GEOCHEMISTRY OF MANTO FLUORITE DEPOSITS, NORTHERN COAHUILA, MEXICO

Several million tons of fluorite have been produced from manto deposits in northern Coahuila, Mexico during the past 30 years. Geologic examinations of these fluorite mantos have shown that they are stratigraphically controlled throughout a region of several thousand square kilometers, that they are epigenetic, and that they formed in part by replacement of the enclosing wall rock. The purpose of the present study is to provide geochemical information useful in further defining the orgin of these deposits. Forty-three manto deposits in nine districts covering an area of 5,000 sq km were studied. Although the study emphasized fluid inclusions in fluorite, attention was also given to the mineralogy of the deposits, their wall-rock alteration, and the composition of associated igneous rocks.