长江中下游成矿带物性结构揭示的成矿深部背景和过程

    Deep background and process of mineralization of the Middle and Lower Reaches of Yangtze River Metallogenic Belt revealed by the geophysical structure

    • 摘要: 长江中下游成矿带是中国重要的铁−铜多金属资源宝库,而成矿带岩石圈构造演化是成矿带成矿全过程和矿床预测的关键。然而,构造对岩浆−成矿作用深部背景和过程的控制仍存在较大争议,主要包括上地幔对流引起的岩石圈伸展和下地壳熔融,以及与古太平洋板块俯冲有关的应力体制转换和岩浆活动两类认识。而且,这一关键地质问题仍然缺乏地球物理深探测资料的约束。为此,基于自然资源部“深部矿产资源探测与评价创新团队”在成矿带主体地区获得的地球物理探测成果,本文分析了壳幔/岩石圈、地壳及上地壳/地壳浅表不同尺度的探测结果和物性模型,总结和补充了长江中下游成矿带成矿深部背景和过程的相关认识,并提出成矿带深部的陆内俯冲板片断离引发的地幔物质上涌控制成矿带成矿系统的深部物源和通道要素。此外,铁−铜成矿系统虽然具有统一的深部背景,但受控于板片下沉引起的应力体制转换,形成于随时间变化的不同构造背景和深部过程。

       

      Abstract: The Middle and Lower Reaches of Yangtze River Metallogenic Belt is an important treasure trove of Fe−Cu polymetallic resources in China. Previous research results have shown that the lithospheric tectonic evolution of the metallogenic belt is the key to understand the entire mineralization process and to predict new deposits. However, there is still great controversy over the tectonic control on deep setting and process of magma−mineral system, including two kinds of understanding: ① lithospheric extension and lower crust melting caused by upper mantle convection; ② stress regime conversion and deep magmatic activity related to the subduction of the ancient Pacific plate. Moreover, this important geological issue still lacks constraints from geophysical deep exploration data. Therefore, based on the geophysical exploration data obtained by the "Deep Mineral Resources Exploration and Evaluation Innovation Team" of the Science and Technology Innovation Team of the Ministry of Natural Resources in the metallogenic belt, we analyze the results and geology−geophysics models of multi depth scale from upper mantle to most upper crust. Then we summarize and supplement the relevant understanding of the deep setting and process of mineralization in the metallogenic belt. Moreover, we, here, propose that the mantle material upwelling caused by the detachment of intracontinental subduction slab beneath the metallogenic belt controled the deep material sources and channel elements of the mineral system in the study area. Therefore, Fe−Cu mineral system was controlled by the stress regime conversion caused by slab sinking, and was formed in a variable tectonic setting over time, although there was a unified deep structure.

       

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