Neoproterozoic Seal Cove intrusion from the Burin Peninsula, Newfoundland: geochemistry, geochronology, petrogenesis, tectonic settings and its relations to Avalonian arc-related volcanic rocks

The Neoproterozoic Seal Cove intrusion from the Burin Peninsula, southeastern Newfoundland (northwestern Appalachians) is hosted by a Neoproterozoic arc-related volcano-sedimentary belt. In the Burin Peninsula, the Avalonian belt is represented by the Marystown Group (610-570 Ma), a several km thick unit made up of felsic volcanic and volcaniclastic rocks with minor tholeiitic basaltic flows. The Seal Cove intrusion (< 5 km2 in area) is composed of tholeiitic gabbro and diorite with a minor granite. The U-Pb zircon age for the Seal Cove mafic rocks is 589.4± 2.8 Ma. The mantle-normalized plots exhibit negative anomalies of Nb and Ti. Their ɛNd(t) values (~-0.35) and initial Sr isotopic ratios (~0.7046) are indicative of the Avalonian subcontinental lithospheric mantle source accompanied by crustal contamination. The Seal Cove granite have a negative ɛNd(t) value (-4.2) and TDM ~1.6 Ga consistent with a derivation from Proterozoic continental crust by partial melting. Mafic rocks of the Marystown Group are continental margin arc tholeiitic basaltic rocks compositionally similar to the tholeiitic mafic rocks of the Seal Cove intrusion suggesting that their mantle sources were comparable and both are genetically related. Marystown rhyolites are peraluminous continental margin arc rocks generated by partial melting of the continental crust triggered by intrusions of mantle-derived basaltic magma. Unlike many continental calc-alkaline arc suites, both the Seal Cove intrusion and Marystown Group are distinctly bimodal, indicating a presence of a thin continental crust under this part of Avalonia and/or reducing conditions during mantle melting.