南岭-武夷转换带壳幔相互作用与钨成矿深部背景

The interaction among the earth spheres is the main driving force for the super-enrichment of low-abundance metal elements. The tungsten deposits are most densely distributed in the Nanling area in Southern China, especially in southern Jiangxi, southern Hunan and Northern Guangdong. It has been recognized by previous studies that the large-scale tungsten-tin mineralization in the middle and late Jurassic of Nanling is closely related to the strong crust-mantle interaction under the background of regional lithospheric extension. In recent years, deep explorations in eastern South China reveal regional lithospheric thinning and a series of isolated regional Moho uplift along the Ganjiang fault, which is the results of paleo-Pacific plate flat-subduction scraping the bottom of the overlying plate, asthenospheric upwelling and the heat flow from mantle transition zone. However, the lack of high-resolution three-dimensional exploration data, makes it hard to connect the magma chambers (reservoirs) and granite domes in shallower crust (＜5 km) to the deep processes, and restricts the deep understanding of crust-mantle interaction and large-scale tungsten-tin metallogenesis under the strong lithospheric extension in this area. Based on the comprehensive studies of previous broadband seismic array data and artificial seismic profiles, join the exploration of the short-period seismic ultra-dense array deployed in southern Jiangxi, to systematically construct the three-dimensional dynamic model including layers from surface to bottom of the upper mantle, to explore the mechanism of crust-mantle interaction restricting the distribution of tungsten and other key minerals in Nanling and its adjacent areas under the background of lithospheric extension .

地球圈层的相互作用是低丰度金属元素超常富集的主要驱动力。南岭地区是我国钨矿分布最密集的成矿区，尤以南岭北地区更为集中。前人已认识到南岭中晚侏罗世大规模钨锡成矿作用与区域岩石圈伸展背景下强烈的壳幔相互作用密切相关。近年来开展的深部探测揭示华南东部岩石圈总体减薄和沿赣江断裂一系列孤立Moho凸起带状分布现象，其深部背景是古太平洋板块平俯冲对上覆岩石圈底部的刮削、软流圈上涌和来自地幔过渡带热流的共同作用。但由于缺乏高分辨率的三维探测资料，无法将深部过程与地壳浅部的岩浆房（库）和花岗岩穹隆相关联，限制了对该区岩石圈强伸展背景下的壳幔相互作用与大规模钨锡成矿作用的深入认识。本研究根据前期宽频带地震流动观测台阵和人工地震剖面的研究结果，通过对赣南地区补充短周期地震高密集台阵探测，系统构建从地表到上地幔底部各圈层三维动力学模型，探讨岩石圈伸展背景下壳幔相互作用对南岭及邻区钨等关键金属矿产分布的制约机制。

地球圈层的相互作用被认为是低丰度金属元素超常富集的主要驱动力。南岭地区钨锡矿分布之密集，实属世界罕见，前人认为钨锡在此超常富集应与其特殊的深部背景有关，因而备受关注。近年来大尺度的地震成像结果，揭示华南东部存在一“Y”形岩石圈极薄带，南岭及邻区钨锡矿产的空间分布明显受其控制，但由于缺乏关键的地壳浅部高分辨率三维探测资料，深部结构研究与地壳浅部成矿作用研究脱节，深部的圈层结构如何控制深-浅部岩浆活动进而制约钨锡等关键金属成矿并不清楚。. 本项目通过补充旨在对地壳浅部0~5km三维结构成像的被动源短周期密集台阵探测，结合对宽频带地震观测和人工地震剖面等地球物理资料的综合研究，主要依据地幔过渡带含水性，以及壳内低速异常与Moho、LAB凸起的空间耦合关系特征，构建了包括地壳、岩石圈、软流圈和地幔过渡带等圈层的华南东部三维动力学模型，提出南岭及邻区钨等与岩浆侵入体有关的关键金属矿产的分布，不仅受板块俯冲-后撤构造环境的制约，而且必须有地幔过渡带脱水诱发的软流圈上涌等深部作用参与的新认识。. 本研究成果有助于形成华南东部钨锡等关键金属超常富集成矿与深部结构背景的规律性认识，对关键金属重大战略具有重要意义。