Three-dimensional magnetic and gravity studies of the Rodriguez Triple Junction in the indian Ocean
Three-dimensional magnetic and gravity studies of the Rodriguez Triple Junction in the indian Ocean
复制标题
印度洋罗德里格斯三重交界处的三维磁力和重力研究
DOI：
10.1029/96jb00644
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发表时间：
1996
影响因子：
--
通讯作者：
H. Fujimoto
中科院分区：
文献类型：
--
作者：
C. Honsho;K. Tamaki;H. Fujimoto
罗德里格斯三脊(RTJ)是连接印度洋中三个洋脊：中印度洋海脊(CIR)、东南印度洋海脊(SEIR)和西南印度洋海脊(SWIR)的海脊-海脊三重交汇处。对三联点200公里×140公里范围内的海束测深、磁、重力异常资料进行了三维分析，得到了磁化强度分布和布格异常场。在磁性反演结果中，在SWIR河谷内识别出了CIR和SEIR的一些磁性线理，尽管SWIR山谷具有大的地形起伏，但布格异常场在SWIR山谷上变化不大。这些结果表明，在没有火山活动的情况下，SWIR的构造裂谷是地壳减薄所致。CIR西侧4公里宽的地堡与CIR东侧相比，具有极高的磁化强度和较低的布格异常。由于CIR和SEIR在三重结处具有相似的扩展方向和速率，我们认为地堑代表了SEIR的一个化石传播裂谷，大约在1 Ma左右开始向CIR扩展，然后当SWIR在大约0.5 Ma增长到CIR+SEIR扩展轴时变得不活跃。我们认为，上述过程重复几次，并构成较长时间尺度上三重结进化的一部分。我们还认为，整个过程与20 Ma以来三重结处CIR段的形成密切相关。
The Rodriguez Triple Junction (RTJ) is a ridge-ridge-ridge triple junction connecting three mid-ocean ridges in the Indian Ocean: the Central Indian Ridge (CIR), Southeast Indian Ridge (SEIR), and Southwest Indian Ridge (SWIR). We carried out three-dimensional analyses of Sea Beam bathymetry, magnetic, and gravity anomaly data covering an area of about 200 km × 140 km at the triple junction and obtained the magnetization distribution and the Bouguer anomaly field. In the magnetic inversion result some of the magnetic lineations of the CIR and SEIR are recognized within the SWIR valley, and the Bouguer anomaly field shows little variation over the SWIR valley in spite of its large topographic relief. These results indicate the tectonic rifting at the SWIR by crustal thinning without volcanic activity. A 4-km-wide graben in the western CIR flank was found to have extremely high magnetization and lower Bouguer anomaly than the eastern flank of the CIR. Because the CIR and SEIR have similar spreading directions and rates at the triple junction, we consider the graben represents a fossil propagating rift of the SEIR, which began to propagate toward the CIR at about 1 Ma and then became inactive when the SWIR grew to reach the CIR + SEIR spreading axis at about 0.5 Ma. We suggest the above process repeats several times and composes part of the triple junction evolution on a longer timescale. We also suggest that the whole process is closely related to formation of the CIR segments at the triple junction since 20 Ma.