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File Created: 24-Jul-1985 by BC Geological Survey (BCGS)
Last Edit:  21-Nov-2012 by George Owsiacki (GO)

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Name SURPRISE, PRISE Mining Division Skeena
BCGS Map 104A023
Status Showing NTS Map 104A04E
Latitude 056º 13' 58'' UTM 09 (NAD 83)
Longitude 129º 33' 05'' Northing 6232124
Easting 465818
Commodities Molybdenum, Copper Deposit Types L05 : Porphyry Mo (Low F- type)
Tectonic Belt Intermontane Terrane Bowser Lake
Capsule Geology

The Surprise showing is located near the headwaters of the west fork of Surprise Creek, about 6.5 kilometres east of Mount Pattullo. The exact location is not known, but is assumed to lie close to an ice cap on the Prise claim.

In 1977, Falconbridge discovered molybdenite-bearing boulders in the area. In 1979, Wesfrob Mines Limited conducted geological, geochemical and geophysical surveys but only the geophysical surveys are on record; the location of the surveys is not clear(Assessment Report 7576). In 1981, Riocanex Inc. optioned the property and drilled three holes (1038.5 metres) to test the mineralization.

The area is underlain by shale, greywacke and siltstone of the Middle-Upper Jurassic Bowser Lake Group (Ritchie-Alger assemblage). The sediments are intruded by a small stock of porphyritic quartz monzonite (Assessment Report 7576).

Two separate rusty zones (800 by 300 metres and 1800 by 900 metres) coincide with areas of biotitic alteration of siltstone and greywacke. The smaller zone is associated with the exposed stock. In the larger rusty zone, biotite alteration is coincident with anomalous fluorine values. The alteration zonation was considered to be centred on a small ice cap in the centre of the Prise claim. Molybdenite-bearing quartz veinlets, in outcrop and float adjacent to the ice cap, suggested the presence of a mineralized stock beneath the ice (Assessment Report 9618).

The three drillholes intersected sediments and, in hole 81-1, two lamprophyre dikes. The sediments are variably altered; biotite, sericitic and argillic alterations are reported. Mineralization in the drillholes consists mainly of disseminated pyrite and/or pyrrhotite that averages 1 to 2 per cent but is locally up to 50 per cent over short core lengths. Molybdenite and minor chalcopyrite accompany pyrite, pyrrhotite, variably present calcite and rare fluorite in quartz veinlets. The veinlets are commonly less than 1 millimetre wide but do occur up to 1.5 centimetres wide. Molybdenite occurs rarely in sections of graphitic siltstone. Chalcopyrite is typically associated with pyrrhotite.

The best molybdenum grades occur in the argillic alteration. One section, 2 metres wide in hole 81-2, was visually estimated to contain 0.1 per cent molybdenum (Assessment Report 9618).

EMPR ASS RPT 7576, *9618
EMPR EXPL 1978-E256
EMPR OF 1987-22; 1994-14
GSC OF 2582; 2779