Magmatism and Igneous Rocks

Magmatic rocks of all ages, from the Precambrian to the Quaternary, are widespread in Iran (e.g., Doran granite, Zarigan–Narigan granite, Torghabeh granite, Ghaen granite, Chaghand gabbro, Alvand granite, Natanz granite). A correlation exists between distribution of magmatic rocks and certain types of ore deposits (e.g., iron deposits in Bafq related to Zarigan–Narigan-type granites, Mazraeh copper deposits related to Sheyvar–Daghi granite, Sarcheshmeh porphyry deposit related to Sarcheshmeh porphyry body).

Several episodes of magmatic activity have been identified in Iran. These episodes could be described as:

Upper Precambrian–Lower Cambrian

Volcanic and plutonic rocks with an age of 630–۵۳۰ million years have been reported from many localities in Iran, particularly in Central Iran and Azerbaijan. These magmatic rocks seem to be related to the Pan-African tectonic-magmatic episode. Most magmatic rocks of this time bear an alkaline nature. The following magmatic series can be attributed to this phase: Doran-type intrusions in Azerbaijan. Narigan and Zarigan-type intrusive bodies extend from Anarak to Bafq and Kuhbonan. Volcanic rocks, mostly of rhyolite composition, in Ghareh Dash, Azerbaijan. Volcanic rocks associated with Kushk Series in the Bafq area. Volcanic rocks of Rizu, Dezu, and Kushk Formations in Central Iran. Most Precambrianmetamorphic rocks of greenschist or even amphibolite facies, such as in Takab and Anarak areas, seem to have originally been volcanic materials, either lava or pyroclastic rocks.

Lower Paleozoic

Magmatic rocks of this time have been reported from many areas in Iran. Examples include basaltic rocks of Shahrud and Khosh Yeilagh, andesitic-basaltic units of Niur Formation in Central Iran, and tuffaceous materials in the upper parts of Mila Formation in Eastern Iran.

Upper Paleozoic

Volcanic rocks of andesitic-basaltic composition accompany Upper Paleozoic sedimentary strata in many areas all over Iran. Basaltic rocks associated with Jeyrud Formation of Upper Devonian are a typical example. There is strong evidence for significant magmatic activities in Late Paleozoic–Early Mesozoic (Early Permian to Early Jurassic) in Iran. Examples include: Magmatic rocks in the Southern Sanandaj–Sirjan (granites and gabbros of Sirjan area) and volcanic rocks of Songhor Series in Northern Sanandaj–Sirjan. Ultramafic and mafic rocks and their metamorphosed equivalents could be observed in Eastern Iran (Fariman area), Taknar Series, Gorgan schists, and Shanderman mafic/ultramafic metamorphic series.

Mesozoic

The Mesozoic magmatic rocks are associated with Cimmerian and Laramide orogenic events that caused continental and oceanic rifting, followed by closures and collisions in vast areas of Iran (e.g., Sanandaj–Sirjan). The Mesozoic magmatic rocks can be divided into three groups: Volcanic rocks: These rocks occurred mainly as a result of extension or tension related to the continental rifting, or subduction of the developed oceanic lithosphere under the continental lithosphere (e.g., Central Alborz for continental rifting; Saghez-Sanandaj axis for subduction). Intrusive rocks: Many intrusive bodies of mafic to granitic composition, with ages varying from early Triassic to Late Cretaceous, have been identified in Iran (e.g., Borujerd–Shamsabad axis). In Triassic–Jurassic, volcanic rocks predominated the plutonic rocks. They are mainly alkaline in nature and are more abundant in Sanandaj–Sirjan. In Jurassic–Cretaceous, intrusive rocks exceed volcanic rocks; a significant number of batholiths in Iran occurred at this time. Kolah Ghazi, Shir Kuh, and Shah Kuh were formed by Jurassic granite; and Mount Alvand was made by Upper Cretaceous-Paleocene granite.

Cenozoic

The Tertiary is of great concern in Iran because of the great volumes and highly diverse types of igneous rocks and associated mineral deposits. Magmatic rocks of this age are widespread all over Iran, except in the Zagros and Kopet Dagh. Data from various structural zones indicate that the volcanic and plutonic activities started in the Late Cretaceous, peaked in the Eocene, and continued, with short stops, into the Quaternary. Some of the more important regions in terms of the Tertiary magmatic activities include: Sahand-Bazman(or Urumiyeh-Dokhtar) volcanic-plutonic belt with a series of famous mountain ranges including the Karkas Mountains and Jebal Barez and important peaks such as Karkas, Marshenan, Hezar and Lalehzar. The Tertiary magmatism could also be observed in Azerbaijan, Tarom–Taleghan, Central Alborz and its southern margins, Kavir–Sabzevar, Kashmar–Torbat-e Jam, Lut and Kavir, Central Iran, Sistan, Bam, Bazman, Taftan, East Iran, and Southern Jazmurian–Sabzevaran. The Quaternary volcanism produced very high peaks such as Sahand, Sabalan, Damavand, Taftan, Bazman and many others.

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