Spatiotemporal constraints on the western Cauaburi Belt tectonics – northwestern Amazon Craton, Brazil

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.

前寒武纪（Precambrian）构造学研究是一项复杂繁复的课题，需采用整体论研究方法方能精准还原地质历史的全貌。本研究旨在梳理亚马孙克拉通（Amazon Craton）西北部奥罗西里纪-斯塔瑟里纪（Orosirian-Statherian）大陆弧——考阿布里带（Cauaburi Belt）的整体概况。通过对钙碱性变花岗岩类（calc-alkaline metagranitoids）、高级变质沉积岩以及过铝质正长变花岗岩（peraluminous metasyenogranites）的野外产出关系、岩石学、地球化学与地质年代学数据开展分析，本研究为该带的构造演化提出了全新认识。约1805 Ma至1759 Ma期间强烈且间歇性发育的钙碱性岩浆活动记录（归属于考阿布里杂岩（Cauaburi Complex）），结合岩浆混合与挤压构造环境下岩浆就位的野外证据，表明其构造背景为大陆弧。在岩浆活动间歇期，变形与变质作用持续增强，并以塔尤阿苏-考埃拉杂岩（Taiuaçu-Cauera Complex）的高级变质沉积岩发生部分熔融达到顶峰。这套岩层构成了前驱古盆地，其最大与最小沉积年龄分别为1819 Ma和1794 Ma，同时也是钙碱性岩浆作用的重要物源。低产出规模的过铝质地壳岩石——伊加拉佩-托坎迪拉花岗岩（Igarapé Tocandira Granite）的地质年代学记录显示，其结晶年龄约为1791 Ma，变质年龄约为1771 Ma，这进一步明确了岩浆活动间歇期的时间跨度与作用效应。考阿布里带的构造格架整体呈东西向至东东北-西西南向展布，在古元古代岩石中表现为同岩浆期及固态变形组构。假设哥伦比亚超大陆（Columbia Supercontinent）的核部于奥罗西里纪晚期完成拼合，我们认为这一同期形成的大陆弧发育于其边缘，并按照当前的空间方位呈现南北向挤压特征。