| 胡振华.内蒙古贺斯格乌拉牧场白音高老组火山岩U-Pb年龄及地球化学特征[J].地质与勘探,2020,56(2):359-371 |
| 内蒙古贺斯格乌拉牧场白音高老组火山岩U-Pb年龄及地球化学特征 |
| U-Pb ages and geochemical characteristics of volcanic rocks in the Baiyingaolao Formation of Hesigewula Ranch, Dongwuqi, Inner Mongolia |
| 投稿时间：2019-03-30 修订日期：2019-10-08 |
| DOI：10.12134/j.dzykt.2020.02.011 |
| 中文关键词: 中生代火山岩 同位素年代学 地球化学 板内拉张 白音高老组 贺斯格乌拉牧场 内蒙古 |
| 英文关键词: Mesozoic volcanic rocks, isotopic geochronology, geochemistry, intraplate extension, Baiyingaolao Formation, Hesigewula Branch, Inner Mongolia |
| 基金项目:中国地质调查局项目（编号：12120113056100、DD20160048-10）资助 |
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| 中文摘要: |
| 白音高老组火山岩在大兴安岭地区广泛分布，本文对大兴安岭中南部贺斯格乌拉牧场白音高老组酸性火山岩进行了锆石U-Pb年代学、岩石地球化学和Sr-Nd同位素分析，探讨其岩石成因及构造背景。位于大兴安岭中南段东乌旗地区的白音高老组火山岩，主要岩性为流纹岩、流纹质凝灰岩等，LA-ICP-MS锆石U-Pb年龄分别为129.8±0.8Ma，128.2±2.8Ma，属早白垩世早期；从岩石地球化学特征上看，其主量元素SiO2含量68.76%~76.18%、Al2O3含量11.84-13.38%，属高钾钙碱性岩石；稀土总量较高，(La/Yb)N>6，(La/Sm)N>3，显示为轻稀土富集型，δEu显示负铕异常（0.4~0.6），微量元素以富集大离子亲石元素K、Rb、Ba，贫高场强元素Nb、P、Ti为特征；Sr-Nd同位素组成上具有低ISr、高εNd(t)和低tDM的特征(ISr=0.7039-0.7045,εNd(t)=2.65-4.39)。火山岩浆来源于下地壳基性物质的部分熔融，综合研究并结合前人资料认为，白音高老组流纹岩形成于滨太平洋板块俯冲后伸展及蒙古-鄂霍次克洋闭合后的综合效应下。 |
| 英文摘要: |
| The volcanic rocks of the Baiyingaolao Formation are widely distributed in the Da Hinggan region. This paper presents zircon U-Pb geochronology，rock geochemistry and Sr-Nd isotopic composition, and discusses the petrogenesis and tectonic background of the volcanic rocks in the Baiyingaolao Formation of the Hesigewula branch, Dongwuqi, Inner Mongolia.. These volcanic rocks are located in central-southern Da Hinggan Mountains, containing rhyolite and rhyotaxitic tuff, with zircon U-Pb ages 129.8 ±0.8Ma and 131 ±2.1Ma, respectively. They formed in Early Cretaceous. Their content of SiO2 is 68.76%~76.18%, and the content of Al2O3 is 11.84-13.38%, indicating high-k calc alkaline rock. The samples have high total REE content, LaN/YbN>6，(LaN/SmN>3, attributed to the enrichment type, with negative Eu anomalies(0.4~0.6);The trace elements are enriched in LILE(K, Rb, Th), while depleted in HFSE (Nb, P, Ti).They have less radiogenic Sr but more radiogenic Nd isotopic compositions (ISr=0.7039~0.7045, εNd(t)=2.65~4.39).The magma of the volcanic rocks originated from the partial anatexis of basic compositions in lower crust. Combined with the distinct geochemical features of the volcanic rocks and many previous studies in the study area, we suggest that the volcanic activity was a response to the extension caused by the subducion of the Pacific plate and compression background after the closure of the Mongolia-Okhotsk ocean |
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