Gold-silver telluride deposits in central Montana contain > 400 t Au and are spatially and genetically related to major faults in the Great Falls Tectonic Zone (GFTZ) and the Lewis and Clark Line. They are also related to alkaline igneous intrusive rocks, including monzonites, syenites, diorites, tinguaites, dacites, lamprophyres, and trachytes. Deposit styles include bonanza veins, carbonate replacement at igneous-carbonate contacts, breccia pipe-hosted, and structurally controlled igneous-hosted. Ore-related breccias are a common feature. The ore mineralogy is complex, and locally contains native gold/electrum, Au-Ag tellurides (calaverite, sylvanite, krennerite, petzite, empressite, stützite, and hessite), Bi-tellurides (tetradymite, tellurobismuthite), Bi sulphosalts, and rare precious-metal sulphotellurides. Alteration related to ore-stage fluids is localised primarily adjacent to veins and characterised by silicification, fluoritisation, adularia-sericite, and roscoelite±clays. Fluid inclusion studies suggest that gold telluride ores were deposited from low-temperature (130o–270 oC), moderately saline (1–12 equiv. wt % NaCl), locally boiling, CO2-poor, near neutral, relatively oxidising fluids. Oxygen and hydrogen isotope studies support the concept that the deposits formed from a continuum between magmatic and meteoric fluids, whereas sulphur isotope compositions of sulphides suggest a magmatic sulphur source or sulphur that was leached from sulphides in volcaniclastic and clastic sedimentary rocks. Lead isotope compositions are permissive of a crustal source with a contribution from Palaeozoic or Proterozoic sedimentary rocks hosting the alkalic igneous rocks. Porphyry molybdenum and Carlin-like Au-Te deposits are also genetically related to the GFTZ and Lewis and Clark Line and represent end-members that form a continuum with epithermal gold-silver telluride deposits.

Gorstian sediments in south-central Wales preserve an asymmetric, compound mixed-process delta system north of the Carreg Cennen Disturbance and east of the Golden Grove Axis. The 30 km SW-NE outcrop, extending from the Cennen Valley to Y Pigwn, is oblique to the NNE delta progradation direction. The Hafod Fawr Formation comprises subaqueous delta slope deposits. Sandstone bed amalgamation indicates shoaling and wave/storm influence within the overlying subaqueous delta platform deposits of the Cwar Glas Member. The succeeding Mynydd Myddfai Sandstone Formation contains shoreline delta lithofacies within three geographical tracts. An embryonic Golden Grove Axis shed shoal water shoreline fan-delta and alluvial fan lithofacies (of the Trichrug Formation) in the Cennen Valley Tract. The SW Tract (Cilmaenllwyd to Banc Celynog) was deposited on the updrift flank of the asymmetric delta, with longshore drift to the NE. Amalgamated sandstone bedsets dominate in the mouth bar and terminal distributary channel lithofacies. Pen y Bicws preserves the axial gravel bed distributary channel lithofacies, which created a headland and palaeogeographic divide between the SW and NE tracts. The latter (Sawdde Gorge to Y Pigwn) records deposition in a low-energy bay that hosted cycles of heterolithic lithofacies. Collectively, these tracts occupied part of a sediment supply route to deeper facies of the subsidence-prone Clun Forest Sub-Basin. Emergent delta plain deposits become dominant within the overlying Trichrug Formation. Thin, locally preserved deposits of the Cribyn Du Member record delta abandonment and transgression during the Ludfordian associated with basin reconfiguration and expansion of the Caer’r mynach Seaway.

This study reports potassium (K) isotope compositions of diamondiferous kimberlites. Altered kimberlite samples exhibit δ41K values ranging from −1.293 ± 0.052 (2SD) to −0.114 ± 0.029 ‰, showing covariations with chemical indicators of alteration. This is consistent with the geochemical dynamics of K isotopes in hydrothermal fluid-related processes. In contrast, pristine kimberlite samples display restricted K isotope compositions, with δ41K values between −0.494 ± 0.057 and −0.270 ± 0.048 ‰. Notably, the δ41K values of these pristine kimberlite samples correlate well with K2O and Rb contents, suggesting that approximately ∼0.2 ‰ of K isotope fractionation is induced by phlogopite crystallization, as indicated by quantitative modelling. The estimated δ41K values of −0.458 ‰ for the primary kimberlite melt and of −0.414 ‰ for the kimberlite source imply a potential link to the bulk silicate Earth. These new measurements, along with literature data from various rocks, indicate that the K isotope composition in the deep mantle (>150 km) is more homogenous than in shallow regions, likely reflecting the efficiency of convection flow and K behaviour during subduction. In addition, the K isotope data reveal temporal variations in mantle-derived magmas from the Palaeozoic to the Cenozoic, highlighting the geological history and lithospheric destruction of the North China Craton. This study underscores the significance of K isotopes in enhancing our understanding of mantle dynamics, crustal recycling and the geochemical evolution of the Earth’s interior.

The pyritization of microfossils serves as a key indicator of paleoenvironmental conditions, yet the controlling factors on pyrite morphology and composition remain poorly constrained. This study encountered different pyrite morphology (framboids and patches) from the foraminiferal tests retrieved from the marine sediment samples of Ocean Drilling Program Hole 763A, southeastern Indian Ocean, during different geological time slices. We hypothesize that distinct microenvironments and controlling factors might have influenced the morphology. Detailed investigations of the morphology, mineralogy and geochemistry of Fe-S coatings within and on foraminiferal tests suggest the dynamics of paleoredox conditions during the Middle Pleistocene and Upper Miocene. The comprehensive geochemical overview and the presence of Ni and Ba associated with Fe-S coatings and sediments suggest deoxygenation of deep-sea sediments driven by climatic shifts rather than hydrothermal activities. The stable anoxic deep ocean setting during the Middle Pleistocene, evidenced by increased organic matter flux and ocean stratification, contributed to low bottom-water oxygen levels. The geochemical evidence from the Upper Miocene samples indicates predominantly oxidising conditions, as shown by the altered reddish-yellow foraminiferal tests, which are mainly composed of calcite. However, localized reducing conditions are evidenced by patches of pyrite associated with foraminiferal shells, suggesting the presence of transitional redox conditions within the oxidising sediments during the Upper Miocene.

