Preprints
Filtering by Subject: Chemistry
Recycling of archaeal biomass as a new strategy for extreme life in Dead Sea deep sediments
Published: 2017-12-15
Subjects: Biogeochemistry, Chemistry, Earth Sciences, Organic Chemistry, Physical Sciences and Mathematics
Archaea and Bacteria that inhabit the deep subsurface (known as the deep biosphere) play a prevalent role in the recycling of sedimentary organic carbon. In such environments, this process can occur over millions of years and requires microbial communities to cope with extremely limited sources of energy. Because of this scarcity, metabolic processes come at a high energetic cost, but the ways [...]
Isotopic composition (238U/235U) of some commonly used uranium reference materials
Published: 2017-11-05
Subjects: Chemistry, Cosmochemistry, Earth Sciences, Geochemistry, Inorganic Chemistry, Physical Sciences and Mathematics
We have determined 238U/235U ratios for a suite of commonly used natural (CRM 112a, SRM 950a, and HU-1) and synthetic (IRMM 184 and CRM U500) uranium reference materials by thermal ionisation mass-spectrometry (TIMS) using the IRMM 3636 233U–236U double spike to accurately correct for mass fractionation. Total uncertainty on the 238U/235U determinations is estimated to be <0.02% (2σ). These [...]
238U/235U Systematics in Terrestrial Uranium-Bearing Minerals
Published: 2017-11-05
Subjects: Chemistry, Cosmochemistry, Earth Sciences, Geochemistry, Inorganic Chemistry, Physical Sciences and Mathematics
The present-day 238U/235U ratio has fundamental implications for uranium-lead geochronology and cosmochronology. A value of 137.88 has previously been considered invariant and has been used without uncertainty to calculate terrestrial mineral ages. We report high-precision 238U/235U measurements for a suite of uranium-bearing minerals from 58 samples representing a diverse range of lithologies. [...]