首页|Geology and genesis of the Aqishan Pb-Zn deposit,NW China:Insights from mineralogy,geochemistry,and in situ U-Pb geochronology

Geology and genesis of the Aqishan Pb-Zn deposit,NW China:Insights from mineralogy,geochemistry,and in situ U-Pb geochronology

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The unique ore-forming processes and the key factors responsible for formation of skarn deposits are still obscure,and challenges exist in the determination of timing of Pb-Zn skarns owing to lacking suitable mineral chronometers.Here we present detailed paragenesis,bulk geochemistry,in situ U-Pb dating of zircon and garnet,and garnet oxygen isotopes together with in situ zircon Hf-O isotopes from the newly discovered Aqishan Pb-Zn deposit in the southern Central Asian Orogenic Belt(CAOB),northwest China.This comprehensive data set revealed a Late Carboniferous subduction-related distal Pb-Zn skarn system associated with the granitic magmatism.Pre-ore stage garnets are generally subhedral to euhedral with oscillatory zoning and show slightly fractionated rare earth element patterns with positive Eu anomalies that point to an infiltration metasomatism origin under high water/rock ratios.The syn-ore stage spha-lerite is typically enriched in Mn and Cd and has moderate Zn/Cd ratios(337-482),with a formation tem-perature of 265 ℃ to 383 ℃,which indicate magmatic-hydrothermal signatures.The isocons defined by P2O5 decipher that the principal factors for skarn formation were elevated activities of Fe,Ca,and Si spe-cies,where remobilization of Pb metals,meanwhile,contributed to ore-forming budgets to mineralizing fluids.SIMS U-Pb dating of zircons from granite porphyry that occurs distal to the skarns and Pb-Zn ore-bodies shows that these intrusions emplaced at ca.311.3-310.6 Ma,recording the subduction of the Paleo-Tianshan oceanic plate.Hydrothermal garnets in close textural association with Pb-Zn sulfides yield indistinguishable in situ LA-ICP-MS U-Pb ages of 310.5±4.1 Ma.Whole-rock geochemistry and in situ zircon Hf-O isotopes(δ18O=4.6‰-6.0‰)indicate that the granite porphyry was derived from par-tial melting of juvenile crust and influenced by subducted oceanic crust.Oxygen isotope compositions of garnets(δ18O=8.0‰-9.0‰)demonstrate that the equilibrated ore fluids were inherited from fluid-rock interactions between a primary magmatic water and host tuff rocks.Our study highlights the application of garnets as a potential robust U-Pb geochronometer and isotopic tracer of ore fluids in skarn mineral-izing systems in subduction-related arc environments.

In situ U-Pb datingGarnet O isotopesAqishan Pb-Zn depositSkarn mineralizationSouthern CAOB

Kang Wang、Yinhong Wang、Jun Deng、Jiajun Liu、Fangfang Zhang、Wei Zhang、Hui Zhang、Wenxin Gu、Hong Chen

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State Key Laboratory of Geological Processes and Mineral Resources,and School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China

National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of China111 Project of the Ministry of Science and Technology of China

420721024177207341702079BP0719021

2024

10.1016/j.gsf.2024.101877

地学前缘(英文版)
中国地质大学（北京） 北京大学

地学前缘(英文版)

CSTPCD
影响因子：0.576
ISSN：1674-9871
年,卷(期)：2024.15(5)
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