Geophysical and geochemical studies of mafic dike swarms of western India and their applications to Deccan flood volcanism.
Item
-
Title
-
Geophysical and geochemical studies of mafic dike swarms of western India and their applications to Deccan flood volcanism.
-
Identifier
-
AAI9808001
-
identifier
-
9808001
-
Creator
-
Sharma, Rajesh.
-
Contributor
-
Adviser: Somdev Bhattacharji
-
Date
-
1997
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Geology | Geophysics | Geochemistry
-
Abstract
-
N-S to NNW-SSE trending dikes of western margin rift and ENE-WSW trending Narmada-Tapti rift are prominent features of Deccan Volcanics, India. Three dimensional gravity modelling of +70 mGal Bouguer and +25 mGal free air gravity highs along western margin rift indicate the presence of gabbroic type high density (2.94 gm/cm{dollar}\sp3{dollar}) mafic bodies at an estimated depth between 6 {dollar}\pm{dollar} 0.6 km and 18 {dollar}\pm{dollar} 1.8 km which are from 300 {dollar}\pm{dollar} 30.0 to 150 {dollar}\pm{dollar} 15 km long, and from 50 {dollar}\pm{dollar} 5.0 to 30 {dollar}\pm{dollar} 3.0 km wide from north to south. Three dimensional gravity modelling of +10 mGal to {dollar}-{dollar}30 mGal gravity highs along Narmada-Tapti rift indicates presence of eight convexly upward high density, isolated gabbroic type mafic bodies occurring at a depth of 6.7 {dollar}\pm{dollar} 0.6 km and have average width of 16 {dollar}\pm{dollar} 1.6 km and length 25 {dollar}\pm{dollar} 2.5 km. Three dimensional gravity modelling of SW-NE trending three Bouguer gravity highs in Saurashtra also reveals presence of high density gabbroic type mafic bodies at a depth of 6.5 {dollar}\pm{dollar} 0.6 km. They have average length of 19 {dollar}\pm{dollar} 1.9 km and width of 10 {dollar}\pm{dollar} 1.0 km. These areas are covered by Deccan volcanics. Based on gravity modelling it is conjectured that these mafic bodies in the upper lithosphere appear to be a major source for Deccan flood basalts. A distinct and striking compositional gap from 51 to 63 wt% of SiO{dollar}\sb2{dollar} exists between acidic rocks and Deccan basalts. Fractional crystallization, crustal contamination and venting were important factors in the geochemical evolution of Deccan basalts. Application of VRAFC (venting, replenishment, assimilation and fractional crystallization) model to Deccan volcanics suggest 10-15% of crustal contamination and 40-60% of venting of magma are important in geochemical characteristics of Deccan Volcanics.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
