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Developments in Earth system research have led to widespread interest in multi‐sphere interactions that may have controlled bauxite formation. Although karst bauxite ores are abundant in the Tethyan Metallogenic Domain (TMD), their genesis and distribution are not yet fully understood. This study utilizes the Random Forest (RF) model to analyze geochemical data sets compiled from three bauxite provinces in the Tethys, including the Mediterranean, Central Asian, and Chinese provinces. Meaningful variables among the provenance, paleolatitude and tectonic setting that affected the formation of the bauxite deposits are identified. The Logistic Regression model is used to verify the importance of various factors. Our study shows that when RF model achieves the best classifier performance, TiO2 is the variable that has the greatest impact on the model. TiO2 content is the highest in the Central Asian Province. The high TiO2 content in bauxites indicates a provenance of magmatic origine associated with the Subduction Provenance Zone. Bauxites with TiO2 content similar to that of the continental basement are derived from siliciclastic and carbonate rocks, identified as the Orogenic Provenance Zone. This study illustrates a novel link between geochemical compositions (TiO2 content) of bauxites, provenance and regional tectonic setting. Plain Language Summary: Abundant bauxite deposits formed in the Tethyan Metallogenic Domain are of great importance to bauxite research. However, previous studies generally focus on local bauxite occurrences formed over certain geologic time. A comprehensive understanding of the genesis and characteristics of bauxite deposits is hence essential. In this study, Machine learning methods (Random Forest and Logistic Regression) are applied to improve the understanding of Tethyan bauxite formation. Our research reveals that the TiO2 content in Tethyan bauxites is related to their provenance. The enrichment of TiO2 in bauxite deposits points to magmatic rock provenance that underwent subduction. Bauxites with a TiO2 content similar to that of continental basement are derived from siliciclastic and carbonate rocks exposed on orogenic belts. As such, this investigation elucidates a previously unexplored association between the geochemical characteristics (TiO2 content) of bauxite deposits, their provenance, and the regional tectonic context. Key Points: Two Provenance Zones in the Tethys Domain are proposed: Subduction Provenance Zone and Orogenic Provenance ZoneHigh TiO2 content in bauxites resulted from magmatic rocks of the Subduction Provenance ZoneTi in bauxites has the potential for tracing provenance and associated tectonic settings [ABSTRACT FROM AUTHOR]

We analyzed the major and rare earth element compositions of siliceous deposits from the Upper Devonian Liujiang Formation, Lower Carboniferous Luzhai Formation, Lower–Middle Permian Sidazhai Formation and Tapi Formation, which are widely distributed as bedded cherts in the interplatform basinal successions of the Youjiang Basin. The Liujiang Formation and Luzhai Formation cherts generally have high Al/(Al+Fe+Mn) values (0.38–0.94) and are non-hydrothermal cherts. These cherts are generally characterized by moderately negative Ce anomalies and high Y/Ho values relatived to PAAS, indicating that the Youjiang Basin might have evolved into an open rift basin during the Late Devonian–Early Carboniferous. The Sidazhai Formation cherts from Ziyun generally have high Al/(Al+Fe+Mn) values (0.60–0.78), suggesting negligible contribution from a hydrothermal component. The Sidazhai Formation cherts from Hechi and the Tapi Formation cherts from Malipo generally have low Al/(Al+Fe+Mn) values (0.09–0.41), indicating an intense hydrothermal input. Relatived to the Sidazhai Formation cherts, the Tapi Formation cherts have higher Ce/Ce* values (0.68±0.19) and lower Y/Ho values (41.83±13.27), which may be affected by the terrigenous input from the Vietnam Block. The Sidazhai Formation cherts from Ziyun and Hechi exhibit negative Ce anomalies (0.43±0.12, 0.33±0.17, respectively) with high Y/Ho values (57.44±16.20, 46.02±4.27, respectively), resembling the geochemical characteristics of open-ocean basin cherts. These cherts were deposited on a passive continental margin adjacent to the Babu branch ocean, which may have contributed to upwelling. Detailed spatial studies on geochemical characteristics of the Late Paleozoic cherts can unravel the evolution of the Youjiang Basin.

