ABSTRACT The petrography, detrital zircon age distribution and 40Ar–39Ar ages of three samples from the Nagurskaya drill core of westernmost Franz Josef Land have been analyzed and are compared to similar rocks from the Lomonosov Ridge. The analyzed rocks, from near the base of the drill hole, consist of fine-grained psammitic to semipelitic schists, metamorphosed under greenschist-facies conditions. They are lithologically very similar to the recently analyzed metasediments from the Lomonosov Ridge. The detrital zircon age spectra of the samples from both the Lomonosov Ridge and beneath Franz Josef Land span the Meso- to Palaeoproterozoic with a main peak around 1.6 Ga, similar to lower Neoproterozoic metasedimentary rocks in East Greenland, on Svalbard and northern Norway, as well as from Cambrian sediments in Estonia and Silurian–Devonian sediments on Novaya Zemlya. Biotite in metasedimentary rocks from the Nagurskaya drill core indicate an Early Devonian 40Ar–39Ar metamorphic age of c. 400 Ma, possibly superimposed on an earlier, Ordovician history similar to that of the metasediments from the Lomonosov Ridge at 470 Ma. Previously published 40Ar–39Ar analyses of Nagurskaya muscovite yielded c. 600 Ma ages, characteristic of the Timanian Orogen. Together with the new biotite data, these isotope ages favor the interpretation that the Caledonian suture is located between Svalbard and Franz Josef Land, and the Caledonian deformation front between the latter and Novaya Zemlya.

中文翻译：

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法兰士约瑟夫地变沉积物的加里东变质作用

摘要 对来自弗朗兹约瑟夫地最西端 Nagurskaya 钻芯的三个样品的岩相学、碎屑锆石年龄分布和 40Ar-39Ar 年龄进行了分析，并与来自罗蒙诺索夫海岭的类似岩石进行了比较。分析的岩石来自钻孔底部附近，由细粒砂岩到半泥质片岩组成，在绿片岩相条件下变质。它们在岩性上与最近分析的罗蒙诺索夫海岭变质沉积物非常相似。罗蒙诺索夫海岭和弗朗兹约瑟夫地下方样品的碎屑锆石年龄谱跨越中古元古代，主峰约 1.6 Ga，类似于东格陵兰、斯瓦尔巴群岛和挪威北部的新元古代变沉积岩，以及来自爱沙尼亚的寒武纪沉积物和新地岛的志留系-泥盆纪沉积物。来自 Nagurskaya 钻芯的变质沉积岩中的黑云母表明早泥盆世 40Ar–39Ar 变质年龄为 c。400 Ma，可能叠加在更早的奥陶纪历史上，类似于 470 Ma 来自罗蒙诺索夫海岭的变质沉积物的历史。先前发表的 Nagurskaya 白云母的 40Ar–39Ar 分析结果为 c。600 Ma 年龄，蒂曼尼亚造山带的特征。连同新的黑云母数据，这些同位素年龄支持加里东缝合线位于斯瓦尔巴群岛和弗朗兹约瑟夫地群岛之间的解释，以及位于后者和新地岛之间的加里东变形前缘。400 Ma，可能叠加在更早的奥陶纪历史上，类似于 470 Ma 来自罗蒙诺索夫海岭的变质沉积物的历史。先前发表的 Nagurskaya 白云母的 40Ar–39Ar 分析结果为 c。600 Ma 年龄，蒂曼尼亚造山带的特征。连同新的黑云母数据，这些同位素年龄有利于解释加里东缝合线位于斯瓦尔巴群岛和弗朗兹约瑟夫地之间，而加里东变形前沿位于后者和新地岛之间。400 Ma，可能叠加在更早的奥陶纪历史上，类似于 470 Ma 来自罗蒙诺索夫海岭的变质沉积物的历史。先前发表的 Nagurskaya 白云母的 40Ar–39Ar 分析结果为 c。600 Ma 年龄，蒂曼尼亚造山带的特征。连同新的黑云母数据，这些同位素年龄有利于加里东缝合线位于斯瓦尔巴群岛和弗朗兹约瑟夫地之间的解释，以及后者和新地岛之间的加里东变形前沿。