زمین‌ شناسی، کانی سازی، ژئوشیمی اکتشافی، پتروژنز، سن‌ سنجی upb و ایزوتوپ‌ های luhf روی کانی زیرکن توده های نیمه‌ عمیق در محدوده اکتشافی سیمرغ، بلوک لوت، شرق ایران

منطقه اکتشافی سیمرغ در مرکز بلوک لوت و جنوب‌غربی نهبندان قرار دارد. در این منطقه طیف گسترده‌ای از توده‌های نیمه‌عمیق به شکل استوک و دایک در درون واحدهای آتشفشانی نفوذ کرده‌اند و دگرسانی‌های مهمی مانند سیلیسی، کوارتز+ سریسیت+ پیریت، کربنات+ کوارتز+ سریسیت+ پیریت، پروپیلیتیک و آرژیلیک را به‌وجود آورده‌‌اند. این توده‌ها متا‌آلومینوس با ماهیت کالک‌آلکالن تا کالک‌آلکالن پتاسیم بالا هستند. غنی‌شدگی عناصر lree نسبت به hree همراه با آنومالی منفی eu نشان‌دهنده تشکیل ماگما در زون فرورانش است. سه نوع کانی‌سازی افشان، رگچه‌ای و برش‌های هیدروترمال در این منطقه دیده می‌شود. میزان عنصر مس از 2 تا 240 گرم در تن، مولیبدن 0.5 تا 49 گرم در تن، آرسنیک 2 تا 207 گرم در تن و طلا 1 تا 93 میلی‌گرم در تن متغیر است. سن‌سنجی upb در دو دایک گرانیت پورفیری سن‌های 0.56±25.37 و 0.76±25.94 میلیون سال و توده پیروکسن دیوریت پورفیری سن 0.51±24.85 میلیون سال را نشان می دهد. مقادیر مثبت پایین ɛhf(t) منشا این توده‌ها را گوشته نشان می‌دهد که مقدار کمی با پوسته آغشتگی پیدا کرده است.

Geology, Mineralization, Geochemical exploration, Petrogenesis, zircon UPb geochronology and LuHf isotopes subvolcanic rocks in the Simorgh prospect area, Lut Block, Eastern Iran

