| 山西新生代汉诺坝玄武岩成因探讨 |
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| 作者姓名： | 张玉生 |
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| 作者单位： | 山西省地质调查院,太原 030001 |
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| 基金项目： | 中国地质科学院地质研究所“山西区域地质调查片区总结与服务产品开发(编号: 121201102000150012-05)”项目资助 |
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| 摘 要： | 根据区域地质调查资料,对山西新生代汉诺坝玄武岩的4个火山洼地、7条剖面进行研究。各个火山旋回底部先出现拉斑玄武岩,向上变为碱性玄武岩,岩石均富集大离子亲石元素和轻稀土元素。由东向西,火山喷发时间由早到晚,岩浆活动由弱到强,拉斑玄武岩减少,碱性玄武岩增多,亚碱性玄武岩的稀土元素和微量元素丰度降低,碱性玄武岩的稀土元素和微量元素丰度升高。在原始地幔标准化微量元素蛛网图上,亚碱性玄武岩具Nb、Ta负异常(槽)或呈双峰式,为岛弧玄武岩; 碱性玄武岩呈“隆起”状,类似于洋岛玄武岩(OIB)。山西汉诺坝玄武岩是板块俯冲与地幔柱联合作用的结果,以地幔柱成因为主,板块俯冲成因为辅。亚碱性玄武岩向碱性玄武岩转变,可能代表玄武岩以板块俯冲成因为主转为以地幔柱成因为主; 碱性玄武岩由钾质向钠质变化、亚碱性玄武岩向富铁镁演化,可能分别代表地幔柱向浅、板块俯冲向深的演化过程。
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| 关 键 词： | 山西汉诺坝玄武岩 岛弧玄武岩 洋岛玄武岩 板块俯冲 地幔柱 |
| 收稿时间： | 2018-04-02 |
Origin discussion of Cenozoic Hannuoba basalts in Shanxi Province |
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| Authors: | ZHANG Yusheng |
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| Institution: | Institute of Shanxi Geological Survey, Taiyuan 030001, China |
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| Abstract: | Based on the regional geological survey, 4 volcanic depressions and 7 profiles of Cenozoic Hannuoba basalts in Shanxi Province were investigated in this paper. Tholeiitic basalts appear first at the bottom of volcano cycle and upwards are alkaline basalts. Large ion lithophile elements and light rare earth elements are enriched in the rocks. The eruption time is from early to late, magmatic activity becomes weak, tholeiitic basalts decrease, alkaline basalts increase, rare earth and trace elements of sub-alkaline basalts reduce, and rare earth and trace elements of alkaline basalts increase from east to west. Sub-alkaline basalts have Nb and Ta negative anomaly (channel) or twin peaks type in the primitive-mantle normalized spider diagram, which were identified as island arc basalts, while alkaline basalts havs an uplift trend, which are similar to ocean island basalts (OIB). Hannuoba basalts in Shanxi Province is the result of an union action of plate subduction and mantle plume, with the main cause of mantle plume and the auxiliary cause of plate subduction. The transition from sub-alkaline basalts to alkaline basalts may represent the shift of the main reason from plate subduction to mantle plume. The change from potassium to sodium in alkaline basalts, and the evolution of the sub-alkaline basalts to the iron rich magnesium can respectively reflect the process of mantle plume becoming shallow, and plate subduction becoming deep. |
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| Keywords: | Hannuoba basalts in Shanxi Province island arc basalt ocean island basalt plate subduction mantle plume |
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