青藏高原东南缘大凉山新生代隆升建造过程——多封闭系统低温热年代学与热模型限制  

Cenozoic mountain-building processes in the Daliangshan,southeastern margin of the Tibetan Plateau:Evidence from low-temperature thermochronology and thermal modeling

作　　者：邓宾[1,2] 雍自权[1] 刘树根[1] 李智武[1] 赵高平[1] 米色子哈[3] 汤聪[4] 

机构地区：[1]成都理工大学油气藏地质及开发工程国家重点实验室,成都610059 [2]德国图宾根大学地球科学系,图宾根72074 [3]四川省地质矿产勘查开发局攀西地质队,四川西昌615000 [4]辽河油田勘探开发研究院计算所,辽宁盘锦124010

出　　处：《地球物理学报》2016年第6期2162-2175,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金(41402119;2014JQ0057;41472107;41572111;41230313)联合资助

摘　　要：长波长、低起伏度大凉山构造带新生代隆升剥露与建造过程是解译青藏高原东向扩展过程的关键核心地区之一.本文基于大凉山构造带喜德剖面和沐川剖面9件样品的多封闭系统低温热年代学年龄（即磷灰石（U-Th）/He（AHe）、磷灰石裂变径迹（AFT）和锆石（U-Th）/He（ZHe））定年,揭示出多封闭系统热年代学年龄与古岩性柱深度具有明显的正相关性,即伴随古岩性柱深度增大,多封闭系统热年代学年龄明显减小.喜徳剖面多封闭系统低温热年代学AHe、AFT和ZHe年龄值分别为7—9Ma、14—22Ma和25—38Ma;沐川剖面多封闭系统低温热年代学AHe和AFT年龄值分别为10—26Ma、23—85Ma,ZHe年龄值为未完全退火年龄.多封闭系统热年代学和QTQt热史模拟揭示,大凉山构造带喜徳和沐川剖面岩性柱所有样品都经历大致相似的三阶段热演化过程,尤其是晚新生代快速隆升剥露阶段（30—20 Ma以来）,其平均剥露速率分别为-0.15mm·a^-1和-0.20mm·a^-1,抬升剥露量分别为-3.0km和-1.5km.结合区域低温热年代学特征的大凉山构造带地表隆升动力学模型,揭示出重力均衡作用下地壳缩短与剥露作用（即构造隆升剥露机制）控制形成了现今大凉山造山带长波长、低起伏和高海拔地貌建造过程.The Daliangshan Mountains,located in the southeastern margin of the TibetanPlateau,is characterized of long-wavelength,low-relief topography,of which the uplift and exhumation have been well documented with controversies concerning eastward growth of the Tibetan Plateau.Based on nine samples of multisystem low-temperature thermochronology（i.e.,apatite and zircon（U-Th）/He（AHe and ZHe）,apatite fission track（AFT））,this study suggests a positive relationship between decreasing thermochronological ages and increasing paleo-depth in the Xide and Muchuan stratigraphic columns.The AHe,AFT and ZHe ages in the Xide section are 7—9 Ma,14—22 Ma and 25—38 Ma,respectively.The AHe and AFT ages in the Muchuan section are 10—26 Ma and 23—85 Ma,while the ZHe ages are partially retentive.Furthermore,the thermal histories modeled by the QTQt and low-temperature thermochronology imply three episodes of uplift and exhumation that occurred across the Daliangshan,in particular,a last period of enhanced cooling and exhumation beginning from 30—20 Ma.Of them,the exhumation rates in the Xide and Muchuan sections are-0.15mm·a^-1 and -0.20mm·a^-1,with magnitude of -3.0km and -1.5km,respectively.Thus,we argued that the mountbuilding processes and their uplift dynamics in the Daliangshan should be attributed to the crustal-shortening-related exhumation rather than the flow of the lower crust.

关 键 词：低温热年代学 QTQt 隆升剥露 隆升动力学 大凉山 

分 类 号：P314[天文地球—固体地球物理学]