Fault-mediated melt ascent in a Neoproterozoic continental flood basalt province, the Franklin sills, Victoria Island, Canada

Abstract

The Neoproterozoic Franklin large igneous province on Victoria Island, Canada, is characterized by continental fl ood basalts and a sill-dominated feeder system. Field relationships indicate that fault-guided transfer zones allowed magma to jump up-section to form higher-level intrusions. Where sills connect to dikes and magmas moved upsection , roof and wall rocks are characterized by wide and intense contact-metamorphic haloes , consistent with throughfl ow of magma. The geometric constraints suggest that conduits may have opened episodically and then closed when magma pressure waned. The episodic nature of conduit opening events can explain the pulsed ascent of crystal slurries, and may also play a role in the deposition of Ni-sulfi des.

The geochemical effects of olivine slurry replenishment and dolostone assimilation in the plumbing system of the Franklin Large Igneous Province, Victoria Island, Arctic Canada

“…2). In places, sills are connected to gabbroic feeder-dyke networks that generally trend NW-SE (Bédard et al 2012). The Shaler Supergroup rocks are overlain by the Natkusiak flood basalts, the extrusive component of the Franklin LIP (Baragar 1976).…”

“…The Franklin LIP has a sill-dominated magmatic plumbing system with local fault-mediated shifts in emplacement level that facilitated magma transgression (Bédard et al 2012). Franklin sills were emplaced primarily into limestones and dolostones, and calc-silicate skarns that formed by magma-carbonate interaction are locally prominent (Nabelek et al 2013).…”

“…The FCSC was emplaced ~3 km stratigraphically beneath the coeval Natkusiak flood basalts. Previous work has documented the field relationships at the Uhuk Massif (Bédard et al 2012), showing that the Uhuk Massif (UM) is a magma upflow zone that extends toward the west as a conformable silllike body, the WUS (Fig. 2).…”

“…The WUS was emplaced into the dolostone-dominated Jago Bay Formation, only ~10 m Fig. 1 Geological map of the Minto Inlier on Victoria Island adapted from Bédard et al (2012), with the olivineenriched sills of the FCSC labeled. WUS West Uhuk Sill, PS P-sill, LPS Lower Pyramid Sill.…”

“…Both have olivine-enriched bases and were emplaced at the same stratigraphic level, just above the Fort Collinson Formation marker unit. The WUS is adjacent to a prominent fault-guided magma upflow zone known as the Uhuk Massif (UM: described in Bédard et al (2012)), which preserves calc-silicate reaction facies at some intrusive contacts (Nabelek et al 2013). These three olivine-enriched sills (WUS, PS, and LPS) are collectively termed the Fort Collinson Sill Complex (FCSC).…”