Rare-metal pegmatite represents the most differentiated magmatic system on earth, containing high concentrations of rare metals (Li, Rb, Cs, Be, Ta, Nb, and Sn) and fluxing components. Recent studies have shown that the Himalayan leucogranite–pegmatite system has considerable potential for rare-metal mineralization. A new spodumene pegmatite-type Li deposit (Gabo) was recently discovered in the Lhozhag region of the eastern Himalaya. However, the lack of precise geochronological and isotopic constraints on the crystallization timing and chemical affinity between spodumene pegmatites and nearby leucogranite has precluded definitive statements on their petrogenetic link. In this study, systematic monazite, xenotime, and columbite group mineral U–(Th)–Pb dating and Li–Nd–Hf isotope analysis were performed on the spodumene pegmatite and nearby leucogranite (Lhozhag pluton). Columbite group mineral LA-ICP-MS UPb dating of spodumene pegmatite indicates that the timing of lithium mineralization occurs at ca. 20–18 Ma, which is consistent with the magmatic crystallization age of the Lhozhag pluton (ca. 19 Ma) within the error margin, as constrained by monazite and xenotime U–(Th) Pb dating. The NdHf isotope analysis also indicates a chemical affinity between the Lhozhag pluton and spodumene pegmatite. Given the consistency in crystallization ages, NdHf isotopic compositions, and close field spatial relationship, the leucogranite probably represents the parent magma of spodumene pegmatites. The continuous evolutionary trend in the composition of spodumene pegmatites, as observed on the spodumene (Spd)– albite (Ab)–orthoclase (Or)–quartz (Qz)–HO phase diagram, suggests that the enrichment of Li in pegmatite is result from fractional crystallization. Li isotopic analysis shows that the spodumene pegmatite has a δLi value of −2.5‰ to +3.3‰, slightly higher than that of the Lhozhag pluton (−2.4‰ to +1.0‰), providing additional support for their fractional crystallization links. These findings warrant a more comprehensive assessment of the lithium potential within the Himalayan orogenic belt.

中文翻译：

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喜马拉雅东部洛扎地区淡色花岗岩和锂辉石伟晶岩之间的成岩联系：来自 U-(Th)-Pb 年代学和 Li-Nd-Hf 同位素的约束

稀有金属伟晶岩代表了地球上差异最大的岩浆系统，含有高浓度的稀有金属（Li、Rb、Cs、Be、Ta、Nb 和 Sn）和熔剂成分。最近的研究表明，喜马拉雅淡色花岗岩-伟晶岩系统具有相当大的稀有金属矿化潜力。最近在喜马拉雅东部洛扎地区发现了一个新的锂辉石伟晶岩型锂矿床（Gabo）。然而，由于锂辉石伟晶岩和附近的淡色花岗岩之间的结晶时间和化学亲和力缺乏精确的地质年代学和同位素限制，因此无法对其岩石成因联系做出明确的陈述。在这项研究中，对锂辉石伟晶岩和附近的淡色花岗岩（Lhozhag 岩体）进行了系统的独居石、磷钇矿和铌铁矿族矿物 U-(Th)-Pb 定年和 Li-Nd-Hf 同位素分析。锂辉石伟晶岩的铌铁矿族矿物 LA-ICP-MS UPb 测年表明，锂矿化的时间发生在大约 100 年前。20-18 Ma，这与 Lhozhag 岩体的岩浆结晶年龄（约 19 Ma）一致，在误差范围内，受到独居石和磷钇矿 U-(Th) Pb 测年的限制。NdHf 同位素分析还表明 Lhozhag 岩体和锂辉石伟晶岩之间存在化学亲和力。鉴于结晶年龄、NdHf 同位素组成和近场空间关系的一致性，淡色花岗岩可能代表锂辉石伟晶岩的母岩浆。在锂辉石（Spd）-钠长石（Ab）-正长石（Or）-石英（Qz）-H2O相图上观察到的锂辉石伟晶岩成分的连续演化趋势表明，伟晶岩中锂的富集是由于分级结晶。Li同位素分析表明，锂辉石伟晶岩的δLi值为-2.5‰至+3.3‰，略高于Lhozhag岩体的δLi值（-2.4‰至+1.0‰），为其分异结晶环节提供了额外的支持。这些发现有助于对喜马拉雅造山带内的锂潜力进行更全面的评估。