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Nature of alkali-carbonate fluids in the sub-continental lithospheric mantle
Citation
Giuliani, A and Kamenetsky, VS and Phillips, D and Kendrick, MA and Wyatt, BA and Goemann, K, Nature of alkali-carbonate fluids in the sub-continental lithospheric mantle, Geology, 40, (11) pp. 967-970. ISSN 0091-7613 (2012) [Refereed Article]
Copyright Statement
Copyright 2012 Geological Society of America
DOI: doi:10.1130/G33221.1
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 Details
Item Type: | Refereed Article |
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Research Division: | Earth Sciences |
Research Group: | Geology |
Research Field: | Igneous and metamorphic petrology |
Objective Division: | Expanding Knowledge |
Objective Group: | Expanding knowledge |
Objective Field: | Expanding knowledge in the earth sciences |
UTAS Author: | Kamenetsky, VS (Professor Vadim Kamenetsky) |
UTAS Author: | Goemann, K (Dr Karsten Goemann) |
ID Code: | 80015 |
Year Published: | 2012 |
Web of Science® Times Cited: | 57 |
Deposited By: | Central Science Laboratory |
Deposited On: | 2012-10-17 |
Last Modified: | 2017-10-30 |
Downloads: | 0 |
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