(2) Timmins Nickel
(4) Timmins Nickel (51%) - BHP-Utah (49%)
(5) Middleton (1975), approximate tonnage
(6) grades supplied by D. Brisbin, Geologist, Falconbridge Limited, Kidd Creek Mine
(7) Concentrate produced, P. Binney, Geologist, Falconbridge Exploration
(8) Coad, 1976.
(9) Giant Yellowknife Mines Limited
(10) Crown Held in Abeyance, pending issuance of exploratory license of occupation (as of May 11, 1990)
4.3- Kidd-Munro Assemblage
This assemblage consists of ultramafic, pyroxenitic, and basaltic komatiite, tholeiitic picrite, magnesium-rich tholeiite, high-alumina basalt, iron-rich tholeiite, icelandite (andesite), and thin units of high-silica rhyolite (Basaltic Volcanism Study Project 1981, Chapter 1.2; see Section 126.96.36.199 for discussion or high-silica rhyolite). Variolitic, massive, and pillowed basalt units also occur (e.g., Leahy and Ginn 1961a,b; Arndt and Nesbitt 1982). Associated with these metavolcanic sequences are layered, tholeiitic (e.g., Munro Lake Complex, Centre Hill Complex, McCool Hill Complex; MacRae 1969) and ultramafic intrusions. Lithologies generally strike east to southeasterly and dip steeply. In the eastern part of the assemblage, units face both to the north and south, which is attributed, in part, to the presence of several east-striking folds and several east- to southeast-striking shear zones. Facing and dip direction of units in the western part of the belt are poorly constrained.
The most comprehensive descriptions of mafic and ultramafic flows are for those which crop out in Munro Township (Arndt and Nesbitt 1982), the location of the classic ultramafic komatiites of Pyke Hill (Pyke et al. 1973). Based on geochemical criteria several types of basalts are recognized (Arndt and Nesbitt 1982): Type 1: LREE-depleted, flat HREE, low abundances of incompatible elements; Type 2: flat REE, enriched in incompatible elements; Type 3: Theo's flow basalts, strongly enriched in incompatible elements, slightly enriched LREE pattern, fractionated HREE; 4) Warden Township basalts, having trace element characteristics similar in some respects to those of "Type 2" basalts (enriched incompatible elements, inferred flat REE patterns). " Type 1" basalts could have been derived from a depleted mantle source (Arndt and Nesbitt 1982). All other magmas could have come from a second source which had roughly chondritic trace element ratios (Arndt and Nesbitt 1982). The extent to which these detailed petrochemical relationships, described from Munro Township, can be applied through the Kidd-Munro assemblage remains to be confirmed.
Rhyolites and high-silica 2715 Ma (Barrie 1990) rhyolites in the western part of the assemblage, near the Kidd Creek Mine, have relatively flat REE patterns ([La/Yb] = 1-4), pronounced negative Eu anomalies (Eu/Eu = 0.20 to 0.61), low Zr/Y (2 to 6), high abundances of high field strength elements, and low abundances of Sc and Sr (Lesher et al, 1986). Felsic metavolcanic rocks from Beatty Township, in the eastern part of the Kidd-Munro assemblage, have an age of 2714 +/ - 2 Ma (Corfu et al. 1989). This dated rhyolite is chemically similar to rhyolites in the western part of Munro Township, and provides the probable age for the komatiites in Munro Township. Rocks and associated base metal mineralization in Munro Township are discussed in more detail In Section 6.3.
4.3.1. Contact Relationships
The northern contact of this assemblage with the Duff-Coulson-Rand assemblage is not exposed, but locally appears to be coincident with a shear zone having a dextral horizontal slip component (see discussion above). The Pipestone shear zone defines the contact with the Hoyle assemblage to the south (e.g., Leahy and Ginn 1961a). No kinematic analysis of this shear zone has been carried out. This western contact of the assemblage is quite irregular and it is not known if this reflects a stratigraphic or structural interleaving of lithologies. It is not known if this assemblage extends to the west of the Mattagami River fault (Fig. 4).
5.1.1. Volcanic-associated, Massive, Base Metal Sulphide Mineralization
In the southwestern part of the Abitibi greenstone belt, polymetallic, massive, base-metal sulphide mineralization occurs in the Kidd-Munro and Kamiskotia assemblages. At the western end of the Kidd-Munro assemblage, the giant (Table 2), stratiform, polymetallic Kidd Creek deposit occurs associated with a sequence of massive to autobrecciated flows and pyroclastic felsic metavolcanic rock and effusive and intrusive mafic and ultramafic igneous rocks (see Section 7.2.). In the eastern part of the Kidd-Munro assemblage, copper-zinc mineralization at the Potter Mine is hosted by hyaloclastite units, within a sequence of tholeiitic olivine basalts and komatiites (Coad 1976; see Section 6.3.3.). Felsic metavolcanic rocks within the Kidd-Munro assemblage have ages of 2714 +/-2 (Beatty Township, immediately west of Munro Township; Corfu et al. 1989) and approximately 2717 Ma (Kidd Creek rhyolite; Barrie and Davis 1990). These dates provide a constraint on the probable age of the Kidd Creek and Potter Mine polymetallic, massive sulphide mineralization in this assemblage.
