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首页> 外文期刊>Journal of South American earth sciences >Hydrothermal alteration related to a deep mantle source controlled by a Cambrian intracontinental strike-slip fault: Evidence for the Meruoca felsic intrusion associated with the Transbraziliano Lineament. Northeastern Brazil
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Hydrothermal alteration related to a deep mantle source controlled by a Cambrian intracontinental strike-slip fault: Evidence for the Meruoca felsic intrusion associated with the Transbraziliano Lineament. Northeastern Brazil

机译：与由寒武纪大陆内部走滑断层控制的深地幔源有关的热液蚀变：与横贯巴西布拉诺系的梅洛卡长英质侵入有关的证据。巴西东北部

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摘要

One of the most prominent geological structures in Borborema Province, northeast Brazil, is the Transbraziliano Lineament that crosscuts most of the South American Platform and was active at least until the Devonian. This continental structure is responsible for the formation of rift and pull-apart basins in Northeastern Brazil, most of which filled with volcanic and continental sedimentary rocks (Parente et al., 2004). In the region of Sobral, Ceara State, this same continental structure controlled the intrusion of the Meruoca pluton and the formation of the Jaibaras Basin, which is bounded by strike-slip shear zones. Hydrothermal alterations seem to have been pervasive in Meruoca, as indicated by disturbances in both the Rb-Sr and U-Pb systems (Sial et al., 1981; Fetter, 1999) and by the large dispersion of anisotropic magnetic susceptibility (AMS) (Archanjo et al., 2009). In this paper, we address the origin of the hydrothermal fluids that affected the borders of the Meruoca batholith and their relationship with the activity of the Transbraziliano Lineament. These fluids were responsible for carbonate veins and Fe—Cu mineral concentrations that are commonly found associated with hydrothermally altered breccias. The carbon and oxygen isotope composition of these carbonate veins suggest that they may be related to C02-bearing mantle-derived fluids that were channelized by the Transbraziliano Lineament. Based on oxygen isotopes, we argue that Fe-Cu concentrations may have formed in isotope equilibrium with the rhyolitic rocks at temperatures between 500 and 560 °C. This scenario points to magmatism as the main process in the formation of these rocks. We also report a K-Ar age of 530 ± 12 Ma for muscovite associated with the last ductile event that affected the Sobral-Pedro II Shear Zone and a U-Pb age of 540.8 ± 5.1 Ma for the Meruoca pluton. We further suggest that this granite is a late-kinematic intrusion that is most likely associated with the Parapui volcanic rocks of the Jaibaras basin (535.6 ± 8.5 Ma, Garcia et al., 2010).
机译：Transbraziliano Lineament是巴西东北部Borborema省最著名的地质构造之一，横穿了大部分南美平台，并且至少活跃到泥盆纪。这种大陆性结构导致了巴西东北部裂谷盆地和拉脱盆地的形成，其中大部分充满了火山岩和大陆沉积岩（Parente等，2004）。在塞阿拉州的索布拉尔地区，这种大陆性结构控制了梅洛卡岩体的侵入和以走滑剪切带为边界的贾巴拉斯盆地的形成。 Ru-Sr和U-Pb系统的扰动（Sial等，1981; Fetter，1999）以及各向异性磁化率（AMS）的大范围分散表明，梅洛卡州普遍存在热液蚀变（（ Archanjo等，2009）。在本文中，我们解决了影响梅洛卡岩床边界的热液的起源及其与跨布拉齐利亚诺线型活动的关系。这些流体是造成碳酸盐矿脉和Fe-Cu矿物质浓度的原因，而碳酸盐矿脉和Fe-Cu矿物质浓度通常与水热改变的角砾岩有关。这些碳酸盐岩脉的碳和氧同位素组成表明，它们可能与由Transbraziliano Lineament引导的含CO2的地幔衍生流体有关。基于氧同位素，我们认为在500至560°C的温度下，与流纹岩的同位素平衡中可能已形成Fe-Cu浓度。这种情况表明岩浆作用是这些岩石形成的主要过程。我们还报告了白云母的K-Ar年龄为530±12 Ma，与最后一次影响Sobral-Pedro II剪切带的延性事件有关，Meruoca岩体的U-Pb年龄为540.8±5.1 Ma。我们进一步认为，该花岗岩是晚期运动学侵入体，很可能与Jaibaras盆地的Parapui火山岩有关（535.6±8.5 Ma，Garcia等，2010）。

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