The Paleoclimatic Signatures of Supergene Metal Deposits

Abstract

Artículo de publicación ISISupergene metal deposits host a comprehensive record of climate-driven geochemical reactions that may span the entire Cenozoic. Products of these reactions can be dated by a variety of radiogenic isotopic methods, such as Ar-40/Ar-39, (U-Th)/He, U-Pb, and U-series; The frequency of mineral precipitation, determined by dating a representative number of samples of a particular mineral collected from distinct parts of the supergene ore body, reflects times in the geological past when weathering conditions were condutive to water-rock interaction. The frequency of mineral precipitation through time permits identifying periods in the geological past when climatic conditions were most conducive to chemical weathering and supergene ore genesis.ICM 13006

Combined dating of goethites and kaolinites from ferruginous duricrusts. Deciphering the Late Neogene erosion history of Central Amazonia

“…The surface repartition by elevation has been extracted using SRTM 1 ARC-SECOND Global images. Location of the laterites and ore-deposits sites dated with 40 Ar/ 39 Ar and (U-Th)/He (Vasconcelos et al, 1994 and2015 and reference therein), EPR (Balan et al, 2005), paleomagnetism Freyssinet, 1999, 2002), together with the 3 sites from this study.…”

“…Those data revealed multiple generations of the oldest ages (about 70-65 Ma) corresponding to the Cretaceous period. In addition, ferruginous duricrusts from this region were also dated by (U-Th)/He and yielded ages ranging from 70 to 1 Ma (Shuster et al, 2012;Vasconcelos et al, 2015). Besides the similar ages recorded by 40 (Carmo and Vasconcelos, 2006;Monteiro et al, 2014;Shuster et al, 2012).…”

“…1B). In the region of Manaus, up to four Quaternary terraces overlying the Içá Formation were identified by Rossetti et al (2005) (Ruffet et al, 1996;Vasconcelos et al, 1994Vasconcelos et al, , 2015. The samples were located on high elevation surfaces (> 300 m a.s.l; Fig.…”

“…In more recent times, three main new dating methods were developed that apply to secondary components of the soil and are consistent with geological time scales > 1 Ma (Cornu et al, 2009). The first one mainly relies on the measurement of the 40 Ar/ 39 Ar ratio on Kbearing manganese oxides, using laser ablation technique on single grains (Beauvais et al, 2008Bonnet et al, 2014Bonnet et al, , 2016Vasconcelos, 1999;Vasconcelos et al, 1994Vasconcelos et al, , 2013Vasconcelos et al, , 2015. This approach provided an outlook of continuous, ancient weathering with clear discrete episodes irregularly distributed from the end of Mesozoic to present.…”

Innovations in (U–Th)/He, Fission Track, and Trapped Charge Thermochronometry with Applications to Earthquakes, Weathering, Surface‐Mantle Connections, and the Growth and Decay of Mountains

“…Figure depicts a typical lateritic profile and its mineralogical compartments, capped by a strong Fe‐enriched weathering horizon, referred to as a duricrust horizon. Mesozoic to Cenozoic laterite chronology has enhanced our understanding of soil formation and opens new research avenues as laterites also record past climatic conditions (e.g., Vasconcelos et al, ) or landscape evolution (e.g., Bonnet et al, ). 40 Ar– 39 Ar analysis of Mn oxides, and more recently, hematite and goethite He geochronology from laterites inform the timing, tempo, and geochemical processes of laterite formation via past climate change (Allard et al, ; Deng et al, ; Monteiro et al, ; Monteiro, Vasconcelos, Farley, & Lopes, ; Shuster, Vasconcelos, et al, ; Vasconcelos et al, ; Vasconcelos et al, ).…”