摘要
湘东南及湘粤赣边区属南岭中段北部,是研究华南中生代构造背景与演化的良好窗口。通过同位素年代学和地质地球化学研究,确定了区内中生代3个时代花岗岩的时限与构造环境,并结合对区内中生代不同时代陆相盆地和火山岩的性质与形成机制,构造变形和成矿作用的期次与特征等研究,厘定出研究区中生代地质事件序列的框架。从早至晚分为早三叠世—中三叠世早期前造山阶段(Ⅰ)、中三叠世后期—中侏罗世初陆内造山阶段(Ⅱ)、中侏罗世早期—晚侏罗世后造山阶段(Ⅲ)、白垩纪板内裂谷阶段(Ⅳ)等4个大的地质发展阶段,其中陆内造山阶段(Ⅱ)进一步划分为4个亚阶段(Ⅱ1～Ⅱ4)。前造山阶段(Ⅰ)为稳定海相沉积阶段。中三叠世后期(Ⅱ1)为陆内俯冲汇聚高峰期,形成大量NNE向为主的逆冲断裂与褶皱,并使陆壳增厚。中三叠世末—晚三叠世后期(Ⅱ2)挤压相对松弛,大量壳源花岗岩浆形成并侵位(233～210Ma)。晚三叠世末—早侏罗世(Ⅱ3)为同造山上隆伸展环境,形成NNE向裂陷含煤盆地,高Na低K的拉斑玄武岩喷发。中侏罗世初期(Ⅱ4)为NNE向左旋汇聚走滑造山,发育逆冲断裂且前期裂陷盆地反转成为山前冲断收缩盆地。中侏罗世早期—晚侏罗世后造山阶段(Ⅲ),大量后造山花岗岩侵位(174～135Ma),同时发生大规模成矿作用;侏罗纪末期发生过短暂的挤压事件。白垩纪板内裂谷阶段(Ⅳ)形成盆-岭构造和变质核杂岩构造、双峰式火山岩和次火山岩、酸性岩脉及具有AA型花岗岩特征的上堡小型岩体等组合。文章最后就华南地区燕山早期构造环境和中生代不同阶段构造-岩浆活动特征的形成机制等问题进行了讨论。
Southeastern Hunan and the Hunan-Guangdong-Jiangx border area belong to the northern part of the central segment of the Nanling Range. This region is a favorable window for studying Mesozoic tectonic setting and evolution in South China. According to isotopic chronological, geological and geochemical studies, the time ranges and tectonic settings of granites of three Mesozoic ages are determined, and on that basis, combined with the characteristics and genetic mechanism of continental basins of different Mesozoic ages and volcanic rocks, stages and characteristics of tectonic deformations and ore-forming processes, a preliminary sequence framework of the Mesozoic geological events is defined. Four major stages of Mesozoic tectonic evolution in the region may be distinguished; from early to late times they are the Early Triassic-early Middle Triassic pre-orogenic stage （Ⅰ）, the late Middle Triassic - early Middle Jurassic intracontinental orogenic stage （Ⅱ）, the early Middle Jurassic - Late Jurassic post-orogenic stage （Ⅲ）, and the Cretaceous intraplate rift stage （Ⅳ）. of these,stage II may be further di- vided into four substages （ Ⅱ 1 - Ⅱ 4）. The pre-orogenic stage （ Ⅰ ） was a stable marine sedimentary stage. The late Middle Triassic （Ⅱ 1） was an intracomtinental subduction-converge peak stage, when a great deal of mainly NNE-directed thrusts and folds formed, resulting in crustal thickening. In the terminal Middle Triassic - latest Triassic （II 2）, compression was relatively relax and a great deal of crustal-derived granitic magma formed and was emplaced （233 - 210 Ma）. There was a syn-orogenic uplift-extensional tectonic setting in the terminal Late Triassic - Early Jurassic （ Ⅱ 3）, when the NNE-directed rift coal-bearing basins formed and high-Na and low-K tholeiitic magma was erupted. The initial Middle Jurassic （ Ⅱ 4） witnessed NNE-directed sinistral convergencestrike-slip orogeny, when thrusts formed and early-formed rift basins underwent inversion to transform to piedmont thrust-contractive basins. In the early Middle Jurassic-Late Jurassic post-orogenic stage （Ⅲ）, voluminous post-orogenic granite was emplaced （at 174-135 Ma）, accompanied by extensive mineralization. At the end of the Jurassic there occurred a transient compression event. In the Cretaceous intraplate-rift stage （Ⅳ）, there occurred such tectonic associations as basin-range tectonics and metamorphic core complexes, bimodal volcanic rocks and subvolcanic rocks, acid dikes and Shangbao small intrusions with the characteristics of AA-type granite. Finally, the paper discusses the early Yanshanian tectonic environment and the formation mechanism of tectonomagmatic characteristics of different stages in the Mesozoic in South China.
出处
《中国地质》
CAS
CSCD
2005年第4期557-570,共14页
Geology in China
基金
中国地质调查局地质大调查项目(200213000035)资助
关键词
中生代
地质发展
框架
湘东南
湘粤赣边区
Mesozoic
geological evolution
framework
southeastern Hunan-Hunan,Guangdong-Jiangxi-provinces border area
