文章摘要
王艳慧.青海卡巴纽尔多地区中-晚三叠世火山岩地球化学特征及构造环境[J].地质与勘探,2019,55(4):975-985
青海卡巴纽尔多地区中-晚三叠世火山岩地球化学特征及构造环境
Geochemical characteristics and tectonic setting of Mid-late Triassic volcanic rocks in the Kabaniuerdo area, Qinghai Province
投稿时间:2018-04-28  修订日期:2018-12-25
DOI:10.12134/j.dzykt.2019.04.008
中文关键词: 地球化学特征 构造环境 甘德组 清水河组 卡巴纽尔多地区 青海省
英文关键词: geochemical characteristics, tectonic setting, Gande formation, Qingshuihe formation, Kabanuerdo area, island arc
基金项目:中国地质调查局地质调查项目(编号:12120113033018)资助。
作者单位E-mail
王艳慧 河南省地质调查院河南郑州 河南省地质科学研究所河南郑州河南省金属矿产成矿地质过程与资源利用重点实验室河南郑州 wangyanhui7@163.com 
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中文摘要:
      青海卡巴纽尔多地区位于华南板块可可西里-松潘甘孜残留洋。该区发育有中-晚三叠世火山岩,呈夹层状产于中三叠统甘德组及上三叠统清水河组。甘德组火山岩为晶屑凝灰岩,其SiO2=46.78%~47.05%,总碱含量ALK为2.38%~2.94%,铝饱和指数A/NK为2.81,山德指数A/CNK=0.66~0.79,里特曼指数σ=1.4~2.3,为亚碱性岩石,属拉斑玄武系列;稀土总量REE在102.84×10-6~179.06×10-6,LREE/HREE比值为4.44~7.07,δEu=0.65~1.01,稀土配分曲线呈向右陡倾型。清水河组火山岩为流纹岩,SiO2含量为74.04%,总碱含量Alk为7.43%,A/NK为1.47,A/CNK=1.31,σ=1.78,为亚碱性岩石,属钙碱性系列;稀土总量REE为26.18×10-6,LREE/HREE比值为5.4,δEu=0.28,具明显铕负异常,稀土配分曲线呈海鸥型。区内火山岩均富集大离子亲石元素,亏损高场强元素,为典型的岛弧火山岩特征。利用里特曼-戈蒂里图解、Ti-Zr图解等判别图解,并结合甘德组与清水河组均为巴颜喀拉边缘前陆盆地的沉积背景,认为该区中-晚三叠世火山岩形成于岛弧环境。
英文摘要:
      In tectonics, the Kabaniuerdo area of Qinghai Province is located in the remnant Kekexili-Songpan Ganz ocean, South China plate. It hosts middle-late Triassic volcanic rocks intercalated in Middle Triassic Gande Formation and Upper Triassic Qingshuihe Formation. Volcanic rocks in Gande Formation are composed of crystal tuff, with SiO2 between 46.78%~47.05%, alkaline contents of 2.38%~2.94%, A/NK of 2.81, A/CNK of 0.66~0.79, and Rittmann Index (σ) of 1.4 to 2.3, belonging to the tholeiite series of subalkaline rocks. REEs of Gande volcanic rocks range from 102.84×10-6 to 179.06×10-6 , and show LREE enrichment, with LREE/HREE of 4.44~7.07, and δEu=0.65~0.72, and the REE patterns are steeply right dipping curves. Volcanic rocks in Qingshuihe Formation are composed of rhyolite with SiO2 of 74.04%, ALK of 7.43%, A/NK of 1.47, A/CNK of 1.31, and σof 1.78, belonging to calc-alkaline suite of subalkaline rocks. The total of REE is 26.18×10-6 with LREE/HREE ratio of 5.4. The δEu value is 0.28, with obvious negative Eu anomalies, and shows seagull-type REE pattern. These volcanics are characterized by LILE enrichmentsand HFSE depletion, typical of arc volcanic signatures. Based on Rittman-Gotieri and Ti-Zr diagrams, considering that Gande and Qingshuihe formations are all at the margin of Bayan Kara foreland basin, the middl-late Triassic volcanic rocks of this area were thought to be formed in an island arc environment.
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