Harmon Nicholas, Rychert Catherine, Agius Matthew, Tharimena Saikiran, Le Bas Tim, Kendall J Michael, Constable Steven
Ocean and Earth Science University of Southampton, Waterfront Campus Southampton UK.
Now at the Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA.
J Geophys Res Solid Earth. 2018 Dec;123(12):11016-11030. doi: 10.1029/2018JB015982. Epub 2018 Dec 14.
The Chain Fracture Zone is a 300-km-long transform fault that offsets the Mid-Atlantic Ridge. We analyzed new multibeam bathymetry, backscatter, gravity, and magnetic data with 100% multibeam bathymetric data over the active transform valley and adjacent spreading segments as part of the Passive Imaging of the Lithosphere Asthenosphere Boundary (PI-LAB) Experiment. Analyses of these data sets allow us to determine the history and mode of crustal formation and the tectonic evolution of the transform system and adjacent ridges over the past 20 Myr. We model the total field magnetic anomaly to determine the age of the crust along the northern ridge segment to better establish the timing of the variations in the seafloor fabric and the tectonic-magmatic history of the region. Within the active transform fault zone, we observe four distinct positive flower structures with several en échelon fault scarps visible in the backscatter data. We find up to -10 mGal residual Mantle Bouguer Anomaly in the region of the largest positive flower structure within the transform zone suggesting crustal thickening relative to the crustal thinning typically observed in fracture zones in the Atlantic. The extensional/compressional features observed in the Chain Transform are less pronounced than those observed further north in the Vema, St. Paul, and Romanche and may be due to local ridge segment adjustments.
链状断裂带是一条长达300公里的转换断层，它使大西洋中脊发生错断。作为岩石圈软流圈边界被动成像（PI-LAB）实验的一部分，我们分析了新的多波束测深、后向散射、重力和磁力数据，其中包括活动转换谷及相邻扩张段的100%多波束测深数据。对这些数据集的分析使我们能够确定过去2000万年里地壳形成的历史和模式以及转换系统和相邻海脊的构造演化。我们对总磁场异常进行建模，以确定北脊段地壳的年龄，从而更好地确定海底构造变化的时间以及该地区的构造-岩浆历史。在活动转换断层带内，我们观察到四个不同的正花状构造，在后向散射数据中可见若干雁列式断层陡崖。我们在转换带内最大正花状构造区域发现高达-10毫伽的剩余地幔布格异常，这表明相对于大西洋断裂带通常观察到的地壳变薄，该区域存在地壳增厚现象。链状转换带中观察到的伸展/挤压特征不如在更北部的韦马、圣保罗和罗曼什转换带中观察到的特征明显，这可能是由于局部海脊段调整所致。
