Zircon U-Pb Age and Geochemical Characteristics of Granitic Magmatic Rocks in the Mailong Gold Deposit，East Kunlun，and Their Geological Significance
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摘要: 为了揭示东昆仑造山带原特提斯洋和古特提斯洋的构造演化过程及其与金矿成矿的成因联系，本文对迈龙金矿区的二长花岗岩和花岗闪长岩开展了岩相学、地球化学和LA-ICP-MS锆石U-Pb年代学研究。结果表明，二长花岗岩和花岗闪长岩的结晶年龄分别为421±11Ma（晚志留世）和228±4Ma（晚三叠世），具有准铝质、高钾钙碱性系列特征，富集轻稀土（LREE），大离子亲石元素（LILE：Rb，K）和地球化学性质活泼的不相容元素（U，Th，Pb），亏损高场强元素（HFSE：Nb，Ta，P，Ti），显示岛弧花岗岩的地球化学特征。结合区域地质背景，认为二者形成于造山后伸展阶段的壳幔相互作用，迈龙金矿的矿化与古特提斯造山后伸展阶段的构造-岩浆作用密切相关。该研究为区域构造演化和金矿成矿背景提供了重要依据，对矿产勘探具有指导意义。Abstract: To reveal the tectonic evolution of the Proto-Tethys and Paleo-Tethys Oceans and their genetic links to gold-polymetallic mineralization in the East Kunlun Orogenic Belt （EKOB），this study conducted petrographic，geochemical，and LA-ICP-MS zircon U-Pb geochronological analyses on monzogranite and granodiorite from the Mailong gold deposit. The results show that the monzogranite and granodiorite crystallized at 421±11 Ma （Late Silurian） and 228±4 Ma （Late Triassic），respectively，exhibiting metaluminous，high-potassium calc-alkaline characteristics. Trace element analyses reveal enrichment in light rare earth elements （LREE），large-ion lithophile elements （LILE：Rb，K），and incompatible elements （U，Th，Pb），with depletion in high-field-strength elements （HFSE：Nb，Ta，P，Ti） and weak negative Eu anomalies，indicating an island arc granite affinity. Combined with regional geological evidence，these rocks formed through crust-mantle interaction during the post-orogenic extensional stage. The Mailong gold deposit，primarily hosted in the granodiorite，is likely associated with tectonic-magmatic activities during the post-orogenic extension of the Paleo-Tethys evolution. This study provides critical age constraints and geochemical insights into the tectonic evolution and gold mineralization in the EKOB，offering valuable guidance for regional mineral exploration.
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Key words:
- East Kunlun orogenic belt /
- U-Pb dating /
- Geochemistry /
- Monzogranite /
- Granodiorite
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