Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
Mineralogical Magazine Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Mineralogical Magazine; December 2005; v. 69; no. 6; p. 937-949; DOI: 10.1180/0026461056960300
© 2005 Mineralogical Society of Great Britain and Ireland
This Article
Right arrow Figures Only
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (2)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tsunogae, T.
Right arrow Articles by Santosh, M.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Ti-free högbomite in spinel- and sapphirine-bearing Mg-Al rock from the Palghat-Cauvery shear zone system, southern India

T. Tsunogae1,2,* and M. Santosh3

1 Graduate School of Life and Environmental Sciences (Earth Evolution Sciences), University of Tsukuba, Ibaraki 305-8572, Japan
2 Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park 2006, Republic of South Africa
3 Faculty of Science, Kochi University, Akebono-cho 2-5-1, Kochi 780-8520, Japan

* E-mail: tsunogae{at}arsia.geo.tsukuba.ac.jp

We report a new type of högbomite in a spinel- and sapphirine-bearing silica-deficient Mg-Al rock from Manavadi at the northern margin of the Madurai Block along the Palghat-Cauvery shear zone system, which defines the Archaean-Proterozoic collisional boundary in southern India. Högbomite occurs here as fine- to medium-grained euhedral to subhedral crystals enclosed within or along grain boundaries of greenish spinel. It is compositionally very unique due to the lack of TiO2 (<0.2 wt.%) and enrichment in Al2O3 (66.4–70.8 wt.%) compared to other occurrences. The variety of högbomite described in this study, confirmed by laser Raman spectroscopy, has not been reported elsewhere previously. Högbomite in this study is subdivided into three groups based on the XMg (=Mg/(FeTotal+Mg)) ratio; 0.54–0.57, 0.61–0.73 and 0.77–0.79. Compositional data suggest a linear element substitution of 3(Fe+Mg) = 2Al for the Ti-free högbomite, a trend that is distinct from previously reported Ti-bearing högbomites. Textures and mineral chemistry data suggest that the following reaction took place at retrograde stage (T <800°C): spinel + H2O + O2 -> högbomite + corundum + magnetite, implying that introduction of hydrous and oxidized fluid as well as low bulk-Ti content played an important role in the formation of Ti-free högbomite.

KEYWORDS: högbomite, sapphirine, spinel, Mg-Al rock, metamorphic fluid, Palghat-Cauvery shear zone system, India






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2008 by Mineralogical Society of Great Britain and Ireland