东南印度洋中脊(108°—134°E区域)断层构造与岩浆活动关系
刘守金(1989—), 男, 山东沂水人, 在读博士研究生, 主要从事海洋地质研究。E-mail: |
Copy editor: 孙淑杰
收稿日期: 2018-10-19
要求修回日期: 2018-11-16
网络出版日期: 2019-07-21
基金资助
中国科学院前沿科学重点研究项目((QYZDY-SSW-DQC005);)
中国科学院南海海洋研究所所拨特聘研究员项目((Y4SL021001);)
中国科学院科研装备项目((YZ201325、YZ201534);)
中国大洋协会项目((DY135-S2-1-04);)
国家重点研发计划专项((2018YFC0309800);)
版权
Variations in tectonic faulting and magmatism at the Southeast Indian Ridge at 108°-134°E
Copy editor: SUN Shu-jie
Received date: 2018-10-19
Request revised date: 2018-11-16
Online published: 2019-07-21
Supported by
Chinese Academy of Sciences Project((Y4SL021001);)
Chinese Academy of Sciences Project((YZ201325、YZ201534);)
China Ocean Mineral Resources R&D Association((DY135-S2-1-04);)
National Key Research and Development Program of China((2018YFC0309800);)
National Natural Science Foundation of China((91628301, U1606401, 41706056).)
Copyright
东南印度洋脊(Southeast Indian Ridge, 简称SEIR)是中速扩张洋中脊, 在其中的108°—134°E区域的全扩张速率为72~76 mm·a -1。但在接近澳大利亚-南极洲不整合带(Australian-Antarctic Discordance, 简称AAD)区内, 海底地貌沿洋中脊的变化强烈, 其变化范围涵盖了从慢速到快速扩张洋中脊上常见的例子, 且出现了明显的地球物理与地球化学异常, 说明洋中脊在AAD区附近的岩浆供应量极不均匀。文章定量分析了高精度多波束测深数据, 计算了洋中脊不同段的地形坡度、断层比例以及平面与剖面的岩浆参数M值, 结合研究区内剩余地幔布格重力异常以及洋中脊轴部地球化学指标Na8.0、Fe8.0等资料, 分析与讨论了研究区的断层构造与岩浆活动特征的关系。研究发现, 东南印度洋脊108°—134°E区域的B区(在AAD区内)及C5段(在AAD区外西侧)发育有大量的海洋核杂岩, 而且B区的海洋核杂岩单体规模更大, 其中最大的位于B3区, 沿洋中脊扩张方向延伸约50km。研究结果首次系统性地显示, 相比东南印度洋的其他区域, B和C5异常区具有偏低的平面与剖面M值、偏高的断层比例、偏正的地幔布格重力异常以及偏高的Na8.0值与偏低的Fe8.0值, 这些异常特征可能反映了B区和C5段的岩浆初始熔融深度较浅以及岩浆熔融程度较低, 因此导致其岩浆供应量异常少, 形成较薄的地壳。研究结果同时表明, 在岩浆供应量极少的洋中脊, 构造伸展作用有利于海洋核杂岩的发育, 导致地壳进一步减薄。
关键词: 东南印度洋脊; 澳大利亚-南极洲不整合带; 海底断层; 岩浆参数M值; 海洋核杂岩; 多波束测深; 剩余地幔布格重力异常
刘守金 , 林间 , 罗怡鸣 . 东南印度洋中脊(108°—134°E区域)断层构造与岩浆活动关系[J]. 热带海洋学报, 2019 , 38(4) : 70 -80 . DOI: 10.11978/2018110
The Southeast Indian Ridge (SEIR) at 108°-134°E has a relatively constant intermediate full spreading rate of 72-76 mm·a -1 but exhibits significant variations in seafloor tectonic faulting and magmatism. This section of the SEIR encompasses the Australian-Antarctic Discordance (AAD), shows a wide range of seafloor morphology similar to the diverse examples from slow- to fast-spreading ridges, and is associated with significant geophysical and geochemical anomalies. We used high- resolution multi-beam bathymetry data to calculate seafloor topographic slopes, ratio of fault scarp areas, map view and profile M factors. Combining residual mantle Bouguer anomaly and geochemical factors of Na8.0 and Fe8.0, we analyzed the fault tectonics and magmatic characteristics in our study area. A large number of Oceanic Core Complexes (OCC) zones are observed in Zone B within the AAD and Segment C5 immediately to the west of the AAD. The OCC features in Zone B are in general larger in size than those of Segment C5. The largest OCC is located in Segment B3, which extends~50 km along the SEIR spreading direction. In comparison to other segments, Zone B and Segment C5 have more negative residual mantle Bouguer anomalies, higher Na8.0 and lower Fe8.0, more fault scarp areas, and lower plane and profile M factors. These anomalies may reflect shallower initial mantle melting and lower degree of partial melting in Zone B and Segment C5, resulting in anomalously low magma supply, thin crust, and the development of OCC features when the magma supply is severely limited.
