| Abstract |
Teranov has undertaken a full suite of geoscientific surveys of the Brimstone Hill geothermal prospect, located on the western slopes of Mount Liamuiga, the northernmost eruption crater on St Kitts Island in the Lesser Antilles, and north of Brimstone Hill. This work involved a combination of geological, geochemical, and geophysical surveys and, in this paper, we highlight an attempt at perusing surface infrared imaging in order to evaluate heat loss and inform resource assessment results. The surveys undertaken include a detailed geological survey, two magnetotelluric surveys, a high resolution gravity survey, a drone based aeromagnetic survey, a surface temperature survey using a radiometric sensor carried by UAV, the geochemical analyses of steam-heated boiling spring samples from the crater of the nearby volcano, Mt Liamuiga, of liquid samples acquired 1m below sea level, where waves break and multigas measurements (in-situ gas ratios) of gas seeps. Liquids from a shallow well (9C-23) located near the sea in which temperatures of 51°C had been previously measured were also resampled. Two magnetotelluric (MT) surveys were undertaken which together highlighted some small dome features in a strongly electrically conductive unit. These features appear to be correlated with the location of N-S faults and are interpreted as showing the locations of preferential upflows along faults. They are interpreted as the marker of hydrothermal alteration above a geothermal upflow, and the base of the conductive zone indicating a temperature of the order of 200-210°C. A resistive body is also clearly apparent below the conductive zone in a NW-SE alignment around Brimstone Hill, and is interpreted to be part of the Brimstone Hill intrusion. The conductive zone wraps around this feature, which indicates that it is likely to act as a heat source to the gas and liquid thermal manifestations observed at the base of Brimstone Hill. The samples acquired at sea or in the shallow well did not allow for the application of chemical geothermometers with confidence, given that the samples were composed of varying parts of seawater and surface waters, besides the deep geothermal signature. In order to supplement MT interpretations, and potentially identify any overlooked surface thermal features, a drone-borne thermal infrared survey of the vicinity of a known outflow area by the coast was undertaken, which highlighted a wide thermal anomaly at sea along the coastline near Brimstone Hill, centred on the known surface outflow. A method is tentatively applied in an attempt to quantify the heat loss resulting from this outflow. A conceptual model of the Brimstone Hill prospect is proposed, which is interpreted to host an inferred geothermal resource according to the principles of the Australian Geothermal Reporting Code, 2nd edition. A stored-heat assessment of its power production potential under a binary development scheme was undertaken, which estimates P50 and P90 values of 28MWe and 19MWe, respectively. |