- 157 - Mineral Exploration in the Athabasca Mining District by G. A. Mueller* Mineral exploration ac tivity in the Atha basca Mining District was fairly light during the past year . The main thrust of exploration was direc t ed towards the location of n e w uranium deposits , whe r e as exploration for base me tals was a lmost nil. The major ura nium discovery at Key Lake , a long the southeastern pe rimete r of the Athabasca sedimentary basin (fig. 1), conce ntrate d exploration activity in that area but also mad e the unconformity at the base of the Athabasca Formation the major target for ura nium explora tion in general . Although the e dge of this unc onformity in the Athabasca Mining Dis tric t is mainly water covered or e xposed in granitic domains , almost ever y probable outc rop a r ea of the unconformity has now been staked. Beaverlodge Domain (Beaverlodge Linear Be lt and Fond-du-Lac Stable Bloc k) The Beaverlodge Dom ain was the focus of activity in the Athabasca Mining District, and Eldorado Nuclear Ltd. was the central figure in the activity . Eldorado's summer exploration prog ram inc lude d three large surface mapping parties working in the Dona ldson-F r e d et t e La kes area near Uranium Ci t y (fig. 2), a nd geochemical and prospec ting crews operating in a n area north of Spring Point, Lake Athabasca (fig . 1). In the latte r a r ea the outcrop of the sub-Athabasca Formation unconformity is covered by thick glacial drift. Eldorado also ,· ontinue d d iamond drilling on known uranium occurrences in the Be ave rlodge area, including t a rget areas on the forme r Cinc h mine prope rty a nd in the Hab mine area . The erratic distribution of uranium d epo s its in the Beav e rlodge area makes d e lineation of ore bodies an expensive and time c onsuming process . Eldorado's Ace-Eagle ope n pit mine continue d in operation, supplementing the ore supply from unde rground operations. Eldorado i s now in the process of up­ grading both its mining and milling operations in ord e r to incre ase produc tion to the design c apacity of approximately 1800 me tric tons of ore pe r d ay . As part of the upgra ding process,it is r e ported tha t Eldorado plans to open a new under­ ground mine in the Foot Bay area of Donald s on Lake (fig. 2) . To supply the anticipated inc r ease in e lec trica l e nergy r e quireme nts, extra g e nerating capacity is being adde d to the powe rhouse at We llington Lake (fig. 2) , where the height * Reside nt Geologist in Uranium City - 1 5P. - 102°00' NORT HWEST TERRITORIES - - - - - -~ 60°00° 110°00' 60°00· ~~~~·~~~~~~-----,.,.....~~~~~~~~~~~-""....,.~--r Wo I \os1on I oomo i n I·. I I I I I z ~ I Lo <( a:: :::!1 w I CD I _J <( I Athobosco Formation ___ _ ------CD Metovolcanic and Metasedimentory __ - ~ Major fault zone _______ _ _ -~ All weather rood - - - - - - - - - - Winter rood _ _ _ _ _ _ _ _ __ - .... Settlement _____ _ ---* Scale Kilometres 20 0 20 4 0 60 80 1 1 1 I I 1 "1 r 1 1 , I 20 40 60 Miles 20 10 O Fig. 1. Ge neralized Geology of Northern Saskatchewan showing At habasca Mining Dis trict (heavy outline) . - 159 - 10 9 °00' 59 ° 30' q 0 Lake Athabasca [? Sea le 5 0 5 Miles 5 0 5 Kilometres G) Fay Mine and Mill, Eldorado ® Proposed new Eldorado M, ne ® Gunnar Mine and Mill (closed) @) Cayzor Mine(closed), New Cayzor Athabasca @ Hab Mine (closed), Eldorado @ Box Mine(closed), Cominco @) Ace Shaft (ventilation), Eldorado c=i Cover Rocks (Martin and Athabasca Formations) @ Verna Shaft, Eldorado CJ Tazin Group Rocks @ Ace-Eagle open pit Mine ,Eldorado • M,ne Site (D Cinch Mine(closed), Eldorado Power Line @ Lorado Mine and M,11 (closed), Conwest Ma ior fault zone Fig . 2 . Gen e r nlize d Geo l ogy a nd location map , Rcavcrlod ge a r Pa . - 160 - of the power dam has been increased by 3 m. A serious problem encountered by Eldorado in their expansion plans is the scarcity of skilled labour . The company hopes to parti~lly alleviate this problem by creating better living conditions, and they are now in the process of building more than 50 single family dwellings and a large apartment block in Uranium City. Goldak Exploration Technology has been operating an underwater radiometric program from the Gunnar townsite in the area of South Crackingstone Peninsula (fig. 2) for a consortium of seven companies. The program involves initially running an underwater seismic and depth profile, on a precise, radar controlled grid, in order to locate outcrop areas and to provide a water depth record for use in boat speed control in the radiometric survey portion of the program. Appropriate outcrop areas are then profiled with underwater radiometric gear which is kept in contact with the lake bottom through careful control of boat speed . The project is to continue next year. Uranerz