中－新生代龙门山的差异隆升

通过对采自龙门山南段、中段和北段花岗岩与砂岩样品中的磷灰石、锆石的裂变径迹年龄的分析，发现中生代以来龙门山的隆升在走向上存在分段性，在近东西方向上存在分带性。从松潘－甘孜褶皱带→龙门山冲断带→川西前陆盆地：松潘－甘孜褶皱带整体发生区域隆升，裂变径迹年龄与高程呈正相关关系；在龙门山冲断带，裂变径迹年龄与高程呈负相关关系或无关，说明冲断层在隆升过程中起主导作用；在川西前陆盆地，样品随埋深发生部分或全部退火。茂县－汶川断裂两侧锆石裂变径迹年龄差异明显而磷灰石裂变径迹年龄无明显差异，显示茂县－汶川断裂以西地区在38～10 Ma发生过更为快速的隆升；北川断裂两侧磷灰石裂变径迹年龄差异明显，表明北川断裂以西地区在10～0 Ma发生过快速隆升。从走向上看，从龙门山北段向南段，锆石裂变径迹年龄呈逐渐增大的趋势，这可能意味着印支末期或燕山早期，龙门山北段发生了更快的隆升；而磷灰石裂变径迹年龄总体上从龙门山北段向中段和南段呈递减趋势，反映新生代期间龙门山中、南段隆升更快。

Differential Uplift Process of Longmen Mountain in Mesozoic-Cenozoic

Based on analysis on fission track dating of apatite and zircon in the granite and sand samples collected from the south,middle and north segment of Longmen Mountain,it is found that the uplift process of Longmen Mountain can be divided into different segments along strike direction and zones in East-West direction.From Songpan-Ganzi fold belt through Longmen thrust belt to western Sichuan foreland basin,the entire Songpan-Ganzi fold belt has experienced regional uplift,and the fission track age shows positive correlation with altitude;while in Longmen thrust belt,the fission track age has negative or no correlation with altitude,suggesting that thrust fault play a dominant role during the uplift process.However,in western Sichuan foreland basin,the samples partly or entirely annealed with burial depth.On both sides of Maoxian-Wenchuan fault,there is an obvious difference in zircon fission track age but no evident difference for apatite,suggesting that the west of Maoxian-Wenchuan fault has undergone more rapid uplift during 38-10 Ma.On both the sides of Beichuan fault,apatite shows obvious fission track age,suggesting a quick uplift process occurred in the west of Beichuan fault during 10-0 Ma.Along strike direction,zircon fission track age increases gradually from north to south part of Longmen Mountain,which may indicate a more rapid uplift process in the northern part during Late Indosinian or Early Yanshanian.Apatite fission track age generally decreases from north through middle and to south,reflecting a more rapid uplift in the middle and south than in the north during Cenezoic.