Geochemistry of Shanderman eclogite, constrains on protolith nature

Abstract

 Shanderman eclogites are exposed at the west of Shanderman town, Talesh Mountains, in north Iran. Protoliths in these rocks has basaltic composition. Geochemical studies indicate that most of the samples have tholeiitic feature. Mg# versus Cr and Ni show that they experienced olivine and clinopyroxene fractionation. Spider diagram shows more fractionation of olivine compared to clinopyroxene. The trace element versus major oxides diagrams show that major oxides had no significant (except Na and to some extent Fe) variation during alteration and subsequent metamorphism. Based on ∑REE, eclogite of the Shanderman can be divided into two groups. First group shows ∑REE= 31.1 ppm and (La/Lu)N=0.6. Second group have ∑REE= 139.2 ppm and (La/Lu)N=2.3. Chondrite REE normalized patterns show that they are comparable with N-MORB and E-MORB. These patterns (N-E MORB) indicate that either Shanderman eclogite protolith magma source was not homogenous or it experienced different melting degrees, changing from LSS (slow spreading ridge) to FSS (fast spreading ridge).

Keywords


[1] Clark G.C., Davies R.G., Hamzepour G., Jones C.R. "Explanatory text of the Bandar-e-Pahlavi quadrangle map, 1:250,000". Geological Survey of Iran, Tehran, Iran, (1975) 198.

[2] Mehdizadeh shahri H., "Pre-rifting evidence of paleotethys in the southwest of Shahrood, Northeastern Iran". Word applied sciences Journal3 (1) (2008) 154-161.

[3] Zanchetta S., Zanchi A., Villa I., Poli S., Muttoni G., "The Shanderman eclogites: a Late Carboniferous high-pressure event in the NW Talesh Mountains (NW Iran)", Geological Society, London, Special Publications. 312 (2009) 57-78.

[4] Axen G.J., Lam P.S., Grove M., Stockli D.F., "Exhumation of the west-central Alborz Mountains, Iran, Caspian subsidence, and collision-related tectonics", Geological Society of America. 29 (2001)559- 562.

[5] Hollingsworth J., Jackson J., Walker R., Nazari H., "Extrusion tectonics and subduction in the eastern South Caspian region since 10 Ma", The Geological Society of America. 36 (2008) 763-766.

[6] Majidi B., "Etude pérostructurale de la région de Mashad (Iran). Les problèmes des méamorphites, serpentinites et granitoides hercyniens. Thèse de Docteur Ingenieur", Université Scientifique ed Médicale de Grenoble. 1978. 277 pp.

[7] Karimpour M.H., Farmer L., Ashouri C., Saadat S., "Major, Trace and REE geochemistry of Paleo-Tethys Collision-Related Granitoids from Mashhad, Iran", Journal of Sciences, Islamic Republic of Iran. 17(2) (2006) 127-145.

]8 [صلواتی م.، کنعانیان ع.، صوفی ع.ص.، زعیمنیا ف.، "شیمی کانی‌های اصلی سنگ‌های اولترامافیک مجموعه افیولیتی جنوب دریای خزر (خاور گیلان): شواهدی از تفریق بلور در فشار بالا". مجله بلور‌شناسی و کانی‌شناسی ایران. شماره 1 (1388) 149 تا 166.

[9] Guest B., Axen G.J., Lam P.S., Hassanzadeh J., " Late Cenozoic shortening in the west-central Alborz Mountains, northern Iran, by combined conjugate strike-slip and thin-skinned deformation", Geosphere. 2 (2006) 35-52.

]10[ افتخارنژاد ج.، اسدیان ع.، راستگار میرزایی ع.، "سن مجموعه دگرگونه‌ها و افیولیت‌های شاندرمن ـ اسالم و ارتباط ژئودینامیکی آنها با پالئوتتیس و پوسته شبه اقیانوسی دریای خزر" ، مجله علوم زمین. شماره 3. صفحه 36 تا 43.

]11[ نبوی م.ح.، "دیباچه‌ای بر زمین‌شناسی ایران" .انتشارات سازمان زمین‌شناسی کشور، (1355)، 109 صفحه.

[12] Davies R.G., Jones C.R., Hamzepour B., Clark G., Ghorashi M., Nava I., "Geological map of the Masuleh area, 1:100,000". Geological Survey of Iran. (1975).

