Quartz matrix polymictic hydrothermal breccia
Virtual Museum ID: 19-BCGS-Cinola-1
Quartz matrix polymictic hydrothermal breccia
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Original Collection:British Columbia Geological Survey (BCGS)
Virtual Museum ID:19-BCGS-Cinola-1
Date Added to VM:2019-05-07
Sample Origin:Haida Gwaii Islands, B.C.
Specific Site:Harmony Property, Graham Island
Datum:08 (NAD 83)
Primary Features:Quartz matrix polymictic hydrothermal breccia
Primary Mineral Formula:-
Advanced Geological Information
The following section provides geological data relating to the specimen or the site it was collected from, when available. Information has been obtained from various sources including private and government datasets but may not be up to date. Any geological time periods or ages listed often relate to the primary geology of the area, and may not be the actual date of an event such as mineral formation.
Geological Formation:Haida Formation (Queen Charlotte Group)
Stratigraphic Age:145 - 66 Ma
Geological Terrane:Overlap Assemblage
Minfile ID:103F 034
The Harmony property is located on Graham Island in the Haida Gwaii Islands archipelago, British Columbia. Access to the Specogna deposit is via logging roads 40 kilometres from the town of Queen Charlotte City and 30 kilometres from Port Clements.
The Specogna deposit and surrounding area is underlain by three major formations, an intrusive igneous sequence, a major fault system and the mid-upper levels of an epithermal hotspring-type (low sulphidation, quartz adularia sub-type) precious metal system.
The gold deposit is localized along the Sandspit fault, which strikes 162 degrees and dips about 45 to 50 degrees northeast in the vicinity of the deposit. The Sandspit fault is a normal right-lateral fault that separates the shale member of the Cretaceous Haida Formation (Queen Charlotte Group) from a downdropped block of Miocene-Pliocene Skonun Formation sediments (east of fault).
The Haida Formation is comprised of black to dark grey variably calcareous mudstone and argillites. The stratigraphic nomenclature of Cretaceous units of the Queen Charlotte Islands, including the Haida Formation, has come under review by various researchers at the Geological Survey of Canada. Cameron and Hamilton (1988) had reassigned the shale member of the Haida Formation to the Skidegate Formation (Geological Survey of Canada (GSC) Paper 88-1E, pages 221-227). J.W. Haggart (1991) dismissed this reassignment and reconfirmed the Haida Formation to include the shale member (GSC Paper 91-10, pages 253-277). Owing to problems in distinguishing the various Cretaceous units J.W. Haggart, et al., 1991 (GSC Paper 91-1A, pages 367-371) and J. Hesthamer, et al., 1991 (GSC Open File 2319) suggest that formation names for the Queen Charlotte Group (excluding the Honna Formation) should be abandoned and the Haida shales should therefore be referred to informally as the "Cretaceous shale" of the Queen Charlotte Group.
The Skonun Formation, at least 600 metres in thickness in the vicinity of the deposit (62 per cent conglomerate; 31 per cent arkosic sandstone; 7 per cent sandstone and siltstone/mudstone), consists of a thick porous pebble conglomerate unit with north striking and gently east-dipping interbeds of sandstone and siltstone. Several horizons of mudflow breccia (lahar deposits) occur interbedded with conglomerates at the deposit. J. Hesthamer, et al., 1991 (GSC Open File 2319) had mapped conglomerates outcropping over the deposit as Cretaceous Honna Formation (Queen Charlotte Group, shown as unit KHo). Macrofossil and palynological evidence suggest an age of deposition of about 15-17 Ma (mid-Miocene) for these rocks (Champigny, 1981). They are therefore included with the Tertiary Skonun Formation.
