摘要
对新疆柯坪地区中奥陶统灰岩和泥岩交互沉积地层中的结核状灰岩的沉积环境和形成机制进行了研究。根据野外观察并结合室内偏光显微镜下阴极发光和染色等方法分析其结构和构造特征,发现有团块状、网纹状、透镜状3种结核状灰岩。运用 X 光衍射仪和质谱仪等化学分析手段对其常量元素、微量元素、碳氧同位素、酸不溶物等进行了测定。综合分析矿物、岩石、生物和地球化学特征,认为它们形成于陆棚中水体较深的沉积环境,灰岩和泥岩交互韵律层是在表层洋流、大洋底流和物源供给的周期变化作用下形成的。结核状灰岩形成于沉积-成岩早期阶段,它们的形成机制分别是：团块状灰岩是在洋流活动后的平静期因水体中碳酸钙沿凝结核凝结、增大、胶结而形成；网纹状灰岩是在盐度不饱和的深海底流的周期作用下冲刷同生期沉积的碳酸盐灰泥而形成；透镜状灰岩是通过上覆水体与沉积物的差异压实作用而形成的。
The author have studied the sedimentary environment and formation mechanism of nodular limestones in the Middle Ordovician rhythms of Keping Area, Xinjiang. In these limestones, thin layers of limestone are interbedded with mudstones. According to detailed field work as well as cathode fluorescence and dyeing under microscope, these nodular stones can be classified into three types on the basis of their structures, namely, massive limestone, wavy limestone and lentoid limestone. Based on a synthetic analysis of elements with XRD, C and O isotopes with MS, and a study of mineralogy, petrology and paleontology, it is believed that they were formed in a sedimentary environment of shelf to deep basin. The carbonate-argillite rhythms were formed under the cyclic influence of surface currents, ocean bottom currents and source of sedimentary substance. Nodular limestones were formed in the early period of sedimentation - diagenesis and their formation mechanism is as follows： under the periodic influence of the surface currents and the deep currents, the massive limestone was formed around the nucleus through coagulation, multiplication and cementation during the quiet period. The wavy limestone resulted from periodic washing of the carbonate marl by the salt-nonsaturated deep water during the period of syngenesis. The lentoid limestone was formed by the differential pressures between the water body and the overlying sediments. Every kind of nodular limestones had its main influential factor.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2006年第2期137-147,共11页
Acta Petrologica et Mineralogica
基金
西北师范大学青年科技资金资助项目(NWNUQN200432)
关键词
中奥陶统
结核状灰岩
沉积环境
形成机制
柯坪
新疆
Middle Ordovician
nodular limestones
sedimentary environment
mechanism
Keping
Xinjiang
