DOI:10.19762/j.cnki.dizhixuebao.2020243
 
Geology, isotope geochemistry, and ore genesis of the Liba gold deposit in the western Qinling orogen, China
Author NameAffiliationE-mail
LI Bei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069 15829384406@163.com 
ZHU Laimin State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069 zhulaimin@nwu.edu.cn 
DING Lele State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069  
MA Yuanbo State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069  
XIONG Xiao State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069  
YANG Tao State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069  
WANG Fei State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 710069  
Abstract:The Liba gold deposit is located in the Liming ore cluster of the west Qinling orogenic belt in the epi- metamorphic fine clastic rocks of the Devonian. It was produced in the thermal contact metamorphic belt outside the Zhongchuan intrusion. Orebodies in the Liba gold field are controlled by the fracture zone. This paper analyzes the geological characteristics of the Liba gold deposit in detail using the S isotopes of the host rocks, granite porphyry, and ore sulfides by LA- MC- ICPMS and MAT- 253 mass spectrometer. The Pb isotopes of different geological bodies were measured by Nu Plasma HR MC- ICPMS. At the same time, the isotopic hydrogen and oxygen compositions of the ore- forming fluid were measured, and LA- ICP- MS zircon U- Pb dating was performed on granite porphyry dykes. The δ 34 S value of the pyrite ranges from 8. 19‰ to 10. 06‰ in granite porphyry, and the host rocks δ 34 S value of the sulfides range from 4. 94‰ to 9. 81‰. However, the δ 34 S value of the ore sulfides varies between 4. 94‰ to 10. 82‰, closer to the value of granite porphyry and host rocks suggesting that the sulfur source is a mixture of formation rocks and magmatic hydrothermal. Zartman’s plumbotectonic model diagram shows that all data fall near the orogenic and upper crust Pb evolutionary curve, and the ore lead coincides with the host rocks and dyke in Liba gold deposit. This indicates a complex source of ore lead that was derived from a mixture of the host rocks and magmatism. The hydrogen and oxygen isotopic data support a mixed origin of the ore- forming fluids, which composed of metamorphic, magmatic and formation waters. Granitic porphyry and ore body were produced together. The U- Pb age determination of zircon indicates that the granite porphyry intruded at 264. 4±1. 3 Ma which is consistent with gold mineralization time, suggesting that mineralization and magmatic activities occurred simultaneously. The Liba gold deposit and the magmatic rock are both products of orogeny. The geological and isotopic geochemical characteristics of the deposit are similar to orogenic gold deposits. It shows that the Liba gold deposit is an orogenic gold deposit formed with a complex source of ore- forming materials under a changing environment ranging from collision to extension in the Qinling orogenic belt.
keywords:Liba gold deposit  multi- isotope geochemistry  zircon U- Pb dating  orogenic gold deposits  western Qinling
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