西沙群岛白云岩-铁白云岩岩相学特征  

PETROGRAPHIC CHARACTERISTICS OF DOLOMITE AND FERROAN DOLOMITE IN XISHA ISLANDS

作　　者：季兆鹏 闫琢玉 许红[2,4,5] 陶萌 纳琴 JI Zhaopeng;YAN Zhuoyu;XU Hong;TAO Meng;NA Qin(College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao 266590,China;Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266071,China;CNOOC EnerTech-Drilling&Production Co.,Zhanjiang 524057,China;Key Laborat-ory of Marine Sedimentology and Environmental Geology,First Institute of Oceanography,Ministry of Natural Resources,Qingdao 266061,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266071,China;School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China)

机构地区：[1]山东科技大学地球科学与工程学院,青岛266590 [2]中国地质调查局青岛海洋地质研究所,青岛266071 [3]中海油能源发展股份有限公司工程技术分公司,湛江524057 [4]海洋沉积与环境地质国家海洋局重点实验室,国家海洋局第一海洋研究所,青岛266061 [5]青岛海洋科学与技术海洋国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266071 [6]中国石油大学(华东)地球科学与技术学院,青岛266580

出　　处：《海洋地质前沿》2021年第6期64-70,共7页Marine Geology Frontiers

基　　金：国家自然科学基金(41872114);国家科技基础资源调查专项课题(2017FY201407)。

摘　　要：西沙群岛永兴岛西永2井和石岛西科1井均发现铁白云岩。主要通过X光粉晶衍射、偏光显微镜和扫描电镜技术完成测试,分析白云岩-铁白云岩分布及岩相学特征。X光粉晶衍射测试结果及综合分析表明,西科1井发育11层铁白云岩,西永2井发育8层铁白云岩。通过偏光显微镜鉴定,发现西永2井中新世白云岩主要为生物碎屑白云岩,白云石晶体呈粉晶-细晶结构;某些层段含较高铁白云石,呈微晶-粉晶状。通过薄片观察分析发现,西科1井发育大量物碎屑白云岩,多细晶-粉晶结构,自形-半自形为主,部分样品可见黑色铁质氧化物或者胶结物。扫描电镜观察发现2个井多数白云石为典型菱形多面体结构,白云化程度高。Ferroan dolomite is found in well Xiyong 2 of Yongxing Island and well Xike 1 of Shidao Island in Xisha Islands. Through three methods including X-ray powder diffraction quantification, polarized light microscopy and scanning electron microscopy, distribution and petrographic characteristics of ferroan dolomite in the aboved two wells were discussed. The X-ray powder crystal diffraction analysis and comprehensive study show that eleven layers of ferroan dolomites are developed in the well Xike 1 of Shidao Island, and eight layers ferroan dolomites in the well Xiyong 2 of Yongxing Island. It was found by polarized light microscopy that the Miocene dolomite in the well Xiyong 2 of Yongxing Island is dominated by bioclastic dolomite, and the dolomite crystals are powder-fine grained;the content of ferroan dolomites is higher in some layers, and the crystal is mainly microcrystal-powder crystal dolomite. Through observing and analyzing the casting thin slices, it is found that a large amount of clastic dolomite is developed in well of Xike 1 and the crystals are mostly fine-grain crystal structure, self-formed to semi-self-shaped, and some samples are black ankerite oxide or cement. Under the scanning electron microscopy, samples from well Xike 1 in Shidao Island and well Xiyong 2 in Yongxing Island show that the dolomite crystals present rhombohedral polyhedral structures, with a high degree of dolomification.

关 键 词：石岛 永兴岛 白云岩 铁白云岩 岩相学 

分 类 号：P744.4[天文地球—海洋科学] P588.24