STRATIGRAPHY AND GEOCHEMISTRY OF LATE DEVONIAN TO EARLY CARBONIFEROUSVOLCANIC-ROCKS OF THE NORTHERN CHIGNECTO PENINSULA, COBEQUID HIGHLANDS, NOVA-SCOTIA

The volcanic succession of the Fountain Lake Group of the northern Chi gnecto peninsula consists of basalt and andesite flows, rhyolite shall ow intrusions and minor flows, and rhyolitic pyroclastic rocks. Fault scarp breccia, fluvial conglomerate and sandstone, and lacustrine silt stone and minor limestone are interbedded with the volcanic rocks. The succession is cut by mafic dykes, some of which predate and others po stdating brittle north-vergent thrusting. Detailed geochemical and pet rographic study shows that the volcanic rocks geochemically resemble t he plutonic rocks of the Cape Chignecto pluton that are thrust over th e volcanic succession. Diabase dykes may record the contamination of g abbroic magma by residual base-of-crust plagioclase-pyroxene granulite from which felsic magma had been extracted. Fractionation of this maf ic magma resulted in enrichment in incompatible elements in some dykes . Andesites evolved from basaltic parents either by fractionation or b y melting of hydrous gabbros. Much of the volcanic succession shows lo w-temperature alteration including silicification.