Low stress deformation of garnet by incongruent dissolution precipitation creep |
| |
| Institution: | 1. Planetary Geosciences Institute, Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA;2. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada;3. V.S. Sobolev Institute of Geology and Mineralogy, Russian Academy of Sciences, Siberian Branch, Novosibirsk, Russia;1. V.S. Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the RAS, 3, Ac. Koptyuga Ave., Novosibirsk 630090, Russian Federation;2. Novosibirsk State University, Pirogova St. 2, Novosibirsk 630090, Russian Federation;3. JV Tairus, 3, Ac. Koptyuga Ave., Novosibirsk 630090, Russia;1. Department of Geological Sciences, University of Cape Town, Rondebosch 7701, South Africa;2. Planetary Geosciences Institute, Earth and Planetary Sciences Dept., The University of Tennessee, Knoxville, TN 37996, USA;1. A.P. Vinogradov Institute of Geochemistry, 1a Favorsky st., Irkutsk, 664033, Russia;2. V.S.Sobolev Institute of Geology and Mineralogy, 3 Koptyuga ave., Novosibirsk, 630090, Russia;3. Novosibirsk State University, 2 Pirogova st., Novosibirsk, 630090, Russia;1. University of British Columbia, Vancouver, BC, Canada;2. Institute of Precambrian Geology and Geochronology RAS, St. Petersburg, Russia;3. University of Alberta, Edmonton, Alberta, Canada;4. University of Cape Town, Cape Town, South Africa;5. Petra Diamonds, Bryanston, South Africa |
| |
| Abstract: | Microstructures indicating incongruent dissolution precipitation creep of garnet in eclogite-facies graphitic micaschist (Tauern window, Eastern Alps) are investigated. Garnet dissolution is observed where garnet poikiloblasts grown at eclogite facies metamorphism approached each other as a consequence of progressive deformation during exhumation, with estimated P-T-conditions between 570 °C, 1.7 GPa and 470 °C, 0.9 GPa. The poikiloblasts are separated by a dissolution seam and flanked by strain shadows filled with quartz, white mica, and chlorite; there is no evidence for crystal plastic deformation of garnet. Two cases are investigated: (A) stylolitic contact zone, (B) smooth contact zone. In both cases, internal fabrics of the poikiloblasts and concentric chemical zoning are truncated. Material previously forming inclusions in the garnet poikiloblasts is now passively enriched in a dissolution seam, the original microstructure of fine-grained mica–graphite aggregates remaining preserved. Though microstructures suggest that garnet dissolution was driven by local stress concentration, the level of differential stress remained too low for plastic deformation of the fine-grained white mica-graphite aggregates set free from the stress supporting garnet. Incongruent dissolution precipitation creep appears to be a particularly effective deformation mechanism at low stress in a subduction channel. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
