上扬子西部地区新生代构造活动的低温热年代学特征

上扬子西部地区磷灰石裂变径迹年龄数据的统计为该区的新生代构造活动建立了宏观的图景，初步构建了区域上新生代构造活动和陆内变形的时空联系。揭示新生代构造活动在时间上存在大约61～43 Ma和大约24 Ma以来两个阶段的显著差异，约24 Ma是上扬子板块西部地区新生代构造活动显著增强的一个重要转折时期。在空间上大致以松潘-安县为界构成南、北分段。构造活动和区域抬升-剥露总体表现为南强北弱，西强东弱的格局。南段是新生代活动的主控区，以强烈地构造抬升和构造改造为主，而北段总体上受制于白垩纪的抬升-剥露，新生代以来主要表现出剥蚀和弱构造改造的特征。新生代的构造活动受制于青藏高原抬升作用向东扩展的影响。上扬子西部地区新生代构造活动在一定程度上制约了该区油气的圈闭环境和成藏条件。

Distribution of low temperature thermochronology for Cenozoic tectonic activities in west Upper Yangtze area

By statistical analysis of apatite fission track(AFT)data from west Upper Yangtze area，a regional macroscopic image is established for Cenozoic tectonic activities and the temporal?spatial correlation is preliminarily constructed between regional Cenozoic tectonic activities and intra?continental deformation. It reveals that Cenozoic tectonic activities in time are composed of two significant phases，about 61 to 43 Ma and about since 24 Ma. It means an important turning point at about 24 Ma and Cenozoic tectonic activities in west Upper Yangtze area are significantly enhanced since then. Cenozoic tectonic activities in space are roughly separated as the south and the north segmentations by Anxian County. The pattern in segmentations shows that tectonic activities and regional uplift?exhumation are strong in south but weak in north and strong in west but weak in east. The Cenozoic activities are dominated in the southern segmentation，with strongly tectonic uplifting and reworking. But the northern segmentation is hosted by Cretaceous uplift?exhumation，with denudating and weakly tectonic reworking in Cenozoic time. Cenozoic tectonic activities are controlled by the eastward propagation of Tibetan Plateau uplift. For exploration，the trap and accumulation conditions of oil and gas in west Upper Yangtze area are constrained to a certain degree by Cenozoic tectonic activities.