Journal articles on the topic 'Volcanic geochemisty'
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1
Price, Jonathan G. "SEG Presidential Address: I Never Met a Rhyolite I Didn’t Like – Some of the Geology in Economic Geology." SEG Discovery, no. 57 (April 1, 2004): 1–13. http://dx.doi.org/10.5382/segnews.2004-57.fea.
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ABSTRACT Rhyolites and their deep-seated chemical equivalents, granites, are some of the most interesting rocks. They provide good examples of why it is important to look carefully at fresh rocks in terms of fıeld relationships, mineralogy, petrography, petrology, geochemistry, and alteration processes. Because of their evolved geochemisty, they commonly are important in terms of ore-forming processes. They are almost certainly the source of metal in many beryllium and lithium deposits and the source of heat for many other hydrothermal systems. From other perspectives, rhyolitic volcanic eruptions have the capacity of destroying civilizations, and their geochemistry (e.g., high contents of radioactive elements) is relevant to public policy decision-making.
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Ganelin, A. V., E. V. Vatrushkina, and M. V. Luchitskaya. "Geochemistry and geochronology of cretaceous volcanism of Chauna region, Central Chukotka." Геохимия 64, no. 1 (January 15, 2019): 20–42. http://dx.doi.org/10.31857/s0016-752564120-42.
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New geochronological and geochemical data on the age and composition of Cretaceous volcanism of Palyavaam River basin (Central Chukotka, Chauna region) are presented. First complex is composed of rhyolites, ignimbrites and felsic tuffs of Chauna Group of Okhotsk-Chukotka volcanic belt (OCVB). Second complex is represented by volcanic rocks of latite-shoshonite series of Early Cretaceous age, distinguished as Etchikun’ Formation. Its origin is still debatable. Some researchers refer deposits of Etchikun’ Formation to magmatic stage before OCVB activity. Other authors include in Chauna Group composition. Obtained data indicate heterogeneity of Etchikun’ Fomation volcanics and allow to divide them in two groups. Andesites of the first group (Etchikun’ Formation sensu stricto) have Early Cretaceous age and belong to magmatic stage before OCVB activity. Andesites of the second group correlate in age and composition with OCVB volcanic rocks. They occur at the base of Chauna Group and indicate homodromous character of volcanism evolution in the Central-Chukotka of Okhotsk-Chukotka volcanic belt.
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Mather, Ben R., R. Dietmar Müller, Maria Seton, Saskia Ruttor, Oliver Nebel, and Nick Mortimer. "Intraplate volcanism triggered by bursts in slab flux." Science Advances 6, no. 51 (December 2020): eabd0953. http://dx.doi.org/10.1126/sciadv.abd0953.
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Long-lived, widespread intraplate volcanism without age progression is one of the most controversial features of plate tectonics. Previously proposed edge-driven convection, asthenospheric shear, and lithospheric detachment fail to explain the ~5000-km-wide intraplate volcanic province from eastern Australia to Zealandia. We model the subducted slab volume over 100 million years and find that slab flux drives volcanic eruption frequency, indicating stimulation of an enriched mantle transition zone reservoir. Volcanic isotope geochemistry allows us to distinguish a high-μ (HIMU) reservoir [>1 billion years (Ga) old] in the slab-poor south, from a northern EM1/EM2 reservoir, reflecting a more recent voluminous influx of oceanic lithosphere into the mantle transition zone. We provide a unified theory linking plate boundary and slab volume reconstructions to upper mantle reservoirs and intraplate volcano geochemistry.
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Koloskov, A. V., M. Yu Puzankov, V. V. Ananiev, and D. V. Kovalenko. "BOLSHOI PAYALPAN VOLCANO (SREDINNY RANGE, KAMCHATKA). PROBLEMATIC ASPECTS OF CONVERGENCE OF ISLAND-ARC AND INTRAPLATE PETROLOGICAL AND GEOCHEMICAL SIGNATURES IN THE MAGMATIC SYSTEM." Tikhookeanskaya Geologiya 41, no. 2 (2022): 3–24. http://dx.doi.org/10.30911/0207-4028-2022-41-2-3-24.
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The paper presents the data on age, mineralogy, geochemistry, and isotope composition of rocks from the Bolshoi Payalpan Volcano (Sredinny Range, Kamchatka). We compared these data with those on the Nosichan and Belogolovsky volcanoes, located within the Belogolovsky volcanic center. The basalts of the neck and the upper lava complex of Bolshoi Payalpan are compositionally similar to the intraplate-type trachybasalts of the Belogolovsky Volcano, and the basaltic andesites of the lower lava and the cone complex are similar to the island arc rocks of the Nosichan Volcano. Analysis of the data obtained evidences that spatial and temporal manifestations of intraplate and island-arc volcanism at the Bolshoi Payalpan Volcano are not accidental, but may be a consequence of a change in the degree and depth of melting of the same deep source with the involvement of a mantle diapir. The Belogolovsky volcanic center formed in a setting of the Late Miocene-Early Pliocene rifting. Its evolution, right up to its extinction, proceeded in the same geodynamic setting with an increase in depth of the mantle source and a decrease in the degree of its melting. Rock compositions of the Lower-Middle Pliocene Nosichan Volcano remain of the island-arc type under conditions of rifting, since they are associated with the mantle reservoir located at a shallower depth, which has experienced a higher degree of melting. There is good reason for considering large volcanic centers as spontaneously-developing geological entities. As the endogenous activity dies down, the degree of melting decreases and the depth of melting increases with the replacement of island-arc volcanism by intraplate volcanism. The volcanic center becomes extinct.
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Zakharikhina, L. V., and Yu S. Litvinenko. "Volcanism and geochemistry of soil and vegetation cover of Kamchatka. Communication 2. Specificity of forming the elemental composition of volcanic soil in cold and humid conditions." Вулканология и сейсмология, no. 3 (May 14, 2019): 25–33. http://dx.doi.org/10.31857/s0203-03062019325-33.
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Volcanic soils of Kamchatka have the low contents of most the chemical elements in relation to their overall prevalence in the soils of continents and volcanic soils of Europe. Relatively increased gross contents of elements typical for volcanic rocks of medium and basic composition: Na, Ca, Mg, Cd, Mn, Co, Cu, and steadily low contents of elements characteristic of acid volcanics: La, Ce, Pr, Nd, Nb, Hf, Tl, Rb and Th, is most characteristic of the soils of different areas of the peninsula. The existing in the past and currently observed different conditions of volcanism in the previously allocated soil areas of Kamchatka determine the diversity of the chemical composition of the soils in these territories.
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Zakharikhina, L. V., and Yu S. Litvinenko. "Volcanism and geochemistry of soil and vegetation cover of Kamchatka. Communication 2. Specificity of forming the elemental composition of volcanic soil in cold and humid conditions." Вулканология и сейсмология, no. 3 (May 14, 2019): 25–33. http://dx.doi.org/10.31857/s0205-96142019325-33.
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Volcanic soils of Kamchatka have the low contents of most the chemical elements in relation to their overall prevalence in the soils of continents and volcanic soils of Europe. Relatively increased gross contents of elements typical for volcanic rocks of medium and basic composition: Na, Ca, Mg, Cd, Mn, Co, Cu, and steadily low contents of elements characteristic of acid volcanics: La, Ce, Pr, Nd, Nb, Hf, Tl, Rb and Th, is most characteristic of the soils of different areas of the peninsula. The existing in the past and currently observed different conditions of volcanism in the previously allocated soil areas of Kamchatka determine the diversity of the chemical composition of the soils in these territories.
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Ko, Kyoungtae, Sungwon Kim, and Yongsik Gihm. "U-Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and Their Tectonic Implications." Minerals 11, no. 5 (May 14, 2021): 520. http://dx.doi.org/10.3390/min11050520.
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Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, systematic geological, geochronological, and geochemical investigations of the volcanic-sedimentary successions were conducted to constrain the origin and timing of SSDS-bearing lacustrine strata. The SSDS-bearing strata is conformably underlain and overlain by volcanic rocks, and it contains much volcaniclastic sediment and is interbedded with tuffs. The studied SSDSs were interpreted to have formed by ground shaking during syndepositional earthquakes. U-Pb zircon ages of volcanic and volcaniclastic rocks within the studied volcano-sedimentary successions were ca. 87–84 Ma, indicating that active volcanism was concurrent with lacustrine sedimentation. Geochemical characteristics indicate that these mostly rhyolitic rocks are similar to subduction-related calc-alkaline volcanic rocks from an active continental margin. This suggests that the SSDSs in the study area were formed by earthquakes related to proximal volcanic activity due to the oblique subduction of the Paleo-Pacific Plate during the Late Cretaceous.
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Amigo, Alvaro. "Volcano monitoring and hazard assessments in Chile." Volcanica 4, S1 (November 1, 2021): 1–20. http://dx.doi.org/10.30909/vol.04.s1.0120.
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Volcanism in Chile occurs in a variety of tectonic settings but mostly in the context of oceanic-continental plate collision, including 92 potentially active volcanoes. There have been more than 30 documented eruptions in the last few centuries. The Servicio Nacional de Geología y Minería (SERNAGEOMIN) is a statutory agency of the Government of Chile responsible for volcano monitoring and hazard assessments across the country. After the impacts derived from volcanic activity at the end of the 20th century, SERNAGEOMIN created the Volcano Hazards Program and the Observatorio Volcanológico de Los Andes del Sur (OVDAS). Despite this effort, most volcanoes in Chile remained unmonitored. In 2008, the aftermath of the eruption of Chaitén led to a nationwide program in order to improve eruption forecasting, development of early warning capabilities and our state of readiness for volcanic impacts through hazard assessments. In the last decade responses to volcanic crises have been indubitably successful providing technical advice before and during volcanic eruptions. El volcanismo en Chile ocurre en una amplia variedad de regímenes tectónicos, aunque principalmente en el contexto de la colisión de placas. Alrededor de 92 volcanes son considerados potencialmente activos y más de 30 presentan actividad histórica documentada en los últimos siglos. El Servicio Nacional de Geología y Minería (SERNAGEOMIN) es la agencia gubernamental responsable de la evaluación de peligros y monitoreo de la actividad volcánica en el país. Como consecuencia de los impactos derivados de las erupciones volcánicas ocurridas hacia finales del siglo pasado, SERNAGEOMIN creó el Programa de Riesgo Volcánico y el Observatorio Volcanológico de los Andes del Sur (OVDAS). No obstante, a pesar de este esfuerzo la mayoría de los volcanes en Chile se mantenían sin monitoreo. Luego de los impactos derivados de la erupción del volcán Chaitén en 2008, un nuevo programa nacional fue creado con el fin de fortalecer la vigilancia y la evaluación de los peligros volcánicos en el país. En la última década, la respuesta a crisis volcánicas ha sido exitosa, proporcionando apoyo técnico en forma previa y durante erupciones.
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Ardian, D. N., H. Darmawan, Wahyudi, B. W. Mutaqin, Suratman, N. Haerani, and Wikanti. "Grain size, mineralogical, and geochemistry of the 1996-2018 Volcanic Products of Anak Krakatau Volcano, Indonesia." IOP Conference Series: Earth and Environmental Science 1071, no. 1 (August 1, 2022): 012017. http://dx.doi.org/10.1088/1755-1315/1071/1/012017.
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Abstract Anak Krakatau Volcano is the only active volcano on Krakatau Volcanic Complex. It is located in the Sunda Strait as part of the Quaternary volcanic arc as a result of the Indo-Australian plate subduction under the Eurasian plate. The volcanic activity of the Anak Krakatau volcano since 1927 is considered to be very active with a combination of explosive and effusive eruptions. Lava flow tends to be concentrated in the southwestern part, except for the 1996 lava flow (north) and 1993 lava flow (northeast). In 2018 there was an eruption accompanied by flank collapse on the southwestern side, caused by the accumulation of the instability volcanic body due to volcanic and tectonic activity. The volcanic activity will be reflected in the resulting deposits. This study was conducted to determine the characteristics of the deposits, especially on the northern part for post-1996. The analysis carried out included the stratigraphic columns, granulometric, petrography, and geochemistry analysis.
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Ibrahim, Khalil M., Julia Shaw, Joel Baker, Hani Khoury, Ibrahim Rabba, and Khalid Tarawneh. "Pliocene-Pleistocene volcanism in northwestern Arabian plate (Jordan): I. Geology and geochemistry of the Asfar Volcanic Group." Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 242, no. 2-3 (December 18, 2006): 145–70. http://dx.doi.org/10.1127/njgpa/242/2006/145.
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Flèche, M. R., and G. Camiré. "Geochemistry and provenance of metasedimentary rocks from the Archean Golden Pond sequence (Casa Berardi mining district, Abitibi subprovince)." Canadian Journal of Earth Sciences 33, no. 5 (May 1, 1996): 676–90. http://dx.doi.org/10.1139/e96-051.
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The Archean Golden Pond sequence is made up of deformed and metamorphosed conglomerates, greywackes, and mafic volcanic rocks, and is overlain by ferrugineous metasedimentary rocks of the North iron formation. The clastic rocks were derived mainly from a volcanic source that had undergone weak chemical weathering. Their source area was dominated by the presence of 60–80% high-Al2O3 felsic volcanics having strongly fractionated [La/Sm]N (= 3.7 ± 0.3) and very low Ta/Th ratios (= 0.09 ± 0.02), with lesser proportions of basaltic (10–30%) and ultramafic volcanic rocks (1–10%). The ferrugineous metasedimentary rocks can be modelled by mixing 20–40% siliciclastic material, of the composition of the average Golden Pond greywacke, with an Fe- and Si-rich precipitate (molecular Fe/Si = 0.6 ± 0.2). The high-Al2O3 felsic source rocks were most likely produced by subduction processes within an oceanic arc environment, but the mafic and ultramafic volcanic rocks were derived by different processes from an asthenospheric mantle source, possibly in an oceanic rift environment. Therefore, it is suggested that the ultramafic, mafic, and felsic volcanic rocks were brought to the same erosional level by dissection of the arc system and rapid exhumation of the felsic arc lithologies and the deeper ocean floor. Intrabasinal hydrothermal activity associated with contemporaneous mafic volcanism and (or) graben development may have also been responsible for the local production of the Fe-rich precipitates of the North iron formation.
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Baryshev, Alexander. "Advective structures of the bottom of lake Natron and its surroundings (Tanzania)." Ores and metals, no. 3 (November 15, 2022): 101–9. http://dx.doi.org/10.47765/0869-5997-2022-10019.
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In this study we consider the features of the development of weakly lithified bottom sediments and the general structure of lake Natron against the background of its seasonal drying and watering. This study takes into account the laws of advection and the periodic placement of cellular zonal advective structures in space. The consedimentary structures in the lake sediments demonstrate the conditions for the formation of sodic ores and their positions. Provided space and aerial photographs depict unique genetic information about the evolution of geochemistry and the development of bottom morphology during sedimentation. This includes the presence of two sources that feed the lake - river and mud eruptions of the adjacent Oldoinyo-Lengai volcano, supposedly the only one on Earth that erupts carbonatite lavas. The combination of two sources and two processes leads to the development of an epimagmatic phreatic-hydrothermal recycling system. In it, the masses of the lake penetrate through fissure structures into the suprafocal space of the volcano, providing mud volcanism with solutions of soda masses containing organic matter of sediments. Volcanic soda eruptions are not carbonatite lavas. The morphological similarities and differences of structures are shown - small craters on the bottom of the lake, associated with the advection of thin layers of sedimentary material; large craters located nearby among volcanic strata along the shores of the lake; and both subsidence calderas and explosion calderas associated with magmatic and mud types of volcanism in the setting of strike-slip transtension.
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Gökten, E., and P. A. Floyd. "Geochemistry and tectonic environment of the Şarkışla area volcanic rocks in central Anatolia, Turkey." Mineralogical Magazine 51, no. 362 (October 1987): 553–59. http://dx.doi.org/10.1180/minmag.1987.051.362.09.
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AbstractThe volcanic rocks of the Şarkışla area in northeastern central Anatolia are associated with volcaniclastics, turbiditic limestones and pelagic-hemipelagic shales of Upper Cretaceous-Palaeocene age. A preliminary geochemical study was undertaken to constrain local tectonic models, and due to the variable altered nature of the volcanics, determine the lithological composition and magma type. Chemically the volcanics are an andesite-dominated suite of calc-alkali lavas, probably developed adjacent to an active continental margin in a local (ensialic back-arc?) basinal area. The volcanic activity was probably related to a postulated magmatic arc just south of the area during the early Tertiary.
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Charland, Anne, Don Francis, and John Ludden. "Stratigraphy and geochemistry of the Itcha Volcanic Complex, central British Columbia." Canadian Journal of Earth Sciences 30, no. 1 (January 1, 1993): 132–44. http://dx.doi.org/10.1139/e93-013.
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The Itcha Volcanic Complex is the youngest and easternmost felsic shield volcano of the Anahim Volcanic Belt of central British Columbia. The main body of the shield erupted over an area of ~300 km2 forming Itcha Mountain and Mount Downton. Volcanism associated with the Itcha Shield extended 20 km south to the Satah Mountain area, where lavas erupted along a north-northwest – south-southeast fault system and covered an additional area of 250 km2. The Itcha Volcanic Complex is characterized by a bimodal population of volcanic rocks, which are dominated by felsic lavas. There were two stages of volcanism: (i) an early felsic shield-building stage dominated by felsic lavas ranging in composition from phonolite to minor quartz-normative trachytes, which erupted as flows, domes, and pyroclastic deposits to form a low-angled shield; and (ii) a late mafic capping stage, which comprises a thin veneer of hawaiite and more primitive mafic lavas ranging in composition from alkali olivine basalt to basanite. The late mafic capping stage lavas erupted from satellite cinder cones and fissures concentrated on the eastern side of the shield.The hawaiites that dominate the late mafic capping stage cannot have been derived from the more primitive basalts with which they are associated by low-pressure crystal fractionation but may instead have originated from the fractionation of a clinopyroxene-dominated assemblage at high pressures. The presence of mafic xenocrysts in a megacrystic trachyte unit, whose eruption terminated the felsic shield-building stage, and anorthoclase xenocrysts in the most evolved alkali olivine basalts of the mafic capping stage indicate that the mafic and the felsic magmas interacted prior to eruption. An overlap in 87Sr/86Sr ratios and a similarity in the high-field-strength element ratios of the felsic and the mafic lavas suggest that they are genetically related. Elevated ratios of large-ion lithophile elements to high-field-strength elements (e.g., Rb/Zr) in the trachytes, however, indicates that the felsic magmas were not derived by closed-system fractional crystallization from the mafic magmas and may instead suggest the assimilation of a crustal component.
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Dawson, J. B. "Neogene–Recent rifting and volcanism in northern Tanzania: relevance for comparisons between the Gardar province and the East African Rift valley." Mineralogical Magazine 61, no. 407 (August 1997): 543–48. http://dx.doi.org/10.1180/minmag.1997.061.407.06.
