Summary:
Crystalline flake graphite mineralization has been the focus of exploration by NMG on its Matawinie Property. No other type of mineralization with economic potential has been observed.
Crystalline flake graphite deposits are usually sedimentary in origin. They occur when carbon-rich organic material, accumulated during sedimentation, is transformed into graphitic carbon crystals, or flakes, during metamorphism. This process is due to the burial of the sediments which are eventually subject to high heat and temperatures in the earths crust. Crystalline graphite deposits are commonly stratabound and hosted by porphyroblastic and granoblastic paragneiss, or pelitic gneiss, marbles, and quartzites (Harben and Kuzvart, 1996). Alumina-rich paragneiss and marble units in upper amphibolite or granulite grade metamorphic terranes are the most favourable host rocks. When present, flake graphite usually occurs in thin, centimeter to metre wide bands. In favourable conditions, wider coalescing bands in fold crests can provide sufficient volume needed for an economic deposit.
Crystalline flake graphite mineralization was first discovered on the Tony Block in mid 2014. Prospecting work, performed as a follow-up to the late 2013 airborne survey (Dubé, 2014, GM 69067), resulted in the collection of nine (9) grab samples that returned values in excess of 5 % C(g) (Cloutier, 2015, GM 69069). Subsequent to this discovery, a short ground TDEM survey was conducted over four (4) areas where the 2013 airborne survey displayed strong conductors. Trenching was then performed in each of these areas, resulting in the discovery of graphitic paragneiss horizons displaying thicknesses of over 20 metres. The best intersections were provided by trenches TO-14-TR-2 and TO-14-TR4, which returned 5.7 % C(g) over 22 m and 5.1 % C(g) over 25.8 m, respectively.
The drilling and trenching of all the mineralized zones located on the Tony Block, including the West Zone, revealed that the mineralized graphitic paragneiss units vary from a few centimetres to tens of metres in thickness. Overall, a stacking of these beds, or horizons, has shown to provide fairly homogeneous and continuous mineralization. The foliation, or gneissosity, of graphitic paragneiss horizons seems to be dipping mostly outwards from the main circular conductive anomaly with the exception of the West Zone, whose mineralized horizons dip at about 60 to 70 degrees towards the South-East (or the interior of the anomaly) at the northern extremity and incrementally dips steeper going South where it becomes sub-vertical and finally dips at about 60 degrees towards the West at the southern extremity. Overall, the dip of the other mineralized horizons varies from 30 degrees to sub vertical. The main graphitic horizons pinch and swell from 4 m to around 80 m in width along strike, and drilling suggests that they are mostly openat depths greater than 250 m from surface.
The graphitic horizons are interbedded with garnet paragneiss units displaying low graphite content and ranging from a few centimetres to tens of metres in width. Both the graphitic and the garnet paragneiss horizons can contain very little to high percentages of leucocratic mobilizate, thought to be the product of partial melting. The paragneiss is given the name of metatexite when the mobilizate layers of varying thickness are common, and are distributed in a lit-par-lit manner parallel to the foliation. These units are usually sub-parallel to the main foliation and often border the mineralized zones. All mineralized zones, with the exception of the West Zone, are limited by unmineralized to poorly mineralized paragneiss and sometimes metatexite. The Mineralization of the West Zone is usually bounded to the West by metatexite or charnockite and to the East by unmineralized paragneiss and further outside of the mineralization (usually less than 100 m), by charnockite.
The crystalline graphite flakes are mostly aligned parallel to the main foliation and they are disseminated fairly homogeneously within the mineralized horizons. Graphite mineralization is often found in the presence of sulphides, or in the case of the Tony Block, mainly pyrrhotite.