论文部分内容阅读
中国东部华北和华南陆块的中生代镁铁质岩浆岩的Nd-Pb同位素存在显著差异:华北陆块中生代幔源岩浆岩的εNd值可低至-15～-21,206Pb/204Pb<17.9,而华南陆块的εNd值>-10,206Pb/204Pb>18.3.大别造山带北部发育的中生代辉石-辉长岩的εNd值可低至-19,206Pb/204Pb<17.3.这说明北大别带深部岩石圈的地球化学特征与华北陆块岩石圈类似,而不同于华南陆块.因此,虽然大别造山带华北与华南陆块地表地缝合线位于北大别带北侧,但是切割中国东部的中生代深部岩石圈Nd同位素剖面显示其深部地缝合线应位于北大别带以南.这与前人建议的郯庐断裂以东深部地缝合线南移现象是一致的,但与华南陆块地壳向北俯冲相矛盾.这一深部地缝合线与地表地缝合线的解耦现象可以用大陆碰撞岩石圈楔入模型来解释.俯冲板片断离后,两陆块的持续会聚可形成缝合带的强挤压环境,从而导致已折返的俯冲陆壳与未折返的镁铁质下地壳及岩石圈地幔分离,并使华北陆块下地壳及岩石圈楔入扬子陆块北缘俯冲陆壳和岩石圈地幔之间.这一构造作用导致华南陆块原俯冲陆壳向北仰冲,而华南陆块深部岩石圈向华北陆块下俯)中.它是导致大别山侏罗纪超高压变质岩的第2次快速抬升和岩石圈拆离(delamination)及相应岩浆作用的重要构造机制.大别-苏鲁造山带深部地缝合线?
The Nd-Pb isotopes of the Mesozoic mafic magmatic rocks in North China and South China continent blocks in east China are significantly different: the εNd values of Mesozoic mantle magmatic rocks in North China can be as low as -15 to -21 and 206Pb / 204Pb <17.9, respectively, whereas the South China ΕNd> -10,206Pb / 204Pb> 18.3. The εNd value of the Mesozoic pyroxene-gabbro developed in the northern part of the Dabie orogenic belt can be as low as -19,206Pb / 204Pb <17.3, indicating that the deep lithosphere Is similar to the lithosphere of the North China continent but different from the South China continent.Therefore, although the surface suture of the North China and South China continent in the Dabie orogenic belt is located on the north side of the North Dabie belt, the deep Mesozoic rocks The circle Nd isotope profile shows that the deep suture line should be located south of the North Dabie belt, which is in agreement with the southward suture phenomenon of deep suture line east of the Tanlu fault suggested by the predecessor. However, The decoupling between this deep suture and the surface suture can be explained by the wedge model of the continental collision lithosphere.Under the subduction plate separation, the continuous convergence of the two blocks can form a strong compression environment for the suture , Which has led to the return The continental crust separated from the unconformable mafic lower crust and the lithospheric mantle and wedged the lower crust and lithosphere of the North China block between the subducted continental crust and the lithospheric mantle in the northern margin of the Yangtze Block. The southern subduction of the southern South China continent subduction continental crust northward overturning, and the deep lithosphere of the South China block to the North China continent down), which is the second rapid uplift and delamination of Jurassic UHP metamorphic rocks in the Dabie Mountains, And the important tectonic mechanism of the corresponding magmatism.The deep suture of the Dabie-Sulu orogenic belt?