ZHANG Wen-lin1*, CAO Hua-wen2, YANG Zhi-min1, XI Xiao-yi1, LIU Wen-wu1, PENG Shi-mian3, ZHENG Luo2
1. Regional Geological survey party, Sichuan Bureau of Geological Exploration and Exploration of Mineral Resources, Chengdu 610213, China;
2. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China;
3. Muli Rongda Mining Co. Ltd., Muli Sichuan 615800, China
Abstract: The Suoluogou large-scale Au deposit, the largest Au deposit in Sichuan Province, developed many lamprophyre veins. This paper studied element geochemistry and genesis of the lamprophyre veins and discussed their geological implications. The K-Ar age of the biotite from the lamprophyres was measured to be 26.6 Ma, indicating that the lamprophyre veins were formed in the Oligocene. The SiO2 content is 42.7%-46.9% and the K2O/Na2O values vary from 0.9 to 1.5 are consistent with the characteristics of alkaline lamprophyres. ∑REE is 623.2×10-6~760.9×10-6; LREE/HREE value is 14.6-16.5; δEu is 0.8-0.9; LILEs and LREEs are relatively enriched; HFSEs and HREEs are depleted; Ta, Nb and Ti show "TNT" negative anomalies. All of above lithological and geochemical characteristics implied that lamprophyre was formed during a conversional period of late-collision and post-collision under the inner-plate environment, that is, the lamprophyre might derive from the metasomatism of residual oceanic plate to mantle wedge. The initial lamprophyritic magma was generated by low-level partial melting of the garnet lherzolite within the lithospheric mantle.
Keywords: Suoluogou gold deposit lamprophyre geochemistry K-Ar age enriched mantle
*Corresponding Author, E-Mail: hellozhangsir@126.com
Bulletin of Mineralogy, Petrology and Geochemistry Vol. 34, No.1, 2015, page 110-119
