黑龙江北部新生地区早白垩世龙江组火山岩年代学、地球化学特征及其地质意义  

Chronological and geochemical characteristics of volcanic rocks from Early Cretaceous Longjiang Formation in Xinsheng area,northern Heilongjiang

作　　者：李云峰[1] 赵玥 孙春林[1] 李华民[3] 陈跃军[1] 

机构地区：[1]吉林大学古生物学与地层学研究中心,长春130026 [2]内蒙古自治区地质勘查基金管理中心,呼和浩特010020 [3]新疆维吾尔自治区地质矿产勘探开发局第一地质大队,新疆昌吉831100

出　　处：《世界地质》2015年第1期12-24,共13页World Geology

基　　金：黑龙江省国土资源厅项目(HLJKD2007-07)

摘　　要：对黑龙江北部新生地区早白垩世龙江组火山岩进行年代学和地球化学研究,结果表明:龙江组底部的流纹岩年龄为120±1.3 Ma;上部的安山岩年龄为110.7±1.2 Ma。即:龙江组是由两期火山事件所构成,事件间隔约10 Ma,这两期火山事件与东北地区相关早白垩世火山事件完全可以对比。龙江组火山岩岩石组合为流纹岩-安山岩,属于钙碱性-高钾钙碱性系列。稀土元素特征显示轻稀土元素富集,重稀土元素亏损,呈负铕异常。微量元素特征显示相对富集大离子亲石元素(LILE)K、Rb、U、Th,亏损Nb、Ta、Ti等高场强元素(HFSE)。结合地球化学特征和前人研究资料,笔者认为,黑龙江北部新生地区早白垩世火山岩来源于下地壳的部分熔融,与古太平洋板块向欧亚板块之下俯冲导致加厚岩石圈拆沉后的伸展作用有关。Chronological and geochemical data on the Mesozoic Longjiang stage volcanic rocks indicate that the rhyolite from the lower part of the Longjiang Formation formed in 120 ± 1. 3 Ma and andesite from the upper part of the Longjiang Formation formed in 110. 7 ± 1. 2 Ma. It implies that the Longjiang Formation formed from two volcanic events during an interval of about 10 Ma,and these two volcanic events could be compared with other related Early Cretaceous volcanic events of Northeast China. The rock assemblages of Longjiang Formation are composed mainly of rhyolites and andesites,belonging to chemically calc-alkaline to high-K calc-alkaline series. The REE patterns demonstrated LREE enrichment and HREE depletion,with weak negative Eu anomalies. The volcanic rocks of Longjiang Formation were strongly enriched in large ion lithophile elements（ LILE） such as K,Rb,Uand Th,with depletion in high field strength elements（ HFSE） such as Nb,Ta and Ti. Combined with geochemical characteristics and previous researches,the authors propose that the Early Cretaceous volcanic rocks in Xinsheng area,northern Heilongjiang were derived from partial melting of lower crust and were related to a post-orogenic extensional environment induced by the subduction of paleo-Pacific Plate to Eurasian Plate.

关 键 词：锆石U-PB年龄 火山事件 早白垩世龙江组 新生地区 黑龙江北部 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]