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That random, non-comagmatic samples collected across an area 1000 km wide and and at various topographic-stratigraphic levels should define an isochron is remarkable, but the goodness-of-fit ( Some authors have explained “the extremely high lava eruption rates” in CFBs by hot plume heads, though there is no direct and simple relationship between melt production and melt eruption (Th. My own fieldwork at scores of places in the Deccan, and on the Kilauea volcano, Hawaii (Sheth, 2003), shows that the size and scale of individual flow units of many large Deccan compound flows are the same as those of modern Kilauea lava flows (Figure 5).
The large volumes of the individual Deccan lava flows compared to the Hawaiian flows may reflect in part the great amount of decompression during India-Seychelles continental breakup (Figure 2 inset), considerable lengths (40 – 50 km) of the fissure systems (Figure 6; see also Figure 5.
Recent , 2001a,b) suggest the total duration to have been no less than ~ 8 – 9 Myr.
The overall appearance of the Deccan, with its roughly circular outcrop, and the linear Laccadives-Chagos (more correctly, Lakshadweep-Chagos) Ridge to the south of India, looks very much like what is expected for a spherical plume head and a narrow plume tail (Figures 2 & 3).
Nevertheless, the following observations and deductions suggest that the plume model is not valid for the Deccan (, 1999a,b, 2005a). Map showing the approximate boundaries of the Precambrian cratons making up the Indian shield (e.g., Pandey & Agrawal, 1999; Naqvi & Rogers, 1987), the granulite terrain, the Precambrian structural trends (heavy broken lines), rift zones crossing peninsular India (e.g., Biswas, 1987), and the present outcrop areas of the Deccan and Rajmahal flood basalts.
Inset shows the breakup of the Seychelles microcontinent, situated along the northern tip of the Mascarene Plateau (black), from India, soon after the Deccan flood basalt episode (after Norton and Sclater, 1979; Mahoney, 1988).
I ascribe the rifting itself not to mantle plume heads but to large-scale plate dynamics, possibly aided by long-term thermal insulation beneath a supercontinent which may have surface effects similar to those predicted for “plume incubation” models.
Non-plume, plate tectonic models are capable of explaining the Deccan in all its greatness., 1990), hundreds of papers have invoked, or supported, a plume head origin for the Deccan Traps of India.