【摘要】 粤北南雄盆地的形成与演化过程受控于华南东部晚白垩世-古近纪构造体制的转换。本文从沉积学角度,利用盆地内沉积碎屑记录、沉积特征和碎屑锆石U-Pb年代学,获得盆地内部的岩石碎屑组分信息和相应源区的特性。研究表明南雄盆地是一个不对称的伸展断陷盆地,与盆地两侧的花岗岩体共同构成了一个半地堑式的构造体系。盆地在侏罗纪-早白垩世挤压造山的基础上,于早白垩世晚期,在区域伸展构造背景下,以前寒武纪-早古生代碎屑岩为基底,发育了一套完整的晚白垩世-古近纪红色碎屑岩沉积。盆地形成初期,碎屑沉积物主要来自前寒武系-下古生界;伴随着两侧花岗岩体的抬升、剥露,后期物源主要来自加里东期、印支期和早燕山期岩体。结合盆地沉积相和物源变化的研究,认为盆地形成和演化经历了一个由扩张到萎缩的过程,反映了在晚白垩世-古近纪华南东部区域经历了由伸展向挤压的构造体制转换,转换时间为古新世中晚期(约60Ma),主要动力学背景为印度板块与欧亚板块汇聚碰撞以及太平洋板块俯冲。更多还原

【Abstract】 Formation and evolution of the Nanxiong Basin were dominated by the transformation of the Late Cretaceous-Paleogene tectonic mechanism in the eastern South China Block. In this paper we report new detrital records and sedimentary characteristics of the sediments and U-Pb geochronology of detrital zircons from siliciclastic rocks in the basin. These results indicate that the Nanxiong Basin is an asymmetrical extensional rift basin and constitutes the half-graben tectonic system with granites on both sides. The basin formed in the late Early Cretaceous under a background of regional tectonic extension, and accumulated the Late Cretaceous to Paleocene red siliciclastic rocks that unconformably overlies the Precambrian and lower Paleozoic sequences. U-Pb ages of detrital zircons from the siliciclastic rocks suggest that the sediments at the base of basin mainly came from the Precambrian-Lower Paleozoic strata, whereas the detritus at the upper part of the basin mainly came from the Caledonian, Indosinian, and Early Yanshanian granites exposed on both sides of the basin, which reveals a history of uplift and denudation of the granites accompanying with the evolution of the basin. Considering the sedimentary facies and provenance changes, it is believed that the formation and evolution of the Nanxiong Basin experienced a transition from expansion to atrophy,which is in accordance with the extension to compression tectonic transformation in the eastern South China Block during Late Cretaceous to Paleocene. The transformation is attributed to both of the collision between the Indian and the Eurasian plates and the subduction of the Pacific plate in Mid-Late Paleocene(ca. 60 Ma).更多还原