The Lara occurrence is located on Solly Creek, approximately 5.5 kilometres south west of Holyoak Lake.
The occurrence is a volcanogenic polymetallic massive sulphide deposit located in the Cowichan uplift, one of three geanticlinal uplifts that expose Paleozoic volcanic and sedimentary rocks on Vancouver Island. The Paleozoic rocks are intruded by mafic sills (informally called the Mount Hall Gabbro) that are coeval with overlying basaltic volcanics of the Upper Triassic Karmutsen Formation, Vancouver Group. All of these sequences have been subsequently intruded by granodioritic stocks of the Early to Middle Jurassic Plutonic Suite (formerly the Island Intrusions). Upper Cretaceous sediments of the Nanaimo Group lie unconformably on the older sequences. The geology of the Paleozoic rocks has recently undergone reinterpretation and the stratigraphy has been reassigned to several new formations of a redefined Sicker Group and to the new Buttle Lake Group (formerly the upper part of the Sicker Group).
The new Buttle Lake Group consists of: (1) the Lower Permian(?) St. Mary's Lake Formation composed of volcanic sandstone, conglomerate, argillites and turbidites; (2) the Upper Pennsylvanian to Lower Permian Mount Mark Formation (formerly Buttle Lake Formation) consisting of massive crinoidal limestone, bedded limestone, marble, chert and argillite; and (3) the Mississippian to Pennsylvanian Fourth Lake Formation (formerly Cameron River Formation, and equivalent to the upper parts of the Myra Formation of Muller) made up of mostly thinly-bedded, often cherty sediments which include ribbon chert, argillite, crinoidal limestone, intercalated sandstone, siltstone and argillite, epiclastic sandstone and conglomerate, thickly bedded tuffite, lithic tuffite, laminated cherty tuff, heterolithic lapilli tuff and breccia.
The Sicker Group, from youngest formation to oldest, consists of: (1) the Upper Devonian McLaughlin Ridge Formation (the equivalent of lower parts of the Myra Formation of Muller) consisting of thickly bedded tuffite and lithic tuffite, feldspar-crystal tuff, heterolithic lapilli tuff and breccia, rhyolite, dacite, laminated tuff and chert; (2) the Devonian Nitinat Formation comprising pyroxene-feldspar phyric agglomerate, breccia and lapilli tuff, massive and pillowed flows, massive tuffite and lithic tuffite, laminated tuff and chert; and (3) the Devonian Duck Lake Formation (ascribed to the Karmutsen Formation by Muller) made up of pillowed and massive basaltic flows and, monolithic basalt breccias and pillow breccias, chert, jasper and cherty tuff, felsic tuffs and lapilli tuff, massive dacite and rhyolite.
The geology of the Duncan area differs, however, in that the McLaughlin Ridge Formation is dominated by volcanics with only minor tuffaceous sediments. The volcanics are predominantly intermediate to felsic pyroclastics, commonly feldspar-crystal lapilli tuffs and heterolithic lapilli tuffs and breccias. A thick package of quartz- crystal, quartz-feldspar-crystal and fine dust tuffs is developed in the Chipman Creek-Mount Sicker area and are host to the massive sulphides. This package thins to the west where it interfingers with andesitic lapilli tuffs and breccias. It appears to be stratigraphically high within the formation. A distinctive maroon schistose heterolithic breccia and lapilli tuff forms the uppermost unit within the McLaughlin Ridge Formation and is seen in the Chipman Creek-Rheinhart Creek area. Most contacts with overlying sediments are faulted.
Southern Vancouver Island has undergone a complex tectonic history involving at least 6 major deformational events, often rejuvenating previous structures (Fieldwork 1987, page 87). The area is dominated by the effects of Tertiary west-northwest trending thrusting which have cut the Cowichan uplift into several slices. Where exposed these are high-angle reverse faults which dip between 45 and 90 degrees to the north-northeast paralleling earlier formed axial foliation in the Sicker Group rocks. Slip planes are relatively sharp and narrow, though wide schistose zones have formed in receptive lithologies. The thrusts generally place older rocks over younger and become listric at mid-crustal depth. Displacements along the faults are unknown but are probably small, on the order of 1 to 10 kilometres. Direction of motion is also unknown.
The metamorphic grade is generally quite low, but increases with age and structural position of the rocks. Nanaimo Group sediments are essentially unmetamorphosed. Basalts of the Karmutsen Formation show characteristics and alteration assemblages typical of the prehnite-pumpellyite facies. Intrusive rocks are unaltered. Sediments of the Fourth Lake Formation are essentially unmetamorphosed except where involved in intense shearing. Volcanic rocks of the McLaughlin Ridge and Nitinat formations in the Chipman Creek to Maple Mountain belt, however, show the effects of greenschist facies metamorphism. The felsic volcanic rocks develop sericite, talc and chlorite along foliation planes and are interbedded with minor chlorite schists. Intermediate to mafic rocks have chloritic schistose matrixes with epidote alteration of feldspars. Lithic lapilli may show almost complete replacement by epidote.
