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  

Zircon U-Pb Dating and Hf Isotopic Study on the Intrusions of the Huaining Basin in the Lower Yangtze River Belt, Central Eastern China

作　　者：陈志洪[1] 赵玲[1] 匡福祥[1] 李亚楠[1] 李功振[2] 

机构地区：[1]南京地质矿产研究所,江苏南京210016 [2]成都理工大学地球科学学院,四川成都610059

出　　处：《大地构造与成矿学》2017年第3期551-560,共10页Geotectonica et Metallogenia

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

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。The Huaining Basin is one of the continental volcanic fault basins in the Middle-Lower Yangtze Region. In this study we first present precise LA-ICP-MS zircon U-Pb dating and Hf isotope analysis for the Songjia and Shijia intrusions in the Huaining Basin. Zircon LA-ICP-MS U-Pb ages and Hf isotopes, indicate that they were formed at 128.5±1.6 Ma and 126.8±1.2 Ma, with εHf（t） values of-12.6 to-6.0 and-12.4 to-4.7, tDM2 model ages of 1576-1979 Ma and 1475-1961 Ma, respectively. Combined with the geochemical data of intrusions in other parts of region, we suggest that the intrusions were likely originated from enriched basaltic magma and lower crust（the Dongling Group）. The Cretaceous magmatic activities（132-122 Ma） in the Huaining Basin coincided with the climax of the lithospheric extension in the eastern China.

关 键 词：侵入岩 锆石U-PB定年 HF同位素 怀宁盆地 长江中下游 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]