10-01

    The Hanford Site is owned by the US Government and operated by the US Department of Energy Field Office, Richland. The Hanford Site manages and produces dangerous waste and mixed waste (containing both radioactive and dangerous components). The dangerous waste is regulated in accordance with the Resource Conversation and Recovery Act of 1976 and the State of Washington Hazardous Waste Management Act of 1976. The radioactive component of mixed waste is interpreted by the US Department of Energy to be regulated under the Atomic Energy Act of 1954; the nonradioactive dangerous component of mixed waste is interpreted to be regulated under the Resource Conservation and Recovery Act of 1976 and Washington Administrative Code 173--303. Westinghouse Hanford Company is a major contractor to the US Department of Energy Field Office, Richland and serves as co-operator of the Hanford Central Waste Complex. The Hanford Central Waste Complex is an existing and planned series of treatment, storage, and/or disposal units that will centralize the management of solid waste operations at a single location on the Hanford facility. The Hanford Central Waste Complex units include the Radioactive Mixed Waste Storage Facility, the unit addressed by this permit application, and the Waste Receiving and Processing Facility. The Waste Receiving and Processing Facility is covered in a separate permit application submittal

  3. Improved Discrimination of Volcanic Complexes, Tectonic Features, and Regolith Properties in Mare Serenitatis from Earth-Based Radar Mapping

    Science.gov (United States)

    Campbell, Bruce A.; Hawke, B. Ray; Morgan, Gareth A.; Carter, Lynn M.; Campbell, Donald B.; Nolan, Michael

    2014-01-01

    Radar images at 70 cm wavelength show 4-5 dB variations in backscatter strength within regions of relatively uniform spectral reflectance properties in central and northern Mare Serenitatis, delineating features suggesting lava flow margins, channels, and superposition relationships. These backscatter differences are much less pronounced at 12.6 cm wavelength, consistent with a large component of the 70 cm echo arising from the rough or blocky transition zone between the mare regolith and the intact bedrock. Such deep probing is possible because the ilmenite content, which modulates microwave losses, of central Mare Serenitatis is generally low (2-3% by weight). Modeling of the radar returns from a buried interface shows that an average regolith thickness of 10m could lead to the observed shifts in 70 cm echo power with a change in TiO2 content from 2% to 3%. This thickness is consistent with estimates of regolith depth (10-15m) based on the smallest diameter for which fresh craters have obvious blocky ejecta. The 70 cm backscatter differences provide a view of mare flow-unit boundaries, channels, and lobes unseen by other remote sensing methods. A localized pyroclastic deposit associated with Rima Calippus is identified based on its low radar echo strength. Radar mapping also improves delineation of units for crater age dating and highlights a 250 km long, east-west trending feature in northern Mare Serenitatis that we suggest is a large graben flooded by late-stage mare flows.

  4. Geophysical expression of caldera related volcanism, structures and mineralization in the McDermitt volcanic field

    Science.gov (United States)

    Rytuba, J. J.; Blakely, R. J.; Moring, B.; Miller, R.

    2013-12-01

    The High Rock, Lake Owyhee, and McDermitt volcanic fields, consisting of regionally extensive ash flow tuffs and associated calderas, developed in NW Nevada and SE Oregon following eruption of the ca. 16.7 Ma Steens flood basalt. The first ash flow, the Tuff of Oregon Canyon, erupted from the McDermitt volcanic field at 16.5Ma. It is chemically zoned from peralkaline rhyolite to dacite with trace element ratios that distinguish it from other ash flow tuffs. The source caldera, based on tuff distribution, thickness, and size of lithic fragments, is in the area in which the McDermitt caldera (16.3 Ma) subsequently formed. Gravity and magnetic anomalies are associated with some but not all of the calderas. The White Horse caldera (15.6 Ma), the youngest caldera in the McDermitt volcanic field has the best geophysical expression, with both aeromagnetic and gravity lows coinciding with the caldera. Detailed aeromagnetic and gravity surveys of the McDermitt caldera, combined with geology and radiometric surveys, provides insight into the complexities of caldera collapse, resurgence, post collapse volcanism, and hydrothermal mineralization. The McDermitt caldera is among the most mineralized calderas in the world, whereas other calderas in these three Mid Miocene volcanic fields do not contain important hydrothermal ore deposits, despite having similar age and chemistry. The McDermitt caldera is host to Hg, U, and Li deposits and potentially significant resources of Ga, Sb, and REE. The geophysical data indicate that post-caldera collapse intrusions were important in formation of the hydrothermal systems. An aeromagnetic low along the E caldera margin reflects an intrusion at a depth of 2 km associated with the near-surface McDermitt-hot-spring-type Hg-Sb deposit, and the deeper level, high-sulfidation Ga-REE occurrence. The Li deposits on the W side of the caldera are associated with a series of low amplitude, small diameter aeromagnetic anomalies that form a continuous

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

    Czech Academy of Sciences Publication Activity Database

    Wenger, E.; Büchner, J.; Tietz, O.; Mrlina, Jan

    2017-01-01

    Roč. 292, September (2017), s. 193-210 ISSN 0169-555X Institutional support: RVO:67985530 Keywords : Lausche * polycyclic volcanism * Lausitz Overthrust (Lusatian Fault) * North Bohemian-Saxonian Cretaceous Basin Subject RIV: DC - Siesmology, Volcanology, Earth Structure OBOR OECD: Volcanology Impact factor: 2.958, year: 2016

  6. Reconstructing the paleo-topography and paleo-environmental features of the Sarno River plain (Italy) before the AD 79 eruption of Somma-Vesuvius volcanic complex

    Science.gov (United States)

    Vogel, Sebastian; Märker, Michael

    2010-05-01

    SSP1.4 Understanding mixed siliciclastic-volcaniclastic depositional systems and their relationships with geodynamics or GD2.3/CL4.14/GM5.8/MPRG22/SSP3.5 Reconstruction of ancient continents: Dating and characterization of paleosurfaces Reconstructing the paleo-topography and paleo-environmental features of the Sarno River plain (Italy) before the AD 79 eruption of Somma-Vesuvius volcanic complex Sebastian Vogel[1] & Michael Märker[1] [1] Heidelberg Academy of Sciences and Humanities c/o University of Tübingen, Rümelinstraße 19-23, D-72070 Tübingen, Germany. Within the geoarchaeological research project "Reconstruction of the Ancient Cultural Landscape of the Sarno River Plain" undertaken by the German Archaeological Institute in cooperation with the Heidelberg Academy of Sciences and Humanities/University of Tübingen a methodology was developed to model the spatial dispersion of volcanic deposits of Somma-Vesuvius volcanic complex since its Plinian eruption AD 79. Eventually, this was done to reconstruct the paleo-topography and paleo-environment of the Sarno River plain before the eruption AD 79. We collected, localized and digitized more than 1,800 core drillings to gain a representative network of stratigraphical information covering the entire plain. Besides other stratigraphical data including the characteristics of the pre-AD 79 stratum, the depth to the pre-AD 79 paleo-surface was identified from the available drilling documentation. Instead of applying a simple interpolation of the drilling data, we reconstructed the pre-AD 79 paleo-surface with a sophisticated geostatistical methodology using a machine based learning approach based on classification and regression trees. We hypothesize that the present-day topography reflects the ancient topography, because the eruption of AD 79 coated the ancient topography, leaving ancient physiographic elements of the Sarno River plain still recognizable in the present-day topography. Therefore, a high resolution

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

    Science.gov (United States)

    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.

  8. A New Sulfur and Carbon Degassing Inventory for the Southern Central American Volcanic Arc: The Importance of Accurate Time-Series Data Sets and Possible Tectonic Processes Responsible for Temporal Variations in Arc-Scale Volatile Emissions

    Science.gov (United States)

    de Moor, J. M.; Kern, C.; Avard, G.; Muller, C.; Aiuppa, A.; Saballos, A.; Ibarra, M.; LaFemina, P.; Protti, M.; Fischer, T. P.

    2017-12-01

    This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015-2016. We report ˜300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ˜500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972-2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015-2016 than in any period since ˜1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time-series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short-lived degassing events and arc systems likely display significant short-term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

  9. A new sulfur and carbon degassing inventory for the Southern Central American Volcanic Arc: The importance of accurate time-series datasets and possible tectonic processes responsible for temporal variations in arc-scale volatile emissions

    Science.gov (United States)

    de Moor, Maarten; Kern, Christoph; Avard, Geoffroy; Muller, Cyril; Aiuppa, Sandro; Saballos, Armando; Ibarra, Martha; LaFemina, Peter; Protti, Mario; Fischer, Tobias

    2017-01-01

    This work presents a new database of SO2 and CO2 fluxes from the Southern Central American Volcanic Arc (SCAVA) for the period 2015–2016. We report ∼300 SO2 flux measurements from 10 volcanoes and gas ratios from 11 volcanoes in Costa Rica and Nicaragua representing the most extensive available assessment of this ∼500 km arc segment. The SO2 flux from SCAVA is estimated at 6,240 ± 1,150 T/d, about a factor of three higher than previous estimations (1972–2013). We attribute this increase in part to our more complete assessment of the arc. Another consideration in interpreting the difference is the context of increased volcanic activity, as there were more eruptions in 2015–2016 than in any period since ∼1980. A potential explanation for increased degassing and volcanic activity is a change in crustal stress regime (from compression to extension, opening volcanic conduits) following two large (Mw > 7) earthquakes in the region in 2012. The CO2 flux from the arc is estimated at 22,500 ± 4,900 T/d, which is equal to or greater than estimates of C input into the SCAVA subduction zone. Time‐series data sets for arc degassing need to be improved in temporal and spatial coverage to robustly constrain volatile budgets and tectonic controls. Arc volatile budgets are strongly influenced by short‐lived degassing events and arc systems likely display significant short‐term variations in volatile output, calling for expansion of nascent geochemical monitoring networks to achieve spatial and temporal coverage similar to traditional geophysical networks.

  10. Sorption behavior of bensulfuron-methyl on andisols and ultisols volcanic ash-derived soils: Contribution of humic fractions and mineral-organic complexes

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza, Jeannette; Fuentes, Edwar [Department of Inorganic and Analytical Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Olivos 1007, Casilla 233, Santiago (Chile); Baez, Maria E., E-mail: mbaez@ciq.uchile.c [Department of Inorganic and Analytical Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Olivos 1007, Casilla 233, Santiago (Chile)

    2009-12-15

    Bensulfuron-methyl sorption was studied in Andisol and Ultisol soils in view of their characteristic physical and chemical properties, presenting acidic pH and variable charge. Humic and fulvic acids (HA and FA) and humin (HUM) contributions were established. Sorption was studied by using two synthetic sorbents, an aluminum-silicate with iron oxide coverage and the same sorbent coated with humic acid. Freundlich model described Bensulfuron-methyl behavior in all sorbents (R{sup 2} 0.969-0.998). K{sub f} for soils (8.3-20.7 mug{sup 1-1/n} mL{sup 1/n} g{sup -1}) were higher than those reported in the literature. Organic matter, halloysite or kaolinite, and specific surface area contributed to the global process. The highest K{sub f} for HA, FA and HUM were 539.5, 82.9, and 98.7 mug{sup 1-1/n} mL{sup 1/n} g{sup -1}. Model sorbents described the participation of variable charge materials with high adsorption capacity. The constant capacitance model was used to assess effects of Bensulfuron-methyl adsorption on the distribution of SOH, SOH{sub 2}{sup +} and SO{sup -} sites of sorbents. - Organic matter, phyllosilicates, variable charge minerals and organo-mineral complexes contribute to bensulfuron-methyl sorption on volcanic ash-derived soils.

  11. Complex landslides in the Trans-Mexican Volcanic Belt - a case study in the State of Veracruz

    Science.gov (United States)

    Wilde, M.; Terhorst, B.; Schwindt, D.; Rodriguez Elizarrarás, S. R.; Morales Barrera, W. V.; Bücker, M.; Flores Orozco, A.; García García, E.; Pita de la Paz, C.

    2017-12-01

    The State of Veracruz (Mexico) is a region which is highly affected by landslides, therefore detailed studies on triggering factors and process dynamics of landslides are required. Profound insights are essential for further hazard assessments and compilation of susceptibility maps. Exemplary landslide sites were investigated in order to determine characteristic features of specific regions. In the Chiconquiaco Mountain Range numerous damaging landslide events occurred in the year of 2013 and our case study corresponds to a deep-seated landslide originating from this slide-intensive year. The main scientific aspects are placed on the reconstruction of the landslides geometry and its process dynamics. Therefore, surface and subsurface analysis form the base of a multimethodological approach. In order to perform surface analysis, aerial photographs were collected by an unmanned aerial vehicle (UAV) aiming at the generation of a 3D model with the Structure from Motion (SfM) work routine. Ground control points (GCP) were used to ensure the geometric accuracy of the model. The obtained DEM of the 2013 slide mass as well as an elevation model representing the topographic situation before the event (year 2011) were used to detect surface changes. The data enabled determination of the most affected areas as well as areas characterized by secondary movements. Furthermore, the volume of the slide mass could be calculated. Geophysical methods, as electrical resistivity tomography (ERT) as well as seismic refraction tomography (SRT), were applied for subsurface analysis. Differences in subsurface composition, respectively density, allowed for separation of the slide mass and the underlying unit. Most relevant for our studies is the detection of an earlier landslide leading to the assumption that the 2013 landslide event corresponds to a reactivation process. This multimethodological approach enables a far-reaching visualization of complex landslides and strongly supports the

  12. Petrology, magnetostratigraphy and geochronology of the Miocene volcaniclastic Tepoztlán Formation: implications for the initiation of the Transmexican Volcanic Belt (Central Mexico)

    OpenAIRE

    Lenhardt, Nils; Böhnel, Harald; Wemmer, Klaus; Torres-Alvarado, Ignacio; Hornung, Jens; Hinderer, Matthias

    2010-01-01

    The volcaniclastic Tepoztlán Formation (TF) represents an important rock record to unravel the early evolution of the Transmexican Volcanic Belt (TMVB). Here, a depositional model together with a chronostratigraphy of this Formation is presented, based on detailed field observations together with new geochronological, paleomagnetic, and petrological data. The TF consists predominantly of deposits from pyroclastic density currents and extensive epiclastic products such as tuffaceous sandstones...

  13. Evolution and relationships between volcanism and tectonics in the central-eastern part of the Oligocene Borovitsa caldera (Eastern Rhodopes, Bulgaria)

    Science.gov (United States)

    Dhont, Damien; Yanev, Yotzo; Bardintzeff, Jacques-Marie; Chorowicz, Jean

    2008-04-01

    The nested Borovitsa caldera emplaced during the collision-related Paleogene volcanism in the Eastern Rhodopes. The pre-caldera succession consists in Priabonian to Early Oligocene sediments and lavas (absarokites, shoshonites, latites). The caldera filling corresponds to an acid volcanism Early Oligocene in age. The tectono-magmatic evolution of the caldera can be divided into six main stages. (1) Ignimbritic units (more than 1.5 km thick) with a trachydacitic to trachytic composition deposited. The K-Ar method yields an age of 34-33.5 Ma. The volcanic products are either strongly or not welded in the western and eastern parts of the caldera, respectively. (2) An initial Murga caldera, 7-10 km in diameter, collapsed. This event was accompanied by the intrusion of a circular body consisting of lenses-bearing rocks of trachyrhyodacitic to rhyolitic composition within the border faults. (3) The emission of pyroclastic rocks continued and a large sub-volcanic body (33 Ma) of trachydacitic to trachyrhyolitic composition intruded in the western part of the circular body. (4) The Borovitsa caldera (15 km × 34 km) collapsed. Rhyolitic and trachydacitic dykes dated at 32.5 Ma intruded along its border faults. (5) High-Si trachyrhyolitic-perlitic domes intruded in the eastern part of the Borovitsa caldera at 30-32 Ma and the Dushka caldera collapsed within the Borovitsa structure. (6) Dykes of various compositions (from shoshonite to rhyolite) and trachydacitic to rhyolitic sub-volcanic stocks finally intruded within the caldera and along its rims at 27.5-29.5 Ma. Observations on radar and optical satellite imagery allowed both a new mapping of the structural pattern in the Borovitsa caldera and the understanding of the relationships between faulting and volcanism in this area. Horse-tail features accommodating the right-lateral throw component at the termination of NW-SE and N-S right-lateral strike-slip faults are superimposed upon the Murga caldera and the eastern part

  14. Volcanic geology and geochemistry of Motuhora (Whale Island), Bay of Plenty, New Zealand

    International Nuclear Information System (INIS)

    Burt, R.M.; Cole, J.W.; Vroon, P.Z.

    1996-01-01

    Motuhora (Whale Island) lies c. 11 km offshore from Whakatane in the Bay of Plenty, New Zealand, and comprises tuffaceous marine sediments of the Camp Bay and Motuhora Formations separated by lavas, volcanic breccias, and slope-wash deposits of the Whale Volcanics. Whale Volcanics can be divided into East Dome, Central Dome Complex, and Pa Hill Dome. East Dome is a flow banded, chaotically jointed dacite that is probably extrusive. Central Dome comprises lava flows, and extensive volcanic breccias and tuffs which thicken into a local depression to the north of the central high, suggesting rapid growth and erosion of the dome. Pa Hill Dome is largely intrusive into Camp Bay Formation, although blocks of Pa Hill dacite in an upper slope-wash cobble bed suggest it was partially extrusive. The lavas are porphyritic with phenocrysts of plagioclase, orthopyroxene, and titanomagnetite with subordinate clinopyroxene and amphibole (particularly in Pa Hill Dome), and rare biotite. Rounded or broken and embayed quartz crystals are found in the Central Dome Complex and Pa Hill domes. Magmatic xenoliths are common in all lavas. Chemically the lavas are medium-K, calc-alkaline andesites and dacites, and show relative LILE enrichment and HFSE depletion typical of arc volcanics. Isotopically, samples tend to have more radiogenic Sr and less radiogenic Nd than volcanics from neighbouring White Island. It is likely that Motuhora lavas were formed by a multi-stage process involving partial melting of N-MORB-type mantle that had been fluxed by fluids rich in incompatible elements derived from the dehydrating downgoing slab and followed by crystal fractionation of the magma. As the magma rose through the lower continental crust it was contaminated, probably by Torlesse metasediment. Petrographic textures and mineral chemistry indicate that magma mixing, while in an upper crustal magma chamber, is the norm for Motuhora lavas. (author). 69 refs., 12 figs., 2 tabs

  15. Neurochemical Architecture of the Central Complex Related to Its Function in the Control of Grasshopper Acoustic Communication

    Science.gov (United States)

    Kunst, Michael; Pförtner, Ramona; Aschenbrenner, Katja; Heinrich, Ralf

    2011-01-01

    The central complex selects and coordinates the species- and situation-specific song production in acoustically communicating grasshoppers. Control of sound production is mediated by several neurotransmitters and modulators, their receptors and intracellular signaling pathways. It has previously been shown that muscarinic cholinergic excitation in the central complex promotes sound production whereas both GABA and nitric oxide/cyclic GMP signaling suppress its performance. The present immunocytochemical and pharmacological study investigates the question whether GABA and nitric oxide mediate inhibition of sound production independently. Muscarinic ACh receptors are expressed by columnar output neurons of the central complex that innervate the lower division of the central body and terminate in the lateral accessory lobes. GABAergic tangential neurons that innervate the lower division of the central body arborize in close proximity of columnar neurons and thus may directly inhibit these central complex output neurons. A subset of these GABAergic tangential neurons accumulates cyclic GMP following the release of nitric oxide from neurites in the upper division of the central body. While sound production stimulated by muscarine injection into the central complex is suppressed by co-application of sodium nitroprusside, picrotoxin-stimulated singing was not affected by co-application of this nitric oxide donor, indicating that nitric oxide mediated inhibition requires functional GABA signaling. Hence, grasshopper sound production is controlled by processing of information in the lower division of the central body which is subject to modulation by nitric oxide released from neurons in the upper division. PMID:21980504

  16. Magmatic controls on eruption dynamics of the 1950 yr B.P. eruption of San Antonio Volcano, Tacaná Volcanic Complex, Mexico-Guatemala

    Science.gov (United States)

    Mora, Juan Carlos; Gardner, James Edward; Macías, José Luis; Meriggi, Lorenzo; Santo, Alba Patrizia

    2013-07-01

    San Antonio Volcano, in the Tacaná Volcanic Complex, erupted ~ 1950 yr. B.P., with a Pelean type eruption that produced andesitic pyroclastic surges and block-and-ash flows destroying part of the volcano summit and producing a horse-shoe shaped crater open to the SW. Between 1950 and 800 yr B.P. the eruption continued with effusive andesites followed by a dacite lava flow and a summit dome, all from a single magma batch. All products consist of phenocrysts and microphenocrysts of zoned plagioclase, amphibole, pyroxene, magnetite ± ilmenite, set in partially crystallized groundmass of glass and microlites of the same mineral phases, except for the lack of amphibole. Included in the andesitic blocks of the block-and-ash flow deposit are basaltic andesite enclaves with elongated and ellipsoidal forms and chilled margins. The enclaves have intersertal textures with brown glass between microphenocrysts of plagioclase, hornblende, pyroxene, and olivine, and minor proportions of phenocrysts of plagioclase, hornblende, and pyroxene. A compositional range obtained of blocks and enclaves resulted from mixing between andesite (866 °C ± 22) and basaltic andesite (enclaves, 932 °C ± 22), which may have triggered the explosive Pelean eruption. Vestiges of that mixing are preserved as complex compositional zones in plagioclase and clinopyroxene-rich reaction rims in amphibole in the andesite. Whole-rock chemistry, geothermometry, experimental petrology and modeling results suggest that after the mixing event the eruption tapped hybrid andesitic magma (≤ 900 °C) and ended with effusive dacitic magma (~ 825 °C), all of which were stored at ~ 200 MPa water pressure. A complex open-system evolution that involved crustal end-members best explains the generation of effusive dacite from the hybrid andesite. Amphibole in the dacite is rimmed by reaction products of plagioclase, orthopyroxene, and Fe-Ti oxides produced by decompression during ascent. Amphibole in the andesite

  17. Evidence for volcanism in NW Ishtar Terra, Venus

    International Nuclear Information System (INIS)

    Gaddis, L.; Greeley, R.

    1989-01-01

    Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas

  18. Metamorphic complexes in accretionary orogens: Insights from the Beishan collage, southern Central Asian Orogenic Belt

    Science.gov (United States)

    Song, Dongfang; Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Yang, Lei

    2016-10-01

    The sources of ancient zircons and the tectonic attributions and origins of metamorphic complexes in Phanerozoic accretionary orogens have long been difficult issues. Situated between the Tianshan and Inner Mongolia orogens, the Beishan orogenic collage (BOC) plays a pivotal role in understanding the accretionary processes of the southern Central Asian Orogenic Belt (CAOB), particularly the extensive metamorphic and high-strained complexes on the southern margin. Despite their importance in understanding the basic architecture of the southern CAOB, little consensus has been reached on their ages and origins. Our new structural, LA-ICP-MS zircon U-Pb and Hf isotopic data from the Baidunzi, Shibandun, Qiaowan and Wutongjing metamorphic complexes resolve current controversial relations. The metamorphic complexes have varied lithologies and structures. Detrital zircons from five para-metamorphic rocks yield predominantly Phanerozoic ages with single major peaks at ca. 276 Ma, 286 Ma, 427 Ma, 428 Ma and 461 Ma. Two orthogneisses have weighted mean ages of 294 ± 2 Ma and 304 ± 2 Ma with no Precambrian inherited zircons. Most Phanerozoic zircons show positive εHf(t) values indicating significant crustal growth in the Ordovician, Silurian and Permian. The imbricated fold-thrust deformation style combined with diagnostic zircon U-Pb-Hf isotopic data demonstrate that the metamorphic rocks developed in a subduction-accretion setting on an arc or active continental margin. This setting and conclusion are supported by the nearby occurrence of Ordovician-Silurian adakites, Nb-rich basalts, Carboniferous-Permian ophiolitic mélanges, and trench-type turbidites. Current data do not support the presence of a widespread Precambrian basement in the evolution of the BOC; the accretionary processes may have continued to the early Permian in this part of the CAOB. These relationships have meaningful implications for the interpretation of the tectonic attributions and origins of other

  19. Volcanic features of Io

    International Nuclear Information System (INIS)

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

    1979-01-01

    The volcanic features of Io as detected during the Voyager mission are discussed. The volcanic activity is apparently higher than on any other body in the Solar System. Its volcanic landforms are compared with features on Earth to indicate the type of volcanism present on Io. (U.K.)

  20. Isotope dates and strontium isotopic ratios for plutonic and volcanic rocks in the Quesnel Trough and Nicola Belt, south central British Columbia

    International Nuclear Information System (INIS)

    Preto, V.A.; McMillan, W.J.; Armstrong, R.L.

    1979-01-01

    Four distinct events of the southern Intermontane Belt are represented in new K-Ar and Rb-Sr dates. The first and regionally most important event is sharply defined by new K-Ar dates between 200 and 209 Ma for the Thuya, Wildhorse, Iron Mask, and Allison batholiths and a 205 +- 10 Ma Rb-Sr isochron for the Guichon Creek batholith. All these plutons were emplaced approximately at the change from Triassic to Jurassic time. The related and slightly older Nicola volcanic rocks are altered by addition of more radiogenic sedimentary Sr (Carnian Nicola limestone having 87 Sr/ 86 Sr=0.7075+- 1) and do not give an isochron date. The Coldwater stock is anomalously old (K-Ar dates range from 215-267 Ma). The Mid- to late Jurassic igneous event is indicated by a 141 Ma K-Ar date for the Mount Martley batholith. Mid-Cretaceous volcanic rocks of the Kingsvale Group give a Rb-Sr isochron date of 112 +- 10 Ma and are postdated by the crosscutting and slightly younger Summers Creek stock (100 Ma by K-Ar). The final event straddles the Cretaceous-Tertiary boundary with the Nicola batholith emplaced about 60 Ma ago (K-Ar) and the Rey Lake stock perhaps slightly earlier (69 Ma by K-Ar). Initial 87 Sr/ 86 Sr ratios range from 0.7025-0.7046 with a mean and mode near 0.7037 which is within the range of modern circum-Pacific volcanoes. Initial ratios of 0.7034 +- 1 for the Guichon Creek batholith, 0.7035 +- 1 for the Iron Mask batholith 70435 +-10 for the Thuya batholith, and 0.70379 +- 4 for the Kingsvale volcanic rocks are the most precisely determined. The Coldwater stock is anomalously low at 0.7025. For the other plutonic bodies only scattered or single analyses are available. The Nicola volcanic rocks appear to have once been similar in initial ratio the the Guichon Creek batholith but their calculated initial ratios now scatter from 0.7034-0.7073. (auth)

  1. Nature and provenance of the Beishan Complex, southernmost Central Asian Orogenic Belt

    Science.gov (United States)

    Zheng, Rongguo; Li, Jinyi; Xiao, Wenjiao; Zhang, Jin

    2018-03-01

    The ages and origins of metasedimentary rocks, which were previously mapped as Precambrian, are critical in rebuilding the orogenic process and better understanding the Phanerozoic continental growth in the Central Asian Orogenic Belt (CAOB). The Beishan Complex was widely distributed in the southern Beishan Orogenic Collage, southernmost CAOB, and their ages and tectonic affinities are still in controversy. The Beishan Complex was previously proposed as fragments drifted from the Tarim Craton, Neoproterozoic Block or Phanerozoic accretionary complex. In this study, we employ detrital zircon age spectra to constrain ages and provenances of metasedimentary sequences of the Beishan Complex in the Chuanshanxun area. The metasedimentary rocks here are dominated by zircons with Paleoproterozoic-Mesoproterozoic age ( 1160-2070 Ma), and yield two peak ages at 1454 and 1760 Ma. One sample yielded a middle Permian peak age (269 Ma), which suggests that the metasedimentary sequences were deposited in the late Paleozoic. The granitoid and dioritic dykes, intruding into the metasedimentary sequences, exhibit zircon U-Pb ages of 268 and 261 Ma, respectively, which constrain the minimum deposit age of the metasedimentary sequences. Zircon U-Pb ages of amphibolite (274 and 216 Ma) indicate that they might be affected by multi-stage metamorphic events. The Beishan Complex was not a fragment drifted from the Tarim Block or Dunhuang Block, and none of cratons or blocks surrounding Beishan Orogenic Collage was the sole material source of the Beishan Complex due to obviously different age spectra. Instead, 1.4 Ga marginal accretionary zones of the Columbia supercontinent might have existed in the southern CAOB, and may provide the main source materials for the sedimentary sequences in the Beishan Complex.

  2. In silico Interrogation of Insect Central Complex Suggests Computational Roles for the Ellipsoid Body in Spatial Navigation

    Directory of Open Access Journals (Sweden)

    Vincenzo G. Fiore

    2017-08-01

    Full Text Available The central complex in the insect brain is a composite of midline neuropils involved in processing sensory cues and mediating behavioral outputs to orchestrate spatial navigation. Despite recent advances, however, the neural mechanisms underlying sensory integration and motor action selections have remained largely elusive. In particular, it is not yet understood how the central complex exploits sensory inputs to realize motor functions associated with spatial navigation. Here we report an in silico interrogation of central complex-mediated spatial navigation with a special emphasis on the ellipsoid body. Based on known connectivity and function, we developed a computational model to test how the local connectome of the central complex can mediate sensorimotor integration to guide different forms of behavioral outputs. Our simulations show integration of multiple sensory sources can be effectively performed in the ellipsoid body. This processed information is used to trigger continuous sequences of action selections resulting in self-motion, obstacle avoidance and the navigation of simulated environments of varying complexity. The motor responses to perceived sensory stimuli can be stored in the neural structure of the central complex to simulate navigation relying on a collective of guidance cues, akin to sensory-driven innate or habitual behaviors. By comparing behaviors under different conditions of accessible sources of input information, we show the simulated insect computes visual inputs and body posture to estimate its position in space. Finally, we tested whether the local connectome of the central complex might also allow the flexibility required to recall an intentional behavioral sequence, among different courses of actions. Our simulations suggest that the central complex can encode combined representations of motor and spatial information to pursue a goal and thus successfully guide orientation behavior. Together, the observed

  3. In silico Interrogation of Insect Central Complex Suggests Computational Roles for the Ellipsoid Body in Spatial Navigation.

