塔里木盆地寒武系—下奥陶统白云岩成因及识别特征

对63口井岩心及薄片的观察以及大量阴极发光、碳氧同位素、包裹体及电子探针能谱的分析,认为塔里木盆地寒武系—下奥陶统白云岩主要有四种成因,分别对应有四种白云岩类型,即萨布哈白云岩、渗透回流白云岩、埋藏白云岩和热液白云岩。前两者受沉积相控制,后两者受成岩相控制。萨布哈白云岩发育于同生—准同生期蒸发成岩环境的潮间—潮上坪,渗透回流白云岩发育于同生—准同生期蒸发成岩环境的澙湖中,埋藏白云岩发育于埋藏期的深、浅埋藏环境,热液白云岩发育于埋藏期的深埋藏环境。总结了四种不同成因的白云岩的岩石特征及地球化学特征。认识到叠合盆地古老海相地层的白云石化机理复杂,白云岩类型多样,白云岩结构特征不但与沉积相密切相关,更受埋藏期白云石化作用的叠加改造。

Genesis and Feature Identification of Cambrian-Lower Ordovician Dolostone in Tarim Basin

According to the observation of cores and thin slices from 63 wells and the analysis of a great many data from cathode luminescence, carbon and oxygen isotope, inclusion enclave test and energy spectrum analysis, Cambrian-Lower Ordovician dolostones are characteristic of four genesis corresponding with four kinds of dolostone including sabakha dolostone, seepage refluxion dolostone, buried dolostone and hydrothermal dolostone. The former two are controlled by sedimentary facies,and the latter two are dominated by lithofacies. Sabkha dolostone devel-oped in intertidal -supratidal flats under synsedimentary -penesynsedimentary evaporate diagenetic environments while seepage refluxion dolostone formed in lagoon. Buried dolostone developed in deep or shallow burial environ-ments during burial stage while hydrothermal dolostone formed in deep burial environments.Petrologic and geochemical features of these four kinds of dolostone are generalized. It is cognized that the dolomization mechanism of ancient marine formations in the superimposed basin is complicated and dolostones are characterized by varied types. Texture of dolostones is not only closely related with sedimentary facies but also is reformatted by multiple dolomizations during buried stage.