TITLE:
Geochemistry and Petrogenesis of Tertiary Volcanic Rocks of the Eastern Roodbar, Alborz Mountain, North of Iran
AUTHORS:
Zahra Shafeie, Mohammad Ali Arian, Shahrouz Haghnazar, Mansour Vossoughi Abedini
KEYWORDS:
Volcanic Rocks, Tertiary, MORB Source Mantle, Crustal Contamination
JOURNAL NAME:
Open Journal of Geology,
Vol.6 No.10,
October
28,
2016
ABSTRACT: In the Alborz Mountains of the eastern Roodbar (north of Iran), Tertiary
volcanic rocks have a variety of composition between olivine basalt, basaltic
andesite, pyroxene andesite and andesite. The presence of different xenoliths
and xenocrysts is among the evidence of crustal contamination of these rocks. The positive
correlations of CaO/Al2O3 vs to MgO and Al2O3 vs. SiO2 are of signs of the olivine and clinopyroxene fractionation
in the variation trend of the area rocks. Positive correlations K2O/P2O5 vs with SiO2 and La/Sm vs. K2O/P2O5 demonstrate contamination of magma with the continental crust. The incompatible
trace element patterns and their comparison with crustal contents indicate
contamination of the rocks of the area with the lower and upper continental
crust. Linear trends in the variation diagram of Nb/Y vs. Zr/Y, introduce two
different source regions: a MORB source and the other continental crust for
the rocks which are the genesis. The
variations of Y/Nb vs. Zr/Nb and Rb/Y vs. Nb/Y reveal a crustal contamination
of the magma originated from the MORB source. Geochemical studies represent
that the area’s rocks were derived from the 15% melting of a mantle source of MORB type with spinel
facies within a continental environment, which was contaminated by varying degrees of continental crustal rocks.