THE FIRST REPORT OF CHIME MONAZITE AGE FROM THE SOUTH INDIAN GRANULITE TERRAIN

This paper reports the chemical Th-U-total Ph isochron method (CHIME) dating of monazite from cordierite-bearing charnockite from Nellikkala in the Kerala Khondalite Belt, southern India, A total of 185 spots o n 25 monazite grains were analysed by an electron microprobe, The vari ous ranges of concentration were: ThO2 from 9.49 to 15.0 wt%, UO2 from 0.035 to 0.835 wt%, and PbO from 0.220 to 0.343 wt%, Data points are arrayed linearly on the PbO vs ThO2 (the measured ThO2 plus ThO2 equi valent to the measured UO2) diagram, and yield an isochron of 527 +/- 10 Ma (MSWD = 0.13) with an intercept value of 0.0004 +/- 0.0051. The 527 +/- 10 Ma monazite age agrees well with the Sm-Nd and Ph-Sr ages s o far reported from the Nellikkala charnockite, and dates the Pan-Afri can granulite facies metamorphic event, The present study demonstrates that the CHIME offers reliable age data, has advantage of high-spatia l resolution, and, hence, has wide geochronological applications.