关于岩石微量元素构造环境判别图解使用的有关问题

HOW TO USE THE TRACE ELEMENT DIAGRAMS TO DISCRIMINATE TECTONIC SETTINGS

针对目前应用愈来愈广泛的不同岩石,特别是岩浆岩的微量元素构造环境判别图解使用过程中存在的问题,从这些判别图解建立的原理,介绍了微量元素构造环境判别图解的使用原则。强调指出所采集的样品必须新鲜(无蚀变或极弱蚀变)、非堆晶的岩石;选择的判别图解必须与判别的岩石类型相一致,即对花岗岩类要用花岗岩的判别图解,不能用玄武岩的判别图解;对特殊类型岩石要选择专门用于该类型岩石的判别图解,如碱性花岗岩,钾质火成岩;要应用多种图解综合判断;不能用单个样品,而应作多个样品分析;要注意所选择判别图解的特别说明等。此外,一些构造环境判别图解还能给出岩石的成岩过程和源区。

There are several misunderstanding or incorrect uses of the trace element diagrams for discriminating the tectonic settings of different rocks. According to the constructive principles of these diagrams, the following aspects must be thought carefully： the rock types to be studied must be the same or nearly the same as those that can be discriminated by the diagram ; To avoid mixed or incorrect signals that could be produced, two or more such diagrams shall have to be jointly used ; For special rock types, such as A-type granites or potassic igneous rocks, special discriminative diagrams have to be determined and selected respectively ; The samples to be studied can not be altered; In general, the diagrams must be used carefully with Archean samples; The petrotectonic assemblage or an expert system are recommended to be used together with the discrimination diagrams. In addition, the discrimination diagrams may tell us more about petrogenetic processes and sources besides tectonic settings.