Atmospheric ozone destruction and the end-Permian crisis: Evidence from multiple sulfur isotopes
2
Citation
79
Reference
10
Related Paper
Citation Trend
Keywords:
Mass-independent fractionation
Isotopic signature
Permian–Triassic extinction event
δ34S
The last ten years have seen big progress and wide applications of a novel field,non-traditional stable isotope(NTSI)geochemistry,to high temperature geo-science studies.Invention of multi-collector-inductively coupled plasma-mass spectrometry(MC-ICP-MS)led to the big breakthrough of analytical methods for heavy stable isotopes.This contribution summarizes Li,Fe,and Mg isotope studies on igneous rocks and minerals,as representative of NTSI geochemistry.Li isotopes have been widely applied to the studies of mantle geochemistry,recycling of subducted materials,and metamorphism to constrain the source of magma and kinetic diffusion process.Fe isotope fractionation is related to partitioning of multi-valent Fe between Fe-bearing phases,which can occur in the course of mantle metasomatism,partial melting,and fractional crystallization.Mg isotopic compositions of igneous rocks most likely reflect the source signatures.Variation of Mg isotopic ratios of mantle peridotites is trivial and this provides a homogenous background for Mg isotope fractionation in low temperature processes.Furthermore,Cl,Si,Cu,Ca,and U isotopes are also promising in the future geochemical studies.Experimental studies and theoretical simulation for the mechanisms of isotope fractionation provide important guidances for understanding the NTIS data.Experimental studies show that light and heavy isotopes have different migration velocity at high temperature processes such as chemical diffusion,evaporation,and desublimation,which could produce significant kinetic isotope fractionation.Equilibrium isotopic fractionation could occur among mineral,melt,and fluid when chemical environment of the isotopes are different between the phases.Recent thermal diffusion and migration experiments on silicate material reveal a new mechanism of magma differentiation and isotope fractionation.Along a temperature gradient in silicate magma,large elemental variation and isotopic fractionation can occur,by which a wet andesite can even be differentiated to granite.This suggests that thermal migration could be important for continental crustal formation and evolution.If temperature gradient exists long enough during magma differentiation,thermal diffusion can produce significant stable isotope fractionation,which is contrast to the mechanism of traditional kinetic and equilibrium isotope fractionations.Such process can be fingerprinted by positive correlations among multi-stable isotopic systems.Due to thermal diffusion,concentration of material loaded or dissolved in the fluid is a function of Soret coefficient(ST).However,because ST is highly variable and sensitive to lots of factors,the basic physics of thermal diffusion is still poorly understood.As shown by Mg,Ca,and Fe isotope measurement of thermal diffusion experiments,isotope fractionation driven by temperature gradient is independent to the bulk composition and temperature of the system,suggesting that the difference of ST between two isotopes of the same element can be considered as a constant.This can simplify and help the studies on thermal diffusion and ST.
Equilibrium fractionation
Mass-independent fractionation
Isotope Geochemistry
Isotopic signature
Metasomatism
Cite
Citations (3)
Equilibrium fractionation
Methylmercury
Mass-independent fractionation
Mercury
Isotope Analysis
Biogeochemical Cycle
Cite
Citations (11)
Isotopes of chlorine
Isotopic signature
Mass-independent fractionation
Ashing
Isotope Analysis
Equilibrium fractionation
Thermal ionization
Cite
Citations (16)
Copper shows limited isotopic variation in equilibrated mantle-derived silicate rocks, but large isotopic fractionation during kinetic processes. For example, lunar and terrestrial samples that have experienced evaporation were found to have an isotopic fractionation of up to 12.5‰ in their 65Cu/63Cu ratios, while komatiites, lherzolites, mid-ocean ridge and ocean island basalts show negligible Cu isotope fractionation as a result of equilibrium partial melting and crystal fractionation. The contrast between the observed magnitudes of equilibrium and kinetic isotope fractionation for Cu calls for a better understanding of kinetic Cu isotope fractionation. One of the mechanisms for creating large kinetic isotopic fractionation even at magmatic temperatures is diffusion. In this study, we performed Cu isotopic measurements on Cu diffusion couple experiments to constrain the beta factor for Cu isotopic fractionation by diffusion. We demonstrate a Monte Carlo approach for the regression and error estimation of the measured isotope profiles, which yielded beta values of 0.16 ± 0.03 and 0.18 ± 0.03 for the two experimental charges measured. Our results are subsequently applied to a quantitative model for the evaporation of a molten sphere to discuss the role of diffusion in affecting the bulk Cu isotopic fractionation between liquid and vapor during evaporation. We apply the model to Cu evaporation experiments and tektite data to show that convection primarily governs mass transport for evaporation during tektite formation. In addition, we show that Cu isotopes can be used as a tool to test the role of kinetics during various magmatic processes such as magmatic sulfide ore deposit formation, porphyry-type ore deposit formation, and fluid-rock interactions.
Equilibrium fractionation
Mass-independent fractionation
Radiogenic nuclide
Cite
Citations (2)
Minerals and rocks exhibit various isotope compositions depending on their origins and histories. In interpreting their isotopic variations, the equilibrium isotope fractionation factor is a key because it depends on the environment parameters such as temperature. Recent studies have shown that the effect of pressure on the isotope fractionation, which was considered negligible compared to temperature, is significant under the conditions of the Earth's interior. In this article we review recent advances in experimental studies to determine the isotope fractionation of iron and hydrogen at high pressure over several GPa, discussing their issues and future perspectives.
Equilibrium fractionation
Mass-independent fractionation
Hydrogen isotope
Kinetic isotope effect
Isotope Geochemistry
Cite
Citations (0)
Permian–Triassic extinction event
δ34S
Sulfur Cycle
Cite
Citations (18)