Carbonaceous debris occur in the Skonun Formation as fragments, varying from logs several tens of centimetres in diameter to slivers. Logs appear to be aligned parallel to the strike of the larger quartz veins (i.e. 020 degrees). The percentage of carbon ranges from 0.04 to 0.23 per cent. The mudflow breccia horizons contain the most plant debris. The Upper Oligocene to Lower Pliocene Masset Formation, consisting of porphyritic andesites and basalts, underlies the area to the immediate northwest and was likely the source of much of the sediments comprising the Skonun Formation.
At least two separate Miocene felsic intrusions occur in the deposit area. A dike of variably plagioclase porphyritic dacite to locally andesite ("main dacite dike") intrudes the Haida mudstone and Skonun sediments along the Sandspit fault. Various other smaller typically flow-banded quartz-feldspar porphyritic rhyolite dikes and irregular bodies occur in the Haida mudstone west of the Sandspit fault (e.g. at the Marino showing). The main dacite dike strikes 160 degrees for at least 900 metres and dips 40 to 60 degrees northeast. The dike is 10 to 30 metres wide, locally swelling to 50 metres and generally narrows and becomes discontinuous with increasing depth. The unit is occasionally pitted and porous as a result of retrograde acid leaching. It is typically bordered to the east by a parallel zone of quartz-rich hydrothermal breccia. An intervening zone of crackle brecciated dacite is transitional between the dike and hydrothermal breccia. Peperitic textures suggest that the dacite dike intruded Skonun sediments during their deposition.
The dacite intrusion immediately predates the epithermal hot-spring suite and may have contributed to the movement of hydrothermal fluids upwards along deep-seated structures. The suite is dominated by a quartz matrix polymictic hydrothermal breccia, containing clasts of Skonun sediments, Haida mudstone and dacite. The breccia body strikes 170 degrees for 750 metres proximal to the Specogna fault and dips 40 to 65 degrees east. It consists of a wedge shaped zone up to 70 metres wide at or near surface that extends downdip for up to 650 metres. Fluidized and milled breccias occur at depth below the polymictic breccia. A zone of early mineralized banded chalcedonic and variably bladed (quartz after calcite) and late barren, vuggy and drusy quartz veins flanks the breccia to the east. These veins comprise a conjugate set with two dominant attitudes; 015 degrees/87 degrees west and 039 degrees/67 degrees northwest. Two main sinter horizons occur near the top of the deposit in Skonun conglomerates. These trend northerly for 350 metres and are up to 13 metres thick. The horizons are cut by all breccias and vein types. The presence of multiple sinter horizons in Skonun sediments and the occurrence of fragments of vein quartz (early mineralized and late barren) and clasts of previously silicified sandstone in the upper part of the Skonun Formation ("upper mudflow breccia") suggest that epithermal activity was contemporaneous with deposition of Skonun sediments.
Both sedimentary and intrusive rocks have been subjected to hydrothermal alteration that extends laterally eastwards away from the hydrothermal breccia over an area of two square kilometres. A zone of silicification and potassic alteration (adularia) developed proximal to the hydrothermal breccia is flanked to the east by a region of clay altered Skonun Formation sediments characterized by the presence of kaolinite-illite with minor alunite and sericite. Chloritic alteration is also reported.
Metallic mineralization at the Specogna deposit is dominated by pyrite and marcasite, which together typically comprise 2 to 4 per cent of altered wallrocks in the form of semimassive replacements of conglomerate clasts to disseminations in finer grained sediments and intrusive dikes. Early mineralized quartz veins tend to be less sulphidic, while later barren veins are largely free of sulphides. Chalcopyrite is occasionally present in quartz veins below the deposit. Other minerals identified in decreasing order of abundance include limonite, hematite, native gold, cinnabar, sphalerite and pyrrhotite (Gasparrini, 1979).
