长江中下游中生代花岗岩类源区的壳-壳混源性质

Crust Crust Mixing Source Characteristics of Mesozoic Granitoids in the Middle Lower Reaches of the

长江中下游地区中生代花岗岩类形成于大别造山带碰撞后岩石圈物质的调整演化过程。Ｓｒ、Ｎｄ、Ｐｂ同位素组成数据表明，早、晚阶段花岗岩类具有相似的壳－壳混合源区性质，其主要源岩端员可能分别相当于以大别杂岩为代表的深变质岩系和中、新元古界底侵（ｕｎｄｅｒｐｌａｔｉｎｇ）基性物质与部分古元古界沉积－火山－侵入岩系组成的扬子陆块下地壳岩石。这两种成分不同的下地壳物质在这里呈指状穿插体结构。长江中下游地区下地壳在碰撞造山过程中曾是大别地块与扬子地块之间的深部构造混杂带。本文主要根据各类已有的Ｓｒ、Ｎｄ。

Mesozoic granitoids in the middle and lower reaches of the Yangtze River were formed in the process of adjustment of lithospheric matters after the collision of North China and Yangtze craton. Systematic studies of Sr, Nd, Pb isotopic data show that the two stages of granitoids are characterized by similar magmatic sources and the existence of crust crust mixing. In the crust crust mixed magmatic sources, the main mixing members may be the source rocks of the granitoids in DL and YZL lithozones, the former equal to high grade metamorphic rocks in Dabie complex and the latter being the basic and intermediate basic meta igneous rocks which underplated and midplated into the lower crust during Pt 2-3 and the Pt 1 sedimentary volcanic rocks in the Yangtze cratonr. Those characteristics indicate that the lower crust in the middle and lower reaches of the Yangtze River was tectonic melange belt between Dabie block and Yangtze block during the Mesozoic collision of the two blocks. Two different substances formed finger like connection texture in the lower crust of YZC block (the middle and lower reaches of the Yangtze River).