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Geochimica et Cosmochimica Acta
IF
4.26
Papers
23151
Papers 23235
1 page of 2,324 pages (23.2k results)
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Abstract Stable hydrogen isotopes (δD values) in animal organic tissues such as collagen and keratin typically correlate with local meteoric water, but little is known about δD in tooth enamel apatite. In this study, we analyzed comminuted tooth enamel for oxygen isotopes (δ18O) of the CO3 component and for δD of bulk enamel. We find positive correlations between enamel δD and δ18O (R2 = 0.70) and between enamel δD and local precipitation δD (R2 = 0.53). However, the slopes of these relationship...
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Abstract Jarosite is a common mineral in acidic, sulfate-rich environments where it is critical in regulating the acidity of aquatic systems and the mobility of trace elements and potential contaminants. This research aims to understand jarosite formation and recrystallization in these environments by examining the stable iron isotope geochemistry of jarosite at two coastal sites in Victoria, Australia: Fossil Beach and Southside Beach. Jarosite occurs at high abundance as beds, veins, surface c...
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Abstract The interaction of FeII and Si is at the heart of many critical geochemical processes in diverse natural and engineered environments. The resulting FeII-silicate phases play important roles in regulating the concentrations and bioavailability of FeII and Si, as well as serve as sinks for trace and hazardous elements. Therefore, a detailed understanding of their structural characteristics and the underlying formation mechanisms may provide insights useful to predicting their reactivity a...
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Abstract Silica activity in fluids is a key factor that controls reaction pathways during the hydrothermal alteration of olivine in the oceanic lithosphere. In this study, we conducted hydrothermal experiments (300°C, 8.58 MPa) on the olivine (Ol)–quartz (Qtz)–H2O system to understand the coupling between silica transport and olivine alteration. Mineral powders were reacted with 0.5 mol kg–1 NaCl solution in a tube-in-tube type vessel, and the spatial distribution of reactant and product mineral...
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Abstract Variations of the stable Ca isotopic compositions (noted as δ44/40Ca relative to the SRM915a standard) of basalts are interpreted as effects of mantle sources. Mantle pyroxenites are a minor but integral part of the mantle and, as fusible components, they are important source rocks to understand chemical and isotopic heterogeneity in mantle-derived magmas. However, the effect of pyroxenites on the Ca isotopic composition of the mantle has been poorly constrained. To which extent mantle ...
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Abstract The steady-state dissolution rates of sepiolite were measured as a function of pH from mixed-flow reactor experiments at 25 oC in both citrate bearing and citrate-free aqueous solutions. Dissolution at pH ≤5.5 and pH ≥9.18 was found to be non-stoichiometric, with relatively more Mg being released at low pH, while Si was preferentially released at high pH. The steady-state dissolution rate of sepiolite at 25 oC, based on Si release rates at far from equilibrium conditions, r+ in mol/cm2/...
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Abstract Leaf carbon isotope fractionation (Δleaf) is sensitive to environmental conditions and can provide insights into the state and evolution of leaf gas-exchange in response to climate and environment factors. In modern plants, water availability is the strongest environmental predictor of Δleaf across sites that experience relatively uniform and low concentrations of CO2 in the atmosphere (pCO2). Growth chamber experiments show Δleaf of modern plants can also be sensitive to changing pCO2....
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Abstract The eastern part of Asia between the North China and Siberian cratons contains orogenic belts formed by the Paleo-Asian and Pacific subduction and older continental blocks. A fundamental question regarding these and all mobile belts is the fate of the continental lithospheric mantle (CLM) during their formation, i.e. whether, or to what extent the CLM may be formed, replaced or affected during orogeny. Insights into these processes can be obtained from mantle xenoliths hosted by Cenozoi...
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Abstract The understanding of porosity evolution in porous media due to mineral reactions and its impact on the transport of fluids and solutes is important, as this is a key factor in the long-term behaviour of underground engineered systems. The implementation of such coupled processes into numerical codes requires a mechanistic understanding of the relevant precipitation/dissolution processes in porous media and model validation with quantitative experiments. In this context, we conducted a s...
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Abstract A newly discovered sedimentary accumulation of micrometeorites in the Sor Rondane Mountains of East Antarctica, close to the Wideroefjellet summit at ∼2750 meter above sea level, is characterized in this work. The focus here lies on 2099 melted cosmic spherules larger than 200 μm, extracted from 3.2 kg of sampled sediment. Although the Wideroefjellet deposit shares similarities to the micrometeorite traps encountered in the Transantarctic Mountains, both subtle and more distinct differe...
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