东天山铜鱼梁铜矿区闪长玢岩SHRIMP锆石U-Pb年代学、岩石地球化学及其地质意义

位于新疆东天山阿齐山-雅满苏成矿带东段的铜鱼梁矿床是近年来新发现的铜矿点，但带内热液型铜矿的研究和找矿勘查程度不高，通过SHRIMP锆石U-Pb定年获得矿区与成矿密切相关的闪长玢岩年龄为317.7±2.4 Ma，表明矿区在晚石炭世可能存在重要的岩浆-成矿事件.通过岩石地球化学特征研究可得铜鱼梁闪长玢岩SiO₂含量为56.71%~66.03%，Mg#=49.75~55.29，Na₂O+K₂O=5.15%~6.40%，Na₂O/K₂O=4.49~53.62，铝指数A/CNK=0.9~1.1，为富钠、准铝质-过铝质、低钾（拉斑）系列岩石.稀土总量较低（39.56×10-6~60.60×10-6），具有轻稀土富集、重稀土亏损的右倾配分模式，富集Ba、U、K、Sr等大离子亲石元素（LILE），亏损Nb、Ta、Ti高场强元素（HFSE），显示弧岩浆的特征.闪长玢岩（87Sr/86Sr）_i变化于0.704 030~0.704 413之间，ε_Nd（t）=1.02~6.42，具有低的锶同位素初始值和正的ε_Nd（t）值，表明其岩浆源区主要来源于亏损地幔源区.综合已有资料，认为研究区闪长玢岩形成于岛弧的构造背景，为石炭世古康古尔洋壳向南俯冲的流体交代地幔后的产物.至晚石炭世早期，古康古尔洋俯冲交代，在上升中富含铜金属元素的岩浆流体当运移到浅部时，次火山岩通过交代岩体本身或火山地层形成了铜鱼梁铜矿床. 

SHRIMP Zircon U-Pb Geochronology and Geochemistry of Diorite Porphyrite in Tongyuliang Copper Deposit,Eastern Tianshan and Its Geological Significance

The Tongyuliang is a newly discovered copper deposit in recent years, which is located in the Aqishan-Yamansu Carboniferous volcanic belt of eastern Tianshan, Xinjiang, NW China. However, the research for this hydrothermal copper deposit is limited. The SHRIMP zircon U-Pb dating of diorite porphyrite which is genetically related with the copper deposit is 317.7±2.4 Ma. It can be inferred that the ore-forming epoch of this deposit may be Late Carboniferous. The major elements data show that the diorite porphyrites contain 56.71%-66.03% of SiO₂, 49.75-55.29 of Mg#, 5.15%-6.40% of Na₂O+K₂O and 4.49-53.62 of Na₂O/K₂O, and the aluminium index (A/CNK)=0.9-1.1. The diorite porphyrites are relatively enriched in sodium and alumina and belong to the low K (IAT) series. They have low ∑REE (39.56×10-6-60.60×10-6) and are enriched in LREE relative to HREE. The primitive mantle normalized trace elements spider diagram is characterized by Ba, U, K, Sr (large ion lithophile elements) enrichment and Nb, Ta, Ti (high field strength elements) depletion, which shows the island-arc volcanic characteristics. The (87Sr/86Sr)_i ratios range from 0.704 030 to 0.704 413, and ε_Nd(t) values vary from 1.02 to 6.42, which indicates that the magma source of diorite porphyrites may be derived from depleted mantle source. The geochronology, geochemistry, and isotope characteristics of diorite porphyrites suggest that the Tongyuliang copper deposit was formed in the arc setting. Combining existing geological data, the ore-bearing materials probably came from the mantle wedge, which had undergone metasomatism induced by southward subduction of Paleo-Kangguer oceanic plate. In early Late Carboniferous, the fluids which contained copper element intruded, and the Tongyuliang copper deposit formed after sub-volcanics replaced their own bodies or volcanic rocks when they reached the upper area.