St. John’s, NFLD — Recognizing the merits of a new geological concept for Carlin-style mineralization in a belt of rocks in central Newfoundland,
Altius has been carrying out reconnaissance exploration in the Botwood Basin area for more than four years now and recognized features indicative of both low-sulphidation epithermal and Carlin-style, sediment-hosted gold mineralization styles.
The Barrick deal covers 10 properties in the eastern Botwood Basin totalling 293 sq. km of mineral licences. The properties extend southwest from Gander Bay to the Baie d’Esoir Highway. Barrick can earn a 75% interest in the project by funding all exploration costs and making annual cash payments ($20,000 in year one, $35,000 in year two, and $25,000 per year thereafter) until a production decision has been made. Altius will manage the exploration programs for at least the first two years of the agreement. Following a production decision, Altius can elect to have Barrick arrange its share of mine financing in exchange for an additional 5% interest.
The Mustang group of properties occurs near the eastern margin of the Exploits sub-zone of the Dunnage zone. In a simplified version, the geology of Newfoundland can be sub-divided into three main zones. The West Coast of Newfoundland represents the Laurentian margin of North America, whereas the eastern part of the province is known as the Avalon zone or the Gondwana margin, an ancient continental margin. In between the two continental blocks is the Dunnage zone, representing the vestiges of an ancient ocean that opened-up and closed in early Paleozoic times. The Dunnage zone is further sub-divided into the Notre Dame and Exploits subzones.
The Mustang properties cover units of the Botwood, Indian Islands and Davidsville groups, from west to east. The Botwood and Indian Island units are Silurian to Devonian in age. The Botwood group consists of shallow marine sedimentary rocks, with a basal volcanic unit overlain by red sandstone with some basal conglomerate. The Indian group comprises shallow marine lithologies, such as fossiliferous grey limestone, grey-brown calcareous sandstone and siltstone.
Thrust faulting during the Devonian Acadian Orogeny is thought to have transported deep marine siltstone and argillite of the older Ordovician-early Silurian Davidsville unit over the Botwood and Indian Island groups. Consequently, the Silurian-Devonian units are bounded by outwardly dipping faults forming a regional structural window. Altius is apparently targeting potential mineralization localized along faults in the favourable carbonate horizon of the Indian Island unit.
During the late 1980s and early 1990s, a number of gold occurrences, with associated arsenopyrite, pyrite and stibnite, were discovered in the Dunnage zone.
“At that time, the only thing we were concerned about was whether they were mesothermal or epithermal,” explained Derek Wilton of Memorial University during a presentation at the annual meeting of the Newfoundland branch of the Canadian Institute of Mining, Metallurgy and Petroleum.
Early stage
Most of the properties comprising the Altius-Barrick joint venture were staked at a very early stage of exploration on the basis of new geological concepts for potential sediment-hosted gold mineralization. Reconnaissance prospecting by Altius had recognized areas of decalcification, barite veining, silicification-jasperoid development and extensive clay alteration. In addition, Altius zeroed in on areas with elevated gold, arsenic and antimony values.
In comparison, the classic multi-million-ounce Carlin-style or sedimentary-hosted gold deposits display decarbonatization and silicification textures in the limestone host, often resulting in the development of jasperoids. The Carlin deposits exhibit chemical halos of arsenic, barium, antimony and mercury. The gold mineralization is fine-grained and associated with arsenian pyrite. Fluid inclusions are somewhat in between the mesothermal and epithermal models.
The Mustang trend properties extend north and south of the past-producing Beaver Brook antimony mine, 43 km southwest of Glenwood. In 2002, Beaverbrook Resources purchased the mine and 450-tonne-per-day mill of Roycefield Resources, which went into receivership in late 2001. The Beaver Brook operation was closed in early 1998. The company is currently exploring the viability of reactivating the mine and mill in 2003.
Prior to the mid-1980s, no gold occurrences were known to exist in the area of the Mustang trend, but with the release of a government lake-sediment survey, Noranda acquired large land positions and began exploring for mesothermal-style gold mineralization. Noranda’s efforts resulted in the discovery of several gold occurrences and the Beaver Brook antimony deposits.
Vuggy quartz veins
Regarding the Altius and Barrick land package, the Mustang and Swiss Lake properties have been previously explored in more detail. Noranda conducted work on the 6.3-sq.-km Mustang property from 1986 to 1989, uncovering gold mineralization in silicified and brecciated sediments adjacent to the northeast striking Piper fault. Trenching yielded values of up to 12.25 grams gold per tonne over 2 metres. Noranda tested the area with 12 holes. The best gold grades, up to 28 grams over 0.8 metre, were encountered in the structural hangingwall of the fault. Typical textures in the mineralized zones include vuggy quartz veins, chalcedonic silicification and vuggy hydrobreccias containing cockade textures.
In late 1998, Altius tested the gold-bearing zones, with 10 holes totalling 1,200 metres. Drill results returned a maximum value of 4.31 grams over 0.3 metre, and more typical values of 1-2 grams over 1-metre intervals.
In the area of the current Swiss properties, which cover 53 sq. km, companies including NALCO and Bell Asbestos Mines explored for asbestos, chromite and magnesite during the 1950s and 1960s. US Borax, Atlantic Goldfields, Falconbridge, Kidd Creek Mines, Homestake and BP Canada, all carried out precious metal exploration in the area during the 1980s. The Swiss Lake properties host five known gold occurrences. In addition, broad areas of anomalous arsenic with locally elevated gold values occur in soils.
