Authigenesis of native sulphur and dolomite in a lacustrine evaporitic setting (Hellin basin, Late Miocene, SE Spain)

Abundant sulphur is present in the Late Miocene evaporitic sequence of the lacustrine Hellín basin in SE Spain. Weathering of Triassic evaporites controlled the chemical composition of the Miocene lake. The lacustrine deposits comprise gypsum, marlstones, diatomites and carbonate beds. Sulphur-bearing carbonate deposits predominantly consist of early diagenetic dolomite. Abundant dolomite crystals with a spheroidal habit are in accordance with an early formation and point to a microbial origin. The carbon isotopic composition of the dolomite (δ13C values between −10 and −4‰) indicates mixing of lake water carbonate and carbonate derived from the remineralization of organic matter by heterotrophic bacteria. Dolomite precipitated syngenetically under evaporitic conditions as indicated by high oxygen isotope values (δ18O between +6 and +11‰). Nodules of native sulphur are found in gypsum, carbonate beds and marlstone layers. Sulphur formed in the course of microbial sulphate reduction, as reflected by its strong depletion in 34S (δ34S values as low as −17‰). Near to the surface many of the sulphur nodules were in part or completely substituted by secondary gypsum, which still reflects the sulphur isotopic composition of native sulphur (−18 to −10‰). This study exemplifies the role of bacterial sulphate reduction in the formation of dolomite and native sulphur in a semi-enclosed lacustrine basin during Late Miocene time

Practical Hybrid Parallel Application Performance Engineering

This tutorial presents state-of-the-art performance tools for leading-edge HPC systems founded on the community-developed Score-P instrumentation and measurement infrastructure, and demonstrates how they can be used for performance engineering of effective scientific applications based on standard MPI, OpenMP, hybrid combination of both and increasingly common usage of accelerators. Parallel performance tools from the Virtual Institute - High Productivity Supercomputing (VI-HPS) are introduced and featured in exercises with Score-P, Scalasca, Vampir and TAU. Emphasis is placed on analyzing measurement results and how tools are used in combination for identifying performance problems and investigating optimization alternatives. Using their own notebook computers with a provided HPC Linux [http://www.hpclinux.org] OVA image containing all the necessary tools, participants will be able to work through the exercises on their own with provided example measurements collected on contemporary HPC systems. This will help to prepare participants to locate and diagnose performance bottlenecks in their own parallel programs

Formation of secondary carbonates and native sulphur in sulphate-rich Messinian strata, Sicily

Microbially formed authigenic carbonates accompanied by native sulphur are present in the ‘Calcare Solfifero’ below a thick succession of gypsum deposited during the Messinian salinity crisis in Sicily. We sampled these carbonates and associated sulphur in five former sulphur mines to subject them to a detailed petrographic and geochemical study in order to explore their different modes of formation. Native sulphur formed in conjunction with microbial sulphate reduction,which is reflected in its depletion in 34S (δ34Svaluesas lowas−2‰vs. V-CDT) and an enrichment of 34S in the residual sulphate (δ34S values as high as+61‰). The oxidation of organic matter by sulphate reduction increased alkalinity, inducing precipitation of secondary carbonate minerals. A set of authigenic limestones lacking sulphate minerals, but characterized by pseudomorphs after gypsumand high δ18O values (as high as +9‰ vs. V-PDB) reflects syngenetic mineral formation within evaporitic settings. Low δ13C values (as low as −52‰ vs. V-PDB) reveal that these carbonate phases were formed by microbial sulphate reduction coupled to the oxidation of biogenic methane. Another set of authigenic carbonates that replaced sulphate minerals is typified by lowδ18O values (as lowas−4‰). These carbonates formed epigenetically during later diagenesis following compaction. Dissolution of gypsum or anhydrite by meteoric waters delivered the sulphate for microbial sulphate reduction. Lowcarbon isotope values of these carbonates (−29 to−5‰) indicate that carbonatewas derived fromthe oxidation of crude oil and possibly minormethane, partly involving different degrees of admixture of dissolved carbonate from other sources. Although the studied rocks with their vast amounts of secondary carbonate minerals and sulphur seem to indicate a similar genesis at first glance – having formed by biogeochemical transformations of sulphate and hydrocarbons – this study reveals that these processes can occur at different times in variable geological environments