Magnetic fabrics of west coast dyke swarm from Deccan volcanic province, Maharashtra, India and their relationship with magma flow direction.

Dykes are one of the primary subvolcanic bodies that transport magma from the shallow magma chamber or from the deep-seated magma reservoir. The mechanism of magma transport and emplacement in dyke swarms can contribute precious details on source and how magma has associated with crustal rocks. Here we are presenting the results obtained from the Anisotropy of magnetic susceptibility (AMS) on their mode of emplacement and to understand magma flow direction. AMS and rock magnetic studies were performed on 33 dykes located on the West coast of Maharashtra, (India) to determine the magma flow direction using magnetic fabric. Thermomagnetic curves and hysteresis loop measurement indicates that titanomagnetite of associated pseudo-single-domain/multi-domain grain sizes are responsible for the magnetic fabrics. Based on the clustering of the principal AMS axes, three types of AMS fabrics were recognized, (i) Normal fabric, interpreted as due to magma flow characterised by clustering of K₁–K₂ axes on the dyke plane and K₃ axes are nearly perpendicular to it, (ii) Inverse fabric with K₂–K₃ plane parallel to the dyke plane and K₃ is perpendicular to it and (iii) Intermediate fabric, with K₁–K₃ axes clustering close to dyke plane. The inclination of the K₁ axis (IK₁) of Normal fabric is the most important to determine the flow of magma for the studied dyke swarm. The IK₁ of the studied dykes were fed dominantly by horizontal (IK₁ < 30°), inclined (30° < IK₁ < 60°) up to vertical fluxes (IK₁ > 60°). These results suggest that the dykes may be closer to the magma source and horizontal magma flow inferred from the dykes reveals source is located further away. The present AMS study along with geophysical, geochemical and petrological study supports the evidence of feeder fed mechanism. [ABSTRACT FROM AUTHOR]