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Provenance and tectonic setting of the Middle Eocene lower Akhoreh Formation, Nain area, Central Iran, assessed using petrography and geochemistry

Salehi Mohammad Ali, Mallah Mohammed, Jafarzadeh Mahdi

Geological Quarterly

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2023

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Vol. 67, No. 2

art. no. 14

EN

The Middle Eocene Akhoreh Formation is superbly exposed in the western corner of the Central-East Iranian Microcontinent (CEIM). This formation covered the northeastern flank of the Cretaceous Nain Ophiolite Mélange (NOM) and is adjacent to the Paleogene Urmieh–Dokhtar Magmatic Arc (UDMA) formed in the southwest of the CEIM. This terrigenous succession is composed of a thin basal conglomerate followed by mostly pink to purple sandstones alternating with shales. The clast composition and clast imbrication of the conglomerates show local source areas towards the north-north-east. Modal components of lower Akhoreh Formation sandstones reveals immature lithic arkose (Q8F48L44) and feldspathic litharenite (Q8F44L48) sandstones that are rich in mafic and ultramafic igneous and volcanic rock fragments. Mafic to ultramafic source rocks are also indicated by geochemical data (enrichment of Mg, Cr and Ni and Cr/V) in the sandstone and shale samples analyzed. However, geochemical data suggests an intermediate igneous rock origin for the shale samples studied, most likely from the nearby continental arc. Based on petrographic data, these sandstones have characteristics of a transitional to undissected arc tectonic setting. Geochemical discrimination diagrams using major and trace elements indicate an oceanic island arc tectonic setting for the lower Akhoreh Formation sandstones and shales, probably due to a predominance of ophiolitic source rocks. Furthermore, the chemical index of alteration and modal analysis indicate a weak to moderate degree of chemical weathering with arid climatic conditions in the source area. The exhumed NOM, together with the UDMA in the southwest, were dominant sources of sediment to the lower Akhoreh Formation, that lay to the northeast in a local retroarc basin of the Central Iranian Microplate, during the Middle Eocene.

2

A Bajocian (Middle Jurassic) marine gastropod assemblage from the Badamu Formation, Central Iran

Ferraris M., Binazadeh T., Kaim A.

Annales Societatis Geologorum Poloniae

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2016

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Vol. 86, No. 3

329--340

EN

Nine species of gastropods are reported from the Bajocian (Middle Jurassic) part of the Badamu Formation of Central Iran. This is the first report of a gastropod assemblage of this age from the shelves of the Kimmerian Continent. Seven species belong to the Vetigastropoda and two to the Caenogastropoda. Two new species, the pleurotomariid Bathrotomaria iranica sp. nov. and the eucyclid Eucycloidea badamuensis sp. nov., are described. The remaining species are left in open nomenclature owing to poor preservation. The composition of the gastropod association is strongly reminiscent of other Tethyan gastropod faunas, in particular those from the southern shores of the Tethys (India and Arabia) and from southern Europe. This indicates a relatively uniform distribution of gastropod faunas along the Middle Jurassic shores of the western Tethys.

3

Application of RQD-number and RQD-volume multifractal modelling to delineate rock mass characterisation in Kahang Cu-Mo porphyry deposit, central Iran

Yasrebi A. B., Wetherelt A., Foster P. J., Afzal P., Coggan J., Ahangaran D. K.

Archives of Mining Sciences

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2013

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Vol. 58, no. 4

1023--1035

EN

Identification of rock mass properties in terms of Rock Quality Designation (RQD) plays a significant role in mine planning and design. This study aims to separate the rock mass characterisation based on RQD data analysed from 48 boreholes in Kahang Cu-Mo porphyry deposit situated in the central Iran utilising RQD-Volume (RQD-V) and RQD-Number (RQD-N) fractal models. The log-log plots for RQD-V and RQD-N models show four rock mass populations defined by RQD thresholds of 3.55, 25.12 and 89.12% and 10.47, 41.68 and 83.17% respectively which represent very poor, poor, good and excellent rocks based on Deere and Miller rock classification. The RQD-V and RQD-N models indicate that the excellent rocks are situated in the NW and central parts of this deposit however, the good rocks are located in the most parts of the deposit. The results of validation of the fractal models with the RQD block model show that the RQD-N fractal model of excellent rock quality is better than the RQD-V fractal model of the same rock quality. Correlation between results of the fractal and the geological models illustrates that the excellent rocks are associated with porphyric quartz diorite (PQD) units. The results reveal that there is a multifractal nature in rock characterisation with respect to RQD for the Kahang deposit. The proposed fractal model can be intended for the better understanding of the rock quality for purpose of determination of the final pit slope.

PL

Identyfikacja właściwości górotworu odgrywa zasadniczą rolę w planowaniu wydobycia i projektowaniu kopalni. Praca niniejsza ma na celu określenie charakterystyki górotworu w oparciu o dane o jakości skał zebrane na podstawie próbek uzyskanych z 48 odwiertów wykonanych w złożu porfiru Cu-Mo w Kahang, zalegającym w środkowym Iranie przy użyciu modeli fraktalnych RQD-V - Rock Quality Determination-Volume [Określenie jakości skał-objętość]) i RQD-N (Rock Quality Determination-Number [Określenie jakości skał-liczba]). Wykresy logarytmiczne wykonane dla modeli RQD-V i RQD-N wykazują istnienie czterech populacji warstw górotworu, określonych na podstawie parametrów progowych: 3.55; 25.12; 89.12% oraz 10.47; 41.68 i 83.17%, odpowiadającym kolejno stopniom jakości: bardzo słaby, słaby, dobry i bardzo dobry, zgodnie z klasyfikacją skał Deere i Millera. Wyniki uzyskane przy zastosowaniu modeli RQD-V i RQD-N wskazują, że najlepsze skały zalegają w północno- zachodniej i centralnej części złoża, z kolei dobrej jakości skały znaleźć można w obrębie całego złoża. Walidacja modeli fraktalnych w oparciu o model blokowy (RQD block model) wskazuje, że model RQD-N dla bardzo dobrej jakości skał jest skuteczniejszy niż model RQD-V dla tej samej jakości skał. Wysoki stopień korelacji pomiędzy wynikami uzyskanymi w oparciu o modele fraktalne i geologiczne pokazuje, że najwyższej jakości skały związane są z obecnością porfirowego diorytu kwarcowego. Badanie wykazuje fraktalną naturę charakterystyki jakości skał w złożu Kahang. Zaproponowany model fraktalny wykorzystać można do lepszego poznania zagadnienia jakości skał w celu obliczenia nachylenia wyrobiska.

