British Columbia Mineral Deposit Profiles
The British Columbia Geological Survey (BCGS) started a mineral potential assessment of the province in 1992. The methodology for this resource assessment process is described by Grunsky et al. (1994), Kilby (1995, 1996) and Grunsky (1995). A fundamental part of this process is compilation of information about mineral deposits including descriptions, classification and resource data (Lefebure et al., 1995a; Lefebure and Ray, 1995, Lefebure and Hõy, 1996). The resulting deposit models can be used to classify known deposits and occurrences, to guide experts in their estimation of the number of possible undiscovered mineral deposits, and to group deposits to allow compilation of representative grade and tonnage data.
The B.C. Geological Survey initially relied on mineral deposit models published by the United States Geological Survey (USGS) and Geological Survey of Canada (GSC). However, it became apparent that some models needed revision, and that there are British Columbia deposit types lacking published USGS models.
This work proceeded using the Survey’s considerable in-house expertise (McMillan et al., 1991) with assistance from economic geologists of the GSC, industry, academia and USGS. At the time the USGS published an Open File of descriptive geoenvironmental mineral deposit models (du Bray, 1995) and the GSC made an important contribution with the publication of a volume describing Canadian mineral deposit types (Eckstrand et al., 1996). The British Columbia deposit models are called ‘deposit profiles’ to distinguish them from other published descriptions, such as the USGS ‘deposit models’. One value of the profiles is that they will provide geologists and prospectors with a reference guide to deposits with which they have little familiarity. In some cases they may encourage consideration of new exploration targets within the province (Lefebure, 1995). The BCGS has published additional industrial mineral deposit profiles which are only available online. We welcome comments and criticisms of the deposit profiles.
“An ore deposit model is a conceptual and/or empirical standard, embodying both the descriptive features of the deposit type, and an explanation of these features in terms of geological processes.” Hodgson, 1993
In recent years there has been considerable discussion of the importance and dangers of deposit models and their relevance to exploration (Cox, 1993). One of the points underscored by this debate is that while models are an extremely useful method of organizing data, they may lead to over simplification of complex natural phenomena.
Important data may be ignored because it does not fit the model. Every model has limitations, particularly those attempting to portray the essential features of natural phenomena. Interactions between the constructors of published models, who are often government and academic geologists, and the explorationists who use them, are critical to the evolution of more accurate and useable models (Hodgson, 1993). Often it is the deposits that can not be classified, or the observation that can not be explained by an existing model, which lead to an advance in our understanding of ore-forming processes or products. Critical elements of mineral potential assessments are standard deposit-type descriptions that are used to group similar deposits. These standard descriptions can then be used as "deposit definitions" for expert analysis of the mineral potential of geological tracts and provide the basis for selecting resource data for quantitative assessments, such as tabulations of grade and tonnage data (Grunsky, 1995). Complete suites of deposit models are desirable, even though mineral assessments and exploration programs tend to focus on a restricted number of deposit types at any given time. For government, it is important to assess the resource values with an eye to future exploitation of resources. The mineral potential of some land tracts will be increased if deposit types of little significance today can be identified as possible mines of tomorrow. For industry, it is critical to be able to decide whether a particular occurrence belongs to a deposit type that is economically interesting at the present time. This helps focus exploration efforts on targets with a greater chance of economic return. The USGS published the first comprehensive set of mineral deposit models and related grade and tonnage probability curves (Cox and Singer, 1986). They presented 85 mineral deposit models and 60 associated grade and tonnage curves. Almost all the deposits described contain metallic commodities.
Since then the USGS has produced a number of other publications containing summary deposit models, including two significant Open File reports with a large number of industrial minerals models (Orris and Bliss, 1991, 1992).
MINERAL DEPOSIT PROFILES
British Columbia mineral deposit profiles are concise descriptions tied to a series of headings which will fit on several pages; a format similar to those of deposit models published by the GSC and the USGS (Eckstrand, 1984; Cox and Singer, 1986). They are primarily descriptive because the ore-forming processes are sometimes poorly understood. As with the USGS models, the profiles are intended to be global models with sufficient information to describe the deposit type anywhere in the world. However, they incorporate more information specific to British Columbia with respect to tectonic setting, age of mineralization, examples, references, resource data and economic factors. The guidelines for authors are published in Open File 1995-13 in Appendix I (Lefebure and Ray, 1995). Profiles are based on a combination of published information and the personal knowledge of the authors and, in many cases, information provided informally by industry geologists. More than 150 general deposit models are thought to be relevant to British Columbia, including more than 80 metal, 70 industrial mineral and four coal profiles. The Survey is currently working towards completing descriptions for approximately 120 of these deposit models. Grade and tonnage data for selected metallic models was published in Open File 1996-13 (Lefebure and Hõy, 1996). With new data being produced every day by industry and research geologists, it is expected that some of today’s models will be out-of-date tomorrow. The BCGS profiles will change as we receive more information from industry and research geologists. Better models assist both the exploration community and resource assessment geologists.
