Petrology
Soghra Razaghi; mohsen nasrabady; Kazem Gholizadeh; Zeinab Davoodi
Abstract
The Gash metamorphic complex is situated at the west of Rasht city. Gasht-e-Rodkhan metamorphic rocks are considered as a part of this metamorphic complex. Metapelites (schist, gneiss and migmatite) are the most important lithological unit of the Gasht-e-Rodkhan area. Index minerals consist of staurolite, ...
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The Gash metamorphic complex is situated at the west of Rasht city. Gasht-e-Rodkhan metamorphic rocks are considered as a part of this metamorphic complex. Metapelites (schist, gneiss and migmatite) are the most important lithological unit of the Gasht-e-Rodkhan area. Index minerals consist of staurolite, garnet, sillimanite and kyanite. The main rock forming minerals of muscovite-free melanosome of migmatites are sillimanite and biotite. There is garnet in some melanosome as well. Quartz, K-feldspar and plagioclase are the rock forming minerals of leucosome. Tourmaline, garnet, muscovite and sillimanite are accessory minerals. Average pressure and temperature calculated by Thermocalc software and conventional thermobarometers for schist, gneiss and migmatite samples are 8.6 Kb, 630°C; 6.7 Kb, 650°C and 6.3 Kb, 720°C respectively. Mineralogical parageneses and geothermal gradient resulted from thermobarometry calculations of the Gasht-e-Rodkhan metapelites are compatible with metamorphic Barrovian gradient or orogenic type. Gash complex probably represents metamorphic rocks of medium crustal depth of a collisional tectonic setting between Alborz block and Turan plate. Partial melting of metapelites and generation of associated leucogranites have taken place as a consequence of muscovite dehydration melting.
Z. Davoodi; A. Yassaghi
Abstract
Geometry and kinematics analyses of structures developed along one of the transverse fault zone (Izeh) in the Zagros fold-thrust belt has been presented to document the origin and to present the effect of this fault zone on the belt structures. Surface deformation of Izeh fault zone on the cover sediments ...
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Geometry and kinematics analyses of structures developed along one of the transverse fault zone (Izeh) in the Zagros fold-thrust belt has been presented to document the origin and to present the effect of this fault zone on the belt structures. Surface deformation of Izeh fault zone on the cover sediments are including changes on the Zagros major structures trends and development of minor structures (such as minor folds and faults) that are overprinted on the belt major structures. Detaeled structural mapping showed the precense of three major restraining zones between the mapped subsurface en-echelon faults along the Izeh fault zone in the Zagros fold-thrust belt. Analysis of isopach maps, facies variation of formations together with interpretation of seismic reflection profiles showed that these subsurfase faults are younger orders of the Izeh fault zone reactivation as a basement fault. Oblique convergence of the Arabian Plate toward the Central Iran is in favor for the reactivation of the fault zone and formation of surface deformations along it. Based on earthquake data this reactivation is continuing until the present time. The result of this study can be used for interpretation of deformation on the sedimentary cover along the similar transvers fault zone in the Zagros fold-thrust belt.
