Universität zu Köln

van Acken, D., Hoffmann, J. E., Schorscher, J. H. D., Schulz, T., Heuser, A. and Luguet, A. (2016). Formation of high-Al komatiites from the Mesoarchean Quebra Osso Group, Minas Gerais, Brazil: Trace elements, HSE systematics and Os isotopic signatures. Chem. Geol., 422. S. 108 - 122. AMSTERDAM: ELSEVIER SCIENCE BV. ISSN 1878-5999

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Abstract

We report highly siderophile element data combined with Re-Os isotopes and major and trace elements of the ca. 2.7-3.0 Ga komatiites from the Quebra Osso Group, Minas Gerais, Brazil. These komatiites resemble the rare high Al-type, characterized by high Al2O3/TiO2 ratios (26.7-59.8). These geochemical similarities are shared with the 3.33 Ga Commondale and 3.26 Ga Weltevreden komatiites from the eastern Kaapvaal Craton pointing to a similar origin of these suites. While anhydrous melting in an unusually hot mantle was inferred for the Weltevreden komatiites, the Commondale komatiites were suggested to have formed by hydrous, multi-stage melting. Significant depletion in LREE is coupled with subchondritic Re/Os, unradiogenic to radiogenic Os-187/Os-188 and fractionated HSE, with enrichments in Ru, Pt, and Pd over Os and Ir. The combination of these signatures suggests minor late-stage crustal influence. Potential late-stage alteration overprint, assimilation of ambient mantle material during magma ascent and complex phase relationships of HSE-hosting phases make it difficult to estimate the composition of the source of the Quebra Osso komatiites and to place constraints on the nature of the late Archean mantle. However, the Quebra Osso komatiites are unlikely to have formed in a single-stage plume setting or in a supra-subduction zone setting. Instead we suggest a multi-stage melting history of the komatiite source to explain the origin of their peculiar geochemical characteristics, as has been suggested for other high-Al2O3/TiO2 komatiite suites. (C) 2015 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code van Acken, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Hoffmann, J. E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schorscher, J. H. D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schulz, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Heuser, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Luguet, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-284133
DOI:	10.1016/j.chemgeo.2015.12.015
Journal or Publication Title:	Chem. Geol.
Volume:	422
Page Range:	S. 108 - 122
Date:	2016
Publisher:	ELSEVIER SCIENCE BV
Place of Publication:	AMSTERDAM
ISSN:	1878-5999
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PLATINUM-GROUP ELEMENTS; IONIZATION MASS-SPECTROMETRY; BARBERTON GREENSTONE-BELT; CONTINENTAL LITHOSPHERIC MANTLE; SOUTHERN WEST GREENLAND; SM-ND AGE; RE-OS; ARCHEAN MANTLE; SIDEROPHILE ELEMENTS; EARLY EARTH Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/28413