CAJ | 학술논문

博格达造山带内出露的晚石炭世辉绿岩,为研究博格达裂谷演化末期地球动力学背景提供了重要信息.色皮口地区辉绿岩主量元素以低TiO2、较高Al2O3、较低MgO、贫P2O5,较低的K2O/Na2O比值(0.12~0.53),ΣREE较高,LREE/HREE为2.45~3.56,铕负异常不明显(δEu=0.82~1.02)等为特征.与原始地幔相比,其不相容元素K,Rb, U,Ba富集,高场强元素Nb,Ta,Zr,Hf无富集,Ti亏损不明显,Nb,Ta,Th表现为明显负异常.U富集可能指示与地壳物质的加入有关,较低的Nb/Zr比值(0.02~0.06),暗示岩浆源区可能为受地壳混染的亏损地幔.辉绿岩LA-ICP-MS锆石U-Pb定年结果为(300.5±1.7) Ma(MSWD=2.3,Th/U比值为0.36~1.3),为晚石炭世晚期,代表了博格达裂谷闭合后地球动力学环境由挤压变为拉张的转折期.
박격체조산대내출로적만석탄세휘록암,위연구박격체렬곡연화말기지구동역학배경제공료중요신식.색피구지구휘록암주량원소이저TiO2、교고Al2O3、교저MgO、빈P2O5,교저적K2O/Na2O비치(0.12~0.53),ΣREE교고,LREE/HREE위2.45~3.56,유부이상불명현(δEu=0.82~1.02)등위특정.여원시지만상비,기불상용원소K,Rb, U,Ba부집,고장강원소Nb,Ta,Zr,Hf무부집,Ti우손불명현,Nb,Ta,Th표현위명현부이상.U부집가능지시여지각물질적가입유관,교저적Nb/Zr비치(0.02~0.06),암시암장원구가능위수지각혼염적우손지만.휘록암LA-ICP-MS고석U-Pb정년결과위(300.5±1.7) Ma(MSWD=2.3,Th/U비치위0.36~1.3),위만석탄세만기,대표료박격체렬곡폐합후지구동역학배경유제압변위랍장적전절기.
The Late Carboniferous Diabase in bogda orogenic belt provides important information on the bogda rift tec-tonic evolution.The geochemistry of the major is characterized by low contents of TiO2(0.81%~2.1%),MgO(5.83%~10.48%), K2O and P2O5, high Al2O3 and low K2O/Na2O ration.Meanwhile,it is showing that the diabase is enrichment in light rare earth elements with abundance rare earth elements,LREE/HREE ration contents between 2.45 and 3.56,the dia-base exhibits slightly negative Eu anomalies (δEu=0.82~1.02).Comparing with the primitive mantle,they are enriched in the large-iron-lithophile elements(such as K,Rb,U,Ba ) and depletion of high-field-strength element(such as Nb and Ta) and Th. U enrichment may be indicating contamination by crustal materials,lower Nb/Zr ration (0.02~0.06).The above characteristics indicate that magma source are originated from depleted mantle of contamination by crustal materi-als.Using LA-ICP-MS method of U-Pb age dating,it is the 300.5±1.7Ma(MSWD=2.3,Th/U=0.36~1.33)that represents the crystallized age of the diabase.It represents the important conversion from compression to extension in Geodynamics.