Vesuvianite: A potential U-Pb geochronometer for skarn mineralization---a case study of tungsten and tin deposits in South China
Vesuvianite: A potential U-Pb geochronometer for skarn mineralization---a case study of tungsten and tin deposits in South China
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DOI：
10.1016/j.chemgeo.2022.121017
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发表时间：
2022-07
期刊：
影响因子：
3.9
通讯作者：
Lan Xing;Jian‐tang Peng;Yuanjun Lv;Yanwen Tang;Jianfeng Gao
中科院分区：
文献类型：
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作者：
Lan Xing;Jian‐tang Peng;Yuanjun Lv;Yanwen Tang;Jianfeng Gao
维苏岩是各种矽卡岩和矽卡岩成矿中常见的一种含铀矿物。作为一种早期矿物，维苏岩通常产于矽卡岩前缘，靠近大理岩，远离岩体，保存较好，因此，准确测定其生长历史可以直接测定矽卡岩体系的热液活动，就像锆石U-Pb地时计记录岩浆过程一样。为了验证维苏岩U-Pb年代表的可靠性，我们选择了中国南方两个矽卡岩矿床的6个维苏岩样品进行LA-ICPMS定年。据此，石竹园W-Sn矿区4个维苏岩样品的U-Pb年龄分别为160.3±1.2 Ma、155.6±2.6 Ma、154.5±3.1 Ma和150.4±3.1 Ma；这些年代与之前公布的该地区相关花岗岩杂岩体侵位和热液成矿年龄（约160 Ma、155 Ma和150 Ma）吻合良好。芙蓉锡矿区另外2个维苏岩样品的精确年龄分别为159.3±1.8 Ma和149.1±1.6 Ma，与研究区侵位时间分别为160 Ma和149 Ma的多期岩浆活动相吻合。理论上，维苏岩中Ca2+的位置略大于共生辉榴石中Ca2+的位置，这使得前者具有更好的结合铀的能力。因此，在LA-ICPMS U-Pb测年过程中，具有高铀浓度和相对低普通铅的维苏岩有利于获得精确的测年结果，是精确确定矽卡岩形成时间和各种矽卡岩成矿时间的理想矿物。
Vesuvianite is one kind of common U-bearing minerals in various skarns and skarn mineralization. As an early phase mineral, vesuvianite can be well preserved since it usually occurs at the front of skarn close to the marble and far away from the pluton, therefore, accurately determining its growth history can directly date hydrothermal activity in the skarn system, just like the zircon U-Pb geochronometer recording magmatic processes. In order to demonstrate reliability of the vesuvianite U-Pb geochronometer, we choose six vesuvianite samples from two skarn deposits in South China for the LA-ICPMS dating. Accordingly, the U-Pb dating of four vesuvianite samples from the Shizhuyuan W-Sn ore district yielded precise ages of 160.3 ± 1.2 Ma, 155.6 ± 2.6 Ma, 154.5 ± 3.1 Ma and 150.4 ± 3.1 Ma, respectively; these dates coincide well with the previously published ages of the relevant granite complex emplacement and hydrothermal mineralization in the region with the ages of ca. 160 Ma, ca. 155 Ma and ca. 150 Ma. The other two vesuvianite samples from the Furong Sn ore district yielded precise ages of 159.3 ± 1.8 Ma and149.1 ± 1.6 Ma,which are consistent with the multi-stage magmatic activities in the studied area with emplacement time of ca. 160 Ma and ca. 149 Ma. Theoretically, the site of the Ca2+position in vesuvianite is slightly larger than that in intergrown grossularite, which gives the former a better ability to incorporate uranium. Therefore, vesuvianite with high uranium concentrations and relatively low common Pb is beneficial for obtaining precise results during the LA-ICPMS U-Pb dating, it is an ideal mineral for accurately determining the time of skarn formation and/or various skarn mineralization.