阿尔金中段吐格曼地区花岗伟晶岩型稀有金属成矿特征与找矿预测

新疆若羌县阿尔金中段吐格曼地区是花岗伟晶岩型稀有金属成矿的有利地区,目前已发现吐格曼铍锂矿、吐格曼北锂铍矿和瓦石峡南锂铍矿,其中发育于吐格曼层状花岗岩中心的吐格曼铍锂矿和北部接触带的吐格曼北锂铍矿已达中型规模。本文总结了吐格曼地区稀有金属花岗伟晶岩的类型,报导了吐格曼铍锂矿和吐格曼北锂铍矿伟晶岩的特征与形成时代。并基于ASTER遥感岩体与伟晶岩光谱信息提取成果揭示花岗岩与花岗伟晶岩的分布,指出托巴片麻状二长花岗岩中段花岗伟晶岩区以及阿亚格黑云斜长花岗岩南接触带花岗伟晶岩群是稀有金属找矿靶区,指出吐格曼铍锂矿花岗伟晶岩形成于中奥陶世晚期(460Ma)南阿尔金洋闭合后阿中地块与柴达木地块碰撞过程的后碰撞阶段。

Metallogenic characteristics and prospecting of granitic pegmatite-type rare metal deposits in the Tugeman area, middle part of Altyn Tagh

The middle part of Altyn Tagh, Ruoqiang County, Xinjiang, is a favorable area for granitic pegmatite-type rare metal mineralization. At present, the Tugeman Be-Li, Tugeman North Li-Be and Washixia South Li-Be deposits have been discovered. Among them, the Tugeman Be-Li and Tugeman North Li-Be ore deposits, occurred in middle and northern part of the Tugeman layered granite, had been evaluated to be medium scale. This paper summarizes types of rare metal granitic pegmatites in the Turgman area, and introduces characteristics and formation ages of the Turgman Be-Li and Turgman North Li-Be deposits. Distribution of granite and granitic pegmatite were revealed based on granitic and pegmatitic spectral information extraction of ASTER remote sensing data. It is pointed out that the Tuoba and Ayag granitic pegmatite groups in the middle part of Tuoba gneissic monzonitic granite and south contact zone of the Ayag biotite-plagioclase granite, respectively, are two potential rare metal prospecting targets. The corresponding dominant rare-metal minerals for the Tugeman Be-Li, Tugeman North Li-Be, and Washixia South Li-Be deposits were beryl, spodumene and lepidolite, respectively. The Tugeman Be-Li granitic pegmatites are characterized by development of K-feldspar, whereas albite crystals are major rock-forming minerals in the Tugeman North Li-Be and Washixia South Li-Be deposits. The Tugeman Be-Li granitic pegmatites were emplaced along some shear fractures or faults with dendritic or echelon shape, some pegmatites contain typical zoning with border aplite zone, intermediate K-feldspar zone, core-margin tourmaline-beryl zone and quartz core. Moreover, the Tugeman Be-Li granitic pegmatite deposit was formed in late Middle Ordovician (ca.460Ma) during post-collision stage of the collision between the Middle Altyn block and Qaidam block after the closure of the southern Altyn Ocean.