Rb-Sr Whole-Rock Chronology of Caledonian Events in Northeast Scotland

Research Article| March 01, 1974 Rb-Sr Whole-Rock Chronology of Caledonian Events in Northeast Scotland R. J. PANKHURST R. J. PANKHURST 1Department of Geology and Mineralogy, University of Oxford, Parks Road, Oxford OX1 3PR, England Search for other works by this author on: GSW Google Scholar Author and Article Information R. J. PANKHURST 1Department of Geology and Mineralogy, University of Oxford, Parks Road, Oxford OX1 3PR, 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 (1974) 85 (3): 345–350. https://doi.org/10.1130/0016-7606(1974)85<345:RWCOCE>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 R. J. PANKHURST; Rb-Sr Whole-Rock Chronology of Caledonian Events in Northeast Scotland. GSA Bulletin 1974;; 85 (3): 345–350. doi: https://doi.org/10.1130/0016-7606(1974)85<345:RWCOCE>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 Rb-Sr whole-rock isochrons are presented for four late Caledonian granites from northeast Scotland. These isochrons are believed to define a single 460–m.y. B.P. magmatic event, which caused isotopic homogenization of strontium on a whole-rock scale in slate of the Macduff Group, which is part of the Upper Dalradian Series intruded by the granites. The geochronology of the region supports the suggestion that all Caledonian deformation and metamorphism took place during a relatively short episode between the Early Ordovician sedimentation of the Upper Dalradian Series and the Middle to Late Ordovician granitic magmatism.A premetamorphic granite at Portsoy, which intrudes strata of the Middle Dalradian Series, yields a Precambrian isochron age of 669 ± 17 m.y. This is probably a late or postorogenic granite related to a pre-Caledonian metamorphism already recognized within the Moine Series. This Precambrian age cannot be used to support a recent hypothesis in which the Older basic igneous rocks of northeast Scotland are related to a Cambrian(?) subduction zone.All the granitic rocks of northeast Scotland have initial Sr87/Sr86 ratios of 0.714 to 0.717, irrespective of age. This indicates that the granites are derived from a deep, underlying crustal layer, possibly Lewisian (Precambrian) gneiss, and not from the mantle or subducted oceanic lithosphere. 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.