Quick
Search: 		  
advanced search
 GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help 
American Mineralogist Don't get GSW? Talk to your librarian.
JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
American Mineralogist; April 1997; v. 82; no. 3-4; p. 392-404
This Article
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Order Hardcopy of Full Text via AGI/GeoRef
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Cartwright, I.
Right arrow Articles by Harley, S. L.
Right arrow Search for Related Content
GeoRef
Right arrow GeoRef Citation

Timing and mechanisms of carbon isotope exchange in granulite-facies calc-silicate boudins, Rauer Group, East Antarctica

Ian Cartwright, Ian S. Buick, and Simon L. Harley

Monash University, Department of Earth Sciences, Clayton, Victoria, Australia
LaTrobe University, Australia
University of Edinburgh, United Kingdom

Mineralogically zoned, decimeter-diameter calc-silicate boudins enclosed within paragneisses from Little Italy Island. Rauer Group, east Antarctica underwent granulite-facies metamorphism (P = 700-900 MPa, T = 840+ or -40 degrees C) followed by near-isothermal decompression to 200-400 MPa. During decompression several mineral reactions occurred in the presence of a pore fluid (X CO2 nearly equal 0.4). The calc-silicate boudins show a general increase in calcite delta 13 C values from core (as low as -17 per mil) to rim (-9 to -10 per mil); by contrast, delta 18 O values show little variation across the boudins. The delta 13 C profiles are similar to those predicted to result from diffusion within a sphere that is surrounded by a homogeneous reservoir. Diffusion of carbon isotopes probably occurred synchronous with the post-peak metamorphic mineral reactions. At that time, centimeter-scale diffusion would have been facilitated by the presence of the fluid, while isotopic exchange between the minerals and the fluid would have been promoted by recrystallization. For metamorphic porosities of 10 (super -5) -10 (super -3) , the delta 13 C profiles could have formed in a few thousand to hundreds of thousands of years. Small (millimeter to centimeter) scale variations in delta 13 C values that may have been initially present within the boudins would have been homogenized on much shorter timescales than those required to form the profiles. The calculated timescales may reflect the time over which metamorphic recrystallization occurred and a reaction-enhanced porosity was present. Graphite formed locally in the paragneisses only at margins of the boudins probably reflects the local escape of CO 2 -bearing fluids from the boudins into relatively low f O2 rocks.

This record provided courtesy of AGI/GeoRef.






JOURNAL HOME HELP CONTACT PUBLISHER SUBSCRIBE ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 2008 by Mineralogical Society of America