British Columbia Geological Survey Geological Fieldwork 1987
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GEOLOGY OF DUKE AND HONEYMOON PIT AREAS, MONKMAN COAL DEPOSIT, NORTHEAST BRITISH COLUMBIA COALFIELD* (93U15) By C. B. Wightson KEYWORDS: Coal geology, Monkman coal deposit, com- The joint venture group has presented a proposal to the puter modelling, Minnes Group, Bullhead Group, Fort St. provincial government for an open-pit mine capable of pro- John Group, Smoky Group. ducing 3 million tonnes per year of metallurgical coal. This proposal has obtained Stage I1 approval. The objectives of INTRODUCTION the author's project are 'to provide a detailed geolo;:ical Coallicences were initiallyacquired on the Monkman interpretation of the proposed mine area and to develop a computer-based model of Ithe coal deposit. Information built property by Mclntyre Mines Limited in 1970. Exploration mapping and drilling programs have been conducted over a into the model will be used to calculate: coal reserves and 17-yearperiod by Mclntyre Mines Limited, Canadian stripping ratios. An assessment of the coal deposit will be Superior Exploration Ltd., Pacific Petroleums Ltd. and Pe- available to the provincid government at thetime that a trocanada Inc. The Monkman project is a joint venture mining project is initiatecl at Monkman. Methodology and between Petro-Canada, Mobil Oil Ltd., Smoky River Coal computer technology developed during this project will be Ltd. and Sumitomo Corporation, with Petro-Canada acting used to model and assess other coal deposits and to assist as operator. with the interpretation of ruuctural geology. LOCATION AND ACCESS The Monkman coal deposit is located in the southern part of the Northeast British Columbia Coalfield approxim;ltely 30 kilometres southeast of the Quintette mine and 35 tilo- metres southeast of Tumbler Ridge (Figwe 4-7-11,The pro- ject area covers 140 square kilometres in the inner foolhills region of theRocky Molmtains. The Monkmanproperty consists of 169 coal liceom which COVI:~39 587 hect;ues. The Duke Mountain Block, in which Duke and Honeymoon pits are located (Figure4-7-Z), encompas:ies 20 745 hect:ms. Coallicences owned by Petro-Canadamark the northern boundary of the study ar,:a and Fearless Creek mark!; the southernboundary. Kinuseo Creek valley cuts acros!: the northernpart of the area. The valley contains upto 100 metres of unconsolidated overburden (Figure 4-7-2)hhich covers part of theproposed Duke and Honeymoon pirs. Elevations vary from 9580 metres in the valley floor of Kinuseo Creek to 1742 metres at the top of Duke Mountain. Vegetation ranges from spceforests to alpine tundra. sl Access into the Monkman areais via the Monkman High- way, a dry-weather road which parallels Kinuseo Creek. and extends to just west of Kinuseo Falls OCI the Murray River. The Monkman Highway c.an be reached by gravel roads From Tumbler Ridge; Elmworth, Alberta; or from Dawson Creek along the HeritageHighway. An airstrip near Thunder Moun- tain permits access by light plane. Numerous coal explora- tion roads, petroleum industry access roads and seismiclines provide excellent access I:O most parts of the project ;area. FIELDWORK -10 krn Prior to the 1987 field season, all pertinent open file coal assessment reports were examined. Geological maps of the Figure 4-7-1.Study area location map with Monkman property area were used to obtain digitized outc~rop informatioxA coal licences. computer-based outcrop database was designed to ston: the ~ ____ * This project is a contribution to the CanaddBritish Columbia Mineral Development Agreement. British Columbia Ministry of Energy, Mines and Petroleum Resources, Geological Fieldwork, 1987. Wper 1'988.1 47 I LEGEND [(3 GATES FM. - PIT BOUNDARY \ \ OVERBURDENTHICKNESS 4 I Figure 4-72, Subcmp map of the Gates Formation showing unconsolidated overburden thickness and Duke and Honeymoon pits 412 information. Once completed, outcrop maps were produced record. Data points can be referenced and retrieved based and examined to identify areas which lacked dataand to upon locational parameters. drill-hole identification, or strat- indicate areas with structural complexities or interpretation igraphic horizon. problems.Subsequent field mapping concentrated on COIL Outcrop data were digitlzed using a GTCO digitizer 'con- lecting additional outcrop data at these locations and verify- nected to a Compaq portable 286 compu1.er. Database main- ing the informationover the remaining parts of themap tainance and data processing and display were managed on a sheet. New data were plotted on topographic maps at a scale Wyse pc286 computer. Peripheral dcvices inc1ud1:d a of 15000. Airphotos at a scale of 1:40 000 were used to Houston Instrument DMP-52plotter and an Epson FX-:!86e produce enlargements at a scale of 1:lO 