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The alleged kimberlite-carbonatite relationship: evidence from ilmenite and spinel from Premier and Wesselton mines and the Benfontein sill, South Africa

Gaspar, Jose C. and Wyllie, Peter J. (1984) The alleged kimberlite-carbonatite relationship: evidence from ilmenite and spinel from Premier and Wesselton mines and the Benfontein sill, South Africa. Contributions to Mineralogy and Petrology, 85 (2). pp. 133-140. ISSN 0010-7999. https://resolver.caltech.edu/CaltechAUTHORS:20160219-092721218

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Abstract

Carbonate-rich, SiO_2-poor residua are developed in some kimberlites solidifying as ocelli, layers, or discrete dikes which satisfy petrographic definitions of carbonatite. Arguments that these rocks have mineralogies, antecedents, and comagmatic rocks differing from those of the carbonatites in alkaline rock complexes, including the specific observation that kimberlites and carbonatites contain ilmenites and spinels of different composition, have been used to refute the “alleged kimberlite-carbonatite relationship”. New microprobe analyses of ilmenites and spinels from carbonate-rich rocks associated with kimberlites in three South African localities correspond to spinels and ilmenites of carbonatites from alkalic complexes, or have characteristics intermediate between those of carbonatites and kimberlites. The ilmenites are distinguished from kimberlite ilmenites by higher MnO, FeTiO_3, and Nb_2O_5, and by negligible Cr_2O_3. The spinels are distinguished from kimberlite spinels by their Al_2O_3 and Cr_2O_3 contents. There is clearly a genetic relationship between the kimberlites and the carbonate-rich rocks, despite the observation that their ilmenites and spinels are distinctly different, which indicates that the same observation is not a valid argument against a petrogenetic relationship between kimberlites and carbonatites. These rocks are among the diverse products from mantle processes influenced by CO_2, and we believe that the petrogenetic links among them are forged in the upper mantle. We see insufficient justification to deny the name “carbonatite” to carbonate-rich rocks associated with kimberlites if they satisfy the petrographic definition in terms of major mineralogy.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1007/BF00371703DOIArticle
http://link.springer.com/article/10.1007%2FBF00371703PublisherArticle
Additional Information:© 1984 Springer-Verlag. We thank I. M. Steele and J. V. Smith for invaluable assistance with microprobe analysis, which were completed while we were at the University of Chicago. Financial support was provided by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) PROC 201.158/80 and PROC 40,1410/81, Funcadao de Amparo a Pesquisa do Estado de Sao Paulo (FASEP) PROC 80/470 and PROC 81/0168-8, and the Earth Science Division of the National Science Foundation Grants EAR 8108599, and EAR 8311758.
Funders:
Funding AgencyGrant Number
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROC 201.158/80
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PROC 40,1410/81
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROC 80/470
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)PROC 81/0168-8
NSFEAR 8108599
NSFEAR 8311758
Issue or Number:2
Record Number:CaltechAUTHORS:20160219-092721218
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160219-092721218
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64605
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:19 Feb 2016 19:03
Last Modified:03 Oct 2019 09:39

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