Radiogenic isotope studies of crust-forming processes in the Lofoten-Vesterålen province of north NorwayReportar como inadecuado




Radiogenic isotope studies of crust-forming processes in the Lofoten-Vesterålen province of north Norway - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Reference: Wade, Stephen James Rochfort., (1985). Radiogenic isotope studies of crust-forming processes in the Lofoten-Vesterålen province of north Norway. Dphil. University of Oxford.Citable link to this page:

 

Radiogenic isotope studies of crust-forming processes in the Lofoten-Vesterålen province of north Norway

Abstract: The Lofoten-Vesterålen province of North Norway consists almostexclusively of Precambrian granulite-facies rocks. The oldest rocksin the province are monzonitic and dioritic migmatitic gneisses, theprotoliths of which were formed at 2.7 Ga.The migmatites are overlain by a series of supracrustal gneisses,from 2.1 Ga, largely volcanogenic in origin, but with interbedded marblesand banded ironstones. The first occurrence of marble in western Lofotenis reported. Deposition in a subsiding back-arc basin or in an Andean-type environment on a thin continental margin is inferred.Both gneiss sequences were intruded by basic rocks at 1.8 Ga. Thebasic rocks could not have been formed simply by extraction from the mantleat 1.8 Ga. The required contribution from 2.7 Ga migmatites could be asmuch as 37%, but less if contamination took place via anatectic melts.The first report of eclogitic rocks from the Lofoten-Vesterålen provinceis made in this study; their formation is associated with shear deformationBoth gneiss sequences and the basic rocks were intruded by mangeriticrocks at 1.8 - 1.7 Ga. Their chemical compositions can be explained byfractional crystallization from magmas formed from 2.7 Ga and 2.1 Gagneisses and 1.8 Ga mantle-derived magmas. Parameters derived from Rb-Sr,Sm-Nd and U-Pb systems to express the relative proportions of crust andmantle contributions to the mangerites mutually correlate, supportingthe crust-mantle source model for the mangerites. Mixing calculationssuggest that the late Archaean contributes in excess of 50% by mass foralmost all mangerites.Anatectic veins present, especially in the Moskenesøy supracrustalgneisses, are inferred to represent partial melts which coalesced toform the mangerites at higher structural levels. Anatexis was causedby basaltic underplating associated with limited crustal extension.Later rock-forming events were the emplacement of dolerite dykes;the 1.65 Ga Lødingen Granite; the Leknes Group metasediments and theCaledonian granite pegmatites.

Type of Award:Dphil Level of Award:Doctoral Awarding Institution: University of Oxford Notes:The digital copy of this thesis has been made available thanks to the generosity of Dr Leonard Polonsky

Contributors

Taylor, P. N.More by this contributor

RoleSupervisor

 

Dr. Paul TaylorMore by this contributor

RoleSupervisor

 Bibliographic Details

Issue Date: 1985Identifiers

Urn: uuid:d57ed241-b1c8-4502-8ee5-8de8be20d80e

Source identifier: 603746127

Source identifier: 602817674 Item Description

Type: Thesis;

Language: eng Subjects: Norway Lofoten (Norway) Isotope geology Granulite Geology, Stratigraphic Migmatite Earth Crust Tiny URL: td:603746127

Relationships





Autor: Wade, Stephen James Rochfort. - institutionUniversity of Oxford facultyMathematical and Physical Sciences Division - - - - Contri

Fuente: https://ora.ox.ac.uk/objects/uuid:d57ed241-b1c8-4502-8ee5-8de8be20d80e



DESCARGAR PDF




Documentos relacionados