摘要
三叠纪(印支期)是华南陆块构造演化过程中最重要的阶段之一,是奠定华南及东亚地区基本构造格局的关键时期,因此阐明印支期变形的几何学和运动学特征对揭示华南腹地造山作用的驱动机制具有重要意义。该文综合了华南地区野外构造解析及热年代学等研究成果,提出了华南陆块南部三叠纪两阶段演变过程。其中印支早期(约250~225 Ma)变形表现为北西西或近东‒西向具右旋走滑压扭性逆冲构造体系。该构造体系的根带位于华南南部海南‒云开一线,以厚皮构造沿中‒上地壳拆离层低角度自南向北扩展为薄皮构造。印支晚期(约230~190 Ma)构造样式以一系列近平行的北东向左旋压扭性脆‒韧性冲断构造及褶皱体系为特征,区域上表现为花状背冲或鳄鱼式样式。结合华南陆块周缘印支期构造样式的基本面貌,认为华南陆块印支期两期变形样式的形成是在华南陆块向华北陆块深俯冲及东侧古太平洋板块阻塞作用围限下,华南南缘东古特提斯洋的剪刀式穿时关闭及随之的扬子与思茅‒印支陆块俯冲碰撞的结果。
The Triassic Indosinian orogenesis is a key period in the tectonic evolution of the South China Block(SCB).The geometry and kinematics of the Triassic deformational event have great implications in revealing the driving mechanism of the intra-continental orogenesis in the SCB.A synthesis of field-and mapping-based structural analysis and thermo-geochronological results suggests a two-stage Triassic deformational patterns including top-to-north dextral thrusting at ca.250–225 Ma and NE-trending sinistral transpression at ca.230–190 Ma.The Early Triassic dextral transpression is marked by NWW-trending high-strain zones and thrust nappes and sheets,which might have been rooted in the Hainan-Yunkai basement across the middle-upper crustal basal detachment.It transformed from a thick-skinned fold-and thrust-to thin-skinned Jura-like patterns with northerly-propagating deformation from south to north in the southern SCB.The Late Triassic NE-trending sinistral transpression was accompanied by a series of the axis-planed sub-parallel folds and top-to NW-or SE-thrust components in the SCB interior,resulting in the development of the regional positive flower-like geometry and reactivation of the pre-existing structures.The two-stage(Early-Middle and Late Triassic)intra-continental orogenesis in the SCB were jointly controlled by its interaction with the adjoining blocks with the clockwise scissor-like closure of the Paleotethyan Ocean,deep-subduction of the SCB beneath the North China Block and the obstruction of the Paleo-Pacific Plate.
作者
王岳军
王洋
张玉芝
钱鑫
WANG Yuejun;WANG Yang;ZHANG Yuzhi;QIAN Xin(Guangdong Provincial Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2022年第3期399-415,共17页
Geotectonica et Metallogenia
基金
国家自然科学基金-广东省联合基金集成项目(U1701641)
广东省基础与应用基础研究基金项目(2018B030312007)联合资助。
关键词
三叠纪
陆内变形
华南陆块
构造样式
热年代学
多陆块围限
Triassic
intracontinental deformation
South China Block
structural pattern
thermochronolgoy
interaction with the adjoining blocks
