فصلنامه زمین شناسی اقتصادی
سال شانزدهم شماره 2 (پیاپی 41، تابستان 1403)

Kourcheshmeh Pb-Zn-Cu deposit is located 40 km southwest of Takestan (Qazvin province) and west of the Mardabad-Bouinzahra volcanic belt. The mineralization occurred as Pb-Zn-Cu-bearing quartz veins hosted by early-middle Eocene tuff and lava strata and show a close spatial relationship with the middle Eocene pyroxene quartz monzodiorite body. The main ore vein ranges from 70 to 200 meters long, and 0.5 to 2 meters thick. Pyrite, chalcopyrite, galena, sphalerite, and tennantite-tetrahedrite, accompanied by minor pyrolusite and psilomelane, are the main ore minerals; quartz, calcite, siderite, barite, and sericite-illite are gangue minerals. Goethite, cerussite, smithsonite, malachite, and covellite are formed by supergene processes. The ore minerals formed as disseminated, vein-veinlets, brecciated, comb, crustiform, colloform, plumose, and vug infill textures. Six stages of mineralization can be distinguished at Kourcheshmeh, where Pb-Zn-Cu mineralization occurred as quartz-pyrite-chalcopyrite-galena-sphalerite ± tennantite-tetrahedrite veins and breccias in the second stage. Wall-rock alteration comprises silicification, intermediate argillic, carbonate, and propylitic alteration. Chondrite–normalized trace elements and REE patterns of ore samples, pyroxene quartz monzodiorite body, and fresh host acidic crystal tuff are comparable. This specifies that alteration and leaching of elements from the host volcanic rocks are involved in mineralization. Features of the Kourcheshmeh Pb-Zn-Cu deposit are similar to the intermediate-sulfidation type of epithermal deposits.

Manto-type copper mines occur in the Bardaskan-Doruneh copper belt.  On the basis of structural sedimentary division of Iran, this belt is located in the northeastern part of the Central Iran.  At the southern border of this belt, the Yazd structural block and in the north of it is the Sabzevar subzone. The important regional structures of the region are Doruneh and Taknar faults. The majority of the units in this belt are Tertiary volcanic rocks that is associated with some sedimentary units, also some intrusive units are sometimes visible in the form of dyke and stock structures. The main host-rock of mineralization is conglomerate, which is different in grain size, clasts and cement. The most common sulphide mineral is chalcocite and the most important copper carbonates are malachite and azurite. The intense alteration is not observed in the region, and the chloritic alteration is partial, and the alteration of Fe-Oxide, zeolite, calcite, and silica is just observed locally. Mineral solution is reduced and poor in iron and silica.

The Godar-e-Siah Eocene monzodiorite stock is located in the southwest of the Jandaq area (NE of Isfahan) and northwest of the Central-East Iranian Microcontinent (CEIM). The main minerals in these monzodiorites are plagioclase, K-feldspar, clinopyroxene, phlogopite, and garnet, which are set in a fine-grained groundmass of feldspars. The main textures are granular, porphyritic, and poikilitic. In some cases, these rocks contain euhedral to subhedral garnet crystals with inclusions of the igneous clinopyroxene and groundmass minerals including feldspar and graphite. These garnets exhibit Ti-andradite and Ca-melanite composition from the solid solution series of andradite-grossular. The chemical zoning patterns of the studied garnets confirm that these garnets have a non-magmatic origin and metamorphic nature. In the investigated monzodiorites, the presence of euhedral garnet crystals with inclusions of igneous clinopyroxenes metasomatic scapolite, and metasomatic phlogopite shows that these garnets are of metasomatic origin, which formed due to the alteration of igneous clinopyroxenes. All geochemical and petrographic evidences from the studied garnets indicate that they have formed as a result of the intrusion of Eocene monzodiotites into the carboniferous limestones (or dolomites), leading to the creation of endoskarn or reactions skarn that can be distinguished at the millimetric scale in microscopic studies.

