Chemical microprobe dating of thorianite in carbonatite from Pakkanadu alkaline-carbonatite complex, Northern Granulite Terrain, Tamil Nadu, India

A new U-Th-Pb chemical date (CHIME dating) of thorianite (ThOz) from the carbonatite of the Pakkanadu alkaline- carbonatite complex (PACC), Tamil Nadu is presented in this study. This is the first U-Th-Pb chemical dating of its kind done for thorianite in India by Electron Probe Micro Analyser. Precise U-Th-Pb measurement in thorianite can be attained by improved analytical method and may be considered as a potential reconnaissance geochronological tool. Thorianite in the carbonatites of the PACC preserve significant geological event(ca. 763±61 Ma), which is very close to the date of co-existing Th/Pb monazite isochron (ca. 750±ll Ma) and Pb-Pb whole rock (759±3 Ma) dates of carbonatite in the PACe. The Th/Pb monazite date, i.e. 715±42 Ma, from Kambam carbonatite is also close to these dates. This investigation endorses the use of multiple geochronometers in understanding the comprehensive age information in the terrains with complex evolutionary history. (author)