論文
カナダにおけるウラン探鉱と鉱山の操業McClean Lake鉱山の操業とMidwest-A鉱床の発見-
-
2009 年 59 巻 2 号 p. 135-144
詳細
2009 年 59 巻 2 号 p. 135-144
The Athabasca Basin in northern Saskatchewan is a well known uranium producing area. Three mines Rabbit Lake, McClean Lake, and McArthur River-Key Lake in 2008 produced 23.4 million lbs U3O8, about 20% of total world production. The uranium mineralization in this area is called unconformity-type, and typically occurs near the unconformity between basal Aphebian meta-sediments and the overlying Helikian age fluvial sandstones. The high grade deposits occur from near surface to about 800 m depth and are difficult to find because of the extensive sandstone cover. Airborne and ground geophysical surveys followed by drilling are the principal exploration methods. Environmental regulatory process for mine development also takes a long time, due to strict regulations; a lead time of 10 to 15 years from discovery to production is common. A Japanese uranium mining company, OURD, joined the Midwest and McClean Lake projects in 1991 and 1993 respectively. The McClean Lake project started production in 1999 and by the end of 2008 has produced 44.7 million lbs U3O8 from the JEB, Sue A, Sue C, Sue E, and Sue B deposits as open pit mines. McClean and Caribou deposits still remain to be mined, pending favorable economic conditions. For the Midwest deposit, found in 1978, various types of mining methods and environment impact studies have been undertaken and a production decision to develop it as an open pit mine was taken in late 2007. However, because of a significant increase in capital costs coupled with the current world economic crisis, a decision to postpone the development was taken in late 2008. The Midwest project is now on hold until the economy and uranium markets improve. Exploration drilling at the Midwest project re-started in 2005 after a long period of inactivity. Follow-up drilling near a mineralized hole drilled in 1980 resulted in discovery of the Midwest A deposit, some 3 km northeast of the Midwest deposit. The Midwest A deposit contains resources of about 10 million lbs U3O8.
