The timing and rate of emplacement, exhumation, and weathering of alkaline-carbonatite complexes associated with failed rift systems in the South Atlantic provide constraints on the thermotectonic conditions of West Gondwana before, during, and after break-up. Ar/Ar geochronology of biotite crystals show that two alkaline-carbonatite complexes – Araxá and Catalão I – from the Alto Paranaíba Igneous Province were shallowly emplaced simultaneously at ∼85 Ma. After rapid cooling, the igneous complexes were rapidly exhumed between 85 and 66 Ma at Araxá (∼52 ) and 85 and 45 Ma at Catalão (∼25 ). Fast exhumation of the complexes occurred under relatively arid to semi-arid climates, conditions that favored physical weathering and erosion. The eroded material was transported in a NE-SW direction and deposited in the adjacent Paraná and São Sanfranciscana basins. After exhumation, wetter climates and more subdued tectonic conditions favored active widespread vegetation cover that favored reduced erosion and deepening of weathering profiles. After 66 Ma, the Araxá complex denuded at rates of 3.4 ; at Catalão I, denudation rates reduced to 4.7 after ∼45 Ma. Favorable geological and climatic conditions promoted the formation of deep and chemically stratified lateritic weathering profiles. The exhumed and weathered carbonatites underwent hypogene and supergene enrichment in Nb, P, Ti, and REEs, critical metals needed for the electrification of our energy base. The preservation of the lateritic profiles and their mineral wealth in the continental interior contrasts with the younger and shallower weathering profiles formed on similar lithologies and at equivalent elevations near the Brazilain South Atlantic margin, confirming that climatic and tectonic conditions along the margin were less conducive to the preservation of valuable mineralized systems because of enhaced erosion.

中文翻译：

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40Ar/39Ar 和 (U-Th)/He 对巴西上帕拉纳伊巴火成岩省 (APIP) 碱性碳酸岩杂岩的侵位、折返和风化的限制

与南大西洋失效裂谷系统相关的碱性碳酸岩杂岩的侵位、折返和风化的时间和速率对西冈瓦纳大陆分裂之前、期间和之后的热构造条件提供了限制。黑云母晶体的 Ar/Ar 地质年代学表明，来自上巴拉那伊巴火成岩省的两个碱性碳酸岩杂岩——Araxá 和 Catalão I——在约 85 Ma 时同时浅层侵位。快速冷却后，火成岩杂岩在 Araxá (~52 ) 的 85 至 66 Ma 和 Catalão (~25 ) 的 85 至 45 Ma 之间迅速被挖掘出来。复合体的快速折返发生在相对干旱到半干旱的气候下，这些条件有利于物理风化和侵蚀。被侵蚀的物质沿东北-西南方向输送并沉积在邻近的巴拉那盆地和圣弗朗西斯卡纳盆地中。折返后，更湿润的气候和更温和的构造条件有利于活跃的广泛植被覆盖，有利于减少侵蚀和加深风化剖面。 66 Ma 后，Araxá 杂岩以 3.4 的速度被剥蚀；在 Catalão I，约 45 Ma 后，剥蚀率降至 4.7。有利的地质和气候条件促进了深层化学分层红土风化剖面的形成。挖出和风化的碳酸岩经历了深生和表生富集铌、磷、钛和稀土元素，这些金属是我们能源基础电气化所需的关键金属。大陆内部红土剖面及其矿物财富的保存与巴西南大西洋边缘附近类似岩性和同等海拔处形成的较年轻和较浅的风化剖面形成鲜明对比，证实了该边缘的气候和构造条件不太有利于由于侵蚀加剧，宝贵的矿化系统得以保存。