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对西天山高压变质带内高压脉的研究表明, 高压脉与寄主岩石具总体一致的Pb和Sr同位素组成, 高压脉206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb及87Sr/86Sr (t = 340 Ma)分别为17.122~17.431, 15.477~15.611, 37.432~38.689和0.70529~0.70705; 主岩上述比值为17.605~17.834, 15.508~15.564, 37.080~38.145和0.70522~0.70685. 与主岩相比, 高压脉具大得多的Pb同位素组成变化. 高压脉和主岩Rb/Ba, Ce/Pb, Nb/U和Ta/U比值均介于洋岛玄武岩(OIB)或洋中脊玄武岩(MORB)与陆壳间, 显示有陆壳物质混入. 西天山古俯冲带深部成脉流体为来自具I类富集地幔特征的大洋玄武岩(主岩原岩)进变质脱水与来自俯冲沉积物(包括陆源沉积物)进变质脱水形成的两种流体的混合.
The study of the high-pressure veins in the high-pressure metamorphic belt in the western Tianshan shows that the high-pressure veins have the same Pb and Sr isotopic composition as the host rocks, with high-pressure veins 206Pb / 204Pb, 207Pb / 204Pb, 208Pb / 204Pb and 87Sr / 86Sr ) Were 17.122 ~ 17.431, 15.477 ~ 15.611, 37.432 ~ 38.689 and 0.70529 ~ 0.70705, respectively.The ratios of the main rocks were 17.605 ~ 17.834, 15.508 ~ 15.564, 37.080 ~ 38.145 and 0.70522 ~ 0.70685, Much higher Pb isotopic composition.The ratios of Rb / Ba, Ce / Pb, Nb / U and Ta / U of high pressure veins and host rocks are all between that of OIB or MORB and continental crust, Shows that the crustal material is mixed in. The deep vein-forming fluid in the ancient western subduction zone is characterized by metamorphic dehydration of the oceanic basalts (primary rock protoliths) characterized by enrichment of a type I enrichment and the metamorphic dehydration from subduction sediments (including terrigenous sediments) The resulting mixture of two fluids.