关键词: 磷灰石裂变径迹, 热史模拟, 构造演化, 区域控制, 合肥盆地

Abstract: Apatite fission-track(AFT)analyses of the Cretaceous sandstones in Hefei Basin were performed. The sample HQ₂-4(K₂¹ Apatite fission-track(AFT)analyses of the Cretaceous sandstones in Hefei Basin were performed. The sample HQ₂-4(K₂¹)from the north part of Hefei Basin yielded an AFT age of(128.2±9.5)million years, that is much older than its depositional age. Its confined track length displays an unimodal distribution with the mean length of(11.9±0.4)μm. The thermal history modeling registers a four-stage development with cooling rates changing from 8.92℃ per million years during 175~150 million years before present, 0.99℃ per million years during 150~85 million years before present, negative 0.49℃ per million years in 85~24 million years before present to 1.96℃ per million years since 24 million years before present, which corresponds to the tectonic evolution from rapid and slow exhumation of sediment provenance to slow subsidence and uplift of the basin. Heishidu Formation(K₁h)in the south part of the basin has an AFT age of(86.3±4.3)million years, that is younger than its stratigraphic age. Its track length with a unimodal distribution has a mean value of(13.6±0.2)μm. Its five-stage AFT cooling history is linked with the evolution of the basin from subsidence reheating, slow and rapid exhumation to two times of slow exhumation. The evolution of Hefei Basin has been successively under the control of activities of the Dabieshan orogen and the Tanlu fault since the Jurassic. The late-orogenic compression of the orogen regionally controlled the compression phase of the basin from the Early Jurassic to 150 million years before present, which was followed by the extensional phase of the basin from 150 million years to 138 million years before present resulted from the orogenic-root delamination. Both the doming extension of the orogen and the strike-slipping of the Tanlu fault spatially created structural variation for Hefei Basin from its southern extension to northern thrusting and eastern strike-slipping from 138 million years to 90 million years before present. The transtension of the Tanlu faulting was responsible for the transtension of the basin from 90 million years to 25 million years before present. The compression of Tanlu fault has been the major factor for producing compressional of exhumation of Hefei Basin since 25 million years before present.)from the north part of Hefei Basin yielded an AFT age of(128.2±9.5)million years, that is much older than its depositional age. Its confined track length displays an unimodal distribution with the mean length of(11.9±0.4)μm. The thermal history modeling registers a four-stage development with cooling rates changing from 8.92℃ per million years during 175~150 million years before present, 0.99℃ per million years during 150~85 million years before present, negative 0.49℃ per million years in 85~24 million years before present to 1.96℃ per million years since 24 million years before present, which corresponds to the tectonic evolution from rapid and slow exhumation of sediment provenance to slow subsidence and uplift of the basin. Heishidu Formation(K₁h)in the south part of the basin has an AFT age of(86.3±4.3)million years, that is younger than its stratigraphic age. Its track length with a unimodal distribution has a mean value of(13.6±0.2)μm. Its five-stage AFT cooling history is linked with the evolution of the basin from subsidence reheating, slow and rapid exhumation to two times of slow exhumation. The evolution of Hefei Basin has been successively under the control of activities of the Dabieshan orogen and the Tanlu fault since the Jurassic. The late-orogenic compression of the orogen regionally controlled the compression phase of the basin from the Early Jurassic to 150 million years before present, which was followed by the extensional phase of the basin from 150 million years to 138 million years before present resulted from the orogenic-root delamination. Both the doming extension of the orogen and the strike-slipping of the Tanlu fault spatially created structural variation for Hefei Basin from its southern extension to northern thrusting and eastern strike-slipping from 138 million years to 90 million years before present. The transtension of the Tanlu faulting was responsible for the transtension of the basin from 90 million years to 25 million years before present. The compression of Tanlu fault has been the major factor for producing compressional of exhumation of Hefei Basin since 25 million years before present.

Key words: apatite fission-track, thermal history modeling, tectonic evolution, regional controls, Hefei Basin