جستجوی مقالات مرتبط با کلیدواژه « Surk » در نشریات گروه « علوم پایه »

The Surk ophiolitic melange, as a narrow belt, is located in western part of Yazd province, between the southwest of Central Iran and Urumieh-Dokhtar magmatic arc, along Naein-Dehshir-Baft fault. This ophiolitic melange consists of mantle peridotites, gabbro, diabasic dykes, quartz andesite, dacite, serpentinite, listwaenite, rodingite, chert and Upper Cretaceous limestones. Petrography and mineral chemistry of mantle peridotites reveal incongruent melting of orthopyroxenes, the formation of excess olivines, the high value of Cr# in spinels of harzburgite and dunite and the occurrence of pargasitic amphibole in lherzolites in the studied ophiolite. All of these evidences suggest melt/oceanic lithosphere reaction. The reactive melt originated from a subducted slab that decreases the melting temperature of the lithospheric mantle and leads to widespread ascending melt/wall rock reaction. The peridotites of this ophiolitic melange consist of harzburgite, dunite and lherzolite in decreasing order. The ophiolite is a harzburgite type ophiolite (HOT) showing characteristics of supra subduction zone ophiolites (back-arc basin).

The Surk ophiolitic mélange is located at the south west of central Iran and along the Naein-Dehshir-Baft ophiolitic belt. In petrological sequence, peridotites are nominated the undermost part of rock unit, and then gabbros and volcanic rocks are at the following ranks respectively. The predominant peridotitet of this ophiolitic mélange is harzburgite. Lherzolite that is the primitive mantle rock consists of olivine, orthopyroxene, clinopyroxene as major minerals and chromian spinel and amphibole (pargasite) as accessory mineral. Petrographical characteristics and mineral chemistry of these peridotites show the lithology evaluation from lherzolite to harzburgite and dunite ultimately. The average SiO2 and Na2O content of volcanic rocks in the ophiolitic melange are 70 and 5 weight percent respectively. Petrographical investigations and also classification of these volcanics based on major and trace elements and norm calculations show that these rocks are dacite. REE/chondrite normalized diagrams of these volcanic rocks show horizontal to positively sloping patterns, LREEs are lower than HREEs and their La/Yb ratio is lesser than 1; suggest tholeitic nature of their parent magma. Moreover, Hf/Zr, U and Pb contant of these rocks is higher than the content in the Primitive mantle but the Sr, Ti and Y contant is lower. These differences can be caused by melt migration of subducted oceanic lithosphere on mantle peridotites. By melt/rock reactions clinopyroxene dissolution, incongruent melting of orthopyroxene, formation of replacive olivines and SiO2 increasing in ascending melt will occur. All these characteristics propose that the Surk ophiolitic mélange is a Harzburgite Ophiolitic Type (HOT) which is formed at the supra-subduction (back-arc basin) zone.