Raising the Resurrection plate from an unfolded-slab plate tectonic reconstruction of northwestern North America since early Cenozoic time
Raising the Resurrection plate from an unfolded-slab plate tectonic reconstruction of northwestern North America since early Cenozoic time
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DOI：
10.1130/b35677.1
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
Spencer L. Fuston;Jonny Wu
中科院分区：
文献类型：
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作者：
Spencer L. Fuston;Jonny Wu
渐新世之前俯冲到北美以下的大洋中脊的构造不受海底等时线的限制，主要是根据上板块地质学（包括近海沟岩浆作用）推断的。然而，许多构造模型都受到这些限制。我们展示了自 60 Ma 以来西北科迪勒拉山脉的完全运动学板块构造重建，该重建是通过结构展开的俯冲板片构建的，通过地幔断层扫描成像返回地球表面。我们以三维方式绘制阿拉斯加板块和卡斯卡迪亚板块的三维地图，以及育空地区西部（加拿大）下方 400-600 公里深度的分离板块，我们称之为“育空板块”。我们在全球板块模型中对这些较低板块的恢复表明阿拉斯加板片解释了自大约 1990 年以来的太平洋-库拉俯冲。位于阿留申群岛下方 60 Ma，而卡斯卡迪亚板片则解释了法拉隆的俯冲作用，至少从大约 100 Ma 开始。美国加利福尼亚州南部以下 75 Ma。然而，中间区域显示出两个持续到 40 Ma 的重建间隙。我们表明，即使考虑到可能的地体平移，这些重建间隙也与已发表的西北科迪勒拉近海沟岩浆活动在时空上相关。我们将这些间隙归因于与洋脊俯冲相关的热侵蚀，并在这些重建间隙中点内模拟洋中脊。我们的重建显示了两个同时代的山脊-海沟交叉点，它们在 40 Ma 之前沿着西北科迪勒拉山脉界定了一个额外的“复活”状板块。在此模型中，育空板块代表复活板块受热侵蚀的残余物。我们的重建支持“北方选项”法拉伦山脊几何形状，并允许自古新世以来长达约 1200 公里的楚加奇地体平移，为巴哈-不列颠哥伦比亚省的争论提供了一个新的“断层扫描穿透点”。
The configuration of mid-ocean ridges subducted below North America prior to Oligocene time is unconstrained by seafloor isochrons and has been primarily inferred from upper-plate geology, including near-trench magmatism. However, many tectonic models are permitted from these constraints. We present a fully kinematic, plate tectonic reconstruction of the NW Cordillera since 60 Ma built by structurally unfolding subducted slabs, imaged by mantle tomography, back to Earth’s surface. We map in three-dimensions the attached Alaska and Cascadia slabs, and a detached slab below western Yukon (Canada) at 400–600 km depth that we call the “Yukon Slab.” Our restoration of these lower plates within a global plate model indicates the Alaska slab accounts for Pacific-Kula subduction since ca. 60 Ma below the Aleutian Islands whereas the Cascadia slab accounts for Farallon subduction since at least ca. 75 Ma below southern California, USA. However, intermediate areas show two reconstruction gaps that persist until 40 Ma. We show that these reconstruction gaps correlate spatiotemporally to published NW Cordillera near-trench magmatism, even considering possible terrane translation. We attribute these gaps to thermal erosion related to ridge subduction and model mid-ocean ridges within these reconstruction gap mid-points. Our reconstructions show two coeval ridge-trench intersections that bound an additional “Resurrection”-like plate along the NW Cordillera prior to 40 Ma. In this model, the Yukon slab represents a thermally eroded remnant of the Resurrection plate. Our reconstructions support a “northern option” Farallon ridge geometry and allow up to ∼1200 km Chugach terrane translation since Paleocene time, providing a new “tomographic piercing point” for the Baja-British Columbia debate.