摘要
燕山期花岗质岩石广泛出露在冀北地区，从中可以识别出碱钙性、过铝质和碱质三个岩石系列。本文系统报道了它们的产状、岩类学、主要元素、痕量元素、稀土元素、年代学和ＩＳｒ资料；重点讨论了它们的地球化学特征和成因类型问题。碱钙性岩石系列主要由石英二长闪长岩元素、二长花岗岩元素、正长花岗岩构成；ＳｉＯ２含量变化范围是６２％～７５％；Ｋ２Ｏ＋Ｎａ２Ｏ在７．６３％～８．８８％之间；Ａ／ＣＮＫ＜１．０５，ＣＡ指数５５。过铝质系列由流纹斑岩为代表，具有高硅（ＳｉＯ２＞７３％）、富钾低钠（Ｋ２Ｏ／Ｎａ２Ｏ为１．４４～９．１３）、过铝质（Ａ／ＣＮＫ是１．１７～１．４３）的特点。碱性系列的岩石组合是碱长正长岩（碱长粗面岩）－碱性石英正长岩（碱流岩）－碱性花岗岩（碱性流纹质熔结凝灰岩）。它们的ＳｉＯ２含量变化于５７％～７７％之间，Ｋ２Ｏ＋Ｎａ２Ｏ、Ｋ２Ｏ、Ｎａ２Ｏ分别大于９％、４％、５％，ＮＫ／Ａ为０．９～１．１２。以过铝质、碱钙性和碱性为序，三个岩石系列的Ｎｂ、Ｔａ、Ｚｒ、Ｈｆ、ＲＥＥ含量依序增高，显示出明显的区别。上述特征表明，三个岩石系列的性质和特征明显不同，分别属于三种岩石成因类型。
Granitoid rocks of Yanshan period occur extensively in northern Hebei province. Three series, which are respectively alkali lime, peraluminous and alkali, can be distinguished among them. The data of occurrence,petrology,major trace rare earth elements, chronology and I Sr of the rocks are reported,and chemical characteristics and genetic implication are discussed in the paper. The granitoid rocks of alkali lime series are composed of quartz monzodiorite, monzogranite and syenogranite, with characteristics of SiO 2 (%) =62%～75%, K 2O+Na 2O=7 63%～8 88%, A/CNK <1 05,and CA=55 The peraluminous series of rock, respresented by rhyoporphyry, is high in SiO 2(>73%)and K 2O, but low in Na 2O(K 2O/Na 2O=1 44～9 13),and peraluminous(A/CNK=1 17～1 43).The alkali series of granite is formed by alkali feldspar syenite (trachyte), alkali quartz syenite (pantellerite), alkali granites (alkali ignimbrite), showing charecteristics of SiO 2=57%～77%, K 2O+Na 2O>9%, K 2O>4%, Na 2O>5%, and NK/A=0 9～1 12. Among these series, the obvious distinction of Nb, Ta, Zr, Hf, REE in content and Th/U, I Sr can be seen. The data show that the three series of granitoid rock are different in nature and characteristics, and can be considered as three types of petrogenesis.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
1999年第2期208-216,共9页
Acta Petrologica Sinica
基金
国家教育部博士点基金
关键词
花岗质岩石系列
地球化学
成因意义
花岗岩
Northern Hebei province,Granitoid series,Geochemistry,Genetic implication
