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Cenozoic Magmatism of the North-Eastern Eurasian Margin: The Role of Lithosphere Versus Asthenosphere 总被引:6,自引:1,他引:6
Sikhote-Alin and Sakhalin are located in the Russian Far Eastflank of the northernmost part of the Sea of Japan. Magmatismin this region preceded, was concurrent with, and continuedafter the extension and sea-floor spreading (2518 Ma)that formed the Sea of Japan. Among the Sikhote-Alin and Sakhalinvolcanic suites, EoceneOligocene (5524 Ma) lavasare characterized by greater large ion lithophile element andrare earth element enrichments compared with EarlyMid-Miocene(2315 Ma) tholeiites, and also show a depletion in highfield strength elements (HFSE). The geochemical characteristicsof the EoceneOligocene and EarlyMid-Miocene basaltsare consistent with migration of the locus of magma generationbeneath the Sikhote-Alin and Sakhalin areas from subduction-modifiedlithospheric mantle into mid-ocean ridge basalt (MORB)-sourceasthenosphere as spreading in the Sea of Japan progressed. Mid-MiocenePliocene(145 Ma) lavas, erupted following the opening of theSea of Japan, include alkaline and sub-alkaline basalts withwide ranges in trace-element abundances, varying between twodistinct end-members: (1) volumetrically minor alkaline basaltswith ZrNb and SrNbPb isotope compositionssimilar to asthenosphere-derived, intra-platehotspotbasalts from eastern China; (2) more abundant, lithosphere-derived,low-alkali tholeiites depleted in HFSE. The similarity of isotopicsignatures coupled with systematically different rare earthelement (REE) abundances in the Mid-MiocenePliocene andChinese basalts are best modeled by similar extents of meltingof spinel lherzolite and garnet lherzolite, respectively. TheMid-MiocenePliocene alkali basalts were generated bysmall degrees of partial melting of hot asthenosphere beneatha thin lithospheric lid; the thin lithospheric mantle beneaththe Sikhote-Alin and Sakhalin region resulted from heating andextension associated with the opening of the Sea of Japan. KEY WORDS: north-eastern Eurasian margin; Sikhote-AlinSakhalin; Japan Sea opening; subcontinental lithosphere; asthenosphere 相似文献
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Metamorphic evolution of the Susunai metabasites in southern Sakhalin, Russian Republic 总被引:2,自引:0,他引:2
M. SAKAKIBARA H. OFUKA G. KIMURA H. ISHIZUKA S. MIYASHITA M. OKAMURA & O. A. MELINIKOV 《Journal of Metamorphic Geology》1997,15(5):565-580
The Susunai Complex of southeast Sakhalin represents a subduction-related accretionary complex of pelitic and basic rocks. Two stages of metamorphism are recognized: (1) a local, low- P / T event characterized by Si-poor calcic amphiboles; (2) a regional, high- P / T event characterized by pumpellyite, actinolite, epidote, sodic amphibole, sodic pyroxene, stilpnomelane and aragonite. The major mineral assemblages of the high- P / T Susunai metabasites contain pumpellyite+epidote+actinolite+chlorite, epidote+actinolite+chlorite, epidote+Na-amphibole+Na-pyroxene+chlorite+haematite. The Na- amphibole is commonly magnesioriebeckite. The Na-pyroxene is jadeite-poor aegirine to aegirine-augite. Application of empirically and experimentally based thermobarometers suggests peak conditions of T =250–300 °C, P= 4.7–6 kbar. Textural relationships in Susunai metabasite samples and a petrogenetic grid calculated for the Fe3+ -rich basaltic system suggest that pressure and temperature increased during prograde metamorphism. 相似文献
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