中文摘要：

柴北缘西段团鱼山花岗闪长岩体SiO2含量为66．35％-70．04％，具有富碱（Na20＋K20=7．20％～7．57％），富钠（Na2O／K2O=2．37～3．38），弱过铝质（A／CNK=1．00～1．02）以及低镁指数（Mg^#=23～26）等特点，为钙碱性弱过铝质花岗岩。岩石具有较低的Y（4．65×10^-6-6．31×10^-6），Yb（0．38×10^-6-0．54×10^-6）以及较高的Sr（858×10^-6-1020×10^-6）含量，Sr／Y=162～192，显示了高Sr低Y的地球化学特征。锆石的U—Pb同位素研究结果显示，团鱼山花岗闪长岩的侵位时代为（437．4±3）Ma。结合柴北缘地区超高压变质年龄（423～458Ma），认为该岩体是在陆壳俯冲背景下，基性下地壳加厚脱水引发部分熔融的结果，熔融温压条件可能为P〉I．2GPa和T〉800℃，源区残留相主要为石榴石＋角闪石。锆石Hf同位素研究结果表明，其￡。f（t）值变化于一11．4～8．15，二阶段模式年龄存在888～1078Ma（具正的εHf（t）值颗粒）和1300—1699Ma（具负的8Hf（t）值颗粒）两组，另有两个核部测点的二阶段模式年龄分别为2．45Ga和3．00Ga（对应测点的U—Pb年龄〉2．4Ga），表明团鱼山花岗闪长岩源区物质组成复杂，主要为中元古代一古元古代地壳物质和新元古代新生地壳，同时暗示柴北缘地区在太古代已有地壳形成。

英文摘要：

Granodiorites from the western segment of the Northern Qaidam have relatively high contents of SiO2 （66.35%-70.04%）, alkali （Na2O＋K20=7.20%-7.57%） and Na （NazO/K2O=2.37-3.38）, but low magnesium indexes （Mg^#=23-26） and A/CNK （1.00- 1.02）, suggesting that these rocks belong to talc-alkaline and weakly peraluminous granites. Moreover, these rocks have high contents of Sr （858 × 10^-6-1020 x 10-6） and low contents of Y （4.65 × 10^-6-6.31× 10^-6）, Yb （0.38 ×10^-6-0.54 ×10^-6）, showing characteristics of high SrfY ratios （162-192）. U-Pb isotopic compositions of zircons yield an intrusion age of （ 437.4 ± 3 ） Ma. Combined with the ultra-high pressure （UHP） metamorphic ages of 423-458 Ma in the Northern Qaidam, this pluton should have resulted from partial melting of thickened mafic lower crust during deep subduction of continental crust under conditions ofP〉l.2 GPa and T〉800 ℃ with residual mineral assemblages of garnet＋amphibole in source rocks. Lu-Hf isotopic compositions display large variations with Hf（t） changing from -11.4 to 8.15, and two-stage model ages can be divided into two groups. One group ranges from 888 to 1078 Ma （positive nf（t） values） and the other from 1300 to 1699 Ma （negative e t） values）. Moreover, two points at the cores of zircon crystals have tDm%2.45 Ga and 3.00 Ga （the associated U-Pb ages are 〉2.4 Ga）, respectively. These results suggest that the Tuanyushan pluton was likely derived from complicated sources which mainly consist of Meso-Neoproterozoic and Paleoproterozoic crust. The results also imply that the earliest crust in the Northern Qaidam may be formed in Archean.