These deposits, in Pennsylvanian limestone and shale, contain barite, fluorite, low-silver galena with "J-type" lead, and quartz, and only minor amounts of other minerals. Mineralization occurs in veins, in blankets of bedded, rhythmically banded "coontail" ore, and in vuggy, coarsely crystalline open-space fillings in tectonic and solution channels in limestone adjacent to faults. Except for widespread silicification, the mineralization is very similar to that of the southern Illinois deposits. The main stages of hypogene mineralization are: 1) sphalerite, pyrite, galena and chalcopyrite; 2) five easily recognizable substages of fluorite with intermittent quartz and barite; and 3) late calcite.More than 500 primary and 2,500 pseudosecondary inclusions, mainly from fluorite, were studied on the freezing and heating microscope stages. Some primary inclusions contain organic matter. Gross supercooling indicates slow ore-fluid movement. Recognizable planes of pseudo-secondaries (each containing 20-200 inclusions) yield data essentially identical with coeval primaries, but the few planes of presumed secondaries do not.The first three substages of fluorite formed from fluids that were essentially constant in temperature at 186°-205° C (assumed pressure correction +10° C), but increased in salinity from aproximately 10 up to 15 weight percent salts. Succeeding substages formed at gradually decreasing temperatures (to about 140° C) and increasing salinity (maximum 17%), with breaks marking several individual substages. A few inclusions in an early barite have anomalously low homogenization temperatures. Coarse selenite has primary inclusions full of fresh water and hence is presumed to be supergene.These data do not prove any given theory or origin for the fluids or the deposits, but they do place some limits on possible mechanisms of origin.
|Title||Environment of ore deposition at the Mex-Tex deposits, Hansonburg District, New Mexico, from studies of fluid inclusions|
|Authors||E. Roedder, A. V. Heyl, J.P. Creel|
|Publication Subtype||Journal Article|
|Series Title||Economic Geology|
|Record Source||USGS Publications Warehouse|