On April 16, 2025, Discovery Silver Corp. announced the completion of its previously disclosed acquisition of Newmont Corporation’s Porcupine Operations.
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Summary:
The Porcupine Complex deposits are classified as orogenic gold deposits as defined by Gebre-Mariam et al., (1995), Groves et al., (1998), and Goldfarb et al., (2001).
Borden Deposit Descriptions
Dimensions
Mineralization has been defined over about 5.8 km of strike, and remains open in the down-plunge direction. The deposit displays a consistent northeast dip and, locally, a shallow southeast plunge. The mineralized zone can be as thick as 120 m, and has been drill tested to about 1,100 m vertical depth.
Metamorphism and Alteration
Rocks in the deposit area have been metamorphosed to upper amphibolite grade. The broad mineralized zone encompasses a number of host rocks, mostly metasedimentary horizons, all of which display feldspathic, chloritic, and biotitic alteration.
Structure
Structurally, the deposit is defined by a north–northeast dip and a generally shallow east–southeast plunge. However, the dominant plunge direction that controls the higher-grade mineralization is slightly steeper and to the east–northeast. In the east– southeast portion of the deposit, the trend of the mineralized horizon splits, with one mineralized zone trending towards the east–southeast and the higher-grade and deeper zone trending east–northeast. Observations to date suggest that the east–southeast trend is dominated by conglomerate footwall rocks whilst the more typical amphibolite footwall rocks dominate the higher-grade east–northeast trend.
Mineralization is constrained to schistose to mylonitic fabrics that anastomose around rotated boudins and foliation boudins, and overprint earlier gneissosity and metatexite migmatites in mafic to felsic plutonic, volcanic, and volcaniclastic lithologies.
Lower-grade gold mineralization is located outside of regional to local brittle–ductile shear zones that lack rotated boudins and rotated foliation boudins.
Mineralization
Gold mineralization occurs as a broad zone of quartz flooding/veining with disseminated and fracture-controlled sulfides. The mineralization generally consists of low to moderate grade gold with minor silver concentrations and is typically characterised by a higher-grade core surrounded by a lower-grade envelope.
The west–northwest portion of the deposit is generally lower grade with some highergrade pods, consisting of disseminated sulphides with localised silicification. It typically lacks strong quartz veining. This lower-grade mineralization rarely hosts visible gold grains.
The well-defined, higher-grade east–southeast portion of the deposit is characterized by a high strain zone that coincides with strong quartz flooding and quartz veining. Visible gold is common in the quartz vein-rich and intensely silicified core of the area.
In the lower-grade area, pyrite occurs as both blocky and anhedral crystals and is commonly associated with pyrrhotite. Pyrrhotite occurs as anhedral blebs of varying sizes. Gold associated with this sulphide assemblage can be identified filling fractures in pyrite and at pyrite grain boundaries, surrounded by anhedral pyrrhotite. Free gold also occurs as inclusions or along fractures in metamorphic minerals (e.g. K-feldspar, hornblende, garnet, biotite, orthopyroxene, and clinopyroxene). Gold is also common in low-strain zones surrounding competent minerals such as garnet, sillimanite, and pyrite.
The higher-grade zone contains abundant quartz, and less abundant pyrite and pyrrhotite than the lower-grade area. Free gold is visible at the contacts between deformed quartz veins and brecciated lithologies and also within the groundmass of the deformed quartz veins.