南黄海北部白垩纪沉积物下的变质岩体演化  

Evolution of metamorphic rocks under the Cretaceous sediments in northern South Yellow Sea

作　　者：倪斌[1] 杨风丽[1] 李筱[1] 于鹏[1] 

机构地区：[1]同济大学海洋与地球科学学院,上海200092

出　　处：《中国矿业大学学报》2016年第3期544-552,共9页Journal of China University of Mining & Technology

基　　金：国家自然科学基金项目(41541027);国家科技重大专项(2011ZX05023-003-003);中国地质调查局油气资源调查中心项目(1211302108024-3)

摘　　要：为了揭示南黄海北部白垩纪沉积物下的地震反射异常体的地质属性和形成过程,进行了地震反射和重、磁反演等研究,结合区域地表地质研究成果,推测该异常体可能为三叠纪下扬子地块深俯冲阶段经历高压变质作用后被拆离折返的岩体,并在南北两大地块汇聚、碰撞造山过程中被推覆至南黄海北部的古生代地层之上.研究结果显示：异常体内部地震反射特征表现为杂乱和空白反射,局部存在发散结构;与上、下地层之间存在2~3个同相轴的较强—强反射;另外,该异常体也具有高层速度（6 000~6 500m/s）、高密度（〉2.7g/cm3）和中低磁化强度（-0.5A/m）等特征.通过海陆区域地质调查和类比,进一步揭示了该异常体和苏鲁三叠系高压变质地体具有时空上的一致性.这一发现为认识印支期东亚大陆碰撞和地质演化提供了参考.Based on the study in seismic reflection as well as gravity and magnetic reversions, the geological feature and formation process of a seismic reflection anomalous body under Cre taceous sediments in the northern depression of the South Yellow Sea basin were studied. Combining with regional geological research, it is speculated that the anomalous body could be the high-pressure metamorphic rock which was detached and exhumed from the deep crust and thrust up to the Paleozoic strata of the northern South Yellow Sea during the Triassic continen- tal collision between lower Yangtze and North China plates. The results indicate that the a- nomalous body is mainly characterized by clutter or blank reflection, with divergent reflection in some areas; two to three seismic events separate it from the overlying and underlying stra- tum. Furthermore, it has high wave velocity （6 000 -6 500 m/s）, high density （〉2.7 g/cm3） and medium to low magnetization （-0.5 A/m）. Regional geological survey further unravels the spatial and temporal consistency between the anomalous body and the Sulu Triassic high- pressure metamorphic block. The findings provide a reference for the understanding of the con- tinental collision and geological evolution of east Asia during Indo-China epoch.

关 键 词：南黄海 苏鲁造山带 地震反射异常体 高压-超高压变质岩体 

分 类 号：P631[天文地球—地质矿产勘探]