近日，中国地质大学教授胡祥云及其课题组利用大地电磁资料揭示了ca.1.1Ga北美大陆中部裂谷下的地幔柱轨迹。相关论文于2024年7月13日发表于国际顶尖学术期刊《国家科学评论》杂志上。

据悉，虽然1.1 Ga北美中部大陆裂谷系统(MCR)与Keweenaw地幔柱的形成相关联，但此前人们对北部第三裂谷臂或裂陷槽(地幔柱的一般特征)的认识并不深入。

为了厘清这种不寻常的地幔柱-裂谷关系，更好地确定受Keweenaw地幔柱影响的区域，研究人员展示了从美国地震阵列和岩石探针大地电磁(MT)数据三维反演得到的第一个MCR的电阻率模型，向北延伸至太古宙苏必利尔省。

研究模型显示，在西苏必尔省克拉通岩石圈地幔底部有一个显著的北西-东南向的高导电性异常，在西裂谷分支两侧横切并延伸超过300公里。研究人员认为，这一异常反映了地幔柱踪迹的古老特征，是在Keweenaw地幔柱撞击过程中，富含硫化物的基底岩石圈地幔的交代和/或部分熔融作用的结果。

附：英文原文

Title: Mantle plume trail beneath the ca. 1.1 Ga North American Midcontinent rift revealed by magnetotelluric data

Author: Lin, Wule, Schultz, Adam, Yang, Bo, Harris, Lyal B, Hu, Xiangyun

Issue&Volume: 2024-07-13

Abstract: Whilst the 1.1 Ga North American Midcontinent Rift system (MCR) is formed in association with the Keweenaw mantle plume, the absence of a northern third rift arm or aulacogen (a general characteristic of mantle plumes) has previously not been well understood. To help clarify this unusual plume-rift relationship and to better establish the region affected by the Keweenaw mantle plume, we present the first electrical resistivity model of the MCR derived from three-dimensional inversion of EarthScope USArray and Lithoprobe magnetotelluric (MT) data, extending northwards into the Archean Superior Province. Our model shows a prominent highly conductive anomaly trending NW-SE at the base of Western Superior's cratonic lithospheric mantle, cross-cutting and extending for over 300 km on both sides of the western rift branch. We propose that this anomaly reflects the ancient signature of a plume trail, resulting from metasomatism and/or partial melting of the sulfide-rich basal lithospheric mantle during impingement of the Keweenaw mantle plume.

DOI: 10.1093/nsr/nwae239

Source: https://dx.doi.org/10.1093/nsr/nwae239