滇西马昌庆斑岩型铜钼矿床岩浆-热液流体演化与成因:流体包裹体和H-O-S同位素约束

IF 3.6 2区 地球科学 Q1 GEOLOGY
Wenyan He , Liqiang Yang , Nuo Sun , Huaqing Wang , Ruirui Zhang , Shaoying Zhang
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引用次数: 0

摘要

马厂青铜钼矿床位于滇西地区,构造上处于北西走向的金沙江—哀牢山褶皱带。铜钼脉成矿发育于蚀变围岩中,与马厂青花岗斑岩伴生。围岩蚀变包括丙基岩、叶基岩和钾质岩,蚀变/矿化脉纹包括4个主要阶段(ⅰ~ⅳ):成矿前贫石英;(II)早期矿石石英硫化物(黄铜矿+黄铁矿);(III)晚矿石英多金属(黄铜矿+辉钼矿+黄铁矿)硫化物;(四)矿后石英-方解石。识别出富液两相(l型)、富气两相(v型)、高盐水(h型)和微量纯蒸汽(p型)四种类型的流体包裹体。FI显微测温表明,矿前(ⅰ期)流体温度较高(375 ~ 510℃),盐度较高(48.2 ~ 62.8 wt% NaCl eqv.),静岩压力为208 ~ 508 bar (eqv.)。0.6 ~ 1.6 km深度);流体温度可能已从synore II级(405°C)降至III级(250°C)流体,流体静压为~ 100 bar (eqv)。水深0.9 km)。矿后阶段(第四阶段)获得的流体显示出最低温度(低于234°C)和盐度(1.1 - 3.2 wt% NaCl eqv),表明有大气水入侵。我们认为ⅰ期蚀变发生在碱性和高氧化流体条件下(pH = 6.4-7.7;logfO2 = -25.4 ~ -23.8),而阶段II和III发生在酸性和低氧化条件下(pH = 3.5 ~ 4.2;logfO2 = -30.1 ~ - 27.2)。氢氧同位素表明成矿流体来源可能由岩浆向大气流体过渡,而硫同位素组成表明成矿流体来源为深部岩浆。本文认为,马厂青铜钼矿床的铜钼矿沉积是由减压沸腾、大气水侵入以及由此引起的浅层(~ 1 km)氧化还原变化触发的。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Magmatic-hydrothermal fluid evolution and genesis of the Machangqing porphyry Cu-Mo deposit, western Yunnan, China: Constraints from fluid inclusion and H-O-S isotopes

Magmatic-hydrothermal fluid evolution and genesis of the Machangqing porphyry Cu-Mo deposit, western Yunnan, China: Constraints from fluid inclusion and H-O-S isotopes
The Machangqing Cu-Mo deposit is situated in the in western Yunnan (southwest China), which is tectonically located in the NW-trending Jinshajiang-Ailaoshan fold belt. The Cu-Mo vein mineralization is developed in altered wall rocks, associated with the Machangqing granite porphyry. Wall rock alterations include propylitic, phyllic, and potassic, and the alteration/mineralization veining comprises four major stages (I to IV): (I) pre-ore barren quartz; (II) early-ore quartz-sulfide (chalcopyrite + pyrite); (III) late-ore quartz-polymetallic (chalcopyrite + molybdenite + pyrite) sulfide; (IV) post-ore quartz-calcite. Four types of fluid inclusions (FIs) were recognized: liquid-rich two-phase (L-type), vapor-rich two-phase (V-type), hypersaline (H-type), and trace pure vapor (P-type). FI microthermometry suggests that the pre-ore (stage I) fluids were of relatively high temperature (375–510 °C) and salinity (48.2–62.8 wt% NaCl eqv.), with lithostatic pressure of 208–508 bars (eqv. 0.6–1.6 km depth); Fluid temperature may have decreased from syn-ore stage II (405 °C) to stage III (250 °C) fluids, with hydrostatic pressure of ∼100 bars (eqv. 0.9 km depth). Fluids obtained during the post-ore phase (stage IV) exhibited the minimum temperature (below 234 °C) and salinity (ranging from 1.1 to 3.2 wt% NaCl eqv.), indicating meteoric water incursion. We suggest that the stage I alteration occurred under alkaline and highly-oxidized fluid conditions (pH = 6.4–7.7; logfO2 = -25.4 to –23.8), whereas stage II and III occurred under acidic and less oxidizing conditions (pH = 3.5–4.2; logfO2 = -30.1 to −27.2). The ore fluid source may have transitioned from magmatic to meteoric, as evidenced by hydrogen–oxygen isotopes, whilst sulfur isotope compositions indicate a deep-seated magmatic source. We suggest that the Cu-Mo ore deposition at Machangqing deposit was triggered by decompression boiling, meteoric water incursion, and the consequent redox change at shallow (∼1 km) depth.
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来源期刊
Ore Geology Reviews
Ore Geology Reviews 地学-地质学
CiteScore
6.50
自引率
27.30%
发文量
546
审稿时长
22.9 weeks
期刊介绍: Ore Geology Reviews aims to familiarize all earth scientists with recent advances in a number of interconnected disciplines related to the study of, and search for, ore deposits. The reviews range from brief to longer contributions, but the journal preferentially publishes manuscripts that fill the niche between the commonly shorter journal articles and the comprehensive book coverages, and thus has a special appeal to many authors and readers.
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