湘鄂西褶皱带中－新生代剥蚀特征及其构造指示：来自磷灰石裂变径迹的证据
Western Hunan-Hubei Fold Belt Exhumation Characteristics and Its Tectonic Implication in Mesozoic-Cenozoic: Evidence from Apatite Fission Track

恢复湘鄂西褶皱带中－新生代以来的剥蚀历史，探讨其变形的时空格架，对于研究陆内褶皱造山以及指导该地区的油气勘探具有重要的意义.利用该地区磷灰石样品进行裂变径迹年龄测定与热史模拟，对中－新生代的剥蚀厚度和速率进行分析.结果表明，湘鄂西地区磷灰石裂变径迹的年龄为71～100 Ma，与川东隔挡式褶皱带中的磷灰石样品年龄进行对比，具有由SE到NW向递进变新的趋势；中新生代以来的热史呈现出“三段式”的特征，这3个阶段的转折时期为115～90 Ma和35～ 20 Ma，分别对应了从晚侏罗世－早白垩世挤压造山到晚白垩世伸展成盆再到新生代整体抬升的构造转换；燕山期为湘鄂西褶皱带的主变形期，变形时序呈现出由SE到NW向递进变新的趋势，剥蚀程度呈现出由SE到NW向变弱的趋势.这些认识为燕山期湘鄂西－川东褶皱带陆内递进变形的形成演化研究提供了有力的证据.
Reconstruction of the Mesozoic-Cenozoic exhumation history in western HunanHubei fold belt and establishing its temporal and spatial evolution play important role in the research of intracontinental orogeny as well as the petroleum exploration in this area. Based on apatite fission track (AFT) analysis and time-temperature thermal history modeling results, this work quantitively constrains the exhumation rate and thickness of the western Hunan Hubei fold belt.The AFT ages here range from 71 to 100 Ma. Integrating with the AFT ages from fold belt in the East Sichuan basin, all the data present a younger trend from southeast to northwest. The time-temperature thermal history since Mesozoic shows a “three-stages” feature with the turning period occurred at 115-90 Ma and 35-20 Ma. The three stages correspond well with the geological evidence and respectively indicate different deformations. The deformations are respectively orogeny during Late Jurassic-Early Cretaceous, basin formation in Late Cretaceous and tectonic uplift since Cenozoic. Yanshannian event is the main cause of the deformation. The deformation occurred earlier in the southeast and later in the northwest and the exhumation also presented a pattern being stronger in the southeast and weaker in the northwest. All the recognization during this work provides strong evidences for the deformation and evolution process of the western Hunan-Hubei to East Sichuan fold belt