长江中下游地区怀宁盆地侵入岩的锆石U-Pb年代学和Hf同位素研究

发布时间：2018-04-27 14:21

本文选题：侵入岩 + 锆石U-Pb定年　；参考：《大地构造与成矿学》2017年03期

【摘要】：怀宁盆地是长江中下游地区晚中生代发育的一系列断陷型火山岩盆地中的一个,盆地内以发育橄榄安粗质的火山岩为特色。本次主要选取该盆地内研究程度相对薄弱且具代表性的宋家和史家岩体首次开展了系统的锆石U-Pb年龄和Lu-Hf同位素测定。测年结果显示,宋家和史家岩体分别形成于128.5±1.6 Ma和126.8±1.2 Ma,与该盆地内火山岩系(122~132 Ma)几乎同期,都为早白垩世岩浆活动的产物,对应于中国东部岩石圈伸展减薄的高峰期,表明怀宁盆地内火山-侵入岩即形成于该地球动力学背景下。相关的锆石εHf(t)值分别介于 12.6~ 6.0和 12.4~ 4.7,二阶段模式年龄分别介于1576~1979 Ma和1475~1961 Ma,这与长江中下游地区橄榄安粗质中基性岩石的锆石Hf同位素组成基本一致。结合区域资料,我们认为怀宁盆地内宋家和史家岩体形成可能与富集幔源岩浆与下地壳物质(类似董岭群)的混合作用有关。
[Abstract]:Huaining basin is one of a series of faulted volcanic basins developed in the middle and lower reaches of the Yangtze River during the late Mesozoic. In this paper, the relatively weak and representative Songjiahe Shijia pluton in this basin was selected to carry out systematic U-Pb dating and Lu-Hf isotopic dating of zircon for the first time. The dating results show that the Songjia and Shijia pluton were formed at 128.5 卤1.6Ma and 126.8 卤1.2Marespectively, which are the products of early Cretaceous magmatism, corresponding to the peak period of lithospheric extension and thinning in eastern China. It is suggested that the volcanic-intrusive rocks in the Huaining basin were formed in the geodynamic background. The correlation values of zircon 蔚 HfT are between 12.6 ~ 6.0and 12.44.7respectively, and the two-stage model ages are between 15766Ma and 147551961 Ma, respectively, which is basically consistent with the zircon HF isotopic composition of the coarse basites in the middle and lower reaches of the Yangtze River. Based on the regional data, we believe that the formation of the Songjiahe Shijia body in the Huaining Basin may be related to the enrichment of mantle magma and the mixing of the lower crust material (similar to the Dongling group).
【作者单位】：南京地质矿产研究所;成都理工大学地球科学学院;
【基金】：国家自然科学基金(41202141) 中国地质调查局项目(12120113069100)联合资助
【分类号】：P588.12;P597

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