Izadyar, J., Mojab, S., Kuroshi, O., Zare, M. (2014). An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran. Iranian Journal of Science and Technology (Sciences), 38(3), 243-252. doi: 10.22099/ijsts.2014.2267
J. Izadyar; S. Mojab; O. Kuroshi; M. Zare. "An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran". Iranian Journal of Science and Technology (Sciences), 38, 3, 2014, 243-252. doi: 10.22099/ijsts.2014.2267
Izadyar, J., Mojab, S., Kuroshi, O., Zare, M. (2014). 'An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran', Iranian Journal of Science and Technology (Sciences), 38(3), pp. 243-252. doi: 10.22099/ijsts.2014.2267
Izadyar, J., Mojab, S., Kuroshi, O., Zare, M. An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran. Iranian Journal of Science and Technology (Sciences), 2014; 38(3): 243-252. doi: 10.22099/ijsts.2014.2267
An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran
Department of Geology, University of Zanjan, University Blvd., Zanjan, Iran
Abstract
For the first time, an unusual assemblage of talc-phengite-chlorite-K-feldspar was found in quartz schists from the
Sanandaj-Sirjan zone in the Nahavand area in western Iran. The talc-bearing quartz schists occur as small bodies
or lenses within pelitic schist layers and contain talc, phengite, chlorite, K-feldspar and quartz as major mineral
constituents with subordinate amounts of calcite and graphite. Textural analysis revealed that talc, phengite,
chlorite and K-feldspar are in sharp contact and no reaction rims between them were observed. Constructed
petrogenetic gird in the K
2O-FeO-MgO-Al2O3-SiO2-H2O (KFMASH) model system containing talc, phengite,
chlorite, K-feldspar, phlogopite and kyanite with excess quartz and H
2O shows that divariant assemblage of talcphengite-
chlorite-K-feldspar is stable over a wide P-T range defined by the following two univariant reactions:
phengite + talc + quartz = chlorite + K-feldspar + kyanite + H
2O and chlorite + phlogopite + quartz = talc +
phengite + K-feldspar + H
2O. Constructed Al2O3-KAlO2-MgO+FeO (AKM) compatibility diagrams predict that
phengite (X
Ph = 0.280, YPh = 0.860), chlorite (XChl = 0.570, YChl = 0.640), talc (XTlc = 0.160, YTlc = 0.02) and Kfeldspar
are stable at P = 11 kbar and T = 400°C. This relatively high-pressure assemblage could be formed during
the subduction of the Neo-Tethys oceanic plate under Iranian microcontinent.
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