M Hajibahrami; N Taghipour; G Ghorbani
Abstract
The Hamyerd iron deposit is located in the northeast of Semnan in the boundary of the southern Alborz and Central Iran structural zones. A sub-volcanic body of monzonite and monzodiorite composition intruded limestone and pyroclastic rocks (equivalent to the middle Eocene Karaj formation). The iron mineralization ...
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The Hamyerd iron deposit is located in the northeast of Semnan in the boundary of the southern Alborz and Central Iran structural zones. A sub-volcanic body of monzonite and monzodiorite composition intruded limestone and pyroclastic rocks (equivalent to the middle Eocene Karaj formation). The iron mineralization occurred at the contact between intrusive bodies and these sedimentary rocks. The extensive hematite content along with minor amounts of magnetite, goetite, limonite, pyrite, dolomite, barite and calcite are important characteristics of the Hamyerd ore deposit. Mineralization occurred as veins and also hematite lenses with minor magnetite content. Fluid inclusion and stable isotope (S, C and O) studies were integrated to explore the Hamyerd iron ore genesis. Petrographic studies display five types of fluid inclusions in quartz and 4 types in barite. Fluid inclusions in quartz include single-phase liquid, single-phase gas, two-phase liquid-rich, two-phase gas-rich, and three-phase (liquid-solid-gas) inclusions. Three-phase liquid-solid-gas inclusions were not detected in barite. Microtermometry studies in two-phase liquid-rich inclusions revealed homogenization temperatures of 200-250 ˚C and 100-200 ˚C, and salinities of 10-20 and 0.5-5 wt% NaCl equivalent for quartz and barite fluid inclusions, respectively. Microthermometry of halite-bearing three-phase fluid inclusions showed homogenization temperature from 200 to 350 ˚C and salinity from 30 to 40 wt% NaCl equivalent. δ34SCDT values of pyrites at Hamyerd iron deposit are in the range of 2.2 to 7.4‰. The isotopic values of barites range from 13.6‰ to 20.2‰ for δ34SCDT and 10.2‰ to 12.1‰ for δ18OVSMOW, respectively. The carbon and oxygen isotopic values of calcite are in the range of -3.4‰ to -4.5‰ and 17.7‰ to 19.1‰, respectively. Microthermometry of fluid inclusions and stable isotopes (S, O, C) at Hamyerd iron deposit suggested mixing of magmatic and meteoric fluids as origin of hydrothermal solutions. Mineralization in the Hamyerd iron deposit is probably similar to Fe-skarn deposits.
K Mohammadi; N Taghipour; H Mosaddegh
Abstract
Due to some environmental variations such as sea level fluctuation and the Hangenberg mass extinction event, geochemical variations of elements have occurred in the Devonian-Carboniferous transition, which some of these elements are useful indicators to display the source of sediments and the sea level ...
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Due to some environmental variations such as sea level fluctuation and the Hangenberg mass extinction event, geochemical variations of elements have occurred in the Devonian-Carboniferous transition, which some of these elements are useful indicators to display the source of sediments and the sea level changes. In this transition, Sr is one of these elements has a reverse relation with sea level changing and a direct relation with amount of sediment deposition. Trace elements such as Sr, Fe, Mn, Mg, Al, and Ca display the depositional environment conditions and their changing is affected by indoor and outdoor environmental conditions such as pH, Eh, climate, etc. This study has focused on investigation of elemental changes at the Devonian-Carboniferous boundary in the Khoshyeilagh and Mobarak Formations in the Labnesar section, North of Damghan.
The elemental changing in Brachiopoda shells and its containing sediments has the same trend as they show the fossil samples are in situ. The environmental situation of fossil organisms and their involving sediments in the study section were semi close to open sea with anoxia conditions. The black shale at D-C boundary shows LREE richer than HREE that confirmed its continental source. The variation of some elements such as Mn, Fe, Na… at D-C boundary in the Labnesar section indicates of LMC (low magnesium calcite) in the Brachiopod shells and involving sediments. The quantity variations of Mn and Sr in D-C boundary are related to sea level fluctuations. These elements are influenced by the sea level changes and impress the amount of other elements such as Fe, Al, Ti, Mg, Ca, Na, and K. The median amount of Na at the boundary indicates a moderate salinity.
Z Solaymani; N Taghipour; R Aharipour
Abstract
This study investigates the organic petrographic of the upper Triassic to Lower Jurassic Olang coal deposits. Olang area is located in 70 km of northeast Shahroud. This area is situated in Gheshlagh Olang synclinal which is a member of eastern Alborz coal basin. Microscopic studies showed that all three ...
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This study investigates the organic petrographic of the upper Triassic to Lower Jurassic Olang coal deposits. Olang area is located in 70 km of northeast Shahroud. This area is situated in Gheshlagh Olang synclinal which is a member of eastern Alborz coal basin. Microscopic studies showed that all three maceral groups of vitrinite, inertinite and liptinite presented in coal deposits of the Olang region and the vitrinite is most important maceral group in these coals. Macerals of vitrinite group include colotelinite, collodetrinite and corpogelinit that collodetrinite is the most abundant of maceral in coal deposits. All of inertinite macerals group observed in these coals which Semifusinite and fusinite are the most abundant in this group. Spornite, cutinite, resinite and lipthodetrinite macerals of liptinite group are present in the coals. Abundance of collodetrinite, presentation of fnginite and the absence of tellinite in these coals are usually thought to indicate deposition in neutral to weakly alkaline waters in an oxygen-rich environment.
