| 大别山石马地区石榴黑云片麻岩的Sm-Nd、K-Ar年龄及冷却速率 |
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| 引用本文： | 李曙光,肖益林,刘德良.大别山石马地区石榴黑云片麻岩的Sm-Nd、K-Ar年龄及冷却速率[J].地质科学,1995,30(2):174-182. |
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| 作者姓名： | 李曙光 肖益林 刘德良 |
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| 作者单位： | 中国科学技术大学地球与空间科学系, 合肥230026 |
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| 摘 要： | 南大别地体中榴辉岩的围岩──石榴黑云片麻岩具有角闪岩相变质矿物组合,其变质温度为525℃,Sm-Nd矿物等时线年龄为(229±3)Ma.黑云母的K-Ar封闭温度为300℃,相应K-Ar年龄为(231±5)Ma.因此该片麻岩在230Ma左右从525℃迅速冷却到300℃以下。然而该区榴辉岩在印支期(221Ma)变质温度为700℃左右,直到134Ma才降至400-450℃。说明该区榴辉岩与该片麻岩具有不同的冷却史。它不支持榴辉岩是原地(in situ)成因的。
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| 关 键 词： | 榴辉岩 高压变质作用 同位素定年 冷却速率 大别山 |
| 收稿时间： | 1993-01-11 |
| 修稿时间： | 1993-01-11; |
Sm-Nd AND K-Ar AGES OF GARNET-BIOTITE GNEISS FROM THE SHIMA AREA,DABIE MOUNTAINS AND ITS COOLING RATE |
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| Li Shuguang,Xiao Yilin,Lion Deliang.Sm-Nd AND K-Ar AGES OF GARNET-BIOTITE GNEISS FROM THE SHIMA AREA,DABIE MOUNTAINS AND ITS COOLING RATE[J].Chinese Journal of Geology,1995,30(2):174-182. |
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| Authors: | Li Shuguang Xiao Yilin Lion Deliang |
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| Institution: | Department of Earth and Space Science, University of Science and Technology of China, Hefei, Anhui 230026 |
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| Abstract: | Garnet-biotite gneiss from the Shima area, south Dabie terrane represents the country rock of ecologites in this area. Its mineral assemblage suggests an amphibolite factes conditions. Application of the garnet-biotite geothermometer yields a temperature of 525℃ for the garnet-biotite gneiss. Its Sm-Nd mineral isochron age is 229± 3 Ma. The K-Ar closure temperature for biotite is about 300℃. Biotite from the same sample gives a K-Ar age of(231±5)Ma. Consequently, the garnet-biotite gneiss experienced metamorphism of amphibolite factes at 230 Ma, then rapidly cooled down to 300℃. In contrast, eclogites from the same area experienced metamorphism of eclogite factes during Triassic(221 Ma), and experienced metamorphism of amphibolite factes by 134 Ma. These suggest that eclogites and their country rock(garnet-biotite gneiss)in the Shima area have different cooling history and thermal state. These results do not support the “in situ” origin of the eclogites in the Shima area. |
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| Keywords: | Dabie Mountains High pressure metamorphism Isotopic dating Cooling rate Eclogite origin |
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