奥连特盆地白垩系海绿石成因类型及沉积地质意义  

Genetic Type and Sedimentary Geological Significance of Cretaceous Glauconite in Oriente Basin,Ecuador

作　　者：阳孝法[1] 谢寅符[1] 张志伟[1] 马中振[1] 郭纯恩 周玉冰[1] 王丹丹[1] 刘亚明[1] 赵永斌[1] 

机构地区：[1]中国石油勘探开发研究院,北京100083 [2]中国石油拉美公司,加拉加斯999188

出　　处：《地球科学（中国地质大学学报）》2016年第10期1696-1708,共13页Earth Science-Journal of China University of Geosciences

基　　金：国家科技重大专项(No.2011ZX05028);国家青年科学基金项目(No.41202079);中国石油天然气股份有限公司重大科技项目(No.2013E-0501);中国石油天然气集团公司科学研究与技术开发项目(No.2014D-0906)

摘　　要：厄瓜多尔奥连特盆地白垩系Napo组UT段发育一套分布广泛的富含海绿石的硅质碎屑岩,针对海绿石的岩相、矿物学、地球化学及时空属性进行分析,可以揭示海绿石的组分、成熟度、形成及成因类型,结合地质约束有助于理解其形成的沉积地质意义.利用偏光显微镜、X射线衍射、电子探针及Qemscan对海绿石矿物的岩相、矿物组成和主量元素进行系统地分析.暗绿色、呈弯曲玫瑰花状的海绿石具有高的K2O含量（平均值为8%,质量百分比）,是形成于海相低沉积速率环境的高演化成熟型海绿石云母矿物或狭义范畴的海绿石.化学组分和时空属性揭示研究层段的海绿石经历了一定程度风暴流和/或潮汐流作用的搬运改造,属于层内准原地海绿石.UT段海绿石含量向上的增大趋势和成熟度的变化,以及横向上从盆地东部斜坡区埋深2~3km到西部盆缘露头区相距约120km的海绿石在形态和化学成分上具有相似性,指示其主要是层内准原地海绿石的特点.UT段垂向上海绿石含量增大的趋势同时反映外陆棚物源区原地海绿石向岸方向的短距离迁移,反映了相对海平面持续上升的海进过程;而且同时期海绿石平面上的广泛分布指示沉积时期的环境属于构造稳定的陆表海.Glauconitic sandstones in Napo UT Member of Cretaceous developed widely in the Oriente Basin, Ecuador. Petro- graphic, mineralogicah geochemical, and spatial and temporal investigations of glauconite can reveal its composition, maturity, formation and genetic types, which, together with geological constraints, can better the understanding of the significance of sedimentary geology. Using the microscopy, X-ray diffraction （XRD）, electron probe microanalyzer （EPMA） and Qemscan, petrography, mineral composition and major elements were analyzed systematically. Glaueonite in LIT Member shows dark green and curved rosette-like nanostructure and has high K20 content （8 wt%）, indicating it evolved to highly evolved and formed at low sedimentation rate in marine environment. Chemical composition and spatial and temporal attributes of glauconite reveal its characteristics of intrasequential （parautochthonous） glaucony, and indicate as well that it has undergone transport of storm surges and/or tidal currents processes. All evidences, including upward increasement of glauconite content, maturity variation, and similarity of morphology and chemical composition between samples from the outcrop and within the basin, indicate characteristics of parautochthonous glaucony. Upward inereasement of glauconite content also suggests that the parautochthonous glauconite formed in the outer shelf shifted landward, indicating the relative sea-level rise during the marine transgressive setting. Widespread distribution of contemporaneous/para-contemporaneous glauconites usually represents the epeiric sea environment with stable tectonic setting.

关 键 词：海绿石 矿物学 地球化学 沉积地质 奥连特盆地 

分 类 号：P571[天文地球—矿物学] P595[天文地球—地质学]