Gold is finely disseminated in elevated concentrations within a broad zone of potassic alteration and silicification between the Sandspit fault to the west and the barren, argillic alteration zone to the east, (generally the contact between argillic alteration and silicification marks the 0.69 gram per tonne gold grade boundary). The gold is mostly free and extremely fine with occasional coarse accumulations. Higher concentrations of gold are associated with quartz veins and breccias, as indicated by channel sampling of the Specogna adit, where quartz veins 10 centimetres or wider were sampled separately from wallrock. One hundred and thirty seven vein samples averaged 9.61 grams per tonne gold, while intervening wallrock samples averaged 3.00 grams per tonne gold (Assessment Report 24972, page 26). Visible gold is almost entirely found in quartz veins, often at or near their margins. Visible gold occurs most often in narrow uniformly textured light grey quartz veins and secondarily in larger banded to mottled and bladed light to dark grey and brownish grey chalcedonic quartz veins.
The orebody is essentially wedge-shaped and extends 800 metres northwest along the Specogna fault. The wedge is approximately 250 metres wide at surface, thinning with depth to 50 metres at sea level (200 metres below surface). The orebody has been traced downdip for 300 to 400 metres. Mineable reserves estimated to June, 1997 are 33.5 million tonnes grading 2.11 grams per tonne gold at a cutoff grade of 1.20 grams per tonne gold (Assessment Report 25393, page 2). A lower grade stockpile is also estimated to contain 17 million tonnes averaging 0.99 gram per tonne gold (Misty Mountain Gold Limited Press Release, May 12, 1997). Independent Mining Consultants Inc., on behalf of Misty Mountain, estimated the deposit has a mineral reserve of 52.7 million tonnes grading 1.7 grams per tonne gold. The ore is distributed in four silicified lithologies. The Skonun Formation contains 55 per cent of the total ore tonnage; hydrothermal breccia, 30 per cent; dacite, 13.0 per cent and Haida Formation mudstone, 2.0 per cent. Drilling in 1988 suggests mineralization may continue northeast of the proposed pit (Assessment Report 18785). Drilling 300 metres north of the deposit in 1998 intersected 9.98 metres of 10.07 grams per tonne gold in sheared and locally weakly silicified dacite dike, suggesting additional zones of mineralization may occur along the Sandspit fault (Press Release, Misty Mountain Gold Limited, February 25, 1999).
Gold recovery tests using a gravity circuit followed by standard flotation techniques were completed on deposit material grading 2.40 grams per tonne gold. Preliminary results indicate that conventional gravity circuits may recover 10 to 20 per cent of the gold, and flotation results indicate an 80 per cent or better overall gold recovery is achievable in a concentrate grading 30 to 40 grams per tonne gold. Tests on the flotation concentrate indicate that it is very amenable to bio-oxidation pre-treatment; oxidation rates are rapid and the gold recovery is excellent. Misty Mountain Gold is also testing bio-oxidation pretreatment of crushed ore, followed by simple heap leaching.
The Specogna deposit was discovered by Efrem Specogna and Johnny Trinco in 1970, while prospecting along the Sandspit fault. The prospect was optioned to a succession of companies during the early 1970s, commencing with Kennco Exploration Ltd. (1971), followed by Cominco Ltd. (1972), Placer Development Ltd. (1973) and finally Quintana Minerals Corp. (1974-75). Work performed by these companies included geological and soil geochemical surveys, and the drilling of 20 diamond-drill holes totaling 1338 metres and 18 percussion holes totalling 603 metres. Consolidated Cinola Mines Ltd. optioned the property in 1977 and by 1980 had completed 139 diamond-drill holes totalling 20,963 metres. Work by the company continued under a joint venture with Energy Reserves Canada Ltd., commencing with the excavation of the Specogna adit in 1981. Some 4500 tonnes were excavated from 465 metres of underground workings and treated at a 45 tonne-per-day pilot mill at site. The joint venture completed 54 diamond-drill holes totalling 7222 metres between 1981 and 1984. In 1986, City Resources (Canada) Ltd. acquired control of Consolidated Cinola Mines and continued exploration by drilling another 98 diamond-drill holes and 63 percussion holes totalling 8483 metres and 6232 metres respectively, between 1986 and 1989. The company completed another 118 metres of underground development at the Specogna adit in 1987. Barrack Mine Management acquired control of City Resources Canada in 1989 and continued metallurgical and feasibility studies. In 1993, Australian interests acquired control and renamed the company Misty Mountain Gold Ltd.
