巴西巴伊亚圣弗朗西斯科克拉通北部地质构造背景、矿床类型及其成矿作用

通过建立描述成矿作用特征的构造和时间框架,探讨圣弗朗西斯科克拉通北部矿床的成因。许多太古宙的矿化作用发生在克拉通形成以前。铬铁矿、镍、金和祖母绿矿床是古元古代造山旋回形成的,那时克拉通合并到大西洋古陆。在中—新元古代,即罗迪尼亚(Rodinia)超级大陆的裂解期间,有拉张事件发生,其与磷矿和铀矿有关。金伯利岩金刚石矿化和金矿化是巴西利亚(Brasiliano)造山旋回形成的,其与西冈瓦纳大陆拼合同期。在寒武纪,该区存在长期和均一的地应力记录。同位素和磁性系统的重置,影响了在520Ma时候的依列斯(Irecê)盆地的新元古代沉积作用。这种重置归因于巴西利亚造山旋回结束时区域尺度流体的迁移和矿化作用。

Geological-structural background, deposit types and mineralization of São Francisco Craton in Bahia, Brazil

This paper aims at establishing a tectonic and temporal framework to characterize the metallogenic processes that made contribution to the formation of the mineral provinces in northern São Francisco Craton. Many Archean ore-forming processes which formed resources such as massive sulfide zinc, lead, zinc and copper, besides magnesite talc, iron-titanium-vanadium, iron, chromite and manganese, occurred before the assembly of the craton. Deposits of chromite, nickel, gold and emerald were formed during the Paleoproterozoic orogenic cycle, when the craton was amalgamated into the Atlantic paleocontinent. An extension event occurred during the breakup of Rodinia in the Neoproterozoic, which was associated with deposits of phosphorite and uranium. Kimberlite diamond and gold mineralization took place during the Brasiliano orogenic cycle, coeval with the amalgamation of West Gondwana. A long-lasting and rather uniform crustal stress happened in this area during the Cambrian period. Resetting of the isotopic and magnetic systems that affected the Neoproterozoic sediments of the Irecê Basin at about 520Ma was attributed to the regional fluid migration and mineralization in the aftermath of the Brasiliano orogenic cycle.