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" Isotopic and trace elemental analyses, and description of authigenic quartz for Pleistocene dolomites, Al Jubayl, Saudi Arabia "
J. Zhang
H. S. Chafetz
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Latin Dissertation
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English
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| Record Number
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1113523
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TLpq304346741
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| Main Entry
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H. S. Chafetz
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J. Zhang
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| Title & Author
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Isotopic and trace elemental analyses, and description of authigenic quartz for Pleistocene dolomites, Al Jubayl, Saudi Arabia\ J. ZhangH. S. Chafetz
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| College
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University of Houston
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| Date
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1997
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| student score
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1997
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| Degree
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M.Sc.
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| Page No
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247
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| Abstract
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The usd\rm\delta\spCusd values of all the samples in Pleistocene dolomite diagenetic facies in a carbonate suite from approximately forty borings, offshore Al Jubayl, Saudi Arabia, range from usd{-}4.77\perthoususd to 5.34usd\perthoususd PDB, and the usd\rm\delta\spOusd values range from usd{-}4.26\perthoususd to 5.02usd\perthoususd PDB. The usd\rm\delta\spCusd and usd\rm\delta\spOusd values are consistent with the interpretation that freshwater diagenesis lowered them. The wide ranges in both usd\rm\delta\spCusd and usd\rm\delta\spOusd values of all dolomite samples indicate that the water/rock ratio varied appreciably. The disintegration of algal mats within the soil zone during the freshwater diagenesis most likely contributed large amounts of C to the groundwater, which produced the large negative usd\rm\delta\spCusd excursions with relatively small amounts of freshwater. The CaCO3 molar percentages of the dolomite samples are quite uniform around 50.8%. The CaCO3 molar percentage is independent of the usd\rm\delta\spCusd values in the borings. There is no linear negative correlation between usd\rm\delta\spCusd values and Fe/(Ca+Mg), Mn/(Ca+Mg), or Zn/(Ca+Mg) molar ratios. Samples of high Fe/(Ca+Mg), Mn/(Ca+Mg), and Zn(Ca+Mg) molar ratios occur, exclusively in the horizons with low usd\delta\spusdC values. Examination of four of the borings revealed that authigenic quartz crystals occur in many samples, in the forms of overgrowths on detrital cores, single euhedral crystals, and fan-shaped crystal clusters. The crystal habits range from doubly terminated crystals to crystals with only a few good crystal faces and edges. Rhombohedron-shaped crystal molds on the surface and extending into the interior of quartz crystals were observed. Their occurrence showed no correlation with the horizons of most intensive freshwater diagenesis. (Abstract shortened by UMI.)
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Earth sciences
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Geochemistry
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Geochemistry
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Geology
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Geology
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Paleontology
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