The Sr, Nd, and Hf isotopic geochemistry of rocks of the gabbro–diorite–tonalite association from the Eastern Segment of the Middle Urals as an indicator of the age of the continental crust in this area

• Published in: Doklady earth sciences Vol. 474; no. 1; pp. 516 - 519
• Main Authors: Smirnov, V. N., Ivanov, K. S., Ronkin, Yu. L., Koroteev, V. A., Serov, P. A., Gerdes, A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.05.2017; Springer; Springer Nature B.V
• Subjects: Age; Analysis; Area; Continental crust; Correlation; Crust (Geology); Crystallization; Depletion; Dikes; Diorite; Earth and Environmental Science; Earth Sciences; Embankments; Gabbro; Geochemistry; Geology; Isotopes; Lava; Magma; Mantle; Mantle (Geology); Parenting; Porphyry; Quartz; Rock; Rocks; Strontium isotopes
• ISSN: 1028-334X; 1531-8354
• DOI: 10.1134/S1028334X17050269

According to isotopic analysis of rocks of the Reft gabbro–diorite–tonalite complex (Middle Urals), gabbro and related diorite and dikes and vein-shaped bodies of plagiogranitoids, crosscutting gabbro, are similar to the depleted mantle substance in ε Nd ( T ) = 8.6–9.7 and ε Hf ( T ) = 15.9–17.9. Their model Hf ages are correlated with the time of crystallization. Here, the tonalites and quartz diorites constituting most of the Reft massif are characterized by lower values: ε Nd ( T ) = 3.7–6.0, ε Hf ( T ) = 11.1–12.7, and T DM values significantly exceeding the age datings. This is evidence that Neoproterozoic crustal rocks were a source of parental magma for these rocks. The primary 87 Sr/ 86 Sr ratio in rocks of both groups is highly variable (0.70348–0.70495). The data obtained allow us to reach the conclusion that the Reft gabbro–diorite–tonalite complex was formed as a result of nearly synchronous processes occurring in the crust and the mantle within a limited area.