Ages of protolith and Neoproterozoic metamorphism of Al-P-bearing quartzites of the Veredas formation (Northern Espinhaço, Brazil): LA-ICP-MS age determinations on relict and recrystallized zircon and geodynamic consequences
Ages of protolith and Neoproterozoic metamorphism of Al-P-bearing quartzites of the Veredas formation (Northern Espinhaço, Brazil): LA-ICP-MS age determinations on relict and recrystallized zircon and geodynamic consequences
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Veredas 地层（巴西埃斯皮尼亚索北部）的原岩年龄和含铝磷石英岩的新元古代变质作用：残余锆石和重结晶锆石的 LA-ICP-MS 年龄测定以及地球动力学后果
DOI：
10.1016/j.precamres.2014.05.011
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发表时间：
2014
影响因子：
3.8
通讯作者：
Gerdes
中科院分区：
文献类型：
--
作者：
Morteani;Gerdes
位于巴西中东部弗朗西斯科克拉通的南北走向埃斯皮尼亚索褶皱带，沿着巴西-泛非（650-500 Ma）变形带帕拉米林走廊将该克拉通分为西部和东部。Espinhaço盆地的（Meta）沉积物由几个主要含硅质沉积物的沉积物组成。其中，北方Espinhaço的Veredas组富含Al和P的含蓝石英岩（相当于磷酸盐砂岩的角闪岩相）形成了一个明显的层位。锆石晶体从这些石英岩已使用激光烧蚀电感耦合等离子体质谱法。锆石晶体都是碎屑和变质的起源，后者表现出非常不寻常的纹理所产生的溶解-再沉淀反应和伴随的交代区：（REE，Y，Th，U）锆石+流体=锆石+磷钇矿。碎屑锆石显示3.1- 3.3Ga、2.6- 2.7Ga、2.0- 2.3Ga和1.5Ga的残余年龄组。因此，圣弗朗西斯科克拉通岩浆岩和变质岩的沉积和剥蚀结束时间可估计为≤ 1.5Ga。再沉淀锆石记录的主要变质事件为新元古代，其下截距年龄为634 ± 19 Ma，这是根据19个颗粒上单个点的分析计算的，其共同的残余Orosirian-Rhyacian年龄为2032 ± 31 Ma，时间相当于Transamazonian。Vereda组变质锆石的新元古代年龄对应于帕拉米林走廊内Espinhaço褶皱带东侧的圣弗朗西斯科-西刚果克拉通沿着的巴西-泛非再活动。
The N-S running Espinhaço fold belt, situated in the São Francisco craton in central-eastern Brazil, separates this craton in a western and an eastern part along the Paramirim Corridor, a Brasiliano-Panafrican (∼650–500 Ma) deformation zone. The (meta)sediments of the Espinhaço basin consist of several synthems with dominantly siliciclastic deposits. Among them, Al- and P-rich, lazulite-bearing blue quartzite, the amphibolite-facies equivalent of a phosphatic sandstone, of the Veredas Formation in the Northern Espinhaço form a conspicuous horizon. Zircon crystals from these quartzites have been dated using laser ablation inductively coupled plasma mass spectrometry. The zircon crystals are both detrital and metamorphic in origin, the latter exhibiting highly unusual textures produced by dissolution–reprecipitation reaction and concomitant replacement of metamict areas: (REE, Y, Th, U) zircon + fluid = zircon + xenotime. Detrital zircons reveal relict age groups of 3.1–3.3 Ga, 2.6–2.7 Ga, 2.0–2.3 Ga, and 1.5 Ga. The end of sedimentation and erosion of the magmatic and metamorphic rocks of the Sao Francisco craton can be estimated therefore as ≤1.5 Ga. The major metamorphic event recorded by reprecipitated zircon is Neoproterozoic and documented by a lower-intercept age of 634 ± 19 Ma, which was calculated from analyses of individual spots on19 grains with a common relict Orosirian-Rhyacian age of 2032 ± 31 Ma, temporal equivalent to Transamazonian. The Neoproterozoic age of the metamorphosed zircons of the Vereda formation corresponds to the Brasiliano-Panafrican remobilization of the São Francisco-West Congo craton along the eastern side of the Espinhaço fold belt in the Paramirim Corridor.
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