Summary:
Deposit Types
Gold mineralization on the Rowan Property belongs to the Archean lode gold class of deposits (Roberts 1986) or, using the term, “orogenic gold deposit” class (Groves et al. 1998, Kerrich et al. 2000).
Mineralization
Three principal gold occurrences known on the Rowan Property include the three past-producing mines (i.e., Rowan Mine, Mount Jamie Mine, and Red Summit Mine), the NT Zone, as well as numerous gold prospects. In general, gold mineralization occurs as visible millimetre-scale blebs in quartz veins, veinlets, and stockworks, which is true for many of the occurrences on the Rowan Property.
All of the vein systems on the Rowan Property are open along strike and down dip due to the limited exploration. Most of the systems strike in a general east-west direction and are steeply dipping.
Rowan Vein System
The best gold grades in the Rowan Vein System often occur when coarse and visible native gold is present, which occurs within distinct bluish to grey, glassy quartz veins/stringer zones ranging in thickness of 10 cm to 30 cm and up to 1 m. These zones rarely exceed 60 cm wide, and broad zones of diffuse silicification have generally not been found. Trace amounts, and up to 1%, of pyrite and pyrrhotite is common within these veins/stringers.
The overall Rowan deposit consists of numerous, narrow, high-grade quartz veins that define an east-northeast trending corridor, approximately 150 m wide.
Within the main corridor, the veins are organized into two principal directions of continuity: an east-northeast direction, parallel to the main trend, which appears to dominate; and a subordinate east-west component, parallel to regionally penetrative S2 foliation.
The apparent contradiction of east-northeast trending continuity with predominantly east-west trending veins is reconciled if the veins are transposed or rotated into an en échelon arrangement of minor folds, parallel to S2 foliation, within a broader enveloping surface following the east-northeast trend. Since the deposit-scale east-northeast trend does not itself appear to be folded, the Rowan Vein System must have been emplaced post-F2 folding, but prior to the development of the intense, penetrative S2 foliation. This sequence of events, with an early to syn-D2 deformation timing of structurally controlled gold mineralization is also seen in other major deposits of the Red Lake Greenstone Belt, including in the deposits of the Madsen and Red Lake mines.
Transposed vein systems can present unique challenges for modelling using drill core due to their irregular geometry. Continuity may be difficult to recognize in the short range due to segmentation and rotation during transposition, but long-range continuity may still be well developed and delineated by using the enveloping surface of the transposed veins.
Mount Jamie Vein System
Most of the descriptions of the mineralized bodies at Mount Jamie vein system are from the Main Zone and the Shaft No. 2 Zone.
The Main Zone strikes 60 degrees (°) north of west (i.e., N60W) and has a dip ranging from 45° to 85" to the south, based on surface observation. The vein splits and branches, but in general, is confined to a width of 1.2 m and occupies a fracture zone in altered greenstone close to and along tongues of quartz porphyry.
The North Vein Zone is not a simple vein structure but a larger linear structure controlling a system of quartz veins and lenses. This zone extends between the Shaft No. 2 area and the southeast, and also through the gold occurrences on the north shore of Rowan Property. The width of the North Vein Zone structure varies from several metres to tens of metres and the individual veins range between 0.6 m and 0.9 mm, which was confirmed by the underground work completed by Jamie Frontier in the mid-1980s.
A second very different and important type of gold mineralization was observed in the underground diamond drill core, and later by a crosscut, sub-drift, and several lifts on the same horizon. Characteristics of this second deposit, the North C Vein, are as follows:
• massive, almost homogeneous smoky quartz vein;
• very fine grain size, almost glassy;
• vertical to steeply north dipping;
• highly stressed, mechanically unstable rock;
• virtually no sulphides;
• very fine-grained free gold content, resulting in fairly significant assays;
• requires special sampling and assaying efforts.
The North C Zone was a distinct en échelon unit, approximately 30 m north of the Main Zone. Because this zone was so different from the usual targets, there were difficulties in drill core evaluation and the North C Zone showed clear evidence of being mechanically unstable rock. This duality of mineralization will be accounted for during the planning of any upcoming exploration programs.
The Mount Jamie vein system strikes N60W and has a dip ranging from 60° to 85° to the south, based on surface observation. The vein splits and branches, but in general, is confined to a width of 1.2 m and the vein occupies a fracture zone in altered volcanics close to and along tongues of quartz porphyry.
The Mount Jamie vein system is a gold-bearing shear zone averaging 1.2 m in width. This vein zone has been traced for 165 m on the 38 m level and was found to be discontinuous at deeper levels. This vein zone strikes S65E and dips 85° south where exposed on surface. Six mineralized zones have been outlined along this vein. Three of these mineralized zones are located along the intermediate volcanic rock-felsic breccia contact. This zone is accessed via Shaft No. 1 and lateral workings on the 38 m, 69 m, and 145 m levels.
In conclusion, the gold mineralization in the Mount Jamie Mine area is hosted by a shear-controlled linear feature striking approximately N30W. The mineralized zones appear to fall into two distinct groups:
• Veins and lenses of gold-bearing quartz in association with a variety of sulphide minerals including pyrite, chalcopyrite, pyrrhotite, sphalerite, galena, and rare flakes of native gold;
• Smoky quartz veins, massive with stress lines and random distribution of fine flakes of gold.
Red Summit Vein System
The Red Summit vein system was described by Horwood (1940) as follows:
The claims are underlain by Keewatin lava flows of andesitic and basaltic composition, a small stock of quartz diorite, and later fine-grained diorite dikes. The lava flows, generally termed greenstones, have been deformed and range from slightly schisted rocks to chloritic schists. A zone of fracturing and shearing with quartz veins as much as 6 feet in width was discovered and opened up in a series of surface trenches. The zone occurs along or close to a contact between a small stock of quartz diorite on the north and Keewatin greenstones on the south.
Newman-Todd Zone
The Newman-Todd (NT) Zone, also known as the NT Horizon, is a northeast trending stratigraphic horizon located in the south-central portion of the Rowan Property. The mineralized zone is typically 50 m to 100 m wide and consists of mixed chemical to clastic sediments, including stromatolitic marbles with discontinuous felsic volcanic layers. The NT Zone has been traced along strike on the Rowan Property for approximately 2 km. Clear evidence of shearing is typically absent within this zone, but it represents a corridor of intense quartz-ankerite alteration and brecciation with varying degrees of gold mineralization.
Gold within the NT Zone occurs as free gold in quartz veins including within massive sulphide units of pyrite and pyrrhotite, associated with sulphide-magnetite zones within the breccia, and in vein arrays within quartz porphyry intrusions internal to the NT Zone. Associated sulphides include pyrite, pyrrhotite, galena, sphalerite, and lesser arsenopyrite and chalcopyrite.