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Finlayson Lake District - Kudz Ze Kayah, ABM, Wolverine, GP4F, Fyre Lake, Kona, Ice |
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Yukon Territory, Canada |
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Zn Cu Pb Ag Au Co
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Super Porphyry Cu and Au
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The Finlayson Lake District, is a crescent shaped area that is ~300 km long and 50 km wide, extending from Watson Lake in the SE to Ross River in the NW, in southeastern Yukon, Canada. It embraces a number of significant volcanic hosted massive sulphide (VHMS) deposits within felsic Devonian-Carboniferous volcanics, including the ABM Wolverine, Kudz Ze Kayah and GP4F Zn-Pb-Cu-Ag-Au, the Fyre Lake Cu-Co-Au and the Ice Cu rich mineralisation.
The Finlayson Lake District is an isolated outlier of the Yukon-Tanana and structurally underlying Slide Mountain terranes. These outliers were laterally offset by ~430 km to the SE relative to the main mass of these terranes during the Eocene, across the continental scale, north-west trending, dextral, strike slip Tintina Fault Zone. This offset block occurs to the north-east of that structure, where it structurally overlies the lower to middle Palaeozoic sedimentary sequences of the Selwyn Basin to the east and north above the NE vergent Late Triassic Inconnu Thrust. The Yukon-Tanana and Slide Mountain terranes represent a continental arc and back arc basin sequence that developed along the Devonian to Permo-Triassic Pacific margin of Laurentia.
The allochthonous Yukon-Tanana terrane commences with the poly-deformed and metamorphosed pre-Late Devonian continental margin Snowcap assemblage (Piercey and Colpron, 2009) that is not exposed in the Finlayson Lake district, but elsewhere is characterized as Laurentian derived, peri-continental crustal material (Piercey et al., 2001, 2003, 2017; Piercey and Colpron, 2009). This basement is overlain by three unconformity-bound Late Devonian to Middle to Late Permian continental arc, back-arc, and ocean basin-related volcano-sedimentary sequences that were subjected to variable degrees of metamorphism and deformation (Mortensen and Jilson, 1985; Mortensen, 1992; Colpron et al., 2006; Murphy et al., 2006).
The rocks of the Finlayson Lake district comprise Late Devonian to Permian metasedimentary, metavolcanic, and plutonic successions that have been subjected to variable degrees of deformation, from amphibolite facies in the core of the Finlayson Lake district, grading outward to lower greenschist facies (Murphy et al., 2006). The Yukon-Tanana terrane in the Finlayson Lake district is represented by three structurally bound stratigraphic sequences, the Big Campbell, Money Creek, and Cleaver Lake thrust sheets. The structurally deepest Big Campbell thrust sheet is volumetrically the largest, and comprises Upper Devonian metaclastic rocks of the North River Formation, the Upper Devonian Grass Lakes Group, and the Lower Carboniferous Wolverine Lake Group (Murphy et al., 2006). The Grass Lakes Group comprises three rock units, which are, from the base, the Fire Lake, Kudz Ze Kayah and Wind Lake formations.
The stratigraphy is as follows, from the above the basement in the Big Campbell thrust sheet:
North River Formation - Pre-Late Devonian quartz-rich meta-clastic sedimentary rocks;
Grass Lakes Group - Upper Devonian, divided into:
• Fire Lake Formation, which mainly comprises chloritic phyllite, interpreted to be after mafic metavolcanic and lesser mafic and ultramafic meta-subvolcanic protoliths, with some carbonaceous phyllite, and rare muscovite-quartz phyllite after a probable felsic volcanic protolith (Piercey et al., 2002; Murphy et al., 2006), probably ~365 Ma in age;
• Kudz Ze Kayah Formation, that is interpreted to be aged at ~360 to 356 Ma and stratigraphically lies above the Fire Lake formation. It is characterized by dominantly felsic volcanic and sedimentary rocks with back-arc geochemical affinities (Piercey et al., 2001; Murphy et al., 2006). It predominantly comprises feldspar-muscovite-quartz phyllite and augen-phyllite of probable felsic volcanic and volcaniclastic origin, with lesser fine grained carbonaceous and siliciclastic rocks.
