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Isotope Study (isotope + study)

Distribution by Scientific Domains
Earth and Environmental Science77%

Kinds of Isotope Study

  • stable isotope study
    		•

    Selected Abstracts

    THE PIEDMONT WHITE MARBLES USED IN ANTIQUITY: AN ARCHAEOMETRIC DISTINCTION INFERRED BY A MINERO-PETROGRAPHIC AND C,O STABLE ISOTOPE STUDY*

    ARCHAEOMETRY, Issue 6 2009
    A. 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]

    Sulfur Isotope Study of Precambrian Basement and Mesozoic Intrusive Rocks in the Southwestern Part of Ryeongnam Massif, Korea

    RESOURCE GEOLOGY, Issue 1 2003
    Chung-Han Yoon
    Abstract. Isotope composition of whole rock sulfur has been measured on 14 schists, 10 gneisses, 7 gabbroids, 7 granitoids and 2 sedimentary rocks, with of 9 sulfide (pyrite) sulfurs in gabbros and granitoids, from the southwestern part of the Ryeongnam Massif, Korea. The ,34S values of schists range from -4.6 to +6.1 % (average +0.9 %), those of gneisses from -4.0 to +0.8 % (-1.9%), those of gabbroids from -2.3 to +3.7 % (+1.0 %), and those of granitoids from -5.9 to +3.2 % (-1.9 %). The ,34S values of pyrite separated from gabbros and granitoids show rather heavier values ranging from +3.1 to +9.4 % with an average of+5.8%. Though the ,34S values of whole rock sulfur give wide range of -5.9 to +6.1 %, the average of about -0.5 % is close to the mantle value. The granitoids sampled at the central parts of intrusive bodies or at the contacts with other plutonic rocks tend to show positive values, while those sampled near the boundary with basement rocks such as granitic gneiss and por-phyroblastic gneiss show negative values. Though the reason of this tendency is not clear at present, the ,34S values of some granitoids in this area seem to represent possible influence by the assimilation of country rocks, particularly of gneisses. Average isotopic compositions of ore sulfur from individual metal deposits in the studied area are summarized to have a range of+1.0 to +7.8 % with an average value of+3.2 %. The values are consistent with the previous finding that the ore sulfur isotopic values of the Ryeongnam Massif are the lowest among the four tectonic belts in Korea; Gyeonggi Massif, Ogcheon Belt, Ryeongnam Massif, and Gyeongsang Basin. This feature may reflect the isotopic compositions of plutonic rocks and basements in this area, which are characterized by relatively low values around zero permil. [source]

    Oxygen and Carbon Isotope Study of Calcite and Dolomite in the Disseminated Au-Ag Telluride Bulawan Deposit, Negros Island, Philippines

    RESOURCE GEOLOGY, Issue 2 2001
    Victor B. MAGLAMBAYAN
    Abstract: The disseminated Au-Ag telluride Bulawan deposit, Negros island, Philippines, is hosted by dacite porphyry breccia pipes which formed in a Middle Miocene dacite porphyry stock. Electrum and Au-Ag tellurides occur mostly as grains intergrown with or filling voids between sphalerite, pyrite, chalcopyrite, galena and tennantite. Calcite, quartz and rare dolomite are the principal gangue minerals. Four types of alteration were recognized in the deposit, namely; propylitic, K-feldspar-sericitic, sericitic and carbonate alteration. Carbonate alteration is correlatable to the gold deposition stage and occurs mostly along fault zones. The ,18O and ,13C compositions of calcite and dolomite in propylite zone and ore-stage dacite porphyry breccia were determined. The ,18O values of calcite in propylitized andesite range from +12.2 to +14.7%, and their ,13C values range from -6.1 to -1.0%. The ,18O values of calcite and dolomite in sericite- and carbonate-altered, mineralized dacite porphyry breccia and dacite porphyry rocks range from +15.1 to +23.1%, and the ,13C values of calcite and dolomite range from -3.9 to +0.9%. The ,18O and ,13C values of the hydrothermal fluids were estimated from inferred temperatures of formation on the basis of fluid inclusion microthermometry. The ,18O values of hydrothermal fluid for the propylitic alteration were calculated to be +8.5 - +9.5%, assuming 375°C. On the other hand, the ,18O values of ore solutions for base metal and Au mineralization were computed to be +13.6 - +14.6%, assuming 270°C. The hydrothermal fluids that formed the Bulawan deposit are dilute and 18O-enriched fluids which reacted with 18O- and 13C-rich wallrocks such as limestone. [source]

    Sulfur Isotope Study and Re-examination of Ore Mineral Assemblage of the Hol Kol and the Tul Mi Chung Skarn-type Copper,Gold Deposits of the Suan Mining District, Korean Peninsula

