The Kangdian iron oxide copper-gold (IOCG) metallogenic province contains a number of economically important Fe-Cu deposits in South China and northern Vietnam. Due to the lack of precise mineralization ages, the metallogenesis of this province has long been a matter of debate. In this study, molybdenite Re-Os, pyrite Re-Os, and Rb-Sr isotope methods are used to date the Yinachang and Elouthang Fe-Cu deposits in the central part of this province.

Fine-grained (<0.1 mm) molybdenite occurs as veinlets along bandings or fractures of magnetite ores and hydrothermal veins in the Yinachang deposit. Molybdenite separates from magnetite ores have highly reproducible Re-Os model ages of 1654 +/- 7 Ma, whereas those from hydrothermal veins have a much younger Re-Os model age of 1451 +/- 6 Ma. Euhedral pyrite grains occur locally along foliations of hematite ores and their proximal alteration assemblages in the E'touchang deposit. Pyrite separates have an Re-Os isochron age of 1487 +/- 110 Ma and a single-grain Rb-Sr isochron age of 1453 +/- 28 Ma, both of which are compatible with the molybdenite Re-Os age of hydrothermal veins from the Yinachang deposit.

The molybdenite age of magnetite ores is in good agreement with zircon U-Pb ages of dolerite intrusions in the region, and is considered to represent the timing of a major ore formation event at similar to 1655 Ma. The younger Re-Os and Rb-Sr ages likely record a secondary hydrothermal overprint event at similar to 1450 Ma, which has not been recognized before. The mineralization potential and implications of this event need to be investigated in future studies. Our new isotopic data set hence demonstrates that the Kangdian IOCG deposits were likely formed at similar to 1655 Ma, synchronous with the late Paleoproterozoic intracontinental rifling event of the western Yangtze block.

Publication name	ECONOMIC GEOLOGY  Volume: 108   Issue: 6   Pages: 1489-1498   Published: SEP-OCT 2013
Author(s)	Zhao, Xin-Fu; Zhou, Mei-Fu; Li, Jian-Wei; Selby, David; Li, Xiang-Hui;Qi, Liang
Corresponding author	ZHOU Meifu  mfzhou@hkucc.hku.hk   Univ Hong Kong, Dept Earth Sci, Hong Kong, Hong Kong, Peoples R China.
Author(s) from IGCAS	QI Liang

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