|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
1 Department of Geological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA
2 Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
Retrograde net transfer reactions significantly affect compositions of metamorphic minerals, yet are rarely considered when determining pressure-temperature (P-T) conditions. Two natural amphibolite facies metapelites from the central Himalaya of Nepal exhibit extremely common compositional patterns, including increases in Mn and Fe/(Fe + Mg) at the rims of garnets, which are the result of retrograde garnet dissolution and Fe-Mg exchange with biotite. However, typical thermobarometric approaches for these rocks result in errors of hundreds of degrees and 3–6 kbar compared with thermobarometry of nearby rocks and petrogenetic grids. These large errors result because dissolution of high-Fe garnet has strongly affected the Fe/Mg ratio of matrix biotite. X-ray maps help evaluate the extent and chemical effects of retrograde reactions in these samples by identifying mineral regions that retain highest-T compositions, or, through a new data-processing approach, by permitting correction of mineral compositions to original high-T values. These approaches ensure against retrograde net transfer reactions and should be applied routinely in thermobarometric studies—they ultimately yield P-T estimates that are more petrologically reasonable, and permit rapid screening of samples for those least affected by retrograde reactions. Reconsideration of thermobarometry in the central and eastern Himalaya indicates that retrograde net transfer reactions are extremely common. Therefore, previous thermobarometric studies based on garnet major element compositions from that region should be reevaluated.
Key Words: geothermometry • geobarometry • metamorphism • Himalaya
This article has been cited by other articles:
|
|
 |
|
  M. J. Dorais, T. K. Pett, and M. Tubrett Garnetites of the Cardigan Pluton, New Hampshire: Evidence for Peritectic Garnet Entrainment and Implications for Source Rock Compositions J. Petrology, November 4, 2009; (2009) egp058v1. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. M. Briggs, A. Yin, C. E. Manning, Z.-L. Chen, and X.-F. Wang Tectonic development of the southern Chinese Altai Range as determined by structural geology, thermobarometry, 40Ar/39Ar thermochronology, and Th/Pb ion-microprobe monazite geochronology Geological Society of America Bulletin, September 1, 2009; 121(9-10): 1381 - 1393. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. L. Booth, C. P. Chamberlain, W. S.F. Kidd, and P. K. Zeitler Constraints on the metamorphic evolution of the eastern Himalayan syntaxis from geochronologic and petrologic studies of Namche Barwa Geological Society of America Bulletin, March 1, 2009; 121(3-4): 385 - 407. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Kohn P-T-t data from central Nepal support critical taper and repudiate large-scale channel flow of the Greater Himalayan Sequence Geological Society of America Bulletin, March 1, 2008; 120(3-4): 259 - 273. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Cesare, M. Satish-Kumar, G. Cruciani, S. Pocker, and L. Nodari Mineral chemistry of Ti-rich biotite from pegmatite and metapelitic granulites of the Kerala Khondalite Belt (southeast India): Petrology and further insight into titanium substitutions American Mineralogist, February 1, 2008; 93(2-3): 327 - 338. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Rossetti, F. Balsamo, I.M. Villa, M. Bouybaouenne, C. Faccenna, and R. Funiciello Pliocene Pleistocene HT LP metamorphism during multiple granitic intrusions in the southern branch of the Larderello geothermal field (southern Tuscany, Italy) Journal of the Geological Society, January 1, 2008; 165(1): 247 - 262. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Chakraborty, S. Dasgupta, and S. Neogi Nucleation kinetics controlled by chemical overstepping and its tectonic implications: an example from the Sikkim Himalaya European Journal of Mineralogy, December 1, 2007; 19(6): 791 - 803. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Johnston, B. R. Hacker, and M. N. Ducea Exhumation of ultrahigh-pressure rocks beneath the Hornelen segment of the Nordfjord-Sogn Detachment Zone, western Norway Geological Society of America Bulletin, September 1, 2007; 119(9-10): 1232 - 1248. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. M. Briggs, A. Yin, C. E. Manning, Z.-L. Chen, X.-F. Wang, and M. Grove Late Paleozoic tectonic history of the Ertix Fault in the Chinese Altai and its implications for the development of the Central Asian Orogenic System Geological Society of America Bulletin, July 1, 2007; 119(7-8): 944 - 960. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Cheng, E. Nakamura, K. Kobayashi, and Z. Zhou Origin of atoll garnets in eclogites and implications for the redistribution of trace elements during slab exhumation in a continental subduction zone American Mineralogist, July 1, 2007; 92(7): 1119 - 1129. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. H. Stowell, G. R. Bulman, C. A. Zuluaga, D. K. Tinkham, R. B. Miller, and E. Stein Mid-crustal Late Cretaceous metamorphism in the Nason terrane, Cascades crystalline core, Washington, USA: Implications for tectonic models Geological Society of America Memoirs, January 1, 2007; 200(0): 211 - 232. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. Dumond, K. H. Mahan, M. L. Williams, and K. E. Karlstrom Crustal segmentation, composite looping pressure-temperature paths, and magma-enhanced metamorphic field gradients: Upper Granite Gorge, Grand Canyon, USA Geological Society of America Bulletin, January 1, 2007; 119(1-2): 202 - 220. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. E. Wilbur and J. J. Ague Chemical disequilibrium during garnet growth: Monte Carlo simulations of natural crystal morphologies Geology, August 1, 2006; 34(8): 689 - 692. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. A. Dutch, M. Hand, and C. Clark Cambrian reworking of the southern Australian Proterozoic Curnamona Province: constraints from regional shear-zone systems Journal of the Geological Society, September 1, 2005; 162(5): 763 - 775. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. GOSCOMBE, D. GRAY, and M. HAND Extrusional Tectonics in the Core of a Transpressional Orogen; the Kaoko Belt, Namibia J. Petrology, June 1, 2005; 46(6): 1203 - 1241. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Prasad, A. Bhattacharya, M.M. Raith, and S. Bhadra The origin of orthopyroxene/biotite + plagioclase coronas from the Bolangir anorthosite complex (India), and implications for reconstructing P-T paths American Mineralogist, February 1, 2005; 90(2-3): 291 - 303. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. GOSCOMBE, D. GRAY, and M. HAND Variation in Metamorphic Style along the Northern Margin of the Damara Orogen, Namibia J. Petrology, June 1, 2004; 45(6): 1261 - 1295. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. R. M. PATTISON, T. CHACKO, J. FARQUHAR, and C. R. M. MCFARLANE Temperatures of Granulite-facies Metamorphism: Constraints from Experimental Phase Equilibria and Thermobarometry Corrected for Retrograde Exchange J. Petrology, May 1, 2003; 44(5): 867 - 900. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 H. H. Stowell and D. K. Tinkham Integration of phase equilibria modelling and garnet Sm-Nd chronology for construction of P-T-t paths: examples from the Cordilleran Coast Plutonic Complex, USA Geological Society, London, Special Publications, January 1, 2003; 220(1): 119 - 145. [Abstract] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
