Composite dikes in four successive granitoid suites from Transbaikalia, Russia: The effect of silicic and mafic magma interaction on the chemical features of granitoids

Autor: N.S. Karmanov, Bor-ming Jahn, B.A. Litvinovsky, S.V. Kanakin, A.N. Zanvilevich, Ye. Vapnik, S.M. Wickham
Rok vydání: 2017
Předmět:
Zdroj: Journal of Asian Earth Sciences. 136:16-39
ISSN: 1367-9120
DOI: 10.1016/j.jseaes.2016.12.037
Popis: In the study area of 60 by 15 km, located south of Lake Baikal, coeval mafic rocks form small intrusive bodies, synplutonic dikes and composite mafic-felsic dikes in four successive Late Paleozoic and Early Mesozoic syenite and granite suites. Mafic rocks in all suites are monzogabbro with similar mineral and chemical composition. This attests that mantle-derived mafic magmas produced at post-collisional and within-plate tectonic settings were not noticeably distinguished in chemical composition within a time interval of about 60–65 m.y. Detailed study of the interaction zones between synplutonic mafic magma and host syenite at two key localities allowed recognition of syenite remelting stage at about 900–950 °C. Remelting was accompanied by Sr and Ba enrichment by diffusion from the adjacent mafic magma. Diffusive transport of Ba also caused enhanced BaO content, 0.37–0.54 wt.%, in alkali feldspars of the newly-formed syenite. Remelting of the host syenite was followed by mingling, chemical interaction and mixing of mafic and silicic magmas within the contact zone. The results of petrographic and geochemical study of the composite and synplutonic dikes are used to interpret the chemical features of the large, about 1000 km2, essentially syenitic Ust-Khilok pluton. Two varieties of syenite are recognized in the pluton, one with Ba
Databáze: OpenAIRE
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