The behavior of 232 Th and the 238 U decay chain nuclides during magma formation and volcanism

• Main Authors: Krishnaswami, S., Turekian, K. K., Bennett, J. T.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier Science 1984
• Subjects: Galapagos; Iceland
• Online Access: http://repository.ias.ac.in/16764/; http://linkinghub.elsevier.com/retrieve/pii/0016703784902783

Concentrations of the members of the 238 U decay chain and 232 Th were determined in volcanic rocks from convergent plate margins, intraplate volcanoes and oceanic spreading centers. Contemporary and historical volcanic rocks from Mt. St. Helens, Arenal, El Chichon, Hawaii and Iceland and submarine basaltic glass from the Galapagos spreading center all show no fractionation of U and Th in the mantle source or during magma formation at least for the past 300,000 years. Mauna Kea (Hawaii) rocks of alkaline composition greater than 4000 years old and an old submarine basalt show disequilibrium for several of the nuclides in the 238 U decay chain. We interpret these as resulting from post-emplacement processes.