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Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction
The δ¹⁸O values of coexisting silicate minerals in rocks comprising the tholeiitic olivine gabbro - quartz monzodiorite suite, are consistent with the attainment of isotope equilibrium and largely closed system conditions. The majority of the temperatures calculated by conventional mineral-pair ther...
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| Format: | Thesis |
| Language: | English |
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Department of Geological Sciences
2016
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| _version_ | 1867613323511463936 |
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| access_status_str | Open Access |
| author | Martinez, Iúma Aparecida |
| author_browse | Martinez, Iúma Aparecida |
| author_facet | Martinez, Iúma Aparecida |
| author_sort | Martinez, Iúma Aparecida |
| collection | Thesis |
| description | The δ¹⁸O values of coexisting silicate minerals in rocks comprising the tholeiitic olivine gabbro - quartz monzodiorite suite, are consistent with the attainment of isotope equilibrium and largely closed system conditions. The majority of the temperatures calculated by conventional mineral-pair thermometers are spurious, as a result of oxygen isotope diffusion during slow cooling. Closure temperatures for oxygen diffusion of 560ᵒC and 540ᵒC have been calculated for the anorthite-clinopyroxene and plagioclase-biotite mineral-pairs in the tholeiitic leucogabbro sample, respectively. The oxygen isotope data for the silicate minerals are consistent with contamination of the magmas by material having the oxygen isotope composition of the southern Etendeka rhyolite (δ¹⁸O = + 11.5‰). It is suggested that the assimilant may have been derived from the same source as the southern Etendeka rhyolite, as opposed to the rhyolite itself, which would be expected to occur at a high crustal level. Simple oxygen and strontium isotope mass balance calculations are used to constrain the lower (14 % and 19.5 % respectively) and upper (57 % and 71.6 % respectively) limits of the maximum possible amount of a southern Etendeka rhyolite contaminant assimilated. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/21694 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:17.944Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Geological Sciences |
| publisherStr | Department of Geological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/21694 Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction Martinez, Iúma Aparecida Geological Sciences Geochemistry The δ¹⁸O values of coexisting silicate minerals in rocks comprising the tholeiitic olivine gabbro - quartz monzodiorite suite, are consistent with the attainment of isotope equilibrium and largely closed system conditions. The majority of the temperatures calculated by conventional mineral-pair thermometers are spurious, as a result of oxygen isotope diffusion during slow cooling. Closure temperatures for oxygen diffusion of 560ᵒC and 540ᵒC have been calculated for the anorthite-clinopyroxene and plagioclase-biotite mineral-pairs in the tholeiitic leucogabbro sample, respectively. The oxygen isotope data for the silicate minerals are consistent with contamination of the magmas by material having the oxygen isotope composition of the southern Etendeka rhyolite (δ¹⁸O = + 11.5‰). It is suggested that the assimilant may have been derived from the same source as the southern Etendeka rhyolite, as opposed to the rhyolite itself, which would be expected to occur at a high crustal level. Simple oxygen and strontium isotope mass balance calculations are used to constrain the lower (14 % and 19.5 % respectively) and upper (57 % and 71.6 % respectively) limits of the maximum possible amount of a southern Etendeka rhyolite contaminant assimilated. 2016-09-06T14:44:02Z 2016-09-06T14:44:02Z 1995 Master Thesis Masters MSc http://hdl.handle.net/11427/21694 eng application/pdf Department of Geological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Geological Sciences Geochemistry Martinez, Iúma Aparecida Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| thesis_degree_str | Master's |
| title | Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| title_full | Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| title_fullStr | Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| title_full_unstemmed | Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| title_short | Stable isotope geochemistry of the Okenyenya igneous complex, Namibia : constraints on contamination and fluid interaction |
| title_sort | stable isotope geochemistry of the okenyenya igneous complex namibia constraints on contamination and fluid interaction |
| topic | Geological Sciences Geochemistry |
| url | http://hdl.handle.net/11427/21694 |
| work_keys_str_mv | AT martineziumaaparecida stableisotopegeochemistryoftheokenyenyaigneouscomplexnamibiaconstraintsoncontaminationandfluidinteraction |