西天山大贝特多金属矿床铜钼差异成矿机制:来自地质、流体包裹体和氧同位素系统学的证据

IF 1.1 4区 地球科学 Q3 GEOLOGY
Resource Geology Pub Date : 2019-11-10 DOI:10.1111/rge.12218
Rui Cao, Shengchao Yan, Bin Chen, Keke Sun, Qinglin Zhang, Haodong Gu
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引用次数: 1

摘要

典型斑岩型铜钼矿多以铜、钼矿化密切的时空关系为特征。北大巴特铜钼矿床是中国西北天山西部新近发现的斑岩型铜钼多金属矿床。铜成矿作用晚于钼成矿作用,位于较浅的层位,不同于大多数典型斑岩型铜钼矿床。通过详细的野外调查,结合显微测温、激光拉曼光谱和流体包裹体的O同位素研究,研究了成矿流体在矿床中从Mo主成矿阶段到Cu主成矿阶段的起源和演化。结果表明:Mo主阶段成矿流体为中高温(280 ~ 310℃)、低盐度(2 ~ 4 wt% NaCl当量)的NaCl + H2O体系,Cu主阶段成矿流体为中高温(230 ~ 260℃)、中低盐度(4 ~ 10 wt% NaCl当量)的富F NaCl + CO2 + H2O体系。成矿流体的δ18O值从Mo主阶段的3.7 ~ 7.8‰降至Cu主阶段的−7.5 ~−2.9‰。这些数据表明,Cu和Mo的分离与早期成矿流体的大规模气卤分离密切相关,形成了含Mo和含Cu流体。随后,流纹斑岩中以岩浆为主的相对还原性(富CH4)含钼成矿流体在流体沸腾作用下成矿,而流纹斑岩与围岩接触处的破碎带中,相对氧化性(富CO2)含铜成矿流体与大气水和沉淀黄铜矿混合成矿。矿床中Cu和Mo的分离可能与Cu和Mo化学性质的差异、早期成矿流体的大规模汽卤分离以及氧逸度的变化有关。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Cu–Mo Differential Mineralization Mechanism of the Dabate Polymetallic Deposit in Western Tianshan, NW China: Evidence from Geology, Fluid Inclusions, and Oxygen Isotope Systematics
Classic porphyry Cu–Mo deposits are mostly characterized by close temporal and spatial relationships between Cu and Mo mineralization. The northern Dabate Cu–Mo deposit is a newly discovered porphyry Cu–Mo polymetallic deposit in western Tianshan, northwest China. The Cu mineralization postdates the Mo mineralization and is located in shallower levels in the deposit, which is different from most classic porphyry Cu–Mo deposits. Detailed field investigations, together with microthermometry, laser Raman spectroscopy, and O‐isotope studies of fluid inclusions, were conducted to investigate the origin and evolution of ore‐forming fluids from the main Mo to main Cu stage of mineralization in the deposit. The results show that the ore‐forming fluids of the main Mo stage belonged to an NaCl + H2O system of medium to high temperatures (280–310°C) and low salinities (2–4 wt% NaCl equivalent (eq.)), whereas that of the main Cu stage belonged to an F‐rich NaCl + CO2 + H2O system of medium to high temperatures (230–260°C) and medium to low salinities (4–10 wt% NaCl eq.). The δ18O values of the ore‐forming fluids decrease from 3.7–7.8‰ in the main Mo stage to −7.5 to −2.9‰ in the main Cu stage. These data indicate that the separation of Cu and Mo was closely related to a large‐scale vapor–brine separation of the early ore‐forming fluids, which produced the Mo‐bearing and Cu‐bearing fluids. Subsequently, the relatively reducing (CH4‐rich) Mo‐bearing, ore‐forming fluids, dominantly of magmatic origin, caused mineralization in the rhyolite porphyry due to fluid boiling, whereas the relatively oxidizing (CO2‐rich) Cu‐bearing, ore‐forming fluids mixed with meteoric water and precipitated chalcopyrite within the crushed zone at the contact between rhyolite porphyry and wall rock. We suggest that the separation of Cu and Mo in the deposit may be attributed to differences in the chemical properties of Cu and Mo, large‐scale vapor–brine separation of early ore‐forming fluids, and changes in oxygen fugacity.
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来源期刊
Resource Geology
Resource Geology 地学-地质学
CiteScore
2.30
自引率
14.30%
发文量
18
审稿时长
12 months
期刊介绍: Resource Geology is an international journal focusing on economic geology, geochemistry and environmental geology. Its purpose is to contribute to the promotion of earth sciences related to metallic and non-metallic mineral deposits mainly in Asia, Oceania and the Circum-Pacific region, although other parts of the world are also considered. Launched in 1998 by the Society for Resource Geology, the journal is published quarterly in English, making it more accessible to the international geological community. The journal publishes high quality papers of interest to those engaged in research and exploration of mineral deposits.
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