Economic Geology
Mohammad Jafar Kupayi; Ebrahim Rastad; Saeed Madanipour; Sajjad Maghfouri
Abstract
Cretaceous sedimentary sequence in the Yazdan area is consisting of four rock units as, from the old to the new, clastic-carbonate (Kc), carbonate (Kl), Shale and marl (Km) sequences, and Sandy limestone and sandstone (Kls). The Kls unit is host of ore mineralization in the study area and formed from ...
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Cretaceous sedimentary sequence in the Yazdan area is consisting of four rock units as, from the old to the new, clastic-carbonate (Kc), carbonate (Kl), Shale and marl (Km) sequences, and Sandy limestone and sandstone (Kls). The Kls unit is host of ore mineralization in the study area and formed from four members. Ore mineralization in the Yazdan Deposit has occurred as a stratiform horizon in the sandstone units of the third member. Texture and structures studies, shown three ore facies with elemental zonation in the Yazdan Deposit. These ore facies includes, stringer zone, massive ore facies and the bedded ore facies. This ore facies formed from laminated and layered sulfide and sulfate minerals. Fluid inclusions studies represents 255-136 ° C of homogeneity temperature with an average temperature of 189 ° C. Also, the salinity of fluid inclusions was calculated to be between 14.6-6% NaCl (on average, 9.5% NaCl). Geological evidence, host rocks type, texture and structures, existence of ore facies with elemental zoning as well as fluid inclusion investigations indicate the Yazdan Deposit has most similarity with Sedex-type deposit.
F Sarjoughian; A Kananian; A Esna-Ashari; J Ahmadian
Abstract
The Kuh-e Dom intrusion with calc-alkaline nature, in the northeast of Ardestan is located in the central part of the Urumieh-Dokhtar Magmatic Arc and includes the felsic and intermediate-mafic units. The felsic unit consists of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite, whereas ...
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The Kuh-e Dom intrusion with calc-alkaline nature, in the northeast of Ardestan is located in the central part of the Urumieh-Dokhtar Magmatic Arc and includes the felsic and intermediate-mafic units. The felsic unit consists of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite, whereas the intermediate-basic rocks comprise gabbro, diorite, quartz diorite, monzodiorite and monzonite. The acidic dykes intruded this intrusion and its surrounding rocks. The various mafic microgranular enclaves of dioritic, quartz dioritic, monzodioritic and quartz monzodioritic composition exposed in the acidic rocks. The zircon U-Pb dating by the LA-ICP-MS method indicates that the ages of the felsic rocks, intermediate-mafic rocks, acidic dikes and enclaves are 51.1±0.4 Ma, 53.9±0.4 Ma, 49.95±0.64 Ma and 50.3±0.8 Ma respectively. These ages are in good agreement with the lower-middle Eocene age of the intrusive body, which is simultaneous with subduction of the Neotethys oceanic crust underneath the Central Iran. This result is in agreement with the previous geochemical result.
F Sarjoughian; A Kananian; J Ahmadian
Abstract
The alkali feldspars and plagioclases in the Kuh-e Dom intrusive rocks show compositionally and microtexturally zoning structure. The feldspar crystals in the various lithologies such as granite- granodiorite samples, diorite- gabbro samples and relatively high frequency microgranular mafic enclaves ...
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The alkali feldspars and plagioclases in the Kuh-e Dom intrusive rocks show compositionally and microtexturally zoning structure. The feldspar crystals in the various lithologies such as granite- granodiorite samples, diorite- gabbro samples and relatively high frequency microgranular mafic enclaves existing in the acidic intrusion were analyzed using electron microprobe. The results of the microprobe analysis in the acidic, basic- intermediate rocks and enclaves indicated the normal and reverse zoning in the samples. The chemical compositions of plagioclases ranges from albite (An 9.4) in the rim to labradorite (An: 50.6) in the core for acidic rocks, and from andesine (An: 30.5) in the rim to labradorite (An: 56.4) in the core for the basic- intermediate rocks, and from oligoclase (An: 19.8) to labradorite (An: 66.5) in the enclaves. The frequently of rare elements such as Ba, Sr, Fe and Mg in the feldspars show various and oscillatory patterns. The oscillatory pattern of the major and minor elements from core to rim in the feldspar crystals suggests an effective role of magma mixing phenomena in forming of the Kuh-e Dom intrusion.
