Is the garnet amphibolite in the Longyou a retrograded eclogite?

Abstract

A paper titled as "Retrograde garnet amphibolite from eclogite of the Zhejiang Longyou area: New evidence of the Caledonian orogenic event in the Cathaysia block" was recently published in Chinese Science Bulletin (Chen et al., 2015). However, the petrographic features and mineral compositions that authors provided cannot demonstrate that high-pressure or ultra-high pressure metamorphism occurred in the area in Early Paleozoic. Moreover, this conclusion is inconsistent with regional geological background. Combined with our field survey and petrographic observations, it can be inferred that this garnet amphibolite did not experience eclogite-facies metamorphism, and cannot be taken as evidence for the Caledonian collisional orogeny.