Discussion of 'the Paleozoic metamorphic history of the Central Orogenic Belt of China from 40Ar/39Ar geochronology of eclogite garnet fluid inclusions by Qiu Hua-Ning and Wijbrans J.R.'

Abstract

The in vacuo crushing procedure employed by Qiu and Wijbrans (2008) is identical to that of Qiu and Wijbrans (2006) and has produced a similar result. The authors provide no description of the sample material analysed and the display of data is highly selective (see also Kendrick, 2007). The new step-heating data produced for crushed garnets are readily explained in terms of degassing from mineral inclusions (Fig. 1) and the argon isotope systematics preclude the ~ 450 Ma 'plateau' or 'isochron' ages being related to primary metamorphic fluid inclusions. The range of apparent ages determined for garnets, phengite and biotite by Qiu and Wijbrans (2006, 2008) extend from ~ 150 Ma to over 1000 ..