(from Vincent, J.S., 1984)
Southwestern Nova Scotia is underlain by rocks of the Meguma series which is comprised of Cambrian Goldenville formation and the overlying Ordovician Halifax Formation. The former consists of interbedded quartzite, slates, schist and greywacke, and the Halifax is predominantly slates wackes and schists. A Carboniferous age suite of granitic rocks intrudes the sediments.
Folding during the Acadian Orogeny in the Devonian resulted in the development of a complex series of northeasterly trending folds which created a distinctive structural signature through the Meguma rocks. The folding occurred over a sufficient period to allow the resulting structural elements to vary significantly in age. The form and attitude varies, and the associated faulting and fracture systems which developed reflect the sequence of orogenic events.
The structural complexities in the Acadian orogenic events created in the Meguma series of rocks have provided a variety of settings conducive to the concentration of mineralization. The resulting fracture systems contain quartz veins of which particular sets are known to be gold bearing. Gold is concentrated in economic proportions where the age of folding and fracturing and subsequent mineralizing events coincide. Fracturing and quartz veining not fulfilling the right conditions, are barren. In the Leipsigate area, at least two sets of quartz veins are gold bearing.
The Leipsigate property is underlain predominantly by the Cambrian Goldenville Formation which is exposed in a broad anticline plunging to the northeast at approximately 25 degrees. The core of the fold consists of intercalated quartzites and slates. The contact with the overlying Halifax slates cuts northeasterly across the top of the property. Quartzite units in the Goldenville create low ridges across the landscape and clearly delineate the fold structure on air photo maps.
The interbedded softer rock units consist of argillites, mudstones, schists and greywackes and have provided the loci for adjustment during folding. Fracturing along these horizons and along bedding planes has created a plumbing system for hydrothermal solutions. Transverse fissure and concordant interbedded veins are recognized as the two important gold-bearing types. The interbedded variety are usually narrow and mineralization is usually limited to small zones developed at points of vein intersection. The transverse fissure veins have the potential to host significant zones of auriferous mineralization where the fractures cross-cut incompetent beds and/or other vein systems.
In addition to the six main shafts occurring along the Main Fissure vein structure, there are approximately 20 smaller shafts in the 10 meter or so range as well as untold numbers of trenches spread throughout the property. Most of the smaller shafts and trenches were exploring high grade bedding parallel veins which were sometimes of limited strike length and of unknown depth extent. The majority of these are on the west side of the anticline. The Main Fissure Vein, from which the bulk of recorded production has taken place, roughly follows the strike of the strata of the southern limb of the anticline, but dips in the opposite direction, towards the anticlinal plane.
At least nine other similar Meguma gold deposits occur within a thirty kilometre radius. The majority of them do not have fissure type veins of a significant size and extent as the Main Fissure Vein of the Leipsigate deposit, but many have concordant (bedding parallel) systems that carry gold of economic interest.
The Main Fissure Vein had underground development for over 2100 meters and to a depths of up to 183 meters. Most historic production occurred above the hundred meter level. It is reported to vary in thickness from 0.4 meters up to nearly 2 meters in the north, where it “splays” into two veins. It averages approximately 0.61 meters in width throughout most of its length. The vein is described as having a glassy texture, being of the ribboned type. Hanging wall to the vein is a 10 cm thick band of incompetent sericite schist which is also reported to carry gold. Minor calcite occurs with the quartz and additional metallic minerals include arsenopyrite with rare pyrrhotite, galena and chalcopyrite. The gold to silver ration is reported as 6 to 1. Scheelite has also been recorded associated with the quartz but no grades were reported. Total metallic content rarely exceeds 2%.
A number of the bedding parallel occurrences on the property may be of some interest as the grades can be quite high. The Rose Lead, which should intersect the Main Fissure Vein at depth, is reported to have returned up to 45 ounces of gold from just 3 tons of quartz taken from a vein a maximum 10 centimetres in width. A short drill hole by NSGold on this structure in 2010 returned a value of 10.9 grams per tonne over 0.5meters.
