In situ trace elements and Sr isotopes in scheelite and S-Pb isotopes in sulfides from the Shiweidong W–Cu deposit, giant Dahutang ore field: Implications to the fluid evolution and ore genesis
In situ trace elements and Sr isotopes in scheelite and S-Pb isotopes in sulfides from the Shiweidong W–Cu deposit, giant Dahutang ore field: Implications to the fluid evolution and ore genesis
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大湖塘巨型矿田石围洞瓦铜矿床白钨矿中的原位微量元素和Sr同位素以及硫化物中的S-Pb同位素：对流体演化和成矿的启示
DOI：
10.1016/j.oregeorev.2020.103696
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发表时间：
2020
影响因子：
3.3
通讯作者：
Dexian Zhang
中科院分区：
文献类型：
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作者：
Jingya Cao;Xiaoyong Yang;Dexian Zhang
石围洞钨铜多金属矿床，WO3资源量30万吨，铜资源量20万吨，是大湖塘巨型矿田主要钨多金属矿床之一。本研究对白钨矿和硫化物进行了一系列原位分析，旨在对该矿床的来源、热液成矿过程、流体演化历史和成因提供新的认识，对认识特大型大湖塘矿田的形成具有重要意义。石英脉、细脉浸染型钨矿体主要赋存于新元古代花岗闪长岩和/或燕山期斑状二云母花岗岩中。该矿床从早到晚划分出四个成矿阶段：1）伟晶岩阶段； 2)硅酸盐-氧化物阶段； 3)氧化物-硫化物阶段； 4)硫化物阶段。第3阶段黄铜矿和黄铁矿的δ34SV-CDT值分别为-1.73‰至-1.46‰和-1.66‰至-0.31‰，表明与岩浆相关的热液成因。黄铁矿的 206Pb/204Pb、2067Pb/204Pb 和 208Pb/204Pb 比值范围分别为 18.169 至 18.295、15.650 至 15.679 和 38.496 至 38.525，揭示了 Pb 的地壳成因。白钨矿的微量元素组成表明，2级白钨矿（白钨矿-II）和3级白钨矿（白钨矿-III）均具有较高的Nb和REE含量。白钨矿-II 的 Y/Ho 比值范围较窄 (16.2–31.0)，明显负 Eu 异常 (Eu/Eu* = 0.04–0.46) 和相对较低的 87Sr/86Sr 比值 (0.72640–0.73336)，而白钨矿-III 显示可变的 Y/Ho 比值为 20.6–96.9，正 Eu 异常异常 (Eu/Eu* = 1.31–7.11) 和相对较高的 87Sr/86Sr 比率 0.73496–0.76098。这些数据表明，白钨矿-II的Eu异常和Sr同位素组成继承自岩浆热液流体，而白钨矿-III的Eu异常和Sr同位素组成则源自由于强烈的流体-岩石相互作用和大气流体输入而改变的流体。我们的数据还表明，白钨矿-II 和白钨矿-III 的稀土元素主要受 3Ca2+= □Ca + 2REE3+ 替代机制控制。富W还原流体和强烈的流体-岩石相互作用，可以提供足够的W和Ca，可能是室围洞钨矿床白钨矿形成的关键因素。
The Shiweidong W–Cu polymetallic deposit, with resources of 300,000 t WO3and 200,000 t Cu, is one of the major tungsten polymetallic deposits in the giant Dahutang ore field. This study conducted a series ofin-situanalyses on scheelite and sulfides, aiming to provide some new insights into the sources, hydrothermal ore-forming processes, fluid evolution history and genesis of this deposit, which is of importance to understand the formation of the super-large Dahutang ore field. Quartz vein- and veinlet-disseminated-type tungsten ore bodies are mainly hosted in Neoproterozoic granodiorite and/or the Yanshanian porphyritic two-mica granites. Four stages of mineralization from early to late are identified in this deposit: 1) pegmatite stage; 2) silicate-oxide stage; 3) oxide-sulfide stage; and 4) sulfide stage. The δ34SV-CDTvalues of stage 3 chalcopyrite and pyrite are from −1.73‰ to −1.46‰ and from −1.66‰ to −0.31‰, respectively, indicating a magma-related hydrothermal origin. The206Pb/204Pb,2067Pb/204Pb and208Pb/204Pb ratios of pyrite range from 18.169 to 18.295, 15.650 to 15.679, and 38.496 to 38.525, respectively, revealing a crust origin for the Pb. Trace element compositions of scheelite show that the both stage 2 scheelite (scheelite-II) and stage 3 scheelite (scheelite-III) have high contents of Nb and REEs. The scheelite-II has a narrow range of the Y/Ho ratios (16.2–31.0), obviously negative Eu anomalies (Eu/Eu* = 0.04–0.46) and relatively low87Sr/86Sr ratios of 0.72640–0.73336, whereas scheelite-III shows variable Y/Ho ratios of 20.6–96.9, positive Eu anomalies (Eu/Eu* = 1.31–7.11) and relatively high87Sr/86Sr ratios of 0.73496–0.76098. These data indicated that the Eu anomalies and Sr isotopic compositions of scheelite-II were inherited from magmatic-hydrothermal fluids, whereas those of scheelite-III were sourced from modified fluids due to intense fluid-rock interaction and input of meteoric fluids. Our data also reveal that the REEs of scheelite-II and scheelite-III are mainly controlled by the substitution mechanism of 3Ca2+= □Ca + 2REE3+. The W-rich reduced fluids and intense fluid-rock interactions, which could provide enough W and Ca, are likely the key factors for the formation of scheelite in the Shiweidong tungsten deposit.