L Salehi; I Rasa; S Alirezaei; A Kazemi Mehrnia
Abstract
The Madan Bozorg deposit is located in the Abbas Abad mining district, about 130 km east of Shahroud. The area is covered by a NE-SW trending belt of intermediate-mafic lava flows and pyroclastic materials, as well as interlayered sedimentary rocks. Eight copper deposits have been identified in the district. ...
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The Madan Bozorg deposit is located in the Abbas Abad mining district, about 130 km east of Shahroud. The area is covered by a NE-SW trending belt of intermediate-mafic lava flows and pyroclastic materials, as well as interlayered sedimentary rocks. Eight copper deposits have been identified in the district. Based on the chemistry, the volcanic rocks can be classified as trachyandesite, trachyandesitic basalt and trachybasalt; the rocks display high potassium calc-alkaline to shoshonitic affinities and bear geochemical attributes characteristic of continental arc settings. The Madan Bozorg deposit is hosted in trachyandesite with porphyritic to megaporphyritic, glomeroporphyritic and amygdaloidal textures. Based on field observations, microscopic studies, Raman spectroscopy and XRD results, two types of alteration, regional and local, can be distinguished. The regional or background alteration, is comparable to a propylitic assemblage and occurs in mineralized and non- mineralized volcanic units. Local alteration associated with copper mineralization includes calcic, silicic, sericitic, chloritic, zeolitic and hematitic. Copper mineralization occurs as disseminated, vein- veinlet, replacement, stockworks and irregular open space fillings. Based on microscopic studies and EPMA data, chalcocite group minerals (chalcocite, djurleite, anilite, digenite and covellite) are the main ore minerals and are accompanied by subordinate bornite, pyrite and hematite. Secondary minerals include covellite, malachite, azurite, chrysocolla and goethite. Nonmetallic minerals are quartz, chlorite, epidote, calcite, and chalcedony. Based on fluid inclusion studies on coexisting quartz, homogenization temperatures are between 90 to 268°C with an average of 176° C. Salinities vary between 3.38 to 21.96 (average, 13.21) wt% NaCl eq. Fluid density varies between 0.8 to 1.1 g.cm-3. The depth of fluid inclusion trapping is estimated to be less than 200 meters, and ore formation occurred at pressures less than 50 bars. The host rocks, ore mineralogy, ore textures and structures, and fluid inclusions characteristics in Madan Bozorg deposit are similar to those reported from Manto type copper deposits in Mesozoic-Cenozoic volcanic belts in South America and elsewhere.
M.R Hezareh; I Rasa
Abstract
In the western part of the Sistan & BaluchestanProvince (continuation of the Jebal- e BarezRange) in southeast Iran, the epithermal type (i. e. gold and associated elements) model is one of the anticipated metallogenic model. The studied area is one of the important targets of regional geochemical ...
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In the western part of the Sistan & BaluchestanProvince (continuation of the Jebal- e BarezRange) in southeast Iran, the epithermal type (i. e. gold and associated elements) model is one of the anticipated metallogenic model. The studied area is one of the important targets of regional geochemical exploration. In this regard, the mineral and geochemical geological map of 1/20000 was prepared in an area of 81 km2. After processing of the data and identifying the ore zones, 30 trenches drilled perpendicular to the veins and one sample was taken in every 5 meters. The results show that a tectonomagmatic event and large scale fracturing with strike of N30E led the hydrothermal solutions and caused an extensive alteration. This alteration caused a regional propylitization in andesites and development of a large argillic-silicious alteration in associated lavas and pyroclastics followed by formation of the thin silicious veins in strike of N30E with chalcedony, colloform, cockade and vesicular structures, having the quartz adularia paragenesis and are assumed to be the sources of gold genesis and the main phase of gold formation.
S.T Delavar; I Rasa; M Lotfi; G Borg; N Rashidnejad Omran; P Afzal
Abstract
Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized ...
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Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized in the deposit: 1-layers and lenses, concordant with layering; and 2-discordant secondary forms along the fractures. In Tangedezan deposit two mineralized carbonate facies have been distinguished: 1- dolomitic limestone facies (Microsparite) containing three major mineralization horizons with simple ore mineral paragenesis such as galena, sphalerite and pyrite replacing the host rock and filling the porosities and fractures; and 2- crystallized argillaceous limestone facies with very weak Zn-Pb mineralization in disseminated form. The deposit includes two parts of supergene in surface and sulfides in depth. The simple ore paragenesis comprises of hemimorphite, smithsonite, cerussite, galena, sphalerite and pyrite. Ag and Cd elements have noticeable grade and could be contemplated as by product. All accomplished investigations and evidences such as geological characteristics, mineralized facies, supergene and sulfide development, ore body geometry, ore minerals paragenesis, texture and structures in different scale, existing alterations specially dolomitization and lithogeochemical studies all reveal that Tangedezan deposit is a Zn-Pb Mississippi Valley Type (MVT) deposit.
Z Adeli; I Rassa; A Darvishzadeh
Abstract
The Haftcheshmeh Porphyry copper deposit is located 28km north of Varzaghan (East -Azerbayjan province). It is associated with quartzdioritic to granodioritic intrusive of Oligo- Miocene ages, which are intensively altered. The porphyritic bodies are intruded by a series of barren andesitic dykes. The ...
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The Haftcheshmeh Porphyry copper deposit is located 28km north of Varzaghan (East -Azerbayjan province). It is associated with quartzdioritic to granodioritic intrusive of Oligo- Miocene ages, which are intensively altered. The porphyritic bodies are intruded by a series of barren andesitic dykes. The principal aim of this paper is to consider the geochemistry and the origin of magma. Trends of major and trace elements indicate a continuous compositional range and a comagmatic origin for these rocks. However, trends of compatible-incompatible elements indicate the important role of fractional crystallization and contamination of the magma with upper crust in genesis of these rocks. Depletion in Ti, Nb and Sr and enrichment in K, Th and Rb are obvious in spider diagrams of these samples. The enrichment in LILE and depletion in HFSE reveal the I-type metaluminous magmatism of volcanic arcs (VAG). َAdditionally, the discrimination tectonic setting diagrams indicate I-type continental volcanic arc magmatism for this intrusion. The Microprobe analysis also confirms that the Biotite crystallized from typical calc-alkaline magma.
