| 地幔热导率的选取对动力学数值模拟的影响——以岩石圈张裂过程为例 |
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| 引用本文： | 谌永强,施小斌,廖杰,许鹤华,任自强.地幔热导率的选取对动力学数值模拟的影响——以岩石圈张裂过程为例[J].地球物理学报,2020,63(5):1998-2012. |
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| 作者姓名： | 谌永强 施小斌 廖杰 许鹤华 任自强 |
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| 作者单位： | 1. 中国科学院边缘海与大洋地质重点实验室, 中国科学院南海海洋研究所, 广州 510301;2. 中国科学院南海生态环境工程创新研究院, 广州 510301;3. 南方海洋科学与工程广东省实验室, 广州 510301;4. 中山大学地球科学与工程学院, 广州 510275;5. 中国科学院大学, 北京 100049 |
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| 基金项目： | 国家自然科学基金项目（41776078，41576036）和"广东省实验室项目（GML2019ZD0104）"资助. |
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| 摘 要： | 目前存在有多种地幔热导率模型,不同模型在数值和随温压变化的特征上有明显的差异.为探究不同热导率模型对动力学数值模拟结果的影响,本文对不同模型下的岩石圈张裂过程进行模拟研究,探讨地幔热导率对岩石圈热传输、变形和熔融过程的影响及其作用机理.结果显示,不同热导率模型下,岩石圈的变形和熔融特征表现出明显差异.高热导率模型下,岩石圈破裂较晚,形成陆缘较为宽阔,地壳熔融强烈而地幔熔融较弱;低热导率模型下,岩石圈破裂较早,形成陆缘较为狭窄,地幔熔融强烈而地壳熔融较弱.这种差异源于不同地幔热导率下岩石圈和地幔热状态的变化及相应力学性质的改变.高热导率下,热传导的增温效应显著,岩石圈呈现较热的状态,其强度整体较低,壳幔耦合减弱;而低热导率下,热对流的增温效应显著,岩石圈呈较冷的状态,其强度整体较高,壳幔耦合增强.基于模拟结果,本文认为地幔热导率的选取对动力学模拟的结果有着较为显著的影响,相对于随温压的变化,热导率数值的差异对动力学数值模拟的结果影响更大,尤其是对于地幔熔融过程的影响.
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| 关 键 词： | 地幔热导率 岩石圈张裂 动力学数值模拟 岩石圈强度 壳幔熔融 |
| 收稿时间： | 2019-10-14 |
The effect of mantle thermal conductivity on dynamic numerical modeling: a case study of lithospheric extension |
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| SHEN YongQiang,SHI XiaoBin,LIAO Jie,XU HeHua,REN ZiQiang.The effect of mantle thermal conductivity on dynamic numerical modeling: a case study of lithospheric extension[J].Chinese Journal of Geophysics,2020,63(5):1998-2012. |
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| Authors: | SHEN YongQiang SHI XiaoBin LIAO Jie XU HeHua REN ZiQiang |
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| Abstract: | So far multiple models of mantle thermal conductivity with different values and featured distribution with depth have been proposed, and some of them has already been applied in thermo-mechanic modeling. The effect of thermal conductivity on numerical modeling, however, still remains unclear. In this study, using two-dimensional thermo-mechanical model, we investigate the lithospheric extension process with different mantle thermal conductivity models, and discuss the impacts of different thermal conductivity models on heat transfer, lithospheric deformation and melting process. The results show that, with different models of mantle thermal conductivity, the characteristics of lithospheric deformation and melting of various numerical models are obviously distinct from each other. Models with a higher thermal conductivity are often featured by later breakup of lithosphere, wider continental margin and intense lower crust melting whereas weak melting of mantle; while models with a lower thermal conductivity often behave as earlier breakup of lithosphere, narrower continental margin and intense mantle melting whereas weak melting of lower crust. These distinct differences are mainly caused by the change of thermal state and mechanical properties of lithosphere or mantle under the control of different mantle thermal conductivity models. With higher mantle thermal conductivity, the Moho temperature elevated by thermal conduction is larger, which lowers the strength of the entire lithosphere and decouples crust and mantle strongly. As a consequence, the strain distributes more evenly and lithospheric thinning rate decreases, which leads a longer stretching stage and wider continental margin. On the contrary, with lower thermal conductivity, the temperature elevated by thermal conduction is smaller, which makes lithosphere stronger than models of higher thermal conductivity except for the region of high strain rates where mantle advection is more intense and the temperature elevated is higher. As a consequence, the strain distributes more centered and lithospheric thinning rate increases, which lead a shorter stretching stage and narrower continental margin. With respect to melting, high conductive heat of higher thermal conductivity model makes it possible for lower crust to be molten and even increases the melt with time, but the high heat loss and lower-rate decompression process in mantle suppress the melting of asthenosphere and even terminate it. But as for lower thermal conductivity model, the melting behavior of crust and mantle is totally opposite to higher thermal conductivity models, with more melt in mantle whereas less or even no melt in lower crust. Based on the results, we argue that mantle thermal conductivity may have greater effect on numerical modeling than we thought before, and compared with the effect of thermal conductivity varying with temperature and pressure, the value of thermal conductivity will bring more influence, especially on modeling of melting process. |
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| Keywords: | Mantle thermal conductivity Lithospheric extension Thermo-mechanical modeling Lithospheric strength Crust and mantle melting |
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