川东弧形带三维构造扩展的AFT记录

Cretaceous transportation of Eastern Sichuan arcuate fold belt in three dimensions:Insights from AFT analysis

对川东弧形褶皱带北段、中段和南段的三条剖面,进行了7件样品的磷灰石裂变径迹(AFT)测试,结合前人已发表的4件样品,分析模拟了主要背斜的隆升-剥露热历史.结果表明川东弧形带主体构造变形时间为135→65Ma,即早白垩世早期到晚白垩世晚期.进而建立并对比了三条剖面的构造变形时序,揭示出川东弧形带的三维构造扩展历史:(1)平行于构造线走向,表现为从中心向两翼的构造扩展,弧形带中段的构造变形最早,起始时间为早白垩世早期(约135Ma),北段和南段的变形较晚,起始时间为早白垩世晚期(约100 Ma);(2)垂直于构造线走向,在弧形带北段和中段均表现为由东向西的构造扩展,而在弧形带南段,由于受到前缘华蓥山断裂的影响,表现为自西向东的变形时序.川东弧形带的三维构造扩展历史暗示了"弯山构造"的成因模式,以及华蓥山先存断裂对弧形构造的限制作用.

The Eastern Sichuan arcuate fold belt, the front of the South China orogen, has not been well dated, because no sediment record can be used for dating. In this paper, we used 11 apatite fission track （AFT） samples, including 7 new samples and 4 published samples, to analyze the exhumation history of the anticlines. The samples were collected along three profiles, with 3 samples along Northeastern Sichuan profile, 4 samples along Eastern Sichuan profile and 4 samples along Southeastern Sichuan profile. The AFT thermal history modeling showed that the rapid cooling event generally occurred from 135 to 65 Ma, indicating the structural deformation of the Eastern Sichuan fold belt was from early period of early Cretaceous to late period of lateCretaceous. Additionally, the transportation history of the Eastern Sichuan arcuate fold belt in three dimensions was revealed by the three profiles~ Along the structural lines, the deformation was transported from the center to the two limbs of the arcuate fold belt, with earlier deformation （~ 135 Ma） in Eastern Sichuan and later deformation （~ 100 Ma） in Northeastern and Southeastern Siehuan; Across the structural from east to west in Northeastern and Eastern Sichuan, because the Huayingshan anticline transportation history of the Eastern Sichuan fol obstruction of the pre-existing Huayingshan fau nes, the deformation was generally transported Sichuan, but from west to east in Southeastern was uplifted earlier than other folds. The d belt suggested the orocline bending process and It during the formation of the arcuate fold belt.