Abstract
The wadi Kid pluton of Iqna Granite, Southern Sinai, which was intruded during the last Precambrian magmatic phase, yields a Rb-Sr total rock isocrhon age of 580±23 m.y., and an initial 87Sr/ 86Sr ratio of 0.7028±0.0028. The magma of the Iqna Granite was derived from a low Rb/Sr source shortly before its crystallization. Partial resetting of biotite ages is detected by both Rb-Sr and K-Ar methods. Mineral isochrons yield higher initial values (0.7045–0.7065) as a result of Sr isotopic redistribution within a closed total rock system.
The Rb-Sr resetting of the biotites is expressed by radiogenic Sr loss accompanied by a proportional enrichment of common Sr. The Rb content was unaffected by this process. Oxidation of the iron within the biotite indicates the opening of the biotite interlayer space, thus making the Sr exchange possible. These effects are attributed to a thermal event some 510–540 m.y. ago.
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Bielski, M., Jäger, E. & Steinitz, G. The geochronology of Iqna Granite (wadi Kid pluton), Southern Sinai. Contr. Mineral. and Petrol. 70, 159–165 (1979). https://doi.org/10.1007/BF00374445
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DOI: https://doi.org/10.1007/BF00374445