【摘要】 <正> 作为复杂的外动力作用的综合产物,一般而言,沉积物的组分之间并不存在化学上的平衡关系,因而也就不能用化学计算的方法来推断沉积物或沉积岩的成因.然而,碳盐酸沉积的情况则有所不同.尽管自然界的大多数碳酸盐沉积也是异地成因的,其原生组分之间一般也不存在化学上的因果关系.但是,一旦碳酸盐沉积形成之后,它们在成岩阶段发生的化学变化却是有规律的,与环境因素有着密切的联系.许多学者对碳酸盐沉积Ca/Mg比的分析已经证明,研究碳酸盐沉积主要化学组分的地球化学特征是有环境意义的(Chilingar,G.V.1953,1967).我国西沙群岛是当代世界上重要的碳酸盐沉积区之一.该区沉积作用的主要特点是,以钙质生物的成礁作用和成岛作用为主的复杂动力-化学-生态系统,形成了多种成因不同、岩石学特征也各异的碳酸盐沉积物.研究这些沉积物的鉴别标志,对古相岩的相分析无疑是有意义的.然而,要解决这个问题并不是轻而易举的.对许多问题的认识上的分歧说明,即使就现化沉积而言,同样也存在相分析问题.古代沉积的复杂性当然就更可想而知了.更多还原

【Abstract】 56 samples were analysed for determination of CaO, MgO, SrO content of the young carbonate sediments on the Xisha Archepelago.On the Archepelago, the main area of modern reef sedimentation in China, the content of CaO, MgO, SrO of the sediments only depends on the authigenetic and diagenetic process.Data indicate that the different genetic types of carbonate sediments show regular pattern of CaO, MgO, SrO conent distribution such as: the eolian biocalcarenite is characterized by high MgO and medium SrO, the terrigenetic beach rock by high MgO and Low SrO, the skeletal calcirudite by medium SrO, the paleosol by medium MgO and SrO, the skeletal beachrock by low MgO and high SrO, calcrete and rhizoliths by low MgO and low SrO.CaO, MgO, SrO content, particularly their mole content is a significant indicator of epidiagenetic history, for instance, high MgO mole content may indicate a evaporitic epidiagenesis and low MgO and low SrO mole content may be related to leaching process of fresh water during the epidiagenetic stage.更多还原