中文摘要：

在柴达木盆地北缘中段的锡铁山地区，夹有榴辉岩或退变榴辉岩透镜体的2个副片麻岩样品的锆石被用于SHRIMP UPb测定。2个片麻岩样品具有类似的特征，主要由石榴子石、夕线石、长石、黑云母和石英组成，这些矿物组合形成的变质条件为0．6-0．9GPa和710-820℃，显示两处片麻岩经历了中压麻粒岩相条件的变质作用。锆石的SHRIMP U—Pb测定显示，2个样品均获得近一致的早古生代变质年龄（分别437Ma±6Ma和441Ma±15Ma）。代表早古生代的高温变质作用时代。样品XTS-1还获得890Ma±14Ma的年龄，所测定的锆石具有明显的变质作用成因特征，代表了新元古代早期的变质事件。反映了这些副片麻岩在早古生代造山旋回之前可能还经历了晋宁期的变质作用。

英文摘要：

Two paragneiss samples containing eclogite or retrograde eclogite lenses from the Xitieshan area in the central segment of the northern margin of the Qaidam basin were used for SHRIMP U-Pb zircon dating. The two samples have similar mineral assemblages composed predominantly of garnet, sillimanite, plagioclase, K-feldspar, quartz and biotite. The p-T conditions were 0.6-0.9 GPa and 710-820℃, suggesting a middle-pressure granulite facies metamorphism. SHRIMP U-Pb dathag of zircons from two samples, combined with CL and BSE images of zircons, indicates that the two samples give similar Early Paleozoic ages （437±6 Ma for sample XT-36 and 441±15 Ma for sample XTS-1）, representing the age of Early Paleozoic high-temperature granulite-facies metamorphism. The age of 890±14 Ma obtained from sample XTS-1 is interpreted as the age of early Neoproterozoic high-grade metamorphism and implies that these paragneisses may have undergone the Jinningian orogeny before the Early Paleozoic orogenic cycle.