基于航磁资料的中国蛇绿岩带研究
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本文为国家自然科学基金地质联合基金重点项目(编号U2244220)和中国地质调查项目(编号DD20230351)联合资助的成果


Research on ophiolite belts in China based on aeromagnetic data
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    摘要:

    通过六十多年的积累,我国已经基本完成了中国陆域的航磁覆盖,为区域地质构造研究提供了详实的地球物理资料。航磁异常主要反映了岩石圈中磁性物质的分布情况,尤其是构造岩浆活动能够产生明显的磁异常,为隐伏岩浆岩的预测研究奠定了基础。镁铁—超镁铁质岩通常具有较强的磁性,可以通过航磁异常进行识别。本文基于全国1100万航磁数据及其岩性构造解释结果,阐述了通过航磁异常识别镁铁—超镁铁质岩的标志和圈定方法,分析了推断镁铁—超镁铁质岩与蛇绿岩带的关系。研究表明,蛇绿岩带通常都具有形态规则、宽度窄、异常幅值大的线性或串珠状磁异常特征,主要与蛇绿岩的保存情况密切相关。蛇绿岩带通常是不同板块的拼接带,呈现出区域磁异常边界的特征,代表不同陆块的基底性质的差异。但是,部分蛇绿岩带,如弧后盆地拉张等形成的蛇绿岩,因两侧地块基底性质相似,通常不具有分割区域磁场的特点。基于航磁推断镁铁—超镁铁质岩分布,在全国划分了22个蛇绿岩型镁铁—超镁铁质岩带,并对岩带的特征进行了详细描述。例如,雅鲁藏布江蛇绿岩带呈现出双磁异常带的特征,北带磁异常的规模较大、延伸长,推断深部存在镁铁—超镁铁质岩。南带磁异常规模较小,仅在日喀则地区连续分布,其余为串珠状磁异常,且不具有分割区域磁场的特点。通过磁异常三维反演,构建了雅鲁藏布江蛇绿岩带的深部结构模型。本文旨在通过磁异常的定性和定量分析,为蛇绿岩带(缝合带)的研究提供更多的信息,尤其是隐伏蛇绿岩,以指导铬铁矿找矿。目前航磁测量以中小比例尺为主,对于蛇绿岩带研究及铬铁矿找矿勘查是不足的,精细的分析和深部结构建模需要15万或更大比例尺航磁数据。

    Abstract:

    The aeromagnetic survey has almost covered the Chinese continent after the work has lasted for nearly 60 years, which provides detailed geophysical data for the study of regional geological structures. Aeromagnetic anomalies mainly reflect the distribution of magnetic materials in the lithosphere, especially the obvious magnetic anomalies produced by tectonicmagmatic activities, which lays a foundation for the prediction of concealed magmatic rocks. Maficultramafic rocks usually have strong magnetic susceptibility and can be identified by aeromagnetic anomalies. Based on 11000,000 aeromagnetic anomaly data and its inferred lithology and structure results in China, this paper systematically describes the identification and delineation methods of maficultramafic rocks, and analyzes the relationship between inferred maficultramafic rocks and ophiolite belts. The results show that the ophiolite belts usually have the characteristics of narrow width, high intensity, linear or beadlike magnetic anomaly with regular shape, which are mainly related to the preservation of the ophiolite. The ophiolite belts are usually splices of different plates, showing the boundaries of regional magnetic anomaly, and representing the differences in basement properties of different continental blocks. However, some ophiolitic belts, such as those formed by backarc basins, usually do not divide the regional magnetic field because of the similar basement properties of the two sides of the block. Based on the inferred distribution of maficultramafic rocks, 22 ophiolitic maficultramafic rock belts are divided in China, and the characteristics of these belts are described in detail. For example, the Yarlung Zangbo ophiolite belt shows double magnetic anomaly zones, the northern zone is large in scale and extends over a long distance, which indicates concealed maficultramafic rocks probably exist in the deep. The southern zone is small in scale and only distributed continuously in Shigatse, while the rest are beaded magnetic anomalies and do not divide regional magnetic fields. Through 3D inversion of magnetic anomalies, the deep structural characteristics of the Yarlung Zangbo ophiolite belt are constructed. Through qualitative and quantitative analysis of magnetic anomalies, this paper aims to provide more information for the study of ophiolite belts, especially the concealed ophiolites, to guide chromite prospecting. At present, aeromagnetic survey is mainly carried out on small and medium scale, which is insufficient for ophiolite belt research and chromite exploration, and 150000 or larger scale aeromagnetic data are needed for detailed analysis and deep structure modeling.

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熊盛青,杨海,范振宇,刘福香.2024.基于航磁资料的中国蛇绿岩带研究[J].地质学报,98(3):725-757.
XIONG Shengqing, YANG Hai, FAN Zhenyu, LIU Fuxiang.2024. Research on ophiolite belts in China based on aeromagnetic data[J]. Acta Geologica Sinica,98(3):725-757.

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  • 在线发布日期: 2024-03-27
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