Economic Geology
Shaghayegh Sadat Hashempour; Sajjad Maghfouri; Ebrahim Rastad
Abstract
The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern ...
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The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern edge of the southern anticline in the unit 4 of regional stratigraphic column and Goft manganese deposit is occurred in the southeastern edge of the northern anticline in the first unit of the regional stratigraphic column. The host rocks of Goft and Mohammadabad deposits include red tuff and Marly tuff and limy tuff, respectively. According to geochemical studies, tectonic environment of manganese deposits in the southwest of Sabzevar is a rifting environment that has been formed in the Sabzevar back-arc basin. The rocks of the region have a wide range of basalt, rhyolite, dacite, olivine-basalt, andesite-basalt and trachy-andesite, which formed aligned with pyroclastic sediment and Late Cretaceous sedimentary units. Dacite rocks are the thickest felsic rock unit in the area. The values of major oxides, the pattern of rare earth elements (REE), and the changes in trace elements in spider diagrams indicate the bimodal and tholeiitic nature of the volcanic rocks of the region, which are deposited in extension environment with a mixed range from basalt to rhyolite.
Stratigraphy and Palaeontology
Mahin mohamadi; R. Shabanian; H. M. Alizadeh
Abstract
This research has aimed to study the biostrtigraphy and lithostratigraphy of late cretaceous deposits in south of Maracan village , with 320 m thickness.This sequence overlaid the lower cretaceous deposits and have been covered by Quaternary sedimentary and magmatic rocks. Based on field ...
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This research has aimed to study the biostrtigraphy and lithostratigraphy of late cretaceous deposits in south of Maracan village , with 320 m thickness.This sequence overlaid the lower cretaceous deposits and have been covered by Quaternary sedimentary and magmatic rocks. Based on field study and lithological diversity 8 lithic zone have been investigated. 102 samples have been picked up systematically from this sequence. This study lead to determining 41 species from 15 genera of planktonic foraminifera.The systematic and classification of fauna are based on The (Postuma 1971) , (Caron1985) , (Loeblich and Tappan 1988) and (Permoli Silva And Verga 2004). .Based on their range chart the bio zonation model for this deposit with 9 Bio Zones as bellow have been suggested and have compared with cretaceous global standard bio zones (Robazynsky and Caron 1985) and (Permoli Silva and Verga, 2004) Dicarinella concavata Interval Zone (Robazynsky and Caron, 1995) Dicarinella asymetrica Total range Zone(Robazynsky and Caron, 1995) Globotruncanita elevata IntervalrangeZone(Robazynsky and Caron, 1995) Globotruncana ventricosa IntervalZone (Robazynsky and Caron, 1995) Rodotruncana calcarata Total range Zone(Robazynsky and Caron, 1995) Globotruncanella havnensis Partial Range Zone (Robaszynski and Caron, 1985) Globotruncana aegyptiaca Interval Zone (Robazynsky and Caron, 1995) Gansserina gansseri Interval Zone (Robazynsky and Caron, 1995) Abathamphalus mayaroensis Total range Zone(Robazynsky and Caron, 1995) The suggested age for th.is sequence based on planktonic foraminifera is upper coniantian to upper Maestrichtian and belong to deep shelf area . Based on the morphology of planktonic foraminifera and their keei we suggest deep sea environment for these deposits.
I. Maghfouri Moghaddam
Abstract
Sedimentary setting and paleoecology of the rudist-bearing Upper Cretaceous strata were studied in three sections in Khorram abad. The sections include: Tang Shabi Khone, Cham Sangar (Tarbur Formation) and Pir Shams Eldin (upper part of Amiran Formation). The Tang- E Shabi Khone and Chamsangar ...
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Sedimentary setting and paleoecology of the rudist-bearing Upper Cretaceous strata were studied in three sections in Khorram abad. The sections include: Tang Shabi Khone, Cham Sangar (Tarbur Formation) and Pir Shams Eldin (upper part of Amiran Formation). The Tang- E Shabi Khone and Chamsangar sections are located in Zagros Trust zone while, the Pir Shams Eldin in Lorestan zone. On the basis of the recognized fossils, the three sections are assigned to the Late Cretaceous (Middle to Late Masstrichtian) and are comparable to Omphalocyclus- Loftusia Assemblage Zone. The petrography study showed that the three sections contain nine microfacies that deposited in an open marine, shoal and restricted marine that based on rudist sedimentary models, are comparable to the Inner- shelf basin prograding margin complexes (Tarbur Formation) and the low- angel open shelf margin complexes (Amiran Formation). Probably, Sepid Kuh Fault was detaching the these settings. Augmentation of entering the detrital and silica due to river injection and runoff and consequently to the eurotrophic conditions in the Tnage Shabi Khone and Pir Shams Eldin, frequency of agglutinate foraminifera were increased but in the chamsangar section due to oligotraphy condition , frequency of hyaline foraminifera is increased. Distribution of the foraminifera and algae indicated that the Tarbur Formation is deposited in a photic zone though, some parts of the carbonates of the Amiran Formation were deposited in a aphotic zone.
