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Oxygen Isotope Microanalysis By Secondary Ion Mass Spectrometry Suggests Continuous 300-million-year History of Calcite Cementation and Dolomitization in the Devonian Bakken Formation

2018; Society for Sedimentary Geology; Volume: 88; Issue: 1 Linguagem: Inglês

10.2110/jsr.2018.1

1938-3681

Mark William Brodie, Andrew C. Aplin, Bruce S. Hart, Ian J. Orland, John W. Valley, Adrian J. Boyce,

Radioactive element chemistry and processing

Research Article| January 23, 2018 Oxygen Isotope Microanalysis By Secondary Ion Mass Spectrometry Suggests Continuous 300-million-year History of Calcite Cementation and Dolomitization in the Devonian Bakken Formation Mark W. Brodie; Mark W. Brodie 1Department of Earth Sciences, Durham University, Durham DH1 3LE, U.K. Search for other works by this author on: GSW Google Scholar Andrew C. Aplin; Andrew C. Aplin 1Department of Earth Sciences, Durham University, Durham DH1 3LE, U.K. Search for other works by this author on: GSW Google Scholar Bruce Hart; Bruce Hart 2Statoil Gulf Services LLC, 6300 Bridge Point Parkway, Austin, Texas 78730, U.S.A. Search for other works by this author on: GSW Google Scholar Ian J. Orland; Ian J. Orland 3WiscSIMS, Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, U.S.A. Search for other works by this author on: GSW Google Scholar John W. Valley; John W. Valley 3WiscSIMS, Department of Geoscience, University of Wisconsin–Madison, Madison, Wisconsin 53706, U.S.A. Search for other works by this author on: GSW Google Scholar Adrian J. Boyce Adrian J. Boyce 4Scottish Universities Environmental Research Centre, Rankine Avenue, East Kilbride G75 0QF, U.K. Search for other works by this author on: GSW Google Scholar Journal of Sedimentary Research (2018) 88 (1): 91–104. https://doi.org/10.2110/jsr.2018.1 Article history first online: 23 Jan 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Mark W. Brodie, Andrew C. Aplin, Bruce Hart, Ian J. Orland, John W. Valley, Adrian J. Boyce; Oxygen Isotope Microanalysis By Secondary Ion Mass Spectrometry Suggests Continuous 300-million-year History of Calcite Cementation and Dolomitization in the Devonian Bakken Formation. Journal of Sedimentary Research 2018;; 88 (1): 91–104. doi: https://doi.org/10.2110/jsr.2018.1 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 SocietyJournal of Sedimentary Research Search Advanced Search Abstract Calcite cementation and dolomitization are key diagenetic processes in many sedimentary systems. Unravelling detailed histories and timescales of cementation and replacement is, however, often compromised by the limited spatial resolution of many analytical techniques; in some cases multiple grains are co-analyzed so that diagenetic histories are blurred and reaction periods are difficult to establish. In this study we have used 10-micrometer-resolution, in situ secondary ion mass spectrometry to determine the oxygen isotope composition of 197 individual, 10–50-micrometer-size crystals of dolomite and calcite from six samples in a single core of Upper Devonian middle Bakken Member siltstones and sandstones, the major tight oil formation of the Williston basin, USA. This amount of data places important constraints on the range of temperatures and times that carbonate cementation and replacement occurred. Petrographic data show that microcrystalline calcite cement is an early phase, and combined with mineralogical data suggest that much of the dolomite replaces calcite. Over spatial scales of less than a centimeter, analyses of individual calcite crystals have a range of 5‰ for δ18O in the group of crystals, and for the group of individual dolomite crystals, 10‰. These sub-centimeter ranges are as great as those observed in previous studies of carbonate cements sampled over many meters and remind us that previous low-resolution studies may have inadvertently analyzed mixed phases. There is no relationship between dolomite texture and isotopic composition at this spatial scale; microscale backscattered electron imagery and scanning electron microscopy cathodoluminescence zoning is seen, but cannot be resolved with a 10-micrometer spot size. Assuming, since it is an early cement, that calcite precipitated from seawater (δ18O = –1.5‰), it formed at ca. 15–40°C, mainly at the lower temperatures. Present-day formation waters in Devonian rocks in this region have oxygen isotope compositions of 7–8‰ VSMOW. Using these values as a likely dolomitizing fluid, we suggest that dolomitization occurred continuously between 40 and 140°C over 150–200 million years, most likely in a fluid with a high Mg/Ca ratio resulting from gypsum formation in local evaporites. We suggest that this exceptionally low rate of dolomitization was controlled by the low rate of supply of Mg in a very sluggish flow regime; dolomitization is incomplete because of a limited supply of Mg. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.