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岩石学报  2012 

Geochemistry, petrogenesis and tectonic setting of the Paleoproterozoic Yanmenguan mafic-ultramafic intrusion in the Hengshan-Wutai-Fuping area
五台地区雁门关早元古代镁铁-超镁铁岩体的岩石地球化学特征、成因及其大地构造意义

Keywords: Yanmenguan mafic-ultramafic intrusion,Paleoproterozoic,Petrogenesis,Continental arc,Trans-North China Orogen
雁门关镁铁-超镁铁质岩体
,古元古代,岩石成因,大陆边缘弧,华北克拉通中部造山带

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Abstract:

A detailed study of petrology, mineralogy, geochemistry and petrogenesis on the Paleoproterozoic Yanmenguan mafic-ultramafic intrusion in the Hengshan-Wutai-Fuping area is presented here. The intrusion is akin to Alaskan-type or arc-related magmatism in mineral geochemistry, especially in the compositions of spinel, clinopyroxene, and amphibole. The rock geochemistry is also comparative to those of Alaskan-type mafic-ultramafic complexes, as characterized by pronounced Nd (Ta), Zr (Hf), Y and Ti trough in primitive mantle normalized trace element patterns. In trace element discrimination diagrams, the Yanmenguan rocks plot in the field of subduction zone-related magmas, indicating a tectonic setting of continental arc. Therefore, we propose that the magma of the Yanmenguan mafic-ultramafic intrusion originated from lithospheric mantle in a continent marginal arc, and experienced fractional crystallization of olivine and clinopyroxene. This intrusion, together with contemporary granitic and volcanic rocks in this area, signifies an important stage of Paleoproterozoic magmatism developed in continent margin of the Trans-North China Orogen.

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