摘要
研究了河南鲁山地区太华变质杂岩的岩性单元和原岩建造类型,结合构造变形和同位素年龄资料分析,认为该杂岩可能包括时代不同的两套深变质岩群.下部岩群属上太古界,由洋壳环境的拉斑玄武岩建造和含铁沉积-火山建造组成;上部岩群可能属下元古界,由陆壳环境的孔兹岩系(含炭沉积岩建造)和富钠火山岩系(细碧角斑岩建造)组成. 两岩群之间构造不协调,接触处有一层厚1～2m的富石榴石深变质岩(石英榴闪岩),可能为风化剥蚀面产物经深变质而成,表明本区在由晚太古代洋壳演化到早元古代大陆地壳过程中,曾经历了一个长期风化剥蚀阶段,根据现有年龄资料推测,与这个古风化剥蚀面相应的构造运动年龄为2500Ma,建议命名为太华运动.
By means of researches on rock units and protolith formation types, followed by analyses of tectonic deformation and isotopic age data, Taihua metamorphic complex ('Taihua Group') inLushan region, Henan province can be dismembered into two different kata-metamorphic rock groups in age. The lower rock group is composed of the double peak volcanic formation dominated by tholeiites and sedimentary-volcanic formation with BIF, both of which were formed in Late Archean oceanic crust environment, while the upper rock group consists of the khondalite series (carbon-bearing sedimentary formation) and the sodium-rich volcanic rock series ( spilite-kerato-phyre formation) which were evolved in continental crust environment and would belong to Early Proterozoic Era.A disharmonic relationship in the structural forms is distinctly displayed between the two groups. Besides tightly compressive folds, the lower rock group has developed many broad folds and gneiss domes, which could be the relics of the early preexisting structures; whereas upper rock group has only exhibited tightly compressive folds and probably repeatedly structural sheets. In addition, there is a thin layer of the garnet-rich kata-metamorphite(quartzic garnet-amphibolite), 1 -2m thick between the two groups, which was probably the residual product on an ancient plane of weathering-denudation and was intensely metamorphosed afterwards. It is shown that this region experienced a long-term weathering and denudation stage during the transformation from Late Archean ocean crust to Early Proterozoic continental crust. The structural movement corresponding to this ancient plane of denudation is inferred to have taken place in ca. 2500 Ma based on the available dating data.In the view of traditional recognition that 'Taihua Group' (Taihua metamorphic complex) has been regarded as the Late Archean, it is suggested that the old name of the Taihua Group is still continued for the lower rock group, whereas the newly-recogniged upper rock group is called Lushan Group. The time break between the two groups would be named Taihua movement.
出处
《华南地质与矿产》
CAS
1996年第4期22-31,共10页
Geology and Mineral Resources of South China
关键词
变质杂岩
原岩建造
类型
时代
古剥蚀面
杂岩
Taihua metamorphic complex protolith formation types dismembering into two eras ancient plane of denudation Taihua movement.
