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Morrison |
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British Columbia, Canada |
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Cu Au Mo
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Morrison porphyry copper-gold-molybdenum deposit is located 21 km north of the Bell mine, north Babine Lake, and 86 km east of Hazelton in central British Columbia, Canada. (#Location: 55° 11' 23"N, 126° 19' 16"W).
The Morrison porphyry copper deposit was discovered by the Norex Group of Noranda in 1962 during a regional stream sediment sampling program in the Babine Lake Region. Follow-up of anomalous stream sediment Cu results led to the recognition of copper-bearing biotite feldspar porphyry in float and then in outcrop in anomalous stream catchments. Trenching of the thin overburden uncovered large areas of relatively unweathered chalcopyrite-bearing bedrock on both sides of the stream over an area 900 x 250 m, where a copper soil geochemical anomaly had been defined. The deposit was delineated between 1963 to 1973 with geochemical soil, electromagnetic, magnetic and IP surveys, together with trenching, geological mapping, alteration studies and 13 890 m of diamond drilling. Following the 1973 drill program, Noranda undertook no further field work at Morrison. Studies were undertaken to ascertain whether Morrison could economically supply feed to the Bell Mine. However, Noranda concluded that, at that time, such an operation would not be economic. No further work was done on the property until Booker Gold Exploration (now Pacific Booker Minerals Inc.) optioned it and initiated further exploration programs in late 1997. Between 1998 and 2003, surface backhoe trenching and 82 diamond drill holes totalling 25 245 m were drilled within the limits of the Morrison deposit previously drilled by Noranda. In 2005, four additional exploration holes for 957 m were completed and four large-diameter PQ 76 mm holes to a depth of 700 m were drilled for metallurgical samples twinning older holes as well as seven geotechnical holes for 1464 m in 2006 (Robertson et al., 2009). In 2014 and 2022, applications for an Environmental Assessment Certificate were refused by the British Columbia Government. No mining has been undertaken to 2024.
Published reserve and resource figures include:
95 Mt @ 0.42% Cu, 0.02% Mo, 0.34 g/t Au, (Reserve, Carson and Jambor, 1976),
190 Mt @ 0.40% Cu, 0.21 g/t Au (Indicated + Inferred Resource to 330 m, 1993)
123 Mt @ 0.38% Cu, 0.20 g/t Au (drill indicated resource, 1998)
12.4 Mt @ 0.53% Cu, 0.26 g/t Au (Measured + Indicated Resources, 2003),
86.9 Mt @ 0.45% Cu, 0.26 g/t Au (open pit resource, 2004),
289.43 Mt @ 0.33% Cu, 0.16 g/t Au, 0.005% Mo (Meas. + Ind. Resource, Pacific Booker Minerals March 2009, 0.1% Cuequiv. cut-off),
224.25 Mt @ 0.330% Cu, 0.163 g/t Au, 0.004% Mo (Prov. + Prob. Reserve, Pacific Booker Minerals May 2024, 0.2% Cuequiv. cut-off).
Geology
The Morrison deposit is located on the northern margin of the Mid-Jurassic Skeena Arch in a region underlain by volcanic, clastic and epiclastic rocks ranging from Lower Jurassic to Lower Cretaceous age, including the Takla Group, Hazelton Group, Bowser Lake Group, Skeena Group, and Sustut Group (Carter, 1976). These units are disrupted by a series of predominantly north to northwest-trending faults into uplifted blocks, downfaulted grabens, and tilted fault blocks, resulting in older lithologic units being juxtaposed and locally truncated against younger units. Intrusive rocks include Early Jurassic diorite and granodiorite of the Topley Intrusions, Eocene rhyolite and rhyodacite intrusions, and by the economically significant Eocene Babine Igneous Suite which consists of quartz, hornblende, biotite, and plagioclase phyric intrusions (Carson and Jambor,1976).
The dominant geological feature at Morrison is the 1.5 to 2.0 km wide NNW-trending Morrison Graben that cuts across the deposit area. The graben is host to the siltstone, sandstone, and greywacke sedimentary sequence of the Upper Jurassic Ashman Formation on the northern half of the deposit area, and younger sandstone, shale, and siltstone units of the Lower Cretaceous Skeena Group to the south. Much of this southern section of the graben is overlain by glacial overburden. These sequences have been down-faulted into the graben structure relative to the older volcanic and sedimentary rock units of the Lower to Middle Jurassic Telkwa Formation, Saddle Hill Volcanics, and Smithers Formation that flank the graben to the east and west. All of these rock units are locally intruded by the Eocene-age Babine Intrusions that are present as small stocks, plugs, and dyke-like bodies of biotite feldspar porphyry, quartz diorite and granodiorite. Within the Morrison deposit area, the copper-gold porphyry mineralisation is developed in a biotite feldspar porphyry plug and related dyke-like bodies that intrude
the siltstone/sandstone unit of the Ashman Formation (Robertson et al., 2009).
