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An unusual assemblage of talc-phengite-chlorite-K-feldspar in quartz schists from the Nahavand area, Sanandaj-Sirjan zone, Iran | ||
| Iranian Journal of Science | ||
| مقاله 7، دوره 38، شماره 3، آبان 2014، صفحه 243-252 اصل مقاله (2.21 M) | ||
| نوع مقاله: Regular Paper | ||
| شناسه دیجیتال (DOI): 10.22099/ijsts.2014.2267 | ||
| نویسندگان | ||
| J. Izadyar* ؛ S. Mojab؛ O. Kuroshi؛ M. Zare | ||
| Department of Geology, University of Zanjan, University Blvd., Zanjan, Iran | ||
| چکیده | ||
| 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. | ||
| کلیدواژهها | ||
| High-pressure metamorphism؛ Nahavand؛ Sanandaj-Sirjan zone؛ Talc-phengite-K-felds parassemblage | ||
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