• Wind Lake Formation, which conformably overlies the Kudz Ze Kayah Formation and comprises interlayered carbonaceous phyllite and chloritic phyllite (probably after alkalic mafic volcanic and intrusive protoliths), with minor quartzite (Piercey et al., 2002).
• Grass Lakes plutonic suite granitic rocks, dated at ~361 Ma (Piercey et al., 2001, 2003; Manor et al., 2022), which intrudes all of the rocks of the Grass Lakes Group and mainly comprises granite, quartz monzonite and augen granite.
Wolverine Lake Group - Lower Carboniferous, which unconformably overlie the Grass Lakes Group and comprise carbonaceous clastic, and mafic and felsic volcanic rocks which include a basal unit of conglomerate, grit sandstone and carbonaceous argillite; a middle unit of quartz-feldspar phyric felsic volcanic rocks, rare chert and sandstone; and an upper unit of aphyric rhyolite, argillite, magnetite iron formation and mafic volcanic and intrusive rocks (Murphy et al., 2006; Peter et al., 2007).
Both the Grass Lakes and Wolverine Lake groups are in the footwall of the SW vergent Money Creek Thrust, and represent two cycles of ensialic back-arc development, separated by an unconformity that marks deformation uplift and erosion (Peter et al., 2007). The Money Creek Thrust, which has a displacement of at least 35 km to the WSW, separates the Big Campbell and the overlying Money Creek thrust sheets. The latter is composed of rocks of the same age, but primarily formed in an arc environment (Murphy et al., 2006). The lower section of the Money Creek thrust sheet in the Finlayson Lake district is occupied by the:
Campbell Ranger Formation, which is of Lower Permian age and part of the Slide Mountain Terrane. It is a mafic dominated sequence of basalt, chert and argillite.
The Cleaver Lake thrust sheet is composed of less deformed Late Devonian, through Early Carboniferous to Early Permian rocks deposited in an arc environment and is the uppermost structural panel (Murphy et al., 2006). The Cleaver Lake Formation comprises calc-alkaline basalt, rhyolite, chert and volcanic-derived sandstone, which are associated with co-magmatic felsic, mafic and ultramafic meta-plutonic rocks and an Upper Carboniferous pluton, the Simpson Range plutonic suite of granite, quartz monzonite and granodiorite of similar age to the Grass Velleys Plutonic Suite in the Big Campbell thrust sheet.
The main mineral deposits within these sequences may be summarised below
ABM
The ABM deposit is a bimodal-felsic, replacement-style volcanogenic hosted massive sulphide (VHMS) deposit within the Finlayson Lake district in Yukon, Canada, ~5 km and ~24 km WNW of the GP4F and Wolverine deposits respectively, and ~30 km NE of the NW-SE striking continental scale Tintina Fault. It is hosted by predominantly felsic volcanic rocks that occupy the top ~350 m of the >500 m thick Kudz Ze Kayah formation, which at ABM dips at between 20 and 30°NNE, and is relatively intact. The deposit occurs 200 ±50 m below the transitional contact between the Kudz Ze Kayah and Wind Lake formations. The Wind Lake formation comprises interbedded mafic tuff and argillite near, and at the contact with, the Kudz Ze Kayah Formation. The NE-SW trending, dextral, regional-scale East Fault displaces and divides the deposit area into two zones, the ABM zone and the Krakatoa zone to the north and south respectively. The upper portion of the Kudz Ze Kayah formation has been informally divided into three sequences that are similar in ABM and the Krakatoa zone, except that the latter contains more voluminous volcanic and sub-volcanic rocks. Each sequence is composed of interbedded felsic volcaniclastic rocks and minor sedimentary rocks, with domes and flows, all of which were intruded by felsic sills and mafic sills and dykes. These sequences are:
Sequence 1 - the stratigraphically lowest, consisting of interbedded felsic tuff, lapilli tuff, felsic subvolcanic rocks, and rare argillite
lenses, that together are at least 100 m thick;
Sequence 2 - consists of interbedded felsic tuff and lapilli tuff with minor argillite lenses and contains felsic lava flows, two mafic sills, and abundant felsic sills. It is the host to mineralisation. At the ABM zone, it varies between 45 and 120 m in thickness, averaging ~100 m, and generally
thins down-dip towards the NNE. At Krakatoa, it is dominantly composed of felsic volcanic and sub-volcanic rocks and mafic sills.
