| Description |
A study was made of the hydrothermal alteration associated with ore deposits of four mining districts. In each case the ore minerals occur as bedding replacements of limestone host rocks Samples were collected along the strike of the formations, beginning in sulfide mineralization and proceeding to apparently unaltered rocks The samples were studied by x-ray diffraction analysis, differential thermal analysis9 spectrographic analysis, chemical analysis, and hydrothermal experimentation In only one case, at the United states mine, west Mountain (Bingham) district, 'Utah, was a correlation between alteration and sulfide mineralization established. Immediately apparent in samples from this locality was a progressive change in color of the alteration products. Samples taken in and near ore were dark green (nearly black,), while those at a distance of approximately forty feet from ore were nearly white. Talc is found in and adjacent to ore. Adjacent to the talc and out from ore, phlogopite and K-feldspar are found. Beyond the phlogopite-K-feldspar zone, only montmorillonite is found. The montmorillonite, however, is zoned compositionally with an iron-aluminum variety nearest the sulfides a magnesium=aluminum variety in an intermediate position, and a high aluminum variety at the point most distant from sulfides examined. Analyses of ten samples taken at five foot intervals showed a distinct enrichment in Fe203 FsOp A1203, and K20 near the sulfides and a less definite enrichment of Na20 away from them Spectrographic analysis or selected samples showed that trace amounts of molybdenum» copper, and silver increase as ore is approached, and trace amounts of zirconium increase away from ore. |