    RESOURCE GEOLOGY, Issue 4 2000
    Akira Imai
    Abstract: Ore specimens collected by the late Professor Takeo Watanabe from the Hol Kol and the Tul Mi Chung deposits, Suan mining district, Korean peninsula, were examined. In addition, measurements of sulfur isotopic ratio of ores and preliminary fluid inclusion microthermometry were carried out. Ores from the New orebody of the Hol Kol deposit consist mainly of bornite, wittichenite and chalcopyrite presently, which exhibit lamellae intergrowth texture, associated with native bismuth and electrum. Bismuthian bornite solid solution is considered to be a principal initial phases, while native bismuth was nucleated as molten bismuth melt initially. The occurrence of cubanite, miharaite, carrollite, siegenite, hessite and geikielite are recognized from the New orebody. Ores from the Eastern orebody of the Hol Kol deposit consist chiefly of chalcopyrite, occasionally associated with trace amounts of pyrrhotite, pyrite, bismuthinite and rare tellurobismuthite, while an ore specimen from the Western orebody consists mainly of sphalerite associated with chalcopyrite, pyrite and galena. Ores from the Tul Mi Chung deposit consist mainly of chalcopyrite and pyrite, occasionally associated with magnetite, sphalerite, galena and rare molybdenite. Some portions of magnetite are revealed to be silician magnetite. Sulfur fugacity is supposed to be below the stability field of bismuthinite in the New orebody. A reducing condition is suggested by the occurrence of geikielite without Fe3+ content. The sulfur and oxygen fugacities for the Eastern and Western orebodies of the Hol Kol deposit and for the Tul Mi Chung deposit were higher than the New orebody of the Hol Kol deposit. On the other hand, the Suan granite (porphyritic granodiorite) and the Chil Sing Dai granite (biotite granite porphyry) from the Hol Kol area can be classified as weakly magnetic magnetite-series. Polyphase fluid inclusions are observed in gangue diopside associated with Cu ore of two specimens. The dissolution temperatures of daughter crystals are 394±26°C and 442±45°C, while the disappearing temperatures of vapor bubble were 475±25°C and > 500°C. Highly saline fluids were responsible for the mineralization at the Hol Kol deposit. The ,34S values of ore sulfides of the Hol Kol and the Tul Mi Chung deposit range from +11. 5% to +16. 1%, having anomalous lower values mainly from the Tul Mi Chung deposit. Such anomalous lower 634S values can be caused by isotopic fractionation against oxidized sulfur species. The ,34S value of bulk sulfur in the ore solutions responsible for the Hol Kol and the Tul Mi Chung deposit is estimated to be +13.5±2.5,. [source]

    Stable Isotope Study of the Langshan Polymetallic Mineral District, Inner Mongolia, China

    RESOURCE GEOLOGY, Issue 1 2000
    Ping 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 study

    DIABETES OBESITY & METABOLISM, Issue 1 2007
    F. 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, Germany

    GEOFLUIDS (ELECTRONIC), Issue 2 2007
    B. 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]

    Isotopic alteration of mammalian tooth enamel

    INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 1-2 2003
    M. J. Schoeninger
    Abstract Mammalian tooth enamel carbonates from a Pliocene site at Allia Bay in northern Kenya show variable carbon and oxygen isotopic alteration. Sample screening by cathodoluminescence, prior to isotopic analysis, identified areas of extensive chemical alteration and others that were minimally altered. The luminescent patterns were used to guide sampling for the isotope study. Carbon stable isotope ratios of the apatite carbonate from luminescent enamel exteriors differ from the ratios in the enamel interiors and the magnitude of difference varies widely. The interior of the enamel usually retains the carbon isotope ratios expected based on faunal identification, but in a minority of cases, all of the enamel appears to be altered isotopically. Among fauna with an apparent mixed feeding signal, it is particularly difficult to determine whether the ,13C value is due to an actual mixed feeding strategy during life or to alteration toward sediment values. Palaeoecological reconstructions based on the ,13C values of enamel carbonate in browsing fauna would be affected, in many cases, since differences of 1, are significant for such reconstructions. Even so, careful selection of unaltered enamel sections should avoid this problem. Palaeodiet reconstruction would be less affected except in those cases where the alteration approaches 5,. In such cases, a mixed feeding strategy would be the erroneous interpretation of the data. Oxygen isotope ratios in the enamel carbonates show no pattern and the retention of biogenic values is unlikely. For this reason, palaeotemperature reconstructions, based on the ,18O values of the enamel carbonate, would not be possible at this site. Copyright © 2003 John Wiley & Sons, Ltd. [source]