摘要
秦岭造山带核部杂岩即秦岭杂岩南北两侧商丹、朱夏边界剪切带逆－左行和逆（正）－右行相配套的剪切、杂岩内部广泛发育的东倾的Ａ型构造、变质作用的近等温降压以及花岗岩体侵位中心的向东偏移的特点揭示，该杂岩相对两侧古生代地层发生过（晚加里东－早海西期）向西的平行造山带的侧向运移、抬升；水平相对位移量约３２－８６ｋｍ：垂向相对抬升量约为１５－４０ｋｍ：其动力学背景是杂岩两侧盆地由东向西剪刀状双向俯冲闭合造成的侧向挤出。
The core complex of the Qinling orogenic belt the Qinling complex, is crystalline basement of the belt and underwent underthrust and formation of metamorphic terrains in Jinningian and plastic reworking during elevation in Caledonian-Variscan. Now it occures as a slender Len in the yonger terrains. This paper shows that the complex underwent large-scale parallel-orogen westward lateral move associated with elevation during late-Caledonian - early-Variscan. The main evidences are ( 1 ) coordinate shearing of two boundary shear zones, i. e. thrust-left- handed shearing in the south Shandan shear zone and thrust (normal)-right-handed shearing in Zhuxia shear zone; (2) widely developed east-dip lineation structures in the complex, e. g. extension (mineral) lineations, AB or A type folds (sheath folds) and long lenses; (3) nearly-isothermal decompression metamorphism, from average 0.66 GPa to 0.45 GPa, eclogites (400 ± 16Ma) decompressed from higher 1.2 GPa to 0.5 GPa; (4) east-ward migration of emplacement centers of the granitic plutons. According to the P-T evolution, the elevation of the complex relative to the two adjacent terrains is abount 25- 50km. In addition, according to the average dip angle (25°) of extension lineations in the boundary shear zones, which mark the motion path the migration of lateral move in horizontal relative to the two sides are about 54- 107km. The dynamic of the lateral move was characterized by twotside scissoring subduction of two finite ocean basins locating in the south and north of the island arc whose basment was composed of the complex. This squeezing had caused the parallel-orogen lateral-extmsion of the complex with higher theology, similar to a dynarnic model of exbusion of soft mud Dom crevasses of hardcn blocks. Parallel-orogen move of the terrains may widely occur in orogenic belts, So it should be paid attention, especially to recongnizadon of direction of migration. This is very impotent to the undentanding of orogeny and to reconstmcdng the palaeottectonic pattems in the view point of dynarnics.
出处
《地质科学》
CAS
CSCD
北大核心
1997年第4期423-431,共9页
Chinese Journal of Geology(Scientia Geologica Sinica)
关键词
秦岭
造山带
杂岩
侧向运移
Lineation structures, Eastward migration of granite emplacement, Westward movement, Qinling complex.