    Science.gov (United States)

    Fiore, Vincenzo G; Kottler, Benjamin; Gu, Xiaosi; Hirth, Frank

    2017-01-01

    The central complex in the insect brain is a composite of midline neuropils involved in processing sensory cues and mediating behavioral outputs to orchestrate spatial navigation. Despite recent advances, however, the neural mechanisms underlying sensory integration and motor action selections have remained largely elusive. In particular, it is not yet understood how the central complex exploits sensory inputs to realize motor functions associated with spatial navigation. Here we report an in silico interrogation of central complex-mediated spatial navigation with a special emphasis on the ellipsoid body. Based on known connectivity and function, we developed a computational model to test how the local connectome of the central complex can mediate sensorimotor integration to guide different forms of behavioral outputs. Our simulations show integration of multiple sensory sources can be effectively performed in the ellipsoid body. This processed information is used to trigger continuous sequences of action selections resulting in self-motion, obstacle avoidance and the navigation of simulated environments of varying complexity. The motor responses to perceived sensory stimuli can be stored in the neural structure of the central complex to simulate navigation relying on a collective of guidance cues, akin to sensory-driven innate or habitual behaviors. By comparing behaviors under different conditions of accessible sources of input information, we show the simulated insect computes visual inputs and body posture to estimate its position in space. Finally, we tested whether the local connectome of the central complex might also allow the flexibility required to recall an intentional behavioral sequence, among different courses of actions. Our simulations suggest that the central complex can encode combined representations of motor and spatial information to pursue a goal and thus successfully guide orientation behavior. Together, the observed computational features

  4. Geochemical, petrographic and physical characterizations and associated alterations of the volcanic rocks of the Romanesque San Nicola Church (Ottana, central Sardinia, Italy)

    Science.gov (United States)

    Columbu, Stefano; Palomba, Marcella; Sitzia, Fabio

    2015-04-01

    In this research, the volcanic rocks belonging to the Sardinia Oligo-Miocene volcanic cycle (32 - 11 Ma) and building up the structure of the San Nicola church, one of the most representative churches of the Romanesque architecture, were studied. These stones were widely used in medieval architecture for the excellent workability, but they present some disadvantages, since they are greatly affected by alteration phenomena. The main objectives of this research are i) to focus the mineral, chemical and petrographic compositions of the San Nicola stones, ii) the chemical and physical alteration processes affecting these materials, and iii) to establish the exactly provenance of the volcanic rocks. Furthermore, a comparative study between the rocks from the ancient quarries and those forming the structure of the church was performed. In the ancient quarries, where presumably a more advanced alteration occurs due to the vertical alteration gradient, different facies of the same volcanic lithology, characterized by macroscopical evidences of chemical-physical degradation degree, were sampled. Petrographic, geochemical (both major elements that the traces) and physical-mechanical features of the collected samples were determined to highlight the compositional differences (density, porosity, water-absorption kinetics, mechanical resistance) as a function of the different alteration degree. Moreover, chemical-mineralogical analysis of the sample surfaces from the church, was performed, to highlight possible presence and nature of secondary newly-formed phases (e.g., salt efflorescence). Several methodologies were applied to carry out physical-chemical and petrographic analysis: X-Ray fluorescence (XRF) and Inductively Coupled Mass Spectrometry (ICP-MS), X-Ray Diffractometry (XRD) for chemical and mineral composition; Optical and Scanning Electron Microscopy (SEM) for textures, mineral assemblages and microstructures studies; He-picnometry, water-absorption and mechanical

  5. LA-ICP-MS and SIMS U-Pb and U-Th zircon geochronological data of Late Pleistocene lava domes of the Ciomadul Volcanic Dome Complex (Eastern Carpathians

    Directory of Open Access Journals (Sweden)

    Réka Lukács

    2018-06-01

    Full Text Available This article provides laser-ablation inductively coupled plasma mass spectrometry (LA-ICP-MS and secondary ionization mass spectrometry (SIMS U-Pb and U-Th zircon dates for crystals separated from Late Pleistocene dacitic lava dome rocks of the Ciomadul Volcanic Dome Complex (Eastern Carpathians, Romania. The analyses were performed on unpolished zircon prism faces (termed rim analyses and on crystal interiors exposed through mechanical grinding an polishing (interior analyses. 206Pb/238U ages are corrected for Th-disequilibrium based on published and calculated distribution coefficients for U and Th using average whole-rock and individually analyzed zircon compositions. The data presented in this article were used for the Th-disequilibrium correction of (U-Th/He zircon geochronology data in the research article entitled “The onset of the volcanism in the Ciomadul Volcanic Dome Complex (Eastern Carpathians: eruption chronology and magma type variation” (Molnár et al., 2018 [1].

  6. New insights into sucking, swallowing and breathing central generators: A complexity analysis of rhythmic motor behaviors.

    Science.gov (United States)

    Samson, Nathalie; Praud, Jean-Paul; Quenet, Brigitte; Similowski, Thomas; Straus, Christian

    2017-01-18

    Sucking, swallowing and breathing are dynamic motor behaviors. Breathing displays features of chaos-like dynamics, in particular nonlinearity and complexity, which take their source in the automatic command of breathing. In contrast, buccal/gill ventilation in amphibians is one of the rare motor behaviors that do not display nonlinear complexity. This study aimed at assessing whether sucking and swallowing would also follow nonlinear complex dynamics in the newborn lamb. Breathing movements were recorded before, during and after bottle-feeding. Sucking pressure and the integrated EMG of the thyroartenoid muscle, as an index of swallowing, were recorded during bottle-feeding. Nonlinear complexity of the whole signals was assessed through the calculation of the noise limit value (NL). Breathing and swallowing always exhibited chaos-like dynamics. The NL of breathing did not change significantly before, during or after bottle-feeding. On the other hand, sucking inconsistently and significantly less frequently than breathing exhibited a chaos-like dynamics. Therefore, the central pattern generator (CPG) that drives sucking may be functionally different from the breathing CPG. Furthermore, the analogy between buccal/gill ventilation and sucking suggests that the latter may take its phylogenetic origin in the gill ventilation CPG of the common ancestor of extant amphibians and mammals. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  7. Hanford Central Waste Complex: Waste Receiving and Processing Facility dangerous waste permit application

    International Nuclear Information System (INIS)

    1991-10-01

    The Hanford Central Waste Complex is an existing and planned series of treatment, and/or disposal (TSD) unites that will centralize the management of solid waste operations at a single location on the Hanford Facility. The Complex includes two units: the WRAP Facility and the Radioactive Mixed Wastes Storage Facility (RMW Storage Facility). This Part B permit application addresses the WRAP Facility. The Facility will be a treatment and storage unit that will provide the capability to examine, sample, characterize, treat, repackage, store, and certify radioactive and/or mixed waste. Waste treated and stored will include both radioactive and/or mixed waste received from onsite and offsite sources. Certification will be designed to ensure and demonstrate compliance with waste acceptance criteria set forth by onsite disposal units and/or offsite facilities that subsequently are to receive waste from the WRAP Facility. This permit application discusses the following: facility description and general provisions; waste characterization; process information; groundwater monitoring; procedures to prevent hazards; contingency plant; personnel training; exposure information report; waste minimization plan; closure and postclosure requirements; reporting and recordkeeping; other relevant laws; certification

  8. Age and tectonomagmatic setting of the Eocene Çöpler-Kabataş magmatic complex and porphyry-epithermal Au deposit, East Central Anatolia, Turkey

    Science.gov (United States)

    İmer, Ali; Richards, Jeremy P.; Creaser, Robert A.

    2013-06-01

    The Çöpler epithermal Au deposit and related subeconomic porphyry Cu-Au deposit is hosted by the middle Eocene Çöpler-Kabataş magmatic complex in central eastern Anatolia. The intrusive rocks of the complex were emplaced into Late Paleozoic-Mesozoic metamorphosed sedimentary basement rocks near the northeastern margin of the Tauride-Anatolide Block. Igneous biotite from two samples of the magmatic complex yielded 40Ar/39Ar plateau ages of 43.75 ± 0.26 Ma and 44.19 ± 0.23, whereas igneous hornblende from a third sample yielded a plateau age of 44.13 ± 0.38. These ages closely overlap with 40Ar/39Ar ages of hydrothermal sericite (44.44 ± 0.28 Ma) and biotite (43.84 ± 0.26 Ma), and Re-Os ages from two molybdenite samples (44.6 ± 0.2 and 43.9 ± 0.2 Ma) suggesting a short-lived (history at Çöpler. No suitable minerals were found that could be used to date the epithermal system, but it is inferred to be close in age to the precursor porphyry system. The Çöpler-Kabataş intrusive rocks show I-type calc-alkaline affinities. Their normalized trace element patterns show enrichments in large ion lithophile and light rare earth elements and relative depletions in middle and heavy rare earth elements, resembling magmas generated in convergent margins. However, given its distance from the coeval Eocene Maden-Helete volcanic arc, the complex is interpreted to be formed in a back-arc setting, in response to Paleocene slab roll-back and upper-plate extension. The tectonomagmatic environment of porphyry-epithermal mineralization at Çöpler is comparable to some other isolated back-arc porphyry systems such as Bajo de la Alumbrera (Argentina) or Bingham Canyon (USA).

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

    Science.gov (United States)

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

    2009-04-01

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

  10. Withdrawal and restoration of central vagal afferents within the dorsal vagal complex following subdiaphragmatic vagotomy.

    Science.gov (United States)

    Peters, James H; Gallaher, Zachary R; Ryu, Vitaly; Czaja, Krzysztof

    2013-10-15

    Vagotomy, a severing of the peripheral axons of the vagus nerve, has been extensively utilized to determine the role of vagal afferents in viscerosensory signaling. Vagotomy is also an unavoidable component of some bariatric surgeries. Although it is known that peripheral axons of the vagus nerve degenerate and then regenerate to a limited extent following vagotomy, very little is known about the response of central vagal afferents in the dorsal vagal complex to this type of damage. We tested the hypothesis that vagotomy results in the transient withdrawal of central vagal afferent terminals from their primary central target, the nucleus of the solitary tract (NTS). Sprague-Dawley rats underwent bilateral subdiaphragmatic vagotomy and were sacrificed 10, 30, or 60 days later. Plastic changes in vagal afferent fibers and synapses were investigated at the morphological and functional levels by using a combination of an anterograde tracer, synapse-specific markers, and patch-clamp electrophysiology in horizontal brain sections. Morphological data revealed that numbers of vagal afferent fibers and synapses in the NTS were significantly reduced 10 days following vagotomy and were restored to control levels by 30 days and 60 days, respectively. Electrophysiology revealed transient decreases in spontaneous glutamate release, glutamate release probability, and the number of primary afferent inputs. Our results demonstrate that subdiaphragmatic vagotomy triggers transient withdrawal and remodeling of central vagal afferent terminals in the NTS. The observed vagotomy-induced plasticity within this key feeding center of the brain may be partially responsible for the response of bariatric patients following gastric bypass surgery. Copyright © 2013 Wiley Periodicals, Inc.

  11. Volcanic risk; Risque volcanique

    Energy Technology Data Exchange (ETDEWEB)

    Rancon, J.P.; Baubron, J.C.

    1995-12-31

    This project follows the previous multi-disciplinary studies carried out by the French Bureau de Recherches Geologiques et Minieres (BRGM) on the two active volcanoes of the French lesser Antilles: Mt Pelee (Martinique) and Soufriere (Guadeloupe) for which geological maps and volcanic risk studies have been achieved. The research program comprises 5 parts: the study of pyroclastic deposits from recent eruptions of the two volcanoes for a better characterization of their eruptive phenomenology and a better definition of crisis scenarios; the study of deposits and structures of active volcanoes from Central America and the study of eruptive dynamics of andesite volcanoes for a transposition to Antilles` volcanoes; the starting of a methodological multi-disciplinary research (volcanology, geography, sociology...) on the volcanic risk analysis and on the management of a future crisis; and finally, the development of geochemical survey techniques (radon, CO{sub 2}, H{sub 2}O) on active volcanoes of Costa-Rica and Europe (Fournaise, Furnas, Etna) and their application to the Soufriere. (J.S.). 9 refs., 3 figs.

  12. Volcanism and associated hazards: the Andean perspective

    Science.gov (United States)

    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 (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 Peru has spurred significant

  13. Age, extent and carbon storage of the central Congo Basin peatland complex.

    Science.gov (United States)

    Dargie, Greta C; Lewis, Simon L; Lawson, Ian T; Mitchard, Edward T A; Page, Susan E; Bocko, Yannick E; Ifo, Suspense A

    2017-02-02

    Peatlands are carbon-rich ecosystems that cover just three per cent of Earth's land surface, but store one-third of soil carbon. Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests. Here we present field measurements from one of the world's most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin. We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene. The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900-156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent. We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 10 15  grams) of carbon belowground (95 per cent confidence interval of 6.3-46.8 petagrams of carbon)-a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin. Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by

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

    Science.gov (United States)

    ,

    2017-06-23

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

  15. Central Coherence in Eating Disorders: A Synthesis of Studies Using the Rey Osterrieth Complex Figure Test.

    Directory of Open Access Journals (Sweden)

    Katie Lang

    Full Text Available Large variability in tests and differences in scoring systems used to study central coherence in eating disorders may lead to different interpretations, inconsistent findings and between study discrepancies. This study aimed to address inconsistencies by collating data from several studies from the same research group that used the Rey Osterrieth Complex Figure Test (Rey Figure in order to produce norms to provide benchmark data for future studies.Data was collated from 984 participants in total. Anorexia Nervosa, Bulimia Nervosa, recovered Anorexia Nervosa, unaffected family members and healthy controls were compared using the Rey Figure.Poor global processing was observed across all current eating disorder sub-groups and in unaffected relatives. There was no difference in performance between recovered AN and HC groups.This is the largest dataset reported in the literature and supports previous studies implicating poor global processing across eating disorders using the Rey Figure. It provides robust normative data useful for future studies.

  16. X/Qs and unit dose calculations for Central Waste Complex interim safety basis effort

    International Nuclear Information System (INIS)

    Huang, C.H.

    1996-01-01

    The objective for this problem is to calculate the ground-level release dispersion factors (X/Q) and unit doses for onsite facility and offsite receptors at the site boundary and at Highway 240 for plume meander, building wake effect, plume rise, and the combined effect. The release location is at Central Waste Complex Building P4 in the 200 West Area. The onsite facility is located at Building P7. Acute ground level release 99.5 percentile dispersion factors (X/Q) were generated using the GXQ. The unit doses were calculated using the GENII code. The dimensions of Building P4 are 15 m in W x 24 m in L x 6 m in H

  17. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.; Delworth, Thomas L.; Ramaswamy, V.; Stouffer, Ronald J.; Wittenberg, Andrew; Zeng, Fanrong

    2009-01-01

    Sulfate aerosols resulting from strong volcanic explosions last for 2–3 years in the lower stratosphere. Therefore it was traditionally believed that volcanic impacts produce mainly short-term, transient climate perturbations. However, the ocean

  18. The γ-tubulin complex in Trypanosoma brucei: molecular composition, subunit interdependence and requirement for axonemal central pair protein assembly

    Science.gov (United States)

    Zhou, Qing; Li, Ziyin

    2015-01-01

    The γ-tubulin complex constitutes a key component of the microtubule-organizing center and nucleates microtubule assembly. This complex differs in complexity in different organisms: the budding yeast contains the γ-tubulin small complex (γTuSC) composed of γ-tubulin, GCP2 and GCP3, whereas animals contain the γ-tubulin ring complex (γTuRC) composed of γTuSC and three additional proteins, GCP4, GCP5 and GCP6. In Trypanosoma brucei, the composition of the γ-tubulin complex remains elusive, and it is not known whether it also regulates assembly of the subpellicular microtubules and the spindle microtubules. Here we report that the γ-tubulin complex in T. brucei is composed of γ-tubulin and three GCP proteins, GCP2-GCP4, and is primarily localized in the basal body throughout the cell cycle. Depletion of GCP2 and GCP3, but not GCP4, disrupted the axonemal central pair microtubules, but not the subpellicular microtubules and the spindle microtubules. Furthermore, we showed that the γTuSC is required for assembly of two central pair proteins and that γTuSC subunits are mutually required for stability. Together, these results identified an unusual γ-tubulin complex in T. brucei, uncovered an essential role of γTuSC in central pair protein assembly, and demonstrated the interdependence of individual γTuSC components for maintaining a stable complex. PMID:26224545

  19. An approximate inversion method of geoelectrical sounding data using linear and bayesian statistical approaches. Examples of Tritrivakely volcanic lake and Mahitsy area (central part of Madagascar)

    International Nuclear Information System (INIS)

    Ranaivo Nomenjanahary, F.; Rakoto, H.; Ratsimbazafy, J.B.

    1994-08-01

    This paper is concerned with resistivity sounding measurements performed from single site (vertical sounding) or from several sites (profiles) within a bounded area. The objective is to present an accurate information about the study area and to estimate the likelihood of the produced quantitative models. The achievement of this objective obviously requires quite relevant data and processing methods. It also requires interpretation methods which should take into account the probable effect of an heterogeneous structure. In front of such difficulties, the interpretation of resistivity sounding data inevitably involves the use of inversion methods. We suggest starting the interpretation in simple situation (1-D approximation), and using the rough but correct model obtained as an a-priori model for any more refined interpretation. Related to this point of view, special attention should be paid for the inverse problem applied to the resistivity sounding data. This inverse problem is nonlinear, while linearity inherent in the functional response used to describe the physical experiment. Two different approaches are used to build an approximate but higher dimensional inversion of geoelectrical data: the linear approach and the bayesian statistical approach. Some illustrations of their application in resistivity sounding data acquired at Tritrivakely volcanic lake (single site) and at Mahitsy area (several sites) will be given. (author). 28 refs, 7 figs

  20. Rock- and Paleomagnetic Properties and Modeling of a Deep Crustal Volcanic System, the Reinfjord Ultramafic Complex, Seiland Igneous Province, Northern Norway

    Science.gov (United States)

    ter Maat, G. W.; Pastore, Z.; Michels, A.; Church, N. S.; McEnroe, S. A.; Larsen, R. B.

    2017-12-01

    The Reinfjord Ultramafic Complex is part of the 5000 km2 Seiland Igneous Province (SIP) in Northern Norway. The SIP is argued to be the deep-seated conduit system of a Large Igneous Province and was emplaced at 25-35 km depth in less than 10 Ma (570-560 Ma). The Reinfjord Ultramafic Complex was emplaced during three major successive events at 22-28km depth at pressures of 6-8kb, with associated temperatures 1450-1500°C (Roberts, 2006). The rocks are divided into three formations: the central series (CS) consisting of mainly dunites, upper layered series (ULS) consisting of dunites and wehrlites, a lower layered series (LLS) containing most pyroxene-rich rocks and a marginal zone (MZ) which formed where the ultramafic melts intruded the gabbro-norite and metasedimentary gneisses. Deep exposures such as the Reinfjord Ultramafic Complex are rare, therefore this study gives a unique insight in the rock magnetic properties of a deep ultramafic system. Localised serpentinised zones provide an opportunity to observe the effect of this alteration process on the magnetic properties of deep-seated rocks. Here, we present the results from the rock magnetic properties, a paleomagnetic study and combined potential-fields modeling. The study of the rock magnetic properties provides insight in primary processes associated with the intrusion, and later serpentinization. The paleomagnetic data yields two distinct directions. One direction corresponds to a Laurentia pole at ≈ 532 Ma while the other, though younger, is not yet fully understood. Rock magnetic properties were measured on > 700 specimens and used to constrain the modelling of gravity, high-resolution helicopter, and ground magnetic data. The intrusion is modelled as a cylindrically shaped complex with a dunite core surrounded by wehrlite and gabbro. The ultramafic part of the complex dips to the NE and its maximum vertical extent is modelled to 1400m. Furthermore, modelling allows estimation of relative volumes of

  1. Central ossifying fibroma, periapical cemento-osseous dysplasia and complex odontoma occurring in the same jaw

    Directory of Open Access Journals (Sweden)

    Farzaneh Agha Hosseini

    2011-05-01

    Full Text Available Central ossifying fibroma is a rare, benign fibro-osseous lesion that arises from the periodontal ligament. Periapical cemento-osseous dysplasia is another variant of fibro-osseous lesion which occurs in the anterior region of the mandible of females. Odontoma is a benign odontogenic tumor that contains enamel, dentine cement and pulp tissue. A 46-year-old woman was referred to the Department of Oral Medicine, School of Dentistry, Tehran University of Medical Sciences, with two nonpainful swellings on both sides of the mandible, which had been slowly growing over a period of one year. Our differential diagnosis was florid cemento-osseous dysplasia, focal cemento-osseous dysplasia for the right side, complex odontoma for the left side and periapical cement-osseous dysplasia for the anterior side. The historical feature revealed ossifying fibroma, complex odontoma and periapical cemento-osseous dysplasia. The occurrence of these three lesions in the same jaw has been rarely reported in the literature. The relationship between the occurrence of these three lesions is not obvious it could be coincidental. It seems that more case reports are needed to establish the relationship between them.

  2. Prediction of extreme floods in the Central Andes by means of Complex Networks

    Science.gov (United States)

    Boers, Niklas; Bookhagen, Bodo; Barbosa, Henrique; Marwan, Norbert; Kurths, Jürgen; Marengo, Jose

    2014-05-01

    Based on a non-linear synchronisation measure and complex network theory, we present a novel framework for the prediction of extreme events of spatially embedded, interrelated time series. This method is general in the sense that it can be applied to any type of spatially sampled time series with significant interrelations, ranging from climate observables to biological or stock market data. In this presentation, we apply our method to extreme rainfall in South America and show how this leads to the prediction of more than 60% (90% during El Niño conditions) of extreme rainfall events in the eastern Central Andes of Bolivia and northern Argentina, with only 1% false alarms. From paleoclimatic to decadal time scales, the Central Andes continue to be subject to pronounced changes in climatic conditions. In particular, our and past work shows that frequency as well as magnitudes of extreme rainfall events have increased significantly during past decades, calling for a better understanding of the involved climatic mechanisms. Due to their large spatial extend and occurrence at high elevations, these extreme events often lead to severe floods and landslides with disastrous socioeconomic impacts. They regularly affect tens of thousands of people and produce estimated costs of the order of several hundred million USD. Alongside with the societal value of predicting natural hazards, our study provides insights into the responsible climatic features and suggests interactions between Rossby waves in polar regions and large scale (sub-)tropical moisture transport as a driver of subseasonal variability of the South American monsoon system. Predictable extreme events result from the propagation of extreme rainfall from the region of Buenos Aires towards the Central Andes given characteristic atmospheric conditions. Our results indicate that the role of frontal systems originating from Rossby waves in polar latitudes is much more dominant for controlling extreme rainfall in

  3. Sr and Nd isotopic characteristics of 1.77-1.58 Ga rift-related granites and volcanics of the Goiás tin province, central Brazil

    Directory of Open Access Journals (Sweden)

    MÁRCIO M. PIMENTEL

    2001-06-01

    Full Text Available Supracrustal rocks of the Araí Group, together with coeval A-type granites represent a ca. 1.77-1.58 Ga old continental rift in Brazil. Two granite families are identified: the older (1.77 Ga group forms small undeformed plutons, and the younger granites (ca. 1.58 Ga constitute larger, deformed plutons. Sr-Nd isotopic data for these rocks indicate that the magmatism is mostly product of re-melting of Paleoproterozoic sialic crust. Initial Sr ratios for both granite families are ca 0.726 and 0.720. Most TDM model ages are between 2.58 and 1.80 Ga. epsilonND(T values are between +3.6 and -11.9. Araí volcanics are bimodal, with basalts and dacites/rhyolites interlayered with continental sediments. The felsic volcanics show Nd isotopic characteristics which are very similar to the granites, and are also interpreted as reworking of Paleoproterozoic crust. Detrital sediments of the Araí Group revealed T DM model ages between 2.4 and 2.16 Ga, indicating that they are the product of erosion of Paleoproterozoic crust. The data indicate that the Araí rift system was established on crust that had just become stable after the Paleoproterozoic orogeny.As rochas supracrustais do Grupo Araí, e os granitos tipo-A associados, representam um rift continental paleo-mesoproterozóico. Duas famílias de granitos são identificadas: a mais antiga (ca. 1,77 Ga forma pequenos plutons circulares enquanto a mais jovem (ca. 1,58 Ga, constitui corpos maiores e deformados. Dados isotópicos Sr-Nd indicam que o magmatismo félsico é predominantemente o produto de re-fusão de crosta de idade paleoproterozóica. Razões 87Sr/86Sr iniciais das duas famílias são ca. 0,726 e 0,720. A maioria das idades modelo T DM caem no intervalo entre 2,58 e 1,80 Ga e os valores de épsilonND(T se distribuem entre +3.6 e -11.9. Rochas vulcânicas do Grupo Araí são bimodais, com basaltos e dacitos/riolitos intercalados em sedimentos continentais. As vulcânicas félsicas mostram

  4. U-Pb SHRIMP and Sm-Nd geochronology of the Silvânia Volcanics and Jurubatuba Granite: juvenile Paleoproterozoic crust in the basement of the Neoproterozoic Brasília Belt, Goiás, central Brazil

    Directory of Open Access Journals (Sweden)

    FISCHEL DANIELLE P.

    2001-01-01

    Full Text Available U-Pb SHRIMP and Sm-Nd isotopic ages were determined for felsic metavolcanic rocks from the Silvânia Sequence and Jurubatuba Granite in the central part of the Brasília Belt. Zircon grains from a metavolcanic sample yielded 2115 ± 23 Ma and from the granite yielded 2089 ± 14 Ma, interpreted as crystallization ages of these rocks. Six metavolcanic samples of the Silvânia Sequence yielded a six-point whole-rock Sm-Nd isochron indicating a crystallization age of 2262 ± 110 Ma and positive epsilonNd(T = +3.0 interpreted as a juvenile magmatic event. Nd isotopic analyses on samples from the Jurubatuba Granite have Paleoproterozoic T DM model ages between 2.30 and 2.42 Ga and epsilonNd(T values vary between -0.22 and -0.58. The oldest T DM value refers to a sedimentary xenolith in the granite. These results suggest crystallization ages of Silvânia volcanics and Jurubatuba Granite are the first evidence of a ca. 2.14-2.08 juvenile magmatic event in the basement of the central part of the Brasília Belt that implies the presence of arc/suture hidden in reworked basement of the Brasília Belt.

  5. Inside the "African cattle complex": animal burials in the holocene central Sahara.

    Directory of Open Access Journals (Sweden)

    Savino di Lernia

    Full Text Available Cattle pastoralism is an important trait of African cultures. Ethnographic studies describe the central role played by domestic cattle within many societies, highlighting its social and ideological value well beyond its mere function as 'walking larder'. Historical depth of this African legacy has been repeatedly assessed in an archaeological perspective, mostly emphasizing a continental vision. Nevertheless, in-depth site-specific studies, with a few exceptions, are lacking. Despite the long tradition of a multi-disciplinary approach to the analysis of pastoral systems in Africa, rarely do early and middle Holocene archaeological contexts feature in the same area the combination of settlement, ceremonial and rock art features so as to be multi-dimensionally explored: the Messak plateau in the Libyan central Sahara represents an outstanding exception. Known for its rich Pleistocene occupation and abundant Holocene rock art, the region, through our research, has also shown to preserve the material evidence of a complex ritual dated to the Middle Pastoral (6080-5120 BP or 5200-3800 BC. This was centred on the frequent deposition in stone monuments of disarticulated animal remains, mostly cattle. Animal burials are known also from other African contexts, but regional extent of the phenomenon, state of preservation of monuments, and associated rock art make the Messak case unique. GIS analysis, excavation data, radiocarbon dating, zooarchaeological and isotopic (Sr, C, O analyses of animal remains, and botanical information are used to explore this highly formalized ritual and the lifeways of a pastoral community in the Holocene Sahara.

  6. Neuroarchitecture and neuroanatomy of the Drosophila central complex: A GAL4-based dissection of protocerebral bridge neurons and circuits.

    Science.gov (United States)

    Wolff, Tanya; Iyer, Nirmala A; Rubin, Gerald M

    2015-05-01

    Insects exhibit an elaborate repertoire of behaviors in response to environmental stimuli. The central complex plays a key role in combining various modalities of sensory information with an insect's internal state and past experience to select appropriate responses. Progress has been made in understanding the broad spectrum of outputs from the central complex neuropils and circuits involved in numerous behaviors. Many resident neurons have also been identified. However, the specific roles of these intricate structures and the functional connections between them remain largely obscure. Significant gains rely on obtaining a comprehensive catalog of the neurons and associated GAL4 lines that arborize within these brain regions, and on mapping neuronal pathways connecting these structures. To this end, small populations of neurons in the Drosophila melanogaster central complex were stochastically labeled using the multicolor flip-out technique and a catalog was created of the neurons, their morphologies, trajectories, relative arrangements, and corresponding GAL4 lines. This report focuses on one structure of the central complex, the protocerebral bridge, and identifies just 17 morphologically distinct cell types that arborize in this structure. This work also provides new insights into the anatomical structure of the four components of the central complex and its accessory neuropils. Most strikingly, we found that the protocerebral bridge contains 18 glomeruli, not 16, as previously believed. Revised wiring diagrams that take into account this updated architectural design are presented. This updated map of the Drosophila central complex will facilitate a deeper behavioral and physiological dissection of this sophisticated set of structures. © 2014 Wiley Periodicals, Inc.

  7. Seismic anisotropy of the French Massif Central and predisposition of Cenozoic rifting and volcanism by Variscan suture hidden in the mantle lithosphere

    Czech Academy of Sciences Publication Activity Database

    Babuška, Vladislav; Plomerová, Jaroslava; Vecsey, Luděk; Granet, M.; Achauer, U.

    2002-01-01

    Roč. 21, č. 4 (2002), s. U407-U429 ISSN 0278-7407 R&D Projects: GA ČR GV205/98/K004; GA ČR GA205/01/1154; GA AV ČR IAA3012908 Institutional research plan: CEZ:AV0Z3012916 Keywords : seismic anisotropy * Massif Central * mantle lithosphere Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.697, year: 2002

  8. Microglomerular Synaptic Complexes in the Sky-Compass Network of the Honeybee Connect Parallel Pathways from the Anterior Optic Tubercle to the Central Complex.

