Now showing items 21-30 of 84
Sulfur isotope fractionations in biological systems: insight into the Proterozoic biosphere
This study focuses on developing a framework for interpreting isotopic fractionations in the four stable sulfur isotopes, with a special focus on microbial effects. Calculations of low temperature equilibrium fractionations ...
Examination of the Thermal Decomposition of Chrysotile
The decomposition of pure chrysotile from Thetford, Quebec heated at constant temperature in air from 200-1000°C for 4 to 720 hours was studied by using X-ray diffraction and optical microscopy techniques. No morphological ...
Age, composition, and origin of the lower continental crust, northern Tanzania
Granulite xenoliths from the East African rift in Tanzania sample the lower continental crust beneath both the stable Tanzanian craton and the adjacent, polymetamorphic Mozambique belt. Protoliths of surface rocks in both ...
A Stable Isotope Investigation of Precipitation Nitrate
The isotopic composition of precipitation nitrate reflects the processes involved in its formation. Silver nitrates prepared from Maryland precipitation were thermally decomposed to gases for mass spectrometric analyses. ...
Quantification of Permeability-Porosity Relationships in Seafloor Vent Deposits: Dependence on Pore Evolution Processes
Hydrothermal mineral deposits formed along seafloor spreading centers help regulate the transfer of heat and mass from Earth's interior to the oceans. Aqueous fluids circulate within the seafloor and are emitted through ...
ISOTOPE GEOCHEMISTRY OF ORGANIC SULFUR COMPOUNDS WITH LINKS TO BIOGEOCHEMICAL SULFUR CYCLING AND RADICAL CHEMISTRY
Isotope and Organic Geochemistry of a Unique Proterozoic, Postglacial Succession: The Lapa Formation, Vazante Group, Brazil
This study is the second to investigate biological characteristics associated with Proterozoic glaciation via molecular fossils from organic matter preserved in shale. In the Vazante Group, Minas Gerais, Brazil, the Serra ...
Highly Siderophile Element and Tungsten Systematics of Hawaiian Picrites
A suite of Hawaiian picrites (MgO > 13 wt.%), and associated basalts, that represent some of the most primitive melts from the Hawaiian mantle source regions were analyzed for their W, highly siderophile element (HSE: Os, ...
Timing of Orogenesis in the Southern Brasília Belt
The Neoproterozoic-Cambrian Brasília Orogeny records suturing of the passive margin on the western side of the São Francisco Craton with magmatic arcs and the Paranapanema Block in the south or the Amazon Craton in the ...
GLOBAL AND REGIONAL REFERENCE MODELS FOR PREDICTING THE GEONEUTRINO FLUX AT SNO+, SUDBURY, CANADA
Determining the radiogenic heat power that is driving plate tectonics and mantle convection is fundamentally important to understanding the Earth's heat budget and its thermal and chemical evolution. The radiogenic heat ...