孙吴—嘉荫盆地早白垩世火山岩地球化学特征及其构造环境意义  

Geochemical characteristics and tectonic setting significance of Early Cretaceous volcanic rocks in Sunwu—Jiayin Basin

作　　者：李敏[1] 冯坚[1] 肖明尧[2] 刘富营[3] 

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国冶金地质总局中南局,武汉430081 [3]河南省地质矿产勘查开发局区域地质调查队,郑州450001

出　　处：《世界地质》2012年第2期255-261,共7页World Geology

基　　金：中国地质调查局项目(1212010561504)和(1212011085484)联合资助

摘　　要：孙吴—嘉荫盆地早白垩世发育一套中酸性火山岩建造,主要为安山岩、流纹岩、英安岩,同时含有少量玄武安山岩,基本属于钙碱性系列。对样品的地球化学特征分析表明,K2O(1.3%～5.27%)含量较高,全碱K2O+Na2O(43.45%～9.97%)含量中等,TiO2(0.26%～1.3%)含量较低,稀土元素总量∑REE(81.68×10-6～172.89×10-6)含量中等。球粒陨石标准化的REE配分曲线表现为轻稀土(LREE)相对于重稀土(HREE)富集,其中(La/Yb)N变化范围为5.37～11.73,轻重稀土分馏明显,全部样品的Eu和大部分样品的Ce表现为弱的负异常。大离子亲石元素(LILE)Rb、Ba、K富集,Pb强烈富集,高场强元素(HFSE)Nb、Ti、Ta亏损。火山岩样品构造环境判别图解表明,孙吴—嘉荫盆地早白垩世火山岩具有活动大陆边缘特征。板块俯冲作用形成的弧后伸展环境是火山岩的形成背景。Sunwu-Jiayin Basin developed a intermediate-acidic volcanic formation in Early Cretaceous. The volcanic rocks include andesites, rhyolite and dacite with a few basaltic andesites, belonging to calc-alkalic series. The geochemical analyses on the volcanic rock samples revealed the K2O （1.3%-5.27% ） relatively high, K2O ＋Na2O （43.45% -9. 97% ） moderate, TiO2 （0. 26% - 1.3% ） relatively low, and earth element （81.68 × 10^-6 - 172. 89 × 10^-6 ） medium rare in contents. Chondrite normalized REE pattern showed that LREE were enrichment compared with HREE, and （La/Yb）N ranged from 5.37 to 11.73, with weak Eu and Ce anomalies. These samples were enriched in LILE （Rb, Ba, K） and Pb, but relatively depleted in HFSE （Nb, Ti, Ta）. According to tectonic environment discrimenation diagrams, Sunwu-Jiayin Basin was active in continental margin characteristics in Early Cretaceous, and back-are extensional environment formed by plate subduction was the formation background of volcanic rocks.

关 键 词：孙吴—嘉荫盆地 下白垩统 火山岩 地球化学 构造环境 

分 类 号：P534.53[天文地球—古生物学与地层学] P595[天文地球—地质学]