| 浙江省中生代火成岩的Nd-Sr同位素研究 |
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| 引用本文： | 沈渭洲,凌洪飞,王德滋,徐步台,俞云文.浙江省中生代火成岩的Nd-Sr同位素研究[J].地质科学,1999,34(2):223-232. |
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| 作者姓名： | 沈渭洲 凌洪飞 王德滋 徐步台 俞云文 |
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| 作者单位： | 1. 南京大学地球科学系 南京大学成矿作用国家重点实验室 南京 210093;2. 浙江省地质矿产研究所 杭州 310007;3. 浙江省区域地质调查大队 萧山 311200 |
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| 摘 要： | 本文报道了浙江省21个中生代火成岩的Nd-Sr同位素组成,其中火山岩的εNd值为-12.6——4.9,ISr值为0.70613-0.71079,tDM年龄为1945-1296Ma;花岗岩类的εNd值为-12.9——5.8,ISr值为0.70533-0.71208,tDM年龄为1900-1230Ma,表明两者具有相似的同位素组成。这种相似性在同一火山-侵入杂岩体中表现更为明显,意味着两者在时、空、源方面具有同一性。与扬子地块的相比,华夏地块的中生代火成岩具有较低的εNd值,较高的ISr值和较古老的Nd模式年龄,这种差异可能主要同这两个区域内基底变质岩在形成时代和成分上的差异有关。通过Sm-Nd同位素组成的对比研究,笔者认为,浙江境内的中生代火成岩可能主要是由基底变质沉积岩衍生的。原始岩浆的形成可能同中、下地壳岩石的熔融有关。
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| 关 键 词： | Nd-Sr同位素 物质来源 中生代火成岩 浙江省 |
| 收稿时间： | 1998-05-04 |
| 修稿时间： | 1998-05-04; |
STUDY ON Nd Sr ISOTOPES OF MESOZOIC IGNEOUS ROCKS IN ZHEJIANG,CHINA |
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| Shen Weizhou ,Ling Hongfei ,Wang Dezi ,Xu Butai ,Yu Yunwen.STUDY ON Nd Sr ISOTOPES OF MESOZOIC IGNEOUS ROCKS IN ZHEJIANG,CHINA[J].Chinese Journal of Geology,1999,34(2):223-232. |
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| Authors: | Shen Weizhou Ling Hongfei Wang Dezi Xu Butai Yu Yunwen |
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| Institution: | 1. Dept. of Earth Sciences and State Key Laboratory of Mineral Deposits, Nanjing University, Nanjing 210093;2. Institute of Geoolgy and Mineral Resources of Zhejiang, Hangzhou 310007;3. Regional Geological Survey, Bureau of Geology and Mineral Resources of Zhejiang, Xiaoshan 311200 |
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| Abstract: | Mesozoic magmatic activities were intensive in Zhejiang province.They occurred m ainly between early stage of Early Cretaceous and early stage of Late Cretaceous (135-90 Ma).Rocks formed by these magmas are distributed mainly in the Cathays ia massif which is at south to the Jiang-Shao Fault Zone.Nd Sr isotopic compositions of 21 Mesozoic igneous bodies are reported in this paper.The Nd-Sr isotopic compositions of the volcanic and granitic rocks are similar.The volcanic rocks have εNd of 12.6——-4.9,ISr of 0.70613——0.7069 and tDM age of 1945——1296Ma;while the granitic rocks have εNd of-12.9——5.8,ISr of 0.70533——0.71208 and tDM ages of 1900——1230Ma.These similarities are more evident between rocks in the same tectonic unit (Cathaysia massif or Yangtze Massif) or between rocks of the same volcanic intrusive complex (e.g. Tonglu complex or North Yan-dangshan complex).However,there are some differences in isotopic compositions of the Mesozoic igneous rocks from Cathaysia Massif to Yangtze massif.Igneous rocks in the Yangtze Massif have relatively small variation range in isotopic compositions,high εNd,low ISr and young Nd model ages, suggesting relatively high contents of mantle-derived components in their sources.While igneous rocks in the Cathaysia massif have relatively large variation in isotopic compositions,low εNd,high ISr and old model ages,implicating relatively complicated compositions and low contents of mantle-derived components in the sources.It is concluded that most of the Mesozoic igneous rocks in Zhejiang province were probaly derived from partial melting of meta-sedimentary rocks of the basement and only a few igneous rocks were derived from partial melting of meat-igneous rocks.In composition,the source material of the igneous rocks in Cathaysia massif were similar to the low mature meta-sedimentary rocks of Chencai Group,while those in Yangtze Massif were similar to meta-sedimentary rocks of Shuangxiwu Group. For the reasonstat (1) the igneous rocks have low εNd,high ISr and old Nd model ages; (2) from the coast towards the inland the igneous rocks have no regular variation in Nd-Sr isotopic compositions,therefore,the initial magma may have not been derived from the subducting plate or upper mantle,but derived from partial melting of rocks in middle-lower crust.The differences in isotopic compositions of these igneous rocks depend principally on the compositions of the deep crustal mateial from which the magmas were derived. |
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| Keywords: | Nd Sr isotopes Material sources Mesozoic igneous rocks Zhejiang province |
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