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西藏多龙矿集区是目前班公湖-怒江成矿带内最具潜力的找矿远景区,矿集区内已发现4处大型斑岩铜矿,但其成矿背景尚有争议。通过开展成矿前的萨玛隆闪长岩锆石U-Pb测年、岩石化学分析,结合区域内构造发育序次,对系列斑岩铜矿的成矿背景进行探讨。对萨玛隆闪长岩中进行LA-ICP-MS锆石U-Pb测年,获得23颗锆石的~(206)Pb/~(238)U年龄加权平均值为121.6±1.7Ma(MSWD=1.9),代表了闪长岩的成岩年龄。萨玛隆闪长岩的全岩岩石化学分析结果显示,该岩石属于中钾富钠岩石,富集轻稀土元素和大离子亲石元素,亏损重稀土元素和高场强元素,具有高Sr、低Y特征,相对富集Cr、Ni等不相容元素,有埃达克岩的亲和性。闪长岩具相对较高的(~(87)Sr/~(86)Sr)i值和较低的(~(143)Nd/~(144)Nd)i值、ε_(Nd)(t)。全岩岩石化学特征显示,萨玛隆闪长岩起源于下地壳角闪岩相,可能有幔源物质混入。矿区内早期走滑断层切穿萨玛隆闪长岩,指示多龙矿集区内主要控岩-控矿走滑断层可能形成于116~121Ma,多龙矿集区内系列斑岩铜矿形成于班公湖-怒江洋向北俯冲末期的构造转换阶段。
The Duolong ore deposit in Tibet is the most potential prospecting prospect in the Bangong Lake-Nujiang metallogenic belt. Four large porphyry copper deposits have been found in the ore-gathering area, but the metallogenic background is still controversial. By carrying out U-Pb dating of zircons from Samang diorite before ore-forming and petrochemical analysis, and combining with the order of tectonic development in the region, the metallogenic background of series of porphyry copper deposits is discussed. The LA-ICP-MS zircon U-Pb dating of the Samaron diorites obtained a weighted average of ~ (206) Pb / ~ (238) U age of 121 zircons of 121.6 ± 1.7 Ma (MSWD = 1.9), representing the diagenetic age of diorite. The whole-rock petrochemical analysis of the Samang diorite shows that the rock is a medium-K-rich rock that is enriched in both light rare earth elements and large ion lithophile elements, depleted in heavy rare earth elements and high field strength elements and has high Sr, Low Y features, relative enrichment of Cr, Ni and other incompatible elements, with adakite affinity. The diorites with relatively high (~ (87) Sr / ~ (86) Sr) and low (~ (143) Nd / ~ (144) Nd) . The petrochemical characteristics of the whole rock show that the Samaron diorite originates from the lower crust amphibolite facies, and mantle-derived materials may be mixed in. The early strike-slip faults in the mining area cut through the Samang diorite, indicating that the main controlled-ore-controlling strike-slip faults in the Duolong ore district may be formed from 116 to 121 Ma. The porphyry copper deposits in the Duolong ore district are formed At the end of the structural transition of the Bangong-Nujiang Ocean to the north subduction.