Petrology of the Mavillette Intrusion Digby County, Nova Scotia
DOI:
https://doi.org/10.4138/1386Abstract
The Mavillette Intrusion is a small gabbroic body located in Digby County, southwestern Nova Scotia. It is dyke-like in form, trending about 150°, with a strike length of at least 1250 m and a width of about 100 m. The igneous mineralogy includes oligoclase-andesine and augite, with accessory magnetite, ilmenite, and apatite, but the intrusion has undergone variably intense alteration/low-grade metamorphism and shearing, and secondary minerals are abundant. In chemical composition the intrusion is highly evolved but probably of continental tholeiitic affinity. It differs from other mafic igneous rocks of southern Nova Scotia, but on the basis of geographic location, mineralogy, and chemistry is considered to be related to the volcanic rocks of the White Rock Formation in the Cape St. Mary's — Yarmouth area. This correlation implies a late Ordovician— early Silurian age for the intrusion. RÉSUMÉ L'intrusion Mavillette est une petite masse gabbrolque située dans le comte de Digby au sud-ouest de la Nouvelle-Écosse. Elle adopte la forme d'un dyke d'une largeur d'environ 100 m et suit une direction d'aziraut 150 sur, une longueur d'au molns 1250 m. La minéralogie ignée comprend des plagioclases (oligoclase-andesine) et de l’augite, avec comme minéraux accessoires de la magnétite, de l’ilménite et de l’apatite. Les minéraux secondaires sont très abondants car l’intrusion à subi les effets varies d'une altération intense et d'un métamorphisme léger, accompagnfis d'un cisalllement. La composition chimique de l’intrusion est très développée mais reflète probablement une affinite tholèiitique continentale. L'intrusion différe des autres roches ignées mafiques du sud de la Nouvelle-Écosse, mais de par sa situation géographique, sa minéralogie et sa chimie, on la considére reliée aux roches volcaniques de la formation White Rock qu'on retrouve dans la région de Cape St. Mary's - Yarmouth. Cette corrélation donne à l'intrusion un âge allant de l'Ordovicien tardif au début du Silurien. [Traduit par le journal)Downloads
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