Petrology of volcanic rocks in Davarzan area

Category Petrology
Group GSI.IR
Location 21th symposium on geosciences
Holding Date 21 May 2008

      The studied area is located in structural zone of Central Iran, and the south east of Jajarm Sheet (scale 1:250000). In this area there are middle and upper Eocene volcanic rocks. From these rocks, lavas with composition alkali basalt, andesitic basalt, trachy andesitic basalt, porphyritic andesite, trachyandesite and latite andesite are investigated. Their microscopic texture is megaporphyritic and porphyritic with matrix of microlitic ? intersertal, holocrystaline, and microlithic.
   Presence of glomeroporphyritic and porphyritic texture (texture evidence), crystallizationand differentiation of high temperature minerals such as olivine, pyroxene, calcic plagioclase and then enrichment of magma from different low temperature minerals as biotite and alkali feldspar (mineralogy evidence), so positive trend in variation diagrams of major elements versus to differentiation index (geochemistry evidence), which all of these evidences present actioning of magmatic differentiation in forming of these rocks.In other hand process such as oscillatory zoning, sieve texture, corroded rims in mineralsSuch as plagioclase, pyroxene and scattered of all trace elements and some of major elements in variation diagrams to differentiation index indicate magmatic contamination with crustal rocks.