湘鄂西-川东中生代陆内递进扩展变形:来自裂变径迹和平衡剖面的证据

从湘鄂西到川东近400km宽阔的中上扬子陆内中古生界变形是江南-雪峰陆内造山作用向西北方向递进扩展变形的结果.利用磷灰石裂变径迹年龄测定和埋藏热历史模拟以及雪峰山-华蓥山构造剖面的平衡演变分析方法,揭示出自湘鄂西向川东华蓥山构造变形发展的时代从165Ma到95Ma,具有递进变新的趋势.湘鄂西断褶带厚皮构造变形缩短率小于川东断褶带薄皮构造的变形缩短率,但侏罗纪时期湘鄂西断褶带的缩短速率却明显大于早白垩世早中时期川东断褶带东南段的缩短速率,而早白垩世早中时期川东断褶带东南段的缩短速率又大于早白垩世晚期川东断褶带北西段的缩短速率,反映基底卷入程度和推挤力源的强度大小是控制缩短率和缩短速率的主要原因.这些结果表明湘鄂西-川东中生代陆内变形具有大跨度穿时递进扩展的特征和方式,并且由于基底的差异和卷入程度的不同以及滑脱层参与深度和程度的不同,不同构造带缩短率和缩短速率的变化反映出明显的陆内变形及其动力学的差异.研究推测,如果江南-雪峰隆起是原地或准原地体,则湘鄂西-川东陆内构造递进扩展变形的"发动机"在桃源-怀化一线,该线亦是江南-雪峰中生代陆内造山作用开始发轫并向南北两侧呈花状扩展的位置.

Mesozoic Intra-Continental Progressive Deformation in Western Hunan-Hubei-Eastern Sichuan Provinces of China: Evidence from Apatite Fission Track and Balanced Cross-Section

The Mesozoic intra-continental evolution of about 400 km wide middle-upper Yangtze thrust belt from western Hunan-Hubei-eastern Sichuan provinces has been established with a time interval of 70 Ma (from 165 Ma to 95 Ma).Based on apatite fission track (AFT),time-temperature thermal history and balanced cross-section,we conclude that the deformation evolution is progressive from southeast (Jiangnan-Xuefeng intra-continental orogeny) to northwest (Huayingshan thrust belt),and younger and younger.The shortening...