摘要
通过偏光显微镜、扫描电镜、阴极发光仪、茜素红-S和铁氰化钾混合溶液染色、X射线衍射等多种技术手段,对东海盆地丽水凹陷古新统明月峰组含片钠铝石砂岩的碎屑成分、自生矿物特征及其共生序列进行研究。结果表明含片钠铝石砂岩为长石岩屑砂岩及岩屑砂岩,以岩屑砂岩为主。粒度为细-中粒级,分选中等-较差。自生矿物主要为石英、菱铁矿、黄铁矿、片钠铝石、铁白云石、方解石及粘土矿物。其中,片钠铝石晶型为针柱状,集合体呈放射状、簇状充填孔隙,部分呈板条状不同程度地交代碎屑颗粒。自生矿物共生序列为粘土矿物包壳-菱铁矿-黄铁矿-高岭石-石英-铁白云石-片钠铝石-方解石。其中,晚于CO2气充注的碳酸盐矿物为片钠铝石和方解石。方解石的形成可能为碱性流体条件下,较低的CO2分压以及含钙长石和火山岩岩屑的溶蚀溶解共同作用的结果。
Dawsonite-bearing sandstones occurred in the Mingyuefeng Formation of Paleogene period have been found in the Lishui sag,Donghai basin.Multiple approaches such as polarizing microscope,scanning electron microscope,cathodoluminescence,alizarine red S and potassium ferricyanide composite stain as well as X-ray diffraction have been used to investigate the characteristics of clastic components,authigenic minerals and paragenetic sequence.It reveals that the dawsonite-bearing sandstones are fine to medium grained,poorly to moderately sorted feldspathic litharenite and litharenite,basically litharenite.Authigenic minerals are predominantly quartz,siderite,pyrite,dawsonite,ankerite,calcite and clay minerals,in which dawsonite occurs either as radiated clusters and bundles consisting of very fine dawsonite blades,or as lath-shaped grains replacing clastics in varying degrees.Paragenetic sequence of dawsonite-bearing sandstones is outlined as follows：authigenic clay coating siderite-pyrite-kaolinite-quartz-ankerite-dawsonite-clacite.Among them,dawsonite and calcite are considered as resulting from carbonates precipitation after CO2injection.The formation of calcite can be attributed to combined effects of the dissolution of anorthite and rock fragments together with the decrease of CO2partial pressure in alkaline fluid.
出处
《矿物岩石》
CAS
CSCD
北大核心
2013年第2期85-93,共9页
Mineralogy and Petrology
基金
中国地质调查局计划工作项目(1212011120048)
国家自然科学基金(41172091)
