华南中生代动力体制转换与钨锡锂铍铌钽稀土矿床成矿系列的叠加演化

Transformation of Mesozoic dynamic systems and superposition of metallogenic series of W-Sn-Li-Be-Nb-Ta-REE mineral deposits in South China

华南陆块中生代受古特提斯构造域和滨太平洋构造域两大动力学体系控制,形成了独具特色的华南大花岗岩区和巨量稀有金属富集的成矿省。在印支期-燕山期动力体制转换的背景下,华南陆块内同一构造单元经历了不同世代、不同源区、多个类型岩浆作用相关的矿床成矿(亚)系列的叠加和演化,其叠加成矿机理是华南中生代大规模成矿作用研究的关键,其复合成矿效应是华南各成矿区带找矿预测工作的重要依据。本文结合近年来华南稀有金属矿产勘查、矿床学研究和深部探测工作的新进展,构筑了华南钨锡锂铍铌钽和风化壳型稀土矿床的时空谱系,对比了相关花岗岩的成矿专属性及其成岩构造环境。明确提出了矿床成矿系列叠加的三种形式,即同构造单元,不同世代岩浆作用相关的同类矿床成矿(亚)系列的叠加,其成矿源区和成矿物质可能具有一定继承性;二是同构造单元或构造岩浆带结合部,同时期不同类矿床成矿(亚)系列的复合成矿;三是同构造单元或构造岩浆带结合部,不同时期构造岩浆事件、不同源区、不同类型矿床成矿(亚)系列的叠加。矿床成矿系列叠加显著提升了区域成矿强度,且多发生于深部构造长期活动区,不同时期的同类矿床成矿亚系列常具有一定继承演化关系。本文进一步探讨了华南中生代两大动力体制转换过渡与钨锡锂铍铌钽稀土矿床成矿(亚)系列的叠加和演化关系,深化了华南中生代花岗岩相关稀有金属区域成矿理论,厘定了华南陆块中生代十五处稀有金属矿床成矿(亚)系列叠加区,为华南稀有金属矿集区的成矿预测提供了理论依据,对下一步勘查工作部署具有重要的实践意义。

South China Block witnessed both the closure of the paleo-Tethys Ocean and the subduction of the paleo-Pacific plate during the Mesozoic,resulting in the intensive and extensive magmatism and associated rare metal mineralizations.During the transformation of Indosinian to Yanshanian dynamic systems,mineral deposits formed in different stages,related to different magmatisms,and originated from different sources,are usually superimposed and occurs in the same tectonic unit(or tectonic transition zone)in the South China.Accordingly,it is necessary to unravel the mechanism of superimposed mineralization,which is key to understand the large-scale Mesozoic mineralization in South China,and is also important for mineral exploration and exploitation in the future.In combination of recent advances of deposit studies,mineral exploration and deep drilling materials,this contribution constructs temporal and spatial linkage between the magmatic-hydrothermal W,Sn,Li,Be,Nb,Ta deposits and the regolith-hosted REE deposits,and also compares the geodynamic settings and affinities of ore-forming granites.Three superposition mineralization forms are proposed:1.Mineralizations with similar mineral assemblages but related to different-stage magmatisms are superimposed in the same tectonic unit,where it may show inheritance of ore-forming materials and sources;2.Mineralizations with different mineral assemblages but related to synchronous magmatisms are superimposed in the same tectonic unit or tectonic transition zone;3.Different mineralizations related to different magmatisms are superimposed in the same tectonic unit or tectonic transition zone.The superposition of mineralizations significantly enhances the regional ore-forming intensity,especially in the long-term active area of deep structure.Furthermore,this contribution discusses the relationship between the transformation of Mesozoic geodynamic settings and the superposition of multiple mineralizations in South China,and improves the reginal metallogenic theory.Totally,this contribution outlines 15 Mesozoic rare metal mineralization superposition zones in South China,which sheds light on reginal mineral prospecting and exploration,and also important for the next-step exploration work arrangement.