Mineralogy, petrology and P-T conditions of the spodumene pegmatites and surrounding meta-sediments in Lhozhag, eastern Himalaya
Mineralogy, petrology and P-T conditions of the spodumene pegmatites and surrounding meta-sediments in Lhozhag, eastern Himalaya
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DOI：
10.1016/j.lithos.2023.107295
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发表时间：
2023-07
期刊：
影响因子：
3.5
通讯作者：
Jia-Min Wang;Kang-Shi Hou;Lei Yang;Xiaochi Liu;Ru-Cheng Wang;Guang-Ming Li;Jianggang Fu;F. H
中科院分区：
文献类型：
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作者：
Jia-Min Wang;Kang-Shi Hou;Lei Yang;Xiaochi Liu;Ru-Cheng Wang;Guang-Ming Li;Jianggang Fu;F. H
最近在喜马拉雅山发现了几个巨大的工业级稀有金属矿床。然而，由于对碰撞带原型中稀有金属成矿作用的矿物学、岩石学和侵位条件研究不足，对碰撞带原型中稀有金属成矿作用的形成机理认识不多。本文报道了东喜马拉雅洛扎地区锂辉石伟晶岩、浅色花岗岩、矽卡岩的全岩和矿物组成以及变岩的P-T轨迹。研究了4条富锂、铍、铯和钽（Li-Cs-Ta亚型）的锂辉石伟晶岩脉，主要赋矿矿物为锂辉石、透锂长石、钾长石、锂云母、锌钠长石和珍珠云母。锂铍珍珠云母最早见于喜马拉雅山脉，其锂和铍来源于锂辉石和绿柱石的分解。周围的矽卡岩富含锂、铍和锡，主要由维苏威岩、方柱石和石榴子石矿物组成。红柱石-十字石千枚岩的岩相学和P-T估计表明，在浅色花岗岩侵位期间，在3.1 ± 0.3 kbar和535°C或580°C（52-56°C/km）的条件下，早期的Barrovian变质作用与Buchan变质作用叠加。结合锆石和独居石的饱和温度和Buchan变质作用的条件，浅色花岗岩应该经历了第一阶段的等温减压结晶条件为650-720°C，在103.1 kbar和第二阶段的等压冷却。伟晶岩可能经历了类似的P-T演化，锂辉石（Spd-1和Spd-2 + Qz）的两阶段生长，锂辉石周围的透锂长石冠，和cymatolite的外观支持。浅色花岗岩/伟晶岩同时侵位于特提斯-喜马拉雅层序中，发生接触变质、矽卡岩化和过冷作用，在侵位过程中促进了伟晶岩和矽卡岩中稀有金属的成矿作用。东喜马拉雅洛扎伟晶岩和矽卡岩具有巨大的稀有金属找矿潜力。
Several giant industrial-grade rare-metal deposits have been discovered in the Himalaya most recently. However, the mechanism of how rare-metals mineralization formed in the prototype of the collisional belt is poorly understood, mainly due to insufficient studies on mineralogy, petrology and emplacement conditions. In this study, we have reported the whole-rock and mineral compositions of spodumene pegmatites, leucogranite, skarns and P-T paths of metapelites from Lhozhag, eastern Himalaya. Four spodumene pegmatite veins were studied that are enriched in lithium, beryllium, cesium and tantalite (Li-Cs-Ta subtype), mainly hosted by minerals of spodumene, petalite, elbaite, lepidolite, zinnwaldite, and margarite. Li-Be margarite is first reported from the Himalaya, and its lithium and beryllium come from the breakdown of spodumene and beryl. The surrounding skarns are enriched in lithium, beryllium, and tin, mainly hosted by minerals of vesuvianite, scapolite and garnet. Petrography and P-T estimates from the andalusite-staurolite phyllites suggest two stages of metamorphism that earlier Barrovian metamorphism was superimposed by Buchan metamorphism at conditions of 3.1 ± 0.3 kbar and 535°C or 580°C (52–56°C/km) during leucogranite emplacement. Combined with zircon and monazite saturation temperatures and conditions of Buchan metamorphism, the leucogranites should have undergone a first-stage isothermal decompression to crystallization conditions at ∼3.1 kbar and 650–720°C and a second-stage isobaric cooling at ∼3.1 kbar. The pegmatite probably underwent a similar P-T evolution supported by the appearance of two-stage growth of spodumene (Spd-1 and Spd-2 + Qz), petalite corona around spodumene, and cymatolite. The leucogranites/pegmatites have emplaced into the surficial Tethyan Himalayan Sequence simultaneously, causing contact metamorphism, skarnization and undercooling, which may have facilitated rare-metals mineralization in the pegmatites and skarns during the emplacement stage. We suggest that the pegmatites and skarns in Lhozhag, eastern Himalaya have enormous potential for rare-metals exploration.