【摘要】 江汉盆地早第三纪火山岩主、微量元素和Sr-Nd同位素以及精确的⁴⁰Ar/³⁹Ar年代学研究表明:该火山岩形成于57．3±0．4Ma,由亚碱性的玄武岩和玄武质安山岩组成,富集LILE和HFSE,（La/Yb）cn=3．5～10．4,Eu/Eu^?=0．99～1．08,具有与洋岛玄武岩（OIB）相似的地球化学特征。微量元素比值和Sr-Nd同位素组成上表明,其地球化学特征与源于EMII型富集岩石圈-软流圈相互作用而形成的华北南缘早第三纪火山岩以及东南沿海新生代玄武质岩石相似。结合长江中下游地区中生代玄武岩Pb同位素的资料,暗示扬子北缘新生代岩石圈地幔属性可能是其中生代属性的继承。江汉盆地早第三纪玄武质岩石是在陆内的岩石圈伸展拉张构造背景下,对流软流圈上涌导致EMII型岩石圈地幔部分熔融的结果。更多还原

【Abstract】 ⁴⁰Ar/³⁹Ar geochronology,major and trace elements and Sr-Nd isotope data are presented for the early Tertiary basaltic rocks from the Jianghan Basin.The volcanic rock were was erupted at ca.57Ma and belong to subalkali series.These basaltic rocks are generally characterized by enrichment in LILE and LREE （（La/Yb） cn=3.5-10.4） with insignificantly negative Eu anomalies （Eu/Eu^*=0.99～1.08）.These rocks display insignificant Nb-Ta positive anomalies,similar to those of ocean island basalt（OIB）. Their elemental and Sr-Nd isotopic signatures are similar to those of early Tertiary volcanic rocks from the southern margin of the North China Block and the late Cenozoic basaltic rocks in Southeast China.Combined with Pb data of Mesozoic basahs from the middle-lower section of the Yangtze river,we propose that the geochemical characteristicsfeature of the Cenozoic lihtospheric mantle beneath the northern Yangtze Block might inherit from that of Mesozoic lithospheric mantle.These basaltic rocks from the Jianghan basin in the northern Yangtze Block were generated from partial melting of EMII-like lithospheric mantle in respondings to the tectonic regime of intracontinental extension regime.更多还原