DBPapers
DOI: 10.5593/SGEM2015/B11/S1.046

PETROLOGY OF SUBVOLCANIC ROCKS OF SHADORONSKY ANDESITE-DACITIC COMPLEX FROM DETACHMENT ZONES (EASTERN TRANSBAIKALIA)

I. Kremer, P.Tishin, S. Maxikov, O. Bukharova
Tuesday 4 August 2015 by Libadmin2015

References: 15th International Multidisciplinary Scientific GeoConference SGEM 2015, www.sgem.org, SGEM2015 Conference Proceedings, ISBN 978-619-7105-31-5 / ISSN 1314-2704, June 18-24, 2015, Book1 Vol. 1, 363-368 pp

ABSTRACT
This work is given up to the study of petrographic and petro-geochemical characteristics of subvolcanic formations of detachment zones by the example of northwestern part of the Borschovochny metamorphic core [6, 11]. The main purpose is to investigate the volcanites of shadoron formation, which are allocated in vertical section of the aginsk-borschovochny mylonitic complex [10]. Mineral composition and microstructural features of the rocks have been ascertained by detai subvolcanic formations led petrographic study of thin sections; petro-geochemical attestation of the rocks has been carried out in accordance with X-ray fluorescence spectroscopy and ICP-MS data. Subvolcanic formations of detachment zone of Borschovochny metamorphic core presented are the sills of andesites, andesidacites, dacites and dacite porphyry from shadoronsky volcanic complex. These rocks form almost concordant bodies which are tracked up through all the dynamometamorphic section of detachment with the upper horizons. Mineral composition of the majority of the examined volcanites shows that these are massive or poorly foliated microfelsitic rocks with microlitic groundmass made up of plagioclase, quartz and also sericite and ore minerals. Petrochemical typification of volcanites of northwestern part of the Borschovochny granite gneiss dome has shown that in compliance with SiO2 (50-77%) and alkali (3-6%) content these rocks conform to basalt-andesite-dacite row and confine to the trend of volcanic formations, which are representative for detachment zone of sills and dikes complexes. The way main indicating geochemical elements are distributed at the northwestern part of the Borschovochny dome gives a possibility to suppose that the volcanites have been formed in conditions of a margin of Andic type over a more developed continental crust.

Keywords: metamorphic core, detachment zone, Eastern Transbaikalia, subvolcanic formations

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