The Hunter Dickinson Group, through Romulus Resources Ltd. optioned the deposit in 1994. Romulus Resources merged with Misty Mountain Gold in 1995, with the Hunter Dickinson Group acquiring full control of the new company. In 1995 and 1996, Romulus Resources and Misty Mountain Gold drilled 147 diamond-drill holes totaling 34,627 metres on a 20 by 20 metre grid, with all holes angled to the southeast at -45 degrees, in order to crosscut at right angles to the northeasterly trending and steeply dipping quartz veins. The company completed an additional four diamond-drill holes totalling 1999 metres in the fall of 1997 to test for potential bonanza-type deposits which may have developed at depths of up to 200 metres below the currently known Specogna deposit in a deeper, throttled portion of the epithermal system. Another four holes totalling 575 metres were drilled in the fall of 1998 to test resistivety and chargeability anomalies near the Sandspit fault north of the deposit. Additional work included bulk sampling of the Specogna adit in 1997 and 1998, and the completion of airborne geophysical surveys (VLF-EM, radiometrics, magnetometer) in 1995 and induced polarization surveys over the Sandspit fault in 1997. The company is continuing with various investigations involving metallurgical, environmental work, deposit modeling, resource estimation, mine designs, mineralogy, site facility locations and infrastructure planning, all leading to the completion of a comprehensive pre-feasibility study.
The Marino showing, located about 150 metres due west of the north end of the Specogna deposit, consists of an elongate body of quartz-feldspar porphyritic rhyolite, subcropping and outcropping over an area 80 by 40 metres. The body occurs in Haida mudstone about 90 metres west of the Sandspit fault. Mineralization at the showing consists of narrow quartz veins typically no more than 2 centimetres wide, that contain visible gold along their drusy and chalky cores.
Efrem Specogna shipped two bulk samples of gold ore from the Marino showing to the Tacoma smelter. The two samples were received on June 26, 1975 and analyzed as follows (T. Schroeter, personal communication, 1996); Shipment 1 Net weight = 2431.7 kilograms (at 0.93 per cent moisture) - 2409.0 kilograms net dry weight Assay = 116.5 grams per tonne gold, 52.1 grams per tonne silver, 0.01 per cent lead, 0.06 per cent copper, 0.01 per cent zinc, 0.25 per cent arsenic, 0.03 per cent bismuth, 91.9 per cent silica Metal Content (payable) = 255.02 grams gold, 93.3 grams silver Shipment 2 Net dry weight = 579.7 kilograms Assay = 563.9 grams per tonne gold, 230.3 grams per tonne silver Metal Content (payable) = 301.67 grams gold, 124.4 grams silver Total production = 3011.45 kilograms yielding 556.69 grams gold and 217.7 grams silver.
In 2001, Taseko Mines Ltd. acquired this property from Misty Mountain Gold Ltd. In late 2007, the area in which this property is located was designated as a mineral development zone by the Queen Charlotte-Haida Gwaii Land and Resource Management Plan. Taseko initiated a review of the metallurgical flow sheet and prior mine develpment planning to establish further work programs and to move the project forward in 2008 (Taseko Mines Ltd. 2007 Annual Report).
In 2015, the Harmony property is held by Gibraltar Mines Ltd., itself a wholly owned subsidiary of Taseko Mines Limited. The work program in 2015 comprised the collection and
analysis of water samples to contribute to the characterization of acid rock drainage (ARD) and metal leaching (ML) potential of the deposit and tailings; and, to study the effectiveness of passive water treatment for potential future development of the project.