BULK COMPOSITIONS AND ZINC CONTENTS OF MICAS FROM THE STERLING HILL AND FRANKLIN ZN-FE-MN DEPOSITS, NEW JERSEY
We examined a variety of micas from the Sterling Hill and Franklin deposits with electron microprobe to determine their bulk compositions and, in particular, their zinc contents. Our preliminary results show that biotite and other micas contain 3-14 wt.% ZnO, and that the ZnO concentrations correlate positively with MnO (ranging from 0.01-9 wt.%). Zinc in mica also correlates negatively with MgO, SiO2, and F (ranging from 0.03 to more than 2.5 wt%). BaO does not correlate with ZnO in mica, but the BaO contents of many micas are elevated to concentrations of 1 to nearly 9 wt%. Barium-rich micas of Franklin have been analyzed previously by Tracy (1991). The TiO2 concentrations of mica show a distinct negative correlation with the (Mg/Mg+Fe) ratios.
We will interpret the relative roles of crystal-chemical constraints and that of metamorphic fluids on the incorporation of the elevated abundances of Zn, Ba, and Mn in these micas.
Frondel, C., Einaudi, M. (1968) Zinc-rich micas from Sterling Hill, NJ. Amer. Mineral. 53, p. 1752.
Tracy, R.J. (1991) Ba-rich micas from the Franklin Marble, Lime Crest and Sterling Hill, New Jersey. Amer. Mineral. 76, 1683-1693.