吉林省青龙村地区超基性岩地球化学特征及其构造意义

发布时间：2018-04-04 14:08

  本文选题：青龙村群　切入点：超基性岩　出处：《吉林大学》2017年硕士论文

【摘要】：研究区位于吉林省延边朝鲜族自治州和龙市。大地构造位置属于华北板块北缘东端的北侧,延边华力西褶皱带的西部边缘。其北侧为佳木斯地块,东侧为兴凯地块,西面为敦密断裂和两江—天桥岭断裂,南侧与华北克拉通以古洞河断裂相隔。论文以分布于和龙市头道镇卧龙至长仁一带晚古生代(二叠纪)青龙村群中的超基性岩体为研究对象。通过野外地质调查、岩相学、岩石地球化学和同位素年代学等方法、手段,研究超基性岩的地质特征、形成时期、岩石成因和形成环境。研究对象的超基性岩体沿北北西向分布于青龙村群变质岩系中。主要由辉石岩、辉石橄榄岩和橄榄岩组成。岩体一般为透镜状、脉状、肾状等,剖面上一般为似板状、透镜状、不规则盆状、漏斗状等。多数岩体规模小:长100~300m,最长1100m;宽十几米至几十米,最宽600m;厚度一般几十米至百余米;延深100~1400m不等。出露面积0.002~0.5km2。青龙村群中的超基性岩体具有低SiO2(39.46%~44.97%)、TiO2(0.373%~0.744%),Al2O3含量(4.26%~9.00%)、CaO含量(2.73%~8.19%)偏高,富MgO(21.53%~30.18%)、FeO(7.52%~9.48%),Na2O+K2O=0.79%~3.51%的特征,说明岩体属于钙碱性系列。镁铁指数MF=24.58~32.91,镁指数Mg#=78.96~84.79,m/f=3.07~5.48,是铁质超基性岩。稀土元素总量变化大(∑REE=34.405×10-6~120.054×10-6,LREE=27.865×10-6~105.690×10-6,HREE=6.372×10-6~14.364×10-6),轻重稀土分异明显(LREE/HREE=3.074~7.358。δEu=0.820~0.953)。微量元素富集K、Rb、Th,亏损Ta、Nb、P、Zr、Hf、Ti和Ba。岩石化学分析结果表明,青龙村群超基性岩来源于幔源岩浆。稀土和微量元素以及常量元素和元素特征值均显示其具有E-MORB特点,属于异常大洋中脊环境,但源区可能经历了富集流体的交代和地壳混染作用的影响。LA-ICP-MS锆石U-Pb测年结果显示,超基性岩中锆石表面年龄集中在210~220Ma。这些年龄在206Pb/238U-207Pb/235U谐和图中形成一条不一致线,与一致线的上交点年龄为251±22Ma,说明青龙村群中超基性岩成岩年龄为251±22Ma,即晚二叠世末期。210~220Ma的表面年龄属于变质年龄,说明开始于晚古生代晚期的延边褶皱带造山作用可能一直延续到晚三叠世。
[Abstract]:The research area is located in Yanbian Korean Autonomous Prefecture, Jilin Province.The tectonic position belongs to the north side of the eastern end of the North China plate and the western edge of the Yanbian Variscan fold belt.The north side is Jiamusi block, the east side is Xingkai block, the west side is Dumi fault and Liangjiang-Tianqiao ridge fault, and the south side is separated from the North China Craton Gudonghe fault.The ultrabasic rocks distributed in the late Paleozoic (Permian) Qinglongcun group from Wolong to Changren in Tudao Town, Helong City, were studied in this paper.By means of field geological survey, petrography, petrogeochemistry and isotopic chronology, the geological characteristics, formation time, genesis and environment of ultrabasic rocks are studied.The ultrabasic rock bodies are distributed in the metamorphic rock series of Qinglongcun Group.Mainly composed of pyroxenite, pyroxene peridotite and peridotite.The rock mass is generally lenticular, veined, renal and so on, and the profile is generally plate-like, lenticular, irregular basin, funnel, etc.Most rock masses are small in size: 100m long, longest 1100m; width 10 meters to tens meters, maximum width 600m; thickness generally tens meters to more than 100 meters; extension depth 100 ~ 1400m.The exposed area is 0.002 ~ 0. 5km2.闈掗緳鏉戠兢涓�鐨勮秴鍩烘�у博浣撳叿鏈変綆SiO2(39.46%~44.97%),TiO2(0.373%~0.744%),Al2O3鍚�閲�(4.26%~9.00%),CaO鍚�閲�(2.73%~8.19%)鍋忛珮,瀵孧gO(21.53%~30.18%),FeO(7.52%~9.48%),Na2O K2O=0.79%~3.51%鐨勭壒寰，

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