Summary:
The southern sector of the central Porcupine Mining Camp is focused on a belt-sequence of mineralized bodies which extend from the Dome Mine (to east), through Buffalo Ankerite, Paymaster, and Fuller claims, to the western Delnite Mine property. They occur within the South Tisdale Anticline sector and are underlain by a sequence of ultramafic and mafic flows of the Hershey Lake Formation, and locally subdivided mafic flows (C-series) of the Central Formation.
The main minerals of these gold-bearing zones are quartz, carbonates, alkali feldspar (most commonly albite), sericite, pyrite, tourmaline, arsenopyrite, scheelite, and molybdenite. Pyrrhotite is common in the deep parts of deposits, as well as in deposits hosted in banded iron formation. Arsenopyrite seems to be common in deposits hosted in sedimentary rocks. The concentration of gold may be considered to be a product of the alteration process, as well as the concentrations of barite, tungsten, antimony, tellurium, molybdenum, and arsenic. Although gold in quartz veins is the most distinctive occurrence, the gold in some deposits is found predominantly within the wall rock.
Davidson Tisdale
The property occurs within the Northern Sector and is underlain by a sequence of overturned east-striking, north dipping, pillowed and massive, magnesium tholeiitic volcanic flows of the Tisdale Assemblage.
The abundance and complexity of faults is one of the most prominent features of the Davidson Tisdale property. Three distinct fault sets have been identified from previous underground mapping (Guy and Puritch, 2007). The faults are moderate to strong shear zones up to 2 m thick. All known mineralized blocks lie within or very close to these faults. The Main Fault strikes 060° and dips 50° to the north. There is a set of faults, which generally run parallel the Main Fault, and dip at 60° to 75° to the north. The second set of faults strikes 025° and dips northwest at 60° to 65°. Two sets occurring between the mine’s No. 4 and 5 Levels represent a dilatant zone between two 060° structures. They contain prominent short veins, locally with gold mineralization. The third set trends 080°, and dips 30° to the north.
Two types of quartz veins were identified on the property (Brooks, 1987). Type 1 are continuous tabular veins striking generally east-west and dipping 15° to 55° to the north. Type 2 are discontinuous, irregular, sub-vertical and steep north-dipping to shallow south-dipping lenses of quartz stringers and veins, striking 040° to 070° azimuth.
The geometries of these mineralized zones were found to have strike lengths up to 40 m, widths of 2 to 4 m, and near vertical dips with dip lengths of approximately 12 m.
Fuller
Fuller is underlain by a generally east-west-trending assemblage of massive and pillowed mafic metavolcanic flows with minor variolitic flows.
In a general south to north direction, the succession of rocks includes talc-chlorite schist (metamorphosed ultramafic rocks), quartz-feldspar porphyry, pillowed amygdaloidal basaltic flows, massive basaltic flows, and a series of alternating units of massive, pillowed, and amygdaloidal volcanic rocks. The porphyry is interpreted to have been intruded prior to folding. Hydrothermally altered volcanic rocks, including a strongly altered unit with more than 50% quartz flooding, green mica, and pyrite mineralization, are spatially associated with the porphyry; there are also large- folded zones of highly carbonate altered volcanic rocks in contact with the porphyry stocks.
Mineralization is characterized by numerous parallel to subparallel quartz-carbonate veinlets hosted within a suite of volcanic rocks. Pyrite is often abundant, both as very fine-grained disseminations and small pyrite trains roughly conformable to the stringers. The Contact Zone meanders along the contact between the pillowed and massive volcanic rock units, and units and frequently occurs entirely within one of the units. The boundaries of the zone are locally gradational.
The Hanging Wall (HW) Zones are located in the structural hanging wall side of the Contact Zone, partly within the pillowed basalt rock sequence and partly within breccia rocks. The zones are similar, but the quartz tends to reflect a pervasive silicification rather than discrete quartz veining.
Mineralization also occurs in highly carbonate-altered zones, and in porphyry bodies with quartz-tourmaline veinlets near the core of the synclinal structure and the Contact and HW Zones. Quartz-tourmaline-calcite veins with minor sulphides occur irregularly distributed throughout the massive volcanic rock unit; they generally vary in width from 9 to 61 cm.
Buffalo Ankerite
In the area of the Buffalo Ankerite, the volcanic flows strike between 065° and 070°, and dip at approximately 60° to the north and thicken to the west. A discontinuous conglomerate unit is located along the contact between a flow-textured mafic volcanic rock unit and the south ultramafic rock unit. Quartz-feldspar porphyries intrude the volcanic rock units and late northwest-trending diabase dykes cut all the above rock types.
The mineralization is associated with tourmaline-quartz-carbonate breccia zones located within a narrow pillowed mafic volcanic flow unit of the Central Series, of the Tisdale Assemblage. Breccia fragments are comprised of ankerite-sericite altered pillowed mafic volcanic rocks within a tourmaline-ankerite rich matrix. The finer the size of the carbonatized mafic fragments within the vein, the higher the gold grade.
Pyrite is widespread within these veins and ranges from 5 to 10% with a halo of 3 to 5% pyrite within the highly carbonatized pillowed volcanic flow. Visible gold is generally not observed but a correlation between pyrite content and gold grade has been observed. Gold likely occurs in fractures within the pyrite or along boundaries of the pyrite grains. Gold values within the conglomerate lithology are associated with quartz and quartz-tourmaline veins with 2 to 5% pyrite content at the vein margins.
Paymaster
The Paymaster property hosts the assemblage of massive and pillowed mafic flows with minor variolitic flows extending east from the Fuller property which strike 075° and dip from 65° to 80° north.
The main producing area of the Paymaster deposit is associated with the Paymaster Porphyry stock and other small porphyry bodies to the north and northwest with quartz ankerite veins occurring to the north, west and southwest of the porphyry.
The gold mineralization found in the Paymaster Porphyry appears to be related to various combinations of tectonized porphyry with variable amounts of silica, tourmaline, and sericite alteration, which seem to define corridors of low-level gold mineralization.
Mineralization in the No. 2 Shaft Porphyry is similar to that in the Main Porphyry although the alteration is heavily weighted in favour of silicification and potassic alteration. Sericitization is generally weak and erratic. The porphyry is laced with quartz veins of varying intensities and orientations. To the south, the porphyry body turns west and mineralization decreases rapidly. A similar situation exists to the north where the porphyry system turns to the east. The overall shape of the porphyry suggests a strong shear or deformation zone sub-parallel to the central and mineralized portion.