No evidence for Archean eclogite-facies metamorphism

Reply to Zou et al.: Neoarchean eclogite-facies oceanic crust in the North China Craton

“…Note that figure 1B of Zou et al. ( 1 ) fails to report the calibrated fields (in green colors), that are close to our data (in purple). ( B ) Diagram of the difference between the calculated pressure [using Grt-Cpx geobarometer of Beyer et al.…”

“…Zou et al. ( 1 ) claim that our exsolution textures indicate cooling from high temperature, “ inconsistent with eclogite-facies metamorphism.” This is misleading. Numerous studies ( 2 ) show similar textures formed during decreasing pressure–temperature (P-T) conditions from eclogite and/or granulite facies ( 8 ).…”

“…The garnet-clinopyroxene (Grt-Cpx) geobarometer ( 3 ) was calibrated at 2 GPa to 7 GPa and 900 °C to 1,550 °C, and, with other experiments, is extrapolatable to eclogitic rocks below 700 °C ( 3 ), not a minimum of 1,200 °C as misreported by ref. 1 , who incorrectly redraw figure 4 of Beyer et al. ( 3 ), omitting original calibration data at low temperature and low Al IV Cpx (the tetrahedral aluminum content in Cpx) in the range of our samples (the complete original figure 4 of Beyer is reproduced as our Fig.…”

“…However, Zou et al. ( 1 )’s claims concerning our geobarometry and petrography ( 2 ) are demonstrably misleading.…”

“…Zou et al. ( 1 ) claim they tested the above geobarometers using “published metamorphic studies” (their figure 1C and D), but no information about their tested data or validity of other pressure estimates is provided.…”