Conference proceeding
Partial eclogitization of the Ambolten gabbro-norite, north-east Greenland Caledonides
Schweizerische mineralogische und petrographische Mitteilungen, Vol.78(2), pp.273-292
Fifth international eclogite conference 1997 (FIEC)
1998
Abstract
Partially eclogitized igneous bodies composed of gabbro, leucogabbro, anorthosite, and cross-cutting diabase dikes are well represented in the North-East Greenland Eclogite Province. A 200X100 meter intrusive body on Ambolten Island (78 degrees 20'N, 19 degrees 15'W) records a prograde transition from gabbro-norite to eclogite facies coronitic metagabbro followed by retrogression to garnet amphibolite. The body is composed of an undeformed core of coronitic gabbro-norite surrounded by hydrated margins of undeformed to strongly foliated amphibolite. Igneous plagioclase+olivine+enstatite+augite+oxides convert to eclogite facies assemblages consisting of garnet, omphacite, diopside, enstatite, kyanite, zoisite, rutile and pargasitic amphibole through several coronitic reactions. Relict cumulus plagioclase laths are replaced by an outer corona of garnet, an inner corona of omphacite and an internal region of sodic plagioclase, garnet, kyanite, omphacite and zoisite. Olivine and intercumulus pyroxene are partly replaced by metamorphic pyroxenes and amphibole. The corona structures, zoning patterns, diversity of mineral compositions in a single thin section, and preservation of metastable assemblages are characteristic of diffusion-controlled metamorphism. The most extreme disequilibrium is found in static amphibolites where igneous pyroxenes, plagioclase domains with eclogite facies assemblages, and matrix amphibole coexist. Complete eclogitization was not attained at Ambolten due to a lack of fluids needed to drive diffusion during prograde and retrograde metamorphism. The P-T conditions of the high-pressure metamorphism are estimated at > or =750 degrees C and >18 kbar. Well-equilibrated, foliated amphibolites from the margin of the gabbro-norite formed at 640-670 degrees C and 12.5-13.5 kbar. Eclogitization of intrusive bodies like the Ambolten gabbro-norite supports our contention that the entire North-East Greenland Eclogite Province experienced Caledonian high-pressure metamorphism, even though no eclogite facies assemblages have been found in the quartzofeldspathic host gneisses to date.
Details
- Title: Subtitle
- Partial eclogitization of the Ambolten gabbro-norite, north-east Greenland Caledonides
- Creators
- Jane A Gilotti - State Education Department, Geological Survey Albany, NY USA United StatesSynnove Elvevold - Geological Survey of Denmark and Greenland
- Resource Type
- Conference proceeding
- Publication Details
- Schweizerische mineralogische und petrographische Mitteilungen, Vol.78(2), pp.273-292
- Conference
- Fifth international eclogite conference 1997 (FIEC)
- Publisher
- Staebli Verlag AG
- ISSN
- 0036-7699
- Alternative title
- IEC 97; Fifth international eclogite conference
- Language
- English
- Date published
- 1998
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229304502771
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