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AbstractThe tectonic position of the intraplate, alkaline volcanic province of N. Tanzania in a broad rift-controlled area astride the boundary between the Tanzania Craton and the circum-cratonic Mozambique Fold Belt, strongly resembles that of the Gardar province of S. Greenland. Earlier-identified petrological analogies between Gardar magmatism and that in the Kenya sector of the East African Rift Valley can be extended to volcanism in N. Tanzania, and analogies specifically with the Gardar agpaitic suite are strengthened by the occurrence of eudialyte and aenigmatite in some Tanzanian peralkaline, silicic volcanics.
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Garcia, Sebastian, and Gabriela Badi. "Towards the development of the first permanent volcano observatory in Argentina." Volcanica 4, S1 (November 1, 2021): 21–48. http://dx.doi.org/10.30909/vol.04.s1.2148.
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Argentina is a country that presents a complex situation regarding volcanic risk, where a total of 38 volcanoes are considered active. Although Argentina has no major cities close to these volcanoes, the continuous increase in economic activity and infrastructure near the Andean Codillera will increase exposure to volcano hazards in the future. Further, volcanic activity on the border between Argentina and Chile poses a unique challenge in relation to volcano monitoring and the management of volcanic emergencies. Additionally, due to atmospheric circulation patterns in the region (from West to East), Argentina is exposed to ashfall and ash dispersion from frequent explosive eruptions from Chilean volcanoes. Considering this, the Servicio Geológico Minero Argentino (SEGEMAR) decided to create and implement a Volcanic Threat Assessment Program, which includes the creation of the the first permanent volcano observatory for the country, the Observatorio Argentino de Vigilancia Volcánica (OAVV). Previously the Decepcion Island volcano observatory was created as a collaboration between the Instituto Antártico Argentino (IAA) and the Museo Nacional de Ciencias Naturales (MNCN) from the Consejo Superior de Investigaciones Científicas (CSIC). Argentina es un país que presenta una compleja situación con respecto al riesgo volcánico, donde un total de 38 volcanes son considerados activos. Aunque Argentina no tiene ciudades importantes cerca de estos volcanes, el continuo incremento de la actividad económica y la infraestructura cerca de la Cordillera de los Andes, generará en el futuro un aumento en la exposición a estos peligros. Además, la actividad volcánica en la frontera entre Argentina y Chile constituye un desafío único en relación con el monitoreo de volcanes y la gestión de emergencias volcánicas. Adicionalmente, debido a los patrones de circulación atmosférica en la región (desde el oeste hacia el este), Argentina está expuesta a la caída y dispersión de cenizas de las frecuentes erupciones explosivas de volcanes chilenos. Teniendo esto en cuenta, el Servicio Geológico Minero Argentino (SEGEMAR) decidió crear e implementar un programa de evaluación de amenazas volcánicas, que incluye, la creación del primer observatorio permanente de volcanes para el país, el Observatorio Argentino de Vigilancia Volcánica (OAVV). Previamente, el Observatorio Volcanológico de la Isla Decepción fue creado como una colaboración entre el Instituto Antártico Argentino (IAA) y el Museo Nacional de Ciencias Naturales (MNCN) del Consejo Superior de Investigaciones Científicas de España (CSIC).
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Ryan, P. D., C. J. Stillman, C. J. Stillman, and S. Pow. "Terrane geochemistry contrasts across the Iapetus Suture in Ireland." Geological Magazine 132, no. 5 (September 1995): 581–97. http://dx.doi.org/10.1017/s0016756800021245.
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AbstractIn the Irish Caledonides, volcanism has been significant in terrane identification and in reconstructions of the Appalachian/Caledonian orogen. Crucial to these reconstructions is the recognition of ocean margins using obducted ocean floor relics (ophiolites) and supra-subduction zone volcanic assemblages. The volcanic rocks provide much evidence for the affinity of a terrane, however, by analogy with present day examples, the ocean floor sediments may provide the best way of tracing both ocean-floor magmatic activity, and continental source areas. This investigation shows that the Irish Lower Palaeozoic volcanogenic terranes can be discriminated in terms of their shale geochemistry, which also gives information on their provenance and environment of deposition. South Mayo shales are dominated by volcaniclastic material derived both from both an arc and from an ophiolitic source. The Northern and Central belts of the Central Terrane show very similar lithogeochemistries, apparently derived in part from intermediate to silicic volcanic complexes. The Ordovician-Silurian inliers that straddle the Suture Zone, here termed the Southern Domain, show a chemistry close to that of the Leinster Terrane, which, coupled with a greater degree of sea-floor weathering, suggests a terrane with sediment of both volcanic and continental provenance being deposited in deeper water further from land. Across the suture the Leinster Terrane shows a mature chemistry which clearly suggests a continental provenance, together with a volcanogenic input from supra-subduction volcanism. This maturity is probably due to slower rates of sedimentation with longer residence times for volcanic detritus, plus the existence of a deeply weathered continental basement.
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Othman, D. Ben, N. T. Arndt, W. M. White, and K. P. Jochum. "Geochemistry and age of Timiskaming alkali volcanics and the Otto syenite stock, Abitibi, Ontario." Canadian Journal of Earth Sciences 27, no. 10 (October 1, 1990): 1304–11. http://dx.doi.org/10.1139/e90-140.
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Tephrites and trachytes of the Timiskaming volcanics from the Kirkland Lake area (Ontario) and syenites and a granite from the nearby Otto Stock are characterized by extreme enrichment of incompatible elements coupled with relative depletion of Nb, Ti, and to a lesser extent Zr and Y.The volcanic rocks have a whole-rock Sm–Nd isochron age of 2740 ± 117 Ma (2σ error), and minerals separated from the Otto Stock, a Sm–Nd age of 2544 ± 50 Ma. Conventional and ion probe U–Pb analyses of zircons from the Otto Stock yielded an upper intercept age of 2700 ± 19 Ma, whereas the more concordant ion probe analyses had a mean 207Pb/206Pb age of 2671 ± 8 Ma (2σ). The latter is interpreted as the age of emplacement of both the volcanics and the pluton, and the Sm–Nd mineral isochron age is thought to reflect a period of later disturbance, probably during regional metamorphism.A high initial εNd of 2.5 ± 1.5 for Kirkland Lake volcanics indicates long-term isotopic depletion of their source. This value is the same as that for volcanic rocks throughout the Abitibi belt and indicates that any chemically enriched material in the source cannot have been much older than the volcanics themselves. An environment remote from older continents is inferred.
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Pointon, Michael A., Michael J. Flowerdew, Peter Hülse, Simon Schneider, and Martin J. Whitehouse. "Mixed local and ultra-distal volcanic ash deposition within the Upper Cretaceous Kanguk Formation, Sverdrup Basin, Canadian Arctic Islands." Geological Magazine 156, no. 12 (June 18, 2019): 2067–84. http://dx.doi.org/10.1017/s0016756819000414.
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AbstractThe Upper Cretaceous Kanguk Formation of the Sverdrup Basin, Canadian Arctic Islands, contains numerous diagenetically altered volcanic ash layers (bentonites). Eleven bentonites were sampled from an outcrop section on Ellesmere Island for U–Pb zircon secondary ion mass spectrometry dating and whole-rock geochemical analysis. Two distinct types of bentonite are identified from the geochemical data. Relatively thick (0.1 to 5 m) peralkaline rhyolitic to trachytic bentonites erupted in an intraplate tectonic setting. These occur throughout the upper Turonian to lower Campanian (c. 92–83 Ma) outcrop section and are likely associated with the alkaline phase of the High Arctic Large Igneous Province. Two thinner (<5 cm) subalkaline dacitic to rhyolitic bentonites of late Turonian to early Coniacian age (c. 90–88 Ma) are also identified. The geochemistry of these bentonites is consistent with derivation from volcanoes within an active continental margin tectonic setting. The lack of nearby potential sources of subalkaline magmatism, together with the thinner bed thickness of the subalkaline bentonites and the small size of zircon phenocrysts therein (typically 50–80 μm in length) are consistent with a more distal source area. The zircon U–Pb age and whole-rock geochemistry of these two subalkaline bentonites correlate with an interval of intense volcanism in the Okhotsk–Chukotka Volcanic Belt, Russia. It is proposed that during late Turonian to early Coniacian times intense volcanism within the Okhotsk–Chukotka Volcanic Belt resulted in widespread volcanic ash dispersal across Arctic Alaska and Canada, reaching as far east as the Sverdrup Basin, more than 3000 km away.
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Perepelov, Alexander, Mikhail Kuzmin, Svetlana Tsypukova, Yuri Shcherbakov, Sergey Dril, Alexey Didenko, Enkhbat Dalai-Erdene, Mikhail Puzankov, and Alexander Zhgilev. "Late Cenozoic Uguumur and Bod-Uul Volcanic Centers in Northern Mongolia: Mineralogy, Geochemistry, and Magma Sources." Minerals 10, no. 7 (July 8, 2020): 612. http://dx.doi.org/10.3390/min10070612.
