Abstract
This work presents the summarization of U–Pb (SIMS, TIMS) zircon dates and petrogeochemical signatures of granitoids of the north of the Urals (Polar, Subpolar, and Northern Urals) obtained over the last decade. Granitе melts were formed from melting of different substrates, highly heterogeneous in composition and age, at all geodynamic stages distinguished in the studied area. Preuralides include island arc–accretionary (735–720 Ma, 670 Ma), collisional (650–520 Ma), and rift-related (520–480 Ma) granitoids. Uralides includes primitive island-arc granitoids (460–429 Ma), mature island-arc granitoids (412–368 Ma), early collisional (360–316 Ma) and late collisional (277–249 Ma) granitoids. As a result, the general trend of variations of oxygen (δ18OZrn, ‰), neodymium (εNd(t)wr), and hafnium (εHf(t)Zrn) isotope compositions identified in time. Mantle isotope compositions (δ18OZrn (+5.6), εNd(t)wr (+1.7), εHf(t)Zrn (+8.7...+10.6)), common for island arc granitoids (Preuralides) are changed by crustal–mantle ones (δ18OZrn (+7.2...+8.5), εNd(t)wr (–4.8...+1.8), εHf(t)Zrn (+2.1 to +13)), typical of collisional granites. According to this, the crustal matter played a significant role during the formation of the latter. The crustal-mantle isotope compositions are changed by the mantle ones, characteristic of rift-related (δ18OZrn (+4.7...+7), εNd(t)wr (+0.7...+5.6), εHf(t)Zrn (–2.04...+12.5)) and island-arc (Uralides; δ18OZrn (+4.2...+5.7), εNd(t)wr (+4.1...+7.4), εHf(t)Zrn (+12...+15.2)) granitoids.
Highlights
The north of the Urals is geographically divided, from north to south, into the Polar, Subpolar, and Northern Urals and is bounded by Mt
The granitoid magmatism in the north of the Uralian collisional orogen is represented by products of two large geodynamic stages – Timanides–Preuralides and Uralides
The Pre uralides are characterized by the change of the island arc magmatism (735–720 Ma; generation of I-type (M-type) granitoids) to the accretionary magmatism (670 Ma, I-type granitoids), and, to the collisional (620–520 Ma; simul taneous generation of A, I, S-type granitoid melts) and the rift-related magmatism (520–480 Ma; mainly, the genera tion of A-type granites)
Summary
The north of the Urals is geographically divided, from north to south, into the Polar, Subpolar, and Northern Urals and is bounded by Mt. Granitoids of the north of the Urals have always been the subject of an increased focus, which is reflected in the ex tensive list of literature [Okhotnikov et al, 1985; Makhlaev, 1996; Goldin et al, 1999; Makhlaev et al, 2005; Kuznetsov et al, 2005а, 2005b, 2007; Andreichev, 1999, 2010; Puchkov, 2010; Melgunov et al, 2010; Soboleva, Udoratina, 2010] Even recently, their age and formation conditions are the sub ject of discussion. The problems to be considered in the given work are as follows: (1) analysis of the available U–Pb dates of single zircon grains obtained over the past decade, (2) analysis of petrogeochemical features of dated granitoids, (3) ana lysis of the change of the granite melt sources based on newly obtained isotope–geochemical characteristics (OZrn, HfZrn, Ndwhole-rock), and (4) geodynamic interpretation using U–Pb, petrogeochemical, and isotope-geochemical data on granitoids
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