Chemistry and chronology of magmatic processes, Central Kenya Peralkaline province, East African Rift
Abstract
We report here a synthesis of the geochemistry of magma evolution correlated with 40Ar/39Ar, 14 C, and U-series chronology for volcanoes in the Central Kenya Peralkaline Province (CKPP). The volcanic centers - Menengai, Eburru, Olkaria, Longonot, and Suswa - are at the apex of the Kenya Dome, and consist of trachyte, phonolite, comendite, and pantellerite. These volcanic centers are within the graben of the EARS and are characterized by a shield-building phase followed by caldera collapse and subsequent post-caldera eruptions. Geochemical modeling demonstrates that the magmas are the result of fractional crystallization of alkali basaltic magmas and magma mixing. Longonot and Suswa have the most chronologic data -14 C, Ar/Ar and U-series - and they show that the youngest eruptions have 230 Th/232Th of 0.8, which was inherited from the magma system prior to eruption. Subsequent changes in 230 Th/232 Th are due to post-eruptive decay of 230 Th and correlate well with 14 C and Ar/Ar.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2014
- Bibcode:
- 2014AGUFM.V51A4731A
- Keywords:
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- 1065 Major and trace element geochemistry;
- GEOCHEMISTRY;
- 1115 Radioisotope geochronology;
- GEOCHRONOLOGY;
- 3651 Thermobarometry;
- MINERALOGY AND PETROLOGY;
- 8413 Subduction zone processes;
- VOLCANOLOGY