Economic Geology
Almasi Alireza; Ghasem Nabatian; Amir Mahdavi; Qiuli Li
Abstract
The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry ...
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The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry Cu deposits. The composition of the major and trace elements of zircon grains related to several ore-bearing monzonite were measured in Maher abad and Khopik porphyry copper indices. Zircon grains show moderate to low Ce4+/Ce3+ with a range of 19 to 610 and an average of 155. The average of oxygen fugacity (logfO2) values of Meher abad and Khopik ore-bearing magmas, range ∆FMQ -3.2 to MFMQ -1.3 with mean ∆FMQ -2.2, indicate formation under moderate oxidation conditions (between Ni-NiO (NNO) and Faylite magnetite-quartz (FMQ) buffers, but magnetite-hematite (HM) buffer, which ), which is not ideal for the formation of porphyry deposits. This is supported by whole-rock and Sr-isotopic data, and absence of high oxidation minerals such as hematite, and the poor adakitic charactristic of rocks in both deposits, which are due to factors involved in magma origin such as rock type and partial melting rate (possibly peridotite with low participation of slab).
B. Shafiei; S. Lali faz; Gh. H. Shamanian; H. Taghizadeh; M. Hossaini; R. Mathur
Abstract
In present study, Re concentration determined in 30 hexagonal (2H) and trigonal (3R) molybdenite samples belong to veinlets of different stages of hypogene mineralization from 7 porphyry Cu and Mo deposits from Kerman region. Re concentration in molybdenites of these ore deposits varied from 49 ...
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In present study, Re concentration determined in 30 hexagonal (2H) and trigonal (3R) molybdenite samples belong to veinlets of different stages of hypogene mineralization from 7 porphyry Cu and Mo deposits from Kerman region. Re concentration in molybdenites of these ore deposits varied from 49 g/t to 1449 g/t which are in Re concentration range of other porphyry Cu and Mo deposits around the world. In general, 3R molybdenites show the higher Re concentration (average ~ 563 g/t) than those of 2H molybdenites (average ~ 479 g/t). Variations of Re concentration in molybdenite types deposited during different stages of hypogene mineralization indicate more concentration of Re in molybdenites precipitated with transitional (B-type veins) and late (D-type veins) stages of mineralization than those of early stage veinlets (A-type veins). This distribution suggest that Re with more acidic and cooler hydrothermal fluids at the transitional and the late stages of porphyry system evolution is more concentrated with silicification, sericitization, and argillization alterations. Present study indicated that molybdenites with high Re content are associated with porphyry copper deposits which are characterized by low average grade of Mo, limited contents of molybdenite, and also their productive intrusive is resulted from significant contribution of mantle-derived magmas respect to crustal materials.In addition to abovementioned signatures, frequency of 3R poly-type of molybdenite in ore deposits, less fractionated and more calcic composition of productive intrusive of ore deposits with their less radiogenic of Sr and Pb isotope ratios, as well as occurrence of late stages of acidic and low temperature hydrothermal alteration and mineralization processes in formation and evolution history of ore deposits are signatures of porphyry copper and molybdenum deposits with high Re contents.
