zircon u-pb dating of maherabad porphyry copper-gold prospect area: evidence for a late eocene porphyry-related metallogenic epoch in east of iran
نویسندگان
چکیده
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.
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عنوان ژورنال:
زمین شناسی اقتصادیجلد ۳، شماره ۱، صفحات ۴۱-۰
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