由于蕴含着潜在的油气勘探和资源储藏信息,岩床复合体在全球范围内被广泛研究.本文基于南海北部三维地震资料以及南极罗斯海地区二维多道地震资料,对岩床复合体的形态特征及分布进行分析,对两个地区岩床复合体的形成时间进行判断,阐述岩床复合体的侵位机制.研究发现,岩床复合体代表性产状除了菱形、碟形及复合型外,还存在沿着层位平行侵入的板状,推测它可能是夭折了的岩床侵入体,以及由几个小型岩床堆叠而成的透镜状岩床复合体.分布上,南海北部岩床主要发育于珠江口盆地白云凹陷三维工区西部,东部只零星可见;南极西罗斯海岩床主要发育于西北角的阿黛尔盆地内.根据岩床上覆的强制褶皱结合区域构造背景,推测南海北部岩床复合体的形成时间为早中新世(15.5 Ma),海底扩张结束之时.残余岩浆将盆地内裂谷时期形成的断层作为岩浆运移的通道,并最终在断层终点处即下中新统近海相砂泥岩地层中实现侵位.南极西罗斯海岩床复合体的形成时间则非常晚,不早于5.5 Ma.该区这期岩浆活动可能与构造作用无关,而是受到冰川消融的影响.研究发现岩床复合体内部的岩床个体互相供给,即深部的大岩床为上覆浅层的小岩床提供岩浆供给,并且互相组合,形成大的岩床复合体.然而,每个岩床复合体则可能由不同的岩浆供给发育而成.%Sill complex has been focus of numerous studies in the past decades because it bears potential important information on energy exploration. The seismic characteristics and spatial distribution of the sill complexes in the northern South China Sea and the Ross Sea, Antarctica were analyzed on the basis of 3D and 2D seismic data of the two regions. We speculated the ages of the sill complexes and discussed their emplacement mechanisms. Our analysis shows that the sill complexes comprise mainly of sills in shapes of rhombus, saucer and a combination of these two, and occasionally tabular-shape and lens-shape lopoliths. The lopoliths occur as layer-parallel intrusions, whereas a few subparallel stacking lopoliths may form a large sill and appear as apparent uplift in the top layer. The sill complexes in the northern South China Sea occur mainly in the western survey area of Baiyun Sag and much less in the eastern part. We suggest that the sill complexes were formed in early Miocene (ca. 15.5 Ma), very close to the cessation of seafloor spreading, according to the geological background of forced fold above igneous sills. Emplacement of the sill complexes were likely resulted from the magma migration along the syn-rift faults. On the contrary, the igneous sills in the Ross Sea are primarily located in the Adare Basin, emplaced not earlier than 5.5 Ma. The sill complexes commonly comprise of many interconnected sills, within which sills at the depth might have been channel ways for magma migration that led to the formation of the sills at the shallow parts. However, the feeders for the construction of sills could not be identified in the seismic profiles because of the depth and high angle features. It is likely that each sill complex has its own magma source.
展开▼