Sequence 3 - comprises interbedded lapilli tuff, crystal-rich tuff, tuff, argillite lenses, and felsic lava flows and sills. At Krakatoa, flows and sills are more common, particularly thin, fine-grained mafic sills.
For detailed descriptions of the sequences and constituent lithofacies see Denisova and Piercey (2022).
Denisova and Piercey (2022) divide the felsic rocks within these sequences into two groups, Felsic A and Felsic B, based on immobile elements and their ratios. The Felsic A group has high Zr concentrations of >550 ppm, relative to Group B, and generally higher contents of high field strength elements (HFSE). The distribution of these groups approximately coincides with the lithostratigraphic sequences, with the host Sequence 2 consisting of the Felsic group B, whilst the hanging-wall Sequence 3 and footwall Sequence 1 felsic rocks have Felsic group A signatures. An argillite lens, representing a period of volcanic quiescence, marks the upper limit of Sequence 2.
As detailed above, the deposit is split into two, the ABM and the Krakatoa zones. In both, the mineralisation is stratabound, sub-cropping at the bedrock interface with till cover, and dips subparallel to the stratigraphy at 20 to 30°. The ABM zone occurs over a 700 m strike length and extends down-dip for ~600 m from the bedrock subcrop. The Krakatoa zone has a strike length of 170 m, and extends from the bedrock subcrop, downdip for 600 m where it remained open in 2021. In both zones, The mineralisation occurs as a series of stacked lenses within Sequence 2 rocks and ranges in thickness from 5 to 55 m in the ABM zone and from 15 to 100 m in the Krakatoa zone. Mineralisation at the ABM zone tapers down-dip to the NNE, laterally to the west, and is truncated by the East fault to the SE. At Krakatoa, mineralisation thins down-dip to the NE and is terminated by post-mineral faults in other directions.
At both the ABM and Krakatoa zones, mineralisation occurs as massive sulphides that comprise pyrite, sphalerite and pyrrhotite, with lesser chalcopyrite, magnetite and galena, and minor tennantite-tetrahedrite and freibergite. The main gangue minerals are barite, carbonate, quartz, chlorite and white mica. Within the massive sulphides, these minerals combine in three main assemblages: i). pyrite-sphalerite-galena with lesser chalcopyrite, tennantite-tetrahedrite, and freibergite, with carbonate, barite, quartz, and white mica; ii). magnetite-chalcopyrite-pyrrhotite-pyrite-sphalerite, minor tennantite-tetrahedrite and freibergite, and minor carbonate and chlorite;iii). chalcopyrite-pyrrhotite-pyrite stringers associated with pervasive chlorite alteration, minor carbonate, and quartz. The massive sulphide lenses are predominantly composed of the first two assemblages, with the third being less common, and typically only found at the upper and lower contacts of the massive sulphide lenses. The second and third assemblages contain greater quantities of chalcopyrite, magnetite and chlorite, and are taken to be indicative of higher temperatures of emplacement of >300°C (e.g., Lydon, 1988). They are interpreted to have formed earlier than the pyrite-sphalerite-galena of the first assemblage.
