西藏多龙矿集区萨玛隆闪长岩LA-ICP-MS锆石U-Pb年龄和岩石化学特征及其对成矿背景的约束

发布时间：2018-11-04 10:41

【摘要】：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。
[Abstract]:The Dulong ore concentration area in Tibet is the most potential ore prospecting area in the Bangonghu-Nujiang metallogenic belt at present. Four large porphyry copper deposits have been found in the ore concentration area, but the metallogenic background is still controversial. The metallogenic setting of a series of porphyry copper deposits is discussed by means of U-Pb dating of zircon and petrochemical analysis of the pre-metallogenic Samaronite diorite combined with the sequence of tectonic development in the region. The LA-ICP-MS zircon U-Pb dating of the Samaron diorite shows that the weighted average of ~ (206) Pb/~ (238) U age of 23 zircons is 121.6 卤1.7Ma (MSWD=1.9), which represents the diagenetic age of the diorite. The chemical analysis of the whole rock of Samaron diorite shows that the rock belongs to medium potassium and sodium rich rock, which is rich in light rare earth elements and large ion lithophile elements, and is depleted of heavy rare earth elements and high field strength elements, and has the characteristics of high Sr, and low Y, Relative enrichment of incompatible elements, such as Cr,Ni, has the affinity of adakite. Diorite has relatively high (87) Sr/~ (86) Sr) i) and lower (~ (143) Nd/~ (144) Nd) i), 蔚 _ (Nd) (t). The petrochemical characteristics of the whole rock indicate that the Samaron diorite originated from the amphibolite facies of the lower crust and may be mixed with mantle source materials. The early strike-slip fault cut through Samaron diorite in the mining area, indicating that the main rock-controlled strike-slip fault may have been formed at 116 ~ 121Ma. A series of porphyry copper deposits were formed in the late stage of northward subduction of Bangong Lake-Nujiang Ocean.
【作者单位】：中国地质调查局成都地质调查中心;西藏地质矿产勘查开发局第五地质大队;
【基金】：国家自然科学基金项目《西藏自治区改则县多不杂斑岩铜金矿床岩浆演化与成矿背景研究》(批准号:41202049)、《西藏冈底斯过铝花岗岩的岩石成因及其对地壳生长的约束》(编号:41272091) 中国地质调查局项目《中国矿产地质与成矿规律综合集成和服务》(矿产地质志)(编号:DD20160346)、《滇西地区三稀等重要矿产地质调查》(编号:DD20179604)、《西南三江有色金属资源基地调查》(编号:DD20160016)
【分类号】：P597.3;P618.41

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