Geology and geochronology of the Huanglongling super-large pegmatite-type lithium deposit, Altyn Tagh, NW China

Abstract

Lithium is a critical element underpinning the 21st-century energy revolution, essential for advancing clean energy technologies and achieving a low-carbon economy. The Huanglongling super-large lithium polymetallic deposit, containing 1,860,800 tons of Li₂O, is a significant recent discovery. It is situated on the southeast flank of the Kumudaban Pluton and the northern flank of the Suwushijie Pluton within the Central Altyn Orogenic Belt, Xinjiang, China. Despite its potential, the deposit remains underexplored, particularly in terms of its precise geochronology, which is currently unclear and poorly constrained. This study employs high-precision U–Pb geochronology of minerals from pegmatites and granites in the Huanglongling deposit to constrain their crystallization ages. The goal is to establish a robust geochronological framework, clarify the temporal evolution of lithium mineralization, and evaluate its genetic relationship with regional tectono-magmatic events during the Early Paleozoic, while further exploring the tectonic processes that controlled lithium enrichment throughout this period. Results reveal that mineralized pegmatites within the deposit formed between 442 and 436 Ma, while barren pegmatites crystallized later, between 422 and 419 Ma. The biotite monzogranite of the Kumudaban Pluton, located north of the deposit, has a crystallization age of 444.6 ± 1.7 Ma (MSWD = 0.89, n = 24). In contrast, the porphyritic medium- to coarse-grained biotite monzogranite of the Suwushijie Pluton to the south has an earlier formation age of 493.8 ± 2.3 Ma (MSWD = 1.4, n = 18). By examining the formation ages of lithium deposits in the Central Altyn region and integrating the regional tectonic framework, three major Early Paleozoic lithium metallogenic stages have been identified:(1) Collision Stage (ca. 500–455 Ma): During this stage, shear heating associated with plate collision facilitated the formation of medium-sized lithium deposits, such as the Tugeman deposit; (2) Post-Collision Extension Stage (ca. 450–430 Ma): Slab detachment and/or lithospheric thinning initiated mantle-derived magma upwelling, which underplated the lower crust, releasing significant mantle heat. This thermal input caused partial melting of the lower crust and magma differentiation, driving the formation of super-large to large lithium deposits, exemplified by the Huanglongling deposit; (3) Post-Collision Residual Heat Stage (ca. 430–400 Ma): As mantle heat flow diminished and the crust cooled, pegmatitic melt volumes decreased. The rapid solidification of residual melts due to reduced heat flow led to a lower degree of crystallization and limited rare metal enrichment. Consequently, this stage predominantly formed small barren pegmatite veins or late-stage superimposed pegmatites with diminished mineralization potential and smaller scales. Among these stages, the post-collision extension stage (450–430 Ma) emerges as the most favorable period for the formation of super-large to large lithium deposits in the Central Altyn Block.