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The nature and development of shear zone junctions

剪切带交界处的性质和发展

基本信息

批准号：
253352143
负责人：
Professor Dr. Cornelis Passchier, Ph.D.
金额：
--
依托单位：
Arbeitsgruppe Geophysik und Geodynamik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2016-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/253352143?language=en
关键词：
nature development shear zone junctions

项目摘要

Ductile shear zones are usually imagined as straight disc-shaped high strain domains in the rock with simple gradients of vorticity and strain. Most shear zones, however, have a more complex geometry and are part of a network of interconnected zones of variable orientation that branch in a complex manner. Much is known about branching and interconnection of brittle faults, mainly due to 3D information obtained by the minerals industry. However, little is known about the branching systems of ductile shear zones and the way in which they form and develop, what the ductile flow conditions are in such environments and how they affect the strength of the crust. Transient brittle deformation and opening of veins may possible in some shear zone junctions, even in low porosity rocks such as granites. Shear zone junctions can act as fluid pathways in the crust, which can lead to accumulation of mineral deposits and has consequences for nuclear waste deposition sites in granites. Junctions of the largest, crustal scale shear zones may play an important role in deciding how crustal fragments interact along strike slip shear zones, and how the continental crust is assembled in collision and dismembered in extension. Furthermore, mineral deposits are commonly bounded to large scale shear zones. Careful study of different types of junctions in selected shear zones can help to find tools to recognize them in all tectonic settings. We plan to study a number of exceptionally well preserved examples of shear zone junctions in the Grimsel granite, Switzerland, and characterize their 3D field geometry, microstructure, and association with brittle deformation. The study is supported by an ongoing computer modelling study of shear zone junctions.

延性剪切带通常被想象为岩石中具有简单涡度和应变梯度的直盘形高应变域。然而，大多数剪切带具有更复杂的几何形状，并且是以复杂方式分支的可变方向互连区域网络的一部分。人们对脆性断层的分支和互连了解很多，这主要归功于矿物工业获得的 3D 信息。然而，人们对韧性剪切带的分支系统及其形成和发展的方式、这种环境中的韧性流动条件以及它们如何影响地壳强度知之甚少。在某些剪切带交界处，甚至在花岗岩等低孔隙率岩石中，可能会发生瞬时脆性变形和脉络张开。剪切带连接处可以充当地壳中的流体通道，这可能导致矿物沉积物的积累，并对花岗岩中的核废料沉积场所产生影响。最大的地壳尺度剪切带的交界处可能在决定地壳碎片如何沿着走滑剪切带相互作用以及大陆地壳如何在碰撞中组装和在伸展中肢解方面发挥重要作用。此外，矿藏通常局限于大范围的剪切带。仔细研究选定剪切带中不同类型的交界处有助于找到在所有构造环境中识别它们的工具。我们计划研究瑞士格里姆瑟尔花岗岩中一些保存异常完好的剪切带交界处的例子，并表征它们的 3D 场几何形状、微观结构以及与脆性变形的关联。该研究得到了正在进行的剪切带交汇处计算机建模研究的支持。