Continental magmatic arc rotation during the assembly of western Gondwana

摘要

The Cear ' a Central Domain (CCD) is part of the Borborema Province and is delimited by two major NE-SW -trending strike-slip zones associated with the Transbrasiliano and Senador Pompeu lineaments. These two strike-slip zones formed in Neoproterozoic/Early Cambrian times under ductile conditions and underwent several brittle-ductile and brittle reactivation events from 540 Ma onwards, which affected Precambrian and Phanerozoic rocks, respectively, causing ductile and brittle-ductile and brittle deformation. The Transbrasiliano Lineament is an NNE-SSW-trending, 4000 km-long structure marked by strong magnetic anomalies. It is inter-preted to represent a mega-suture active during the Gondwana amalgamation and/or the post-collisional shearing. The Santa Quite ' ria Continental Magmatic Arc, located between both lineaments, consists of a Neo-proterozoic (830-620 Ma) gneissic-migmatitic association affected by collisional metamorphism (640-615 Ma). This arc has been dissected, dislocated, and rotated under brittle-ductile and brittle conditions by a set of sec-ondary strike-slip faults, possibly interconnected with the two major Transbrasiliano and Senador Pompeu lin-eaments, and most likely have been contemporarily active throughout history. The roughly NNW-SSE-trending Tau ' a Fault, located southwest of CCD, appears to relate to both fault systems. A closer inspection of gamma-ray spectrometric data suggests a complex network of interconnecting E-W-trending brittle transcurrent faults, some of which show dextral and/or sinistral kinematics, displacing the Santa Quite ' ria Continental Magmatic Arc and Caninde '-Independencia units. We suggest a paleo-dextral ductile deformation of the Santa Quite ' ria Continental Magmatic Arc resulting from the coeval transcurrent activity along Transbrasiliano and Senador Pompeu line-aments. These strike-slip mega-shear zones developed an intricate pattern of the minor (first-, second-, and third stages) interconnecting strike-slip faults, along which the Santa Quite ' ria Continental Magmatic Arc has been displaced and rotated, under conditions that changed from ductile to brittle-ductile to brittle through time.