Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded...Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e. the rapid uplifting of the the Songpan-Garze fold belt was corresponding to the rapid subsidence of the basin;the Songpan-Garze fold belt has uplifted at a much greater rate than the West Sichuan foeland basin in the last 60 Ma;and (7) the palaeogeothermal gradient was 25℃ /km in the West Sichuan foreland basin.展开更多
Following the 2008 Wenchuan M8 earthquake,the seismic risk of the northeastern section of the Longmenshan fault zone and the adjacent Hanzhong basin has become an issue that receives much concern.It is facing,however,...Following the 2008 Wenchuan M8 earthquake,the seismic risk of the northeastern section of the Longmenshan fault zone and the adjacent Hanzhong basin has become an issue that receives much concern.It is facing,however,the problem of a lack of sufficient data because of little previous work in these regions.The northeastern section of the Longmenshan fault zone includes three major faults：the Qingchuan fault,Chaba-Lin＇ansi fault,and Liangshan south margin fault,with the Hanzhong basin at the northern end.This paper presents investigations of the geometry,motion nature,and activity ages of these three faults,and reveals that they are strike slip with normal faulting,with latest activity in the Late Pleistocene.It implies that this section of the Longmenshan fault zone has been in an extensional setting,probably associated with the influence of the Hanzhong basin.Through analysis of the tectonic relationship between the Longmenshan fault zone and the Hanzhong basin,this work verifies that the Qingchuan fault played an important role in the evolution of the Hanzhong basin,and further studies the evolution model of this basin.Finally,with consideration of the tectonic setting of the Longmenshan fault zone and the Hanzhong basin as well as seismicity of surrounding areas,this work suggests that this region has no tectonic conditions for great earthquakes and only potential strong events in the future.展开更多
综合利用露头构造解析、地震剖面解释、锆石和磷灰石裂变径迹年龄和沉降-沉积等资料,对川西-龙门山盆山系统沿走向的构造变形、差异隆升-剥蚀和沉积记录进行系统梳理,探讨龙门山冲断带和川西前陆盆地系统的走向差异演化特征及其关键构...综合利用露头构造解析、地震剖面解释、锆石和磷灰石裂变径迹年龄和沉降-沉积等资料,对川西-龙门山盆山系统沿走向的构造变形、差异隆升-剥蚀和沉积记录进行系统梳理,探讨龙门山冲断带和川西前陆盆地系统的走向差异演化特征及其关键构造变革期。受控于本身的地质结构差异及周缘多个构造带的多期交互作用,龙门山冲断带和川西前陆盆地在构造、隆升和沉积等方面都表现出明显的走向差异。龙门山冲断带自北向南总体上具有韧性减弱、脆性增强、构造定型时间变新的趋势,龙门山北段和盆地北部定型于燕山期,而龙门山中、南段和盆地南部定型于喜马拉雅期。中生代期间,龙门山北段隆升较快;而新生代期间,龙门山中、南段隆升较快。川西前陆盆地同样表现出南北差异隆升的特点,北部隆升较早,大约在45 Ma B.P.;而南部隆升较晚,在20~25 Ma B.P.。川西(北)前陆盆地的沉降中心经历了4次明显的迁移,即从晚三叠世的龙门山中段前缘向东北迁移,中侏罗世到大巴山-米仓山前缘,晚侏罗世-早白垩世向西迁移至米仓山-龙门山北段前缘,于晚白垩世-新生代期间再次向南迁移到龙门山中-南段前缘。龙门山冲断带和川西前陆盆地的走向差异演化表现为印支期向南递进扩展、燕山早-中期南北分异和燕山晚期-喜马拉雅期北隆南降。龙门山冲断带和川西前陆盆地经历了晚三叠世、中侏罗世、早白垩世和古近纪4个关键构造变革期。晚三叠世构造变革期包括龙门山水下隆起和海相前陆盆地(马鞍塘组上部至小塘子组)、龙门山局部隆升和海陆过渡相前陆盆地(须家河组第二至第三段)以及龙门山全面隆升和陆相前陆盆地(须家河组第四至第五段)三大阶段,主要受控于扬子构造域并受秦岭构造域的强烈影响。中侏罗世构造变革表现为扬子构造域向秦岭构造域的转变;早白垩世构造变革表现为秦岭构造域向青藏高原构造域的转变;古近纪构造变革表现为川西前陆盆地由沉积向剥蚀状态的转变。展开更多
基金the National Natural Science Foundation of china (poject No. 49070140)
文摘Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e. the rapid uplifting of the the Songpan-Garze fold belt was corresponding to the rapid subsidence of the basin;the Songpan-Garze fold belt has uplifted at a much greater rate than the West Sichuan foeland basin in the last 60 Ma;and (7) the palaeogeothermal gradient was 25℃ /km in the West Sichuan foreland basin.
