海南岛北部晚新生代沉积物Sr-Nd同位素组成及其物源示踪  

Sr-Nd isotopic composition and provenance tracing of Late Cenozoic sediments in the northern Hainan Island

作　　者：张磊 麦发海[4] 王超群 贾丽云[1,2,3] 张耀玲[1,2,3] 孙东霞 胡道功[1,2,3] ZHANG Lei;MAI Fahai;WANG Chaoqun;JIA Liyun;ZHANG Yaoling;SUN Dongxia;HU Daogong(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Active Tectonics and Geological Safety,Ministry of Natural Resources,Beijing 100081,China;Research Center of Neotectonism and Crustal Stability,China Geological Survey,Beijing 100081,China;Hainan Geological Survey and Design Institute,Haikou 570206,Hainan,China)

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]自然资源部活动构造与地质安全重点实验室,北京100081 [3]中国地质调查局新构造与地壳稳定性研究中心,北京100081 [4]海南省地质综合勘察院,海南海口570206

出　　处：《地质通报》2022年第11期1996-2006,共11页Geological Bulletin of China

基　　金：国家自然科学基金项目《淮北平原更新世沉积物中记录的黄河入淮事件研究》(批准号:41807421);中国地质调查局项目《海南岛及近海活动断裂与地壳稳定性调查评价》(编号:DD20190306);《地表过程与系统演变地质调查》(编号:DD20221644);中国地质科学院地质力学研究所中央财政科研项目结余经费新开项目(编号:所科研62)。

摘　　要：海南岛北部(琼北)巨厚的晚新生代沉积物记录了海南岛晚新生代气候与环境演化信息。但关于该沉积物Sr-Nd同位素方法的物源示踪研究还比较缺乏。以琼北钻遇基岩的钻孔(ZK1-5)为研究对象,以Sr-Nd同位素组成为示踪手段,开展了其物源示踪研究。结果表明:海南岛北部于晚新生代中新世—更新世经历了从滨浅海相沉积—海陆交互相沉积—陆相沉积—火山喷发环境的转变,中新世海相沉积Sr同位素比值(平均值0.727002)整体高于上新世海陆过渡相和更新世陆相沉积的Sr同位素比值(平均值0.714917),表明海相沉积比海陆过渡相和陆相沉积风化程度更高。海相、海陆过渡相及陆相沉积的Nd同位素组成没有发生明显变化,较一致,表明海陆环境变迁并没有引起该地区物源发生重大变化。而琼北晚新生代沉积物εNd(0)值分布范围(-14.0~-5.1)与岛内花岗质岩石的εNd(0)值分布范围(-14.1~-5.2)基本一致,与岛内变质岩(1.2~8.5)和玄武岩类岩石(1.9~7.8)的εNd(0)值差别较大,表明其源岩主要来自海南岛花岗质岩石,变质岩和玄武岩贡献较小,这可能与岛内花岗质岩石分布范围广有关。对琼北地区晚新生代沉积物Sr-Nd同位素组成特征的认识,有助于深入理解晚新生代海南岛风化过程及环境变化,并对南海物源及古海陆环境重建具有重要意义。The thick Late Cenozoic deposits of northern Hainan Island(Qiongbei)provide a record of paleoclimatic and paleoenvironmental changes in Hainan Island.However,there is a lack of source tracing studies on Sr-Nd isotopic methods in this sediment.In this paper,we carried provenance tracing using a borehole(ZK1-5)drilling encounter with bedrock in northern Hainan Island by Sr-Nd isotopic method.The results show that the Late Cenozoic of northern Hainan Island underwent a transition from coastal shallow marine sedimentation-marine and continental alternative deposition-terrestrial sedimentation-volcanic eruption environment from the Miocene to the Pleistocene,and that the Sr isotopic ratio of the Miocene marine sediment(mean:0.727002)is overall higher than that of the Pliocene marine and terrestrial transition and Pleistocene terrestrial deposits(mean:0.714917),suggesting that marine deposits were more weathered than the marine and terrestrial transitional phases.The Nd isotopic compositions of the marine,marine-terrestrial transitional and terrestrial deposits do not change significantly and are relatively consistent,suggesting that provenance did not change obviously caused by environmental changes from marine to terrestrial in the area.The distribution ofεNd(0)values in the Late Cenozoic sediments of Qiongbei(-14.0~-5.1)is generally consistent with the distribution ofεNd(0)values in the granitic rocks of Hainan Island(-14.1~-5.2),and differs considerably from theεNd(0)values in the metamorphic rocks(1.2~8.5)and basaltic rocks(1.9~7.8)of Hainan Island,indicating that the source rocks are mainly from the local granitic rocks in Hainan Island,and the contribution of metamorphic rocks and basalt is small.This is probably related to the wide distribution of granitic rocks in the island.The understanding of the Sr-Nd isotopic characteristics of the Late Cenozoic sediments in the northern Hainan Island can help to deeply understand the weathering process and environmental changes on Hainan Island during the Late Cenozoi

关 键 词：海南岛 晚新生代 SR-ND同位素 物源 沉积环境 地球化学 南海北部 地质调查工程 

分 类 号：P534.6[天文地球—古生物学与地层学] P597[天文地球—地质学]