    Science.gov (United States)

    Held, Martina; Berz, Annuska; Hensgen, Ronja; Muenz, Thomas S; Scholl, Christina; Rössler, Wolfgang; Homberg, Uwe; Pfeiffer, Keram

    2016-01-01

    While the ability of honeybees to navigate relying on sky-compass information has been investigated in a large number of behavioral studies, the underlying neuronal system has so far received less attention. The sky-compass pathway has recently been described from its input region, the dorsal rim area (DRA) of the compound eye, to the anterior optic tubercle (AOTU). The aim of this study is to reveal the connection from the AOTU to the central complex (CX). For this purpose, we investigated the anatomy of large microglomerular synaptic complexes in the medial and lateral bulbs (MBUs/LBUs) of the lateral complex (LX). The synaptic complexes are formed by tubercle-lateral accessory lobe neuron 1 (TuLAL1) neurons of the AOTU and GABAergic tangential neurons of the central body's (CB) lower division (TL neurons). Both TuLAL1 and TL neurons strongly resemble neurons forming these complexes in other insect species. We further investigated the ultrastructure of these synaptic complexes using transmission electron microscopy. We found that single large presynaptic terminals of TuLAL1 neurons enclose many small profiles (SPs) of TL neurons. The synaptic connections between these neurons are established by two types of synapses: divergent dyads and divergent tetrads. Our data support the assumption that these complexes are a highly conserved feature in the insect brain and play an important role in reliable signal transmission within the sky-compass pathway.

  9. A Study of the Dětaň Locality (Oligocene, Doupovské hory Mts. Volcanic Complex, Czech Republic): Collection of Field Data and Starting Points for Interpretation

    Czech Academy of Sciences Publication Activity Database

    Mikuláš, Radek; Fejfar, O.; Ulrych, Jaromír; Žigová, Anna; Kadlecová, Eva; Cajz, Vladimír

    2003-01-01

    Roč. 15, - (2003), s. 91-97 ISSN 1210-9606. [Hibsch 2002 Symposium. Teplá near Třebenice, Ústí nad Labem, Mariánské Lázně, 03.06.2002-08.06.2002] R&D Projects: GA ČR GA205/00/1000 Institutional research plan: CEZ:AV0Z3013912 Keywords : volcanic lastic rocks * Oligocene * Doupovské hory Mts. Subject RIV: DB - Geology ; Mineralogy http://geolines.gli.cas.cz/fileadmin/volumes/volume15/G15-091.pdf

  10. Functional integration of complex miRNA networks in central and peripheral lesion and axonal regeneration.

    Science.gov (United States)

    Ghibaudi, M; Boido, M; Vercelli, A

    2017-11-01

    New players are emerging in the game of peripheral and central nervous system injury since their physiopathological mechanisms remain partially elusive. These mechanisms are characterized by several molecules whose activation and/or modification following a trauma is often controlled at transcriptional level. In this scenario, microRNAs (miRNAs/miRs) have been identified as main actors in coordinating important molecular pathways in nerve or spinal cord injury (SCI). miRNAs are small non-coding RNAs whose functionality at network level is now emerging as a new level of complexity. Indeed they can act as an organized network to provide a precise control of several biological processes. Here we describe the functional synergy of some miRNAs in case of SCI and peripheral damage. In particular we show how several small RNAs can cooperate in influencing simultaneously the molecular pathways orchestrating axon regeneration, inflammation, apoptosis and remyelination. We report about the networks for which miRNA-target bindings have been experimentally demonstrated or inferred based on target prediction data: in both cases, the connection between one miRNA and its downstream pathway is derived from a validated observation or is predicted from the literature. Hence, we discuss the importance of miRNAs in some pathological processes focusing on their functional structure as participating in a cooperative and/or convergence network. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. The 2016-2017 Central Italy Seismic Sequence: Source Complexity Inferred from Rupture Models.

    Science.gov (United States)

    Scognamiglio, L.; Tinti, E.; Casarotti, E.; Pucci, S.; Villani, F.; Cocco, M.; Magnoni, F.; Michelini, A.

    2017-12-01

    The Apennines have been struck by several seismic sequences in recent years, showing evidence of the activation of multiple segments of normal fault systems in a variable and, relatively short, time span, as in the case of the 1980 Irpinia earthquake (three shocks in 40 s), the 1997 Umbria-Marche sequence (four main shocks in 18 days) and the 2009 L'Aquila earthquake having three segments activated within a few weeks. The 2016-2017 central Apennines seismic sequence begin on August 24th with a MW 6.0 earthquake, which strike the region between Amatrice and Accumoli causing 299 fatalities. This earthquake ruptures a nearly 20 km long normal fault and shows a quite heterogeneous slip distribution. On October 26th, another main shock (MW 5.9) occurs near Visso extending the activated seismogenic area toward the NW. It is a double event rupturing contiguous patches on the fault segment of the normal fault system. Four days after the second main shock, on October 30th, a third earthquake (MW 6.5) occurs near Norcia, roughly midway between Accumoli and Visso. In this work we have inverted strong motion waveforms and GPS data to retrieve the source model of the MW 6.5 event with the aim of interpreting the rupture process in the framework of this complex sequence of moderate magnitude earthquakes. We noted that some preliminary attempts to model the slip distribution of the October 30th main shock using a single fault plane oriented along the Apennines did not provide convincing fits to the observed waveforms. In addition, the deformation pattern inferred from satellite observations suggested the activation of a multi-fault structure, that is coherent to the complexity and the extension of the geological surface deformation. We investigated the role of multi-fault ruptures and we found that this event revealed an extraordinary complexity of the rupture geometry and evolution: the coseismic rupture propagated almost simultaneously on a normal fault and on a blind fault

  12. Volcanic stratigraphy: A review

    Science.gov (United States)

    Martí, Joan; Groppelli, Gianluca; Brum da Silveira, Antonio

    2018-05-01

    Volcanic stratigraphy is a fundamental component of geological mapping in volcanic areas as it yields the basic criteria and essential data for identifying the spatial and temporal relationships between volcanic products and intra/inter-eruptive processes (earth-surface, tectonic and climatic), which in turn provides greater understanding of the geological evolution of a region. Establishing precise stratigraphic relationships in volcanic successions is not only essential for understanding the past behaviour of volcanoes and for predicting how they might behave in the future, but is also critical for establishing guidelines for exploring economic and energy resources associated with volcanic systems or for reconstructing the evolution of sedimentary basins in which volcanism has played a significant role. Like classical stratigraphy, volcanic stratigraphy should also be defined using a systematic methodology that can provide an organised and comprehensive description of the temporal and spatial evolution of volcanic terrain. This review explores different methods employed in studies of volcanic stratigraphy, examines four case studies that use differing stratigraphic approaches, and recommends methods for using systematic volcanic stratigraphy based on the application of the concepts of traditional stratigraphy but adapted to the needs of volcanological environment.

  13. γ-Tubulin complex in Trypanosoma brucei: molecular composition, subunit interdependence and requirement for axonemal central pair protein assembly.

    Science.gov (United States)

    Zhou, Qing; Li, Ziyin

    2015-11-01

    γ-Tubulin complex constitutes a key component of the microtubule-organizing center and nucleates microtubule assembly. This complex differs in complexity in different organisms: the budding yeast contains the γ-tubulin small complex (γTuSC) composed of γ-tubulin, gamma-tubulin complex protein (GCP)2 and GCP3, whereas animals contain the γ-tubulin ring complex (γTuRC) composed of γTuSC and three additional proteins, GCP4, GCP5 and GCP6. In Trypanosoma brucei, the composition of the γ-tubulin complex remains elusive, and it is not known whether it also regulates assembly of the subpellicular microtubules and the spindle microtubules. Here we report that the γ-tubulin complex in T. brucei is composed of γ-tubulin and three GCP proteins, GCP2-GCP4, and is primarily localized in the basal body throughout the cell cycle. Depletion of GCP2 and GCP3, but not GCP4, disrupted the axonemal central pair microtubules, but not the subpellicular microtubules and the spindle microtubules. Furthermore, we showed that the γTuSC is required for assembly of two central pair proteins and that γTuSC subunits are mutually required for stability. Together, these results identified an unusual γ-tubulin complex in T. brucei, uncovered an essential role of γTuSC in central pair protein assembly, and demonstrated the interdependence of individual γTuSC components for maintaining a stable complex. © 2015 John Wiley & Sons Ltd.

  14. Extreme pointer years in tree-ring records of Central Spain as evidence of volcanic eruptions (Huaynaputina, Peru, 1600 AC) and other climatic events

    Science.gov (United States)

    Génova, M.

    2011-12-01

    The study of pointer years based on the numerous tree-ring chronologies of the central Iberian Peninsula (Sierra de Guadarrama) could provide complementary information about climate variability over the last 405 years. In total, 64 pointer years have been identified: 30 negative (representing minimum growths) and 34 positive (representing maximum growths), the most significant of these being 1601, 1963 and 1996 for the negative ones, and 1734 and 1737 for the positive ones. Given that summer precipitation has been the most incident factor in the general variability of growth of Pinus in the Sierra de Guadarrama in the second half of the 20th century, it is also an explanatory factor in almost 50% of the extreme growths. Furthermore, the data show that there has been variability over the centuries in the distribution of the frequencies of pointer years and intervals. The first half of the 17th century, together with the second half of the 20th century, constitute the two most notable periods for the frequency of negative pointer years in Central Spain. This variability was sufficiently notable to affirm that, both in the 17th and 20th centuries, the macroclimatic anomalies that affected growth were more frequent and more extreme than in the other two centuries analysed. The period 1600-1602 is of special significance, being one of the most unfavourable for tree growth in the centre of Spain, with 1601 representing the minimum index in the regional chronology. It is possible to infer that these phenomena are the effect of the eruption of Huaynaputina, which occurred in Peru at the beginning of 1600 AD. This is the first time that the effects of this eruption in the tree-ring records of central and southern Europe have been demonstrated.

  15. The Volcanism Ontology (VO): a model of the volcanic system

    Science.gov (United States)

    Myer, J.; Babaie, H. A.

    2017-12-01

    We have modeled a part of the complex material and process entities and properties of the volcanic system in the Volcanism Ontology (VO) applying several top-level ontologies such as Basic Formal Ontology (BFO), SWEET, and Ontology of Physics for Biology (OPB) within a single framework. The continuant concepts in BFO describe features with instances that persist as wholes through time and have qualities (attributes) that may change (e.g., state, composition, and location). In VO, the continuants include lava, volcanic rock, and volcano. The occurrent concepts in BFO include processes, their temporal boundaries, and the spatio-temporal regions within which they occur. In VO, these include eruption (process), the onset of pyroclastic flow (temporal boundary), and the space and time span of the crystallization of lava in a lava tube (spatio-temporal region). These processes can be of physical (e.g., debris flow, crystallization, injection), atmospheric (e.g., vapor emission, ash particles blocking solar radiation), hydrological (e.g., diffusion of water vapor, hot spring), thermal (e.g., cooling of lava) and other types. The properties (predicates) relate continuants to other continuants, occurrents to continuants, and occurrents to occurrents. The ontology also models other concepts such as laboratory and field procedures by volcanologists, sampling by sensors, and the type of instruments applied in monitoring volcanic activity. When deployed on the web, VO will be used to explicitly and formally annotate data and information collected by volcanologists based on domain knowledge. This will enable the integration of global volcanic data and improve the interoperability of software that deal with such data.

  16. Assessing hydraulic connections across a complex sequence of volcanic rocks - Analysis of U-20 WW multiple-well aquifer test, Pahute Mesa, Nevada National Security Site, Nevada

    Science.gov (United States)

    Garcia, C. Amanda; Fenelon, Joseph M.; Halford, Keith J.; Reiner, Steven R.; Laczniak, Randell J.

    2011-01-01

    Groundwater beneath Pahute Mesa flows through a complexly layered sequence of volcanic rock aquifers and confining units that have been faulted into distinct structural blocks. Hydraulic property estimates of rocks and structures in this flow system are necessary to assess radionuclide migration near underground nuclear testing areas. The U.S. Geological Survey (USGS) used a 12 month (October 1, 2008— October 1, 2009) intermittent pumping schedule of well U-20 WW and continuously monitored water levels in observation wells ER-20-6 #3, UE-20bh 1, and U-20bg as a multi-well aquifer test to evaluate hydraulic connections across structural blocks, bulk hydraulic properties of volcanic rocks, and the hydraulic significance of a major fault. Measured water levels were approximated using synthetic water levels generated from an analytical model. Synthetic water levels are a summation of environmental water-level fluctuations and a Theis (1935) transform of the pumping signal from flow rate to water-level change. Drawdown was estimated by summing residual differences between measured and synthetic water levels and the Theis-transformed pumping signal from April to September 2009. Drawdown estimates were used in a three‑dimensional numerical model to estimate hydraulic properties of distinct aquifers, confining units, and a major fault.

  17. Observations and modelling of inflation in the Lazufre volcanic region, South America

    Science.gov (United States)

    Pearse, J.; Lundgren, P.

    2010-12-01

    The Central Volcanic Zone (CVZ) is an active volcanic arc in the central Andes, extending through Peru, southwestern Bolivia, Chile, and northwestern Argentina [De Silva, 1989; De Silva and Francis, 1991]. The CVZ includes a number of collapsed calderas, remnants of catastrophic eruptions, which are now thought to be inactive. However, recent Interferometric Synthetic Aperture Radar (InSAR) observations [Pritchard and Simons, 2004] show surface deformation occurring at some of these large ancient volcanic regions, indicating that magma chambers are slowly inflating beneath the surface. The mechanisms responsible for the initiation and growth of large midcrustal magma chambers remains poorly understood, and InSAR provides an opportunity for us to observe volcanic systems in remote regions that are otherwise difficult to monitor and observe. The Lastarria-Cordon del Azufre ("Lazufre" [Pritchard and Simons, 2002]) volcanic area is one such complex showing recent deformation, with average surface uplift rates of approximately 2.5 cm/year [Froger et al., 2007; Ruch et al, 2008]. We have processed InSAR data from ERS-1/2 and Envisat in the Lazufre volcanic area, including both ascending and descending satellite tracks. Time series analysis of the data shows steady uplift beginning in about 2000, continuing into 2010. We use boundary-element elastic models to invert for the depth and shape of the magmatic source responsible for the surface deformation. Given data from both ascending and descending tracks, we are able to resolve the ambiguity between the source depth and size, and constrain the geometry of the inflating magma source. Finite element modelling allows us to understand the effect of viscoelasticity on the development of the magma chamber.

  18. U-Pb age in zircon of intrusive granite at Acopiara complex, Crystal region, domain Central Ceara, Brazil

    International Nuclear Information System (INIS)

    Neri, T.F.O.; Hamelak, G.M.S.; Azevedo, L.R.; Mattos, I.C.; Verissimo, C.U.V.; Nogueira Neto, J.A.; Lima, M.N.

    2015-01-01

    Granitic body mineralogically composed by two micas, located at Crystal region, Ceara Central domain and intruded into lithotypes from Acopiara complex, provided an age of ∼526 Ma, indicating important period of magma generation of granitic composition associated with crustal anatexia, during Paleozoic

  19. Motor dysfunction of complex regional pain syndrome is related to impaired central processing of proprioceptive information.

    Science.gov (United States)

    Bank, Paulina J M; Peper, C Lieke E; Marinus, Johan; Beek, Peter J; van Hilten, Jacobus J

    2013-11-01

    Our understanding of proprioceptive deficits in complex regional pain syndrome (CRPS) and its potential contribution to impaired motor function is still limited. To gain more insight into these issues, we evaluated accuracy and precision of joint position sense over a range of flexion-extension angles of the wrist of the affected and unaffected sides in 25 chronic CRPS patients and in 50 healthy controls. The results revealed proprioceptive impairment at both the patients' affected and unaffected sides, characterized predominantly by overestimation of wrist extension angles. Precision of the position estimates was more prominently reduced at the affected side. Importantly, group differences in proprioceptive performance were observed not only for tests at identical percentages of each individual's range of wrist motion but also when controls were tested at wrist angles that corresponded to those of the patient's affected side. More severe motor impairment of the affected side was associated with poorer proprioceptive performance. Based on additional sensory tests, variations in proprioceptive performance over the range of wrist angles, and comparisons between active and passive displacements, the disturbances of proprioceptive performance most likely resulted from altered processing of afferent (and not efferent) information and its subsequent interpretation in the context of a distorted "body schema." The present results point at a significant role for impaired central processing of proprioceptive information in the motor dysfunction of CRPS and suggest that therapeutic strategies aimed at identification of proprioceptive impairments and their restoration may promote the recovery of motor function in CRPS patients. Copyright © 2013 American Pain Society. Published by Elsevier Inc. All rights reserved.

  20. Benthic foraminifera baseline assemblages from a coastal nearshore reef complex on the central Great Barrier Reef

    Science.gov (United States)

    Johnson, Jamie; Perry, Chris; Smithers, Scott; Morgan, Kyle

    2016-04-01

    Declining water quality due to river catchment modification since European settlement (c. 1850 A.D.) represents a major threat to the health of coral reefs on Australia's Great Barrier Reef (GBR), particularly for those located in the coastal waters of the GBR's inner-shelf. These nearshore reefs are widely perceived to be most susceptible to declining water quality owing to their close proximity to river point sources. Despite this, nearshore reefs have been relatively poorly studied with the impacts and magnitudes of environmental degradation still remaining unclear. This is largely due to ongoing debates concerning the significance of increased sediment yields against naturally high background sedimentary regimes. Benthic foraminifera are increasingly used as tools for monitoring environmental and ecological change on coral reefs. On the GBR, the majority of studies have focussed on the spatial distributions of contemporary benthic foraminiferal assemblages. While baseline assemblages from other environments (e.g. inshore reefs and mangroves) have been described, very few records exist for nearshore reefs. Here, we present preliminary results from the first palaeoecological study of foraminiferal assemblages of nearshore reefs on the central GBR. Cores were recovered from the nearshore reef complex at Paluma Shoals using percussion techniques. Recovery was 100%, capturing the entire Holocene reef sequence of the selected reef structures. Radiocarbon dating and subsequent age-depth modelling techniques were used to identify reef sequences pre-dating European settlement. Benthic foraminifera assemblages were reconstructed from the identified sequences to establish pre-European ecological baselines with the aim of providing a record of foraminiferal distribution during vertical reef accretion and against which contemporary ecological change may be assessed.

  1. Comparison of different wind data interpolation methods for a region with complex terrain in Central Asia

    Science.gov (United States)

    Reinhardt, Katja; Samimi, Cyrus

    2018-01-01

    While climatological data of high spatial resolution are largely available in most developed countries, the network of climatological stations in many other regions of the world still constitutes large gaps. Especially for those regions, interpolation methods are important tools to fill these gaps and to improve the data base indispensible for climatological research. Over the last years, new hybrid methods of machine learning and geostatistics have been developed which provide innovative prospects in spatial predictive modelling. This study will focus on evaluating the performance of 12 different interpolation methods for the wind components \\overrightarrow{u} and \\overrightarrow{v} in a mountainous region of Central Asia. Thereby, a special focus will be on applying new hybrid methods on spatial interpolation of wind data. This study is the first evaluating and comparing the performance of several of these hybrid methods. The overall aim of this study is to determine whether an optimal interpolation method exists, which can equally be applied for all pressure levels, or whether different interpolation methods have to be used for the different pressure levels. Deterministic (inverse distance weighting) and geostatistical interpolation methods (ordinary kriging) were explored, which take into account only the initial values of \\overrightarrow{u} and \\overrightarrow{v} . In addition, more complex methods (generalized additive model, support vector machine and neural networks as single methods and as hybrid methods as well as regression-kriging) that consider additional variables were applied. The analysis of the error indices revealed that regression-kriging provided the most accurate interpolation results for both wind components and all pressure heights. At 200 and 500 hPa, regression-kriging is followed by the different kinds of neural networks and support vector machines and for 850 hPa it is followed by the different types of support vector machine and

  2. Indoor radon related to uranium in granitoids of the Central Bohemian plutonic complex

    International Nuclear Information System (INIS)

    Barnet, I.; Fojtikova, I.

    2004-01-01

    The study is based on the indoor radon data (one year measurements, Kodak LR 115 track etch detectors), vectorized geological maps 1:50000, vectorized coordinates of dwellings and uranium data for granitoid types of the Central Bohemian Plutonic Complex (CBPC). Using ArcGis 8.2 programme, the position of 16145 dwellings was linked to a geological database covering the CBPC (approx. 3200 km 2 ), and the type of underlying rock type was specified for each house. The resulting databases enabled us to calculate the mean EEC indoor Rn data for particular granitoid types and to study the relationship between the indoor Rn and the U concentrations. The petrogenetically variable CBPC was emplaced during Variscan orogenesis (330-350 Ma) and is among the most radioactive rock types within the Bohemian Massif. A long-term process of CBPC genesis resulted in more than 20 granitoid types, differing by their petrogenetic characteristics as well as mineralogical and chemical composition, including uranium concentration. The relation between the mean indoor radon values and uranium concentrations in particular rock types was examined. A positive regression between indoor Rn and uranium as the source of Rn soil gas clearly demonstrates how regional geology influences the indoor radon activity concentration in dwellings. The highest indoor Rn concentrations were observed in the Sedlcany granodiorite and Certovo bremeno syenite, where also the highest gamma dose rates (150-210 nGy.h -1 ) within all granitoid types in the Czech Republic were observed. The two rock types differ from other granitoids by a relatively high zircon concentration, which is the main source of U and subsequently of soil gas Rn being released from the bedrock. The lower indoor Rn values of Certovo bremeno syenite which do not correspond with the high U concentrations can be explained by a relatively low permeability of its clayey weathering crust. This feature was also observed for soil gas radon concentration

  3. Degassing of different magma batches as the main controlling factor for fumarolic fluid chemistry at the Planchón-Peteroa-Azufre Volcanic Complex (Argentina-Chile) in 2010-2015

    Science.gov (United States)

    Tassi, Franco; Aguilera, Felipe; Benavente, Oscar; Paonita, Antonio; Chiodini, Giovanni; Caliro, Stefano; Agusto, Mariano; Gutierrez, Francisco; Capaccioni, Bruno; Vaselli, Orlando; Caselli, Alberto

    2016-04-01

    This study presents the first geochemical data of gas discharges collected during five sampling campaigns (February 2010 to March 2015), from the NNE-oriented Planchón-Peteroa-Azufre Volcanic Complex (PPAVC), located in the Transitional Southern Volcanic Zone (TSVZ) at the border between Argentina and Chile. In 2012, the acidic gas species of the low temperature (up to 102 °C) fumaroles from the Peteroa summit showed a huge increase (SO2>CO2) with respect to the 2010-2011 period, whereas the typical hydrothermal compounds (CH4 and light hydrocarbons) decreased. Such a dramatic compositional change was apparently indicating a pulse of magmatic fluids. By contrast, the temporal evolution of the δ18O-H2O, δD-H2O, R/Ra and 13C-CO2 values suggested an enhanced fluid contribution from a shallow source. In 2014-2015, the dominant hydrothermal signature characterizing the 2010-2011 fumaroles was almost completely restored. The temporary decoupling of the chemical and isotopic parameters can only be reconciled by admitting the occurrence of a double source of magmatic fluids: a basaltic batch, controlling the fumarolic chemistry in 2010-2011 and 2014-2015, and a small, shallower dacitic batch, likely affected by a significant crustal contamination, whose contribution to the fumarolic fluid emissions achieved its maximum in 2012. It cannot be ruled out that the phreatic to phreatomagmatic eruptions (VEI ≤2) that have affected Peteroa volcano from January 2010 to July 2011 have played a significant role for the modification of the deep feeding source of the fumarolic gases. The disturbance created by the volcanic events and the related seismic activity (MW<3), possibly related to the devastating Maule earthquake occurred on February 27 2010, could have activated a silent dacitic magma batch that in 2012 imposed over that of basaltic composition. Although this scenario provides a reliable explanation for the peculiar compositional changes that affected the Peteroa

  4. Volcanic spreading forcing and feedback in geothermal reservoir development, Amiata Volcano, Italia

    Science.gov (United States)

    Borgia, Andrea; Mazzoldi, Alberto; Brunori, Carlo Alberto; Allocca, Carmine; Delcroix, Carlo; Micheli, Luigi; Vercellino, Alberto; Grieco, Giovanni

    2014-09-01

    We made a stratigraphic, structural and morphologic study of the Amiata Volcano in Italy. We find that the edifice is dissected by intersecting grabens that accommodate the collapse of the higher sectors of the volcano. In turn, a number of compressive structures and diapirs exist around the margin of the volcano. These structures create an angular drainage pattern, with stream damming and captures, and a set of lakes within and around the volcano. We interpret these structures as the result of volcanic spreading of Amiata on its weak substratum, formed by the late Triassic evaporites (Burano Anhydrites) and the Middle-Jurassic to Early-Cretaceous clayey chaotic complexes (Ligurian Complex). Regional doming created a slope in the basement facilitating the outward flow and spreading of the ductile layers forced by the volcanic load. We model the dynamics of spreading with a scaled lubrication approximation of the Navier Stokes equations, and numerically study a set of solutions. In the model we include simple functions for volcanic deposition and surface erosion that change the topography over time. Scaling indicates that spreading at Amiata could still be active. The numerical solution shows that, as the central part of the edifice sinks into the weak basement, diapiric structures of the underlying formations form around the base of the volcano. Deposition of volcanic rocks within the volcano and surface erosion away from it both enhance spreading. In addition, a sloping basement may constitute a trigger for spreading and formation of trains of adjacent diapirs. As a feedback, the hot hydrothermal fluids decrease the shear strength of the anhydrites facilitating the spreading process. Finally, we observe that volcanic spreading has created ideal heat traps that constitute todays' exploited geothermal fields at Amiata. Normal faults generated by volcanic spreading, volcanic conduits, and direct contact between volcanic rocks (which host an extensive fresh

  5. Basaltic volcanic episodes of the Yucca Mountain region

    International Nuclear Information System (INIS)

    Crowe, B.M.

    1990-01-01

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

  6. Gravity study of the Central African Rift system: a model of continental disruption 2. The Darfur domal uplift and associated Cainozoic volcanism

    Science.gov (United States)

    Bermingham, P. M.; Fairhead, J. D.; Stuart, G. W.

    1983-05-01

    Gravity studies of the Darfur uplift, Western Sudan, show it to be associated with a circular negative Bouguer anomaly, 50 mGal in amplitude and 700 km across. A three-dimensional model interpretation of the Darfur anomaly, using constraints deduced from geophysical studies of similar but more evolved Kenya and Ethiopia domes, suggests either a low-density laccolithic body at mid-lithospheric depth (~ 60 km) or a thinned lithosphere with emplacement at high level of low-density asthenospheric material. The regional setting of the Darfur uplift is described in terms of it being an integral part of the Central African Rift System which is shown to be broadly equivalent to the early to middle Miocene stage in the development of the Afro-Arabian Rift System. Comparisons between these rift systems suggest that extensional tectonics and passive rifting, resulting in the subsiding sedimentary rift basins associated with the Ngaoundere, Abu Gabra, Red Sea and Gulf of Aden rifts, are more typical of the early stage development of passive continental margins than the active domal uplift and development of rifted features associated with the Darfur, Kenya and Ethiopia domes.

  7. Seismic evidence for arc segmentation, active magmatic intrusions and syn-rift fault system in the northern Ryukyu volcanic arc

    Science.gov (United States)

    Arai, Ryuta; Kodaira, Shuichi; Takahashi, Tsutomu; Miura, Seiichi; Kaneda, Yoshiyuki

    2018-04-01

    Tectonic and volcanic structures of the northern Ryukyu arc are investigated on the basis of multichannel seismic (MCS) reflection data. The study area forms an active volcanic front in parallel to the non-volcanic island chain in the eastern margin of the Eurasian plate and has been undergoing regional extension on its back-arc side. We carried out a MCS reflection experiment along two across-arc lines, and one of the profiles was laid out across the Tokara Channel, a linear bathymetric depression which demarcates the northern and central Ryukyu arcs. The reflection image reveals that beneath this topographic valley there exists a 3-km-deep sedimentary basin atop the arc crust, suggesting that the arc segment boundary was formed by rapid and focused subsidence of the arc crust driven by the arc-parallel extension. Around the volcanic front, magmatic conduits represented by tubular transparent bodies in the reflection images are well developed within the shallow sediments and some of them are accompanied by small fragments of dipping seismic reflectors indicating intruded sills at their bottoms. The spatial distribution of the conduits may suggest that the arc volcanism has multiple active outlets on the seafloor which bifurcate at crustal depths and/or that the location of the volcanic front has been migrating trenchward over time. Further distant from the volcanic front toward the back-arc (> 30 km away), these volcanic features vanish, and alternatively wide rift basins become predominant where rapid transitions from normal-fault-dominant regions to strike-slip-fault-dominant regions occur. This spatial variation in faulting patterns indicates complex stress regimes associated with arc/back-arc rifting in the northern Okinawa Trough.[Figure not available: see fulltext.