000. Outcrop infor- printer. mation was also plotted on the photo enlargements. Database construction and maintainance were performed Field mapping was conducted in conjunction with map- using the Geological Analysis Package of Cal Data Ltd. ping carried out by W. Kilby and S. Johnston (1988) on NTS Display of the geological data was facilitated by the Slruc- map sheets 931114,931i15 and 93Pi02 at a scale of 150 000. tural Analysis module of !.he Geological Analysis Package, Some outcrop datain the southeast comer of the geology map with a number of modifications by the author. StNc:ural (Figure 4-7-3) is from this source. Information from 1955 analysis of the outcrop data and drill-hole information pro- outcrop data points and 21 1 drill holes was examined and cessing was performed wil:h programs written by the author. incorporated into the geological interpretation. Outcrop data were digitized from geologicalmaps using programs written by W. Kilby. Figures were produced using the ECAD computer-aided drafting program. METHODOLOGY AND DATA HANDLING STRATIGRAPHY Computer-based methods have been used extensively to assist with data handling and display. Orientation parameters Strataexposed in thearea range from theLower describing the geological structural features were calculated Cretaceous to Jurassic M.innes Group, to the Upper Cre- using computer-based numerical procedures (Charlesworth taceous Kaskapau Formati,sn.The stratigraphy in the are.i has ef a/.,1976). beendescribed extensive!!y by Stott (1968 and 1982) and others. Descriptions of sedimentology and depositional en- Cross-sections were constructed by projecting outcropand vironments are beyond the scope of thi:s study and arc not drill-hole data down plunge onto planes of cross-section. includedhere. Table 4-7-.1 summarizes each formatica in Assuming that the folded surfaces approximate cylindricity, terms of a general description and the thickness specific to the data can be reliably projected parallel to the fold axis. the Monkman location. Thicknesses and descriptions were Lack of data, or poordistribution of orientations along both obtained from outcrop information, coalexploration drill limbs and across the hinge zone of a fold, may result in holes and petroleum industry exploration wells. Texaco Ex- unreliable fold axes orientations. In these cases an appropri- ploration Canada Ltd. drilled an explaration well, ExEx ate projection axisor fold axis orientation may he obtained by Flatbed a-21-Fi93-1-15, in the northeas): comer of the map visually best-fitting the data by trial and error, using several area (Figure The entire stratigraphic sequence, from different projection orientations. 4-7-3). the Minnes to the Kaskapau, is penetratemi by this hole. Brief Thick unconsolidated overburden covers parts of both the descriptions of the stratigaphy follow. Duke and Honeymoon pit areas. Visual best-fit fold axes orientations were determined in these areas. MINNES GROUP General data-handling methods are similar to those de- scribed by Kilby and Wrightson (1987). Drill-hole data have The Minnes Group con,iistsof both marine and nonmarine been incorporated into this study in a computer processible strata rangingin age from Jurassic to Early Cretaceous. format. Information wasdivided intoprimary,secondary and Lithologies include interbedded sandstones, siltstone!; and tertiary categories and entered into three independent raw shales with minor coal seams. data files. Primary data consist of drill-hole identification, location (easting, northing and elevation), overburden thick- BULLHEADGROUP ness, total depth and original hole orientation measured as the hole trend and plunge. Secondary data consist of drill- CADOMINFORMATION hole deviation data entered as the measurement depth, the The Cadomin Formationunconfonnably overlie$ the hole trend and the deviation measured in degrees from ver- Minnes Group. It is approximately 45 metres thick and tical.Tertiary data consist of thedrilled depths and the consists of two hands of chert and qua.rtzite conglom.erate identifying names of the horizons of interest. The raw data separated by sandstone.The conglomerate framework is files were then processed to yield three additional files con- poorly sorted and ranges From grit to cobhle-size fragments. taining the data in formats ready to be processed or plotted on The Cadomin Formation is easily mappable with prominent maps or cross-sections. Primary data for each drill hole are ridges often indicating its; outcrop. stored as separate records with indexing information used to locate the specific secondary and tertiary data for that hole. Secondary and tertiary data are stored in separate files as GETHINCFORMATION eastings, northings and elevationsin format ready for posting Gething strata consist of 140 metres of interbedded sand-