南桥高度亏损N-MORB的发现及其地质意义  

The discovery of Nanqiao highly depleted N-MORB and geological significance

作　　者：周金城[1] 王孝磊[1] 邱检生[1] 高剑锋[1] 

机构地区：[1]南京大学地球科学系南京大学成矿作用国家重点实验室,江苏南京210093

出　　处：《岩石矿物学杂志》2003年第3期211-216,共6页Acta Petrologica et Mineralogica

基　　金：国家自然科学基金资助项目 (49872 0 30 )

摘　　要：对赣西北九岭古岛弧西延部分的湖南浏阳南桥玄武岩进行了单颗粒锆石蒸发法2 0 7Pb/ 2 0 6Pb年龄测定 ,结果为 12 71± 2Ma。该玄武岩辉绿岩显示高度亏损的地球化学特性 :K2 O极低 ,不相容的高场强元素和稀土元素的丰度均低于 (少数接近 )N_MORB的平均丰度 ,εNd(12 71Ma)为 6 .86～ 8.98,具典型N_MORB特性 ,可能为沿古俯冲带分布的洋壳残片 ,为九岭古岛弧提供了新的证据。With single-zircon evaporation technique, the authors determined 207Pb/ 206Pb age of Nanqiao basalt in Hunan, which is located along the westward extension of ancient Jiuling island arc in northwest Jiangxi. The data yield a zircon crystallization age of 1?271±2 Ma for the basalt. The basalt and diabase show highly depleted geochemical features: K 2O values are very low, abundances of their incompatible HFSE and REE are mostly lower than those of N-MORB (with a few close to the latter), and ε Nd(1?271 Ma)values vary from 6.86 to 8.98, suggesting typical N-MORB geochemical characteristics. This basalt may represent a relict of the ocean crust distributed along an ancient subduction zone and can serve as new evidence for ancient Jiuling island arc.

关 键 词：锆石^207Pb/^206Pb年龄 地质意义 玄武岩—辉绿岩 高度亏损N—MORB 南桥 九岭古岛弧 湖南 

分 类 号：P588.145[天文地球—岩石学]