WU Xiao-hong1, XIAO Cheng-gang1, CHENG Peng-lin2, ZHOU Jia-xi3,4*, LIU Song1, WU Wen-ming1, WAN Da-xue1
(1. No. 105 Geological Team, Bureau of Geology and Mineral Exploration and Development of Guizhou Province, Guiyang 550018, China;
2. No. 115 Geological Team, Bureau of Geology and Mineral Exploration and Development Guizhou Province, Guiyang 551400, China;
3. School of Resource Environment and Earth Science, Yunnan University, Kunming 650504, China;
4. Stake Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China)
Abstract: Rock gold deposits in Guizhou Province are mainly distributed in a part of the transitional zone, called the Jiangnan composite orogenic belt, between the Yangtze and Cathaysia blocks. This part of the Jiangnan belt in Guizhou Province has been divided into four second-order tectonic units, including: 1) the Xingyi uplift area, in which the Zhenfeng-Pu’an metallogenic district hosts the giant Shuiyindong Au deposit; 2) the Youjiang foreland basin, in which the Ceheng-Wangmo metallogenic district hosts the giant Lannigou Au deposit; 3) the Qiannan depression region comprising of the Duyun NS-trending trough deformation zone, containing the Sandu-Danzhai Au metallogenic belt, and the Tongren deformation zone of open compound folds, containing the Fanjinshan Au metallogenic belt; and 4) the Rongjiang Caledonian fold belt, hosting the Tianzhu-Jinping-Liping Au metallogenic belt. From north to south, ages of ore-hosting strata of those rock gold deposits in various second-order tectonic units are decreased. This is because the division of the second-order tectonic units is based on the basin- and phase-controlled fractures, strata, and lithology. The statistics of lithologies of Au-bearing underlying and overlying strata in the second-order tectonic units show that the underlying rocks of rock gold deposits are brittle rocks, such as carbonate, sandstone, lava, and metamorphic rocks, which are easily cracked by structural movement to provide effective channels for the transport of hydrothermal fluids, whereas the overlying rocks are thickly bedded claystone or mudstone, which acted as a barrier for blocking fluids. Based on all kinds of previous geological data, we have proposed that the ore-forming materials of rock gold deposits in Guizhou Province could be sourced from deep crust, and the Au-bearing fluids were migrated from deep to shallow levels of crust where the ore-forming fluid then were trapped by the sealing layer of rocks (cap rocks) with poor permeability. This process caused the filling of the ore-forming fluids and alteration of wall rocks, and resulted in the Au enrichment and mineralization gradually. The Au-bearing strata in different second-order tectonic units are different due to relatively different positions of the overlying rocks. This means that the rock gold deposits hosted in different layers are not vertically distributed in the same deposit area, but are distributed laterally in different deposit areas. This provides a new clue for further guiding the ore prospecting in the region.
Keywords: rock gold deposit; distribution characteristics; controlling factor; ore-controlling lithologic association; ore prospecting model; Guizhou province
