نتایج جستجو برای: stable isotope geochemistry
تعداد نتایج: 287576 فیلتر نتایج به سال:
The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abu...
We use the mineralogy, trace element compositions and elemental mass balance of volcanic materials collected from propylitic, potassic phyllic alteration facies in Eshtehard area Iran to document nature effects hydrothermal alteration. Incompatible abundances hydrothermally–altered samples show transformations that include: (i) depletion alkalis alkaline earth elements (i.e., Ba, Sr), (ii) vari...
a r t i c l e i n f o Keywords: Secondary ion mass spectrometer Isotope ratios Oxygen High precision Instrumental bias We have developed highly precise and accurate in situ SIMS stable isotope analytical protocols using the IMS-1280 at the University of Wisconsin, through careful tuning of the instrument, stable electronics, and improved protocols for sample preparation, standardization and aut...
Planktonic foraminifera record oceanic conditions in their shell geochemistry. Many palaeoenvironmental studies have used fossil planktonic foraminifera to constrain past seawater properties by defining species based on their shell morphology. Recent genetic studies, however, have identified ecologically distinct genotypes within traditionally recognized morphospecies, signaling potential reper...
The O/O and C/C ratios of carbonate minerals formed by supergene oxidation of Zn–Pb deposits and submarine alteration of ancient slags were studied in order to constrain isotope fractionation factors for smithsonite, cerussite, and phosgenite, and to characterize conditions of nonsulfide ore formation. We present new isotope data of carbonate-hosted ores from the Iglesiente district (Sardinia, ...
The Pb-Zn-Cu deposit of Ulldemolins occurs within the Carboniferous sedimentary series of the southernmost Catalonian Coastal Ranges. It consists of sulphide-bearing calc-silicate assemblages, with epidote, Ca-amphiboles and Ca-garnet, which develop selectively along a dolomicrite bed near the contact with a granite porphyry. Two mineralisation styles can be differentiated: a) banded and b) irr...
Vertebrate fossils and continental sediments provide a rich record of variations in the isotopic composition of surface environments. To interpret these records, a greater understanding of isotopic sources, as well as fractionations associated with animal physiology, soil geochemistry, and diagenesis, has been essential. Tooth enamel and fish otoliths yield subannual records of surface environm...
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