Structural Deformation Characteristics of the Paleoproterozoic Crystaline Basement in the Northern Segment of Helan Mountains and Its Regional Tectonic Implications
详细信息
- 责任者：Huang Xiongnan (Key Laboratory of Active Tectonics and Volcano ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Zhang Jiasheng
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：麻粒岩相 ; granulite facies ; 孔兹岩 ; khondalite ; 构造变形 ; tectonic deformation ; 贺兰山 ; Helan Mountains
- 页码：p.2353-2370
- 图表：7 illus., 1 table, 73 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Ductile deformation shear zones in varied degrees are preserved in the crystalline basement in the northern segment of Helan Mountain.Four stages of ductile shearing are identified by detailed outcrop research and microstructure study from the Paleoproterozoic crystalline basement in the northern segment of Helan Mountain.The earliest one is a kind of layer-paralleled shear zone composed by banded khondalite and granitic gneisses along with lots of parallellying folds,boudinages and sheathe folds,showing north to south extension with deforming characteristics of mid-lower crust level.The second one is mylonitic gneiss shear zone in high amphibolite to granulite facies resulted from a compressional tectonic movement in N-S direction to cause fast uplift of the high temperature and high pressured metamorphosed khondalite from lower crust to middle crust.The third kind of shear zone metamorphosed in low amphibolite to high greenshist facies maybe happened in the late extensional collapse stage in the same orogenic cycle with the khondalite,lifting the crystalline basement more up into the middle crust.They are composed of two sets of molynitic shear zones caused by a NW-SE extension followed another NE-SW extension.The latest kind of ductile shear zones are NE to EW trending greenshist-faced mylonitic shear zones in left-lateral thrusting sense,bring the crystalline basement up into the upper crust through the brittle-ductile transition zone.They could be resulted in another orogeny different from the khondalite because owning an obviously different kinematic character from the extensional shear zones.Similar structural deformation characters and ductile shear zones occurred in the Wula Mountains and Daqing Mountains as the northern segment of Helan Mountain indicate the existence of a EW-trending Paleoproterozoic collision orogenic belt in west part of the north edge of the North China Craton and perhaps followed by another orogeny in late-Paleoproterozoic.
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