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The paper presents new data on mineralogy, geochemistry, and Sr-Nd-Pb isotope systematics of Late Cenozoic eruption products of Uguumur and Bod-Uul volcanoes in the Tesiingol field of Northern Mongolia, with implications for the magma generation conditions, magma sources, and geodynamic causes of volcanism. The lavas and pyroclastics of the two volcanic centers are composed of basanite, phonotephrite, basaltic trachyandesite, and trachyandesite, which enclose spinel and garnet peridotite and garnet-bearing pyroxenite xenoliths; megacrysts of Na-sanidine, Ca-Na pyroxene, ilmenite, and almandine-grossular-pyrope garnets; and carbonate phases. The rocks are enriched in LILE and HFSE, show strongly fractioned REE spectra, and are relatively depleted in U and Th. The low contents of U and Th in Late Cenozoic volcanics from Northern and Central Mongolia represent the composition of a magma source. The presence of carbonate phases in subliquidus minerals and mantle rocks indicates that carbon-bearing fluids were important agents in metasomatism of subcontinental lithospheric mantle. The silicate-carbonate melts were apparently released from eclogitizied slabs during the Paleo-Asian and Mongol-Okhotsk subduction. The parent alkali-basaltic magma may be derived as a result from partial melting of Grt-bearing pyroxenite or eclogite-like material or carobantized peridotite. The sources of alkali-basaltic magmas from the Northern and Central Mongolia plot different isotope trends corresponding to two different provinces. The isotope signatures of megacrysts are similar to those of studied volcanic centers rocks. The P-T conditions inferred for the crystallization of pyroxene and garnet megacrysts correspond to a depth range from the Grt-Sp phase transition to the lower crust. Late Cenozoic volcanism in Northern and Central Mongolia may be a response to stress propagation and gravity instability in the mantle associated with the India-Asia collision.
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KIIPLI, TARMO, TOIVO KALLASTE, and VIIU NESTOR. "Composition and correlation of volcanic ash beds of Silurian age from the eastern Baltic." Geological Magazine 147, no. 6 (April 21, 2010): 895–909. http://dx.doi.org/10.1017/s0016756810000294.
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AbstractSanidine composition and bulk geochemistry of volcanic ash beds from the East Baltic indicate the subalkaline nature of the volcanism near the margins of the Baltica plate during the Silurian. Several bentonites in the Wenlock include a previously unknown sanidine with 48 to 58 mol % of the Na+Ca component. In contrast to the earlier Telychian volcanism, sodium-rich sanidine occurs in ash beds which originate from relatively moderately evolved dacitic magma. The studied material from two drill cores integrated with previous research enables production of a more complete list of 49 volcanic eruption layers for the lower to middle Wenlock in the East Baltic. This updated list of bentonites characterized by their sanidine compositions forms a good basis for future integrated bio- and chemostratigraphic correlations in northern Europe.
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RILEY, TEAL R., MICHAEL J. FLOWERDEW, MORAG A. HUNTER, and MARTIN J. WHITEHOUSE. "Middle Jurassic rhyolite volcanism of eastern Graham Land, Antarctic Peninsula: age correlations and stratigraphic relationships." Geological Magazine 147, no. 4 (January 7, 2010): 581–95. http://dx.doi.org/10.1017/s0016756809990720.
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AbstractSilicic volcanism atc.168 Ma has been identified previously on the Antarctic Peninsula, and the Mapple Formation, which includes those volcanic rocks, has been defined and documented from one area of the east coast of Graham Land. Based on age and geochemical criteria, correlations have been made to the extensive Chon Aike Province of South America, which has been demonstrated to be one of the largest silicic volcanic provinces in the world. Rhyolitic and intermediate composition volcanic successions from six separate localities on the east coast of the Antarctic Peninsula are described here and are confirmed as correlatives of the Mapple Formation, based on newly acquired geochronology and field observations. They are dominantly rhyolitic crystal tuffs and/or ignimbrites with ages in the interval 162–168 Ma, overlapping with the age of the Mapple Formation (167–171 Ma) at the type locality. Andesitic agglomerates are also described, which are included in the same event and demonstrate the occurrence of rare intermediate volcanism, which is also seen in the Chon Aike Province. A new group, the Graham Land Volcanic Group, is defined here, and criteria are established which allow the separation of some volcanic successions out of the previously defined Antarctic Peninsula Volcanic Group, which takes no account of tectonic setting, eruption age or geochemistry.
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Wasowski, Janusz J., and Robert D. Jacobi. "Geochemistry and tectonic significance of the mafic volcanic blocks in the Dunnage mélange, north central Newfoundland." Canadian Journal of Earth Sciences 22, no. 9 (September 1, 1985): 1248–56. http://dx.doi.org/10.1139/e85-129.
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Abundant volcanic blocks are present in the Dunnage mélange. These mafic volcanic rocks consist predominantly of pillow lava, tuff breccia, isolated pillow–tuff breccia, and minor amounts of ropy lava.Major- and trace-element compositions of the basalts reveal that these volcanics do not resemble calc-alkaline or low-potassium island-arc suites. Rather, the majority of the samples are enriched-type ocean-floor tholeiites, whereas some show alkali basalt affinities. Discrimination diagrams suggest that these basalts may have been erupted as within-plate basalts. However, the chemical composition of the volcanic blocks is most similar to that of basalts generated at bathymetric highs located astride (or slightly off) mid-ocean ridges.The geochemistry of the Dunnage mélange basalts is very similar to that of the mafic volcanic rocks from the nearby Summerford Group and the Lawrence Head Formation. This correlation is further supported by sedimentary and petrographic evidence and by partial age equivalency.
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Marini, L., A. Agostini, R. Cioni, M. Guidi, and O. Leon. "Guagua pichincha volcano, Ecuador: fluid geochemistry in volcanic surveillance." Journal of Volcanology and Geothermal Research 46, no. 1-2 (May 1991): 21–35. http://dx.doi.org/10.1016/0377-0273(91)90073-9.
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Sommer, Carlos Augusto, Felipe Padilha Leitzke, Evandro Fernandes de Lima, Carla Joana Santos Barreto, Jean Michel Lafon, Vinicius Matté, Ruy Paulo Philipp, Rommulo Vieira Conceição, and Miguel Ângelo Stipp Basei. "Zircon U-Pb geochronology, Sm-Nd and Pb-Pb isotope systematics of Ediacaran post-collisional high-silica Acampamento Velho volcanism at the Tupanci area, NW of the Sul-Rio-Grandense Shield, Brazil." Brazilian Journal of Geology 47, no. 4 (December 2017): 545–60. http://dx.doi.org/10.1590/2317-4889201720170064.
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ABSTRACT: We present new U-Pb zircon ages and Sm-Nd-Pb isotopic data for volcanic and hypabyssal acid rocks from the northernmost exposure of the Acampamento Velho Formation in the NW portion of the Sul-Rio-Grandense Shield, Brazil. The first volcanic episode, grouped in the high-Ti rhyolites from the Tupanci hill, shows age of 579 ± 5.6 Ma, which is in agreement with the post-collisional Acampamento Velho Formation volcanism in the Bom Jardim Group of the Camaquã Basin. A poorly constrained age of 558 +/- 39 Ma was obtained for rhyolites from the low-Ti group at the Picados Hill, which may indicate a younger acid volcanism, or a greater time span for the volcanism of the Acampamento Velho Formation in southernmost Brazil. Regarding magmatic sources, Sm/Nd isotopic data coupled to Pb isotopes and a review of trace element geochemistry indicate different amounts of Paleoproterozoic (Dom Feliciano, Pinheiro Machado Suite) to Neoproterozoic (Rio Vacacaí terrane) lower crust melting. Our data, coupled with literature data, contribute to a better understanding of the stratigraphic evolution for the Neoproterozoic post-collisional volcanic successions of the Camaquã Basin in the Sul-Rio-Grandense Shield.
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Begét, James E., Richard D. Reger, DeAnne Pinney, Tom Gillispie, and Kathy Campbell. "Correlation of the Holocene Jarvis Creek, Tangle Lakes, Cantwell, and Hayes Tephras in South-Central and Central Alaska." Quaternary Research 35, no. 2 (March 1991): 174–89. http://dx.doi.org/10.1016/0033-5894(91)90065-d.
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AbstractThe geochemistry, petrography, and distribution of the Jarvis Creek Ash (Péwé, 1965, 1975a) indicate that this tephra from the lower Delta River area of central Alaska is correlative with vol volcanic ash from sites in south-central Alaska near Tangle Lakes (upper Delta River area) and the Cantwell ash from Hayes volcano found in the upper Nenana River area (Riehle et al., 1990). Volcanic glass compositions of distal Jarvis Creek and Tangle Lakes tephra samples are compositionally restricted, while several discrete glass populations are present in some samples are compositionally collected nearer Hayes volcano. These correlations extend the known distribution of Hayes volcano tephras across the Alaska Range and into central Alaska, a distance of more than 650 km. New geochronologic data for the Jarvis Creek Ash suggest it was deposited ca. 3660 ± 125 yr B.P., consistent with previous age estimates of tephra eruptions at the Hayes volcano. The name “Jarvis Creek Ash” has well-established priority with respect to “Cantwell ash” or other local names for this tephra layer from the Hayes volcano.
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Αρίκας, Κ., Π. Βουδούρης, M. R. Kloos, and Ch Tesch. "PETROLOGY - GEOCHEMISTRY AND METALLOGENESIS OF VOLCANIC ROCKS IN THE PETROTA GRABEN/MARONIA, W.THRACE." Bulletin of the Geological Society of Greece 36, no. 1 (January 1, 2004): 482. http://dx.doi.org/10.12681/bgsg.16740.
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The penological, mineralogical and geochemical study of tertiary volcanic rocks from Petrota Graben/Maronia, resulted in the distinction of the following pétrographie groups: a) a high-K calcalkaline group (andesites-dacites), b) a shoshonitic group (shoshonitic andésites, trachytic lavas, c) rhyodacitic ignimbrites and ignimbritic tuffs with high-K calc-alkaline to shoshonitic affinity, and d) rhyolites. The shoshonitic volcanic rocks and the rhyolites are probably originated from the neighbouring Maronia plutonio complex. In addition the calc-alkaline group is related to similar volcanics outcroping in the Mesti-Kassiteres area (the northeastern extension of the Graben). The petrogenesis of the volcanic rocks of the Petrota gragen is attibuted to fractional crystallization and/or magma mixing processes. Epithermal style mineralizations in Mavrokoryfi, Perama Hill and Odontoto are believed to be genetically related to the rhyolitic magmatism in the area.
