عنوان مقاله [English]
A gabbro to monzonite sill is injected into the Karaj tuffs at the north of Parachan village, North of Karaj.. The main minerals of these rocks are plagioclase, pyroxene, K feldspar, olivine and biotite. Clinopyroxene mineral chemistry studies carried out on the intrusive bodies, indicate two types of diopside and augite clinopyroxene composition. The chemical composition of the pyroxenes shows that these rocks have been crystallized in a subduction geological setting. The average crystallization temperature of clinopyroxenes is about 1120 to 1170 °C, and it seems that clinopyroxenes crystallized at lower temperature than orthopyroxenes. Plagioclase composition in these rocks is variable, changing from andesine to labradorite. K feldspars are in the orthoclase range and olivine are hyalosiderite. Biotite is one of the most prominent ferromagnesian minerals in the studied bodies. Compositionally, it is plotted between the fields of annite and siderophyllite. Most of these biotites are primary magmatic and some are plotted in the re-equilibrated filed. Petrological evidence represent that fractional crystallization from gabbro to monzonite had main role in genesis of these rocks. Enrichment in LILE) Ba, Rb and Th(and also depletion in HFSE (Nb and Ti) in Rare Earth Elements distribution pattern in spider diagrams, indicate features of subduction-related rocks. Also they are enriched in LREE rather than HREE, the characteristic which is usually observed in the rocks from subduction environments and active continental margins. Chemical and petrological studies, indicate role of fractional crystallization in the evolution of magma, although, minor amounts of assimilation and contamination of magma by crustal rocks occurred. This alkaline magma has been formed by low degree of partial melting of an enriched sub-continental lithospheric garnet-lherzolite mantle source.
خوشحال خمیران ف.، 1392- شواهد ماگماتیسم پس از الیگوسن در مناطق آوه و پراچان، ناحیه طالقان، پایاننامه کارشناسیارشد، دانشگاه تربیت مدرس.
Abdel-Rahman, A., 1994- Nature of biotites from alkaline, calc-alkaline and peraluminous magmas, Journal of Petrology 35: 525– 541.
Aldanmaz, E., Pearce, J. A., Thirlwall, M. F. and Mitchell, J. G., 2000- Petrogenetic evolution of late Cenozoic, post-collision volcanism in western Anatolia, Turkey, J. of. Volcan. geotherm. Res. 102, 67-95.
Boynton, W. V., 1984- Geochemistry of the rare earth elements: Meteorite studies. In: Rare Earth element geochemistry (Ed. Henderson, P.) 63-114. Elsevier, Amsterdam.
Conceicao, R. V. and Green, D. H., 2004- Derivation of potassic (shoshonitic) magmas by decompression melting of phlogopite+pargasite lherzolite. Journal of Geology 72: 209-229.
Conly, A. G., Bernan , J. M., Bellon, H. and Scott, S. D., 2005- Arc to rift transitional volcanism in the Sanata Rosalia Region, Baja California Sur, Maxico. Journal of Geology 72: 303-341.
Cotton, J., Le, D. A., Bau, M., Caroff, M., Maury, R. C., Dulski, P., Fourcade, S., Bohn, M. and Brousse, R., 1995- Origin of anomalous rare earth element and yttrium enrichments in subaerially exposed basalts, evidence from French Polynesia. Chemical Geology 119: 115-138.
De La Roche, H., Leterrier, J., Grandclaude, P. and Marchal, M., 1980- A classification of volcanic and plutonic rocks using R1R2-diagram and major element analyses – its relationships with current nomenclature. Chemical Geology 29: 183–210.
Deer, W. A., Howie R. A. and Zussman J., 1992- An Introduction to the Rock Forming Minerals" 2nd ed., Longman, London 696p.
Ellam, R. M. and Cox, K. G., 1991- An interpretation of Karoo picrite basalts in terms of interaction between asthenospheric magmas and the mantle lithosphere. Earth and Planetary Science Letters 105, 330-342.
Forster, M. D. 1960- Interpretation of the composition of tri octahedral mica. United State Geological Survey. Professional Paper 354-B: 1-48.
Furman, T., 2007- Geochemistry of East African Rift basalts: An overview: Journal of African Earth Sciences, v. 48, 147-160.
Juteau, T. and Maury, R., 1997- Geologie de la croute oceanique, petrologie et dynamique endogens. Masson, Paris.
Koroll, H., Evangelakakkis, C. and Voll, G., 1993- Two feldspar Geothermometry: a review and revision for slowly cooled rocks. Contributions to Mineralogy and Petrology 510–518.
Letterrier, J., Maury, C. R., Thonon, P., Girard, D. and Marchal, M., 1982- Clinopyroxene composition as a method of identification of the magmatic affinities of paleo-volcanic series", Earth and Planetary Science Letter, 59: 139-154.
Lindsley, I., 1983- Pyroxene thermometry, American Mineralogist 68 477-493.
Middlemost, E. A. K., 1985- Magmas and magmatic rocks, longman. London and NewYork.266 p.
Morimoto, N., 1988- Nomenclature of pyroxenes. Canadian Mineralogist, 27: 143-156.
Nachit, H., Ibhi, A., Abia, E. H. and Ohoud, M. B., 2005- Discrimination between primary magmatic biotites, reequilibrated biotites and neoformed biotites, Comptes Rendus Geoscience 337 1415-1420.
Pearce, J. A., Harris, N. W. and Tindle, A. G., 1984- Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology 25: 956-983.
Peccerillo, A. and Taylor, S. R., 1976- Geochemistry of Eocene calc-alkaline volcanic rocks from the Kastamonu area, northern Turkey. Contribution to Mineralogy and Petrology 58: 68-81.
Rolinson, H., 1993- Using geochemical data, evaluation, presentation, interpretation. Harlow, Longman, London 352 p.
Ryerson, F. J. and Watson, E. B., 1987- Rutile saturation in magmas: implications for Ti Nb-Ta depletion in island-arc basalts. Earth and Planetary Science Letters 86: 225-239.
Schandl, E. S. and Gorton, M. P., 2002- Application of high field strength elements to discriminate tectonic setting in environments, Economic Geology 97: 629-642.
Soesoo, A. A., 1997- Multivariate statistical analysis of clinopyroxene composition: empirical coordinates for the crystallisation PT-estimations. Geological Society of Sweden (Geologiska Föreningen) 119: 55-60.
Spear, J. A., 1984- Mica in igneous rock Mineralogical Society of America, Review in Mineralogy 13: 299-356.
Sun, S. S. and Mc Donough, W. F., 1989- Chemical and isotopic systematic of oceanic basalts: implication for mantle composition and process. In: Magmatism in the ocean basins (Eds. Saunders, A. D. and Norry, M. J.) 42: 313-345. Geological society, London
Thompson, R. N., 1982- British Tertiary volcanic province. Scottish Journal of Geology 18: 49-107.
Wilson, M., 1989- Igneous Petrogenesis, Springer Verlag466 p.