卡尔斯伯格脊 60°~61°E洋脊段多波束后向散射特征及其对构造与岩浆作用强度的指示

doi:10.3969/j.issn.1001-909X.2018.03.004

摘要/Abstract

摘要： 多波束声纳数据可以有效记录海底地形地貌和底质特征信息。本文利用船载多波束数据对慢速扩张的卡尔斯伯格脊60°~61°E洋脊段的典型构造地貌单元的后向散射强度特征进行了研究,在此基础上,分析了该洋脊段的构造和岩浆作用强度特征。结果表明,洋脊段I以构造拉张作用占主导,脊轴及附近后向散射强度为-29 dB左右,裂谷壁高差可达1 200 m以上,裂谷内断裂发育,裂谷侧翼高度与裂谷宽度的比值为78.7~126.2,裂谷两侧翼部线性构造较少,但轴向正断层面更宽,倾角更小;与洋脊段裂谷中段相比,末端火山活动频率较低但喷发规模较大,火山机构数量和体积也更大,且可发育深大断裂获取深部热源。洋脊段II以岩浆作用占主导,脊轴及附近后向散射强度达-35 dB,裂谷内轴向火山脊发育,裂谷壁高差小于500 m,裂谷侧翼高度与裂谷宽度的比值为77.6~116.8,裂谷两侧翼部线性构造数量众多、长宽比较大且呈近似对称,相邻线性构造之间沉积物广泛分布。通过提取挖掘与底质属性密切相关的多波束后向散射强度数据,结合海底地形地貌的分析,可以为洋中脊的构造和岩浆作用强度的定量研究提供有效的证据。

关键词: 多波束后向散射, 卡尔斯伯格脊, 构造和岩浆作用, 西北印度洋

Abstract: Multibeam sonar data can effectively reflect the features of seafloor topography and its substrates. The shipboard multibeam data were used to characterize the topography, geomorphology and the backscatter intensity characteristics of typical tectono-geographic units of the 60°-61°E segment in Carlsberg Ridge, Northwestern Indian Ocean, aiming to describe the strength of the magmatism and tectonism of the studied ridge segments. Basically, the 60°-61°E segment of Carlsberg Ridge showed symmetrical spreading with discontinuous zone. The Segment I was more influenced by tectonism, with more fractures occurred in the rift valley. The segment axis and nearby backscatter intensity reached -29 dB, with the rift wall height difference over 1 200 m. The segment also had deeper valley bottoms, higher rift valley walls, higher flank/width ratio (78.7-126.2) but less off-axial linear structures. In the rift flank, the normal fault plane was wider and the dip angle was smaller. Compared to the center of the segment, the volcanic activities in segment end had lower eruption frequency but larger eruption scale, and erupted volcanic edifices were larger in the aspect of number and volume. In contrast, the Segment II was dominated by magmatism with axial volcanic ridges and numerous symmetrically developed off-axial linear structures. The segment axis and nearby backscatter intensity reached -35 dB. The rift flank/width ratio was 77.6-116.8. The difference of the rift wall height was less than 500 m. The linear structures had relatively high aspect ratio, and were approximately symmetric on the flank of the rift. It is suggested that multibeam backscatter data combining with the topography analysis can provide quantitative evidence for the study of the strengths of the tectonism and magmatism of the mid-ocean ridge.

Key words: multibeam backscatter, Carlsberg Ridge, tectonism and magmatism, Northwestern Indian Ocean

中图分类号:

P736

杨驰, 韩喜球, 王叶剑, 李洪林, 邱中炎, 吴招才. 卡尔斯伯格脊 60°~61°E洋脊段多波束后向散射特征及其对构造与岩浆作用强度的指示[J]. 海洋学研究, 2018, 36(3): 37-49.

YANG Chi, HAN Xi-qiu, WANG Ye-jian, LI Hong-lin, QIU Zhong-yan, WU Zhao-cai. Characteristics of the multibeam backscatter of Carlsberg Ridge(60°-61°E) and its indication on the tectonism and magmatism[J]. Journal of Marine Sciences, 2018, 36(3): 37-49.

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