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File Created: 15-Jan-1995 by Garry J. Payie (GJP)
Last Edit:  30-Jul-1997 by Keith J. Mountjoy (KJM)

Summary Help Help

BCGS Map 092H031
Status Prospect NTS Map 092H05W
Latitude 049º 20' 10'' UTM 10 (NAD 83)
Longitude 121º 58' 43'' Northing 5465322
Easting 574202
Commodities Zinc, Copper, Lead, Gold Deposit Types G06 : Noranda/Kuroko massive sulphide Cu-Pb-Zn
Tectonic Belt Coast Crystalline Terrane Harrison
Capsule Geology

The Fleetwood and 33 zones are located 3 kilometres northwest of the Seneca deposit (092HSW013) along the east side of the Chehalis River, about 9 kilometres north of Harrison Mill, British Columbia.

The area of the Seneca deposit and its related occurrences the Vent (092HSW139) and the Fleetwood/33 zones are underlain primarily by volcanic rocks of the Lower to Middle Jurassic Harrison Lake Formation. McKinley et al. (1995) subdivided the stratigraphy into three principal volcanic facies as follows: 1) Facies 1 - Lavas (vent-proximal facies) consist of basaltic to rhyolitic composition flows, domes and associated in situ hyaloclastites and autoclastic breccias. 2) Facies 2 - Volcaniclastic rocks (vent-proximal to distal facies) consist of juvenile to reworked coarse volcanic breccia and tuffs to fine-grained siltstone. 3) Facies 3 - Synvolcanic intrusions consist of basaltic to rhyolitic sills and dikes that have intruded lavas and wet volcaniclastic sediments. A fourth facies consists of an argillite that often contains flattened pumice clasts and is often in close proximity to mineralization. This fourth facies is restricted to the main Seneca deposit, also referred to as the Pit area, and does not correlate across the property.

In general, the strata on the property strike approximately northwest and are essentially flat lying or moderately east dipping. The stratigraphy has undergone very little deformation or metamorphism and retains pristine volcanic textures. Metamorphic grade in the area is zeolite facies.

Three types of mineralized zones are present in the Seneca area: 1) Conformable massive sulphide lenses. 2) Semimassive and disseminated sulphides associated with volcaniclastic rocks. 3) Stockwork and stringer mineralized zones.

Stockwork and stringer sulphides are the dominant style of mineralization in the Fleetwood zone. A drillhole intersected 1.1 metres of massive sphalerite, pyrite and chalcopyrite, immediately above about 30 metres of stockwork sphalerite-pyrite-chalcopyrite- quartz-anhydrite veinlets in altered dacite and fine volcaniclastics similar to the Vent zone. Shorter intersections of similar stockwork mineralization occur in drillholes between the Fleetwood and Vent zones. All the mineralized zones in the Fleetwood area occur at the same stratigraphic level and have similar lithologic associations. The stockwork zones are most commonly hosted by felsic lavas and autobreccias which immediately overlie mafic lavas and reworked mafic-dominated volcaniclastic rocks, and which occur below the fine grained volcaniclastic rocks. These overlying fine volcaniclastics are essentially unmineralized and unaltered except for occasional fine sulphide laminations. The mineralized zones are often associated with narrow fault zones and moderate to strong, fine anhydrite veining.

Conformable, stratabound lenses of semimassive sphalerite, pyrite and chalcopyrite with lesser galena are exhibited chiefly in the main Seneca deposit or Pit area, but also to a lesser degree in the 33 zone of the Fleetwood area. The sulphides are hosted by fragmental rocks and occur as discontinuous pods. In the 33 zone, a 2 metre intersection of massive sulphides is underlain by a quartz-carbonate-chlorite zone and a dacite porphyry intrusion, and is sharply overlain by a cherty sulphide layer and a zone of strongly chloritized fragmental material. Blades of barite are intergrown with the sulphides. A drillhole intercept of 2 metres of massive sulphide at 170 metres depth analysed 2.2 per cent copper, 28 per cent zinc and 4 grams per tonne gold (Assessment Report 22915, page 7).

Generally, most of the rocks at the Seneca occurrences are relatively unaltered, exhibiting pristine preservation of volcanic textures. Macroscopically recognizable alteration is restricted to the Vent and Fleetwood zones where it is characterized by intense silicification and sericitization associated with massive to flow banded and flow brecciated dacite porphyry. The stockwork veining is restricted to the dacites but alteration extends 10 to 20 metres into the surrounding fragmental rocks, obliterating original textures.

EMPR AR 1897-578; 1898-1113; 1961-88; 1962-93
EMPR EXPL 1975-E62; 1976-E77; 1977-E122; 1978-E141; 1982-165; 1983-234; 1986-C201,202
EMPR FIELDWORK 1984, pp. 120-131; 1985, pp. 95-97; *1993, pp. 345-350 *1994, pp. 503-512
EMPR GEM 1971-265; *1972-102-114; *1973-125-128; 1974-102
EMPR MAP 65 (1989)
EMPR OF 1992-1; 1999-2
EMR MIN BULL MR 223 B.C. 111
EMR MP CORPFILE (Zenith Mining Corporation Ltd.; Chevron Standard Ltd.)
GSC EC GEOL Vol.60, No.5 (1965), p. 955
GSC MAP 12-1969; 737A; 41-1989
GSC MEM 335, p. 276
GSC P 69-47, p. 67; 86-1B, pp. 715-720
CIM Special Volume 8, p. 101
CJES Vol.10 (1973), pp. 1688-1692
GAC Special Paper 3 (1966), p. 43; 6 (1970), p. 137
GAC Proceedings Vol.16 (1965), p. 63
GCNL #29,#144, 1976; #27, 1977; Dec.14, 1983; Jan.10,Mar.30, 1984; #224, 1986; #116(Jun.15), 1990; #44(Mar.4),#157(Aug.15), #186(Sept.26),#215(Nov.7), 1991; #72(Apr.10),#112(June 10), 1992
GSA Vol.72 (1961), p. 1409
N MINER Mar.18,Jun.3, 1976; Feb.3, 1986; Aug.5, Sept.9, Oct.7, 1991; June 22, 1992
Arthur, A.J. (1987): Mesozoic Stratigraphy and Paleontology of the West Side of Harrison Lake, Southwestern British Columbia, M.Sc. Thesis, University of British Columbia
Crickmay, C.H. (1925): The Geology and Paleontology of the Harrison Lake District, British Columbia, Ph.D. Thesis, Leland Stanford Junior University, California, 140 pp.; (1962): Gross Stratigraphy of the Harrison Lake Area, British Columbia, Evelyn de Mille Books, Calgary, Alberta, p. 12
Mahoney, J.B. (1994): Nd Isotopic Signatures and Stratigraphic Correlations: Examples from Western Marginal Basins and Middle Jurassic Rocks of the Southern Canadian Cordillera; unpublished Ph.D thesis, University of British, 289 pages
Pride, K.R. (1973): Mineral Graphic Study of Selected Sulphide Samples from the Seneca Property near Harrison Mills, British Columbia, unpub. B.Sc. Thesis, University of British Columbia
Ray, G.E. et al. (1985): Precious Metal Mineralization in Southwestern British Columbia; Field Guides to Geology and Mineral Deposits in the Southern Canadian Cordillera, GAC Section Meeting, Vancouver, British Columbia, May 1985