Late Neoproterozoic amphibolite-facies metamorphism of a pre-Caledonian basement block in southwest Wedel Jarlsberg Land, Spitsbergen: new evidence from U–Th–Pb dating of monazite
Late Neoproterozoic amphibolite-facies metamorphism of a pre-Caledonian basement block in southwest Wedel Jarlsberg Land, Spitsbergen: new evidence from U–Th–Pb dating of monazite
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DOI：
10.1017/s001675680800530x
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发表时间：
2008-09
影响因子：
2.3
通讯作者：
J. Majka;S. Mazur;M. Manecki;J. Czerny;D. Holm
中科院分区：
文献类型：
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作者：
J. Majka;S. Mazur;M. Manecki;J. Czerny;D. Holm
斯匹次卑尔根群岛西南部的韦德尔雅尔斯贝格地由两个变质历史不同的元古代地壳块体组成。两个地块都经历了加里东期绿片岩相变质作用，但只有南部地块记录了更早的普遍M1角闪岩相变质作用和强烈的变形组构。原位EMPA独居石全铅年代学研究表明，M1变质作用发生在643 ± 9 Ma，与已发表的c. 620 Ma（角闪石）和580 Ma（云母）。因此，该地区包含了岩石地层剖面和变质历史，这是斯瓦尔巴群岛内唯一的。普遍晚新元古代巴罗变质作用的文件是很难调和的静态非构造政权通常推断这一地区，根据发生的裂谷漂移序列的波罗的海和劳伦特被动边缘。相反，我们的新的变质年龄意味着一个外来的起源前泥盆纪基底暴露在西南斯匹次卑尔根和支持模型的Svalbard群岛假定的Svalbard装配。
Abstract Southwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic crustal blocks with differing metamorphic histories. Both blocks experienced Caledonian greenschist-facies metamorphism, but only the southern block records an earlier pervasive M1 amphibolite-facies metamorphism and strong deformational fabric. In situ EMPA total-Pb monazite geochronology from both matrix and porphyroblast inclusion results indicate that the older M1 metamorphism occurred at 643 ± 9 Ma, consistent with published cooling ages of c. 620 Ma (hornblende) and 580 Ma (mica) obtained from these same rocks. This region thus contains a lithostratigraphic profile and metamorphic history which are unique within the Svalbard Archipelago. Documentation of a pervasive late Neoproterozoic Barrovian metamorphism is difficult to reconcile with a quiescent non-tectonic regime typically inferred for this region, based on the occurrence of rift-drift sequences on the Baltic and Laurentian passive margins. Instead, our new metamorphic age implies an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen and supports models of terrane assembly postulated for the Svalbard Archipelago.