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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Well-preserved Late Paleoproterozoic volcanic centers in the Sao Felix do Xingu region, Amazonian Craton, Brazil
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Well-preserved Late Paleoproterozoic volcanic centers in the Sao Felix do Xingu region, Amazonian Craton, Brazil

机译：位于巴西亚马孙克拉顿的圣菲利克斯·杜新古地区保存完好的古元古代晚期火山中心

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摘要

The Amazonian craton in the Sao Felix do Xingu city, southeast region of the Para state, north of Brazil, hosts exceptionally well-preserved Paleoproterozoic bimodal magmatic units grouped in the Sobreiro and Santa Rosa formations. These formations are correlated to the Uatuma magmatic event, which is largely distributed in the Amazonian craton occupying more than 1,500,000 km~2. Geological mapping and petrographical observations reveal distinct spectra of volcanic facies in both formations. The basal calc-alkaline Sobreiro Formation is composed mainly of andesitic and dacitic lava flows and associated volcaniclastic facies of autoclastic origin, with subordinate pyroclastic flow deposits. This formation shows inferred eruption style that is similar to those in Flood Basalt Provinces, with rare scutulum-type lava shields. The upper A-type Santa Rosa Formation was generated by multicyclic explosive and effusive episodes predominantly associated with large fissures and is materialized by voluminous ignimbrites with subordinated ash-fall tuff, crystal tuff, lapilli-tuff, co-ignimbritic breccias, rhyolitic dikes and domes, and associated granitic porphyries and equigranular granitic intrusions. Ignimbrite and rhyolite dikes reveal conspicuous vertical flow pattern pointing to a fissure-controlled eruption, similar to Sierra Madre Occidental ignimbrite province. The proposed evolutionary model for the Sao Felix do Xingu units differs from those of other occurrences related to the Uatuma magmatic event in the Amazonian craton, characterized by predominance of A-type volcanism and contemporaneous granites.
机译：位于巴西北部帕拉州东南部的圣菲利克斯·德·新古市的亚马逊河克拉通拥有保存完好的古元古代双峰岩浆单元，这些岩体分布在Sobreiro和Santa Rosa地层中。这些地层与Uatuma岩浆事件有关，后者主要分布在亚马逊克拉通中，占地超过1,500,000 km〜2。地质测绘和岩石学观测揭示了两种地层中火山相的独特光谱。钙基碱性索布雷罗地层主要由安第斯山脉和达喀什熔岩流以及自碎屑起源的相关火山碎屑相组成，并具有次生碎屑流沉积物。这种岩层显示出与洪水玄武岩省类似的推断喷发样式，带有罕见的盾片型熔岩盾。上层A型圣罗莎组是由主要与大裂缝相关的多周期爆炸性和喷发性事件形成的，并由大量火山灰伴有灰烬凝灰岩，结晶凝灰岩，青金石凝灰岩，共燃烧角砾岩，流纹岩堤和穹顶形成，以及相关的花岗岩斑岩和等粒花岗岩侵入体。火成岩和流纹岩堤坝显示出明显的垂直流型，指向裂隙控制的喷发，类似于塞拉马德雷（Sierra Madre Occidental）西方火成岩省。拟议的圣菲利克斯-杜新古单元演化模型与其他与亚马逊克拉通Uatuma岩浆事件有关的事件的演化模型不同，其特征是A型火山作用和同期花岗岩为主。

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