基金supported by the Key Projects in the National Science & Technology Pillar Program during the Twelfth Five-year Plan Period (Grant No. 2012BAK15B01-03)the National Science & Technology Major Project (Grant No. 2011ZX06002-010-15)
文摘Following the 2008 Wenchuan M8 earthquake,the seismic risk of the northeastern section of the Longmenshan fault zone and the adjacent Hanzhong basin has become an issue that receives much concern.It is facing,however,the problem of a lack of sufficient data because of little previous work in these regions.The northeastern section of the Longmenshan fault zone includes three major faults：the Qingchuan fault,Chaba-Lin＇ansi fault,and Liangshan south margin fault,with the Hanzhong basin at the northern end.This paper presents investigations of the geometry,motion nature,and activity ages of these three faults,and reveals that they are strike slip with normal faulting,with latest activity in the Late Pleistocene.It implies that this section of the Longmenshan fault zone has been in an extensional setting,probably associated with the influence of the Hanzhong basin.Through analysis of the tectonic relationship between the Longmenshan fault zone and the Hanzhong basin,this work verifies that the Qingchuan fault played an important role in the evolution of the Hanzhong basin,and further studies the evolution model of this basin.Finally,with consideration of the tectonic setting of the Longmenshan fault zone and the Hanzhong basin as well as seismicity of surrounding areas,this work suggests that this region has no tectonic conditions for great earthquakes and only potential strong events in the future.
文摘综合利用露头构造解析、地震剖面解释、锆石和磷灰石裂变径迹年龄和沉降-沉积等资料,对川西-龙门山盆山系统沿走向的构造变形、差异隆升-剥蚀和沉积记录进行系统梳理,探讨龙门山冲断带和川西前陆盆地系统的走向差异演化特征及其关键构造变革期。受控于本身的地质结构差异及周缘多个构造带的多期交互作用,龙门山冲断带和川西前陆盆地在构造、隆升和沉积等方面都表现出明显的走向差异。龙门山冲断带自北向南总体上具有韧性减弱、脆性增强、构造定型时间变新的趋势,龙门山北段和盆地北部定型于燕山期,而龙门山中、南段和盆地南部定型于喜马拉雅期。中生代期间,龙门山北段隆升较快;而新生代期间,龙门山中、南段隆升较快。川西前陆盆地同样表现出南北差异隆升的特点,北部隆升较早,大约在45 Ma B.P.;而南部隆升较晚,在20~25 Ma B.P.。川西(北)前陆盆地的沉降中心经历了4次明显的迁移,即从晚三叠世的龙门山中段前缘向东北迁移,中侏罗世到大巴山-米仓山前缘,晚侏罗世-早白垩世向西迁移至米仓山-龙门山北段前缘,于晚白垩世-新生代期间再次向南迁移到龙门山中-南段前缘。龙门山冲断带和川西前陆盆地的走向差异演化表现为印支期向南递进扩展、燕山早-中期南北分异和燕山晚期-喜马拉雅期北隆南降。龙门山冲断带和川西前陆盆地经历了晚三叠世、中侏罗世、早白垩世和古近纪4个关键构造变革期。晚三叠世构造变革期包括龙门山水下隆起和海相前陆盆地(马鞍塘组上部至小塘子组)、龙门山局部隆升和海陆过渡相前陆盆地(须家河组第二至第三段)以及龙门山全面隆升和陆相前陆盆地(须家河组第四至第五段)三大阶段,主要受控于扬子构造域并受秦岭构造域的强烈影响。中侏罗世构造变革表现为扬子构造域向秦岭构造域的转变;早白垩世构造变革表现为秦岭构造域向青藏高原构造域的转变;古近纪构造变革表现为川西前陆盆地由沉积向剥蚀状态的转变。