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Ibáñez, Jesús M., Ignacio Castro-Melgar, Ornella Cocina, Luciano Zuccarello, Stefano Branca, Edoardo Del Pezzo, and Janire Prudencio. "First 2-D intrinsic and scattering attenuation images of Mt Etna volcano and surrounding region from active seismic data." Geophysical Journal International 220, no. 1 (October 7, 2019): 267–77. http://dx.doi.org/10.1093/gji/ggz450.
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SUMMARY We present 2-D attenuation images of the Mt Etna volcanic region on the basis of separation of intrinsic and scattering effects. The analysis presented here exploits a large active seismic database that fully covers the area under study. We observe that scattering effects dominate over intrinsic attenuation, suggesting that the region is very heterogeneous. Comparison with analyses conducted at other volcanoes reveals that the Mt Etna region is characterized by high intrinsic attenuation, resulting from the presence of large volcanoclastic deposits at shallow depth. The 2-D distributions of intrinsic and scattering anomalies show the presence of regions characterized by high and low attenuation effects, corresponding to several tectonic and volcanic features. In particular, we identify a high attenuation region in the SW sector of the Mt Etna volcanic complex, which is correlated with high seismicity rates and volcanism. This work supports the hypothesis of a link between the dynamics of the SW flank and the recharge of the volcano in the last decades, occurring under the summit crater and, secondarily, the upper South rift zone.
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KRÖCHERT, JÖRG, and ELMAR BUCHNER. "Age distribution of cinder cones within the Bandas del Sur Formation, southern Tenerife, Canary Islands." Geological Magazine 146, no. 2 (September 16, 2008): 161–72. http://dx.doi.org/10.1017/s001675680800544x.
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AbstractThe Quaternary Bandas del Sur Formation in the south of Tenerife comprises a complex sequence of pyroclastic rocks and lavas. In contrast to the NW- and NE-Rift zone on Tenerife, the S-Rift zone comprises a number of characteristics with respect to the morphological features, eruption cyclicity and the geochemistry of the volcanic deposits. Various flank eruptions of the Las Cañadas volcano associated with basaltic lavas and the formation of cinder cones within the Bandas del Sur are important volcanic units for understanding the explosive volcanic cycles during the Pleistocene on Tenerife. A number of palaeomagnetic studies, as well as major and trace element geochemistry and two radio-isotope dates (K–Ar), have been carried out on prominent cinder cones, in order to discover their stratigraphic position. Combining our results with previous K–Ar data, the cones and lavas can be subdivided into three stratigraphic units. The first unit contains cinder cones with reverse magnetization and Y/Nb ratios between 0.37 and 0.41. Cinder cones which belong to the second unit show normal magnetization and Y/Nb ratios of < 0.35. The third unit comprises cinder cones with normal magnetization and Y/Nb ratios of about 0.47. The first two units were constructed between c. 0.948–0.779 Ma and 0.323–0.300 Ma. These units define volcanic cycles ending in violent Plinian eruptions. The third and youngest unit possibly marks the beginning of a further volcanic cycle that started c. 0.095 Ma ago.
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BAĞCI, Utku, Tamer RIZAOĞLU, Güzide ÖNAL, and Osman PARLAK. "Petrology of the late Triassic mafic volcanic rocks from the Antalya Complex, southern Turkey: evidence for mantle source characteristics during the Neotethyan rifting." TURKISH JOURNAL OF EARTH SCIENCES 29, no. 7 (November 16, 2020): 1049–72. http://dx.doi.org/10.3906/yer-2003-1.
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The Antalya Complex in southern Turkey comprises a number of autochthonous and allochthonous units that originated from the Southern Neotethys. Late Triassic volcanic rocks are widespread in the Antalya Complex and are important for the onset of the rifting stage of the southern Neotethys. The studied Late Triassic volcanic rocks within the Antalya Complex are exposed in the southern part of Saklıkent (Antalya) region. They are represented by pillow, massive, and columnar-jointed lava flows with volcaniclastic breccias and pelagic limestone intercalations. Spilitic basalts exhibit intersertal, microlithic porphyritic, and ophitic textures and are represented by plagioclase, pyroxene, and olivine. Secondary phases are characterized by serpentine, calcite, chlorite, epidote, zeolite, and quartz. Based on Zr/Ti vs. Nb/Y ratios, the volcanic rocks are represented by alkaline basalts (Nb/Y = 1.54–2.82). A chondrite normalized REE diagram for the volcanic rocks displays significant LREE enrichment with respect to HREE ([La/Yb]N = 15.14–19.77). Trace element geochemistry of the studied rocks suggests that these rocks are more akin to ocean island basalt (OIB) and were formed by small degrees (~2–4%) of partial melting of an enriched mantle source (spinel + garnet-bearing lherzolite). The volcanic rocks of the Saklıkent region exhibit similarities to the Late Triassic volcanics of the Koçali Complex in SE Anatolia and the Mamonia Complex (Cyprus) in terms of their geochemical features. All evidence suggests that the Late Triassic alkaline volcanics in Antalya, Mamonia (Cyprus), and the Koçali (Adıyaman) Complexes were formed in an extensional environment at the continent-ocean transition zone during the rifting of the southern Neotethyan Ocean.
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Pe-Piper, Georgia, and David J. W. Piper. "Volcanic ash in the Lower Cretaceous Chaswood Formation of Nova Scotia: source and implicationsGeological Survey of Canada Contribution 20100082." Canadian Journal of Earth Sciences 47, no. 11 (November 2010): 1427–43. http://dx.doi.org/10.1139/e10-078.
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Lignites and coals, because of their low sedimentation rates of terrigenous detritus, may preserve a record of volcanic ash fall. Lignite from the Lower Cretaceous Chaswood Formation in central Nova Scotia was studied to identify whether any volcanic ash is present and can be correlated to known Early Cretaceous volcanism in southeastern Canada and adjacent New England. The bulk mineralogy and geochemistry of lignite and lignitic mudstones was determined by X-ray diffraction and whole-rock geochemical analysis of ashed samples; selected samples were examined by electron microprobe and scanning electron microscope. Much of the terrigenous component of some lignites consists of detrital sediments. In some lignites, distinctive rare earth element patterns are due to leaching from monazite and concentration in organic matter. Some lignites, however, lack illite and (or) quartz indicative of detrital sources, but show unusual abundance of stable high-field-strength elements such as Nb, Ta, and Hf, suggesting a volcanic source. Wood or charcoal fragments appear mineralized and diagenetic talc is present. Most of any ash component has been altered to kaolinite. Bulk composition of original ash ranges from basaltic to rhyolitic and matches chemically with subalkaline volcanic rocks on the SW Grand Banks and Orpheus graben. Coeval volcanic rocks on the U.S. continental margin and the New England–Quebec igneous province are more alkaline. Altered ash in lignite in the lower member of the Chaswood Formation correlates with Neocomian volcanism on the SW Grand Banks; and in the middle and upper members with Aptian–Albian volcanism in Orpheus graben.
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de Mello, Caio Ribeiro, Fernando Tornos, Carmen Conde, Colombo Celso Gaeta Tassinari, Angelo Farci, and Raquel Vega. "Geology, Geochemistry, and Geochronology of the Giant Rio Tinto VMS Deposit, Iberian Pyrite Belt, Spain." Economic Geology 117, no. 5 (August 1, 2022): 1149–77. http://dx.doi.org/10.5382/econgeo.4907.
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Abstract The Rio Tinto deposit is a giant volcanogenic massive sulfide deposit (VMS) that contains more than 500 Mt of pyrite-rich massive sulfides and more than 2 Gt of mineralized stockwork. Three broad lithostratigraphic groups occur in the regional stratigraphy: the phyllite-quartzite group, the volcano-sedimentary complex, and the Baixo Alentejo Flysch Group. These three major packages reflect the evolution of a depositional environment from a stable platform to deposition in pull-apart continental basins during oblique subduction and collision and coeval synorogenic flysch sequence. The volcano-sedimentary complex, which hosts massive sulfide mineralization at Rio Tinto, can be divided into four major units: (1) the Mafic Siliciclastic Unit, (2) the Lower Sedimentary Unit, (3) the Felsic Unit, and (4) the Upper Sedimentary Unit. The Felsic Unit is further subdivided based on new U-Pb zircon geochronology into three distinct subunits. Felsic Unit I (ca. 356 Ma) includes dome complexes dominated by rhyodacite and reflects the onset of felsic magmatism in the region. Felsic Unit II (ca. 352–348 Ma) represents the main interval of volcanic activity, also dominated by rhyodacite domes and related aprons, and is associated with widespread VMS mineralization. Felsic Unit III (ca. 340 Ma) reflects a late pulse of rhyolitic volcanism. Massive sulfides occur as two different styles of mineralization: (1) replacive ores as discordant pipes hosted by glass-rich felsic rocks and enclosed by a large zone of stockwork-like mineralization and (2) overlying shale-hosted exhalative mineralization in small anoxic basins, probably formed during the collapse of the volcanic domes of Felsic Unit II in the Middle-Late Tournaisian. New lithogeochemical data illustrate two types of mafic rocks in the Mafic Siliciclastic Unit: a basaltic andesite and a high–Ti-Zr basalt, both of tholeiitic affinity. Using immobile element ratios (heavy rare earth elements [HREEs], Al, Y, Zr, and Ti) of the Felsic Unit, fundamental differences have been recognized between the subunits. The unmineralized Felsic Unit I is characterized by high Zr content (225–300 ppm) and a pronounced Eu negative anomaly, and probably represents the most fractionated rocks. Felsic Unit II is characterized by Zr values between 50 and 200 ppm. The low Zr values of the mineralized unit contrast with the typically high Zr values of the felsic rocks related to volcanogenic massive sulfides elsewhere and, at a regional scale, can help to discriminate potentially fertile domes from barren volcanism.
