Mineral chemistry and P-T estimation of formation of cummingtonite and coexisting minerals in the calc-silicate rocks from the Takht-e-Soleyman area, NW Iran

Abstract

The calcareous rocks in the Takht-e- Soleyman area (NW Iran) crop out in association with a variety of metamorphic rocks including amphibolites, granitic gneisses, pelitic schists and meta-ultramafic rocks. Retrogressive metamorphism of these rocks occurred during decompressional cooling during exhumation. Cummingtonite-bearing rocks resulted from retrogression of the calc-silicates in the area. Their dominant mineral assemblage is plagioclase + garnet + calcic – amphibole + ferromagnesian – amphibole + quartz + calcite ± titanite ± epidote. Calcic - and ferromagnesian - amphiboles were determined by petrographical observations and EMPA analysis. Hornblende and cummingtonite compositions dominate the analysed amphiboles. Formation of Ca-poor cummingtonite coexisting with calcite and calcic - hornblende in the retrograde calc - silicates of the Takht-e-Soleyman area is a rare petrological occurrence. Thermometric estimates using mineral compositions of cummingtonite co-existing with hornblende is in the range of 550 -600 ºC. Al in hornblende barometry yields a pressure of 6.5 ± 0.6 kbar, corresponding to medium pressure amphibolite facies.

Keywords


[1] Alavi, M., "Regional stratigraphy of the Zagros Fold-Thrust belt of Iran and its proforelenad evolution", American Journal of Science 304 (2004) 1–20.

[2] Miyano T., Klein C., "Fluid behavior and phase relations in the system Fe-Mg-Si-C-O-H: application to high grade metamorphism of iron-formations", American Journal of Science 286 (1986) 540-575.

[3] Evans B.W., Ghiorso M.S., "Thermodynamics and petrology of cummingtonite", American Mineralogist, 80 (1995) 649-663.

[4] Evans B.W., "Reactions among sodic, calcic, and ferromagnesian amphiboles", sodic pyroxene, and deerite in high-pressure metamorphosed ironstone, Siphnos Greece, American Mineralogist, 71 (1986) 1118-1125.

[5] Lattard D., Le Breton N., "The P-T-fO2 stability of deerite Fe122+ Fe63+ [Si12O40]OH10", Contributions to Mineralogy and Petrology, 115 (1993) 474-487.

]6[ نبوی م. ح.، "مقدمه ای بر زمین‌شناسی ایران". سازمان زمین‌شناسی ایران،(1355) 109 ص.

]7[ افتخارنژاد ج.، "طبقه بندی تکتونیکی ایران در ارتباط با حوضه‌های رسوبگذاری". مجله انجمن نفت ایران، شماره 82، (1359) 19-28.

]8[ بابا خانی ع. ر. قلمقاش ج.، "نقشه زمین‌شناسی 100000/1 تخت سلیمان". سازمان زمین‌شناسی ایران، تهران، (1371).

[9] Gilg H. A., Boni M., Balassone G., Allen C. R., Banks D., Moore F., "Marble-hosted sulfide ores in the Angouran Zn-(Pb–Ag) deposit, NW Iran: interaction of sedimentary brines with a metamorphic core complex", Mineral Deposita 41 (2006) 1–16.

[10] Kretz R., "Symbols for rock-forming minerals", American Mineralogist 68 (1983) 277-279.

[11] Leake B.E., "Nomenclature of amphiboles", Mineralogical Magazine 42 (1978) 533-563.

[12] Hynes A., "A comparison of amphiboles from medium and low pressure metabasites, Contributions to Mineralogy and Petrology", 81 (1982) 119-125.

[13] Graham C. M., Powell R., "A garnet-hornblende geothermometer: calibration, testing and application to the Pelona Schists, Southern California", Journal of metamorphic Geology, 2 (1984) 13-34.

[14] Perchuk L.L., Aranovich L.Y., Podlesski K.K., Lavrant'eva I.V., Gerasimov V.Y., Fed'Kin V.V., Kitsul V.I., Karasakov L.P., Brednikov N.V., "Precambrian granulites of the Aldan shield", eastern Siberia, USSR, Journal of metamorphic Geology, 3 (1985) 265–310.

[15] Otten M.T., "The origin of brown hornblende in the Artfjället gabbro and dolerites", Contribution to Mineralogy and Petrology, 86 (1984) 189-199.

[16] Johnson M.C., Rutherford M.J., "Experimental calibration of the aluminum-in hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks", Geology 17 (1989) 837–841.

[17] Hammarstrom J.M., "Zen E.-A., Aluminium in hornblende: an empirical igneous geobarometer", American Mineralogist 71 (1986) 1297–1313.

[18] Hollister L.S., Grissom G.C., Peters E.K., Stowell H.H., Sisson V.B., "Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of calc-alkaline plutons", American Mineralogist, 72 (1987) 231–239.



















































[19] Powell R., Holland T.J.B., "An internally consistent dataset with uncertainties and correlations: Applications to geobarometry", worked examples and a computer program. Journal of Metamorphic, Geology, 6 (1988) 173-204.

[20] Holland T.J.B., Powell R., "An enlarged and updated internally consistent thermodynamic dataset with uncertainties and correlations: the system K2O-Na2O-CaO-MgO-MnO-FeO-Fe2O3-Al2O3-TiO2-SiO2-C-H-O2.", J. of Metamorphic Geology, 8 (1990) 89-124.

[21] Holland T.J.B., Powell R., "An internally consistent thermodynamic data set for phases of petrological interest", J. of Metamorphic Geology, 16 (1998) 309-343.

[22] Will TM., Powell R., "Activity-composition relationships in multi-component amphiboles: an application of Darken's Quadratic Formalism", American Mineralogist 77 (1992) 954-966

]23[ لطفی م.، "نقشه زمین شناسی 100000/1 ماه نشان"، سازمان زمین شناسی ایران، تهران، (1380).