Bell Creek and Timmins West mines, together "Timmins Mine", are 100% owned and operated by Lake Shore Gold Corp., a wholly-owned subsidiary of Pan American Silver Corp.
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Summary:
Gold mineralization in the Timmins, Thunder Creek, and 144 Gap Deposits occurs in steep northnorthwest plunging mineralized zones which plunge parallel to the local orientations of the L4 lineation features which also plunge parallel to the lineation, including folds and elongate lithologies. Mineralization occurs within, or along favourable lithostructural settings within 100 metres of the Holmer and Rusk Shear Zones. Mineralization comprises multiple generations of quartz-carbonate-tourmaline ± albite veins, associated pyrite alteration envelopes, and disseminated pyrite mineralization. Textural evidence suggests that veining formed progressively through D3 and D4 deformation. All phases of gold-bearing veins cut and postdate the AIC and syenitic to monzonitic intrusions, although mineralization is often spatially associated with ore preferentially developed within these intrusive suites (Rhys, 2010).
At the Timmins Deposit, the character and sequence of veining in the Main, V1 and V2 veins is similar in all exposures. Rhys (2003) defined three phases of veining in the Timmins Deposit surface showings, all of which were also apparent in his recent observations (Rhys, 2010 and 2011), although an additional phase of shallow dipping quartz extension veins was also recognized during this field work (Rhys, 2010). The sequence of veining observed is as follows, with most veins in the upper Timmins Deposit mineralization forming composite veins which have this paragenetic sequence.
In the Thunder Creek area, there are two main styles of mineralization: 1) the Rusk Shear Zone adjacent to and in the footwall of the pyroxenite unit, and; 2) the Porphyry Zone which is hosted by the quartz monzonite intrusion which lies to the southeast in the immediate footwall to the Rusk Shear Zone below an elevation of approximately 500 metres below surface.
Mineralization in the Rusk Shear Zone comprises areas of either higher quartz-carbonate-pyrite vein density, and/or areas of elevated medium- to coarse-grained disseminated pyrite and associated pyritequartz veinlets. Both of these styles were observed to occur in the intensely foliated, often compositionally laminated carbonate-albite-quartz-magnetite portions of the shear zone. Mineralization also locally preferentially overprints pink, K-feldspar-rich syenite dykes and local plagioclase-dominant probable diorite dykes in the shear zone, with clots and aggregates of coarsepyrite, often associated with quartz-albite-carbonate veinlets.
“Porphyry Zone” mineralization is developed in the quartz monzonite intrusion that occurs at depth in the footwall to the Rusk Shear Zone immediately adjacent to areas of mineralization in the shear zone. Mineralization is associated with sheeted sets of quartz extension veins which occur in abundance of up to several veins per metre within the intrusion. Most veins are less than 3 centimetres thick and comprise white quartz with pyrite. Disseminated pyrite locally occurs in the wall rock adjacent to the veins and free visible gold was locally observed in association with pyrite both in veins and disseminated in the host rock.
Gold mineralization in the 144 Gap Deposit occurs generally between 600 and 1,000 metres below surface in the footwall of the high strain zone within and adjacent to syenite bodies in the footwall mafic volcanic lobe. The main mineralized areas occur between approximately 20 to 120 metres into the footwall of the high strain zone; however, mineralization also occurs locally within the shear zone itself. There are two main styles of mineralization identified in the 144 Gap Deposit area: 1) syenite-hosted quartz-pyrite extension vein sets and associated mineralization, and; 2) disseminated and vein-controlled pyrite in carbonate-sericite altered areas of higher strain in the shear zone and in altered mafic units along and within dyke margins.
Mesothermal shear hosted gold mineralization in the Bell Creek mine area occurs along selvages of quartz veins and wall rocks, in stylolitic fractures in quartz veins, in fine grained pyrite, and in association with amorphous carbon. High grade gold mineralization occurs within quartz veins contained in alteration zones.
Gold mineralization in the Bell Creek area as occurring along selvages of quartz veins and wall rocks, in stylolitic fractures in quartz veins, in fine grained pyrite, and in association with amorphous carbon. High grade gold mineralization occurs within quartz veins contained in alteration zones. The alteration zones are characterized by carbonate, graphitic and amorphous carbon, fine grained pyrite, sericite, and/or paragonite and are enriched in Au, As, Bi, and W. This style of alteration is referred to by mine geologists as “grey zones” and is an exploration target in Hoyle Township.
The Bell Creek mineralization differs in style from many deposits in the Porcupine Mining camp in being composed largely of disseminated pyrite-pyrrhotite-related mineralization; slightly younger gold-bearing quartz veins may be present but are not predominant. This style of mineralization occurs in the deeper parts of the Dome Mine and in the Rusk Zone at the Timmins West mine, but is more common to the east, in the Holloway-Holt McDermott area and at the Larder Lake, where pyritic mineralization is often termed “flow ore” (Rhys 2012).