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Fyffe, L. R., and S. M. Barr. "Petrochemistry and tectonic significance of Carboniferous volcanic rocks in New Brunswick." Canadian Journal of Earth Sciences 23, no. 9 (September 1, 1986): 1243–56. http://dx.doi.org/10.1139/e86-121.
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Carboniferous volcanic rocks from the New Brunswick Platform in the Maritimes Basin are divided into three age groups. Late Tournaisian to early Visean volcanic rocks are tholeiitic basalts and andesites that, in southern New Brunswick, are inter-bedded with abundant calc-alkalic rhyolite. Late Visean to Namurian volcanic rocks consist of an interbedded sequence of alkalic basalts and trachyandesites. Late Westphalian volcanic rocks change in composition up section from trachyte to peralkalic rhyolite. All three age groups display petrochemical features indicative of an intraplate tectonic setting. The volcanic geochemistry is consistent with the development of the Maritimes Basin either as a failed rift formed along the margin of a late Paleozoic ocean or as a rhomb graben formed within a transcurrent zone; the former model is preferred. The change in basaltic composition from tholeiitic to alkalic apparently coincided with a decrease in rate of extension between the Tournaisian and Namurian. Local peralkalic volcanism occurred during regional sagging of the basin as extension ceased and basement rocks cooled in the Late Carboniferous.
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Houghton, B. F., and H. U. Schmincke. "Mixed deposits of simultaneous strombolian and phreatomagmatic volcanism: Rothenberg volcano, east Eifel volcanic field." Journal of Volcanology and Geothermal Research 30, no. 1-2 (November 1986): 117–30. http://dx.doi.org/10.1016/0377-0273(86)90069-7.
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Zanchetta, Giovanni, Marta Pappalardo, Alessio Di Roberto, Monica Bini, Ilenia Arienzo, Ilaria Isola, Adriano Ribolini, et al. "A Holocene tephra layer within coastal aeolian deposits north of Caleta Olivia (Santa Cruz Province, Argentina)." Andean Geology 48, no. 2 (May 31, 2021): 267. http://dx.doi.org/10.5027/andgeov48n2-3290.
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In this paper we illustrate the stratigraphy, geochronology, and geochemistry (major, minor, trace elements and Sr-isotopes) of a Holocene tephra layer found within coastal sedimentary deposits north of Caleta Olivia (Santa Cruz Province, Argentina). The stratigraphic succession comprises beach deposits with basal erosive surface resting on the local substrate (“Formación Patagonia”) followed by a poorly developed paleosoil. The paleosoil is covered by a lenticular fine-grained (Mdφ: 5.2, 0.027 mm), well sorted (σφ: 1.2) volcanic ash layer and aeolian sands. The geochemical composition of shard fragments points to an origin from the Hudson volcano, located in the southern Andes, ca. 400 km to the west. The geochemistry, Sr-isotopes and the radiometric constraints (younger than the age of the underlying marine layer dated at ca. 4,100 a cal BP) further allow correlating this tephra with the so-called H2 eruption (ca. 3,900 a cal BP). This finding is of interest owing to the poor preservation potential of tephra within the Late Holocene sedimentary deposits of the Atlantic coast of Patagonia and represents the first finding of H2 eruption in this area, improving our knowledge of the dispersion of the fine-grained distal deposit of the Hudson volcanic explosive activity, thus allowing a better estimate of the eruptive dynamics and the risks associated with the Hudson volcano.
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Forte, Pablo, Lizzette Rodríguez, Mariana Patricia Jácome Paz, Lizeth Caballero García, Yemerith Alpízar Segura, Emilce Bustos, Constanza Perales Moya, Eveling Espinoza, Silvia Vallejo, and Mariano Agusto. "Volcano monitoring in Latin America: taking a step forward." Volcanica 4, S1 (November 1, 2021): vii—xxxiii. http://dx.doi.org/10.30909/vol.04.s1.viixxxiii.
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Monitoring the state of active volcanoes is the foundational component of volcanic risk reduction strategies. To a large extent, these responsibilities rest with volcano observatories. Based on the 11 Reports that constitute this Special Issue—“Volcano Observatories in Latin America”—we provide a comprehensive overview of the work that has been carried out by the observatories in Latin America, a region in which tens of millions of people are exposed to volcanic activity. Since the first steps taken in the 1980s, volcano observatories of the region have made significant progress in assessing and monitoring volcanic activity. Currently, 17 institutions officially contribute to monitoring 135 volcanoes in 10 countries. Along with the improvements in the instrumental, technical, and operational capabilities, advancements have been made in long-term hazard assessment and hazard communication. But despite all the progress accomplished, several challenges and limiting factors still remain, such as the lack of financial resources and training opportunities. Efforts should be focused on increasing the number and quality of monitoring networks. El monitoreo del estado de los volcanes activos es un componente fundamental de las estrategias para la reducción del riesgo volcánico. En gran medida, estas responsabilidades recaen en los observatorios volcánicos. A partir de los 11 Reportes que constituyen este Número Especial –“Observatorios volcanológicos en América Latina”– brindamos un detallado resumen del trabajo llevado adelante por los observatorios en Latinoamérica, una región con decenas de millones de personas expuestas a la actividad volcánica. Desde sus primeros pasos a principios de 1980, los observatorios volcanológicos de la región han logrado avances significativos en la evaluación y vigilancia de la actividad volcánica. Actualmente, 17 instituciones contribuyen oficialmente al monitoreo de 135 volcanes en 10 países. Junto con las mejoras en sus capacidades instrumentales, técnicas y operativas, se produjeron avances también en la evaluación y comunicación de peligros a largo plazo. A pesar del avance logrado, aún persisten desafíos y factores limitantes, como la falta de recursos económicos y oportunidades de capacitación. Los esfuerzos futuros deben centrarse en aumentar el número y la calidad de las redes de monitoreo.
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Wiart, Pierre, and Clive Oppenheimer. "Large magnitude silicic volcanism in north Afar: the Nabro Volcanic Range and Ma?alalta volcano." Bulletin of Volcanology 67, no. 2 (May 25, 2004): 99–115. http://dx.doi.org/10.1007/s00445-004-0362-x.
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Castro Carcamo, Rodolfo Antonio, and Eduardo Gutiérrez. "Volcanic monitoring and hazard assessment in El Salvador." Volcanica 4, S1 (November 1, 2021): 183–201. http://dx.doi.org/10.30909/vol.04.s1.183201.
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The Salvadorean volcanic range forms part of Central America Volcanic Arc and is located on the Pacific ring of fire. El Salvador is a country with at least twenty Holocene-active volcanic structures and where most of the population, including the metropolitan area of San Salvador, live near a volcanic complex. Currently, there are six active volcanoes that are continuously monitored by the Observatorio de Amenazas y Recursos Naturales, which is part of the Ministerio del Medio Ambiente y Recursos Naturales. Volcano monitoring involves seismic, geochemical, and visual monitoring techniques, among others. In addition to volcano monitoring and with the aim of early warning of future eruptions, volcanic hazard maps and networks of local observers have been developed. These initiatives together with the general directorate of civil protection, seek to meet the goal of reducing risk from volcanic activity in El Salvador. La cadena volcánica salvadoreña forma parte del Arco Volcánico de América Central y está localizada dentro de la zona conocida como cinturón de fuego del Pacífico. El Salvador es un país donde se encuentran al menos 20 estructuras volcánicas que han estado activas durante el Holoceno y donde la mayor parte de la población, incluyendo la ciudad capital San Salvador, está ubicada en las proximidades de algún complejo volcánico. Actualmente, seis volcanes activos son continuamente monitoreados por el Observatorio de Amenazas y Recursos Naturales, que es parte del Ministerio del Medio Ambiente y Recursos Naturales. El monitoreo volcánico se realiza mediante técnicas de monitoreo sísmicas, geoquímicas, visuales, entre otras. Como complemento del trabajo de monitoreo, se han desarrollado mapas de amenaza volcánica y redes de observadores locales constituyendo así sistemas de alerta temprana ante futuras erupciones. Estas iniciativas, en conjunto con la dirección general de la protección civil, persiguen el objetivo de reducir el riesgo por actividad volcánica en El Salvador.
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CHERVYAKOVSKIY, Vasiliy Stanislavovich. "Geological features and the first isotopic data of volcanic rocks in the Iset river basin, East-Urals megazone." NEWS of the Ural State Mining University 1 (March 15, 2021): 55–64. http://dx.doi.org/10.21440/2307-2091-2021-1-55-64.
