Ore genesis of Kongxigou and Nanmushu Zn-Pb deposits hosted in Neoproterozoic carbonates, Yangtze Block, SW China: Constraints from sulfide chemistry, fluid inclusions, and in situ S-Pb isotope analyses
Ore genesis of Kongxigou and Nanmushu Zn-Pb deposits hosted in Neoproterozoic carbonates, Yangtze Block, SW China: Constraints from sulfide chemistry, fluid inclusions, and in situ S-Pb isotope analyses
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中国西南扬子地块新元古代碳酸盐岩孔西沟和楠木树锌铅矿床成因：硫化物化学、流体包裹体和原位硫铅同位素分析的制约
DOI：
10.1016/j.precamres.2019.105405
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发表时间：
2019
影响因子：
3.8
通讯作者：
He Dong Zhao
中科院分区：
文献类型：
--
作者：
Suo-Fei Xiong;Shao-Yong Jiang;Ying Ma;Tao Liu;Kui Dong Zhao;Man Rong Jiang;He Dong Zhao
新近发现的孔西沟和楠木树铅锌矿床产于扬子地块北方缘陕西省马元古宙灯影组碳酸盐岩中。矿床具有成矿前沉积成岩、主矿热液成矿（Ⅰ、Ⅱ、Ⅲ期）和成矿后表生三个阶段的成矿历史。可区分多个硫化物世代，包括闪锌矿的两个世代，例如，Sp（a）来自第I阶段，Sp（B）来自第II阶段; Py（s）来自成岩期，Py（a）来自成岩Ⅰ期，Py（B）来自成岩Ⅱ期。孔西沟和楠木树矿床的沉积和成岩期以Py（s）为特征，δ 34 S值为高正值（+16.2 ~+19.9‰）。热液沉积阶段Zn-Pb硫化物的δ 34 S值为正（+11.4 ~+23.9‰），可能是海水或碳酸盐来源的硫酸盐的热化学还原（TSR）所致，热液阶段I ~阶段II的原位δ 34 S特征记录了不同的硫源。成矿流体具有中高温（137 °C ~ 329 °C）、高盐度（可达27.7wt%NaCl + CaCl 2当量）、以Na-Ca-（Mg）-Cl为主、富含烃类（如碳酸盐、碳酸热液期硫化物的原位铅同位素分析表明，208 Pb/204 Pb、207 Pb/204 Pb和206 Pb/204 Pb比值分别为37.865-37.979、15.635-15.661和17.885-18.101，表明铅来自基底和容矿岩石。提出孔溪沟和楠木树矿床的成因不同于典型的MVT型锌铅存款矿床模式，并提出了一种新的热液期盆地卤水聚集与锌铅硫化物沉淀混合模式。
The recently discovered Kongxigou and Nanmushu Zn-Pb deposits are hosted in the Neoproterozoic Dengying Formation carbonates in the Mayuan district of Shaanxi Province, SW China, the northern margin of Yangtze Block. The deposits show a three-period mineralization history: (1) pre-ore sedimentary and diagenetic, (2) main-ore hydrothermal mineralization (stages I, II, and III), and (3) post-ore supergene. Multiple sulfide generations are distinguished, including two generations for sphalerite, e.g., Sp(a) from the stage I and Sp(b) from the stage II; and three generations for pyrite, e.g., Py(s) from the diagenetic period, Py(a) from the stage I and Py(b) from the stage II. The sedimentary and diagenetic period of the Kongxigou and Nanmushu deposits are characterized by Py(s) with high positive δ34S values (+16.2 to +19.9‰). The hydrothermal Zn-Pb sulfide precipitation stages are characterized by positive δ34S values (+11.4 to +23.9‰) that were likely caused by thermochemical sulfate reduction (TSR) of seawater or evaporitic sourced sulfates.In situδ34S characteristics from the hydrothermal stage I to stage II record different sulfur sources. The ore-forming fluids show features of moderate-high temperature (137 °C–329 °C), high salinity (can reach up to 27.7 wt% NaCl + CaCl2equivalent) with a Na-Ca- (Mg) -Cl dominant composition, hydrocarbon-rich (e.g., CH4and bitumen), which are interpreted as basin brines.In situlead isotope analyses of hydrothermal stage sulfides show208Pb/204Pb,207Pb/204Pb, and206Pb/204Pb ratios of 37.865–37.979, 15.635–15.661 and 17.885–18.101, respectively, which suggest a mixing of lead from the basement and the host rocks. We suggest the ore genesis of Kongxigou and Nanmushu deposits differs from the typical MVT Zn-Pb deposit models, and propose a new mixing model of basin brine accumulation and Zn-Pb sulfide precipitation in the hydrothermal stages.