The São Francisco paleocontinent comprises Archean nuclei and Paleoproterozoic magmatic arcs which were amalgamated during Siderian to Orosirian thermal-tectonic events (ca. 2.4–2.0 Ga). Located in the Porteirinha domain, one of these Archean segments, the Riacho dos Machados metavolcanosedimentary sequence encompasses metamafites and metaultramafites intercalated with metasedimentary rocks. The metamafites clustered in the Type I category are tholeiitic, present MORB-like affinities and flat REE patterns with enrichment in La, Rb, and Cs. The metamafites from Type II are calc-alkaline, showing arc signatures with enrichment in LILE (Cs, Ba, U, Rb, K) and LREE, and depletion in the HFSE. The associated metaultramafites were classified as high-Mg ultramafic rocks similar to Barberton-Type komatiites, with enrichment in LILE and LREE, Al₂O₃/TiO₂< 16 and Gd/Yb_(N) > 1. U–Pb (LA–SF–ICP-MS) zircon analyses were carried out on the Type II hornblendite, unraveling a concordant crystallization age of 2071 ± 9 Ma. Inherited zircons yield a discordant age of 2922 ± 22 Ma and a lower intercept at 473 ± 48 Ma. The hybrid magmatism of the studied metamafites coupled with the inherited zircon grains, indicate that this metavolcanosedimentary sequence was developed in an intra-continental back-arc basin. The rocks from Type I have been originated from MORB-like source with a slightly input of subduction-derived fluids. In its turn, Type II samples represent melts more influenced by the fluids from the dehydrated slab. This assumption implies that the São Francisco paleocontinent, in the region of the Porteirinha block and surroundings, were under an accretionary stage at the late Rhyacian. During this orogenic process the metamorphic PT conditions reached lower-amphibolite facies. Moreover, this thermal-tectonic event in likely responsible for the auriferous fluid percolation of the Riacho dos Machados Gold Mine.

圣弗朗西斯科古大陆包括太古代核和古元古代岩浆弧，它们在Siderian至Orosirian热构造事件（约2.4–2.0 Ga）期间合并。Riacho dos Machados中火山岩沉积序列位于这些太古宙岩段之一的Porteirinha区域中，其中包括变质沉积岩和嵌有准沉积岩的美托拉菲岩。聚类在I型类别中的超物质是可塑性的，呈现出类似于MORB的亲和力和平坦的REE模式，并富含La，Rb和Cs。来自II型的超物质是钙碱性的，显示出具有丰富的LILE（Cs，Ba，U，Rb，K）和LREE以及富含HFSE的电弧特征。与巴伯顿型科马铁矿相似，伴生的亚铁陨石被分类为高镁超镁铁质岩，富含LILE和LREE，Al₂ O ₃ / TiO ₂ <16和Gd / Yb _（N） > 1.在II型角闪石上进行了U–Pb（LA–SF–ICP-MS）锆石分析，揭示了2071±9 Ma的一致结晶年龄。继承的锆石产生的年龄不一致，为2922±22 Ma，较低的截距为473±48 Ma。研究的超大型熔岩的混合岩浆作用与遗传的锆石颗粒相结合，表明该超火山岩沉积序列是在大陆内部的后弧盆地发育的。类型I的岩石起源于类似MORB的烃源，并带有少量的俯冲衍生流体。反过来，II型样品代表受脱水平板流体影响更大的熔体。这一假设表明，Porteirinha地块和周围地区的圣弗朗西斯科古大陆在Rhyacian晚期处于增生阶段。在造山过程中，变质的PT条件达到了较低的闪石相。此外，这种热构造事件很可能是造成Riacho dos Machados金矿的耳孔渗流的原因。