CAJ | 학술논문

铧厂沟地区碧口群玄武岩呈带状和透镜状分布于凝灰岩和凝灰质千枚岩中。在详细野外观察基础上,利用显微镜观察、主微量元素及放射性同位素分析等综合分析技术对玄武岩的岩石学、地球化学以及年代学特征进行了研究。结果表明：碧口群玄武岩普遍经历了绿片岩相的变质作用,主要矿物为斜长石、绿泥石和绿帘石；SiO2(44.67%~49.76%)、TiO2(1.14%~1.34%)含量较低, TFe2O3(12.03%~15.47%)、MgO(7.57%~9.3%)、CaO(7.29%~10.54%)含量较高。稀土总量较低,轻稀土亏损,重稀土富集。岩石微量元素和锆石Hf同位素特征显示玄武岩形成环境可能类似N-MORB,起源于软流圈,并在上升过程中混入了古老的地壳物质。LA-ICP-MS锆石测年结果显示玄武岩的形成年龄为(316.3±6.0) Ma (MSWD=0.78；n=7),表明碧口群火山岩系至少是两期(新元古代时期和晚古生代时期)火山作用的产物。其大规模形成时期为新元古代,后经晚古生代火山作用的叠加改造而成。
화엄구지구벽구군현무암정대상화투경상분포우응회암화응회질천매암중。재상세야외관찰기출상,이용현미경관찰、주미량원소급방사성동위소분석등종합분석기술대현무암적암석학、지구화학이급년대학특정진행료연구。결과표명：벽구군현무암보편경력료록편암상적변질작용,주요광물위사장석、록니석화록렴석；SiO2(44.67%~49.76%)、TiO2(1.14%~1.34%)함량교저, TFe2O3(12.03%~15.47%)、MgO(7.57%~9.3%)、CaO(7.29%~10.54%)함량교고。희토총량교저,경희토우손,중희토부집。암석미량원소화고석Hf동위소특정현시현무암형성배경가능유사N-MORB,기원우연류권,병재상승과정중혼입료고로적지각물질。LA-ICP-MS고석측년결과현시현무암적형성년령위(316.3±6.0) Ma (MSWD=0.78；n=7),표명벽구군화산암계지소시량기(신원고대시기화만고생대시기)화산작용적산물。기대규모형성시기위신원고대,후경만고생대화산작용적첩가개조이성。
The Bikou Group basalt lenticular or banded in form is distributed in tuffs and tuffaceous phyllites of Huachanggou area. Based on detailed field geological survey and systematic laboratory studies including microscope observation, major and trace element analysis and radioactive isotope analysis, the authors investigated the petrological, geochemical and chronological characteristics of the basalt. The result shows that the basalt in Bikou Group has been subjected to metamorphism of greenschist facies, and mainly consists of plagioclase, chlorite and epidote. The basalt exhibits low SiO2 (44.67%-49.76%), TiO2 (1.14%-1.34%) and REE, high TFe2O3 (12.03%-15.47%), MgO (7.57%-9.3%) and CaO (7.29%-10.54%), with LREE depletion and HREE enrichment. It originated from asthenosphere, occurred in N-MORB setting and was mixed with the old crust. The basalt sample yielded zircon LA-ICP-MS U-Pb age of (316.3±6.0) Ma (MSWD=0.78;n=7), which indicates that the Bikou Group volcanic rocks are products of at least two periods of volcanic activities, i.e., Neoproterozoic and late Paleozoic. They were formed massively in Neoproterozoic and reformed by the volcanic activity in late Paleozoic.