The results of U-Pb SHRIMP-II and Ar-Ar dating of magmatic formations in Sertynya-Shekurya interfluve (Prepolar Urals)
The relevance of work. In recent years much attention is paid to the problem of age identification of intrusive formations of the Eastern slope of the Middle, Northern and Prepolar Urals due to the absence of inclosing stratigraphic formations with reliable paleontological characteristics in their s...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | Russian |
| Published: |
Tomsk Polytechnic University
2019-05-01
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| Series: | Известия Томского политехнического университета: Инжиниринг георесурсов |
| Subjects: | |
| Online Access: | http://izvestiya-tpu.ru/archive/article/view/1614 |
| Summary: | The relevance of work. In recent years much attention is paid to the problem of age identification of intrusive formations of the Eastern slope of the Middle, Northern and Prepolar Urals due to the absence of inclosing stratigraphic formations with reliable paleontological characteristics in their surroundings. The obtained results are often much more ancient than it was believed. This fact has initiated a revision of ideas about the evolution of magmatism of this area. The main aim of the study is to refine the territory magmatism schemes on the basis of geological observations complex and the results of the analytical research. The methods used in the study. Mineralogical studies are being carried out with scanning electron microscope JSM-6510LV (Jeol Ltd) with energy-dispersive spectrometer INCAEnergy 350 detector-X-Max-80 (Oxford Instruments Analytical Ltd) at accelerating voltage of 20 kV, electron beam current of 0,3 to 0,5 at a time when the set of spectra 10 (Novosibirsk, Institute of Geology and Mineralogy SB RAS, analyst N.S. Karmanov). Absolute age is defined by Ar-Ar method on rock-forming amphiboles of the gabbro and diorite (Novosibirsk, Institute of Geology and Mineralogy SB RAS, analyst A.V. Travin). U-Pb local dating of zircons from gabbro and diorite was performed using secondary ion microprobe of high resolution SHRIMP-II (TION, VSEGEI) according to the method described by Williams I.S. (1998). Nonradiogenic lead compensation was carried out by the measured 204 Pb and modern lead isotopic composition in Stacey-Kramer model. The results. The authors have studied and dated gabbro and diorite, forming the major structural-material units on the Eastern slope of the Prepolar Urals - Shchekurinskiy and Sertyninsko-Shchekurinskiy massifs. The majority of the studied zircons have a closed U-Pb isotopic system with concordant (consistent) or subconcordant ages (degree of discordantly from 5 to -5 %). The received dates demonstrate a significantly earlier age of the studied objects than it was believed: the magmatic age of the gabbro of tagilokytlymskiy complex in structure of Shchekurinskiy massif was accepted 498±6,5 million years for Ar-Ar dating on amphibole, gabbro of severorudnichnyy complex was accepted 465,2±6,5 million years for Ar-Ar dating on amphibole, diorites of Sertyninsko-Shchekurinskiy massif were accepted 461-471 million years by U-Pb dating on zircon. It is supposed that: 1) the «young» (430±5 mA) zircons indicate the time of metamorphism of gabbros tagilokytlymskiy complex; 2) the «ancient» (1992-1994 and 620-650 mA) zircons of diorites of severorudnichnyy complex are xenogenic and they indicate events under Tagil island-arc terrane in the basement of the adjacent to the West of the platform, got in a subduction zone, and events in the upper mantle respectively. The determined RT-parameters of intrusive rocks formation indicate the time lag between the introduction of the melt and the beginning of crystallization of amphiboles that indicates the earlier age of intrusions than that which the authors accepted according to the results of Ar-Ar dating. |
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| ISSN: | 2500-1019 2413-1830 |