Geotectonic framework of the Blueschist Unit on Anglesey–Lleyn, UK, and its role in the development of a Neoproterozoic accretionary orogen
Geotectonic framework of the Blueschist Unit on Anglesey–Lleyn, UK, and its role in the development of a Neoproterozoic accretionary orogen
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DOI：
10.1016/j.precamres.2006.11.002
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发表时间：
2007-02
影响因子：
3.8
通讯作者：
T. Kawai;B. Windley;M. Terabayashi;H. Yamamoto;S. Maruyama;S. Omori;T. Shibuya;Y. Sawaki;Y. Isozaki
中科院分区：
文献类型：
--
作者：
T. Kawai;B. Windley;M. Terabayashi;H. Yamamoto;S. Maruyama;S. Omori;T. Shibuya;Y. Sawaki;Y. Isozaki
一个560-550 Ma，5公里×25公里的蓝片岩单元在英国威尔士的安格尔西岛上向东北-西南方向延伸，并沿着林恩半岛的北部海岸向西南方向继续延伸超过70公里。它的形状是从俯冲带挖出的厚达几公里的浅倾斜板片或板片，并部署到西北方向的吸积杂岩中。今天，板块的顶部边界通常是俯冲带中的逆冲断层，其顶部原本是俯冲带中的一条低角度正断层；其上方是一个增生杂岩和一个高品位片麻岩单元。底界是今天的逆冲层(最初是逆冲层)，其下是一个低品位或未变质的岩石单元，属于一种蛇形岩浆型的增生杂岩。当它在俯冲带中被挖出时，这一逆冲断层最初是在板片的底部。夹层组合是通过蓝片岩在其他单元之间的构造插入而形成的。褶皱，特别是在构造夹层的晚期穹隆期间，将顶部正断层边界旋转为逆冲。后来，高角度、北东-南西向的正断层取代了地垒和地堑的构造地层。一条长200公里、宽200公里、680-450 Ma的钙碱性火山-深成岩带从蓝片岩带经威尔士北部向东南延伸至英格兰中部，表明大洋岩石圈向东南俯冲，这与向西北挤压薄高压板块进入增生杂岩相一致。这发生在阿瓦洛尼亚的西部增积边缘。最后，我们概述了拆解太平洋型吸积杂岩结构所涉及的关键步骤。
A 560–550Ma, 5km×25km Blueschist Unit extends NE–SW on the island of Anglesey, Wales, UK, and continues to the southwest for more than 70km along the northern coast of the Lleyn Peninsula. It has the shape of a shallow-dipping slab or sheet up to a few kilometres thick that was exhumed from the subduction zone and emplaced into the accretionary complex to the northwest. Today the top boundary of the slab is commonly a thrust that was originally a low-angle normal fault at its top in the subduction zone; above it is an accretionary complex and a unit of high-grade gneisses. The bottom boundary is today a thrust (that was originally a thrust), below which is a unit of low-grade or unmetamorphosed rocks belonging to an olistostrome-type accretionary complex. This thrust was originally at the bottom of the slab when it was exhumed in the subduction zone. The sandwiched assemblage was created by the tectonic insertion of the blueschist between the other units. Folding, particularly during late doming of the tectonic sandwich, rotated the top normal-fault boundary into a thrust. Later, high-angle, NE–SW-trending normal faults displaced the tectonic stratigraphy in horst and graben. A 200km long and 200km wide, 680–450Ma calc-alkaline volcano-plutonic belt extends southeastwards from the blueschist belt via northern Wales to central England, suggesting that the subduction of oceanic lithosphere was to the southeast, and this is consistent with the extrusion of the thin high-pressure slab into the accretionary complex to the northwest. This took place on the western accretionary margin of Avalonia. Finally, we outline the key steps involved in unravelling the structure of a Pacific-type accretionary complex.