In the western boundary region of Central Iran with Sanandaj-Sirjan, considering the widespread carbonate units in the northeastern Isfahan area, the barite deposits have considerable potential. The Komsheche barite, hosted in the Middle Triassic Shotori dolomite Formation, is the most active mine in the region. Barite mineralization has occurred in two styles, banded-layered and veined-brecciated. Fluid inclusions in the bedded barite homogenize at temperatures from 78 to 122 ºC, with salinity between 10.9 to 17.0 wt.% eq. NaCl, while the homogenization temperature for two-phase inclusions of the second type barite is between 130 to 187 ºC and associated halite-bearing tri-phase inclusions range from 192 to 210 ºC, with an average salinity of 14.3 and 36.6 wt.% eq. NaCl, respectively. The δ34S values of the samples range from 18.40 to 26.34 per mil CDT, and their δ18O values range from 8.9 to 14.7 per mil SMOW. Based on conducted studies, ore-forming fluids were formed in an open and near-bottom seawater system during the early diagenetic stage. The heavy isotope values related to pore water are locked in a closed system during the final stages of diagenetic. Sedimentary type, associated minerals, REE composition, finding of fluid inclusion and isotope reveal that Komsheche barite has the most similarity to diagenetic/cold-seep types of marine barites.

Anambra and Gongola basins are part of the sedimentary inland basins in Nigeria characterized by fossil fuels and in response to its present energy problem, Nigeria has shifted its power generating focus to coal. The studied coals were obtained from two localities, namely Ankpa and Maiganga in Kogi and Gombe States, respectively. The coals were investigated to determine its quality in terms of use and resource potential. The coals were analyzed by proximate, ultimate, elemental, mineralogy and scanning electron microscopy-energy dispersive spectrometry analyses. The objectives of the study are to determine the coals cokability, rank, paleoenvironments, hydrocarbon potential, and slagging tendency. The average values of moisture content, ash, volatile matter, and fixed carbon are 5.54%, 16.42%, 48.45%, and 30.71%, respectively, for Ankpa coals, while Maiganga recorded 10.68%, 8.60%, 44.33%, and 36.41%, indicating high volatile sub-bituminous non-coking coals that are optimum for combustion and electric power generation. The Van Krevelen plot based on the H/C vs. O/C showed Type IV kerogen. The XRD results, correlation plots, and Detrital Authigenic Index (DAI) values of 7.49 and 13.49 in Ankpa and Maiganga coals, respectively, indicated that Ankpa coals are enriched in authigenic minerals like quartz, pyrite, and calcite, while kaolinite and quartz were probable detrital minerals in the Maiganga coals. The agglomeration of the coals deduced by Base/Acid (B/A), Silicon ratio (G), Silica/Alumina (S/A), Iron/Calcium (I/C), Carbon/Hydrogen (C/H), and Fixed Carbon/Volatile matter (FC/V) showed weak–medium-strong for the Ankpa coals and strong for Maiganga coals.

The Kuh-e-Esfand copper deposit is located in the southernmost part of the Urmia-Dokhtar magmatic belt. The Oligocene-Miocene intrusive bodies, ranging from diorite to quartz diorite and granodiorite, are emplaced within the Eocene volcanic complex. Based on the classification of veins- veinlets, the main mineralization stage consists of quartz pyrite chalcopyrite associated with potassic alteration. Based on petrographic studies, fluid inclusions in quartz minerals are categorized into three main groups and seven subgroups: 1- Vapor-rich fluid inclusions comprising single-phase vapor inclusions (V), vapor-rich two-phase inclusions (VL), and vapor-rich inclusions with a opaque phase (VLS), 2- Liquid-rich fluid inclusions including liquid-rich two-phase inclusions (LV) and liquid-rich inclusions with a opaque phase (LVS) and 3- Saline fluid inclusions consisting of simple brine three-phase inclusions (LVH), and multi-phase brine inclusions (LVHS) containing solid phases of halite± hematite± anhydrite± sylvite± chalcopyrite. The multi-phase saline inclusions with high temperature and salinity (358-598°C and 42-70 wt.% NaCl equivalent) of magmatic origin are the primary fluid inclusions forming the deposit. The two-phase liquid-rich inclusions with lower temperature and salinity (290-490°C and 11-20 wt.% NaCl equivalent) of magmatic-meteoric origin are related to the final stages of hydrothermal fluid circulation and mixing with lower salinity fluids. The temperature decrease due to secondary boiling and mixing of magmatic and meteoric fluids led to the instability of the chloride complex carrying copper and subsequent mineralization under favorable conditions.