地球学报Issue(5)：552-559,8.DOI:10.3975/cagsb.2014.05.04
135~130 Ma：大别山第二次“去根”时间？
135~130 Ma：The Timing of Slab Breakoff again in the Dabie Mountains?
摘要
Abstract
The Dabie complex is mainly composed of Early Cretaceous intrusive rocks and Triassic metamorphic rocks. On the four sides of the complex, there are four regional shearing belts: the Tancheng-Lujiang Fault, the Shangcheng-Macheng Fault, the Xiangfan-Guangji Fault and the Xiaotian-Mozitan Fault. Among them, the strike-slip directions of the Xiangfan-Guangji Fault and Xiaotian-Mozitan Fault were opposite in Early Cretaceous. The northern boundary (Xiaotian-Mozitan Fault) is a sinistral ductile shear zone, and the southern boundary (Xiangfan-Guangji Fault) is a dextral ductile one. In the inner part of the Dabie complex, low-angle mylonitic foliations, which were formed in Early Cretaceous, mostly dip toward SE or NW. Lineations on these later foliations also plunge toward SE or NW. Generally, the Dabie complex is characterized by southeastward extrusion and top-to-NW shearing along the orogen. These structures indicate that Late Mesozoic tectonic processes were very important for the later evolution of the complex. The deformation characteristics in the shear zone and the inner part of the Dabie complex suggest a low-angle exhumation along the orogen (SE-NW), which led to the exhumation of the HP/UHP metamorphic rocks and the synkinematic magmatic rocks to the Earth’s surface. Meanwhile, geochronological data indicate that, during Late Jurrassic-Early Cretaceous, the Dabie complex (or the northeastern margin of the Yangtze plate) underwent large-scale migmatization in 145~135 Ma, synkinematic magmatism in 145~135 Ma, and post-orogenic magmatism in 135~120 Ma. Therefore, Early Cretaceous exhumation recorded in the Triassic metamorphic rocks from the Dabie complex is not the continuation of the Endosinian event, but associated with the Yanshanian intraland orogeny and the subsequent extension. Though the starting time of the orogeny remains unclear, the available dating results for the undeformed plutons (130~120 Ma) and the new zircon U-Pb age of the synkinematic pegmatite dyke obtained by the authors provide better timing constraints on the end of the crustal deformation in Early Cretaceous along the Dabie orogen. In conclusion, the Dabie complex underwent Triassic collisional orogeny-extension, and Late Jurrassic-Early Cretaceous interland orogeny-extension two processes.关键词
大别杂岩/同构造伟晶岩脉/SHRIMP锆石U-Pb定年/中国东部/早白垩世伸展Key words
Dabie complex/syn-kinematic pegmatite dyke/zircon SHRIMP U-Pb dating/eastern China/Early Cretaceous extension分类
天文与地球科学引用本文复制引用
崔建军,董树文,马立成,施炜..135~130 Ma：大别山第二次“去根”时间？[J].地球学报,2014,(5):552-559,8.基金项目
国家专项“深部探测技术与实验研究”(编号：SinoProbe-08-1)资助。 （编号：SinoProbe-08-1）
