Discovery of organic-rich black shale xenolith from kimberlite on the Hall Peninsula, Nunavut and its implication for petroleum potential in Cumberland Sound

Abstract

The Chidliak kimberlite province covers an area of 40 × 70 km on the eastern Hall Peninsula, southeastern Baffin Island, Nunavut, between Frobisher Bay and the Cumberland Sound (Fig. 1). The eastern Hall Peninsula is an Archean gneissic terrain, into which all the Late Jurassic–Early Cretaceous aged kimberlites (156.7–139.1 Ma; Heaman et al., 2012) intruded. At present, there is no consolidated Phanerozoic sedimentary cover on the Hall Peninsula; however, a great number of sedimentary rock xenoliths yielding conodont microfossils were entrained by the kimberlites. These xenoliths suggest that Upper Ordovician and Lower Silurian strata with a total thickness about 270–305 m were present on the Hall Peninsula at least until Early Cretaceous time (Zhang and Pell, 2013; 2014). Figure 1 A). Simplified geologic map of the Foxe Basin and vicinity (modified from Wheeler et al., 1997), showing the location of the Chidliak project area (red polygon), the drill hole CHI-482-10-DD01 with the black shale xenolith (red star), suspect natural hydrocarbon seep (yellow dots; location data from Budkewitsch et al., 2013) and Paleozoic (black cross) and Mesozoic (red cross) cores collected by shallow drillings during 1970s and 1980s (location data from Zhang, 2013a). B). Enlargement of the area enclosed by black rectangle in (A). Cumberland Sound, to the northeast, is partially underlain by Cretaceous clastic and Paleozoic carbonate sedimentary rocks (Fig. 1; MacLean et al., 1986). On the sea surface of Cumberland Sound, 28 suspect natural hydrocarbon seep occurrences were identified (Fig. 1; Budkewitsch et al., 2013), indicating an active petroleum system may occur in the sound; however, the source rocks remain uncertain. A rare black shale xenolith (Fig. 2A) was discovered from a kimberlite on the Hall Peninsula. Given the geologic and geographic position of the peninsula, it provides valuable evidence about the possible existence of an active …