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The age and emplacement of obducted oceanic crust in the Urals from Sm-Nd and Rb-Sr systematicsThe Sm-Nd and Rb-Sr isotopic characteristics of two mafic-ultramafic bodies, the Kemperai Massif in the South Ural Mountains and the Voykar-syninsky Massif in the Polar Ural mountains are examined. The data are found to be consistent with the hypothesis that these bodies represent fragments of old oceanic crust. Whole rock samples of pillow basalt, troctolite, gabbros, diabase, and a metasediment give Sm-Nd values which lie on this isochron indicating that the rock units are genetically related and formed 397 My ago. Basic and ultrabasic rocks from Kempersai and Voykar-Syninsky have an initial isotopic composition at time T, epsilon Nd(397 My), of +8.4, indicating derivation for an ancient depleted mantle source. The Sr isotopic data and the correlation with epsilon Nd indicate extensive alteration by seawater which is particularly strong on ultrabasic rocks. The results show that the segments of oceanic crust formed at least 80 My before the collision that produced the Urals.
Document ID
19850048648
Document Type
Reprint (Version printed in journal)
Authors
Edwards, R. L. (California Inst. of Tech. Pasadena, CA, United States)
Wassburg, G. J. (California Institute of Technology Pasadena, CA, United States)
Date Acquired
August 12, 2013
Publication Date
March 1, 1985
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 72
Issue: 4 Ma
ISSN: 0012-821X
Subject Category
GEOPHYSICS
Funding Number(s)
CONTRACT_GRANT: NSF EAR-83-12882
CONTRACT_GRANT: NAG9-43
Distribution Limits
Public
Copyright
Other