The contact between mineralisation and host rocks is generally sharp at ABM, although locally, massive sulphides grade into unmineralised but altered rocks over distances of 1 to 2 m, and is mainly associated with felsic volcanic and volcaniclastic rocks. At the Krakatoa zone, the bulk of the massive sulphide mineralisation is localised on the contacts between the mafic sills and volcaniclastic rocks or, locally, within the mafic sills themselves. Throughout the ABM deposit, preserved lapilli and other clasts and remnant bedding are evident within the massive sulphide lenses and on their contacts, and massive sulphides are seen to be replacing likely glassy groundmass within perlitic and brecciated textures. This is implied to suggest the mineralisation formed by replacement (Doyle and Allen, 2003). Thin, discontinuous stratabound bands of massive sulphide that are <30 cm thick occur in the footwall of the major massive sulphide lenses within the volcaniclastic rocks of Sequence 2 and at the top of Sequence 1. Rare subrounded to subangular clasts that are up to 30 cm across occur in the the hanging wall of the massive sulphide lenses, composed of pyrite-pyrrhotite-carbonate within the felsic volcaniclastic rocks of Sequence 2 and Sequence 3.
Hydrothermal alteration is widespread in both the hanging wall and footwall of the massive sulphide mineralisation in both the ABM and Krakatoa zones, and is irregularly zoned and distributed, although the intensity of alteration increases with the proximity to mineralised lenses. Alteration assemblages can vary within any of the lithofacies units, although white mica ±quartz ±chlorite is the most widespread in felsic rocks. Felsic volcaniclastic rocks and lavas commonly contain pervasive white mica alteration at the contacts with massive sulphide lenses, but locally, pervasive chlorite ±carbonate alteration is found. Carbonates, occurring as calcite, dolomite and ankerite, are common alteration products in both the ABM and Krakatoa zones, and occur within the massive sulphides, in proximity to mineralisation, or in more distal parts of the deposit. Calcite, dolomite and Fe carbonate alteration is widespread in Sequences 2 and 3, and commonly occurs as patches or veins with an orange tint, commonly overprinting the primary fabric and/or the mineralisation. Amphibole-chlorite-carbonate-biotite-epidote-quartz is a common alteration assemblage in the altered mafic subvolcanic sills of Sequence 2, where amphibole and chlorite replace the primary pyroxene, and biotite locally overprints chlorite. Post-mineral carbonate, carbonate-quartz, quartz, quartz-tourmaline, and tourmaline veins are found throughout the deposit and crosscut the rock fabric of the volcaniclastic rocks and the mineralisation.
The ABM deposit contains a mineral resource of 19.1 Mt @ 6.6 wt.% Zn, 0.9 wt.% Cu, 2.0 wt.% Pb, 1.4 g/t Au, 156 g/t Ag (van Olden et al., 2020).
The information in this ABM summary is drawn from Denisova and Piercey (2022). See also "Olden, K., Green, A., and Davidson, G., 2020 - NI 43-101 feasibility
study technical report Kudz Ze Kayah property, Yukon, Canada; prepared by CSA Global for BMC Minerals, 373p."
Wolverine
The host rocks to the Wolverine deposit are part of the Wolverine Succession and comprise from the base:
Unit 1 - Footwall sedimentary volcaniclastic and intrusive rocks, comprising black to grey carbonaceous argillite which grades upwards into greenish-grey quartz and feldspar crystal rhyolite volcaniclastics containing subrounded fragments of rhyolite and several percent K feldspar phenocrysts. The abundance and size of felsic volcanic fragments decrease markedly laterally away from the deposit. K feldspar-phyric rhyolite intrusives, which are 6 to 15 m thick are locally found around 20 m below the massive sulphides and represent sills emplaced contemporaneously with the massive sulphides. Similar sills are found at the same stratigraphic position at the Sable and Fisher massive sulphide occurrences 3 km to the SE and 8 km to the NW respectively. At Wolverine these have been dated at 347.8±1.3 Ma.
Unit 2 - Interbedded argillite, rhyolite and magnetite-carbonite-sulphides, which are composed predominantly of intecalated black, graphitic argillite and massive to banded aphyric, silicified rhyolite containing millimetric quartz-pyrite veinlets. Up to 10 m thick, lenslike bands of massive sulphide occur at or near the contact between units 1 and 2, at what is known as the Wolverine Horizon, recognised regionally by the transition from quartz- and feldspar-phyric rhyolite of Unit 1, to the aphyric rhyolite of Unit 2. The hangingwall of the massive sulphide is typically composed of graphitic argillite. The massive sulphides are closely overlain by carbonate dominated 'exhalites', while 80 to 100 m higher there are laterally extensive, magnetite dominant iron formation 'exhalites' which occur over strike lengths of up to 12 km.
