| 钾长石K—Ar定年若干问题的讨论 |
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| 引用本文： | 高晶晶,刘玉琳.钾长石K—Ar定年若干问题的讨论[J].高校地质学报,2006,12(3):375-377. |
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| 作者姓名： | 高晶晶 刘玉琳 |
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| 作者单位： | 北京大学造山带与地壳演化教育部重点实验室,地球与空间科学学院,北京100871 |
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| 基金项目： | 泰兆基金
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国家自然科学基金 |
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| 摘 要： | 现有的测试数据反映，钾长石在K—Ar定年中存在很多问题，最常见的情况是年龄值偏年轻，有时也出现比共存矿物年龄偏老的情况。钾长石在实验过程中不完全释氩是造成年龄值偏年轻的原因之一，对此前人已经提出几个解决方案，但在实际应用中都不够完善。钾长石的封闭温度低（130～150℃）是放射成因氩丢失的最主要因素，个别情况下也出现捕获围岩中的放射成因氩，从而出现过剩氩。低温钾长石（如冰长石）的氩保存能力和结构有关系，通常情况下随着三斜度的升高所保存的放射成因氩会相应减少。不同地质环境中产出的钾长石在K—Ar定年中适用性有所不同，侵入岩中的钾长石（微斜长石和条纹长石等）不适合于K—Ar定年，而喷出岩中的钾长石（透长石和歪长石等）是非常好的定年矿物；低温钾长石可有条件应用
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| 关 键 词： | 钾长石 K-Ar定年 应用条件 |
| 文章编号： | 1006-7493（2006）03-0375-03 |
| 收稿时间： | 2006-04-27 |
| 修稿时间： | 2006-06-10 |
Discussion on K-Ar Dating of K-feldspar |
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| GAO Jing-jing,LIU Yu-lin.Discussion on K-Ar Dating of K-feldspar[J].Geological Journal of China Universities,2006,12(3):375-377. |
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| Authors: | GAO Jing-jing LIU Yu-lin |
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| Institution: | Key Laboratory of Orogenic Belts and Crustal Evolution, MOE, China and Department of Geology, Peking University, Beijing 100871, China |
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| Abstract: | K-feldspar, a ubiquitous mineral in igneous and metamorphic rocks, has long been used in K-Ar dating. However, a number of problems exist in K-Ar dating of K-feldspar. For example, K-feldspar usually yields younger ages than the co-existed minerals such as biotite. K-feldspar may also yield older ages in some cases. It is suggested that incomplete extraction of radiogenic argon from K-feldspar is one of the main reasons that leads to a younger age. Several solutions have been put forward to resolve the problem, but none of them has been successfully used in experiments. K-feldspar has low closure temperature （about 130 -150℃ ）, which can easily cause radiogenic argon lose; In addition, radiogenic argon from the wall rock as excess argon may also enter the K- feldspar. The low temperature K-feldspar （such as adularia ） shows capability to maintain various amounts of radiogenic argon which is related to their textures. The content of radiogenic argon in adularia is decreased with the increase of their triclinities. In summary, the applicabilities of K-feldspars from different geological environments are various in K-Ar dating. K-feldspars （such as micro cline and perthite） from intrusive rocks can not be used in K-Ar dating, while those （sanidine and anorthoclase） from extrusive rocks are very good ones, and the low temperature K-feldspars （adularia） can be used in dating conditionally |
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| Keywords: | K-feldspar K-Ar dating application |
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