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A study of brittle-ductile transition in naturally deformed crustal materials

自然变形地壳材料脆性转变的研究

基本信息

批准号：
09640542
负责人：
TOYOSHIMA Tsuyoshi
金额：
$ 2.05万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

We have investigated brittle-ductile transition, modes of deformation, and deformation histories under the upper to lower crustal conditions in natural examples, using integrated field observations and structural and petrological analyses. The examples are from the Hidaka, Unazuki, Ryoke, and Higo metamorphic belts, Napier Complex, Budo and Gozu granitic massifs, Jurassic Toi Formation, and Tertiary sediments at western Joetsu and eastern Nagaoka cities.Gabbroic mylonites, pseudotachylytes, and tonalitic small mylonite zones in the northern Hidaka metamorphic belt, Hokkaido, formed under granulite facies conditions. These rocks suggest that seismic faulting and brittle failure occurred under lower crustal conditions, resulting from the effects of variations of pore fluids and/or strain rate. In the Napier Complex, Enderby Land, mylonites, mylonitized pseudotachylytes, and pseudotachylytes formed during the same deformation stage under retrograde granulite facies conditions. Complex rel … More ationships of the pseudotachylytes with the mylonites suggest that seismic faulting and plastic deformation alternated at lower crustal levels. The change in mode of deformation would have resulted from the changes in microstructures and/or strain rate. In the Budo and Gozu granites, Niigata Prefecture, foliated cataclasites, random-fabric cataclasites, and ultracataclasites formed in turn in the same fault zones. The sequential formation shows that deformation mechanisms change from breaking to grinding during the structural evolution of the faults. The foliation of the foliated cataclasites, which formed in the initial phase of brittle faulting, is defined either by the alignment of elongated biotite fragments or by the alignment of elongated lenses made of the same kinds of mineral fragments, such as quartz or feldspar. The fault zone originated from the former cataclasite widened in thickness during faulting, but the latter did not. The former cataclasite is associated with pseudotachylyte, indicating that seismic faulting occurred. Mainly temperature change produced the brittle-ductile transition in the above metamorphic belts, granitic massifs, and sedimentary basins. Less

我们已经调查了脆韧性转换，变形模式，和变形历史下的上地壳到下地壳的条件下，在自然的例子中，使用综合的现场观察和结构和岩石学分析。这些例子来自日高、宇那月、良岳和日后变质带、纳皮耶杂岩、布多和五津花岗质岩、侏罗纪土井组以及上越市西部和长冈市东部的第三纪沉积物。北海道北方日高变质带的辉长糜棱岩、假玄武玻璃岩和英云闪长质小糜棱岩带形成于麻粒岩相条件下。这些岩石表明，地震断层和脆性破坏发生在下地壳条件下，造成的孔隙流体和/或应变速率的变化的影响。在恩德比地的纳皮耶杂岩中，糜棱岩、糜棱岩化的假玄武玻璃和假玄武玻璃形成于同一变形阶段的退变质麻粒岩相条件下。复关系 ...更多信息假玄武玻璃与糜棱岩的关系表明，地震断层和塑性变形交替在较低的地壳水平。变形模式的变化可能是由于微观结构和/或应变速率的变化。在新泻县的Budo和Gozu花岗岩中，片理化碎裂岩、随机组构碎裂岩和超碎裂岩依次形成于同一断裂带中。序列的形成表明，在断裂构造演化过程中，变形机制由破碎变形向磨粒变形转变。在脆性断裂作用的初始阶段形成的片理化碎裂岩的叶理，要么是由拉长的黑云母碎片排列，要么是由相同种类的矿物碎片（如石英或长石）组成的拉长的透镜体排列。前者碎裂岩形成的断裂带在断裂过程中厚度增宽，而后者没有增宽。前者碎裂岩与假玄武玻璃共生，表明发生过地震断层作用。上述变质带、花岗质火山岩和沉积盆地的脆韧性转变主要是温度变化引起的。少