Maryam Souri1 
, Ahmad Ahmadi Khalaji *1 , Jiamin Wang2 , Rasoul Esmaeili3 , Mohammad Ebrahimi3 , Mirmohammad Miri4
, Ahmad Ahmadi Khalaji *1 , Jiamin Wang2 , Rasoul Esmaeili3 , Mohammad Ebrahimi3 , Mirmohammad Miri4
1- Lorestan University
2- Academy of Sciences
3- University of Zanjan
4- Shahid Chamran University
2- Academy of Sciences
3- University of Zanjan
4- Shahid Chamran University
Abstract: (268 Views)
The study amphibolites are located in Hashtbandi village (east of Minab). The Makran amphibolites form a part of the metamorphic rocks of northern Makran ophiolitic belt, which are found in massive and orientated forms. Based on the indicator minerals, these rocks include ordinary amphibolite, epidote-garnet amphibolite and garnet-pyroxene amphibolite. The minerals in the ordinary amphibolites include amphibole, plagioclase, zircon apatite, quartz and sphene. In addition to these minerals, garnet and pyroxene are found in the garnet-pyroxene amphibolites, and epidote, garnet and pyroxene in the epidote-garnet amphibolites. Amphiboles in these rocks are calcic type and composition from magnesian to ferrohornblende. The clinopyroxene is calcic type and mostly in the diopside range. Garnets have a compositional range from almandine to grossular, and the trend of changes in composition and elements such Mn, Mg, Ca and Fe2+ from the rim to core in this mineral does not show a specific trend and is linear. The lack of clear zoning of elements such Mn, Mg, Ca and Fe2+ and their flat patterns in garnet indicate rapid diffusion during progressive metamorphism and at temperatures above 600 °C. The composition of plagioclases is mostly in the albite- labradorite range. The sphene is in the metamorphic/hydrothermal range, and epidote is classified in the epidote subgroup. The hornblende-plagioclase geothermometery and Al-in-hornblende geobarometery result 590 – 690 ºC and 5.5 – 7.9 kbar P for the oriented amphibolites and 550 to 720 ºC and 4–6 kbar for the massive ones. A P-T phase diagram shows that the amphibole + plagioclase + epidote+ sphene assemblage is stable at 450 – 650 ºC T and < 8 kbar P corresponding to the hornblende – plagioclase thermobarometry results. In higher temperatures and pressures, clinopyroxene and garnet occur in the assemblages, respectively. On this basis, the garnet + pyroxene bearing amphibolites endured higher metamorphism degrees, at comparative temperature and pressure of > 650 ºC and > 8 kbar.
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