Abstract
Plagioclase replacement textures in partially eclogitized gabbros from the Sanddal mafic-ultramafic complex, North-East Greenland eclogite province
Abstracts with programs - Geological Society of America, Vol.31(7), pp.167-168
Geological Society of America, 1999 annual meeting
1999
Abstract
The North-East Greenland Eclogite Province (NEGEP) contains widespread outcrops of eclogite and related high pressure rocks with a Caledonian metamorphic age (Brueckner, et al., 1998, Contrib. Mineral. Petrol., 130, 103-120). In addition to the true eclogites, there are many mafic and ultramafic bodies enclosed in the dominant quartzo-feldspathic gneisses that are partially eclogitized and have experienced varying degrees of retrogression to amphibolite facies assemblages.In the northwest corner of Sanddal (78 degrees 05'N, 21 degrees 30'W), a cluster of variably eclogitized mafic and ultramafic bodies (the Sanddal Mafic-Ultramafic Complex, SMUK) was sampled extensively. Partially eclogitized gabbroic rocks from SMUK exhibit a wide range in development of eclogite facies mineral assemblages. Except for plagioclase, relict igneous minerals (olivine, orthopyroxene, clinopyroxene, biotite and spinel) show systematic replacement textures that vary little from sample to sample. Plagioclase domains, which display the widest variety of different textures and minerals, can be placed in a roughly progressive sequence that provides insight into the eclogite-forming process. In the least eclogitized gabbro, plagioclase was initially replaced by an omphacite-spinel symplectite. Locally, garnet nucleated (on spinel?) and the omphacite-spinel symplectite was abruptly replaced by fine, granular garnet in contact with minor omphacite and amphibole. In other samples, where more plagioclase was present and eclogitization was further progressed, plagioclase domains are typically coronitic with an outer rim of garnet surrounding a layer of omphacitic pyroxene with corundum, clinozoisite and/or kyanite inclusions around a core of inclusion-rich relict plagioclase. Garnet eventually engulfs the plagioclase domains and omphacite is preserved only as inclusions in garnet. In the most thoroughly recrystallized sample, a garnet hornblende clinopyroxenite, plagioclase is rare and sodium is distributed in clinopyroxene (Jd18) and amphibole.
Details
- Title: Subtitle
- Plagioclase replacement textures in partially eclogitized gabbros from the Sanddal mafic-ultramafic complex, North-East Greenland eclogite province
- Creators
- Helen M Lang - West Virginia UniversityJane A Gilotti - University of Iowa
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.31(7), pp.167-168
- Conference
- Geological Society of America, 1999 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 1999 annual meeting
- Language
- English
- Date published
- 1999
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240909602771
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