The Lara property is underlain by the McLaughlin Ridge Formation which has been thrust over younger rocks of the Fourth Lake Formation and the Nanaimo Group by the Fulford fault, a regional west-northwest trending fault that dips at about 47 degrees and crosscuts bedding in the volcanic rocks at a shallow angle. The McLaughlin Ridge Formation consists of northerly dipping, west-northwest striking rhyolitic to andesitic rocks. Bedding in the rocks generally dips steeply at 60 to 75 degrees north, although dips of between 30 and 45 degrees are common between Humbird and Silver creeks. The Fourth Lake Formation south of the Fulford fault consists of basal pebble conglomerate and volcaniclastic units grading upward into a sandstone-argillite series and then to an upper argillite series with siltstone and chert interbeds. The Nanaimo Group, which unconformably overlies the Fourth Lake Formation includes basal conglomerates, sandstone, and fossil-bearing mudstone.
The strata on the property is cut by a number of mafic intrusions which are probably feeders to the Karmutsen Formation. The intrusions are composed of medium to coarse-grained diabase, gabbro and leucogabbro with minor diorite. They are commonly porphyritic with feldspar phenocrysts often forming glomero-porphyritic clusters up to 3 centimetres in diameter. Mafic phenocrysts are generally absent. Equigranular gabbros are also common. The intrusive bodies also vary in form. Sill-like bodies are generally subconcordant with bedding, but also may follow foliation where this is strongly developed. As a result of this they can show a variety of attitudes from shallow dipping to vertical. They may range in thickness from a few metres to 200 metres. Discordant dykes are also common, varying from 10 to 20 centimetres in width.
Also occurring are a number of quartz-feldspar porphyry dykes. These dykes, related to the Upper Devonian Saltspring Intrusive Suite (formerly Saltspring Intrusions and Tyee Intrusions), are coeval with the felsic volcanics of the McLaughlin Ridge Formation. The porphyries are usually well-foliated and sometimes difficult to distinguish from crystal tuffs.
The package of rocks which hosts the Lara deposits has been extensively tested by drill holes. It consists of an andesitic sequence referred to as the "Green Volcaniclastic Sequence", overlying rhyolite which are host to the massive sulphides. The rhyolite has been subdivided into two units which are referred to as the "Rhyolite Sequence" and the "Footwall Sequence", the latter underlying the lowermost sulphide sequence.
The Green Volcaniclastic Sequence is greater than 250 metres thick and dominated by fragmental rocks of intermediate composition. The sequence grades from coarse-grained locally silicified andesite at the base, to relatively fine-grained dacite tuff at the top. Thin argillite beds and laminae occur throughout the unit. An important argillite marker, locally greater than 1 metre thick, occurs in the transition zone from andesite to dacite. The contact between the Green Volcaniclastic and Rhyolite sequences is generally abrupt and is characterized by pronounced changes in colour, lithology and grain size. The contact is commonly accentuated by a well-developed gouge which may indicate a splay off the Fulford fault.
The Rhyolite Sequence hosts the polymetallic zones along the Coronation trend and is up to 75 metres thick. The sequence is lithologically uniform and consists predominantly of light grey, fine to coarse-grained rhyolite crystal and ash tuff. Quartz eyes are commonly present but are generally small (less than 2 millimetres) and comprise less than 10 per cent of the rock. These rocks are usually siliceous and cherty. Black argillite and buff-coloured volcanic mudstone beds are a common constituent of the sequence, typically ranging from less than 1 millimetre up to several millimetres in thickness. Argillite beds up to about a metre thick occur locally in the immediate footwall of the Coronation zone.
The Footwall Sequence, like the Rhyolite Sequence, is dominated by light grey rhyolites, but is characterized by the presence of coarse-grained massive quartz porphyry units up to 40 metres thick. These rocks are texturally variable but are distinguishable by the presence of abundant large quartz eyes. Feldspar porphyry dykes, rhyolite dykes, rhyolite breccia and mudstone and argillite beds are also present.
The Lara deposits include 3 polymetallic zones known as the Coronation zone, the Coronation Extension zone and the Hanging Wall zone. The deposits are classified as Kuroko-type massive sulphides and are volcanic-hosted, stratiform accumulations of copper, lead, zinc, silver and gold. Although classified as massive sulphides, the predominant facies actually consists of bands, laminae and stringers of sulphide minerals in a strongly silicified rhyolite host. The massive sulphide facies makes up about 20 per cent of the reserve.
