桂南钦防构造带两侧中新生代差异隆升的磷灰石裂变径迹证据

运用裂变径迹年代学方法对桂南钦防构造带两侧的8个样品进行磷灰石裂变径迹（AFT）分析,结果表明：构造带南东侧4个样品中有3个样品的磷灰石裂变径迹年龄在（44.5±2.3）～（53.2±5.7）Ma,样品磷灰石裂变径迹年龄相对较年轻,44.5～66.2Ma期间的隆升速率为0.007～0.012 mm/a,47.4 Ma以来平均剥露速率为0.095 mm/a,平均隆升速率0.095 mm/a;而构造带北西侧的磷灰石裂变径迹年龄在（58.2±3.70）～（63.1±4.93）Ma,年龄较老,61.5 Ma以来平均剥露速率为0.073 mm/a,平均隆升速率为0.084 mm/a,反映出自始新世以来,钦防构造带两侧存在有较明显的差异隆升过程。此外,裂变径迹年龄的平面分布格局和热模拟结果表明,钦防构造带两侧自晚白垩世以来的构造活动并非是整体统一抬升的过程,而是表现为北西侧先隆升、南东侧后隆升的演化规律。反映了区域性的差异隆升作用由北西向南东具逐渐增强趋势。

Apatite Fission Track Evidence for Mesozoic-Cenozoic Differential Uplift on Both Sides of Qinfang Tectonic Belt in Southern Guangxi

The apatite fission track（AFT） chronology from the eight samples in both sides of the Qinfang tectonic belt shows that the AFT ages of three out of four samples in the southeast side of the tectonic belt are between 44.5±2.3 Ma and 53.2±5.7 Ma which is relatively younger.During 44.5-66.2 Ma,the uplift rate in the southeast side of the tectonic belt is 0.007-0.012 mm/a.Since 47.4 Ma,the average denudation rate is 0.095 mm/a,and the average uplift rate is 0.095 mm/a in the southeast side.Meanwhile,the AFT ages in the northwest side of the tectonic belt is（58.2±3.7）-（63.1±4.93） Ma which is obviously older.The average rate of denudation and uplift is 0.073 mm/a and 0.084 mm/a in the northwest side of the Qinfang tectonic belt since 61.5 Ma,obvious differential uplifting process in both sides of the Qinfang tectonic belt since Eocene.Moreover,the space pattern of the AFT ages and thermal-simulation results indicate that the tectonic activity in both sides of the Qinfang tectonic belt are not an integral unified uplifting process since Late Cretaceous.In this area,the uplifting of mountains firstly commenced in the northwest and then gradually immigrated toward the southeast that shows a generally increasing trend from the northwest to the southeast.