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Kabbaldurga-type charnockitization: a local phenomenon in the granulite to amphibolite grade transition zone
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Hoernes, S. Staehle, H. J. Raith, M. |
| Copyright Year | 1988 |
| Description | In the deeply eroded Precambrian crust of South India and Sri Lanka, a series of spectacular exposures shows progressive development of coarse-grained charnockite through dehydration of amphibolite grade gneisses in different arrested stages. At Kabbaldurga, charnockitization of Archaean grey biotite-hornblende gneisses occurred about 2.5 Ga ago and evidently was induced by the influx of external carbonic fluids along a system of ductile shears and the foliation planes. The results of oxygen isotope thermometry and of geothermobarometry in adjacent areas indicate a P-T regime of 700 to 750 C and 5 to 7 kb. The decrease of water activity in the fluid infiltrated zones caused an almost complete breakdown of hornblende and biotite and the new growth of hypersthene. Detailed petrographic and geochemical studies revealed marked changes in mineralogy and chemistry from granodioritic to granitic which document the metasomatic nature of the process. |
| File Size | 148649 |
| Page Count | 2 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19890012870 |
| Archival Resource Key | ark:/13960/t81k49d94 |
| Language | English |
| Publisher Date | 1988-01-01 |
| Access Restriction | Open |
| Subject Keyword | Geophysics Grain Size Precambrian Period Water Growth Ductility Sri Lanka Mineralogy Dehydration Oxygen Isotopes Gneiss India Temperature Measurement Petrology Biotite Earth Crust Coarseness Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |