Genesis of the Dongpuzi Gold Deposit in the Liaodong Peninsula, NE China: Constraints from Geology, Fluid Inclusion, and C-H-O-S-Pb Isotopes

The Dongpuzi deposit is an epithermal gold deposit located in the southern margin of the Shaozihe volcanic fault basin in the Liaodong Peninsula. On the basis of fluid inclusion and C-H-O-S-Pb isotope data, a metallogenic model is established for the Dongpuzi deposit. The mineralization at the Dongpuzi deposit has experienced quartz-pyrite (I), quartz-sulfide (II), and quartz-calcite (III) stages. The quartz from ore stage II has liquid-dominated aqueous inclusions, which have homogenization temperatures ranging from 113 to 162 degrees C and salinities varying from 3.2 to 9.6 wt% NaCl equiv. The quartz from the quartz-calcite stage has decreasing homogenization temperatures (106 similar to 143 degrees C) and salinities (21 similar to 6.9 wt% NaCl equiv.). The fluid inclusion data indicate that the gold ores were precipitated from low-temperature and low-salinity solutions, with an obvious decrease in temperature and salinity from ore stages II to III. The calculated delta O-1(8)water values for the quartz of ore stage II range from -14.71 parts per thousand to -13.31 parts per thousand, and the corresponding delta O-1(8)water values range from -103.3 parts per thousand to -96.1 parts per thousand, indicating that the ore-forming fluids could be of a meteoric origin. The calcite from ore stage III has delta C-1(3)V-PDB values of -4.5 parts per thousand to -4.2 parts per thousand and delta O-1(8)V-SMOW values of +7.0 parts per thousand to +7.4 parts per thousand, indicating a mantle source for the carbon. The pyrite yielded delta S-34 values of +4.1 parts per thousand to +6.6 parts per thousand and Pb isotopes consistent with those of the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, which suggests that the S and Pb in gold ores were dominantly derived from the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, with some combination of Paleoproterozoic metamorphic rocks of the Gaixian Formation. These results, together with the ore geology, indicate that the Dongpuzi deposit is a typical low-sulfidation epithermal gold deposit with important ore-forming materials input from the host trachyte porphyry, volcanic rocks of the Xiaoling Formation, and Paleoproterozoic metamorphic rocks of the Gaixian Formation. The Dongpuzi deposit was formed under an extensional setting related to the Early Cretaceous lithospheric extension and thinning of the eastern North China Craton.