Geochronology and Genesis of the Tiegelongnan Porphyry Cu(Au) Deposit in Tibet: Evidence from U-Pb, Re-Os Dating and Hf, S, and H-O Isotopes
Geochronology and Genesis of the Tiegelongnan Porphyry Cu(Au) Deposit in Tibet: Evidence from U-Pb, Re-Os Dating and Hf, S, and H-O Isotopes
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西藏铁格隆南斑岩铜（金）矿床的年代学和成因：来自 U-Pb、Re-Os 测年和 Hf、S、H-O 同位素的证据
DOI：
10.1111/rge.12113
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发表时间：
2017
期刊：
影响因子：
1.4
通讯作者：
Feng Jun
中科院分区：
文献类型：
--
作者：
Lin Bin;Tang Ju-Xing;Chen Yu-Chuan;Song Yang;Hall Greg;Wang Qin;Yang Chao;Fang Xiang;Duan Ji-lin;Yang Huan-Huan;Liu Zhi-Bo;Wang Yi-Yun;Feng Jun
铁格隆南铜(金)矿床是班公怒江成矿带新发现的最大铜矿床。矿床具有明显的蚀变分带，从核心到边缘，由钾质到青绿岩型，叠加有千粒状和高级泥质蚀变。矿床浅部为高硫化态叠加，主要为浸染型黄铁矿和铜S矿物，如斑铜矿、金银矿、闪长岩、辉绿岩等。深部斑岩型矿化主要为浸染状黄铜矿、斑铜矿、黄铁矿和少量脉状辉钼矿。矿化呈浸染状，与斑岩侵入体及其围岩中的矿脉伴生。矿化闪长斑岩和花岗闪长斑岩的锆石U-Pb年龄分别为123.1±11.7 Ma(2σ)和121.5±11.5 Ma(2σ)。辉钼矿Re-Os年龄为121.2 Ma±71.2 Ma，表明成矿作用与岩浆活动密切相关。安山岩熔岩(锆石U-Pb年龄111.7±11.6 Ma，2σ)覆盖矿体，是成矿后火山活动的产物，对矿体的保存起到了至关重要的作用。金属硫化物的−4.6值、‰值、‰δ34S值(平均值−、1.55、‰)表明，S主要有深部岩浆源区。氢、氧同位素组成为(δD=−87‰to−‰；δ18OH2O=95.5‰~9.0‰)，表明成矿流体以岩浆-热液为主，可能混入少量大气降水。闪长斑岩的锆石εHf(T)为3 7~8 3，花岗闪长斑岩为1 8~7 5。辉钼矿具有382.2×10~(-6)~1600×10~(-10)−~6~1600×10~(-6)−~6的高Re。稀土和Hf同位素组成表明铁格隆南具有一定的地幔来源，可能是来自壳幔混合源的年轻下地壳。铁格隆南巨型斑岩系的成矿作用与早白垩世(~120 Ma)中酸性岩浆有关。铁格隆南矿床的岩浆源区有一些地幔成分，可能与壳源物质混合在一起。
The Tiegelongnan Cu (Au) deposit is the largest copper deposit newly discovered in the Bangong–Nujiang metallogenic belt. The deposit has a clear alteration zoning consisting of, from core to margin, potassic to propylitic, superimposed by phyllic and advanced argillic alteration. The shallow part of the deposit consists of a high sulphidation‐state overprint, mainly comprising disseminated pyrite and Cu–S minerals such as bornite, covellite, digenite, and enargite. At depth porphyry‐type mineralization mainly comprises disseminated chalcopyrite, bornite, pyrite, and a minor vein molybdenite. Mineralization is disseminated and associated with veins contained within the porphyry intrusions and their surrounding rocks. The zircon U–Pb ages of the mineralized diorite porphyry and granodiorite porphyry are 123.1 ± 1.7 Ma (2σ) and 121.5 ± 1.5 Ma (2σ), respectively. The molybdenite Re–Os age is 121.2 ± 1.2 Ma, suggesting that mineralization was closely associated with magmatism. Andesite lava (zircon U–Pb age of 111.7 ± 1.6 Ma, 2σ) overlies the ore‐bodies and is the product of post‐mineralization volcanic activity that played a critical role in preserving the ore‐bodies. Values of −4.6 ‰ to + 0.8 ‰ δ34S for the metal sulfides (mean − 1.55 ‰) suggest that S mainly has a deep magmatic source. The H and O isotopic composition is (δD = −87 ‰ to −64 ‰; δ18OH2O= 5.5 ‰ to 9.0 ‰), indicating that the ore‐forming fluids are mostly magmatic‐hydrothermal, possibly mixed with a small amount of meteoric water. The zircon εHf(t) of the diorite porphyry is 3.7 to 8.3, and the granodiorite porphyry is 1.8 to 7.5. Molybdenite has a high Re from 382.2 × 10−6to 1600 × 10−6. Re and Hf isotope composition show that Tiegelongnan has some mantle source, maybe the juvenile lower crust from crust–mantle mixed source. Metallogenesis of the Tiegelongnan giant porphyry system was associated with intermediate to acidic magma in the Early Cretaceous (~120 Ma). The magma provenance of the Tiegelongnan deposit has some mantle‐derived composition, possibly mixed with the crust‐derived materials.