Mineral chemistry and retrograde temperature-pressure conditions of Ol-bearing marbles from the Takab metamorphic complex-NW Iran

Abstract

The Precambrian Takab complex consists of various metamorphic rocks including metabasites, metaultramafic rocks, calc-silicates and marbles which are metamorphosed under green schist to granulite facies. The pick metamorphic rocks are retrogressively metamorphosed during crustal exhumation related to pressure and temperature decreasing as well as H2O-rich fluid infiltrations. Retrograde metamorphism of the Ol-bearing marbles caused their transformation from granulite to amphibolite facies. Some mineralogical and textural evidence of retrograde metamorphism in the Takab dolomitic marbles are (a) appearance of low temperature and H2O-bearing phases such as tremolite, clinonochlore, (±) titanite and (±) epidote, (b) formation of tremolite+dolomite assemblages as pseudomorph after olivine and (c) titanite corona around ilmenite. The temperature and pressure of retrograde metamorphism are calculated by using mineral chemistry of the retrograde phases and the equilibria reactions at 650±25◦C and 6.5±0.5kbar, respectively. The estimated temperatures and pressures are consistent with the amphibolites facies. Due to lack of appropriate chemical composition, retrograde tremolite is the stable phase of Takab dolomitic marbles at the amphibolite facies. Retrograde clinochlore is appeared in the dolomitic marbles having Al2O3 impurities at the high temperature 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] 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.

[3] Hajialioghli R., Moazzen M., Droop G.T.R., Oberhansli R., Bousquet R., Jahangiri A., Ziemann M., "Serpentine polymorphs and P-T evolution of meta-peridotites and serpentinites in the Takab area, NW Iran", Mineralogical Magazine, 71 (2007) 155–174.

[4] Moazzen M., Hajialioghli R., "Zircon SHRIMP dating of mafic migmatites from NW Iran; Reporting the oldest rocks from the Iranian crust", 5th Annual Meeting AOGS, Busan, Korea (2008) SE62.

[5] Hajialioghli R., Moazzen M., Jahangiri A., Oberhänsli R., Mocek B., Altenberger U., "Petrogenesis and tectonic evolution of metaluminous sub-alkaline granitoids from the Takab Complex, NW Iran", Geological Magazine. doi: 10.1017/S0016756810000683.

[6] Stockli D.F., Hassanzadeh J., Stockli L.D., Axen G., Walker J.D., Dewane T.J., "Structural and geochronological evidence for Oligo-Miocene intra-arc low-angle detachment faulting in the Takab-Zanjan area, NW Iran", Abstract, Programs Geological Society of America, 36 (2004) 319.

[7] حمدی ب.، "رسوبات پرکامبرین-کامبرین در ایران". هوشمند زاده، ع. (مؤلف) زمین شناسی ایران. سازمان زمین‌شناسی ایران، 20، (1374) 535 ص.

[8] باباخانی ع.، قلمقاش ج.، "نقشه زمین شناسی 100000/1 تخت سلیمان"، سازمان زمین شناسی ایران (1371).

[9] Mehrabi B., Yardley B. W. D., Cann J. R., "Sediment-hosted disseminated gold mineralization at Zarshuran, NW Iran", Minerlium Deposita, 34 (1999) 673–696.

[10] Droop G.T.R., "A general equation for estimating Fe3+ concentrations in ferromagnesian

silicates and oxides from microprobe analyses using stoichiometric criteria", Mineralogical Magazine, 51 (1987) 431–435.

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

[12] Hynes A., "A comparison of amphiboles from medium and lowpressure metabasites", Contributions to Mineralogy and Petrology, 81 (1382) 119-125.

[13] Hey M.H., "A new review of the chlorites", ineralogical Magazine, 30 (1954) 277-292.

[14] Moazzen M., Oberhänsli R., Hajialioghli R., Moller A., Bousquet R., Droop G., Jahangiri A., "Peak and post-peak P-T conditions and fluid composition for scapolite-clinopyroxene-garnet calc-silicate rocks from the Takab area, NW Iran", European Journal of Mineralogy, 21 (2009) 149 - 162.

[15] Bucher K., Frey M., "Petrogenesis of metamorphic rocks. 6th edition", Springer-Verlag, Berlin (1994) 318 pp.

[16] Ramberg H., "Intergranular precipitation of albite formed by unmixing of alkali feldspar", Neues Jahrbuch für Mineralogie, Abhandlungen, 98 (1962).

[17] Ashworth J. R., "Myrmekites of exsolution and replacement origins", Geological Magazine, 109 (1972) 45-62.

[18] Phillips E. R., "On polygenetic myrmekite", Geological Magazine, 117 (1980) 29-36.

[19] Phillips E. R., "Myrmekite - One hundred years later", Lithos, 7 (1974) 181-194.

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

[21] Trommsdorff V., Schwander H., "Brucitmarmore in den Bergelleralpen", Bulletin

Suisse de Mineralogie et Petrographie, 49 (1969) 333-340.

[22] 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.

[23] 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", Journal of Metamorphic Geology, 8 (1990) 89-124.

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

[25] Spear F.S., "Metamorphic phases equilibria and pressure-temperature-time paths", Minralogical Society of America, 1 (1993) 799 p.