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| 青海鄂拉山地区陆相火山岩地球化学特征及构造环境 | |
| 引用本文： | 李永祥,李善平,王树林,王磊,商健,张志青,赵海霞.青海鄂拉山地区陆相火山岩地球化学特征及构造环境[J].西北地质,2011,44(4):23-32. |
| 作者姓名： | 李永祥 李善平 王树林 王磊 商健 张志青 赵海霞 |
| 作者单位： | 1. 青海省第八矿产勘查院,青海西宁,810001 2. 青海省地质调查院,青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 3. 青海省第五矿产勘查院,青海西宁,810001 |
| 基金项目： | 青海省科技计划项目(2009-G-119) |
| 摘 要： | 鄂拉山岩浆岩带晚三叠世火山岩为中-中酸性火山岩组合,由玄武安山岩、安山岩、英安岩、流纹岩及少量火山碎屑岩等组成,岩石蚀变强烈,成层性差,柱状节理发育,具典型的陆相喷发特点.火山岩属铝饱和类型,里特曼指数(δ)及岩石学等显示具钙碱性特征, (FeO/MgO)、K2 O/Na2O显示可能具有陆缘岛弧环境的特性；轻稀土元素分馏程度高且富集,δEu小于1,为弱负异常,稀土元素配分模式曲线与岛弧型稀土元素配分模式图相似；微量元素Rb、Ba、Th等元素明显富集,而Ti、Y、Yb、Sc、Cr等元素较亏损.Nb/Zr、La/Nb、Th/Ta、Th×Ta/Hf2等特征反映鄂拉山组火山岩产于陆缘火山弧环境.结合区域地质背景、岩石地球化学及构造环境等特征,认为鄂拉山地区晚三叠世火山岩产于大陆碰撞与陆缘弧并存的环境. |
| 关 键 词： | 鄂拉山岩浆岩带 陆相火山岩 陆陆碰撞 陆缘弧 |
Geochemical Characteristics and Tectonic Environment of the Continental Facies Volcanic Rocks in Elashan Area,Qinghai Province |
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| LI Yong-xiang , LI Shan-ping , WANG Shu-lin , WANG Lei , SHANG Jian , ZHANG Zhi-qing , ZHAO Hai-xia.Geochemical Characteristics and Tectonic Environment of the Continental Facies Volcanic Rocks in Elashan Area,Qinghai Province[J].Northwestern Geology,2011,44(4):23-32. | |
| Authors: | LI Yong-xiang LI Shan-ping WANG Shu-lin WANG Lei SHANG Jian ZHANG Zhi-qing ZHAO Hai-xia |
| Institution: | LI Yong-xiang1,LI Shan-ping2,WANG Shu-lin2,WANG Lei3,SHANG Jian3,ZHANG Zhi-qing2,ZHAO Hai-xia2,(1.The Eighth Institute of Mineral Exploration in Qinghai,Xining 810001,China,2.Qinghai Institute of Geological Survey,Laboratory with Geological Processes and Mineral of Northern Qinghai-Tibetan Plateau in Qinghai Province,Xining 810012,3.The fifth Institute of Mineral Exploration in Qinghai,China) |
| Abstract: | Late Triassic volcanic rocks with the combination of neutral-acidic volcanic rock of magmatic belt in Elashan area,composed of the basaltic andesite,andesite,dacite,rhyolite and a little of pyroclastic rock etc.The volcanic rock altered strongly,layered poorly,columnar joints developed,which showed the typical characteristics of terrestrial eruptions.Volcanic rocks are Al saturation type,and Rittmann index(δ) and petrologic features display a calc-alkaline,(FeO/MgO) and K2O/Na2O show that the volcanic rock may have the characteristics of continental margin island arc environment.It has high degree of LREE fractionation and enrichment,δEu is less than 1,with a weak negative anomalies.It has similar curves of REE distribution patterns and island-arc curve REE patterns.The trace elements such as Rb,Ba,Th and other elements significantly enriched while Ti,Y,Yb,Sc,Cr and other elements are poor.The characteristics of Nb/Zr,La/Nb,Th/Ta,Th×Ta/Hf2 and other elements reflected that the volcanic rock in Elashan Formation was formed in the environment of continental margin volcanic arc.According to these characteristics of the regional geological setting and geochemical,structural environment of the volcanic rock,we have summarized this conclusion that late Triassic volcanic rocks in Elashan area were produced in the environment of the coexistence of East Kunlun block and West Qinling block mutually collision with continental margin arc environment. |
| Keywords: | magmatic belt in Elashan area continental volcanic rocks blocks collision continental margin arc |
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