| 大别山北缘中生代火山—侵入岩铅同位素组成特征及其地质意义 |
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| 引用本文： | 杨祝良,沈渭洲.大别山北缘中生代火山—侵入岩铅同位素组成特征及其地质意义[J].高校地质学报,1999,5(4):384-389. |
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| 作者姓名： | 杨祝良 沈渭洲 |
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| 作者单位： | [1]南京地质矿产研究所 [2]南京大学地球科学系和成矿作用国家重点实验室 |
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| 基金项目： | 原地质矿产部地质调查局地调专项!(地科专 96 3 2 )，教育部博士点基金资助项目 |
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| 摘 要： | 大别山北缘中生代火山－侵入岩的１４个夺铅同位素组成表现为高的非放射性成因＾２０４Ｐｂ，较低的＾２０６Ｐｂ／＾２０４Ｐｂ比值和低且相对一致的＾２０７Ｐｂ／＾２０４Ｐｂ比值，属于明显的低Ｕ／Ｐｂ体系，并暗示它们由具低μ值的源岩衍生的。
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| 关 键 词： | 铅同位素 火山－侵入岩 中生代 大别山北缘 |
| 收稿时间： | 1999-12-20 |
| 修稿时间： | 1999-12-20 |
LEAD ISOTOPIC COMPOSITION AND ITS GEOLOGICAL SIGNIFICANCE FOR MESOZOIC VOLCANO-INTRUSIVE ROCKS FROM THE NORTHERN MARGIN OF DABIE MOUNTAINS |
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| Yang Zhuliang , Shen Weizhou Xie Fanggui Tao Kuiyuan Shen Jialin.LEAD ISOTOPIC COMPOSITION AND ITS GEOLOGICAL SIGNIFICANCE FOR MESOZOIC VOLCANO-INTRUSIVE ROCKS FROM THE NORTHERN MARGIN OF DABIE MOUNTAINS[J].Geological Journal of China Universities,1999,5(4):384-389. |
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| Authors: | Yang Zhuliang Shen Weizhou Xie Fanggui Tao Kuiyuan Shen Jialin |
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| Institution: | 1．Najing Institute of Geology and Mineral Resources，Nanjing 210016; 2．Department of Earth Sciences and State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing, 210093 |
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| Abstract: | This paper presents 14 whole rock lead-lead isotopic compositions，contents of U, Th and Pb and hence the calibrated Pb isotopic composition of Mesozoic volcano-intrusive rocks from the northern margin of Dabieshan Mt．These rocks have relatively high 204Pb(1.371-1.439％, averaging 1.411％), low206Pb/204Pb ratios(15.975-17.363, averaging 16.713), slightly varied 207Pb/204Pb ratios(15.305-15.537, averaging 15.422)and varied 208Pb/204Pb ratios(36.856-38.816, averaging 37.500). It suggests that these rocks were derived from a source of low μ values which was mainly related to the basement metamorphic rocks with obvious U loss during intermediate to high grade metamorphism. Comparative studies with published regional lead isotopic data show that they are to a great extent similar to the feldspar- lead isotopic composition of the Mesozoic granitoids from Dabie Block within Dabie-Jiaonan
subprovince and generally have the lead isotopic characteristics of North China plate. In view of rock series of the research region, we found that, except basaltic andesite from Shangcheng, the shoshonitic series have the highest content of 204Pb and the lowest ratios of Pb isotopes (204Pb= l.438-1.439, 206Pb/204Pb=15.975-16.010, 207Pb/204Pb= 15.349-15.442 and 208Pb/204Pb =36.873-36.931); the alkaline series have the lowest content of 204Pb and the highest ratios of Pb isotopes(204Pb=1.385-1.387, 206P/204Pb= 17.308- 17.363, 207Pb/204Pb= 15.494-15.537and 208Pb/204Pb= 37.984-38.088); while the high-potassium cale-alkaline series have the intermediate content and ratios (204Pb= 1.415-1.427, 206Pb/204Pb= 16.385-16.621, 207Pb/204Pb= 15.305-15.435 and 208Pb/204Pb= 36.965-37.487). These indicate that the source of these three different rock series re quite different in forming age and nature. Compared with those of the other samples,the basaltic andesite samples from Shangcheng, Henan Province were of abnormal lead isotopic compositions(204Pb= 1.371, 206Pb/204Pb= 17.307-17.315, 207Pb/204Pb= 15.405-15.419 and 208Pb/204Pb= 38.738 -38.816).It can be inferred that the source was of distinct Th-enrichment character. |
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| Keywords: | lead isotope volcano-intrusive rocks Mesozoic northern margin of Dabieshan Mt |
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