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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Implications of pre-eruptive magmatic histories of zircons for U-Pb geochronology of silicic extrusions
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Implications of pre-eruptive magmatic histories of zircons for U-Pb geochronology of silicic extrusions

机译：锆石的喷发前岩浆史对硅质挤压的U-Pb年代学的意义

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Zircons in silicic magmas begin to crystallize 10's to 100's of thousands of years (ka) prior to their eruption. U/Pb and U/Th dating for zircons from 32 young extrusions indicate a range of mean pre-eruption ages from similar to 33 to 247 ka, with a median of 92 ka. Explosive large volume (widespread) eruptions show a narrower range and a younger median of 70 ka. These results indicate that the difference between initial zircon growth and eruption age measured by other (e.g., Ar-40/Ar-39) techniques is in excess of the achievable analytical uncertainty for eruptions <30 million years (Ma), and likely for eruptions of up to 300 Ma. Protracted pre-eruption zircon growth is well established by an increasing number of studies on magma process time scales, but this source of eruption age bias has been largely ignored in chronostratigraphic applications of high-precision U/Pb data. Until intrinsic properties of zircons or their host deposits enable a priori estimates of pre-eruption age bias, it is prudent to expand the uncertainties attending all U/Pb zircon ages interpreted as deposition ages (in e.g., chronostratigraphic studies) by +0/-200 ka. (c) 2007 Elsevier B.V. All rights reserved.
机译：硅质岩浆中的锆石在喷发前已经开始结晶十到几百年（ka）。来自32个年轻挤压的锆石的U / Pb和U / Th日期表明，平均喷发前年龄范围从33到247 ka，中位数为92 ka。爆炸性的大爆炸（散布）表明射程更窄，中值更年轻，为70 ka。这些结果表明，其他锆石（如Ar-40 / Ar-39）技术测量的初始锆石生长与喷发年龄之间的差异超过了<3000万年（Ma）的喷发可达到的分析不确定性，并且可能对喷发而言高达300 Ma。越来越多的岩浆过程时间尺度研究很好地证明了火山爆发前锆石的长期生长，但是在高精度U / Pb数据的年代地层应用中，这种火山爆发年龄偏差的来源已被很大程度上忽略。在锆石或其宿主沉积物的内在特性能够对喷发前年龄偏差进行事前估计之前，谨慎的做法是将所有被解释为沉积年龄（例如年代地层研究）的U / Pb锆石年龄的不确定性扩大+ 0 /- 200 ka。 （c）2007 Elsevier B.V.保留所有权利。

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