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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Wide-angle seismic transect across the Torngat Orogen, northern Laborator: Evidence for a Proterozoic crustal root
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Wide-angle seismic transect across the Torngat Orogen, northern Laborator: Evidence for a Proterozoic crustal root

机译：北部实验室的Torngat造山带上的广角地震剖面：元古代地壳根的证据

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摘要

A refraction/wide-angle reflection seismic transect across the Labrador peninsula covers the Core Zone of the SE Churchill Province, the Paleoproterozoic Torngat Orogen, and the Archean Nain Province including a portion of the Labrador continental margin. An airgun array was used as source, and 11 ocean-bottom seismometers and 16 land stations recorded the shots. Forward modeling of travel times and amplitudes reveals a deep asymmetric crustal root beneath the Torngat Orogen, with a crustal thickness of > 49 km and with P-wave velocities of 6.9-7.0 km/s. The geometry of the velocity model and the root can be best explained by either westward dipping subduction or westward underthrusting of the Nain crust. Gravity modeling suggests a correlation of the crustal root with a gravity low that extends approx 100 km in an E-W direction and approx 200 km from north to south. The preservation of the crustal root is attributed to the lack of postorogenic heating and ductile reworking consistent with the lack of abundant postcollisional magmatism in the SE Churchill Province. A discontinuity possibly cutting through the entire crust is interpreted as a zone of major transcurrent shearing associated with the main phase of deformation. West of the Torngat Orogen, the crustal thickness in the Core Zone of the Churchill Province varies between 35 and 38 km (P-wave velocities of 5.8-7.0 km/s). East of the orogen, the crystalline crust in the Nain Province is approx 38 km thick (velocities from 5.8 to 6.9 km/s) but thins to 9 km in the shelf area of the Labrador margin, where it is covered with up to 8 km of sediments. No high-velocity zone was found beneath the thinned continental crust at the margin.
机译：横跨拉布拉多半岛的折射/广角反射地震样带覆盖了东南丘吉尔省的核心区，古元古代的托尔加特造山带和太古代的奈恩省，其中包括拉布拉多大陆边缘的一部分。使用气枪阵列作为源，并记录了11个海底地震仪和16个陆地站。对行进时间和振幅的正演模型揭示了Torngat造山带下方的深不对称地壳根，地壳厚度> 49 km，P波速度为6.9-7.0 km / s。速度模型和根部的几何形状可以通过纳因地壳的向西俯冲俯冲或向西俯冲来最好地解释。重力模型表明地壳根与重力低点的相关性，重力低点在E-W方向延伸约100 km，从北向南延伸约200 km。地壳根的保存归因于东南丘吉尔省缺乏后造山加热和韧性返工，这与东南丘吉尔省缺乏大量的碰撞后岩浆作用有关。可能切穿整个外壳的不连续性被解释为与变形主相相关的主要横流剪切区。在Torngat造山带以西，丘吉尔省核心区的地壳厚度在35至38 km之间变化（P波速度为5.8-7.0 km / s）。在造山带以东，奈因省的晶体壳厚约38 km（速度从5.8到6.9 km / s），但在拉布拉多边缘的陆架区域稀薄到9 km，在那里覆盖了8 km沉积物。在边缘变薄的大陆壳下方未发现高速带。

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