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Impact Of Calcium Carbonate Reactant Size And Mineralogy On Dolomite Stoichiometry, Katharine G. Rose

Masters Theses

Dolomite is a common, diagenetic, Mg-Ca carbonate mineral. Dolomitization occurs by a dissolution-precipitation reaction between a CaCO₃ precursor (calcite or aragonite) and Mg bearing fluids. The amount of Mg in dolomite, referred to as dolomite stoichiometry (mol% MgCO₃), varies in natural dolomites (38-50 mol% MgCO₃). Laboratory experiments have shown that dolomite stoichiometry is dependent on physiochemical factors of the diagenetic fluids (i.e., temperature, salinity, and Mg/Ca). The impact of the CaCO₃ precursor on stoichiometry, however, has not been studied directly. This study tests how the CaCO₃ precursor size (sieve size) and mineralogy (calcite …

Evaluating The Effects Of Sodium, Potassium, Magnesium, And Calcium Concentrations On Dolomite Stoichiometry, Cation Ordering, And Reaction Rate, Hanna F. Cohen

Masters Theses

Numerous environmental factors affect dolomitization. Shallow peritidal and restricted marine environments, for example, are often associated with more abundant and more stoichiometric dolomite than deeper marine environments. Higher fluid Mg/Ca ratios resulting from gypsum precipitation are often invoked to explain this observation, even when evidence of evaporites is absent. In this study, high-temperature dolomitization experiments show that the concentrations of major cation concentrations (Na, K, Mg, and Ca) impact dolomite stoichiometry and reaction rate. Nearly 200 batch dolomitization experiments were run whereby 100 mg of natural aragonite ooids were dolomitized at 215°C in ionic solutions. Fluid [NaCl] and [KCl] correlate …

Anomalous Thermal Indicators From Authigenic Minerals In Upper Paleozoic Strata Of The Michigan Basin, Kyle Cox

Masters Theses

Indications of anomalous paleo-temperatures exist in strata of the Michigan basin, USA. The thermal history of the basin was investigated through identification and analysis of authigenic components in two Upper Paleozoic strata, the Devonian Dundee Formation and Mississippian Marshall Sandstone. Formation conditions for diagenetic phases in both units were estimated through a variety of means and compared to conditions expected for a simple burial model. Authigenic clays identified in the Marshall via X-ray diffraction are expected to have formed at temperatures above what would have been produced by burial alone. Stable isotope and fluid inclusion analysis indicate the same for …

Analysis Of Depositional Facies And Geological Controls On Reservoir Quality In Lower-Middle Devonian Sylvania Sandstone, Midland County, Michigan, Katherine A. Pollard

Masters Theses

The early-Middle Devonian Sylvania “Sandstone” is considered a target for potential CO₂ geosequestration. In order to develop geostatic models for CO₂ injection simulations, controls on reservoir properties must be addressed. The three objectives of this study involve: 1) develop an overview of depositional lithofacies and their vertical stacking relationships, 2) determine fluid sources and controls of diagenesis (dolomitization and silicification), and 3) examine geological controls on the distribution and character of reservoir facies.

The grossly transgressive Sylvania-Bois Blanc interval is a complex lithologic assemblage. Sylvania “Sandstone” strata transition from high energy, subtidal to lower-intertidal mixed carbonate-siliciclastic facies to …