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新疆西部托云盆地晚白垩世玄武质岩石中有麻粒岩捕虏体.它们的矿物组合是Opx+Cpx+Pl±Grt±Qtz±Kfs.本文报道了这些捕虏体的矿物成分、岩石地球化学和锆石U-Pb颗粒年龄,并对其成因及所反映的西南天山下地壳性质和壳-幔作用过程进行了讨论.托云麻粒岩以基性为主、含少量中性成分,是岩浆物质经变质改造所形成的下地壳产物.它们的平衡温度和最大压力估计分别是910±35℃和13.5×108Pa,表明寄主岩喷发时西南天山的地壳厚度≤44km并有高的古地温特征(>80mW/m2).在这些捕虏体的岩石成因中,曾发生过橄榄石、辉石和钛铁矿的结晶分异,斜长石的结晶分异和堆积,以及陆壳组分的混染作用或流体的交代作用.253Ma的锆石变质年龄,可能记录着西南天山造山带根部塌陷的壳-幔相互作用事件.
There are granulite xenoliths in the Late Cretaceous basaltic rocks in the Torun Basin, western Xinjiang, and their mineral assemblages are Opx + Cpx + Pl ± Grt ± Qtz ± Kfs. In this paper, the mineral composition of these xenoliths, Chemical and zircon U-Pb ages are discussed, and its genesis and the reflection of the crust beneath the Southwest Tianshan and the process of crust-mantle interaction are discussed.The Tuoyun granulites are mainly basic and contain a small amount of neutral components, Are the products of the lower crust formed by the metamorphism and alteration of magmatic materials.The estimated equilibrium temperature and maximum pressure of them are respectively 910 ± 35 ℃ and 13.5 × 108Pa, indicating that the crustal thickness of the southwest Tianshan during the host rock eruption is less than or equal to 44km with high paleogeothermal (> 80 mW / m 2). Among these rocks, the xenoliths, pyroxenes and ilmenites, the crystal differentiation and accumulation of plagioclase, and Metasomatism or fluid metasomatism. The metamorphic age of 253 Ma for zircons may record the event of crust-mantle interaction in the root collapse of the Southwest Tianshan orogen.