Listric normal faulting during postorogenic extension revealed by 40Ar/39Ar thermochronology near the Robertson Lake shear zone, Grenville orogen, Canada
Article Abstract:
The argon isotope cooling ages of the hornblendes of the Robertson Lake shear zone, Grenville orogen, Canada, show that the area has had uniform unroofing since 950 Ma. The orogen separates the Mazinaw and Sharbot Lake areas. The Mazinaw area underwent slow cooling after maximum metamorphosis, followed by rapid cooling and then slow cooling. The Sharbot Lake area underwent slow cooling after metamorphosis followed by rapid cooling. The hanging wall adjacent to the shear zone was unroofed from the deep crust before the wall away from the shear zone.
Publication Name: Tectonics
Subject: Earth sciences
ISSN: 0278-7407
Year: 1996
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Comparison of garnet-biotite, calcite-graphite, and calcite-dolomite thermometry in the Grenville Orogen; Ontario, Canada
Article Abstract:
Consistency was noted with regards to temperatures taken from matrix biotites paired prograde garnet near-rim analysis and those taken using calcite-graphite thermometry. However, occassional occurence of low temperatures were recorded with calcite-graphite thermometry. Such occurrence can be attributed to the absence of equilibration of anomalously light graphite. Temperatures that are higher than those taken from calcite-dolomite can be obtained from amphibolite facies rocks with use of calcite-graphite and garnet-biotite systems.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1999
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Differential unroofing within the Central Metasedimentary Belt of the Grenville Orogen: constraints from 40Ar/39Ar thermochronology
Article Abstract:
Thermochronological analysis of rock samples from the Central Metasedimentary Belt (CMB) in Ontario was undertaken to investigate the pattern of isotopic argon cooling and to study the tectonic history of the area. CMB underwent a considerable differential unroofing as inferred from the incremental argon release spectrum. The older argon cooling ages observed along the southeast border of northeast shear zones, on the other hand, are indicative of displacement resulting from extensional deformation.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1992
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