文章摘要
马延景,李成福,谢晓岚,马文,李戬.青海扎日加地区马尔争组基性火山岩地球化学特征、锆石U-Pb年龄及构造环境分析[J].矿产勘查,2018,9(10):1841-1851
青海扎日加地区马尔争组基性火山岩地球化学特征、锆石U-Pb年龄及构造环境分析
Geochemical Characteristics,Zircon U-Pb Age and Tectionic Signficance of Maerzheng Formation Basic Volcanic Rocks in Zharijia Area,Qinghai
投稿时间:2018-05-16  
DOI:
中文关键词: 马尔争组  基性火山岩  锆石U-Pb  地球化学  扎日加地区
英文关键词: Maerzheng formation,basic volcanic rock,zircon U-Pb age,geochemistry,Zharijia
基金项目:青海省地质勘查基金项目(编号:青国土资矿[2010]96-NO.4)资助。
作者单位
马延景 青海省地质调查局,西宁 810001 
李成福 青海省地质调查局,西宁 810001 
谢晓岚 青海省有色地质矿产勘查院测试中心,西宁 810007 
马文 青海省地质调查局,西宁 810001 
李戬 青海省第五地质矿产勘查院,西宁 810001 
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中文摘要:
      青海扎日加地区集中分布一套基性火山岩,赋存于早-中二叠统马尔争组地层中。通过对该套基性火山岩岩石组合、地球化学及锆石U-Pb测年研究,表明该套火山岩主要由玄武岩组成,具有低硅、铝、钠、钾、贫铁,高钛、镁,富钙的特点。岩石SiO2平均含量47.75%,K2O含量为0.44%~4.06%,岩石属低钾系列,里特曼指数σ在0.13~3.15,碱度率为1.04~1.66,属铝过饱和低钾拉斑玄武岩系列。稀土元素∑REE含量为43.81×10-6~134.61×10-6,总量偏低,LREE/HREE=1.13~8.31,(La/Yb)n=0.44~13.16,轻重稀土分馏不明显,部分样品轻稀土亏损。微量元素大离子亲石元素Sr、K、Rb较亏损,Ba、Th较富集,可能代表了快速扩张的洋脊及洋岛富集的环境。在马尔争组灰绿色玄武岩中获得LA-ICP-MS锆石U-Pb年龄为(278.0±1.9)Ma,形成时代为早二叠世晚期-中二叠世早期。综合分析认为,马尔争组火山岩形成构造环境主要为大洋中脊环境区,兼有富集洋岛型的特征。
英文摘要:
      A set of basic volcanic rocks is found in Zharijia area of Qinghai province, existing in Maerzheng formation of early-middle Permian.The study on the rock assemblage, geochemical characteristics and zircon U-Pb dating of the basic volcanic rocks shows that the volcanic rocks are mainly composed of basalts with characteristics of low silicon, aluminum, sodium, potassium, iron and rich titanium, magnesium and calcium. With the average content of SiO2( 47.75%) and K2O (0.44%-4.06%), it can be concluded that the rocks belong to low potassium series.The reitman index ( 0.13-3.15) and the Alkalinity rate(1.04-1.66) show that they are a series of tholeiite with supersaturated aluminum and low potassium. Further study found out that the content of ∑REE is as low as 43.81×10-6-134.61×10-6,the LREE/HREE is 1.13-8.31 and the(La/Yb)N equals to 0.44-13.16. In addition, the HREE fractional distillation of the rocks is not obvious and there is a deficit of LREE in partial samples. The deficit of Sr, K and Rb as microelement large ionic lithophile elements and richness of Ba andTh may represent the rapid expansion of the ridge and the environment of the oceanic island. The U-Pb age of the LA-ICP-MS zircon in the gray- green basalt of Maerzheng formation was 278.0±1.9Ma and its forming era may be in the duration of early Permian and middle Permian. Therefore, it is concluded that the tectonic environment in which the volcanic rock formed in Maerzheng formation is mainly the mid-ocean ridge environment, which has the characteristics of ocean island enrichment.
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