PETROGRAPHY OF ORGANIC MATERIAL AND MINER AL-CONTENT OF CLAYS FROM THE PINE-POINT MINING DISTRICT AND ITS SURROUNDING REGION IN CANADA - A CHARACTERIZATION OF ANOMALIES ASSOCIATED WITH THE DEPOSITS

The alteration of organic matter and clays is studied in the Devonian Pine Point Formation carbonate muds, ''F'' facies, and its lateral equ ivalents the Evie Formation and the bituminous unit at the base of the Horn River Formation. The organic matter is mainly composed of solid bitumen with few fossil fragments (organoclasts). Most samples contain only illite and mixed layer illite/smectite. If we compare the Th(100 -degrees-C) from fluid inclusions of sphalerite and dolomites associat ed with mineralization to the temperatures calculated from the reflect ance (Ro) of the collinite (84-degrees-C to 117-degrees-C), we cannot detect a thermal anomaly in the Pine Point mining district. This resul t is based on the reflectance values of organoclasts from the mining d istrict that are not higher than those reflectance values measured on organic matter (OM) away from the ore deposit. A similar conclusion is reached from the clay study: none of the parameters used allow us to identify a thermal anomaly in the samples from the mining district. Th e kaolinite and the altered OM showing anomalous Ro values mainly occu r with sulfides and sulfur. This association suggests an authigenic or igin for the kaolinite and an alteration of the OM due to the minerali zation events.