Origin of Metallogenic Materials of the Chang'an Gold Deposit in the Southern Ailaoshan Belt: Evidence from Sulfur and Lead Isotopic Composition

Abstract

Abstract:

The Changan deposit is one of large gold deposits in the Southern Ailaoshan metallogenic belt in Sanjiang region, and the occurrence of ore bodies is controlled by the brittle fractured zone of Ganhe fault. The ore-hosted rocks are dominated by Lower Ordovician sandstone and clastic rocks. The δ34S values of pyrites in the magmatite and ores range from-3.49‰ to +3.57‰, concentrating between +1‰ and +3‰. The comparative study on sulfur isotopic compositions of the ores, wall rocks and magmatic dikes suggests that the sulfur in ore-forming fluid was most probably sourced from the ore-hosted strata and partly mixed with that in the Himalayan period magmatic hydrothermal fluid. The Pb isotopic values of the ore vary in a narrow range, i.e., 208Pb/204Pb=38.722-40.649, 207Pb/204Pb=15.604-15.813 and 206Pb/204Pb=18.788-19.761, respectively, showing that the gold ores are relatively rich in radiogenic lead. It is suggested that the ore lead was sourced from the upper crust with higher maturity, indicating that the lead and other ore-forming elements should be mainly derived from the Devonian dolomite and clastic rocks, the Ordovician sandstone in mining area. At the same time, the lead isotopic compositions of altered rock and magmatite mainly show the characteristics of orogenetic belt. Comprehensive research proves that the metallogenic materials only have a little relationship to the magmatite. That is to say, the ore-forming materials were mainly sourced from the ore-hosted wall rocks, and the Cenozoic magmatism provided the heat source and part metallogenic materials for the further enrichment of the Changan gold deposit.

Key words: sulfur and lead isotope, origin of metallogenetic material, Changan gold deposit, Ailaoshan metallogenic belt

CLC Number:

P618.5

LI Shi-hui1，2, ZHANG Jing1, YANG Li-qiang1, WANG Huan1. Origin of Metallogenic Materials of the Chang'an Gold Deposit in the Southern Ailaoshan Belt: Evidence from Sulfur and Lead Isotopic Composition[J]. Geoscience, 2013, 27(4): 879-887.

References

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