Journal article
Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia
Lithos, Vol.134-135, pp.91-107
03/2012
DOI: 10.1016/j.lithos.2011.12.008
Abstract
Northern Idaho contains Belt-Purcell Supergroup equivalent metamorphic tectonites that underwent two regional deformational and metamorphic events during the Mesoproterozoic. Garnet-bearing pelitic schists from the Snow Peak area of northern Idaho yield Lu–Hf garnet-whole rock ages of 1085±2Ma, 1198±79Ma, 1207±8Ma, 1255±28Ma, and 1314±2Ma. Garnet from one sample, collected from the Clarkia area, was micro-drilled to obtain separate core and rim material that produced ages of 1347±10Ma and 1102±47Ma. The core versus rim ages from the micro-drilled sample along with the textural and spatial evidence of the other Lu–Hf garnet ages indicate two metamorphic garnet growth events at ~1330Ma (M1) and ~1080Ma (M2) with the intermediate ages representing mixed ages. Some garnet likely nucleated and grew M1 garnet cores that were later overgrown by younger M2 garnet rims. Most garnet throughout the Clarkia and Snow Peak areas are syntectonic with a regional penetrative deformational fabric, preserved as a strong preferred orientation of metamorphic matrix minerals (e.g., muscovite and biotite). The syntectonic garnets are interpreted to represent one regional, coeval metamorphic and deformation event at ~1080Ma, which overlaps in time with the Grenville Orogeny. The older ~1330Ma ages may represent an extension of the East Kootenay Orogeny described in western Canada. These deformational and metamorphic events indicate that western Laurentia (North America) was tectonically active in the Mesoproterozoic and during the assembly of the supercontinent Rodinia.
► Northern Idaho contains Belt Supergroup equivalent metamorphic tectonites. ► This study utilized Lu–Hf garnet geochronology and porphyroblast–fabric relationships. ► The Belt Supergroup underwent two episodes of Proterozoic deformation and metamorphism. ► M1 metamorphism and D1 deformation occurred in the Belt Supergroup at 1.4–1.3Ga. ► Grenvillian age (1.1–1.0Ga) metamorphism (M2) and deformation (D2) overprinted M1/D1.
Details
- Title: Subtitle
- Mesoproterozoic syntectonic garnet within Belt Supergroup metamorphic tectonites: Evidence of Grenville-age metamorphism and deformation along northwest Laurentia
- Creators
- Timothy O Nesheim - Washington State UniversityJeffrey D Vervoort - Washington State UniversityWilliam C McClelland - University of IowaJane A Gilotti - University of IowaHelen M Lang - West Virginia University
- Resource Type
- Journal article
- Publication Details
- Lithos, Vol.134-135, pp.91-107
- Publisher
- Elsevier B.V
- DOI
- 10.1016/j.lithos.2011.12.008
- ISSN
- 0024-4937
- eISSN
- 1872-6143
- Grant note
- DOI: 10.13039/100005720, name: Geological Society of America; name: Tobacco Root Geological Society; DOI: 10.13039/100008893, name: University of Iowa; name: National Science Foundation, award: EAR-0711326, EAR-0755392, EAR-0710939
- Language
- English
- Date published
- 03/2012
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229179602771
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