中国东部陆壳洋幔型岩石圈及其形成机制  

The Formation and Mechanism of the Continental Crust and Oceanic Mantle Type Lithosphere in Eastern China

作　　者：万天丰[1] 卢海峰[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《大地构造与成矿学》2014年第3期495-511,共17页Geotectonica et Metallogenia

基　　金：中国地质调查局地质调查工作项目(编号:科[2011]01-48-11)资助

摘　　要：长期以来中国东部岩石圈具有何种特殊性,其类型是否转变,其形成年代与形成机制等问题一直存在着不同意见。通过系统研究中国东部地质、地球化学与地球物理资料,笔者提出中国东部大陆地壳在侏罗纪晚期,受北美板块WSW向强烈的挤压以及特提斯洋朝东北方向张开的共同作用,使东亚大陆地壳发生逆时针转动,以致中国东部陆壳水平滑移到古老的洋壳或洋幔之上。在中国东部,原来的大陆型岩石圈的边部就出现较薄的陆壳洋幔型岩石圈（陆壳厚30-40 km,洋幔厚40-50 km）。幔源包体的资料表明中国东部岩石圈地幔与软流圈是未经扰动或轻微扰动,它们均发生在太古宙或中新元古代,还没有足够的在中、新生代发生扰动的证据。看来造成上述岩石圈结构类型的转换,不大可能是中、新生代大洋板块俯冲作用的直接结果,也不像是深部热地幔上涌或底侵作用的产物。强构造–岩浆活动源区形成于区域性断层与中地壳或莫霍面的构造滑脱的交切带,只有极少数的断层可深达岩石圈底面。中国东部岩石圈的构造滑脱面主要在中地壳或莫霍面,而不是在软流圈。中国东部中新生代强烈的构造-岩浆作用与内生金属成矿作用,正是受此种特殊岩石圈结构的控制而形成的。总之笔者认为：亚洲与中国大陆东部的岩石圈（包括其中的华北地区）在中、新生代并没有发生＂克拉通的裂解＂,而只是岩石圈的类型发生了变化,出现了一种洋陆过渡类型的陆壳洋幔型岩石圈。The eastern China lithosphere, including its type transformation, the formation period and mechanism, has been a hotspot for a long time. The authors proposed that there is a special thin lithosphere, consisting of continental crust（about 35 km thick） and oceanic mantle（about 40 km thick） in Eastern China. It probably caused by 20°-30° of counter clockwise rotation of the Eastern Asian continental crust in Late Jurassic, due to the WSW wards movement of the North American Plate and the NE wards extending of the Tethys Ocean; rather than the uplift of hot mantle plume or the subduction influences of oceanic plate directly, which subducted deep into the middle mantle（500-600 km depth）. The mantle xenoliths show that the lithospheric mantle underneath the eastern China is not disturbed or only slightly disturbed, which occurred in the Archaean and Meso-Neoproterozoic. Most regions with strong tectono-magmatism formed at the intersections among the regional faults and tectonic detachments occurred at middle crust or Mohorovicic discontinuity（up to 35 km depth）, and few faults cut the lithosphere. It means that the main tectonic detachments in the Eastern China lithosphere plate occur near the middle crust or Mohorovicic discontinuity, rather than the asthenosphere. Thus, the internal structure of the eastern Asian continental crust changed more complex than was believed, which resulted in the strong intraplate deformation, magmatism and metallogeny. The Eastern China lithosphere is different from most of continental lithospheres worldwide. To sum up, the authors consider that the Eastern Asia and China continental lithosphere was not formed by ＂destruction of craton＂ during the Meso-Cenozoic, and instead, only the lithosphere type changed, forming the continental crust and oceanic mantle type.

关 键 词：岩石圈 陆壳洋幔型岩石圈 陆壳水平转动与滑脱 侏罗纪 形成机制 

分 类 号：P541[天文地球—构造地质学]