三维大地电磁方法揭示的吉林龙岗板内单成因火山深部岩浆系统  

The deep magma system in the Longgang intraplate monogenetic volcano of Jilin Province revealed by 3D magnetotelluric method

作　　者：赵凌强 詹艳[2] 胡亚轩[1] 赵波[2] 操聪 孙翔宇[2] 王庆良[1] 汶宇龙 李仲巍 綦伟 ZHAO LingQiang;ZHAN Yan;HU YaXuan;ZHAO Bo;CAO Cong;SUN XiangYu;WANG QingLiang;WEN YuLong;LI ZhongWei;QI Wei(The Second Monitoring and Application Center,China Earthquake Administration,Xi'an 710054,China;Jilin Changbaishan Volcano National Field Scientific Observation and Research Station,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Jilin Earthquake Agency,Changchun 130022,China)

机构地区：[1]中国地震局第二监测中心,西安710054 [2]吉林长白山火山国家野外科学观测研究站,中国地震局地质研究所,北京100029 [3]吉林省地震局,长春130022

出　　处：《地球物理学报》2024年第11期4220-4232,共13页Chinese Journal of Geophysics

基　　金：吉林长白山火山国家野外科学观测研究站项目(NORSCBS21-04);国家自然科学基金项目(42304089、41972315);地震动力学国家重点实验室开放基金(LED2021B06);西藏拉萨地球物理国家野外科学观测研究站项目(NORSLS22-04)共同资助.

摘　　要：板内火山作用是指在远离板块构造边界的大陆内部发生的火山活动,位于中国东北的龙岗火山是研究板内火山活动的天然实验区. 我们分别于2020年和2022年在吉林龙岗火山区及其周围区域连续开展大地电磁测量工作,获得了覆盖龙岗火山区的141个宽频带测点数据,通过三维反演获得了该区域地壳上地幔尺度精细的三维电性结构模型. 该模型揭示出龙岗火山区及其周边地区上地壳基本上为高阻体,代表着火山区岩浆早期活动时大面积喷发冷凝所产生的火山岩. 龙岗火山区下方存在着多条岩浆通道穿过莫霍面在上地幔尺度合并且向下继续延伸. 这些岩浆通道自下而上可能主导了近期火山喷发和地壳隆升以及小震活动. 该模型清晰的显示了一个大陆板内火山系统从地幔源到地表跨岩石圈的形成机制,结合岩石学和地球化学资料,推测龙岗火山区的岩浆系统可能直接从软流圈地幔快速上升至地壳内部减压熔融导致喷发作用. 这些结果不但可以为龙岗火山区喷发风险的预测提供深层地球物理依据,也能为理解板内火山形成机制提供启发.The intraplate volcanic activity refers to the volcanic activity that occurs within the continent far from the boundary of plate tectonics. The Longgang volcano located in northeastern China is a natural experimental area for studying intraplate volcanic activity. We conducted continuous magnetotelluric surveys in the Longgang volcanic area and its surrounding areas in Jilin Province in 2020 and 2022, respectively and obtained 141 broadband measurement sites that covered the Longgang volcanic area. Through 3D inversion, we obtained a detailed 3D electrical structure model of the crust and upper mantle in the area. This model reveals that the crust in the Longgang volcanic area and its surrounding areas are a high-resistivity body, representing the volcanic rocks generated by the large-scale eruption and condensation during the early magmatic activity in the volcanic area. There are multiple magma channels beneath the Longgang volcanic area that merge and continue to extend downwards at the upper mantle scale through the Moho. These magma channels may have dominated recent volcanic eruptions, crustal uplift, and small earthquake activity. This model clearly shows the formation mechanism of a continental intraplate volcanic system across the lithosphere from the mantle source to the surface. Combined with petrology and geochemical data, it is speculated that the magma system in the Longgang volcanic area may rise rapidly from the asthenosphere mantle to the decompression melting in the crust, leading to eruption. These results can not only provide a deep geophysical basis for predicting the risk of eruption in the Longgang volcanic area but also inspire an understanding of the formation mechanism of intraplate volcanoes.

关 键 词：龙岗火山 三维大地电磁 电性结构 岩浆系统 

分 类 号：P541[天文地球—构造地质学] P631[天文地球—地质学]