| 贺根山镁铁-超镁铁岩与缝合带的关系——来自地球物理的证据 |
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| 引用本文： | 邵济安,张丽莉,周新华,张履桥,唐克东.贺根山镁铁-超镁铁岩与缝合带的关系——来自地球物理的证据[J].地球物理学报,2020,63(5):1867-1877. |
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| 作者姓名： | 邵济安 张丽莉 周新华 张履桥 唐克东 |
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| 作者单位： | 1. 北京大学造山带与地壳演化教育部重点实验室, 地球与空间科学学院, 北京 100871;2. 中国科学院地质与地球物理研究所, 中国科学院油气资源研究重点实验室, 北京 100029;3. 中国科学院地质与地球物理研究所岩石圈演化国家重点实验室, 北京 100029;4. 中国科学院大学地球与行星科学学院, 北京 100049;5. 内蒙古地质研究所, 呼和浩特 010020;6. 沈阳地质矿产研究所, 沈阳 110034 |
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| 基金项目： | 国家重点研发计划"深地资源勘查开采"重点专项（2017YFC0601206）；中国地质调查局项目"中国及邻区海陆大地构造总体框架和演化过程及其对资源-环境的控制"（12120110200050009）；国家自然科学基金（41774086）资助. |
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| 摘 要： | 长期以来,对内蒙古贺根山缝合带中的镁铁-超镁铁岩,有着"蛇绿岩"、"岩浆岩"、"幔源熔-流体"等不同认识.近年来在铬铁矿中发现了金刚石等深部地幔矿物,如何认识携带这些物质的幔源熔-流体的上涌?缝合带在镁铁-超镁铁岩的形成过程中起到什么作用?解决问题的关键之一是弄清镁铁-超镁铁岩的深部产状,这需要来自地球物理观测数据的依据.本文基于航磁和重力数据的研究表明,贺根山地区的蛇绿岩块均呈现高磁异常特征,其中贺根山岩块埋深明显大于其他岩块,表现为高磁异常与低重力异常,与地表出露的蛇纹石化的镁铁-超镁铁岩带对应.对航磁化极异常与布格重力异常数据做了向上延拓处理,进行了磁源形态及底界深度的估算,并利用基于相异度算子的边缘增强方法辅助识别断裂.结果表明,贺根山岩块贯穿地壳,且附近存在超壳断裂.地表至中地壳主要由蛇纹石化的镁铁-超镁铁岩组成,下地壳主要为超镁铁质岩组成,它们充填在一组宽约30km的NEE向断裂带中,大地电磁测深剖面揭示的壳-幔电性结构进一步证实控制缝合带的是岩石圈断裂,贺根山缝合带具有明显的根部.由此推测,在地幔底辟上涌的背景下,幔源熔-流体沿着岩石圈断裂持续上升到达浅表,暗示该区板块的拼合可能是通过深部幔源物质的侵入而成的.
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| 关 键 词： | 缝合带 镁铁-超镁铁岩 航磁异常 重力异常 向上延拓 幔源熔-流体 |
| 收稿时间： | 2019-03-12 |
The relationship between mafic-ultramafic rocks and suture zone in Hegenshan,Inner Mongolia—evidence from geophysical data |
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| SHAO JiAn,ZHANG LiLi,ZHOU XinHua,ZHANG LvQiao,TANG KeDong.The relationship between mafic-ultramafic rocks and suture zone in Hegenshan,Inner Mongolia—evidence from geophysical data[J].Chinese Journal of Geophysics,2020,63(5):1867-1877. |
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| Authors: | SHAO JiAn ZHANG LiLi ZHOU XinHua ZHANG LvQiao TANG KeDong |
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| Abstract: | The mafic-ultramafic rocks in Erlian-Hegenshan of Inner Mongolia suture zone have been recognized as "ophiolite", "magmatic rock", "mantle-source melt-fluid" and other petrological terms by a variety of authors for last few decades. Diamond and other deep mantle-derived minerals have been identified in chromite in Hegenshan region in recent years, which raised the question of mafic-ultramafic rocks. This study presents the new geophysical observation data dealing with deep occurrence of the mafic-ultramafic rocks. The newly gained aeromagnetic data indicate that the ophiolite zone in Hegenshan area appears to be with high-value magnetic anomalies, whereas the Hegenshan block has shown, due to its burying depth much deeper than that of adjacent blocks, obviously higher magnetic and lower Bouguer gravity anomalies, which are in accordance with the mafic-ultramafic rocks exposing on the surface. The aeromagnetic and Bouguer gravity anomaly data are processed with upward continuation and estimation of the shape and bottom surface depth of the magnetic source. And the faults are identified with the assistance of the dissimilarity-based edge enhancement algorithm. The results show that the Hegenshan block is extended through the crust and trans-crust faults were developed nearby. From the surface to the middle crust, main components are serpentinization mafic-ultramafic rocks, and the lower crust mainly consists of ultramafic rocks. A group of NEE trending faults with a width of about 30 km was intruded by above mentioned rocks. Electrical resistivity structure of the crust and mantle revealed from magnetotelluric data further demonstrates that the suture zone was controlled tectonically by the lithospheric faults. It is inferred that the mantle melt-fluid continuously permeated along the lithospheric faults and finally reached the shallow surface of the crust under the background of regional upwelling of mantle diapir. It is suggested that the amalgamation of the plates is completed by intrusion of the deep mantle-derived materials. |
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| Keywords: | Suture zone Mafic-ultramafic rock Aeromagnetic anomaly Gravity anomaly Upward continuation Mantle-source melt-fluid |
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