巴西圣弗朗西斯科克拉通地质演化与重要成矿作用

Geological evolution and important mineralization of São Francisco Craton in Brazil

【研究目的】本文旨在梳理构建巴西圣弗朗西斯科克拉通构造演化过程,概述与之成矿作用地质背景及矿床成矿系列的耦合关系,并查明典型矿床的时空分布,目的是服务于克拉通演化与成矿理论。【研究方法】本文在中巴合作开展野外地质调查的基础上,结合巴西圣弗朗西斯科克拉通基底太古宙片麻岩和元古代的碎屑岩锆石U-Pb、Sm-Nd同位素年代学等文献资料,初步归纳出圣弗朗西斯科克拉通重大地质构造演化事件和重要成矿作用。【研究结果】圣弗朗西斯科克拉通4个重要地质演化过程:(1)太古宙3.5 Ga前克拉通古陆核与微陆块形成,3.3~2.9 Ga和2.8~2.5 Ga间则由克拉通北区的盖维奥、索布拉迪纽、塞里尼亚和吉基耶等4个古陆核及南区的近圆形古陆核相互碰撞、拼合和绿岩-增生造山岩浆作用而形成稳定的克拉通陆块;(2)2.5~1.9 Ga古元古代泛亚马逊造山岩浆作用;(3)1.78~1.20 Ga克拉通基底隆升与裂谷改造阶段,形成大量基性岩墙群及陆内非造山型岩浆,完成陆块增厚和最终克拉通化;(4)新元古代克拉通边缘经历巴西利亚/泛非运动(0.64~0.54 Ga)改造,又形成巴西利亚等6个活动造山带。圣弗朗西斯科克拉通形成4期重要成矿作用及相应矿床成矿系列:(1)太古宙(2.5 Ga前)形成绿岩型金矿、苏必利尔湖型硅铁建造为主的变质火山-沉积矿床等成矿系列;(2)古元古代早中期(2.5~1.8 Ga)形成与(超)基性岩相关的铜镍钴硫化物矿床、VMS型铅锌银矿床、IOCG等系列矿床;(3)固结纪-中元古代(1.8~1.0 Ga)形成与非造山岩浆作用相关的铌钽矿、铀矿床,与陆内(缘)裂谷型的钒-钛-铁矿床等系列;(4)新元古代(1.0~0.54 Ga)主要形成铁锰矿、砂锡矿及磷矿等矿床,包括古陆缘-浅海沉积环境有关的(冲积)金刚石砂矿等系列矿床。【结论】构建了巴西圣弗朗西斯科克拉通4个重要地质演化过程,相应划分出4期重要成矿作用。

This paper is Geological evolution and important mineralization of São Francisco Craton in Brazil.[Objective]This paper aims to sort out and construct the tectonic evolution process of the São Francisco Craton in Brazil,outline the coupling relationship with its metallogenic geological setting and ore deposit series,and identify the temporal and spatial distribution of typical deposits,in order to serve the theory of craton evolution and ore formation.[Methods]Based on the field geological survey conducted in China-Brazil cooperation,and combined with the zircon U-Pb and Sm-Nd isotope chronology of basement Archean gneiss and Proterozoic detrital rocks of the São Francisco Craton in Brazil,this paper summarizes the major geological tectonic evolution events and important mineralization processes of the São Francisco Craton.[Results]Four important geological evolution process of the São Francisco Craton were preliminarily constructed:(1)Before 3.5 Ga,the formation of paleo continental nuclei and microcontinental masses,between 3.3~2.9 Ga and 2.8~2.5 Ga,the four paleo continental cores of Archean Gavião block,Sobradinho block,Serrinha block,Jequiéblock in the north and the nearly circular paleo continental nuclei in the south collided,stitched and proliferated the greenstone-arc magma belt to form a stable cratonic mass.(2)2.3~1.9 Ga Paleoproterozoic Pan-Amazonian orogenic arc magmatic activity.(3)1.78~1.20 Ga basement uplift,rift stage,forming a large number of basic dikes and non-orogenic magmatism activities and other transformation processes to complete the thickening of landmass and cratonization(.4)Forming 6 active orogenic belts such as Brazilian orogenic belt,the Neoproterozoic craton margin underwent the transformation of the Brasilia/Pan-African movement(0.64~0.54 Ga).São Francisco craton has formed 4 important mineralization and corresponding deposit metallogenic series:(1)Archean mineralization(>2.5 Ga)formed metamorphic volcanosedimentary metallogenic series such as greenstone-type gold deposits and Lake Superior-type iron deposits(BIF).(2)The earlymiddle Paleoproterozoic mineralization(2.5~1.8 Ga)formed Cu-Ni-Co sulfide deposits,Pb-Zn volcanogenic massive sulfide(VMS)deposits,and iron oxide-copper-gold(IOCG)deposits related to(super)mafic rocks.(3)Mesoproterozoic-Consolidated mineralization(1.8~1.0 Ga)formed series of deposits such as V-Ti-Fe deposits related to its intracontinental(marginal)rifts,Nb-Ta and Cu deposits related to non-orogenic magmatism(.4)The Neoproterozoic mineralization(1.0~0.54 Ga)formed Fe-Mn,alluvial tin and P deposits,including(alluvial)diamond placer deposits related to paleo continental margin-neritic sedimentary environment.