Articles
Bulletin of Geosciences (12141119)100(2)pp. 187-211
The Persian Gulf is the remains of an ancient seaway that connected the Indo–Pacific Region to the Mediterranean– Atlantic Region and the Paratethys Ocean. The Mishan Formation in Zagros Basin, Qeshm Island (Persian Gulf), and the Miocene strata of Minab Province in the Makran Basin, southern Iran, have yielded a rich fauna of bryozoans. A total of 22 species are here identified from four sections of in the Qeshm and Minab areas, including 13 species belonging to the order Cyclostomata, and 9 species belonging to the order Cheilostomata. The distribution and occurrences of the bryozoan fauna show the studied intervals were deposited during Early to Middle Miocene while the Iranian Seaways was connected to the Indo–Pacific Region from southeast, and to Mediterranean–Atlantic Region from northwest. Also, the most similar occurrences of the species described are with bryozoan faunas of the Paratethys Ocean. • Key words: Bryozoa, Miocene, Iran, taxonomy. © 2025, Czech Geological Survey. All rights reserved.
Boletin de la Sociedad Geologica Mexicana (14053322)77(1)
The present study investigates the pectinid bivalve record characterizing the Mio-Pliocene of Mishan and Aghjari formations in Qeshm Island of the Persian Gulf and Minab region of Makran Basin (Hormozgan Province). Thick-bedded deposits of highly accumulated levels of epifaunal free-lying pectinids were investigated in terms of paleoecology and taphonomy. Eight species of the family Pectinidae (Bivalvia) and nine species of Ostracoda are reported from the Direstan rural area, Qeshm Island, Persian Gulf, Southern Iran. Most bivalve shells display extreme taphonomic features such as breakage, bioerosion, encrustation, disarticulation, and abrasion. Encrusting Cheilostomata bryozoans, as well as polycheata worms, encrust pectinid valves; Langian (Middle Miocene) Cheilostomata are identified as Microporella berningi. The studied pectinids are represented by the following species: Pecten aff. rotundatus, Pecten cf. subarcuatus, Flabellipecten piramidesensis, Argopecten gratus, Chlamys varia, Chlamys multistriata, C. actinodes, and Talochlamys articulata. Ostracoda were also collected from two more outcrops in Qeshm Island (Kendaloo and Star Valley) and one outcrop of Minab region (Bemani section). The studied ostracods are: Alocopocythere kendengensis, Actinocythereis iraqensis, Loxoconcha hamrinensis, Neomonoceratina iniqua, Bairdoppilata triangulata, Bairdia rafidainensis, Hermanites transversicoststs, Costa tricostata, and Cytherelloidea hamrinensis. © (2025), (Boletin de la Sociedad Geologica Mexicana). All rights reserved.
Rajabi A.,
Mahmoodi P.,
Alfonso P.,
Canet C.,
Andrew C.,
Azhdari S.,
Rezaei S.,
Alaminia, Z.,
Tamarzadeh S.,
Yarmohammadi A.,
Khan Mohammadi G.,
Saeidi R.,
Sattari, E.,
Bahrami, A.,
Vaziri moghaddam, H.,
Taheri a., A. Minerals (2075163X)(7)pp. 1-25
Iran hosts more than 350 Precambrian to Cenozoic sediment-hosted Zn-Pb±Ba and barite-sulfide deposits, including shale-hosted massive sulfide (SHMS, also called SEDEX) and Irish-type and Mississippi Valley-type (MVT) mineralization, and barite is a common mineral in these deposits. In the SHMS deposits, barite is typically found as fine-grained disseminations in thin laminae. In these deposits, the sulfide laminae often occur as diagenetic replacements and as bands containing authigenic and diagenetic barite and pyrite framboids. In the Irish-type Zn-Pb-Ba and stratabound barite-sulfide deposits, barite exhibits various textures, including fine-grained disseminated barite, banded zebra textures, veins, and massive barite lenses. In some of the giant Irish-type deposits, as well as in the stratabound barite-sulfide mineralization, the main stratabound sulfide ore is developed within a barite envelope and is characterized by the replacement of barite and pyrite by chalcopyrite, galena, and sphalerite. In the MVT deposits, the formation of barite is often related to dolomitization, and sulfide mineralization involves the replacement of the dolomitized carbonate rocks, as well as associated barite. Fluid inclusion studies on the Irish-type deposits indicate that the temperatures and salinities of the sulfide-forming fluids are higher compared to those of the barite-forming fluids. Fluid inclusion analyses of coarse-grained barites from Irish and MVT deposits reveal their hydrothermal origin. The δ3⁴S values of sulfide minerals (pyrite, sphalerite, and galena) in Irish-type deposits exhibit a broad range of low values (mostly −28 to +5‰), primarily revealing a process of bacterial sulfate reduction (BSR). However, the textures (replacement, colloform, and banded) and more positive sulfur isotope values (+1 to +36‰) in the SHMS Zn-Pb deposits suggest that bacterial sulfate reduction (BSR) plays a less significant role. We suggest that thermochemical sulfate reduction (TSR) connected to the direct replacement of barite plays a more relevant role in providing sulfur for the sulfide mineralization in the SHMS, barite-sulfide, and MVT deposits. Based on the textual evidence, sulfur isotopic data, and fluid inclusion studies, barite has been identified as a key controller for the subsequent Zn-Pb mineralization by providing a suitable host and significant sulfur contribution in the sediment-hosted Zn-Pb and stratabound barite-sulfide deposits. This implies that diagenetic barite might be a precursor to all types of sediment-hosted Zn-Pb mineralization. © 2024 by the authors.