Unit 3 - Fragmental rhyolite, which occurs above the uppermost iron formation where interbedded rhyolite and argillite grade into rhyolite volcaniclastics which have fragmental textures comprising sub-angular to sub-rounded cm-sized aphanitic volcanic clasts. The rhyolite has local interbeds of carbonaceous argillite.
Unit 4 - Interbedded carbonaceous argillite, greywacke, basalt and rhyolite, with the carbonaceous argillite and black to grey, medium grained greywacke interbedded to form around 60% of the unit, with the next most common lithology being fine grained basalt, with minor felsic volcaniclastics. The upper most part of the represents the transition from the dominantly felsic volcanic rocks of the Wolverine succession to the overlying mafic volcanic unit.
The deposit comprises two discrete, tabular, Zn-Pb-rich massive sulphide lenses, the Wolverine and Lynx zones, each around 250 m long, separated to the NW and SE respectively by a 200 m long zone of Cu-rich semi-massive, replacement and sulphide-stringers known as the Hump zone. These three zones constitute the Wolverine deposit which is around 700 m long, 475 m wide and 1 to 10 m thick. It strikes NW-SE and dips at 30°NE. Locally, as in the thickest part of the Lynx zone, there are multiple sulphide bands, separated by 4 to 8 m of argillite or rhyolite. The sulphides pinch out up-dip, approximately 50 m below the surface, and persists for more than 500 m down-dip. Four discrete sulphide stringer vein zones extend up to 13 m below the Wolverine massive sulphide and Hump semi-massive zones, while another two occur on the western and south-western up-dip edge of the deposit. The stringer zones are surrounded above and laterally by chalcopyrite rich replacement style sulphide mineralisation, which grades into sphalerite replacement on the lateral margins of the massive sulphide lenses.
The massive sulphides are banded, and comprise 70 to 95% fine grained sulphides, dominantly pyrite and sphalerite, with subordinate pyrrhotite, chalcopyrite, galena, tetrahedrite and arsenopyrite and trace marcasite, native gold, meneghinite, bournonite, boulangerite and miargyrite.
The semi-massive sulphides comprise 10 to 50% sulphides which have partially or wholly replaced the host forming discrete, fine-grained, semi-massive sulphide lenses from several cm to 1 m thick. These lenses are composed of chalcopyrite, sphalerite, pyrite and minor pyrrhotite. Chalcopyrite is more abundant in the semi-massive compared to the massive sulphides and is asscoaited with chlorite alteration. Semi-massive replacement sphalerite occurs as lenses, blebs and disseminations, associated with sericite and ankerite, distal to the massive sulphides.
The stringer vein sulphides occur as 2 to 3 cm thick quartz-sulphide stringer veins which parallel the S1 foliation and comprise 5 to 10% of the rock. Individual veins are enveloped by 5 to 10 cm selvages of silicification, while groups of veins may occur within a silicified zone up to 25 cm wide which contains pyrite and sphalerite with subordinate chalcopyrite, pyrrhotite and arsenopyrite. Common gangue includes quartz, calcite, dolomite, ankerite, siderite, chlorite, biotite and muscovite.
The geologic resource at Wolverine comprises:
6.237 Mt @ 12.7% Zn, 1.6% Pb, 1.3% Cu, 371 g/t Ag, 1.8 g/t Au (Bradshaw, et al., 2008).
Measured + Indicated resources - 4.51 Mt @ 12.04% Zn, 1.15% Cu, 1.57% Pb, 351.5 g/t Ag, 1.68 g/t Au; plus
Inferred resource - 1.69 Mt @ 12.16% Zn, 1.23% Cu, 1.74% Pb, 385.1 g/t Ag, and 1.71 g/t Au (Peter et al. 2007).
