Zircon U-Pb geochronology, geochemistry, Sr-Nd isotopic compositions, and tectonomagmatic implications of Nay (NE Iran) postcollisional intrusives in the Sabzevar zone

The mafic to felsic intrusive rocks of Nay (IRN) are located in the northeast of the central Iranian block. In this study, we present new major and trace element geochemistry, U-Pb zircon ages, and Sr-Nd isotopic data to discuss the origin of the IRN postcollisional units. The oldest units in the Nay area belong to Paleocene–early Eocene volcanic and pyroclastic series including basalt-andesite, latite, dacite, and tuff. These series are crosscut by subvolcanic and granitoid rocks with lithological composition varying from quartz gabbro to K-feldspar granite. The youngest igneous activity is represented by quartz monzodiorite dikes. Hornblende-biotite quartz monzonite from Nay granitoids was dated at 40 Ma (zircon U-Pb). The IRN rocks are metaluminous to peraluminous with high-K calc-alkaline and shoshonitic affinities. They display enrichment in light REEs [(La/Yb)N = 3.79–8.71] and LILEs (such as Ba, Th, Rb, U, and K), with depletion in HFSEs (such as Nb, Zr, Y, and Ti). All rocks have negative Eu anomalies [(Eu/Eu*)N = 0.17–0.88] and relatively flat heavy REE patterns [(Gd/Yb)N = 1.12–1.69]. Granitoids have initial 87Sr/86Sr values from 0.7053 to 0.7061 and εNd values from –1.65 to –0.02 calculated at 40 Ma. The geochemical composition of IRN rocks along with the low ISr and positive εNd values and mantle model ages of 0.6–0.8 Ga indicate that two end-members, enriched mantle and a continental crust, were involved in the magma generation. We argue that the Eocene IRN magmatism occurred as a postcollisional product by asthenospheric upwelling owing to the convective removal of the lithosphere during an extensional collapse of the central Iranian block.publishe

Geology, mineralization, U-Pb dating and Sr-Nd isotope geochemistry of intrusive bodies in northeast of Kashmar

سن 40 میلیون ) I محدوده مطالعاتی در 30 کیلومتري شمالشرق کاشمر قرار دارد. براساس سنسنجی زیرکن تودههاي نفوذي نوع سال)، در زمان ائوسن و در پاسخ به فشارش ناحیهاي، حرکات امتدادلغز چپ گرد گسلهاي درونه و تکنار سبب رخداد زون برشی، و شکستگیهاي ریدل شده که شرایط را براي صعود ماگما و محلول گرمابی مهیا کرده است. طی تکامل ساختاري pull-apart حوضه در منطقه نفوذ کرده است. A و یک پالس نوع I منطقه، چند ضربان ماگمایی کالکوآلکالن تا آلکالن پتاسیم بالا تا شوشونیتی نوع منشأ پوسته قارهاي با دخالت گوشته ،I 0/5125-0/5126 ) براي سري ) 143Nd/144Nd 0/705-0/706 ) و ) 87Sr/86Sr مقادیر اولیه در IOCG سبب دگرسانیها و کانیسازي ،I (فرورانش) را نشان میدهد. ماگماي عامل دسته دایکهاي کوارتزمونزونیتی جدید نوع منطقه شده است. دو مرحله چرخش محلول گرمابی اکسیدان آهندار سبب دگرسانیهاي آرژیلیک پیشرفته، سرسیتی، سیلیسی، غنی از اسپکیولاریت در منطقه شده IOCG اکسیدآهن، کربناتی، اپیدوتی و کلریتی و کانیسازي رگهاي سولفید فلزات پایه و رگههاي است.The study area is located in central part of the Khaf-Kashmar-Bardeskan belt which is volcano-plutonic belt at the north of the Dorouneh fault in the north of Lut block. The north of the Lut block is affected by tectonic rotation and subduction processes which occur in the east of Iran (Tirrul et al., 1983). The magmatism of Lut block begins in Jurassic and continues in Tertiary (Aghanabati, 1995). Karimpour (Karimpour, 2006) pointed out the Khaf-Kashmar- Bardeskan belt has significant potential for IOCG type mineralization such as Kuh-e-Zar, Tannurjeh, and Sangan (Karimpour, 2006; Mazloumi, 2009). The data gathered on the I-type intrusive rocks include their field geology, petrography, U–Pb zircon dating and Sr–Nd isotope and also alteration and mineralization in the study area