| Autor: |
Negi, J.G., Agrawal, P.K., Singh, A.P., Pandey, O.P. |
| Zdroj: |
Tectonophysics; January 1992, Vol. 206 Issue: 3 p341-350, 10p |
| Abstrakt: |
The western margin of India, especially the area surrounding the gravity high of Bombay, is covered by a thick pile of Deccan flood basalts. The massive eruption is one of the largest continental volcanic events at the Cretaceous/Tertiary biological mass extinction boundary ( ∼ 65 Ma ago). The area is characterized by several hidden tectonic features, and their origin and evolution have remained controversial. In the search for magma source structure, attention was focused on an unusual oval-shaped positive gravity anomaly over the Bombay coastal zone. The gravity analysis indicates the presence of two subsurface structures at depths of 4.5 ± 0.5 km and 18 ± 2 km. These depths correspond to the top of the crustal basaltic layer and an upwarped Moho discontinuity, respectively. The positive gravity anomaly in three-dimensional analysis reveals a possible magma conduit structure and the near absence of the granitic layer. The unusually shallow Moho layer coincides with the region of a broad high heat flow anomaly (average heat flow more than 80 mW/m 2). The geophysical signatures from the neighborhood show that the asthenosphere has welled up considerably and is located at a depth of about 40 km. High heat flow and asthenospheric depth estimates suggest melting conditions at very shallow depths. |
| Databáze: |
Supplemental Index |
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