Kudz Ze Kayah
This deposit is hosted by the Kudz Ze Kayah Unit, comprising a felsic volcanic and sediment dominated sequence comprising mainly Devonian to Lower Carboniferous, 360 to 356 Ma felsic volcanics with variably carbonaceous sediments in the lower sections of the unit. The deposit comprises a coherent lens of massive to semi-massive sulphides deformed into a large isoclinal synform with a fold vergence and dip to the NNE. The limbs of the isoclinal synform are known as the upper and lower lenses that show a near symmetric base-metal and hydrothermal alteration zonation around the fold axis. It extends down dip for around 300 m and has a strike lenght of approximately 750 m. The mineralisation reaches a maximum thickness of 34 m and predominantly comprises pyrite, sphalerite, minor chalcopyrite, galena, pyrrhotite, barite and trace arsenopyrite, tetrahedrite, electrum and boulangerite.
The stratigraphic footwall rocks are extensively altered with stringer and/or replacement mineralisation characterised by and upward transition of pyrite, chalcopyrite, sphalerite and galena, with white mica, chlorite and albite concentrated towards the base. The hangingwall rocks, in contrast have little visible alteration or mineralisation.
Several metre scale granitic pegmatite dykes cut the footwall meta-volcanics and massive sulphides and have chloritised margins and when in massive sulphides have associated centimetric scale sulphide recrystallisation aggregates.
The geologic resource at Kudz Ze Kayah comprises:
13 Mt @ 5.5% Zn, 1.3% Pb, 1% Cu, 125 g/t Ag, 1.2 g/t Au (Bradshaw, et al., 2008).
GP4F
This deposit is also hosted by the Kudz Ze Kayah Unit, as descibed above and is approximately 5 km SE of Kudz Ze Kayah and 20 km west to WNW of Wolverine. Mineralisation occurs as a single, narrow, massive to semi-massive sulphide lens that dips at 30 to 35°N and is up to 3.2 m thick. The sulphides zones comprise pyrite and sphalerite, with minor galena and pyrrhotite, and trace chalcopyrite. The mineralised zone occur in an overturned homoclinal sequence. The stratigraphic footwall/structural hangingwall have a well developed hydrothermal alteration assemblage of muscovite-tourmaline-chlorite-biotite-garnet and a weakly developed base-metal zonation.
The massive sulphides of the deposit are cut with sharp margins by numerous, metre-scale, dark-grey intemediate to basalt dykes.
The geologic resource at GP4F comprises:
1.5 Mt @ 6.4% Zn, 3.1% Pb, 0.1% Cu, 89.7 g/t Ag, 2.0 g/t Au (Bradshaw, et al., 2008).
Fyre Lake
The Fyre Lake deposit, also known as Kona, is located ~160 km NW of Watson Lake, 140 km southeast of Ross River, and ~24 km south and 30 km SW of the GP4F and Wolverine deposits respectively in Yukon, Canada. It is ~10 km NE of the NW-SW continental scale Tintina Fault and is hosted within the ~365 Ma, Late Devonian, Fire Lake Formation of the Grass Lakes Group. The Fire Lake Formation is a metamorphosed volcanic sequence, now predominantly composed of chloritic phyllite after mafic volcanic protoliths, with some carbonaceous phyllite, and rare muscovite-quartz phyllite of probable felsic volcanic origin. It immediately overlies clastic rocks of the North River Formation. The immediate host rocks to mineralisation are chlorite-quartz and chlorite-actinolite-quartz schists after mafic volcanic and volcaniclastic protoliths, and the turbiditic meta-sedimentary rocks of the immediate stratigraphic hanging wall. The latter are predominantly finely laminated carbonaceous phyllite which overlie the volcanic rocks. Intercalated quartz biotite schists after mafic volcaniclastic protoliths, and chlorite-mica-quartz schists after wackes that occur at the base of the sedimentary sequence and grade up into the carbonaceous sedimentary rocks.
