Petrogenesis and Geochemical Properties of Dome-shaped Subvolcanic Complexes in Southwest of Shahrab (Northeast of Isfahan)

Mohammad Ali Arian,Afsaneh Ranjbar,Alikhan Nasr Isfahani

doi:10.15421/2017_122

Abstract

<p>The studied area is located in southwest of Shahrab village near Ardestan city. This zone is part of Uremia- Dokhtar magmatic belt. Outcrops composed of rhyolite and rhyodacite dome-shaped volcanic complexes are scattered in the studied area; some of which are exploited as ornamental stone. The main rhyolite minerals include quartz, plagioclase and alkali feldspar. Minor minerals include Apatite, Sphene and opaque minerals and of the secondary minerals in these rocks Christie, Chlorite, Epidote and calcite could be mentioned. Calcite exists in rocks in form of filler of micro-fissures. The ignimbrite presence in this group of rocks in form of xenolith is one of the features of this rock group. The main primary texture in rhyolite and rhyodacite is porphyritic and the secondary texture includes pull-apart, snow flake and spherulitic textures. Geochemical evidences indicate that these rocks are sub-alkaline, Calc-alkaline compositions with high potassium and meta-alumina. These rocks have negative EU anomaly that is the feature of acidic igneous rocks. The studied rocks show high enrichment of LREE and LILE elements. The primary magmas constituting these rocks have mantel origin raised under extreme compressional conditions on continental crust in a tectonic environment of volcanic arc. It seems that these rocks are formed in connection with continuance of volcanic activities associated with subduction of Neolithic oceanic plate beneath continental plate of Iran. </p>

Highlights

The distribution of these sub-volcanic groups is mostly in southwest of Shahrab village in southeast of Ardestan in Isfahan province
Felsic sub-volcanic rocks in the studied area are classified in rhyolite rocks group in terms of mineralogy and chemical composition
The texture features in phenocrysts such as gulf texture in quartz, margined quartz, zoning in plagioclases and some corrosion in them and the presence of basic micropiles, all indicate chemical imbalance, magma quick swelling and sudden drop of pressure. These observations make clear the role of crust contamination or magma mix (Raymond, 2002). These sub-volcanic stones are geochemically sub-alkali with calc-alkaline nature, Metaloumin indicates negative EU anomaly, enriched of potassium

Summary

ORIGINAL ARTICLE

Petrogenesis and Geochemical Properties of Dome-shaped Subvolcanic Complexes in Southwest of Shahrab (Northeast of Isfahan). The studied area is located in southwest of Shahrab village near Ardestan city. Geochemical evidences indicate that these rocks are sub-alkaline, Calc-alkaline compositions with high potassium and meta-alumina. These rocks have negative EU anomaly that is the feature of acidic igneous rocks. The primary magmas constituting these rocks have mantel origin raised under extreme compressional conditions on continental crust in a tectonic environment of volcanic arc. It seems that these rocks are formed in connection with continuance of volcanic activities associated with subduction of Neolithic oceanic plate beneath continental plate of Iran.

Introduction

Geology of the area

Methodology

LOI Total

Discussion and conclusion