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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq supracrustal belt, northern Quebec
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Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq supracrustal belt, northern Quebec

机译：来自魁北克北部Nuvvuagittuq地壳带的3750年前Ma地壳岩

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摘要

Geochemistry and U-Pb ion microprobe zircon geochronology guided by high-resolution mapping (1:50 scale) was used to define a minimum age of ca. 3750 Ma for supracrustal rocks from the Nuvvuagittuq supracrustal belt (NSB) in the northern Superior Province, Quebee (Canada). Mineralogy and geochemistry of critical field relationships preserved at the Porpoise Cove locality describe a supracrustal succession of (mafic) amphibolites and ultramafic rocks, finely banded quartz-magnetite units with intermixed coarse-grained ferruginous quartz-pyroxene rocks and quartz-biotite schists that superficially resemble polymict metaconglomerates with large (up to 10 cm) deformed polycrystalline quartz and mafic clasts. All units in the mapped outcrop have sharp lithological contacts. Narrow (dominantly trondhjemitic) orthogneiss sheets locally preserve intrusive contact relationships to the supracrustals. The total extent of the supracrustal enclave is similar to 8 km(2); it is strongly deformed and the full deformation history appears to be shared by all units with later modifications from leucogranitoid intrusions. The quartz-biotite schists record complex zircon growth at similar to 3500 and similar to 2800 Ma, interpreted to reflect metamorphic events. Zircons separated from orthogneisses in the enclave - including one sheet that transects a banded quartz-pyroxene (+/- magnetite) unit - yield magmatic Pb-207/Pb-206 ages of ca. 3750 Ma. These ages are slightly younger than earlier provisional reports for an NSB orthogneiss from Porpoise Cove. The Nuvvuagittuq supracrustals are the oldest rocks thus far reported for the Minto Block, they overlap in age with the ca. 3.70-3.83 Ga Isua supracrustal belt and Akilia association rocks in West Greenland, and they represent an important new area for exploration of the early Earth. (c) 2006 Elsevier B.V All rights reserved.
机译：地球化学和U-Pb离子微探针锆石地质年代学由高分辨率制图（1:50比例尺）指导，用于定义ca的最小年龄。来自北部优越省魁北克（加拿大）的Nuvvuagittuq上壳带（NSB）的上壳岩3750 Ma。 Porpoise Cove地区保存的关键场关系的矿物学和地球化学描述了（镁铁质）角闪石和超镁铁质岩的表壳层序，带状石英-磁铁矿单元与粗粒状铁质石英-辉石岩和石英-黑云母片岩混合聚变巨砾岩，具有大（最多10厘米）变形的多晶石英和镁铁质碎屑。映射露头中的所有单元都具有尖锐的岩性接触。狭窄的（主要是斜生的）斜生片在局部保持与上壳的侵入性接触关系。上飞地的总范围与8 km（2）相似。它发生了强烈的变形，所有变形单元似乎都共享了完整的变形历史，后来又因白粉刺侵入而进行了修改。石英黑云母片岩记录了复杂的锆石生长，其生长速率接近3500 Ma，接近2800 Ma，被解释为反映了变质事件。在飞地中从原片麻岩中分离出的锆石-包括一个横切带状石英-辉石（+/-磁铁矿）单元的薄片-产生的岩浆Pb-207 / Pb-206年龄大约为。 3750毫安。这些年龄比Porpoise Cove的NSB直立性片麻岩的早期临时报告要年轻。 Nuvvuagittuq上壳岩是迄今为止报告的Minto区块最古老的岩石，它们的年龄与ca重叠。 3.70-3.83西格陵兰的Ga Isua上壳带和Akilia联合岩石，它们代表了早期地球探索的重要新领域。 （c）2006 Elsevier B.V保留所有权利。

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