Petrology
Arefeh Heidarianmanesh; Seyed Mohsen Tabatabaimanesh; Narges Shirdashtzadeh
Abstract
Based on field observation and petrographic evidence, by progress in metamorphic degrees, a wide variety of metabasites have formed following the metamorphism at amphibolite facies (metamorphism M1) in the east of Jandaq. Thermobarometry of plagioclase- amphibole pairs indicate temperature ranges were ...
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Based on field observation and petrographic evidence, by progress in metamorphic degrees, a wide variety of metabasites have formed following the metamorphism at amphibolite facies (metamorphism M1) in the east of Jandaq. Thermobarometry of plagioclase- amphibole pairs indicate temperature ranges were 642-692ºC and 688-712 ºC for epidote amphibolites and garnet amphibolite, respectively, in a pressure range of 8 and 11 Kbar, correlating with transition from middle amphibolite to upper amphibolite facies. In addition to this metamorphic phase, petrographic signatures indicate further metamorphic phases concerning this region's geological phenomena. Based on brittle deformation in amphiboles, and epidote and quartz formation in their fractures, these rocks have undergone some degrees of retrograde metamorphism (<700 ºC; metamorphism M2) at greenschist to lower amphibolite facies. Rock foliation and mineral orientation, aggregate shape preferred orientation (ASPO) of titanite crystals along foliation, and syn-tectonic euhedral garnets indicate prograde metamorphism toward amphibolite-upper amphibolite facies (metamorphism M3). Finally, under greenschist facies condition, minerals such as chlorite and actinolite were formed in these rocks (metamorphism M4). The formation of chlorite and actinolite in the rims of the primary crystals shows that these rocks were finally affected by metamorphism at greenschist facies (M4 metamorphism).
Petrology
S. M. Tabatabaei Manesh; M. A. Mackizadeh; saeideh ranjbar; R. Gholinezhad
Abstract
Javinan skarn is located at 115 km north west of Isfahan (40 km south of Kashan and east of Ghohrud), is included in Central Iran structural zone and spread in contact with Ghohrud granitoid (Middle Miocene age) with shale, sandstone and limestone succession of the Jurassic age known ...
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Javinan skarn is located at 115 km north west of Isfahan (40 km south of Kashan and east of Ghohrud), is included in Central Iran structural zone and spread in contact with Ghohrud granitoid (Middle Miocene age) with shale, sandstone and limestone succession of the Jurassic age known as Shemshak Formation. Skarnification is made up of endo- and exoskarn subzones. Wide mineralization in these skarns hasn’t observed. Endoskarn subzone has limited occurence (from a few millimeters to a few centimeters) and exoskarn has the greatest development (from 1 meter to more than 10 meters). Endoskarn with the formation of the skarn minerals garnet, pyroxene, plagioclase, epidote and sphene, is formed in the intrusive host rock and is in the vicinity of the carbonate part. In its immediate neighborhood, exoskarn subzone starts with the formation of minerals garnet, pyroxene, idocrase, epidote, phlogopite, chlorite, quartz and calcite in the carbonate section. Mineralogical studies and textural relationship of minerals have shown that the metamorphic facies اhas reached to pyroxene hornfels in skarn rocks of this area.
S. M. Tabatabaei Manesh; F. Javadi; F. S Zohouri2
Abstract
The Nabar skarn is located about 35 km southwest of Kashan and within the Urumieh- Dokhtar magmatic belt and is formed along the contact between limestone of Qom formation with a probably middle to upper Miocene intermediate and basic intrusion body. The main minerals forming this skarn are garnet, ...
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The Nabar skarn is located about 35 km southwest of Kashan and within the Urumieh- Dokhtar magmatic belt and is formed along the contact between limestone of Qom formation with a probably middle to upper Miocene intermediate and basic intrusion body. The main minerals forming this skarn are garnet, clinopyroxene, epidote and accessory minerals are vesuvianite, chlorite, tremolite- actinolite, sphene, quartz and calcite. Ore minerals are pyrrhotite, pyrite with smaller amounts of chalcopyrite, sphalerite and magnetite. According to the presence of magnesium minerals like diopside and calcium minerals such as garnet, vasuvianite and epidote the type of host rock is probably calcite-dolomite. Skarn formation and mineralization in this region was occurred during three development stages. Presence of high temperature anhydrous minerals such as grossular and diopside specifies the formation of the first Stage in these rocks. Stage 2 is associated with the formation of andradite and sphene. Stage 3 is specified by replacement of anhydrous minerals at temperatures below 470 ° C by hydrous minerals such as tremolite-actinolite, epidote, chlorite and vesuvianite.
S Ranjbar; S.M Tabatabaei manesh; M.A Mackizadeh
Abstract
The Khuni skarn has been developed in the contact between small tongues of the Late Eocene-Oligocene I-type Kal-e kafi granitoidic intrusive body and the Precambrian Lakh marble-dolomite unit, Located 220 km northeast of Esfahan in the Central Iran structural zone. Skarnification could be divided into ...
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The Khuni skarn has been developed in the contact between small tongues of the Late Eocene-Oligocene I-type Kal-e kafi granitoidic intrusive body and the Precambrian Lakh marble-dolomite unit, Located 220 km northeast of Esfahan in the Central Iran structural zone. Skarnification could be divided into two subzones: endoskarn and exoskarn. There is no significant mineralization in relation to this skarn system. The extent of the endoskarn subzone is very limited (often from 2 mm to 2 cm), but the exoskarn has the most extension across the contact. The endoskarn subzone can be recognized by formation of euhedral garnets adjacent to the carbonate part. In the immediate vicinity of the endoskarn, the exoskarn subzone initiates with formation of garnet and clinopyroxene in the carbonates and is extended far away from the contact as represented by vesuvianite and phlogopite minerals. Garnet is one of the most abundant minerals in this skarn system and is found in different sizes and forms. In this paper, the zonation pattern of garnet crystals in the exoskarn subzone in the immediate vicinity of intrusive body is investigated. These garnets are mainly euhedral and isotropic and in some cases anhedral and anisotropic. They are commonly cored by a grossular-rich inner part, and a sharp considerable increase in their andradite content is found toward the rim in most cases. Most studies on skarn systems consider boiling to be the most important cause for this phenomenon. This means that boiling increases the Fe content and oxygen fugacity in the final stages of the system evolution, which consequently increases the andradite content of garnet in its solid solution
S. M. Tabatabaeimanesh; H. Safaei; A. S. Mirlohi
Abstract
In south of Kashan, early Paleozoic volcanic rocks are a part of Ghohrudmountains. In Iran structural- sedimentary division, these volcanic rocks located inUrumieh- Dokhtar zone. These volcanic rocks are basic to semibasic and mostly involved basalt. Geochemical investigations of these rocks show the ...
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In south of Kashan, early Paleozoic volcanic rocks are a part of Ghohrudmountains. In Iran structural- sedimentary division, these volcanic rocks located inUrumieh- Dokhtar zone. These volcanic rocks are basic to semibasic and mostly involved basalt. Geochemical investigations of these rocks show the alkaline nature and the intra-continental rift geotectonic setting in their formation time. The Isfahan fault is a north-trending fault across the Sanandaj-Sirjan zone. This fault is one of the old and basement fault that was active in the early Paleozoic. The unique present of Silurian volcanic rocks in this area can refer to the activation of the north part of this fault that was created by extension phases after Caledonian orogeny.