Affiliation:
1. Minmetals Exploration and Development Co., Ltd., Beijing 100010, China
2. Hunan Shuikoushan Nonferrous Metals Group Co., Ltd., Hengyang 421513, China
Abstract
Various magmatic–hydrothermal activities have resulted in different styles of polymetallic mineralization in South China. Shuikoushan is a large Fe-Cu-Pb-Zn-Au-Ag orefield situated in fold-and-thrust belts within the South China Block. Two types of granodiorite have been identified in recent drilling work. The early-stage, coarse-grained granodiorite has developed magnetite-bearing skarns in the deep level. The late-stage, fine-grained granodiorite is associated with garnet-hematite–magnetite–pyrite–sphalerite–chalcopyrite-bearing skarns in its contact zone. Away from the garnet-bearing skarn are calcite–quartz–pyrite–sphalerite–galena veinlets in faulted breccia. Fieldwork has identified iron mineralization in both skarns, whereas copper mineralization was only discovered in the garnet-bearing skarns. Lead, zinc, gold, and silver mineralization were observed in the garnet-bearing skarns and faulted breccia. Zircon U–Pb analyses suggested the emplacement of two granodiorite at 167.8 ± 0.8 Ma (MSWD = 1.1, N = 31) and 163.6 ± 0.7 Ma (MSWD = 1.3, N = 32). Apatite and garnet U–Pb dating further indicated the magnetite-bearing skarns of 166.2 ± 1.9 Ma (MSWD = 4.5, N = 27), the hematite–magnetite–sulfide-bearing skarns of 158.6 ± 2.8 Ma (MSWD = 1.3, N = 34), and the calcite–quartz–sulfide veinlets of 159.5 ± 5.2 Ma (MSWD = 1.7, N = 24). The time–space relationship between the two intrusions and hydrothermal activities suggests that the fine-grained granodiorite is responsible for polymetallic mineralization. Whole-rock geochemistry analyses demonstrated the enrichment of LILEs and the depletion of Nb and Ta in two granodiorites, with a slight enrichment in LREEs and flat HREE patterns. These granodiorite bodies therefore belong to high-K calc-alkaline magma generated via the crust’s partial melting. The fine-grained granodiorite generally has a lower HREE and higher Dy/Yb, Sr/Y ratios than coarse-grained granodiorite, corresponding to the source of magma in garnet stable lower crust. The residual garnet keeps ferric iron in melts, leaving the fine-granodiorite more oxidized for copper and gold concentration. Through these analyses and our drilling work, a continuous skarn–hydrothermal–epithermal system has been identified for Cu-Pb-Zn-Au-Ag targeting in Shuikoushan.
Funder
Minmetals Technological Program
National Key Research and Development Program
Subject
Geology,Geotechnical Engineering and Engineering Geology