The Dora-Maira Massif offers a unique window into the pre-Alpine and Alpine tectonic history of continental crust involved in the collision that formed the Western Alps. Whereas high-pressure Alpine metamorphism has strongly affected the rocks, zircon crystals still retain age domains from earlier magmatic events, offering a reliable tool for reconstructing the evolution of the continental basement. Combining new U–Pb LA-ICP-MS zircon geochronology with whole-rock geochemistry, this study unveils a more complex magmatic and tectonic evolution than previously recognized. New findings reveal that the Dora-Maira basement preserves three distinct magmatic cycles: Ediacaran–Early Cambrian (c. 550–530 Ma), Ordovician–Silurian (c. 460–440 Ma) and Permian (c. 280–260 Ma). These results challenge the overestimated presence of Permian intrusions in the Massif, instead highlighting a significant Lower Paleozoic magmatic component that was previously overlooked. We document the oldest magmatic suite recognized to date in the area (540.0 ± 5.4 and 548.0 ± 5.5 Ma), which sheds light on the Cambrian-to-Precambrian tectonic history of the northern margin of Gondwana. This contribution refines the geodynamic framework of the Dora-Maira Massif. It demonstrates that its polycyclic basement was assembled through successive crust-forming events during the Ediacaran–Early Paleozoic and subsequently reworked during the Variscan and Alpine orogenies. This underlines the key role of Lower Paleozoic tectono-magmatic processes in shaping the continental crust of the Western Alps.

Deserts must be supplied with sediment in order to accrete. The Thar Desert, lying east of the Indus River in South Asia, might be expected to be largely supplied with sediment from that drainage. In this study, we use a combination of major and trace element bulk-sediment geochemistry, together with Sr and Nd isotopes, to constrain the provenance of postglacial dune sand. Our data indicate a stronger influence from mafic source rocks in the Sindh Desert compared to that in Cholistan. Nd isotopes imply sediment was largely derived from the lower Indus River during the early and pre-Holocene post-glacial time. The sand is coarser grained in Sindh and retains higher ϵNd values in sediment that eroded from mafic rocks in Kohistan and the Karakorum as a result of deflation of deltaic and floodplain areas in the lower reaches by southwesterly summer monsoon winds. The composition of Cholistan dunes, like that in the Eastern Thar Desert, reveals instead more supply from Himalayan sources and more negative ϵNd values. The greater Himalayan influence in Cholistan and the Eastern Thar Desert largely reflects finer grain size, a result of the longer transport from the delta source and a preference for more Himalayan supply in the form of finer sediment.

The Silurian of Podolia, Ukraine, is renowned for its arthropod fauna, including eurypterids and the synziphosurine Pasternakevia. Here, we describe one of several new arthropods recently discovered in the vicinity of the Smotrych River. Smotrychaspis kurtopleurae gen. et sp. nov. is a synziphosurine euchelicerate with semicircular carapace lacking eyes, an unfused opisthosoma with 11 visible segments, the posterior tergites wide and bearing falcate epimera and a relatively long and stout telson. Smotrychaspis resembles pseudoniscid and bunodid synziphosurines but cannot be placed in either of these families.

Marine molluscs are exceptional in Cretaceous ambers. Palaeoellobium decampsi gen. nov., sp. nov. is the first gastropod ever preserved in French uppermost Albian-lowermost Cenomanian opaque amber. It belongs to the Ellobiidae that are distributed in the Cenozoic supralittoral zones in close vicinity of the mangroves. It has been discovered by non-destructive X-ray phase-contrast imaging. The forest of conifers that produced the amber embedding this gastropod did not form its habitat, and it may have been transported to the foreshore detritus. Palaeoellobium decampsi contributes to the understanding of the ellobiid early adaptive radiation known by few taxa, compared with the significant Cenozoic diversification.

The Dwarka Basin in the Kathiawar Peninsula, western margin of the Indian subcontinent, offers crucial insights into marine sedimentation processes and faunal evolution during the Miocene epoch. This research employs a combination of biostratigraphy, microfacies analysis and geochemical data to examine the Gaj Formation, a major stratigraphic unit of the Dwarka Basin, with the aim of reconstructing the paleoclimatic and depositional conditions. Foraminiferal biostratigraphy suggests that the Gaj Formation ranges from the Aquitanian to the Langhian stage, with the intermediate Burdigalian stage comprising most of the succession. Microfacies analysis reveals that the formation was primarily deposited in shelf environments, influenced by regional tectonic and climatic factors. The fossil assemblages and morphological adaptations observed in foraminiferal shells provide clear evidence of the Middle Miocene Climatic Optimum (MMCO). Climate-driven global warming during this climatic phase caused morphological evolution (e.g., dwarfism) and decreased faunal diversity in response to environmental stress. This study also aims to reconcile discrepancies in stratigraphic classification in the basin through lithostratigraphic data and high-resolution faunal analyses. Results highlight the dynamic nature of marine depositional environments as impacted by global sea-level changes, regional tectonics and climatic fluctuations. The study foregrounds the importance of multi-proxy analyses in reconstructing complex depositional histories and Miocene climatic transitions and their effects on regional marine ecosystems.