The Longshan deposit is one of the most important Au-Sb deposits in central Hunan Province. However, the mineralization age of this deposit is still not well constrained due to lacking of suitable minerals for conventional radiometric dating, limiting the recognition of its genesis. Pyrite Re-Os isotopic dating has been proved to be a reliable technique to determine the age of hydrothermal sulfides with low contents of Re and Os, which can be thus used to constrain the age of epithermal mineralization. The zircon U-Th/He isotopic dating is a newly developed technique, which can provide a potential constraint on the ages of low-temperature metallogenic events. Re-Os isotopic dating of the hydrothermal pyrites and U-Th/He isotopic dating of the zircons recording metallogenic event were carried out in this paper, aiming to constrain the mineralization age of the Longshan Au-Sb deposit. Dating results show that the Re-Os isochron age of hydrothermal pyrites is 195 +/- 36 Ma, corresponding to Late Indosinian, whereas the U-Th/He ages of zircons from altered wallrock are 51.2 similar to 133.3Ma. After correction by Ft, the U-Th/He ages are distributing in the range of 93.78 to 258.29 Ma with an average of 160.7 +/- 7.3Ma, corresponding to Early Yanshanian. It can be thus concluded that the Longshan Au-Sb deposit may have experienced two episodes of mineralization (i.e., similar to 200Ma and similar to 160Ma) or the Sb-Au mineralization may have occurred at similar to 200Ma which was remobilized by magmatic event at similar to 160Ma. Pyrite Re-Os age represented the timing of Au-Sb mineralization, whereas the zircon U-Th/He age represented the timing of the second thermal event. Thus, whether the Longshan Au-Sb deposit formed due to the single mineralization event at similar to 200Ma, or also experienced an overlapping of the mineralization event at similar to 160Ma, the two ages were roughly consistent with those of two magmatic events in the district, indicating that magmatism may have played a vital role in the formation of the Longshan Sb-Au deposit.

Publication name	ACTA PETROLOGICA SINICA, 32 (11):3507-3517; 2016
Author(s)	Fu ShanLing; Hu RuiZhong; Chen YouWei; Luo JinCheng
Corresponding author	FU Shanling   fushanling@mail.gyig.ac.cn Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550081, Peoples R China.

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