BRITISH COLUMBIA DEPOSIT TYPES
Over 90% of the occurrences (more than 9900) in the MINFILE provincial mineral occurrence database have been classified by industry experts according to BCGS deposit type. This provided a check on the effectiveness of existing deposit models to adequately describe the complete array of mineral occurrences in British Columbia. Geologists classifying occurrences quickly pointed out that there were a number that did not fit any of the existing profiles or any of the USGS models. In some cases this reflected the difficulty of classifying poorly described showings and prospects. However, it also identified new deposit models that applied to British Columbia. This exercise should be completed for any area where mineral potential is being assessed, as it provides a very useful check on the applicability of global models being applied. The most abundant groups of deposit types in British Columbia are vein, porphyry and skarn (see Table 1). This reflects the mineral industry exploration emphasis over the last century, the abundance of island arc volcanic terranes and the current levels of erosion of many of these terranes. The single most abundant deposit type is polymetallic silver-lead-zinc veins which comprise 25% of the occurrences in the province. No other deposit type exceeds 5%; porphyry copper, alkalic porphyry, copper skarn, gold-bearing quartz veins and basaltic copper are the next most common deposit types.
Table 1. Distribution of Classified British Columbia MINFILE Occurrences by Deposit Group.
A number of deposit types that are thought to be irrelevant to British Columbia will not be addressed by completing profiles. For example, there seems very little likelihood of Bushveld type Fe-Ti-V or komatiitic nickel deposits occurring in the province. In other cases very specific deposit models have been combined to provide a more general model. There are also some styles of mineralization which have yet to produce any significant orebodies in a free market economy, but are believed by some to have economic potential as a future metal resource. For example, the thin shale-hosted Ni- Zn-Mo-PGE layers (Nick in the Yukon and the Chinese deposits) which have been the targets of a number of exploration programs but still must be regarded more as mineralogical oddities than proven economic resources. These deposits are difficult to include in resource assessments because they are typically poorly understood and not widely known. These deposits can become more attractive development targets with advances in technology. The British Columbia profiles include several of these as deposit types because we believe they could be important resources in the future. However, some other styles of mineralization, such as Prairie-style Au, are excluded until it becomes clearer that they are an economic resource.
Table 2. Mineral Deposit Types Span an Economic Feasibility Spectrum.
“ ever since Agricola first classified ore deposits, successive writers have attempted classification of mineral deposits, none of which has obtained unanimous endorsement” (Jensen and Bateman, 1979)
The different methods of grouping of the different deposit types has generated considerable discussion. This reflects the difficulties in any subdivision of complex natural phenomena, particularly when some deposit types are end members of a continuum. The many classification systems developed since Agricola are testimony to the elusive nature of a satisfactory classification scheme for mineral deposits. This is not surprising given ongoing advances in our understanding of ore-forming processes. The reader is directed to Jensen and Bateman (1979) and Peters (1978) for a review of different classification systems.
With our profiles, the approach has been to regard the deposit models as the key element and any classification system as merely an index for placing the models into a useful context for the user. An admirable example of providing multiple indexes to mineral deposit types is Laznicka’s text (1985).
Three classification schemes for British Columbia deposit profiles are included with these files. The first is organized by deposit groups which uses a combination of characteristics to separate deposits into groupings frequently used by geologists. This is a single entry listing with headings, such as porphyry, industrial rocks, organic and placer deposits, divisions which relate well to areas of expertise of economic geologists. The second classification system classifies profiles according to the most commonly associated host lithologies. This is a multiple entry index. It is particularly useful for mineral potential assessments where the bedrock geology is often the most important criterion for estimating the number of undiscovered deposits. For many users, the listing of deposit profiles by commodity could easily prove the most useful. The first two tables provide some related information that may be of use to the reader. Alternate deposit model names are included under synonyms. In many cases example deposits from British Columbia and other parts of Canada and the world are listed for each profile. These are meant to provide knowledgeable readers with suitable reference deposits. There has been considerable effort put into checking that the examples are representative of the deposit type; however, we are aware that some of the deposits, particularly those from outside the province, may be incorrectly classified.