The thickest, most extensive of these deposits is the Coronation zone which occurs primarily to the west of Solly Creek. The Coronation Extension zone which occurs to the east of Solly Creek is generally narrower and less continuous, but typically consists of high-grade massive sulphides. The Hanging Wall zone has only been recognized to the west of Solly Creek and is clearly at a different stratigraphic level than the other two. Although the zone locally attains ore-grade it is somewhat sporadic. The Coronation deposits occur in the Rhyolite Sequence immediately north of the Fulford fault. The deposits strike west-northwest, dip to the north at 60 degrees and exhibit considerable variation in both thickness and grade. Intercepts are up to 16 metres thick and average about 6 metres. One massive sulphide lens exposed by trenching in the Coronation zone graded 24.58 grams per tonne gold, 513.60 grams per tonne silver, 3.04 per cent copper, 43.01 per cent zinc and 8.30 per cent lead over 3.51 metres (Bailes et al., 1987).
The Coronation deposits can be divided into a massive sulphide facies, a banded and laminated facies and a stringer facies. The sulphide mineralogy of these facies is similar and consists primarily of sphalerite, chalcopyrite, galena and pyrite. Minor amounts of tetrahedrite and tennantite have also been noted. Minerals present in trace amounts include rutile, bornite, electrum, pearceite, arsenopyrite and barite. Gangue consists mainly of quartz and calcite with smaller amounts of muscovite, feldspar and barium-bearing feldspar. Sphalerite in the massive sulphide facies is typically medium to dark brown, as opposed to the very pale brown sphalerite characteristic of the other facies.
The massive sulphide facies is a relatively coarse-grained massive intergrowth of sulphide minerals and gangue (predominantly calcite). Interbeds of rhyolite or sedimentary rock are rare, although small siliceous pods may be included in the sulphide mass. This facies occasionally exhibits a banded texture which is best represented by chalcopyrite-rich bands of 1 to 2 centimetres. Local accumulations of massive pyrite occur. These are commonly barren but may contain significant gold or zinc values. The massive sulphide facies is consistently high grade except for the massive pyrite sections.
The predominant facies of the Coronation deposits is the banded and laminated facies which consist of sulphide laminae and bands up to a few centimetres thick in a siliceous host. The host rock varies from a silicified rhyolite to very fine-grained siliceous mass with various amounts of felsic tuffaceous debris. The mineralization is broadly conformable, however crosscutting features are common within the conformable zones. Crosscutting mineralization varies from occasional sulphide stringers to well-developed breccia zones with sulphides in the matrix. Sulphides also occur disseminated in the rhyolite host. Primary textures are masked by pronounced cataclastic overprint. Although these features to some extent mask the primary depositional style, the overall stratiform character of the facies is demonstrated by the presence of sedimentary units which enclose and occur within the deposit, and which can be correlated over considerable distances.
The banded and laminated facies varies up to about 16 metres true thickness. Although not as high grade as the massive sulphide facies, laminated and banded sulphides can achieve significant grade. Diamond-drill hole 85-36 for example, intersected 4.18 metres grading 9.91 grams per tonne gold, 82.63 grams per tonne silver, 0.86 per cent copper, 3.47 per cent zinc and 0.50 per cent lead. These intersections typically contain up to about 20 per cent sulphide bands and laminae, and relative to the massive sulphide facies contain a higher ratio of pyrite to total sulphides. Intersections usually contain from 3 to 5 per cent pyrite but concentrations of 10 to 15 per cent are not uncommon.
The stringer facies, which is restricted, is best developed in the Hanging Wall zone. The facies consists of narrow sulphides, generally less than 1 or 2 millimetres, in a silicified rhyolite host. It is generally low grade but may be thick and is commonly rich in precious metals relative to base metals. A 10.52-metre diamond-drill hole interval graded 0.96 grams per tonne gold, 43.89 grams per tonne silver, 0.06 per cent copper, 0.90 per zinc and 0.29 per cent lead (Bailes et al., 1987).
In 1998, the best intersection on the Coronation and Coronation Extension zones was encountered in Hole 98-05 where a length 4.54 metres returned values of 3.86 per cent zinc, 0.5 per cent copper, and 1.01 grams per tonne in gold. Another 0.7 metre section in Hole 98-09 assayed as high as 8.09 grams per tonne gold, 225 grams per tonne silver, 1.42 per cent copper, 5.38 per cent lead and 32.3 per cent zinc (Assessment Report 26021).
These zones have been traced over a strike length of about 2 kilometres and to a depth of 440 metres downdip from surface. The Coronation Zone is likely overturned and disrupted by numerous faults that apparently move the zone northward.