The deposit comprises three parallel, NW trending tabular massive sulphide lenses that make up the East Kona (Upper and Lower horizons) and West Kona zones. The two zones are interpreted to be separated by a steeply dipping reverse fault with a west-side down displacement of ~100 m. The upper and lower lenses of the East Kona zone each have average thicknesses of 8 to 12 m and average widths perpendicular to plunge of 100 to 125 m. The upper lens is at the contact between the overlying sedimentary and underlying volcanic rocks, whilst the lower lens, which is 40 to 70 m stratigraphically lower, is hosted by mafic volcanic rocks. The massive sulphides in these lenses is essentially composed of massive pyrite, with lesser pyrrhotite, chalcopyrite, sphalerite and local lenses of massive magnetite. The West Kona zone extends over a strike length of 1500 m and dips gently to the NE, but in 2007 was unclosed.
The massive sulphides are generally zoned, from pyrite ±sphalerite at the top, to pyrrhotite and chalcopyrite predominating at the base of each lens, and in the underlying semi-massive and disseminated mineralisation which is accompanied by chlorite and quartz alteration. Quartz-rich bands within this mineralisation have been interpreted to be stringer veins that have been tectonically transposed parallel to the prominent foliation (Sebert et al., 2004). The West Kona massive sulphides are dominated by magnetite-pyrite-chalcopyrite in a grey siliceous matrix in the east, grading westward through pyrite-chalcopyrite, to massive pyrrhotite in the western-most margins. The top of massive sulphide lenses at West Kona and the base of the East Kona zone are marked by a unit of fine grained chert with a few percent sulphides, mainly chalcopyrite and pyrite, with and magnetite. This unit is typically 15 to 40 cm, but locally ranges up to several metres in thickness (Columbia Gold Mines Ltd., 1999; Sebert et al., 2004). Textures and mineral relationships suggest magnetite predates sulphide, and sulphides have brecciated and partly replaced magnetite, with subsequent deformation imparting a crudely banded texture of alternating magnetite and sulphide-rich layers.
The Fyre Lake deposit contains a mineral resource of 8.5 Mt of Cu-Co-Au ore (Piercey, et al., 2001).
or 15.4 Mt @ 1.2% Cu, 0.8% Co, 0.46 g/t Au (cut off of 0.5 % Cu),
or 8.2 Mt at 2.1 % Cu, 0.11 % Co, and 0.73 g/t Au (cut off of 1% Cu). (Peter et al. 2007).
The information in this Fyre Lake summary is drawn from Peter et al. (2007).
Ice
The Ice deposit is located in the northwestern part of the Finlayson Lake District, ~60 km east of Ross River and 60 km NW of the ABM deposit. Host rocks are basalts, cherts and mudstones of the Campbell Range Formation in the Slide Mountain Terrane. The immediate hosts are massive basalts, porphyritic-pillowed basalts and variably autobrecciated pillowed basalts that are plagioclase porphyritic immediately below the deposit (Becker, 1997, 1998; Eaton and Pigage, 1997; Pigage, 1997). These basalts are interbedded with black, grey, green and red ribbon cherts, with minor greywackes and carbonaceous mudstones. Mineralisation at Ice occurs as a massive sulphide lens that is up to 28 m thick, and is underlain by a zone of stringer sulphide veining. Primary textures are considerably better preserved at Ice than at the Kudz Ze Kayah, GP4F and Wolverine deposits. The massive sulphide lens is composed of a basal Cu-rich core of chalcopyrite, bornite and Cu-rich sphalerite that occurs directly stratigraphically above a zone of stringer sulphide vein mineralization that is locally present in brecciated footwall porphyritic basalt. Stringer veins are mainly pyrite-quartz-chalcopyrite with specular hematite. The basal core of Cu-rich massive sulphides grades outward into a thinner periphery of lower grade Cu mineralisation, and is overlain by a thin, ~5 to 50 cm thick siliceous hematitic chert band that passes upwards into a hanging wall of massive basalt flows and interlayered chert. The massive sulphides are characterised by low Pb, and very low As, Sb, Hg, and Se contents. Secondary mineralisation is confined to a zone of near surface weathering that typically ranges from 5 to 50 m below surface, but may persist for up to 80 m depth along fractures. Secondary mineralogy includes minerals that have wholly or partially replaced primary sulphide minerals and others that were precipitated from groundwater.
The Ice deposit contains a mineral resource of 4.56 Mt @ 1.48% Cu and an estimated but un-calculated 1% Zn, (Peter et al. 2007).
