锂的圈层循环与资源富集过程: 从高原盐湖到造山带伟晶岩

盐湖卤水型锂矿与富锂伟晶岩是目前最为主要的可利用锂资源, 前者是经地表风化/高温水岩淋滤形成的水体通过蒸发作用浓缩而成的卤水, 而后者被认为是陆表风化沉积物熔融产物经高演化形成的富锂硬岩。大陆地壳是此类表生物质循环最根本的物源, 因而探究富锂地壳的形成及其表生风化剥蚀对于理解盐湖与伟晶岩锂成矿至关重要。本文将从元素循环视角切入, 结合内生高温-外生低温过程中锂的元素地球化学行为, 梳理锂在俯冲带各圈层的循环过程, 探讨富锂地壳的形成机制及其对高原盐湖与造山带伟晶岩锂资源发育的影响。研究发现: (1)俯冲板片对弧岩浆锂的物质贡献有限; (2)厚地壳环境下的弧岩浆具有更高的锂含量; (3)造山带富锂弧岩石的循环应是盐湖与伟晶岩锂成矿的重要控制因素。

Lithium mineralization in plateau brines and orogen pegmatites: A lithium cycling perspective

Continental brines and Li-enriched pegmatites are two primary lithium resources nowadays, with the former concentrated from streams derived from the weathering of subaerial crust or springs derived from the crust-fluid interaction in high temperature, and the latter highly fractionated from the crustal sediment-derived melts as Li-enriched hard rocks. Continental crust serves as the source rocks in both weathering scenarios. Exploring how Li-enriched continental crust grows and weathers is vital for a fundamental understanding of how lithium mineralizes in continental brines and pegmatites. From a perspective of elemental cycling in subduction zones, we first review lithium geochemical behaviors in both endogenous and exogenous geological processes. We further discuss the primary factors for lithium enrichment in arc magmas and the significance of Li-enriched arcs to the lithium mineralization of continental brines in plateau and pegmatites in orogen. Three conclusions are reached here: (1) Subduction contributes limited lithium input to arc magma; (2) Arc magma with thicker crust has higher lithium contents; (3) Cycling of Li-enriched arc rocks in orogen shall be a crucial step in the lithium mineralization in continental brine and pegmatite.