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Zircon U-Pb dating of Maherabad porphyry copper-gold prospect area: evidence for a late Eocene porphyry-related metallogenic epoch in east of Iran

Journal: Journal of Economic Geology (Vol.3, No. 1)

Publication Date:

Authors : ; ;

Page : 41-60

Keywords : Lut block; Middle Eocene; Zircon; Geochronology; Laser ablation ICP-MS;

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Abstract

Eastern Iran has great potential for porphyry copper deposits, as a result of its past subduction zone tectonic setting that lead to extensive alkaline to calc-alkaline magmatic activity in Tertiary time. Maherabad is the first porphyry Cu-Au prospecting area which is discovered in eastern Iran. This is related to a succession o f monzonitic to dioritic porphyries stocks that were emplaced within volcanic rocks. Monzonitic porphyries have basic role in mineralization. Hydrothermal alteration zones are well developed including potassic, sericitic-potassic, quartz-sericite-carbonate-pyrite, quartz-carbonate-pyrite, silicified-propylitic, propylitic, carbonate and silicified zones. Mineralization occurs as Disseminated, stockwork and hydrothermal breccia. Based on early stage of exploration, Cu is between 179- 6830 ppm (ave. 3200 ppm) and Au is up to 1000 ppb (ave. 570 ppb). This prospect is gold- rich porphyry copper deposit. Laser-ablation U-Pb dating of two samples from ore-related intrusive rocks indicate that these two monzonitic porphyries crystallized at 39.0 ± 0.8 Ma to 38.2 ± 0.8 Ma, within a short time span of less than ca. 1 Ma during the middle Eocene. This provides the first precise ages for metallogenic episode of porphyry-type mineralization. Also, the initial 87Sr/86Sr and (143Nd/144Nd)i was recalculated to an age of 39 Ma. Initial 87Sr/86Sr ratios for monzonitic rocks are 0.7047-0.7048. The (143Nd/144Nd)i isotope composition are 0.512694-0.512713. Initial ε Nd isotope values 1.45-1.81. Based on isotopic data the magma had originated beyond the continental crust. The study will be used for tectonic-magmatic setting and evolution of eastern Iran.

Last modified: 2015-07-01 13:40:11