NAZKO CINDER CONEAND A NEW PERLITE OCCURRENCE

By Z.D. Hora and K.D. Hancock "."

KEYWORDS: industrialminerals, Nazko , Holocenevolcanics, light-weight aggregate, rock, barbecue rock, volcanic glass, perlite

NAZKO CINDER CONE

Location: Lat. 52" 55' 45" Long. 123' 44' 00 93G1/4. Carib Mining Division.Approximately 14 kilometres west of Nazko village, 75 kilometres west of Quesnel. Access: Vi,a the Michelle Creek forest service road and Baezaeko (Fishpot Lake) road. Owner: Pumice Corporation. Operator: Canada Pumice Corporation Commodities: Lightweightaggregate, lavarock. anti-skid sand, ornamental cinder aggregate.

GEOLOGY

The Nazko cinder cone is the most easterly volcanic centre in the Anahim . The edifice of this Holocenevolcano is a product of threemain volcanic events, one preglacial, one subglacial and one postglacial fl Black 0rx)rBcbous > liruptive (Souther el a/, 1987). The conical mound of the Nazko basail tephra cone raises about 120 metres above thesurrounding Road terrain and its circular base is approximately1000 metres in diameter. Two pyroclastic ejecta units comprise this composite cone (Figure 1). A conical mound some 100 metres high

on the west side of the edifice is made of red tuff- ~ breccia. This unit predates the subaerial, crescent-shaped Figure 1. Location map and geology of the hazko COIIB (aller eastern rims of three craters and has been interpreted as Souther el ai.,1987) of subglacial origin (Souther el a/,1987). Because of its attractive coloun, material from this unit is of economic Two lava flows of different ages fo m part of t le interest for a varietyof granular cinderproducts. compositecone. A basal flowof subaerial basalt is A second unit forms much of the composite cone. It exposed to thenorth. I1 predates tht Wisconjin:m consists of fresh, blackscoriaceous basalt tephrawith glaciation and is extensively eroded. A K Ar date of this irregular and round-shaped bombs up to 60 centimetres basalt has been determined as 0.34*0.03 hla. indiameter. On the surface, theblack tephra weathers The secondflow unit comprisestwo separa1.e lava bright yellowish brown. A fine-grained member of this streams that issued through narrow breac,les on the wcst unit forms a gradually thinning eliptical blanket to the flank of the cone. These flows are a prod Jct of thae !;am northeast of th8e cone.This blanket extends up to 8 volcanicepisode which resulted inarcumulaticm of kilometres east and northeast from the vents. According pyroclastics on the eastern flank of Nazko cone and the to Souther et a/,(1987), the eruption which deposited the tephra blanket to the east. pyroclasticrocks of this second unittook place about 7200 years B.P, Material from this unit is also processed into general commercial products.

Geologicnl Fieldwork 1994, Paper 1995-1 Photo 4. Sized red scoria- landscaping aggegate

Photo 1. Unsortednature of pyroclasticdeposit. Black, scoriaceous basalt tephra, pitI

Photo 5. Sized black scoria - barhewe rock Photo 2. View of pit la, opened in line pyroclastic layer

406 Geological Survey Branc,CI PRODUCTIONAND DEELOPMENT can be found throughout the outwash depsit. The large size of many of the perlite boulders (50 c n in dian&r), CanadaPumice Corporation has developed three low physical strength ofthe rock and pror imity to a lalge production sites in the Nazko cone area. The first is a exposure of Eocene rhyolites (Rouse and ldathews, 19118; small pit atthe north side of the toeof thevolcanic Tipper, 1961), points to a nearby source most prrbal)ly mound (Photo I). Because of a large number of volcanic associated with the adjacentrhyolite outcr ~ps. bombs in the unsorted pyroclastic material, this source of The perlite rock isblack todark green, with black scoria is now abandoned and has been reclaimed. microfractures resulting in platy, rod-lik: and isolnelric The company opened a new pit several hundred metres to fragments.Four distinct types of volcanicglass w,:re the north, where there are no large bombs (Photo 2). On collected for expansiontests. the south side of the Nazko cone, the company operates A sample of each of the four types was crushed to another pit asa source of red scoria (Photo 3). less than l-centimetre size fragments, which werc: then Productionequipment consists of a2 by 3-metre, placed under a propane torch flame for bout 1 xrinute. minus IO-centimetre grizzly, a Powerscreen double deck All types expanded, increasing the volur,le of individual portable screen, Cata 980B loader and Cata D8 particlesfrom approximately two to f;wr timestheir bulldozer. Typncal production is about 115 cubic metres original size. (150 cu. yards) per day with current annual productionof The significance of this perlite occunence isthat it is 11 475 cubicmetres (15 000 cu yard). Products are the logistically best-located and access ble site 111 the availablein four screened sizes and also as oversize BritishColumbia interior. andthe authm believe: that landscaping rocks. Most of the present production is used prospecting will locate the bedrock sourc: of perlit: rock in decorative applicationsfor landscaping (Photo 4). sand in nearby Eocene rocks. traps on golf courses and barbecue lavarock (Photo 5). Otherapplications include anti-skid highway tractionsand and light-weight aggregate. While both ACKNOWLEDGEMENTS colours, black and red, are readily available, the greatest demand so far has been forred cinder products. The authors thank Brian Wear for asisting wlllh the visit to the Nazko propert)..

PERLITE REFERENCES Location: Lat. 53" 01' 30"Long. 123" 12' 05" 93B114. Carib Mining Division.Approximately 59 Rouse, G.E. andMathews, W.H. (1988) Palynolo,:y and kilometres west of Quesnel. Geochronology of liccene Beds from ( heslatta Fds and Access: F'rom Quesnel on Nazko road. Nazko Areas, Central British Co umba; Ccnadian Journal of Earl/] Sciences, Volume 25, pager 1:!68- Commodities: Perlite, volcanic glass. 1276. Souther, J.G., Clague, J.J. and Mathewes, R W. (1987) Nilzko Apreviously unreported occurrence of perlitehas Cone: A Quaternary in lhr Eastern Anshim beenfound during cursorya examination of large Belt; Canadian Journal of Earth Scb nces, Volune 24, rhyolite outcrops and an adjacent bank of glacial outwash pages 2477-2485. exposedin a cut on the road fromQuesnel to Nazko Tipper, H.W. (1961): Prince George, Bntislt Columbi:; Sheet 93G; Geological S~rvvqvofCanada, b ap 49-191XI (Photo 6). While no bedrock outcrops containing volcanic glass are known in the area, abundant clasts of perlitic rock

Geological Fieldwork 1994, Papcr 1995-1 NOTES