P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two ...
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The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two sections are 424 and 440 m respectively and contain red and green sandstone, conglomerate and marl which are bounded unconformably between the Jahrum Formation and Bakhtiari conglomerate. Based on the field and petrographic studies, 14 sedimentary facies related to proximal, mid fan-delta; transition zone, delta slope and prodelta have been recognized for the Miocene succession. Due to the slope facies formed by the turbidity currents, grain fall and debris flows, the coarse grained clasts and poorly sorted texture, a fan-delta model is suggested for the succession. Also, the development of the slope facies indicates a paleo-slope and slope-type, deep-water fan-delta. The frequent intra-formational disconformities, irregular changes in grain size and present of gravity flows indicate an active tectonic sedimentary basin and reflux of coarse grained sediments (catastrophic events) to the proximal parts of Zagros Basin.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast ...
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Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast and the Neyrizophiolite zone at the southwest in the Neyriz region. They contain about 700 m red and green sandstone, conglomerate and marl which overlay the Jahrum Formation with a disconformity and covered by Bakhtiari conglomerate with an angular unconformity.Petrography of thin sections indicates that the rock fragments are the most constituent, and then quartz and feldspar respectively. The low compositional and textural maturity of the studied samples (angular grains and poorly sorted sandstones) shows the proximity to the source area. Petrography of the rock fragments and the bulk chemical composition of samples display that their provenance is multiple and the sediments were derived from Sanandaj-Sirjan Zone (Cretaceous limestone- metamorphic rocks- Eocene volcanic) and Zagros Zone (ophiolite sequence- radiolarites- Eocene limestone). Also, point-count data plotted on the QFL and QmFLt triangles indicate the recycled orogen and magmatic arc provenance. Based on geochemical data tectonic setting of Neyriz Miocene sediments is continental island arc and active continental margin. The averages of Cullers' index, CIW΄ (for calculation of the chemical weathering), ICV Index (to determine the maturity source), and SiO2versus Al2O3 + K2O + Na2O diagram for these sediments show a poor weathering and dry climatic condition during their deposition which is supported by the high percentage of calcareous cement and frequency of the rock fragments. The results of this study suggest a sedimentlogical framework for the proximal part of Zagros Basin and the Miocene syn-depositional processes.
S.H Ghetmiri; S.M.A Aleyasin
Abstract
Surveying the uptake of metal substances by plants has a very important role in mineral exploration, but biogeochemical exploration has not been paid much attention in Iran. The aim of current study was surveying vegetative species of Khajeh-jamali mineral area to evaluate the probability of biogeochemical ...
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Surveying the uptake of metal substances by plants has a very important role in mineral exploration, but biogeochemical exploration has not been paid much attention in Iran. The aim of current study was surveying vegetative species of Khajeh-jamali mineral area to evaluate the probability of biogeochemical exploration of chromite and to evaluate the uptake of Iron, Copper, Lead and Nickel in the floral plants providing biological absorption coefficient (BAC). Also it aimed to evaluate the reliability of comparing metal uptake of the plants with control groups as an assisting method of exploration. The area is located on the Zagros thrust zone belong to the Alps ophiolitic band. Rock units of this area are mainly composed of rocks from Neyriz ophiolite assemblage, which are mostly of Harzburgite and Dunite types with chromite as the major mineral. The concentrations of metal substances in this area are assessed in previous studies.To study six substances of Chrome, Nickel, Iron, Cupper, Lead, and Zinc, in five herbal species including Amygdalus carduchorum ,Pistacia atlantica, Ebenus stellata, Asragalus sp. and Rheum ribes, twenty five samples (5 from each species) were collected in the study area and five samples (one for each species) were collected from an area outside of the region as control. The samples were analyzed by ICP-OES method. The resultant data was statistically analyzed using One-way Anova and T-test. BAC was in “low” or “very low” range for all the five plant species. The results showed that Rheum Ribes could be useful in Nickle exploration and Ebenus stellata for Lead exploration. This study suggests future biogeochemical investigations of areas with flora having undefined or low BAC to consider comparison of plants’ substance uptake with controls as an assisting method.
B Taghipour; M Nejadhadad; M.A Makizadeh; M Noghreian; P Rahimi
Abstract
Dunite and serpentinized harzburgite from northwest of the Neyriz ophiolites are host rocks of some podiform chromite deposits in Cheshmeh-Bid area. These chromite deposits occurred as aligned massive lenses in various sizes. The most important ore textures are massive, nodular, layered and disseminated ...
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Dunite and serpentinized harzburgite from northwest of the Neyriz ophiolites are host rocks of some podiform chromite deposits in Cheshmeh-Bid area. These chromite deposits occurred as aligned massive lenses in various sizes. The most important ore textures are massive, nodular, layered and disseminated grains. These textures are goodevidences of crystals settling crystals during the process of magma cooling in the chamber. The mineralogical studies revealed that the pyroxene melting tookplace in the peridotite host rock and olivine is recrystallized in dunite envelope. Mineral chemistry of chromite indicates high Cr number(72-77), high Mg number(69-62) and low TiO2 content(0.04-0.14 %) in chromite samples. These amounts are comparable with those chromitites, which areformed from the high partial melting rate of mantle. The medium amount of PGE determined about 212ppb, which is much lessthan the Tang-e-Hana chromite (1556ppb) deposits. The trace element content of chromitite samples and dunite envelope like Ga, V, Zn, Co, Ni and Mn are between 17-24, 466-842, 852-1048, 22-84, 115-171, and 852-1220 ppm respectively. The U shape of REY pattern indicates the interaction of high volatile and REE bearing melt(boninitic source of parent magma) with host rock. Therefore,the Cheshmeh-Bid chromitite resulted likely from the intrusion of boninitic magma ofprimary mantle with high partial melting in the peridotite host rock. The geotectonic setting is above supra-subduction zone of island arc.
