The stratigraphy, structure and petrochemistry of the Clode Sound map area, northwestern Avalon Zone, Newfoundland

Hussey, Eric Maurice (1979) The stratigraphy, structure and petrochemistry of the Clode Sound map area, northwestern Avalon Zone, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Clode Sound map area (Lat. 48°15’N, 48°39’N and Long. 54°00’W, 54°13’W) is underlain by portions of three major units of late Precambrian age which dominate the northwestern Avalon Zone. They include sedimentary, volcanic, and intrusive rocks of the Love Cove, Connecting Point, and Musgravetown Groups, and the Georges Pond pluton. These rocks form a number of alternating, north trending fault-bounded belts. -- The Love Cove Group has been informally redefined to include some of the sedimentary and volcanic rocks previously referred to the Musgravetown Group (Widmer, 1949; Jenness, 1963) with which it is conformable. The redefined Love Cove Group is divided into three formations. In ascending stratigraphic order these include: -- 1. White Point Formation - a sequence of deformed dominantly pyroclastic subaqueous (?) to subaerial volcanic rocks ranging from basalt to rhyolite in composition, which are intruded by a comagmatic pluton (Georges Pond pluton). -- 2. Thorburn Lake formation - a sequence of variably deformed siltstones, greywackes and related volcanic rocks up to 1300 meters thick which overlie, and are partially equivalent to, the White Point Formation. -- 3. Southwest River Formation (Musgravetown Group of Jenness, 1963) - a subaerial basalt - rhyolite volcanic assemblage and an associated sequence of alluvial-fluviatile sedimentary rocks 1280 meters thick. -- The Connecting Point Group, only locally examined, includes thin bedded marine siltstone and slate. It may be equivalent to portions of the Love Cove Group. The Musgravetown Group, in its type area, unconformably overlies the connecting point Group. It includes in ascending order: 1. The Cannings Cove Formation (530 meters) - locally derived fanglomerates, sandstones and basalt flows. 2. Clode Sound Formation (Bull Arm Formation of Jenness, 1963) (800-2300 meters): subaerial basalt/pantellerite volcanic sequence, and 3. Charlottetown Formation: fluviatile red beds. -- The Georges Pond pluton is genetically related to the White Point Formation; both appear to have a continental calcalkaline geochemistry. Volcanic rocks of the Southwest River Formation appear mildly alkaline. They may be equivalent to the Clode Sound Formation which includes peralkaline alilicic volcanic rocks and alkali basalts. -- The major structure of the Love Cove Group trends north and is dominated by isoclinal folding with steeply dipping axial surfaces, with development of a penetrative foliation, in the lower portions of the section. In the west, the rocks are overturned to the east and tightly folded. The upper portions of the section show more open folding with only poor fabric development. Two major faults in the area have juxtaposed contrasting structural levels or domains. The principal deformation (F₁) of the Love Cove Group was Palaeozoic, probably Acadian, in age. It is not clear how structures in the Connecting Point Group relate to those in the Love Cove Group. -- Metamorphic grades in the field area vary from greenschist in the lower portions of the section, to prehnite pumpellyite facies at higher stratigraphic levels. -- The lithostratigraphic units in the map area are similar in both petrography and chemistry to, and can be correlated with equivalent units in other parts of the western Avalon Zone.

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