PETROLOGY AND GEOCHEMISTRY OF ALKALINE GRANITOID ROCKS FROM

THE MISHOW MOUNTAIN (NW IRAN)

Pirmohammadi F.*, Modjtahedy M.**, Gahangiry A.**, Amery A.**

*Geology Department, Faculty of science, Islamic Azad University/Shabestar Branch, Iran petrofarhad@yahoo.com

**Geology Department, Faculty of science, Tabriz University, Iran

Abstract

The intrusive body with an area of 10 kmІ is located 20 km northwest of Shabestar, northwest Iran. This batholith is a part of west Alborz-Azarbaigaan zone that cuts Paleozoic rocks. The intrusive body consists of alkaline feldspar granite and granite in which the main mafic mineral is biotite. Furthermore, there is some enclave in these rocks. The study of the investigated samples shows that intrusive rocks north-west of Shabestar have two different generations. A part of the collected samples belongs to I-type granite and another one represents the A-type granite. It seems that this process is caused by contamination of alkaline magma with crustal materials, and primary magma of mantle is considered alkaline. Geochemistry of the rare earth elements shows that the tectonic setting of the body is compatible with Post Orogenic Granitoids (POG).

Key word: Shabestar, A-type granite, I-type granite, orogenic, biotite, alkaline.

References

Batchelor R.A., Bowden P. (1985). Petrogenetic interpretation of granitoid rock series using multicationic parameters. Chem. Geol, P.48-55.

De La Roche H., Leterrier J., Grandlauale P., Marcher M. (1980). A classification of volcanic and plutonic rocks using R1-R2 diagrams and major element analysis. Chem. Geol. Vol.29.

Furnes H., El – Sayed M.M., Khalil S.O., Hassanen M.A. (1996) – Pan- African magmatism in the waid El- lmra district, Central Desert, Egypt: geochemistry & tectonic environment. Jou. Geo. Soc. Vol. 153.

Irvine T.N., Barager W.R.A. (1971). A guide to the chemical classification of the common volcanic rocks. Lan. J. Earth Sci 8, P.523-548.

Le Maitre R.W. (1989).A classification of igneous rocks and glossary of terms, Black well, Oxford.

Maniar P.D., Piccoli P.M. (1989). Tectonic discrimination of granitoids. Geo. Soc. Am. Bull. Vol. 101.

Middlemost E.A.K. (1985). Magma and magmatic rocks. Longman journal.

Pearce J.A., Harris N.B.W., Tindle A.G. (1984). Trace element discrimination diagrams for the tectonic interpretation of granite rocks. Geol, Soc. Spec. Publ., 7, P.14-24.

Rickwood P.C. (1989). Boundary lines within petrological diagrams that use oxides of major and minor elements. Lithos 22. P.247-263.

Rollinson H.R. (1993).Using the geochemical data: evaluation, presentation, interpretation. Longman Scientific and Technical, England, 352p.

Whalen J.B., Currie K.L., Chappell B.W. (1987). A-type granites: geochemical characteristics, discrimination and petrogenesis. Contrib. min. pet., 95, P.407-419.