塔里木盆地玉北地区蓬莱坝组白云岩类型及成因
发布时间：2018-09-09 13:06
【摘要】：塔里木盆地玉北地区蓬莱坝组发育粉-细晶自形白云岩、中晶自形-半自形白云岩、粗晶自形-他形白云岩三种白云岩类型。粉-细晶白云岩具纹层状构造,稀土元素配分模式、总稀土含量与同期灰岩相似,氧同位素组成与同期海水成因的白云岩相近,表明白云岩化流体为同期海水,较高的盐度指数指示了相对浓缩的海水条件,较低的有序度值反应出快速的白云岩化过程,为准同生白云岩化的产物,白云石晶间均匀充填富Fe、富Si及高~(87)Sr/~(86)Sr比值的陆源物质,表明玉北地区在蓬莱坝组粉-细晶白云岩沉积期由于相对海平面较低从而受到陆源物质混入的影响。中晶白云岩和粗晶白云岩的稀土元素配分模式、总稀土含量、~(87)Sr/~(86)Sr比值等与同期海水特征相似,表明白云岩化流体为海水,可见残余颗粒结构,成岩温度较低,埋藏较浅,为埋藏的海水以及沿原始颗粒灰岩的粒间孔及可能存在的裂缝等通道向下运移的海水提供的Mg~(2+)导致的白云岩化,后期重结晶作用破坏了粗晶白云岩中的残余颗粒结构并导致其Fe、Mn含量及成岩温度、有序度值高于中晶白云岩,Sr含量及δ~(18)O值低于中晶白云岩。部分中-粗晶白云石边缘可见加大边,表明后期存在少量他源流体导致的次生加大作用。
[Abstract]:There are three types of dolomite in Penglai formation of Yubai formation in Tarim Basin: silt-fine-crystalline automorphic dolomite, mesomorphic and semi-automorphic dolomite, coarse allogeneic dolomite. The silt-fine-grained dolomite has a lamellar structure, a REE distribution model, a total rare earth content similar to that of the corresponding limestone, and an oxygen isotope composition similar to the dolomite formed in the same period, which indicates that the dolomitization fluid is the contemporaneous seawater. The higher salinity index indicates the relatively concentrated sea water condition, the lower order value reflects the rapid dolomization process and the product of quasi-syngenic dolomitization, and the dolomite intergranular is evenly filled with Fe, rich Si and high ~ (87) Sr/~ _ (86) Sr. The results show that the silt-fine dolomite of Penglai formation in Yubei area was influenced by the mixing of land-based materials due to the relatively low sea level during the sedimentary period of the silt-fine-grained dolomite. The REE distribution model of mesocrystalline dolomite and coarse dolomite and the ratio of total rare earth content of ~ (87) Sr/~ (86) Sr are similar to those of seawater in the same period, indicating that the dolomitization fluid is seawater with residual grain structure, low diagenetic temperature and shallow burial, and the distribution pattern of REE in mesocrystalline dolomite and coarse-grained dolomite is similar to that in seawater. The dolomization caused by Mg~ (2) for buried seawater and seawater that moves downward along channels such as intergranular pores and possible fractures of the original granular limestone, Later recrystallization destroyed the residual grain structure of coarse dolomite and resulted in its Fe,Mn content and diagenetic temperature. The order value was higher than that in mesocrystalline dolomite Sr content and 未 ~ (18) O value lower than that in mesocrystalline dolomite. The edge of some meso-coarse dolomite is enlarged, which indicates that there is secondary augmentation caused by a small amount of other fluids in the later stage.
【作者单位】： 北京大学地球与空间科学学院;北京大学石油与天然气研究中心;
【基金】：中国石油化工股份有限公司科技开发部项目(P14128、P16112) 中国地质调查局项目(DD20160175-1-1) 国家自然科学基金项目(41572117)联合资助
【分类号】：P618.13
[Abstract]:There are three types of dolomite in Penglai formation of Yubai formation in Tarim Basin: silt-fine-crystalline automorphic dolomite, mesomorphic and semi-automorphic dolomite, coarse allogeneic dolomite. The silt-fine-grained dolomite has a lamellar structure, a REE distribution model, a total rare earth content similar to that of the corresponding limestone, and an oxygen isotope composition similar to the dolomite formed in the same period, which indicates that the dolomitization fluid is the contemporaneous seawater. The higher salinity index indicates the relatively concentrated sea water condition, the lower order value reflects the rapid dolomization process and the product of quasi-syngenic dolomitization, and the dolomite intergranular is evenly filled with Fe, rich Si and high ~ (87) Sr/~ _ (86) Sr. The results show that the silt-fine dolomite of Penglai formation in Yubei area was influenced by the mixing of land-based materials due to the relatively low sea level during the sedimentary period of the silt-fine-grained dolomite. The REE distribution model of mesocrystalline dolomite and coarse dolomite and the ratio of total rare earth content of ~ (87) Sr/~ (86) Sr are similar to those of seawater in the same period, indicating that the dolomitization fluid is seawater with residual grain structure, low diagenetic temperature and shallow burial, and the distribution pattern of REE in mesocrystalline dolomite and coarse-grained dolomite is similar to that in seawater. The dolomization caused by Mg~ (2) for buried seawater and seawater that moves downward along channels such as intergranular pores and possible fractures of the original granular limestone, Later recrystallization destroyed the residual grain structure of coarse dolomite and resulted in its Fe,Mn content and diagenetic temperature. The order value was higher than that in mesocrystalline dolomite Sr content and 未 ~ (18) O value lower than that in mesocrystalline dolomite. The edge of some meso-coarse dolomite is enlarged, which indicates that there is secondary augmentation caused by a small amount of other fluids in the later stage.
【作者单位】： 北京大学地球与空间科学学院;北京大学石油与天然气研究中心;
【基金】：中国石油化工股份有限公司科技开发部项目(P14128、P16112) 中国地质调查局项目(DD20160175-1-1) 国家自然科学基金项目(41572117)联合资助
【分类号】：P618.13
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