| Liu Shoujin,Lin Jian,Zhou Zhiyuan,Zhang Fan. 2020. Large along-axis variations in magma supply and tectonism of the Southeast Indian Ridge near the Australian-Antarctic Discordance. Acta Oceanologica Sinica, 39(1):118－129 |
| Large along-axis variations in magma supply and tectonism of the Southeast Indian Ridge near the Australian-Antarctic Discordance |
| 东南印度洋中脊澳大利亚-南极洲不整合带地区岩浆供应与构造作用沿洋脊的变化 |
| Received:October 08, 2018 |
| DOI：10.1007/s13131-019-1518-z |
| Key words:Oceanic Core Complexes magma supply Southeast Indian Ridge lithospheric deformation Australian-Antarctic Discordance |
| 中文关键词: 海洋核杂岩 岩浆供应 东南印度洋脊 岩石圈变形 澳大利亚-南极洲不整合带 |
| 基金项目:The National Key R&D Program of China under contract Nos 2018YFC0310105 and 2018YFC0309800; the China Ocean Mineral Resources R&D Association under contract No. DY135-S2-1-04; the National Natural Science Foundation of China under contract Nos 41890813, 91628301, 41976066, 41706056, 41976064, 91858207 and U1606401; the Chinese Academy of Sciences under contract Nos Y4SL021001, QYZDY-SSW-DQC005 and 133244KYSB20180029; the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) under contract No. GML2019ZD0205. |
| Author Name | Affiliation | E-mail | | Liu Shoujin | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
University of Chinese Academy of Sciences, Beijing 100049, China | | | Lin Jian | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA | | | Zhou Zhiyuan | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 523936, China | zyzhou@scsio.ac.cn | | Zhang Fan | Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences, Guangzhou 523936, China | |
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| Abstract: |
| We analyzed seafloor morphology and geophysical anomalies of the Southeast Indian Ridge (SEIR) to reveal the remarkable changes in magma supply along this intermediate fast-spreading ridge. We found systematic differences of the Australian-Antarctic Discordance (AAD) from adjacent ridge segments with the residual mantle Bouguer gravity anomaly (RMBA) being more positive, seafloor being deeper, morphology being more chaotic, M factors being smaller at the AAD. These systematic anomalies, as well as the observed Na8.0 being greater and Fe8.0 being smaller at AAD, suggest relatively starved magma supply and relatively thin crust within the AAD. Comparing to the adjacent ridges segments, the calculated average map-view M factors are relatively small for the AAD, where several Oceanic Core Complexes (OCCs) develop. Close to 30 OCCs were found to be distributed asymmetrically along the SEIR with 60% of OCCs at the northern flank. The OCCs are concentrated mainly in Segments B3 and B4 within the AAD at~124°-126°E, as well as at the eastern end of Zone C at~115°E. The relatively small map-view M factors within the AAD indicate stronger tectonism than the adjacent SEIR segments. The interaction between the westward migrating Pacific mantle and the relatively cold mantle beneath the AAD may have caused a reduction in magma supply, leading to the development of abundant OCCs. |
| 中文摘要: |
| 通过分析东南印度洋脊（SEIR）的海底形态和地球物理异常，揭示了沿着这个中速扩张脊岩浆供应的显著变化。结果发现澳大利亚-南极洲不整合带（AAD）与邻近洋脊段存在系统性地差异，包括AAD区的剩余地幔布格重力异常（RMBA）更正，海底更深，形态更混乱，M值更小。结合前人观测到的更大的Na8.0和更小的Fe8.0等地球化学异常，表明AAD地区的岩浆供应相对匮乏以及地壳偏薄。同时AAD地区海洋核杂岩大量发育，计算得到的M也比相邻的洋脊段小。沿着东南印度洋脊发现了近30个不对称分布的OCC，60%的OCC位于北翼。OCC主要集中在AAD区~124°-126°E的B3和B4段，以及在C区~115°E的东端。AAD中相对较小的M值表明AAD区的构造作用比相邻洋脊段更强烈。向西移动的太平洋地幔与AAD下相对较冷的地幔之间的相互作用可能导致岩浆供应减少，进而造成OCC的大量发育。 |
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