GEOSCAN, résultats de la recherche


TitreStructural and tectonic controls on Devonian intrusion related mineralisation on the Connaigre Peninsula
AuteurRuberti, G; Rogers, N; Kellet, D; van Staal, C; Hanchar, J
SourceL'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 37, 2014 p. 238-239
LiensOnline - En ligne (PDF 8.75 MB)
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130603
RéunionGAC-MAC Joint annual meeting; Fredericton, NB; CA; mai 2014
Documentpublication en série
Mediaen ligne; numérique
Lat/Long OENS -56.0000 -55.5000 47.7500 47.5000
Sujetsgisements minéraux; tungstène; molybdène; étain; minéralisation; interpretations structurelles; modèles tectoniques; milieux tectoniques; éléments tectoniques; molybdenite; Granite de Belleoram ; géologie structurale; tectonique; Dévonien
ProgrammeÉtude des gîtes porphyriques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
The Canadian Appalachians represent an archetypal ancient, accretionary orogen the study of which has played a substantial role in developing modern geological concepts. From the initial simplistic models of a mountain belt deriving from the closure of the Iapetus Ocean, our understanding has evolved, recognising a richer, more complex geological history. Current models define multiple collisions between arcs and microcontinents due to the closures of interposed oceans and seaways. Delineating specific tectonic events provides context to the various periods and styles of mineralisation produced, which in turn can define new exploration models for the next generation of deposits.
One of the least understood deposit types in the Canadian Appalachians are the Devonian granitoid intrusion-related Sn -- W -- Mo mineralisation. The Connaigre Peninsula was selected to study such deposits as it contains a variety of supracrustal units plus (apparently) barren and mineralised intrusives within a relatively constrained and accessible area. The distributions of the main lithotectonic packages indicate three distinct tectonic blocks that were amalgamated by the Middle Devonian, and subsequently intruded by Upper Devonian granitoids concurrent with clastic sedimentation.
The c. 376 Ma Old Woman Stock contains several known Mo occurrences. Molybdenite is disseminated and associated with vugs containing dog-tooth quartz, and intense alteration zones (up to 5 cm wide) are localised along north -- south to north-west -- south-east trending joints. The distribution of deposits demonstrates a potential linkage between regional structures and the localisation of mineralisation. At the large scale, the Connaigre Peninsula in the Upper Devonian is interpreted to be in extension associated with far removed non-orthogonal accretion of other peri-Gondwanan elements to composite Laurentia. It is notable however that the mineralisation does not occur at a major fault, but rather at the intersection of a prominent northeast to south-west lineament and well-developed north -- south to north-west -- south-east jointing. The implication is that the high-angle intersection of breaks that are contemporaneous with intrusion but have relatively little motion provide ideal pathways for mineralising fluids. In contrast to the Old Woman Stock, the adjacent, approximately coeval to slightly younger Belleoram Granite is apparently barren. It remains unclear why the Belleoram Granite contains no known Sn - W - Mo mineralisation. Possible explanations include: i) its hybrid nature makes it compositionally unsuitable; ii) it formed at too shallow a crustal depth; or iii) it was too 'dry' and did not develop fluid pathways.