  8. Quantification of the CO2 emitted from volcanic lakes in Pico Island (Azores)

    Science.gov (United States)

    Andrade, César; Cruz, José; Viveiros, Fátima; Branco, Rafael

    2017-04-01

    This study shows the results of the diffuse CO2 degassing surveys performed in lakes from Pico volcanic Island (Azores archipelago, Portugal). Detailed flux measurements using the accumulation chamber method were made at six lakes (Capitão, Caiado, Paul, Rosada, Peixinho and Negra) during two field campaigns, respectively, in winter (February 2016) and late summer (September 2016). Pico is the second largest island of the Azores archipelago with an area of 444.8 km2; the oldest volcanic unit is dated from about 300,000 years ago. The edification of Pico was mainly due to Hawaiian and Strombolian type volcanic activity, resulting in pahoehoe and aa lava flows of basaltic nature, as well as scoria and spatter cones. Three main volcanic complexes are identified in the island, namely (1) the so-called Montanha Volcanic Complex, corresponding to a central volcano located in the western side of the island that reaches a maximum altitude of 2351 m, (2) the São Roque-Piedade Volcanic Complex, and (3) the Topo-Lajes Volcanic Complex, this last one corresponding to the remnants of a shield volcano located in the south coast. The studied lakes are spread along the São Roque-Piedade Volcanic Complex at altitudes between 785 m and 898 m. Three are associated with depressions of undifferentiated origin (Caiado, Peixinho, Negra), two with depressions of tectonic origin (Capitão, Paul), while Rosada lake is located inside a scoria cone crater. The lakes surface areas vary between 1.25x10-2 and 5.38x10-2 km2, and the water column maximum depth is 7.9 m (3.5-7.9 m). The water storage ranges between 3.6x104 to 9.1x104 m3, and the estimated residence time does not exceed 1.8x10-1 years. A total of 1579 CO2 flux measurements were made during both surveys (868 in summer and 711 in the winter campaign), namely 518 in Caiado lake (293; 225), 358 in Paul (195; 163), 279 in Capitão (150, 129), 200 in Rosada (106, 94), 171 in Peixinho (71, 100) and 53 measurements in Negra lake. Negra

  9. INTEGRATING GEOPHYSICS, GEOLOGY, AND HYDROLOGY TO DETERMINE BEDROCK GEOMETRY CONTROLS ON THE ORIGIN OF ISOLATED MEADOW COMPLEXES WITHIN THE CENTRAL GREAT BASIN, NEVADA

    Science.gov (United States)

    Riparian meadow complexes found in mountain ranges of the Central Great Basin physiographic region (western United States) are of interest to researchers as they contain significant biodiversity relative to the surrounding basin areas. These meadow complexes are currently degradi...

  10. Volcanism on Io

    Science.gov (United States)

    Davies, Ashley Gerard

    2014-03-01

    Preface; Introduction; Part I. Io, 1610 to 1995: Galileo to Galileo: 1. Io, 1610-1979; 2. Between Voyager and Galileo: 1979-95; 3. Galileo at Io; Part II. Planetary Volcanism: Evolution and Composition: 4. Io and Earth: formation, evolution, and interior structure; 5. Magmas and volatiles; Part III. Observing and Modeling Volcanic Activity: 6. Observations: thermal remote sensing of volcanic activity; 7. Models of effusive eruption processes; 8. Thermal evolution of volcanic eruptions; Part IV. Galileo at Io: the Volcanic Bestiary: 9. The view from Galileo; 10. The lava lake at Pele; 11. Pillan and Tvashtar: lava fountains and flows; 12. Prometheus and Amirani: Effusive activity and insulated flows; 13. Loki Patera: Io's powerhouse; 14. Other volcanoes and eruptions; Part V. Volcanism on Io: The Global View: 15. Geomorphology: paterae, shields, flows and mountains; 16. Volcanic plumes; 17. Hot spots; Part VI. Io after Galileo: 18. Volcanism on Io: a post-Galileo view; 19. The future of Io observations; Appendix 1; Appendix 2; References; Index.

  11. Geochemistry and petrogenesis of serpentinite from the Ingalls ophiolite complex, central Cascades, Washington

    Science.gov (United States)

    MacDonald, J. H., Jr.; Milliken, S. H.; Zalud, K. M.

    2017-12-01

    The Jurassic Ingalls ophiolite complex is located in the central Cascades, Washington State. This ophiolite predominantly consists of three variably serpentinized mantle units. Serpentinite occurs as massive replacing peridotite, or as highly sheared fault zones cutting other rocks. Mylonitic serpentinite forms a large-scale mélange in the middle of the ophiolite, and is interpreted as a fracture zone. Whole-rock and mineral geochemistry of the massive serpentinite was done to understand the metasomatic process and identify the possible protoliths of these rocks. Whole-rock major and trace elements of the massive serpentinite are similar to modern peridotites. The majority of samples analyzed are strongly serpentinized, while a few were moderately to weakly altered. Ca, Mg, and Al suggest these rocks formed from serpentinized harzburgite and dunite with minor lherzolite. All samples have positive Eu/Eu*. Serpentinites plot in fields defined by modern abyssal and forearc peridotites. Trace elements suggests the protoliths underwent variable amounts of mantel depletion (5-20%). Serpentine and relic igneous minerals were analyzed by EPMA at the Florida Center for Analytical Electron Microscopy. The serpentine dose not chemically display brucite mixing, has minor substitution of Fe, Ni, and Cr for Mg, and minor Al substitution for Si. Bastites have higher Ni than replaced olivine. Mineral chemistry, high LOI, and X-ray diffraction suggest lizardite is the primary serpentine polymorph, with minor chrysotile also occurring. Relic Al-chromite and Cr-spinel commonly have Cr-magnetite rims. These relic cores have little SiO2 and Fe3+, suggesting the spinels are well preserved. Most spinels plot in overlap fields defined by abyssal and arc peridotite, while two samples plot entirely in arc fields. Relic olivine have Fo90 to Fo92 and plot along the mantle array. Relic pyroxene are primarily enstatite, with lesser high-Ca varieties. Relic minerals plot near fields defined by

  12. The 40Ar/39Ar and U/Pb dating of young rhyolites in the Kos-Nisyros volcanic complex, Eastern Aegean Arc, Greece: Age discordance due to excess 40Ar in biotite

    Science.gov (United States)

    Bachmann, O.; Schoene, B.; Schnyder, C.; Spikings, R.

    2010-08-01

    High-precision dating of Quaternary silicic magmas in the active Kos-Nisyros volcanic center (Aegean Arc, Greece) by both 40Ar/39Ar on biotite and U/Pb on zircon reveals a complex geochronological story. U/Pb ID-TIMS multi and single-grain zircon analyses from 3 different units (Agios Mammas and Zini domes, Kefalos Serie pyroclasts) range in age from 0.3 to 0.5 to 10-20 Ma. The youngest dates provide the maximum eruption age, while the oldest zircons indicate inheritance from local continental crust (Miocene and older). Step-heating 40Ar/39Ar experiments on 1-3 crystals of fresh biotite yielded highly disturbed Ar-release patterns with plateau ages typically older than most U/Pb ages. These old plateau ages are probably not a consequence of inheritance from xenocrystic biotites because Ar diffuses extremely fast at magmatic temperatures and ratios are reset within a few days. On the basis of (1) elevated and/or imprecise 40Ar/36Ar ratios, (2) shapes of the Ar release spectra, and (3) a high mantle 3He flux in the Kos-Nisyros area, we suggest that biotite crystals retained some mantle 40Ar that led to the observed, anomalously old ages. In contrast, sanidine crystals from the only sanidine-bearing unit in the Kos-Nisyros volcanic center (the caldera-forming Kos Plateau Tuff) do not appear to store any excess 40Ar relative to atmospheric composition. The eastern edge of the Aegean Arc is tectonically complex, undergoing rapid extension and located close to a major structural boundary. In such regions, which are characterized by high fluxes of mantle volatiles, 40Ar/39Ar geochronology on biotite can lead to erroneous results due to the presence of excess 40Ar and should be checked either against 40Ar/39Ar sanidine or U/Pb zircon ages.

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

    International Nuclear Information System (INIS)

    Hackett, W.R.; Smith, R.P.

    1994-12-01

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

  14. Seasonal oscillation of liver-derived hibernation protein complex in the central nervous system of non-hibernating mammals

    Science.gov (United States)

    Seldin, Marcus M.; Byerly, Mardi S.; Petersen, Pia S.; Swanson, Roy; Balkema-Buschmann, Anne; Groschup, Martin H.; Wong, G. William

    2014-01-01

    Mammalian hibernation elicits profound changes in whole-body physiology. The liver-derived hibernation protein (HP) complex, consisting of HP-20, HP-25 and HP-27, was shown to oscillate circannually, and this oscillation in the central nervous system (CNS) was suggested to play a role in hibernation. The HP complex has been found in hibernating chipmunks but not in related non-hibernating tree squirrels, leading to the suggestion that hibernation-specific genes may underlie the origin of hibernation. Here, we show that non-hibernating mammals express and regulate the conserved homologous HP complex in a seasonal manner, independent of hibernation. Comparative analyses of cow and chipmunk HPs revealed extensive biochemical and structural conservations. These include liver-specific expression, assembly of distinct heteromeric complexes that circulate in the blood and cerebrospinal fluid, and the striking seasonal oscillation of the HP levels in the blood and CNS. Central administration of recombinant HPs affected food intake in mice, without altering body temperature, physical activity levels or energy expenditure. Our results demonstrate that HP complex is not unique to the hibernators and suggest that the HP-regulated liver–brain circuit may couple seasonal changes in the environment to alterations in physiology. PMID:25079892

  15. Central intake to improve access to physiotherapy for children with complex needs: a mixed methods case report.

    Science.gov (United States)

    Wittmeier, Kristy D M; Restall, Gayle; Mulder, Kathy; Dufault, Brenden; Paterson, Marie; Thiessen, Matthew; Lix, Lisa M

    2016-08-31

    Children with complex needs can face barriers to system access and navigation related to their need for multiple services and healthcare providers. Central intake for pediatric rehabilitation was developed and implemented in 2008 in Winnipeg Manitoba Canada as a means to enhance service coordination and access for children and their families. This study evaluates the process and impact of implementing a central intake system, using pediatric physiotherapy as a case example. A mixed methods instrumental case study design was used. Interviews were completed with 9 individuals. Data was transcribed and analyzed for themes. Quantitative data (wait times, referral volume and caregiver satisfaction) was collected for children referred to physiotherapy with complex needs (n = 1399), and a comparison group of children referred for orthopedic concerns (n = 3901). Wait times were analyzed using the Kruskal-Wallis test, caregiver satisfaction was analyzed using Fisher exact test and change point modeling was applied to examine referral volume over the study period. Interview participants described central intake implementation as creating more streamlined processes. Factors that facilitated successful implementation included 1) agreement among stakeholders, 2) hiring of a central intake coordinator, 3) a financial commitment from the government and 4) leadership at the individual and organization level. Mean (sd) wait times improved for children with complex needs (12.3(13.1) to 8.0(6.9) days from referral to contact with family, p physiotherapy (i.e., decreasing wait times) for families of children with complex needs. Future research is needed to build on this single discipline case study approach to examine changes in wait times, therapy coordination and stakeholder satisfaction within the context of continuing improvements for pediatric therapy services within the province.

  16. Volcanic signals in oceans

    KAUST Repository

    Stenchikov, Georgiy L.

    2009-08-22

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

  17. Role of centrality for the identification of influential spreaders in complex networks.

    Science.gov (United States)

    de Arruda, Guilherme Ferraz; Barbieri, André Luiz; Rodríguez, Pablo Martín; Rodrigues, Francisco A; Moreno, Yamir; Costa, Luciano da Fontoura

    2014-09-01

    The identification of the most influential spreaders in networks is important to control and understand the spreading capabilities of the system as well as to ensure an efficient information diffusion such as in rumorlike dynamics. Recent works have suggested that the identification of influential spreaders is not independent of the dynamics being studied. For instance, the key disease spreaders might not necessarily be so important when it comes to analyzing social contagion or rumor propagation. Additionally, it has been shown that different metrics (degree, coreness, etc.) might identify different influential nodes even for the same dynamical processes with diverse degrees of accuracy. In this paper, we investigate how nine centrality measures correlate with the disease and rumor spreading capabilities of the nodes in different synthetic and real-world (both spatial and nonspatial) networks. We also propose a generalization of the random walk accessibility as a new centrality measure and derive analytical expressions for the latter measure for simple network configurations. Our results show that for nonspatial networks, the k-core and degree centralities are the most correlated to epidemic spreading, whereas the average neighborhood degree, the closeness centrality, and accessibility are the most related to rumor dynamics. On the contrary, for spatial networks, the accessibility measure outperforms the rest of the centrality metrics in almost all cases regardless of the kind of dynamics considered. Therefore, an important consequence of our analysis is that previous studies performed in synthetic random networks cannot be generalized to the case of spatial networks.

  18. How to Identify the Most Powerful Node in Complex Networks? A Novel Entropy Centrality Approach

    Directory of Open Access Journals (Sweden)

    Tong Qiao

    2017-11-01

    Full Text Available Centrality is one of the most studied concepts in network analysis. Despite an abundance of methods for measuring centrality in social networks has been proposed, each approach exclusively characterizes limited parts of what it implies for an actor to be “vital” to the network. In this paper, a novel mechanism is proposed to quantitatively measure centrality using the re-defined entropy centrality model, which is based on decompositions of a graph into subgraphs and analysis on the entropy of neighbor nodes. By design, the re-defined entropy centrality which describes associations among node pairs and captures the process of influence propagation can be interpreted explained as a measure of actor potential for communication activity. We evaluate the efficiency of the proposed model by using four real-world datasets with varied sizes and densities and three artificial networks constructed by models including Barabasi-Albert, Erdos-Renyi and Watts-Stroggatz. The four datasets are Zachary’s karate club, USAir97, Collaboration network and Email network URV respectively. Extensive experimental results prove the effectiveness of the proposed method.

  19. Natural factors and mining activity bearings on the water quality of the Choapa basin, North Central Chile: insights on the role of mafic volcanic rocks in the buffering of the acid drainage process.

    Science.gov (United States)

    Parra, Amparo; Oyarzún, Jorge; Maturana, Hugo; Kretschmer, Nicole; Meza, Francisco; Oyarzún, Ricardo

    2011-10-01

    This contribution analyzes water chemical data for the Choapa basin, North Central Chile, for the period 1980-2004. The parameters considered are As, Cu Fe, pH, EC, SO₄⁻², Cl⁻¹, and HCO[Formula: see text], from samples taken in nine monitoring stations throughout the basin. Results show rather moderate contents of As, Cu, and Fe, with the exception of the Cuncumén River and the Aucó creek, explained by the influence of the huge porphyry copper deposit of Los Pelambres and by the presence of mining operations, respectively. When compared against results obtained in previous researches at the neighboring Elqui river basin, which host the El Indio Au-Cu-As district, a much reduced grade of pollution is recognized for the Choapa basin. Considering the effect of acid rock drainage (ARD)-related Cu contents on the fine fraction of the sediments of both river basins, the differences recorded are even more striking. Although the Los Pelambres porphyry copper deposit, on the headwaters of the Choapa river basin, is between one and two orders of magnitude bigger than El Indio, stream water and sediments of the former exhibit significantly lower copper contents than those of the latter. A main factor which may explain these results is the smaller degree of H( + )-metasomatism on the host rocks of the Los Pelambres deposit, where mafic andesitic volcanic rocks presenting propylitic hydrothermal alteration are dominant. This fact contrast with the highly altered host rocks of El Indio district, where most of them have lost their potential to neutralize ARD.

  20. Closeness-Centrality-Based Synchronization Criteria for Complex Dynamical Networks With Interval Time-Varying Coupling Delays.

    Science.gov (United States)

    Park, Myeongjin; Lee, Seung-Hoon; Kwon, Oh-Min; Seuret, Alexandre

    2017-09-06

    This paper investigates synchronization in complex dynamical networks (CDNs) with interval time-varying delays. The CDNs are representative of systems composed of a large number of interconnected dynamical units, and for the purpose of the mathematical analysis, the leading work is to model them as graphs whose nodes represent the dynamical units. At this time, we take note of the importance of each node in networks. One way, in this paper, is that the closeness-centrality mentioned in the field of social science is grafted onto the CDNs. By constructing a suitable Lyapunov-Krasovskii functional, and utilizing some mathematical techniques, the sufficient and closeness-centrality-based conditions for synchronization stability of the networks are established in terms of linear matrix inequalities. Ultimately, the use of the closeness-centrality can be weighted with regard to not only the interconnection relation among the nodes, which was utilized in the existing works but also more information about nodes. Here, the centrality will be added as the concerned information. Moreover, to avoid the computational burden causing the nonconvex term including the square of the time-varying delay, how to deal with it is applied by estimating it to the convex term including time-varying delay. Finally, two illustrative examples are given to show the advantage of the closeness-centrality in point of the robustness on time-delay.

  1. WOVOdat: A New Tool for Managing and Accessing Data of Worldwide Volcanic Unrest

    Science.gov (United States)

    Venezky, D. Y.; Malone, S. D.; Newhall, C. G.

    2002-12-01

    WOVOdat (World Organization of Volcano Observatories database of volcanic unrest) will for the first time bring together data of worldwide volcanic seismicity, ground deformation, fumarolic activity, and other changes within or adjacent to a volcanic system. Although a large body of data and experience has been built over the past century, currently, we have no means of accessing that collective experience for use during crises and for research. WOVOdat will be the central resource of a data management system; other components will include utilities for data input and archiving, structured data retrieval, and data mining; educational modules; and links to institutional databases such as IRIS (global seismicity), UNAVCO (global GPS coordinates and strain vectors), and Smithsonian's Global Volcanism Program (historical eruptions). Data will be geospatially and time-referenced, to provide four dimensional images of how volcanic systems respond to magma intrusion, regional strain, and other disturbances prior to and during eruption. As part of the design phase, a small WOVOdat team is currently collecting information from observatories about their data types, formats, and local data management. The database schema is being designed such that responses to common, yet complex, queries are rapid (e.g., where else has similar unrest occurred and what was the outcome?) while also allowing for more detailed research analysis of relationships between various parameters (e.g., what do temporal relations between long-period earthquakes, transient deformation, and spikes in gas emission tell us about the geometry and physical properties of magma and a volcanic edifice?). We are excited by the potential of WOVOdat, and we invite participation in its design and development. Next steps involve formalizing and testing the design, and, developing utilities for translating data of various formats into common formats. The large job of populating the database will follow, and eventually

  2. The geothermal system of Caviahue-Copahue Volcanic Complex (Chile-Argentina): New insights from self-potential, soil CO2 degassing, temperature measurements and helium isotopes, with structural and fluid circulation implications.

    Science.gov (United States)

    Roulleau, Emilie; Bravo, Francisco; Barde-Cabusson, Stephanie; Pizarro, Marcela; Muños, Carlos; Sanchez, Juan; Tardani, Daniele; Sano, Yuji; Takahata, Naoto; de Cal, Federico; Esteban, Carlos

    2016-04-01

    Geothermal systems represent natural heat transfer engines in a confined volume of rock which are strongly influenced by the regional volcano-tectonic setting controlling the formation of shallow magmatic reservoirs, and by the local faults/fracture network, that permits the development of hydrothermal circulation cells and promote the vertical migration of fluids and heat. In the Southern Volcanic Zone of Chile-Argentina, geothermal resources occur in close spatial relationship with active volcanism along the Cordillera which is primarily controlled by the 1000 km long, NNE Liquiñe-Ofqui Fault Zone (LOFZ), an intra-arc dextral strike-slip fault system, associated with second-order intra-arc anisotropy of overall NE-SW (extensional) and NW-SE orientation (compressional). However there is still a lack of information on how fault network (NE and WNW strinking faults) and lithology control the fluid circulation. In this study, we propose new data of dense self-potential (SP), soil CO2 emanation and temperature (T) measurements within the geothermal area from Caviahue-Copahue Volcanic Complex (CCVC), coupled with helium isotopes ratios measured in fumaroles and thermal springs. We observe that inside the geothermal system the NE-striking faults, characterized by a combination of SP-CO2 and T maxima with high 3He/4He ratios (7.86Ra), promote the formation of high vertical permeability pathways for fluid circulation. Whereas, the WNW-striking faults represent low permeability pathways for hydrothermal fluids ascent associated with moderate 3He/4He ratios (5.34Ra), promoting the infiltration of meteoric water at shallow depth. These active zones are interspersed by SP-CO2- T minima, which represent self-sealed zones (e.g. impermeable altered rocks) at depth, creating a barrier inhibiting fluids rise. The NE-striking faults seem to be associated with the upflow zones of the geothermal system, where the boiling process produces a high vapor-dominated zone close to the

  3. Structural controls on fluid circulation at the Caviahue-Copahue Volcanic Complex (CCVC) geothermal area (Chile-Argentina), revealed by soil CO2 and temperature, self-potential, and helium isotopes

    Science.gov (United States)

    Roulleau, Emilie; Bravo, Francisco; Pinti, Daniele L.; Barde-Cabusson, Stéphanie; Pizarro, Marcela; Tardani, Daniele; Muñoz, Carlos; Sanchez, Juan; Sano, Yuji; Takahata, Naoto; de la Cal, Federico; Esteban, Carlos; Morata, Diego

    2017-07-01

    Natural geothermal systems are limited areas characterized by anomalously high heat flow caused by recent tectonic or magmatic activity. The heat source at depth is the result of the emplacement of magma bodies, controlled by the regional volcano-tectonic setting. In contrast, at a local scale a well-developed fault-fracture network favors the development of hydrothermal cells, and promotes the vertical advection of fluids and heat. The Southern Volcanic Zone (SVZ), straddling Chile and Argentina, has an important, yet unexplored and undeveloped geothermal potential. Studies on the lithological and tectonic controls of the hydrothermal circulation are therefore important for a correct assessment of the geothermal potential of the region. Here, new and dense self-potential (SP), soil CO2 and temperature (T) measurements, and helium isotope data measured in fumaroles and thermal springs from the geothermal area located in the north-eastern flank of the Copahue volcanic edifice, within the Caviahue Caldera (the Caviahue-Copahue Volcanic Complex - CCVC) are presented. Our results allowed to the constraint of the structural origin of the active thermal areas and the understanding of the evolution of the geothermal system. NE-striking faults in the area, characterized by a combination of SP, CO2, and T maxima and high 3He/4He ratios (up to 8.16 ± 0.21Ra, whereas atmospheric Ra is 1.382 × 10- 6), promote the formation of vertical permeability preferential pathways for fluid circulation. WNW-striking faults represent low-permeability pathways for hydrothermal fluid ascent, but promote infiltration of meteoric water at shallow depths, which dilute the hydrothermal input. The region is scattered with SP, CO2, and T minima, representing self-sealed zones characterized by impermeable altered rocks at depth, which create local barriers for fluid ascent. The NE-striking faults seem to be associated with the upflowing zones of the geothermal system, where the boiling process

  4. Petrologic evolution of Miocene-Pliocene mafic volcanism in the Kangal and Gürün basins (Sivas-Malatya), central east Anatolia: Evidence for Miocene anorogenic magmas contaminated by continental crust

    Science.gov (United States)

    Kocaarslan, Ayça; Ersoy, E. Yalçın

    2018-06-01

    in the region was derived from subduction-modified mantle sources in response to subduction of the Arabian Plate under the Anatolian Plate. This hypothesis further implies that either delamination of the sub-continental lithosphere or slab break-off processes beneath the central to eastern Anatolia might took place well before the Miocene, thus allowing upwelling unaltered mantle to provide the source of the Miocene to Pliocene volcanic rocks.

  5. Speciation on the rocks: integrated systematics of the Heteronotia spelea species complex (Gekkota; Reptilia from Western and Central Australia.

    Directory of Open Access Journals (Sweden)

    Mitzy Pepper

    Full Text Available The isolated uplands of the Australian arid zone are known to provide mesic refuges in an otherwise xeric landscape, and divergent lineages of largely arid zone taxa have persisted in these regions following the onset of Miocene aridification. Geckos of the genus Heteronotia are one such group, and have been the subject of many genetic studies, including H. spelea, a strongly banded form that occurs in the uplands of the Pilbara and Central Ranges regions of the Australian arid zone. Here we assess the systematics of these geckos based on detailed examination of morphological and genetic variation. The H. spelea species complex is a monophyletic lineage to the exclusion of the H. binoei and H. planiceps species complexes. Within the H. spelea complex, our previous studies based on mtDNA and nine nDNA loci found populations from the Central Ranges to be genetically divergent from Pilbara populations. Here we supplement our published molecular data with additional data gathered from central Australian samples. In the spirit of integrative species delimitation, we combine multi-locus, coalescent-based lineage delimitation with extensive morphological analyses to test species boundaries, and we describe the central populations as a new species, H. fasciolatus sp. nov. In addition, within the Pilbara there is strong genetic evidence for three lineages corresponding to northeastern (type, southern, and a large-bodied melanic population isolated in the northwest. Due to its genetic distinctiveness and extreme morphological divergence from all other Heteronotia, we describe the melanic form as a new species, H. atra sp. nov. The northeastern and southern Pilbara populations are morphologically indistinguishable with the exception of a morpho-type in the southeast that has a banding pattern resembling H. planiceps from the northern monsoonal tropics. Pending more extensive analyses, we therefore treat Pilbara H. spelea as a single species with

  6. Volcanic Rocks and Features

    Data.gov (United States)

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

  7. Martian volcanism: A review

    International Nuclear Information System (INIS)

    Carr, M.H.

    1987-01-01

    Martian volcanism is reviewed. It is emphasized that lava plains constitute the major type of effusive flow, and can be differentiated by morphologic characteristics. Shield volcanoes, domes, and patera constitute the major constructional landforms, and recent work has suggested that explosive activity and resulting pyroclastic deposits may have been involved with formation of some of the small shields. Analysis of morphology, presumed composition, and spectroscopic data all indicate that Martian volcanism was dominantly basaltic in composition

  8. Volcanics of the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Iyer, S.D

    stream_size 2 stream_content_type text/plain stream_name J_Geol_Soc_India_70_883.pdf.txt stream_source_info J_Geol_Soc_India_70_883.pdf.txt Content-Encoding ISO-8859-1 Content-Type text/plain; charset=ISO-8859-1 ...

  9. Integrated centralized utility services to a chemical complex on Jurong Island, Singapore.

    Science.gov (United States)

    Yan, Y G; Wong, P C Y; Tan, C G; Tang, K F

    2003-01-01

    SUT pioneered centralized utility services for the chemical industry on Jurong Island, which are cost-effective due to economies of scale, reliable due to inter-connection of satellite operations, and customer tailored for special requirements. The utility services range from the supply of steam and water, wastewater treatment, incineration, terminalling, service corridor to fire fighting. Among the services, water management achieves the complete cycle from wastewater treatment to effluent recycling.

  10. Evaluation of the Theoretical Geothermal Potential of Inferred Geothermal Reservoirs within the Vicano–Cimino and the Sabatini Volcanic Districts (Central Italy by the Application of the Volume Method

    Directory of Open Access Journals (Sweden)

    Daniele Cinti

    2018-01-01

    Full Text Available The evaluation of the theoretical geothermal potential of identified unexploited hydrothermal reservoirs within the Vicano–Cimino and Sabatini volcanic districts (Latium region, Italy has been made on the basis of a revised version of the classical volume method. This method is based on the distribution of the partial pressure of CO2 (pCO2 in shallow and deep aquifers to delimit areas of geothermal interest, according to the hypothesis that zones of high CO2 flux, either from soil degassing and dissolved into aquifers, are spatially related to deep hydrothermal reservoirs. On the whole, 664 fluid discharges (cold waters, thermal waters, and bubbling pools have been collected from shallow and deep aquifers in the Vicano–Cimino Volcanic District and the Sabatini Volcanic District for chemical and isotopic composition, in an area of approximately 2800 km2. From this large hydro-geochemical dataset the pCO2 values have been computed and then processed to obtain a contour map of its spatial distribution by using geostatistical techniques (kriging. The map of pCO2 has been used to draw up the boundaries of potentially exploitable geothermal systems within the two volcanic districts, corresponding to the areas where endogenous CO2 raise up to the surface from the deep hydrothermal reservoirs. The overall estimated potential productivities and theoretical minimum and maximum thermal power of the two volcanic districts are of about 45 × 103 t/h and 3681–5594 MWt, respectively. This makes the Vicano–Cimino Volcanic District and the Sabatini Volcanic District very suitable for both direct and indirect exploitation of the geothermal resources, in view of the target to reduce electricity generation from conventional and poorly sustainable energy sources.

  11. Environmental assessment: Solid waste retrieval complex, enhanced radioactive and mixed waste storage facility, infrastructure upgrades, and central waste support complex, Hanford Site, Richland, Washington

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-09-01

    The U.S. Department of Energy (DOE) needs to take action to: retrieve transuranic (TRU) waste because interim storage waste containers have exceeded their 20-year design life and could fail causing a radioactive release to the environment provide storage capacity for retrieved and newly generated TRU, Greater-than-Category 3 (GTC3), and mixed waste before treatment and/or shipment to the Waste Isolation Pilot Project (WIPP); and upgrade the infrastructure network in the 200 West Area to enhance operational efficiencies and reduce the cost of operating the Solid Waste Operations Complex. This proposed action would initiate the retrieval activities (Retrieval) from Trench 4C-T04 in the 200 West Area including the construction of support facilities necessary to carry out the retrieval operations. In addition, the proposed action includes the construction and operation of a facility (Enhanced Radioactive Mixed Waste Storage Facility) in the 200 West Area to store newly generated and the retrieved waste while it awaits shipment to a final disposal site. Also, Infrastructure Upgrades and a Central Waste Support Complex are necessary to support the Hanford Site`s centralized waste management area in the 200 West Area. The proposed action also includes mitigation for the loss of priority shrub-steppe habitat resulting from construction. The estimated total cost of the proposed action is $66 million.

  12. Environmental assessment: Solid waste retrieval complex, enhanced radioactive and mixed waste storage facility, infrastructure upgrades, and central waste support complex, Hanford Site, Richland, Washington

    International Nuclear Information System (INIS)

    1995-09-01

    The U.S. Department of Energy (DOE) needs to take action to: retrieve transuranic (TRU) waste because interim storage waste containers have exceeded their 20-year design life and could fail causing a radioactive release to the environment provide storage capacity for retrieved and newly generated TRU, Greater-than-Category 3 (GTC3), and mixed waste before treatment and/or shipment to the Waste Isolation Pilot Project (WIPP); and upgrade the infrastructure network in the 200 West Area to enhance operational efficiencies and reduce the cost of operating the Solid Waste Operations Complex. This proposed action would initiate the retrieval activities (Retrieval) from Trench 4C-T04 in the 200 West Area including the construction of support facilities necessary to carry out the retrieval operations. In addition, the proposed action includes the construction and operation of a facility (Enhanced Radioactive Mixed Waste Storage Facility) in the 200 West Area to store newly generated and the retrieved waste while it awaits shipment to a final disposal site. Also, Infrastructure Upgrades and a Central Waste Support Complex are necessary to support the Hanford Site's centralized waste management area in the 200 West Area. The proposed action also includes mitigation for the loss of priority shrub-steppe habitat resulting from construction. The estimated total cost of the proposed action is $66 million

  13. Mount Oku, Cameroon Volcanic Line

    African Journals Online (AJOL)

    and continental sectors especially for trace elements in basalts. ... continental sector of the trend is a complex .... values higher than those of HIMU but is within ...... (Mount Cameroon, Central Africa): petrogenetic implications. Miner. Petrol.,.

