四川甲基卡稀有金属矿床134号脉锡石U-Pb定年与地质意义

周雄; 周玉; 孙宝伟; 谭洪旗; 岳相元; 朱志敏

doi:10.15898/j.cnki.11-2131/td.202005060006

四川甲基卡稀有金属矿床134号脉锡石U-Pb定年与地质意义

Cassiterite U-Pb Dating of No.134 Pegmatite Vein in the Jiajika Rare Metal Deposit, Western Sichuan and Its Geological Significances

摘要

摘要: 伟晶岩型锂矿是重要的新兴产业资源，具有重要的战略价值，是我国亟需紧缺的关键矿产。然而，成矿年代学制约了该类型锂矿的成矿作用和成矿机理研究。四川甲基卡稀有金属矿床是我国最大的锂矿床，以134号伟晶岩脉为典型代表。134号伟晶岩脉主要由锂辉石、钽铌铁矿、锆石、曲晶石、绿柱石、锡石、微斜长石、正长石、石英、白云母等组成。本文采集了134号脉中部矿石样品，分选获得锡石，通过LA-MC-ICP-MS锡石U-Pb测年，获得134号伟晶岩脉的锡石U-Pb年龄为203.7±4.6Ma (n=19，MSWD=2.8)，代表了该伟晶岩型锂矿床的成矿年龄，表明其成矿作用发生在印支晚期。印支运动晚期稳定的构造环境，为稀有金属的聚集、成矿创造了有利条件，有助于形成甲基卡超大型稀有金属矿床。

Abstract:
BACKGROUNDThe pegmatite lithium deposit has become important for modern industries with strategic value, which is a key mineral resource in urgent need in China. However, the mineralization age restricts the research on the mineralization process and mechanism of this type of lithium deposit. The Jiajika rare metal deposit is the largest pegmatite lithium deposit of China in the western Sichuan, and the No.134 vein is the most typical pegmatite vein. The No.134 pegmatite vein is mainly composed of spodumene, tantalite, zircon, beryl, cassiterite, plagioclase, orthoclase, quartz and muscovite.
OBJECTIVESTo accurately constrain the mineralization age of the No.134 pegmatite vein.
METHODSLaser ablation-multiple collector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) U-Pb geochronology was used on cassiterite.
RESULTSThe concordant age in the ore samples was 203.7±4.6Ma, which represented the mineralization age of No.134 pegmatite vein. This age indicated mineralization in the Late Indosinian period.
CONCLUSIONSThe stable tectonic environment in the Late Indosinian movement is the favorable condition for accumulation and mineralization of rare metals, which is beneficial for the formation of the super-large Jiajika rare metal deposit.

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