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首页> 外文期刊>Geochemistry, geophysics, geosystems >Seismological structure of the 1.8 Ga Trans-Hudson Orogen of North America
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Seismological structure of the 1.8 Ga Trans-Hudson Orogen of North America

机译：北美1.8 Ga Trans-Hudson造山带的地震构造

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摘要

Precambrian tectonic processes are debated: what was the nature and scale of orogenic events on the younger, hotter, and more ductile Earth? Northern Hudson Bay records the Paleoproterozoic collision between the Western Churchill and Superior platesthe approximate to 1.8 Ga Trans-Hudson Orogeny (THO)and is an ideal locality to study Precambrian tectonic structure. Integrated field, geochronological, and thermobarometric studies suggest that the THO was comparable to the present-day Himalayan-Karakoram-Tibet Orogen (HKTO). However, detailed understanding of the deep crustal architecture of the THO, and how it compares to that of the evolving HKTO, is lacking. The joint inversion of receiver functions and surface wave data provides new Moho depth estimates and shear velocity models for the crust and uppermost mantle of the THO. Most of the Archean crust is relatively thin (approximate to 39 km) and structurally simple, with a sharp Moho; upper-crustal wave speed variations are attributed to postformation events. However, the Quebec-Baffin segment of the THO has a deeper Moho (approximate to 45 km) and a more complex crustal structure. Observations show some similarity to recent models, computed using the same methods, of the HKTO crust. Based on Moho character, present-day crustal thickness, and metamorphic grade, we support the view that southern Baffin Island experienced thickening during the THO of a similar magnitude and width to present-day Tibet. Fast seismic velocities at >10 km below southern Baffin Island may be the result of partial eclogitization of the lower crust during the THO, as is currently thought to be happening in Tibet.
机译：讨论了前寒武纪的构造过程：在更年轻，更热，更易延展的地球上造山活动的性质和规模是什么？北哈德逊湾记录了西部丘吉尔和上层板块之间的古元古代碰撞，大约1.8 Ga跨哈德逊造山带（THO），是研究前寒武纪构造结构的理想场所。综合的野外，年代学和热压法研究表明，THO与当今的喜马拉雅-喀喇昆仑山-西藏造山带（HKTO）相当。但是，缺乏对THO的深层地壳结构以及如何与不断发展的HKTO进行比较的详细了解。接收器功能和表面波数据的联合反演为THO的地壳和最上层地幔提供了新的Moho深度估计和剪切速度模型。大部分的太古宙地壳相对较薄（约39公里），结构简单，有尖锐的莫霍面。上地壳波速变化归因于后地层事件。但是，THO的魁北克-巴芬段的莫霍面更深（约45公里），地壳结构更为复杂。观测结果显示，与使用相同方法计算的HKTO地壳的最新模型有些相似。基于莫霍面特征，当今地壳厚度和变质梯度，我们支持这样一种观点，即巴芬岛南部在THO期间经历了与当今西藏相似的幅度和宽度的增厚。如目前认为的那样，在THO期间，南巴芬岛下方10公里以下的地震速度加快可能是下地壳部分凝结的结果。

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