Universität zu Köln

Muenker, Carsten, Fonseca, Raul O. C. ORCID: 0000-0002-0897-4884 and Schulz, Toni ORCID: 0000-0003-1248-7832 (2017). Silicate Earth's missing niobium may have been sequestered into asteroidal cores. Nat. Geosci., 10 (11). S. 822 - 830. NEW YORK: NATURE PUBLISHING GROUP. ISSN 1752-0908

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Abstract

Geochemical models describing the behaviour of niobium during Earth's growth rely on the general paradigm that niobium was delivered by Earth's asteroidal building blocks at chondritic abundances. This paradigm is based on the observation that niobium is traditionally regarded as a refractory and strongly lithophile element, and thus stored in the silicate portions of Earth and differentiated asteroids. However, Earth's silicate mantle is instead selectively depleted in niobium, in marked contrast to the silicate mantles of many asteroids and smaller planets that apparently lack any significant depletion in niobium. Here we present results of high-precision measurements for niobium and other lithophile elements in representative meteorites from various small differentiated asteroids. Our data, along with the results of low-pressure experiments, show that in more reduced asteroids-such as Earth's first building blocks-niobium is moderately chalcophile and more so than its geochemical twin tantalum by an order of magnitude. Accordingly, niobium can be sequestered into the cores of more reduced asteroids during differentiation via the segregation of sulfide melts in a carbon-saturated environment. We suggest that the niobium deficit in Earth's silicate mantle may be explained by the Earth's silicate mantle preferentially accreting the silicate portions of reduced asteroidal building blocks.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED Fonseca, Raul O. C. UNSPECIFIED orcid.org/0000-0002-0897-4884 UNSPECIFIED Schulz, Toni UNSPECIFIED orcid.org/0000-0003-1248-7832 UNSPECIFIED
URN:	urn:nbn:de:hbz:38-212971
DOI:	10.1038/ngeo3048
Journal or Publication Title:	Nat. Geosci.
Volume:	10
Number:	11
Page Range:	S. 822 - 830
Date:	2017
Publisher:	NATURE PUBLISHING GROUP
Place of Publication:	NEW YORK
ISSN:	1752-0908
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language METAL-SULFUR SYSTEMS; THERMODYNAMIC CONSTRAINTS; PHASE-RELATIONSHIPS; LIQUID-PHASE; FE-C; DIFFERENTIATION; EVOLUTION; RICH; HF; NB Multiple languages Geosciences, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/21297