Showing 2 results for Sanandaj-Sirjan Zone
Syed Naeim Emami, Hamidreza Peyrowan, Zahra Eliasi,
Volume 12, Issue 2 (11-2012)
Abstract
The volcano - sedimentary complex in the North of Shahrekord , center of Chahar mahal and bakhtiary province as a NW-SE trend belt has located in the central part of the Sanandaj- Sirjan structural zone is composed of volcanics (basalts, andesitic basalts and andesites),subvolcanics (dolerites and microdiorites), volcaniclastics (tuffs, lapilli tuffs, agglomerates, volcanic breccia and tuffites) belong to Upper Jurassic, Middle Kimmerian orogenic phase. These rocks with calc-alkaline to tholeiitic affinity were erupted in a subduction environment as island arc.
The above mentioned lithological unites have been affected by hydrothermal fluids with pH=8-9, T=226◦C(in intermediate argillic zone) to 300◦C (in quartz- epidote veins) under 200 bar pressure. The secondary minerals have replaced primary rock components (selective pervasive) or have occurred as vein and vesicle fillings (non pervasive). There are three alteration zones in the study area including propylitic (chloritic), sericitic and intermediate argillic based on variety amounts of the chlorite, epidote, clinozoisite, calcite and illite. Vesicles in basalts are filled by chlorite-epidote-clinozoisite-calcite- quartz assemblages too. The investigation of mass changes show that the volcanic rocks have lossed their mass as result of hydrothermal alteration partially in chloritic zone. CaO enrichment and Na2O depletion in chloritic zone, Na2O, K2O depletion and MgO enrichment in sericitic zone, FeO, Na2O, K2O enrichment in intermediate argillic zone are key indices to determination of fossil alteration zones.
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Esmaiel Darvishi, Mahmood Khalili, Alireza Nadimi,
Volume 16, Issue 42 (5-2015)
Abstract
Marziyan granitic pluton is one of the numerous intrusive bodies in Sanandaj-Sirjan structural zone. The pluton is composed of locogranite, granite and granodiorite and its contact metamorphic rocks are consisting of cordierite and andalusite schist. Tourmaline and garnet bearing locogranite, aplite, pegmatite, mylonite and injected migmatite are exposed in the metamorphic halo. The major minerals include quartz, plagioclase, K-feldspar, biotite as well as muscovite, tourmaline and garnet. Structural studies indicate the presence of shear zones, especially in the southeastern parts with NNW-SSE trend. Four types of microstructures are present in the region 1) magmatic microstructures, 2) high temperature solid state microstructure, 3) low temperature solid state microstructure and 4) sub-mylonitic and mylonitic microstructure. All rocks of the region have been subjected to shear deformation which led the formation of S-C foliations and other sense of shear markers. The presence of asymmetric porphyroclasts and porphyroblast, biotite and feldspar kink bands, mica-fish mica and andalusite and domino and boudinaged structures of feldspar and tourmaline are evidences of ductile deformation in a contractional and dextral shear regime. All evidences indicate that high temperature solid state zones in greenschist facies to lower amphibolite conditions (300-500°C) have formed simultaneously with emplacement of granitic bodies. Low temperature solid state, sub-mylonitic and mylonitic zones developed following the emplacement of granitic bodies.