The information in this Ice summary is drawn from Peter et al. (2007).
The most recent source geological information used to prepare this decription was dated: 2022.
Record last updated: 8/7/2022
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Bradshaw G D, Rowins S M, Peter J M and Taylor B E 2008 - Genesis of the Wolverine Volcanic Sediment-Hosted Massive Sulfide Deposit, Finlayson Lake District, Yukon, Canada: Mineralogical, Mineral Chemical, Fluid Inclusion, and Sulfur Isotope Evidence: in Econ. Geol. v103 pp 35-60
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Denisova, N. and Piercey, S.J., 2023 - Evolution of the Hydrothermal System Associated with the ABM Replacement-Style Volcanogenic Massive Sulfide Deposit, Finlayson Lake District, Yukon, Canada: in Econ. Geol. v.118, pp. 1055-1083. doi:https://doi.org/10.5382/econgeo.5004.
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Denisova, N. and Piercey, S.J., 2022 - Lithostratigraphy, Lithogeochemistry, and Tectono-Magmatic Framework of the ABM Replacement-Style Volcanogenic Massive Sulfide (VMS) Deposit, Finlayson Lake District, Yukon, Canada: in Econ. Geol. v.117, pp. 1299-1326
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Denisova, N., Piercey, S.J. and Walle, M., 2024 - Mineralogy and mineral chemistry of the ABM replacement-style volcanogenic massive sulfide deposit, Finlayson Lake district, Yukon, Canada: in Mineralium Deposita v.59, pp. 473-503.
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Layton-Matthews D, Peter J M, Scott S D and Leybourne M I 2008 - Distribution, Mineralogy, and Geochemistry of Selenium in Felsic Volcanic-Hosted Massive Sulfide Deposits of the Finlayson Lake District, Yukon Territory, Canada: in Econ. Geol. v103 pp 61-88
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Manor, M.J., Piercey, S.J., Wall, C.J. and Denisova, N., 2022 - High-Precision CA-ID-TIMS U-Pb Zircon Geochronology of Felsic Rocks in the Finlayson Lake VMS District, Yukon: Linking Paleozoic Basin-Scale Accumulation Rates to the Occurrence of Subseafloor Replacement-Style Mineralization: in Econ. Geol. v.117, pp. 1173-1201.
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Peter, J.M., Layton-Matthews, D., Piercey, S., Bradshaw, G., Paradis, S. and Boulton, A., 2007 - Volcanic-hosted massive sulphide deposits of the Finlayson Lake District, Yukon: in Goodfellow, W.D., (Ed.), 2007 Mineral Deposits of Canada: A Synthesis of Major Deposit-Types, District Metallogeny, the Evolution of Geological Provinces, and Exploration Methods, Geological Association of Canada, Mineral Deposits Division, Special Publication No. 5, pp. 471-508.
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Piercey S J, Peter J M, Mortensen J K, Paradis S, Murphy D C and Tucker T L 2008 - Petrology and U-Pb Geochronology of Footwall Porphyritic Rhyolites from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon, Canada: Implications for the Genesis of Massive Sulfide Deposits in Continental Margin Environments: in Econ. Geol. v103 pp 5-33
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Piercey S J, Paradis S, Murphy D C, Mortensen J K 2001 - Geochemistry and paleotectonic setting of felsic volcanic rocks in the Finlayson Lake volcanic-hosted massive Sulfide district, Yukon, Canada: in Econ. Geol. v96 pp 1877-1905
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Piercey, S.J. and Kamber, B.S., 2019 - Lead Isotope Geochemistry of Shales from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon: Implications for Pb Isotope Vectoring in Exhalative Ore Systems: in Econ. Geol. v.114, pp. 47-66.
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Piercey, S.J., Gibson, H.L., Tardif, N. and Kamber, B.S., 2016 - Ambient Redox and Hydrothermal Environment of the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon: Insights from Lithofacies and Lithogeochemistry of Mississippian Host Shales: in Econ. Geol. v.111, pp. 1439-1463
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