{"title":"Decoding Calymmian juvenile mafic magmatism in the Ribeira Belt, Brazil: Evidence for a long-lived arc system along the margin of Columbia","authors":"","doi":"10.1016/j.precamres.2024.107588","DOIUrl":null,"url":null,"abstract":"<div><div>The combined São Francisco-Congo Craton, now preserved in South America and Africa, existed from 2050 Ma to 130 Ma, is an important Archean-Paleoproterozoic block for reconstructions of the Proterozoic supercontinents Columbia (Nuna) and Rodinia. Both counterparts contain Calymmian-Stenian rock assemblages along their western margins and as inliers in Neoproterozoic-Cambrian marginal belts. New U–Pb–Hf–Nd isotopic and geochemical data of Calymmian metamafic rocks from the southern Ribeira Belt (Brazil) are integrated with data from the Brasília, Dom Feliciano and Kaoko Belts (Brazil, Uruguay and Namibia) and Angola Shield (Angola and Namibia) to unravel the Mesoproterozoic evolution of the cratonic block. Metamafic rocks from South America present variable geochemical and Hf–Nd isotopic signatures, suggesting contrasting tectonic settings. Rocks with crystallization ages of 1570–1540 Ma and 1500–1450 Ma show signatures of juvenile magmas derived from supra-subduction zone metasomatized mantle sources. Rocks formed at 1310–1280 Ma are dominated by signatures of intracontinental mafic magmatism. The Angola Shield presents voluminous granitoid rocks with crustal and juvenile signatures emplaced within 1530–1360 Ma, recently inferred as related with a convergent margin setting. There are also records of regional high-grade metamorphism and deformation involving a prograde stage at 1530–1510 Ma, peak conditions of 950–1000 °C and 9–10 kbar at ca. 1490 Ma, and a late stage at ca. 1450 Ma, suggesting a protracted orogenic metamorphic event. In a regional context, the available data supports a long-lived convergent margin setting along the present-day western margin of the São Francisco-Congo Craton. In a global perspective, this belt requires an extensive and long-lived (120–210 million years) Calymmian-Stenian ocean subducting beneath an active margin comprising stages of oceanic island arc–back-arc environments between 1570–1450 Ma that evolved to a continental arc on the margin of Columbia between 1450 and 1360 Ma. Regional metamorphism and deformation at 1340–1320 Ma support the existence of a collisional event related with ocean closure, while metamafic rocks of 1310–1280 Ma record lithospheric extension in a continental rifting setting.</div></div>","PeriodicalId":49674,"journal":{"name":"Precambrian Research","volume":null,"pages":null},"PeriodicalIF":3.2000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Precambrian Research","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0301926824003012","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The combined São Francisco-Congo Craton, now preserved in South America and Africa, existed from 2050 Ma to 130 Ma, is an important Archean-Paleoproterozoic block for reconstructions of the Proterozoic supercontinents Columbia (Nuna) and Rodinia. Both counterparts contain Calymmian-Stenian rock assemblages along their western margins and as inliers in Neoproterozoic-Cambrian marginal belts. New U–Pb–Hf–Nd isotopic and geochemical data of Calymmian metamafic rocks from the southern Ribeira Belt (Brazil) are integrated with data from the Brasília, Dom Feliciano and Kaoko Belts (Brazil, Uruguay and Namibia) and Angola Shield (Angola and Namibia) to unravel the Mesoproterozoic evolution of the cratonic block. Metamafic rocks from South America present variable geochemical and Hf–Nd isotopic signatures, suggesting contrasting tectonic settings. Rocks with crystallization ages of 1570–1540 Ma and 1500–1450 Ma show signatures of juvenile magmas derived from supra-subduction zone metasomatized mantle sources. Rocks formed at 1310–1280 Ma are dominated by signatures of intracontinental mafic magmatism. The Angola Shield presents voluminous granitoid rocks with crustal and juvenile signatures emplaced within 1530–1360 Ma, recently inferred as related with a convergent margin setting. There are also records of regional high-grade metamorphism and deformation involving a prograde stage at 1530–1510 Ma, peak conditions of 950–1000 °C and 9–10 kbar at ca. 1490 Ma, and a late stage at ca. 1450 Ma, suggesting a protracted orogenic metamorphic event. In a regional context, the available data supports a long-lived convergent margin setting along the present-day western margin of the São Francisco-Congo Craton. In a global perspective, this belt requires an extensive and long-lived (120–210 million years) Calymmian-Stenian ocean subducting beneath an active margin comprising stages of oceanic island arc–back-arc environments between 1570–1450 Ma that evolved to a continental arc on the margin of Columbia between 1450 and 1360 Ma. Regional metamorphism and deformation at 1340–1320 Ma support the existence of a collisional event related with ocean closure, while metamafic rocks of 1310–1280 Ma record lithospheric extension in a continental rifting setting.
