Two stages of isotopic exchanges experienced by the Ertaibei granite pluton, northern Xinjiang, China

¹⁸O/¹⁶O and D/H of coexisting feldspar, quartz, and biotite separates of twenty samples collected from the Ertaibei granite pluton, northern Xinjiang, China are determined. It is shown that the Ertaibei pluton experienced two stages of isotopic exchanges. The second stage of¹⁸O/¹⁶O and D/H exchanges with meteoric water brought about a marked decrease in the δ¹⁸O values of feldspar and biotite from the second group of samples. The D/H of biotite exhibits a higher sensitivity to the meteoric water alteration than its¹⁸O/¹⁶O. However, the first stage of¹⁸O/¹⁶O exchange with the¹⁸O-rich aqueous fluid derived from the dehydration within the deep crust caused the Δ¹⁸O_{Quartz-Feldspar} reversal. It is inferred that the dehydration-melting may have been an important mechanism for anatexis. It is shown that the deep fluid encircled the Ertaibei pluton like an envelope which serves as an effective screen to the surface waters.