摘要
在济阳坳陷3000m以下的古近系中,可见含纹层状方解石脉的黑色页岩,往往与钙质纹层页岩、油页岩、钙质页岩相伴生或薄互层出现。镜下研究表明,这些纹层状方解石脉干净、明亮,晶粒垂直纹层生长,具有明显的近距离经溶解再重结晶的特征,而且与有机质的含量密切相关,页岩中并无石膏的发育和残留。在岩石地球化学上,较相邻的其他页岩,Mg/Ca、Mn/Ca值明显降低,而Sr/Ca值则明显升高,同时碳酸盐的δ18O明显降低,δ13C小幅上升或波动。这些证据表明黑色页岩中的纹层状方解石脉是钙质纹层页岩或富碳酸盐油页岩在晚成岩期随有机质的热演化经溶解和再沉淀作用的产物,并随孔隙水的排出伴有碳酸盐的流失。
Paleogene black shale with lamellar calcite veins in the Jiyang Depression develop below the depth of 3000 m. The shale with lamellar calcite veins usually co-exists with calcite laminar shale, oil shale and calcite shale. Observation under the microscope shows that the lamellar calcite veins are clean, bright and vertical crystals between laminae, and have obvious character of near-range dissolution and recrystallization. The development of lamellar calcite veins is related to organic matter. There is no gypsum in the shale. Compared with other shales, the black shale with lamellar calcite veins has lower Mg/Ca and Mn/Ca ratios, and higher Sr/Ca ratio with obviously lower 3180 and indistinctive rise or fluctuation of 313C of carbonate. These evidence shows that the lamellar calcite veins in the black shale are the product of the dissolution and recrystallization of calcite laminar shale and oil shale enriched in calcite in the thermal development of organic matter during late diagenesis. In the meantime, carbonate reduces with the outflow of pore water.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2005年第6期834-838,共5页
Acta Geologica Sinica
基金
国家"十五"科技攻关项目(编号2001BA605A09)资助成果。
