摘要
青岛八仙墩剖面出露了一套海相陆源碎屑沉积层序。这套碎屑岩受崂山花岗岩侵入已经发生变质,岩性以硬砂岩为主,夹有页岩、含锰细砂岩、长石砂岩,富含白云质。这套地层保留了各种原生的沉积构造,发育有浊积岩的底模构造,同沉积变形,水平层理、微粒序层理。岩石地球化学分析结果表明:碎屑岩的SiO_2含量在59.6%～71.6%之间,含量的多少与岩性无相关性;而黑色页岩的Al_2O_3含量变化于12.31%～16.39%之间,多在15%以上,高于灰白色砂岩的含量(普遍小于14.5%)。镜下特征和Al203含量都表明砂岩的成熟度低。除一个样品外,碎屑岩的∑REE含量高,在146.75×10^(-6)～245.78×10^(-6)之间,La在30.35×10^(-6)～61.39×10^(-6)之间,对球粒陨石标准化的(La/Yb)_N在8.68×10^(-6)～21.89×10^(-6)之间。对PASS标准化碎屑岩的(La/Ce)_N值为1.07～1.18,显示了陆源碎屑物质的主要贡献。该地层弱的Ce/Ce*负异常和富含白云质岩层指示了海相沉积环境。主量元素判别图解和微量元素判别图解表明这套碎屑岩具有活动大陆边缘背景和大陆岛弧的共同特征,但高的∑REE含量、La和Ce丰度支持了活动大陆边缘的沉积环境,但有待于采用更准确的重矿物分析来确定其物源区的大地构造性质。这套碎屑岩的出露指示了南黄海盆地深部应有奥陶统盆地相浊积沉积体系的存在,可能具有良好的浊积砂岩油气储层。
A set of marine sedimentary sequences of terrigenous siliciclastic are developed in Baxiandun, Qingdao. These metamorphosed clastic rocks intruded by Laoshan granite are dominated by greywacke with shale,manganiferous fine-grained sandstone,arkose and dolomite layers. This formation preserves various native sedimentary structures, such as sole markings of turbidite,syndepositional deformation,horizontal bedding and micro graded bedding. The result of a petrogeochemical study of this formation shows that the content of SiO2 of clastic rocks, ranging from 59.6% to 71.6% ,is not influenced by lithology,white the content of Al2O3 of black shale ranging from 12.31% to 16. 39% ,mostly more than 15% ,is higher than that of hoar sandstone（commonly lower than 14.5% ）. Microscopic features and the content of Al2O3 of clastic rocks indicate the low compositional maturity of sandstone. The content of EREE of clastic rocks is up to 146.75×10^-6～245.78×10^-6,La to 30.35×10～～61.39×10^-6 , and （La/Yb） N（chondrite） to 8. 86 -- 21. 89. The（La/Ce） N of PASS-normalized clastic rocks is 1.07 - 1.18, indicating the major contribution of terrigenous siliciclastic material. Weak negative Ce/Ce anomaly as well as abounding dolomite layers reveal that this clastic formation is the marine origin. The description of major elements and trace elements shows a combined nature of active continental margin and island arc in tectonic setting of this clastic formation, and more closely to an active continental margin indicated by higher EREE,La and Ce abundance,but it needs more precise analysis of heavy minerals to define the tectonic setting of provenance. The clastic rocks imply the possible existence of Ordovician turbidite depositional systems of basin facies with potential turbidite sandstone oil-gas reservoir deep in the South Yellow Sea Basin.
出处
《地质科学》
CAS
CSCD
北大核心
2010年第4期1156-1169,共14页
Chinese Journal of Geology(Scientia Geologica Sinica)
基金
中国科学院知识创新重要方向项目(编号:KZCX2-YW-229)资助
关键词
扬子板块
南黄海盆地
上奥陶统浊积岩
海相硅质碎屑岩地层
Yangtze plate,South Yellow Sea Basin,Upper Ordovician turbidites,Marinesiliciclastic sequence
