Microstructural, chemical and textural records during growth of snowball garnet
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Download: Robyr et al. (2009).pdf (4117.83 [Ko])
State: Public
Version: Final published version
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State: Public
Version: Final published version
License: Not specified
Serval ID
serval:BIB_53BD5F8EC277
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
Microstructural, chemical and textural records during growth of snowball garnet
Journal
Journal of Metamorphic Geology
ISSN
0263-4929
Publication state
Published
Issued date
2009
Peer-reviewed
Oui
Volume
27
Pages
423-437
Language
english
Abstract
The growth history of two populations of snowball garnet from the Lukmanier Pass area (central Swiss Alps) was examined through a detailed analysis of three-dimensional geometry, chemical zoning and crystallographic orientation. The first population, collected in the hinge of a chevron-type fold, shows an apparent rotation of 360 degrees. The first 270 degrees are characterized by spiral-shaped inclusion trails, gradual and concentric Mn zoning and a single crystallographic orientation, whereas in the last 90 degrees, crenulated inclusion trails and secondary Mn maxima centred on distinct crystallographic garnet domains are observed. Microstructural, geochemical and textural data indicate a radical change in growth regime between the two growth sequences. In the first 270 degrees, growth occurred under rotational non-coaxial flow, whereas in the last 90 degrees, garnet grew under a non-rotational shortening regime. The second population, collected in the limb of the same chevron-type fold structure, is characterized by a spiral geometry that does not exceed 270 degrees of apparent rotation. These garnet microstructures do not record any evidence for a modification of the stress field during garnet growth. Concentric Mn zoning as well as a single crystallographic orientation are observed for the entire spiral. Electron backscatter diffraction data indicate that nearly all central domains in the snowball garnet are characterized by one [001] axis oriented (sub-)parallel to the symmetry axis and by another [001] axis oriented (sub-)parallel to the orientation of the internal foliation. These features suggest that the crystallographic orientation across the garnet spiral is not random and that a relation exists among the symmetry axis, the internal foliation and the crystallographic orientation.
Keywords
electron backscatter diffraction, lukmanier, snowball garnet, tomography
Create date
03/07/2009 14:01
Last modification date
21/07/2022 6:10