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Relevance of the work. The Iset river basin contains the most extensive outcrops of volcanogenic formations of the Beklenishchevsky complex of the East Ural megazone, the age of which is determined as Early Carboniferous by the ratio of volcanic rocks with faunistically characterized sedimentary deposits. Volcanics here compose flows of andesite-basaltic and andesitic lavas and lava breccias. There are no geochronological dates specifying the age of the rocks, which makes it difficult to assess their role in the formation of the megazone. Therefore, isotopic dating of these formations is very important. Methods. The U – Pb age and data on the geochemistry of zircons were obtained by laser ablation (LA – ICP – MS). Purpose of the research is to study the features of the geological structure, the material composition of volcanic rocks in the Iset river basin, the geochemistry of zircons from andesites and the determination of their isotopic age. Results of the work and the scope of their application. Lava flows of andesites and basaltic andesites with minor amounts of basalts and dacites have tectonic contact with sedimentary rocks of the Early Carboniferous age. The distribution of rare elements in volcanics is typical of supra-subduction formations. Zircons in andesites are represented by prismatic and isometric crystals. Prismatic differences in the nature of the distribution of REE and the content of Li, Ti, Sr, Th, U refer to zircons of magmatic genesis, isometric – to “hydrothermal”. According to the U / Yb – Y ratios, the former correspond to the zircons of the ocean floor, while the latter are related to the continental ones. Isotopic dating of zircons from andesites was carried out for the first time. Their age was 311 million years. The data can be used in geological mapping, as well as in the compilation of large-scale geodynamic maps and diagrams. Conclusions. Volcanic rocks in the Iset river basin were formed in supra-subduction continental-marginal geodynamic conditions that took place in the Urals in the Carboniferous. The obtained value of the age of zircons from andesites, possibly, fixes the stage of their transformation. Keywords: East-Ural megazone, volcanic rocks, zircon, isotopic age.
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Martinez, Amancay, Adrian Gallardo, Laura Giambiagi, and Laura Tobares. "The Choiyoi Group in the Cordón del Plata range, western Argentina: structure, petrography and geochemistry." Earth Sciences Research Journal 24, no. 2 (April 1, 2020): 121–32. http://dx.doi.org/10.15446/esrj.v24n2.79515.
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The Choiyoi Group from the Permo-Triassic, is one of the most conspicuous volcano-sedimentary suites of southern South America, considered critical to understand the geological evolution of the western margins of Gondwana. In this regard, petrography, geochemistry, and structural data were examined to better elucidate the physical character and emplacement conditions of the unit in the Cordon del Plata range, within the Frontal Cordillera of Mendoza, Argentina. The site is representative of the magmatism and deformation through different Andean cycles. Results of the study indicate three lithological facies of increasing acidity upwards. Mafic units consist of basalts, andesite and andesitic breccias at the base of the sequence. Felsic rocks such as rhyodacites, granites and welded tuffs are predominant above. The fault zone of La Polcura – La Manga is the most prominent structural feature in the region, which presumably controlled the emplacement of breccias and ignimbrites within the middle and upper members. These compositional variations suggest a magma evolution from subduction to a rifting environment after the San Rafael orogeny in the Late Palaeozoic. In this line, the Lower Choiyoi was observed to overlie the San Rafael structures indicating thus, that compression ceased before the volcanic extrusion. Geochemistry data indicate that mafic rocks are mostly high-potassium, calc-alkaline volcanics derived from the mantle wedge above the subduction zone. In contrast, the felsic rocks range from high-potassium rhyolites to shoshonites, typically depleted in Eu. This indicate partial melting of a lithospheric mantle in an average to thin crust.
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Infante-Paez, Lennon, and Kurt J. Marfurt. "Seismic expression and geomorphology of igneous bodies: A Taranaki Basin, New Zealand, case study." Interpretation 5, no. 3 (August 31, 2017): SK121—SK140. http://dx.doi.org/10.1190/int-2016-0244.1.
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Very little research has been done on volcanic rocks by the oil industry due to the misconception that these rocks cannot be “good reservoirs.” However, in the past two decades, significant quantities of hydrocarbons have been produced from volcanic rocks in China, New Zealand, and Argentina. In frontier basins, volcanic piles are sometimes misinterpreted to be hydrocarbon anomalies and/or carbonate buildups. Unlike clastic and carbonate systems, the 3D seismic geomorphology of igneous systems is only partially documented. We have integrated 3D seismic data, well logs, well reports, core data, and clustering techniques such as self-organizing maps to map two distinct facies (pyroclastic and lava flows), within a Miocene submarine volcano in the Taranaki Basin, New Zealand. Three wells; Kora-1–3 drilled the pyroclastic facies within the volcano encountering evidence of a petroleum system, whereas the Kora-4 well drilled the lava-flow facies, which was barren of hydrocarbons. By integrating results from geochemistry and basin modeling reports prepared for Crown Mineral, New Zealand, we concluded that the reason that Kora-4 was dry was due to a lack of source charge — not to the absence of reservoir quality. Moreover, the Kora-1 well drilled a thick sequence (>[Formula: see text]) of pyroclastic flows in this submarine volcano by chance and found high peaks of gas in the mudlogs near the top 25 m of this sequence. A long-term test in this upper volcanic section resulted in 32 API oil flow of 668 barrels of oil per day for 254 h — a result that challenges the misconception that volcanic rocks cannot be good reservoirs.
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Mulyaningsih, Sri, Sutikno Bronto, Arie Kusniadi, Lilis Apriyanti, L. Budiyanto, and Danis Agoes Wiloso. "The Petrology and Volcano-Stratigraphy of The Muria-Peninsula High-K Volcanic Rocks, Central Java, Indonesia." Journal of Geoscience, Engineering, Environment, and Technology 7, no. 2 (June 30, 2022): 69–80. http://dx.doi.org/10.25299/jgeet.2022.7.2.9602.
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The Muria-Peninsula is a Quaternary volcano located in the northern Sunda arc. Its activity was controlled under high potassic and very high potassic magma series resulting in leucite-rich trachyte and pyroxene-rich basaltic-andesite. It is a strato-type volcano that is composed of lava, breccia, and tuff layers, and some dikes have some volcanic craters and maars varying in age and composition. The study area is covering the volcanoes of Muria, Genuk, and Patiayam. This paper aims to describe the petrology, mineralogy, and volcano-stratigraphy of the different volcanic materials. The data and materials were sourced from the primary and secondary data. The methods are field mapping, stratigraphy measurements, collecting samples, thin section analyses, and major element geochemistry using X-Ray fluorescence (XRF). The results describe two groups of volcanic rocks consisting of pyroxene-rich andesitic-basaltic volcanic materials and leucite-rich trachytic volcanic materials. Augite presents in the andesitic basalt together with small grains of olivine and a few anorthite and foid minerals. Aegirine (Na-Pyroxene) is present in the leucite-rich trachyte that is often associated with biotite and hornblende. Na-Ca Plagioclase such as labradorite-andesine is often present in the basaltic-trachy-andesite that is usually rarely leucite. The major elements show high-K volcanic rocks with % K2O is 4-5.9% and very high-K volcanic rocks (with % K2O is between 6-8.24%) and low-K volcanic rocks that contain % K2O is 2-3,9%. There are two groups of high-K to very high-K volcanic materials consisting of silicic-rich volcanic materials (~57-64% of SiO2) and low-silicic volcanic materials (~46-50%). The TAS diagram identifies tephrite, phonolite, and trachyte. Stratigraphic data identifies calcareous sediments of the Bulu Formation as the basement rocks of the Muria trachyandesite. Beds of pumice-rich volcanic breccia of the Ujungwatu Formation are the basement rocks of the basanite-tephrite of the Genuk Volcano, and the tuff of the Ujungwatu is also exposed consisting of the basanite-tephritic-phonolite of the Patiayam Volcano. The leucite-like feldspars are very common in the andesite lava and dikes that compose the crater of Muria. Most of the Muria volcanic materials are rarely in leucite, while some maars contain pumice-rich pyroclastic flows and basaltic lava. The results of the major elemental analysis of the Muria materials indicate that the rock tends to be of medium to high K affinity (~2% K2O). The Genuk and older Muria are consisting of leucite-rich tephrite-phonolite. It was two periods of magmatic series developed in the Muria-Peninsula that was resulting in the high-K to very high-K magmatism and the medium K Kalk-alkaline magmatism.
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Kumarapeli, P. Stephen, Greg R. Dunning, Hillar Pintson, and Jim Shaver. "Geochemistry and U–Pb zircon age of comenditic metafelsites of the Tibbit Hill Formation, Quebec Appalachians." Canadian Journal of Earth Sciences 26, no. 7 (July 1, 1989): 1374–83. http://dx.doi.org/10.1139/e89-117.
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Metafelsites in Waterloo area, Quebec, represent the only known silicic volcanic rocks in the predominantly basaltic Tibbit Hill Formation. Low-grade metamorphism accompanied by hydration and albitization has converted the felsic volcanic rocks mainly to muscovite–quartz–albite schists. The volcanic parent of these metafelsites was formed partly as lava flows and partly as tuffs. The principal compositional type was a comendite. A component of intermediate rocks is also present but its extent is undetermined and probably minor. U–Pb zircon studies of the metafelsites have yielded a reliable age of [Formula: see text]. This Early Cambrian age is probably representative of the age of the Tibbit Hill Formation as a whole.The Tibbit Hill Formation accumulated at one of the clearest examples of a RRR (rift–rift–rift) triple junction–the Sutton Mountains triple junction–of the continental rift system formed as a prelude to the opening of the Iapetus Ocean. Its volcanic rocks are products of the youngest major episode of rift-related volcanism known from the continental margin of Laurentia. The volcanic event may have occurred as a harbinger of the onset of sea-floor spreading at the Sutton Mountains triple junction.
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D’hulst, Alan, Georges Beaudoin, Michel Malo, Marc Constantin, and Pierre Pilote. "Geochemistry of Sainte-Marguerite volcanic rocks: implications for the evolution of Silurian–Devonian volcanism in the Gaspé Peninsula." Canadian Journal of Earth Sciences 45, no. 1 (January 1, 2008): 15–29. http://dx.doi.org/10.1139/e07-012.
