Akademik Veri Yönetim Sistemi
CHEMIE DER ERDE / GEOCHEMISTRY INTERDISCIPLINARY JOURNAL FOR CHEMICAL PROBLEMS OF THE GEOSCIENCES AND GEOECOLOGY, cilt.84, ss.1-25, 2024 (SCI-Expanded)
The Eastern Iranian Ranges are considered to be either a suture zone produced by closure of a Neo-Tethyan backarc basin between the Lut and Afghan blocks or an oroclinal buckling of multiple terranes accreted to the active margin of the Neo-Tethyan Ocean. Both models are based on the presence of Cretaceous ophiolite complexes and sequences of Eocene turbiditic sedimentary rocks. The Dumak ophiolitic m´elange, a significant ophiolitic assemblage that crops out in the western portion of the orogen adjacent to Lut, contains all the essential elements of a typical ophiolite in a matrix of serpentinite and clay-rich sediments. Ultramafic-mafic cumulates in the m´elange are characterized by medium, non-rhythmic bedding in limited outcrops where they are in tectonic contact with other ophiolitic units. The cumulates consist of plagioclase-bearing dunite, troctolite, Cpx-troctolite and gabbro composed chiefly of olivine, plagioclase, and clinopyroxene accompanied by rare orthopyroxene. This assemblage is very similar to the differential crystallization sequence of tholeiitic magma at modern midocean ridges. The clinopyroxene in these rocks is diopside (En = 47–49) and the plagioclase is bytownite (An = 71–77). Whole-rock geochemistry of samples from the crustal sequence of Dumak m´elange are characterized by low TiO2 (0.03–0.17 wt%). Investigation of this crystalline sequence and geochemical properties of the rocks suggests that they can be considered as the low-Ti ophiolite originated from mid-ocean ridges. Additionally, the positive Eu anomalies as well as comparison of frequency of LREE and HREE in the mafic and ultramafic samples indicate the cumulates formed by fractional crystallization and differentiation of mantle-derived magmas. According to petrographic, geochemical, and structural evidence, it is possible that the Dumak ophiolite, after being formed or displaced between Lut and Afghan blocks, was firstly accreted to the south of the Lut block and then re-mixed into Eocene sediments emplaced in the current position.