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Alabandite play a dominant role in the magnetic properties of natrocarbonatites magnetic mineralogy and rock magnetic properties of silicate and carbonatite rocks from Oldoinyo Lengai volcano (Tanzania)

Mattsson, H. B. and Balashova, A. and Almqvist, B. S. G. and Hirt, A. M. and Bosshard-Stadlin, S. A. and Weidendorfer, D. (2018) Alabandite play a dominant role in the magnetic properties of natrocarbonatites magnetic mineralogy and rock magnetic properties of silicate and carbonatite rocks from Oldoinyo Lengai volcano (Tanzania). Journal of African Earth Sciences, 142 . pp. 193-206. ISSN 1464-343X. http://resolver.caltech.edu/CaltechAUTHORS:20180227-085311774

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Abstract

Oldoinyo Lengai, a stratovolcano in northern Tanzania, is most famous for being the only currently active carbonatite volcano on Earth. The bulk of the volcanic edifice is dominated by eruptive products produced by silica-undersaturated, peralkaline, silicate magmas (effusive, explosive and/or as cumulates at depth). The recent (2007–2008) explosive eruption produced the first ever recorded pyroclastic flows at this volcano and the accidental lithics incorporated into the pyroclastic flows represent a broad variety of different rock types, comprising both extrusive and intrusive varieties, in addition to various types of intrusive rocks and cumulates. This mix of different accidental lithics provides a unique insight into the inner workings of the world's only active carbonatite volcano. Here, we focus on the magnetic petrology, magnetic mineralogy and the rock magnetic properties of a wide selection of samples spanning the spectrum of Oldoinyo Lengai rock types compositionally, as well from a textural point of view. Here we show that the magnetic properties of most extrusive silicate rocks are dominated by magnetite-ulvöspinel solid solutions, and that pyrrhotite plays a larger role in the magnetic properties of the intrusive silicate rocks. The natrocarbonatitic lavas, for which the volcano is best known for, show distinctly different magnetic properties in comparison with the silicate rocks. This discrepancy can be explained by abundant alabandite crystals/blebs in the groundmass of the natrocarbonatitic lavas. A detailed combination of petrological/mineralogical studies with geophysical investigations is an absolute necessity in order to understand, and to better constrain, the overall architecture and inner workings of the subvolcanic plumbing system. The results presented here may also have implications for the quest in order to explain the genesis of the uniquely natrocarbonatitic magmas characteristic of Oldoinyo Lengai.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1016/j.jafrearsci.2018.02.018DOIArticle
https://www.sciencedirect.com/science/article/pii/S1464343X18300505PublisherArticle
Additional Information:© 2018 Elsevier Ltd. Received 29 July 2017, Revised 16 February 2018, Accepted 22 February 2018, Available online 24 February 2018.
Subject Keywords:Oldoinyo lengai; Rock magnetic properties; Magnetic mineralogy; Nephelinite; Phonolite; Natrocarbonatite; Alabandite
Record Number:CaltechAUTHORS:20180227-085311774
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180227-085311774
Official Citation:H.B. Mattsson, A. Balashova, B.S.G. Almqvist, S.A. Bosshard-Stadlin, D. Weidendorfer, Magnetic mineralogy and rock magnetic properties of silicate and carbonatite rocks from Oldoinyo Lengai volcano (Tanzania), Journal of African Earth Sciences, Volume 142, 2018, Pages 193-206, ISSN 1464-343X, https://doi.org/10.1016/j.jafrearsci.2018.02.018. (http://www.sciencedirect.com/science/article/pii/S1464343X18300505)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84966
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:27 Feb 2018 19:09
Last Modified:04 Apr 2018 21:53

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