New Insights Into the Volcanic Margin Evolution of Northern Labrador and Hydrocarbon Prospectivity of Offshore Labrador

Abstract

The passive margin of Labrador is a rifted margin, which initiated during the Late Jurassic/Early Cretaceous as an off-axis segment of North Atlantic opening. Sea floor spreading ceased during the Late Eocene, leaving an inactive mid-ocean ridge between Labrador and Greenland. We utilize new, deep-penetration 2D-regional seismic data, which reveal evidence that the continental margin of northeastern Labrador was subject to intense magmatism during the time of rifting. Previous interpretations of the margin suggest that the presence of seaward dipping reflectors (SDRs) were emplaced via voluminous subaerial flows from the Proto-Icelandic Hotspot in the Davis Strait, north of the Labrador Sea. In this study we observe large rifted, half grabens of the continental margin that are in-filled with apparent SDRs which reach thicknesses of 6-7 km and show steep dip angles of 10-20°. Poly-phase units of SDRs overlie the outer limit of continental crust and transition to a domain of transitional, 8 km thick igneous crust. This transitional crust of volcanically-derived material occupies 53,000 km² and positions between the continental and oceanic domains. The presence of opposing SDRs is supportive of the on-axis emplacement of volcanic material detected on the conjugate margin of Greenland. Based on the employed geological model here, the evacuation of magma chamber below the sub-aerially emplaced SDRs, provides a mechanism for high-angle rotation and minor faulting. Continued depletion of volcanic material within the magma chamber and/or moving away thermal source eventually leads to oceanic crust with vertically-emplaced dykes. Our research shows that the previously interpreted origin of igneous material in the Labrador Sea is not associated with the northern magmatic hot-spot events; rather it was sourced from rift related magmatism at the continental margin in the South. Additionally, the presence of hydrocarbons has been proven at the Labrador Shelf area. It is probable that the same functioning petroleum system is present in the deepwater regions of Hopedale and Saglek Basins. Possible hydrocarbon plays consist of rifted basement structures (faulted horsts / half-grabens) and bright amplitudes terminated against fault flanks. Direct hydrocarbon indicators (DHIs) are present in the stratigraphic units as bright seismic amplitudes and gas chimneys. Bjarni (synrift) and Gudrid Formation (postrift) sandstones hold the best reservoir rock potential in the region.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016