In 2006, two grab samples (929 and 930) of massive sphalerite-galena-tetrahedrite mineralization yielded values up to 57.13 per cent zinc, 581.0 grams per tonne silver, 3.40 per cent copper, 21.20 per cent lead and 6.91 grams per tonne gold (Kelso, L. (2007-11-15): Independent Technical Report and Mineral Resource Estimation – Lara Polymetallic Propert).
In 2007, a resource assessment of the Coronation Trend was compiled:
1 per cent Zinc Block Cut-off
Category Tonnes Zn Ag Cu Pb Au
(%) (g/t) (%) (%) (g/t)
Indicated 1,146,700 3.01 32.97 1.05 0.58 1.97
Inferred 669,600 2.26 32.99 0.90 0.44 1.90
2 per cent Zinc Block Cut-off
Category Tonnes Zn Ag Cu Pb Au
(%) (g/t) (%) (%) (g/t)
Indicated 428,600 5.65 47.04 2.25 1.18 2.39
Inferred 207,900 3.99 37.57 1.73 0.84 2.30
3 per cent Zinc Block Cut-off
Category Tonnes Zn Ag Cu Pb Au
(%) (g/t) (%) (%) (g/t)
Indicated 189,600 9.74 60.85 4.44 2.23 3.07
Inferred 91,100 6.15 40.79 3.15 1.45 2.50
(Assessment Report 29840)
Other zones of mineralization have been identified out side of the main Corona trend and include the 262, 162 and Silver Creek zones.
The 262 zone is sub-parallel to the main Corona trend zones and has been drill tested over a strike length of 6.5 kilometres. The zone comprises felsic volcanic rocks hosting a distal exhalite composed of pyritic cherts, ashes, and thin, copper-rich, semi-massive to massive sulphides and occurs within 40 metres of the contact between the felsic and the underlying andesite rocks. The best development of exhalative sulphides, cherts and stringer mineralization is found in shallow, near surface holes. At depth, there is a fine-grained, siliceous felsic ash that is depleted in base metals and hosted in unaltered felsic rocks, suggesting that this zone has limited opportunity for development.
The 126 and Silver Creek zones comprise stringer style mineralization consisting of chalcopyrite in quartz veins hosted by chloritic volcanic flows/tuffs, which overlie a thick sequence of felsic volcanic rocks. Drilling indicates the presence of a gabbro intrusion. The zones appear to be on a more northerly trend as part of the northern limb of a synclinal structure than the main Corona trend occurrences.
In 1982, the property was optioned to Abermin Corporation who carried out line cutting, geological mapping and trenching, ground geophysics and soil geochemical surveys. In 1983, eighteen backhoe trenches were placed over coincident geochemical and geophysical anomalies. In 1984, twelve diamond drill holes for a total of 1346 metres was drilled to test a number of targets from the above trenching and geological programs. In 1985, sixty-one drill holes for a total 7437 metres was carried out to further test the Coronation zone for over 990 metres along strike and to a depth of 160 metres down-dip. In 1986, a further program of drilling was carried out to continue testing the Coronation Zone and other reconnaissance targets on the property. Seventy-five holes for 11,339 metres was completed and extended the Coronation Zone for a total of 2100 metres of strike length. In 1987, further drilling increased the Coronation Zone mineralization, extended the Randy Zone to more than 2 kilometres of strike length and down-dip to
180 metres and tested several reconnaissance targets in other parts of the property. In this program, eighty-three holes were drilled for a total footage of 15,038 metres along with one backhoe trench over 87-44 located in the Coronation area. In 1988, the program was extended to include the potential of the Coronation Zone and included surface and underground drilling, mine cost studies, and a metallurgical test from a bulk sample of the main mineralized zone. Underground development work included 770 metres of ramping and drifting. In 1989, 43 drill holes for a total of 10,328 meters was added in which 6457 metres further delineated the Coronation Zone and 3871 metres was used to test other zones and geophysical targets. In 1990, a further 49 drill holes for anotherr 11,167 metres was completed on the property. Nineteen holes for 4139 metres tested the eastern extension of the Coronation mineralization, twenty-six holes for 6188 metres was drilled along the ‘262’ Zone mineralization, and four holes for 840 metres drilled to test other reconnaissance targets. In 1998, Nucanolan Resources, for Laramide Resources, completed a program of ground magnetics and VLF-EM surveys over discrete sections of the Coronation and Coronation Zone Extension and 12 diamond drill holes, totalling 2550 metres. In 2007, Laramide Resources, for Treasury Metals Inc., completed a program of airborne geophysical surveys, totalling 500.1 line kilometres, drill core re-sampling and a resources estimate of the Lara property. In 2009, Treasury Metals completed a program of structural mapping and whole rock geochemical sampling on the Lara property.