Magmatic reservoir evolution of Lingshan rare-metal granite, South China
Xiao-Long Huang, Sheng-Zhu Zhu, Meng-Jing Li, Wu-Xian Li
Affiliations: State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
Presentation type: Poster
Presentation time: Thursday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 239
Programme No: 1.1.25
Abstract
The formation of highly evolved granites and associated rare-metal mineralization in South China is considered to be linked with the evolution of trans-crustal magmatic reservoirs. However, concrete examples illustrating this relationship are scarce. This study, based on field investigation, petrographic observation, bulk and in situ analyses, develops a comprehensive model of the shallow magma reservoir evolution within a trans-crustal magmatic system for the Lingshan Early Cretaceous pluton in South China. The pluton primarily comprises coarse-grained porphyritic granite in the central region, transitioning to medium-grained granite at the margins, with Nb-Ta mineralization associated with fine-grained granites and pegmatite veins along the periphery. The coarse-grained porphyritic granite represents a shallow magma reservoir. Recharge from high-temperature magma originating from the mantle and middle-lower crustal mush reservoir resulted in complex mineral structures and abundant intermediate-mafic inclusions within coarse-grained porphyritic granites. Medium-fine-grained porphyritic granites and fine-grained granites, as magma pockets within coarse-grained porphyritic granite, contain abundant rounded, coarse-grained quartz, indicating their origins from a reactive deep reservoir driven by high-temperature magmatic recharge. This process is critical for the growth, construction, and differentiation of shallow reservoirs. Within the coarse-grained granite, near-horizontal veins represent melts filtered from the mush reservoir, while near-vertical veins serve as channels for upward migration of the melt. Medium-grained granites along the margin gradually transitions to finer-grained near the contact with the surrounding wall-rock, indicating it represents an early-formed shell resulting from the initial crystallization of the magma reservoir, facilitating the ongoing evolution of the central mush and magma reservoir.