科研之友
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摘要
The relationships between tectonic processes, magmatism, and hydrothermal venting along similar to 600 km of the slow-spreading Mariana back-arc between 12.7 degrees N and 18.3 degrees N reveal a number of similarities and differences compared to slow-spreading mid-ocean ridges. Analysis of the volcanic geomorphology and structure highlights the complexity of the back-arc spreading center. Here, ridge segmentation is controlled by large-scale basement structures that appear to predate back-arc rifting. These structures also control the orientation of the chains of cross-arc volcanoes that characterize this region. Segment-scale faulting is oriented perpendicular to the spreading direction, allowing precise spreading directions to be determined. Four morphologically distinct segment types are identified: dominantly magmatic segments (Type I); magmatic segments currently undergoing tectonic extension (Type II); dominantly tectonic segments (Type III); and tectonic segments currently undergoing magmatic extension (Type IV). Variations in axial morphology (including eruption styles, neovolcanic eruption volumes, and faulting) reflect magma supply, which is locally enhanced by cross-arc volcanism associated with N-S compression along the 16.5 degrees N and 17.0 degrees N segments. In contrast, cross-arc seismicity is associated with N-S extension and increased faulting along the 14.5 degrees N segment, with structures that are interpreted to be oceanic core complexes-the first with high-resolution bathymetry described in an active back-arc basin. Hydrothermal venting associated with recent magmatism has been discovered along all segment types.
- 出版日期2017-6
