Extension in the Central Metasedimentary Belt of the Ontario Grenville: Timing and tectonic significance

Abstract

Research Article| February 01, 1989 Extension in the Central Metasedimentary Belt of the Ontario Grenville: Timing and tectonic significance Ben A. van der Pluijm; Ben A. van der Pluijm 1Department of Geological Sciences, University of Michigan, 1006 C.C. Little Building, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar Katherine A. Carlson Katherine A. Carlson 1Department of Geological Sciences, University of Michigan, 1006 C.C. Little Building, Ann Arbor, Michigan 48109 Search for other works by this author on: GSW Google Scholar Author and Article Information Ben A. van der Pluijm 1Department of Geological Sciences, University of Michigan, 1006 C.C. Little Building, Ann Arbor, Michigan 48109 Katherine A. Carlson 1Department of Geological Sciences, University of Michigan, 1006 C.C. Little Building, Ann Arbor, Michigan 48109 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1989) 17 (2): 161–164. https://doi.org/10.1130/0091-7613(1989)017<0161:EITCMB>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Ben A. van der Pluijm, Katherine A. Carlson; Extension in the Central Metasedimentary Belt of the Ontario Grenville: Timing and tectonic significance. Geology 1989;; 17 (2): 161–164. doi: https://doi.org/10.1130/0091-7613(1989)017<0161:EITCMB>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A laterally extensive zone of southeast-dipping marble mylonites in the Central Metasedimentary Belt (CMB) of the southern Ontario Grenville (the "Bancroft shear zone") records southeast-directed extension and a displacement of about 10-12 km. Calcite-graphite carbon isotope thermometry indicates that the maximum temperature at which shearing occurred was ca. 450 °C. In contrast, carbon isotope fractionations (Δ13Ccc-gr) within the marble protolith consistently give temperatures of 650-700 °C. The Bancroft shear zone postdates 1060 Ma and older high-grade shear zones in the Central Gneiss Belt and the CMB that are associated with northwest-directed thrusting. Comparison of the temperature data from the retrograde marble mylonites with cooling curves for the CMB gives a late Grenvillian age range of 935-1010 Ma for the extensional event. The geometric relation between thrusting and normal faulting in the CMB is comparable to that in parts of the Himalayas and southern Tibet, and similarly we interpret late normal faulting in the CMB to be a result of gravitational collapse of a thrust thickened crust. In contrast to the Himalaya-Tibet region, however, accretion in the Grenville becomes older in the direction of regional thrusting. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.