Late Triassic lithium mineralization in the Kumusayi-Shaliangxi deposit (Altyn Tagh, NW China): provenance and high-precision timing constraints

The Kumusayi-Shaliangxi lithium deposit in the Altyn Tagh orogenic belt, NW China, represents a central Late Triassic rare-metal system within the Paleo-Tethyan domain. This study integrates multi-mineral U-Pb geochronology, whole-rock geochemistry, Sr-Nd isotopes, and zircon Lu-Hf analyses to constrain the timing and sources of Li-rich pegmatites. U-Pb dating of cassiterite yields ages of 215.0 ± 6.3 Ma for Li-rich pegmatites and 237.0 ± 8.7 Ma for Li-poor pegmatites; similarly, columbite-group minerals (CGM) provide ages of 213.6 ± 2.1 Ma for Li-rich variants and 235.9 ± 2.5 Ma for Li-poor ones, revealing two discrete pulses of pegmatite magmatism in the Late Triassic, indicating that Li mineralization postdated barren pegmatite emplacement by approximately 25 Myr. Detrital zircon from host schists constrains a Neoproterozoic maximum depositional age (approximately 750 Ma), with inherited grains in pegmatites reflecting predominantly similar patterns but additionally containing subordinate Early Paleozoic zircons (420–460 Ma). The whole-rock geochemistry of the pegmatites displays LCT-type signatures (Li up to 15216 ppm, Cs up to 1581 ppm, Ta up to 499 ppm, A/CNK = 1.11–1.76), low ∑REE (4–13 ppm), and LREE-enriched patterns (LREE/HREE = 1.41–5.59). Nd isotopes (ε_Nd(t) = −11.3 to −9.0; T_DM2 = 1735–1949 Ma) and zircon Hf data (ε_Hf(t) = −4.8 to +11.1; T_DM2 = 1484–2077 Ma) overlap with host schists, supporting an origin predominantly from ancient metasediments, with subordinate contributions from Early Paleozoic granites. These results indicate that Late Triassic lithium mineralization in the Altyn Tagh represents an independent metallogenic event, distinct from earlier Caledonian lithium mineralization, and linked to post-orogenic transpression along the Altyn Tagh Fault during Late Triassic intracontinental deformation. By establishing a genetic link between this deposit and the vast Triassic West Kunlun-Songpan-Ganzi lithium metallogenic belt via provenance analysis, our study provides a new framework for rare-metal exploration in Tethyan-type orogens and identifies a substantial new frontier for strategic lithium resources amid growing global demand.