冀东昌黎地区碱性花岗岩年代学和地球化学特征及其地质意义  

Geochronologicalandgeochemicalcharacteristicsofthe Changli alkaline granitic intrusion and its geological implication in eastern Hebei province

作　　者：张永 辛后田 滕学建 王山亮[2] 

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]北京市地质研究所,北京100120

出　　处：《地质调查与研究》2017年第4期253-262,共10页Geological Survey and Research

基　　金：国家地质调查项目"阴山成矿带小狐狸山和雅布赖地区地质矿产调查(DD20160039)"

摘　　要：冀东昌黎地区碱性花岗岩体位于华北克拉通东部,本文对该岩体开展了地质、年代学、岩相学和全岩地球化学特征研究,据此初步探讨其成因。昌黎花岗岩以碱性长石(如钾长石)和石英为特征,含有霓辉石、角闪石等碱性暗色矿物,并且具有富硅(SiO_2>71 wt%)、富碱(Na_2O+K_2O=10.6%~11.0%)、富钠(Na_2O/K_2O>1),相对低铝(Al_2O_3=14.50%~14.96%)的碱性花岗岩特征。锆石LA-ICPMS U-Pb定年结果显示,昌黎碱性花岗岩形成于约2 500 Ma,为华北克拉通新太古代-古元古代大规模岩浆事件的产物。昌黎碱性花岗岩全岩地球化学特征显示其明显亏损重稀土元素,具有Eu正异常,相对高的Sr、Ba和Sr/Y比值以及低的Y和Yb含量,暗示昌黎碱性花岗岩来源于下地壳的部分熔融,熔融压力>15 kbar,源区残留矿物为石榴子石。综合分析显示,昌黎碱性花岗岩的形成可能与区域性伸展构造有关,为深部地幔物质底侵形成的新生地壳部分熔融的产物。The Changli alkaline granitic intrusion is located at the eastern Hebei province, North China Craton. This study focused on the geology, geochronology and geochemitry of it. The results show that the Changli granites comprise alkaline-feldspar and quartz, with subordinate amphibole and aegirine-augite. Changli granites are characterized as alkali granite with high SiO2 （〉71%）, Na2O＋K2O（10.6% - 11.0% ） and Na2O/K2O 〉 1, while low A1203 （14.5% - 14.96%）. The zircon LA-ICPMS U-Pb isotopic age dating shows that the Changli alkali granites were formed at about 2 500 Ma, indicating products of the extensive Neoarchean-Paleoproterozoic magmatism in North China Craton. The Changli alkali granites are depleted in HREE, with positive Eu anomalies, and have relatively high Sr, Ba and Sr/Y ratios, but low Y and Yb concentrations, suggesting that the melt originated from partial melting of lower crust at 15 kbar, with garnet in the residue minerals. Above all, the Changli alkali granite intrusion was considered to be formed by partial melting of juvenile crust derived from underplated mantle materials in an extensional setting.

关 键 词：河北昌黎 晚太古代 碱性花岗岩 锆石U—Pb年龄 华北克拉通东部 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]