Genesis of the vein-type Gaocheng Ag-Pb-Zn deposit in the western Guangdong Province of China and its implication for regional exploration
Genesis of the vein-type Gaocheng Ag-Pb-Zn deposit in the western Guangdong Province of China and its implication for regional exploration
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粤西高城脉型银铅锌矿床成因及区域找矿意义
DOI：
10.1016/j.oregeorev.2021.104137
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发表时间：
2021-03
期刊：
影响因子：
--
通讯作者：
Shunda Yuan
中科院分区：
文献类型：
--
作者：
Haijie Zhao;Leon Bagas;Shunda Yuan
粤西大干山地区是重要的钨、锡、银铅锌矿化区。尽管脉型银铅锌矿床通常与钨锡矿床和锡矿床在空间上相关，但它们之间的成因联系仍不清楚。新发现的藁城矿床是该地区典型的脉型银铅锌矿床，矿体主要为志留系黑云母二长花岗岩，其次为晚白垩世石英斑岩。在这里，我们介绍了闪锌矿的新 Rb-Sr 测年、流体包裹体显微测温、矿床的 H-O-S 同位素地球化学，以及矿化石英斑岩的全岩主量和微量元素地球化学。目的是更好地了解银-铅-锌矿化的成因及其与该地区钨和锡矿床的联系。闪锌矿Rb-Sr年龄为90±6Ma，表明成矿作用为晚白垩世，与石英斑岩类似。在石英斑岩周围已发现了三个矿脉组，包括早期毒砂-黄铁矿-石英矿脉，其中硫化物-石英-银矿脉和晚期（未矿化）方解石-石英-萤石矿脉。第一脉组的流体包裹体均一温度为 360–300 °C，盐度为 8.2–6.4% NaCl 当量；第二脉组的流体包裹体均一温度为 320–240 °C，盐度为 6.5–4% NaCl 当量；晚期脉组的流体包裹体均质温度为 220–160 °C，相应的盐度为 4.2–3.4% NaCl 当量。这表明矿化流体的温度和盐度逐渐降低。包裹体中含盐流体所伴随的蒸气成分为H2O，并含有少量CO2和CH4，这表明成矿流体包括H2O–NaCl(–CO2–CH4)。早期脉组流体包裹体含+6.52～+6.13‰δ18OH2O和–91～–85‰δDH2O，矿化第二脉组流体包裹体含+5.72～+2.41‰、δ18OH2O和-72～-42‰δDH2O。这些资料表明，以Ⅰ期和Ⅱ期脉组为代表的矿化流体中含有逐渐被大气流体污染的岩浆液。 δ34S 值在-2.2 至-2.4‰ 之间的狭窄范围也表明了成矿流体的岩浆来源。全岩分析表明，晚白垩世石英斑岩是一种高分异过铝质花岗岩，与大干山地区的钨、锡相关花岗岩相似。因此，藁城脉型银铅锌矿床在成因上与晚白垩世石英斑岩有关，与大干山地区含锡花岗岩具有相似的地球化学特征，也具有锡矿化前景。
The Daganshan region in the western part of the Guangdong Province is an important mineralised area containing W, Sn, and Ag–Pb–Zn occurrences. Although vein-type Ag-Pb-Zn deposits are usually spatially related to W-Sn and Sn deposits, the genetic links between them are still not understood. The newly discovered Gaocheng deposit is a typical vein-type Ag-Pb-Zn deposit in this region, which is hosted predominantly by a Silurian biotite monzogranite and to a lesser extent by a Late Cretaceous quartz porphyry. Here, we present new Rb-Sr dating of sphalerite, fluid inclusion microthermometry, and H-O-S isotopic geochemistry of the deposit, and whole-rock major and trace elements geochemistry of the mineralised quartz porphyry. The aim is to better understand the genesis of the Ag-Pb-Zn mineralisation and its link with W, and Sn deposits in the region. The sphalerite Rb-Sr age is 90 ± 6 Ma, indicating that mineralisation is Late Cretaceous similar to that of the quartz porphyry. Three vein sets have been recognised around the quartz porphyry comprising early arsenopyrite–pyrite–quartz veins crossed by sulphides–quartz–Ag veins and late (non-mineralised) calcite–quartz–fluorite veins. The fluid inclusions have homogenisation temperatures of 360–300 °C with salinities of 8.2–6.4% NaCl equivalent for the first vein set, 320–240 °C with salinities of 6.5–4% NaCl equivalent for the second vein set, and 220–160 °C with a corresponding salinity of 4.2–3.4% NaCl equivalent for the late vein set. This indicates a gradual decrease of temperature and salinity of the mineralising fluids. The composition of the vapour accompanying the saline fluid in the inclusions is H2O with minor amounts of CO2and CH4, which indicates that the mineralising fluid included H2O–NaCl(–CO2–CH4). The fluid inclusions in the early vein set assays +6.52 - +6.13‰ δ18OH2Oand –91 - –85‰ δDH2O, and the fluid inclusions in the mineralised second vein set contains +5.72 to +2.41‰, δ18OH2Oand −72 to −42‰ δDH2O. These data indicate that the mineralised fluids represented by the stage I and II vein sets included magmatic fluids that were gradually contaminated by meteoric fluids. The magmatic source of the mineralising fluid is also indicated by the narrow range of δ34S values between −2.2 and −2.4‰. The whole-rock analyses show that the Late Cretaceous quartz porphyry is a highly fractional peraluminous granite, similar to the W- and Sn-related granites in the Daganshan region. The Gaocheng vein-type Ag-Pb-Zn deposit is therefore genetically related to the Late Cretaceous quartz porphyry and shares similar geochemical characteristics at Sn-bearing granites in the Daganshan region and is also prospective for Sn mineralisation.
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DOI：
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