近日，昆明理工大学刘毅等在研究滇东南官房钨矿床的多阶段钨矿化中取得新进展，研究提供了对白钨矿原位微量元素和锶同位素分析的启示。这一研究成果于2024年7月24日发表在国际顶尖学术期刊《地球化学学报》上。

本研究对KT6矿体进行了详细的野外地质调查，系统采样，以圈定其成矿阶段。研究使用白钨矿的CL图像、原位LA-ICP-MS微量元素和Sr同位素，对不同时期形成的不同世代白钨矿进行了精细矿物学研究。这些发现确定了成矿过程中流体的演化，为矿床的成因提供了线索。

研究结果表明，官房钨矿床的成矿阶段为：前进矽卡岩阶段、后退矽卡岩阶段、石英—硫化物阶段和碳酸盐—萤石阶段。在前三个阶段观察到不同世代的白钨矿(SchI, SchII, SchIII)，呈现明显的球粒状标准化稀土元素模式。SchI的稀土元素主要通过REE³⁺+□_Ca置换到Ca位点上。Nb对REE也可能存在类似的置换，但不是主要的替代方法。

SchII的稀土元素主要以REE³⁺+Na⁺的形式进入白钨矿晶格中，并且可能存在Nb对REE类质同相的替代。在早期阶段，SchIII的REE主要被Nb取代，形成REE类质同相，后期REE³⁺+□_Ca的置换模式与之共存。白钨矿中的Mo含量以及白钨矿和石榴子石中相应的Eu异常共同表明，成矿流体在其不同成矿阶段以氧化性为主，仅在SchII中观察到轻微的还原性。

白钨矿精矿的原位Sr同位素比值在0.7093-0.7153之间，与薄竹山花岗岩相似，表明钨矿化与花岗岩存在一定的关系。此外，各成矿阶段白钨矿的Y/Ho比值范围较窄(19-31)，Y与Ho含量相关性显著，变化趋势相似。这种一致性表明官房矿床经历了一个均匀或相似的演化过程，表明在不同的成矿阶段具有稳定的成矿流体。

据介绍，官房大型钨矿床位于中国云南东南薄竹山钨多金属矿集中地区。尽管前人已经在此进行了广泛的研究，但该矿床的流体演化过程仍不明确，导致其成因存在争议。

附：英文原文

Title: Multiple-stage W mineralization in the Guanfang W deposit, southeastern Yunnan Province, China: Insights from scheelite in-situ trace elemental and Sr isotopic analyses

Author: Sun, Bin, Liu, Yi, Kong, Zhigang, Liu, Xuelong, Jiang, Xiaojun, Li, Chao, Li, Wenchang

Issue&Volume: 2024-07-24

Abstract: The Guanfang large-scale W deposit is located in the W polymetallic ore concentration area of Bozhushan in southeastern Yunnan, China. Despite extensive research, the fluid evolution process of the deposit remains ambiguous, leading to controversy regarding its genesis. This study conducted a detailed field geological survey, with systematic sampling of the KT6 orebody, to delineate mineralization stages. Fine mineralogy work, including the use of CL images of scheelite, in-situ LA-ICP-MS trace elements, and Sr isotopes, was carried out on different generations of scheelite formed in various stages. The findings identified the evolution of fluids in the mineralization process, shedding light on the genesis of the deposit. The study revealed four mineralization stages at the Guanfang W deposit: prograde skarn stage, retrograde skarn stage, quartz-sulfide stage, and carbonate-fluorite stage. Different generations of scheelite (Sch I, Sch II, Sch III) were observed in the first three stages, displaying distinct chondrite-normalized REE patterns. The REE of Sch I mainly substituted into the Ca site by REE³⁺ +□_Ca, and there may be a similar substitution of Nb for REE, whereas it is not the main substitution method. The REE of Sch II mainly enter the scheelite lattice in the form of REE³⁺ +Na⁺, and there may be a substitution of Nb for REE isomorphism. In the early stage, The REE of Sch III was mainly replaced by Nb for REE isomorphism, while in the later stage, the replacement mode of REE³⁺ +□_Ca coexisted with it. The Mo content in scheelite, along with the corresponding Eu anomalies in both scheelite and garnet, collectively imply that the ore-forming fluids during various mineralization stages were predominantly oxidizing, with only slight reducibility observed in Sch II. The in-situ Sr isotope ratios of scheelite concentrates ranged from 0.7093 to 0.7153, resembling those of the Bozhushan granite, indicating a relationship between W mineralization and granite. In addition, the Y/Ho ratios of scheelite from various mineralization stages exhibit a narrow range (19–31), with a pronounced correlation between the contents of Y and Ho and a similar trend in their variation. This consistency suggests that the Guanfang deposit has undergone a uniform or comparable evolutionary process, implying a stable ore-forming fluid across different mineralization stages.

DOI: 10.1007/s11631-024-00722-1

Source: https://link.springer.com/article/10.1007/s11631-024-00722-1