ABSTRACT

The study of Precambrian tectonics is an intricate task, demanding a holistic approach to take an accurate view of geologic history. Here we attempt to set up the overview of an Orosirian-Statherian continental arc in the northwestern Amazon Craton, the Cauaburi Belt. Field relations, petrological, geochemical, and geochronological data of calc-alkaline metagranitoids, high-grade metasedimentary rocks, and peraluminous metasyenogranites yielded new interpretations about its tectonic evolution. The record of intense and episodic calc-alkaline magmatism between ca. 1805 and 1759 Ma, assign to the Cauaburi Complex, with field evidence of magma mixing and lodgement in a compressional tectonic regime, suggest a continental arc as the tectonic setting. During the magmatic lulls, deformation and metamorphism increase, culminating with the partial fusion of the high-grade metasedimentary rocks of the Taiuaçu-Cauera Complex. This succession composes the precursor paleobasin, presenting maximum and minimum depositional ages of 1819 and 1794 Ma, and was a relevant source for the calc-alkaline magmatism. The geochronological record of a low-volume production of peraluminous crustal rocks (Igarapé Tocandira Granite), with crystallization age at ca. 1791 Ma and metamorphic age at ca. 1771 Ma, also highlights the time and effect of the magmatic lulls. The Cauaburi Belt structural framework follows a general E-W to ENE-WSW trend, expressed in the Paleoproterozoic rocks as syn-magmatic and solid-state deformation fabrics. Assuming that Columbia Supercontinent nucleus assembled in the late Orosirian, we interpret that this coeval continental arc developed at its border and followed a north-south shortening direction, at current orientation.

摘要

前寒武纪构造研究是一项复杂的任务，需要采用整体方法来准确了解地质历史。在这里，我们试图建立亚马逊克拉通西北部考阿布里带的奥罗西里亚-斯塔瑟里亚大陆弧的概览。钙碱性变花岗岩、高品位变沉积岩和过铝质变正花岗岩的野外关系、岩石学、地球化学和年代学数据对其构造演化产生了新的解释。约 10 年之间强烈和间歇性钙碱性岩浆活动的记录。1805 年和 1759 年 Ma，归属于 Cauaburi 杂岩，现场证据表明岩浆在挤压构造体系中混合和沉积，表明大陆弧作为构造环境。在岩浆间歇期，变形和变质作用加剧，最终以 Taiuaçu-Cauera Complex 的高级变质沉积岩的部分融合而告终。该序列构成了前体古盆地，最大和最小沉积年龄分别为 1819 和 1794 Ma，是钙碱性岩浆作用的相关来源。过铝质地壳岩石（Igarapé Tocandira Granite）的小批量生产的地质年代记录，结晶年龄约为 1791 年 Ma 和大约在变质时代。1771 Ma，也突出了岩浆静止的时间和影响。Cauaburi 带构造框架遵循 EW 到 ENE-WSW 的一般趋势，在古元古代岩石中表现为同质岩浆和固态变形结构。假设哥伦比亚超大陆核在奥罗西纪晚期聚集，