洛南-栾川过渡带及其两侧火山岩的地球化学特征

过渡带的南北界线大体为铁炉子—黑河断裂和石门—马超营断裂,称之为洛南—栾川过渡带。本文通过对熊耳群、栾川群大红口组和宽坪群下部火山岩的造岩元素、微量元素扣稀土元素特征的研究表明,中晚元古时期,在华北地台南缘、洛南—栾川过渡带及北秦岭造山带上存在着三条不同性质的裂谷,它们分别为大陆内部裂谷、近活动大陆边缘的大陆裂谷和弧后盆地拉张裂谷,从而也表明当时洛南—栾川过渡带所处大地构造环境及地壳性质就已介于南北两大构造单元之间。

THE GEOCHEMICAL FEATURES OF VOLCANIC ROCKS IN THE LUONAN-LUANCHUAN TRANSITIONAL BELT AND THE BOUNDING STRUCTURAL ELEMENTS

Based on .the study of the major, trace and rare earth elements of the Xiong'er Group, the Da Hongkou formation of the Luanchuan Group and the low basic volcanic rocks of the Kuanping group, it has been proved that three rifts on the south margin of the North China platform, the Luonan--Luanchuan transitional belt and the North Qinling orogenic belt had been developed during the Middle-late Proterozoic. Their sorts are respectively of the intercontinental rift, and the continental rift in a back arc basin.So the tectonic setting and the crustal nature of the Luonan-Luanchuan transitional belt are between the tectonic elements of the south and north sides.