【摘要】 为了揭示黄骅坳陷歧口凹陷古近系沙河街组白云岩的成因,对64件白云岩样品的岩石学特征、阴极发光程度、碳氧同位素组成和主量元素含量进行分析。岩石学的研究表明,该区白云岩岩石类型为泥晶白云岩、微晶白云岩、藻纹层白云岩和亮晶生物碎屑白云岩。地球化学分析显示,自沙三段至沙一段沉积时期,湖泊的古盐度经历了高-低-高的过程,古气温逐渐降低。泥晶白云岩的铁、锰含量和埋藏温度在4类白云岩中最高,盐度值最低,主要为埋藏成因,形成于还原性较强的低盐度环境中。微晶白云岩的铁、锰含量和埋藏温度相对较低,盐度值相对较高,形成于氧化性较强的近地表高盐度环境中,为渗透回流成因,部分样品受生物发酵作用的影响具有极高的δ13C。藻纹层白云岩的铁、锰含量和埋藏温度相对较高,盐度值在4类白云岩中最高,形成于浅埋藏环境中,成岩环境受海水的影响表现出高盐度特征。亮晶生物碎屑白云岩的铁、锰含量和埋藏温度在4类白云岩中最低,盐度值相对较低,形成于氧化性较强的低盐度浅埋藏环境中,同时受到大气水渗流的影响。更多还原

【Abstract】 In order to determine the genesis of doloston from the Paleogene Shahejie Formation in the Qikou sag,Huanghua depression,the petrological characteristics,cathodoluminescence characteristics,carbon-oxygen isotopes and major elements of 64 doloston samples were analysed. The petrological study shows that the main lithologies of study area include dolomicrite,crystallitic dolostone,laminar algal dolostone and crystalline bioclastic dolostone. Through the geochemistry experiments of doloston samples,it found that the salinity of Qikou sag have experienced the process of high-low-high during Es3 to Es1,and with a decreasing temperature. The dolomicrite shows the highest Fe-Mn contents and buried temperature,and lowest Z value,indicating a low-salinity deep burial dolomitization. Both Fe-Mn contents and buried temperature of crystallitic dolostones are low and Z values are high,which is related to a near-surface seepage reflux dolomitization with high salinity. Partial samples have extremely high δ13 C due to the effect of biological fermentation. Laminar algal dolostones have high Fe-Mn contents and buried temperature,and highest Z values,suggesting a shallow burial diagenetic condition controlled by high salinity seawater. Bioclastic dolostone shows the lowest Fe-Mn contents and buried temperature,and low Z values,which is related to the low-salinity shallow burial dolomitization and is influenced by the atmospheric water seepage.更多还原