Strain variations across the Proterozoic Penokean Orogen, USA and Canada
Strain variations across the Proterozoic Penokean Orogen, USA and Canada
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DOI：
10.1016/j.precamres.2018.09.004
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发表时间：
2018-11
影响因子：
3.8
通讯作者：
J. Craddock;D. Malone;M. Schmitz;Jennifer N. Gifford
中科院分区：
文献类型：
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作者：
J. Craddock;D. Malone;M. Schmitz;Jennifer N. Gifford
休伦盆地（2.5-2.0 Ga）和阿尼米奇盆地（2.2-1.85 Ga）的地层沉积在太古代上级省的南缘。这些岩石变形期间Penokean造山运动（1850年），随后在1750年（Yavapai）和1630年（Mazatzal）的南部增生造山带。应变模式是独特的每个造山带，没有远场效应：太古代瓦瓦岩在Penokean前陆保存变形与太古代加积没有年轻的Penokean，Yavapai或Mazatzal应变叠印。Penokean造山带使休伦-阿尼米奇盆地沉积物变形为北向褶皱冲断带，没有Yavapai或Mazatzal应变叠加。与年轻的Mazatzal缩短（N20°W）相比，Yavapai造山带应变（SW-NE边缘平行缩短）是独特的，没有应变叠加。Penokean变形的特征是从南部缩短，包括隆起的太古代片麻岩和向北的薄皮褶皱冲断带，以及向北的推覆体和缓倾的前陆。我们的研究有限和方解石孪晶应变（n = 60）沿着（约1500公里）和横跨（约200公里）的Penokean带表明，该orthopathic层平行缩短轴是平行的整个带，或平行于构造搬运方向（N-S）。边缘附近的Penokean推覆体埋藏导致垂直缩短应变叠加，其中一些是层正常的。萨德伯里的影响层（1850马）被发现在整个阿尼基盆地，并提供了一个广泛的变形标记与许多地方，独特的应变观测。我们还报告了新的地质年代学（U-Pb锆石和磷灰石）的Wissota（Chippewa福尔斯，WI）和Arbutus（河流瀑布，WI）大坝的片麻岩-镁铁质岩脉岩石，分别承担在太古代沼泽地的Penokean Yavapai变形，这是在Penokean造山带增生。伪玄武玻璃岩形成在上级省太古代基底岩石中很常见，特别是沿着由同时代的Penokean、Trans-Hudson、Cape Smith和新魁北克变形重新激活的岩石边界。在腹地（南部），年轻的Yavapai造山带（1750马; n = 8）变形被保存为边缘平行水平缩短（EPWSW-NE）在Yavapai地壳和高达200公里以北的Penokean冲断带的应变和Barrovian变质叠加。Mazatzal变形（1630 Ma; n = 16）保存在Yavapai和Penokean地壳的石英岩中，具有N20°W方向的层平行和层法缩短应变。
Strata in the Huron (2.5–2.0 Ga) and Animikie (2.2–1.85 Ga) basins were deposited on the southern margin of the Archean Superior province. These rocks were deformed during the Penokean orogeny (∼1850 Ma) followed by subsequent accretionary orogens to the south at 1750 Ma (Yavapai) and 1630 Ma (Mazatzal). Strain patterns are unique to each orogenic belt with no far-field effect: Archean Wawa terrane rocks in the Penokean foreland preserve deformation associated with Archean accretion with no younger Penokean, Yavapai or Mazatzal strain overprint. The Penokean orogeny deformed Huron-Animikie basin sediments into a north-vergent fold-and-thrust belt with no Yavapai or Mazatzal strain overprint. Yavapai orogen strains (SW-NE margin-parallel shortening) are unique when compared to the younger Mazatzal shortening (N20°W) shortening, with no strain overprint.Penokean deformation is characterized by shortening from the south including uplifted Archean gneisses and a northerly thin-skinned fold-and-thrust belt, with north-vergent nappes and a gently-dipping foreland. Our study of finite and calcite twinning strains (n = 60) along (∼1500 km) and across (∼200 km) the Penokean belt indicate that this orogeny was collisional as layer-parallel shortening axes are parallel across the belt, or parallel to the tectonic transport direction (∼N-S). Penokean nappe burial near the margin resulted in vertical shortening strain overprints, some of which are layer-normal. The Sudbury impact layer (1850 Ma) is found across the Animikie basin and provides a widespread deformation marker with many local, unique strain observations. We also report new geochronology (U-Pb zircon and apatite) for the gneiss-mafic dike rocks at Wissota (Chippewa Falls, WI) and Arbutus (Black River Falls, WI) dams, respectively, which bears on Penokean-Yavapai deformation in the Archean Marshfield terrane which was accreted during the Penokean orogen. Pseudotachylite formation was common in the Superior province Archean basement rocks, especially along terrane boundaries reactivated by contemporaneous Penokean, Trans-Hudson, Cape Smith and New Quebec deformation. In the hinterland (south), the younger Yavapai orogen (1750 Ma; n = 8) deformation is preserved as margin-parallel horizontal shortening (∼SW-NE) in Yavapai crust and up to 200 km to the north in the Penokean thrust belt as a strain and Barrovian metamorphic overprint. Mazatzal deformation (1630 Ma; n = 16) is preserved in quartzites on Yavapai and Penokean crust with layer-parallel and layer-normal shortening strains oriented N20°W.