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| 青藏高原北羌塘盆地查涌蛇绿岩的地球化学特征及其构造意义 | |
| 引用本文： | 李善平,陈有顺,李伍福,王钦元,祁生胜.青藏高原北羌塘盆地查涌蛇绿岩的地球化学特征及其构造意义[J].现代地质,2009,23(6). |
| 作者姓名： | 李善平 陈有顺 李伍福 王钦元 祁生胜 |
| 作者单位： | 1. 青海省地质矿产研究所,青海,西宁,810012;青海省地质调查院,青海,西宁,810012 2. 青海省地震局,青海,西宁,810001 3. 青海省地质调查院,青海,西宁,810012 4. 青海省地质矿产研究所,青海,西宁,810012 |
| 基金项目： | 中国地质调查局"1:25万治多、杂多幅区域地质调查"项目 |
| 摘 要： | 查涌蛇绿岩为甘孜—理塘缝合带在青藏高原北羌塘盆地治多地区的北延部分,由基性堆晶岩、辉绿岩墙群、基性喷出岩及沉积成因的硅质岩组成,缺乏地幔橄榄岩。受后期构造强烈破坏,岩石变质变形较强,多呈被肢解的构造岩块、岩片产出。堆晶岩包括蚀变橄榄辉石岩、辉长岩,蚀变橄榄辉石岩具有低SiO2、TiO2、P2O5含量及高MgO含量的特征,Rb、Th、Cr等元素呈强富集型,Sr、Nb、Y等元素具亏损型;辉长岩低SiO2及K2O含量,高MgO、TiO2及Al2O3含量;辉绿岩墙以Rb、Ba、Th等元素的明显富集和Y、Yb的轻微亏损为特征,微量元素蛛网图曲线与洋中脊玄武岩类似;玄武岩具高TiO2含量、低K2O含量,属低钾拉斑玄武岩系列,轻重稀土元素分馏程度明显,具有轻稀土富集型,铕不显异常,玄武岩REE模式呈近平坦型曲线,与大洋玄武岩特征相似。由上述蛇绿岩地球化学特征及结合区域地质、构造环境等特征,推测查涌蛇绿岩产于洋盆环境。 |
| 关 键 词： | 青藏高原 北羌塘盆地 蛇绿岩 甘孜—理塘缝合带 洋盆环境 |
Geochemistry of the Chayong Ophiolite in North Qiangtang Basin, Qinghai-Tibet Plateau: Implications for Tectonics |
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| LI Shan-ping,CHEN You-shun,LI Wu-fu,WANG Qin-yuan,QI Sheng-sheng.Geochemistry of the Chayong Ophiolite in North Qiangtang Basin, Qinghai-Tibet Plateau: Implications for Tectonics[J].Geoscience——Journal of Graduate School,China University of Geosciences,2009,23(6). | |
| Authors: | LI Shan-ping CHEN You-shun LI Wu-fu WANG Qin-yuan QI Sheng-sheng |
| Abstract: | The Chayong ophiolite is a part of the northern extension of Ganze-Litang suture zone in Zhiduo area of the North Qiangtang basin in Qinghai-Tibet Plateau,it consists of basic cumulates,diabase dyke swarms,basic lavas and sedimentary-origin cherts,but mantle peridotites are absent.Due to the effect of structures after the ophiolite formed,they are strongly metamorphized and deformed, and mostly dismembered to tectonic blocks and slabs. The cumulates comprise altered olivine pyroxenite and gabbro. The former is characterized by low SiO_2,TiO_2,P_2O_5 and high MgO contents,significant enrichment of Rb,Th,Cr and depletion of Sr,Nb,Y . In contrast, the latter is characterized by low SiO_2 and K_2O contents,high MgO,TiO_2 and Al_2O_3 contents. The diabase dykes are geochemically characterized by significant enrichment of Rb,Ba,Th and slight depletion of Y and Yb coupled with similar trace element spidergrams to mid-ocean ridge basalts. The basalts exhibit high TiO_2 and low K_2O contents, typical feature of a low potassium tholeiite series. Additionally, they display fractionation of LREE from HREE fractionation, i.e.,enrichment of LREE no significant Eu anomalies and near flat REE curves,resembling oceanic basalts. In combination with geochemical characteristics, regional geology and tectonic environment, we propose that the Chayong ophiolite was possibly produced in an ocean basin setting. |
| Keywords: | Qinghai-Tibet Plateau the North Qiangtang basin ophiolite Ganze-Litang suture zone ocean basin setting |
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