中文摘要：

江浪穹窿位于扬子陆块西缘,其间的甲坝岩组发育一套顺层产出的角闪岩,主要由角闪石（80%-85%）、斜长石（10%-15%）与少量石英（〈3%）组成。为查明角闪岩的原岩性质、成岩时代及构造背景,对其进行岩石地球化学分析及LA-ICP-MS锆石U-Pb定年研究。主微量元素测试结果表明：（1）角闪岩w（SiO2）介于48.10%-54.44%,具有较高的Al2O3（平均13.82%）、Fe2O3-T（平均10.56%）、MgO（平均8.07%）、CaO（平均9.09%）含量;（2）轻、重稀土元素具中等程度分异（（La/Yb）N平均3.57）,无明显Ce异常与Eu异常;（3）富集大离子亲石元素（如Rb,Th和Sr）,亏损高场强元素（如Nb,P,Zr,Hf和Ti）,多数微量元素含量与N-MORB相当。原岩恢复及构造背景判别显示,角闪岩原岩可能是弧后盆地玄武岩。锆石U-Pb年代学分析表明,角闪岩中锆石具有清晰的振荡环带及较高的Th/U值（平均0.51）,应属岩浆成因;锆石-（207）Pb/-（206）Pb加权平均年龄分为2 385Ma及2 211 Ma两组,前者应为捕获锆石的年龄,后者可以代表原岩结晶年龄。这一结果暗示,至少有部分甲坝岩组地层形成于古元古代。综合分析,江浪穹窿很可能发育古元古代基底,且部分地层时代亟待重新厘定。

英文摘要：

A suite of bedded amphibolites occur in the Jiaba Rock Formation of the Jianglang dome in the western margin of the Yangtz block.The rocks are mainly composed of hornblende（80%-85%）,plagioclase（10% -15%）and minor quartz（3%）.Geochemical analyses and LA-ICP-MS zircon U-Pb dating are carried out to investigate the protolith,formation age and tectonic setting of the amphibolites.Analyses of major and trace elements indicate that：（1）the SiO2 contents range from 48.10% to 54.44% accompanied by high content of Al2O3（average13.82%）,Fe2O3-T（average 10.56%）,MgO（average 8.07%）,CaO（average 9.09%）abundances;（2）the LREEs and HREEs show medium fractionation（（La/Yb）Naverage 3.57）with no apparent Ce and Eu anomalies;and（3）the amphibolites are rich in large ion lithophile elements（such as Rb,Th and Sr）with depletion in high field strength elements（such as Nb,P,Zr,Hf and Ti）,and the abundances of most of the trace elements are close to those of N-MORB.The study reveals that the protolith of the amphibolites are most likely back-arc basin basalt.Zircon U-Pb dating indicates that magmatic zircons in the amphibolites have clear oscillatory zonings with high Th/U ratios（average 0.51）.The -（207）Pb/-（206） Pb weighted mean ages yield 2 385 Ma and 2 211 Ma.The former is the age of captured zircons,and the latter represents the crystallization age of metabasalt.It suggests that at least some part of the Jiaba Rock Formation formed in the Palaeoproterozoic and Palaeoproterozoic or Archean metamorphosed basements may exist in the Jianglang dome.Therefore,the formation ages of some strata in the area need to be reassessed.