大港滩海区第三系湖相混积岩的成因与成岩作用特征

大港滩海第三系沙河街组一段下部分布的混积岩主要为陆源碎屑质-碳酸盐混积岩, 其次为碳酸盐质-陆源碎屑混积岩和含碳酸盐-陆源碎屑混积岩.其中白水头地区的混积岩发育于辫状河-扇三角洲前缘水下分流河道沉积体系之中,为相缘渐变混合沉积的产物;而马东-马东东地区的混积岩发育于重力流沉积体系之中,为浊流沉积的产物.本区混积岩主要经历了压实作用、胶结作用和溶蚀溶解作用.孔隙流体的化学性质经历了由碱性到酸性,最后又回到碱性的变化历程.其中海绿石、微晶方解石、部分石英溶蚀和连生方解石为碱性流体条件下的共生组合;次生加大石英、油气侵位、溶蚀溶解、高岭石为酸性条件下的共生组合;伊利石、绿泥石、钠长石化、孔隙充填方解石和白云石为碱性流体条件下的共生组合.

Sedimentary and Diagenetic Characteristics of Paleogene Lacustrine "Hunji" Rock in Beach District, Dagang

“Hunji” rocks of the lower part of number 1 of Shahejie Formation,Beach district,Dagang, are dominantly terrigenous clastithic-carbonate “Hunji” rock, subordinately carbonatic-terrigenous clastic “Hunji” rock and carbonate bearing-terrigenous clastic “Hunji” rock.“Hunji” rock of Baishuitou district lies in braided stream-fan delta front subfluvial branching river deposits,which mixed by gradual facies change.While Madong-Madong dong district is distributed in gravity flow deposit systems, mixed by turbidites.“Hunji” rocks of this area experienced compaction, cementation and dissolution /alteration process.Pore fluid experienced alkaline to acid and return to alkaline.The association of glauconite and micro-calcite cement, calcite precipi ation and a part of quartz dissolution is with alkaline pore fluid;The association of hydrocarbon emplacement, dissolution, quartz overgrowth and kaolinite precipitation is with acid pore fluid;And the association of illite, chlorite, albitization, pore-filling calcite and dolomite is with alkaline pore fluid.