This year’s exploration on the Mustang trend properties includes prospecting, regional mapping and baseline till sampling, along with soil sampling and trenching on three selected target areas. To date, the joint venture has collected more than 750 rock samples, 300 tills, 60 heavy mineral concentrates and 550 soils. All the data are being compiled in digital form to assist in the interpretation and design of the next work program.
Elsewhere in the Botwood Basin,
Mafic dykes
Sudbury Contact can earn an initial 51% interest in the property by spending $800,000 on exploration and paying Altius $100,000 over three years. Sudbury, an exploration affiliate of
The property is underlain mainly by sedimentary and volcanic rocks of the Botwood Group that are intruded by younger mafic dykes. Lithologies within the exploration area have been affected by a pervasive iron carbonate, sericite and clay mineral alteration event, which is presumably associated with the gold mineralizing event. High-grade gold is confined to a set of banded-to-massive quartz veins. Gold mineralization has a spatial association with northwest-striking magnetic linear fault zones.
The mineralizing system has been classified as low-sulphidation epithermal, owing to evidence of high-level brecciation and the results of fluid inclusion studies that indicated low-homogenization temperatures, low salinity and low carbon dioxide.
The neighbouring Island Pond project of
Following the release of a government lake-sediment geochemical survey in 1988, Noranda discovered several angular quartz vein boulders on the Moosehead property along the northwest shoreline of the North and South ponds. Grab samples from the boulders ran as high as 149 grams. Noranda completed grid sampling and geophysical surveys, and uncovered anomalous gold, arsenic and mercury. Three 100-metre-long holes were drilled in 1990.
Option
The property was later staked by Cape Broyle Exploration in 1994 and optioned to Royal Oak Mines, which conducted additional geochemical sampling followed by the drilling of seven holes totalling 653 metres. The most significant intercept was a 10-cm-wide quartz vein assaying 259 grams gold. After Royal Oak withdrew from the property, Altius acquired a 100% option in 1997 and conducted additional line cutting, geophysical surveying, reconnaissance prospecting, and till sampling prior to entering into a joint-venture arrangement with Teck (now Teck Cominco) in November 1998. The results from a 7-hole, 756-metre drilling program in 1999 proved disappointing and Teck walked away. The best hole yielded 1.53 grams over 0.93 metre.
To gain a better understanding on the orientation of the gold-bearing structures, Altius undertook a structural review of the property prior to doing the deal with Sudbury Contact in 2001. A fall 2001 drilling program was designed as a reconnaissance program aimed at locating the source of high-grade boulders distributed throughout the property, and to establish the orientation of the quartz veins.
Highlights from the drilling program, in which 36 diamond drill holes totalling 3,200 metres were completed, included 170 grams across 1.53 metres (including 0.6 metre of 414 grams) in hole 23, and 96.7 grams over 1.5 metres in hole 13. The joint venture began 2002 by conducting a small winter program consisting of six holes totalling 600 metres. The program was designed to test several geophysical conductors in areas accessible during freeze-up. In all cases, the conductors were found to be caused by fault zones. Though no high-grade values were encountered, the drilling did show that low-grade gold was synonymous with faulting and associated altered mafic dykes.
During the summer, Altius and Sudbury completed a further 33 holes in more than 3,200 metres of drilling as it tried to prove up continuity around the higher-grade intercepts on the Discovery and North Pond fault zones, and test new targets. Twenty-one of the holes returned either anomalous or insignificant values.
Highlights included the discovery of a new fault zone that ran 63.5 grams over 0.2 metre in hole 18. Drilling on the southern end of the Discovery fault yielded 18.3 grams across 1.05 metres within a wider zone of 4.2 grams over 5.5 metres. A spectacular narrow zone of high-grade in hole 38 ran 1,154 grams over 0.18 metre near the lower part of a broader interval of quartz veins, breccia and altered mafic dykes that represent the north end of the North Pond fault. The entire fault zone intercept, including the bonanza-grade intercept and several intervals containing only anomalous values, averaged 14.07 grams across 16.8 metres.
The last hole of the 2002 program was drilled to test a topographic linear that is spatially associated with newly discovered quartz vein boulders, 800 metres north of hole 38. Samples of some 17 boulders averaged 3.72 grams gold, with a high value of 19.3 grams gold and 144 grams silver. The final hole intersected a fault zone with visible gold-bearing quartz veins that ran 0.3 gram over 6.5 metres.
Upon completing the summer’s drilling, Altius flew the Moosehead property with an airborne magnetic and electromagnetic (EM) survey to expand coverage outside of the small area that has been the focus of exploration to date.
The Botwood Basin offers several styles of gold mineralization. Wilton suggests mesothermal styles occur in the Ordovician-to-early Silurian rocks, such as the Davidsville group. Epithermal styles occur in Silurian and older rocks on the west and south margins of the Botwood Basin.
“But the occurrences on the east side of the basin encompassing the Silurian Indian Island group have mixed symptoms of mesothermal and epithermal, perhaps Carlin,” concludes Wilton.
Be the first to comment on "Botwood lures juniors to The Rock"