Magmatic Ni-Cu-PGE deposits in the Qilian-Longshou mountains, Northwest China — part of a Proterozoic large igneous province

The Jinchuan intrusion occurs in the Qilian-Longshou mountains, China and contains a world-class Proterozoic Ni-Cu-PGE deposit. It has a Sm-Nd isochron age of 1508±31 Ma. Zangbutai is a non-mineralized complex of metamorphic and ultramafic rocks with komatiite features located on the western side of the Jinchuan intrusion, and has been dated at 1511±67 Ma. Proterozoic continental flood basalts form part, of the Zhulongguan group of the Jingtieshan micro-continental block in the western part of North Qilian, and in the Hualong micro-continental block of South Qilian Lashuixia. Small intrusive-hosted Ni-Cu-sulfide (PGM) deposits are associated with other mafic-ultramafic intrusions of Proterozoic age. The Proterozoic continental flood basalts, komatiites, mafic-ultramafic rock bodies and magmatic Ni-Cu sulfide (PGM) deposits are interpreted to define a Proterozoic large igneous province in the Qilian-Longshou mountains. This province was created by large scale magmatism in response to rifting of the Columbia super-continent and extension of the Qilian paleocontinent at about 1.5Ga. At Jinchuan up to 60% of the rock body is sulfide mineralized, whereas at Lashuixia sulfides comprise up to 90%. Such high concentrations of metallic sulfides imply formation via injection of metallic sulfide-bearing magma and/or metallic sulfide liquid.