Polymetallic, massive, sulphide mineralization also occurs within the Kamiskotia meta-igneous assemblage, associated with felsic and mafic metavolcanic, rock within the Kamiskotia metavolcanic complex (see Section 7.1.). Zircon ages for the Kamiskotia gabbroic complex and the Kamiskotia rhyolite are 2707+/-2 Ma and 2705 +/-2 Ma, respectively (Barrie and Davis 1990). Hence, the polymetallic massive sulphide deposits in the Kamiskotia area appear to have formed approximately 10 Ma after those in the Kidd-Munro assemblage.
Polymetallic, massive, base-metal sulphide mineralization occurs elsewhere in the southern Abitibi greenstone belt in older (e.g., Normetal deposit in 2730 +/-1.5 Ma felsic volcanic rocks; Mortensen l987) and younger (e.g., Noranda deposits in 2700 Ma felsic metavolcanic rock; Mortensen 1987) metavolcanic assemblages.
KOMATIITE-ASSOCIATED NI-CU-PGE MINERALIZATION
The most important association of nickel mineralization in the Timmins area is the komatiite-hosted one, and the area represents one of the best examples of this type outside of the type example at Kambalda in the Yilgarn block of Western Australia.
The purpose of this chapter is to provide basic information on nickel deposits of this association in the Timmins area, and on the komatiites and other rocks with which they are closely spatially associated. It is the intention to provide information of a nature that will be helpful in the development and refinement of ore deposit models for these deposits. Some specific descriptions of field trip stops are given but, as with other sections of the guide, it is not possible to guarantee access to mines at the time of writing this guide.
Sufficient evidence from precise U-Pb dating shows that the komatiites are not all of the same age (see Sections 4.3, 4.6., 4.11.). However, there are insufficient data to confirm the probably different ages of the komatiites hosting nickel deposits in the Alexo-Dundonald and Shaw-Bartlett Dome areas.
The Pyke Hill outcrop is unique and has already suffered damage from visitors. Please do not use hammers or dislodge samples here. This outcrop lies 300 m east of the abandoned Potter Mine, at the edge of the tailings pond. The outcrop is comprised of unusually well exposed and little altered komatiitic lava flows described by Pyke et al. (1973) and Arndt and Naldrett (1987). The spectacular spinifex bearing flows are an end member of a continuum from spinifex rich flows to uniform ones in which spinifex is absent. A map of the outcrop is shown in figure Nl3. Typical sections through the end member flows are shown in figure Nl4. The following description is taken from Arndt and Naldrett (1989).
Al zone - sparse olivine phenocrysts in a matrix of altered glass. This is the flow top and displays joints (cooling cracks) breaking it up into polyhedra;
A2 zone - skeletal olivine blades become progressively coarser, and are randomly oriented in altered glass with augite needles;
A3 zone - olivine blades develop as randomly oriented books that begin to align at right angles to the flow;
B1 zone - thin zone of tabular skeletal olivine grains;
B2 zone - polyhedral and equant olivine occupies up to 80 percent of the rock with interstitial augite needles and altered glass;
B3 zone - knobby weathering of clots of augite rich matrix is distinctive here, but not common In komatiites outside Munro township;
B4 zone - olivine gives way to altered glass in this basal chill zone of the flow.
The flows at the top of the sequence are normal spinifex-textured and massive komatiites. They range in thickness from one to thirteen metres and have textures and mineralogies just like those of Pyke Hill, described above. The flow sequence underlying the lava lake is made up of komatiites and pyroxene spinifex-textured basalts.
The lava lake is about 120 metres thick (Fig. Nl5). The lower two-thirds is composed of massive, medium-grained dunite, now largely but not completely serpentinized, and upper third is composed of fine-grained olivine porphyry. The upper 30 to 40 metres of the unit are cut by veins with unusual swirling tabular olivines, and in the uppermost 10 to 20 metres numerous spinifex-textured veins appear.
