Documents disponibles écrits par cet auteur

A sulphur isotope study of the Caledonian granites of Britain and Ireland / Rabah Laouar 

Public ISBD Titre : A sulphur isotope study of the Caledonian granites of Britain and Ireland Type de document : texte imprimé Auteurs : Rabah Laouar, Auteur ; Bernard E. Leake, Directeur de thèse ; Colin Farrow, Directeur de thèse Editeur : Glasgow : University of Glasgow Année de publication : 1987 Importance : 130 f. Présentation : ill. Format : 27 cm. Note générale : Mémoire de Master : Génie Minier : Ecosse, University of Glasgow : 1987 Bibliogr. f. 131 - 144 Langues : Anglais (eng) Mots-clés : Caledonian  granites S-type  granites I-type  granites Sulphur  isotopes Dalradian Index. décimale : Ms00187 Résumé : The Caledonian fold belt is thought to have formed as a result of the closure of the 'Iapetus' ocean basin during Lower Palaeozoic times. Granitic magmas were intruded into Precambrian and Lower Palaeozoic country rocks between approximately 640 and 390 Ma. Most important, spatially and volumetrically, are the late Caledonian granites, the 'Newer' and 'Last' granites of Read. In general, the late Caledonian granites have the calc-alkaline characteristics typical of plutonic rocks emplaced at destructive plate margins. They range in composition from diorite and tonalite, through granodiorute, to peraluminous granite with chemical variation continuous among the various rock types. Petrographically and chemically, the granitoids span the range from S 'sedimentary' to I 'igneous' types as defined by Chappell and White, with no discernible geographical pattern to their distribution. There have been few sulphur isotope studies on primary sulphides in granites; yet such data have considerable potential in understanding the petrogenesis; that is in terms of granites derived either from igneous or metasedimentary protoliths. From about 50 British and Irish Caledonide granites, including both 'Newer' and 'Older' intrustions, conventional separation techniques have yielded sulphide separates from only 19 granites for analyses. Mineralogical, the sulphides consist of maily pyrite and pyrrhotite, although chalcopyrite is present in a few intrusions. It was noticeable that granites with high δ¹⁸0 and high initial ⁸⁷Sr/⁸⁶Sr yielded very little sulphides. Sulphur isotope analyses of coexisting sulphide minerals are also useful as a geothermometer as long as the sulphide-bearing phases are in equilibrium. The putative temperature of formation of two coexisting mineral pairs from the Oughterard granite has been calculated; 418°C from a pyrite-pyrrhotite pair and 441°C from a pyrite-chalcopyrite pair. The results of sulphur isotope analyses coupled with the above geochemical and isotopic parameters have proved useful in understanding granite genesis, and hence distinguishing the Caledonian intrusions in terms of precursor protolith. A sulphur isotope study of the Caledonian granites of Britain and Ireland [texte imprimé] / Rabah Laouar, Auteur ; Bernard E. Leake, Directeur de thèse ; Colin Farrow, Directeur de thèse . - Glasgow : University of Glasgow, 1987 . - 130 f. : ill. ; 27 cm. Mémoire de Master : Génie Minier : Ecosse, University of Glasgow : 1987 Bibliogr. f. 131 - 144 Langues : Anglais (eng) Mots-clés : Caledonian  granites S-type  granites I-type  granites Sulphur  isotopes Dalradian Index. décimale : Ms00187 Résumé : The Caledonian fold belt is thought to have formed as a result of the closure of the 'Iapetus' ocean basin during Lower Palaeozoic times. Granitic magmas were intruded into Precambrian and Lower Palaeozoic country rocks between approximately 640 and 390 Ma. Most important, spatially and volumetrically, are the late Caledonian granites, the 'Newer' and 'Last' granites of Read. In general, the late Caledonian granites have the calc-alkaline characteristics typical of plutonic rocks emplaced at destructive plate margins. They range in composition from diorite and tonalite, through granodiorute, to peraluminous granite with chemical variation continuous among the various rock types. Petrographically and chemically, the granitoids span the range from S 'sedimentary' to I 'igneous' types as defined by Chappell and White, with no discernible geographical pattern to their distribution. There have been few sulphur isotope studies on primary sulphides in granites; yet such data have considerable potential in understanding the petrogenesis; that is in terms of granites derived either from igneous or metasedimentary protoliths. From about 50 British and Irish Caledonide granites, including both 'Newer' and 'Older' intrustions, conventional separation techniques have yielded sulphide separates from only 19 granites for analyses. Mineralogical, the sulphides consist of maily pyrite and pyrrhotite, although chalcopyrite is present in a few intrusions. It was noticeable that granites with high δ¹⁸0 and high initial ⁸⁷Sr/⁸⁶Sr yielded very little sulphides. Sulphur isotope analyses of coexisting sulphide minerals are also useful as a geothermometer as long as the sulphide-bearing phases are in equilibrium. The putative temperature of formation of two coexisting mineral pairs from the Oughterard granite has been calculated; 418°C from a pyrite-pyrrhotite pair and 441°C from a pyrite-chalcopyrite pair. The results of sulphur isotope analyses coupled with the above geochemical and isotopic parameters have proved useful in understanding granite genesis, and hence distinguishing the Caledonian intrusions in terms of precursor protolith.

Exemplaires

Code-barres	Cote	Support	Localisation	Section	Disponibilité	Spécialité	Etat_Exemplaire
Ms00187	Ms00187	Papier	Bibliothèque centrale	Mémoire de Master	Disponible

Documents numériques

LAOUAR.Rabah.pdf URL