Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa - Signals from a recycled mantle component?

Günther T, Haase K, Junge M, Oberthür T, Wölki D, Krumm S (2018)

Publication Language: English

Publication Status: Published

Publication Type: Journal article, Original article

Publication year: 2018

Journal

Publisher: ELSEVIER SCIENCE BV

Book Volume: 310

Pages Range: 332-341

DOI: 10.1016/j.lithos.2018.04.017

Abstract

Platiniferous dunite pipes occur in the lower mafic/ultramafic portion of the Rustenburg layered Suite of the Bushveld large igneous province (LIP). Olivine compositions in these pipes range from forsterite (Fo) 80 to 35 mol% and suggest crystallization from variably evolved magmas at high temperatures (similar to 1200 degrees C). The most primitive olivines are from a stock unit and have the highest contents of Ni (>0.15 wt%) and lowest contents of Mn (<0.3 wt%). Fractional crystallization and partial melting of pyroxenite host rock play a significant role in the formation of the fayalitic olivines with its high Mn contents (>0.3 wt%). High delta O-18 values of olivine (5.7-7.0 parts per thousand) and pyroxene (6.7-7.4 parts per thousand) are akin to those of the Lower and Critical Zone of the Bushveld intrusion suggesting a common origin. The constant high O isotope ratios with variable Fo contents in the olivines are unlike trends observed in olivine phenocrysts in magmas forming by assimilation-fractional crystallization. We suggest that the high delta O-18 in the most primitive dunites reflect that of the primary melt of the Bushveld pipes, indicating either a bulk assimilation of crust prior to pipe formation or a contribution from recycled oceanic crust in the subcontinental lithospheric mantle (SCLM). The latter scenario is supported by the high Ni/Mn ratios in primitive pipe olivine that might be inherited from melting of a pyroxene-rich mantle source. (C) 2018 Elsevier B.V. All rights reserved.

Authors with CRIS profile

Involved external institutions

Bundesanstalt für Geowissenschaften und Rohstoffe (BGR) Germany (DE) Albert-Ludwigs-Universität Freiburg Germany (DE)

How to cite

APA:

Günther, T., Haase, K., Junge, M., Oberthür, T., Wölki, D., & Krumm, S. (2018). Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa - Signals from a recycled mantle component? Lithos, 310, 332-341. https://doi.org/10.1016/j.lithos.2018.04.017

MLA:

Günther, Thomas, et al. "Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa - Signals from a recycled mantle component?" Lithos 310 (2018): 332-341.

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