Mechanism of burial metamorphism of argillaceous sediments: 3. O-isotope evidence

Abstract

Research Article| September 01, 1977 Mechanism of burial metamorphism of argillaceous sediments: 3. O-isotope evidence HSUEH-WEN YEH; HSUEH-WEN YEH 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar SAMUEL M. SAVIN SAMUEL M. SAVIN 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Search for other works by this author on: GSW Google Scholar Author and Article Information HSUEH-WEN YEH 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 SAMUEL M. SAVIN 1Department of Earth Sciences, Case Western Reserve University, Cleveland, Ohio 44106 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (9): 1321–1330. https://doi.org/10.1130/0016-7606(1977)88<1321:MOBMOA>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation HSUEH-WEN YEH, SAMUEL M. SAVIN; Mechanism of burial metamorphism of argillaceous sediments: 3. O-isotope evidence. GSA Bulletin 1977;; 88 (9): 1321–1330. doi: https://doi.org/10.1130/0016-7606(1977)88<1321:MOBMOA>2.0.CO;2 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 SocietyGSA Bulletin Search Advanced Search Abstract O-isotope analysis of shales sampled from wells drilled through sedimentary deposits in the Gulf of Mexico region indicates that the sediments and rocks are not isotopically equilibrated systems — even those that have been buried to depths where temperatures are as high as 170 °C. In comparison with the coarser fractions, the finer fractions of both clay minerals and quartz are almost always richer in O18. O-isotope disequilibrium among the clay fractions becomes less marked as burial temperature increases. O-isotope exchange between clay and pore water become more extensive at higher temperatures; this corresponds to more extensive diagenetic alteration of mixed-layer illite-smectite. There is no evidence for O-isotope exchange between detrital quartz and pore water. However, quartz that forms diagenetically as an accompaniment to the conversion of smectite to illite layers in the mixed-layer clay forms in equilibrium with the pore water.The usefulness of O-isotope geothermometry for determination of the maximum temperatures to which shales have been heated during burial was investigated. Temperatures were calculated from the O-isotope fractionations between coexisting fine-grained quartz and clay from three wells; these calculated temperatures progressively approached the measured well (logged) temperatures as depth of burial and temperature increased. In one well, good agreement between calculated and measured temperatures was obtained for measured temperatures between 100 and 180 °C. In two other wells, satisfactory agreement was approached but not obtained at measured temperatures as high as 120 °C. Temperatures calculated from the O-isotope fractionations of quartz and calcite or calcite and clay were not reasonable. This probably reflects isotope exchange between calcite and pore water after the silicates attained their measured isotope ratios. Consequently, calcite is not a suitable mineral for use in isotope geothermometry of diagenetically altered shales. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.