PERMIAN-TRIASSIC ULTRAMAFIC-MAFIC MAGMATISM OF NORTHERN VIETNAM AND SOUTHERN CHINA AS EXPRESSION OF PLUME MAGMATISM
A.E. Izokh, G.V. Polyakov, Tran Trong Hoa*, P.A. Balykin, and Ngo Thi Phuong*
Institute of Geology, Siberian Branch of the RAS, 3 prosp. Akad. Koptyuga, Novosibirsk, 630090, Russia
* Institute of Geological Sciences of Vietnam Academy of Sciences and Technologies, Hanoi, Vietnam
Keywords: Permian-Triassic, picrites, Emeishan, plume
Pages: 922-932
Abstract
This paper is aimed at characterizing the Permian-Triassic mafic-ultramafic magmatism of the southeastern segment of Eurasia. Given a sinistral strike-slip fault in the Song Hong zone (ASRR) that occurred at about 40-25 Ma, the ultramafic-mafic complexes of the Song Da zone and intrusive bodies of the Cao Bang complex are considered the southwestern flank and southeastern continuation of the Emeishan traps, respectively. It has been shown that petrochemical and geochemical characteristics of the products of the Permian-Triassic ultramafic-mafic magmatism are controlled by effects of the interaction of a mantle-derived plume with blocks characterized by different structure of the lithosphere. It is supposed for the Song Da rift zone that heavily depleted mantle is in places beneath the continental lithosphere. Geochemical features of the picrites from northeastern Vietnam (Cao Bang complex) indicate that the subduction-related lithosphere mantle is present there. High contents of PGE in picritoids and basaltoids of the Permian-Triassic step in southeastern Asia are bearing on the plume originated in the lower mantle.
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