Geochemistry of Elements, Sulphur-Lead Isotopes and Fluid Inclusions from Jinla Pb-Zn-Ag Poly-Metallic Ore Field at the Joint Area across China and Myanmar Border
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摘要: 跨越中缅边境的金腊铅-锌-银多金属矿田包括南腊和金厂两处铅锌银矿床, 大地构造上处于保山-掸泰地块东缘, 勐统-耿马-西盟元古宙-古生代被动大陆边缘活动带南段.通过对容矿围岩、与矿化有关的花岗岩和矿石元素地球化学以及矿石硫、铅同位素和流体包裹体的研究, 结论如下: (1) 与同类岩石相比, 与矿化有关的花岗岩普遍富集Pb、Zn、Cu、Au、Sn、W等成矿元素, 其中钾长花岗斑岩与Pb-Zn-Ag矿化关系最密切. (2) 铅同位素表明, 矽卡岩型致密块状矿石铅同位素比值(206Pb/204Pb、207Pb/204Pb和208Pb/204Pb) 皆低于热液充填型角砾状矿石和似层状硅化白云岩型矿石, 意味着形成于岩体接触带的矽卡岩型矿石相对形成于远离岩体的热液充填型角砾状矿石和似层状硅化白云岩型矿石含有更低的放射性成因铅. (3) 铅-锌-银矿化主要经历了两个成矿期: 矽卡岩化成矿期和中低温热液成矿期, 前者主要形成铅-锌-铜(金) 矿化, 后者主要形成铅-锌-银矿化; 中低温热液成矿期又可划分为两个成矿阶段: 中温成矿阶段(200~290℃) 和低温成矿阶段(140~200℃), 前者主要形成交代充填型硅化角砾岩矿体, 后者主要形成层间破碎带充填型硅化矿体. (4) 金腊铅锌矿床、保山-镇康地块某些铅锌矿床和昌宁-孟连火山岩带的铅锌矿床, 虽然产于不同的地质构造单元, 但矿石铅同位素组成却具有类似的特征, 而且矿化皆与喜马拉雅期侵位的花岗岩密切相关.这表明: 虽然上述矿床产出于不同的地质构造单元, 但成矿皆与喜马拉雅期构造岩浆活动具有某种内在联系.
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关键词:
- 铅-锌-银多金属矿化 /
- 地球化学 /
- 硫铅同位素 /
- 流体包裹体 /
- 中缅邻接区
Abstract: Jinla Pb-Zn-Ag poly-metallic ore field across China and Myanmar, located at the south segment of the Mengtong-Gengma-Ximeng passive continental margin of Proterozoic era-Palaeozoic era, the eastern margin of the Baoshan-Shantai Massif, includes the Nanla and the Jinchang Pb-Zn-Ag deposits.According to the studies on both the element geochemistry of the host rocks, the granites, and the ore deposits and the sulphur-lead isotopes as well as fluid inclusion from the ore deposits in Jinchang Pb-Zn-Ag deposits.The conclusions are drawn as follows. (1) The granites in this ore field are richer in Pb, Zn, Cu, Au, Sn, and W than in other granites, and the K-feldspar granite porphyry has a closer relationship with the mineralization. (2) The Pb isotope ratios (206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb) from the massive skarn Pb-Zn-Cu ores are lower than those from the brecciated Pb-Zn-Ag ores with quartzification and the stratiform Pb-Zn-Ag ores with chalcedonization, which may indicate that the former contains radioactive Pb less than the latter. (3) The Pb-Zn-Ag mineralizations may be divided into two ore-forming epochs: the skarn ore-forming epoch and the hydrotherma ore-forming epoch; the former is associated with Pb-Zn-Cu mineralization, the latter with Pb-Zn-Ag mineralization.The hydrothermal ore-forming epoch may be subdivided into two hydrothermal ore-forming stages: the mesothermal ore-forming stage (200-290 ℃) at which the brecciated ores were deposited, and the epithermal ore-forming stage (140-200 ℃) at which the stratiform ores were formed. (4) The Jinla Pb-Zn-Ag deposits not only have the same features of Pb isotope ratios as some Pb-Zn deposits formed at the Baoshan-Zhengkang terrain and as some Pb-Zn deposits formed at the Changning-Menglian volcanic belt but also these Pb-Zn deposits are associated with the granites emplaced at Himalayan orogenic episode, which may indicate that although forming different geological tectonic terrains, these Pb-Zn deposits have intrinsic connection with the Himalayan technomagmaism. -
图 1 中缅毗邻区金(金厂) 腊(南腊) 铅锌银矿田地质矿产简图
1.古新统-始新统砂砾岩; 2.白垩系砂岩; 3.三叠系灰岩; 4.奥陶系石英砂岩; 5.寒武系千枚岩和板岩; 6.新元古界千枚岩和板岩; 7.新元古界千枚岩和片岩; 8.新元古界大理岩化白云岩; 9.二长花岗岩; 10.钾长花岗岩; 11.变辉绿岩; 12.地层界线; 13.地层不整合界线; 14.断层; 15.国界; 16.铅锌银矿床(矿点); Ⅰ.扬子板块亚构造域; Ⅱ.东特提斯亚构造域; Ⅲ.西藏-缅甸亚构造域; Ⅲ1.勐统-西盟元古宙-古生代被动边缘活动带; Ⅲ2.保山-掸泰地块; Ⅲ3.腾冲-瑞丽地块
Fig. 1. Simplified map showing geology and Pb-Zn-Ag mineralization of Jinla ore field across China and Myanmar border
图 2 金腊铅-锌-银矿床206Pb/204Pb-207Pb/204Pb关系(Zartman and Doe (1981))
Fig. 2. Map showing relationships between206Pb/204Pb-207Pb/204Pb in the Pb-Zn-Ag mineralization of Jinla ore field across China and Myanmar border
图 3 金腊铅锌矿床成矿流体温度分布
Fig. 3. Temperature frequency histogram of the primary fluid inclusions from the Jinla lead-zinc deposits across China and Myanmar border
表 1 金腊Pb-Zn-Ag多金属矿田容矿岩微量元素组成
Table 1. Average contents of trace elements from the host rocks of the Jinla Pb-Zn-Ag ore field across China and Myanmar border
表 2 金腊花岗岩化学组成
Table 2. Average contents of some major and trace elements from the Jinla granites of the Jinla Pi-Zn- Ag ore fied across China and Myanmar border
表 3 金腊Pb-Zn-Ag多金属矿田矿石组分
Table 3. Average contents of trace elements from the ores of of the Jinla Pb-Zn-Ag ore field across China and Myanmar border
表 4 金腊铅锌矿田矿石硫同位素组成
Table 4. Sulfur isotope composition from the ores of the Jinla Pb-Zn-Ag deposits across Chinma and Myanmar border
表 5 金腊铅锌矿田矿石铅同位素组成
Table 5. Lead isotope composition from the ores of the Jinla Pb-Zn-Ag deposits across China and Myanmar border
表 6 金厂铅锌矿床矿物包裹体特征及均一法测试结果
Table 6. Features of fluid inclusions and their analytical results by homogenization method of the Jinchang Pb-Zn deposits across China and Myanmar border
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