Craig C. Lundstrom

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The Trinity peridotite (northern CA) contains numerous lithologic sequences consisting of dunite to harzburgite to spinel lherzolite to plagioclase lherzolite. Previous workers have documented geochemical gradients in these sequences consistent with melt-rock reaction processes occurring around dunites, interpreted to reflect conduits for melt ascent. We(More)
Uncertainties surround the timing of modern human emergence and occupation in East and Southeast Asia. Although genetic and archeological data indicate a rapid migration out of Africa and into Southeast Asia by at least 60 ka, mainland Southeast Asia is notable for its absence of fossil evidence for early modern human occupation. Here we report on a modern(More)
The phenomenon of thermal diffusion (mass diffusion driven by a temperature gradient, known as the Ludwig-Soret effect) has been investigated for over 150 years, but an understanding of its underlying physical basis remains elusive. A significant hurdle in studying thermal diffusion has been the difficulty of characterizing it. Extensive experiments over(More)
Antarctic toothfish (Dissostichus mawsoni) are the target of an important commercial fishery in the Southern Ocean, yet age data used for management have not been comprehensively tested for accuracy. In this study, Antarctic toothfish were aged using counts of otolith growth zones based on criteria established for Patagonian toothfish, D. eleginoides, a(More)
During the last century, the Earth Sciences underwent two major revolutions in understanding. The first was the recognition of the great antiquity of the Earth and the second was the development of plate tectonic theory. These leaps in knowledge moved geology from its largely descriptive origins and established the modern, quantitative, Earth sciences. For(More)
Keyword: Mg isotopes Igneous rock standards MC-ICP-MS To provide inter-lab comparison for high-precision Mg isotope analysis, Mg isotope compositions (expressed as δMg relative to DSM-3) for commercially accessible peridotite, basalt, andesite, and granite geostandards have been measured by multi-collector inductively coupled mass-spectrometry (Nu-Plasma)(More)
The attenuation of groundwater contamination via chemical reaction is traditionally evaluated by monitoring contaminant concentration through time. However, this method can be confounded by common transport processes (e.g., dilution, sorption). Isotopic techniques bypass the limits of concentration methods, and so may provide improved accuracy in(More)
Groundwater samples were collected from the Integrated Field Research Challenge field site in Rifle, Colorado, over the course of a bicarbonate-induced U desorption-adsorption experiment. Uranium concentrations and high precision U isotopic compositions ((238)U/(235)U) of these groundwater samples were determined and used to assess the impact of(More)
Variations in stable isotope ratios of redox sensitive elements are often used to understand redox processes occurring near the Earth's surface. Presented here are measurements of mass-dependent U isotope fractionation induced by U(VI) reduction by zerovalent iron (Fe0) and bacteria under controlled pH and HCO3- conditions. In abiotic experiments, Fe0(More)
Natural waters universally show fractionation of uranium series (U-series) parent–daughter pairs, with the disequilibrium between U and U (U)/(U) commonly used as a tracer of groundwater flow. Because speleothems provide a temporal record of geochemical variations in groundwater precipitating calcite, (U)/(U) variations in speleothems provide a unique(More)