Skip to main content
U.S. flag

An official website of the United States government

Sr isotopic tracer study of the Samail ophiolite, Oman

January 1, 1981

We have measured Rb and Sr concentrations and Sr isotopic compositions in 41 whole-rock samples and 12 mineral separates from units of the Samail ophiolite, including peridotite, gabbro, plagiogranite, diabase dikes, and gabbro and websterite dikes within the metamorphic peridotite. Ten samples of cumulate gabbro from the Wadir Kadir section and nine samples from the Wadi Khafifah section have mean 87Sr/86Sr ratios and standard deviations of 0.70314 ± 0.00030 and 0.70306 ± 0.00034, respectively. The dispersion in Sr isotopic composition may reflect real heterogeneities in the magma source region. The average Sr isotopic composition of cumulate gabbro falls in the range of isotopic compositions of modern midocean ridge basalt. The 87Sr/86Sr ratios of noncumulate gabbro, plagiogranite, and diabase dikes range from 0.7034 to 0.7047, 0.7038 to 0.7046, and 0.7037 to 0.7061, respectively. These higher 87Sr/86Sr ratios are due to alteration of initial magmatic compositions by hydrothermal exchange with seawater. Mineral separates from dikes that cut harzburgite tectonite have Sr isotopic compositions which agree with that of cumulate gabbro. These data indicate that the cumulate gabbro and the different dikes were derived from partial melting of source regions that had similar long-term histories and chemical compositions.

Publication Year 1981
Title Sr isotopic tracer study of the Samail ophiolite, Oman
DOI 10.1029/JB086iB04p02709
Authors M. A. Lanphere, R. G. Coleman, C.A. Hopson
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geophysical Research Solid Earth
Index ID 70011691
Record Source USGS Publications Warehouse