Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Minerals of the rhonite-kuratite series in paralavas from a new combustion metamorphic complex in the Choir-Nyalga Basin (central Mongolia); composition, mineral assemblages and formation conditions

Igor S. Peretyazhko, Elena A. Savina and Elena A. Khromova
Minerals of the rhonite-kuratite series in paralavas from a new combustion metamorphic complex in the Choir-Nyalga Basin (central Mongolia); composition, mineral assemblages and formation conditions
Mineralogical Magazine (August 2017) 81 (4): 949-974

Abstract

This is the first description of rare minerals found in paralavas from a recently discovered combustion metamorphic complex in the Choir-Nyalga basin, Central Mongolia. The identified minerals contain strongly variable concentrations of Si, Ti, Mg, Fe (super 2+) and Fe (super 3+) and most commonly have compositions intermediate in a series from kuratite Ca (sub 4) Fe (sub 10) (super 2+) Ti (sub 2) O (sub 4) [Si (sub 8) Al (sub 4) O (sub 36) ] and rhonite Ca (sub 4) (Mg, Fe (super 2+) ) (sub 8) Fe (sub 2) (super 3+) Ti (sub 2) O (sub 4) [Si (sub 6) Al (sub 6) O (sub 36) ] to low-Ti kuratite and unnamed Ti-free Fe (super 2+) -analogue of rhonite Ca (sub 4) Fe (sub 8) (super 2+) Fe (sub 4) (super 3+) O (sub 4) [Si (sub 8) Al (sub 4) O (sub 36) ]. The minerals crystallized in residual Si-Al-K and Si-Al-Ca-Fe immiscible melts after spinel, anorthite-bytownite, melilite, Al-clinopyroxene + or - Mg-Fe olivine, together with Fe (super 3+) -bearing hercynite, Ca-rich fayalite, kirschsteinite, pyrrhotite + or - native iron, wustite, magnetite, celsian, hyalophane, Ba-orthoclase and fresnoite, but before nepheline + or - kalsilite, and later sulfates, carbonates, an unidentified 'X-mineral' close to Al- and Fe-rich tobermorite and goethite. Micro-Raman spectroscopy of kuratite shows five bands near 133-155 (strong), 399-401, 545-566, 684-693 (strongest) and 828-839 cm (super -1) . The kuratite-bearing Nyalga paralavas have bulk compositions with MgO/(MgO+FeO+Fe (sub 2) O (sub 3) ), mol.% approximately 0.5 and a CIPW normative ratio of Ne/(Ne+Lc) = 0.23-0.76. Minerals of the rhonite-kuratite series formed during paralava crystallization at approximately 1100 degrees C. The diversity of the paralava mineral assemblages might result from local composition variations of Ca-rich silica-undersaturated melts derived from Fe-bearing carbonate-silicate sediments which were affected by nearby coal combustion sources at reducing conditions (IW-WM-QFM buffers) and at a nearly atmospheric pressure.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 81
Serial Issue: 4
Title: Minerals of the rhonite-kuratite series in paralavas from a new combustion metamorphic complex in the Choir-Nyalga Basin (central Mongolia); composition, mineral assemblages and formation conditions
Affiliation: Russian Academy of Sciences, Vinogradov Institute of Geochemistry, Irkutsk, Russian Federation
Pages: 949-974
Published: 201708
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 45
Accession Number: 2017-072971
Categories: Mineralogy of silicatesIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N42°00'00" - N52°00'00", E87°00'00" - E120°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201738
Close Modal

or Create an Account

Close Modal
Close Modal