M. Lotfi; S.F Sadjadi AleHashem; M. H. Emami
Abstract
Boznein manganese deposit is located in 25 km south-southwest of Ardestan, part of Urmiyeh-Dokhtar magmatic belt. The main units in the studied area are volcanic-pyroclastic sequences & intrusive bodies of middle Eocene-lower Oligocene. Porphyroid rhyolitic dome (upper Eocene-lower Oligocene) is ...
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Boznein manganese deposit is located in 25 km south-southwest of Ardestan, part of Urmiyeh-Dokhtar magmatic belt. The main units in the studied area are volcanic-pyroclastic sequences & intrusive bodies of middle Eocene-lower Oligocene. Porphyroid rhyolitic dome (upper Eocene-lower Oligocene) is host rock of economic Mn mineralization. The mineralization occurred as veins trending mostly NE-SW of interrupted total length of 1.5 m width at two active mines of 1 and 2. Exploitable reserve of the mine is estimated to be 60,000 tons of an average grade of 50.18% MnO. The main Mn ore minerals including braunite, bixbyite, hausmanite, spessartine rhodochrosite, manganite, pyrolusite, psillomelane, cryptomelane that by As and Cu minerals. Ores shows massive, microcrystalline, euhedral, colloform, colloidal, bubble form, acicular, tabular, veinlet, breccia, stockwork and residual textures. In base of ore samples geochemical characteristics and comparison with studied Mn types and deposits, indicate a good match with hydrothermal Mn-deposits. In base of mineralization form, host rock petrography and age, ore texture and structure, mineralogy, geochemical characteristics and genetic controlling factors, the Boznein deposit shows similarities with epithermal Mn-deposit. Non-economic syngenetic Mn-mineralization in the unit older than rhyolitic dome can be considered as the possible source of the Mn. Contemporaneous with intrusion rhyolitic dome, Mn concentration led to high grade epigenetic Mn vein in surrounding porphyroid rhyolitic dome.
A. Kananian; F. Sarjoughian; J. Ahmadian
Abstract
The Kuh-e Dom intrusion is a small section of Upper Eocene Urumieh- Dokhtar magmatic belt in the Central Iran tectonic zone. This intrusion is composed of two separate phases which include an acidic and intermediate- mafic units. The acidic rocks consist of monzogranite, granodiorite, quartz monzonite ...
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The Kuh-e Dom intrusion is a small section of Upper Eocene Urumieh- Dokhtar magmatic belt in the Central Iran tectonic zone. This intrusion is composed of two separate phases which include an acidic and intermediate- mafic units. The acidic rocks consist of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite whereas the intermediate-mafic rocks comprise gabbro, diorite, quartz diorite, monzodiorite and monzonite. Mafic microgranular enclaves of dioritic, quartz dioritic, monzodioritic and quartz monzodioritic composition are common in the acidic rocks. Based on geochemical data, magma mixing along with fractional crystallization has important role in evolution of the plutonic rocks. Also, Kuh-e Dom intrusive rocks have low TiO2, P2O5 and Nb/Zr ratio which are characteristics of active continental margin. The isotopic signature of plutonic rocks is not exactly like those of mantle- or crustal-derived magma, but these rocks have some features commonly found both in the crustal and mantlic sources so that the enclaves tend to illustrate mantlic composition and the acidic rocks tend to show crustal composition, but the intermediate- mafic rocks are in the range from acidic rocks to enclaves. This result along with field and petrographical studies indicate that magma mixing/magma or mingling processes may play an important role in evolution of the intrusion. The upper mantle magma forming the microgranular enclaves, after emplacement in the crust may lead to partial melting of lower crust and because of magma mixing between crustal and mantlic melts, the mafic to intermediate rocks may form.
