Samenvatting
Bora-Baricha-Tullu Moye is a Late Quaternary volcanic system in the Main Ethiopian Rift, characterised by products of both explosive and effusive volcanic eruptions. The petrological and geochemical characteristics of the volcanic products are investigated using a combination of petrography, major and trace element whole rock analyses and in-situ major element analyses of phenocryst phases, matrix glass and melt inclusions. The bulk rock compositions vary from basalt to peralkaline rhyolite (comendite and pantellerite), and the chemical variability can largely be explained by fractional crystallisation processes with minor crustal assimilation and magma mixing. The dominant mineral phases such as clinopyroxenes and feldspars show a tendency for Fe and Na enrichment respectively from the basalts towards the pantellerites. The comendite and pantellerite deposits show systematic variations towards more evolved glass and mineral composition with the stratigraphy. The combination of thermometry (i.e., clinopyroxene-liquid, feldspar-liquid, olivine-liquid and clinopyroxene-only) and barometry (i.e., clinopyroxene-liquid and clinopyroxene-only) modelling suggests that the basaltic magmas are stored at high temperature (1070–1190 °C) at mid-to-deep-crustal levels (∼7–29 km). The peralkaline rhyolite melts are stored at lower temperature (i.e., 805–900 °C for comendite; 700–765 °C for pantellerite) at shallow crustal levels (∼4 km). The conditions of pre-eruptive storage as recorded in the comendite and pantellerite rocks in combination with stratigraphic constraints, suggests a progressive temporal evolution of the magma reservoirs to cooler storage temperatures.
| Originele taal-2 | English |
|---|---|
| Artikelnummer | 107088 |
| Aantal pagina's | 20 |
| Tijdschrift | Lithos |
| Volume | 442-443 |
| Nummer van het tijdschrift | 2023 |
| DOI's | |
| Status | Published - apr. 2023 |
Bibliografische nota
Funding Information:AT is supported by a Fonds National de la Recherche Scientifique (F.R.S.-FNRS) Aspirant doctoral scholarship. Several samples and an extensive mineral chemistry dataset were collected under the NERC-funded RiftVolc Large Grant (NE/L013649/1) by KF along with others. KF further acknowledges FNRS MIS grant F.4515.20, and the Wiener Anspach Foundation grant “The Magmatic Evolution of Geothermally Active Calderas in Ethiopia”. VD thanks the F.R.S.-FNRS for support. We would like to thank Tamsin Mather and David Pyle for continued support and giving the permission to access the dataset and samples from the RiftVolc project, which also supported additional fieldwork and laboratory analyses from AT's PhD work. We sincerely thank Kathy Whaler and Anne Galbraith (University of Edinburgh) for the continued facilitation of the work. Field work and sample export was kindly permitted by authorities of the Oromia region and Ministry of Mines and Petroleum of Ethiopia, respectively. Professional logistical support was provided by Ethioder Pvt. Ltd. Co and their drivers. Sabrina Cauchies and Cécilia Teller helped with whole rock data collection at ULB. We thank Paul Wallace and Oliver Higgins for the fruitful discussion on geothermobarometry modelling. Our gratitude goes to Gareth Fabbro and John White for detailed and constructive comments which improved the paper. We thank Di-Cheng Zhu for the editorial handling.
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© 2023 Elsevier B.V.
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Copyright 2023 Elsevier B.V., All rights reserved.