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首页> 外文期刊>Chemical geology >Zircon U-Pb geochronology and Hf isotope data from the Yangtze River sands:Implications for major magmatic events and crustal evolution in Central China
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Zircon U-Pb geochronology and Hf isotope data from the Yangtze River sands:Implications for major magmatic events and crustal evolution in Central China

机译：长江砂的锆石U-Pb年代学和Hf同位素数据：对华中地区重大岩浆事件和地壳演化的启示

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摘要

In situ U-Pb and Hf isotope analyses were made on detrital zircons isolated from sands of the Yangtze River in order to understand the evolution and history of crust in that river basin. A total of 2277 detrital zircon grains were dated by the LA-ICP-MS U-Pb technique and 674 grains were also analyzed for Hf isotopes on the same spots of concordant grains. Our results show five major groups of U-Pb ages:at 2.4-2.6 Ga, 1.8-2.0 Ga, 700-850 Ma, 400-550 Ma and 200-300 Ma, which correspond to known granitoid magmatic events within the drainage (Lüliangian, Jinningian, Caledonian, Hercynian and Indo-Sinian/Yanshanian). The initial Hf isotope ratios [εHf(t)] of the zircons exhibit a wide range from negative to positive for each of the five major age groups, revealing that existing crustal materials were mixing with variable volumes of new mantle melt at these times. Zircon Hf model ages (T_(DM2)) display two major ranges of crustal growth, one being Mesoproterozoic (1.0-1.5 Ga) and the other Archean-Paleoproterozoic (2.5-2.8 Ga). These zircons were mainly sourced from the Yangtze Craton and the Cathaysia Block, respectively. Crustal growth rates based on TDM2 model ages suggest that 30% of the present crustal volume was formed by 2.5 Ga, 48% by 1.8 Ga, 70% by 1.4 Ga and 96% was formed by 1.0 Ga.
机译：为了了解长江流域地壳的演化和历史，对从长江沙中分离出的碎屑锆石进行了原位U-Pb和Hf同位素分析。通过LA-ICP-MS U-Pb技术测算了总计2277个碎屑锆石晶粒，还分析了674个晶粒中一致晶粒上相同点的Hf同位素。我们的研究结果显示了U-Pb年龄的五个主要类别：在2.4-2.6 Ga，1.8-2.0 Ga，700-850 Ma，400-550 Ma和200-300 Ma，对应于流域内已知的花岗岩类岩浆事件（吕梁，金宁尼亚，喀里多尼亚，海西和印度洋-震旦纪/燕山纪）。锆石的初始Hf同位素比[εHf（t）]在五个主要年龄组中均显示出从负到正的宽范围，这表明现有的地壳物质在这些时间与不同体积的新地幔熔体混合。锆石Hf模型年龄（T_（DM2））显示出两个主要的地壳生长范围，一个是中元古生界（1.0-1.5 Ga），另一个是古宙-古古生界（2.5-2.8 Ga）。这些锆石分别主要来自扬子岩和华夏地块。基于TDM2模型年龄的地壳生长速率表明，当前地壳体积的30％由2.5 Ga形成，48％由1.8 Ga形成，70％由1.4 Ga形成，96％由1.0 Ga形成。

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