海南三亚地区全新世海滩岩地球化学特征及沉积古地理环境意义  

Geochemical characteristics of Holocene beach rocks in Sanya area of Hainan Province and sedimentary paleographic environment implication

作　　者：林义华 吕昭英[1,2] 魏昌欣 吴迪[1,2] 梁定勇 黄武轩[1,2] LIN Yihua;LYU Zhaoying;WEI Changxin;WU Di;LIANG Dingyong;HUANG Wuxuan(Hainan Key Laboratory of Marine Geological Resources and Environment,Haikou 570206,Hainan,China;Hainan Geological Survey,Haikou 570206,Hainan,China;Comprehensive Institute of Geological Investigation of Hainan Province,Haikou 570206,Hainan,China)

机构地区：[1]海南省海洋地质资源与环境重点实验室,海南海口570206 [2]海南省地质调查院,海南海口570206 [3]海南省地质综合勘察院,海南海口570206

出　　处：《矿产与地质》2023年第1期86-94,共9页Mineral Resources and Geology

基　　金：2019年海南省自然科学基金层次人才项目(2019RC346、2019RC348);中国地质调查局基础地质调查项目(12120114072001)共同资助

摘　　要：通过野外调查、薄片分析、扫描电子显微镜、X射线衍射技术、^(14)C年龄测试、微区微量元素分析等,对海南岛南部海岸线上分布的三亚地区海滩岩的表面性质和胶结物特征进行了分析,探讨了海滩岩形成机制及形成的沉积古环境。三亚地区海滩岩由与现在海岸线平行的向海倾斜的低角度岩层构成,岩性为以浅褐色—灰黄色钙质胶结的含砾粗中粒长石(石英)砂岩和以灰黄色钙质胶结的含生物屑砂质砾岩为主,其胶结物主要是钙质,主要由亚稳态碳酸盐相、高镁方解石以及文石组成,从扫描电镜和薄片来看,主要形态是针状、泥晶,是典型的海相潜水沉淀。海滩岩中贝壳AMS ^(14)C年龄结果为(4570±30)a BP,表明海滩岩形成于全新世中期。胶结物的稀土元素总量较低,总体表现呈微弱的左倾轻稀土亏损型曲线,轻、重稀土分异不强,具有弱的Eu正异常,轻微的Ce负异常及弱的La正异常,Sr/Ba、Th/U、V/Cr、V/(V+Ni)及Sr/Cu比值特征指示了海滩岩形成于海洋环境和干旱气候条件。Through field investigation,rockslice analysis,scanning electron microscopy,X-ray diffraction,^(14)C dating age,micro-area trace element analysis,etc.,the study has analyzed the surface properties and cement characteristics of beach rocks in Sanya area on the southern coastline of Hainan Island,and the formation mechanism and sedimentary paleographic environment of beach rocks is also discussed.The beach rocks in Sanya area are composed of low angle rock layers inclining to the sea parallel to the current coastline.The lithology is mainly light brown-grayish yellow calcareous cemented-gravelly coarse medium grained feldspar(quartz)sandstone and grayish-yellow calcareous cemented bioclastic sandy conglomerate,the cement is mainly calcareous,mainly composed of metastable carbonate facies,high magnesium calcite and aragonite.From the scanning electron microscope and rock slice analysis,the main forms are needle,magnesia calcium stone and mud crystal,which are typical marine phreatic sediments.The MAS ^(14)C dating age of the shell in the beach rocks is(4570±30)a BP,on the middle Holocene.The REE total content of the cement is relatively lower,indicating a weak left inclining pattern of LREE loss curve.The differentiation of LREE and HREE is not strong,with the weak Eu positive anomaly,slight Ce negative anomaly and weak La positive anomaly.The parameter characteristics of Sr/Ba,Th/U,V/Cr,V/(V+Ni)and Sr/Cu ratio suggests that the beach rocks are formed under the arid climate condition and in the marine environment.

关 键 词：海滩岩 地球化学特征 沉积古地理环境 海南岛南部 全新世 

分 类 号：P58[天文地球—岩石学]