CHANGE IN THE MAGNETIC-PROPERTIES OF BITUMINOUS COAL INTRUDED BY AN IGNEOUS DIKE, DUTCH-CREEK-MINE, PITKIN COUNTY, COLORADO

Magnetization measurements have been made on natural coke-coal samples collected at various distances from a felsic porphyry dike in a coal seam in Dutch Creek Mine, Colorado to help characterize the nature and distribution of the iron-bearing phases. The magnetization passes thr ough a maximum at the coke-to-coal transition about 31 cm from the dik e contact. The magnetic measurements support the geochemical data indi cating that magmatic fluids along with a high-temperature gas pulse mo ved into the coal bed. Interaction of the magmatic fluids with the coa l diminished the reducing power of the thermal gas pulse from the dike to a point about 24 cm into the coal. The hot reducing gas penetrated further and produced a high temperature (similar to 400-525 degrees C ) zone (at about 31 cm) just ahead of the magmatic fluids. Metallic ir on found in this zone is the principal cause of the observed high magn etization, Beyond this zone, the temperature was too low to alter the coal significantly. (C) 1998 Elsevier Science B.V.