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首页> 外文期刊>Geochemistry, geophysics, geosystems >Heterogeneous and asymmetric crustal accretion: New constraints from multibeam bathymetry and potential field data from the Rainbow area of the Mid-Atlantic Ridge (36 degrees 15'N)
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Heterogeneous and asymmetric crustal accretion: New constraints from multibeam bathymetry and potential field data from the Rainbow area of the Mid-Atlantic Ridge (36 degrees 15'N)

机译：异质和非对称地壳增加：来自多波束测深的新限制和来自大西洋中脊（36度15'N）彩虹区的潜在场数据

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摘要

At slow-spreading mid-ocean ridges, crustal accretion style can vary significantly along and across ridge segments. In magma-poor regions, seafloor spreading can be accommodated largely by tectonic processes, however, the internal structure and formation mechanism of such highly tectonized crust are not fully understood. We analyze multibeam bathymetry and potential field data from the Rainbow area of the Mid-Atlantic Ridge (35 degrees 40'N-36 degrees 40'N), a section of the ridge that shows diverse accretion styles. We identify volcanic, tectonized and sedimented terrain and measure exposed fault area to estimate the tectonic strain, T, and the fraction of magmatic accretion, M. Estimated T values range from 0.2-0.4 on ridge segments to 0.6-0.8 at the Rainbow nontransform discontinuity (NTD). At segment ends T is asymmetric, reflecting asymmetries in accretion rate, topography and faulting between inside and outside offset corners. Detachment faults have formed preferentially at inside corners, where tectonic strain is higher. We identify at least two oceanic core complexes on the fossil trace of the NTD, in addition to the Rainbow massif, which occupies the offset today. A gravity high and low magnetization suggest that the Rainbow massif, which hosts a high-temperature hydrothermal system, was uplifted by a west dipping detachment fault. Asymmetric plate ages indicate localization of tectonic strain at the inside corners and migration of the detachment toward and across the ridge axis, which may have caused emplacement of magma into the footwall. Hydrothermal circulation and heat extraction is possibly favored by increased permeability generated by fracturing of the footwall and deep-penetrating second-generation faults.
机译：在洋中脊缓慢蔓延的情况下，沿脊段和跨脊段的地壳吸积样式可能会发生很大变化。在岩浆稀少的地区，海底扩展可以通过构造过程大幅度地适应，但是，这种构造构造高度的地壳的内部结构和形成机理尚不完全清楚。我们分析了中大西洋海脊（35度40'N-36度40'N）彩虹区域的多波束测深和潜在场数据，该区域显示了多种吸积样式。我们确定火山，构造和沉积的地形，并测量裸露的断层面积，以估计构造应变T和岩浆增生的比例M。估计的T值范围在脊段为0.2-0.4，在彩虹非变换不连续处的范围为0.6-0.8。 （NTD）。在线段末端，T是不对称的，反映出吸积率，形貌以及内外偏角之间的断层的不对称性。断裂断层优先形成于构造应变较高的内角。除了彩虹断层块（今天占据了偏移量）外，我们还确定了新台币化石迹线上的至少两个海洋核心复合体。重力的高磁化强度和低磁化强度表明，承载高温水热系统的Rainbow断层由于西倾剥离断层而抬升。板块年龄的不对称性表明构造应变在内角处的定位以及向和穿过山脊轴方向的位移迁移，这可能导致岩浆进入底盘。水热循环和热量提取可能因底盘破裂和深部穿透的第二代断层所产生的渗透率增加而受到青睐。

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