闽中裂谷系的格局演化及成矿系统时空结构

Framework Evolution and Transformation-Extension Metallogenic System of Central-Fujian Rift System

闽中裂谷系为转换-伸展型裂谷盆地系,其形成发展和复合-成矿作用是福建地史上的一个重大事件。研究认为:闽中裂谷系在古元古代结晶基底上形成于新元古代-早古生代(850～500Ma),盆山反转于奥陶-志留纪(447～412Ma);沉降中心迁移、伸展轴向改变并复活发展于中石炭世-中三叠世(315～223Ma),构造动力反转复合于侏罗纪(188～137Ma)-白垩纪(134～90Ma);构造格局演化驱动了喷流沉积-改(再)造成矿系统与斑岩(矽卡岩)-浅成热液成矿系统之间的复合交融。研究提出:(1)裂谷体内"麻源群"(部分改划古元古代迪口组变质核杂岩系)与马面山群、万全群同归南华纪;(2)裂谷成矿系统时空结构所昭示的闽省找矿主攻方向:在伸展体制主导的裂谷纵向(NNW、NE)"先张后压"型断层带特定层位找中大型喷流沉积-改(再)造型矿床,在挤压体制主导的裂谷横向(NEE)"先压后张"型断裂带特定岩系找大中型斑岩(矽卡岩)-浅成热液型矿床。

The Central-Fujian rift system is a transitional-extensional rift basin system,whose formation,development and composite-mineralization are important events in Fujian geohistory. The study shows that the central-Fujian rift system was formed during the Neoproterozoic-Early Paleozoic( 850 ~ 500 Ma) on the Palaeoproterozoic crystalline basement. Its basin-mountain was reversed in the Ordovician-Silurian( 447 ~ 412 Ma),with subsiding center migration,extensional axis change and revival development in the Middle Carboniferous-Middle Triassic( 315 ~ 223 Ma). The tectonic dynamic inversion was combined in the Jurassic( 188 ~ 137 Ma) and Cretaceous( 134 ~ 90 Ma). Tectonic framework evolution drove the compound blending of exhalative sedimentation-alteration( reforestation) metallogenic system and porphyry( skarn)-epithermal metallogenic system.( 1) The Mayuan group in the rift body( partially reformed Paleoproterozoic Dikou Formation metamorphic core complex series) belongs to the Nanhua period with the Mamianshan group and Wanquan group.( 2) The main direction of prospecting in Fujian Province indicated by the temporal and spatial structure of the rift metallogenic system is as follows. In the specific horizon of rift( NW,NE) 'pre-tension and post-compression'type fault zone,dominated by extension system,the prospecting of large-scale exhalative sedimentation-alteration( reforestation) deposit should be carried out. Large and medium porphyry( skarn)-epithermal deposits should be focused on in the specific rock series of rift transverse( NEE) 'compression before tension'fault zone which is dominated by compression system.