Hercynian orogeny in the Montagne Noire (France): Application of Rb87-Sr87 systematics

Abstract

Research Article| October 01, 1976 Hercynian orogeny in the Montagne Noire (France): Application of Rb87-Sr87 systematics J. HAMET; J. HAMET 1Laboratoire de Géochimie et Cosmochimie, Institut de Physique du Globe, Université de Paris VI, 4 Place Jussieu, 75230 Paris, France Search for other works by this author on: GSW Google Scholar C. J. ALLÈGRE C. J. ALLÈGRE 2Départment des Sciences de la Terre, Université de Paris VII, 4 Place Jussieu, 75230 Paris, France Search for other works by this author on: GSW Google Scholar Author and Article Information J. HAMET 1Laboratoire de Géochimie et Cosmochimie, Institut de Physique du Globe, Université de Paris VI, 4 Place Jussieu, 75230 Paris, France C. J. ALLÈGRE 2Départment des Sciences de la Terre, Université de Paris VII, 4 Place Jussieu, 75230 Paris, France Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1976) 87 (10): 1429–1442. https://doi.org/10.1130/0016-7606(1976)87<1429:HOITMN>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 MailTo Tools Icon Tools Get Permissions Search Site Citation J. HAMET, C. J. ALLÈGRE; Hercynian orogeny in the Montagne Noire (France): Application of Rb87-Sr87 systematics. GSA Bulletin 1976;; 87 (10): 1429–1442. doi: https://doi.org/10.1130/0016-7606(1976)87<1429:HOITMN>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 The Rb87-Sr87 whole-rock isochrons of Hercynian granites in the Montagne Noire (southern Massif Central, France) show that two different episodes of granitization occurred during Hercynian time: early alkalic granites were emplaced 340 to 330 m.y. ago, and calc-alkalic granites were emplaced 290 to 280 m.y. ago. The Hercynian orogeny may have occurred between 340 and 270 m.y. ago in this area. Tectonic phases are apparently confined to the beginning of the orogenesis and are short compared to the total lapse of time of the orogeny.The Sr87/Sr86 initial ratios of the granites and of surrounding crustal rocks allow us to put some limitations on the relative amounts of mantle-derived material in each granitic type. The early granites represent remobilized continental crust, whereas in the later ones the mantle contribution increases with time. The mantle-derived material is presumed to be a highly differentiated product, probably of a dioritic composition.Rb and Sr concentrations are used as tracers to test models of granite genesis, equilibrium partial melting, and (or) fractional crystallization. The mineral isochrons reveal that no important thermal event occurred after the Hercynian episode. The youngest rehomogenization is dated at 280 to 290 m.y. ago. A temperature-time curve summarizes the Hercynian orogeny and represents an attempt to connect the tectonic phases with periods of granitization and metamorphism. 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.