Genesis of the Aqishan skarn Zn-Pb deposit in the Eastern Tianshan, NW China: Constraints from geology, geochronology and Hf-S-Pb isotopic geochemistry
Genesis of the Aqishan skarn Zn-Pb deposit in the Eastern Tianshan, NW China: Constraints from geology, geochronology and Hf-S-Pb isotopic geochemistry
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东天山阿旗山矽卡岩锌铅矿床成因：地质、年代学和Hf-S-Pb同位素地球化学的制约
DOI：
10.1016/j.oregeorev.2020.103608
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发表时间：
2020-08
影响因子：
3.3
通讯作者：
Zhao Yun
中科院分区：
文献类型：
--
作者：
Dai Junfeng;Xue Chunji;Chi Guoxiang;Gao Rongzhen;Ming Hao;Zhao Xiaobo;Zhao Yun
阿其山矿床位于中国新疆东天山，是新发现的大型锌铅矿床，探明铅锌金属储量为1.94 Mt，平均品位为1.05%。锌铅矿体呈板状和透镜状，发育在雅曼苏组的矽卡岩碳酸盐岩和钙质火山碎屑岩中。夕卡岩矿物组合的特点是富含石榴石、绿帘石、绿泥石、阳起石、方解石和石英，以及少量的辉石。金属矿物主要有闪锌矿、方铅矿、黄铜矿、黄铁矿、磁黄铁矿、毒砂等，主要呈浸染状和不规则斑块状赋存于夕卡岩中。对五个同矿阶段黄铁矿样品进行铼锇测年，得出等时线年龄为 301 ± 13 Ma，与阿旗山锌铅矿床东南部花岗闪长斑岩测得的 306 ± 2.8 Ma 年龄一致。花岗闪长斑岩中锆石的 εHf(t) 值在 + 9.62 到 + 14.69 之间变化，表明是新生地壳来源。 22个硫化物样品的δ34SV-CDT值范围为-11.6‰~-2.76‰，平均值为-5.08‰。 9个硫化物样品的206Pb/204Pb、207Pb/204Pb和208Pb/204Pb比值范围分别为18.102～18.336、15.539～15.655和37.929～38.479，与阿旗山地区石炭系陨石相似，部分与雅曼苏组火山碎屑岩重叠。根据这些数据，我们推测阿奇山矿床是由花岗闪长斑岩发出的岩浆热液形成的。大部分金属来自岩浆侵入，火山碎屑岩的贡献较小，而硫可能主要是从围岩中提取的，岩浆源的贡献较小。阿旗山地区石炭纪岩浆作用与矽卡岩型锌铅矿化以及该地区其他矿床之间的密切成因关系表明，在东天山发现更多类似矿床的潜力很大，那里发育与晚古生代北天山大洋板片俯冲到伊犁-中天山地体之下有关的碳酸盐岩或钙质火山碎屑岩和岩体。
The Aqishan deposit, located in the Eastern Tianshan, Xinjiang, China, is a newly discovered large-scale Zn-Pb deposit with a proven reserve of 1.94 Mt Pb and Zn metal at an average grade of 1.05%. The Zn-Pb orebodies are tabular and lentoid in shape, developed within skarnized carbonates and calcareous volcanoclastic rocks of the Yamansu Formation. The skarn mineral assemblages are characterized by abundant garnet, epidote, chlorite, actinolite, calcite and quartz, with minor amounts of pyroxene. Metallic minerals, comprising sphalerite, galena, chalcopyrite, pyrite, pyrrhotite and arsenopyrite, mainly occur as disseminations and irregular patches within the skarn. Re-Os dating of five syn-ore stage pyrite samples yielded an isochron age of 301 ± 13 Ma, which is in agreement with the 306 ± 2.8 Ma age obtained from the granodiorite porphyry occurring at southeast part of the Aqishan Zn-Pb deposit. The εHf(t) values of zircon from the granodiorite porphyry vary from + 9.62 to + 14.69, suggesting a juvenile crust source. Theδ34SV-CDTvalues of 22 sulfide samples range from −11.6‰ to −2.76‰, with an average of −5.08‰. The206Pb/204Pb,207Pb/204Pb and208Pb/204Pb ratios of 9 sulfide samples range from 18.102 to 18.336, 15.539 to 15.655, and 37.929 to 38.479, respectively, which are similar to the Carboniferous grantoids of the Aqishan area and partly overlap with the volcanoclastic rocks of the Yamansu Formation. Based on these data, we propose that the Aqishan deposit formed from magmatic-hydrothermal fluids that emanated from the granodiorite porphyry. Much of the metals were derived from the magmatic intrusions with minor contributions from the volcanoclastic rocks, whereas the sulfur may have been mainly extracted from the country rocks with slight contributions from a magmatic source. The close genetic relationships between the Carboniferous magmatism and skarn type Zn-Pb mineralization in the Aqishan area as well as other deposits in the region suggests a great potential of finding more analogous deposits in the Eastern Tianshan, where carbonates or calcareous volcanoclastic rocks and plutons that related to the subduction of the Northern Tianshan Oceanic slab beneath the Yili-Central Tianshan Terrane during Late Paleozoic are well-developed.
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