PALEOMAGNETIC INSIGHTS INTO SINGHBHUM CRATON

India is comprised of 5 major Archean cratonic nuclei. Three of these cratons make up the Southern Indian Block: Dharwar, Bastar, and Singhbhum. Singhbhum Craton (SC), located in northeast India, consists of a complex Archean basement succession. As is typical in these terranes worldwide, remarkable exposures of mafic dykes, known as the “Newer Dolerites,” cut the basement rocks. These dykes range in age with 3 major swarms dated from the Neoarchean (~2762 Ma) to the Paleoproterozoic (~2250 Ma and ~1770 Ma). Based on dyke trends and single dyke ages, as many as 7 intrusive pulses have been proposed for Singhbhum Craton (Srivastava et al., 2018). The actual number of dyke swarms remain to be tested by field observations and geochronological constraints. Extensive paleomagnetic sampling of these mafic dykes (103 sites over 3 field seasons) allowed a detailed investigation into the magnetic record of Singhbhum Craton throughout time.

Our results allow for a critical appraisal of recent paleomagnetic data from Singhbhum Craton. Kumar et al. (2017) found a steeply-inclined paleomagnetic direction in ~2760 Ma dykes (NNE-trending) which they viewed as primary. Our results indicate that this direction is likely the result of remagnetization. Shankar et al. (2017) found a paleomagnetic direction inclined shallowly northwest in ~1765 Ma dykes (WNW-trending). Our data indicate a more complicated magnetic story, but one that overall suggests these paleomagnetic data are primary. Future work is necessary to fully deconvolve these data. Primary paleomagnetic data from the Singhbhum Craton allows researchers to track its paleo-position and compare it to other Southern India Block cratons (Dharwar and Bastar). Additionally, we can examine their relationship with the Northern India Block cratons (Aravalli and Bundelkhand) to assess the assembly of the “United Plates of India” as a whole.