| 内蒙古突泉县牤牛海地区超镁铁质岩地球化学及源区特征 |
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| 引用本文： | 付俊彧,汪岩,钟辉,宋维民,孙巍,那福超,钱程,杨雅军,庞雪娇,江山.内蒙古突泉县牤牛海地区超镁铁质岩地球化学及源区特征[J].吉林大学学报(地球科学版),2017,47(4). |
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| 作者姓名： | 付俊彧 汪岩 钟辉 宋维民 孙巍 那福超 钱程 杨雅军 庞雪娇 江山 |
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| 作者单位： | 中国地质调查局沈阳地质调查中心,沈阳,110034 |
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| 基金项目： | 中国地质调查局地质调查项目(121201207000171401 |
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| 摘 要： | 内蒙古突泉县牤牛海地区发育超镁铁质岩,主要岩石类型为蛇纹石化橄榄岩、辉石橄榄岩、异剥辉石橄榄岩和蛇纹岩,局部蛇纹岩中可见显微鬣刺假象结构,包括蛇纹石呈假像的柱状中空骸晶结构、鱼骨状或羽状结构。岩石化学具有高镁(w(MgO)为33.63%~39.44%)、铬(2 200×10~(-6)~17 200×10~(-6))、镍(1 900×10~(-6)~3 000×10~(-6)),高CaO/Al_2O_3(0.56~39.01,平均为7.05),低钛(w(TiO_2)为0.01%~0.02%)、低铝(w(Al2O3)为0.03%~0.36%)、低碱(w(K_2O+Na_2O)为0.03%~0.65%)特征,类似科马提岩;Mg#值(平均为87)与纯橄榄岩(86)接近;稀土元素(w(∑REE)为0.32×10~(-6)~2.79×10~(-6))明显低于大洋脊含量,轻稀土富集(LREE/HREE为2.80~16.68),Eu正异常明显(δEu为0.59~4.84);微量元素富集大离子亲石元素(LILE)Rb、Ba、Sr,亏损高场强元素(HFSE)Nb、P等。说明超镁铁质岩石岩浆源自亏损软流圈地幔,并受到俯冲流体交代作用,形成于岛弧环境。牤牛海超镁铁质岩与西部包括突泉围场、好老鹿场、超日海乌拉、梅劳特乌拉、苏尼特左旗二道井一带超镁铁质岩共同构成一条近东西向展布的超镁铁质岩(蛇绿岩)带,通过地质建造分析,认为该构造带可能为华北板块与西伯利亚板块最终缝合带。
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| 关 键 词： | 内蒙古 牤牛海 超镁铁质岩 岩石地球化学 亏损软流圈地幔 |
Geochemistry and Source Characteristics of Ultramafic Rocks in Tuquan Mangniuhai,Inner Mongolia |
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| Fu Junyu,Wang Yan,Zhong Hui,Song Weimin,Sun Wei,Na Fuchao,Qian Cheng,Yang Yajun,Pang Xuejiao,Jiang Shan.Geochemistry and Source Characteristics of Ultramafic Rocks in Tuquan Mangniuhai,Inner Mongolia[J].Journal of Jilin Unviersity:Earth Science Edition,2017,47(4). |
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| Authors: | Fu Junyu Wang Yan Zhong Hui Song Weimin Sun Wei Na Fuchao Qian Cheng Yang Yajun Pang Xuejiao Jiang Shan |
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| Abstract: | There are ultramafic rocks in Tuquan Mangniuhai, Inner Mongolia.The main rock types are serpentine peridotite,pyroxene peridotite,diallage peridotite,and serpentinite.Under a microscope,the"spinifex"structure is visible,and the columnar hollow skeleton crystal structure in the fake image of serpentine, fishbone, or pinnate structure as well.The petrochemistry is characterized by high Mg (w(MgO)33.63%-39.44%),Cr(2 200×10-6-17 200×10-6),and Ni(1 900×10-6-3 000×10-6);high CaO/Al2O3(0.56-39.01, an average of 7.05);low Ti (w(TiO2) 0.01%-0.02%),Al (w(Al2O3)0.03%-0.36%),and alkali (w(K2O+Na2O) 0.03%-0.65%), similar to that of komatite.The average forsteritic index (87) closes to that of dunite (86);w(∑REE)(0.32×10-6-2.79×10-6)is significantly lower than that of ocean ridge, and the LREE/HREE (2.80-16.68) show LREE enrichment with a positive Eu anomaly;the rock is enriched in large ion lithophile elements (LILE) Rb, Ba、Sr, while it is depleted of high field-strength element (HFSE) Nb, P.The results indicate that the mafic magma originated from the depleted asthenosphere mantle, and was altered by subduction in an island arc tectonic environment.The Mangniuhai ultramafic rocks with those in Tuquanweichang, Haolaoluchang, Chaorihaiwula, Meilaotewula Erdaojing of Sonid Left Banner constitute a nearly East-West ultramafic rocks (ophiolite) belt.Based on the analysis of the geological formation, the authors conclude that the structural belt may be the final suture zone of the North China plate and the Siberia plate. |
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| Keywords: | Inner Mongolia Mangniuhai ultramafic rock petrogechemistry depleted asthenosphere mantle |
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