Geology and Rank Distribution of the Elk Valley Coalfield, Southeastern British Columbia (82C/15, 82J/2, 6, January 1993 7
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Province of British Columbia Ministly of Energy, Mines and MINERAL RESOURCES DIVISION Petroleum Resources Geological Survey Branch Hon. Anne Edwards GEOLOGY AND RANKDISTRIBUTION OF THE ELK VALLEYCOALFIELD, SOUTHEASTERNBRITISH COLUMBIA (82G115, 82J12, 6, 7, 10, 11) by D. A. Grieve This project was partially funded by the Canada-British Columbia Mineval Development Agreement 1985-1990. BULLETIN 82 MINERALRESOURCES DIVISION Geological Survey Branch VICTORIA BRITISH COLUMBIA Canadian Cataloguing in Publication Data CANADA Grieve, David Austin, 1952- Geology and rank distribution of the Elk Valley coalfield, southeastern British Columbia (82C/15, 82J/2, 6, January 1993 7. IO. II) (Bulletin, ISSN 0226-7497 : 82) Geological fieldwork for this Issued by Geologicai Survey Branch. publication was completed Includes bibliographical references: p. during the period 1979 to 1987 ISBN 0-7718-9306-X I. Coal - Geology - British Columbia - Elk River Valley (East Kootenay) 2. Coal - British Columbia - Elk River Valley (East Kootenay) - Composition, 3. Geology, Economic -British Columbia - Elk River Valley (Easl Kootenay) I. British Columbia. Ministry of Energy, Mines and Petroleum Resources. 11. British Columbia. Geological Survey Branch. Ill. Title. IV. Series: Bulletin (British Columbia. Ministry of Energy, Mines and Petroleum Resources): 82. I TN806.C32B73 1992 553.2'4'0971 165 C92-092398-4 - ABSTRACT The Elk Valley coalfield is one of three structurally separate coalfields in southeastern British Columbia. Total potential in siru coal resources are a minimum of 7.8 billion tonnes. The coal-bearing Mist Mountain Formation ranges from less than 425 to approximately 700 metres in thickness in the study area. An average of approximately IO per cent of its total thickness is composed of coal seams, which range up to 13 metres in thickness. The basal 20 metres of the formation, referred to informally as the “basal coal zone”. consistently contains coal and other carbonaceous strata. The ”Imperial seam”, in the lower half of the formation, is correlated laterally in drill core and surface exposures over a distance of approximately 17 kilometres. Lithologies in the Mist Mountain Formation form a Markov chain. The data confirma general fining-upward sequence typical of fluvial-alluvial depositional systems. The coal-forming environment is believed to have been relatively isolated from sources of clastic material. In terms of statistical sequence modelling, the lower half of the Mist Mountain Formation is not significantly different from the upper half. Tonsteins are found throughoutthe Mist Mountain Formation. Lateral continuity of tonsteins over a distance of 1.4 kilometres is documented in two cases. The tonsteins are believed to represent volcanic ash, possibly reworked. All are kaolinite rich, and one example is also rich in the phosphate mineral gorceixite. Vitrinite is the most abundant maceral in coals from the study area, comprising 5 I to 93 per cent of total organic material. In general, the amount of vitrinite increases up-section. Semi- fusinite is the most abundant inertinite maceral and its concentration is inversely related to that of vitrinite. Liptinite is generally rare or nonexistent, although coals in sections of predomi- nantly high-volatile rank contain 1 to 5 per cent liptinite. Petrographic indices suggest vegeta- tion was deposited in siru, although there is some indication that the relative amount of movement of vegetation prior to deposition decreased up-section. It is also apparent that the height of the water table generally increased higher in the stratigraphy. The major structureof the Elk Valley coalfield is the Alexander Creek syncline. Overall it has a north-northwest trend, and no net plunge. Locally its plunge is subhorizontal to gentle. It is generally asymmetric, open, and has an upright to steeply inclined axial plane. Thrust faults, including the Ewin Pass fault, are more commonon the east limb than on the west. Other major structures in the coalfield are the Greenhills syncline, which is separated from the Alexander Creek syncline to the east by the west-dipping Erickson normal fault, and the Bourgeau thrust fault, which marks the western boundary of the northern part of the coalfield. Based on meanmaximum vitrinite reflectance coal ranks in the MistMountain Formation generally range from low-volatile IO high-volatile A bituminous, with a few instances of high-volatile B bituminous. Reflectance gradients withinmeasured stratigraphic sections range from 0.057 to 0.1 19 per cent per 100 metres, with no systematic geographic variation. At most locations, the lower part of the formation contains coals of medium-volatile bituminous rank, typically