REGIONAL GEOLOGY AND SETTING

LAURION’s Ishkoday project is located in the Onaman-Tashota Greenstone Belt (“OTGB”), which lies to the N and contiguous to the Beardmore-Geraldton Greenstone Belt (“BGGB”), situated in the Wabigoon Sub province in the Superior Geological Province (Stott et al., 2002) .

The 30 km wide southern BGGB extends for 180km from Lake Nipigon eastward to the town of Longlac (Ontario). The BGGB is interpreted as a transitional metavolcanic and metasedimentary terrain separating the granite-greenstone OTGB to the N from the metasedimentary Quetico Subprovince further to the S.  The N boundary of the BGGB against the OTGB is defined by the Paint Lake Fault, a major regional deformation zone similar to Cadillac-Larder Lake, Destor-Porcupine and Casa Berardi Breaks, major gold bearing regional deformation zones of the Abitibi Greenstone Belt in Quebec and Ontario, located some 650km to the E.

The south boundary of the BGGB is separated from the 2698Ma to 2688Ma Quetico Subprovince wackes and arenites by the Blackwater River Fault near Beardmore. The Quetico Subprovince rocks are metamorphosed to greenschist facies next to the BGGB and to granulite facies further S. The OTGB consists of 2980Ma to 2710Ma supracrustal rocks intruded by 2690Ma to 2920Ma granitoid plutons. The OTGB just north of the BGGB consists of a succession of felsic, intermediate and mafic metavolcanic rocks, part of the 2740Ma Elmhirst-Rickaby Assemblage, which correlate with the metasedimentary rocks in the BGGB.

Historical gold mines and current gold exploration camps are located throughout the BGGB and there are numerous gold-silver and base metal occurrences present in the OTGB that highlight this prospective but underexplored area. Total production from this region totals 4.4 million ounces of gold which emanated from 19 mines. Most of the production came from two gold areas, the Geraldton Camp and the Beardmore Camp. The balance of gold production came from several small mines scattered 35km NE of Beardmore and one deposit S of Long Lac. Most of the gold emanated from narrow, high grade, lode gold bearing quartz veins.

ISHKODAY GENERAL GEOLOGY

Taken in part from the “Metal Earth – 2019 Geraldton-Onaman Field Trip Guide: The Geraldton-Onaman Transect – Volcanology, Metamorphism, Deformation and Mineralization, by Z. Tóth, K. Strongman, A. Haataja, B. Mark, B. Lafrance and H. Gibson, Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury ON, Canada P3E 2C6

The Ishkoday lies in the southern most portion of the OTGB, hosted within the uppermost member of the 2740 Ma Elmhirst-Rickaby assemblage (Stott et al., 2002), a calc-alkaline volcanic assemblage composed of a lower formation of pillowed mafic flows overlain by an upper formation of monolithic and locally heterolithic intermediate volcaniclastic rocks and minor felsic flows. The local stratigraphy of Ishkoday consists of a lower unit of heterolithic, vitric fragment-bearing lapilli stones, tuff breccias and minor lapilli tuffs that are interpreted as dome collapse-related block and ash flow deposits related to partial collapse of the underlying flow-banded rhyolite dome. Top indicators tend to face westerly. In addition, a high silica-rich rhyolite flow was also observed north of the Sturgeon River. This outcrop exhibited large spherulites which may be lithophysae, suggesting the possibility of subaerial eruption of the rhyolite flows at this location.

Tourmaline breccia was observed at one location in the SW part of the Project. The outcrop which is several hundred meters long consists of a massive tourmaline breccia. It is spatially located in the vicinity of a felsic volcanic breccia believed to indicate proximity to an eruptive volcanic vent. It is possible that the tourmaline breccia may be evidence of a volcanic fumarole activity.

This sequence is intruded by a series of sheet-like syn-volcanic intermediate, felsic, and minor mafic dykes. Small (up to a few meters width) dioritic (locally feldspar porphyritic) dykes were observed and are also thought to be part of the volcanic feeder network. The largest of which is an approximately 1 km wide aphanitic, aphyric, intermediate plug termed the “Sturgeon River Stock” which hosts the majority of the mineralization. This unit is in-turn intruded by coarser syn-volcanic intrusions to the NW and SE.