[13] Crawford M.A., "A summary of isotopic age data for Iran, Pakistan and India", In : Libre a la memoire del A.F. de Lapparent. Mémoire hors-serie 8. Societé Géologique de France, (1977) 251-260.

[14] Kertz R., "Symbols for rock forming minerals", Amrican mineralogist. 68 (1983) 227-229.

[15] Floyd P.A., Winchester J.A., "Magma-type and tectonic setting discrimination using immobile elements". Earth and Planetary Science letter, 27 (1975) 211-218.

[16] Winchester J.A., Floyd P.A., " Geochemical discrimination of different magma series and their differentiation products using immobile elements", Chemical Geology, 20 (1977) 325-343.

[17] Volkova N.I., Frenkel A.E., Budanov V.I., Lepezin G.G., "Geochemical signatures for eclogite protolith from the MaksyutovbComplex, South Urals". Journal of Asian Earth Sciences. 23 (2004) 745-759.

[18] Pearce J.A., Cann J.R., "Tectonic setting of basic volcanic rocks determined using trace element analyses". Earth and Planetary Science letter, 19 (1973) 290-300.

[19] Meschede M., "A method of discriminating between different types of mid-Ocean ridge basalts and continental tholeiites with the Nb-Zr-Y diagram". Chem. Geol., 56 (1986) 207-218.

[20] Shervais J.w., "Ti-V plots and the petrogenesis of modern and ophiolitic lavas". Earth Planet. Sci. Lett., 59 (1982) 101-118.

[21] Barth M.G., Gluhak T.M., "Geochemistry and tectonic setting of mafic rocks from the Othris Ophiolite, Greece". Contribution of Mineralogy and Petrology. 157 (2009) 23-40.

[22] Debaille V., Blichert-Toft j., Agranier A., Doucelance R., Schiano P., Albarede F., "Geochemical component relationships in MORB from the Mid-Atlantic Ridge, 22–35° N". Earth and Planetary Science Letters. 241 (2006) 844-862.

[23] Usui T., Nakamura E., Helmstaedt H., "Petrology and geochemistry of eclogite xenoliths from the Colorado plateau: Implications for the evolution of subducted oceanic crust". Journal of Petrology. (2006) 1-36.

[24] Pearce J.A., "Statistical Analysis of Major Element Patterns in Basalts". Journal of Petrology. 17 (1976) 15-43.

[25] Evensen N.M., Hamilton P.J., O’nions R.k., "Rare earth abundances in chondritic meteorites". Geochim. Cosmochim. Acta. 42 (1978) 1199-1212.

[26] Cotten J., Le Dez A., Bau M., Caroff M., Maury R.C., Dulski P., Fourcade S., Bohn M., Brousse R., "Origin of anomalous rare-earth element and yttrium enrichments in subaerially exposed basalts: evidence from French Polynesia". Chem. Geol., 119 (1995) 115-138.

[27] Xiao L., He Q., Pirajno F., Ni P., Du J., Wei Q., "Possible correlation between a mantle plume and the evolution of Paleo-tethys Jinshajiang Ocean: Evidence from a volcanic rifted margin in the Xiaru-Tuoding area, Yunnan, SW China". Lithos. 100 (2007) 112-126.

[28] Sun S.S., McDonough W.F., "Chemical and isotopic systematics of ocean basalts:Implication for mantle composition and processes", In: Saunders, A.D., Norry, M.J., (Eds.), Magmatism in Ocean Basins. Geological Society of London, Special publication. 42 (1989) 313-345.

[29] Taylor St.R., McLennan S.M., "The Continental Crust: its Composition and Evolution", Blackwell Scientific Publications. Geoscience texts. Oxford (1985).

]30 [رولینسون، ه. "کاربرد داده‌های ژئوشیمیایی، ارزیابی، نمایش". ترجمه علیرضا کریم‌زاده ثمرین. انتشارات دانشگاه تبریز. (1381).

[31] Sinton J.M., Detrick R.S., "Mid-ocean ridge magma chambers", J Geophys Res. 97 (1992) 197-216.

[32] Stampfli G.M., Borel G.D., "A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrones", Earth and Planetary Science Letters, 196 (2002) 17-33.