The Ashman Formation is primarily composed of siltstone, sandstone, greywacke sequences, with minor conglomerate and contain Upper Jurassic age fossils.
At the Morrison deposit area, the sequence is composed of siltstone, sandstone, silty argillite, minor conglomerate and greywacke that have been down-faulted into the Morrison Graben. Medium to dark grey, very fine to fine grained siltstone is the most abundant lithology. The siltstone in and around the Morrison deposit as seen in drill core is commonly biotised and locally chloritised, which generally imparts a dark greyish green to almost black colouration. The siltstone appears to be locally hornfelsed into an almost cherty-textured rock. The sandstones of the formation are occasionally silicified, giving unit a fine sugary texture (Robertson et al., 2009).
The Eocene-age Babine Intrusions in the deposit area is represented by a biotite feldspar porphyry plug which intrudes the older siltstone and greywacke sequence of the Ashman Formation. The plug is near vertical and has been faulted and offset with dextral movement along the two principal north-trending East and West Faults and related subparallel subsidiary faults within the centre of the graben. The original plug is estimated to have had dimensions of 600 to 700 m, occurring as an irregularly-elongated to semi-circular shaped body that bifurcates to the north and south into several 40 to 100 m wide dyke-like offshoots and smaller fingers. Trenching and drilling have defined a number of 1 to 10 m wide biotite feldspar porphyry dykes around the periphery of the main plug. These dykes and elongated bodies crudely conform to the dominant northerly structural trend. The biotite feldspar porphyry plug of the Morrison deposit is typically a fine to medium grained, crowded biotite-hornblende-feldspar porphyry of quartz diorite composition. There are abundant 1.0 to 5.0 mm-size plagioclase phenocrysts that impart a distinctive speckled texture. The porphyry is commonly potassically altered with weak to strong secondary biotite in the form of fine to medium-sized grains, as well as fine matted clots. Locally, the biotitisation is developed within the porphyry as a very dark pervasive overprint (Robertson et al., 2009).
Rocks interpreted to belong to the Lower Cretaceous Skeena Group are found down-faulted within the Morrison Graben immediately to the south of the Morrison deposit, but have not been encountered with the deposit. These include quartzo-feldspathic sandstone, dark grey siltstone, and dark grey to black carbonaceous mudstone.
Mineralisation
Morrison is a strongly zoned, annular porphyry copper deposit that is largely within a multi-phase Eocene 'Babine-type' biotite-hornblende-plagioclase porphyry plugs, sills and dykes, enclosed within Middle to Upper Jurassic Ashman Formation (Bowser Lake Group)s iltstone, silty argillite, and minor conglomerate.
These sediments are massive and strongly altered and bedding has been largely obliterated, although where observed, the strike is north to northwest and dips steeply. On the outer margin of the deposit are the sediments have considerable introduced carbonate and a fawn to medium grey colour. As the copper zone is approached, the rocks become darker greyish green and fawn, indurated, chlorite-carbonate-rich greywackes and argillites, while in the copper zone these are dark grey and jet-black as a result of biotite alteration. Conglomerates are evident at a few localities distant from the porphyry plug.
The main porphyry body at Morrison, prior to faulting, was roughly circular in plan, with a diameter of ~700 m. It was subsequently disrupted
by the East and West Faults and now forms an elongated body extending some 1500 m in the northwest direction as a NW oriented elliptical multiphase plug with dimensions of with a width of 150 to 300 m, and near vertical sides. Numerous dyke and sill offshoots of the plug are common in the surrounding Hazelton Group sediments. The unaltered porphyry comprises abundant 0.25 to 1 mm phenocrysts of plagioclase (zoned oligoclase-andesine), biotite and hornblende in a fine grained matrix of the same components as well as K-feldspar and quartz (Carson & Jambour, 1976).
The Morrison deposit lies within the central part of a major graben that is part of the regional northwest trending block-fault structural framework of the region. The dominant structure in the deposit area is the NNW trending, Morrison fault, which bisects and offsets both the porphyry plug and copper zone with an apparent a dextral throw of approximately 300 metres. The vertical displacement is believed to be considerable. The fault is a linear zone of parallel shears and fractures that averages about 25 m in width, but ranges from 50 m in the central portion to only a few metres at the extremities.
At Morrison, chalcopyrite, pyrite and minor bornite occur in the copper zone with a large pyrite halo, with three very strong segments peripheral to the copper zone. The orebody was a vertical, annular cylinder that conforms to the shape of the porphyry plug, but has been dextrally displaced along the NNW trending Morrison fault. Its restored outer dimensions, as defined by a 0.3% Cu cut-off, are of the order of 700 x 400 m, with the central barren core being around 250 x 50 to 100 m. The copper zone is bounded by inner and outer grade boundaries of 0.3% Cu. In most places the outer margin is relatively sharp with a decline outwards to <0.1% Cu in about 40 m. The low grade core has 0.15 to 0.2% Cu. Within the ore annulus, which is 15 to 150 m wide, Cu grades exceed 0.5%, with >0.7% Cu over appreciable widths, and an average of 0.42% Cu. Mo averages 0.01%, and Au and Ag, 0.3 and 3 g/t respectively. The pyrite halo, which also contains minor pyrrhotite, is of the order of 50 to 250 m wide, but lenses out on the western extremity. The >0.3% Cu ore is predominantly within the plug, with only around 10% within the surrounding sediments (Carson & Jambour, 1976).
