PERMO-TRIASSIC PLUME MAGMATISM IN THE KUZNETSK BASIN ( Central Asia ): GEOLOGY, GEOCHRONOLOGY AND GEOCHEMISTRY
M.M. Buslova, I.Yu. Safonovaa, G.S. Fedoseeva, M. Reichowb, C. Daviesc, and G.A. Babind
a V.S. Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Sciences, prosp. Akad. Koptyuga 3, Novosibirsk, 630090, Russia
b Leicester University, University Rd., Leicester, LE1 7RH, UK
c Woodside Ltd., St. George St. 240, Perth, WA 6000, Australia
d FGUP SNIIGGiMS, Krasnyi prosp. 67, Novosibirsk, 630091, Russia
Keywords: Basaltic magmatism, Siberian superplume, Permian-Triassic boundary, Ar-Ar dating, trace-element composition of basalts
Pages: 1021-1036
Abstract
The Kuznetsk Basin is located in the northern part of the Altai-Sayan Folded Area (ASFA), southwestern Siberia. Its Late Permian-Middle Triassic section includes basaltic stratum-like bodies, sills, formed at 250-248 Ma. The basalts are medium- and high-Ti tholeiites enriched in Nb and La. Compositionally they are close to the Early Triassic basalts of the Syverma Formation in the Siberian flood basalt large igneous province, basalts of the Urengoi Rift in the West Siberian Basin, and the Triassic basalts of the North Mongolian rift system. The basalts probably formed in relation to mantle plume activity: They are enriched in light rare-earth elements (LREE; Lan = 90-115, (La/Sm) n = 2.4-2.6) but relatively depleted in Nb (Nb/La) n = 0.34-0.48). Low to medium differentiation of heavy rare-earth elements (HREE; (Gd/Yb) n = 1.4-1.7) suggests a spinel facies mantle source for basaltic melts. Our obtained data on the composition and age of the Kuznetsk basalts support the previous idea of their genetic and structural links with the Permian-Triassic continental flood basalts of the Siberian Platform (Siberian Traps) possibly related to the action of the Siberian superplume peaked at 252-248 Ma. The abruptly changing thickness of the Kuznetsk Late Permian-Middle Triassic units suggests their formation within an extensional structure similar to the exposed rifts of southern Ural and northern Mongolia and buried rifts of the West Siberian Basin.
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