مشخصات پژوهش

صفحه نخست /Rare sapphire-bearing ...
عنوان Rare sapphire-bearing syenitoid pegmatites and associated granitoids of the Hamedan region, Sanandaj–Sirjan zone, Iran: analysis of petrology, lithogeochemistry and zircon geochronology / trace element geochemistry
نوع پژوهش مقاله چاپ‌شده در مجلات علمی
کلیدواژه‌ها sapphire; syenitoid; zircon geochemistry; geochronology; pegmatite; Sanandaj–Sirjan; Iran
چکیده Pegmatites and associated granitoids are integral parts of the Alvand plutonic complex in the Sanandaj–Sirjan zone, Iran. Whole rock major- and trace-element lithogeochemistry together with zircon U–Pb geochronology and zircon geochemistry are examined to evaluate the petrogenesis of sapphire-bearing pegmatites and other peraluminous pegmatites in the region. Pegmatites vary in their chemical compositions from mostly peraluminous, high-K calc-alkaline to shoshonitic signatures. A rare variety of extremely peraluminous sapphire-bearing syenitoid pegmatite (Al2O3 > 30 wt %; A/CNK > 2) exists. This silica-undersaturated pegmatite and its sapphire crystals have a primary igneous origin. U–Pb zircon geochronology of three separate samples fromthis pegmatite indicates the following ages: 168 ±1Ma, 166 ±1Ma and164 ± 1Ma. The zircon grains have notable amounts of Hf (up to 17 200 ppm), U (up to 13 580 ppm), Th (up to 5148 ppm), Y (up to 4764 ppm) and ΣREE (up to 2534 ppm). There is a positive correlation between Hf and Th, Nb and Ta, U and Th, and Y and HREE and a negative correlation between Hf and Y values in the zircons. These zircons exhibit pronounced positive Ce anomalies (Ce/Ce* = 1.15–68.06) and negative Eu anomalies (Eu/Eu* = 0.001–0.56), indicative of the relatively oxidized conditions of the parent magma. Ti-in-zircon thermometry reveals temperatures from as low as ~683 °C up to ~828 °C (average = 755° ± 73°C). Zircon and monazite saturation equilibria are also consistent with these temperatures. Zircon grains are magmatic (average La < 1.5, (Sm/La)N > 100 and Th/U > 0.7), with chemical characteristics similar to zircons from continental crust.
پژوهشگران علی اصغر سپاهی گرو (نفر اول)، حامد وحیدپور (نفر دوم)، دیوید ار. لنتز (نفر سوم)، کریستوفر مک فالین (نفر چهارم)، محمد معانی جو (نفر پنجم)، مهرک منصوری (نفر ششم به بعد)، صدیقه سلامی (نفر ششم به بعد)، میرمحمد میری (نفر ششم به بعد)، راضیه محمدی ترک (نفر ششم به بعد)