Introduction;The Simorgh prospect area is located in 113 km southwest of the Nehbandan in South Khorasan province. This area is part of the Tertiary volcanicplutonic rocks in the center of the Lut block. The Lut Block, which is located at the eastern part of the Central Iranian Microcontinent (CIM), is famous by its complex tectonic evolution and extensive magmatic activities with a range of interesting geochemistry. Extensive magmatic activities in Lut Block have produced several types of mineralization events (Karimpour et al., 2012). Around the Simorgh prospect area, various mineral deposits, including CuMo porphyry Dehsalm in 90 km southwest of Nehbandan have been reported (Arjmandzadeh and Santos 2013) and Mahoor copper (Miri Beydokhti et al., 2015).;Until now there has not been a detailed studies on the Simorgh prospect area especially on granitoids. In this study, we present field investigations, geology, alteration, mineralization, geochemical exploration, Petrogenesis, zircon UPb geochronology and Hf isotopes of subvolcanic rocks in the Simorgh prospect area.; ;Materials and methods;1 Preparation of 336 thin sections for the study of petrography, alteration and mapping of geological and alteration maps.;2 Preparation and study of twentyfive polished thin sections and thirtytwo polished blocks for mineralization studies.;3 Analysis of fortyfive chip composite samples in the Zar Azma laboratory by using the fire assay method for Au element and ICPOES for thirtyfour elements. The solubilization method of 4 Acid (1EX) was used.;4 Analysis of one hundred and sixty core samples in the Zar Azma laboratory by using the fire assay method for Au element and ICPOES for 34 elements (method 1EX).;5 Chemical analysis of seventeen samples of synmineralization subvolvanic intrusive rocks with at least alteration, by ICPMS for thirtyone trace and rare earth elements with LF100 method (alkali fusion) at the AcmeLabs Laboratory.;6 Separation of three samples from synmineralization subvolcanic intrusive rocks for UPb zircon geochronolg by Quadruple LaserAblation ICPMS at the CODES, the Tasmania University of Australia.;7 Analysis of three samples of synmineralization subvolvanic intrusive rocks for LuHf isotopes with multicollector ICPMS at the CCFS of Macquarie University of Sydney, Australia.; ;Discussion and results ;Petrographic studies indicated that the composition of subvolcanic rocks in the Simorgh area are diorite porphyry and pyroxene diorite porphyry stocks with granite porphyry and granodiorite porphyry dikes. Several alteration zones such as: propylitic, argillic, silicified quartzsericitepyrite (QSP) and carbonatequartzsericitepyrite (CQSP) based on field and laboratory studies are identified Major oxides analysis shows that intrusive units are metaluminous to peraluminus, calcalkaline to highK calcalkaline. More of these rocks belong to the Itype granitoid (Chappell and White, 2001), and they have been formed in a volcanic arc granitoids (VAG) tectonic setting (Pearce et al., 1984). Mantlenormalized, traceelement spider diagrams display enrichment in large ion lithophile elements, such as Rb, Sr, K, and Cs, and depletion in high field strength elements, e.g., Nb, Ti, P. Enrichment of LREE versus HREE and enrichment of LILE and depletion in HFSE indicate magma formation in the subduction zone. In the subduction zones, high oxygen fugacity leads to the depletion of Ti. All of the intrusive rocks have a negative Eu anomaly. The amount of Eu/Eu* in subvolcanic units of the Simorgh area varies from 0.49 to 0.91. Therefore, negative Eu anomaly can be evidence of the partial presence of plagioclase in the origin (Tepper et al., 1993).;Three types of mineralization occur in this area such as: veinlet, disseminated and hydrothermal breccia among which hydrothermal breccia is the most important. Pyrite is the most sulfide mineralization in the subvolcanic and hydrothermal breccias.;Compositional variations of elements within the Simorgh prospect are as follows: Cu = 2240 ppm, Mo = 0.549 ppm, Zn = 9935 ppm, Pb = 7582 ppm, ppm, As = 2207 ppm and Au = 193 ppb.;In the Simorgh area, zircon UPb geochronology was carried out on synmineralization subvolcanic intrusive rocks. The age of two granite porphyry dikes are 25.37±0.56 Ma and 25.94±0.76 Ma and the age of pyroxene porphyry diorite is 24.85±0.51 Ma (Chattian). Diorite porphyry is premineralization because it is cut by granite porphyry dikes and pyroxene diorite porphyry, so diorite porphyry is the oldest subvolcanic intrusive rock in this area. The low positive values of εHf(i) indicate that the origin of these subvolcanic intrusive rocks is mantle, which has low contamination with the crust.;According to the above evidence, the subvolcanic units of this area are related to porphyry systems, and the hydrothermal breccias are the main host rock mineralization in this system. This system does not have any valuable mineralization expect pyrite, from the surface to 180 m depth.; ;References;Arjmandzadeh, R. and Santos, J.F., 2013. SrNd isotope geochemistry and tectonomagmatic setting of the Dehsalm CuMo porphyry mineralizing intrusives from Lut Block, eastern Iran. International Journal of Earth Sciences, 103(1): 123–140.;Chappell, B. and White, A., 2001. Two contrasting granite types: 25 years later. Australian Journal Earth Sciences, 48(4): 489–499.;Karimpour, M.H., Malekzadeh shafaroudi, A., Farmer, G.L. and Stern, C.R., 2012. Petrogenesis of Granitoids, UPb zircon geochronology, SrNd Petrogenesis of granitoids, UPb zircon geochronology, SrNd isotopic characteristics, and important occurrence of Tertiary mineralization within the Lut block, eastern Iran. Journal of Economic Geology, 4(1): 1–28. (in Persian with English abstract);Miri Beydokhti, R., Karimpour, M.H., Mazaheri, S.A., Santos, J.F. and Klötzlid, U., 2015. UPb zircon geochronology, SrNd geochemistry, petrogenesis and tectonic setting of Mahoor granitoid rocks (Lut Block, Eastern Iran). Journal of Asian Earth Sciences, 111(1): 192–205.;Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25(4): 956–983.;Tepper, J.H., Nelson, B.K., Bergantz, G.W. and Irving, A.J., 1993. Petrology of the Chilliwack batholith, North Cascades, Washington: generation of calcalkaline granitoids by melting of mafic lower crust with variable water fugacity. Contributions to Mineralogy and Petrology, 113(3): 333–351.