摘要
CCSD主孔岩芯中发育有十分丰富的脆性微断层,孔深5158m以上,按其空间分布,可将其主体归纳为北北东向微断层系、北西向微断层系、北东向微断层组和近于东西向微断层组等四个微断层系(组)和SEE-NWW向水平挤压构造应力场、NE-SW向水平挤压构造应力场等二期区域构造应力场。SEE-NWW向水平挤压构造应力场贯穿于高压-超高压变质岩折返的全过程,表明在折返过程中,深层韧性变形阶段的构造应力场和浅层脆性变形阶段的构造应力场,具有高度的一致性。但流劈理和微断层的极点等值线图表明,韧性变形阶段的变形较脆性变形阶段的变形简单,深部发生的基本上是一种以逆冲型剪切应变为主导的变形,而浅部脆性变形域,除继承性的逆冲型剪切应变外,往往叠加有后期的构造伸展作用和走滑作用, 因此具有更为复杂的应变图象。NE-SW向水平挤压构造应力场,在时间上晚于SEE～NWW向水平挤压构造应力场,它是导致先存的北北东向逆冲型流劈理发生自北东向南西方向滑动的主因。对比不同岩石类型的微断层和流劈理的极点等值线图,无论是极密类型,还是极密的分布,均不受岩石类型的影响,说明微断层和流劈理的形成与岩石类型(岩性)无关,而主要受构造因素制约,因此,运用微断层和流劈理(叶理)相结合的分析法,研究高压-超高压变质岩带折返阶段的构造应力场和动力学过程,有其他方法无可替代的效果。
There development a very rich brittle microfaults within CCSD main hole core, more than 5158m deep hole, according to their spatial distribution, can be summed up as four microfault systems (or groups), i.e., the main NNE microfault system, the NW microfault system, the NE microfault group and the near EW microfault group, and two stage tectonic stress fields, i.e., dominantly SEE-NWW level compression tectonic stress fields and NE-SW level compression tectonic stress fields. The SEE-NWW level compression tectonic stress field throughout in the whole process of exhumation of the high-pressure-ultrahigh pressure metamorphic rocks, indicating that (luring the exhumation process, tectonic stress field of the deep-seated ductile deformation phase and tectonic stress field of the shallow brittle deformation stage, is highly consistency. However, flow cleavage and microfault Pole isogram showed that the deformation of ductile deformation stages is relatively simple than that of brittle deformation stages, deep happened basically is a thrust-type shear strain, while the shallow brittle deformation domain, with the exception of the succession of thrust-type shear strain, the latter often have a structure superimposed extension and strike-slip effect and hence has a more complex strain images. The NE-SW level compression tectonic stress field, in time later than the SEE-NWW level compression tectonic stress field, which is the main reason leading to pre-existing NE thrust-type flow cleavage (associated with early SEE-NWW level compression) occurred from NE to SW sliding. Comparison microfaults and flow cleavage isogram Pole of different rock types, whether it is a very dense type, or a very dense distribution of rock types are not subject to the impact on microfaults and flow cleavage formation and rock types (lithology) has nothing to do, and is mainly affected by structural factors, therefore, the use of microfaults and flow cleavage (foliation) a combination of analysis, Study tectonic stress field and dynamic processes of high pressure - ultrahigh pressure metamorphic belt exhumation phase, there are other ways irreplaceable effect.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2009年第7期1619-1626,共8页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划(973)项目(2003CB716504)
国家自然科学基金重大项目(40399141)
中国地质调查局地质大调查项目(121201056606)
国土资源部大陆动力学重点实验室的成果
关键词
中国大陆科学钻探
微断层
空间分布
脆性变形
水平挤压
构造应力场
Chinese Continental Sciences Drilling (CCSD)
Microfaults
Spatial distribution
Brittle deformation
Level compression
Tectonic stress field