圣弗朗西斯科-刚果联合克拉通现在保存在南美洲和非洲,存在于2050万年至130万年之间,是重建新生代超大陆哥伦比亚(努纳)和罗迪尼亚的一个重要的Archean-Paleoproterozoic区块。这两个超大陆的西缘都含有卡利米安-天成岩集合体,并且是新元古代-寒武纪边缘带的异常值。巴西里贝拉带(Ribeira Belt)南部的Calymmian变质岩的新U-Pb-Hf-Nd同位素和地球化学数据与巴西、乌拉圭和纳米比亚的巴西利亚带、Dom Feliciano带和Kaoko带以及安哥拉地盾(安哥拉和纳米比亚)的数据相结合,揭示了板块的中新生代演化。南美洲的基性岩呈现出不同的地球化学和 Hf-Nd 同位素特征,表明了截然不同的构造环境。结晶年龄分别为1570-1540Ma和1500-1450Ma的岩石显示出源自超俯冲带变质地幔源的幼年岩浆特征。形成于1310-1280Ma的岩石则以大陆内部的岩浆岩为主。安哥拉地盾呈现出大量花岗岩岩石,具有地壳和幼年特征,形成于 1530-1360 Ma,最近推断与汇聚边缘环境有关。此外,还有区域性高品位变质和变形的记录,包括 1530-1510 Ma 的前级阶段、约 1490 Ma 的 950-1000 °C 和 9-10 kbar 的峰值条件,以及晚期阶段。约 1490 Ma 的峰值条件,以及约 1450 Ma 的晚期阶段。这表明这是一次旷日持久的造山变质事件。在区域背景下,现有数据支持沿今天的圣弗朗西斯科-刚果克拉通西缘的长期辐合边缘环境。从全球角度看,该带需要一个广泛而持久(1.2亿-2.1亿年)的卡利米安-天文学海洋俯冲在一个活跃的边缘之下,包括1570-1450Ma之间的海洋岛弧-后弧环境阶段,并在1450-1360Ma之间演化为哥伦比亚边缘的大陆弧。1340-1320Ma的区域变质和变形支持了与海洋闭合有关的碰撞事件的存在,而1310-1280Ma的变质岩则记录了大陆裂陷环境下岩石圈的延伸。
期刊介绍:
Precambrian Research publishes studies on all aspects of the early stages of the composition, structure and evolution of the Earth and its planetary neighbours. With a focus on process-oriented and comparative studies, it covers, but is not restricted to, subjects such as:
(1) Chemical, biological, biochemical and cosmochemical evolution; the origin of life; the evolution of the oceans and atmosphere; the early fossil record; palaeobiology;
(2) Geochronology and isotope and elemental geochemistry;
(3) Precambrian mineral deposits;
(4) Geophysical aspects of the early Earth and Precambrian terrains;
(5) Nature, formation and evolution of the Precambrian lithosphere and mantle including magmatic, depositional, metamorphic and tectonic processes.
In addition, the editors particularly welcome integrated process-oriented studies that involve a combination of the above fields and comparative studies that demonstrate the effect of Precambrian evolution on Phanerozoic earth system processes.
Regional and localised studies of Precambrian phenomena are considered appropriate only when the detail and quality allow illustration of a wider process, or when significant gaps in basic knowledge of a particular area can be filled.