GECLCGY 409 KAY GROTJF; QIENICA MINING DISTRICT 1964 Tpm Richards INDEX Summary Introduction page 1 General Geology 1 Procedure 2 Megascopic Description 2 Microscopic Description 3 Paragenesis 11 Temperature of formation 18 Some Genetic Considerations 19 Alteration Minerals 20 Plates 22 Acknowledgements 29 Bibliography 29 The mineralization of the Kay Group occurr. i in a small fault zone, associated with a sheard argillite and feldspar porphyry. The following primary minerals were found: pyrrhotite, pyrite, marcasite, arsenopyrite, sphalerite, tetiahedrite chalcopyrite, jamesonite, native gold, andorite, st i.khtte,: , berthierite galena, an unknown Bismuth mineral and a hydrocarbon, A brief and incomplete study of the secondary minerals was under• taken and goethite, realgar, orpiment, scorodite, gypsy bimdheimite, valentenite and various other amorphous or ill defined alteration products were found. From the characteristics of the ore, the deposit was classified as either xenothermal or epithermal ^ INTRODUCTION The Kay Group was originally staked in 1944. It is located on a hillside west of the Bralorne Takla mercury mine; the main showing being between 4500 and 4500 feet. The property is located 36 miles by road from Takla Landing. The property was optioned to Leta Explorations in 194b, but was dropped In the same year. GENERAL GEOLOGY The area is underlain by a blue-grey limestone of JPennsylvanian and/or Permian age. A band of crushed argillite occurs near the snowing and several dykes of feldspar porphyry cut the limestone and the argillite. The deposit lies along a fault zone 25 feet wide and strides 15°W of N, and follows ap• proximately along the crushed band of argillite. The fault dips vary from 60°N to 75° SW. Mineralization can be traced along the surface for 700 feet, with the ore occuririg in lenses, the largest of these lenses is several feet wide and about 20 feet long. The ore minerals determined ±n trie report (CsC TAeww- 2.5 Z ) are as follows in the order of abundance: stibnite, jamesonite, arsenopyrite, sphalerite, pyrite, andorite, argentiferous tetra- hedrite, native silver, quartz and realgar. An analysis of the andorite ( Qsc m^0vC 2-5 ?„ ) follows: Pb: 20.89$ Ag: 9.18$ Gu: 1.45% pe: 2.07$ Zn> 0.50$ As: 0.76$ Sb: 41.07$ S: 21.85$ insoluble: 1.83$ Assays from the surface exposures went up to 100 oz/Ton of silver and an appreciable content of gold, but underground development was disappointing. The fault zone crossing the property probably forms part of the pinchi Laite fault zone. PROCEDURE The specimens from the Kay Group were first studied under the binocular microscope and certain ore minerals and oxidation products were noted. The microscope work consisted of the inspection of about 50 polished sections using the mineralographic microscope, accompanied by etch tests and microchemical analysis. X-ray powder photographs were taken to confirm certain ore minerals and secondary minerals. MEGASCOPIC DESCRIPTION Only a few ore minerals could be identified positively from the hand specimen. These were stibnlte, jamesonite, sphalerite, tetrahedrite, arsenopyrite and pyrite. The ore usually occurred In two iitypes, as massive ore, or as open space fillings. These two textures are strongly controlled by the type of rock they occur in, the massive ore was more closely related to the incompetent sheared argillite, and the open space fillings confined to the competent, partially sericitized feldspar porphyry. The ore minerals in the massive zone are Invariably arsenopyrite, pyrite, argentiferous tetrahedrite, sphalerite and minor sulphosalts. Occasionally massive zones of pyrite ^re visible, but. arsenopyrite wis the major sulphide. Some small quartz lenses resembling quartz rods foilOWL L the foliation 3 of the sheared argillite. Pyrite is the only sulphide in these lenses. Quartz veins in. to 2 in. in width) follow approximately parallel to the foliation of the argillite out !J<oci%s^\^i<cross the foliation. Pyrite is the main sulphide with some sphalerite. The Veins are often locally zoned, pyrite predominant In the centre, with sphalerite increasing outwards to the edge of the vein. At the edge of the vein sphalerite is predominant but gives way to trie sulpnosalts. In a few in• stances the outward extremity of this ill defined zoning is characterized by stibnite displaying an open work texture. The fissures in trie open space fillings are usually very thin (less than ^ In. in width) to about 1 inch ia width.") In the closed portion of the vein, quartz and sphalerite alter• nate as trie major fillings, while in the open cavities stibnite crystals predominate, with minor quartz crystals. In the larger cavities well formed sphalerite tetrahedrons also occur. Stibnite usually occurs alone as