| 白垩纪以来太平洋上地幔组成和温度变化 |
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| 引用本文： | 张国良.白垩纪以来太平洋上地幔组成和温度变化[J].海洋学报(英文版),2016,35(4):19-25. |
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| 作者姓名： | 张国良 |
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| 作者单位： | 中国科学院海洋研究所, 海洋地质与环境重点实验室, 青岛 266071;青岛海洋科学与技术国家实验室, 海洋地质过程与环境功能实验室, 青岛 266235 |
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| 基金项目： | The Strategic Priority Research Program of the Chinese Academy of Sciences under contract No.XDA11030103; the National Natural Science Foundation of China under contract Nos 41376065, 41176043 and 41522602; the project of "AoShan" excellent scholar for Qingdao National Laboratory for Marine Science and Technology. |
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| 摘 要： | The geological evolution of the Earth during the mid-Cretaceous were shown to be anomalous, e.g., the pause of the geomagnetic field, the global sea level rise, and increased intra-plate volcanic activities, which could be attributed to deep mantle processes. As the anomalous volcanic activities occurred mainly in the Cretaceous Pacific, here we use basalt chemical compositions from the oceanic drilling(DSDP/ODP/IODP) sites to investigate their mantle sources and melting conditions. Based on locations relative to the Pacific plateaus, we classified these sites as oceanic plateau basalts, normal mid-ocean ridge basalts, and near-plateau seafloor basalts. This study shows that those normal mid-ocean ridge basalts formed during mid-Cretaceous are broadly similar in average Na8, La/Sm and Sm/Yb ratios and Sr-Nd isotopic compositions to modern Pacific spreading ridge(the East Pacific Rise). The Ontong Java plateau(125–90 Ma) basalts have distinctly lower Na8 and143Nd/144 Nd, and higher La/Sm and 87Sr/86 Sr than normal seafloor basalts, whereas those for the near-plateau seafloor basalts are similar to the plateau basalts, indicating influences from the Ontong Java mantle source. The super mantle plume activity that might have formed the Ontong Java plateau influenced the mantle source of the simultaneously formed large areas of seafloor basalts. Based on the chemical data from normal seafloor basalts, I propose that the mantle compositions and melting conditions of the normal mid-ocean ridges during the Cretaceous are similar to the fast spreading East Pacific Rise. Slight variations of mid-Cretaceous normal seafloor basalts in melting conditions could be related to the local mantle source and spreading rate.
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| 关 键 词： | 地幔温度 地幔源区 超级地幔柱 白垩纪 洋中脊玄武岩 |
| 收稿时间： | 2014/12/3 0:00:00 |
| 修稿时间： | 7/2/2015 12:00:00 AM |
Compositional and temperature variations of the Pacific upper mantle since the Cretaceous |
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| ZHANG Guoliang.Compositional and temperature variations of the Pacific upper mantle since the Cretaceous[J].Acta Oceanologica Sinica,2016,35(4):19-25. |
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| Authors: | ZHANG Guoliang |
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| Institution: | Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266235, China |
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| Abstract: | The geological evolution of the Earth during the mid-Cretaceous were shown to be anomalous, e.g., the pause of the geomagnetic field, the global sea level rise, and increased intra-plate volcanic activities, which could be attributed to deep mantle processes. As the anomalous volcanic activities occurred mainly in the Cretaceous Pacific, here we use basalt chemical compositions from the oceanic drilling(DSDP/ODP/IODP) sites to investigate their mantle sources and melting conditions. Based on locations relative to the Pacific plateaus, we classified these sites as oceanic plateau basalts, normal mid-ocean ridge basalts, and near-plateau seafloor basalts. This study shows that those normal mid-ocean ridge basalts formed during mid-Cretaceous are broadly similar in average Na8, La/Sm and Sm/Yb ratios and Sr-Nd isotopic compositions to modern Pacific spreading ridge(the East Pacific Rise). The Ontong Java plateau(125-90 Ma) basalts have distinctly lower Na8 and 143Nd/144Nd, and higher La/Sm and 87Sr/86Sr than normal seafloor basalts, whereas those for the near-plateau seafloor basalts are similar to the plateau basalts, indicating influences from the Ontong Java mantle source. The super mantle plume activity that might have formed the Ontong Java plateau influenced the mantle source of the simultaneously formed large areas of seafloor basalts. Based on the chemical data from normal seafloor basalts, I propose that the mantle compositions and melting conditions of the normal mid-ocean ridges during the Cretaceous are similar to the fast spreading East Pacific Rise. Slight variations of mid-Cretaceous normal seafloor basalts in melting conditions could be related to the local mantle source and spreading rate. |
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| Keywords: | mantle temperature mantle source super mantle plume Cretaceous mid-ocean ridge basalt |
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