Role of metalliferous mudstones and graphitic shales in the location, genesis, and paleoenvironment

The Cambrian Tally Pond volcanic belt in central Newfoundland contains numerous volcanogenic massive sulphide (VMS) deposits, prospects, and showings that are locally associated with metalliferous mudstones and/or graphitic shales. Deposits in the belt are bimodal felsic-type VMS that are both base metal- (e.g., Duck Pond, Boundary) and precious metal-enriched (e.g., Lemarchant). At the Lemarchant deposit metalliferous mudstones are genetically and spatially associated with mineralization, whereas the relationship of other mudstones and shales to massive sulphide mineralization is more intricate and remains not fully understood. Metalliferous mudstones represent a hiatus in the volcanic activity where the deposition of hydrothermal products dominated over the abiogenic background sedimentation and/or dilution by volcaniclastic-epiclastic material. Lithogeochemical signatures allow one to distinguish between predominantly hydrothermally or detritally (i.e., non-hydrothermal) derived material. Metalliferous mudstones with a significant hydrothermal component, like those at Lemarchant, have elevated Fe/Al and base-metal contents, compared to detrital shales, and shale-normalized negative Ce and positive Eu anomalies, indicative of deposition from high temperature (>250°C) hydrothermal fluids within an oxygenated water column. Mudstones and shales sampled from other locations in the Tally Pond volcanic belt have more variable signatures ranging from hydrothermal (signatures as above) to non-hydrothermal (no positive Eu-anomalies, flat REE patterns), with some that have mixed (hydrothermal and detrital) signatures. Both S and Pb isotopic compositions indicate that proximal sulphides hosted in mudstones immediately associated with massive sulphide mineralization within the Lemarchant deposit contain a higher proportion of sulphur derived from hydrothermal sources and processes, and have more juvenile lead contributions, when compared to sulphides distal (not associated with massive sulphides) from mineralization. Lead and Nd isotopic compositions of both whole rock and minerals in the Lemarchant mudstones indicate involvement of underlying crustal basement during massive sulphide formation and throughout the evolution of the Tally Pond belt. Metalliferous mudstones precipitated early in the massive sulphide depositional history, but also have undergone syn- and post-ore-forming processes and have a larger lateral extent than the mineralization. Using lithogeochemistry, whole rock and in situ stable and radiogenic isotopes it is possible to distinguish prospective vent proximal (immediately associated with massive sulphide mineralization) from less prospective distal (not associated with massive sulphides) depositional environments and to reconstruct the paleotectonic setting on a deposit- to regional-scale for the Lemarchant deposit and other mudstone-associated prospects in the Tally Pond volcanic belt.

Coastal geomorphology, processes and erosion at the tourist destination of Ferryland, Newfoundland and Labrador

The community of Ferryland is located on the southeastern coast of the Avalon Peninsula. The town traditionally relied on a fishing-based economy until the collapse of the fishery in the early 1990s. The present economy emphasizes sustainable development in the tourism sector with focus on archaeology, geotourism and other recreational uses. This paper discusses coastal erosion and impacts on sites and infrastructure using methods including: local knowledge, Real Time Kinematic (RTK) surveying and other survey techniques, seawater level measurement, meteorological data from a locally-installed station, custom-made drifter tube buoys, photography, HD video, and investigation using various modes of transport including inflatable boat. The major findings of the study include that the residents and stakeholders are genuinely interested in and knowledgeable of coastal erosion. The causes of coastal erosion include: large waves, surge, longshore currents, harbour oscillations, mass wasting, and location of infrastructure causing alterations of these processes. Freeze-thaw Cycles (FTC), rainfall, and gravity loosen and transport rock, till, and fill materials downslope. Large waves and currents transport the materials alongshore or into the nearshore. Harbour oscillations causing high velocity currents (> 2 m/s) are responsible for shoreline erosion and damage to property in The Pool. Historical resources such as gun batteries and ordnance pieces which date to the 1700s are being lost or threatened through coastal erosion of till and rock cliffs. Improper drainage and maintenance is responsible for erosion of roads and supporting shoulders, necessitating mitigation measures. Sediment transport and deposition during and after large wave and surge events lead to undercutting of infrastructure and increased risk of washover of existing infrastructure. Erosion is ongoing at Bois Island and Ferryland Head Isthmus through slope processes and undercutting; The Pool and the lower Colony of Avalon site through harbour oscillations and related undermining; the tombolo and the main breakwater through wave attack; and Meade’s Cove including the East Coast Trail through wave attack and undercutting. The floor of the latrine in the lower Colony of Avalon site indicates that sea level was approximately 1.25m below present in the 1620s, a relative sea level rise rate of 3.2 mm/y. The recommendations include suggested mitigation to reduce impacts specific to each site.