Early Paleoproterozoic supracrustal assemblages of the Rae domain, Nunavut, Canada: Intracratonic basin development during supercontinent break-up and assembly
Early Paleoproterozoic supracrustal assemblages of the Rae domain, Nunavut, Canada: Intracratonic basin development during supercontinent break-up and assembly
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DOI：
10.1016/j.precamres.2010.06.005
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发表时间：
2010-08
影响因子：
3.8
通讯作者：
R. Rainbird;W. Davis;S. Pehrsson;N. Wodicka;N. Rayner;T. Skulski
中科院分区：
文献类型：
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作者：
R. Rainbird;W. Davis;S. Pehrsson;N. Wodicka;N. Rayner;T. Skulski
加拿大北方丘吉尔省的古元古代基底表壳岩系包括覆盖在太古代Rae和Hearne域之上的沉积盆地。Rae域表壳序列（如Amer群、Ketyet河群、Chantrey群和Montresor群）由4个岩石构造组合组成，在上升地层位置上，它们包括：（1）以新太古代碎屑锆石为主的浅海-河流相石英砂岩，（2）以碳酸盐岩±镁铁质火山岩流为主的浅海相石英砂岩，（3）以新太古代碎屑锆石为主的浅海相石英砂岩，（4）以碳酸盐岩±镁铁质火山岩流为主的浅海相石英砂岩，（5）以碳酸盐岩±镁铁质火山岩流为主的浅海相石英砂岩。（3）盆地暗色页岩和上覆台地状碳酸盐岩的突然整合过渡，向上进入粉砂岩和砂岩，记录了台地的逐渐出露。该组合中的砂岩显示出明显不同的碎屑锆石物源特征，以早古元古代锆石为主，年龄为1.95Ga;（4）不整合至整合覆盖的未成熟海相砂岩，包括浊积岩，其中2.0-1.9Ga碎屑组分可能来自本地和远源的组合。基底岩石构造组合1的厚度和相对成分成熟度记录了缓慢沉降但稳定的超大陆（如Kenorland）上长期的风化增强。其次是镁铁质火山作用和海侵，与部分裂谷的Rae域和地壳伸展出席超大陆解体（岩石构造组合2）。岩石构造组合3的地层记录了沿伸展大陆块体边缘沿着台地沉积的盆地洪水和加深。组合4被解释为代表沉积在前陆盆地在早期融合劳伦蒂亚（努纳的一部分）在约。1.9Ga.赫尔维茨群的地层学和碎屑锆石地质年代学，覆盖在赫恩域，大致类似于表壳序列的雷域，但不同的是通过存在的基础杂岩和缺乏2.5Ga碎屑，一个主要的本地来源的雷。我们的数据表明，Rae和Hearne域组装在一起的最大。1.91Ga（即最大值最高的Hurwitz和Amer组的沉积年龄）。丘吉尔省的古元古代地层组合格架与其他地区的古元古代地层组合格架具有很好的可比性，这些古元古代地层组合格架是由凯诺兰的分裂产生的，并最终在努纳合并而成。劳伦蒂亚的例子包括覆盖在上级省南部边缘的表壳岩（南部省，例如休伦超群、阿尼基群、马奎特岭超群、白水群和米斯塔西尼-奥蒂斯群）。南部和丘吉尔省的古元古代组合具有一级地层相似性，表明它们都经历了稳定的大陆沉积，然后是裂谷、盆地打开和盆地关闭。
The basal Paleoproterozoic supracrustal succession of the Churchill Province in northern Canada comprises sedimentary basins overlying the Archean Rae and Hearne domains. The Rae domain supracrustal succession (e.g. Amer, Ketyet River, Chantrey and Montresor groups) comprises four lithotectonic assemblages which include, in ascending stratigraphic position: (1) shallow marine-fluvial quartzarenite with mainly Neoarchean detrital zircons of local provenance; (2) shallow marine quartzarenite with mainly local provenance that locally includes carbonates±mafic volcanic flows; (3) abrupt but conformable transition to basinal dark shales and overlying platformal carbonates that pass upward into siltstones and sandstones that record gradual emergence of the platform. Sandstones within this assemblage display a substantially different detrital zircon provenance signature dominated by early Paleoproterozoic zircons, with grains as young as 1.95Ga; (4) unconformably to conformably overlying immature marine sandstones, including turbidites, with a significant component of 2.0–1.9Ga detritus probably derived from a combination of local and distal sources. The thickness and relative compositional maturity of the basal lithotectonic assemblage 1 records a protracted period of enhanced weathering on a slowly subsiding but stable supercontinent (e.g. Kenorland). This was followed by mafic volcanism and marine transgression, consistent with partial rifting of the Rae domain and crustal extension attending supercontinent break-up (lithotectonic assemblage 2). Strata of lithotectonic assemblage 3 record basin flooding and deepening followed by platformal sedimentation along the margins of extended continental blocks. Assemblage 4 is interpreted to represent deposition in foreland basins during early amalgamation of Laurentia (part of Nuna) at ca. 1.9Ga. The stratigraphy and detrital zircon geochronology of the Hurwitz Group, which overlies the Hearne domain, is broadly similar to the supracrustal sequence of the Rae domain, but differs through the presence of basal diamictites and lack of 2.5Ga detritus, a major local source in the Rae. Our data suggest that the Rae and Hearne domains were assembled together by max. 1.91Ga (i.e. max. age of deposition of the uppermost Hurwitz and Amer groups). The Paleoproterozoic stratigraphic assemblage framework for the Churchill Province compares well with that of other cratons derived from break-up of Kenorland and ultimately amalgamated in Nuna. Examples from Laurentia include supracrustal rocks that overlie the southern margin of the Superior Province (Southern Province, e.g. Huron Supergroup, Animikie Group, Marquette Range Supergroup, Whitewater Group and Mistassini-Otish Group). The Paleoproterozoic assemblages of the Southern and Churchill provinces exhibit first-order stratigraphic similarities that indicate a shared history of stable continental sedimentation followed by rifting, basin opening and basin closure.