皖东滁州盆地晚中生代火山岩的SHRIMP锆石U-Pb年龄及其地质意义
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深部探测技术与实验研究专项(SinoProbe-05-05);中国地质调查局地质调查项目(1212010711814);地质矿产调查评价专项资助项目(1212011121116)


SHRIMP zircon U-Pb age of late Mesozoic volcanic rocks from the Chuzhou basin, eastern Anhui Province, and its geological significance
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    摘要:

    滁州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,但与其他在早中生代坳陷基础上发育起来的“继承式”火山岩盆地不同,它直接叠置在大别山造山带之上,盆地基底岩石的时代较老,属新元古代-早古生代地层。盆地内的火山岩主要为一套中酸性偏碱性的粗安质和粗面英安质岩石,属高钾钙碱性系列,地球化学特征上明显不同于长江中下游地区大多数盆地中火山岩所表现出的橄榄玄粗岩系列的特点(如宁芜盆地、庐枞盆地、溧水盆地、怀宁盆地)。应用SHRIMP锆石U-Pb法测得滁州盆地黄石坝组粗安岩的锆石206Pb/238U加权平均年龄为128±1 Ma。该年龄与长江中下游地区其他盆地中火山岩-潜火山岩的形成时代类似,表明整个长江中下游地区的火山活动是在很短的时间内发生的。滁州盆地内的火山岩具有比长江中下游其他盆地中火山岩低得多的εNd(t)值,而类似于大别山造山带内晚中生代的花岗岩类侵入体,指示其成因可能主要与古老下地壳物质的部分熔融有关。

    Abstract:

    The Chuzhou basin, one of the several late Mesozoic volcanic basins developed in the middle and lower reaches of the Yangtze River, is the only basin directly superimposed upon the Dabie orogenic belt, with relatively old basement composed of Neoproterozoic-lower Paleozoic strata. The volcanic rocks in the Chuzhou basin are mainly intermediate-acidic trachyandesite and trachydacite, which belong to high-K cal-alkaline series and greatly differ from most late Mesozoic volcanic basins in the middle and lower reaches of the Yangtze River such as Ningwu basin, Luzong basin, Lishui basin and Huaining basin which belong to the shoshonitic series in geochemistry. In this study, the authors used zircon SHRIMP U-Pb technique to perform accurate dating of a trachyandesitic sample from the Huangshiba Formation in the Chuzhou basin, which yielded an emplacement age of 128±1 Ma. This age is similar to the emplacement ages of volcanic/sub-volcanic rocks in other late Mesozoic volcanic basins, suggesting that the whole volcanism in the middle and lower reaches of the Yangtze River were developed in a very short period of time. The volcanic rocks in the Chuzhou basin have remarkably lower εNd(t) values than those in other volcanic basins but are similar to those of the late Mesozoic granitoid intrusive bodies in the Dabie orogen, indicating that their parent magma might have been mainly derived from partial melting of "old" lower crust.

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马芳,薛怀民,2011,皖东滁州盆地晚中生代火山岩的SHRIMP锆石U-Pb年龄及其地质意义[J].岩石矿物学杂志,30(5):924~934. MA Fang, XUE Huai-min,2011,SHRIMP zircon U-Pb age of late Mesozoic volcanic rocks from the Chuzhou basin, eastern Anhui Province, and its geological significance[J]. Acta Petrologica et Mineralogica,30(5):924~934.

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  • 收稿日期:2011-06-15
  • 最后修改日期:2011-07-06
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