| MVT矿床中与成矿有关热液方解石的地球化学判据——以青海多才玛超大型铅锌矿床为例 |
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| 引用本文： | 吴畏,宋玉财,庄亮亮,黄世强,胡戈,黄钢,田力丹,岳龙龙.MVT矿床中与成矿有关热液方解石的地球化学判据——以青海多才玛超大型铅锌矿床为例[J].岩石矿物学杂志,2023,42(1):47-70. |
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| 作者姓名： | 吴畏 宋玉财 庄亮亮 黄世强 胡戈 黄钢 田力丹 岳龙龙 |
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| 作者单位： | 中国地质科学院 地质研究所, 北京 100037;科罗拉多矿业大学 地质与地质工程系, 美国科罗拉多州 戈尔登 80401;山东省地质科学研究院, 山东 济南 250013 |
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| 基金项目： | 国家自然科学基金(42125204,92155305,91855214,91962105,41922022);国家重点研发计划项目(2021YFC2901805);青藏高原第二次科考项目 |
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| 摘 要： | 碳酸盐矿物是MVT型铅锌矿床最为常见的热液蚀变矿物，记录了成矿流体特征，其元素或同位素组成对示踪和定位矿体具有一定的指示意义，但由于该类矿床中碳酸盐矿物成因多样，单一的岩相学观察往往难以准确识别与成矿有关和无关的方解石，需要辅以地球化学手段来确定方解石成因。本文利用钻孔编录、岩相学观察、C-O-Sr同位素和原位微量与稀土元素组成分析等手段，探讨了青海多才玛超大型MVT铅锌矿床中与成矿有关和无关两期方解石的矿物化学特征。结果表明，多才玛矿床成矿前方解石(Cal1)空间上与矿体无相关关系，遍布于中二叠统九十道班组灰岩内，阴极发光呈暗棕色至棕黄色，无明显生长环带；成矿期方解石(Cal2)主要产于铅锌矿体内及其上盘围岩中，多呈砂糖粒状-皮壳状充填于围岩裂隙和溶孔内，阴极发光呈暗黄色至亮橙色，常发育生长环带。相对于Cal2, Cal1与围岩的C-O-Sr同位素组成更为接近，这表明水岩反应期间，Cal1组成受围岩影响更大，Cal2组成受影响更小；相比于Cal1,Cal2具有较高的Mn、Fe、Zn、Pb含量和U/Th、V/Cr值以及较低的LREE/HREE值、Mg、Sr含量和弱的Ce负异常，指示成矿...
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| 关 键 词： | MVT型矿床 方解石 微量和稀土元素 C-O-Sr同位素 多才玛 |
| 收稿时间： | 2022/6/1 0:00:00 |
| 修稿时间： | 2022/10/15 0:00:00 |
Trace elemental compositions of ore-related hydrothermal calcite for Mississippi Valley-type deposit: A case study of the Duocaima giant Pb-Zn deposit, Qinghai, China |
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| WU Wei,SONG Yu-cai,ZHUANG Liang-liang,HUANG Shi-qiang,HU Ge,HUANG Gang,TIAN Li-dan,YUE Long-long.Trace elemental compositions of ore-related hydrothermal calcite for Mississippi Valley-type deposit: A case study of the Duocaima giant Pb-Zn deposit, Qinghai, China[J].Acta Petrologica Et Mineralogica,2023,42(1):47-70. |
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| Authors: | WU Wei SONG Yu-cai ZHUANG Liang-liang HUANG Shi-qiang HU Ge HUANG Gang TIAN Li-dan YUE Long-long |
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| Institution: | Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;Department of Geology and Geological Engineering, Colorado School of Mines, Golden 80401, USA;Shandong Institute of Geological Sciences, Jinan 250013, China |
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| Abstract: | Carbonate minerals are the most common hydrothermal alteration minerals in Mississippi Valley-type lead-zinc (MVT) deposits. They record the characteristics of ore-forming fluids and their elemental or isotopic compositions can be a vector to ore bodies. However, there are different genesis types of carbonate minerals in MVT deposits, so it is difficult to distinguish ore-related carbonate minerals from those ore-unrelated carbonate minerals only by virtue of petrographic observation. As such, additional geochemical information is helpful. This paper carried out borehole assay, petrography observation, analyses of C-O-Sr isotopes and in situ trace elements for ore-related and ore-unrelated calcite from the giant Duocaima MVT Pb-Zn deposit in Qinghai province of China. The ore-unrelated calcite that formed earlier than Pb-Zn mineralization (pre-ore, Cal1) is spatially independent of the ore zones and distributed throughout the country rocks, i.e., the Late Permian Jiushidaoban Formation limestone. It shows dark brown to brownish yellow color in cathodoluminescence (CL) images without obvious oscillatory zone. The ore-related calcite precipitated slightly younger than Pb-Zn mineralization (syn-ore, Cal2) and mainly occurs within and above the ore zones. It has granular crystal shape and the assemblage with residual vugs, with dark yellow to bright orange color in CL images with oscillatory zone. Relative to Cal2, Cal1 is more similar in C-O-Sr isotopes and elemental compositions to the wall-rock limestone, suggesting the compositions of Cal1 were greatly affected by the wall rocks during the water-rock interaction. Compared with Cal1, Cal2 has higher Mn, Fe, Zn, and Pb concentrations and U/Th and V/Cr ratios, lower Mg and Sr concentrations and LREE/HREE ratios, and weaker negative Ce anomaly. It indicates that the Cal2-related ore-forming fluid has higher temperature and relatively reduced conditions. Together with data from MVT Pb-Zn deposits worldwide, it shows that higher Mn, Fe, Zn (possibly including Pb) concentrations and lower LREE/HREE ratio can help identify ore-related carbonate minerals in MVT deposits. |
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| Keywords: | MVT deposit calcite trace and rare earth elements C-O-Sr isotopes Duocaima |
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