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New typology and origin of tsavorite based on trace-element chemistry

Julien Feneyrol, Gaston Giuliani, Daniel Ohnenstetter, Benjamin Rondeau, Emmanuel Fritsch, Anthony E. Fallick, Daniel Ichang'i, Edward Omito, Michel Rakotondrazafy, Madison Ranatsenho and Florent Lallier
New typology and origin of tsavorite based on trace-element chemistry
European Journal of Mineralogy (February 2014) 26 (2): 293-308


New electron-microprobe analyses of "tsavorites" from the Neoproterozoic Metamorphic Mozambique Belt deposits allow the characterization of green grossular according to its trace-element chemistry (V, Cr, Mn). Five chemical types are defined: type 1, vanadian grossular with V >Cr >Mn (in atoms per formula unit); type 2, vanadian grossular with V >Mn >Cr; type 3, Mn-bearing vanadian grossular with Mn > V > Cr; type 4, Mn-bearing chromian grossular with Mn > Cr > V; and type 5, Cr- and Mn-bearing grossular with Cr > Mn > V. These types are also characterized by different absorption spectra in the ultraviolet-visible-near infrared. Type 1 tsavorite spectra show a total absorption below 430 nm due to the high vanadium contents. Type 2 tsavorite spectra present the classical absorption bands of V. Types 3 and 4 tsavorite spectra display additional shoulders at 407 and 408 nm due to Mn (super 2+) , whereas spectra of Cr-bearing types 4 and 5 tsavorite show the two additional bands of Cr (super 3+) at 697 and 701 nm. The different absorption spectra also indicate Fe (super 2+) -Ti (super 4+) charge transfer. We measured OH (super -) equivalent to 0.08 to 0.38 wt% eq. H (sub 2) O within the structure. Concentrations of vanadium, chromium and manganese are good chemical "fingerprints" for determining the geographic provenance of economic tsavorite from Kenya, Tanzania and Madagascar.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 26
Serial Issue: 2
Title: New typology and origin of tsavorite based on trace-element chemistry
Affiliation: Universite de Lorraine, Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy, France
Pages: 293-308
Published: 201402
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
References: 47
Accession Number: 2014-028707
Categories: Mineralogy of silicatesEconomic geology, geology of nonmetal deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
S04°30'00" - N04°30'00", E34°00'00" - E42°00'00"
S25°40'00" - S11°52'00", E43°00'00" - E50°30'00"
S11°40'00" - S01°00'00", E29°30'00" - E40°30'00"
Secondary Affiliation: Universite de Nantes, FRA, FranceScottish Universities Environmental Research Centre, GBR, United KingdomUniversity of Nairobi, KEN, KenyaMines and Geology Department, KEN, KenyaUniversite d'Antananarivo, MDG, Madagascar
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201418
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