Abstract Collisional orogens are one of the most conspicuous features of plate tectonics on Earth. They record the dynamics of continent-continent amalgamation, often confined to linear deformational belts. The Southern Brasilia Orogen is one of the most well-studied and complete orogens of West Gondwana. Newly obtained isotopic data, coupled with previously published analyses, expand the occurrence of metamorphosed passive margin sequences (maximum depositional age of ~900 Ma), with a main source in the Sao Francisco paleocontinent, to large sections of the orogen previously interpreted, by some investigators, as related to younger active margin deposits. This has implications for the location of the suture zone: as most of the upper and lower nappes are dominated by metamorphosed passive margin deposits, the suture is probably located at the base of the uppermost nappe, related to the active margin (Paranapanema paleocontinent). Zircon (U Pb and Lu Hf) and whole-rock (Sm Nd and geochemistry) data obtained for syn-collisional meta-graywackes (~650–630 Ma), that uncomformably overlie passive-margin-related successions, point to a bimodal provenance from both the passive (Sao Francisco paleocontinent) and active (Paranapanema paleocontinent) margins, depending on the structural level from which the samples were collected. Despite the conspicuous zircon age differences, the maximum depositional age is the same for samples from the upper and the lower nappes. Furthermore, the meta-graywackes from the lower and upper nappes are petrographically and geochemically similar. This suggests concomitant deposition in a common collisional setting. Two metamorphic ages were obtained by U Pb monazite dating at ~633 and 606 Ma, indicating that protracted medium-grade metamorphic conditions affected the Southern Brasilia Orogen.

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被动边缘和同碰撞单元的来源：对巴西利亚造山带、西冈瓦纳盆地地球动力学演化的影响

摘要 碰撞造山带是地球板块构造最显着的特征之一。他们记录了大陆-大陆融合的动力学，通常仅限于线性变形带。巴西利亚南部造山带是西冈瓦纳大陆研究最充分、最完整的造山带之一。新获得的同位素数据，加上先前发表的分析，将主要来源在圣弗朗西斯科古大陆的变质被动边缘序列（最大沉积年龄约 900 Ma）的发生扩大到先前由一些人解释的造山带的大部分调查人员，与年轻的活跃保证金存款有关。这对缝合带的位置有影响：由于大部分上、下推覆以变质被动边缘沉积物为主，缝合线可能位于最上层推覆的基部，与活动边缘（Paranapanema 古大陆）有关。锆石（U Pb 和 Lu Hf）和全岩（Sm Nd 和地球化学）数据为同碰撞元灰岩（~650-630 Ma）获得，它们不合规地覆盖在被动边缘相关的序列上，指向双峰出处来自被动（圣弗朗西斯科古大陆）和活动（帕拉纳帕内马古大陆）边缘，这取决于收集样本的结构水平。尽管锆石年龄差异明显，但上下推覆岩样品的最大沉积年龄相同。此外，来自下推覆体和上推覆体的元灰岩在岩石学和地球化学上是相似的。这表明在共同的碰撞环境中伴随沉积。