碳酸盐岩中方解石胶结物的阴极发光环带与微量元素构成的关系——以塔河油田奥陶系碳酸盐岩为例

对塔河油田奥陶系碳酸盐岩中方解石胶结物的阴极发光性和微量元素构成研究发现,一些与大气水成岩环境有关的方解石胶结物显示出亮、暗相间阴极发光环带,微量元素含量与阴极发光环带之间具有良好的对应关系,亮带具有较高的Mn、Fe含量,暗带则具有较高的Sr、Na含量,显示方解石胶结过程中大气水作用强度的变化。这些碳酸盐矿物的阴极发光环带受元素构成变化控制,并反映成岩流体中元素含量的变化和/或结晶速率的变化,这在一定程度上与大气水环境相对开放的成岩条件有关。相对晚期的环带发光较亮,并具有较高的Mn和较低的Sr、Na含量,显示与加里东—海西期构造运动有关的古岩溶过程中大气水作用逐渐加强的总体成岩趋势。

Cathodoluminescence Zonal Texture of Calcite Cement in Carbonate Rock and Its Relationship with Trace Element Composition: A Case of Ordovician Carbonate Rock of Tahe Oilfield, Tarim Basin

The study of Ordovician carbonate rock from Tahe Oil Field indicates that some of calcite cements related with meteoric diagenetic environment show bright-and-weak luminescence zones and the concentration of Sr,Na, Mn and Fe elements has a good corresponding relationship with luminescence zones. That is, bright luminescence zone has high concentration of Mn and Fe and low concentration of Sr and Na while weak luminescence zone has high concentration of Sr and Na and low concentration of Mn and Fe, which implies the effect of meteoric fresh water to calcite cementation. The luminescence zones are controlled by different element textures and they reveal the change of element concentration within diagenetic fluid and the crystallization rate of calcite. It is suggested that this instance is related, in some extent, with the open fluid condition in meteoric diagenetic environment. In general, the late-stage zones of calcite cement show relative bright luminescence with relative high concentration of Mn and relative low concentration of Sr and Na, which reveals the increasing meteoric diagenesis during palaeokarst process related with Caledonian-Hercynian tectonic movement.