文章摘要
保善斌,谈艳,李嘉泰,杨延乾,张得鑫,魏小林.藏北猫耳山地区早二叠世岛弧玄武岩地球化学特征及构造意义[J].矿产勘查,2019,(10):2467-2474
藏北猫耳山地区早二叠世岛弧玄武岩地球化学特征及构造意义
Geochemical characteristics and tectonic significance of early Permian island arc basalts in Maoershan area, northern Tibet
投稿时间:2018-11-13  
DOI:
中文关键词: 藏北  猫耳山地区  早二叠世  岛弧玄武岩
英文关键词: northern Tibet, Maoershan area, early Permian, island arc basalt
基金项目:中国地质调查局项目(编号:1212011121243)资助。
作者单位
保善斌 青海省地质调查局,西宁 810029 
谈艳 青海省地质调查局,西宁 810029 
李嘉泰 青海省地质调查局,西宁 810029 
杨延乾 青海省地质调查局,西宁 810029 
张得鑫 青海省地质调查局,西宁 810029 
魏小林 青海省地质调查局,西宁 810029 
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中文摘要:
      藏北羌塘西部猫耳山地区发现的岛弧玄武岩,其锆石阴极发光图像显示震荡环带发育,为岩浆成因。定年结果表明该岛弧玄武岩形成于(280.1±1.1)Ma,为早二叠世。岩石具有高铝、低TiO2和P2O5特征,稀土元素分布型式呈近平坦型并具弱的正Eu异常;微量元素富集大离子亲石元素Rb、U、K、Sr,亏损高场强元素Nb、Ta、Zr、Ti,且Nb/ La<0.5;在构造判别图上,样品落入岛弧—活动大陆边缘区域。以上特征表明,典型岛弧玄武岩源于俯冲流体交代的地幔楔的部分熔融,揭示出古特底洋在早二叠世进入了岛弧俯冲消减阶段。
英文摘要:
      Zircon cathodoluminescence images of island arc basalts found in Maoershan area, western Qiangtang, northern Tibet show that the oscillation zones are developed, indicating that they are magmatic origin. Dating results show that the island arc basalts were formed at (280.1±1.1) Ma and belong to Early Permian. The rocks are characterized by high aluminium, low TiO2 and P2O5, and the REE distribution pattern is nearly flat with weak positive Eu anomaly. The trace elements enrich large ion lithophile elements Rb, U, K, Sr, and deplete high field strength elements Nb, Ta, Zr and Ti, and Nb/La < 0.5. On the tectonic discriminant map, the samples fall into the island arc-active continental margin region. These characteristics indicate that the typical island arc basalts originated from partial melting of mantle wedges metasomatized by subduction fluids, revealing that the Paleo-Tethyan Ocean entered the stage of island arc subduction in Permian.
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