with reflectance values of 1.3 to 1.4 per cent. At three locations (Crown Mountain, Mount Banner and Weary Creek) the coals in the lower part of the formation are of low-volatile rank. At one location (Bleasdell Creek), the entireformation contains high-volatile coals. Determination of the principal axes of the reflecting indicating surface (RIS) of coal samples suggests that all coals in the study area are biaxial. Values of R,,, the reflectance parameter which represents the style of the RIS, range from - 16.537 (biaxial negative) to f5.209 (biaxial positive) and, for the most part, do not vary sysematiglly. All of the following reflectance parameters are effectiveindices of rank variation: R,,,,,, R,, (mean random reflectance), R,,, (the radius of a sphere of volume equal to that of the RIS) and R,,,;,, (the magnitude of the maximum axis of the RIS). There is no firm evidence of down-dip rank increases indicating the occurrence of post- folding coalificaton in the Elk Valley coalfield. However, the RIS analysis suggests that coalification was at least partly concurrent with compressional deformation, and other aspects of the rank distribution suggest that it continued after the compressional deformation stage. On balance, it is believed that coalification occurred before, during and after compressional deformation, but completely predated the later extensional phase. A wide spread of bituminous coal quality is available in the coalfield. Volatile matter content (dry, ash-free) in selected raw bulk-sample analyses from three properties ranges from 20.9 to 30.9 per cent. Ash content in the same samples varies from 6.5 to 33. I per cent, while sulphur values are all less than or equal to 0.7 per cent. Current products from the coalfield include coking coals of varying volatile matter content, semicoking coals and thermal coals. ... 111 TABLE OF CONTENTS Page... Page ABSTRACT ..................................... :....................................................................... 111 18 CHAPTER 1: INTRODUCTION ................................................ 1 i8 Development History................................................................................ 1 19 Coal Rights Tenure ..................................................................................... I 19 Coal Resources ................................................................................................ 4 19 Access and Topography......................................................................... 4 19 Previous Work .................................................................................................. 5 19 Study Methods................................................................................................. 5 19 Field Methods............................................................................................ 5 19 Mapping..................................................................................................... 5 19 Measurement of Stratigraphic Sections .................. 5 19 Core Logging....................................................................................... 5 20 Coal Sampling.................................................................................... 5 20 Grab Sampling............................................................................. 6 20 Channel Sampling.................................................................... 6 21 Laboratory Methods............................................................................ 6 21 Coal ................................................................................................................ 6 22 Sample Preparation................................................................. 6 24 Pellet Preparation...................................................................... 6 24 Coal Petrography...................................................................... 6 25 Tonsteins................................................................................................... 8 28 Methods of Structural Analysis.............................................. 8 31 Acknowledgments........................................................................................ 8 31 32 CHAPTER 2: STRATIGRAPHY ................................................ 9 32 Stratigraphic Setting .................................................................................. 9 32 Older Strata .................................................................................................. 9 32 Kootenay Group...................................................................................... 9 33 Tectonic Setting and Provenance................................... 10 33 Morrissey Formation................................................................... 10 33 Mist Mountain Formation.....................................................