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Susumu Nohda - One of the best experts on this subject based on the ideXlab platform.
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rbsr dating of acidic rocks from the middle part of the inner zone of southwest japan tectonic implications for the migration of the cretaceous to paleogene Igneous Activity
Chemical Geology, 1993Co-Authors: Yasutaka Terakado, Susumu NohdaAbstract:Abstract RbSr age determinations by mineral and whole-rock isochron methods have been performed on Cretaceous to Paleogene granitic and rhyolitic rocks from the middle part of the Inner Zone of southwest Japan in order to examine some chronological problems and tectonic models for the migration of Igneous Activity. Our chronological results include: (1) isotopic homogenization of granitic and rhyolitic rocks in the Miyazu-Izushi area was disturbed by mixing of acidic and basic magmas; (2) the Rokko granite was emplaced at 77.8 Ma and reheated at 72 Ma; (3) mineral isochron ages obtained for the acidic volcanic rocks range from 62.6 to 85.8 Ma and are considered to date the time of eruption. Igneous Activity migrated eastward from ∼ 95 Ma to ∼ 70 Ma, which may be related to a similar eastward migration of the development of sedimentary basins in fore-arc regions. The observed eastward migration has been discussed with relevance to a ridge subduction model in which the heated position by subducted ridge moved from west to east. Although the cause for the migration of the Igneous Activity is poorly understood, several difficulties with the simple ridge subduction model are pointed out.
Michele Lustrino - One of the best experts on this subject based on the ideXlab platform.
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eocene miocene Igneous Activity in provence se france 40 ar 39 ar data geochemical petrological constraints and geodynamic implications
Lithos, 2017Co-Authors: Michele Lustrino, Lorenzo Fedele, Samuele Agostini, Gianfranco Di Vincenzo, Vincenzo Brescia MorraAbstract:Abstract Provence (SE France) was affected by two main phases of sporadic Igneous Activity during the Cenozoic. New 40 Ar/ 39 Ar laser step-heating data constrain the beginning of the oldest phase to late Eocene (40.82 ± 0.73 Ma), with Activity present until early Miocene (~ 20 Ma). The products are mainly andesites, microdiorites, dacites and basaltic andesites mostly emplaced in the Agay-Esterel area. Major- and trace-element constraints, together with Sr Nd Pb isotopic ratios suggest derivation from a sub-continental lithosphere mantle source variably modified by subduction-related metasomatic processes. The compositions of these rocks overlap those of nearly coeval (emplaced ~ 38–15 Ma) late Eocene-middle Miocene magmatism of Sardinia. The genesis of dacitic rocks cannot be accounted for by simple fractional crystallization alone, and may require interaction of evolved melts with lower crustal lithologies. The youngest phase of Igneous Activity comprises basaltic volcanic rocks with mildly sodic alkaline affinity emplaced in the Toulon area ~ 10 Myr after the end of the previous subduction-related phase. These rocks show geochemical and isotopic characteristics akin to magmas emplaced in intraplate tectonic settings, indicating a sub-lithospheric HiMu + EM-II mantle source for the magmas, melting approximately in the spinel/garnet-lherzolite transition zone. New 40 Ar/ 39 Ar laser step-heating ages place the beginning of the volcanic Activity in the late Miocene–Pliocene (5.57 ± 0.09 Ma). The emplacement of “anorogenic” Igneous rocks a few Myr after rocks of orogenic character is a common feature in the Cenozoic districts of the Central-Western Mediterranean area. The origin of such “anorogenic” rocks can be explained with the activation of different mantle sources not directly modified by subduction-related metasomatic processes, possibly located in the sub-lithospheric mantle, and thus unrelated to the shallower lithospheric mantle source of the “orogenic” magmatism.
