Abstract This study presents the results of mineralogical analysis and (U Th)/He dating of micrometric grains of hematite, goethite, cryptomelane and hollandite from six samples of bauxite, Fe, Mn, Mn-Al-Fe, Mn Al and Mn-Al-P duricrusts located in southwestern Amazonia (Brazil). The samples were collected at different elevations to constrain temporal epochs of lateritization and to provide insights into the cratonic landscape evolution of Proterozoic and Paleozoic terrains in Brazil. Three main phases of duricrust formation were recognized, indicating a long period of lateritic weathering: The first phase, preserved as a fragment in Fe duricrust on the Paleozoic sedimentary rocks, began in the Permian (~290 Ma) and lasted until the Late Cretaceous (~65 Ma). The second (and best preserved) phase formed Mn duricrusts on the Paleoproterozoic Apui lateritic surface (150–250 m a.s.l.) and on the Aripuana lateritic surface (

中文翻译：

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基于铁和锰红土硬壳的 (U Th)/He 定年的亚马逊西南部偶发风化作用

摘要 本研究介绍了铝土矿、Fe、Mn、Mn-Al-Fe、Mn Al 和 Mn-Al 六种样品中赤铁矿、针铁矿、锂锰矿和荷兰铁矿的微米颗粒的矿物学分析和 (U Th)/He 测年结果。 -P duricrusts 位于亚马逊西南部（巴西）。这些样本是在不同海拔处收集的，以限制红土化的时间时代，并提供对巴西元古代和古生代地形的克拉通景观演化的见解。确认了三个主要的硬壳层形成阶段，表明红土风化期很长：第一阶段作为古生代沉积岩上的 Fe 硬壳层中的碎片保存，开始于二叠纪（~290 Ma）并持续到晚白垩世（ ~65 毫安）。