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On the mechanisms of sulfur isotope fractionation during microbial sulfate reduction
(2014-06-06)
Underlying all applications of sulfur isotope analyses is our understanding of isotope systematics. This dissertation tests some fundamental assumptions and assertions, drawn from equilibrium theory and a diverse body of ...
Volatiles in the Earth and Moon: Constraints on planetary formation and evolution
(2014-06-06)
The volatile inventories of the Earth and Moon reflect unique histories of volatile acquisition and loss in the early Solar System. The terrestrial volatile inventory was established after the giant impact phase of accretion, ...
Chronology and geochemistry of Taxinan basalts from the Tarim basin: evidence for Permian plume magmatism
(Chinese Academy of Sciences, 2008)
A new K-Ar age of 289.6Ma has been obtained for Taxinan basalt in the southwest Tarim basin of the northwest China. This age is consistent with the Ar-Ar age of 290. 1Ma from the same sample. This dating confirms the ...
A Theory of Atmospheric Oxygen
(2015-05-08)
There is no direct geologic record of the level of free oxygen in the atmosphere over Earth history. Indirect proxy records have led to a canonical view of atmospheric pO2, according to which the atmosphere has passed ...
Rapid Climate Change in the Cenozoic: Insights from Geochemical Proxies
(2014-10-21)
Studying the mean state and variability of past climate provides important insight into the dynamically coupled climate system, directly aiding projections of future climate. Reconstruction of past climate conditions can ...
Application of noble gas isotopic systems to identify mantle heterogeneities
(2014-10-21)
This study addresses the origin of the combined He-Ne-Ar-Xe noble gas isotopic variation in mantle derived oceanic basalts. High precision heavy noble gas compositions of basalts from the Rochambeau Rift along the Northwestern ...
Multiple Sulfur Isotope Applications in Diagenetic Models and Geochemical Proxy Records
(2016-09-09)
Many of the long-term geochemical fluxes influencing the surface sulfur cycle are microbially catalyzed and a substantial portion of active S cycling occurs in organic-rich continental margin sediments. Stable S isotopes ...
Constraining Subduction Zone Processes Through Local, Regional, and Global Chemical Systematics
(2015-04-08)
Subduction zones recycle material from Earth’s surface into the mantle, and are an important means of continent building. The subduction system serves as a stamp, imprinting the distinct chemical characteristics of our ...
Elemental Fluxes to the Seafloor: Pleistocene Climate and Submarine Hydrothermal Activity
(2018-01-03)
Marine sedimentary records of major and trace element deposition provide a means to examine the temporal variability and interactions between a wide variety of Earth processes, including fluctuations in atmospheric and ...
The Chemical Structure, Composition, Extent of Mixing, and the Origin of Heterogeneities in the Earth’s Mantle
(2018-09-25)
Formation of chemical heterogeneities and the extent of mixing in the mantle are relevant questions to understanding large scale processes that dominate the bulk silicate Earth, which can be addressed using different methods ...