The Appalachian Inner Piedmont: an exhumed strike-parallel, tectonically forced orogenic channel
The Appalachian Inner Piedmont: an exhumed strike-parallel, tectonically forced orogenic channel
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阿巴拉契亚内皮埃蒙特：挖掘出的走向平行、受构造强迫的造山河道
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
A. Merschat
中科院分区：
文献类型：
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作者：
R. Hatcher;A. Merschat
摘要 阿巴拉契亚内皮埃蒙特 (IP) 沿造山带从北卡罗来纳州延伸至阿拉巴马州约 700 公里。它的物理属性与其他阿巴拉契亚构造元素形成鲜明对比：主要叶理的平缓倾斜；叠瓦状的褶皱绒毛；主要的硅线石级变质作用和几乎无处不在的混合岩作用；异质、非平面变形；中古生代布里瓦德断裂带东南部的早期 S 面向 C 面转换，沿 IP 西翼形成 10-20 公里宽的角闪岩相剪切带。该IP包含西向和西南向的逆冲层和矿物拉伸线理、所有尺度的鞘褶皱以及定义整个带的弯曲地壳流动模式的其他指标。现场和现代地质年代学数据证实该知识产权并非奇异。它包含劳伦系成分（东图加卢地体）和内部地体（Cat Square），其中包含劳伦系和冈瓦南碎屑锆石，由 Brindle Creek 断层隔开。猫方地体岩石很可能堆积在泥盆纪残余海洋中，该海洋大约在公元 10 世纪开始闭合。 400马。整个IP区复杂但始终不对称，从西北到西到西南方向的流动模式反映了在沿着中央皮埃蒙特缝合线逼近的卡罗莱纳超级地体俯冲到猫广场和劳伦斯成分期间产生的> 15公里厚的覆盖层之下的限制。超过 15 公里深度的斜 NE 向 SW 压俯冲引发了部分熔融，迫使沿走向造山通道逃离碰撞带。随着碰撞带收紧和IP质量流动，IP从中古生代布里瓦德断层带以西的岩石分离。位于海峡西南200公里处。在IP的NE端保留了通道的顶部，在西侧和西南侧保留了底部（Brevard断裂带）。作为挖出的造山河道，弯曲的IP流动路径可以为现代造山带中下地壳变形和流动提供洞察力。
Abstract The Appalachian Inner Piedmont (IP) extends along orogenic strike some 700 km from North Carolina to Alabama. Its physical attributes contrast with those of other Appalachian tectonic elements: gentle dip of dominant foliation; imbricate stack of fold nappes; dominant sillimanite-grade metamorphism and near ubiquitous migmatization; heterogeneous, non-plane deformation; and earlier S-foliations transposed to C-foliations southeast of the mid-Palaeozoic Brevard fault zone forming a 10–20 km wide amphibolite-facies shear zone along the western flank of the IP. The IP contains west- and SW-directed thrust sheets and mineral stretching lineation, sheath folds on all scales, and other indicators that define a curved crustal flow pattern throughout the belt. Field and modern geochronologic data confirm that the IP is not exotic. It contains a Laurentian component (eastern Tugaloo terrane) and an internal terrane (Cat Square) that contains both Laurentian and Gondwanan detrital zircons, separated by the Brindle Creek fault. Cat Square terrane rocks likely accumulated in a Devonian remnant ocean that closed beginning c. 400 Ma. The complex but consistently asymmetric, NW- to west- to SW-directed flow pattern throughout the IP reflects confinement beneath a > 15 km thick overburden produced during subduction of Cat Square and Laurentian components beneath the approaching Carolina superterrane along the Central Piedmont suture. Oblique NE-to-SW transpressive subduction to > 15 km depth initiated partial melting, forcing escape from the collision zone in an along-strike orogenic channel. The IP detached from rocks to the west of the mid-Palaeozoic Brevard fault zone as the collision zone tightened and the IP mass flowed c. 200 km southwestward in the channel. The top of the channel is preserved at the NE end of the IP, and the base (Brevard fault zone) is preserved to the west and SW. As an exhumed orogenic channel, the curved IP flow paths may provide insight for middle to lower crustal deformation and flow in modern orogens.