Gang Lu

Passive continental margins may have a wide variety of structural and magmatim styles, but the controlling factors of magmatism remain controversial. Common explanations attribute the variation of magmatism to the change of mantle temperature, and associate volcanic margins to high temperature mantle plumes. However, this interpretation has been challenged due to the lack of evidences of plume tracks at some volcanic margins. Furthermore, anomalously low mantle temperature is required for non-volcanic margins, which is too low to produce normal oceanic crust. Here we use numerical models to investigate melt generation for margins with realistic rifting styles. Our results demonstrate a surprising correlation of enhanced magmatism with wide margin. This relationship is explained by the dynamic process of differential rifting, in which the lithospheric mantle ruptures earlier than the crust. On the basis of differential rifting, we derive an analytical prediction of melt volume over margin width, which is in agreement with both numerical results and nature observations. The new mechanism proposed here provides an alternative interpretation for enhanced magmatism, and suggests that mantle temperature at wide volcanic margins was probably over-estimated.