Examination of chloritization of biotite as a tool for reconstructing the physicochemical parameters of mineralization and associated alteration in the Zafarghand porphyry copper system,Ardestan, Central Iran: mineral-chemistry and stable isotope analyses

Mineralogy and Petrology - The chloritization of biotite and stable isotopes of silicate have been studied for the Zafarghand porphyry copper deposit, Ardestan, Iran. The studied area, in the...     

High-temperature study and thermal expansion of phlogopite

 Unit-cell dimensions of a natural phlogopite from Pargas, Finland, have been determined in the temperature interval of 27–1050 °C by X-ray powder diffraction technique. Expansion rates vary discontinuously with temperature with a break at 412 °C. Below this temperature, the linear expansions (α) for a, b and c axis lengths are 3.74 × 10⁻⁵ K⁻¹, 1.09 × 10⁻⁵ K⁻¹, and 1.19 × 10⁻⁵ K⁻¹, respectively, and above that they are 0.86 × 10⁻⁵ K⁻¹, 0.80 × 10⁻⁵ K⁻¹, and 1.93 × 10⁻⁵ K⁻¹. The volume thermal expansion coefficients are 6.26 × 10⁻⁵ K⁻¹ and 3.71 × 10⁻⁵ K⁻¹ for low-temperature and high-temperature intervals, respectively. The observed kink in the rate of thermal expansions with temperature could be due to the different mode of structural changes. Thermogravimetric analysis of the sample indicates the oxidation of iron in the temperature range of 500–600 °C and dehydroxylation as well as decomposition of phlogopite in the temperature range of 900–1200 °C. Received: 8 September 1998 / Accepted: 28 February 2000