The study of parental rock of post Jurassic dolerites of volcano-sedimentary belt in north of Shahrekord


Department of Watershed Researches, Agriculture and Natural Resources Researches Center of Chaharmahal and Bakhtiari Province, Shahrekord, Iran


Subvolcanic basic rocks have been exposed in the north of Shahrekord, as a part of Sanandaj-Sirjan structural zone in the form of stocks and dykes in post Jurassic to early Cretaceous owing to their intrusion and emplacement into upper Jurassic volcano-sedimentary suite. These rocks are dolerites and show subvolcanic particular textures such as intergranular, intersertal and ophitic. The main constituent minerals of dolerites are plagioclase (Labradorite) which has altered to albite due to spilitization and clinopyroxene including augite and diopside. Secondary minerals are chlorite, calcite, epidote, clinozoisite and some minor minerals such as apatite, magnetite, titanomagnetite, ilmenite and sphene. Dolerites, based on geochemical and mineralogical signitures, are classified into the two distinct groups. The first group with tholeiitic affinity originated from an upper lherzolith source rock in a post subduction tension environment. The second group with alkaline and transitional nature generated from an eclogite source rock in an oceanic intraplate basalts environment. Dolerites have been formed after upper Jurassic or early Cretaceous due to their intrusion and translocation in the upper Jurassic volcano-sedimentary rocks.