...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Contributions to Mineralogy and Petrology >Timing of magmatism and metamorphism in the Gruinard Bay area of the Lewisian Gneiss Complex: comparison with the Assynt Terrane and implications for terrane accretion-reply
【24h】

Timing of magmatism and metamorphism in the Gruinard Bay area of the Lewisian Gneiss Complex: comparison with the Assynt Terrane and implications for terrane accretion-reply

机译：刘易斯片麻岩复合体格鲁纳德湾地区的岩浆作用和变质作用的时机：与Assynt地形的比较及其对地形增生-回复的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Corfu urges us to keep discussions more firmly rooted in "the reality". Unfortunately, no individual has a monopoly on "the reality". We all emphasize different aspects of a complex reality according to our experience and prejudices. Whereas Corfu et al. (1998) concluded that their age data were consistent with longstanding conventional concepts envisaging "major crustal accretion of the entire Lewisian complex during plate convergence, tectonism and widespread magmatism in the period 2850-2700 Ma ...", we have concluded from our age data (e.g. Friend and Kinny 2001) that the complex represents a collage of accreted terranes of differing age and early history. In order to resolve these two alternative realities, we need to examine the origins of the different data sets further. The strengths and weaknesses of TIMS and SIMS approaches to zircon U-Pb geochronology have been discussed at length elsewhere, and in simple geological scenarios both methods yield ages that agree to within error. When results disagree and neither analyst nor equipment is technically at fault (neither is at issue here), the complexity of the geological scenario is to blame, manifest in the isotopic complexity of the zircon populations sampled at the different analytical scales. A technically perfect analysis of a mixed age domain is likely to result in ambiguity regardless of the analytical method employed. TIMS age data comes with spectacular analytical precision which tends to lull the non-specialist into a false sense of security when ages are quoted. Nevertheless, interpretations of TIMS age data are based on comparatively few data points, which in complex populations have a high likelihood of representing average compositions of multiple domains. Extrapolation errors can be large. SIMS age data come with comparatively low analytical precision for individual data points which can mask fine age structure and slight discordance. This is well illustrated in Corfu's Fig. la which highlights the size of SIMS error boxes for extremely low U domains. However, with many more points analysed of much smaller volumes, SIMS can yield a more complete picture of the range of isotopic subdomains in the population and, through cathodoluminescence (CL) imaging, comes with detailed documentation of the analysed sites. As Corfu has reiterated, our understanding of what the isotopic domains in complex zircon crystals really mean, and our ability to link age dates to specific geological events and structures, are imperfect. The zircon populations from the high-grade rocks of the Assynt and Gruinard terranes of the Lewisian Gneiss Complex are as complex as any we have dealt with. It is not surprising that their interpretation has proven contentious.
机译：科孚岛敦促我们使讨论更加牢固地扎根于“现实”。不幸的是，没有人能垄断“现实”。根据我们的经验和偏见，我们都强调复杂现实的不同方面。而科孚岛等。 （1998年）得出结论，他们的年龄数据与长期的传统观念相一致，即“在2850-2700 Ma的板块汇聚，构造和广泛的岩浆作用期间整个刘易斯复合体的主要地壳增生”，我们从我们的年龄得出结论。数据（例如Friend和Kinny 2001），该复合体代表了不同年龄和早期历史的增生地的拼贴。为了解决这两个替代现实，我们需要进一步检查不同数据集的起源。 TIMS和SIMS锆石U-Pb地质年代学方法的优缺点已经在其他地方详细讨论过，在简单的地质情况下，两种方法得出的年龄都在误差范围内。当结果不一致时，无论是分析师还是设备都没有技术过失（此处都不存在问题），应归咎于地质情况的复杂性，表现为以不同分析规模采样的锆石种群的同位素复杂性。无论采用哪种分析方法，对混合年龄域进行技术上完美的分析都可能导致歧义。 TIMS年龄数据具有出色的分析精度，当引用年龄时，倾向于使非专业人士陷入一种错误的安全感。然而，对TIMS年龄数据的解释是基于相对较少的数据点，在复杂的人群中，该数据点很有可能代表多个域的平均组成。外推误差可能很大。 SIMS年龄数据对单个数据点的分析精度较低，这可能掩盖了精细的年龄结构和轻微的不一致。这在Corfu的图1a中得到了很好的说明，该图突出显示了针对极低U域的SIMS错误框的大小。但是，通过对体积较小的更多点进行分析，SIMS可以得出种群中同位素亚域范围的更完整图片，并且通过阴极发光（CL）成像，可以提供被分析位点的详细文档。正如科孚（Corfu）重申的那样，我们对复杂锆石晶体的同位素域真正含义的理解以及我们将年龄数据与特定地质事件和结构联系起来的能力是不完善的。 Lewisian片麻岩复合体的Assynt和Gruinard地表的高级岩石中的锆石种群与我们所处理的一样复杂。事实证明，他们的解释引起争议。

著录项

相似文献

  • 外文文献
  • 中文文献
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号