New Mexico Geological Society Annual Spring Meeting — Abstracts

The Lee Ranch Mine is located in the southeasterly part of the San Juan basin (approximately 30 miles northeast of Grants), New Mexico. The coal-bearing sequence occurs within the Cleary Member of the Menefee Formation. The Cleary consists of a combination of sandstone, siltstone, mudstone, shale, and coal. Coal beds strike northwest and are interpreted to have been deposited in near-shore fresh to brackish paludal swamps, and back-barrier lagoons. Coal samples and bounding lithologies, from three drill holes penetrating the BB seam, were analyzed for their sulfur and elemental content. Samples were taken in 5 to 10 centimeter increments. The lithotype composition varies from a cIaraindominated section to durain, and vitrain-dominated sections along a northwest-southeast transect. The distribution of sulfur varies both horizontally and vertically. Two general distribution patterns are observed: (1) a general increase in sulfur content with depth and, (2) sulfur content higher in the middle of the seam and lower at the top and base. The total sulfur content per sample ranges from a low of about 0.4% to 3.9% with an average of 1% or less. Some carbonaceous partings have sulfur content as low as 0.2%. Pyritic and organic sulfur are the dominant forms of sulfur. Sulfate sulfur occurs in negligible amounts. Fe₂O₃ content of the ash ranges from approximately 1% to as high as 40%. Ash content ranges from about 4% to over 40%. There is no good correlation between iron, sulfur, and ash con tent. A combination of one or more of factors such as pH, sulfate content, and the availability of reactive iron minerals in the original coal-forming environment may have caused the observed distribution patterns.