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Stable Isotope Study (stable + isotope_study)
Selected AbstractsTHE PIEDMONT WHITE MARBLES USED IN ANTIQUITY: AN ARCHAEOMETRIC DISTINCTION INFERRED BY A MINERO-PETROGRAPHIC AND C,O STABLE ISOTOPE STUDY*ARCHAEOMETRY, Issue 6 2009A. BORGHI The metamorphic rocks outcropping in the Western Alps are characterized by a great variety of white marbles, which have been poorly studied in the archaeometric field even though they have been used since antiquity. Typical examples are the Arc of August of Roman times in Susa (Piedmont, Italy) and lots of monuments and historical buildings of Turin (Italy). A multi-analytical approach based on petrographic (optical and scanning electron microscopy), electron microprobe and stable isotope analysis of Piedmont white marbles has been performed in order to carry out a detailed description, summarizing their main microtextural, mineralogical and isotopic features. Eight historical Piedmont marbles have been sampled from well-known quarry sites belonging to different metamorphic geological units of the Western Alps (Ornavasso, Crevola, Pont Canavese, Foresto, Chianocco, Prali, Brossasco and Garessio marbles). Their different metamorphic conditions, ages and structural evolution allowed us to draw a discriminative flowchart based on microscopic and minero-chemical data. [source] Stable Isotope Study of the Langshan Polymetallic Mineral District, Inner Mongolia, ChinaRESOURCE GEOLOGY, Issue 1 2000Ping DING The lead isotope study shows that these deposits were probably formed from 2. 0 to 1. 5 Ga, and were deformed and metamorphosed 1. 45 Ga. Ore lead could be a mixture of mantle lead and crustal lead. The C and S isotope results indicate that these deposits were precipitated in closed or semi-closed rift basins, and the source of sulfur might be Proterozoic ocean sulfate. The H and O isotope results indicate that the ,D and ,18O values of rocks were changed by water-rock interaction during metamorphism and hydrothermal alteration. The scale of ,D and ,18O shift of rocks reflects the grade of metamorphism and alteration as well as the water-rock ratios. However, the water-rock ratios in the metamorphic processes of Langshan mineral district were relatively low, and the source of water during metamorphism is suggested to be ancient meteoric water. Based on isotopic results and the geological background, it is concluded that these deposits may belong to Proterozoic sedimentary exhalative (SEDEX) type. [source] Metabolism of high density lipoprotein apolipoprotein A-I and cholesteryl ester in insulin resistant dog: a stable isotope studyDIABETES OBESITY & METABOLISM, Issue 1 2007F. Briand Aims:, In reverse cholesterol transport (RCT), hepatic Scavenger Receptor class B type I (SR-BI) plays an important role by mediating the selective uptake of high-density lipoprotein cholesteryl ester (HDL-CE). However, little is known about this antiatherogenic mechanism in insulin resistance. HDL-CE selective uptake represents the main process for HDL-CE turnover in dog, a species lacking cholesteryl ester transfer protein activity. We therefore investigate the effects of diet induced insulin resistance on RCT. Methods:, Five beagle dogs, in healthy and insulin resistant states, underwent a primed constant infusion of [1,213C2]acetate and [5,5,5- 2H3]leucine, as labelled precursors of CE and apolipoprotein (apo) A-I, respectively. Data were analysed using modelling methods. Results:, HDL-apo A-I concentration did not change in insulin resistant state but apo A-I absolute production rate (APR) and fractional catabolic rate (FCR) were both higher (2.2- and 2.4-fold, respectively, p < 0.05). HDL-CE levels were lower (1.2-fold, p < 0.05). HDL-CE APR and FCR were both lower (2.3- and 2-fold, respectively, p < 0.05), as well as selective uptake (2.6-fold, p < 0.05). Conclusions:, Lower HDL-CE selective uptake suggests that RCT is impaired in obese insulin resistant dog. [source] Contrasting paleofluid systems in the continental basement: a fluid inclusion and stable isotope study of hydrothermal vein mineralization, Schwarzwald district, GermanyGEOFLUIDS (ELECTRONIC), Issue 2 2007B. BAATARTSOGT Abstract An integrated fluid inclusion and stable isotope study was carried out on hydrothermal veins (Sb-bearing quartz veins, metal-bearing fluorite,barite,quartz veins) from the Schwarzwald district, Germany. A total number of 106 Variscan (quartz veins related to Variscan orogenic processes) and post-Variscan deposits were studied by microthermometry, Raman spectroscopy, and stable isotope analysis. The fluid inclusions in Variscan quartz veins are of the H2O,NaCl,(KCl) type, have low salinities (0,10 wt.% eqv. NaCl) and high Th values (150,350°C). Oxygen isotope data for quartz range from +2.8, to +12.2, and calculated ,18OH2O values of the fluid are between ,12.5, and +4.4,. The ,D values of water extracted from fluid inclusions vary between ,49, and +4,. The geological framework, fluid inclusion and stable isotope characteristics of the Variscan veins suggest an origin from regional metamorphic devolatilization processes. By contrast, the fluid inclusions in post-Variscan fluorite, calcite, barite, quartz, and sphalerite belong to the H2O,NaCl,CaCl2 type, have high salinities (22,25 wt.% eqv. NaCl) and lower Th values of 90,200°C. A low-salinity fluid (0,15 wt.% eqv. NaCl) was observed in late-stage fluorite, calcite, and quartz, which was trapped at similar temperatures. The ,18O values of quartz range between +11.1, and +20.9,, which translates into calculated ,18OH2O values between ,11.0, and +4.4,. This range is consistent with ,18OH2O values of fluid inclusion water extracted from fluorite (,11.6, to +1.1,). The ,D values of directly measured fluid inclusion water range between ,29, and ,1,, ,26, and ,15,, and ,63, and +9, for fluorite, quartz, and calcite, respectively. Calculations using the fluid inclusion and isotope data point to formation of the fluorite,barite,quartz veins under near-hydrostatic conditions. The ,18OH2O and ,D data, particularly the observed wide range in ,D, indicate that the mineralization formed through large-scale mixing of a basement-derived saline NaCl,CaCl2 brine with meteoric water. Our comprehensive study provides evidence for two fundamentally different fluid systems in the crystalline basement. The Variscan fluid regime is dominated by fluids generated through metamorphic devolatilization and fluid expulsion driven by compressional nappe tectonics. The onset of post-Variscan extensional tectonics resulted in replacement of the orogenic fluid regime by fluids which have distinct compositional characteristics and are related to a change in the principal fluid sources and the general fluid flow patterns. This younger system shows remarkably persistent geochemical and isotopic features over a prolonged period of more than 100 Ma. [source] | ||||||||||