The end of the Palaeozoic is marked by two mass-extinction events during the Middle Permian (Capitanian) and the Late Permian (Changhsingian). Given similarities between the two events in geochemical signatures, such as large magnitude negative dC anomalies, sedimentological signatures such as claystone breccias, and the approximate contemporaneous emplacement of large igneous provinces, many a...

introduction the shahrestanak mn deposit is located in southern qom province, 12 km southwest of the city of kahak. based on geological-structural divisions of iran, the deposit belongs to central volcanic belt or urumieh-dokhtar zone. the venarch deposit is one the most important known manganese deposits in iran. the sharestanak and venarch deposits are spatially and temporally related to each...

The subaerial surface of Koolau volcano is composed of lavas that define the distinctive endmember composition for Hawaiian shield lavas, known as the Koolau component, now designated as the Makapuustage. The geochemical characteristics of lavas recovered by the Koolau Scientific Drilling Project (KSDP) show that this distinctive composition forms a <300-m thick veneer. Below this veneer, from ...

Tailings deposits from gold and uranium (U) mining in the Witwatersrand basin often contain elevated levels of radioactive and chemo-toxic heavy metals. Through seepage, dissolved U and other metals migrate from tailings deposits via groundwater into adjacent fluvial systems. The subsequent transport through flowing surface water is one of the most effective pathways of distributing contaminant...

The description of the geochemical properties of the bentonite backfill that serves as engineered barrier for nuclear repositories is a central issue for performance assessment since these play a large role in determining the fate of contaminants released from the waste. In this study the porewater chemistry of bentonite was assessed with a thermodynamic modelling approach that includes ion exc...

Ab&r&-Sulphur isotope abundances of thirty-nine specimens of seventeen meteorites are reported. The resultril show again the remarkable constancy of the sulphur isotope ratios for meteorites of all types. However, differences in the SBa/Sa* ratios of 0.4 %a would appear to be significant. The Ssz/P4 ratio for meteorites is discussed as a possible base level from which fr~tion&tion in the earth’...

This study reports major, minor, and trace element data and Sr isotope ratios for 11 uranium ore (uraninite, UO2þx) samples and one processed uranium ore concentrate (UOC) from various U.S. deposits. The uraninite investigated represent ores formed via different modes of mineralization (e.g., highand lowtemperature) and within various geological contexts, which include magmatic pegmatites, meta...

A compilation of geochemical data from >50 active volcanoes where seismically defi ned Moho depth measurements are available, representing most volcanic arcs around the world, indicates a relation exists between crustal thickness (Moho depth) and the trace element composition of basalts. The best correlation exists for maximum light/heavy rare earth element (REE) ratios, and we use maximum Ce/Y...