HR: 1340h
AN: V33A-1160    [Abstracts]
TI: Towards an Improved Eruptive History for Mauritius
AU: * Moore, J C
EM: jcm86@cornell.edu
AF: Cornell University, Department of Earth and Atmospheric Sciences, Ithaca, NY 14853, United States
AU: White, W M
EM: wmw4@cornell.edu
AF: Cornell University, Department of Earth and Atmospheric Sciences, Ithaca, NY 14853, United States
AU: Paul, D
EM: debajyoti.paul@utsa.edu
AF: University of Texas San Antonio, Department of Earth and Environmental Science, San Antonio, TX 78249, United States
AB: The volcanic island of Mauritius (20°20' S, 57°30' E) is located in the western Indian Ocean, and is understood to be the product of the Réunion mantle plume. Mauritius has a well-established history of episodic volcanism and erosional hiatus, traditionally characterized as three chemically and temporally distinct eruptive phases: 1) the voluminous shield-building lavas of the Older Series (7.8 to 5.5 Ma), 2) the Intermediate Series (3.5 to 1.9 Ma), and 3) the Younger Series (1.00 to 0.00 Ma; Duncan, unpublished data). The Older Series is exposed in remnants of the old shield volcano and is hence analogous to the Hawaiian shield-building phase. Lavas of the Intermediate and Younger Series cover 90% or more of the surface of the island, but are thought to be volumetrically minor. The Intermediate and Younger Series are enriched in incompatible elements, and but have more depleted isotopic signatures than the Older Series and in this and other ways are analogous to Hawaiian post-erosional volcanism. Recent collaboration with the Mauritian Water Resources Unit has permitted the study of a series of newly available drill cores. Dense sampling of a 220-meter core section (#89, Beau Bois, 20°12'25.9'' S, 57°33'50.8'' E) has revealed the presence of nine flow sequences, separated by highly weathered and altered basalt and lateritic soils varying in thickness up to 20 meters. The drill site is located on Intermediate Series lavas, approximately one kilometer inside the topographic rim of the large central caldera complex. Isotopic analysis shows relatively uniform ⁸⁷Sr/⁸⁶Sr (0.70377 ± 0.00018) and \varepsilonNd (+5.1 ± 0.3) throughout the upper 180 meters of the core. These compositions match those previously reported for the rejuvenescent Intermediate and Younger Series. The deepest sample has more enriched ⁸⁷Sr/⁸⁶Sr (0.70422) and \varepsilonNd (+4.1), values that fall well within previously established fields for the Older Series. In contrast to recent work ( Paul et al, 2007, Compositional diversity among primitive lavas of Mauritius, Indian Ocean: Implications for mantle sources, JVGR, 164, 76-94) that assumed the sole presence of Older Series lavas at depth and interpreted variation as diversity within the Older Series, we interpret this core to be predominantly Intermediate Series with only the deepest sample classified as Older Series. These results suggest that volumes of rejuvenescent lavas on Mauritius are greater than had been realized. Rejuvenescent volcanism on Mauritius thus contrasts strongly with that occurring on Hawaii and other Pacific islands, both in erupted volumes and in duration. Rejuvenescent volcanism on oceanic islands remains enigmatic in the context of models and intraplate volcanism, and nowhere more so than on Mauritius.
DE: 1033 Intra-plate processes (3615, 8415)
DE: 1037 Magma genesis and partial melting (3619)
DE: 1040 Radiogenic isotope geochemistry
DE: 3037 Oceanic hotspots and intraplate volcanism
DE: 9340 Indian Ocean
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting