| 洋中脊扩张速率对洋壳速度结构的约束 |
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| 引用本文： | 李龑,牛雄伟,阮爱国,刘绍文,Syed Waseem Haider,卫小冬.洋中脊扩张速率对洋壳速度结构的约束[J].地球物理学报,2020,63(5):1913-1926. |
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| 作者姓名： | 李龑 牛雄伟 阮爱国 刘绍文 Syed Waseem Haider 卫小冬 |
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| 作者单位： | 1. 南京大学地理与海洋科学学院, 海岸与海岛开发教育部重点实验室, 南京 210046;2. 自然资源部第二海洋研究所, 自然资源部海底科学重点实验室, 杭州 310012;3. National Institute of Oceanography, Karachi, Pakistan |
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| 基金项目： | 国家自然科学基金（41876060），国际海域资源调查与开发"十三五"课题（DY135-S1-01-05，DY135-G2-01-01），中国博士后科学基金（2019M652041）资助. |
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| 摘 要： | 洋中脊速度结构是揭示大洋岩石圈演化过程的重要约束.为探讨不同扩张速率下洋中脊的洋壳速度结构特征,挑选了全球152处快速(全扩张速率 90mm·a-1)、慢速(全扩张速率20～50mm·a-1)和超慢速(全扩张速率20mm·a-1)扩张洋中脊和非洋中脊的洋壳1-D地震波速度结构剖面,通过筛选统计、求取平均值等方法对分类的洋壳1-D速度结构进行对比研究,获得了不同扩张速率下洋中脊洋壳速度结构差异以及洋中脊与非洋中脊洋壳速度结构差异的新认识:(1)快速、慢速和超慢速扩张洋中脊的平均正常洋壳厚度分别为6.4km、7.2km和5.3km,其中洋壳层2的厚度基本相似,洋壳厚度差异主要源自洋壳层3;其洋壳厚度变化范围分别为4.9～8.1km、4.6～8.7km和4.2～10.2km,随着洋中脊扩张速率减小,洋壳厚度的变化范围逐渐增大;(2)快速扩张洋中脊的洋壳速度大于慢速和超慢速,可能与快速扩张脊洋壳生成过程中深部高密度岩浆上涌比较充足有关;(3)非洋中脊(10Ma)的洋壳比洋中脊(10Ma)的洋壳厚～0.3km,表明洋壳厚度与洋壳年龄有一定的正相关性.
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| 关 键 词： | 洋中脊 扩张速率 洋壳厚度 洋壳速度结构 |
| 收稿时间： | 2019-11-20 |
On spreading rates and crustal structure at mid-ocean ridges |
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| LI Yan,NIU XiongWei,RUAN AiGuo,LIU ShaoWen,Syed Waseem Haider,WEI XiaoDong.On spreading rates and crustal structure at mid-ocean ridges[J].Chinese Journal of Geophysics,2020,63(5):1913-1926. |
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| Authors: | LI Yan NIU XiongWei RUAN AiGuo LIU ShaoWen Syed Waseem Haider WEI XiaoDong |
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| Institution: | 1. School of Geography and Ocean Science, Ministry of Education Key Laboratory of Coastal and Island Development, Nanjing University, Nanjing 210046, China;2. Key Laboratory of Submarine Geosciences, Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China;3. National Institute of Oceanography, Karachi, Pakistan |
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| Abstract: | Understanding the velocity structure of mid-ocean spreading ridge is a key factor to investigate the evolution of oceanic lithosphere. In order to explore the characteristics of velocity structure of crust with different spreading rates,we select global 152 1-D seismic wave velocity structure profiles of both on and off-axis oceanic crust with spreading rates at fast (full spreading rate >90 mm·a-1), slow (full spreading rate 20~50 mm·a-1) and ultra-slow (full spreading rate <20 mm·a-1). The study is based on statistical analysis of average values of global on and off-axis oceanic crust with different spreading rates. It shows that:(1)The average oceanic crust thickness of fast,slow and ultra-slow spreading ridges is 6.4 km,7.2 km and 5.3 km,respectively,where the oceanic layer 2 shows similar thickness value,while the layer 3 has large variations. In addition,the oceanic crust thickness variation ranges are 4.9~8.1 km,4.6~8.7 km and 4.2~10.2 km from fast to ultra-slow ridges. The slower the spreading rates,the larger variations of the oceanic crust thickness are observed.(2)At a given depth, oceanic crust with fast spreading has faster velocity compared to the middle and slow one,this is probably related to the formation mechanism of oceanic crust at different spreading rates.(3)The thickness of oceanic crust at age older than 10 Ma is 0.3 km thicker compared to the one younger than 10 Ma. This is smaller but comparable to previous studies,which indicates that there is probably correlation between the seafloor age and oceanic crust thickness. |
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| Keywords: | Mid-ocean ridge Spreading rate Oceanic crustal thickness Oceanic crustal velocity structure |
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