Geological interpretation of a high resolution reflection seismic survey at the Buchans mine, Newfoundland

Abstract

Sixteen kilometres of high resolution Vibroseis reflection seismic data have been acquired in the vicinity of the former Buchans mine. Direct identification of the cause of several reflectors is possible because the geology is tightly constrained by underground workings and drill holes both of which locally exceed 1 km depth. Many of the mine-scale thrust faults are imaged as reflectors but conformable and intrusive contacts generally responded poorly. A significant shallow-dipping thrust, the Powerline Fault, is recognized below the orebodies and traced throughout the Buchans area, primarily as a result of the seismic survey. It truncates ore stratigraphy and forms the floor thrust of a large duplex–stack, which hosts all the orebodies. Its presence has negative implications for exploration in the immediate mine area. Several lines of evidence suggest that this fault has a significant component of out-of-sequence movement. A strong reflector 4.5 km below Buchans is correlated with the surface expression of the Victoria River Delta Fault, an important regional structure, newly recognized southeast of Red Indian Lake. This shallow, north-dipping sole thrust forms the structural base of the Buchans Group and brings it above a younger fossiliferous Llanvirn volcanic sequence. This fault is not itself the Red Indian Line but is one of a series of faults that collectively effect substantial geological contrasts in central Newfoundland. The seismic survey was a cost-efficient means of gaining knowledge of Buchans structure, which might otherwise have been acquired at much higher cost and over a longer period of time.

Microstructure, metamorphism, thermochronology and P‐T‐t‐deformation history of the Port aux Basques gneisses, south‐west Newfoundland, Canada*

“…The vergence of thrusting was dominantly westward, in contrast with a dominantly eastward vergence displayed in other parts of the Canadian Appalachians (New Brunswick-van Staal et al, 1990NewfoundlandLafrance & Williams, 1992;Thurlow et al, 1992). Furthermore, the exposed width of the Central Mobile Belt in both south-western Newfoundland and Cape Breton Island is significantly narrower than in northeastern Newfoundland or New Brunswick (Fig.…”

From Large Zones to Small Terranes to Detailed Reconstruction of an Early to Middle Ordovician Arc–Backarc System Preserved Along the Iapetus Suture Zone: A Legacy of Hank Williams

“…2). The terranes of the AAT were fully assembled and accreted to the composite Laurentian margin during the Middle Ordovician Taconic orogeny (Thurlow et al 1992;van Staal et al 1998 Zagorevski and Rogers 2009). Accretion involved an independent northwest-dipping subduction zone situated in the backarc region of the progressively east-migrating arc (Fig.…”

Time-Transgressive Salinic and Acadian Orogenesis, Magmatism and Old Red Sandstone Sedimentation in Newfoundland

“…This suggests that the final increments Syn-tectonic ca. 432 Ma felsite intruded into mélange of the Victoria River delta fault (Thurlow et al 1992;Zagorevski et al 2007), a subsidiary thrust fault of the Red Indian Line. E. Tilted and normally faulted sequence of Silurian (Chandler et al 1987) terrestrial columnar jointed andesite (i), siltstone and bentonite (ii), conglomerate (iii) and columnar jointed rhyolite ignimbrite (iv) at Hind's Lake dam.…”

“…Flow-banded (inset) Topsails Suite rhyolitic dike (correlative of Harry's River rhyolite) cuts across foliation and a minor thrust fault, Buchans area. The minor thrust is a subsidiary structure to the Hungry Mountain and Airport thrusts (Thurlow et al 1992). …”