Chalcopyrite is the main Cu mineral, with minor to moderate amounts of bornite. Chalcopyrite is distributed as fine grained disseminations in the biotite-feldspar porphyry and siltstone, as fracture coatings or as stockworks of quartz veinlets in which the chalcopyrite occurs as coarse 1 to 3 mm grains within veinlets that range from 1.0 to ~15 mm in width. Minor bornite occurs within the higher grade copper zones as disseminations and associated with
the quartz-sulphide stockwork style of mineralisation. Anomalous amounts of pyrite (>1%) are ubiquitous in all rock types, although the most pronounced concentrations (5 to 15%) are found in three segments of the pyrite halo surrounding the copper zone. Chalcopyrite predominantly occurs as thin seams and veinlets with or without quartz, and is distributed chiefly in fracture stockworks, while around 20 to 30% occurs as disseminations in the porphyry plug matrix and in peripheral sedimentary rocks. Very minor molybdenite accompanies some chalcopyrite-pyrite seams but also occurs as minute disseminated flakes. Some iron-bearing sulphides are altered to iron oxides and minor jarosite. Minor marcasite is present and is most commonly associated with pyrite, arsenopyrite, galena, sphalerite, geocronite, and boulangerite which occur with quartz and carbonate in small vuggy veinlets and pockets in minor faults and in the clay-carbonate altered rocks of the Morrison fault zone. Where exposed the copper minerals are oxidised to malachite, brochantite, and small amounts of pale blue copper silicates.
Pyrite and chalcopyrite exhibit a well-defined zonal relationship, with pyrite predominating in the pyrite halo, with the transition closely corresponding to the 0.3% Cu contour. The pyrite halo is developed in the chlorite-carbonate altered wall rock surrounding the copper zone. The pyrite mineralisation characteristically occurs as thin (0.1 to 5.0 cm) fracture-fillings and quartz-pyrite-minor chalcopyrite stringers in the form of a stockwork within the halo. There is a crude zonation to the pyrite development, with coarse (0.5 to 5.0 mm) disseminated crystals within the inner parts of the halo where pyrite content ranges from 5 to 15 vol.%. Pyrite in the outer zone is predominantly developed as a stockwork and averages 1 to 2 vol.%, accompanied by weak copper mineralisation (<0.1%). While pyrite decreases toward the centre of the deposit, disseminations persist throughout and into the low grade core, where magnetite and minor bornite are also found. Polished-section studies show this magnetite and minor bornite in the low-grade core of the deposit. The magnetite is a finely disseminated original constituent of the BFP and siltstones, and is most abundant in the western segment of the copper zone. Many magnetite grains are partly altered to hematite, which seems to be most abundant at the outer 0.2% Cu boundary. No iron oxides have been observed in the pyrite halo.
Hydrothermal alteration is characterised by biotite-chlorite zoning. Biotitisation (dated at 52.1 Ma) is directly related to Cu grades, with >0.3% Cu being within the centrally located biotite zone, while chlorite-carbonate alteration is strongest in peripheral pyritised rocks. Minor K-feldspar alteration is evident on the inner rim of the copper zone. Disseminated fine-grained apatite is anomalously abundant in the porphyry plug and in some large dykes. In the fault zone, and along subsidiary shears, late stage clay-carbonate alteration and associated Pb and Zn sulphides are superimposed on the earlier biotite and chlorite alteration (Carson and Jambour, 1976).
Along the Morrison Fault, where it cuts the ore, there is a 5 to 20 m thick zone that has been downgraded to about 0.2 to 0.25% Cu due to dilution by sheared rock during fault movement, and by leaching by late hydrothermal solutions and possibly by ground-water. Irregularly distributed quartz-chalcopyrite veinlets and small blobs of chalcopyrite occurring along the fault zone may have originated from such leaching (Carson & Jambour, 1976).
Sections of this summary have been updated from "Robertson, J., Siepka, A. and Wells, P., 2009 - Morrison Copper/Gold Project – Feasibility Study, an NI 43-101 Technical Report prepared for Pacific Booker Minerals Inc., 246p."
The most recent source geological information used to prepare this decription was dated: 2009.
Record last updated: 12/2/2025
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.
Morrison
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Carson D J T and Jambor J L, 1976 - Morrison: Geology and evolution of a bisected annular porphyry copper deposit: in Sutherland Brown A (Ed.), 1976 Porphyry Deposits of the Canadian Cordillera, Canadian Institute of Mining and Metallurgy, Special Volume 15, pp 264-273
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