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The Lower Devonian Sainte-Marguerite volcanic rocks are part of a Silurian–Devonian volcanic sequence deposited between the Taconian and Acadian orogenies in the Gaspé Peninsula, Quebec, Canada. The Sainte-Marguerite unit includes basaltic and dacitic lava flows with calc-alkaline and volcanic-arc affinities. Such affinities are also recorded by the trace-element signature in Lower Silurian and most Lower Devonian volcanic units of the Gaspé Peninsula. However, most of the other Silurian–Devonian volcanic rocks occurring in the Gaspé Peninsula have been previously interpreted to have erupted in an intracontinental setting. A back-arc setting for the Gaspé Peninsula between the Taconian and Acadian orogenies could account for these subduction volcanic-arc signatures, though a metasomatized lithospheric mantle magma source, unrelated to subduction, cannot be excluded. Lower Silurian and Lower Devonian volcanic rocks in the central part of the Gaspé Peninsula show an arc affinity, whereas Upper Silurian and Lower to Middle Devonian volcanic rocks, located in the south and north of the Gaspé Peninsula, respectively, show a within-plate affinity. The Lower Devonian Archibald Settlement and Boutet volcanic rocks of the southern and northern Gaspé Peninsula, respectively, show a trend toward a within-plate affinity. This suggests that within-plate volcanism migrated from south to north through time in an evolving back-arc environment and that the subduction signature of Lower Silurian and Lower Devonian rocks results from a source that melted only under the central part of the Gaspé Peninsula.
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Rosa, D. R. N., A. A. Finch, T. Andersen, and C. M. C. Inverno. "U-Pb geochronology of felsic volcanic rocks hosted in the Gafo Formation, South Portuguese Zone: the relationship with Iberian Pyrite Belt magmatism." Mineralogical Magazine 72, no. 5 (October 2008): 1103–18. http://dx.doi.org/10.1180/minmag.2008.072.5.1103.
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AbstractFelsic volcanic rocks exposed in the Frasnian Gafo Formation, in the Azinhalinho area of Portugal, display very similar geochemical signatures to volcanic rocks from the Iberian Pyrite Belt (IPB). located immediately to the south. The similarities include anomalously low high field-strength elements (HFSE) concentrations, possibly caused by low-temperature crustal melting, which translate into classification problems.A geochronological study, using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of zircon grains from these rocks, has provided concordia ages of 356±1.5 Ma and 355±2.5 Ma for two samples of rhyodacite porphyry, and 356±1.4 Ma for a granular rhyodacite. These results show that volcanism at Azinhalinho was broadly contemporaneous with IPB volcanism, widely interpreted as being of Famennian to Visean age. Considering that the host rocks of the Azinhalinho volcanic rocks are Frasnian, and therefore deposited synchronously with the Upper Devonian Phyllite-Quartzite Group sedimentation in the IPB basin, the radiometric ages imply that the Azinhalinho felsic rocks are intrusive and likely represent conduits or feeders to the volcanism of the IPB.
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Watt, Sebastian F. L., David M. Pyle, and Tamsin A. Mather. "Geology, petrology and geochemistry of the dome complex of Huequi volcano, southern Chile." Andean Geology 38, no. 2 (August 9, 2011): 335. http://dx.doi.org/10.5027/andgeov38n2-a05.
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Huequi, a little-known volcano in the southern part of the Andean southern volcanic zone (SSVZ), shows a regionally unusual eruption style, mineralogy and geochemistry. The volcano comprises multiple highly-eroded lava domes. Past eruptions were accompanied by relatively minor explosive activity, most recently from 1890-1920. The rocks erupted by Huequi range from basaltic andesite to dacite, and are highly distinctive when compared to other volcanoes of the SSVZ, being K-poor and Al-rich, and containing euhedral hornblende phenocrysts. Overall compositions suggest a notably water-rich magma source, evolving through high levels of fractionation and subsequent degassing to produce highly porphyritic dome-forming andesites. The ultimate causes of water-rich magmas at this point in the arc remain unclear.
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Andrew, Anne, and Colin I. Godwin. "Lead- and strontium-isotope geochemistry of Paleozoic Sicker Group and Jurassic Bonanza Group volcanic rocks and Island Intrusions, Vancouver Island, British Columbia." Canadian Journal of Earth Sciences 26, no. 5 (May 1, 1989): 894–907. http://dx.doi.org/10.1139/e89-072.
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Whole-rock and galena lead-isotope analyses have been obtained from the Sicker Group Paleozoic island-arc volcanic package and from a Jurassic island-arc represented by the Bonanza Group volcanics and Island Intrusions. Galena lead-isotope analyses from the volcanogenic ore deposits at the Buttle Lake mining camp in the Sicker Group provide estimates of the initial lead ratios for the Sicker Group. Lead-isotope signatures are uniform within each of the major orebodies, but the Myra orebody is less radiogenic than the older H–W orebody. This has major significance in terms of ore genesis for these important deposits.There are significant differences in isotopic composition between the Sicker Group and Devonian island-arc type rocks in the Shasta district, California, which rules out direct correlations between the rock units of these two areas. Relatively high initial values of 207Pb/204Pb (> 15.56) and 208Pb/204Pb (> 38.00) suggest that large quantities of crustal lead must have been involved in the formation of the Sicker Group volcanic rocks. Thus it is proposed that the trench related to the Paleozoic island arc had a substantial input of continental detritus and may have lain near a continent.The Jurassic island arc is characterized by low 207Pb/204Pb ratios (< 15.59), suggesting a more primitive arc environment than for the Paleozoic arc. Bonanza Group volcanic rocks contain lead that is less radiogenic than lead in the Island Intrusions. Present and initial lead-isotope ratios of both the Bonanza Group volcanics and Island intrusions follow the same trend, supporting the hypothesis that they are comagmatic. Lead isotopes from a galena vein within the Island Copper porphyry deposit plot with the initial ratios for Bonanza Group volcanics and Island Intrusions. This confirms the hypothesis that this mineralization is related to the Jurassic island-arc volcanic event.Initial lead-isotope ratios for the Jurassic rock suite form a linear array on both 207Pb/204Pb versus 206Pb/204Pb and 208Pb/204Pb versus 206Pb/204Pb plots. If interpreted as due to isotopic mixing, the more radiogenic end member has a composition that is lower in 207Pb/204Pb and higher in 206Pb/204Pb than typical upper continental crust. Assimilation of Sicker Group material during the emplacement of the Jurassic arc can explain the mixing trend.
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Abbaspour Shirjoposht, Leila, Sayed Jamal al-Din Sheikh Zakariaee, Mohammad Reza Ansari, and Mohammad Hashem Emami. "Geochemistry of mid- upper eocene intra-continental alkaline volcanic range, south part of central alborz mountains, north of Iran." Nexo Revista Científica 33, no. 02 (December 31, 2020): 511–24. http://dx.doi.org/10.5377/nexo.v33i02.10788.
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The Ziaran volcanic Belt (ZVB), North of Iran contains a number of intra-continental alkaline volcanic range situated on South part of central Alborz Mountains, formed along the localized extensional basins developed in relation with the compressional regime of Eocene. The mid-upper Eocene volcanic suite comprises the extracted melt products of adiabatic decompression melting of the mantle that are represented by small volume intra-continental plate volcanic rocks of alkaline volcanism and their evaluated Rocks with compositions representative of mantle-derived, primary (or near-primary) melts. Trace element patterns with significant enrichment in LILE, HFSE and REEs, relative to Primitive Mantle. Chondrite-normalized of rare earth elements and enrichment in incompatible elements and their element ratios (e. g. LREE/HREE, MREE/HREE, LREE/MREE) shown these element modelling indicates that the magmas were generated by comparably variable degrees of partial melting of garnet lherzolite and a heterogeneous asthenospheric, OIB mantle sources.
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Dostal, J., V. Gale, and B. N. Church. "Upper Triassic Takla Group volcanic rocks, Stikine Terrane, north-central British Columbia: geochemistry, petrogenesis, and tectonic implications." Canadian Journal of Earth Sciences 36, no. 9 (September 1, 1999): 1483–94. http://dx.doi.org/10.1139/e99-048.
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The Upper Triassic Takla Group volcano-sedimentary assemblage is part of the Stikine Terrane of the Intermontane Belt in the Canadian Cordillera and covers an area of more than 30 000 km2 in a belt up to 50 km wide and more than 800 km long. In the McConnell Creek area of north-central British Columbia, the assemblage consists of plagioclase-clinopyroxene-phyric, dominantly basaltic to andesitic flows and pyroclastic rocks, interlayered with volcanogenic sedimentary rocks. Compositionally, the volcanic rocks are intermediate between tholeiitic and calc-alkaline. Their mantle-normalized trace element patterns are characterized by a moderate large-ion lithophile element enrichment and Nb and Ti depletion, suggesting that magmatism occurred in a volcanic-arc setting. Flat, heavy rare earth element chondrite-normalized patterns with (La/Yb)n ratios from 2 to 4.5 suggest that the parent magma was produced by mantle melting in the spinel stability field. The low Sr isotopic ratios (87Sr/86Sri approximately equal to 0.7033-0.7043) and positive εNd values (~ +7) indicate that an older sialic crust was not involved in their genesis. A coeval and compositionally similar volcano-sedimentary assemblage, also of the Takla Group, occurs in the adjacent Quesnel Terrane, in fault contact with the Stikinian Takla Group. Chemical resemblances between the Takla Groups of the Stikine and Quesnel terranes suggest that the volcanic assemblages may have had similar source compositions and melt histories. These results emphasize larger scale similarities between the Stikine and Quesnel terranes and suggest the Upper Triassic volcanic suites represent different fragments of the same early Mesozoic arc system.
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Grib, E. N., V. L. Leonov, and A. B. Perepelov. "The Karymskii Volcanic Center: Volcanic rock geochemistry." Journal of Volcanology and Seismology 3, no. 6 (December 2009): 367–87. http://dx.doi.org/10.1134/s0742046309060013.
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