Paleomagnetism and geochronological studies on a 450 km long 2216 Ma dyke from the Dharwar craton, southern India.

Paleomagnetic and geochronological studies were carried out on a ∼450 km long (from 17 sites) N-S strikingPaleoproterozoic dyke swarm exposed along a natural crustal cross section of about 10 km (increasing fromNorth to South) in the Dharwar Craton, to study the characteristics of paleomagnetism and geochronology invertical dimension. U-Pb/Pb-Pb dating on baddeleyite gives a crystallisation age of 2216.0 ± 0.9 Ma for long
dyke AKLD. Paleomagnetic data from this well dated ∼2216 Ma dyke swarm in DharwarCraton are of excellentquality. High coercivity and high blocking temperature components are carried by single domain magnetite andshow dual polarity remanence directions. Combined normal and reverse polarity remanences on AKLD and otherN-S dykes define the most reliable paleomagnetic pole for ∼2216 Ma at latitude 36°S and longitude 312°E(A95 = 7°). Though paleomagnetic data is unavailable on other N-S dykes below the Cuddapah basin, high
precision geochronology suggest that they are of similar age within errors. Though there is a variation in thecrustal depth of Dharwar craton from north to south, consistent Pb-Pb/U-Pbbaddeleyite geochronology andpaleomagnetic studies along the AKLD established its continuity and preservation along its entire strike length.The virtual geomagnetic poles of these sites confirm a stable remanence and are almost identical to the previously reported paleomagnetic pole and also supported by positive reversal test. Positive paleomagnetic reversal test on these dykes signify that the remanent magnetization is primary and formed during initial cooling ofthe intrusions. Updated apparent polar wander path of Dharwar craton indicates relatively low drift rate during2.21–2.08 Ga interval. Magnetogranulometry and SEM studies show that remanent magnetization in this dykewas carried by single domain magnetite residing within silicate minerals.



Nagaraju, E., Parashuramulu V., Kumar, Anil; Sarma D. Srinivas, Physics of the Earth and Planetary Interiors 274 (2018) 222–231. external link