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Autochthonous origin of the Encruzilhada Block, Dom Feliciano Belt, southern Brazil, based on aerogeophysics, image analysis and PT-paths
Journal of Geodynamics ( IF 2.1 ) Pub Date : 2021-02-04 , DOI: 10.1016/j.jog.2021.101825
Giuseppe Betino De Toni , Maria de Fátima Bitencourt , Jiří Konopásek , Matheus Ariel Battisti , Elisa Oliveira da Costa , Jairo Francisco Savian

The Encruzilhada Block lies between the eastern hinterland and western foreland of the Dom Feliciano Belt (southern Brazil) and its tectonic meaning in the orogenic evolution of the belt is still poorly understood. Its low magnetic signal is similar to that of the foreland supracrustal sequences, whereas the high gammaspectrometric signal appears due to the hinterland post-collisional granitoids. Satellite image lineament analysis points to tectonic similarities between the Encruzilhada Block and the foreland, as the structures in both domains show predominantly NNW and NNE trends, while the hinterland mostly presents NE-trending structures. The pre-orogenic connection between the Encruzilhada Block and the foreland is indicated by the correlation between the Várzea do Capivarita and Cerro da Árvore complexes. Both contain 800 – 780 Ma metaigneous rocks with arc-like geochemistry, and parametamorphic rocks with similar sedimentary provenance. Common syn-orogenic deformation history of both complexes is suggested by progressive to P-T o-th E-W transpressive deformation and similar peak metamorphic age (660 – 640 Ma). PT-paths suggest exhumation of the hinterland Várzea do Capivarita Complex from high-T/low-P conditions of 790–820 °C/4.4–4.8 kbar to 660–720 °C/2.5–3.4 kbar at ca. 630 Ma. On the other hand, the foreland Cerro da Árvore Complex was subject to progressive metamorphism from 555 to 565 °C/5.4–5.7 kbar to 560–580 °C/5.8–6.3 kbar, which is interpreted as a result of orogenic thickening. Evidence suggests that both complexes have originated in a similar, if not a single, basin on an attenuated lithosphere with high geothermal gradient, possibly a (back-arc?) rift. Oblique collision has caused basin inversion and thrusting of the lower crust over the rift margin, which may have been accompanied by lithosphere delamination. Progressive transpressional deformation and voluminous post-collisional magmatism (640 – 578 Ma) controlled by major lineaments have blurred the original tectonic contact and finally caused thermal metamorphism in both complexes at ca. 3 kbar, when the autochthonous Encruzilhada Block was stabilized in its present geological configuration. The intracontinental character of major shear zones limiting hinterland and foreland requires a review of the existing evolutionary model for the Dom Feliciano Belt in the context of Western Gondwana amalgamation.



中文翻译:

基于航空地球物理学,图像分析和PT路径的巴西南部Dom Feliciano带Encruzilhada区块的自发起源

Encruzilhada地块位于Dom Feliciano带(巴西南部)的东部腹地和西部前陆之间,其构造意义在该带的造山演化中仍然鲜为人知。它的低磁信号类似于前陆超壳层序列,而高伽马能谱信号则是由于腹地碰撞后的花岗岩而出现的。卫星图像线质分析指出了恩库鲁兹哈达地块与前陆之间的构造相似性,因为这两个区域的结构都显示出主要的NNW和NNE趋势,而腹地则主要呈现NE趋势结构。恩祖鲁兹哈达地块与前陆之间的造山前联系由Várzeado Capivarita与Cerro daÁrvore复合体之间的相关性表明。两者都包含具有弧状地球化学特征的800 – 780 Ma变质岩和具有相似沉积物源的准变质岩。渐进性至PT oth EW超压变形和相似的峰值变质年龄(660 – 640 Ma)表明了这两种复合物的共同造山变形历史。PT路径表明腹地Várzeado Capivarita Complex的发掘温度从大约790–820°C / 4.4–4.8 kbar的高T /低P条件到大约660–720°C / 2.5–3.4 kbar。630毫安。另一方面,前陆Cerro daÁrvore复合体经历了从555到565°C / 5.4-5.7 kbar到560-580°C / 5.8-6.3 kbar的渐进变质作用,这被解释为造山带增厚的结果。有证据表明,这两种复合物都起源于地热梯度较高的衰减岩石圈中的相似盆地(如果不是单一盆地),可能是(后弧?)裂谷。斜向碰撞导致盆地倒转和裂谷边缘下地壳的逆冲作用,可能伴有岩石圈分层。受主要构造控制的渐进性压变形和大量的碰撞后岩浆作用(640 – 578 Ma)已经模糊了原始的构造接触,并最终导致了两个复合体的热变质。当土生的Encruzilhada区块稳定在目前的地质构造中时,压力为3 kbar。限制内陆和前陆的主要剪切带的洲内特征需要对西贡多瓦纳合并背景下的Dom Feliciano带的现有演化模型进行回顾。斜向碰撞导致盆地倒转和裂谷边缘下地壳的逆冲作用,可能伴有岩石圈分层。受主要构造控制的渐进性压变形和大量的碰撞后岩浆作用(640 – 578 Ma)已经模糊了原始的构造接触,并最终导致了两个复合体的热变质。当土生恩克鲁兹哈达区块稳定在目前的地质构造中时,压力为3 kbar。限制内陆和前陆的主要剪切带的洲内特征需要对西贡多瓦纳合并背景下的Dom Feliciano带的现有演化模型进行回顾。斜向碰撞导致盆地倒转和裂谷边缘下地壳的逆冲作用,可能伴有岩石圈分层。受主要构造控制的渐进性压变形和大量的碰撞后岩浆作用(640 – 578 Ma)已经模糊了原始的构造接触,并最终导致了两个复合体的热变质。当土生恩克鲁兹哈达区块稳定在目前的地质构造中时,压力为3 kbar。限制内陆和前陆的主要剪切带的洲内特征需要对西贡多瓦纳合并背景下Dom Feliciano带的现有演化模型进行回顾。由主要纹路控制的渐进压变形和大量的碰撞后岩浆作用(640 – 578 Ma)使原始构造接触变得模糊,并最终导致两个复合体的热变质。当土生恩克鲁兹哈达区块稳定在目前的地质构造中时,压力为3 kbar。限制内陆和前陆的主要剪切带的洲内特征需要对西贡多瓦纳合并背景下的Dom Feliciano带的现有演化模型进行回顾。受主要构造控制的渐进性压变形和大量的碰撞后岩浆作用(640 – 578 Ma)已经模糊了原始的构造接触,并最终导致了两个复合体的热变质。当土生的Encruzilhada区块稳定在目前的地质构造中时,压力为3 kbar。限制内陆和前陆的主要剪切带的洲内特征需要对西贡多瓦纳合并背景下的Dom Feliciano带的现有演化模型进行回顾。

更新日期:2021-02-15
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