Continent-ocean transition and voluminous magmatic underplating derived from P-wave velocity modelling of the East Greenland continental margin
Continent-ocean transition and voluminous magmatic underplating derived from P-wave velocity modelling of the East Greenland continental margin
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DOI：
10.1111/j.1365-246x.2007.03438.x
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发表时间：
2007-08
影响因子：
2.8
通讯作者：
M. Voss;W. Jokat
中科院分区：
文献类型：
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作者：
M. Voss;W. Jokat
摘要 2003年，在北纬72°至75°之间的扬马延断裂带以北的整个东格陵兰裂谷边缘收集了深部地震折射数据。对该大陆边缘深部地壳结构的研究为晚白垩世-早第三纪裂谷和大陆裂解期间和之后的边缘形成及其结构演化提供了约束。我们在这里展示位于 Godthab 湾延伸部分和 Kejser Franz Joseph 峡湾的两个剖面的结果。区域 P 波速度模型是根据陆地站的正向走时模型和海底水听器 (OBH) 记录得出的。东格陵兰岛附近的长深度地震探测横断面首次提供了对从大陆地壳到海洋地壳过渡过程中的地壳结构的全面了解。一个平均结果是识别出大量的岩浆底侵，其比之前想象的更宽更厚。底板材料的 P 波速度范围在 7.1 和 7.4 km s−1 之间，剖面上的水平范围为 225 和 190 km。底板材料的最大厚度为 15-16 公里。此外，基于对混有玄武岩侵入的白垩纪同裂谷沉积物范围和地壳层速度横向增加的解释，P波速度模型揭示了120-130公里宽的大陆-海洋过渡带（COT）。过量的岩浆作用一定是在长期的裂谷过程中出现的，伴随着大陆地壳的扩张，并产生了大量的岩浆底侵。我们对地震折射数据的解释的结果是格陵兰海可能存在从北到南的裂谷传播。此外，东格陵兰边缘和沃林边缘的纵波速度模型的比较揭示了明显不对称的地壳结构。大量的岩浆底侵和不对称的共轭边缘地层被认为是复杂的前裂谷和同裂谷过程的镜子。
SUMMARY Deep seismic refraction data were gathered across the entire East Greenland rifted margin north of the Jan Mayen Fracture Zone between 72°N and 75°N in 2003. Investigations of the deep crustal structure of this continental margin provide constraints on the formation of the margin and its structural evolution during and after late Cretaceous–early Tertiary rifting and continental break-up. We present here the results along two profiles located in the prolongation of the Godthab Gulf and the Kejser Franz Joseph Fjord. Regional P-wave velocity models were derived from forward traveltime modelling of land stations and ocean bottom hydrophone (OBH) recordings. For the first time, long deep seismic sounding transects off East Greenland provide a full insight into the crustal architecture of the transition from continental to oceanic crust. A mean result is the identification of voluminous magmatic underplating, which is wider and thicker than previously thought. P-wave velocities of the underplated material range between 7.1 and 7.4 km s−1 and the horizontal extents on the profiles are 225 and 190 km. The maximum thickness of the underplated material is 15–16 km. Furthermore, the P-wave velocity models reveal a 120–130 km wide continent–ocean transition zone (COT), based on an interpretation of the extent of Cretaceous syn-rift sediments mixed with basaltic intrusions and the lateral increase of velocities in the crustal layers. Excess magmatism must have been present during a long-term rifting process, accompanying the extension of the continental crust and giving rise to the voluminous magmatic underplating. A consequence of our interpretation of the seismic refraction data is a likely rift propagation in the Greenland Sea from north to south. Additionally, a comparison of P-wave velocity models of the East Greenland Margin and Voring Margin reveals significantly asymmetric crustal architectures. The voluminous magmatic underplating and asymmetrical conjugate margins formations are considered as a mirror of complex pre- and syn-rift processes.