  14. The Snake River Plain Volcanic Province: Insights from Project Hotspot

    Science.gov (United States)

    Shervais, J. W.; Potter, K. E.; Hanan, B. B.; Jean, M. M.; Duncan, R. A.; Champion, D. E.; Vetter, S.; Glen, J. M. G.; Christiansen, E. H.; Miggins, D. P.; Nielson, D. L.

    2017-12-01

    The Snake River Plain (SRP) Volcanic Province is the best modern example of a time-transgressive hotspot track beneath continental crust. The SRP began 17 Ma with massive eruptions of Columbia River basalt and rhyolite. After 12 Ma volcanism progressed towards Yellowstone, with early rhyolite overlain by basalts that may exceed 2 km thick. The early rhyolites are anorogenic with dry phenocryst assemblages and eruption temperatures up to 950C. Tholeiitic basalts have major and trace element compositions similar to ocean island basalts (OIB). Project Hotspot cored three deep holes in the central and western Snake River Plain: Kimama (mostly basalt), Kimberly (mostly rhyolite), and Mountain Home (lake sediments and basaslt). The Kimberly core documents rhyolite ash flows up to 700 m thick, possibly filling a caldera or sag. Chemical stratigraphy in Kimama and other basalt cores document fractional crystallization in relatively shallow magma chambers with episodic magma recharge. Age-depth relations in the Kimama core suggest accumulation rates of roughly 305 m/Ma. Surface and subsurface basalt flows show systematic variations in Sr-Nd-Pb isotopes with distance from Yellowstone interpreted to reflect changes in the proportion of plume source and the underlying heterogeneous cratonic lithosphere, which varies in age, composition, and thickness from west to east. Sr-Nd-Pb isotopes suggest <5% lithospheric input into a system dominated by OIB-like plume-derived basalts. A major flare-up of basaltic volcanism occurred 75-780 ka throughout the entire SRP, from Yellowstone in the east to Boise in the west. The youngest western SRP basalts are transitional alkali basalts that range in age from circa 900 ka to 2 ka, with trace element and isotopic compositions similar to the plume component of Hawaiian basalts. These observations suggest that ancient SCLM was replaced by plume mantle after the North America passed over the hotspot in the western SRP, which triggered renewed

  15. Volcano crisis response at Yellowstone volcanic complex - after-action report for exercise held at Salt Lake City, Utah, November 15, 2011

    Science.gov (United States)

    Pierson, Thomas C.; Driedger, Carolyn L.; Tilling, Robert I.

    2013-01-01

    A functional tabletop exercise was run on November 14-15, 2011 in Salt Lake City, Utah, to test crisis response capabilities, communication protocols, and decision-making by the staff of the multi-agency Yellowstone Volcano Observatory (YVO) as they reacted to a hypothetical exercise scenario of accelerating volcanic unrest at the Yellowstone caldera. The exercise simulated a rapid build-up of seismic activity, ground deformation, and hot-spring water-chemistry and temperature anomalies that culminated in a small- to moderate-size phreatomagmatic eruption within Yellowstone National Park. The YVO scientific team's responses to the unfolding events in the scenario and to simulated requests for information by stakeholders and the media were assessed by (a) the exercise organizers; (b) several non-YVO scientists, who observed and queried participants, and took notes throughout the exercise; and (c) the participants themselves, who kept logs of their actions during the exercise and later participated in a group debriefing session and filled out detailed questionnaires. These evaluations were tabulated, interpreted, and summarized for this report, and on the basis of this information, recommendations have been made. Overall, the YVO teams performed their jobs very well. The exercise revealed that YVO scientists were able to successfully provide critical hazards information, issue information statements, and appropriately raise alert levels during a fast-moving crisis. Based on the exercise, it is recommended that several measures be taken to increase YVO effectiveness during a crisis: 1. Improve role clarification within and between YVO science teams. 2. Improve communications tools and protocols for data-sharing and consensus-building among YVO scientists, who are geographically and administratively dispersed among various institutions across the United States. 3. Familiarize YVO staff with Incident Command System (ICS) procedures and protocols, and provide more in

  16. CUMULATE ROCKS ASSOCIATED WITH CARBONATE ASSIMILATION, HORTAVÆR COMPLEX, NORTH-CENTRAL NORWAY

    Science.gov (United States)

    Barnes, C. G.; Prestvik, T.; Li, Y.

    2009-12-01

    The Hortavær igneous complex intruded high-grade metamorphic rocks of the Caledonian Helgeland Nappe Complex at ca. 466 Ma. The complex is an unusual mafic-silicic layered intrusion (MASLI) because the principal felsic rock type is syenite and because the syenite formed in situ rather than by deep-seated partial melting of crustal rocks. Magma differentiation in the complex was by assimilation, primarily of calc-silicate rocks and melts with contributions from marble and semi-pelites, plus fractional crystallization. The effect of assimilation of calcite-rich rocks was to enhance stability of fassaitic clinopyroxene at the expense of olivine, which resulted in alkali-rich residual melts and lowering of silica activity. This combination of MASLI-style emplacement and carbonate assimilation produced three types of cumulate rocks: (1) Syenitic cumulates formed by liquid-crystal separation. As sheets of mafic magma were loaded on crystal-rich syenitic magma, residual liquid was expelled, penetrating the overlying mafic sheets in flame structures, and leaving a cumulate syenite. (2) Reaction cumulates. Carbonate assimilation, illustrated by a simple assimilation reaction: olivine + calcite + melt = clinopyroxene + CO2 resulted in cpx-rich cumulates such as clinopyroxenite, gabbro, and mela-monzodiorite, many of which contain igneous calcite. (3) Magmatic skarns. Calc-silicate host rocks underwent partial melting during assimilation, yielding a Ca-rich melt as the principal assimilated material and permitting extensive reaction with surrounding magma to form Kspar + cpx + garnet-rich ‘cumulate’ rocks. Cumulate types (2) and (3) do not reflect traditional views of cumulate rocks but instead result from a series of melt-present discontinuous (peritectic) reactions and partial melting of calc-silicate xenoliths. In the Hortavær complex, such cumulates are evident because of the distinctive peritectic cumulate assemblages. It is unclear whether assimilation of

  17. Volcanic hazards to airports

    Science.gov (United States)

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

    2009-01-01

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

  18. Architecture and evolution of an Early Permian carbonate complex on a tectonically active island in east-central California

    Science.gov (United States)

    Stevens, Calvin H.; Magginetti, Robert T.; Stone, Paul

    2015-01-01

    The newly named Upland Valley Limestone represents a carbonate complex that developed on and adjacent to a tectonically active island in east-central California during a brief interval of Early Permian (late Artinskian) time. This lithologically unique, relatively thin limestone unit lies within a thick sequence of predominantly siliciclastic rocks and is characterized by its high concentration of crinoidal debris, pronounced lateral changes in thickness and lithofacies, and a largely endemic fusulinid fauna. Most outcrops represent a carbonate platform and debris derived from it and shed downslope, but another group of outcrops represents one or possibly more isolated carbonate buildups that developed offshore from the platform. Tectonic activity in the area occurred before, probably during, and after deposition of this short-lived carbonate complex.

  19. Rb-Sr geochronology from Barro Alto Complex, Goias: metamorphism evidence of high degree and continental collision around 1300 Ma ago in Central Brazil

    International Nuclear Information System (INIS)

    Fuck, R.A.; Neves, B.B.B.; Cordani, U.G.; Kawashita, K.

    1989-01-01

    Rb-Sr geochronologic investigation carried out on rocks from the Barro Alto Complex, Goias, yielded iso chronic ages of 1266 +- 17 Ma, for felsic rocks from the granulite belt and 1330 +- 67 Ma, for gneisses belonging to the Juscelandia Sequence. Rb-Sr isotope measurements suggest that Barro Alto rocks have undergone an important metamorphic event during middle Proterozoic times, around 1300 Ma ago. During that event, volcanic and sedimentary rocks of Juscelandia Sequence, as well as the underlying gabbros-anorthosite layered complex, underwent deformation and recrystallization under amphibolite facies conditions. Deformation and metamorphism took place during the collision of two continental blocks, which resulted in a southeastward directed thrust complex, allowing the exposure of granulite slices from the middle-lower crust of the overthrusted block. (author)

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

    Science.gov (United States)

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

    2008-01-01

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

  1. Robustness analysis of complex networks with power decentralization strategy via flow-sensitive centrality against cascading failures

    Science.gov (United States)

    Guo, Wenzhang; Wang, Hao; Wu, Zhengping

    2018-03-01

    Most existing cascading failure mitigation strategy of power grids based on complex network ignores the impact of electrical characteristics on dynamic performance. In this paper, the robustness of the power grid under a power decentralization strategy is analysed through cascading failure simulation based on AC flow theory. The flow-sensitive (FS) centrality is introduced by integrating topological features and electrical properties to help determine the siting of the generation nodes. The simulation results of the IEEE-bus systems show that the flow-sensitive centrality method is a more stable and accurate approach and can enhance the robustness of the network remarkably. Through the study of the optimal flow-sensitive centrality selection for different networks, we find that the robustness of the network with obvious small-world effect depends more on contribution of the generation nodes detected by community structure, otherwise, contribution of the generation nodes with important influence on power flow is more critical. In addition, community structure plays a significant role in balancing the power flow distribution and further slowing the propagation of failures. These results are useful in power grid planning and cascading failure prevention.

  2. CENTRAL REGION COMPONENT1, a Novel Synaptonemal Complex Component, Is Essential for Meiotic Recombination Initiation in Rice[C][W

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-01-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated CENTRAL REGION COMPONENT1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID RECEPTOR-INTERACTING PROTEIN13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with HOMOLOGOUS PAIRING ABERRATION IN RICE MEIOSIS1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13. PMID:23943860

  3. Central region component1, a novel synaptonemal complex component, is essential for meiotic recombination initiation in rice.

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-08-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated central region component1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID receptor-interacting protein13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with homologous pairing aberration in rice meiosis1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13.

  4. Volcanic hazards and public response

    Science.gov (United States)

    Peterson, Donald W.

    1988-05-01

    Although scientific understanding of volcanoes is advancing, eruptions continue to take a substantial toll of life and property. Some of these losses could be reduced by better advance preparation, more effective flow of information between scientists and public officials, and better understanding of volcanic behavior by all segments of the public. The greatest losses generally occur at volcanoes that erupt infrequently where people are not accustomed to dealing with them. Scientists sometimes tend to feel that the blame for poor decisions in emergency management lies chiefly with officials or journalists because of their failure to understand the threat. However, the underlying problem embraces a set of more complex issues comprising three pervasive factors. The first factor is the volcano: signals given by restless volcanoes are often ambiguous and difficult to interpret, especially at long-quiescent volcanoes. The second factor is people: people confront hazardous volcanoes in widely divergent ways, and many have difficulty in dealing with the uncertainties inherent in volcanic unrest. The third factor is the scientists: volcanologists correctly place their highest priority on monitoring and hazard assessment, but they sometimes fail to explain clearly their conclusions to responsible officials and the public, which may lead to inadequate public response. Of all groups in society, volcanologists have the clearest understanding of the hazards and vagaries of volcanic activity; they thereby assume an ethical obligation to convey effectively their knowledge to benefit all of society. If society resists, their obligation nevertheless remains. They must use the same ingenuity and creativity in dealing with information for the public that they use in solving scientific problems. When this falls short, even excellent scientific results may be nullified.

  5. Volcanic ash in ancient Maya ceramics of the limestone lowlands: implications for prehistoric volcanic activity in the Guatemala highlands

    Science.gov (United States)

    Ford, Anabel; Rose, William I.

    1995-07-01

    In the spirit of collaborative research, Glicken and Ford embarked on the problem of identifying the source of volcanic ash used as temper in prehistoric Maya ceramics. Verification of the presence of glass shards and associated volcanic mineralogy in thin sections of Maya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonal wind rose patterns, target volcanoes include those from the area west of and including Guatemala City. Joint field research conducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala, 300 km north of the volcanic zone and 150 km from the nearest identified ash deposits, was unsuccessful in discovering local volcanic ash deposits. The abundance of the ash in common Maya ceramic vessels coupled with the difficulties of long-distance procurement without draft animals lead Glicken to suggest that ashfall into the lowlands would most parsimoniously explain prehistoric procurement; it literally dropped into their hands. A major archaeological problem with this explanation is that the use of volcanic ash occurring over several centuries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanic ash procurement, one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for the last half of the first millennium AD. Should this be documented through careful petrographic, microprobe and tephrachronological studies, a number of related archaeological phenomena would be explained. In addition, the proposed model of volcanic activity has implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer time span than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinary problem is extended in this paper.

  6. Segmentation pattern and structural complexities in seismogenic extensional settings: The North Matese Fault System (Central Italy)

    Science.gov (United States)

    Ferrarini, Federica; Boncio, Paolo; de Nardis, Rita; Pappone, Gerardo; Cesarano, Massimo; Aucelli, Pietro P. C.; Lavecchia, Giusy

    2017-02-01

    We investigated the northern slope of the Matese Mts. (Molise, Central Italy) with the aim of characterizing the N- to NE-dipping active normal fault system in the Bojano basin, a sector of primary importance from a seismic hazard perspective. We collected field data to define the geometry and segmentation pattern of two sub-systems (Patalecchia-Colle di Mezzo and Bojano-Campochiaro). New evidence of late Quaternary faulting was obtained by exploiting well log interpretations. Kinematic analysis revealed the interaction of pre-Quaternary inherited (mainly E-W-striking) and newly formed (NW-SE-striking) normal faults. Slip accommodation through linkage was clearly noted in the case of the Patalecchia-Colle di Mezzo sub-system. Detailed topographic profiles across the active fault segments provided post-LGM (15 ± 3 kyr) slip rates up to ∼2 mm/yr which agree with the high deformation rates based on different approaches in the literature. Finally, the instrumental seismicity analysis constrained the bottom of the seismogenic layer to depths of 13-14 km, and the gathered information allowed us to reconstruct the North Matese seismogenic source. Its 3D geometry and dimensions agree with both the dimension-magnitude relationships and macroseismic information available for the 1805 earthquake (Mw 6.6), the main historical earthquake to have struck the Bojano basin.

  7. COMPLEX OF PATHOGENES ON VEGETABLE CROPS IN CONDITION OF CENTRAL REGION OF RUSSIA

    Directory of Open Access Journals (Sweden)

    L. T. Timina

    2015-01-01

    Full Text Available As a result of monitoring of causative agents of diseases of vegetable crops and studying of its species specification, the genus and species of fungi and bacteria, were found. Previously unknown in the Central region of Russia pathogens of carrot were identified: Sclerotinia nevales, Gleocladium roseum, Verticillium spp, Trichotecium roseum, Streptomyces scabies, F. nivale, F. chlamidosporum, F. equiseti, F. proliferatum, Chaetomium spp., Erysiphe umbelliferum, Erwinia carotovora. Main causative agents of diseases  of carrot during storage were also described: Alternaria infectoria, A. alternatа, A. arborescens, A. radicina, A. cheiranthi, A. corotiincultae, A. cinerariae, Embellisia spp., Nimbia spp., Cladosporium spp. It was found new pathogen for onion (Aspergillus niger, garlic (Fusarium semitectum, F. subglutinans, F. proliferatum, F.avenacium, red beet (Typhula ishikariensis, and radish (Drechslera Bondartseva.

  8. Large Volcanic Rises on Venus

    Science.gov (United States)

    Smrekar, Suzanne E.; Kiefer, Walter S.; Stofan, Ellen R.

    1997-01-01

    Large volcanic rises on Venus have been interpreted as hotspots, or the surface manifestation of mantle upwelling, on the basis of their broad topographic rises, abundant volcanism, and large positive gravity anomalies. Hotspots offer an important opportunity to study the behavior of the lithosphere in response to mantle forces. In addition to the four previously known hotspots, Atla, Bell, Beta, and western Eistla Regiones, five new probable hotspots, Dione, central Eistla, eastern Eistla, Imdr, and Themis, have been identified in the Magellan radar, gravity and topography data. These nine regions exhibit a wider range of volcano-tectonic characteristics than previously recognized for venusian hotspots, and have been classified as rift-dominated (Atla, Beta), coronae-dominated (central and eastern Eistla, Themis), or volcano-dominated (Bell, Dione, western Eistla, Imdr). The apparent depths of compensation for these regions ranges from 65 to 260 km. New estimates of the elastic thickness, using the 90 deg and order spherical harmonic field, are 15-40 km at Bell Regio, and 25 km at western Eistla Regio. Phillips et al. find a value of 30 km at Atla Regio. Numerous models of lithospheric and mantle behavior have been proposed to interpret the gravity and topography signature of the hotspots, with most studies focusing on Atla or Beta Regiones. Convective models with Earth-like parameters result in estimates of the thickness of the thermal lithosphere of approximately 100 km. Models of stagnant lid convection or thermal thinning infer the thickness of the thermal lithosphere to be 300 km or more. Without additional constraints, any of the model fits are equally valid. The thinner thermal lithosphere estimates are most consistent with the volcanic and tectonic characteristics of the hotspots. Estimates of the thermal gradient based on estimates of the elastic thickness also support a relatively thin lithosphere (Phillips et al.). The advantage of larger estimates of

  9. Sources of Quaternary volcanism in the Itasy and Ankaratra volcanic fields, Madagascar

    Science.gov (United States)

    Rasoazanamparany, C.; Widom, E.; Kuentz, D. C.; Raharimahefa, T.; Rakotondrazafy, F. M. A.; Rakotondravelo, K. M.

    2017-12-01

    We present new major and trace element and Sr, Nd, Pb and Os isotope data for Quaternary basaltic lavas and tephra from the Itasy and Ankaratra volcanic fields, representing the most recent volcanism in Madagascar. Mafic magmas from Itasy and Ankaratra exhibit significant inter- and intra-volcanic field geochemical heterogeneity. The Itasy eruptive products range in composition from foidite to phonotephrite whereas Ankaratra lavas range from basanite to trachybasalts. Trace element signatures of samples from both volcanic fields are very similar to those of ocean island basalts (OIB), with significant enrichment in Nb and Ta, depletion in Rb, Cs, and K, and relatively high Nb/U and Ce/Pb. However, the Itasy volcanic rocks show enrichment relative to those of Ankaratra in most incompatible elements, indicative of a more enriched source and/or lower degrees of partial melting. Significant inter- and intra-volcanic field heterogeneity is also observed in Sr, Nd, Pb and Os isotope signatures. The Itasy volcanic rocks generally have less radiogenic Sr and Nd isotopic ratios but more radiogenic Pb isotopic signatures than the Ankaratra volcanic field. Together, the Itasy and Ankaratra volcanic rocks form a well-defined negative correlation in Sr vs. Pb isotopes that could be attributed to lithospheric contamination or variable degrees of mixing between distinct mantle sources. However, the lack of correlation between isotopes and indices of crustal contamination (e.g. MgO and Nb/U) are inconsistent with shallow lithospheric contamination, and instead suggest mixing between compositionally distinct mantle sources. Furthermore, although Sr-Pb isotope systematics are apparently consistent with mixing between two different sources, distinct trends in Sr vs. Nd isotopes displayed by samples from Itasy and Ankaratra, respectively, argue for more complex source mixing involving three or more sources. The current data demonstrate that although the Itasy and Ankaratra volcanic

  10. Stratigraphic and compositional complexities of the late Quaternary Lethe tephra in South-central Alaska

    Science.gov (United States)

    Riehle, J.R.; Ager, T.A.; Reger, R.D.; Pinney, D.S.; Kaufman, D.S.

    2008-01-01

    Recently discovered Lethe tephra has been proposed as a latest Pleistocene marker bed in Bristol Bay lowland NE to the Cook Inlet region, Alaska, on the basis of correlations involving a single "Lethe average" glass composition. Type deposits in the Valley of Ten Thousand Smokes, however, are chemically heterogeneous-individual lapilli as well as aggregate ash deposits have glass compositions that range from the average mode to much higher SiO2 and K2O. Moreover, a lake-sediment core from the Cook Inlet region contains one ash deposit similar to "Lethe average" and other, closely underlying deposits that resemble a mixture of the average mode and high-Si high-K mode of proximal deposits. Synthesis of previously published radiocarbon ages indicates a major eruption mainly of "Lethe average" mode about 13,000 14C yr BP. As many as six deposits in the Cook Inlet region-five chiefly "Lethe average" mode-range from about 13,000 to 15-16,000 14C yr BP, and an early Holocene deposit in the Bristol Bay lowland extends the minimum age range of Lethe tephra throughout this region to 8000 14C yr BP. Because of the appearance of "Lethe average" composition in multiple deposits spanning thousands of years, we urge caution when using a Lethe-like composition as a basis for inferring a latest Pleistocene age of a tephra deposit in south-central Alaska. Linear variation plots suggest that magma mixing caused the Lethe heterogeneity; multiple magmas were involved as well in other large pyroclastic eruptions such as Katmai (Alaska) and Rotorua (New Zealand). Lethe is an example of a heterogeneous tephra that may be better compared with other tephras by use of plots of individual analytical points rather than by calculating similarity coefficients based on edited data. ?? 2006 Elsevier Ltd and INQUA.

  11. THE COMPLEXITY IN COPING CONFLICTING GROUPS IN SURROUNDING NUSAKAMBANGAN ISLANDS CENTRAL JAVA INDONESIA

    Directory of Open Access Journals (Sweden)

    Khairu Roojiqien Sobandi

    2016-01-01

    Full Text Available This study explores social and political conflicts in grassroots level, specifically, the challenge of natural degradations on a mangrove-fringed lagoon in Central Java, Indonesia. Segara Anakan is a significant environmental zone, with many unique ecosystem features, all of which are under threat from illegal land reclamation and timber theft, which have caused great damage. This study analyses how conflict arises between groups and how the rulers interact with villagers in Kampung Laut sur-rounding Nusakambangan Island. The result shows, as Reichel et al. (2009 notes, population growth and lagoon sedimentation indeed have directing to crucial conflicts between groups. However, histori-cal and the rulers approach factors also contribute to Kampung Laut conflicts. Long historical journey contribute to the formation of Kampung Laut villagers’ characters. It is the history of Galuh and Mata-ram Kingdoms’ networks through Babad Pasirluhur and Tanah Jawi in conquering Nusakambangan. More importantly, rulers’ policies and state apparatuses approaches also contribute to the creation of Kampung Laut villagers’ identity. The policies are often inconsistent and create more problems than solutions. Thus, dissatisfaction has directing to the creation of Kampung Laut identity marker as rebel-lions. In short, this hard situation led to conflicts between villagers and rulers. Our study suggest that it is very important to bring the state back in on the isolated and poor area like Kampung Laut Sub-District through more affirmative regional public policies and more over create additional income re-sources, for example eco-tourism that could support its sustainable outcomes.

  12. Local seismic hazard assessment in explosive volcanic settings by 3D numerical analyses

    Science.gov (United States)

    Razzano, Roberto; Pagliaroli, Alessandro; Moscatelli, Massimiliano; Gaudiosi, Iolanda; Avalle, Alessandra; Giallini, Silvia; Marcini, Marco; Polpetta, Federica; Simionato, Maurizio; Sirianni, Pietro; Sottili, Gianluca; Vignaroli, Gianluca; Bellanova, Jessica; Calamita, Giuseppe; Perrone, Angela; Piscitelli, Sabatino

    2017-04-01

    This work deals with the assessment of local seismic response in the explosive volcanic settings by reconstructing the subsoil model of the Stracciacappa maar (Sabatini Volcanic District, central Italy), whose pyroclastic succession records eruptive phases ended about 0.09 Ma ago. Heterogeneous characteristics of the Stracciacappa maar (stratification, structural setting, lithotypes, and thickness variation of depositional units) make it an ideal case history for understanding mechanisms and processes leading to modifications of amplitude-frequency-duration of seismic waves generated at earthquake sources and propagating through volcanic settings. New geological map and cross sections, constrained with recently acquired geotechnical and geophysical data, illustrate the complex geometric relationships among different depositional units forming the maar. A composite interfingering between internal lacustrine sediments and epiclastic debris, sourced from the rim, fills the crater floor; a 45 meters thick continuous coring borehole was drilled in the maar with sampling of undisturbed samples. Electrical Resistivity Tomography surveys and 2D passive seismic arrays were also carried out for constraining the geological model and the velocity profile of the S-waves, respectively. Single station noise measurements were collected in order to define natural amplification frequencies. Finally, the nonlinear cyclic soil behaviour was investigated through simple shear tests on the undisturbed samples. The collected dataset was used to define the subsoil model for 3D finite difference site response numerical analyses by using FLAC 3D software (ITASCA). Moreover, 1D and 2D numerical analyses were carried out for comparison purposes. Two different scenarios were selected as input motions: a moderate magnitude (volcanic event) and a high magnitude (tectonic event). Both earthquake scenarios revealed significant ground motion amplification (up to 15 in terms of spectral acceleration

  13. Monogenetic volcanism: personal views and discussion

    Science.gov (United States)

    Németh, K.; Kereszturi, G.

    2015-11-01

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

  14. Modeling volcanic ash dispersal

    CERN Multimedia

    CERN. Geneva

    2010-01-01

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

  15. VOLCANIC TSUNAMI GENERATING SOURCE MECHANISMS IN THE EASTERN CARIBBEAN REGION

    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis

    2004-01-01

    Full Text Available Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic processes have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity from Strombolian to Plinian. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure perturbations, nuéss ardentes, pyroclastic flows, lahars, or cascading debris avalanches. Submarine volcanic caldera collapses can also generate locally destructive tsunami waves. Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be generated from aerial and submarine volcanic edifice mass edifice flank failures, which may be triggered by volcanic episodes, lava dome collapses, or simply by gravitational instabilities. The present report evaluates volcanic mechanisms, resulting flank failure processes and their potential for tsunami generation. More specifically, the report evaluates recent volcanic eruption mechanisms of the Soufriere Hills volcano on Montserrat, of Mt. Pel

  16. Origins of cryptic variation in the Ediacaran-Fortunian rhyolitic ignimbrites of the Saldanha Bay Volcanic Complex, Western Cape, South Africa

    Science.gov (United States)

    Clemens, J. D.; Stevens, G.; Frei, D.; Joseph, C. S. A.

    2017-12-01

    The Saldanha eruption centre, on the West Coast of South Africa, consists of 542 Ma, intracaldera, S-type, rhyolite ignimbrites divided into the basal Saldanha Ignimbrite and the partly overlying Jacob's Bay Ignimbrite. Depleted-mantle Nd model ages suggest magma sources younger than the Early Mesoproterozoic, and located within the Neoproterozoic Malmesbury Group and Swartland complex metasedimentary and metavolcanic rocks that form the regional basement. The Sr isotope systematics suggest that the dominant source rocks were metavolcaniclastic rocks and metagreywackes, and that the magmas formed from separate batches extracted from the same heterogeneous source. No apparent magma mixing trends relate the Saldanha to the Jacob's Bay Ignimbrites, or either of these to the magmas that formed the Plankiesbaai or Tsaarsbank Ignimbrites in the neighbouring Postberg eruption centre. The magmas were extracted from their source rocks carrying small but significant proportions of peritectic and restitic accessory minerals. Variations in the content of this entrained crystal cargo were responsible for most of the chemical variations in the magmas. Although we cannot construct a cogent crystal fractionation model to relate these groups of magmas, at least some crystal fractionation occurred, as an overlay on the primary signal due to peritectic assemblage entrainment (PAE). Thus, the causes of the cryptic chemical variation among the ignimbrite magmas of the Saldanha centre are variable, but dominated by the compositions of the parent melts and PAE. The preservation of clear, source-inherited chemical signatures, in individual samples, calls into question the common interpretation of silicic calderas as having been formed in large magma reservoirs, with magma compositions shaped by magma mingling, mixing, and fractional crystallization. The Saldanha rocks suggest a more intimate connection between source and erupted magma, and perhaps indicate that silicic magmas are too

  17. Central Asia as a Regional Security Complex from the Perspectives of Realism, Liberalism and Constructivism

    Directory of Open Access Journals (Sweden)

    Caroline Putri Pratama

    2013-05-01

    Full Text Available Tulisan ini bertujuan menganalisis kawasan Asia Tengah, dilihat dari perspektif Realisme, Liberalisme dan Konstruktivisme, melalui teori Regional Security Complex oleh Barry Buzan dan Ole Waever. Teori ini hendak menunjukkan keamanan regional berdasarkan interdependensi antar unit dalam kawasan dilihat dari struktur power dan proses sekuritisasi di dalamnya, demikian pola hubungan keamanan dalam kawasan Asia Tengah berusaha dijelaskan dengan elemen-elemen dari ketiga paradigma yang terdapat dalam teori tersebut. Hasil analisis tulisan ini menunjukkan bahwa Asia Tengah dipandang sebagai bentuk insecurity interdependence by external forces dari perspektif Realis, security interdependence by interest dari perspektif Liberalis dan securitization interdependence by understanding of threat/security dari perspektif Konstruktivis. Kompleks keamanan Asia Tengah termasuk dalam tipe kompleks keamanan Great Power, terlihat dari peran besar kekuatan-kekuatan eksternal terutama Rusia dan Cina dalam kawasan tersebut; baik dalam pembentukan pola pertemanan dengan kerjasama, pola permusuhan dengan persaingan dan ketakutan, juga proses sekuritisasi isu separatisme, ekstremisme dan terorisme sebagai ancaman terhadap keamanan regional.Tulisan ini diambil dari tugas karya akhir penulis yang diajukan untuk medapatkan gelar Sarjana Sosial dari Departemen Ilmu Hubungan Internasional, Universitas Indonesia.

