Abstract
Veins are of two orientations: 000 degrees /35 degrees E (Lawrence Vein) and 090 degrees /33 degrees N (Hibbard and Prout veins). To date, approximately 1 million short tons of ore grading 3.0 to 3.5 percent Sb have been mined from Hibbard, the dominant vein. Two-way chemical mass balance reveals that wall-rock alteration accompanying stibnite quartz vein emplacement involved major additions of Sb, As, S, and volatiles, with minor introduction of K 2 O, Rb, and Si. Fe 2 O 3 , MgO, CaO, and Na 2 O along with Co, Ni, Ba, and Zn were stripped, whereas Sc, Ti, and Al behaved essentially isochemically. The argillic alteration developed at 360 degrees to 490 degrees C from fluids with a delta 18 O = 10 per mil. The Hibbard Vein was precipitated at 325 degrees to 350 degrees C from a saline hydrothermal fluid with a delta 18 O value of 11 to 12 per mil and a delta D value of -20 to -30 per mil, undergoing transient boiling at a pressure of 270 to 420 bars. Salinity is estimated at 38 to 40 weight percent NaCl. Hematitic alteration was formed at 200 degrees to 350 degrees C in the presence of a fluid with a delta 18 O value of 2 to 8 per mil. The ore-forming solutions may have been a late-stage magmatic fluid evolved off a high 18 O granitic intrusion.--Modified journal abstract.
