The Rio Piranhas-Seridó Domain, Borborema Province, Northeastern Brazil: Review of geological-geochronological data and implications for stratigraphy and crustal evolution

Abstract. The depth-dependent anisotropic structure of the lithosphere under the Borborema Province in northeast Brazil has been investigated via harmonic stripping of receiver functions developed at 39 stations in the region. This method retrieves the first (k=1) and second (k=2) degree harmonics of a receiver function dataset, which characterize seismic anisotropy beneath a seismic station. Anisotropic fabrics are in turn directly related to the deformation of the lithosphere from past and current tectonic processes. Our results reveal the presence of anisotropy within the crust and the lithospheric mantle throughout the entire province. Most stations in the continental interior report consistent anisotropic orientations in the crust and lithospheric mantle, suggesting a dominant northeast–southwest pervasive deformation along lithospheric-scale shear zones developed during the Brasiliano–Pan-African orogeny. Several stations aligned along a northeast–southwest trend located above the (now aborted) Mesozoic Cariri–Potiguar rift display large uncertainties for the fast-axis direction. This non-azimuthal anisotropy may be related to a complex anisotropic fabric resulting from a combination of deformation along the ancient collision between Precambrian blocks, Mesozoic extension and thermomechanical erosion dragging by sublithospheric flow. Finally, several stations along the Atlantic coast reveal depth-dependent anisotropic orientations roughly (sub)perpendicular to the margin. These results suggest a more recent overprint, probably related to the presence of frozen anisotropy in the lithosphere due to stretching and rifting during the opening of the South Atlantic.

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Geochronological data from TTG-type rock associations of the Arroio dos Ratos Complex and implications for crustal evolution of southernmost Brazil in Paleoproterozoic times

Journal of South American Earth Sciences ◽

10.1016/j.jsames.2014.11.009 ◽

2015 ◽

Vol 57 ◽

pp. 49-60 ◽

Cited By ~ 27

Author(s):

Tiago Rafael Gregory ◽

Maria de Fátima Bitencourt ◽

Lauro Valentim Stoll Nardi ◽

Luana Moreira Florisbal ◽

Farid Chemale

Keyword(s):

Crustal Evolution ◽

Geochronological Data

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Petrogenesis and Geochronology of the late-Archean Na-rich A Type granite from the Bundelkhand Craton, India: Implication for tectonic and crustal evolution

10.5194/egusphere-egu2020-16436 ◽

2020 ◽

Author(s):

Mohd Baqar Raza ◽

Fernando Corfu ◽

Pritam Nasipuri

Keyword(s):

High Pressure ◽

Iron Formation ◽

Crustal Evolution ◽

Geochronological Data ◽

Banded Iron Formation ◽

Emplacement Temperature ◽

Eu Anomaly ◽

Type Granite ◽

High Silica ◽

Concordia Diagram

Tonalite-trondhjemite-granodiorite gneisses (TTG) are the oldest litho-units of the Bundelkhand craton. The supracrustal rocks include variable deformed mafic volcanics and Banded Iron Formation. Magmatic zircons from the TTG&#8217;s yield an upper intercept of ~ 3590 Ma. The TTG&#8217;s gradually grades to a Na-feldspar rich A type porphyric granite towards the south. In this abstract, we report mineralogical, geochemical, and geochronological information of high silica- low Ca - high Na A-type granite from Bundelkhand craton.In the TAS diagram, the studied samples plot in the field of granite and have a metaluminous affinity with high Ga/Al and Ce + Y + Nb + Zr values typical of A-type granites. In a primitive normalized multi-element spider diagram, the studied samples exhibit negative Nb, Ti, and P anomalies characteristics of a subduction zone setting. The chondrite normalized REE&#8217;s exhibit a strong fractionated pattern with negative Eu anomaly; the LREE are enriched and the HREE depleted with moderate to high (La/Yb)CN ratios ranging from 11.12 to 26.24 ppm. The studied samples have plagioclase compositions that vary from XAb = 0.980-0.997 and chlorite compositions varying from XMg = 0.309-0.469.Phase equilibria modeling yield an emplacement temperature of 700-750OC, at 1.0 GPa. Most of the zircon grains are prismatic with visible cores and rims in optical examinations. In a U-Pb concordia diagram, the grains yield an upper intercept of 2536.6 &#177; 1.8 Ma. The geochemical and geochronological data taken together, indicate the Na-rich A-type granite generated by the high temperature and high-pressure partial melting of Archaean supracrustal rocks.

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