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the central western mediterranean anomalous Igneous Activity in an anomalous collisional tectonic setting
Earth-Science Reviews, 2011Co-Authors: Michele Lustrino, Svend Duggen, Claudio L RosenbergAbstract:Abstract The central-western Mediterranean area is a key region for understanding the complex interaction between Igneous Activity and tectonics. In this review, the specific geochemical character of several ‘subduction-related’ Cenozoic Igneous provinces are described with a view to identifying the processes responsible for the modifications of their sources. Different petrogenetic models are reviewed in the light of competing geological and geodynamic scenarios proposed in the literature. Plutonic rocks occur almost exclusively in the Eocene–Oligocene Periadriatic Province of the Alps while relatively minor plutonic bodies (mostly Miocene in age) crop out in N Morocco, S Spain and N Algeria. Igneous Activity is otherwise confined to lava flows and dykes accompanied by relatively greater volumes of pyroclastic (often ignimbritic) products. Overall, the Igneous Activity spanned a wide temporal range, from middle Eocene (such as the Periadriatic Province) to the present (as in the Neapolitan of southern Italy). The magmatic products are mostly SiO2-oversaturated, showing calcalkaline to high-K calcalcaline affinity, except in some areas (as in peninsular Italy) where potassic to ultrapotassic compositions prevail. The ultrapotassic magmas (which include leucitites to leucite-phonolites) are dominantly SiO2-undersaturated, although rare, SiO2-saturated (i.e., leucite-free lamproites) appear over much of this region, examples being in the Betics (southeast Spain), the northwest Alps, northeast Corsica (France), Tuscany (northwest Italy), southeast Tyrrhenian Sea (Cornacya Seamount) and possibly in the Tell region (northeast Algeria). Excepted for the Alpine case, subduction-related Igneous Activity is strictly linked to the formation of the Mediterranean Sea. This Sea, at least in its central and western sectors, is made up of several young ( Compared to classic collisional settings (e.g., Himalayas), the central-western Mediterranean area shows a range of unusual geological and magmatological features. These include: a) the rapid formation of extensional basins in an overall compressional setting related to Africa-Europe convergence; b) centrifugal wave of both compressive and extensional tectonics starting from a ‘pivotal’ region around the Gulf of Lyon; c) the development of concomitant Cenozoic subduction zones with different subduction and tectonic transport directions; d) subduction ‘inversion’ events (e.g., currently along the Maghrebian coast and in northern Sicily, previously at the southern paleo-European margin); e) a repeated temporal pattern whereby subduction-related magmatic Activity gives way to magmas of intraplate geochemical type; f) the late-stage appearance of magmas with collision-related ‘exotic’ (potassic to ultrapotassic) compositions, generally absent from simple subduction settings; g) the relative scarcity of typical calcalkaline magmas along the Italian peninsula; h) the absence of Igneous Activity where it might well be expected (e.g., above the hanging-wall of the Late Cretaceous–Eocene Adria–Europe subduction system in the Alps); i) voluminous production of subduction-related magmas coeval with extensional tectonic regimes (e.g., during Oligo-Miocene Sardinian Trough formation). To summarize, these salient central-western Mediterranean features, characterizing a late-stage of the classic ‘Wilson Cycle’ offer a ‘template’ for interpreting magmatic compositions in analogous settings elsewhere.
Yasutaka Terakado - One of the best experts on this subject based on the ideXlab platform.
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rbsr dating of acidic rocks from the middle part of the inner zone of southwest japan tectonic implications for the migration of the cretaceous to paleogene Igneous Activity
Chemical Geology, 1993Co-Authors: Yasutaka Terakado, Susumu NohdaAbstract:Abstract RbSr age determinations by mineral and whole-rock isochron methods have been performed on Cretaceous to Paleogene granitic and rhyolitic rocks from the middle part of the Inner Zone of southwest Japan in order to examine some chronological problems and tectonic models for the migration of Igneous Activity. Our chronological results include: (1) isotopic homogenization of granitic and rhyolitic rocks in the Miyazu-Izushi area was disturbed by mixing of acidic and basic magmas; (2) the Rokko granite was emplaced at 77.8 Ma and reheated at 72 Ma; (3) mineral isochron ages obtained for the acidic volcanic rocks range from 62.6 to 85.8 Ma and are considered to date the time of eruption. Igneous Activity migrated eastward from ∼ 95 Ma to ∼ 70 Ma, which may be related to a similar eastward migration of the development of sedimentary basins in fore-arc regions. The observed eastward migration has been discussed with relevance to a ridge subduction model in which the heated position by subducted ridge moved from west to east. Although the cause for the migration of the Igneous Activity is poorly understood, several difficulties with the simple ridge subduction model are pointed out.
Franco Pirajno - One of the best experts on this subject based on the ideXlab platform.
