| 中国东南部花岗岩类Nd—Sr同位素研究 |
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| 引用本文： | 沈渭洲,凌洪飞,李武显,黄小龙,王德滋.中国东南部花岗岩类Nd—Sr同位素研究[J].高校地质学报,1999,5(1):22-32. |
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| 作者姓名： | 沈渭洲 凌洪飞 李武显 黄小龙 王德滋 |
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| 作者单位： | 南京大学地球科学系 |
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| 摘 要： | 根据本文测定的５８个数据以已发表的１２７个数据讨论了中国东南部不同时代花岗岩类的Ｎｄ－Ｓｒ同位素特征，工通过与基底变质岩Ｓｍ－Ｎｄ同位素组成的对比，研究了这些花岗岩类的物质来源与成因。仅分布于浙西南的古元古代花岗岩娄是由成分上类似干被其侵入的八都群片麻岩经部分熔融形成的。沿江绍断裂带分布的新元古代花岗岩类是由地幔来源岩浆或初生地壳形成的；浙西－皖南－赣北地区的新元古代花岗岩类可能是由中元古代地层中的低成熟度组分形成的。古生代和大部分中生代花岗岩类主要是由所在区域内出露的中元古代变质沉积岩的相当物衍生的。沿浙闽沿海地区分布的大多数晚中生代花岗岩娄含有较多的地幔组分．两种来诹岩浆混台可能是其一种重要的成岩方式。
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| 关 键 词： | 花岗岩 Nd-Sr同位素 物质来源 中国东南部 |
| 收稿时间： | 1999-03-20 |
| 修稿时间： | 1999-03-20 |
STUDY ON THE Nd Sr ISOTOPIC COMPOSITIONS OF GRANITOIDS IN SE CHINA |
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| Shen Weizhou,Ling Hongfei,Li Wuxian,Huang Xiaolong,Wang Dezi.STUDY ON THE Nd Sr ISOTOPIC COMPOSITIONS OF GRANITOIDS IN SE CHINA[J].Geological Journal of China Universities,1999,5(1):22-32. |
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| Authors: | Shen Weizhou Ling Hongfei Li Wuxian Huang Xiaolong Wang Dezi |
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| Institution: | Department of Earth Sciences and State Key Laboratory of Mineral Deposit Research, Nanjing University, Nanjing 210093 |
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| Abstract: | Nd-Sr isotopic compositions of 58 granitoid bodies in SE China are reported in this paper. Based on these data and previously published isotopic compositions of other 127 granitoid bodies and comparison with Nd isotopic compositions of basement metamorphic rocks, we studied the Nd-Sr characteristics of granitoids of various ages in SE China and their sources. The Palaeoproterozoic grantoids are only distributed in southeastern Zhejiang province within the Cathaysia Block. These granitoids have εNd: -6.2 to-3.0 and initial 87Sr/86Sr ratio (Isr) of 0.7083 to
0.7l17. On the εNd-t diagram they are plotted within the evolution zone for the Palaeoproterozoic metamorphic rocks in the same region. This suggests that these Palaeoproterozoic granitoids be formed by partial melting of rocks similar to the Palaeopmterozoic metamorphic rocks.
The Neoproterozoic granitoids in SE China are distributed in the southeast margin of the Yangtze Block. The Neoproterozoic granitoids distributed along the Jiang-Shao Fau1t Zone have high εNd value (2.0 to 4.2), low Isr value(0.7011 to 0.7032) and low δ18O value(6.3 to 6.7‰) which are similar to those of middle Proterozoic spilite-keratophyre of Shuangxiwu Group. Therefore, these granitoids may have been derived from a mantle source similar to the source for the spilite-keratophyre, or from partial melting of juvenile crust consisting mainly of spillte-keratophyre. The Neoproterozoic granitoids in western Zhejiang, southern Anhui and northern Jiangxi provinces have εNd: -0.4 to -2.2, Isr=0.7040 to 0.7064 and δ18O=10.5 to 11.7‰. On εNd-t diagram, they are plotted in upper part of the evolution zone for the middle Proterzozic metasediments of the Shangxi Group and Shuangqiaoshan Group. This suggests that they be derived from the low maturity components of basement metamorphic rocks in this region.
Almost all Paleozoic granitoids are distributed in the Cathaysia Block. They have variable isotopic compositions (εNd= -18.1 to -2.1, Isr=0.7071 to 0.7287). On εNd-t diagram, most granitoids are plotted within the evolution zone for the middle Proterozoic basement metasediments, suggesting they be derived mainly from crustal materials. Mantle component was involved in formation of sonic Paleozoic granitoids.
Mesozoic granitoids are distributed all over SE China. Their isotopic compositions are evidently variable(εNd=-16.4 to 1.9, Isr=0.7043 to 0.7404). On εNd-t diagram, more than half of the granitoids are plotted above the evolution zone for the middle Proterozoic crust in the region, indicating their crustal derivation. However, many granitoids mainly distributed at the coast of Zhejiang and Fujian provinces are plotted above the evolution zone for the middle Proterozoic Crust in the region, suggesting more mantle-derived materials in their sources. These granitoids may have been formed by mixing of the basaltic magma induced by subduction of the Pacific Plate in the late Mesozoic era with the felsic magma formed during partial melting of crustal rocks caused by underplating of basaltic magma. |
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| Keywords: | granite Nd Sr isotopes material sources SE China |
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