The first report of CHIME monazite age from the South Indian granulite terrain

摘要

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 on 25 monazite grains were analysed by an electron microprobe, The various 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 equivalent 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 so far reported from the Nellikkala charnockite, and dates the Pan-African granulite facies metamorphic event, The present study demonstrates that the CHIME offers reliable age data, has advantage of high-spatial resolution, and, hence, has wide geochronological applications. [References: 34]