摘要
美国东部阿巴拉契亚造山带北端缅因州Rangeley地区志留—泥盆纪中温低压片岩测得的面理弯切轴与褶皱轴面数据有很好的对应关系。西部科迪勒拉造山带落基山脉南端科罗拉多州阿肯色河地区Texas Creek以东高温低压前寒武纪堇青石片岩中测得的褶皱轴面方向和片理走向数据与该地区堇青石、斜长石变斑晶内测得的5期面理弯切轴也表现出很好的一致性。而在Rangeley北东200 km的佛蒙特州Chester Dome地区奥陶—泥盆纪中温中压片麻岩中测得的类似褶皱轴面数据却只反映了该地区5期面理弯切轴中较晚的北北西-南南东走向和北北东-南南西走向的两期面理弯切轴,未测得与其余3期面理弯切轴对应的褶皱轴面数据。通过对变质峰期温度相近、压力不同的两个造山带内3个典型变质岩区面理弯切轴、褶皱轴面方向和片理走向数据的对比分析认为,造山作用发生的地壳深度差异是早期褶皱经历多期造山运动后能否保存下来的主要影响因素。重力形成的去褶皱作用使得早期形成的规模较小褶皱经历复杂造山过程后难以保存。区域内早期形成的规模较大褶皱和造山过程晚期形成的褶皱由于受到重力塌陷作用影响较小,所以能够较好保存下来。
The FIA trends （foliation intersection or inflection axes in porphyroblasts） measured from Siluro- Devonian garnet sillimanite gneiss in kangeley, Appalachians, when plotted on a rose diagram, reflect the trends of axial planes of all map scale folds. Similar FIA trends data measured in high temperature-low pressure regime Precambrian rocks in the Texas Creek, Cordillera, are reflected by the fold axial plane traces and schistosity data in this region. But the fold axial plane trace data, which were measured in high temperature to medium pressure regime Palaeozoic rocks in Chester Dome, 200 km southwest of Rangeley, only preserve the effects of the youngest FIA of the all 5 FIA sets that were obtained in this region. This difference of the orogenic regimes from the shallow part to the depth reflects decreasing competency contrasts under greater pressures with collapse and unfolding of earlier formed folds. This investigation shows that the greater overlying loads of rocks flatten folds more obviously under higher pressures.
出处
《中国地质》
CAS
CSCD
北大核心
2013年第6期1818-1828,共11页
Geology in China
基金
教育部留学回国人员科研启动基金(2013693)
国家自然科学基金项目(41202153)
国土资源公益性行业科研专项(201211093)
中国地质科学院地质研究所中央级公益性基本业务费专项基金(J1101)共同资助
关键词
造山运动
重力塌陷
面理弯切轴
褶皱轴面
orogenesis
gravitational collapse
foliation intersection or inflection axes
fold axial plane
