Supplemental Material: Two key switches in regional stress field during multi-stage deformation in the Carboniferous–Triassic southernmost Altaids (Beishan, NW China): Response to orocline-related roll-back processes

Table S1: (STS1) Samples collected near the study area; Table S2: Sample information from the shear zone and mélange zone: Table S3: (1) U-Pb isotope dates of magmatic zircons in granitic mylonites (11HYJ02 and 11QJJ01) from the Huoshishan ophiolitic mélange and the Qijiaojing shear zone. See Figure 2 for sample locations, (2) 40Ar/39Ar step-heating results of muscovites and biotite in granitic mylonites (11QJJ01, 11HYJ02, 11HYJ01-2, 11HYJ04 and 10TZHD03) from the Hongyangjing shear zone, the Huoshishan ophiolitic mélange, and the Qijiaojing shear zone. See Figure 2 for sample locations, (3) Methods：Methods divide into analytical method-EBSD (Electron backscatter diffraction), analytical method-U-Pb age dating, analytical method- 39Ar-40Ar age dating; Table S4. the raw data of 40Ar/39Ar from Institute of Geology and Geophysics, Chinese Academy of Science (IGGCAS) are given in the Supplementary data Table S4.

Supplemental Material: Two key switches in regional stress field during multi-stage deformation in the Carboniferous–Triassic southernmost Altaids (Beishan, NW China): Response to orocline-related roll-back processes

Table S1: (STS1) Samples collected near the study area; Table S2: Sample information from the shear zone and mélange zone: Table S3: (1) U-Pb isotope dates of magmatic zircons in granitic mylonites (11HYJ02 and 11QJJ01) from the Huoshishan ophiolitic mélange and the Qijiaojing shear zone. See Figure 2 for sample locations, (2) 40Ar/39Ar step-heating results of muscovites and biotite in granitic mylonites (11QJJ01, 11HYJ02, 11HYJ01-2, 11HYJ04 and 10TZHD03) from the Hongyangjing shear zone, the Huoshishan ophiolitic mélange, and the Qijiaojing shear zone. See Figure 2 for sample locations, (3) Methods：Methods divide into analytical method-EBSD (Electron backscatter diffraction), analytical method-U-Pb age dating, analytical method- 39Ar-40Ar age dating; Table S4. the raw data of 40Ar/39Ar from Institute of Geology and Geophysics, Chinese Academy of Science (IGGCAS) are given in the Supplementary data Table S4.

Rapid cooling during late-stage orogenesis and implications for the collapse of the Scandian retrowedge, northern Scotland

New 40Ar/39Ar thermochronological and deformation temperature analyses in the Scandian (c. 435–420 Ma) orogenic retrowedge of northern Scotland demonstrate accelerated cooling during late syn- to post-orogenic exhumation of the high-grade orogenic core. Initial cooling rates of 10–30°C myr−1 immediately following peak orogenesis transitioned to rapid rates of 45–90°C myr−1 during final exhumation of the Naver thrust sheet in the orogenic core. The flanking ductile thrust sheets exhibit a similar, albeit less pronounced, acceleration of cooling, with rates increasing by c. 150–300% following peak orogenesis. Closer to the foreland, the Moine thrust sheet did not experience increased cooling rates. Calculated unroofing rates of 3.75 mm a−1 in the high-grade Naver thrust sheet suggest increasing, rapid exhumation in the orogenic core during a presumed collapse phase of orogenesis. This is contrary to the expectation of decreasing erosional efficiency as topography is diminished and is interpreted to suggest that unroofing of the Scottish Caledonides may have been partially enhanced by upper crustal extensional deformation during ductile flow of the infrastructure of the orogenic core. Similar processes have been interpreted in the East Greenland Caledonides, which form the northern extension of the Scandian retrowedge.Supplementary material:40Ar/39Ar analytical data for muscovite (Supplementary Data Table 1), 40Ar/39Ar analytical data for amphibole (Supplementary Data Table 2), and electron microprobe analytical data for amphibole samples (Supplementary Data Table 3) is available at: https://doi.org/10.6084/m9.figshare.c.5087057