The BCGS alphanumeric reference code for the deposit profiles is recorded in all tables. This is a single letter followed by a two digit number which provides a short code for the profiles. If the BCGS does not yet have an existing draft profile for a deposit type, this is indicated by an asterisk after the code (e.g. B01*). For the convenience of readers familiar with the USGS models published by Cox and Singer (1986), Orris and Bliss (1991, 1992) and in a few scattered articles (for example, Rytuba, J. J. and Cox, D. P. , 1991) the relevant codes of USGS models are listed in the deposit groups index. Note that we have included codes for deposit types listed by Orris and Bliss (1991, page 66) that have not yet been published. As with the BCGS profiles, these codes are marked by an asterisk (39f*) to show that they are not published. In a few cases Orris and Bliss (1991) have created a USGS model code (13g*, 27e, 25ka*) that also has been used by other USGS authors for a metallic deposit , therefore references to these three industrial mineral models of Orris and Bliss are prefixed with IM.
Within the classification schemes the reader will notice several new deposit types that reflect the influence of new discoveries or new data. For example, there is a deposit model for G07 - “subaqueous hot spring Au-Ag”. This is based on the Eskay Creek deposit and recent research results from the southeast Pacific (Hannington, 1993) documenting shallow, precious metal-rich, exhalative sulphide deposits. As more data are collected on these new deposits our increased understanding may allow them to be merged with an existing deposit model.
The British Columbia Geological Survey would like to thank all the geologists who have contributed their input to the deposit profiles as this is truly a team effort. Survey geologists have contributed the majority of the deposit models and participated in number of meetings to determine which deposit types should be included. A number of geologists from government (GSC, USGS), universities and industry have also written or co-authored profiles allowing us to tackle more deposit models. Currently the author list includes Dani Alldrick, Chris Ash, Tyson Birkett, Robert Cameron, Peter Cerny, Neil Church, E.R. Force, Dave Grieve, Gordon Gross, Eric Grunsky, Kirk Hancock, Dan Hora, Trygve Höy, W.M. Kenan, Ian Knuckey, Dave Lefebure, Vic Levson, Don MacIntyre, Nick Massey, W.H. McCracken, Ron McMillan, JoAnne Nelson, Graham Nixon, Greta Orris, Andre Panteleyev, Suzanne Paradis, C. Pilarski, Howard Poulsen, Vic Preto, Gerry Ray, Barry Ryan, Don Sangster, R.A. Sheppard, A. Sabina, George Simandl, Dave Sinclair, D.M. Sutphin, Tom Schroeter, and J. Townsend.
Cox, D.P. (1993): Mineral Deposit Models, Their Use and Misuse - A Forum Review; Society of Economic Geologists, Newsletter No. 14, pages 12-13.
Cox, D.P. and Singer, D.A., Editors (1986): Mineral Deposit Models; U.S. Geological Survey, Bulletin 1693, 379 pages.
du Bray, Edward A. (1995): Preliminary Compilation of Descriptive Geoenvironmental Mineral Deposit Models; ; U.S. Geological Survey, Open File 95-831, 272 pages.
Eckstrand, O.R., Editor (1984): Canadian Mineral Deposit Types: A Geological Synopsis; Geological Survey of Canada, Economic Geology Report 36, 86 pages.
Eckstrand, O.R., Sinclair, W.D. and Thorpe, R.I, Editors (1996): Geology of Canadian Mineral Deposit Types; Geological Survey of Canada, Geology of Canada, Number 8, 640 pages.
Grunsky, E.C., Kilby, W.E. and Massey, N.W.D. (1994): Resource Assessment in British Columbia; Nonrenewable Resources, Volume 3, No. 4, pages 271-283.
Grunsky, E.C. (1995): Grade-Tonnage Data for Mineral Deposit Models in British Columbia; in Geological Fieldwork 1994, Grant, B. and Newell, J.M., Editors, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, pages 417-423.
Hannington, M.D. (1993): Shallow Submarine Hydrothermal Systems in Modern Island Arc Settings; Geological Association of Canada, Mineral Deposits Division Newsletter, The Gangue, No. 43, pages 6- 9.
