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首页> 外文期刊>Brazilian Journal of Geology >Age, provenance and tectonic setting of the high-grade Jequitinhonha Complex, Ara?§ua?- Orogen, eastern Brazil
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Age, provenance and tectonic setting of the high-grade Jequitinhonha Complex, Ara?§ua?- Orogen, eastern Brazil

机译：巴西阿拉奥拉州奥罗根的高级Jequitinhonha建筑群的年龄，物源和构造环境

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The Jequitinhonha Complex of the northeastern Ara?§ua?- orogen is an extensive sedimentary unit metamorphosed in the amphibolite-granulite facies transition around 580-545 Ma. The unit consists of Al-rich (kinzigitic) paragneisses with decametric intercalations of graphite gneisses and quartzites, and centimetric to metric lenses of calcsilicate rocks. A new detrital zircon U-Pb age spectrum is reported for a sample of quartzite, and whole-rock geochemical (major and trace elements, 9 samples) and Sm-Nd isotope data (10 samples) for Jequitinhonha Complex paragneiss. Together with published data these show that: (1) the geochemistry of paragneiss samples of the Jequitinhonha Complex are similar to those of passive margin sedimentary protoliths; (2) detrital zircon data yield U-Pb age populations between ca. 0.9 and 2.5 Ga; and (3) Sm-Nd T DM model ages range from 1.6 to 1.8 Ga and ?μNd (575 Ma) around -7.5. The data reveal a mixture of Cryogenian to Mesoproterozoic rift-related igneous rocks with the Palaeoproterozoic-Archaean basement rocks of the S?￡o Francisco-Congo palaeocontinent as the main source areas, and also support the correlation between the Jequitinhonha Complex and the passive margin units of the upper Maca?obas Group, constituting the precursor basin of the orogen. Our results, with the absence of ophiolites in the Jequitinhonha Complex, reinforce the interpretation that the S?￡o Francisco-Congo palaeocontinent was not divided to the north of the focused region, suggesting an ensialic termination of a gulf during the Neoproterozoic.
机译：东北Ara？uaua-造山带的Jequitinhonha复合体是一个广泛的沉积单元，在580-545 Ma左右的闪石-粒状相转变中变质了。该单元由富含铝的（扭结）石蜡和石墨片麻岩和石英岩的十度夹层构成，以及钙硅酸盐岩石的百分度到公制度数。据报道，Jequitinhonha Complex paragneiss的一个石英岩样品，全岩石地球化学（主要和微量元素，9个样品）和Sm-Nd同位素数据（10个样品）的新碎屑锆石U-Pb年龄谱。连同已公开的数据，这些结果表明：（1）Jequitinhonha复杂区的石蜡样品的地球化学与被动边缘沉积原岩的地球化学相似; （2）碎屑锆石数据可得出大约介于的U-Pb年龄种群。 0.9和2.5 Ga; （3）Sm-Nd T DM模型的年龄范围为1.6至1.8 Ga，？μNd（575 Ma）约为-7.5。数据显示，低温-中元古代裂谷相关的火成岩与圣弗朗西斯科-刚果古大陆的古元古代-Archaean基底岩混合为主要来源，也支持了Jequitinhonha复杂体与被动缘之间的相关性。 Macaobabas组上部的单元，构成造山带的前兆盆地。我们的研究结果表明，在Jequitinhonha情结中没有蛇绿岩，这进一步说明了弗朗西斯科－刚果刚果古大陆未在受关注区域的北部划分的现象，这表明在新元古代发生了一条巨大的海湾封端。

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