黔东南新元古代下江群碎屑岩地球化学特征及其大地构造意义

发布时间：2018-04-22 04:32

本文选题：黔东南 + 下江群　；参考：《地质论评》2017年05期

【摘要】：黔东南下江群是一套具复理石特征的陆源碎屑岩夹火山碎屑岩建造,由下向上分别为甲路组、乌叶组、番昭组、清水江组、平略组和隆里组。本文研究了该套岩石的主量元素、微量元素和Nd同位素特征。结果显示:下江群各个组样品均显示出不同程度的Co、La、Ce、Nd、Y和Lu元素的富集,Ta和Ni元素亏损以及明显的Eu负异常,ε_(Nd)(t)表现出负异常(ε_(Nd)(t):-0.35~-3.36)。岩石地球化学特征显示源岩以遭受了中等程度化学风化作用(CIA:52~79)的酸性岩为主,并混有适量的基性岩。结合已有研究成果,判断物源区主要以盆地周缘的近源沉积为主,如分布在桂北一带的花岗质岩石和基性岩。构造背景判别表明盆地处于与岛弧活动相关的活动大陆边缘背景,如此的构造背景暗示,江南造山带西段在下江群沉积期可能仍存在消减作用,扬子板块与华夏板块此时还未完全拼合。综合对比江南造山带东、西两段消减—碰撞的时间,暗示扬子板块和华夏板块之间可能具有一个"东早西晚"的碰撞造山过程。
[Abstract]:The Lower Yangtze Group in the southeast of Guizhou is a set of continental clastic rocks with the characteristics of clastic rocks and volcanic clastic rocks. The lower ones are respectively Jialu formation, Wuye formation, Fanzhao formation, Qingshuijiang formation, Pinglio formation and Longli formation. In this paper, the main elements, trace elements and ND isotopic characteristics of this set of rocks are studied. The results show that the samples of each group of Xiajiang Group show different degrees of enrichment of elements Coe LaCeCe NdCY and Lu, and the depletion of Ta and Ni elements, as well as the obvious negative EU anomaly, and the negative anomaly of 蔚 _ S _ T _ N _ D _ T _ t (蔚 _ S / N _ D _ T _ T ~ (-1): -0.35 ~ (-3.36) ~ (-1) ~ (-1) ~ (-0.35) ~ (-3.36) ~ (-1)). The petrogeochemical characteristics show that the source rocks are mainly acidic rocks with moderate chemical weathering and mixed with some basic rocks. In combination with the existing research results, the source area is mainly determined by the near-source deposits around the basin, such as granitic rocks and basic rocks distributed in the northern part of Guangxi. Tectonic background discrimination indicates that the basin is in the active continental margin background associated with island arc activity. Such a tectonic setting suggests that the west segment of the Jiangnan orogenic belt may still have subtractive effects during the sedimentary period of the Lower Yangtze Group. Yangtze plate and Huaxia plate at this time has not been fully combined. Comparing the time of subtractive collision between east and west sections of Jiangnan orogenic belt, it is suggested that there may be a collision orogenic process between Yangtze plate and Huaxia plate.
【作者单位】：中国地质大学地球科学学院;贵州省地质矿产勘查开发局;
【基金】：国家自然科学基金资助项目(编号:41472086,41772106)的成果~~
【分类号】：P542;P588.21

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