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秦岭造山带的蛇绿岩中存在MORB型岩石,它们有高的放射性铅同位素组成,计算得到的初始铅同位素比值分布在p为8.5的增长线附近。古MORB型岩石代表的古洋幔与特提斯洋幔和南半球冈瓦纳域古地幔相似,表明秦岭地区曾经存在分隔华北古陆和扬子古陆的古洋,该古洋曾是冈瓦纳域和特提斯域古洋的一部分。古MORB型岩石的铅同位素特征显示出DUPAL异常,证明至少在10亿年以前就有DUPAL异常存在,该铅同位素异常可能是南半球的DUPAL异常在古时的表现。
There are MORB-type rocks in the ophiolites of the Qinling orogen, which have high radioactive Pb isotopic composition. The calculated initial Pb isotopic ratios are distributed around the growth line at p 8.5. The paleo-mantle represented by the ancient MORB-type rocks is similar to the Tethyan and the Gantan area ancient mantle in the southern hemisphere, indicating that there was once a paleo-ocean in the Qinling area that separates the ancient North China from the Yangtze from the ancient Gondwana Part of the ocean and the old ocean of Tethyan. The Pb isotopic signatures of the ancient MORB-type rocks show DUPAL anomalies, demonstrating that DUPAL anomalies existed at least 1 billion years ago and that this Pb isotopic anomaly may be an ancient manifestation of DUPAL anomalies in the southern hemisphere.