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首页> 外文期刊>Geochemistry, geophysics, geosystems >Crustal Magmatic System Beneath the East Pacific Rise (8°20' to 10°10'N): Implications for Tectonomagmatic Segmentation and Crustal Melt Transport at Fast-Spreading Ridges
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Crustal Magmatic System Beneath the East Pacific Rise (8°20' to 10°10'N): Implications for Tectonomagmatic Segmentation and Crustal Melt Transport at Fast-Spreading Ridges

机译：东太平洋下层（8°20'至10°10'n）的地壳岩石系统：在快速扩散脊时对Tectonomagmatic细分和地壳熔体运输的影响

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摘要

Detailed images of the midcrustal magmatic system beneath the East Pacific Rise (8°20'-10°10'N) are obtained from 2-D and 3-D-swath processing of along axis seismic data and are used to characterize properties of the axial crust, cross-axis variations, and relationships with structural segmentation of the axial zone. Axial magma lens (AML) reflections are imaged beneath much of the ridge axis (mean depth 1,640 ± 185 m), as are deeper sub-AML (SAML) reflections (brightest events ~100-800 m below AML). Local shallow regions in the AML underlie two regions of shallow seafloor depth from 9°40'-55'N and 8°26'-33'N. Enhanced magma replenishment at present beneath both sites is inferred and may be linked to nearby off-axis volcanic chains. SAML reflections, which are observed primarily from 9°20' to 10°05'N, indicate a finely segmented magma reservoir similar to the AML above, composed of subhorizontal, 2- to 7 km-long AML segments, often with stepwise changes in reflector depth from one segment to the next. We infer that these melt bodies are related to short-lived melt instability zones. In many locations including where seismic constraints are strongest the intermediate scale (~15-40 km) structural segmentation of the ridge axis identified in this region coincides with (1) changes in average thickness of layer 2A (by 10%-15%), (2) changes in average depth of AML (100 m), and (3) with the spacing of punctuated low velocity zones mapped in the uppermost mantle. The ~6 km dominant length of multiple AML segments within each of the larger structural segments may reflect the spacing of local sites of ascending magma from discrete melt reservoirs pooled beneath the crust.
机译：东太平洋上升（8°20'-10°10°10°10°）下方的半公分岩浆系统的详细图像从沿轴震动数据的2-D和3-D-SWATH处理获得，并且用于表征性质轴向壳，横轴变化和轴向区结构分割的关系。轴向岩浆镜头（AML）反射在大部分脊轴（平均深度1,640±185米）下方成像，如更深的子AML（SAML）反射（最亮的事件〜100-800米以下）。 AML中的地方浅地区底部的两个区域浅海底深度从9°40'-55'n和8°26'-33'n。推断出在两个地点下方的增强的岩浆补充，并且可以与附近的轴外火山链相关联。从9°20'观察到的SAML反射，表示与上述AML相似的精细分段的岩浆储存器，这些岩浆储存器由Subohorizo​​NTAL，2至7km-Long AML段组成，通常具有逐步变化从一个段到下一个段的反射器深度。我们推断这些熔体体与短寿命熔体不稳定区有关。在许多地方，包括地震约束最强的位置，该区域中鉴定的脊轴的中间尺度（〜15-40km）结构分割与（1）层2a的平均厚度的变化相一致（通过10％-15％）， （2）AML（＆LT 19米）的平均深度的变化，（3），带有标点的低速区的间距映射在最上面的地幔中。在每个较大的结构段中的多个AML段的〜6km主导长度可以反映来自在地壳下方的离散熔体储存器的升序岩浆局部位点的间隔。

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