Showing 3 results for Granite
Volume 8, Issue 3 (2-2009)
Abstract
Malayer granitoid rocks, as a part of Sanandaj-Sirjan plutonism, are located at latitude 34°00´-34°18´ and longitude 48°30´-48°52´. Tectono-magmatic investigation on the history of Sanandaj-Sirjan Zone attributed the formation of these plutonic rocks to convergence of Iranian and Arabian plates in conjunction with subduction of Neo-Tethys in the western part of Sanandaj-Sirjan Zone. Geochemical studies of Major and Trace elements on Malayer granitic rocks reveal that these granitic plutons are formed in a compressive environment, such as active continental margin in the convergent zone of oceanic crust and continental plate at the magmatic arc of continental margin. High ratio of LILEs/HFSEs and negative anomaly of Sr, Nb, Ba and Ta confirm the relation of these granitoids to subduction zone. These, also point out the role of shallow continental crust in formation and evolution of granitoidic magma. Broad range of mineral composition in petrographical observations and large variations in field studies, high-K calc-alkaline affinity and assessment of trends observed in AFM, K2O-SiO2, FeO-MgO diagrams versus those of plutons of known tectonic setting accentuate the similarities between Malayer granitic rocks and Andian type Magmatic Arc of Active Continental Margins and as a result highlights the role of upper mantle mafic magmas and tectonic movement in formation of their parental magma.
Vahid Ahadnejad,
Volume 13, Issue 4 (2-2014)
Abstract
The magnetic anisotropy of rocks results from the contributions of diamagnetic, paramagnetic, & ferromagnetic minerals. This bulk anisotropy of magnetic susceptibility, which can be rapidly measured with modern instruments, generally provides a better understanding of the rock deformation history. Different minerals in a rock can form at different times and also respond to deformation in different manners. Therefore it is useful to separate their respective contributions to the whole rock magnetic fabric. Various techniques available to achieve this separation among them measurement of the magnetic properties at high fields, above the saturation magnetization of ferromagnetic minerals, effectively separates the diamagnetic-paramagnetic magnetic anisotropy. In this paper, the anisotropies of ferromagnetic and paramagnetic components are separated using High-Field Analysis torque for 37 samples of natural rocks. These samples are igneous rocks of Malayer that are mainly composed of paramagnetic minerals (e.g. biotite and amphibole) and few portions of ferromagnetic minerals (e.g. titanomagnetite) which are located in the quratz-feldespathic (diamagnetic) context. Anisotropy of Magnetic Susceptibility (AMS) in low field analyses indicated that paramagnetic phases are the dominant control of the magnetic fabric. This is confirmed by High Field Analyses (HFA) which implied that magnetic characteristics are dominated by paramagnetic minerals, except for three samples.
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.
