Research Article| April 01, 2013 Anticorrelation between low δ13C of eclogitic diamonds and high δ18O of their coesite and garnet inclusions requires a subduction origin Daniel J. Schulze; Daniel J. Schulze 1Department of Earth Sciences, University of Toronto, Mississauga, Ontario L5L 1C6, Canada Search for other works by this author on: GSW Google Scholar Ben Harte; Ben Harte 2Centre for Science at Extreme Conditions, School of GeoSciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3JW, Scotland, UK Search for other works by this author on: GSW Google Scholar Edinburgh Ion Microprobe Facility staff; Edinburgh Ion Microprobe Facility staff Search for other works by this author on: GSW Google Scholar F. Zeb Page; F. Zeb Page 4Wisconsin Secondary Ion Mass Spectrometer Laboratory, Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, USA5Department of Geology, Oberlin College, Oberlin, Ohio 44074, USA Search for other works by this author on: GSW Google Scholar John W. Valley; John W. Valley 4Wisconsin Secondary Ion Mass Spectrometer Laboratory, Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, USA Search for other works by this author on: GSW Google Scholar Dominic M. DeR. Channer; Dominic M. DeR. Channer 6Guaniamo Mining Company, Centro Gerencial Mohedano, 9D Urbanización La Castellana, Caracas, Venezuela *Current address: Kinross Gold Corporation, Edificio Eurocenter, Piso 5, Avenida Amazonas N37-29 y UNP, Quito, Ecuador. Search for other works by this author on: GSW Google Scholar A. Lynton Jaques A. Lynton Jaques 7Geoscience Australia, Canberra, ACT 2601, Australia †Current address: The Australian National University, Canberra, ACT 0200, Australia. Search for other works by this author on: GSW Google Scholar Geology (2013) 41 (4): 455–458. https://doi.org/10.1130/G33839.1 Article history received: 08 Jul 2012 rev-recd: 25 Oct 2012 accepted: 28 Oct 2012 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Daniel J. Schulze, Ben Harte, Edinburgh Ion Microprobe Facility staff, F. Zeb Page, John W. Valley, Dominic M. DeR. Channer, A. Lynton Jaques; Anticorrelation between low δ13C of eclogitic diamonds and high δ18O of their coesite and garnet inclusions requires a subduction origin. Geology 2013;; 41 (4): 455–458. doi: https://doi.org/10.1130/G33839.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Diamond is essentially impermeable and unreactive under many conditions, and tiny mineral inclusions within natural diamonds can faithfully preserve information on the chemical and physical conditions during diamond growth. The stable isotope ratios of carbon, nitrogen, oxygen, and sulfur in diamonds and their mineral inclusions have been used to constrain models of diamond formation, but interpretations of the data have differed dramatically. The crux of the controversy lies in the interpretation of the carbon isotope ratios of eclogite-suite diamonds, which range well outside those expected for typical mantle materials such as peridotites, basalts, and carbonatites. Proposed explanations for these anomalous carbon isotope ratios include derivation from primordial mantle inhomogeneities, fractionated mantle fluids, and subducted biogenic carbon. Working with samples from three continents, we have analyzed the carbon isotope compositions of eclogite-suite diamonds and the oxygen isotope composition of their mineral inclusions, primarily by ion microprobe methods. We have discovered a previously unrecognized, remarkably consistent anticorrelation between these two isotopic systems, in that virtually all diamonds with anomalously low carbon isotope ratios have silicate inclusions with anomalously high oxygen isotope ratios. This is a fundamental observation that can only be explained by formation of eclogite-suite diamonds through subduction of seafloor altered basalt, admixed with marine biogenic carbon, into the field of diamond stability. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Ion microprobe analysis with a sub-micrometer diameter spot reveals a sharp, 2 μm gradient in oxygen isotope ratio proving that oxygen diffusion in zircon is slow even under prolonged high-grade metamorphism. The data are consistent with an oxygen diffusion coefficient of 10-23.5±1 cm2/s. Furthermore, this gradient is found in a zircon that contains clear textural evidence of recrystallization in nearby regions. This finding shows that through careful textural and chemical analysis, primary information can be extracted from a zircon that has also undergone partial recrystallization. The oxygen isotope ratios found in zircon have been used to infer magmatic and pre-magmatic histories, including the presence of liquid water on the surface of earliest Earth. Recently, these interpretations have been questioned with the assertion that zircon may not retain its primary oxygen isotope signature through metamorphism. The slow diffusion confirmed by these results supports interpretations that assume preservation of magmatic compositions.
Cemented, fragic and intergrade-cemented horizons of five soil series of Quebec were studied using submicroscopic, micromorphological and chemical processes. The quantities of bonding agents present in the bonding material were expressed as a relative percentage. These bonding agents consist of organic matters, Fe, Al and Si hydroxides assumed to be present as FeO(OH), AlO(OH) and SiO(OH) 2 , and clays (< 2 μm). The Fe, Al and Si hydroxides were extracted by dithionite-citrate-bicarbonate, ammonium oxalate and NaOH, respectively. The clays were obtained by sedimentation after treating soils with dithionite and H 2 O 2 . The sub-microstructure of the bonding material varied with the horizons as indicated by the relative percentages of bonding agents. In the Bhc ortstein horizon, the coatings consist of discrete four-sided polyhedric units, these in turn are subdivided into spheroids of 0.2- to -1 μm diameter and contain 68% organic bonding agents, 20% hydroxide bonding agents and 12% particulate bonding agents (clays < 2 μm). In the Bhfc ortstein horizon, the grain coatings are subdivided into partly joined polyhedric units having a smooth or fluffy surface, these coatings contain 39% organic bonding agents, 32% hydroxide-bonding agents and 29% particulate-bonding agents. In the Bfc ortstein horizon, the grain coatings are continuous and appear as a smooth surface covered by many microplanes. These coatings contain 21% organic matter, 33% hydroxide-bonding agents and 46% particulate-bonding agents. In the BCcgj duric horizon, the grain coatings are also continuous with a smooth surface but crossed by few microplanes. These coatings contain 2% organic bonding agents, 36% hydroxide-bonding agents and 62% particulate-bonding agents. In the BCcjgj and BCcj intergrade-cemented horizons, the bonding material consists of various ultramicrostructures and concentration of bonding agents. In the Btjx fragic horizon, the particulate bonding agents are largely dominant (92%) and form an ultramicrostructure having simple packing. Microanalysis of bonding materials found in cemented and cemented-intergrade horizons confirmed earlier proportion reported for these coatings. It appears that coating strength is a result of the interaction between the bonding agents present. On the other hand, the brittleness of humid fragic horizons is probably caused by stress forces generated by the packing of soil mineral grains. Two principal factors have been described as responsible for this packing. The attractive clay (< 2 μm) forces on larger soil grains during soil dessications and the compaction of soil grains by glaciers during the Ice age. Key words: Binders, ultramicroscopy, Ortstein, Duric and Fragic A horizons