  18. The Visual Orientation Memory of "Drosophila" Requires Foraging (PKG) Upstream of Ignorant (RSK2) in Ring Neurons of the Central Complex

    Science.gov (United States)

    Kuntz, Sara; Poeck, Burkhard; Sokolowski, Marla B.; Strauss, Roland

    2012-01-01

    Orientation and navigation in a complex environment requires path planning and recall to exert goal-driven behavior. Walking "Drosophila" flies possess a visual orientation memory for attractive targets which is localized in the central complex of the adult brain. Here we show that this type of working memory requires the cGMP-dependent protein…

  19. Propiedades insecticidas de la ceniza del complejo volcánico Puyehue-Cordón Caulle y su posible impacto ambiental: Insecticidal properties of ashes from the volcanic complex Puyehue-Caulle Range and their possible environmental impact

    Directory of Open Access Journals (Sweden)

    Micaela Buteler

    2011-12-01

    insecticidal effect of volcanic ash and its environmental impact, focusing on the ash accumulated as a result of the eruption of the volcanic complex Puyehue- Caulle Range currently affecting an area of over 7.5 million hectares in the Argentine Patagonia. The chemical composition of ashes from the Puyehue-Caulle Range was analyzed by EDS showing that its major components are O, Si, Al, Fe, Na and K. Laboratory bioassays using two species of insects as a biological model, found that the ashes thoroughly adhere to the insect body surface and are toxic to both species tested, when mixed into the substrate at low concentrations. Susceptibility to ashes differs between the two species when tested in a seven day continuous exposure bioassay [CL99(Oryzaephilus surinamensis L. = 10.25 mg.g-1; CL99((Tribolium castaneum (Herbst = 4.96 mg.g-1]. These results agree with those reported in the literature on effects of volcanic eruptions and suggest that the impact of the ashes from the Puyehue-Caulle Range volcanic complex on the insect community may be radical in the acute deposition phase, with substantial qualitative effects in the chronic phase of exposure. Also, the recovery of populations affected by ash in desert areas where dry ash persists will be slower, and this will have tangible and long-term consequences for insect host plants, pollination and on the development of populations of vertebrate insectivores. By contrast, the presence of ash in humid regions will impact the ecosystem by the addition of nutrients, which in combination with water retention by the ash will lead to a qualitative and quantitative recovery of the populations under favorable conditions.

  20. Developing International Guidelines on Volcanic Hazard Assessments for Nuclear Facilities

    Science.gov (United States)

    Connor, Charles

    2014-05-01

    tremendous challenge in quantitative volcanic hazard assessments to encompass alternative conceptual models, and to create models that are robust to evolving understanding of specific volcanic systems by the scientific community. A central question in volcanic hazards forecasts is quantifying rates of volcanic activity. Especially for long-dormant volcanic systems, data from the geologic record may be sparse, individual events may be missing or unrecognized in the geologic record, patterns of activity may be episodic or otherwise nonstationary. This leads to uncertainty in forecasting long-term rates of activity. Hazard assessments strive to quantify such uncertainty, for example by comparing observed rates of activity with alternative parametric and nonparametric models. Numerical models are presented that characterize the spatial distribution of potential volcanic events. These spatial density models serve as the basis for application of numerical models of specific phenomena such as development of lava flow, tephra fallout, and a host of other volcanic phenomena. Monte Carlo techniques (random sampling, stratified sampling, importance sampling) are methods used to sample vent location and other key eruption parameters, such as eruption volume, magma rheology, and eruption column height for probabilistic models. The development of coupled scenarios (e.g., the probability of tephra accumulation on a slope resulting in subsequent debris flows) is also assessed through these methods, usually with the aid of event trees. The primary products of long-term forecasts are a statistical model of the conditional probability of the potential effects of volcanism, should an eruption occur, and the probability of such activity occurring. It is emphasized that hazard forecasting is an iterative process, and board consideration must be given to alternative conceptual models of volcanism, weighting of volcanological data in the analyses, and alternative statistical and numerical models

  1. Thrusting and transpressional shearing in the Pan-African nappe southwest El-Sibai core complex, Central Eastern Desert, Egypt

    Science.gov (United States)

    El-Wahed, Mohamed A. Abd.

    2008-01-01

    The Wadi El-Shush area in the Central Eastern Desert (CED) of Egypt is occupied by the Sibai core complex and its surrounding Pan-African nappe complex. The sequence of metamorphic and structural events in the Sibai core complex and the enveloping Pan-African nappe can be summarized as follows: (1) high temperature metamorphism associated with partial melting of amphibolites and development of gneissic and migmatitic rocks, (2) between 740 and 660 Ma, oblique island arc accretion resulted in Pan-African nappe emplacement and the intrusion of syn-tectonic gneissic tonalite at about 680 ± 10 Ma. The NNW-SSE shortening associated with oblique island arc accretion produced low angle NNW-directed thrusts and open folds in volcaniclastic metasediments, schists and isolated serpentinite masses (Pan-African nappe) and created NNE-trending recumbent folds in syn-tectonic granites. The NNW-SSE shortening has produced imbricate structures and thrust duplexes in the Pan-African nappe, (3) NE-ward thrusting which deformed the Pan-African nappe into SW-dipping imbricate slices. The ENE-WSW compression event has created NE-directed thrusts, folded the NNW-directed thrusts and produced NW-trending major and minor folds in the Pan-African nappe. Prograde metamorphism (480-525 °C at 2-4.5 kbar) was synchronous with thrusting events, (4) retrograde metamorphism during sinistral shearing along NNW- to NW-striking strike-slip shear zones (660-580 Ma), marking the external boundaries of the Sibai core complex and related to the Najd Fault System. Sinistral shearing has produced steeply dipping mylonitic foliation and open plunging folds in the NNW- and NE-ward thrust planes. Presence of retrograde metamorphism supports the slow exhumation of Sibai core complex under brittle-ductile low temperature conditions. Arc-accretion caused thrusting, imbrication and crustal thickening, whereas gravitational collapse of a compressed and thickened lithosphere initiated the sinistral movement

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

    Science.gov (United States)

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

    2017-08-09

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

  3. The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism

    Science.gov (United States)

    Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.

    2001-12-01

    over 60 volcanoes, with an average of 10 volcanoes discussed each week. Notable volcanic activity during November 2000-November 2001 included an eruption beginning on 6 February at Nyamuragira in the Democratic Republic of the Congo; it issued low-viscosity lava flows that traveled towards inhabited towns, and also produced ash clouds that adversely effected the health of residents and livestock near the volcano. Eruptions at Mayon in the Philippines on 24 June and 25 July caused local authorities to raise the alert to the highest level, close area airports, and evacuate thousands of residents near the volcano. Most recently a large flank eruption at Etna in Italy began on 17 July and gained worldwide attention as extensive lava flows threatened a small town and a tourist complex. While the information found in the Weekly Volcanic Activity Report, ranging from large eruptions to small precursory events, is of interest to the general public, it has also proven to be a valuable resource to volcano observatory staff, universities, researchers, secondary schools, and the aviation community.

  4. Central ossifying fibroma, periapical cemento-osseous dysplasia and complex odon-toma occurring in the same jaw.

    Science.gov (United States)

    Hosseini, Farzaneh Agha; Moslemi, Elham

    2011-05-16

    Central ossifying fibroma is a rare, benign fibro-osseous lesion that arises from the periodontal ligament. Periapical cemento-osseous dysplasia is another variant of fibro-osseous lesion which occurs in the anterior region of the mandible of females. Odontoma is a benign odontogenic tumor that contains enamel, dentine cement and pulp tissue. A 46-year-old woman was referred to the Department of Oral Medicine, School of Dentistry, Tehran University of Medical Sciences, with two non-painful swellings on both sides of the mandible, which had been slowly growing over a period of one year. Our differential diagnosis was florid cemento-osseous dysplasia, focal cemento-osseous dysplasia for the right side, complex odontoma for the left side and periapical cement-osseous dysplasia for the anterior side. The historical feature revealed ossifying fibroma, complex odontoma and periapical cemento-osseous dysplasia. The occurrence of these three lesions in the same jaw has been rarely reported in the literature. The relationship between the occurrence of these three lesions is not obvious it could be coincidental. It seems that more case reports are needed to establish the relationship between them.

  5. The role of beaver in shaping steelhead trout (Oncorhynchus mykiss) habitat complexity and thermal refugia in a central Oregon stream

    Science.gov (United States)

    Consolati, F.; Wheaton, J. M.; Neilson, B. T.; Bouwes, N.; Pollock, M. M.

    2012-12-01

    The incised and degraded habitat of Bridge Creek, tributary to the John Day River in central Oregon, is thought to be limiting the local population of ESA-listed steelhead trout (Oncorhynchus mykiss). Restoration efforts for this watershed are aimed to improve their habitat through reconnecting the channel with portions of its former floodplain (now terraces) to increase stream habitat complexity and the extent of riparian vegetation. This is being done via the installation of over a hundred beaver dam support (BDS) structures that are designed to either mimic beaver dams or support existing beaver dams. The overall objective of this study is to determine if the BDS structures have had an effect on stream channel habitat complexity and thermal refugia in selected sections of Bridge Creek. Analysis of stream temperature data in restoration treatment and control areas will show the effects of beaver dams on stream temperature. Analysis of aerial imagery and high resolution topographic data will exhibit how the number and types of geomorphic units have changed after the construction of beaver dams. Combined, the results of this research are aimed to increase our understanding of how beaver dams impact fish habitat and stream temperature.

  6. Colonization of a Central Venous Catheter by the Hyaline Fungus Fusarium solani Species Complex: A Case Report and SEM Imaging

    Directory of Open Access Journals (Sweden)

    Alberto Colombo

    2013-01-01

    Full Text Available The incidence of opportunistic infections by filamentous fungi is increasing partly due to the widespread use of central venous catheters (CVC, indwelling medical devices, and antineoplastic/immunosuppressive drugs. The case of a 13-year-old boy under treatment for acute lymphoblastic leukemia is presented. The boy was readmitted to the Pediatric Ward for intermittent fever of unknown origin. Results of blood cultures drawn from peripheral venous sites or through the CVC were compared. CVC-derived bottles (but not those from peripheral veins yielded hyaline fungi that, based on morphology, were identified as belonging to the Fusarium solani species complex. Gene amplification and direct sequencing of the fungal ITS1 rRNA region and the EF-1alpha gene confirmed the isolate as belonging to the Fusarium solani species complex. Portions of the CVC were analyzed by scanning electron microscopy. Fungi mycelia with long protruding hyphae were seen into the lumen. The firm adhesion of the fungal formation to the inner surface of the catheter was evident. In the absence of systemic infection, catheter removal and prophylactic voriconazole therapy were followed by disappearance of febrile events and recovery. Thus, indwelling catheters are prone to contamination by environmental fungi.

  7. Assessment of the uranium potential of the Jurassic volcanism (Bahía Laura and El Quemado Complexes), Province of Santa Cruz, using ground-borne gamma-ray spectrometry and rock geochemistry

    International Nuclear Information System (INIS)

    Kleinman, L.E.; Maloberti, A.L.; Gayone, M.R.; Kaufmann, C.; Sruoga, P.

    2013-01-01

    Radiometric surveys are a rapid tool to measure uranium (U), thorium (Th) and potassium (K) concentrations in rocks and are very useful in the exploration for radioactive minerals. The distribution of uranium in Jurassic volcanic rocks of the province of Santa Cruz is evaluated in this work using ground gamma-ray spectrometry and rock geochemistry in order to assess its potential to form uranium deposits. Five areas were selected, which had some previous data of high radiometric values and detailed geological information. Measurements were carried out with a portable gamma-ray spectrometer (Exploranium-GR 320®) in andesites, ignimbrites, rhyolites, silicified areas, ash-fall tuffs and lacustrine sediments corresponding to the Bahía Laura and to El Quemado complexes. The results were similar in the five surveyed areas: radiometric concentrations show good positive correlations with chemical composition of the studied rocks for both K and Th, and a relatively poorer correlation for U. Different processes such as magmatic differentiation, vapor phase crystallization, hydrothermal alteration and supergene alteration are reflected in the distribution of these elements. U concentrations increase in the more glassy rocks, in areas with hydrothermal silicification, and in fracture zones, features that should be considered in future surveys. The calkalkaline composition and arc-signatures of the Jurassic magmatism are not the most favorable for uranium enrichment and for concentration of significant mineralizations. However, the extensional tectonic setting; the occurrence of calderas with facies slightly enriched in U and Th, in addition to hydrothermal activity are positive factors for U exploration. (authors) [es

  8. Conceptual model of volcanism and volcanic hazards of the region of Ararat valley, Armenia

    Science.gov (United States)

    Meliksetian, Khachatur; Connor, Charles; Savov, Ivan; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Ghukasyan, Yura; Gevorgyan, Hripsime

    2015-04-01

    Armenia and the adjacent volcanically active regions in Iran, Turkey and Georgia are located in the collision zone between the Arabian and Eurasian lithospheric plates. The majority of studies of regional collision related volcanism use the model proposed by Keskin, (2003) where volcanism is driven by Neo-Tethyan slab break-off. In Armenia, >500 Quaternary-Holocene volcanoes from the Gegham, Vardenis and Syunik volcanic fields are hosted within pull-apart structures formed by active faults and their segments (Karakhanyan et al., 2002), while tectonic position of the large in volume basalt-dacite Aragats volcano and periphery volcanic plateaus is different and its position away from major fault lines necessitates more complex volcano-tectonic setup. Our detailed volcanological, petrological and geochemical studies provide insight into the nature of such volcanic activity in the region of Ararat Valley. Most magmas, such as those erupted in Armenia are volatile-poor and erupt fairly hot. Here we report newly discovered tephra sequences in Ararat valley, that were erupted from historically active Ararat stratovolcano and provide evidence for explosive eruption of young, mid K2O calc-alkaline and volatile-rich (>4.6 wt% H2O; amph-bearing) magmas. Such young eruptions, in addition to the ignimbrite and lava flow hazards from Gegham and Aragats, present a threat to the >1.4 million people (~ ½ of the population of Armenia). We will report numerical simulations of potential volcanic hazards for the region of Ararat valley near Yerevan that will include including tephra fallout, lava flows and opening of new vents. Connor et al. (2012) J. Applied Volcanology 1:3, 1-19; Karakhanian et al. (2002), JVGR, 113, 319-344; Keskin, M. (2003) Geophys. Res. Lett. 30, 24, 8046.

  9. A multi-disciplinary approach to study coastal complex landslides: the case of Torino di Sangro (Central Italy)

    Science.gov (United States)

    Sciarra, Marco; Carabba, Luigi; Urbano, Tullio; Calista, Monia

    2016-04-01

    This work illustrates the studies carried out on a complex landslide phenomenon between the Sangro and Osento River's mouths, near Torino di Sangro village in Southern Abruzzo Region (Italy). Historical activity of this landslide is well-documented since 1916; the activation/reactivation of the movements caused several interruptions of a national railway and the damage of few houses. The Torino di Sangro case study can be regarded as representative of many large landslides distributed along the central Adriatic coast (e.g., Ancona, Ortona, Vasto and Petacciato Landslides) that affect densely populated urban areas with a large amount of man-made infrastructure. The main controlling factors of these large and deep-seated landslides are still debated. From the geological and geomorphological viewpoint, the central Adriatic coast is characterized by a low-relief landscape (mesa) carved on clay-sandstone-conglomerate bedrock belonging to the Upper Pliocene - Lower Pleistocene marine deposits and locally to the Middle Pleistocene marine to continental transitional deposits. This high coast is widely affected by slope instability (rock falls, rotational, complex and shallow landslides) on both active and inactive sea cliffs, the first being mainly affected by wave-cut erosion and the latter influenced by heavy rainfall and changes of pore pressure. The main landslide has the typical characteristics of a deep-seated gravitation deformation. The landslide study was based on a multidisciplinary approach including: 1) definition and GIS mapping of geology and geomorphology factors (slope, aspect, topographic curvature, bedrock lithology, near-surface deposits, deposit thickness and land use), by means of DTM processing, multi-temporal analysis, and large-scale geomorphological field survey; 2) monitoring system in the landslide; 3) application of empiric models for the analysis of unstable sandstone-conglomerate escarpments; 4) slope stability analysis performed using a

  10. Backprojection of volcanic tremor

    Science.gov (United States)

    Haney, Matthew M.

    2014-01-01

    Backprojection has become a powerful tool for imaging the rupture process of global earthquakes. We demonstrate the ability of backprojection to illuminate and track volcanic sources as well. We apply the method to the seismic network from Okmok Volcano, Alaska, at the time of an escalation in tremor during the 2008 eruption. Although we are able to focus the wavefield close to the location of the active cone, the network array response lacks sufficient resolution to reveal kilometer-scale changes in tremor location. By deconvolving the response in successive backprojection images, we enhance resolution and find that the tremor source moved toward an intracaldera lake prior to its escalation. The increased tremor therefore resulted from magma-water interaction, in agreement with the overall phreatomagmatic character of the eruption. Imaging of eruption tremor shows that time reversal methods, such as backprojection, can provide new insights into the temporal evolution of volcanic sources.

  11. The use of Remote Sensing for the Study of the Relationships Between Tectonics and Volcanism

    Science.gov (United States)

    Chorowicz, J.; Dhont, D.; Yanev, Y.; Bardintzeff, J.

    2004-12-01

    Observations of geometric relationships between tectonics and volcanism is a fruitful approach in geology. On the one hand analysis of the distribution and types of volcanic vents provides information on the geodynamics. On the other hand tectonic analysis explains the location of volcanics vents. Volcanic edifices often result from regional scale deformation, forming open structures constituting preferred pathways for the rise of magmas. Analysis of the shape and the distribution of vents can consequently provide data on the regional deformation. Remote sensing imagery gives synoptic views of the earth surface allowing the analysis of landforms of still active tectonic and volcanic features. Shape and distribution of volcanic vents, together with recent tectonic patterns are best observed by satellite data and Digital Elevation Models than in the field. The use of radar scenes for the study of the structural relationships between tectonic and volcanic features is particularly efficient because these data express sensitive changes in the morphology. In various selected areas, we show that volcanic edifices are located on tension fractures responsible for fissure eruptions, volcanic linear clusters and elongate volcanoes. Different types of volcanic emplacements can be also distinguished such as tail-crack or horse-tail features, and releasing bend basins along strike-slip faults. Caldera complexes seem to be associated to horse-tail type fault terminations. At a regional scale, the distribution of volcanic vents and their relationships with the faults is able to explain the occurrence of volcanism in collisional areas.

  12. X-ray microanalysis of volcanic ash

    International Nuclear Information System (INIS)

    Kearns, S L; Buse, B

    2012-01-01

    The 2010 eruption of Eyjafjallajökull volcano in Iceland demonstrated the disruptive nature of high-level volcanic ash emissions to the world's air traffic. The chemistry of volcanic material is complex and varied. Different eruptions yield both compositional and morphological variation. Equally a single eruption, such as that in Iceland will evolve over time and may potentially produce a range of volcanic products of varying composition and morphology. This variability offers the petrologist the opportunity to derive a tracer to the origins both spatially and temporally of a single particle by means of electron microbeam analysis. EPMA of volcanic ash is now an established technique for this type of analysis as used in tephrachronology. However, airborne paniculate material may, as in the case of Eyjafjallajökull, result in a particle size that is too small and too dispersed for preparation of standard EPMA mounts. Consequently SEM-EDS techniques are preferred for this type of quantitative analysis . Results of quantitative SEM-EDS analysis yield data with a larger precision error than EPMA yet sufficient to source the original eruption. Uncoated samples analyzed using variable pressure SEM yield slightly poorer results at modest pressures.

  13. Volcanic eruptions on Io

    Science.gov (United States)

    Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Hansen, C.; Cook, A. F.

    1981-01-01

    Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

  14. Soil CO2 efflux measurement network by means of closed static chambers to monitor volcanic activity at Tenerife, Canary Islands

    Science.gov (United States)

    Amonte, Cecilia; García-Merino, Marta; Asensio-Ramos, María; Melián, Gladys; García-Hernández, Rubén; Pérez, Aaron; Hernández, Pedro A.; Pérez, Nemesio M.

    2017-04-01

    Tenerife (2304 km2) is the largest of the Canary Islands and has developed a central volcanic complex (Cañadas edifice), that started to grow about 3.5 My ago. Coeval with the construction of the Cañadas edifice, shield basaltic volcanism continued until the present along three rift zones oriented NW-SE, NE-SW and NS (hereinafter referred as NW, NE and NS respectively). Main volcanic historical activity has occurred along de NW and NE rift-zones, although summit cone of Teide volcano, in central volcanic complex, is the only area of the island where surface geothermal manifestations are visible. Uprising of deep-seated gases occurs along the aforementioned volcanic structures causing diffuse emissions at the surface environment of the rift-zones. In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs. Diffuse degassing studies are even more important volcanic surveillance tool at those volcanic areas where visible manifestations of volcanic gases are absent. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. One of the most popular methods used to determine CO2 fluxes in soil sciences is based on the absorption of CO2 through an alkaline medium, in its solid or liquid form, followed by gravimetric, conductivity, or titration analyses. In the summer of 2016, a network of 31 closed static chambers was installed, covering the three main structural zones of Tenerife (NE, NW and NS) as well as Cañadas Caldera with volcanic surveillance porpoises. 50 cc of 0.1N KOH solution is placed inside the chamber to absorb the CO2 released from the soil. The solution is replaced weekly and the trapped CO2 is then analyzed at the laboratory by titration. The are expressed as weekly integrated CO2 efflux values. The CO2 efflux values ranged from 3.2 to 12.9 gṡm-2

  15. Gas measurements from the Costa Rica-Nicaragua volcanic segment suggest possible along-arc variations in volcanic gas chemistry

    Science.gov (United States)

    Aiuppa, A.; Robidoux, P.; Tamburello, G.; Conde, V.; Galle, B.; Avard, G.; Bagnato, E.; De Moor, J. M.; Martínez, M.; Muñóz, A.

    2014-12-01

    Obtaining accurate estimates of the CO2 output from arc volcanism requires a precise understanding of the potential along-arc variations in volcanic gas chemistry, and ultimately of the magmatic gas signature of each individual arc segment. In an attempt to more fully constrain the magmatic gas signature of the Central America Volcanic Arc (CAVA), we present here the results of a volcanic gas survey performed during March and April 2013 at five degassing volcanoes within the Costa Rica-Nicaragua volcanic segment (CNVS). Observations of the volcanic gas plume made with a multicomponent gas analyzer system (Multi-GAS) have allowed characterization of the CO2/SO2-ratio signature of the plumes at Poás (0.30±0.06, mean ± SD), Rincón de la Vieja (27.0±15.3), and Turrialba (2.2±0.8) in Costa Rica, and at Telica (3.0±0.9) and San Cristóbal (4.2±1.3) in Nicaragua (all ratios on molar basis). By scaling these plume compositions to simultaneously measured SO2 fluxes, we estimate that the CO2 outputs at CNVS volcanoes range from low (25.5±11.0 tons/day at Poás) to moderate (918 to 1270 tons/day at Turrialba). These results add a new information to the still fragmentary volcanic CO2 output data set, and allow estimating the total CO2 output from the CNVS at 2835±1364 tons/day. Our novel results, with previously available information about gas emissions in Central America, are suggestive of distinct volcanic gas CO2/ST (= SO2 + H2S)-ratio signature for magmatic volatiles in Nicaragua (∼3) relative to Costa Rica (∼0.5-1.0). We also provide additional evidence for the earlier theory relating the CO2-richer signature of Nicaragua volcanism to increased contributions from slab-derived fluids, relative to more-MORB-like volcanism in Costa Rica. The sizeable along-arc variations in magmatic gas chemistry that the present study has suggested indicate that additional gas observations are urgently needed to more-precisely confine the volcanic CO2 from the CAVA, and from

  16. Rb-Sr systematics of granitoids of the central gneissic complex, Arunachal Himalaya: implications on tectonism, stratigraphy and source

    Energy Technology Data Exchange (ETDEWEB)

    Dikshitulu, G R; Dhana Raju, R [Dept. of Atomic Energy, Bangalore (India). Atomic Minerals Division; Pandey, B K; Krishna, Veena [Department of Atomic Energy, Hyderabad (India). Atomic Minerals Div.

    1995-01-01

    Precambrian central gneissic complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela group thrusting over the Bomdila group, with the Salari group being the youngest. Augen gneiss of the Bomdila group, granite of the Salari group and hornblende granite gneiss of the Sela group define Rb-Sr isochron ages of 1914{+-}23, 1536{+-}60 and 481{+-} 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the main central thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy ({sup 87}Sr/{sup 86}Sr), of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060{+-}250, 1530{+-}90 and 530{+-} 75 Ma. (author). 22 refs., 2 figs., 3 tabs.

  17. Rb-Sr systematics of granitoids of the central gneissic complex, Arunachal Himalaya: implications on tectonism, stratigraphy and source

    International Nuclear Information System (INIS)

    Dikshitulu, G.R.; Dhana Raju, R.; Pandey, B.K.; Krishna, Veena

    1995-01-01

    Precambrian central gneissic complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela group thrusting over the Bomdila group, with the Salari group being the youngest. Augen gneiss of the Bomdila group, granite of the Salari group and hornblende granite gneiss of the Sela group define Rb-Sr isochron ages of 1914±23, 1536±60 and 481± 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the main central thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy ( 87 Sr/ 86 Sr), of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060±250, 1530±90 and 530± 75 Ma. (author). 22 refs., 2 figs., 3 tabs

  18. Assessment of volcanic hazards, vulnerability, risk and uncertainty (Invited)

    Science.gov (United States)

    Sparks, R. S.

    2009-12-01

    A volcanic hazard is any phenomenon that threatens communities . These hazards include volcanic events like pyroclastic flows, explosions, ash fall and lavas, and secondary effects such as lahars and landslides. Volcanic hazards are described by the physical characteristics of the phenomena, by the assessment of the areas that they are likely to affect and by the magnitude-dependent return period of events. Volcanic hazard maps are generated by mapping past volcanic events and by modelling the hazardous processes. Both these methods have their strengths and limitations and a robust map should use both approaches in combination. Past records, studied through stratigraphy, the distribution of deposits and age dating, are typically incomplete and may be biased. Very significant volcanic hazards, such as surge clouds and volcanic blasts, are not well-preserved in the geological record for example. Models of volcanic processes are very useful to help identify hazardous areas that do not have any geological evidence. They are, however, limited by simplifications and incomplete understanding of the physics. Many practical volcanic hazards mapping tools are also very empirical. Hazards maps are typically abstracted into hazards zones maps, which are some times called threat or risk maps. Their aim is to identify areas at high levels of threat and the boundaries between zones may take account of other factors such as roads, escape routes during evacuation, infrastructure. These boundaries may change with time due to new knowledge on the hazards or changes in volcanic activity levels. Alternatively they may remain static but implications of the zones may change as volcanic activity changes. Zone maps are used for planning purposes and for management of volcanic crises. Volcanic hazards maps are depictions of the likelihood of future volcanic phenomena affecting places and people. Volcanic phenomena are naturally variable, often complex and not fully understood. There are

  19. Las cuencas cenozoicas y su control en el volcanismo de los Complejos Nevados de Chillan y Copahue-Callaqui (Andes del Sur, 36-39°S Cenozoic basins and their control on volcanism of Nevados de Chillan and Copahue-Callaqui complexes (36-39°S, Southern Andes

    Directory of Open Access Journals (Sweden)

    Juan Pablo Radic

    2010-01-01

    previous extensional faults and sedimentary fill. The accommodation zones prevailed as first order structures and acted as weakened zones that enabled the volcanism and magmatism at the Nevados de Chillan and Copahue-Callaqui volcanic complexes. Each one of these volcanic complexes is characterized by an oriented series of emission centers, volcanic morphology and deposits that are subparallel to the underlying accommodation zone.

  20. U-Pb age in zircon of intrusive granite at Acopiara complex, Crystal region, domain Central Ceara, Brazil; Idade U-PB em zircao de granito intrusivo no Complexo Acopiara, Regiao de Cristais, Dominio Ceara Central

    Energy Technology Data Exchange (ETDEWEB)

    Neri, T.F.O.; Hamelak, G.M.S.; Azevedo, L.R.; Mattos, I.C.; Verissimo, C.U.V.; Nogueira Neto, J.A., E-mail: neri@ufc.br [Universidade Federal do Ceara (UFC), Fortaleza (Brazil). Departamento de Geologia; Lima, M.N. [Universidade Federal de Goias (UFGO), Goiania, GO (Brazil). Curso de Geologia

    2015-07-01

    Granitic body mineralogically composed by two micas, located at Crystal region, Ceara Central domain and intruded into lithotypes from Acopiara complex, provided an age of ∼526 Ma, indicating important period of magma generation of granitic composition associated with crustal anatexia, during Paleozoic.

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

    Science.gov (United States)

    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

  2. The Role of Volcanic Activity in Climate and Global Change

    KAUST Repository

    Stenchikov, Georgiy L.

    2015-09-23

    Explosive volcanic eruptions are magnificent events that in many ways affect the Earth\\'s natural processes and climate. They cause sporadic perturbations of the planet\\'s energy balance, activating complex climate feedbacks and providing unique opportunities to better quantify those processes. We know that explosive eruptions cause cooling in the atmosphere for a few years, but we have just recently realized that volcanic signals can be seen in the subsurface ocean for decades. The volcanic forcing of the previous two centuries offsets the ocean heat uptake and diminishes global warming by about 30%. The explosive volcanism of the twenty-first century is unlikely to either cause any significant climate signal or to delay the pace of global warming. The recent interest in dynamic, microphysical, chemical, and climate impacts of volcanic eruptions is also excited by the fact that these impacts provide a natural analogue for climate geoengineering schemes involving deliberate development of an artificial aerosol layer in the lower stratosphere to counteract global warming. In this chapter we aim to discuss these recently discovered volcanic effects and specifically pay attention to how we can learn about the hidden Earth-system mechanisms activated by explosive volcanic eruptions. To demonstrate these effects we use our own model results when possible along with available observations, as well as review closely related recent publications.

