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The Mn-Al-Si-O system; an experimental study of phase relations applied to parageneses in manganese-rich ores and rocks

Irmgard Abs-Wurmbach and Tjerk Peters
The Mn-Al-Si-O system; an experimental study of phase relations applied to parageneses in manganese-rich ores and rocks
European Journal of Mineralogy (February 1999) 11 (1): 45-68

Abstract

The solubility of Al in braunite, partridgeite and hausmannite, and of Mn (super 3+) in galaxite and viridine, was investigated at 600 degrees C and 4 kbar, with f (sub O) (sub 2) controlled by the solid buffers Mn (sub 2) O (sub 3) /MnO (sub 2) , Mn (sub 3) O (sub 4) /Mn (sub 2) O (sub 3) , Cu (sub 2) O/CuO, Cu/Cu (sub 2) O, Fe (sub 3) O (sub 4) /Fe (sub 2) O (sub 3) and Ni/NiO. The f (sub O) (sub 2) for the reaction pyrolusite (pyr) + quartz = braunite (brn) + O (sub 2) and Al (sub 2) SiO (sub 5) + pyr + qz = viridine (vir) or kanonaite (kan) lies above the Mn (sub 2) O (sub 3) /MnO (sub 2) buffer. The reaction brn + qz + vir = spessartine (sps) takes place at f (sub O) (sub 2) between the Mn (sub 2) O (sub 3) /MnO (sub 2) and Mn (sub 3) O (sub 4) /Mn (sub 2) O (sub 3) buffers, whereas the reaction brn + vir = sps + corundum (cor) + O (sub 2) lies just below the latter. Between the f (sub O) (sub 2) of the Cu (sub 2) O/CuO and Cu/Cu (sub 2) O buffers, the reactions brn + qz = rhodonite (rdn) + O (sub 2) , vir = sps + sillimanite (sil) + cor, brn + cor = hausmannite (haus) + sps + O (sub 2) , brn + rdn = tephroite (teph) + O (sub 2) , brn = haus + teph + O (sub 2) , haus + cor = galaxite (gal) + O (sub 2) and haus + sps = gal + teph + O (sub 2) take place with decreasing O (sub 2) . At lower total P, higher T and appropriate f (sub O) (sub 2) , braunite is not stable with tephroite, and will decompose to rhodonite and hausmannite. Most of the variability of mineral assemblages within a Mn deposit and the persistence of such minerals as braunite, piemontite and viridine from very-low-grade to amphibolite-facies conditions can be explained by these experimentally derived equilibrium reactions; the most critical parameters are f (sub O) (sub 2) and, to a lesser extent, T and total P.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 11
Serial Issue: 1
Title: The Mn-Al-Si-O system; an experimental study of phase relations applied to parageneses in manganese-rich ores and rocks
Affiliation: Technische-Universitaet-Berlin, Berlin, Federal Republic of Germany
Pages: 45-68
Published: 199902
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 70
Accession Number: 1999-033843
Categories: Economic geology, geology of ore depositsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables
Secondary Affiliation: Universitaet Bern, DEU, Federal Republic of Germany
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 199912
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