A sodian sulfatian fluorapatite from an epithermal calcite-quartz vein of the Kushikino Mine, Kagoshima Prefecture, Japan

Abstract

A sodian-sulfatian fluorapatite, a new variety of apatite, was found in sulfide concentrates of gold-silver-tellurium ores from the Shinpi No. I epithermal-type calcite-quartz vein of the Kushikino mine, Kagoshima Prefecture, Japan. This paper is the first detailed report on the occurrence of sulfate and sulfatian apatite from this type of ore deposit. The mineral is closely associated with quartz, interstrati fied chlorite-smectite, and ore minerals. The chemical composition of the mineral was determined by electron microprobe: CaO 51.51-54.30, Na2O 0.13-2.26, K2O 0.00-0.02, MgO 0.@-0.02, IvInO 0.03-0.10, FeO 0.01-0.10, p2o5 35.09-40.82, SO3 0.44-7.39, SiO2 0.05-0.66, Cl 0.00-0.01, F 3.03-3.62 wt.Vo. The (Na+Si): S atomic ratio is close to one. The charge increase involved by the substitution of (So)2- for @O/3- is considered to be electrostat! cally compensated for by the concomitant substitutions of Na+ for Ca2+ and, although minor, of (SiOr+ for (POJ3-. The general formula, disregarding trace to minor constituents, is expressed as follows: Ca5_rNar(P3-S;) Ol2 (FpHl- ,), where .r ranges from 0.02 to 0.41, and y, frori (),so tob.96. The naturally occurring sulfate ahd sulfatian apatites should be divided into two series, apatiteellestadite and apatite-cesanite, on the basis of mode of substitution. These minerals form under highl(O), and are rather independent of temperature, pH, l(S), and halogen species in solution. The Kushikino apatite, an intermediate member of the second series, seems to have formed from a F-rich oxidizing solution at 200 to 250oC.