The thickness, temperature and mechanical strength of the lithosphere vary greatly across South America and have controlled tectonic and magmatic processes during its evolution. Here, we introduce a new tomographic model of South America’s lithosphere and underlying mantle, SACI-24, and analyse this and other state-of-the-art models together with other geological and geophysical data. The new model is obtained by waveform inversion of surface, S and multiple S waveforms globally, but is optimised for South America and the surrounding oceans. SACI-24 is constrained by ∼ 970,000 seismograms from 9259 stations and maps detailed structure of cratonic lithosphere across the continent, highlighting previously unknown complexities and fragmentation. Within the Amazon Craton, the Guiana and Central Brazil blocks show high Vs exceeding 4.8 km/s in the 80–150 km depth range but are separated by lower velocities below the Amazon Basin, matching the locations of ancient rifting and the flood basalts of the Central Atlantic Magmatic Province. In the São Francisco Craton, high velocities extend north and southwest beyond the previously proposed boundaries. Warmer, thinner lithosphere underlies the Paramirim and Pirapora aulacogens, locations of magmatic and rifting cycles. A fragmented cratonic root underlies the Paraná Basin, with thinner lithosphere along its central rift. High velocities south of the Paraná Block indicate the northern Rio de la Plata Craton’s thick root. The Cenozoic intraplate basalts in the Borborema province, along the southern Atlantic coast and in Paraguay occurred in areas of thin lithosphere and near thick-thin lithospheric boundaries. Most flood basalts of the Phanerozoic large igneous provinces also map on low velocity areas. Smaller flood-basalt portions sit atop cratonic lithosphere and offer new evidence on lateral flow of flood-basalt lava and magma within the crust. About 80 % of known diamondiferous kimberlites are on thick lithosphere, with the exceptions indicating cratonic erosion and thinning since their emplacement.

中文翻译：

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地震断层扫描下的南美洲岩石圈：构造和岩浆作用的结构、演变和控制


南美洲岩石圈的厚度、温度和机械强度差异很大，并在其演化过程中控制了构造和岩浆过程。在这里，我们介绍了南美洲岩石圈和下伏地幔的新层析模型 SACI-24，并分析了该模型和其他最先进的模型以及其他地质和地球物理数据。新模型是通过对表面、S 和全球多个 S 波形进行波形反演获得的，但针对南美洲和周围海洋进行了优化。SACI-24 受来自 9259 个站点的约 970,000 张地震图的限制，绘制了整个大陆克拉通岩石圈的详细结构，突出了以前未知的复杂性和碎片化。在亚马逊克拉通内，圭亚那和巴西中部区块在 80-150 公里的深度范围内显示出超过 4.8 公里/秒的高 Vs，但在亚马逊盆地以下被较低的速度隔开，这与中大西洋岩浆省的古代裂谷和洪水玄武岩的位置相匹配。在圣弗朗西斯科克拉通，高速向北和向西南延伸到先前提议的边界之外。更温暖、更薄的岩石圈是 Paramirim 和 Pirapora aulacogen 的基础，是岩浆和裂谷循环的所在地。一个支离破碎的克拉通根位于巴拉那盆地的基础，沿其中央裂谷的岩石圈较薄。巴拉那区块以南的高速表明 Rio de la Plata 克拉通北部的根部很粗。Borborema 省、南大西洋沿岸和巴拉圭的新生代板块内玄武岩出现在薄岩石圈区域和厚薄岩石圈边界附近。显生代大型火成岩省份的大多数泛滥玄武岩也位于低速地区。 较小的泛洪玄武岩部分位于克拉通岩石圈的顶部，为地壳内泛滥玄武岩熔岩和岩浆的横向流动提供了新证据。大约 80% 的已知含金刚石金伯利岩位于较厚的岩石圈上，但有例外表明自其放置以来发生了克拉通侵蚀和变薄。