A Quantitative Approach to Regional Metallogeny in the Vancouver

INTRODUCTION Regional metallogeny deals with broad aspects of the genesis of mineral deposits, particularly their distribution in time and space. Here we are concerned with such a study of a 28 700-square-kilometre area in the southwestern corner of British Columbia, including much of the Vancouver and Hope map-areas (NTS 92 G and H) and small parts of the adjoining mapareas to the north (NTS92 J and I) This region is of interest because it contains two large past producers and one present producer; as welll, many mineral occurrences are known in the area. Geologically the area is complex and i!; centred on the intersection of three major tectonic belts (Fig. 58). The Coast Crystalline Belt forms the northwestern part of the area, the Intermontane Belt underlies the eastern part, and the Cascade Belt forms the south-central part. For purposes of the following discussion the Intermontane Belt has been further !;ubdivided from east to west into the Tectonic history of the area is summarized briefly in Table 1 (for tables and figures,see Pagl?s 169-1771. METHOD OF DATA ACCUMULATION Mineral deposit data were compiled from the literature for 258 metal occurrences. Some deposits we1. e examined in the field, and, in many cases, information was discussed with exploration personnel who had greater familiarity with some areas than the authors. Eventually, verified information was coded in the MINDEP system and entered into a computer file for storage and retrieved in a variety of forms. A simple example is illustrated in Table 2 which summarizes general information for the major deposits in the area. A classification of deposit types was required for our study and, because of limitations ctf published descriptions , we adopted the following rudimentary categories as a basis for data collection and subsequent data analvsis. Magmatic-nickel-copper sulphides, for example, Giant Mascot. Porphyry-type-large, low-grade accumulations of copper and/or molybdenum sulphides commonly in or near felsic to intermediate intrusions, for example, Canam. Skarn-calc-silicate and oremineral assemblages produced by replacement a t contacts of intrusions. Volcanogenic-tabular sheets of syn-sediment sulphides within volcanic sequences, for example, Britannia. Vein-tabular discordant zones of epigenetic, hydrothermal origin, for example, Aurum. Shear-coatings of minerals on shear surfaces. Disseminated-sparsely distributed grains or aggregates of ore minerals. Massive-pods of massive ore minerals of uncertain origin. The detailed structure of the MINDEP file is included elsewhere (Wynne-Edwards and Sinclair. 1978). In general, for each deposit we recorded information on commodities, location, physiography, …