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Interaction between tectonics, plutonism and mineralization of the Duna Pb-Ba ore deposit regarding fluid inclusion study (Central Alborz, Iran)

Sadeghi Alireza, Asiabar Saeid Hakimi, Nezafati Nima, Ganji Alireza, Mukherjee Soumyajit

Acta Geologica Polonica

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2023

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Vol. 73, no. 2

201--222

EN

This article discusses the impacts of overprinting of tectonic and plutonic events on the mineralization of the Duna Pb-Ba ore deposit, according to geologic settings and fluid inclusion studies. The Duna carbonate-hosted deposit contains a significant amount of Ag (18.9–264.3 ppm ), Cu (77–41600 ppm), Sb (32.7–11000 ppm), Sr (63.5–15100 ppm), and Fluid inclusions with 7.34–23.65 wt.% NaCl equivalent. The homogenization temperature of about 110–285°C, as well as the paragenesis of the minerals shows a difference compared with other Pb-Zn deposits such as the Irish-type and MVT. The ore mineralization in the Duna mine occurred as stratabound, open space-filling, and along the brecciated fault zones. The concordant (stratabound) type of mineralization, with salinity and homogenization temperature of 18.54 to 23.65 wt.% NaCl equivalent, and 113°C to 165°C respectively, is usually typical of MVT-ore deposits, which in this area evolved during the Early Cimmerian orogeny and was later interrupted by mineralization along younger brecciated fault zones with salinity and homogenization temperature of 7.34 to 23.65 wt.% NaCl equivalent, and 113°C to 285°C respectively. This discordant mineralization, which occurred along the faults, formed by the end of the Late Cretaceous and during the Cenozoic as a result of the intrusion of a plutonic mass, and is comparable to the Irish-type ore deposits.

2

Temporal variations of seismicity parameters in the Central Alborz, Iran

Agh-Atabai M., Mirabedini M.S.

Acta Geophysica

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2014

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Vol. 62, no. 3

486--504

EN

Temporal changes of b-value, fractal (correlation) dimensions of epicenters (De) and occurrence time of earthquakes (Dt) and relations between these parameters were calculated to investigate precursory changes before 28May 2004, Baladeh-Kojour earthquake (Mw = 6.3) of Central Alborz, Iran. 2086 events with MN ≥ 1.7 were selected for our analyses. A wide range of variation was seen in these parameters: b-value ~ 0.61.11, De ~ 0.97-1.64, and Dt ~ 0.13-0.93. The results showed decreases in all fractal parameters several months before the main shock. This decrease, which might have arisen due to clusters of events occurred between 2002-2003, was followed by a systematic increase, corresponding to the increased level of low-magnitude seismicity. It seems that changes in fractal parameters may be precursors of Baladeh-Kojour earthquake which was caused by seismic activation and quiescence. Furthermore, a positive correlation between b-value and De was detected before the main shock (De = 0.87 + 0.7b) and during aftershock sequences (De = 2b ± 0.09), which was further on changed to a negative one (De = 2.56 – 1.32b).

3

Early Carboniferous chondrichthyans from the Mobarak Formation, Central Alborz Mountains, Iran

Habibi T., Ginter M.

Acta Geologica Polonica

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2011

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Vol. 61, no. 1

27-34

EN

Well exposed Tournaisian, mainly carbonate, rocks of the Mobarak Formation in the area of Shahmirzad village, Central Alborz, Iran, yielded almost 200 chondrichthyan teeth and scales, associated with numerous actinopterygian microremains. Ten different taxa were recognised among the chondrichthyan teeth, of which the most abundant are those representing Euselachii (Protacrodus and Lissodus), Symmoriiformes (Denaea), and Phoebodontiformes (Thrinacodus). The high relative abundance of protacrodont crushing teeth, but lack of holocephalian dental elements suggest that the sediments forming the Shahmirzad section were deposited in a shallow shelf environment, but probably not on a carbonate platform.