可可西里东部地区新生代钾质火山岩地球化学特征
Geochemical Characteristics of Cenozoic Potassic Volcanic Rocks in the Eastern Hoh Xil
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摘要: 对研究区火山岩进行主量元素、微量元素、稀土元素分析，主量元素具有高SiO2（59.35%~63.85%）、富碱（K2O+Na2O=7.89%~8.47%）、富K（K2O/Na2O>1）、高MgO（1.76%~2.46%）、高Mg#值（39.96~49.82）等特征，在TAS图中落在钾玄岩系列。火山岩不相容元素原始地幔标准化配分型式图总体呈谷峰相间的右倾型式，富集大离子亲石元素，相对亏损高场强元素，具有Th、La、Pb三个峰值和Ta、Nb、Ti三个亏损槽，指示钾玄岩具有板内碱性玄武岩和岩浆源区可能有较多的地壳物质加入的岛弧岩浆的特点。稀土总量非常高，ΣREE为442.44×10-6~681.53×10-6，LREE为425.94×10-6~657.26×10-6， HREE为12.53×10-6~24.27×10-6，LREE/ΣREE值为0.96~0.97，轻稀土元素强烈富集。无明显的负Eu异常（δEu=0.69~0.77）。随La含量的增加， La/Sm值呈增加趋势，指示源区岩石是部分熔融的产物，结晶分异作用较弱。钾玄岩地球化学特征表明，其是在大陆地壳加厚背景下被具有大洋沉积物和地壳物质所混染的富含大离子亲石元素和轻稀土元素强烈富集的地幔源区的部分熔融产物。Abstract: The major trace element and rare earth element of potassic volcanic rocks in the studied area have been analyzed in this paper.The results show that these rocks have high SiO2 contents (59.35%~63.85%), alkali content (K2O+Na2O=7.89%~8.47%), K2O/Na2O ratio (K2O/Na2O>1), MgO content (1.76%~2.46%) and Mg# values.In the TAS diagram, these rocks are located in the range of shoshonite series.In the primitive mantle normalized distribution pattern, the incompatible elements of these volcanic rocks present as rightist type, the heavy ion lithophile elements are enriched, and the high field strength elements are relatively depleted.In addition, the pattern exhibits three peak values of Th, La and Pb and three losses groove of Ta, Nb and Ti, indicating that the shoshonite has the characteristics of the intraplate alkali basalt and it has the geochemical characteristics of the arc magma mixed with more crustal material in the magma source area.The total content of rare earth is very high, ΣREE, LREE and HREE vary from 442.44×10-6 to 681.53×10-6, from 425.94×10-6 to 657.26×10-6 and from 12.53×10-6 to 24.27×10-6, respectively, and the LREE/ΣREE ratios range from 0.96 to 0.97, with strong enrichment of light rare earth element.The potassic volcanic rocks exhibit weakly negative Eu (δEu=0.69~0.77), and the La/Sm ratios show an increasing trend with the raising of La content, which indicate that these rocks serve as the products of partial melting, with weak fractional crystallization.The geochemical characteristics of Shoshonitic rocks indicates that, they were formed by the partial melting of mantle materials in the thickened crust continental setting, and these mantle materials were contaminated by oceanic sediments and crust materials, with enrichments of light rare earth elements and large ion lithophile elements.
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Key words:
- petrogeochemistry /
- shoshonite /
- cenozoic volcanic rock /
- Eastern Hoh Xil
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李光明.藏北羌塘地区新生代火山岩岩石特征及其成因探讨[J].地质地球化学,2000,28(2):38-44.
LI Guangming.Petrologic Features and Genesis of Cenozoic Volcanic Rock,QiangTang are,Northen Tibetan Plateau[J].Geological and Geochemical, 2000,28(2):38-44.
史连昌,郭通珍,杨延兴,等.可可西里湖地区新生代火山岩同位素地球化学特征及火山成因、源区性质讨论[J].西北地质,2004,37(1):19-25.
SHI Lianchang,GUO Tongzhen,YANG Yanxing, et al.Isotopic geochemistry and volcanic genesis and magmatic origin of the Cenozoic volcanic rocks in Hoh Xil lake area[J].Northwestern Geology, 2004,37(1):19-25.
朱迎堂,贾全香,伊海生,等.青海可可西里湖地区新生代两期火山岩[J].矿物岩石,2005,25(4):23-29.
