Geology, petrology and geochemistry of the Hermitage Peninsula, Southern Newfoundland

• Main Author: O'Driscoll, Cyril F. (Cyril Francis)
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1977
• Subjects: Tickle; Long Harbour; Island Harbour; Tickle Point; Newfoundland
• Online Access: https://research.library.mun.ca/6856/; https://research.library.mun.ca/6856/1/CyrilFrancisODriscoll.pdf; https://research.library.mun.ca/6856/3/CyrilFrancisODriscoll.pdf

The Hermitage Peninsula, at the southwestern extremity of the Avalon Zone in Newfoundland is underlain by a late Precambrian conformable succession of volcanic and sedimentary rocks named the Connaigre Bay Group which is subdivided into four formations: a lowest formation of corundum-normative and garnet-bearing acidic volcanic rocks (Tickle Point Formation), a sedimentary sequence (Great Island Formation), a formation of sub-alkaline mafic volcanic rocks (Doughball Point Formation) and at the top a sequence of red sandstones, conglomerates and shales (Down's Point Formation). -- Igneous rocks which intrude the Connaigre Bay Group include a hornblende-rich gabbroic-granitic intrusion (Hermitage Complex) and a granitic intrusion (Straddling Granite). These plutonic rocks are chemically similar to the volcanic rocks, which along with field and petrographic evidence suggests that they are related. The assemblage is classified as a bimodal calc-alkaline suite dominated by amphibole fractionation. -- The late Precambrian Hermitage-Connaigre Bay assemblage, and the presumed correlative Simmons Brook Batholith and Long Harbour Group about 10 kilometres to the east, are intruded by Upper Devonian - Lower Carboniferous homogeneous granitic plutons, the Pass Island, Harbour Breton and Belleoram stocks. They are readily distinguished from the older calc-alkaline suite both petrographically and chemically, especially by their higher alkalies and associated trace elements. -- These relatively undeformed rocks of the Avalon Zone are juxtaposed against deformed granitic rocks of the Gander Zone by the Hermitage Bay Fault. The fault is characterized by a 50-100 metre wide zone of brecciation with the main movement having a reverse southeastward component. This movement is post-Ordovician and possibly Devonian, but the Hermitage Bay Fault does not represent the original structure which marked the boundary between the two zones.