海拉尔盆地贝尔凹陷含片钠铝石沉凝灰岩的成岩作用

以海拉尔盆地贝尔凹陷大磨拐河组-伊敏组的含片钠铝石火山碎屑岩为研究对象，采用偏光显微镜、扫描电镜及配套能谱、茜素红 S染色、阴极发光和X 射线衍射分析等技术手段，对研究样品的岩石类型、自生矿物种类及共生序列进行了详细研究。贝尔凹陷发育片钠铝石的宿主岩石类型为沉凝灰岩，自生矿物以发育片钠铝石、铁白云石和菱铁矿三种碳酸盐矿物为主，片钠铝石含量高达25%。成岩共生序列为菱铁矿Ⅰ→高岭石、石英次生加大→片钠铝石→微晶石英→方解石→铁白云石→菱铁矿Ⅱ→沥青。不同于国内外其它地区发现片钠铝石的主要产状为充填孔隙，本区内发育的片钠铝石以交代长石、石英、岩屑颗粒和高岭石基质为赋存特征，表明沉凝灰岩中的长石、岩屑、高岭石基质可以为其提供金属离子物质来源，并在CO2参与下，与成岩流体反应生成片钠铝石。大量碳酸盐矿物（15-44%）的发育证明了火山碎屑岩具有较高的CO2矿物捕获能力。

Diagenesis of Dawsonite bearing Tuffite in Beier Sag,Hailar Basin

The dawsonite bearing pyroclastic rock from Damoguaihe Yimin Formation in Beier Sag of Hailar Basin was taken as the research object. Polarization microscope, Scanning Electron Microscope, Energy Disperse Spectroscope, alizarin red S staining, Cathode Luminescence and X ray Diffractomer are used in this research to study its rock type, types of authigenic minerals and paragenetic sequences. It is ascertained that the host rock type of dawsonite is tuffite and carbonates are the main authigenic mineral such as dawsonite, ankerite and siderite. Content of dawsonite is up to 25%. The paragenetic sequence is shown as sideriteⅠ→ kaolinite, overgrowth quartz → dawsonite → microcrystalline quartz → calcite → ankerite → sidriteⅡ→ bitumen. Dawsonite is characterized by replacing feldspar, quartz, debris and kaolinite matrix, which is different from pore filling dawsonite found in other field, implicating that these mass in tuffite could provide origin of metal ions, and reacting with diagenetic fluid under the participation of CO2 which results in precipitation of dawsonite. Large amount of carbonates (15%~44%) developed proves that pyroclastic rock owns a relatively well capacity of CO2 fixation.