Carbon and oxygen isotope evolution in the Magnet Cove Complex, Arkansas

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dc.contributor.advisorBaker, Donald R.en_US
dc.creatorJohnson, Michael Leeen_US
dc.date.accessioned2018-12-18T21:16:08Zen_US
dc.date.available2018-12-18T21:16:08Zen_US
dc.date.issued1975en_US
dc.description.abstractThe Magnet Cove Complex is a highly differentiated ring dike sequence of alkaline igneous rocks and carbonatite. Analyses of silicate rocks show increasing -values (vs. SMOW) from early to late differentiates: trachyte (+8.6%;), phonolite (+7.9%), nepheline syenites (+8.8 to +9.7%) , jacupriangite (+9.4%), melteigite (+11.%) , ijolite (+11.1%) and late dikes (+12.6 to +13.8%). 6-values of calcites from silicate rocks display a similar trend. Carbonatite, a supposed late-stage differentiate, has a 6 -value of +8.6%. Unexpectedly, this value corresponds with the -values shown by early silicate rocks and associated calcite. OC -values of calcites from the silicate rocks show a decrease with differentiation ranging from -4.8 to -6.7% vs. PDB. Similarly the OC -value of the carbonatite, -5.4, coincides with early rather than late differentiates. Early crystallization and removal of A-enriched mafic minerals shifts the late residuals to higher 6 -values. The 6C -trend is explained by loss of isotopically heavy CO during differentiation. The discrepancy between 6 and 6C values of the late stage silicate rocks and the carbonatite may result from early separation of an immiscible carbonate liquid. The narrow range of 6C values displayed by the complex indicates that the carbonatite carbon source (mantle C?) was uniform in isotopic composition and isotopically similar to supposed sources of carbonatites world wide.en_US
dc.format.digitalOriginreformatted digitalen_US
dc.format.extent85 ppen_US
dc.identifier.callnoThesis Geol. 1975 Johnsonen_US
dc.identifier.citationJohnson, Michael Lee. "Carbon and oxygen isotope evolution in the Magnet Cove Complex, Arkansas." (1975) Master’s Thesis, Rice University. <a href="https://hdl.handle.net/1911/104007">https://hdl.handle.net/1911/104007</a>.en_US
dc.identifier.digitalRICE1633en_US
dc.identifier.urihttps://hdl.handle.net/1911/104007en_US
dc.language.isoengen_US
dc.rightsCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.en_US
dc.titleCarbon and oxygen isotope evolution in the Magnet Cove Complex, Arkansasen_US
dc.typeThesisen_US
dc.type.materialTexten_US
thesis.degree.departmentEarth Scienceen_US
thesis.degree.disciplineNatural Sciencesen_US
thesis.degree.grantorRice Universityen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Artsen_US
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