Stabilization of the Aravalli Craton of northwestern India at 2.5 Ga: An ion microprobe zircon study

In order to establish the stabilization age of the Aravalli Craton of northwestern India, we have used an ion microprobe to measure 207Pb206Pb ages of zircons from six samples collected from the southern Aravalli Mountains. Our analyses gave precise results for four granitoids whose minimum crystallization ages ranged between 2562 ± 6 and 2440 ± 8 Ma (1 σ). A single sample of gneiss gave an age of 2502 ± 4 Ma, which is unexpectedly younger than an age of 3281 Ma which we previously obtained from another gneissic sample. We interpret the 2502 Ma age as the time of emplacement of the sampleʹs igneous protolith, suggesting that the Mewar Gneiss contains multiple metamorphic components of differing ages. Based on our data, we conclude that the southern segment of the Aravalli Craton had broadly stabilized by ∼ 2.5 Ga. This stabilized landmass formed the basement on which the younger Aravalli Supergroup was unconformably deposited. This study represents the first application of a small geometry ion microprobe for routine geochronology.