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首页> 外文期刊>Contributions to Mineralogy and Petrology >U-Pb and Hf isotopic analysis of zircon in lower crustal xenoliths from the Navajo volcanic field: 1.4 Ga mafic magmatism and metamorphism beneath the Colorado Plateau
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U-Pb and Hf isotopic analysis of zircon in lower crustal xenoliths from the Navajo volcanic field: 1.4 Ga mafic magmatism and metamorphism beneath the Colorado Plateau

机译：纳瓦霍火山场下地壳异质岩中锆石的U-Pb和Hf同位素分析：科罗拉多高原以下1.4 Ga镁铁质岩浆作用和变质作用

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摘要

Zircon from lower crustal xenoliths erupted in the Navajo volcanic field was analyzed for U-Pb and Lu-Hf isotopic compositions to characterize the lower crust beneath the Colorado Plateau and to determine whether it was affected by approx 1.4 Ga granitic magmatism and metamorphism that profoundly affected the exposed middle crust of southwestern Laurentia. Igneous zircon in felsic xenoliths crystallized at 1.73 and 1.65 Ga, and igneous zircon in mafic xenoliths crystallized at 1.43 Ga. Most igneous zircon has unradiogenic initial Hf isotopic compositions (epsilon_(Hf)= +4.1- +7.8) and 1.7-1.6 Ga depleted mantle model ages, consistent with 1.7-1.6 Ga felsic protoliths being derived from "juvenile" Proterozoic crust and 1.4 Ga mafic protoliths having interacted with older crust. Metamorphic zircon grew in four pulses between 1.42 and 1.36 Ga, at least one of which was at granulite facies. Significant variability within and between xenoliths in metamorphic zircon initial Hf isotopic compositions (epsilon_(Hf)= - 0.7 to +13.6) indicates growth from different aged sources with diverse time-integrated Lu/Hf ratios. These results show a strong link between 1.4 Ga mafic magmatism and granulite facies metamorphism in the lower crust and granitic magmatism and metamorphism in the exposed middle crust.
机译：分析了纳瓦霍火山场喷出的下地壳异质岩中的锆石的U-Pb和Lu-Hf同位素组成，以表征科罗拉多高原以下的下地壳，并确定其是否受到约1.4 Ga花岗岩岩浆作用和变质作用的影响西南劳伦西亚的裸露中地壳。镁铁质异质岩中的火成锆石结晶于1.73和1.65 Ga，镁铁质异质岩中的火成锆石结晶于1.43 Ga。大多数火成锆石具有不辐射的初始Hf同位素组成（ε_（Hf）= + 4.1- +7.8）和1.7-1.6 Ga贫化地幔模型年龄，与从“幼”元古代地壳中获得的1.7-1.6 Ga镁铁质原始岩和与较早地壳相互作用的1.4 Ga镁铁质原始岩相一致。变质锆石在1.42和1.36 Ga之间以四个脉冲生长，其中至少一个处于粒岩相。变质锆石初始Hf同位素组成（epsilon_（Hf）=-0.7至+13.6）中异种体内部和之间的显着变异性表明不同年龄的Lu / Hf比值不同的衰老源的生长。这些结果表明，下地壳的1.4 Ga铁镁质岩浆作用与花岗石相变质与裸露的中地壳的花岗质岩浆作用和变质之间有很强的联系。

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