GEOLOGY OF A PORTION OF THE PIEBITER CREEK PROPERTY '80-&.5-/4- #kG'a/7 BRALORNE AREA LILLOOET MINING DISTRICT, B. C. NTS 92J/10E Prepared for CHOPPER MINES LTD. ARCTEX ENGINEERING SERVICES L. B. GOLDSMITH, P.ENG. CONSULTING GEOLOGIST L. M. TYRALA GEOLOGIST AUGUST, 1980 TABLE OF CONTENTS Summary .......................................... 1 Introduction ..................................... 2 History and Previous Work ........................ 2 Location Map ..................................... 3 Geographic Setting ............................... 4 Geomorphology .................................... 5 General Geology .................................. 6 Rock Units ....................................... 7 Structures ....................................... 9 Rose Diagram - Foliations ........................ 10 Rose Diagram - Joints ............................ 11 Alteration ....................................... 12 Mineralization ................................... 13 Sampling ......................................... 15 Conclusions ...................................... 16 Recommendations .................................. 16 Cost Estimate .................................... 17 Engineer's Certificate ........................... 18 Appendix: Sample Descriptions Assays Geology Map with Cross Sections (pocket inside back cover) GEOLOGY OF A PORTION OF THE PIEBITER CREEK PROPERTY, BRALORNE AREA, B. C. Summary Geology was mapped in the vicinity of a quartz vein which is exposed discontinuously near a ridge crest between Royal Peak and Mount McGillivray. Chip-channel samples were cut across the vein and wallrocks in five sections. A weighted average of 3.65 ounces of silverlton across 5 metres was obtained in vein material on section B-B'. It is thought that gold values may increase with depth in shoots where silver is present at higher levels. A drill programme of approximately 1200 metres is planned as a preliminary test beneath portions of the vein where the highest silver assays were obtained. Cost of the programme is estimated to be $220,000. A shorter programme could be initiated in order to utilize favourable weather conditions this year prior to an anticipated freeze-up near the first of October. 2 Introduction The period of July 16th to August 2nd was used by the writer for examining and reporting on the mineral holdings of Chopper Mines Ltd. in the upper Piebiter Creek area, Bralorne, B. C. The purpose of the project was to examine, map, and sample in detail the quartz vein structure found in the area of Mount McGillivray and Royal Peak, Bendor Range. The area was mapped at a scale of 1 cm. to 25 metres. Enlarged profiles, at 1 cm. to 10 metres, were constructed for the major vein exposures. Field assistance for this project was given by Kerry McKintosh. Tom Illidge of Goldbridge provided local assistance. History Previous Work As far as known to this writer, no significant work has been done within the mapped area. A short adit, less than 4 metres, was driven into the most westerly quartz vein outcrop, located northerly of Mount McGillivray. The area has been prospected, but no real geologic work has been carried out. The area has been generally reported upon by the Bureau of Geology and Topography personnel, C. E. Cairnes (1934, 1935), Mem. 213; and W. E. Cockfield (1931), S.R. 1931A (46-57). 4 Geographic Setting The mineral holdings are located on the northerly slope between Mount McGillivray and Royal Peak, Piebiter Creek. The mapped area is covered by the 1:50,000 Birkenhead Lake topographic sheet no. 925/10, Lillooet Mining District. The mapped area is bounded by grip map references 264181 to the northwest, 307158 to the northeast, 304153 to the southeast, and 263172 to the southwest (see Diagram no. 1). The central coordinates of the mapped area are approximately longitude 122035.5'W7 latitude 50'42.5". The area is approximately 15 kilometres southwesterly of Bralorne. A partially completed tote road along Cadwallader and Piebiter Creeks provides walking access to the property. For the purpose of this project a helicopter was used, services provided by Pemberton Helicopter Services, Pembcrton, B.C. The area is of moderate to very rugged terrain with slopes ranging from 20 degrees to near vertical. The mapped area is incised by northerly flowing creeks draining into the westerly flowing Piebiter Creek. The general area is lightly wooded with treeline at about 1900 metres. The mapped area is barren of trees and is partially covered with small isolated patches of alpine ground cover. A glacier and small permanent snowfields dot the area. 5 Geomorphology Within the mapped area, glacial activity has been the controlling mechanism of surface form. Within the claim group, and occupying an area of about 15 