ZHU Yingtang,JIA Quanxiang,YI Haisheng,et al.Two Periods of CenozicVolcanic Rocks from Hoh XilLakeArea,Qinghai[J].Journal of Mineralogy & Petrology, 2005,25(4):23-29.
赖绍聪,秦江锋,李永飞,等.藏北羌塘比隆错一带新生代火山岩的成因:壳幔过渡带局部熔融的地球化学证据[J].地质通报, 2006,25(1-2):64-69.
LAI Shaocong, QIN Jiangfeng, LI Yongfei, et al.Cenozoic volcanic rocks in the Belog Co area, Qiangtang, northern Tibet, China:Petrochemical evidence for partial melting of the mantle-crust transition zone[J].Geological Bulletin of China, 2006,25(1-2):64-69.
江东辉,刘嘉麒,丁林.青藏高原北部可可西里地区新生代钾质火山岩地球化学特征及成因[J].岩石学报, 2008, 24(2):279-290.
JIANG Donghui, LIU Jiaqi, DING Lin.Geochemistry and petrogenesis of Cenozoic potassic volcanic rocks in the Hoh Xil area, northern Tibet plateau.[J].Acta Petrologica Sinica, 2008, 24(2):279-290.
邓万明,郑锡澜,松本征夫.青海可可西里地区新生代火山岩的岩石特征与时代[J].岩石矿物学杂志, 1996,15(4):289-298.
DENG Wangming, ZHENG Xilan, MATSUMOTO Y.Petrological Characteristics and Ages of Cenozoic Volcanic Rocks from the Hoh Xil Mts., Qinghai Province[J].Acta Petrrologica et Mineralogica, 1996,15(4):289-298.
邓万明,孙宏娟.青藏北部板内火山岩的同位素地球化学与源区特征[J].地学前缘, 1998,5(4):307-317.
DENG Wangming,SUNH Hongjuan.Isotopic Geochemistry and Source of Intraplate Volcanic Rocksin North Tibet,China[J].Earth Science Frontiers, 1998,5(4):307-317.
赖绍聪,刘池阳.青藏高原北羌塘榴辉岩质下地质及富集型地幔源区——来自新生代火山岩的岩石地球化学证据[J].岩石学报, 2001, 17(3):459-468.
LAI Shaocong, LIU Chiyang.Enriched upper mantle and eclogitic lower crust in north Qiangtang, Qinghai-Tibet Plateau:petrological and geochemical evidence from the Cenozoic volcanic rocks[J].Acta Petrologica Sinica,2001, 17(3):459-468.
莫宣学,赵志丹,邓晋福,等.印度-亚洲大陆主碰撞过程的火山作用响应[J].地学前缘,2003, 10(3):135-148.
MO Xuanxue, ZHAO Zhidan, DENG Jinfu, et al.Response of volcanism to the India-Asia collision[J].Earth Science Frontiers,2003,10(3):135-148.
王碧香,叶和飞,彭勇民.青藏羌塘盆地中、新生代火山岩同位素地球化学特征及其意义[J].地质论评, 1999, 45(S1):946-951.
WANG Bixiang,YE Hefei,PENG Yongming.Isotope Geochemistry of Meso-Cenozoic Volcanic Rocks in the QiangtangBasin,Qinghai-Tibet Plateau and Its Significance[J].Geological Review, 1999, 45(S1):946-951.
ARNAUDN O, VIDAL P, TAPPONNIER P, et al.The high K2O volcanism of northwestern Tibet:Geochemistry and tectonic implications[J].Earth & Planetary Science Letters, 1992, 111(s 2-4):351-367.
RAPP R P, SHIMIZU N, NORMAN M D, et al.Reaction between slab-derived melts and peridotite in the mantle wedge:experimental constraints at 3.8 GPa[J].Chemical Geology, 1999, 160(4):335-356.
XIAO L, CLEMENS J D.Origin of potassic (C-type) adakite magmas:Experimental and field constraints[J].Lithos, 2007, 95(3-4):399-414.
TURNER S, HAWKESWORTH C, LIU J, et al.Timing of Tibetan uplift constrained by analysis of volcanic rocks:Nature[J].Nature, 1993, 364(6432):50-54.
WANG Q, MCDERMOTT F, XU J F, et al.Cenozoic K-rich AdakiticVolcanic Rocks in The HohxilArea, Northern Tibet:Lower-crustal Melting in An Intracontinental[J].Geology, 2005, 33(6):465-468.
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