Cathodoluminescence in Post-Miocene Carbonates
Cathodoluminescence in Post-Miocene Carbonates
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后中新世碳酸盐中的阴极发光
DOI：
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发表时间：
1991
期刊：
影响因子：
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通讯作者：
R. Major
中科院分区：
文献类型：
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作者：
R. Major
阴极发光现象普遍存在于古碳酸盐岩中，但地质上年轻的阴极发光碳酸盐岩的报道相对较少。通过对年轻阴极发光碳酸盐岩的综述，对埋藏前阴极发光的形成提供了制约，并有助于解释古碳酸盐岩。现代的骨骼颗粒很少是阴极射线发光的。在古骨骼颗粒中观察到的阴极发光，虽然不一定表明成岩蚀变，但肯定应该鼓励岩石学家考虑置换或重结晶的可能性。现代的无机海洋沉淀物一般也不是射线发光的，尽管在深水和浅水海洋环境中都有阴极发光的镁方解石胶结物的报道。在这些例子中，阴极射线发光显然是在低Eh孔隙水中形成的结果，其中二价锰是可用的。然而，这些条件并不一定反映在微量阳离子和稳定碳同位素组成的水泥。更新世阴极发光碳酸盐已被报道，从银行边缘设置，这些沉积物经历了陆上暴露在冰川海平面低水位。然而，在陆上暴露期间的陨石成岩作用并不总是导致阴极发光产物。例如，Ene wetak环礁的后中新世珊瑚帽缺乏阴极射线发光，尽管有充足的结构和地球化学证据表明其暴露于大气降水中并在大气降水中重结晶。
: Cathodoluminescence is commonly observed in ancient carbonate rocks, yet relatively few examples of geologically young cathodoluminescent carbonates have been reported. Review of young cathodoluminescent carbonates provides constraints on formation of Cathodoluminescence by pre- burial processes and aids in interpreting ancient carbonates. Modern skeletal grains are rarely cathodoluminescent. Cathodoluminescence observed in ancient skeletal grains, although not necessarily indicative of diagenetic alteration, certainly should encourage the petrographer to consider the possibility of replacement or recrystallization. Modem inorganic marine precipitates are generally not calhodoluminescent either, although cathodoluminescent magnesian calcite cements have been reported from both deep-water and shallow-water marine environments. Cathodoluminescence in these examples is apparently the result of formation in low-Eh porewaters in which divalent manganese is available. However, these conditions are not necessarily reflected in the trace cation and stable carbon isotope composition of the cements. Pleistocene cathodoluminescent carbonates have been reported from bank-margin settings where these sediments underwent subaerial exposure during glacio-eustatic sea-level lowstands. Meteoric diagenesis during subaerial exposure does not always result in a cathodoluminescent product, however. For example, the post-Miocene coral cap of Ene wetak Atoll lacks Cathodoluminescence despite ample textural and geochemical evidence of subaerial exposure and recrystallization in meteoric water.