Neoproterozoic and Cambrian arc magmatism along the eastern margin of the Victoria Lake Supergroup: A remnant of Ganderian basement in central Newfoundland?
Neoproterozoic and Cambrian arc magmatism along the eastern margin of the Victoria Lake Supergroup: A remnant of Ganderian basement in central Newfoundland?
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DOI：
10.1016/j.precamres.2006.01.025
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发表时间：
2006-07
影响因子：
3.8
通讯作者：
N. Rogers;C. V. Staal;V. Mcnicoll;Jeffrey Pollock;A. Zagorevski;J. Whalen
中科院分区：
文献类型：
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作者：
N. Rogers;C. V. Staal;V. Mcnicoll;Jeffrey Pollock;A. Zagorevski;J. Whalen
复合的、构造复杂的维多利亚湖超群的东缘先前已被绘制为志留系罗杰逊湖砾岩不整合地覆盖在寒武纪Tally Pond火山岩上的地方。然而，认识到这种接触的形式在不整合和脆韧性断裂之间变化，结合克里普尔贝克侵入岩套的新元古代时代，决定了上述对该边缘性质的解释需要修正。这些差异通过识别新元古代以双峰式为主的火山岩序列(沙溪群)而得到解决，该火山岩序列东面被罗杰森湖岩石不整合地覆盖，这些组合单元与西面的Tally Pond群断层接触。沙溪群和克里普尔贝克侵入岩套形成了一个约563 Ma的岩石地体，具有大陆弧状的地球化学特征。该地体长英质岩石的ɛNd563值明显为负(平均−3)，这意味着它来自一个结晶基底，它比西阿瓦洛尼亚同生火山岩下的主要是泛非地壳更古老，但与甘德带的推断相似。因此，该地体很可能是冈德瓦周缘微大陆Ganderia的前缘。约511 Ma的Tally Pond群弧岩浆活动代表了纽芬兰爱彼特俯冲的一些最古老的产物。尽管塔里湖群只与距今约5000万年的桑迪溪群有断层接触，但长英质火山岩的高比例、桑迪河/克里普尔巴克年龄继承的锆石和铅同位素数据都支持塔里塘群是在桑迪河/克里普尔巴克大陆地壳上形成的。
The eastern margin of the composite and structurally complex Victoria Lake Supergroup has previously been mapped where the Silurian Rogerson Lake conglomeratic rocks unconformably overlie Cambrian Tally Pond volcanic rocks. However, the recognition that the form of this contact changes between an unconformity and a brittle-ductile fault, in conjunction with the Neoproterozoic age of the Crippleback Intrusive Suite, dictate that the above interpretation of the nature of this margin requires revision. These discrepancies are resolved by the recognition of a Neoproterozoic, largely bimodal volcanic sequence (Sandy Brook Group), which is unconformably overlain by Rogerson Lake rocks to the east, with these combined units in fault contact with the Tally Pond Group to the west. The Sandy Brook Group and Crippleback Intrusive Suite form a terrane of ca. 563Ma rocks with continental arc-like geochemical signatures. The distinctly negative ɛNd,563values for the felsic rocks (mean −3) of this terrane imply derivation from a crystalline basement older than the largely Pan-African crust that underlies contemporaneous volcanic rocks in West Avalonia, but similar to that inferred for the Gander Zone. Thus this terrane is likely to be the leading edge of the peri-Gondwanan microcontinent Ganderia. The ca. 511Ma Tally Pond Group arc magmatism represent some of the oldest products of Iapetean subduction in Newfoundland. Although the Tally Pond Group are only observed to be in fault contact with the ca. 50 million year older Sandy Brook Group, the high proportion of felsic volcanic rocks, Sandy Brook/Crippleback age inherited zircons and Pb isotopic data all support the inference that the Tally Pond Group was formed on Sandy Brook/Crippleback continental crust.