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Neoproterozoic island arcs in East Sayan; duration of magmatism (from U-Pb zircon dating of volcanic clastics)

A. B. Kuzmichev and A. N. Larionov
Neoproterozoic island arcs in East Sayan; duration of magmatism (from U-Pb zircon dating of volcanic clastics)
Russian Geology and Geophysics (January 2013) 54 (1): 34-43

Abstract

Two island arcs of different ages have been reconstructed in the Neoproterozoic history of southeastern East Sayan: Dunzhugur and Shishkhid. According to earlier concepts, the Dunzhugur arc formed at approximately 1020 Ma and underwent collision with the Siberian(?) continent at approximately 810 Ma. The Shishkhid arc formed somewhat earlier than 800 Ma and existed till the end of the late Baikalian ( approximately 600 Ma, from indirect data). This primitive geologic history, when each arc existed for 200 Myr, was suggested because of the deficit of direct data, and its reconstruction cast doubt. In this work we present results of preliminary dating of detrital zircons separated from the volcaniclastic rocks composing the above arcs. We analyzed 12 zircon crystals from the Dunzhugur volcanic clastics, whose (super 206) Pb/ (super 238) U age varies from 844 + or - 8 to 1048 + or - 12 Ma (1sigma ). Five most ancient zircons form a concordant cluster with an age of 1034 + or - 9 Ma (2sigma ). Hence, the arc formed earlier than it was assumed and existed for a long time, most likely, till its collision with the continent. We also studied two zircon samples from the volcaniclastic rocks of the Oka accretionary prism, which probably formed in the Shishkhid Arc. All ten crystals of the first sample form a concordant cluster with an age of 813 + or - 7 Ma (2sigma ). The analyzed zircons of the second sample arrange in two clusters, with an age of 775 + or - 8 Ma (2sigma , nine crystals) and 819 + or - 17 Ma (three crystals). Thus, the Shishkhid arc formed earlier than it was assumed, at the end of the early Baikalian, and underwent active volcanism at least till 775 Ma. Dating of detrital zircons from the volcaniclastics generated at the mature stage of the Shishkhid Arc evolution will help to reconstruct partly or completely its history in the period 775-600 Ma.


ISSN: 1068-7971
Serial Title: Russian Geology and Geophysics
Serial Volume: 54
Serial Issue: 1
Title: Neoproterozoic island arcs in East Sayan; duration of magmatism (from U-Pb zircon dating of volcanic clastics)
Affiliation: Russian Academy of Sciences, Geological Institute, Moscow, Russian Federation
Pages: 34-43
Published: 201301
Text Language: English
Publisher: Allerton Press, New York, NY, United States
References: 25
Accession Number: 2021-036958
Categories: Geochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N51°00'00" - N52°30'00", E99°00'00" - E101°00'00"
Secondary Affiliation: Karpinsky Russian Geological Research Institute, RUS, Russian Federation
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2021, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2021
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