S Lali faz; B Shafiei; Gh.H Shamanian; H Taghizadeh
Abstract
Present study is the first report of the rhenium and osmium isotopic data in the hypogene Cu-Fe sulfides (chalcopyrite and pyrite) from the Kerman porphyry copper deposits. Although data set was limited in this study, their interpretation helped to understand the possible sources of the metal for mineralization ...
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Present study is the first report of the rhenium and osmium isotopic data in the hypogene Cu-Fe sulfides (chalcopyrite and pyrite) from the Kerman porphyry copper deposits. Although data set was limited in this study, their interpretation helped to understand the possible sources of the metal for mineralization in the porphyry copper system. Based on this study, initial 187Os/188Os value in deposits recorded at least 0.1 to maximum 10 that the variation range for this ratio is much larger than the range detected in the Chilean porphyry copper deposit (from 0.15 to 5.2). The recorded non-radiogenic to radiogenic values for initial osmium ratio in primary sulfides of the Kerman porphyry copper deposits revealed isotopic heterogeneity and diversity in metal source for mineralization in these deposits. The record of the non-radiogenic values for initial 187Os/188Os (0.10- 0.15) in sulfides of the Miduk and Now Chun deposits, in the range of mantle values (0.13- 0.15), showed the main role of ore-forming fluids derived from mantle-derived magma (intrusive body) for supplying of the metal required for mineralization in these deposits. In contrast, too large deviation observed in initial 187Os/188Os values in sulfides of the Kerver (10) and Abdar (1) deposits respect to the mantle values showed the greater share of crustal sources (continental crust) rather than mantle sources in supplying of the metal for mineralization in these deposits. The Sar Cheshmeh deposit revealed less radiogenic value of initial osmium ratio in potassically sulfides (0.22) respect to phyllically sulfides (0.79), showing the contribution both the mantle and the crustal materials in supplying of the metal for mineralization, although the role of crust during the final stages of mineralization has been more important. The observed general trend in 187Os/188Os values being more radiogenic from old, high-grade deposits (middle Miocene) to young, low-grade deposits (upper Miocene- Pliocene) in the Kerman porphyry copper belt is attributed to increasing of the crustal sources contribution in generation of the young sub-productive-to-barren magmas and also in supplying of the metal for associated weak mineralization. This relationship can be suggested as a key for distinguishing and exploration of porphyry copper deposits with economic grades, the deposits that have been inherited greater share of the mantle source for generation of productive magma and also required metal for mineralization in porphyry system.
M. H. Ahmadi; G.H Shamanian; H. Azmi
Abstract
The Motrabad vein system is located 30 Km southwest of Bajestan in the northern part of the Lut Block. The vein host rocks consist of intermediate to silicic volcanic rocks. The mineralization occurs as irregular veins, veinlets and hydrothermal breccias. Based on field geology and textural evidences ...
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The Motrabad vein system is located 30 Km southwest of Bajestan in the northern part of the Lut Block. The vein host rocks consist of intermediate to silicic volcanic rocks. The mineralization occurs as irregular veins, veinlets and hydrothermal breccias. Based on field geology and textural evidences four types of quartz veins (A, B, C and D) were identified. Hydrothermal alteration is developed around the veins and tends to be more intense in the vicinity of the veins. Hydrothermal alteration consists of silicic, sericitic, propylitic and argilic assemblages. The plot of the Ishikawa alteration index (AI) Vs. chlorite-carbonate-pyrite index (CCPI), known as alteration box plot, display the main alteration trends. The hydrothermal alteration assemblage of quartz, adularia, chlorite, illite, calcite, and pyrite that envelopes the Motrabad vein system formed from the upwelling of near-neutral to weakly alkaline chloride waters. The mineralogic, alteration and geochemical characteristics of the studied area and their comparison with epithermal ore deposits represent an epithermal system of the low-sulfidation type.
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.