The Centre Hill outcrop area is the only one showing a complete stratigraphic section of the Munro Lake sill between its lower and upper contacts. Within the exposure at Centre Hill, the intrusion is essentially vertical. It generally has an east strike, but it is folded sharply southward at its western end where MacRae (1969) interpreted it to be dragged against and cut off by the Centre fault (Fig. Nl2). Both the northern and southern (or upper and lower) contacts of the sill with volcanic rock are exposed. On the north it has intruded a mafic fragmental rock and on the south, basalt. The contacts are sharp and at places there is a slight intertonguing of the intrusive and volcanic rocks. Immediately adjacent to the lower contact, the intrusive rock may have been slightly chilled, but an exact interpretation is difficult because of the subsequent metamorphism and alteration of the rock.
The following description of the Complex is provided by Coad (1976). "The complex is not a simple layered body, but is composed of many alternating layers of ultramafic and mafic rocks. MacRae (1969) recognizes seven cyclic units. The lower five consist of successive layers of peridotite and clinopyroxenite, the sixth is composed of clinopyroxenite and gabbro and the upper most seventh unit consists of a layer of melanocratic gabbro overlain by normal gabbro. The ultramafic layers range in thickness from one to fifty metres and lie in sharp contact with each other. The uppermost gabbroic unit is over 200 metres thick. At the lower contact there is a unit of hornblendite ten to thirty metres thick."
The uppermost gabbro unit is overlain by a fragmental rock which is best described as a pillow breccia. This particular rock unit was previously mapped as a rhyolite agglomerate (Satterly 1951); however, It has a composition intermediate between a tholeiitic olivine basalt and picritic basalt. The contact between the pillow breccia and gabbro appears to be faulted where examined in aerial photographs and is seen to be sheared where exposed. The pillow breccia outcrops over a stratigraphic thickness of approximately 60 metres. Drill hole information, together with extrapolation of rook unit thicknesses along strike, indicate that this thick unit of fragmental rock is approximately 75 metres thick in the east, but becomes progressively thinner towards the west, along strike. The eastern extension of the pillow breccia is not exposed because of extensive drift cover and major north south faulting along the eastern edge of the Centre Hill complex. Pillow breccia is stratigraphically overlain by komatiitic lava. To the west, outcrop exposure of the pillow breccia is not continuous along the top of the Centre Hill complex, but drill hole data, together with outcrop exposure further to the west, indicates that this rock unit grades laterally along strike into hyaloclastite (Coad 1976).
It seems a curious coincidence that the mine overlies the junction of the Centre Hill complex to the east and the Komatiite lava lake to the west. The zone of shearing between these was always assumed to be a fault by MacRae (1969) and others. However the excellent mapping, drill core logging and petrography described by Coad (1976), which is referenced extensively in this section, permits another interpretation. He shows that the hyaloclastite and the mineralized horizons of the Potter Mine lie at the same levels without offset either side of the shear zone. Although some faulting undoubtedly did occur, part of it may have been synvolcanic, and the zone is an excellent candidate for a feeder zone for the mineralization. It is quite possible that the lava lake and the Centre Hill sill or flow lie close to their original positions and represent a facies change.
The following descriptions are directly taken from Coad (1976). "The mine geology is characterized by two distinct volcanic series, namely komatiitic lavas and tholeiitic olivine basalts. The komatiitic lavas consist predominantly of picritic flows and intercalated with these flows are massive peridotitic komatiites, characterized by an MgO content greater than 30 percent. The massive peridotitic komatiites are not characterized by associated flow tops marked by spinifex texture. The tholeiitic and olivine basalts are chemically distinct from the komatiitic lavas and consist of three different rock types: 1) hyaloclastite; 2) quench-textured tholeiite; and 3) pillow breccia. Although volumetrically insignificant, thin beds of volcanic ash occur at the top of the hyaloclastite horizon and actually represent a third distinct rock sequence, having a dacitic composition."
The predominant rock type in the central portion of the map area is hyaloclastite, a term used to describe a fragmental consisting of pea-sized fragments of pillow breccia and glass (Coad 1976). The hyaloclastite is commonly stratigraphically underlain by quench-textured tholeiitic lava which outcrops over a stratigraphic thickness of approximately 12 metres. The hyaloclastite matrix can consist of ash and fine grained carbonate, quartz, plagioclase and up to 19 percent disseminated graphite (Coad 1976). Volcanic ash occurs at the top of the hyaloclastite units. This ash is composed of grains of quartz and broken plagioclase crystals and it locally is banded and shows load-cast structures (Coad 1976). Thin layers (<0.5 metres) of chert also occur within the ash unit (Coad 1976). The hyaloclastite and quench-textured tholeiite form a wedge-shaped mass at the western end of the Center Hill complex which have been drag-folded and down-faulted stratigraphically into place, or, may have formed approximately in their current position (Coad 1976).