Canada Ltd. operated a large boulder prospecting program in an area south of Spring Point, near the Saskatchewan-Alberta border, during the past summer. The area is believed to be near to the outcrop of the sub-Athabasca Formation unconformity, but is largely blanketed by glacial deposits. It has been reported that several boulders of coarse-grained, arkosic sandstone contain­ ing uranium mineralization, grading in the order of 2 to 3 per cent , were u3o8 discovered in the course of the work. Uranerz also staked more than 40,000 acres covering an area of Aphebian sediments, known as the Thluicho Formation, immedi­ ately west of Wellington Lake (fig. 2). Significant uranium mineralization in the Thluicho Formation has not been reported previously. Amok Ltd. continued with a detailed drilling program to further outline known uranium deposits in the Cluff Lake area, where three separate orebodies are estimated to contain 50 million pounds of . Production plans, announced this u3o8 year, call for initial open pit development of the "D-zone" orebody, parts of which are reported to grade in the order of 100 tons of ore per day, with a mill start-up scheduled for early 1979. The company continued with geological and geophysical surveys and exploratory drilling on properties in the Cluff-Carswell Lakes area during the summer. The Saskatchewan Mining Development Corporation opened a permanent regional office in Uranium City to co-ordinate and expedite exploration in the Athabasca Mining District. Two field parties operated in the Beaverlodge Domain during the summer, one near Bushell Inlet, Lake Athabasca, and the other near Fontaine Lake, - 161 - north of the Grease River fault in the Fond -du-Lac area . The field programs included surface mapping , geochemical sediment and water sampling, airborne radio­ metric surveys, boulder prospecting, track etch surveys, and trenchi11g. Donegal Developments Ltd., under contract with Thor Explorations Ltd., completed a track etch survey last winter and a follow-up trenching program in the spring on an optioned property about four miles north of Uranium City. One geological target neglected during the past year in the Beaverlodge Domain was radioactive pegmatites . Surface chip samples from one uraniferous pegmatite zone in the vicinity of Hill Lake (fig. 2) in places assayed in the order of 0.25 per cent combined uranium-thorium. Despite this, there has been very little interest shown in these pegmatites. Stony Rapids Domain Eldorado Nuclear Ltd. operated an exploration party on a group of claim blocks south and east of Fond-du-Lac in a joint venture with Saskatchewan Mining Develop­ ment Corporation and Famok Ltd. The focus of interest in this area was a uranium­ mineralized boulder zone originally discovered in the 1950's and rediscovered by Mokta Ltd. in the early 1970's. It is reported that the main thrust of the summer's work in the area was of a geophysical nature designed to d e lineate the trace of the sub-Athabasca Formation unconformity. Saskatchewan Mining Development Corporation operated a large field party during the summer on properties underlain by Aph~bian metamorphic rocks along the Grease River fault lineament. The program covered a wide spectrum of activities involving, at various times and in various combinations, boulder prospecting, geological mapping, water and sediment geochemical sampling, airborne radiometric surveys, and track etch surveys . Fossago Explorations Ltd. carried out a prospecting and 1:1apping program on a property at Hunt Falls on the Grease River. Wollaston Domain (Eastern Stable Block) Urangesellschaft Canada Ltd. operated a samll expJoration party in the Charlebois-Spreckly Lakes area during the s ummer in a joint venture program with the Saskatchewan Mining Development Corporation. The program, carried out mainly on properties optioned from Fossago Explorations Ltd., consisted basically of mapping and evaluating outcroppings of fine-grained, uraniferous pegmatites originally mapped by J. B. Mawdsley for the Department of Mineral Resources in - 162 - the early 1950's. Some of the 1976 mapping was carried out on a very detailed scale in conjunction with trenching which was done in an attempt to establish possible connections between individual radioactive pegmatite showings. The pegmatites have a mineralogical composition intermediate between granite and diorite, and the uranium is contained in disseminated, fine-grained, uraninite crystals. Structurally the pegmatites have little or no foliation . Urangesellschaft also had a large prospecting and mapping party in the Hatchet Lake area, north of Gulf ' s Rabbit Lake mine, in a joint venture project with the Saskatchewan Mining Development Corporation on the latter's Permits No.