摘要
成矿系统是在深部过程驱动下形成的、具有自组织的能量及物质迁移-汇聚系统。系统在形成和演化过程中,在岩石圈不同尺度上留下"痕迹",这种"痕迹"可以通过地球物理、地球化学和遥感等方法进行探测或观测。文章尝试在成矿系统理论框架下,对近10多年来在长江中下游成矿带进行的多尺度地球物理、地球化学探测结果进行分析,识别典型陆内成矿系统"源区""通道""场所"的地球物理、地球化学"痕迹",尝试构建陆内成矿系统的空间结构模型。主要结论有:(1)长江中下游晚中生代的大规模铁、铜多金属成矿作用是一个完整的成矿系统。该系统包括3个子系统,分别为与高钾钙碱性岩浆岩有关的夕卡岩-斑岩成矿子系统、与橄榄安粗岩有关的陆相火山岩铁(硫)成矿子系统和与碱性岩有关的铜-金(铀)成矿子系统。(2)成矿系统的"源区"来自富集地幔的熔融、底侵,并在壳/幔边界与下地壳物质的混合,具有多级分布特点。幔源岩浆与地壳物质混合的比例决定了成矿金属的类型。(3)成矿带发育的"鳄鱼嘴"构造是铁铜成矿系统的主干"通道"。成矿系统"末端"矿质沉淀的"场所"主要受近地表褶皱、断裂、层间滑脱断层,以及由它们形成的断裂(裂隙)网络控制。(4)区域磁异常、放射性和地球化学异常是成矿系统残留"痕迹"的响应和"标识"。通过分析不同尺度的"标识"特征,可以深入认识成矿系统的空间结构,并可用于深部成矿预测。
Mineral systems driven by deep Earth processes are self-organized critical systems involving the transfer and accumulation of mass and energy.During the formation and evolution of such a system,"fingerprints"are left at different scales across the lithosphere,which can be detected or observed through geophysical,geochemical,and remote sensing methods.In this study,we first analysed multi-scale geophysical and geochemical data over the last decade from the Middle and Lower Yangtze River Metallogenic Belt.Based on the theoretical framework of a deep-seated mineral system,we then attempted to identify the geophysical and geochemical"fingerprints"for the source,channel,and site of a typical intracontinental mineral system.Finally,we attempt to establish a structural model of the mineral system.We concluded that the Late Mesozoic large-scale Fe-Cu polymetallic mineralization in the Middle and Lower Yangtze River Metallogenic Belt may be considered a holistic mineral system,consisting of three subsystems:(1)a skarn-porphyry subsystem related to high-K calc-alkaline magmatic rocks,(2)a terrestrial volcanic iron(sulphur)subsystem related to shoshonite formation,and(3)a Cu-Au(uranium)subsystem related to alkaline rocks.The source area of the mineral system was derived from the melting and underplating of an enriched mantle and subsequent multi-level mixing with lower crustal materials at the crust/mantle boundary.The type of metal formed depended upon the mixing ratio of the mantle-derived magma and crust materials.Moreover,the"crocodile"structure developed in the Middle and Lower Yangtze River Metallogenic Belt is the main channel of the Fe-Cu mineral system.The site of ore precipitation("termination"of the mineral system)was predominantly controlled by near-surface folds,faults,interlayer detachment faults,and their resultant fracture network.Regional magnetic,radioactive,and geochemical data are the signatures(or "fingerprints")of a mineral system;by analysing these multi-scale signatures,we can deepen our understanding of the spatial structures of mineral systems and effectively predict deep targets.
作者
吕庆田
孟贵祥
严加永
张昆
龚雪婧
高凤霞
LVQingtian;MENG Guixiang;YAN Jiayong;ZHANG Kun;GONG Xuejing;GAO Fengxia(Chinese Academy of Geological Sciences,Beijing 100037,China;SinoProbe Center,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2020年第2期232-253,共22页
Earth Science Frontiers
基金
国家自然科学基金重点项目(41630320)
国家重点研发计划项目(2016YFC0600200)。
关键词
长江中下游成矿带
岩石圈结构
深部过程
成矿系统
地球物理探测
Middle and Lower Reaches of Yangtze River Metallogenic Belt
lithosphere architecture
deep processes
mineral system
geophysical exploration
