近日，中国科学院地球化学研究所Gao Jian-Feng课题组取得一项新突破。他们通过研究岩浆和热液石英中的微量元素，揭示了华南行洛坑钨矿床的成因。2024年4月9日出版的《地球化学学报》发表了这项成果。

课题组人员对侵入岩和热液细脉和矿脉中的石英成分进行了原位分析。微量元素相关性表明，三价Al³⁺和Fe³⁺取代了石英晶格中的Si⁴⁺，而一价阳离子(如Li⁺、Na⁺和K⁺)主要充当电荷补偿器。花岗岩中石英的低Ge/Al比(<0.013)表明其源于岩浆。低Al/Ti和Ge/Ti比以及石英中的高Ti含量，表明斑岩型黑云母花岗岩和黑云母花岗岩分异程度较低，结晶温度较高。

相比之下，细粒花岗岩的分馏程度较高，结晶温度较低，与钨矿化关系密切。石英脉中石英的Ti含量表明，Qz-I在400℃以上形成，而Qz-II至Qz-V在350℃以下形成。不同世代石英的变化，如Al含量和(Al + Fe)/(Li+Na+K)比值表明，Qz-I是从pH稳定的低酸性流体中沉淀出来的，而Qz-II至Qz-V则从pH变化明显的高酸性流体中沉淀出来的。因此，碱性蚀变和酸性蚀变分别为白钨矿和黑钨矿的沉淀提供了必需的钙和铁，这是行洛坑钨矿床矿化的关键机制。

据介绍，行洛坑矿床是华南武夷成矿带内最大的花岗岩钨矿床。行洛坑岩体主要由斑岩型黑云母花岗岩、黑云母花岗岩和细粒花岗岩组成。矿床以细脉浸染型矿化，含钾长石化和黑云母化，以及含云英岩化和绢云母化的石英脉矿化为代表。

附：英文原文

Title: Trace elements in magmatic and hydrothermal quartz: Implications on the genesis of the Xingluokeng Tungsten Deposit, South China

Author: Zhang, Qing-Qing, Chen, You-Wei, Gao, Jian-Feng

Issue&Volume: 2024-04-09

Abstract: The Xingluokeng deposit is the largest granite-related tungsten deposit within the Wuyi metallogenic belt in South China. The Xingluokeng intrusion primarily consists of porphyritic biotite granite, biotite granite, and fine-grained granite. The deposit is represented by veinlet-disseminated mineralization with K-feldspathization and biotitization, alongside quartz-vein mineralization with greisenization and sericitization. This study investigates in-situ analyses of quartz compositions from both the intrusion and hydrothermal veinlets and veins. Trace element correlations indicate that trivalent Al³⁺ and Fe³⁺ replace Si4+ within the quartz lattice, with monovalent cations (such as Li⁺, Na⁺, and K⁺) primarily serving as charge compensators. Low Ge/Al ratios (<0.013) of quartz from granites suggest a magmatic origin. The low Al/Ti and Ge/Ti ratios, accompanied by high Ti contents in quartz, suggest that the porphyritic biotite granite and biotite granite are characterized by relatively low levels of differentiation and high crystallization temperatures. In contrast, the fine-grained granite exhibits a higher degree of fractionation, lower crystallization temperatures, and a closer association with tungsten mineralization. Ti contents in quartz from quartz veins indicate Qz-I formed at temperatures above 400 °C, while Qz-II to Qz-V formed at temperatures below 350 °C. Variations in different generations of quartz, as indicated by Al content and (Al+Fe)/(Li+Na+K) ratio, suggest that Qz-I precipitated from a less acidic fluid with a stable pH, whereas Qz-II to Qz-V originated from a more acidic fluid with notable pH variations. Consequently, alkaline alteration and acidic alteration supplied the essential Ca and Fe for the precipitation of scheelite and wolframite, respectively, highlighting a critical mechanism in tungsten mineralization at the Xingluokeng deposit.

DOI: 10.1007/s11631-024-00688-0

Source: https://link.springer.com/article/10.1007/s11631-024-00688-0