频谱分析法在反演造山带地形高差演化中的应用--以中国大别山、米仓山和美国内华达山脉为例  

Quantifying the late stage topographic evolution of orogenic belts by Fast Fourier Transform spectral analysis:Applications in the Dabie and Micang Shan,China and Sierra Nevada,U.S.A.

作　　者：苏哲[1,2] 刘静[3] 张鲁新[2,4] 王二七[1,5] 

机构地区：[1]中国科学院地质与地球物理研究所,岩石圈演化国家重点实验室,北京100029 [2]中国科学院研究生院,地球科学学院,北京100049 [3]中国科学院青藏高原研究所,大陆碰撞与隆升国家重点实验室,北京100085 [4]中国科学院地质与地球物理研究所,地球深部研究国家重点实验室,北京100029 [5]中国科学院地球环境研究所,黄土与第四纪地质国家重点实验室,西安710075

出　　处：《地质科学》2011年第3期743-762,共20页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家重点基础研究计划“973”项目(编号:2011CB403106);中国科学院知识创新工程项目(编号:KZCX2-YW12);国家自然科学创新群体基金项目(编号:40721003);国家自然科学基金(编号:40872131)资助

摘　　要：近年来迅速发展的低温热年代学已极大改善了人们对地壳内(1～6 km)隆升和剥蚀过程的认识。然而在实际工作中,样品的采集除了受到气候、地理环境等恶劣条件的制约以外,在对低温热年代学数据进行解释或以此计算造山带的隆升剥露速率时,使用的一些有关近地表热结构的假定条件通常是不科学的,如将易受地表起伏影响的地热等温线形态考虑成水平分布,往往造成数据解释的误导性。本文引入了Braun(2002b)的一种在信号学中常用的方法,利用快速傅立叶变换(FFT)和分形几何学的思想,把样品的高程(h)和对应年龄(a)分别作为输入和输出信号,将高程和年龄所代表的时频域信号转换为地形空间波数域信号,从而得到造山带在后造山作用阶段的地形演化情况。这种方法综合考虑了地表的地形起伏对等温线形态的影响。我们将该方法成功应用于中国的大别山、米仓山地区和美国的内华达山脉,估算出大别山核部地区35 Ma以来地形高差缩小了40%～50%(β≈-0.45),其边部地区50 Ma以来地形起伏降低l了约70%(β≈-0.33);米仓山—汉南地区90 Ma以来地形起伏变化不大,隆升与剥蚀量基本相抵(β≈-1);美国内华达山脉65 Ma以来地形起伏缩小了近1/2(β≈-0.4)。Recent advances in low-temperature thermochronology and its applications have shed lights on the detailed processes in the shallowest crustal depth （1 - 6 km）, such as uplift, exhumation and cooling. However, in practice, much information is lost by imperfect sampling locations due to difficulties in geographic accessibility. In addition, assumptions of the unkown subsurface isotherms, which for instance are topographically-dependent and thus can be non- horizontal, bring more uncertainties in interpretations. This article introduces a method of the Fast Fourier Transform （FFT） spectral analysis which is produced by Braun （2002b） , combined with the fractual thought to take the elevation（h）and AHe age（a）of samples as the input（I） and output signals（F） ,then make a transformation from the time domain to spatial one by the FFT. Through it,we could inverse the last-stage of relief change of topography in the orogenic belt. Synthetically, this method considers the influence from the surface topographic fluctuation which could cause the isotherm to be curved. We succeed to apply the method into the Dabie Shan region and the Micang Shan Mt. in China and the Sierra Nevada range, the U. S. A. We find that in the Dabie Shan,the relief has decreased by -40% - 50% （β≈-0.45 ）in the core since 35 Ma and reduced by -70% （β≈-0.33）on the flank of the range since 50 Ma. In the Micang Shah,the relief keeps its relief stable （β≈-1 ） since 90 Ma ; the Sierra Nevada range has experienced relief reduction by more than 50% since - 65 Ma.

关 键 词：隆升与剥蚀 古地形 快速傅立叶变换频谱分析 构造地貌学 封闭温度等温线 地形的临界波长 

分 类 号：P313[天文地球—固体地球物理学] P542[天文地球—地球物理学]