A small dioritic pluton intrudes into the volcanic pile located between the historic Sturgeon River Mine and the Sturgeon River, termed the Sturgeon Lake Pluton. Roughly triangular to oval in shape body of fine to coarse diorite outcrops on the hill between the river and historic mine. It was also observed in the underground workings of the mine where it was informally identified and referred to as “granodiorite”. It is easily discerned by the airborne magnetic data as a distinct magnetic low. It is dioritic in composition and locally tonalitic and in rare cases gabbroic. It consists of 50-55% plagioclase, rare quartz and 45-50% disseminated magnetite. It is generally equigranular to locally porphyritic. Grain size varies from medium-coarse to fine-grained (aphanitic).

A large foliated granodiorite is located in the northern and eastern part of Ishkoday and is considered part of the Coyle Lake Batholith. The unit is only weakly deformed. The batholith exhibits a distinct magnetic halo which has been identified as disseminated magnetite forming a contact aureole. A similar intrusion, the Elmhirst Batholith occurs to the NE.

Whole rock chemistry of least altered rocks agrees with previous interpretations (Lafrance et al. 2004, Gibson, 2014) of calc-alkaline chemical affinity of the majority of the volcanic and intrusive rocks on Ishkoday

MINERALIZATION ON THE ISHKODAY

Taken in part from the “Metal Earth – 2019 Geraldton-Onaman Field Trip Guide: The Geraldton-Onaman Transect – Volcanology, Metamorphism, Deformation and Mineralization, by Z. Tóth, K. Strongman, A. Haataja, B. Mark, B. Lafrance and H. Gibson, Mineral Exploration Research Centre, Harquail School of Earth Sciences, Laurentian University, Sudbury ON, Canada P3E 2C6

Mineralization at Ishkoday occurs in three separate and diachronous styles:

  1. An early, likely syn-volcanic hydrothermal system, termed the “Ishkoday” style, manifested as discordant, zoned, stockwork-style veins consisting of a magnetite-actinolite(-sulphide) core (“Oxide-Sulphide Veins”), and an peripheral zone of comb-textured quartz veins, patchy to pervasive epidote alteration, with minor pods of chlorite alteration and pseudo-breccia:
  1. The system extends for a minimum 1.2km in length over a known width approaching 450m; and
  • Some of the Oxide-Sulphide Veins are late 030°-045° trending shears, post-dating the earlier 320°-020° trending Sulphide Veins, unless the latter are transposed parallel to the former.
  • Sphalerite-rich metric long and wide veins, also containing pyrite, chalcopyrite, galena, silver and gold (“Sulphide Veins”), centered on the “A” and CRK Zones; and
  1. Syn- to early-tectonic, fault-fill style, crack-seal textured, gold-silver bearing quartz veins, termed the “Sturgeon River” style (“Quartz Veins”), with a distinct chlorite alteration halo that locally includes iron carbonate and pyrite:
  • More than 160 Quartz Veins have been historically identified and systematically named;
  • Most vein sets extend 100’s to 1,000’s of meters in lengths;
  • They occur as multiple individual sinuous and anastomosing centimeter to meter wide veins that also pinch and swell, and form corridors tens to several hundred meters wide:
  • Within these corridors, individual veins trend in at least three different directions, likely due to the changing strain field during the progressive deformation of the belt:
  • 320°-020°. as the No. 3 Quartz Vein from the historic Sturgeon Mine, and the M17 Quartz Vein along the SW extension of the M25;
  • 030°-045°. as the No. 1, 2 and 8/11 Quartz Veins in the vicinity of the No. 3 Quartz Vein, and the No. A-2 Quartz Vein from the CRK Zone; and
  • 060°-075°, as the M51, 53B and 53C Quartz Veins from the SW boundary claims of Ishkoday.

There may be at least three generations of quartz veining:

  • An early crack and seal veining, with centimeter-wide laminar, foliated veins lined with chlorite and sulphide disseminations and stringers, that may host altered and sheared host rock;
  • A later central massive white quartz, barren in sulphide, but containing rare altered and sheared host rock; and
  • Late crosscutting massive veins with chlorite as disseminations and centimeter aggregates, commonly found at right angles in the necks of quartz boudins.

Cross-cutting relationships between the veins and the various porphyritic dykes indicate that the “Sturgeon River” style veins postdate the “Ishkoday” style mineralization; however, the two mineralized systems have similar NE-SW orientations and spacing, suggesting similar, structurally controlled fluid conduits.

Some of the intermediate dykes comprising the porphyritic dike swarm crosscut the Ishkoday style alteration, while others are altered by it, therefore the hydrothermal activity was concomitant with extension and rifting, a possible underlying geodynamic driving force to deposit “Ishkoday” style mineralization.

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