M. Khalatbari Jafari; H. Sepehr
Abstract
The south Dehshir tectonized Ophiolite located at the extreme northern part of Sharbabak-Dehshir Ophiolite belt comprise of mantle peridotite and crustal sequence. The mantle peridotites are well serpentinized and consist of cpx- bearing harzburgite and lherzolite, cross cut by isolated diabasic dikes. ...
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The south Dehshir tectonized Ophiolite located at the extreme northern part of Sharbabak-Dehshir Ophiolite belt comprise of mantle peridotite and crustal sequence. The mantle peridotites are well serpentinized and consist of cpx- bearing harzburgite and lherzolite, cross cut by isolated diabasic dikes. There is no layered gabbro in the crustal sequence and that comprise of high level isotrope gabbro with cumulative character which gradually change to diabase sheeted dike complex on top of the sequence intruded by wherlitic intrusion, quartz diorite, pegmatite gabbro and plagiogranite- tronjemite. The volcanic sequence of this association consist of alternation of chert, radiolarite, pelagic limestone have Upper Cretaceous microfaunas at base and hyaloclastic breccia, hyaloclastite, tuff and pillow lava on top the sequence. The sheeted dike complex oriented in N- S direction with couples of inclinations toward either the east or the west. Listvenite and rodingite are the sporadic metasomatic rocks that expose inside the tectonized assemblage. A few dislocated amphibolites and calc-silicate blocks are tectonically exposed. Base of chemical analyses the crustal sequence show variety in composition and have tholeitic to calc-alkaline trends. In the tectonomagmatic diagrams, these rocks are often placed in the regions associated with the volcanic arcs and in some occasions they are plotted in the oceanic basin regions. The primitive mantle-normalized spider diagrams show depletion of Nb in most of analysis and depletion of Zr and Ti in some of them which indicating a supra- subduction origin. These types of patterns located in different levels and characterized by enrichment of LILE, might be related to diversity in mantle source and different degree of partial melting. The behavior of elements in different diagrams and comparation with the different tectonic setting, show that they tend located far from MORB type and near by the Arc type. The values of the elements such as Ba, Th, Nb, Yb, indicate the influence of the fluids releaved from the subducted slab on the mantle wedge. These geochemical characters and the expose of wherlitic intrusions and the small intrusions of quartz diorite-quartze monzodiorite indicate that the South Dehshir tectonized Ophiolite display a consistent sequence of events during their formation and evolution, includes birth, youth and maturity stages which is a natural consequence of the Supra- subduction zones. It seam that the Dehshir Ophiolite formed in a forearc basin with a distance from margin could be interpret with the downgoing of Neo-Tehytis in Late Cretaceous.
M. Khalatbari Jafari; H. Sepehr
Abstract
The Kahduiyeh tectonized Ophiolite exposed at the extreme northern part of Dehshir-Baft Ophiolite belt in the southern margin of centeral Iran microcontinent, comprise of mantle peridotites and crustal sequence. The serpentinized peridotites have cpx- bearing harzhburgite and lherzholite compositions ...
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The Kahduiyeh tectonized Ophiolite exposed at the extreme northern part of Dehshir-Baft Ophiolite belt in the southern margin of centeral Iran microcontinent, comprise of mantle peridotites and crustal sequence. The serpentinized peridotites have cpx- bearing harzhburgite and lherzholite compositions which cross cut by diabase isolated dikes. The plutonic part of crustal sequence consist isotropic gabbro, diabase sheeted dike complex, intruded by wherlitic intrusion, quartz diorite, pegmatite gabbro and plagiogranite-tronjemite. The volcanic sequence consist of the intercalation of the chert and radiolarite, pelagic limestone have the Upper Cretaceous micro faunas at base of sequence and hyaloclasic braccia, hyaloclastite, sheet flow, tuff and pillow lave on top of the sequence. Study of chemical analysis indicating a supra-subduction origin and enrichments for REE, Rb, Ba and Th might be affecting of slab-derived fluids. It seem that Kahduiyeh tectonized Ophiolite display a consistent sequence of events during their formation and evolution, includes birth, youth and maturity stages which is a natural consequence of ophiolite formation in the Supra-subduction zones.
