Preliminary results on crust and upper mantle structure in the Rungwe Volcanic Province, Tanzania from the SEGMeNT project

Abstract:

While well-developed magmatic and tectonic segmentation is observed in late-stage rifts, little is known about the controls on the initiation and development of magmatism and segmentation in young rifts. The Lake Malawi/Nyasa region in the East African Rift System (EARS) is a region of early rifting that exhibits tectonic segmentation and little volcanism. The only magmatism in this region occurs in an accommodation zone between segments at the northern end of the lake, in the Rungwe Volcanic Province, rather than in the segment center as observed in mid-ocean ridges and late-stage rifts. This phenomenon is also observed elsewhere in EARS and in other young rifts, but the origin and distribution of magma at depth and its role in extension and segmentation is unknown. In the initial phase of the SEGMeNT project, 14 broadband seismometers were deployed in the Rungwe Volcanic Province during August 2013. Data from teleseismic events recorded on these stations, in combination with data from previous seismic networks deployed in southern Tanzania, are being used to develop preliminary models of crust and upper mantle structure for elucidating the role of magmatism in early-stage rifting. Crustal structure is being investigated using H-k stacking of receiver functions and upper mantle structure is being modeled tomographically using P and S arrival times.