| 库鲁克塔格基性岩墙群K—Ar等时年龄测定及其有关问题讨论 |
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| 引用本文： | 刘玉琳,张志诚,郭召杰,黄宝玲,穆志国.库鲁克塔格基性岩墙群K—Ar等时年龄测定及其有关问题讨论[J].高校地质学报,1999,5(1):54-58. |
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| 作者姓名： | 刘玉琳 张志诚 郭召杰 黄宝玲 穆志国 |
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| 作者单位： | 北京大学地质学系 |
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| 基金项目： | 国家“九五”重点科技攻关资助 |
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| 摘 要： | 新疆库鲁克塔格基性岩墙群的四个样品的Ｋ－Ａｒ表观年龄为４５５－６７３Ｍａ，等时年龄为２８７±１３Ｍａ。这一年龄与近几年报道的沿天山构造带的早二叠世火山岩年龄一致。氩初始值为５０８，在Ｐ型岩浆范围内，结合稀土、微量元素特征，认为岩墙群与地幔热柱有成因联系。
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| 关 键 词： | 库鲁克塔格 基性岩墙群 等时年龄 氩初始值 地幔热柱 |
| 收稿时间： | 1999-03-20 |
| 修稿时间： | 1999-03-20 |
K Ar ISOCHRON DATING OF KULUKTAG MAFIC DYKES, XINJIANG AUTONOMOUS REGION,
AND DISCUSSION ON SOME RELATED QUESTIONS |
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| Liu Yulin,Zhang Zhicheng,Guo
Zhaojie,Huang Baoling and Mu Zhiguo.K Ar ISOCHRON DATING OF KULUKTAG MAFIC DYKES, XINJIANG AUTONOMOUS REGION,
AND DISCUSSION ON SOME RELATED QUESTIONS[J].Geological Journal of China Universities,1999,5(1):54-58. |
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| Authors: | Liu Yulin Zhang Zhicheng Guo
Zhaojie Huang Baoling and Mu Zhiguo |
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| Institution: | Department of Geology, Peking University 100871 |
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| Abstract: | There has been increasing interest in the study of dyke swarms which are related to rifting and continental break-up. Ku1uktag dyke swarms are located in the northeast part of Tarim Basin, Xinjiang, China. The dykes, parallel to each other, intruded into the Archaean and early Proterozoic rocks. Four samples collected from the dykes are dated with K-Ar method. The apparent ages are discordant, ranging from 455 to 673 Ma. Using the Ludwing’s ISOPLOT, an isochron age of 287± 13 Ma was obtained with a correlation cotfficicent of 0.9850, This age is concordant with the ages of volcanic rocks along the Tianshan Mt. structure zone dated around
280Ma.
The K-Ar isochrom method has some advantage for dating mafic dykes：(1)These rocks are often fresh and slightly affected by alteration; (2) The closure temperature of mafic rocks for argon is high; (3) The measurement precision of mass spectrometer is much higher than it was before, so that low K samples can be well measured; The potassium abundance of mafic dykes is about 0.5-1.5％ and suitable for K-Ar dating; (4) The whole rock method is used, so that the tough work of selecting monomineral fraction is not necessary. Moreover, the initial argon can be eliminated by this method, but the atmospheric argon must be removed in the experimental process.
Igneous rocks originated from different sources have different initial argon ratios. The initial argon ratio for Kuluktag dykes is 508, belonging to mantle plume-type according to Kaneoka and Takaoka(1985). We infer that the magma of the dykes originated from “enriched mantle”. The REE and trace elements features of the dykes am also typical of “enriched mantle” and are in good agreement with those of basalts related to plume. |
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| Keywords: | mafic dykes K Ar isochron age 40 Ar/ 36 Ar initial ratio mantle plume |
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