Coad (1976) provides the following description of the pyroclastic rocks in this area. "The pyroclastic sequence contains a lower portion of crudely-bedded well-sorted basaltic scoria and an upper portion of coarser agglomerates and welded spatter, also with basaltic composition and also crudely bedded or massive. Fragments in the scoria average 0.5 to 1 millimetres across. Most are approximately equidimensional, with shapes varying from subangular to rounded, to amoeboid or ribbon-like. Some smaller grains in the matrix have shard shapes. Textures vary considerably, from originally completely glassy (now altered to chlorite), to fine-grained porphyritic with small, altered olivine and clinopyroxene phenocrysts, and in rare cases microspinifex. Most fragments are not amygdaloidal or contain only sparse amygdules (1 to 2 percent), but some fragments have 10 to 15 percent. Amygdules are less than 0.5 millimetres across. One or two fragments in each thin section have a wispy, patchy, ribbon-like form and may be squashed pumice. Each thin section also contains a few, usually larger, angular fragments of exotic rock types such as feldspar-porphyritic felsic volcanics, pale cream relatively pure cherts, and dark-coloured graphite- rich (?) cherts. The matrix is cryptocrystalline cherty quartz, feldspar and chlorite, or carbonate."
"The agglomerates higher in the unit have fragment sizes between one and fifty centimetres, usually around two to five centimetres. Fragments are rounded or have complex amoeboid shapes. They are commonly deformed and moulded against adjacent fragments. They also have basaltic composition and fine grained aphanitic or olivine clinopyroxene porphyritic texture."
Massive and matrix sulphide mineralization at the Potter Mine consists predominantly of pyrrhotite, equal proportions of sphalerite and chalcopyrite, and minor pyrite (Coad 1976). Economic concentrations of sulphide mineralization are restricted to the hyaloclastite horizon, but sulphides were remobilized along shears into the adjacent picritic basalt flows (Coad 1976). Iron-rich sphalerite occurs throughout the hyaloclastite horizon, associated with chalcopyrite and pyrrhotite. Iron-poor sphalerite occurs at the top of the hyaloclastite horizon (Coad 1976).
Matrix sulphide is the more common habit, whereby sulphides occupy the interstices between fragments of glass, pillow breccia of the hyaloclastite (Coad 1976). The matrix or disseminated sulphide grades into massive sulphide lenses. Massive ore lenses occur within the upper hyaloclastite horizon, although some massive ore may also have occurred in the lower hyaloclastite (Coad 1976). These lenses, ranging from 15 to 30 metres in length, lie directly on top of the hyaloclastite horizon. The massive sulphide lenses average one metre in thickness, but are continuous in the vertical dimension to a depth of 365 metres (Coad 1976). The massive sulphide lenses were commonly banded with respect to chalcopyrite, sphalerite, and pyrrhotite (Coad 1976).
The massive sulphide is intimately related to volcanic ash which occurs throughout the hyaloclastite unit, but which is more abundant at the top of the unit (Coad 1976). The upper surface of the massive sulphide lense lies in sharp contact with the chilled base of the overlying picritic (komatiitic) flows (Coad 1976). A thin concentration of iron-poor sphalerite may occur along this upper contact (Coad 1976).
Coad (1976) did not observe stringer mineralization. However, stringer mineralization, associated with chlorite alteration, was reported to occur in an area of the mine that was disrupted by shearing (Coad 1976, p.144). Chlorite also occurs as a matrix mineral where the hyaloclastite is sheared or mineralized with sulphides (Coad 1976).
188.8.131.52. Metal Zoning
Despite the abundance of komatiites in this area, the sulphide mineralization did not contain significant nickel, and averaged only 0.03 weight percent (Coad 1976, p. 172). The copper/zinc ratio was close to or less than one (Coad 1976), although the massive ore was zoned from a zinc-rich top to a copper-rich base (Coad 1976). Zinc grades were much less in the vicinity of the strong chlorite alteration zone, supporting the premise that the chlorite alteration represented a feeder-pipe (Coad 1976). Nickel/cobalt ratios of the ore were less than one (Coad 1976).
According to Coad (1976), the source of metals concentrated in that
mine is probably the mafic-ultramafic magma represented by the Centre Hill
Complex, in particular the gabbro member. The metals were probably transported
either by primary hydrothermal fluids escaping during magmatic differentiation
or by secondary leaching involving the convection of sea water. Whether
or not sea water penetrated the gabbro, a combination of solutions was
probably instrumental in the transportation of metals from the gabbro member
of the Centre Hill complex through the overlying hyaloclastite units. The
sulphur may have been derived from both sea water and the magma (Coad 1976).
|email@example.com © 2005 Millstream Mines. All rights reserved|