Lin Wule, Schultz Adam, Yang Bo, Harris Lyal B, Hu Xiangyun
Hubei Subsurface Multi-scale Imaging Key Laboratory, School of Geophysics and Geomatics, China University of Geosciences, Wuhan 430074, China.
Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518005, China.
Natl Sci Rev. 2024 Jul 13;11(8):nwae239. doi: 10.1093/nsr/nwae239. eCollection 2024 Aug.
Whilst the 1.1 Ga North American Midcontinent Rift (MCR) system 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 3D 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.
虽然11亿年前的北美中大陆裂谷（MCR）系统是与基韦诺地幔柱相关联形成的，但此前人们尚未很好地理解其北部缺少第三个裂谷臂或坳拉槽（地幔柱的一个普遍特征）的原因。为了帮助阐明这种不寻常的地幔柱-裂谷关系，并更好地确定受基韦诺地幔柱影响的区域，我们展示了首个基于地球深部观测台阵美国阵列（EarthScope USArray）和岩石探测计划大地电磁（MT）数据的三维反演得出的MCR电阻率模型，该模型向北延伸至太古宙的苏必利尔省。我们的模型显示，在苏必利尔湖西部克拉通岩石圈地幔底部有一个显著的高导电异常，呈西北-东南走向，横切西部裂谷分支两侧并延伸超过300公里。我们认为，这一异常反映了地幔柱轨迹的古老特征，它是在基韦诺地幔柱撞击期间，富含硫化物的岩石圈底部地幔发生交代作用和/或部分熔融的结果。
