阿尔金南缘长沙沟超镁铁岩岩石地球化学特征及构造环境分析  

Petrogeochemical Characteristics and Tectonic Setting Analysis of Changshagou Ultramafic Rocks in the Southern Margin of Altyn

作　　者：梁孝伟 毛红伟 王雪杰 Liang Xiaowei;Mao Hongwei;Wang Xuejie(XinJiang Geological Explration institute,China Metallurgical Geology Bureau,Urumqi,Xinjiang,830000,China)

机构地区：[1]中国冶金地质总局新疆地质勘查院,新疆乌鲁木齐830000

出　　处：《新疆地质》2022年第2期155-160,共6页Xinjiang Geology

基　　金：中国冶金地质总局山东局青年科技基金项目(SDYJ-QNKY202110)资助。

摘　　要：对阿尔金南缘长沙沟超镁铁岩进行野外地质调查、岩石学及岩石地球化学等方面研究,结果显示:长沙沟超镁铁岩已发生强烈蛇纹石化,基本已蚀变成蛇纹岩。主量元素具高Mg(MgO=36.98%~37.26%)、低Si(SiO2=39.90%~41.44%)、贫Al(Al2O3=1.81%~2.64%)、低Fe(FeOT=6.46%~7.48%)特征。Mg#值为89.80~91.08,m/f值为8.65~10.01,属典型镁质超镁铁岩,推测原岩为斜方辉石橄榄岩。稀土元素总量ΣREE=4.49×10^(-6)~5.06×10^(-6),分布模式为轻稀土微弱富集,近平坦型,(La/Yb)N=1.10~3.43,Eu异常不明显,δEu=0.86~0.93,具正的Ce异常,δCe=1.16~1.96。微量元素富集Ba,U,Ta,Pb,Zr,Hf,亏损Th,Nb。长沙沟超镁铁岩属变质橄榄岩,为“SSZ”型蛇绿岩底部组成单元,由原始地幔经2%~10%熔融形成的亏损地幔岩,形成于俯冲带环境中的洋内弧后盆地。Field investigation,petrological and geochemical study on the ultramafic rock occurred in the Changshagou,the southern margin of Altyn,The results show that the Ultramafic Rock have subjected to strong serpentinization and turned into serpentinite.Geochemical analysis shows that the main elements of the rock are characteristic of high Mg(MgO=36.98%~37.26%),low Si(SiO2=39.90%~41.44%),poor Al(Al2O3=1.81%~2.64%)and low Fe(FeOT=6.46%~7.48%),with Mg#value of 89.80~91.08 and m/f value of 8.65~10.01,belong to typical magnesium ultra basic rock,whose primary rock may be harzburgite.Rare earth element analysis indicates that theΣREE is extremely low(ΣREE=4.49-5.06ppm)and the normalized rare earth element partition pattern is characterized by a weak enrichment of near flat type pattern.(La/Yb)N is 1.10~3.43,with slight negative Eu anomalies(δEu=0.86~0.93)and significant negative Ce anomalies(δCe=1.16~1.96).Trace elements are enriched in Ba,U,Ta,Pb,Zr,Hf and depleted in Nb,Ti.It is considered that the Changshagou ultra-basic rocks are metamorphic peridotites and belong to the bottom unit of SSZ type ophiolite and to the lossy mantle rocks resulted from the partial melting(2%~10%)of original mantle.These ultra basic rocks formed in the intra-oceanic back-arc basin setting in the subduction zone.

关 键 词：阿尔金 洋内弧后盆地 长沙沟超镁铁质岩 岩石地球化学 

分 类 号：P618.46[天文地球—矿床学] P618.31[天文地球—地质学]