HALOGEN-ACID ALTERATION OF ASH AT FUMAROLE NO. 1, VALLEY OF TEN THOUSAND SMOKES, ALASKA
A series of specimens of ash and pumice, collected outward from the throat of Fumarole No. 1 of Zies in the Valley of Ten Thousand Smokes in 1952, has been analyzed for major and minor constituents. The bulk density—approximately 1.00 gm/cc for unaltered ash—was determined by weighing blocks of known volume, and chemical addition or subtraction was calculated for unit volume. Elements readily converted to volatile fluorides or chlorides were leached near the hot throat, but hydrolysis resulted in some late-stage addition in the innermost zone. Condensation of steam and inward movement of hot acid water resulted in outer zones of oxidation and leaching and an intermediate zone of boiling and evaporation, which was especially enriched in alumina and water of hydration. Appreciable quantities of Pb, Zn, Cu, As, Cl, F, and SO 4 were added to the innermost zone (1 inch), and Ni, Co, B, and Sc were concentrated in the intermediate zone about 2 feet from the throat. No carbonate is present in any zone. Magnetite, hematite, goethite, hydromica, opal, montmorillonite, and kaolinite are the chief alteration minerals. The alteration is similar to that produced by strong sulfur acids elsewhere, but the gas of Fumarole No. 1 contained only 7 ppm S in 1917, and 70 ppm in 1919. In contrast it carried 240 ppm of HCl, and 30 ppm HF in 1917—the only year in which samples of halogen gases were collected in the valley. The halogen-acid alteration differs from sulfur-acid alteration chiefly in the greater loss of SiO 2 relative to A1 2 O 3 .