Early Carboniferous quartz diorite in the Baxi copper deposit, East Junggar: Insight into potential for porphyry copper deposits
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P618.41;P588.12+2

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    Abstract:

    The Qiongheba area in the East Junggar terrain is located in the middle section of the Central Asian metallogenic domain. Although many Paleozoic porphyry copper (molybdenum) deposits have been discovered in this area in recent years, these deposits are all small in scale and the metallogenic potential requires further evaluation. The Baxi copper deposit is one of the typical and representative porphyry copper deposits. The quartz diorite and quartz monzodiorite are closely related to porphyry copper mineralization. The zircon mean U-Pb weighted average age of quartz diorite is 345.7±3.0 Ma, indicating that it was formed in the Early Carboniferous. The plagioclase in quartz diorite and quartz monzonite is not andesine that is common in intermediate rocks, but calcium-richer labradorite. The bulk-rock geochemical characteristics show that they have meta-aluminum-weak peraluminum calc-alkaline I-type geochemical signatures. The primitive mantle normalized incompatible element patterns show the enrich-ment of large ion lithophile elements relative to high field strength elements as well as significantly negative Nb, Ta and Ti anomalies, suggesting a typical island arc-like geochemical feature. The mafic microgranular enclaves (MMEs), positive εHf(t) values (+13.66~+15.56) and the calcium-rich plagioclase in the rocks suggest that the magma originated from the mantle-derived basic magma mixed with felsic magma derived from juvenile crust. Based on the amphibole compositions, the authors calculated the pressure (28.6~166.9 MPa, equivalent to 0.6~3.1 km), temperature (673~908℃), water content (3.18%~4.64%), and oxygen fugacity (ΔNNO-0.22~ΔNNO+3.27). Combined with the tectonic setting and geophysical anomaly of the mining area, the high water content and oxygen fugacity of magmas indicate that the area has good prospecting potential for porphyry copper deposits.

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张铭鸿,姚勇,程志国,张招崇,2021,新疆东准噶尔坝西早石炭世石英闪长岩及其对斑岩铜矿的指示意义[J].岩石矿物学杂志,40(1):153~168. ZHANG Ming-hong, YAO Yong, CHENG Zhi-guo, ZHANG Zhao-chong,2021,Early Carboniferous quartz diorite in the Baxi copper deposit, East Junggar: Insight into potential for porphyry copper deposits[J]. Acta Petrologica et Mineralogica,40(1):153~168.

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History
  • Received:July 25,2020
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  • Online: January 16,2021
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