WHAT DO VOLCANOES AND UNCONTROLLED COAL FIRES HAVE IN COMMON?

Active volcanoes with smoke billowing from their vents are an awesome sight. In contrast, many countries house uncontrolled coal fires that emit wisps of smoke from cracks in the ground, which rapidly dissipate in the air. Yet these starkly different events produce nearly identical suites of condensates. Using an SEM-EDX, we examined a small (1cm by 2cm) crust taken from an active vent of an underground coal fire in the Jharia region of India. We found about 30 different phases that had condensed from the emissions. Many of these phases have also been reported from fumaroles on Mt. Vesuvius and other volcanoes from around the world. Phases common to both distinct environments include: sulfur, ammonium silici-fluoride, ammonium chloride, bismuth chloride, copper chloride, iron chloride, lead chloride, lead fluoride, lead sulfate, copper sulfate, iron sulfate, barium sulfate, aluminum sulfate, aluminum fluoride, bismuth molybdenum selenide, zinc sulfate, silica, and iron oxide. Unique phases (tentative identifications) found in the small coal fire crust include: bismuth iodide, lead iodide, ammonium fluoride, ammonium aluminum fluoride, iodine selenide, molybdenum selenide, bismuth chloride, molybdenum cadmium sulfate, copper fluoride, bismuth cadmium iodide, ammonium boron chloride, boron carbonate, aluminum silici-sulfate and boron carbonate. All phases form at temperatures around 500° C or lower, indicating a similar temperature regime at both sites. A major difference is the abundance of iodine phases at the coal fire site. Nevertheless, the common mineral suites could be used to deduce similarities in chemical mechanism, pressure, and temperature conditions where results from one system may prove to be a useful analog to the other.