YANG Chang-bi, PU Chao, WANG Yun-zhong, SI Guo-fu, YANG Fei-xiang, ZHENG Tian-ping, ZHANG Xing-hen

(The Second Geological Brigade, Bureau of Geology and Mineral Resources Exploration and Development of Yunnan Province, Wenshan 663000, China)

Abstract: The Gaji area in Xiuchou County, Yunnan Province, is located in the northern margin of the Laojunshan Yanshanian polymetallic mineralization province. A series of good mineralization information have been obtained by the recent geological exploration in the area. The Gaji Cu-Pb-Zn polymetallic deposit, a medium sized one based on the newly explored reserves of Cu+Pb+Zn, has prospective of a large-sized deposit. The geological exploration showed that there are complicated mineral assemblages, dominant silicification and skarnization for the wall rock alterations, the concealed Yanshanian granite stock in depth, and the good W-Sn-Mo mineralization around outer contact zone of the granite in the deposit. There is an obvious vertical mineralization zonation, with the variation of low-temperature association of ore-forming elements (Pb-Zn-Cu) to high-temperature association of ore-forming elements (W-Sn-Mo-Cu) from the shallow to the deep parts of the deposit. Based on the geological characteristics of the deposit, it is suggested that the mineralization of the Gaji Cu-Pb-Zn polymetallic deposit is related to the Laojunshan Yanshanian granite rather than the Caledonian granite, with its ore-forming elements and fluids mainly sourced from magma of the concealed Yanshanian granite in depth, and ore genesis belonging to a post-magmatic hydrothermal deposit. Furthermore, the combination of various methods including the identification of wall rock alteration zones and ore-forming element association zones, geophysical and geochemical information for exploration, geological engineering work, and geological investigation and evaluation is an effective geological exploration mode for prospecting concealed Cu-Pb-Zn mineral resources in the area.

Keywords: The Gaji Cu-Pb-Zn polymetallic deposit; tin polymetallic mineralization; late Yanshanian granite; Laojunshan granite complex; Xiuchou County, Yunnan Province

ACTA MINERALOGICA SINICA Vol. 40, No.3, 2020, page 255-266