黔东南及邻区加里东运动的表现及地质意义

Appearance and geologic significance of Caledonian Movement in southeastern Guizhou,China and its adjacent area

加里东运动对黔东南地区的沉积格局、岩浆活动、变形变质影响明显,形成了上古生界与下伏地层之间的不整合接触关系。广西罗城-龙胜、湖南通道地区是加里东运动的构造高位区,向西至黔东地区在平面上出现有规律的变化,表现为下伏地层分别为震旦系、寒武系、奥陶系和志留系;加里东运动之后泥盆纪早期的沉积反映出在构造高位区缺失沉积物,为剥蚀区,而在构造高位区的东、西两侧出现了泥盆纪早期的沉积,为坳陷区;接触界面的特征表现为从高角度不整合、低角度不整合至平行不整合;变形变质程度逐渐减弱,下古生界的变质程度从明显至不明显,从紧闭型阿尔卑斯式褶皱至开阔型阿尔卑斯式褶皱。同样,从广西罗城—龙胜向东也具有相同的变化趋势。反映该地区加里东运动的中心位置为广西罗城—龙胜、湖南通道一线,是该地区加里东期造山带的中心,在区域上可能向北东方向沿桃江、景德镇一线延伸,是南华裂谷海槽萎缩、消亡的具体体现。

Caledonian Movement in southeastern Guizhou area has a significant affect on the deposition pattern,magmatism,deformation and metamorphism,and it leads to unconformity contact between the Late Paleozoic strata and underlying strata. Luocheng-Longsheng in Guangxi and Tongdao region in Hunan are high-position tectonic areas of Caledonian Movement,which appears on a regular change westwards to eastern Guizhou area in the plane with underlying strata respectively Sinian,Cambrian,Ordovician and Silurian; after Caledonian Movement,the deposition of the early Devonian is featured by lack of sediments in the high-position tectonic area,namely erosion zone,while in east and west sides of high-position tectonic area it appears early Devonian sedimentation,namely depression area; contact interface is characterized by high-angle unconformit,low-angle unconformity and parallel unconformity; degree of deformation and metamorphism gradually weakens,and metamorphic degree of early Paleozoic strata decreases from obvious to not obvious,thus from a close Alpine-style fols to the open-type Alpine folds. Similarly,eastwards of Guangxi Luocheng -Longsheng area also has the same trend. This fact has reflected center activating spot of the Caledonian Movement is Guangxi Luocheng-Longsheng and Hunan Tongdao line,also it＇s the center of the Caledonian orogeny belt,namely the inner belt,regionally it may extends to the north along Taojiang,Jingdezhen line,which can be evidence of the shrink and extinction of South China rift valley.