發(fā)布時(shí)間：2018-04-04 14:08

  本文選題：青龍村群　切入點(diǎn)：超基性巖　出處：《吉林大學(xué)》2017年碩士論文

【摘要】：研究區(qū)位于吉林省延邊朝鮮族自治州和龍市。大地構(gòu)造位置屬于華北板塊北緣東端的北側(cè),延邊華力西褶皺帶的西部邊緣。其北側(cè)為佳木斯地塊,東側(cè)為興凱地塊,西面為敦密斷裂和兩江—天橋嶺斷裂,南側(cè)與華北克拉通以古洞河斷裂相隔。論文以分布于和龍市頭道鎮(zhèn)臥龍至長仁一帶晚古生代(二疊紀(jì))青龍村群中的超基性巖體為研究對(duì)象。通過野外地質(zhì)調(diào)查、巖相學(xué)、巖石地球化學(xué)和同位素年代學(xué)等方法、手段,研究超基性巖的地質(zhì)特征、形成時(shí)期、巖石成因和形成環(huán)境。研究對(duì)象的超基性巖體沿北北西向分布于青龍村群變質(zhì)巖系中。主要由輝石巖、輝石橄欖巖和橄欖巖組成。巖體一般為透鏡狀、脈狀、腎狀等,剖面上一般為似板狀、透鏡狀、不規(guī)則盆狀、漏斗狀等。多數(shù)巖體規(guī)模小:長100~300m,最長1100m;寬十幾米至幾十米,最寬600m;厚度一般幾十米至百余米;延深100~1400m不等。出露面積0.002~0.5km2。青龍村群中的超基性巖體具有低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,說明巖體屬于鈣堿性系列。鎂鐵指數(shù)MF=24.58~32.91,鎂指數(shù)Mg#=78.96~84.79,m/f=3.07~5.48,是鐵質(zhì)超基性巖。稀土元素總量變化大(∑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),輕重稀土分異明顯(LREE/HREE=3.074~7.358。δEu=0.820~0.953)。微量元素富集K、Rb、Th,虧損Ta、Nb、P、Zr、Hf、Ti和Ba。巖石化學(xué)分析結(jié)果表明,青龍村群超基性巖來源于幔源巖漿。稀土和微量元素以及常量元素和元素特征值均顯示其具有E-MORB特點(diǎn),屬于異常大洋中脊環(huán)境,但源區(qū)可能經(jīng)歷了富集流體的交代和地殼混染作用的影響。LA-ICP-MS鋯石U-Pb測(cè)年結(jié)果顯示,超基性巖中鋯石表面年齡集中在210~220Ma。這些年齡在206Pb/238U-207Pb/235U諧和圖中形成一條不一致線,與一致線的上交點(diǎn)年齡為251±22Ma,說明青龍村群中超基性巖成巖年齡為251±22Ma,即晚二疊世末期。210~220Ma的表面年齡屬于變質(zhì)年齡,說明開始于晚古生代晚期的延邊褶皺帶造山作用可能一直延續(xù)到晚三疊世。
[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殑瓚呭熀鎬у博浣撳叿鏈変綆SiO2(39.46%~44.97%),TiO2(0.373%~0.744%),Al2O3鍚噺(4.26%~9.00%),CaO鍚噺(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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