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首页> 外文期刊>Brazilian Journal of Geology >Lithogeochemistry of the meta-igneous units from Arroio Grande Ophiolitic Complex, southernmost Brazil
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Lithogeochemistry of the meta-igneous units from Arroio Grande Ophiolitic Complex, southernmost Brazil

机译：巴西最南端的Arroio Grande蛇绿岩复合体的亚火成岩单元的岩石地球化学

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Ophiolites are defined as slices of genetically-related upper mantle serpentinized peridotites and oceanic crustal rocks, tectonically displaced from its primary igneous origin of formation by plate convergence and associated (meta) sedimentary rocks of marine origin. From this premise, a meta-ultramafic-mafic-sedimentary complex (Cr-rich magnesian schists - upper mantle or crustal ultramafic cumulate candidates; epidote amphibolites, metadiorites and metagabbros - oceanic crust candidates; metasedimentary schists, quartzites and marbles - marine sedimentary rocks candidates), located in southeastern Dom Feliciano Belt (southernmost Brazil), started to be interpreted as possible slices of an ophiolitic complex related to the closure of a paleo-ocean during Brasiliano/Pan-African orogenic cycle and was called Arroio Grande Ophiolitic Complex. The present research fills the lack of geochemical data from previous studies and tests the hypothesis of an oceanic setting for the meta-igneous units of this complex from a lithogeochemistry point of view. The meta-ultramafics were interpreted as peridotites (mantle or crustal cumulates) that were subsequently serpentinized (probably in the ocean floor) and posteriorly metasomatized (probably in a continental setting). The meta-mafics were interpreted as oceanic gabbros/basalts formed in a back-arc basin. The results, together with field relationships, rock associations and petrographic evidences, support an oceanic origin for the protoliths of the meta-igneous units. The hypothesis that these rocks represent metamorphosed slices of an ophiolitic complex is still the most reasonable one. This work updates the geologic knowledge of the area and supports discussions about the evolution of Dom Feliciano Belt and Western Gondwana paleocontinent.
机译：蛇绿岩被定义为与遗传有关的上地幔蛇纹化橄榄岩和海洋地壳岩石的切片，它们通过板块汇聚和相关的（成因）海洋成因沉积岩从构造上从其主要火成岩成因地移位。从这个前提出发，形成了一个超铁质-镁铁质-沉积物复合体（富铬镁质片岩-上地幔或地壳超镁铁质累积候选物;附生的闪石，变闪石和变质辉长岩-大洋地壳候选物;沉积的片岩，石英岩和大理石-海洋沉积岩候选物）位于巴西最南端的Dom Feliciano带东南部，开始被解释为与Brasiliano / Pan-African造山周期中古海洋的封闭有关的片岩复合体的可能切片，被称为Arroio Grande蛇绿复合体。本研究填补了先前研究缺乏的地球化学数据，并从岩地球化学的角度测试了该复合物的亚火成岩单元的海洋环境假设。后超音阶学被解释为橄榄岩（地幔或地壳累积物），随后被蛇形化（可能在海床中）并后变质（可能在大陆环境中）。这些超基性岩体被解释为在后弧盆地中形成的洋辉石/玄武岩。研究结果，加上田间关系，岩石关联和岩石学证据，为亚火成岩单元的原生质提供了海洋起源。这些岩石代表一种卵石质复合体变质层的假说仍然是最合理的。这项工作更新了该地区的地质知识，并支持有关Dom Feliciano Belt和Gondwana Western古大陆演化的讨论。

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