CAJ | 학술논문

岩芯和露头剖面观察结果表明,鄂尔多斯盆地长7优质烃源层中广泛分布薄层和纹层状凝灰岩,薄层凝灰岩的SiO_2含量介于49.37%～72.45%之间,以中、酸性为主.岩石薄片的镜下观察结果表明,常见晶屑凝灰岩、玻屑凝灰岩和双屑凝灰岩,并可见到呈有序结构(成分和粒度)的凝灰岩纹层,同期喷发、大气降落沉积特征明显.根据其岩石类型、主元素和微量元素组成、锆石U-Pb年龄等的对比,以及凝灰岩的平面分布特征判断,盆地内长7优质烃源层中的凝灰岩可能主要来自秦岭地区的同期火山喷发活动.扬子与华北陆块碰撞、秦岭造山的区域构造活动的活跃是引起长7最大湖泛的主要动力因素,为优质烃源岩发育提供了基本的地质条件,同期频繁的火山喷发活动与湖底热液活动等共同促进了优质烃源岩的大规模发育.
암심화로두부면관찰결과표명,악이다사분지장7우질경원층중엄범분포박층화문층상응회암,박층응회암적SiO_2함량개우49.37%～72.45%지간,이중、산성위주.암석박편적경하관찰결과표명,상견정설응회암、파설응회암화쌍설응회암,병가견도정유서결구(성분화립도)적응회암문층,동기분발、대기강락침적특정명현.근거기암석류형、주원소화미량원소조성、고석U-Pb년령등적대비,이급응회암적평면분포특정판단,분지내장7우질경원층중적응회암가능주요래자진령지구적동기화산분발활동.양자여화북륙괴팽당、진령조산적구역구조활동적활약시인기장7최대호범적주요동력인소,위우질경원암발육제공료기본적지질조건,동기빈번적화산분발활동여호저열액활동등공동촉진료우질경원암적대규모발육.
Based on field observation of a great number of drill cores, outcrops and rock profiles, it was found that thin-layered and laminated tuff was extensively developed in the high grade hydrocarbon source rock of Chang 7 Member of Yanchang Formation in the Ordos Basin. The thin-layer tuff is mainly intermediate to acidic in composition, with SiO_2 contents varying between 49.37% and 72.45%. According to results of petrographic observation, the tuff can be divided into crystalline tuff, vitric tuff and crystalline-vitric tuff. Also, laminated tuff sometimes shows ordered structure in terms of both composition and grain size, which is characteristic ofsimultaneous volcanic eruption, atmospheric precipitation and subsequent sedimentation. Based on rock types,composition of both major and trace elements, zircon U-Pb dating results as well as features of spatial distribution of the tuff, it can be inferred that the tuff occurring in Chang 7 high grade hydrocarbon source rock in the basin may be resulted from the simultaneous volcanic eruption in the Qinling orogen. Collision between the Yangtze and North China blocks and consequent regional structural movements in the Qinling orogen were the major dynamic elementsleading to the maximum lake flooding event at the Chang 7 period, which provides the basic geological conditions for the development of the high grade hydrocarbon source rock. Meanwhile, the frequent volcanic eruptions andhydrothermal activities that occurred simultaneously at the lake bottom would together facilitate large scale development of the source rock.