TITLE:
Petrogenesis of Volcanic Rocks in Alasht, Mazandaran, Iran
AUTHORS:
Mohammad Ali Arian, Mohammad Hasan Bazoobandi, Reza Elmi
KEYWORDS:
Alasht Area, Crustal Contamination, Olivine Basalt, Sub-Alkaline
JOURNAL NAME:
Open Journal of Geology,
Vol.6 No.3,
March
9,
2016
ABSTRACT: Area studied in this paper
is located in the northwest of city of Alasht. The most important varieties of
studied rocks are volcanic and semi-volcanic rocks of basic nature. These
rocks, which form a distinguishable solid mass on 1:100,000 geological map,
belong to Cretaceous period. According to results of petrographic study, rocks
of this area include olivine basalt, dolerite, gabbro and microgabbro, and all
have almost similar chemical compositions. According to chemistry-basednaming process carried out through TAS
method, these rocks are entirely basalt and basic and are all products of
Sub-alkaline-Tholeiitic magma. According to Harker diagrams, a magmatic
differentiation can be observed in all volcanic rocks; furthermore, basaltic
magma erupted in this area has undergone an alteration and possibly a crustal
contamination. The spider diagrams plotted in this paper show that basic rocks
of Alasht area (basalts, andesite basalts, dolerites, gabbros and microgabbros)
are all mostly similar to ocean island basalts (OIB). Once field study,
sampling andmicroscopic study
stages were complete, ten samples were selected for chemical analysis andwere analyzed by XRF method.