大别山超高压变质带燕山期花岗岩地球化学特征及成因探讨  

Geochemical characteristics and genesis of Yanshanian granite in the Dabie ultrahigh-pressure (UHP) metamorphic belt

作　　者：钱存超[1] 路玉林[2] 刘丽利[2] 

机构地区：[1]西北大学地质学系,陕西西安710069 [2]安徽省地质调查院,安徽合肥230001

出　　处：《中国地质》2004年第2期147-154,共8页Geology in China

基　　金：中国地质调查局国土资源地质大调查项目(20001300002041)资助。

摘　　要：依据花岗岩类的岩性组合、产出状况、结构、侵位机制和地球化学特征等,将大别山超高压变质带中燕山期花岗岩大致可以划分为两大类一类为高钾钙碱性系列,以大同岩体和司空山早、主期岩体为代表,岩性为花岗闪长岩—二长花岗岩,表现为SiO2>56%,Al2O3一般≥14%,MgO<3%,富集LREE,低HREE和Y、Yb(如Y<18×10-6,Yb<1.9×10-6),高Sr、Ba,高La/Yb>39和Sr/Y≥30,Sr、Eu异常不明显,与Adakite岩相似;另一类属正常钙碱性系列,以英山尖岩体为代表,岩性以二长花岗岩为主,具有高硅、低铝的特点,一般SiO2>70%,Al2O3<14%,LREE略显亏损,HREE略显富集和高Y、Yb(如Y>18×10-6,Yb>1.9×10-6),低Sr和La/Yb<10、Sr/Y<10,Sr、Eu负异常明显。高钾钙碱性花岗岩可能为增厚的下地壳部分熔融的产物,正常钙碱性花岗岩可能为正常的地壳重熔形成。According to the rock composition, occurrence, textures, emplacement mechanism and geochemical characteristics, the Yanshanian granitoids in the Dabie UHP metamorphic belt may be classified into two major types: the high-K calc-alkaline series and the normal calc-alkaline series. The high-K calc-alkaline series is represented by the Datong rock body and the early-stage and main-stage Sikongshan rock bodies and composed lithologically of granodiorite-monzogranite. The chemical composition is characterized by SiO2 >56%, Al2O3≥14%, MgO <3%, high Sr and Ba contents, enrichment in LREE, strong depletion in HREE, high Sr/Y and La/Yb ratios (≥30 and ≥39, respectively), low Y(<18×10-6) and Yb (<1.9×10-6) contents, and indistinct Eu and Sr negative anomalies. These characteristics are similar to those of adakite. The normal calc-alkaline series is represented by the Yingshanjian rock body, consisting dominantly of monzogranite. It is characterized by high SiO2 (>70%), low Al2O3 (<14%), low Sr and Ba contents, low Sr/Y (<10) and La/Yb (<10) ratios, high Y (>18×10-6) and Yb (>1.9×10-6) contents, depletion in LREE, enrichment in HREE, and pronounced negative Sr and Eu anomalies. The high-K calc-alkaline granites might be derived by partial melting of the thickened lower crust, while the normal calc-alkalis granites probably originated by anatexis of the normal crust.

关 键 词：花岗岩 高钾钙碱性系列 燕山期:超高压变质带 大别山 地球化学特征 侵位机制 结构 岩性组合 

分 类 号：P595[天文地球—地球化学]