大兴安岭北部新林石英二长岩-花岗岩的地球化学特征及其成因  

Geochemical characteristics and petrogenesis of adamellite-granite in Xinlin Town,northern Da Hinggan Mountains

作　　者：孙如江[1] 孙德有[1] 苟军[1] 王广婷[1] 杨东光[1] 李旭[1] 

机构地区：[1]吉林大学地球科学学院,长春130061

出　　处：《世界地质》2016年第2期309-323,共15页World Geology

基　　金：中国地质调查局项目(121201112108)资助

摘　　要：对额尔古纳地块东南部新林镇附近的侵入岩进行了锆石U-Pb年龄测定、Lu-Hf同位素和岩石地球化学研究。结果表明,岩体形成于141.1~123.8 Ma,是早白垩世岩浆活动的产物。新林石英二长岩-花岗岩高硅较富铝贫镁,属于准铝质、高钾钙碱性系列;具有中等-弱负Eu异常（δEu=0.53~0.72）,轻重稀土分异比较明显[（La/Yb）_N=12.42~25.38];相对富集大离子亲石元素Rb、Th、U和LREE,高场强元素Ti、Nb、Ta、P和HREE表现出亏损。新林石英二长岩-花岗岩具有高Sr、低Yb及低Y的特征,且相对富K,属于C型埃达克岩,形成于加厚下地壳的部分熔融。Lu-Hf同位素研究显示其ε_（Hf）（t）为2.1~6.2,二阶段模式年龄（T_（DM2））为1025~786 Ma,认为其岩浆源区为新元古代增生的地壳物质。The authors studied the zircon U-Pb dating and geochemical characteristics of Lu-Hf isotope,major,trace and REE elements of intrusive adamellite-granite near Xinlin Town,southeastern Erguna terrane block.The results show the adamellite-granite were formed in Early Cretaceous,ranged from 141. 1 Ma to 123. 8 Ma in age. The study suggests that adamellite-granite is rich in silicon,alkalis,poor in magnesium,which all belong to quasi-aluminous and high-kalium calc-alkaline series,and display moderate-weak negative europium anomalies（ δEu = 0. 53 ~ 0. 72）,showing significant fractionation of HREE and LREE [（ La /Yb）_N= 12. 42 ~ 25. 38]; The adamellite-granite is also characterized by enrichment in Rb,Th,U and LREE and depletion in Ti,Nb,Ta,P and HREE. The adamellite-granite in Xinlin is characterized by enrichment in Sr and K,depletion in Yb and Y,belonging to C-type adakite,origrinated from partial melting of thicken lower crusts. The research on Lu-Hf isotope shows ε_（Hf）（ t） ranging from 2. 1 to 6. 2,T_（DM2） ranging from 1 025 Ma to 786 Ma,which is considered the adamellitegranite magma origrinated from juvenile crusts during the Neoproterozoic.

关 键 词：新林 埃达克 锆石年龄 地球化学 岩石成因 大兴安岭北部 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]