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秦岭造山带分隔着中国南北大陆,这两个陆块在地质历史时期可能分别是冈瓦纳与劳亚大陆的一部分。因此,研究秦岭造山带可对两个大陆的分界作出限定。秦岭造山带可分为北秦岭和南秦岭构造单元,它们曾被认为分别是华北陆块和扬子陆块的大陆边缘。若北秦岭确是华北陆块的大陆边缘,它们应具有相同的组成。近年来的研究表明,岩石的铅同位素组成存在明显的“块体效应”,不同的陆块具有不同的铅同位素组成。本文通过研究北秦岭地区元古宙基性岩的铅同位素组成并与两侧陆块相同时代的基性岩作对比,发现北秦岭地区的岩石不同于两侧陆块且具有独特的高放射成因铅同位素组成特征,它是华北陆块与扬子陆块的分界(带),据此本文还讨论了北秦岭的归属及其与秦岭古洋的关系等。
The Qinling orogenic belt separates China from its northern and southern continents. These two terrains may be part of the Gondwanaland and Lauya continent respectively during geological history. Therefore, the study of Qinling orogenic belt can limit the boundaries of the two continents. The Qinling orogenic belt can be divided into North Qinling and South Qinling tectonic units, which were once considered as the continental margin of the North China block and the Yangtze block, respectively. If the North Qinling is indeed the continental margin of the North China block, they should have the same composition. In recent years, studies have shown that there is a clear “block effect” of lead isotopic composition in rocks and different lead isotope compositions in different terrestrial blocks. By studying the Pb isotopic composition of the Proterozoic basic rocks in the North Qinling Mountains and comparing them with the basic rocks of the same age on both sides of the block, it is found that the rocks in the North Qinling area are different from those on both sides of the block and have a unique high-lead-lead content Isotope composition, which is the boundary between the North China terrane and the Yangtze block, according to which this article also discusses the attribution of North Qinling and its relationship with the ancient Qinling Mountains.