dense radiating crystals, fine hair-like crystals or compact radiating masses enclosed entirely by the quartz gangue. MICROSCOPIC DESCRIPTION Fourteen sulphides and sulpnosalts and one hydrocarbon were determined or verified by microscopic analysis. These are listed below, followed by a description of various relationships, associations and properties. a.) niclaliferipous pyrrhotite b •) pyrite Pe S2 c .) marcasite Pe S2 d.) arsenopipite Pe As S e.) sphalerite (Zn Pe)S to ZnS f •) tetrahedrite (Cu Pe Ag)12 Sb4 S13 sO chalcopyrite Gu Pe S2 h.) andorite Fo Ag Sb3 S6 i •) jamesonite Pb4Pe Sb6 S11 J •) stibnite Sb2 S3 k.) berthierite Pe Sb2 S4 1-) galena Pb S m.) gold AU n*) bitumen hydrocarbon o •) unknown "B^" mineral a. ) Nickliferjrous pyrrhotite Fyrrhotite was seen only In one section. Its appearance, which first seems to be somewhat incongruous with the other low temperature associations, can be attributed to a previous period of mineralization^ (plate 1), The pyrrhotite is invariably associated with early pyrite and sphalerite (var. marmatite) and in places has been altered to marcasite. b. ) pyrite pyrite ..is associated with all stages of mineralizatio The pyrite with the pyrrhotite occurs as small, bright yellow perfectly formea cubes. The alteration of pyrrhotite to marcasite has not affected these cubes (pyrite after pyrrhotite may exist^ (plate l)t Pyrite, with minor arsenopyrite is very common as a wall rock alteration in the feldspar porphyry, but pyrite alone occurs in the silicified sheared argillite. Massive pyrite, showing very few crystal faces occurs associated with the wall rock, and massive arsenopyrite. Sphalerite, jamesonite and an• dorite often fill fractures in the pyrite. Pyrite, with a porphyritic texture, occurs in jamesonite (Plate 2), the jamesonite effectively rounding some of the pyrite crystals. Pyrite also occurs in the low temperature sphalerite phase, as small spheroidal blebs within the sphalerite. The more Fe the sphalerite contains, the more conspicious the pyrite becomes, c. ) Marcasite The marcasite forms as small, pale yellow radiating crystals, which under crossed nicols display' , well developed twin lamellae. The marcasite is an alteration product of pyrrhotite, and is concentrated around the pyrite but does not replace it, d. ) Arsenopyrite A large percentage of the arsenopyrite forms tightly intergrown, crystalline aggregates. The open spaces between crystals are usually filled with quartz, sphalerite and/or tetra• hedrite. Like the pyrite some arsenopyrite occurs as single highly corroded crystals in jamesonite (Plate 2). Some of the massive arsenopyrite has been cataclastically deformed on a small scale. Arsenopyrite also occurs as wall rock alteration with the pyrite. 6 ^ e•) Sphalerite There are three distinct sphalerites in the oitc. The firstf the variety marmatite*associated with the pyrrhotite. The internal reflection of this variety is very dull to almost non-exsistent• The second sphalerite is the most predominant variety. In the hand specimen its colour is reddish to reddish brown, and in the polished section it has an orange red internal reflection. Plates 3$ ^ and 5 show the typical textural relationships and ore relationships of the sphalerite. Occasionally exsolved chalcopyrite is present. The third sphalerite is easily recognized by its red to yellow internal reflection and its association with calcite, galena and occasionally bitumen (Plate 6 and 7)# This sphalerite is locally zoned from relatively high Fe content (estimated at about 2 - 3$) to very low Fe content (estimated at about 0.3$), forming the red to yellow sphalerite respectively. The yellow sphalerite is much coarser grained than the red variety. r f. ) Tetrahedrite CM VC^W^NW) Tetrahedrite is very restricted in its occurrence, either as fillings between the crystals of arsenopyrite or as rounded blebs in jamesonite. The tetrahedrite in the arsenopyrite is occasionally very massive, (these gave a good bichromate test for silver). Large exsolution blebs of chalcopyrite are -common, but more so in the jamesonite association than in the arsenopyrite. g. ) Chalcopyrite Chalcopyrite occurs as minute exsolution blebs in sphalerite seen only under high power, M larger exsolution and/or reaction products in the tetra• hedrite. The blebs in sphalerite strfc. r<arAotn\^ <^\<\\>\>\,eA - ~ h. ) Andorite / The source of most of the silver values from the property was from the andorite. The following properties were used to determine the mineral. 7 Optical: r Colour: white to white grey Hardness: B Anisotropism: distinct - colours grey to tan to brownish to light blueish Habit: massive grains to stubby corroded aggregates Etch tests: aqua Vega: efferveses vigorously, stains iridescent to black HNOx : etches