华南中生代构造转换和古太平洋俯冲启动

发布时间：2018-05-03 23:26

本文选题：华南地块 + 构造体制转换　；参考：《地学前缘》2017年04期

【摘要】：长期的华南地块研究取得了一系列重要成果,但是古太平洋俯冲作用于华南的地质记录不是很清晰,尚存争论。一派认为始于二叠纪,另一派认为中生代。本文试图通过华南中生代EW向特提斯构造域和NE向古太平洋构造域的构造转换过程及转换时间入手,探讨古太平洋俯冲启动。雪峰山地区早侏罗世地层以及侏罗纪类磨拉石建造呈NE或NNE向展布,燕山期主要发育2期褶皱变形,早期褶皱轴向为NE—NNE向,晚期为NNE或近南北向的隔槽式褶皱;而印支期也发育2期褶皱变形,D1期为EW—NEE向,D2期为NNE向的紧闭褶皱。这些都说明晚三叠世雪峰山地区已经从EW向特提斯构造域向NE—NNE向太平洋构造域的构造方向转换。而南岭地区,以及更南部的南海北部海域,构造转换时间相对较晚,为早—中侏罗世。综合前人的测年数据,德兴斑岩型铜矿三个含矿斑岩体形成于大约172 Ma,形成于古太平洋板块俯冲所形成的活动大陆边缘环境,成矿物质来源于俯冲洋壳的部分熔融,与地幔楔发生混染,推测与该时期古太平洋板块的平板俯冲、板片撕裂、拆沉和俯冲后撤一系列过程密切相关。同期,华南东南部发育了NE—NNE向、NW向和近EW向三组断裂,其中白垩纪(135~100 Ma)华南NE—NNE向的走滑断裂强烈活动,从东向西依次为:滨海断裂、长乐—南澳断裂、政和—大埔、邵武—河源—阳江断裂、吴川—四会断裂和合浦—北流断裂,主要表现为右旋走滑作用,在东南沿海地区形成一系列的拉分盆地,并非典型的"盆岭构造"。根据群速度和S波速度层析成像,华南地块总体上从西向东地壳的厚度整体上逐渐减薄;华南地块东部发生两次壳幔相互作用,对应两次岩石圈拆沉,这两次拆沉都与古太平洋板块的俯冲有关,第一次拆沉为古太平洋板块平板俯冲时板片撕裂所致,第二次拆沉为俯冲板片俯冲后撤和高角度俯冲造成。
[Abstract]:A series of important achievements have been made in the study of the South China landmass for a long time, but the geological records of the subduction of the ancient Pacific Ocean in South China are not very clear. One school of thought began in the Permian and the other believed that the Mesozoic era. This paper attempts to discuss the initiation of paleo-Pacific subduction through the tectonic transformation process and transition time of Mesozoic EW to Tethys tectonic domain and NE to paleo-Pacific tectonic domain in South China. The early Jurassic strata and Jurassic Molarasite formations in Xuefengshan area were distributed in NE or NNE direction. In Yanshanian period, the fold deformation was mainly in 2 stages, the axial direction of the early fold was NE-NNE, and the late stage was NNE or the near south-north trench fold. In the Indosinian period, there are also two stages of fold deformation, namely, the closed fold in the D _ 1 stage of EW-NEE and NNE direction in D _ 2 phase. All these indicate that the late Triassic Xuefeng Mountain area has been transformed from EW to Tethys tectonic domain to NE-NNE to Pacific tectonic domain. The tectonic transition time of Nanling region and the northern waters of the South China Sea is relatively late, which is early and Middle Jurassic. Based on the previous dating data, the three ore-bearing porphyry deposits of Dexing porphyry copper deposit were formed at about 172 Ma, formed in the active continental margin environment formed by the subduction of the paleo-Pacific plate, and the ore-forming materials originated from the partial melting of the subducted oceanic crust. Mixing with the mantle wedge is inferred to be closely related to a series of processes of plate subduction, plate tearing, delamination and subduction backward of the paleo-Pacific plate during this period. In the same period, there are three groups of faults in the southeast of South China: the NE-NNE trending NW and the near EW. Among them, the Cretaceous NE-NNE trending strike-slip faults are strongly active. The sequence from east to west is Binhai fault, Changle Nanao fault, Zheng he Tai Po, etc. Shaowu-Heyuan-Yangjiang fault, Wuchuan-Sihui fault and Hepu-north current fault, mainly manifested as dextral strike-slip, formed a series of pull-apart basins in the southeast coastal area, not typical "basin-ridge structure". According to the group velocity and S-wave velocity tomography, the thickness of the crust of South China block decreases gradually from west to east, and two crust-mantle interactions occur in the eastern part of South China block, corresponding to two lithospheric delamination. These two desinks are related to the subduction of the paleo-Pacific plate. The first was caused by the tearing of the plate during the subduction of the paleo-Pacific plate, and the second was caused by the subduction of the subduction plate and the high-angle subduction.
【作者单位】：海底科学与探测技术教育部重点实验室中国海洋大学海洋地球科学学院;青岛海洋科学与技术国家实验室海洋地质功能实验室;
【基金】：国家自然科学基金杰出青年基金项目(41325009) 山东省泰山学者特聘教授项目鳌山卓越科学家计划(2015ASTP-0S10) 国家海洋局重大专项(GASI-GEOGE-01)
【分类号】：P542

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