11:15 AM - 11:30 AM
[SMP31-03] Preliminary paleomagnetic studies on the mafic dykes in Western Dharwar craton, South India.
Keywords:Mafic dykes, Precambrian, Paleomagetism, Geochemistry
Understanding paleo- positions in which the dykes were emplaced is key while correlating the present, spatially distant cratons. Paleomagnetic studies will help to understand the paleo-position of the cratons and mafic dykes are expected to provide excellent records of the earth’s magnetic field as they cool rapidly when emplaced (Belica et al., 2014). For the preliminary paleomagnetic analyses, 86 core specimens were prepared from 33 sites including both dolerite and meta-dolerites and progressive demagnetization experiment has been conducted to assess the stability of natural remanent magnetization (NRM). Pilot specimens were subjected to alternating-field or thermal demagnetization and the NRMs were measured with a spinner magnetometer. Dolerite specimens yielded better magnetic behaviors with stable magnetic components. On the other hand, meta-dolerites show magnetic components probably carried by pyrrhotite and the magnetic behaviors were very unstable. Fig. 1 shows demagnetization behaviors of dolerite sample plotted on orthogonal vector-endpoint diagrams and equal area stereonets.
Studying the dykes in the Dharwar craton is key to understanding the evolution of the mantle during the Precambrian, especially in the Archean to Proterozoic transitional period. Dykes are emplaced after the period of major continental crust formation at around 2.7 Ga and hence the variation in mantle composition through time can be constrained. The dykes can be a result of a plume activity or an indicator of large igneous province and hence the study of which will give valuable information about the mantle source, the degree of melting and the source regions where melting occurred. Dyke swarms and LIPs are the products of major magmatic events in the Earth’s history that probably was the driving force in the breaking up of supercontinents, and they provide clues regarding the cratonic evolution through time. Due to their wide distribution, geochemically coherent dykes can be found in many cratons, thus providing key information on the close proximity of now separated supercontinents.
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