江西昆山钼钨铜多金属矿床辉钼矿Re-Os年代及其对成矿地球动力学演化的启示

林锐华; 尹青青; 项新葵; 梁锋; 杨秀峰; 王天晨; 柳和清; 周文俊; 朱斌

doi:10.12029/gc20200115001

江西昆山钼钨铜多金属矿床辉钼矿Re-Os年代及其对成矿地球动力学演化的启示

Molybdenite Re-Os isotopic age of the Kunshan Mo-W-Cu polymetallic deposit in the Jiangxi Province and its evolution of metallogenic geodynamics

摘要

摘要:
研究目的 昆山钼钨铜多金属矿床行政区划分属于江西修水县境内，大地构造位置位于江南造山带中段之九岭隆起东段。本次研究试图对昆山W-Cu-Mo多金属矿床成矿年龄进行精准约束，为该矿床成矿作用研究、成矿规律总结提供年代学证据，同时对该矿床成岩成矿关系、成矿物质来源作简要探讨，并对大湖塘钨多金属矿集区成矿期次进行划分。
研究方法 本文对昆山钼钨铜多金属矿床开展了辉钼矿Re-Os同位素年代学研究。
研究结果 实验获得的10件辉钼矿等时线年龄为(148.8±1.0) Ma，MSWD=0.42，Re-Os加权平均年龄为(148.7±0.7) Ma，MSWD=0.10，加权平均年龄与等时线年龄基本一致，因此本次所采集的样品Re-Os体系是封闭的。¹⁸⁷Re和¹⁸⁷Os沿等时线距离拉开的较远，表明本次定年数据较为可靠。昆山矿床成矿作用发生稍滞后于似斑状黑云母花岗岩侵位时限，与晚侏罗世这期岩浆活动有成因联系。昆山钼钨铜多金属矿床的成矿物质以壳源为主，考虑到存在较高Re两个样品(n×10^-5)，说明可能存在部分幔源的成矿物质参与了该矿床的形成。
结论软流圈物质自晚侏罗世开始，沿着NNE向深断裂与先期（晋宁晚期）形成的NEE向古断裂的交汇部位上涌，通过热传导效应引起地壳物质发生部分熔融，于大湖塘地区形成了似斑状黑云母花岗岩（岩株）、细粒黑云母花岗岩（小岩株）、花岗斑岩（岩脉或岩枝）等一系列中酸性侵入岩。

Abstract:
This paper is the result of mineral exploration engineering.
Objective Kunshan molybdenum polymetallic deposit is located in Xiushui County, Jiangxi Province, and belongs to eastern segment of the Jiuling uplift from mid-segment of the Jiangnan orogen. This study attempts to precisely constrain the metallogenic age of the Kunshan W-Cu-Mo polymetallic deposit, provide geochronological evidence for the study of mineralization and the summary of the metallogenic regularity of the deposit, study the metallogenic relationship of the deposit and the source of metallogenic material, and divide the metallogenic periods of the Dahutang tungsten polymetallic ore concentration area.
Methods The Re-Os isotopic geochronology for the molybdenite from the Kunshan molybdenum polymetallic deposit was carried out in this paper.
Results An isochron age of (148.8±1.0) Ma, and a weighted mean age of (148.7±0.7) Ma for 10 molybdenite samples were obtained, which were approximately simultaneous with each other, and the Re-Os system was closed accordingly. The points of ¹⁸⁷Re and ¹⁸⁷Os are far away along the isochron, which indicates that the geochronology data are reliable. Metallogenesis lags behind the emplacement of porphyritic-like biotitic granite in the Kunshan deposit, caused by Late Jurassic granitic magmatism. Metallogenic materials of the Kunshan molybdenum polymetallic deposit mainly came from crust materials, in addition, there are two samples with higher Re, it shows that partial mantle source metallogenic materials participated in the formation of the deposit.
Conclusions The intrusion of asthenospheric materials began from the Late Jurassic epoch, through the intersection part of NNE deep faults and NEE ancient faults formed from Late Jinningian. Partial melting of crustal material was caused by the heat conduction effect, which forms a series of intermediate-acid intrusive rocks in the Dahutang area, such as porphyritic-like biotitic granite, fine-grained biotitic granite, and granite-porphyry.

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