Hodgson, C.J. (1993): Uses (and Abuses) of Ore Deposit Models in Mineral Exploration; Geoscience Canada, Reprint Series 6, pages 1-11.
Jensen, M.L. and Bateman, A.M. (1979): Economic Mineral Deposits; John Wiley & Sons, New York, 593 pages.
Kilby, W. (1995): Mineral Potential Project -Overview; in Geological Fieldwork 1994, Grant, B. and Newell, J.M., Editors, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, 411-416.
Kilby, W. (1996): Mineral Potential Project -Overview; in Geological Fieldwork 1995, Grant, B. and Newell, J.M., Editors, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1996-1.
Laznicka, P. (1985): Empirical Metallogeny - Depositional Environments, Lithologic Associations and Metallic Ores, Vol. 1: Phanerozoic Environments, Associations and Deposits, Elsevier, New York, 1758 pages.
Lefebure, D.V. (1995): Two Intriguing Mineral Deposit Profiles for British Columbia, in Geological Fieldwork 1994, Grant, B. and Newell, J.M., Editors, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, pages 491-499.
Lefebure, D.V., Alldrick, D.J.; Simandl, G.J. and Ray G.E. (1995a): British Columbia Mineral Deposit Profiles; in Geological Fieldwork 1994, Grant, B. and Newell, J.M., Editors, B.C. Ministry of Energy, Mines and Petroleum Resources, Paper 1995-1, pages 469-490.
Lefebure, D.V., Alldrick, D.J. and Simandl, G.J. (1995b): Mineral Deposit Profile Tables - Listed by Deposit Group and Lithological Affinities; B.C. Ministry of Energy, Mines and Petroleum Resources, Open File 1995-8.
Lefebure, D.V. and Ray, G.E. (1995): Selected British Columbia Mineral Deposit Profiles, Volume I - Metallics and Coal; B.C. Ministry of Energy, Mines and Petroleum Resources, Open File 1995-20, 136 pages.
Lefebure, D.V. and Hõy, T. (1996): Selected British Columbia Mineral Deposit Profiles, Volume II - More Metallic Deposits; B.C. Ministry of Employment and Investment, Open File 1996-13, 172 pages.
McMillan, W.J.; Hõy, T.; MacIntyre, D.G.; Nelson, J.L.; Nixon, G.T.; Hammock, J.L.; Panteleyev, A.; Ray, G.E. and Webster, I.C.L. (1991): Ore Deposits, Tectonics and Metallogeny of the Canadian Cordillera; B. C. Ministry of Energy, Mines and Petroleum Resources, Paper 1991-4, 276 pages.
Peters, W.C. (1978): Exploration and Mining Geology; John Wiley & Sons, Inc., New York, 696 pages.
Orris, G.J. and Bliss, J.D. (1991): Some Industrial Mineral Deposit Models - Descriptive Deposit Models; U.S. Geological Survey; Open-File Report 91-11A, 73 pages.
Orris, G.J. and Bliss, J.D. (1992): Industrial Mineral Deposit Models: Grade and Tonnage Models; U. S. Geological Survey; Open-File Report 92-437, 84 pages.
Rytuba, J.J. and Cox, D.P. (1991): Porphyry Gold: A Supplement to U. S. Geological Survey Bulletin 1693, U.S. Geological Survey, Open File Report 91-116, 7 pages?.
Singer, D.A. (1993): Development of Grade and Tonnage Models for Different Deposit Types; in Kirkham, R.V., Sinclair, W.D., Thorpe, R.I. and Duke, J.M., Editors, Mineral Deposit Modeling, Geological Association of Canada, Special Paper 40, pages 21-30.
Singer, D.A. (1993): Basic Concepts in Three-part Quantitative Assessments of Undiscovered Mineral Resources; Nonrenewable Resources, Volume 2, pages 69-81.
Singer, D.A. (1995): World Class Base and Precious Metal Deposits: a Quantitative Analysis; Economic Geology, Volume 90, pages 88-104.
Singer, D.A.; Menzie, W.D.; DeYoung, J.H., Jr.; Sander, M. and Lott, A. (1980): Grade and Tonnage Data Used to Construct Models for the Regional Alaskan Mineral Resource Assessment Program, U.S. Geological Survey, Open-File Report 80-799, 58 pages.
Singer, D.A.; Mosier, D.L. and Menzie, W.D. (1993): Digital Grade and Tonnage Data for 50 Types of Mineral Deposits; U.S. Geological Survey, Open File 93-280, digital file.