摘要
甘肃北山造山带红石山地区的海西-印支期花岗岩类岩石属于钙碱性岩浆系列，具有岛弧花岗岩的特点，但岩石化学、地球化学和同位素组成等的研究表明，它们具有埃达克岩的特征。这些岩石SiO2含量均大于56％，Al2O3含量多≥15％，富Na，MgO含量〈3％，Mg^#为30．71～59．13，Sr含量高，Sr／Y在19．71～72．86之间，8个样品中有6个比值大于40；Y〈18×10^-6（6．0×10^-6～14．7×10^-6）；Eu异常不明显或具弱的Eu负异常，稀土元素分异强烈，属强烈的轻稀土元素富集型；Nb负异常十分明显，Sr也具有较明显的正异常，其εNd（t）为正值[εNd（t）=4．09～5．67]，（La／Yb）。N-YbN和Sr／Y—Y图解上样品主要落入埃达克质岩区域。这些埃达克质岩石的发现，对于研究北山造山带晚古生代的构造演化、地球动力学特征及找矿具有十分重要的意义。
The Hercynian-Indosinian granitoids in Hongshishan area of the Beishan orogenic belt belong to the calc-alkaline series and have characteristics of island-arc granitoids. A study of their petrochemical, geochemical and Nd-isotopic characteristics shows that they have the characteristics of ＂adakite＂. These rocks have the following characteristics： SiO2〉56%,Al2O3≥15%, Na2O and Sr are high, MgO〈3%, Mg^# =30.71-59.13, Sr/Y= 19.71-72.86, Y〈 18 × 10^-6（6.0 × 10^-6- 14.7 × 10^-6）; no Eu anomaly or only weak negative Eu anomaly can be observed; REE distribution patterns show strong REE segregation and belong to the type of enriched LREE; and there exist very prominent negative Nb anomaly and obvious positive Sr anomaly in the trace element spidergram, εNd（t ） values are positive [εNd（ t ）= 4.09- 5.67], major samples fall into the area of adakite on （La/Yb）N - YbN and Sr/Y- Y diagrams. Therefore, the discovery of the adakitic rock has great significance in the study of Late Paleozoic tectonic evolution and geodynamics and the search for ore deposits in the Beishan orogenic belt of Gansu Province.
出处
《岩石矿物学杂志》
CAS
CSCD
北大核心
2007年第3期232-238,共7页
Acta Petrologica et Mineralogica
基金
中国地质调查局区调项目(200113000057)
