Deformation Mechanisms During the Syn-Orogenic Extrusion of the High-Pressure Phyllites-Quartzites Unit in the Central and Northern Peloponnese, Greece

IF 3.3 1区 地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS
Tectonics Pub Date : 2024-08-14 DOI:10.1029/2023tc008116
Vincent Wicker, Simon Bufféral
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Abstract

The High-Pressure Phyllites-Quartzites (PQ) unit of the External Hellenides is exposed in tectonic windows in the central and northern Peloponnese (Greece). Understanding the deformation history of this unit is essential to interpreting the Oligo-Miocene evolution of the External Hellenides belt and its associated exhumation events. This study integrates new field observations and microtectonic analyses with previous studies to offer a comprehensive deformation model of the PQ unit since the Late Oligocene. The first deformation phase (D1), captures the progressive incorporation of the PQ into an orogenic wedge. This phase is largely overprinted and only preserved as relict features. The second phase (D2) displays coeval top-to-the-ENE and top-to-the-WSW localized ductile shear. A transition is observed from top-to-the-ENE non-coaxial deformation at the upper parts of the nappe to intense isoclinal folding (refolding S1) at the lower structural levels. We associate D2 with the ductile syn-orogenic exhumation of the PQ within an extrusion wedge, accompanied by greenschist-facies retrogression. In the third phase (D3), semi-brittle to brittle extensional fault planes cut through the previous ductile structures. D3 faults exhibit extensional kinematics in all directions on the flanks of exhumation domes. This phase correlates with a late-orogenic doming event, marking the final exhumation stage of the PQ unit in the upper crust. The exhumation of high-pressure units results from the interplay between ductile syn-orogenic extrusion and continuous underplating within the subduction zone. This underplating maintains vertical movements and uplift of the units, initiating a 3D upper-crustal extensional collapse along low-angle normal faults.
希腊伯罗奔尼撒半岛中部和北部高压辉绿岩-石英岩单元同步造山挤压过程中的变形机制
希腊外希腊带高压辉绿岩-石英岩(PQ)单元出露于希腊伯罗奔尼撒半岛中部和北部的构造窗口。了解该单元的变形历史对于解释外希腊尼德斯带的中新世演化及其相关的掘起事件至关重要。本研究将新的野外观测结果和微构造分析与之前的研究相结合,提供了自晚渐新世以来 PQ 单元的综合变形模型。第一个变形阶段(D1)捕捉到了 PQ 逐渐融入造山楔的过程。这一阶段在很大程度上被覆盖,只保留了遗迹特征。第二阶段(D2)显示了同时期的自上而下-ENE 和自上而下-WSW 局部韧性剪切。我们观察到,在岩层的上部,从自上而下的非同轴变形过渡到在较低的结构层次上的强烈同轴折叠(折叠 S1)。我们将 D2 阶段与挤压楔内 PQ 的韧性同步成因掘起相联系,并伴有绿理派的逆退。在第三阶段(D3),半脆到脆性延伸断层平面切割了之前的韧性结构。D3 断层在出露穹隆侧翼的各个方向上都表现出延伸运动学特征。这一阶段与成因晚期的穹隆事件相关,标志着上地壳PQ单元的最后掘起阶段。高压单元的掘起是韧性同步成因挤压和俯冲带内持续的底侵相互作用的结果。这种欠充填维持了单元的垂直运动和隆起,并沿低角度正断层引发了三维上地壳延伸塌陷。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Tectonics
Tectonics 地学-地球化学与地球物理
CiteScore
7.70
自引率
9.50%
发文量
151
审稿时长
3 months
期刊介绍: Tectonics (TECT) presents original scientific contributions that describe and explain the evolution, structure, and deformation of Earth¹s lithosphere. Contributions are welcome from any relevant area of research, including field, laboratory, petrological, geochemical, geochronological, geophysical, remote-sensing, and modeling studies. Multidisciplinary studies are particularly encouraged. Tectonics welcomes studies across the range of geologic time.
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