Due to routine maintenance, access to the Library Open Repository will be interrupted on the morning of Friday 12th February.
We apologise for any inconvenience.

Library Open Repository

Nature of alkali-carbonate fluids in the sub-continental lithospheric mantle

Downloads

Downloads per month over past year

Giuliani, A and Kamenetsky, VS and Phillips, D and Kendrick, MA and Wyatt, BA and Goemann, K (2012) Nature of alkali-carbonate fluids in the sub-continental lithospheric mantle. Geology, 40 (11). pp. 967-970. ISSN 0091-7613

[img] PDF
Geology_2012_Al...pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.

Abstract

Mantle xenoliths sampled by kimberlite and alkali basalt magmas show a range of metasomatic styles, but direct evidence for the nature of the metasomatising fluids is often elusive. It has been suggested that carbonate-rich melts produced by partial melting of carbonated peridotites and eclogites play an important role in modifying the composition of the lithospheric mantle. These mantle-derived carbonate melts are often inferred to be enriched in alkali elements; however, alkali-rich carbonate fluids have only been reported as micro-inclusions in diamonds and as unique melts involved in the formation of the Udachnaya-East kimberlite (Yakutia, Russia). In this paper we present the first direct evidence for alkali-carbonate melts in the shallow lithospheric mantle (~110–115 km), above the diamond stability field. These alkali-carbonate melts are preserved in primary multiphase inclusions hosted by large metasomatic ilmenite grains contained in a polymict mantle xenolith from the Bultfontein kimberlite (Kimberley, South Africa). The inclusions host abundant carbonates (magnesite, dolomite, and K-Na-Ca carbonates), kalsilite, phlogopite, K-Na titanates, and phosphates, with lesser amounts of olivine, chlorides, and alkali sulfates. Textural and chemical observations indicate that the alkali-carbonate melt likely derived from primary or precursor kimberlite magmas. Our findings extend the evidence for alkali-carbonate melts/fluids permeating the Earth mantle outside the diamond stability field and provide new insights into the chemical features of previously hypothesized melts. As metasomatism by alkali-rich carbonate melts is often reported to affect mantle xenoliths, and predicted from experimental studies, the fluid type documented here likely represent a major metasomatising agent in the Earth’s lithospheric mantle.

Item Type: Article
Journal or Publication Title: Geology
Page Range: pp. 967-970
ISSN: 0091-7613
Identification Number - DOI: 10.1130/G33221.1
Additional Information: Copyright 2012 Geological Society of America
Date Deposited: 19 Oct 2012 03:33
Last Modified: 18 Nov 2014 04:43
Item Statistics: View statistics for this item

Repository Staff Only (login required)

Item Control Page Item Control Page