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引用本文:王利杰,姚永坚,孙珍,李付成,杨楚鹏,徐子英. 南海东南部中生界识别及其构造属性[J]. 中国地质, 2020, 47(5): 1337-1354.
WANG Lijie,YAO Yongjian,SUN Zhen,LI Fucheng,YANG Chupeng,XU Ziying. The discrimination of Mesozoic sequence and its tectonic attribute in the southeastern South China Sea[J]. Geology in China, 2020, 47(5): 1337-1354(in Chinese with English abstract).
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南海东南部中生界识别及其构造属性
王利杰1,2, 姚永坚1,2, 孙珍2,3, 李付成2,3, 杨楚鹏1,2, 徐子英1,2
1.自然资源部海底矿产资源重点实验室, 中国地质调查局广州海洋地质调查局, 广东 广州 510760;2.南方海洋科学与工程广东省实验室 (广州), 广东 广州 511458;3.中国科学院南海海洋研究所边缘海与大洋地质重点实验室, 广东 广州 510301
摘要:
正确识别南海东南部中生界及其分布,对认识南海形成演化和油气资源潜力具有重要意义。受资料条件约束和地层系统划分差异的影响,南海东南部中生界分布和构造特征一直存在争议。本文在钻井、拖网约束下,通过井震对比、地震反射特征、层速度分析、岩浆岩体与地层接触关系和构造变形特征来综合识别中生界。结果表明,中生界呈平行、连续、低频的反射特征,层速度3400~4200 m/s,随着埋深或(和)变质程度增强,层速度增大(4500~5500 m/s),反射波组模糊,多数未见明显底界反射。研究区中生代地层发育局限,地震反射波组特征明显,但较难进行区域对比和解释。其中,西北、西南巴拉望盆地、礼乐滩和安渡北盆地中生界呈现低角度掀斜或近水平层状;礼乐滩西南部九章盆地中生界层速度3500~4500 m/s,高于上覆新生界,与钻井层速度吻合,地层呈高角度掀斜或挠曲变形,可能与岩浆活动侵位相关。结合中生代火山弧和识别的岩体分布,推测前者零散分布在弧前盆地靠火山弧一侧,构造活动相对弱,后者分布于岩浆活动强烈的弧间盆地。
关键词:  南海东南部|中生代火山弧|层速度|构造变形|弧间盆地|海洋地质调查工程
DOI:10.12029/gc20200504
分类号:P736.1;P714+.6
基金项目:中国地质调查局国家海洋专项项目(DD20160138,DD20201118)、南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0208)、广东省自然科学基金研究团队项目(2017A030312002)及国家自然科学基金项目(41606080)联合资助。
The discrimination of Mesozoic sequence and its tectonic attribute in the southeastern South China Sea
WANG Lijie1,2, YAO Yongjian1,2, SUN Zhen2,3, LI Fucheng2,3, YANG Chupeng1,2, XU Ziying1,2
1.MNR, Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Guangzhou 510760, Guangdong China;2.Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou), Guangzhou 511458, Guangdong, China;3.CAS, Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, Guangdong, China
Abstract:
Discriminating the distribution of the Mesozoic strata on the southeastern South China Sea (SCS) continental margin is of great importance for understanding the SCS evolution as well as the oil and gas potential. Due to limited data constraints and varied stratigraphic system divisions, the distribution and tectonic features of the Mesozoic sequences in the southeastern SCS have remained controversial. Assisted by drilling and dredging data, the authors comprehensively identified the Mesozoic sequence using a combination of well-seismic comparison, seismic reflection characteristics, internal velocity analysis, contact relationship between igneous edifices and strata, and structural deformation characteristics. The results show that the Mesozoic sequence is characterized by parallel, continuous, and low-frequency reflections, with internal velocity of 3400-4200 m/s. As the burial depth or/and the degree of metamorphism increases, the internal velocity increases to 4500-5500 m/s. The seismic reflections of the Mesozoic strata in the depth is fuzzy, and most of them have no obvious bottom reflection. Despite the fact that the characteristics of seismic reflection are clear in a specific area, it is still difficult to make a comparative study and conduct a whole region seismic explanation because the range of the Mesozoic strata is limited. Among them, the Mesozoic strata in the Northwest, Southwest Palawan basin, Liyue and Andubei basin show low-angle tilting or nearly horizontal characteristics. By contrast, the Mesozoic strata in the northern part of Jiuzhang basin located in the southwest of Liyue have a velocity of 3500-4500 m/s, which is higher than the overlying Cenozoic velocity and coincides with the result constrained by drilling layer. In addition, the Mesozoic strata tilt or deflect at a high angle, which may be related to the emplacement of magmatic activity. Compared with the distribution of Mesozoic volcanic arc and identified igneous bodies, the authors infer that the first style Mesozoic strata are scattered in the forearc basin near volcanic arc and thus show a relatively weak tectonic activity, whereas the second style strata are distributed in the inter-arc basin and have a strong magmatic activity.
Key words:  southeastern South China Sea|Mesozoic volcanic arc|internal velocity|tectonic deformation|inter-arc basin|marine geological survey engineering