The Lebombo monocline and associated feeder dyke swarm: Diagnostic of a successful and highly volcanic rifted margin?

New geophysical compilations link crustal block motion to Jurassic extension and strike-slip faulting in the Weddell Sea Rift System of West Antarctica

“…We therefore suggest that the intrusions underlying the SWMP magnetic anomalies most likely consist of a mixture of dense mafic rocks and lower density silicic-intermediate rocks. This would be consistent with the recognition of locally significant volumes of silicic rocks of the Chon Aike province (Pankhurst et al, 1998), the wider inferred ignimbrite flare-up in the developing Scotia arc region and the significant silicic component of the Lebombo Monocline in southern Africa (Cleverly et al, 1984;Klausen, 2009). …”

“…However, a transtensional model would be consistent with some regional reconstructions of later Gondwana breakup, which show dextral strike slip motion extending directly along strike from the Explora Anomaly (Klausen, 2009). Models for the subsequent earliest stages of ocean spreading, which likely followed on from development of the NWMP, also suggest oblique divergence at this margin (Eagles, 2016;Eagles and Vaughan, 2009).…”

“…4b), and therefore prefer a simpler extensional or transtensional model for this region. An extensional model would be consistent with tectonic models for the earliest stages of rifting between South African and East Antarctica (Klausen, 2009;Kristoffersen et al, 2014). …”

“…The synchronous models for NWMP and SWMP development should, however, not be ruled out, but likely require further testing with more detailed aerogeophysical data acquisition and careful consideration of the kinematic interplay between broadly sinistral WSRS extension and predominately dextral rifting inferred between South Africa and East Antarctica (Eagles, 2016;Klausen, 2009). We suggest that new surveys targeting the critical boundaries of the SWMP with the NWMP and PSZ could significantly constrain these alternative kinematic models.…”

A historical review of the methods for inferring paleostresses from dike orientations

“…The dotted line shows the roughly constant increase in the number of papers dealing with both dikes and stress since the 1970s. , 1969, 1989Nakamura et al, , 1980, 1973, 1975 198019821983Yokoyama 198319831984Tsunakawa 19861991Hoshi and Takagawa, 2008, 2009;Yoshida 19841987a, b Geshi, 2000, 2001, 2003 1980 , plotted on equal-area projections. The attitude of a crack is represented by the orientation of its pole; for example, the center of each stereogram represents a crack perpendicular to the σ 3 -axis.…”