Reconnaissance geochronology of the crystalline basement rocks of the Coastal Cordillera of southern Peru

Research Article| February 01, 1977 Reconnaissance geochronology of the crystalline basement rocks of the Coastal Cordillera of southern Peru E. J. COBBING; E. J. COBBING 1Institute of Geological Sciences, 154 Clerkenwell Road, London EC1R 5DU, England Search for other works by this author on: GSW Google Scholar J. M. OZARD; J. M. OZARD 2Defence Research Establishment Pacific, Fleetmail Office, Victoria, B.C., Canada Search for other works by this author on: GSW Google Scholar N. J. SNELLING N. J. SNELLING 3Institute of Geological Sciences, 64/78 Gray's Inn Road, London WC1X 8NG, England Search for other works by this author on: GSW Google Scholar Author and Article Information E. J. COBBING 1Institute of Geological Sciences, 154 Clerkenwell Road, London EC1R 5DU, England J. M. OZARD 2Defence Research Establishment Pacific, Fleetmail Office, Victoria, B.C., Canada N. J. SNELLING 3Institute of Geological Sciences, 64/78 Gray's Inn Road, London WC1X 8NG, England Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1977) 88 (2): 241–246. https://doi.org/10.1130/0016-7606(1977)88<241:RGOTCB>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation E. J. COBBING, J. M. OZARD, N. J. SNELLING; Reconnaissance geochronology of the crystalline basement rocks of the Coastal Cordillera of southern Peru. GSA Bulletin 1977;; 88 (2): 241–246. doi: https://doi.org/10.1130/0016-7606(1977)88<241:RGOTCB>2.0.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 SocietyGSA Bulletin Search Advanced Search Abstract Granulite-facies gneiss of the Arequipa massif extensively developed along the Coastal Cordillera of southern Peru gives a whole-rock isochron age of 1,811 ± 39 m.y. (λ 87Rb = 1.47 × 10−11yr−1) and an initial 87Sr/86Sr ratio of 0.7086 ± 0.0009. Migmatitic granite within the gneiss is probably of late Precambrian or early Paleozoic age. Mineral ages, both K-Ar and Rb-Sr, from the gneisses and granites are disturbed. Potassium feldspar from the gneiss appears to have been reset by the migmatitization event, whereas mica and potassium feldspar from the migmatitic granite appear to reflect established tectonic-thermal events of Late Devonian and Late Triassic time.In both metamorphic grade and age pattern, these rocks are similar to those of the Trans-Amazonian nucleus of the Guianas, Brazil, Uruguay, and the Buenos Aires province of Argentina. We suggest that the Arequipa massif has always been an integral part of the Trans-Amazonian nucleus and that the Andean belt is ensialic, at least in Peru. The manner in which the structural trends in the Arequipa massif strike into the Pacific Ocean leads to speculation concerning the evolution of the Pacific. Simple rifting, tectonic erosion, and major transcurrent faulting are considered as possible mechanisms to explain the truncation. This content is PDF only. Please click on the PDF icon to access. 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.