Writers : Nimrouzi, Atefeh; Emami, Mohammad Hashem; Moafpourian, Gholam Ali
Refference : The 26th Symposium on Geoscieences;Tehran
Publishing Year : 1386

Abstract :
Our recent studies on ultramafic - mafic rocks at the East of Fariman and West of Mashhad, located at the North of Torbat-e-Jam - Fariman Lineament , Northeast of Iran, have revealed several field and petrographic evidences which demonstrate their volcanic to subvolcanic origin * For example in the Nodareh , Northwest of Mashhad ,there are several out crops of ultramafic pillow lavas with brecciated crust ,so investigation of massive ultramafic lavas in the same area revealed presence of some devtrified and/or altered glass to chlorite and carbonate minerals more over these rocks have a uniform aphanitic texture in hand samples , and under the microscope they show a variety of cumulate textures , including orthcumulate and adcumulate At the Northeast and North of Fariman as well, there are ultramafic lava flows with pillow and brecciated features , and in a detail petrographic studies of them we have found varieties of disequilibrated textures including pyroxene spinifex and micro olivine spinifex textures in mafic and ultramafic samples respectively , and as there are special geochemical criteria introduced for komatiitic rocks , we have named them so. It is may be that mafic rocks have been olivine fractionated products of ultramafic parent melts which have theire out crops in the same area , as there is a close spatial and time relationship between them and regard to some petrographic evidences In the cited area ultamafic - mafic rock out crops are seen as lava flows sills and rarely as small dikes and they have contained an unique collection of disequilibrated textures .Here we have described disequilibrium textures in mafic and ultramafic rocks of Fariman's samples and attributed their formation to an unusual high temperature of their ultramafic parent magma ,an assumption which have favored as well by our crystal chemistry data on olivines because there are olivines with high Fo contents that should be in equilibrium with hot and high Mg melts ,approximately 1430° C temperature and 18.53 % MgO content These values are too high to correspond with subdoction or even MORE related environments and rather are similar to a hot spot tectonic setting.
Subject List : Volcanism