The Mariposite showing is located on the east side of Thirteen Creek, west of Ecstall River. It is 74.7 kilometres southeast of Prince Rupert and 62.3 kilometres southwest of Kitimat.
The Ecstall Greenstone Belt is a north-northwest trending, high-grade metamorphic belt bounded by the elongate mid-Cretaceous Ecstall pluton on the west and the Paleocene Quottoon pluton on the east.
Massive pyrite, up to 50 per cent, and mariposite occurs in an 80-metre-wide belt of quartz-sericite schist. The schist is strongly chloritized and sericitized. A heavily mineralized sample assayed 0.22 per cent zinc (Assessment Report 15488).
The belt of altered pyritic quartz-sericite schist that makes up the three Mariposite prospects is first described in the Minister of Mines Annual Report for 1917, “Another group of claims was staked during the summer across the Ecstall River from the (Ecstall) property. No work has been done on them as yet; the surface shows a strong mineralization of pyrite for a width of 20 feet.” A pre-war claim map (Mason, 1937) shows the belt of pyritic rock staked with the Sulphide 7, Sulphide 8 and Sulphide 13 claims over a band of ‘Rusty Shear”. Holyk (1952, p. 34-35) labels this same schistose zone the “Allaire Creek shear” and describes “disseminated pyrite…in fissile sericite schist. Green mariposite is a frequent associate.” The bright green mica has more recently been identified as the chromium-rich muscovite, fuchsite, by SEM-EDX analysis (McLeod, 1984). This mica varies in abundance from 1 per cent to 20 per cent of the rock and averages 5 per cent. Fuchsite is concentrated along foliation planes and is preferentially displayed along fracture surfaces. The probable protolith to this silica-rich schist has been identified as felsic tuff or a pyritic tuffaceous chert (exhalite).
The quartz-sericite schist units of the `Mariposite belt’ are exposed discontinuously for 3.5 kilometres between Allaire Creek and Thirteen Creek and are typically anomalous in zinc. The first major exploration program on the showings was completed in 1986 by Falconbridge (Hassard et al, 1987a). Airborne and ground geophysical surveys, geological mapping, prospecting, trenching and sampling of the entire belt was followed up with two diamond drill holes; one on the North Mariposite and one on the Mariposite prospect (Hassard et al, 1987a, Figures 32 and 33).
North Mariposite is the northward continuation of the main Mariposite prospect (46). North Mariposite hosts up to 50 per cent pyrite in six separate units of bright green, pyritic, fuchsite-rich, quartz-sericite schist (Hassard et al., 1987a, p.27-28 and Figures 7 and 8). One strongly pyritic sample, collected 1.2 kilometres north of Mariposite Lake, assayed 0.22 per cent zinc. In the area of the North Mariposite prospect, the formations display their thickest intervals, highest pyrite concentrations and best base metal grades.
Drillhole 86MAR-2 at the North Mariposite prospect was drilled to 243.2 metres depth at a dip of -45 degrees and azimuth of 270 degrees. This hole intersected 6 intervals of quartz-sericite schist, with best assays of 180 parts per million copper, 130 parts per million zinc, 4 parts per million lead, 3 parts per million silver and 20 parts per billion gold.
The South Mariposite showing includes all the schistose rocks which trend south from Mariposite Lake, along Mariposite Creek to Allaire Creek, and beyond - more than 2.0 kilometres. The prospect consists of a thick unit of bright green, pyritic quartz-mica semischist within a steeply dipping unit of charcoal to black, weakly pyritic metasiltstone. The thickness of individual units ranges up to 120 metres, and six separate units have been identified within the stratigraphic succession in the North Mariposite zone. Pyrite content of the quartz-mica schist typically ranges from 1 per cent to 5 per cent, but local concentrations up to 50 per cent pyrite are exposed at the North Mariposite prospect.
At the Mariposite showing the geologic setting differs where the western margin of the volcano-sedimentary succession is intruded by a large body of foliated diorite (variably mapped as amphibolite or pyroxenite). The South Mariposite zone is a simpler sericite schist zone within a metasiltstone package.
The Mariposite showing was included in the 2019 airborne VTEM survey over Kingfisher Resources Ltd.'s Ecstall property. The airborne survey was aimed at detection of structures and/or conductors related to potential Cu-Au-Zn-Ag VMS-style mineralization (Assessment Report 39155).
