Temperature constraints on microfabric patterns in quartzofeldsphatic mylonites, Ribeira belt (SE Brazil)

Submagmatic to Solid-State Deformation Microstructures Recorded in Cooling Granitoids during Exhumation of Late-Variscan Crust in North-Eastern Sicily

“…The earliest granitoid magmas were produced by water-fluxed melting of metagreywackes at pressure likely close to 1.0 GPa ( [47]; and references therein), near the collision-related baric peak, giving rise to the trondhjemitic plutons that emplaced at ~310 Ma [49,50]. According to the evidence obtained in this study, shearing started just after the emplacement of the magmatic trondhjemites, as documented by development of submagmatic fractures and chessboard patterns in quartz, and The similar distribution of deformation microstructures observed in both trondhjemites and low-Ca granitoids supports the proposal that temperature is the main factor controlling the activation of specific deformation mechanisms (e.g., [98,129]), compared to the confining pressure and rock grain size. The only exception might be the different occurrence of core-and-mantle structures in quartz that appears to be higher in the finer-grained low-Ca granitoids.…”

“…Deformation microstructures developed from a submagmatic to low-temperature solid-state regime in trondhjemites and granites from the Peloritani Mountains give the opportunity to investigate the relationships between fabric development and syn-tectonic cooling of granitoids emplaced at middle to upper crustal conditions. Changing temperatures during prograde or retrograde orogenic evolution are largely considered to exert the main role influencing the mechanisms of deformation in crustal rocks (e.g., [98,129]). Nevertheless, other factors can also affect the rheological behaviour of the crust, such as the rock composition and grain size, the limiting pressure, the strain rate, the flow vorticity, and the presence of a fluid or a melt phase [130,131].…”

Variations in the P‐T‐t of Deformation in a Crustal‐Scale Shear Zone in Metagranite

“…We use the Ti‐in‐quartz thermobarometer calibration of Thomas et al. (2010), because it takes both pressure and a TiO2 into account; subsequent experiments have confirmed the reproducibility of those used for calibration (Thomas et al., 2015), and it is widely used (e.g., Ackerson et al., 2018; Ashley et al., 2013; Ashley & Law, 2015; Cavalcante et al., 2018; Grujic et al., 2020; Menegon et al., 2011), allowing our data to be compared to that in the literature. However, we note that debate regarding calibrations for the Ti‐in‐quartz thermobarometers is ongoing (see e.g., discussion in Nachlas and Hirth [2015]), and some have suggested that temperatures derived using the Thomas et al.…”

“…However, some of these studies found that the lower estimates derived from Thomas et al. (2010) better matched independent T constraints (Ashley et al., 2013; Cavalcante et al., 2018), whereas other concluded that they were truly too low (Grujic et al., 2011; Nachlas and Hirth, 2015). Our P‐T estimates based on the Thomas et al.…”

“…The temperature dependence of the Ti content of quartz (TitaniQ) was experimentally calibrated by Wark and Watson (2006), and subsequent experiments have quantified a lesser pressure dependence (Huang & Audetat, 2012;Thomas et al, 2010). We use the Ti-in-quartz thermobarometer calibration of Thomas et al 2010, because it takes both pressure and a TiO2 into account; subsequent experiments have confirmed the reproducibility of those used for calibration (Thomas et al, 2015), and it is widely used (e.g., Ackerson et al, 2018;Ashley et al, 2013;Ashley & Law, 2015;Cavalcante et al, 2018;Grujic et al, 2020;Menegon et al, 2011), allowing our data to be compared to that in the literature. However, we note that debate regarding calibrations for the Ti-in-quartz thermobarometers is ongoing (see e.g., discussion in Nachlas and Hirth [2015]), and some have suggested that temperatures derived using the Thomas et al (2010) calibration appear too low (Ashley et al, 2013(Ashley et al, , 2014Grujic et al, 2011).…”