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mesozoic metallogeny in east china and corresponding geodynamic settings an introduction to the special issue
Ore Geology Reviews, 2011Co-Authors: Jingwen Mao, Franco Pirajno, Nigel J CookAbstract:Abstract The giant East China Mesozoic metallogenic province hosts some of the World’s largest resources of tungsten, tin, molybdenum, antimony and bismuth. Ores of gold, silver, mercury, lead, zinc, copper, uranium and iron are also of major importance. The province and its constituent metallogenic belts or regions (South China; Middle–Lower Yangtze River Valley; East Qinling–Dabie; Interior of North China Craton; Yan-Liao and North-east China) are the products of several pulses of Igneous Activity and mineralisation between ~240 and ~80 Ma. Each successive stage has produced a distinctive suite of deposits that can be readily related to the geodynamic evolution of the region during the Mesozoic. This geodynamic evolution is linked to a complex series of tectonic events, involving far-field-subduction, plate collisions, crustal thickening, post-collision collapse and rifting.
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geology and tectonic evolution of the palaeoproterozoic bryah padbury and yerrida basins formerly glengarry basin western australia implications for the history of the south central capricorn orogen
Precambrian Research, 1998Co-Authors: Franco Pirajno, S A Occhipinti, C P SwagerAbstract:Abstract The Palaeoproterozoic Bryah, Padbury and Yerrida Basins are situated along the northwestern margin of the Archaean Yilgarn Craton, central Western Australia. These basins form part of the Capricorn Orogen, which developed between 2.0 and 1.8 Ga as a result of the collision between the Archaean Pilbara and Yilgarn cratons. The Bryah, Padbury and Yerrida Basins, which at the present day cover a total area of ca 20 000 km2, were formerly considered as one geological entity, the Glengarry Basin. These three basins are characterized by distinct stratigraphy, Igneous Activity, structural and metamorphic history, and mineral deposit types. Igneous Activity only affected the Bryah and Yerrida Basins, with voluminous eruptions of tholeiitic magma. In the Bryah Basin tholeiitic volcanic rocks are Mg-rich and have mixed MORB to oceanic island chemical signatures, but with a boninitic (subduction-related) component. In the Yerrida Basin tholeiites are Fe-rich and have chemical signatures that suggest a mixed tectonic environment ranging from oceanic to continental. It is considered possible that this tholeiitic magmatism is related to a mantle plume. Two models for the tectonic evolution of the Bryah, Padbury and Yerrida Basins are proposed: (1) the Bryah and Yerrida Basins were formed in a back-arc setting, whilst the Padbury Basin developed as a retro-arc foreland basin over the Bryah Basin; and/or (2) strike-slip transtension, during and following the Pilbara-Yilgarn collision, created the Bryah and Yerrida strike-slip pull-apart Basins. A change in regional stress regime resulted in the inversion of the basins and the development of a foreland basin in the northwest (Padbury Basin).
Dandan Chen - One of the best experts on this subject based on the ideXlab platform.
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revisiting early middle jurassic Igneous Activity in the nanling mountains south china geochemistry and implications for regional geodynamics
Journal of Asian Earth Sciences, 2013Co-Authors: Jianren Mao, Xilin Zhao, Kai Liu, Dandan ChenAbstract:Abstract Early–Middle Jurassic Igneous rocks (190–170 Ma) are distributed in an E–W-trending band within the Nanling Tectonic Belt, and have a wide range of compositions but are only present in limited volumes. This scenario contrasts with the uniform but voluminous Middle–Late Jurassic Igneous rocks (165–150 Ma) in this area. The Early–Middle Jurassic rocks include oceanic-island basalt (OIB)-type alkali basalts, tholeiitic basalts and gabbros, bimodal volcanic rocks, syenites, A-type granites, and high-K calc–alkaline granodiorites. Geochemical and isotopic data indicate that alkaline and tholeiitic basalts and syenites were derived from melting of the asthenospheric mantle, with asthenosphere-derived magmas mixing with variable amounts of magmas derived from melting of metasomatized lithospheric mantle. In comparison, A-type granites in the study area were probably generated by shallow dehydration-related melting of hornblende-bearing continental crustal rocks that were heated by contemporaneous intrusion of mantle-derived basaltic magmas, and high-K calc-alkaline granodiorites resulted from the interaction between melts from upwelling asthenospheric mantle and the lower crust. The Early–Middle Jurassic magmatic event is spatially variable in terms of lithology, geochemistry, and isotopic systematics. This indicates that the deep mantle sources of the magmas that formed these Igneous rocks were significantly heterogeneous, and magmatism had a gradual decrease in the involvement of the asthenospheric mantle from west to east. These variations in composition and sourcing of magmas, in addition to the spatial distribution and the thermal structure of the crust–mantle boundary during this magmatic event, indicates that these Igneous rocks formed during a period of rifting after the Indosinian Orogeny rather than during subduction of the paleo-Pacific oceanic crust.
