摘要
利用广州海洋地质调查局在神狐海域采集的高分辨率地震数据,结合2007年第一次水合物钻探航次(GMGS01)获取的岩心资料,从地震反射结构和岩心粒度特征两个方面对GMGS01区块内残留在峡谷群脊部的细粒浊积体进行了识别和特征刻画。过水合物钻探站位的准3D地震剖面显示,GMGS01区块似海底反射(bottom simulating reflectors,BSR)之上的沉积体表现为2套特征迥异的反射单元:位于下部的薄层透镜状的杂乱反射单元,位于上部的厚层波状起伏形态的连续性中—强振幅反射单元。实际钻获岩心的粒度分析结果表明,沉积物的粒度为4~63μm,为细粒的粉砂或粉砂质泥。自下而上,沉积物的岩性和粒度特征没有发生大的变化,较为相似。但通过粒度CM图,可以发现,含水合物层段与不含水合物层段的沉积物表现为不同的特征,含水合物层段沉积物的结果近似与C=M基线平行,暗示了细粒浊积体的存在。结合神狐海域区域性覆盖的2D地震资料,研究认为发育在神狐海域北部的一系列小型水道,将会侵蚀下部地层的沉积物,使其沿着陆坡坡降的方向发生自北向南的再次搬运,在中—下陆坡的位置以细粒浊积体的形式再次沉积下来。神狐海域细粒浊积体的识别,将为从深水沉积的角度探讨GMGS01区块内水合物的不均匀性分布提供依据,从而有助于进一步揭示该区域水合物的成藏机制和富集规律。
Based upon the high-resolution seismic data acquired by the Guangzhou Marine Geological Survey and the cores collected by the First Hydrate Drilling Expedition（GMGS01）,a kind of fine-grained turbidite is identified in the Shenhu Area of the northern South China Sea.According to the seismic profiles crossing hydrate drilling sites,two seismic units are recognized above the BSR（bottom simulating reflectors）：the Unit 1 at the bottom consisting of thin-bedded lenticular chaotic seismic reflectors and the Unit2 at the top consisting of thick continuous moderate-amplitude seismic reflectors with wavy structures.Grain size analysis illustrates that the deposits are composed of fine-grained silt or silty clay ranging 4-63μm in grain size.Both the lithological features and grain size parameters are consistent from bottom to top without significant changes.It implies that all the deposits should be the results of a similar depositional process.Moreover,on the C-M diagram,the samples from the hydrate bearing sediments show a distribution pattern parallel to the C=M baseline,indicating an origin of fine-grained turbidites.Regional survey suggests that these fine-grained turbidites might be associated with some small-scale channels in the north of the Shenhu Area.The sediments provided by these small channels move downslopewards and re-deposited in the middle to lower slope as fine-grained turbidites.Based upon the above interpretation,a model is proposed to reveal the relationships between fine-grained tuebidites and hydrates,It says that the heterogeneous distributions of gas hydrates in GMGS01 of the Shenhu Area,northern South China Sea probably owes its origin to the uneven distribution of fine grained turbidites.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2017年第5期131-140,共10页
Marine Geology & Quaternary Geology
基金
国家自然科学基金项目(41576048)
油气藏地质及开发工程国家重点实验室(成都理工大学)开放基金(PLC201407)
广州市珠江科技新星(201710010198)
中国石油-中国科学院科技合作项目(2015A-4813)
关键词
细粒浊积体
天然气水合物
神狐海域
南海北部陆坡
fine-grained turbidites
gas hydrate
northern continental slope of the South China Sea
Shenhuarea
