Cenozoic Magmatism of the North-Eastern Eurasian Margin: The Role of Lithosphere Versus Asthenosphere |
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Authors: | OKAMURA SATOSHI; ARCULUS RICHARD J; MARTYNOV YURI A |
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Institution: | 1 SAPPORO CAMPUS, HOKKAIDO EDUCATION UNIVERSITY, SAPPORO 002-8502, JAPAN
2 DEPARTMENT OF EARTH AND MARINE SCIENCES, AUSTRALIAN NATIONAL UNIVERSITY, CANBERRA, ACT 0200, AUSTRALIA
3 FAR EAST GEOLOGICAL INSTITUTE, VLADIVOSTOK 690022, RUSSIA |
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Abstract: | 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 |
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Keywords: | : north-eastern Eurasian margin Sikhote-Alin Sakhalin Japan Sea opening subcontinental lithosphere asthenosphere |
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