Writers : Ghasemi.H , Sabzehie.M, Juteau.T, Bllon.H,Rastad.E and Emami.H
Refference : Geosciences Scientific Quarterly Journal,No.:39-40,P.:46
Publishing Year : 1380

Abstract :

The Sikhoran Liltramafic- Mafic Complex is located in the Sanandaj-Sirjan metamorphic belt, Southeast Iran. This complex is surrounded by palasozoic metamorphics, overlain by mesozoic glaucophan. schists with Ashin reverse fault and consists of three main units including porphyroclastic harzburgites (mantle unit?), transitonal and layered Ultramafic-matic unit. The Abshour isotropic gabbros with a late- middle Triassic age occurr as a huge intrusion cutting this complex. It has produced an intense contact metamorphism in the palaeozoic metamorphics. Scattered dlabasic dykes with late-middle Jurassic ages cut all of them. This polygenetic complex does not include certain essential units of a classic ophiolite sequence such as dyke swarms and pillow lavas, hence we can not name it an ophiolite sensce stricto. Porphyrociastic harzburgites and porphyrodlastic dunites of the transitional zone have deformational fabrics and mineral and whole rock compositions of alpine mantle peridotites. The upper part of transitional zone composed of a rhythmic sequence of layered dunite-wehrlite-pyroxenite with mamgmatic origin. Layered ultramafic-mafic cumulates consist of an ultramafic (feldspathid peridotites) section in the lower and a thick mafic (gabbroic) section in the upper part. Detailed studies of the main lithologic units of this complex indicate, that the lower part (ultramafics) crystallized in an open system replenisihed by new magmatic injections and the upper (gabbroic) part in a closed system. This trend is similar to that of low-Ti Ophiolites magmatic secuerce.
Field relations of different lithologic units, regional geology, and absolute age determinations show that this compex has been formed in an extensional tectonic environment by partial melting (29-30%) of an upper mantle diapir during the upper Carboniferous-Permian (simultaneously with Hercynian orogeny and Initation of riftng of Zagros and Sanandaj-Sirjan Neotethys basins) and subsequently by isotropic gabbros and diabasic dykes in the late- middle Triassic (Early Cimerian) and Jurassic (Late Cimerian) times respectively.

Subject List : Mafic & ultramafic