4

Prospecting of Au and Cu bearing targets by exploration data combination in southern part of Dalli Cu-Au porphyry deposit, central Iran

Yousefifar S., Khakzad A., Asadi Harooni H., Karami J., Jafari M. R., Vosoughi Abedin M.

Archives of Mining Sciences

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2011

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Vol. 56, no 1

21-34

EN

Dali copper-gold porphyry deposit is situated in margin of the Urmieh-Dokhtar magmatic belt and the Sanandaj-Sirjan zone, central Iran. In this paper, southern part of the Dali deposit has been investigated in order to prospect the potential copper and gold-bearing target areas. The survey layers consist of the lithologic units, alteration, geophysical and geochemical data, tectonics, and copper mineralization. As a correct decision can have a considerable effect on next exploration stages, so in this research efforts have been made to make use of new combination methods including weighting method of layers, fuzzy logic method, and the analytical hierarchy process. These three methods support and complement each other and have revealed highly potential copper and gold mineralization areas. According to these researching, Analytical Hierarchy Process is the better than others for combining the exploration data in this area. The investigations concluded field evidences of outcrops, mineralization and also sampling of 7 trenches carried out in the study area confirm this substance. Finally, an area (about 0.2 km2) has been suggested for next exploration stage and drilling.

PL

Złoże porfirów zawierających złoto i miedź leży na granicy pasa magmatycznego Urmieh-Dokhtar i strefy Sanadai-Sirian, w środkowym Iranie. Zbadano część południową złoża Dali w celu poszukiwania formacji złoto-miedzionośnych. Dane do badania obejmowały dane o warstwach i pokładów skał, alteracji, dane geofizyczne i geochemiczne, dane tektoniczne oraz informacje o mineralizacji miedzi. Ponieważ podjecie właściwych decyzji będzie mieć poważny wpływ na dalszy przebieg prac poszukiwawczych, badacze dołożyli wszelkich starań by odpowiednio zastosować nową metodę łączenia danych, obejmującą metody ważone, metody logiki rozmytej oraz podejście AHP (Analytic Hierarchy Process). Te trzy metody wzajemnie się uzupełniają i wykazały wysoką skuteczność w badaniu stref mineralizacji złota i miedzi. Wyniki badań wykazały, że podejście AHP jest korzystniejsze niż pozostałe, umożliwiając skuteczną kombinację danych poszukiwawczych. W końcowym etapie badań zaprezentowano wyniki polowe uzyskane dla wydobycia, mineralizacji, i próbkowania 7 wyrobisk. Wyniki te potwierdzają przyjęte założenia badawcze. Wskazano obszar o powierzchni 0.2 km2 dla prowadzenia dalszych prac poszukiwawczych i wiertniczych.

5

Visean and Bashkirian ammonoids from Central Iran

Hairapetian V., Korn D., Bahrami A.

Acta Geologica Polonica

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2006

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Vol. 56, no. 3

229-240

EN

Two successions of Carboniferous sedimentary rocks in Central Iran yielded ammonoid assemblages from one horizon each. In the Ramsheh section, a siltstone with Neoglyphioceras yazdii n. sp. and Dombarites can be assigned to the latest Visean. The assemblage from the Shesh Angosht Mountain is more diverse with species of the genera Proshumardites, Eumorphoceras, Homoceras, Glaphyrites, Syngastrioceras, and Dombarocanites. This is the first time that the co-occurrence of the genera Eumorphoceras and Homoceras has been recorded. This fauna contains elements of the South Urals and Central Asian occurrences of Bashkirian ammonoids and suggests close palaeobiogeographic relationships.

6

First record of Jurassic (Toarcian - Bajocian) ammonites from the northern Lut Block, east-central Iran

Seyed-Emami K., Fürsich F. T., Wilmsen M., Schairer G., Majidifard M. R.

Acta Geologica Polonica

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2004

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Vol. 54, no. 1

77--94

EN

A very thick and lithologically rather unusual marine sedimentary succession is described from the Kuh-e-Shisui area, northwestern Lut Block (east-central Iran). It contains a low diversity ammonite fauna comprising the families Dactylioceratidae, Hildoceratidae, Graphoceratidae, Hammatoceratidae, and Sonniniidae, which are concetrated in several levels, indicating the Lower-Lower Middle Toarcian, Upper Toarcian, Aalenian, and Lower Bajocian. The ammonite fauna, consisting of 21 taxa, descibed for the first time from the Lut Block, corresponds to that of the Badamu Formation of the Kerman-Ravar region (southern Tabas Block, to the west of the Lut Block), but is far less diverse. An exception is the occurrence of Lower Toarcian Harpoceratinae and Hildoceratinae, which hitherto have not been recorded from east-central Iran. The ammonite fauna is closely related to that of northwestern Europe.