Os, Sr and Nd Isotope Research on the Shizhuyuan Polymetallic Tungsten Deposit, South Hunan, China

摘要

The Shizhuyuan polymetallic tungsten deposit was formed in the contact zone between the Qianlishan granite stock and Devonian limestone. The Qianlishan granite stock is composed of pseudoporphyritic biotite granite, equigranular biotile granite and granite porphyry, from early to late. The Rb-Sr whole rock isochron ages of these three phases of granitic rocks are 152Ma, 137-136Ma and 131Ma, respectively. There are close spatial-temporal relationships between the multiple phases of granitic rocks and multiple periods of mineralization in the deposit. Massive skarn ores of the first period arc associated with the pseudoporphyritic biotite granite. Using the Re-Os isochron method on molybdenite, we directly measured the ore-forming age of skarn W-Sn-Mo ore related to the first-phase granite, and obtained a Re-Os age of 151.0±3.5Ma. This proves that polymetallic tungsten mineralization can occur in the early phase of granite series, Isotopic evidence also indicates the granites and the ore have characteristics of both continental crust and mantle. The granitic rocks are enriched in ore-forming elements and, therefore, are considered to have been the main source of the ore- forming materials.