Dados da Submissão

Título

TIME-CONSTRAINED MULTIPLE REACTIVATIONS OF THE MALTA FAULT IN THE RIO DO PEIXE BASIN THROUGH RB-SR IN-SITU DATING

Texto do resumo

The Rio do Peixe Basin, an intracontinental rift basin in Northeast Brazil, was originated during the breakup of Western Gondwana and the opening of the South Atlantic. The Malta Fault is the major fault of the southern border of the basin with around 70 km of extension. It strikes E-W and has high-angle dips northward. Its kinematic indicators indicate a down-dip movement, suggesting normal fault kinematics. This fault's evolution is linked to the brittle reactivation of the Patos ductile shear zone.
Advancements in mass spectrometer reaction cells now enable in-situ Rb-Sr dating, facilitating the correlation of geochronological data with microstructural observations. To elucidate the Malta Fault's deformation history, we integrated meso- and microstructural analyses with in-situ Rb-Sr dating.
Our study identified three distinct episodes of fault reactivation and fluid infiltration at 350±20 Ma, 212±10 Ma, and 124±11 Ma through the examination of syn- to post-kinematic K-bearing minerals such as illite and biotite along the fault planes. These findings suggest that the Malta Fault has been accommodating stress since the late Devonian. The oldest date coincides with the Santa Helena group, a pre-rift sequence of the Rio do Peixe Basin, and parallels stratigraphic sequences in the Parnaíba and Jatobá basins, indicating regional tectonic activity during that period. The Triassic and Cretaceous ages align with U-Pb dating of carbonates from related brittle structures in the Borborema basement, correlating with the Central Atlantic rift and CAMP magmatism, and the South Atlantic rift and EQUAMP, respectively. A fourth episode is described in literature as related to inversion structures detected through geological and geophysical data. The basin inversion is interpreted as correlated with the Mid-Atlantic Ridge and Andes. Thus, the Malta Fault exemplifies a regional-scale shear zone with a complex, protracted history marked by multiple reactivation events.

Palavras Chave

Rb-Sr in situ geochronology; Rio do Peixe Basin; Rift