Cuartel Ophiolite: Structure, timing and exhumation mechanisms for a Cadomian suture zone in the peri-Gondwanan Realm (SW Iberia)

IF 7.2 1区地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY

Gondwana Research Pub Date : 2024-10-09 DOI:10.1016/j.gr.2024.10.002

Diana Moreno-Martín , Rubén Díez Fernández , Richard Albert , Sonia Sánchez Martínez , Esther Rojo-Pérez , Axel Gerdes , Ricardo Arenas

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Abstract

The Cadomian Orogeny formed as an accretionary orogen surrounding Gondwana. The structure resulting from the Cadomian Orogeny is pervasively reworked during the Paleozoic, within the frame of the Variscan Cycle. In SW Iberia (Mina Afortunada Massif), a tectonometamorphic and geochronological analysis revealed two Cadomian deformation phases. The first phase (D_C1; 586 Ma, U-Pb dating in inherited metamorphic garnet from Mina Afortunada Gneiss) is associated with ophiolite accretion during the closure of a back-arc or intra-arc basin (Cuartel Ophiolite). A metamorphic fabric related to this phase is preserved as an internal foliation in Ediacaran (meta)sedimentary rocks. The second phase (D_C2; 515–485 Ma) is constrained by the age of the igneous protolith of Mina Afortunada Gneiss (∼515 Ma), which is affected by a penetrative foliation formed during D_C2, and by the unconformable deposit of Ordovician sediments, which are not affected. The telescoping of metamorphic isograds during D_C2 and the geometry of detachment faults associated with this phase suggest extensional tectonics as the driving mechanism for the early exhumation of the Cadomian suture zone in Mina Afortunada Massif. The superimposition of Variscan folds and shear zones onto the Cadomian structures contributed to the subsequent exhumation of the Cadomian suture zone. The analysis and reconstruction of Cadomian and Variscan structures, plus the geochronological data, allow us to correlate the Cuartel Ophiolite with the Mérida Ophiolite, being two pieces of the same, yet dismembered, Cadomian suture zone. The number of Cadomian suture zones in Gondwana does not coincide with that of Cadomian suture zone exposures. Reworked orogens such as the Cadomian could be subjected to duplication of their suture zones. Assessments regarding the Cadomian paleogeography should consider the multiplier effect of the structural overprints after ophiolite accretion.

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Cuartel蛇绿岩：近贡瓦南地块（伊比利亚西南部）卡多米安时期缝合带的结构、时间和掘起机制

卡多米造山带是围绕冈瓦纳形成的增生造山带。卡多米造山运动所形成的构造在古生代的瓦利斯坎周期框架内被普遍重塑。在伊比利亚西南部（Mina Afortunada Massif），构造变质和地质年代分析揭示了两个卡多米亚变形阶段。第一阶段（DC1；586 Ma，Mina Afortunada 片麻岩中的继承变质石榴石的 U-Pb 测定）与弧后或弧内盆地（Cuartel 蛇绿岩）关闭期间的蛇绿岩吸积有关。在埃迪卡拉（元）沉积岩中，与这一阶段有关的变质构造作为内部折线保存下来。第二阶段（DC2；515-485 Ma）受到米纳阿福图纳达片麻岩火成岩原岩（∼515 Ma）年龄的限制，该原岩受到 DC2 期间形成的穿透性褶皱的影响，同时也受到奥陶纪沉积物的不整合沉积的影响，该沉积物未受到影响。DC2期间变质等距线的伸缩以及与这一阶段相关的剥离断层的几何形状表明，延伸构造是Mina Afortunada地块卡多米期缝合带早期隆起的驱动机制。Variscan褶皱和剪切带叠加到Cadomian构造上，促进了Cadomian缝合带随后的隆起。通过分析和重建卡多米安构造和瓦里斯科构造，再加上地质年代数据，我们可以将夸特尔蛇绿岩和梅里达蛇绿岩联系起来，它们是同一条卡多米安缝合带的两个部分，但被肢解了。冈瓦纳的卡多米氏缝合带数量与卡多米氏缝合带出露的数量并不一致。像卡多米亚这样的重造造山带可能会出现缝合带重复的情况。在评估卡多米亚古地理时，应考虑蛇绿混杂岩增生后的构造叠加效应。

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来源期刊

Gondwana Research 地学-地球科学综合

CiteScore

12.90

自引率

6.60%

发文量

298

审稿时长

65 days

期刊介绍： Gondwana Research (GR) is an International Journal aimed to promote high quality research publications on all topics related to solid Earth, particularly with reference to the origin and evolution of continents, continental assemblies and their resources. GR is an "all earth science" journal with no restrictions on geological time, terrane or theme and covers a wide spectrum of topics in geosciences such as geology, geomorphology, palaeontology, structure, petrology, geochemistry, stable isotopes, geochronology, economic geology, exploration geology, engineering geology, geophysics, and environmental geology among other themes, and provides an appropriate forum to integrate studies from different disciplines and different terrains. In addition to regular articles and thematic issues, the journal invites high profile state-of-the-art reviews on thrust area topics for its column, ''GR FOCUS''. Focus articles include short biographies and photographs of the authors. Short articles (within ten printed pages) for rapid publication reporting important discoveries or innovative models of global interest will be considered under the category ''GR LETTERS''.