Tracing mineralization history from the compositional textures of sulfide association: A case study of the Zhenzigou stratiform Zn-Pb deposit, NE
Tracing mineralization history from the compositional textures of sulfide association: A case study of the Zhenzigou stratiform Zn-Pb deposit, NE
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从硫化物组合的成分结构追踪成矿历史：以东北地区珍珠沟层状锌铅矿床为例
DOI：
10.1016/j.oregeorev.2020.103792
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发表时间：
2020
影响因子：
3.3
通讯作者：
Chen Peiwen
中科院分区：
文献类型：
--
作者：
Zhou Lingli;Zeng Qingdong;Liu Jianming;Duan Xiaoxia;Sun Guotao;Wang Yongbing;Chen Peiwen
青城子矿田位于我国东北部，有十多个铅锌矿床和多个金银矿床。其中，榛子沟铅锌存款矿床为典型的层状矿床，矿体呈层状、透镜状分布。矿石矿物组成简单，主要为闪锌矿、方铅矿、黄铁矿、磁黄铁矿及少量毒砂、白铁矿、辉银矿。选取闪锌矿-方铅矿-黄铁矿-毒砂硫化物组合为研究对象，通过LA-ICPMS斑点和作图分析，研究了硫化物组合的内部成分结构，旨在制约矿床成因、流体演化历史和元素分配行为。结果表明，成矿作用经历了3个不同的流体阶段，即形成黄铁矿核（Py 0）的2052 Ma的沉积流体阶段，形成黄铁矿核（Py 1）的1800 Ma的变质流体阶段，形成黄铁矿核（Py 1）的增生和闪锌矿（Sph 1）、毒砂（Aspy 1）的新结晶，最后一幕与三叠纪岩浆活动有关的热液流体，形成了黄铁矿（Py 2）、闪锌矿（Sph 2）和毒砂（Aspy 2）的另一次过度生长，并伴随少量方铅矿（Ga）的沉淀。沉积流体温度较低（<150 °C），富集Cu、Pb、Zn、Ag，贫Co、Ni、As。黄铁矿是主要的沉淀硫化物矿物，清除大部分有效微量元素。晚期变质和岩浆流体温度高（>300 °C），对As、Co和Ni有再活化作用，但仅限于矿物颗粒尺度。晚变质岩浆流体富集In、Cd、Au、As、Ag、Cu、Pb、Sb、Sn、Co、Ni，亏损Bi、W、Mo、Te、Se。流体中的大多数金属进入硫化物矿物的分配是由流体中金属的有效性和通过直接或耦合取代与晶体结构的相容性控制的。黄铁矿是Co、Ni、Pb、As的主要赋存矿物;毒砂以Sb、Pb为主，其次为Au;闪锌矿是Cd、In、Cu的主要赋存矿物，其次为Ag、Sn;方铅矿是Ag、Sb、Sn的主要赋存矿物，其次为Cd、In、As。特别是与三叠纪岩浆活动有关的热液流体携带了大量的In和Cd，表明岩浆热液流体对成矿作用的贡献是显著的。总之，我们的硫化物矿物的原位地球化学证据加强了沉积-变质-岩浆-热液改造模式的榛子沟层状锌铅矿化。该案例研究强调了共生硫化物矿物的组成结构在评价矿石成因时的重要性。总之，我们的研究表明，通过整合微量元素制图和现场分析共存的硫化物矿物，它是可能的重建流体演化历史，解决与流体演化相关的金属行为，并审查个别流体对成矿作用的贡献。
The Qingchengzi Orefield located in northeastern China hosts more than ten Pb-Zn deposits and several Au-Ag deposits. Among those, the Zhenzigou Zn-Pb deposit displays a typical stratiform morphology, comprising ore bodies in layers and lenses. The ore minerals are simply composed of sphalerite, galena, pyrite, and pyrrhotite, together with minor arsenopyrite, marcasite, and argentite. A sulfide association of sphalerite-galena-pyrite-arsenopyrite was selected for this study; the interior compositional texture of the sulfide association was investigated by means of LA-ICPMS spot and mapping analysis, with the aim of constraining the ore genesis, fluid evolution history and element partitioning behavior. The results show that three distinct fluids were involved in the mineralization, namely an episode of sedimentary fluids at ∼2052 Ma which is responsible for the precipitation of pyrite core (Py0), an episode of metamorphic fluids at ∼1800 Ma which formed an overgrowth of pyrite (Py 1) and new crystallization of sphalerite (Sph1) and arsenopyrite (Aspy1), and a final episode of hydrothermal fluids related to the Triassic magmatism, forming another overgrowth of pyrite (Py2), sphalerite (Sph2) and arsenopyrite (Aspy2), together with minor precipitation of galena (Ga). The sedimentary fluids are relatively low in temperature (<150 °C), enriched in Cu, Pb, Zn, Ag, and depleted in Co, Ni, and As. Pyrite is the main precipitated sulfide mineral, scavenging most of the available trace elements. The late metamorphic and magmatic fluids are high in temperature (>300 °C) and have remobilized As, Co and Ni but only at mineral grain scale. The late metamorphic and magmatic fluids are enriched in In, Cd, Au, As, Ag, Cu, Pb, Sb, Sn, Co and Ni, and depleted in Bi, W, Mo, Te, and Se. The partitioning of most of the metals from the fluids into the sulfide minerals was controlled by the metals’ availability in the fluids and by the compatibility with crystal structure through direct or coupled substitutions. Pyrite acts as the main host of Co, Ni, Pb, and As; arsenopyrite hosts a major amount of Sb and Pb, and a minor amount of Au; sphalerite is the primary host of Cd, In, Cu, and the secondary host of Ag and Sn; galena is the primary host of Ag, Sb, Sn, and subordinately hosts Cd, In and As. In particular, a remarkable amount of In and Cd was carried by the hydrothermal fluids associated with the Triassic magmatism, indicating that the contribution of magmatic hydrothermal fluids to the mineralization is significant. In conclusion, our in-situ geochemical evidence of sulfide minerals reinforces a sedimentation-metamorphism-magmatic-hydrothermal reworking model for the Zhenzigou stratiform Zn-Pb mineralization. This case study underlines the significance of compositional textures of coexisting sulfide minerals when assessing the ore genesis. Overall, our study demonstrates that, by integrating trace element mapping and spot analysis on coexisting sulfide minerals, it is possible to re-construct the fluid evolution history, resolve the metal behaviors associated with fluids evolution, and review the contribution of individual fluids to mineralization.