Journal of Earth system science | |
Two- and three-dimensional gravity modeling along western continental margin and intraplate Narmada-Tapti rifts: Its relevance to Deccan flood basalt volcanism | |
Rajesh Sharma11  Somdev Bhattacharji11  Nilanjan Chatterjee22  | |
[1] Department of Geology, Brooklyn College and Graduate Center of the City University of New York, Brooklyn, New York 11210, U.S.A.$$;Department of Earth, Atmospheric and Planetary Sciences, Room 54-1216, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, U.S.A.$$ | |
关键词: Gravity modeling; Bouguer gravity; rift; Deccan volcanism.; | |
DOI : | |
学科分类:天文学(综合) | |
来源: Indian Academy of Sciences | |
【 摘 要 】
The western continental margin and the intraplate Narmada-Tapti rifts are primarily covered by Deccan flood basalts. Three-dimensional gravity modeling of +70 mgal Bouguer gravity highs extending in the north-south direction along the western continental margin rift indicates the presence of a subsurface high density, maï¬c-ultramaï¬c type, elongated, roughly ellipsoidal body. It is approximately 12.0 ± 1.2 km thick with its upper surface at an approximate depth of 6.0 ± 0.6km, and its average density is 2935 kg/m3. Calculated dimension of the high density body in the upper crust is 300 ± 30km in length and 25 ± 2.5 to 40 ± 4 km in width. Three-dimensional gravity modeling of +10 mgal to −30 mgal Bouguer gravity highs along the intraplate Narmada-Tapti rift indicates the presence of eight small isolated high density maï¬c bodies with an average density of 2961 kg/m3. These maï¬c bodies are convex upward and their top surface is estimated at an average depth of 6.5 ± 0.6 (between 6 and 8 km). These isolated maï¬c bodies have an average length of 23.8 ± 2.4 km and width of 15.9 ± 1.5 km. Estimated average thickness of these maï¬c bodies is 12.4 ± 1.2 km. The difference in shape, length and width of these high density maï¬c bodies along the western continental margin and the intraplate Narmada-Tapti rifts suggests that the migration and concentration of high density magma in the upper lithosphere was much more dominant along the western continental margin rift. Based on the three-dimensional gravity modeling, it is conjectured that the emplacement of large, ellipsoidal high density maï¬c bodies along the western continental margin and small, isolated maï¬c bodies along the Narmada-Tapti rift are related to lineamentreactivation and subsequent rifting due to interaction of hot mantle plume with the lithospheric weaknesses (lineaments) along the path of Indian plate motion over the R´eunion hotspot. Maï¬c bodies formed in the upper lithosphere as magma chambers along the western continental margin and the intraplate Narmada-Tapti rifts at estimated depths between 6 and 8 km from the surface (consistent with geological, petrological and geochemical models) appear to be the major reservoirs for Deccan flood basalt volcanism at approximately 65 Ma.
【 授权许可】
Unknown
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