Petrography And Geochemistry Of Ore-bearing Complex Of Yinan Gold Deposit, Shandong Province

The Yinan gold deposit is located on the west side of the Yishu fault zone (the middle segment of the Tanlu fault zone) at the southeastern margin of the North China plate. It includes the Tongjing and Jinchang ore districts which are 6 km away from each other. The Yinan gold deposit is a typical Au-Cu-Fe skarn deposit. The deposit occurs at the contact zone between the intermediate-acidic complexes of the Yanshanian and their wall rocks of the Neoproterozoic to Cambrian. Based on comprehensive field investingations and synthetic studies on petrology, mineral deposit geology, and geochemistry, the origin of ore-bearing complexes, their tectonic environments and effects in metallogenic processes are ascertained in this paper.Complexes of the Yinan gold deposit are intermediate-acidic minitype intrusions of the Cretaceous, including the Tongjing complexes, Jinchang complexes and Gaoguzi complexes. The Yinan gold deposit is composed of diorite porphyrite, quartz diorite porphyrite, monzonite granite, monzonite granite-porphyfy, granite-porphyfy and eurite-porphyfy complexes. Complexes belongs to calc-alkaline series, whose w(SiO₂) ranges from 54.09% to 74.60% and w(K₂O)+w(Na₂O) varies in 5.51%-9.15%.The rare earth elements (REE) of ore-bearing complexes have some strong REE fractionation models that the light REE is enrichment and the heavy REE deficit. It has the right-tilting pattern in the REE distribution. Diorites related-metallogenesis show weak low Eu abnormality or no abnormality, and granitoids related-metallogenesis show strong low Eu abnormality. They show mantle magma characteristic.Analysing major element and trace element of the Yinan gold deposit complexes, it shows ore-forming magmas were derived from the deep mantle and evolution was the magma fractional crystallization, and were contaminated by the crust to some degree during their ascending process. The complexes show characteristics of adakite-like rocks in chemical composition. Magmas intrusions formed in the orogenic environment.Integrating petrology and geochemistry of ore-bearing complexes and synthesizing sulfur, carbon, hydrogen and oxygen isotopic studies, ore-bearing magmas provided the ore-forming materials and the ore-forming fluids during every mineralization stages.