  3. Rare earth element and strontium isotopic study of seamount-type limestones in Mesozoic accretionary complex of Southern Chichibu Terrane, central Japan. Implication for incorporation process of seawater REE into limestones

    International Nuclear Information System (INIS)

    Tanaka, Kazuya; Miura, Noriko; Asahara, Yoshihiro; Kawabe, Iwao

    2003-01-01

    Ishimaki and Tahara limestones occur as exotic blocks juxtaposed in the Mesozoic (Jurassic) accretionary complex of Southern Chichibu Terrane in eastern Aichi Prefecture, central Japan. They are supposed to be of the seamount-type limestone, since they have no terrigenous materials and are intimately associated with greenstones. REE (rare earth elements) and Sr isotopic studies for the limestones have been made in order to know their geochemical characteristics, ages and origins. Their 87 Sr/ 86 Sr ratios, when referred to the seawater 87 Sr/ 86 Sr curve and relevant geological data, suggest that Ishimaki and Tahara limestones are the late Permian and the Carboniferous to the Early Permian, respectively. Two greenstone fragments found inside the Ishimaki limestone block and one greenstone sample associated with Tahara limestone block, resemble the Hawaiian alkali basalt in the their REE and Y patterns. This is supporting the idea that the limestone blocks may be parts of reef limestones on ancient volcanic seamounts. All the limestone samples, except three unusual Tahara ones, show seawater REE and Y signatures in their chondrite-normalized patterns. Their REE/Ca ratios, however, are 10 2 -10 4 times as high as those ratios of modern biogenic carbonates like corals and the seawater. Accordingly, seawater REE and Y were incorporated into the limestones, when originally biogenic carbonates transformed into inorganic calcite and its secondary growths occurred in diagenesis in contact with sufficient seawater. This view is favored by the reported REE partition experiment between calcite overgrowths and seawater solution. The seawater Ce anomaly as a function of water depth in the modern ocean is a key to infer the water depth of the REE and Y incorporation. The Ce anomalies given by log (Ce/Ce*) for about a half of Ishimaki samples and most of Tahara ones are between -0.5 and -0.2, which are compatible with the shallow water origin. Another half of Ishimaki samples

  4. Selective extraction methods for aluminium, iron and organic carbon from montane volcanic ash soils

    NARCIS (Netherlands)

    Jansen, B.; Tonneijck, F.H.; Verstraten, J.M.

    2011-01-01

    Montane volcanic ash soils contain disproportionate amounts of soil organic carbon and thereby play an often underestimated role in the global carbon cycle. Given the central role of Al and Fe in stabilizing organic matter in volcanic ash soils, we assessed various extraction methods of Al, Fe, and

  5. Geophysical imaging of buried volcanic structures within a continental back-arc basin

    DEFF Research Database (Denmark)

    Stratford, Wanda Rose; Stern, T.A.

    2008-01-01

    Hidden beneath the ~2 km thick low-velocity volcaniclastics on the western margin of the Central Volcanic Region, North Island, New Zealand, are two structures that represent the early history of volcanic activity in a continental back-arc. These ~20×20 km structures, at Tokoroa and Mangakino, fo...

  6. Microphysical Properties of Alaskan Volcanic Ash

    Science.gov (United States)

    Puthukkudy, A.; Espinosa, R.; Rocha Lima, A.; Remer, L.; Colarco, P. R.; Whelley, P.; Krotkov, N. A.; Young, K.; Dubovik, O.; Wallace, K.; Martins, J. V.

    2017-12-01

    Volcanic ash has the potential to cause a variety of severe problems for human health and the environment. Therefore, effective monitoring of the dispersion and fallout from volcanic ash clouds and characterization of the aerosol particle properties are essential. One way to acquire information from volcanic clouds is through satellite remote sensing: such images have greater coverage than ground-based observations and can present a "big picture" perspective. A challenge of remote sensing is that assumptions of certain properties of the target are often a pre-requisite for making accurate and quantitative retrievals. For example, detailed information about size distribution, sphericity, and optical properties of the constituent matter is needed or must be assumed. The same kind of information is also needed for atmospheric transport models to properly simulate the dispersion and fallout of volcanic ash. Presented here is a laboratory method to determine the microphysical and optical properties of volcanic ash samples collected from two Alaskan volcanoes with markedly different compositions. Our method uses a Polarized Imaging Nephelometer (PI-Neph) and a system that re-suspends the particles in an air flow. The PI-Neph measures angular light scattering and polarization of the re-suspended particles from 3o to 175o in scattering angle, with an angular resolution of 1o . Primary measurements include phase function and polarized phase function at three wavelengths (445nm, 532nm, and 661nm). Size distribution, sphericity, and complex refractive index are retrieved indirectly from the PI-Neph measurements using the GRASP (Generalized Retrieval of Aerosol and Surface Properties) inversion algorithm. We report the results of this method applied to samples from the Mt. Okmok (2008) and Mt. Katmai (1912) volcanic eruptions. To our knowledge, this is the first time direct measurements of phase matrix elements of ash from Mt. Okmok and Mt. Katmai have been reported. Retrieved

  7. A novel mouse synaptonemal complex protein is essential for loading of central element proteins, recombination, and fertility.

    Directory of Open Access Journals (Sweden)

    Sabine Schramm

    2011-05-01

    Full Text Available The synaptonemal complex (SC is a proteinaceous, meiosis-specific structure that is highly conserved in evolution. During meiosis, the SC mediates synapsis of homologous chromosomes. It is essential for proper recombination and segregation of homologous chromosomes, and therefore for genome haploidization. Mutations in human SC genes can cause infertility. In order to gain a better understanding of the process of SC assembly in a model system that would be relevant for humans, we are investigating meiosis in mice. Here, we report on a newly identified component of the murine SC, which we named SYCE3. SYCE3 is strongly conserved among mammals and localizes to the central element (CE of the SC. By generating a Syce3 knockout mouse, we found that SYCE3 is required for fertility in both sexes. Loss of SYCE3 blocks synapsis initiation and results in meiotic arrest. In the absence of SYCE3, initiation of meiotic recombination appears to be normal, but its progression is severely impaired resulting in complete absence of MLH1 foci, which are presumed markers of crossovers in wild-type meiocytes. In the process of SC assembly, SYCE3 is required downstream of transverse filament protein SYCP1, but upstream of the other previously described CE-specific proteins. We conclude that SYCE3 enables chromosome loading of the other CE-specific proteins, which in turn would promote synapsis between homologous chromosomes.

  8. Nonradioactive Air Emissions Notice of Construction (NOC) Application for the Central Waste Complex (CSC) for Storage of Vented Waste Containers

    International Nuclear Information System (INIS)

    KAMBERG, L.D.

    2000-01-01

    This Notice of Construction (NOC) application is submitted for the storage and management of waste containers at the Central Waste Complex (CWC) stationary source. The CWC stationary source consists of multiple sources of diffuse and fugitive emissions, as described herein. This NOC is submitted in accordance with the requirements of Washington Administrative Code (WAC) 173-400-110 (criteria pollutants) and 173-460-040 (toxic air pollutants), and pursuant to guidance provided by the Washington State Department of Ecology (Ecology). Transuranic (TRU) mixed waste containers at CWC are vented to preclude the build up of hydrogen produced as a result of radionuclide decay, not as safety pressure releases. The following activities are conducted within the CWC stationary source: Storage and inspection; Transfer and staging; Packaging; Treatment; and Sampling. This NOC application is intended to cover all existing storage structures within the current CWC treatment, storage, and/or disposal (TSD) boundary, as well as any storage structures, including waste storage pads and staging areas, that might be constructed in the future within the existing CWC boundary

  9. Stratigraphy, sedimentology and petrology of neogene rocks in the Deschutes Basin, Central Oregon: a record of continental-margin volcanism and its influence on fluvial sedimentation in an arc-adjacent basin

    International Nuclear Information System (INIS)

    Smith, G.A.

    1986-07-01

    Neogene rocks of the Deschutes basin include the middle Miocene Columbia River Basalt Group and Simtustus Formation, and late Miocene to early Pliocene Deschutes Formation. Assignment of Prineville chemical-type flows to the Grande Ronde Basalt of the Columbia River Basalt Group is based on correlation of these lavas from their type area through the Deschutes basin and onto the Columbia Plateau, where they have been previously mapped as Grande Ronde Basalt. Simtustus Formation is a newly defined unit intercalated with and conformable upon these basalts, and is unconformably overlain by Deschutes Formation. Burial of mature topography by middle Miocene basalts raised local base levels and initiated aggradation by low-gradient streams within the basin represented by the tuffaceous sandstones and mudstones of the Simtustus Formation. These sediments are enriched in pyroclastic constituents relative to contemporaneous Western Cascades volcanics, reflecting preferential incorporation of easily eroded and more widespread pyroclastic debris in distal sedimentary sequences compared to epiclastic contributions from lavas. The abundance of basalts, combined with the paucity of hydrous minerals and FeO and TiO 2 enrichment in intermediate lavas, characterizes early High Cascade volcanics as atypical for convergent-margin arcs. These petrologic characteristics are consistent with high-level fractionation in an extensional regime. Extension culminated in the development of an intra-arc graben, which ended Deschutes Formation deposition by structurally isolating the basin from the High Cascade source area

  10. Groundwater flow in a relatively old oceanic volcanic island: The Betancuria area, Fuerteventura Island, Canary Islands, Spain

    Energy Technology Data Exchange (ETDEWEB)

    Herrera, Christian, E-mail: cherrera@ucn.cl [Universidad Católica del Norte, Av. Angamos 0610, Antofagasta (Chile); Custodio, Emilio [Department of Geo-Engineering, Technical University of Catalonia (UPC), Barcelona (Spain)

    2014-10-15

    The island of Fuerteventura is the oldest of the Canary Islands' volcanic archipelago. It is constituted by volcanic submarine and subaerial activity and intrusive Miocene events, with some residual later volcanism and Quaternary volcanic deposits that have favored groundwater recharge. The climate is arid, with an average rainfall that barely attains 60 mm/year in the coast and up to 200 mm/year in the highlands. The aquifer recharge is small but significant; it is brackish due to large airborne atmospheric salinity, between 7 and 15 g m{sup −2} year{sup −1} of chloride deposition, and high evapo-concentration in the soil. The average recharge is estimated to be less than about 5 mm/year at low altitude and up to 10 mm/year in the highlands, and up to 20 mm/year associated to recent lava fields. Hydrochemical and water isotopic studies, supported by water table data and well and borehole descriptions, contribute a preliminary conceptual model of groundwater flow and water origin in the Betancuria area, the central area of the island. In general, water from springs and shallow wells tends to be naturally brackish and of recent origin. Deep saline groundwater is found and is explained as remnants of very old marine water trapped in isolated features in the very low permeability intrusive rocks. Preliminary radiocarbon dating indicates that this deep groundwater has an apparent age of less than 5000 years BP but it is the result of mixing recent water recharge with very old deep groundwater. Most of the groundwater flow occurs through the old raised volcanic shield of submarine and subaerial formations and later Miocene subaerial basalts. Groundwater transit time through the unsaturated zone is of a few decades, which allows the consideration of long-term quasi-steady state recharge. Transit times are up to a few centuries through the saturated old volcanics and up to several millennia in the intrusive formations, where isolated pockets of very old water may

  11. Volcanic systems of Iceland and their magma source

    Science.gov (United States)

    Sigmarsson, Olgeir

    2017-04-01

    Several active hot-spot volcanoes produce magma from mantle sources which composition varies on decadal time scale. This is probably best demonstrated by the recent work of Pietruszka and collaborators on Kilauea, Hawaii. In marked contrast, basalt lavas from volcanic system in Iceland located above the presumed centre of the Iceland mantle plume have uniform isotope composition over the last 10 thousand years. Volcanic systems are composed of a central volcano and a fissure swarm, or a combination of both and they represent a fundamental component of the neovolcanic zones in Iceland. Four such systems, those of Askja, Bárðarbunga, Kverkfjöll and Grímsvötn in central Iceland were chosen for investigation. The last three have central volcanoes covered by the Vatnajökull ice-sheet whereas part of their fissure swarms is ice-free. Tephra produced during subglacial eruptions together with lavas from the fissure swarms of Holocene age have been collected and analysed for Sr, Nd and Th isotope ratios. Those volcanic formations that can be univocally correlated to a given volcanic system display uniform isotope ratio but different from one volcanic system to another. An exception to this regularity is that Askja products have isotope ratios indistinguishable from those of Gímsvötn, but since these volcanic systems lies far apart their lava fields do not overlap. A practical aspect of these findings was demonstrated during the rifting event of Bárðarbunga and fissure eruption forming the Holuhraun lava field. Relatively low, O isotope ratios in these basalts and heterogeneous macrocrystal composition have been ascribed to important metabasaltic crustal contamination with or without crystal mush recycling. In that case a surprisingly efficient magma mixing and melt homogenization must have occurred in the past beneath the volcanic systems. One possibility is that during the rapid deglaciation much mantle melting occurred and melts accumulated at the mantle

  12. Geochemical characteristics and petrogenesis of phonolites and trachytic rocks from the České Středohoří Volcanic Complex, the Ohře Rift, Bohemian Massif

    Czech Academy of Sciences Publication Activity Database

    Ackerman, Lukáš; Ulrych, Jaromír; Řanda, Zdeněk; Erban, V.; Hegner, E.; Magna, T.; Balogh, K.; Frána, Jaroslav; Lang, Miloš; Novák, Jiří Karel

    224/225, May (2015), s. 256-271 ISSN 0024-4937 R&D Projects: GA AV ČR IAA3048201 Institutional support: RVO:67985831 ; RVO:61389005 Keywords : phonolite * trachyte * Sr–Nd–Li isotopes * Cenozoic alkaline volcanism * Ohře (Eger) Rift * Bohemian Massif Subject RIV: DD - Geochemistry Impact factor: 3.723, year: 2015

  13. New insight from noble gas and stable isotopes of geothermal/hydrothermal fluids at Caviahue-Copahue Volcanic Complex: Boiling steam separation and water-rock interaction at shallow depth

    Science.gov (United States)

    Roulleau, Emilie; Tardani, Daniele; Sano, Yuji; Takahata, Naoto; Vinet, Nicolas; Bravo, Francisco; Muñoz, Carlos; Sanchez, Juan

    2016-12-01

    We measured noble gas and stable isotopes of the geothermal and hydrothermal fluids of the Caviahue-Copahue Volcanic Complex (CCVC), one of the most important geothermal systems in Argentina/Chile, in order to provide new insights into fluid circulation and origin. With the exception of Anfiteatro and Chancho-co geothermal systems, mantle-derived helium dominates in the CCVC fluids, with measured 3He/4He ratios up to 7.86Ra in 2015. Their positive δ15N is an evidence for subducted sediment-derived nitrogen, which is commonly observed in subduction settings. Both He-N2-Ar composition and positive correlation between δD-H2O and δ18O-H2O suggest that the fluids from Anfiteatro and Chancho-co (and partly from Pucon-Mahuida as well, on the southern flank of Copahue volcano) represent a meteoric water composition with a minor magmatic contribution. The Ne, Kr and Xe isotopic compositions are entirely of atmospheric origin, but processes of boiling and steam separation have led to fractionation of their elemental abundances. We modeled the CCVC fluid evolution using Rayleigh distillation curves, considering an initial air saturated geothermal water (ASGW) end-member at 250 and 300 °C, followed by boiling and steam separation at lower temperatures (from 200 °C to 150 °C). Between 2014 and 2015, the CCVC hydrogen and oxygen isotopes shifted from local meteoric water-dominated to andesitic water-dominated signature. This shift is associated with an increase of δ13C values and Stotal, HCl and He contents. These characteristics are consistent with a change in the gas ascent pathway between 2014 and 2015, which in turn induced higher magmatic-hydrothermal contribution in the fluid signature. The composition of the magmatic source of the CCVC fluids is: 3He/4He = 7.7Ra, δ15N = + 6‰, and δ13C = - 6.5‰. Mixing models between air-corrected He and N suggest the involvement of 0.5% to 5% of subducted sediments in the magmatic source. The magmatic sulfur isotopic

  14. Timing and compositional evolution of Late Pleistocene to Holocene volcanism within the Harrat Rahat volcanic field, Kingdom of Saudi Arabia

    Science.gov (United States)

    Stelten, M. E.; Downs, D. T.; Dietterich, H. R.

    2017-12-01

    Harrat Rahat is one of the largest ( 20,000 km2) of 15 active Cenozoic volcanic fields that stretch 3,000 km along the western Arabian Peninsula from Yemen to Syria. The Harrat Rahat volcanic field is 310 km long (N-S) by 75 km wide (E-W), and is dominated by alkalic basalts with minor hawaiite, mugearite, benmoreite, and trachyte eruptives. The timing of volcanism within greater Harrat Rahat is poorly constrained, but field relations and geochronology indicate that northern Harrat Rahat hosted the most recent eruptions. To better constrain the timing and compositional evolution of Harrat Rahat during this recent phase, we present 743 geochemical analyses, 144 40Ar/39Ar ages, and 9 36Cl exposure ages for volcanic strata from northernmost Harrat Rahat. These data demonstrate that volcanism has been ongoing from at least 1.2 Ma to the present, with the most recent eruption known from historical accounts at 1256 CE. Basalt has erupted persistently from 1.2 Ma to the present, but more evolved volcanism has been episodic. Benmoreite erupted at 1.1 Ma and between 550 to 400 ka. Trachytic volcanism has only occurred over the past 150 ka, with the most recent eruption at 5 ka. Aside from the well-documented basaltic eruption at 1256 CE, prior workers interpreted 6 additional basaltic eruptions during the Holocene. However, our 36Cl exposure ages demonstrate that these erupted between 60 to 13 ka. Interestingly, in the northern part of our field area, where the spatial density of volcanic vents is low, young volcanism (<150 ka) is dominated by basaltic eruptions. Conversely, young volcanism in the southern part of our field area, where volcanic vent density is high, is dominated by trachyte. This observation is consistent with a process wherein the time-integrated effects of basaltic influx into the crust in the south produced a mafic intrusive complex, through which younger basaltic magmas cannot ascend. Instead, these magmas stall and produce trachyte, likely through

  15. Volcanic Eruptions and Climate

    Science.gov (United States)

    LeGrande, Allegra N.; Anchukaitis, Kevin J.

    2015-01-01

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

  16. The operational eEMEP model version 10.4 for volcanic SO2 and ash forecasting

    Science.gov (United States)

    Steensen, Birthe M.; Schulz, Michael; Wind, Peter; Valdebenito, Álvaro M.; Fagerli, Hilde

    2017-05-01

    This paper presents a new version of the EMEP MSC-W model called eEMEP developed for transportation and dispersion of volcanic emissions, both gases and ash. EMEP MSC-W is usually applied to study problems with air pollution and aerosol transport and requires some adaptation to treat volcanic eruption sources and effluent dispersion. The operational set-up of model simulations in case of a volcanic eruption is described. Important choices have to be made to achieve CPU efficiency so that emergency situations can be tackled in time, answering relevant questions of ash advisory authorities. An efficient model needs to balance the complexity of the model and resolution. We have investigated here a meteorological uncertainty component of the volcanic cloud forecast by using a consistent ensemble meteorological dataset (GLAMEPS forecast) at three resolutions for the case of SO2 emissions from the 2014 Barðarbunga eruption. The low resolution (40 × 40 km) ensemble members show larger agreement in plume position and intensity, suggesting that the ensemble here does not give much added value. To compare the dispersion at different resolutions, we compute the area where the column load of the volcanic tracer, here SO2, is above a certain threshold, varied for testing purposes between 0.25 and 50 Dobson units. The increased numerical diffusion causes a larger area (+34 %) to be covered by the volcanic tracer in the low resolution simulations than in the high resolution ones. The higher resolution (10 × 10 km) ensemble members show higher column loads farther away from the volcanic eruption site in narrower clouds. Cloud positions are more varied between the high resolution members, and the cloud forms resemble the observed clouds more than the low resolution ones. For a volcanic emergency case this means that to obtain quickly results of the transport of volcanic emissions, an individual simulation with our low resolution is sufficient; however, to forecast peak

  17. Geothermal and volcanism in west Java

    Science.gov (United States)

    Setiawan, I.; Indarto, S.; Sudarsono; Fauzi I, A.; Yuliyanti, A.; Lintjewas, L.; Alkausar, A.; Jakah

    2018-02-01

    Indonesian active volcanoes extend from Sumatra, Jawa, Bali, Lombok, Flores, North Sulawesi, and Halmahera. The volcanic arc hosts 276 volcanoes with 29 GWe of geothermal resources. Considering a wide distribution of geothermal potency, geothermal research is very important to be carried out especially to tackle high energy demand in Indonesia as an alternative energy sources aside from fossil fuel. Geothermal potency associated with volcanoes-hosted in West Java can be found in the West Java segment of Sunda Arc that is parallel with the subduction. The subduction of Indo-Australian oceanic plate beneath the Eurasian continental plate results in various volcanic products in a wide range of geochemical and mineralogical characteristics. The geochemical and mineralogical characteristics of volcanic and magmatic rocks associated with geothermal systems are ill-defined. Comprehensive study of geochemical signatures, mineralogical properties, and isotopes analysis might lead to the understanding of how large geothermal fields are found in West Java compared to ones in Central and East Java. The result can also provoke some valuable impacts on Java tectonic evolution and can suggest the key information for geothermal exploration enhancement.

  18. Fragments of deeper parts of the hanging wall mantle preserved as orogenic peridotites in the central belt of the Seve Nappe Complex, Sweden

    NARCIS (Netherlands)

    Clos, F.; Gilio, M.; van Roermund, H.L.M.

    Formation conditions of olivine microstructures are investigated in the Kittelfjäll spinel peridotite (KSP), a fragment of lithospheric mantle which occurs as an isolated body within high grade metamorphic crustal rocks of the Seve Nappe Complex (SNC), southern Västerbotten, central Sweden. The KSP

  19. Volcanic passive margins: another way to break up continents.

    Science.gov (United States)

    Geoffroy, L; Burov, E B; Werner, P

    2015-10-07

    Two major types of passive margins are recognized, i.e. volcanic and non-volcanic, without proposing distinctive mechanisms for their formation. Volcanic passive margins are associated with the extrusion and intrusion of large volumes of magma, predominantly mafic, and represent distinctive features of Larges Igneous Provinces, in which regional fissural volcanism predates localized syn-magmatic break-up of the lithosphere. In contrast with non-volcanic margins, continentward-dipping detachment faults accommodate crustal necking at both conjugate volcanic margins. These faults root on a two-layer deformed ductile crust that appears to be partly of igneous nature. This lower crust is exhumed up to the bottom of the syn-extension extrusives at the outer parts of the margin. Our numerical modelling suggests that strengthening of deep continental crust during early magmatic stages provokes a divergent flow of the ductile lithosphere away from a central continental block, which becomes thinner with time due to the flow-induced mechanical erosion acting at its base. Crustal-scale faults dipping continentward are rooted over this flowing material, thus isolating micro-continents within the future oceanic domain. Pure-shear type deformation affects the bulk lithosphere at VPMs until continental breakup, and the geometry of the margin is closely related to the dynamics of an active and melting mantle.

  20. Fungal community, Fusarium head blight complex and secondary metabolites associated with malting barley grains harvested in Umbria, central Italy.

    Science.gov (United States)

    Beccari, Giovanni; Senatore, Maria Teresa; Tini, Francesco; Sulyok, Michael; Covarelli, Lorenzo

    2018-05-20

    In recent years, due to the negative impact of toxigenic mycobiota and of the accumulation of their secondary metabolites in malting barley grains, monitoring the evolution of fungal communities in a certain cultivation area as well as detecting the different mycotoxins present in the raw material prior to malting and brewing processes have become increasingly important. In this study, a survey was carried out on malting barley samples collected after their harvest in the Umbria region (central Italy). Samples were analyzed to determine the composition of the fungal community, to identify the isolated Fusarium species, to quantify fungal secondary metabolites in the grains and to characterize the in vitro mycotoxigenic profile of a subset of the isolated Fusarium strains. The fungal community of barley grains was mainly composed of microorganisms belonging to the genus Alternaria (77%), followed by those belonging to the genus Fusarium (27%). The Fusarium head blight (FHB) complex was represented by nine species with the predominance of Fusarium poae (37%), followed by Fusarium avenaceum (23%), Fusarium graminearum (22%) and Fusarium tricinctum (7%). Secondary metabolites biosynthesized by Alternaria and Fusarium species were present in the analyzed grains. Among those biosynthesized by Fusarium species, nivalenol and enniatins were the most prevalent ones. Type A trichothecenes (T-2 and HT-2 toxins) as well as beauvericin were also present with a high incidence. Conversely, the number of samples contaminated with deoxynivalenol was low. Conjugated forms, such as deoxynivalenol-3-glucoside and HT-2-glucoside, were detected for the first time in malting barley grains cultivated in the surveyed area. In addition, strains of F. avenaceum and F. tricinctum showed the ability to biosynthesize in vitro high concentrations of enniatins. The analysis of fungal secondary metabolites, both in the grains and in vitro, revealed also the presence of other compounds, for which

  1. Friction in volcanic environments

    Science.gov (United States)

    Kendrick, Jackie E.; Lavallée, Yan

    2016-04-01

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

  2. Proteomic analysis of the crayfish gastrolith chitinous extracellular matrix reveals putative protein complexes and a central role for GAP 65.

    Science.gov (United States)

    Glazer, Lilah; Roth, Ziv; Weil, Simy; Aflalo, Eliahu D; Khalaila, Isam; Sagi, Amir

    2015-10-14

    Chitin is a major component of arthropod cuticles, where it forms a three-dimensional network that constitutes the scaffold upon which cuticles form. The chitin fibers that form this network are closely associated with specific structural proteins, while the cuticular matrix contains many additional structural, enzymatic and other proteins. We study the crayfish gastrolith as a simple model for the assembly of calcified cuticular structures, with particular focus on the proteins involved in this process. The present study integrates a gastrolith-forming epithelium transcriptomic library with data from mass spectrometry analysis of proteins extracted from the gastrolith matrix to obtain a near-complete picture of gastrolith protein content. Using native protein separation we identified 24 matrix proteins, of which 14 are novel. Further analysis led to discovery of three putative protein complexes, all containing GAP 65 the most abundant gastrolith structural protein. Using immunological methods we further studied the role of GAP 65 in the gastrolith matrix and forming epithelium, as well as in the newly identified protein complexes. We propose that gastrolith matrix construction is a sequential process in which protein complexes are dynamically assembled and disassembled around GAP 65, thus changing their functional properties to perform each step in the construction process. The scientific interest on which this study is based arises from three main features of gastroliths: (1) Gastroliths possess partial analogy to cuticles both in structural and molecular properties, and may be regarded, with the appropriate reservations (see Introduction), as simple models for cuticle assembly. At the same time, gastroliths are terminally assembled during a well-defined period, which can be controlled in the laboratory, making them significantly easier to study than cuticles. (2) Gastroliths, like the crayfish exoskeleton, contain stable amorphous calcium carbonate (ACC) rather

  3. On a Possible Unified Scaling Law for Volcanic Eruption Durations.

    Science.gov (United States)

    Cannavò, Flavio; Nunnari, Giuseppe

    2016-03-01

    Volcanoes constitute dissipative systems with many degrees of freedom. Their eruptions are the result of complex processes that involve interacting chemical-physical systems. At present, due to the complexity of involved phenomena and to the lack of precise measurements, both analytical and numerical models are unable to simultaneously include the main processes involved in eruptions thus making forecasts of volcanic dynamics rather unreliable. On the other hand, accurate forecasts of some eruption parameters, such as the duration, could be a key factor in natural hazard estimation and mitigation. Analyzing a large database with most of all the known volcanic eruptions, we have determined that the duration of eruptions seems to be described by a universal distribution which characterizes eruption duration dynamics. In particular, this paper presents a plausible global power-law distribution of durations of volcanic eruptions that holds worldwide for different volcanic environments. We also introduce a new, simple and realistic pipe model that can follow the same found empirical distribution. Since the proposed model belongs to the family of the self-organized systems it may support the hypothesis that simple mechanisms can lead naturally to the emergent complexity in volcanic behaviour.

  4. Attempts of whole-rock K/Ar dating of mesozoic volcanic and hypabissal igneous rocks from the Central Subbetic (Southern Spain: A case of differential Argon loss related to very low-grade metamorphism

    Directory of Open Access Journals (Sweden)

    Sanz de Galdeano, C.

    1988-04-01

    Full Text Available 12 samples of basic intrusives within Triassic rocks «ophites» and 11 samples of volcanic and associated intrusives within Jurassic to Early Cretaceous sequences of the Subbetic Zone were subjected to whole-rock K/Ar dating in combination with chemical/petrological analysis. Satisfactory results were obtained only from a number of samples of volcanic rocks, however, analytical ages commonly agree, within about 10 relative percent, with those deduced from stratigraphic location. «Ophite» samples, on the other hand, may reveal considerably lower analytic ages than the volcanics and show much stronger scattering, even among samples collected within a small area. It is argued that the inferred loss of Ar results from very-low-grade alpine metamorphic alteration, which affected the «ophites» more intensely than the higher volcanic rocks. Other post-emplacement chemical changes, such as the degree of secondary oxidation of Fe, are also distintive among the two groups of samples, and are to some extent consistent with the above view in that the alteration environment of the ophites should have produced conditions for more penetrative fluid-rock interactions and homogeneous recrystallization. Overall, the magmatic activity from which the ophitic rocks originated might have started in the Late Triassic and continued in the Lower Jurassic. 80th, the «ophites» and the volcanics are though to be the result of magmatic events Collowing tensional to transtensive crustal movements affecting the external basins of the Betic Cordilleras Crom Late Triassic to Early Cretaceous times.Doce muestras de cuerpos básicos intrusivos en rocas triásicas («ofitas» y 11 muestras de volcanitas y rocas intrusivas asociadas en secuencias jurásico-cretáceas de la zona Subbética han sido objeto de datación radiométrica K/Ar (roca total en combinación con análisis químico-petrográfico. Las edades analíticas obtenidas son 's

  5. Self-potential anomalies in some Italian volcanic areas

    Directory of Open Access Journals (Sweden)

    C. Silenziario

    1996-06-01

    Full Text Available The study of Self-Potential (SP space and time variations in volcanic areas may provide useful information on both the geometrical structure of the volcanic apparatuses and the dynamical behaviour of the feeding and uprising systems. In this paper, the results obtained on the islands of Vulcano (Eolian arc and Ponza (Pontine archipelago and on the Mt. Somma-Vesuvius complex are shown. On the island of Vulcano and on the Mt. Somma-Vesuvius apparatus areal SP surveys were performed with the aim of evidencing anomalies closely associated to the zones of major volcanic activity. On the island of Vulcano a profile across the fumaroles along the crater rim of the Fossa Cone was also carried out in order to have a direct relationship between fumarolic fracture migration and flow rate and SP anomaly space and time variations. The areal survey on the island of Ponza, which is considered an inactive area, is assumed as a reference test with which to compare the amplitude and pattern of the anomalies in the active areas. A tentative interpretation of the SP anomalies in volcanic areas is suggested in terms of electrokinetic phenomena, related to the movement of fluids of both volcanic and non-volcanic origin.

