Document Type : Original Research Paper
Authors
1 Associate Professor, Islamic Azad University, Tehran North Branch; Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran.
2 Associate Professor, Islamic Azad University, Islamshahr Branch; Research Institute for Earth Sciences, Geological Survey of Iran, Tehran, Iran
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 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.
Keywords
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