图1 研究区水深及构造图黑色点线表示洋中脊的位置。OCC的位置用黄色星号表示。近南北向的线表示转换断层, 破碎带和非转换不连续带.黄色框线表示洋中脊分段及多波束水深数据的范围。红点和黄色短线是计算M值剖面的位置 Fig. 1 Topography and tectonic map of the study area. Black dots indicate the ridge axis. Yellow stars denote the locations of OCCs. Transform faults, fracture zones, and none-transform discontinuities are visible in the bathymetry map. White lines and frames define the ridge segments and regions with multi-beam bathymetry data. Red dots and yellow short lines show the locations of profiles for M factor calculations |
图3 岩浆参数M值计算卡通图a. 垂直于不含OCC的洋中脊剖面; b. 垂直于含OCC的洋中脊剖面。灰色垂直矩形表示洋中脊轴部岩浆注入的位置。箭头代表断块的位错方向。剖面修改自Smith(2013)。其中$M=\frac{\sum{{{X}_{\text{m}}}}}{\sum{{{X}_{\text{m}}}-\sum{{{X}_{\text{f}}}}}}$ Fig. 3 Cartoons for M factor calculations. Profiles perpendicular to normal mid-oceanic ridge: (a) without OCC; and (b) an OCC is located on the ridge flank. Vertical grey rectangles indicate the regions with magma intrusion. Arrows denote motion directions of fault blocks. Modified from Smith (2013). The M factor is given by $M=\frac{\sum{{{X}_{\text{m}}}}}{\sum{{{X}_{\text{m}}}-\sum{{{X}_{\text{f}}}}}}$ |
图4 研究区各段水深图(每子图的上方)及坡度图(子图的下方)黑色箭头代表洋中脊轴部位置及走向, 黑色圈指示OCCs高坡度区, 红色箭头指示OCCs. 白色线为剖面所在位置 Fig. 4 Water depth (top figure in each subpanel) and topographic slope (bottom figure) maps of ridge segments in our study area.Black arrows indicate the location and strike of the ridge axis. Black circles indicate regions with high slopes caused by OCCs. Red arrows indicate the OCCs.White lines denote locations of profiles |
图5 剖面的位置与水深(a)、剖面断裂位置(b)和坡度剖面(c)黑色箭头表示主要断层的位置和范围 Fig. 5 Profiles of water depth and slope of each segment. Locations of the profiles and water depth (top), faults locations (middle), and calculated slopes (bottom). Black arrows and short black lines denote the locations and extents of faults, respectively |
图6 研究区各分段坡度频率图研究区各段坡度被分为1000等份。黑点代表各分段坡度的频率, 曲线为三参数分布的拟合结果。阴影表示坡度≥10°区域的比例 Fig. 6 Slope frequency of each segment in the study area.Each segment was divided into 1000 parts. Black dots represent the slope frequency of the ridge segments. Black curves indicate the fitting results of three-parameter distribution. Areas with slope over 10° are shaded in light grey |
图7 研究区RMBA(a)、M值与RMBA的相关性(b)、RMBA与水深的相关性(c)图a中的白色圈线圈出了OCCs的范围; 图b中垂直误差棒与水平误差棒分别代表M值, RMBA的极值; 图c中红点表示研究区按0.1°×0.1°网格采样的平均水深与平均RMBA的关系, 蓝点代表OCC的平均水深与平均RMBA的关系, 垂直误差棒与水平误差棒分别为OCC区域RMBA的极值与水深的极值 Fig. 7 (a) RMBA in our study area. White curve lines outline the regions of OCCs. (b) Correlation between M factor and RMBA. Vertical and horizontal error bars show extremums of M factor and RMBA, respectively. (c) Correlation between RMBA and water depth. Red and blue dots denote average water depth versus average RMBA in 0.1°×0.1° grid of the whole study area and the OCC regions, respectively. Vertical and horizontal error bars represent extremums of RMBA and water depth of the OCC regions, respectively |
图8 研究区沿洋中脊的水深(a)、RMBA(b)、Na8.0(c)、Fe8.0(d)及平面和剖面M值(e)的剖面黑色箭头表示转换断层或者非转换不连续带的位置, 灰色虚线表示Na8.0值和Fe8.0值的变化趋势, 阴影表示发育OCC的洋脊段 Fig. 8 Profiles of (a) water depth, (b) RMBA, (c) Na8.0, (d) Fe8.0, and (e) map view M factor along the ridge axis in the study area. Black arrows indicate locations of the transform fault and the none-transform discontinuity. Gray dashed lines show trends of Na8.0 and Fe8.0 values. Ridge segments with OCCs are shaded in pink |
图9 研究区洋中脊的岩浆活动模型三角形表示上地幔部分熔融三角, 最上部浅蓝色长方体为地壳, 红色粗线条为洋中脊轴部, 黑色粗箭头为板块扩张方向 Fig. 9 Magmatic progress map of the study area. The triangles represent partial melting zones in the upper mantle. Red bold line on the crust surface represents the ridge axis. The black bold arrows represent the seafloor spreading directions |
[1] |
|
[2] |
|
[3] |
|
[4] |
|
[5] |
|
[6] |
|
[7] |
|
[8] |
|
[9] |
|
[10] |
|
[11] |
|
[12] |
|
[13] |
|
[14] |
|
[15] |
|
[16] |
KOJIMA, Y,
|
[17] |
|
[18] |
|
[19] |
|
[20] |
|
[21] |
|
[22] |
|
[23] |
|
[24] |
|
[25] |
|
[26] |
|
[27] |
|
[28] |
|
[29] |
|
[30] |
|
[31] |
|
[32] |
|
[33] |
|
[34] |
|
[35] |
|
[36] |
|
/
〈 |
|
〉 |