The concentrations of redox-sensitive trace elements, such as uranium (U), vanadium (V), molybdenum (Mo), cobalt (Co), chromium (Cr) and rare earth elements (REE+Y) were determined in a given carbonate succession in the Gaoyuzhuang Formation (~1.56 Ga), which spans depths from outer shelf to intertidal, to explore the Early Mesoproterozoic ocean redox conditions. The values of the Zr-normalized redox-sensitive trace element concentrations and some relevant ratios show obvious changes from bottom to top in the succession. Samples from the outer shelf setting (M1 interval) demonstrate significantly enhanced values in Zr-normalized redox-sensitive trace element concentrations and relevant ratios (the peaks of Mo/U, V/Cr and Ni/Co ratios larger than 8, 4.25, and 7, respectively). Authigenic framboidal pyrites were also found within oncolite-like carbonate concretions and surrounding host rocks in this interval. These all indicate a euxinic state in the outer shelf environment. Less enrichment of Zr-normalized redox-sensitive elemental abundances and a mild decrease in the values of geochemical ratios were present in the inner shelf environment (M2 interval) (the V/Cr and Ni/Co ratios fall into a range of 2.5-4.25 and 4-5, respectively), suggesting dysoxic conditions dominant in the inner shelf setting. Samples from the shallower subtidal and intertidal settings (M3 and M4 intervals) are mostly invariable with much lower values of Zr-normalized redox-sensitive elements and relevant ratios, with the V/Cr and Ni/Co ratios typically near or less than 2 and 5 respectively, indicative of oxic conditions in the high-energy subtidal/intertidal zones. A remarkable negative Ce anomaly exhibited in the shale-normalized REE+Y diagram in the M4 interval may provide evidence in support of the hypothesis. Taken together, our results suggest a relatively shallow chemocline in the Early Mesoproterozoic ocean: the transitions between euxinic, dysoxic and oxic may occur in quiet-water outer shelf and highenergy subtidal zone, respectively. The presence of euxinic ocean bottom waters is compatible with low concentrations of seawater sulfate and reduced levels of atmospheric oxygen during this period. The extreme environmental conditions induced by these anoxic oceans could have been responsible for the delayed oxygenation of the biosphere and hindered the evolution of multicellular life.

The Pennsylvanian to lower Permian succession at Madiyi, South China, represents a nearshore mixed siliciclastic‐carbonate system characterized by cyclic sedimentation patterns along a depth gradient from continental siliciclastics to marine open platform carbonates. Various palaeokarst features related to subaerial exposure are widely distributed. Additionally, pedogenesis was pervasive. The identification of twenty‐eight sedimentary cycles grouped into five sequences allows the reconstruction of a relative sea‐level curve. The cycles represent higher frequency changes superimposed on the long‐term evolution. After the initial transgression, the sea level remained relatively low in the late Bashkirian to early Moscovian. Then, it rose stepwise until a major drop occurred in the late Moscovian. Afterwards, the sea level rose again, but marine sedimentation ceased during at least the early Kasimovian. The area was flooded in the late Kasimovian, and the sea level rose until a late Gzhelian sea‐level drop. The subsequent marine sequence contains uppermost Gzhelian to upper Asselian deposits, which are capped by lower Permian continental facies associated with a major regional regression. Shallow to deeper marine sedimentary settings recorded high‐frequency sea‐level changes throughout South China during the late Bashkirian to Asselian. The main transgression–regression cycles are clearly associated with different depositional settings during several time intervals. Furthermore, the good correlations among South China, Ukraine, and the U.S. Mid‐continent are rooted in the impact of Gondwanan glaciations on the global sedimentation patterns. However, not all changes at Madiyi are the result of glacio‐eustatic sea‐level fluctuations; some are related to the local subsidence history and the rise of the Xuefeng Uplift. [ABSTRACT FROM AUTHOR]