中国东部大陆岩石圈地幔置换作用的内外原因

克拉通大陆通常有古老、巨厚且难熔的岩石圈地幔。这种地幔高度亏损玄武质组分，有密度低、刚性程度高的特点，能长期漂浮于软流圈之上而稳定存在。中国东部大陆主要由华北和华南两个古老地块在古生代—早中生代沿中央造山带拼合形成，在晚中生代时强烈活化，表现为构造变形、盆地形成、岩浆活动、巨量成矿等，其深部原因是什么？在分析东部大陆形成过程和岩石圈地幔属性基础上发现:块体初始规模小且发育薄弱带，后期容易受改造；特别是显生宙以来中国大陆受周边多个构造域夹持，板块俯冲作用会引起软流圈物质扰动和上涌并沿薄弱带侵蚀和改造上覆岩石圈，使之发生有效减薄、明显再富集和最终地幔置换。改造和置换后的岩石圈地幔富含玄武质组分，有较高密度和较低刚性程度，容易发生变形和部分熔融，使克拉通大陆活化。因此，块体规模大小并发育薄弱带以及周边构造环境是大陆稳定性控制重要的内、外在因素；中国东部大陆岩石圈显生宙强烈活化和地幔置换是由于块体规模较小而且周边多体系俯冲作用等内、外在有利因素协同作用下的结果。 

Internal and external factors in continental lithosphere mantle replacement in eastern China

Cratonic continent usually has an ancient, thick and refractory lithosphere mantle. Depleted basaltic composition, low density and high rigidity make the cratonic lithosphere float above the asthenosphere enclosure and exist stably for a long time. The eastern China continent was formed through the collision of the North and South China blocks along the Qinling-Dabie-Sulu Orogenic Belt during the Paleozoic and the early Mesozoic, and was reactive in the Phanerozoic, especially in the late Mesozoic. Since then, the eastern China continent showed the charateristics of strong tectonic deformation, basin formation, magmatism and massive mineralization. What are the deep reasons which caused these effects? Based on the analysis of formation and evolution of the eastern continent and the properties of the lithosphere mantle, it can be found that the initial scale of the block was small, and the developed zones were weak and easily affected by later transformation. Especially since the Phanerozoic, the Chinese mainland has been clamped by several surrounding tectonic domains, and the asthenospheric upwellings caused by subductions in different stages and directions have eroded along the weak zones and reformed the overlying lithosphere. These effects led to the thinning lithosphere, significant re-enrichment and ultimate mantle replacement. After the transformation and replacement, the lithosphere mantle that was enriched in basaltic components and had high density and low rigidity, was prone to deformation and partial melting, which made the stable cratonic continent activated. The block scale, internal weak zones and surrounding tectonic environment are, therefore, important internal and external factors in controlling continental stability. The lithospheric evolution of eastern China in the Phanerozoic reflects comprehensive records of these favorable factors.