  6. Scaling properties of planetary calderas and terrestrial volcanic eruptions

    Directory of Open Access Journals (Sweden)

    L. Sanchez

    2012-11-01

    Full Text Available Volcanism plays an important role in transporting internal heat of planetary bodies to their surface. Therefore, volcanoes are a manifestation of the planet's past and present internal dynamics. Volcanic eruptions as well as caldera forming processes are the direct manifestation of complex interactions between the rising magma and the surrounding host rock in the crust of terrestrial planetary bodies. Attempts have been made to compare volcanic landforms throughout the solar system. Different stochastic models have been proposed to describe the temporal sequences of eruptions on individual or groups of volcanoes. However, comprehensive understanding of the physical mechanisms responsible for volcano formation and eruption and more specifically caldera formation remains elusive. In this work, we propose a scaling law to quantify the distribution of caldera sizes on Earth, Mars, Venus, and Io, as well as the distribution of calderas on Earth depending on their surrounding crustal properties. We also apply the same scaling analysis to the distribution of interevent times between eruptions for volcanoes that have the largest eruptive history as well as groups of volcanoes on Earth. We find that when rescaled with their respective sample averages, the distributions considered show a similar functional form. This result implies that similar processes are responsible for caldera formation throughout the solar system and for different crustal settings on Earth. This result emphasizes the importance of comparative planetology to understand planetary volcanism. Similarly, the processes responsible for volcanic eruptions are independent of the type of volcanism or geographical location.

  7. Sr isotope tracing of multiple water sources in a complex river system, Noteć River, central Poland

    Energy Technology Data Exchange (ETDEWEB)

    Zieliński, Mateusz, E-mail: mateusz.zielinski@amu.edu.pl [Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Dzięgielowa 27, 61-680 Poznań (Poland); Dopieralska, Jolanta, E-mail: dopieralska@amu.edu.pl [Poznań Science and Technology Park, Adam Mickiewicz University Foundation, Rubież 46, 61-612 Poznań (Poland); Belka, Zdzislaw, E-mail: zbelka@amu.edu.pl [Isotope Laboratory, Adam Mickiewicz University, Dzięgielowa 27, 61-680 Poznań (Poland); Walczak, Aleksandra, E-mail: awalczak@amu.edu.pl [Isotope Laboratory, Adam Mickiewicz University, Dzięgielowa 27, 61-680 Poznań (Poland); Siepak, Marcin, E-mail: siep@amu.edu.pl [Institute of Geology, Adam Mickiewicz University, Maków Polnych 16, 61-606 Poznań (Poland); Jakubowicz, Michal, E-mail: mjakub@amu.edu.pl [Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Dzięgielowa 27, 61-680 Poznań (Poland)

    2016-04-01

    Anthropogenic impact on surface waters and other elements in the environment was investigated in the Noteć River basin in central Poland. The approach was to trace changes in the Sr isotope composition ({sup 87}Sr/{sup 86}Sr) and concentration in space and time. Systematic sampling of the river water shows a very wide range of {sup 87}Sr/{sup 86}Sr ratios, from 0.7089 to 0.7127. This strong variation, however, is restricted to the upper course of the river, whereas the water in the lower course typically shows {sup 87}Sr/{sup 86}Sr values around 0.7104–0.7105. Variations in {sup 87}Sr/{sup 86}Sr are associated with a wide range of Sr concentrations, from 0.14 to 1.32 mg/L. We find that strong variations in {sup 87}Sr/{sup 86}Sr and Sr concentrations can be accounted for by mixing of two end-members: 1) atmospheric waters charged with Sr from the near-surface weathering and wash-out of Quaternary glaciogenic deposits, and 2) waters introduced into the river from an open pit lignite mine. The first reservoir is characterized by a low Sr content and high {sup 87}Sr/{sup 86}Sr ratios, whereas mine waters display opposite characteristics. Anthropogenic pollution is also induced by extensive use of fertilizers which constitute the third source of Sr in the environment. The study has an important implication for future archeological studies in the region. It shows that the present-day Sr isotope signatures of river water, flora and fauna cannot be used unambiguously to determine the “baseline” for bioavailable {sup 87}Sr/{sup 86}Sr in the past. - Highlights: • Sr isotopes fingerprint water sources and their interactions in a complex river system. • Mine waters and fertilizers are critical anthropogenic additions in the river water. • Limited usage of environmental isotopic data in archeological studies. • Sr budget of the river is dynamic and temporary.

  8. Closer look at lunar volcanism

    International Nuclear Information System (INIS)

    Vaniman, D.T.; Heiken, G.; Taylor, G.J.

    1984-01-01

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

  9. Major-element geochemistry of the Silent Canyon--Black Mountain peralkaline volcanic centers, northwestern Nevada Test Site: applications to an assessment of renewed volcanism

    International Nuclear Information System (INIS)

    Crowe, B.M.; Sargent, K.A.

    1979-01-01

    The Silent Canyon and Black Mountain volcanic centers are located in the northern part of the Nevada Test Site. The Silent Canyon volcanic center is a buried cauldron complex of Miocene age (13 to 15 m.y.). Black Mountain volcanic center is an elliptical-shaped cauldron complex of late Miocene age. The lavas and tuffs of the two centers comprise a subalkaline-peralkaline association. Rock types range from quartz normative subalkaline trachyte and rhyolite to peralkaline commendite. The Gold Flat Member of the Thirsty Canyon Tuff (Black Mountain) is a pantellerite. The major-element geochemistry of the Black Mountain--Silent Canyon volcanic centers differ in the total range and distribution of SiO 2 , contents, the degree of peralkalinity (molecular Na 2 O + K 2 O > Al 2 O 3 ) and in the values of total iron and alumina through the range of rock types. These differences indicate that the suites were unrelated and evolved from differing magma bodies. The Black Mountain volcanic cycle represents a renewed phase of volcanism following cessation of the Timber Mountain--Silent Canyon volcanic cycles. Consequently, there is a small but numerically incalculable probability of recurrence of Black Mountain-type volcanism within the Nevada Test Site region. This represents a potential risk with respect to deep geologic storage of high-level radioactive waste at the Nevada Test Site

  10. The unzipping of Africa and South America; New insights from the Etendeka and younger volcanic events along the Angola/Namibia margin.

    Science.gov (United States)

    Jerram, D. A.

    2015-12-01

    The volcanic margin along Angola is relatively poorly constrained. This study uses new petrographic, geochronological and geochemical observations on a new sample set collected along the margin to help understand the various types and relative timings of volcanic events along the margin. This new study has identified 3 main volcanic events that occur at ~100Ma (Sumbe event 1), 90-92Ma (Serra de Neve (SDN)-Elefantes event 2) and 80-81Ma (Namibe event 3), with the oldest event in the north of the margin and younging southwards. This is contrasting with the main Etendeka pulse in Namibia at around 130 Ma. There is a marked variety of igneous rocks along the margin with a grouping of evolved alkaline rocks in the central SDN-Elefantes section, basic submarine volcanics in the north, and basanite eruptions in the southern section. There is some overlap with geochemical types along the margin. The Sumbe event contains predominantly submarine volcanics and shallow Intrusions. SDN-Elefantes rocks have a mixed type but with a distinctive feldspar rich evolved alkali suite of rocks (nepheline syenites and variations around this composition) which occur as lava flows and shallow intrusions as well as making up the core of the SDN complex. The SDN complex itself is analogous in size to the main volcanic centres in Namibia (such as Messum, Brandberg etc.) and suggests that large volcanic feeding centres are still active along the margin as young as 90ma. These in turn will form large volcano-topographic features. In the south the Ponta Negra and Canico sites mainly contain basanites in the form of lava flows, invasive flows and shallow intrusions. At Canico one intrusive plug was sampled with a similar composition to the evolved SDN-Elefantes suite. In all three events it is clear that the volcanic systems have interacted with the sedimentary systems, in some cases dynamically, in others with regional implications for volcano-tectonic uplift. Specific thanks is given for

  11. Volcanology: Volcanic bipolar disorder explained

    Science.gov (United States)

    Jellinek, Mark

    2014-02-01

    Eruptions come in a range of magnitudes. Numerical simulations and laboratory experiments show that rare, giant super-eruptions and smaller, more frequent events reflect a transition in the essential driving forces for volcanism.

  12. Lidar sounding of volcanic plumes

    Science.gov (United States)

    Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

    2013-10-01

    Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

  13. Modelling ground deformation patterns associated with volcanic processes at the Okataina Volcanic Centre

    Science.gov (United States)

    Holden, L.; Cas, R.; Fournier, N.; Ailleres, L.

    2017-09-01

    The Okataina Volcanic Centre (OVC) is one of two large active rhyolite centres in the modern Taupo Volcanic Zone (TVZ) in the North Island of New Zealand. It is located in a complex section of the Taupo rift, a tectonically active section of the TVZ. The most recent volcanic unrest at the OVC includes the 1315 CE Kaharoa and 1886 Tarawera eruptions. Current monitoring activity at the OVC includes the use of continuous GPS receivers (cGPS), lake levelling and seismographs. The ground deformation patterns preceding volcanic activity the OVC are poorly constrained and restricted to predictions from basic modelling and comparison to other volcanoes worldwide. A better understanding of the deformation patterns preceding renewed volcanic activity is essential to determine if observed deformation is related to volcanic, tectonic or hydrothermal processes. Such an understanding also means that the ability of the present day cGPS network to detect these deformation patterns can also be assessed. The research presented here uses the finite element (FE) modelling technique to investigate ground deformation patterns associated with magma accumulation and diking processes at the OVC in greater detail. A number of FE models are produced and tested using Pylith software and incorporate characteristics of the 1315 CE Kaharoa and 1886 Tarawera eruptions, summarised from the existing body of research literature. The influence of a simple ring fault structure at the OVC on the modelled deformation is evaluated. The ability of the present-day continuous GPS (cGPS) GeoNet monitoring network to detect or observe the modelled deformation is also considered. The results show the modelled horizontal and vertical displacement fields have a number of key features, which include prominent lobe based regions extending northwest and southeast of the OVC. The results also show that the ring fault structure increases the magnitude of the displacements inside the caldera, in particular in the

  14. Volcanic ash impacts on critical infrastructure

    Science.gov (United States)

    Wilson, Thomas M.; Stewart, Carol; Sword-Daniels, Victoria; Leonard, Graham S.; Johnston, David M.; Cole, Jim W.; Wardman, Johnny; Wilson, Grant; Barnard, Scott T.

    2012-01-01

    Volcanic eruptions can produce a wide range of hazards. Although phenomena such as pyroclastic flows and surges, sector collapses, lahars and ballistic blocks are the most destructive and dangerous, volcanic ash is by far the most widely distributed eruption product. Although ash falls rarely endanger human life directly, threats to public health and disruption to critical infrastructure services, aviation and primary production can lead to significant societal impacts. Even relatively small eruptions can cause widespread disruption, damage and economic loss. Volcanic eruptions are, in general, infrequent and somewhat exotic occurrences, and consequently in many parts of the world, the management of critical infrastructure during volcanic crises can be improved with greater knowledge of the likely impacts. This article presents an overview of volcanic ash impacts on critical infrastructure, other than aviation and fuel supply, illustrated by findings from impact assessment reconnaissance trips carried out to a wide range of locations worldwide by our international research group and local collaborators. ‘Critical infrastructure’ includes those assets, frequently taken for granted, which are essential for the functioning of a society and economy. Electricity networks are very vulnerable to disruption from volcanic ash falls. This is particularly the case when fine ash is erupted because it has a greater tendency to adhere to line and substation insulators, where it can cause flashover (unintended electrical discharge) which can in turn cause widespread and disruptive outages. Weather conditions are a major determinant of flashover risk. Dry ash is not conductive, and heavy rain will wash ash from insulators, but light rain/mist will mobilise readily-soluble salts on the surface of the ash grains and lower the ash layer’s resistivity. Wet ash is also heavier than dry ash, increasing the risk of line breakage or tower/pole collapse. Particular issues for water

  15. Volcanic eruption plumes on Io

    International Nuclear Information System (INIS)

    Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.

    1979-01-01

    The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

  16. Volcanic hazards and aviation safety

    Science.gov (United States)

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

    1996-01-01

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

  17. Hanford facility dangerous waste Part A, Form 3, and Part B permit application documentation for the Central Waste Complex (WA7890008967) (TSD: TS-2-4)

    International Nuclear Information System (INIS)

    Saueressig, D.G.

    1998-01-01

    The Hanford Facility Dangerous Waste Permit Application is considered to be a single application organized into a General Information Portion (document number DOE/RL-91-28) and a Unit-Specific Portion. The scope of the Unit-Specific Portion is limited to Part B permit application documentation submitted for individual, operating, treatment, storage, and/or disposal units, such as the Central Waste Complex (this document, DOE/RL-91-17). Both the General Information and Unit-Specific portions of the Hanford Facility Dangerous Waste Permit Application address the content of the Part B permit application guidance prepared by the Washington State Department of Ecology (Ecology 1996) and the U.S. Environmental Protection Agency (40 Code of Federal Regulations 270), with additional information needed by the Hazardous and Solid Waste Amendments and revisions of Washington Administrative Code 173-303. For ease of reference, the Washington State Department of Ecology alpha-numeric section identifiers from the permit application guidance documentation (Ecology 1996) follow, in brackets, the chapter headings and subheadings. A checklist indicating where information is contained in the Central Waste Complex permit application documentation, in relation to the Washington State Department of Ecology guidance, is located in the Contents section. Documentation contained in the General Information Portion is broader in nature and could be used by multiple treatment, storage, and/or disposal units (e.g., the glossary provided in the General Information Portion). Wherever appropriate, the Central Waste Complex permit application documentation makes cross-reference to the General Information Portion, rather than duplicating text. Information provided in this Central Waste Complex permit application documentation is current as of May 1998

  18. High-resolution numerical simulation of summer wind field comparing WRF boundary-layer parametrizations over complex Arctic topography: case study from central Spitsbergen

    Czech Academy of Sciences Publication Activity Database

    Láska, K.; Chládová, Zuzana; Hošek, Jiří

    2017-01-01

    Roč. 26, č. 4 (2017), s. 391-408 ISSN 0941-2948 Institutional support: RVO:68378289 Keywords : surface wind field * model evaluation * topographic effect * circulation pattern * Svalbard Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 1.989, year: 2016 http://www.schweizerbart.de/papers/metz/detail/prepub/87659/High_resolution_numerical_simulation_of_summer_wind_field_comparing_WRF_boundary_layer_parametrizations_over_complex_Arctic_topography_case_study_from_central_Spitsbergen

  19. Hanford facility dangerous waste Part A, Form 3 and Part B permit application documentation, Central Waste Complex (WA7890008967)(TSD: TS-2-4)

    Energy Technology Data Exchange (ETDEWEB)

    Saueressig, D.G.

    1998-05-20

    The Hanford Facility Dangerous Waste Permit Application is considered to be a single application organized into a General Information Portion (document number DOE/RL-91-28) and a Unit-Specific Portion. The scope of the Unit-Specific Portion is limited to Part B permit application documentation submitted for individual, operating, treatment, storage, and/or disposal units, such as the Central Waste Complex (this document, DOE/RL-91-17). Both the General Information and Unit-Specific portions of the Hanford Facility Dangerous Waste Permit Application address the content of the Part B permit application guidance prepared by the Washington State Department of Ecology (Ecology 1996) and the U.S. Environmental Protection Agency (40 Code of Federal Regulations 270), with additional information needed by the Hazardous and Solid Waste Amendments and revisions of Washington Administrative Code 173-303. For ease of reference, the Washington State Department of Ecology alpha-numeric section identifiers from the permit application guidance documentation (Ecology 1996) follow, in brackets, the chapter headings and subheadings. A checklist indicating where information is contained in the Central Waste Complex permit application documentation, in relation to the Washington State Department of Ecology guidance, is located in the Contents section. Documentation contained in the General Information Portion is broader in nature and could be used by multiple treatment, storage, and/or disposal units (e.g., the glossary provided in the General Information Portion). Wherever appropriate, the Central Waste Complex permit application documentation makes cross-reference to the General Information Portion, rather than duplicating text. Information provided in this Central Waste Complex permit application documentation is current as of May 1998.

  20. Volcanic crisis in

    Directory of Open Access Journals (Sweden)

    Mgs. Víctor Manuel Pérez Martínez

    2007-01-01

    Full Text Available The article is the result of an investigation which is focussed on some deontological aspects of the scientificjournalism. In the first place it gives a theoretical vision about science, journalism, internet and including some reflectionsabout the deontological principles in handling the information about science and technology. This focus is useful as it formsthe base of an investigation where we deal with the information about a possible ”volcanic crisis” in El Teide during the years2004-2005 done by the digital newspaper” El Dïa” a canarian newspaper from Tenerife. The work required the revision of theinformation which was published and a followed analysis of its context. It was used the digital version with the purpose ofvisualizing the news which was published. It was also compared with a printed version, with local cover but divulged theinformation to the public who was most affected by this particular news. The results give rise to some questions regardinghow the information is given to a topic which is of local interest as well as national and international interest due to therepercussions in the social, economical and tourist field (the tourist field is the main industrial sector in Tenerife by receivingthis type of news.

  1. K-Ar and Ar-Ar dating of the Palaeozoic metamorphic complex from the Mid-Bosnian Schist Mts., Central Dinarides, Bosnia and Hercegovina

    International Nuclear Information System (INIS)

    Pamic, J.; Balogh, K.; Hrvatovic, H.; Balen, D.; Palinkas, L.; Jurkovic, I.

    2004-01-01

    K-Ar and Ar-Ar whole rock and mineral ages are presented for 25 samples of metamorphic rocks from the Mid-Bosnian Schist Mts., representing one of the largest allochthonous Palaeozoic terranes incorporated within the Internal Dinarides. Four main age groups can be distinguished: 1) Variscan (∼ 343 Ma), 2) post-Variscan (288-238 Ma), 3) Early Cretaceous (mainly 121-92 Ma), and 4) Eocene (59--35 Ma) ages. Apart from this, an Oligocene (31 Ma) age was obtained on Alpine vein hyalophane. The radiometric dating indicates a polyphase metamorphic evolution of the Palaeozoic formations and suggests a pre-Carboniferous age of the volcano-sedimentary protoliths, an Early Carboniferous age of Variscan metamorphism and deformation, post-Variscan volcanism, an Early Cretaceous metamorphic overprint related to out-of-sequence thrusting of the Palaeozoic complex, and an Eocene and Oligocene metamorphic overprint related to the main Alpine compressional deformation and subsequent strike-slip faulting, and uplift of the metamorphic core. Accordingly, the Mid-Bosnian Schist Mts. can be correlated in its multistage geodynamic evolution with some Palaeozoic tectonostratigraphic units from the Austroalpine domain in the Eastern Alps. (author)

  2. Systematic change in global patterns of streamflow following volcanic eruptions.

    Science.gov (United States)

    Iles, Carley E; Hegerl, Gabriele C

    2015-11-01

    Following large explosive volcanic eruptions precipitation decreases over much of the globe1-6, particularly in climatologically wet regions4,5. Stratospheric volcanic aerosols reflect sunlight, which reduces evaporation, whilst surface cooling stabilises the atmosphere and reduces its water-holding capacity7. Circulation changes modulate this global precipitation reduction on regional scales1,8-10. Despite the importance of rivers to people, it has been unclear whether volcanism causes detectable changes in streamflow given large natural variability. Here we analyse observational records of streamflow volume for fifty large rivers from around the world which cover between two and 6 major volcanic eruptions in the 20 th and late 19 th century. We find statistically significant reductions in flow following eruptions for the Amazon, Congo, Nile, Orange, Ob, Yenisey and Kolyma amongst others. When data from neighbouring rivers are combined - based on the areas where climate models simulate either an increase or a decrease in precipitation following eruptions - a significant (peruptions is detected in northern South American, central African and high-latitude Asian rivers, and on average across wet tropical and subtropical regions. We also detect a significant increase in southern South American and SW North American rivers. This suggests that future volcanic eruptions could substantially affect global water availability.

  3. Pedogenesis of a catena of the Farmdale-Sangamon Geosol complex in the north central United States

    Science.gov (United States)

    Jacobs, P.M.; Konen, M.E.; Curry, B. Brandon

    2009-01-01

    The Farmdale-Sangamon Geosol pedocomplex consists of the Sangamon Geosol and the overlying Farmdale Geosol, which form the most extensive terrestrial record of the last interglacial to glacial transition in the Midwest United States. The geosol complex formed for upwards of 100??ka, extending from the end of MIS 6 through 4 for the Sangamon Geosol, then the Farmdale Geosol for during a brief episode at the end of MIS 3 following slow accumulation and pedogenic modification of eolian silt deposited on top of the Sangamon Geosol. Our study site consists of a buried paleo-hillslope transect that forms a catena, enabling evaluation of slope effects on interglacial-scale soil formation. The Sangamon Geosol is formed in calcareous and illitic glaciogenic sediment. Along the catena the Sangamon Geosol profiles display some morphological changes, namely in terms of colors that we interpret as indicators of differences in drainage. Most thickness and horizonation characteristics are similar all along the transect, with intact upper sola horizons (AE and E horizons) that overlie clay-enriched Bt horizons. The Bt horizons contain abundant clay that exists as illuvial clay coatings, matrix infills, and as mosaic-speckled domains. The clay originated both by in situ weathering and through illuviation from the clay depleted upper sola. Slope does not appear to affect Bt characteristics beyond redder hues of the matrix and clay coatings in the upper slope position. With depth, effects of carbonate leaching and infilling of clay in the matrix decrease and clay coatings are restricted to walls of voids adjacent to aggregates. Clay mineralogy shows illite depletion, but no interstratified kaolinite-expandable minerals, indicating the degree of weathering is not as great as is typical of Sangamon Geosol profiles formed in loess or in glaciogenic sediment of the central Illinois type area. Clay mineralogy is also stratified with depth, coincident with particle size, which probably

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

    Science.gov (United States)

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

    2016-04-01

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

  5. Optimization Review: Bunker Hill Mining and Metallurgical Complex Superfund Site, Central Treatment Plant (CTP), Kellogg, Shoshone County, Idaho

    Science.gov (United States)

    The Bunker Hill Mining and Metallurgical Complex Superfund Site includes all areas of the Coeur d’Alene Basin where mining-related contamination occurred and encompasses a 21-square mile “Box” along Interstate 90 surrounding the former smelter complex.

  6. New insights on intraplate volcanism in French Polynesia from wavelet analysis of GRACE, CHAMP, and sea surface data

    Science.gov (United States)

    Panet, I.; Chambodut, A.; Diament, M.; Holschneider, M.; Jamet, O.

    2006-09-01

    In this paper, we discuss the origin of superswell volcanism on the basis of representation and analysis of recent gravity and magnetic satellite data with wavelets in spherical geometry. We computed a refined gravity field in the south central Pacific based on the GRACE satellite GGM02S global gravity field and the KMS02 altimetric grid, and a magnetic anomaly field based on CHAMP data. The magnetic anomalies are marked by the magnetic lineation of the seafloor spreading and by a strong anomaly in the Tuamotu region, which we interpret as evidence for crustal thickening. We interpret our gravity field through a continuous wavelet analysis that allows to get a first idea of the internal density distribution. We also compute the continuous wavelet analysis of the bathymetric contribution to discriminate between deep and superficial sources. According to the gravity signature of the different chains as revealed by our analysis, various processes are at the origin of the volcanism in French Polynesia. As evidence, we show a large-scale anomaly over the Society Islands that we interpret as the gravity signature of a deeply anchored mantle plume. The gravity signature of the Cook-Austral chain indicates a complex origin which may involve deep processes. Finally, we discuss the particular location of the Marquesas chain as suggesting that the origin of the volcanism may interfere with secondary convection rolls or may be controlled by lithospheric weakness due to the regional stress field, or else related to the presence of the nearby Tuamotu plateau.

  7. Miocene magmatism in the Bodie Hills volcanic field, California and Nevada: A long-lived eruptive center in the southern segment of the ancestral Cascades arc

    Science.gov (United States)

    John, David A.; du Bray, Edward A.; Blakely, Richard J.; Fleck, Robert J.; Vikre, Peter; Box, Stephen E.; Moring, Barry C.

    2012-01-01

    The Middle to Late Miocene Bodie Hills volcanic field is a >700 km2, long-lived (∼9 Ma) but episodic eruptive center in the southern segment of the ancestral Cascades arc north of Mono Lake (California, U.S.). It consists of ∼20 major eruptive units, including 4 trachyandesite stratovolcanoes emplaced along the margins of the field, and numerous, more centrally located silicic trachyandesite to rhyolite flow dome complexes. Bodie Hills volcanism was episodic with two peak periods of eruptive activity: an early period ca. 14.7–12.9 Ma that mostly formed trachyandesite stratovolcanoes and a later period between ca. 9.2 and 8.0 Ma dominated by large trachyandesite-dacite dome fields. A final period of small silicic dome emplacement occurred ca. 6 Ma. Aeromagnetic and gravity data suggest that many of the Miocene 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 Miocene volcanism.Compositions of Bodie Hills volcanic rocks vary from ∼50 to 78 wt% SiO2, although rocks with Bodie Hills rocks are porphyritic, commonly containing 15–35 vol% phenocrysts of plagioclase, pyroxene, and hornblende ± biotite. The oldest eruptive units have the most mafic compositions, but volcanic rocks oscillated between mafic and intermediate to felsic compositions through time. Following a 2 Ma hiatus in volcanism, postsubduction rocks of the ca. 3.6–0.1 Ma, bimodal, high-K Aurora volcanic field erupted unconformably onto rocks of the Miocene Bodie Hills volcanic field.At the latitude of the Bodie Hills, subduction of the Farallon plate is inferred to have ended ca. 10 Ma, evolving to a transform plate margin. However, volcanism in the region continued until 8 Ma without an apparent change in rock composition or style of eruption. Equidimensional, polygenetic volcanoes and the absence of dike swarms suggest a low differential horizontal stress regime

  8. Regional Sm-Nd isotopic study of the central part of the Brasilia belt, Goias: implications of the age and origin of the Anapolis-Itaucu granulitic complex and metasedimentary rocks of the Araxa Group, central region, Brazil

    International Nuclear Information System (INIS)

    Pimentel, Marcio Martins; Fuck, Reinhardt Adolfo; Fischel, Danielle Piuzanna

    1999-01-01

    In the central part of the Brasilia Belt, central Brazil, a high grade terrain, the Anapolis-Itaucu Complex, is exposed within the metasedimentary rocks of the Araxa Group. The Anapolis-Itaucu Complex in Goias represents a complex association of high-grade rocks including mafic-ultramafic bodies, charnockites, enderbites, as well as aluminous granulites of sedimentary origin, associated with marbles and quartzites, Narrow volcano-sedimentary belts formed mainly by amphibolites and micashists are also recognized within the complex. This high-grade terrain has been traditionally interpreted as part of the old (Archaean/Paleoproterozoic) sialic basement to the Neo- or mesoproterozoic sediments of the Araxa Group, Brasilia Belt. The granulites and metasediments of the Araxa Group are intruded by a large number of granite intrusions, many of which slow peraluminous character. Sm-Nd isotopic analyses for the garnet-and sillimanite-bearing aluminous granulites indicate T DM model ages between ca. 1.3 and 1.6 Ga. These values represent the upper limit for the age of the protoliths of the granulites, demonstrating that they are (at least in part) younger than suggested in previous models. The intrusive granites have a Sm-Nd isotopic pattern which is not much different from that observed for the felsic granulites, with T DM model ages ranging in the interval between ca. 1.37 and 1.85 Ga. The isotopic compositions of the granitic and granulitic rocks investigated are also similar to those determined for metasediments of the internal zone of the Brasilia Belt (Araxa Group) in central-southern Goias. These metasediments show Nd model ages between ca. 1.2 and 2.2 Ga. The preliminary isotopic data presented are consistent with a model in which the voluminous granitic magmatism identified in the Anapolis-Itaucu Complex and adjacent areas is Neoproterozoic in age, being the result of re-melting of the older sialic crust. The peraluminous nature of many of these granites

  9. Natural radioactivity in volcanic ash from Mt. Pinatubo eruption

    International Nuclear Information System (INIS)

    Duran, E.B.; De Vera, C.M.; Garcia, T.Y.; Dela Cruz, F.M.; Esguerra, L.V.; Castaneda, S.S.

    1992-01-01

    Last June 15, 1991, a major pyroclastic eruption occurred from Mt. Pinatubo volcano located in Zambales, Central Luzon. The radiological impact of this eruption was assessed based on the concentrations of the principal naturally occurring radionuclides observed in volcanic ash. The volcanic ash samples were collected from locations which are within 50-km radius of Mt. Pinatubo at various times after the eruption. The mean activity concentrations in Bq/kg wet weight of the natural radionuclides in volcanic ash were as follows: 12.6 for 238 U, 14.0 for 232 Th and 330 for 40 K. These values are significantly higher than the mean activity concentrations of these radionuclides observed in topsoil in the same provinces before the eruption. This suggests that with the deposition of large quantities of volcanic ash and lahar in Central Luzon and concomitant topographic changes, the distribution and quantities of radionuclides which gave rise to terrestrial radiation may have also changed. Outdoor radon concentrations measured three days and later after the eruption were within normal background values. (auth.). 4 refs.; 5 tabs.; 1 fig

  10. Inside the volcanic boiler room: knowledge exchange among stakeholders of volcanic unrest

    Science.gov (United States)

    Gottsmann, Joachim; Christie, Ryerson; Bretton, Richard

    2014-05-01

    The knowledge of the causative links between subsurface processes, resulting monitoring signals and imminent eruption is inco