Shear zone cooling and fabrics of synkinematic plutons evidence timing and rates of orogenic exhumation in the northwest Borborema Province (NE Brazil)

The Borborema Strike-Slip Shear Zone System (NE Brazil): Large-Scale Intracontinental Strain Localization in a Heterogeneous Plate

“…40 Ar- 39 Ar Geochronology. In the Granja and Senador Pompeu shear zones, 40 Ar- 39 Ar amphibole and biotite ages (in the ranges, respectively, of 570-575 Ma and 559-569 Ma) imply fast cooling rates of c. 20 °C/Ma [104,123]. Slower cooling during the final steps of exhumation is supported by the 536 Ma U-Pb ages of magmatic rocks crosscutting the units of the molassic basins formed by reworking of these shear zones [124,125].…”

“…These plutons are elongated with their long axes parallel to the nearby shear zones or have en cornue shapes. Several have been studied through field and anisotropy of magnetic susceptibility mapping [51,66,72,80,87,102,[104][105][106]. They have magmatic/magnetic foliation parallel to mylonitic foliation in the host rock and shallowly plunging magnetic lineation, indicating syn-shear intrusion and progressive fabric development during cooling and crystallization.…”

“…585 Ma [80,108]. Near the junction of the two shear zones, U-Pb ages of 576 and 571 Ma of plutons unaffected or only slightly affected by shearing indicate emplacement during the waning stages of shear zone development [104].…”

Fabric Analysis in Upper Crustal Post-Collisional Granitoids from the Serre Batholith (Southern Italy): Results from Microstructural and AMS Investigations

“…Relationships between magma emplacement and deformation have been widely documented by different authors and in various contexts all over the world (e.g., [1][2][3][4][5][6][7][8][9][10][11]) and, in particular, a close connection between granitic intrusion and shear zone systems has been highlighted in many cases (e.g., [12][13][14][15][16][17][18][19][20]). This is because granitoid magmatism is often synchronous with regional tectonic events, such as those involved in the building or the exhumation of orogenic belts [10,11,17,19].…”

“…Relationships between magma emplacement and deformation have been widely documented by different authors and in various contexts all over the world (e.g., [1][2][3][4][5][6][7][8][9][10][11]) and, in particular, a close connection between granitic intrusion and shear zone systems has been highlighted in many cases (e.g., [12][13][14][15][16][17][18][19][20]). This is because granitoid magmatism is often synchronous with regional tectonic events, such as those involved in the building or the exhumation of orogenic belts [10,11,17,19]. However, the establishment of a link between shear zone activity and granite emplacement must be carefully assessed, since different portions of a pluton may exhibit different fabrics or no fabric at all, therefore making structural interpretations quite challenging.…”