Mineralogy, Petrography and Petrogenesis of Sahand Volcanic Suite (Northwest Iran)
Subject Areas :
Farhad Pirmohammadi
1
(
استادیار دانشگاه آزاد اسلامی واحد شبستر
)
Ali Ameri
2
(
دانشیار گروه زمین شناسی دانشگاه تبریز
)
Ahmad Jahangiri
3
(
دانشیار دانشگاه آزاد اسلامی واحد شبستر
)
Mansoor Mojtahedi
4
(
دانشیار دانشگاه آزاد اسلامی واحد شبستر
)
Mahmat Keskin
5
(
استاد گروه زمین شناسی دانشگاه استانبول ترکیه
)
Keywords: Central Iran, Sahand, Plio-Quaternary, Subalkaline lava, Post-Collisional,
Abstract :
Southeast Tabriz, Sahand volcanic rocks with Plio-Quaternery age located in the northwest part of Central Iran.These rocks are mainly composed of pyroclastics (tuff and ignimberite) and lava flows (rhyolite, rhyodacite,dacite and andesite) that unconformably cover the Miocene sedimentary formations. The major constituentminerals include plagioclase and hornblende which is surrounded by a matrix of fine grained and glassy.Theirtexture are porphyritic. Heterogenous mineralogy, field and textural evidences such as sieve texture inplagioclase, resorption rims in crystals, oscillatory zoning in plagioclase, high normative quartz and roundedenclaves suggest that the primary magma undergone magmatic evolution including fractional crystallization ,fractionation, contamination and magma mixing during ascending. There are mineralogical as well asgeochemical evidences that AFC-type processes were involved in the evolution of the Sahand volcanic rocks.The chemistry of the felsic- intermediate volcanic rocks indicates that the parent magmas are medium-K calcalkaline and metaluminous in nature. The volcanic rocks display highly fractionated REE patterns, with nonegative Eu anomaly. Their geotectonic environment is post-collision and continental margin arcs.