hectares, is an active glacier located immediately northwesterly of Mount McGillivray (elevation: 2603 metres). Preglacial features, as erosonial surfaces and other modified land forms, are lacking. The glacier covers about a 700 metre strike-length interval of the quartz vein projection. The glacier occupies a hanging valley with movement and drainage to the northwest. The local rocks show very well developed striations and polishing. Easterly of the glacier, across the divide of Mount McGillivray, the slope is mostly covered with talus. The central area of the vein structure is occupied by a shallow tarn with the vein apparently trending immediately south. A talus slope here covers any bedrock that might indicate the location of the vein. A relatively broad, somewhat subdued glacial divide is located at the westerly end of the vein structure. It is here that the vein is best exposed. Immediately across the divide to the west is another tarn occupy- ing a well defined deeply cut cirque. This former glacial centre occupies a hanging valley perched almost 300 metres above the valley floor of Piebiter Creek. The creek itself has been subject to active glacial alteration. 6 The western end of the vein structure disappears in the talus area immedi- ately easterly of Royal Peak (2317 metres). The whole of the mapped area is completely denuded by glacial activity. The area is made up of outcrops and talus slopes. No moraines are present. Immediately outside of the mapped area, to the north, are several well defined flanking moraines in Piebiter Creek. There are no developed soil profiles in the area. The locations of the local valleys and drainages do not appear to be related to the general orientation of the country rocks or foliation. General Geology The region is composed of sedimentary and volcanic rocks and intrusive bodies. The relationship of these units is frequently made complex by the intricate structural history of the region. Also, thermal metamorphism has in places so altered the original lithology that identification of formations is doubtful. The general structural feature of the Bralorne region is a syncline within a major anticlinal arch trending northwesterly-southeasterly. Along the fold axes, igneous rocks have been emplaced. Throughout the region the general trend of the formations is northwesterly-southeasterly, forming an overall arcuate course with orientations nearly north-south near Goldbridge to nearly east-west in the southern Bendor Range. The areal location of the Bendor batholith, at its western extent, roughly parallels this pattern.fl 7 The sediments and intercalcated extrusive rocks are almost always steeply- dipping because of the intrusion of the Bendor batholith. The region is well dissected by faults, frequently with significant amounts of.vertica1 and lateral displacement. With reference to the mineralization of the region, the Bridge River district is noted for its high-grade lode occurrences of gold in the quartz veins of Cadwallader Creek. Most of the gold production from this district came from these veins. The deposits are considered to be genetically related to the intrusives of the region. Additionally, placer gold has been recovered since the earliest days of the camp. Presently two firms are operating placer gold recovery operations in the Hurley River immediately south of Goldbridge. --Rock Units The mapped area is composed of metamorphosed sediments. The units trend uniformly westnorthwest-eastsoutheast and dip steeply to the south. The Bendor diorite is well exposed in the extreme western portion of the area, and in Piebiter Creek immediately north of the mapped area. Most of the sediments appear to have had a largely argillaceous composition, and metamorphosed to a dark grey phyllite occasionally grading to a well defined schist. The metamorphosed sediments display a mineralogy that suggests a shallow marine quiet water environment. Immediately north of the 8 mapped area, thin lenses, up to 1.5 cm. thick, of moderately recrystallized limestone were observed. In the north-central portion of the mapped area the sediments are intercalcated with numerous quartz-rich thin beds, ranging from 1 mm. to 2 cm.; the beds occasionally have a boudinage-like appearance. Frequently the quartz-rich beds will display intricate folding with the adjacent beds completely undisturbed. Interlayered within this thick sequence of phyllite-schist is a horizon that shows a distinctly different composition and texture. The bed is light to medium-greyy and is made up of euhedral biotite and muscovite with porphyroblasts of what appear to be plagioclase in a fine-grained groundmass of anhedral quartz. The unit stands out prominently in outcrop and has a distinct "spotted" appearance. A persistent