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Neshveh intrusion which is located in the NW of Saveh City is apart of Sahand-Bazman magmatic arc within the Central Iranian zone.
Thisintrusion consists of quartz-monzogabbro, quartz-monzodiorite, granodiorite andgranite that have intruded into the Eocene volcano-sedimentary rocks.
Thisintrusion is medium to high-K calc alkaline, metaluminous, and I-typegranitoid.
All phases of the Neshveh granitoid are characterized by LREE-richpatterns with high LREE-HREE ratio and negative Eu anomalies.
Similarity ofpatterns suggests a comagmatic source for these rocks and demonstrates the roleof magmatic differentiation in their evolution.
Clinopyroxene classified ascalcic type with varying from clinoenstatite-clinofferosillite to diopside andaugite from quartz-monzogabbros to quartz-monzodiorite and granodiorite.Plagioclase composition varies from bytownite and labradorite inquartz-monzogabbros to andesine in quartz-monzodiorites and oligoclase ingranodiorites and granites.
Core of some plagioclases in granodiorites andgranites shows the calcic composition which is labradorite and andesine ingranodiorite and andesine in granites.
Field investigations along withpetrographic and geochemical studies indicate that all phases of the Neshvehintrusion derived from a common magma source as a result of mineraldifferentiation.
Geochemical evidences show smooth differentiation trends inwhich most of major elements except Al2O3, K2O and Na2O are negatively correlated with SiO2 and K2O, Ba, Rb, Ce, Nb, and Zr are positivelycorrelated with SiO2.
Some elements such as Na2O, Sr, Eu and Yfollow curves that reflect crystal fractionation of clinopyroxene, plagioc1aseand hornblende.
Furthermore, large volumes of quartz-monzogabbros compared togranites, as well as the lack of mafic enclaves in more evolved rocks, are alsoindicative of crystal fractionation.
Clinopyroxene fractionation was the maincontrol in the evolution of the magmas up to 55 wt% SiO2.
Hornblende tookover from 55 wt% SiO2, resulting in decreasing Dy-Yb with increasingsilica content in the most siliceous rocks.
Fractionation of opaque mineralsand apatite throughout the sequence, and the continuous increase in K2O and Ba vs.
SiO2 reflect the absence of significant fractionation ofbiotite and K-feldspar.

KEYWORDS

Mineral Chemistry, Magmatic Differentiation, Intrusion, Granitoid, Neshveh, Saveh

Cite this paper

Keshavarzi, R.
, Esmaili, D.
, Kahkhaei, M.
, Mokhtari, M.
and Kordlou, M.
2014 Mineral Chemistry and Magmatic Differentiation Evidences in the Neshveh Intrusion NW Saveh, Central Iran.
Open Journal of Geology, 4, 262-288.
doi: 10.4236-ojg.2014.46020.






Autor: Reza Keshavarzi, Dariush Esmaili, Mehdi Rezaei Kahkhaei, Mir Ali Asghar Mokhtari, Mehdi Kordlou

Fuente: http://www.scirp.org/





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