Structural and Tectonic Evolution of K-Rich Silica-Deficient Volcanic Provinces of Different Continents - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 414

Chapter 14
Structural and Tectonic Evolution
of K-Rich Silica-De cient Volcanic
Provinces of Different Continents

Genesis of an ultrapotassic magma in the central part of east Africa (Ruwenzori and
Birunga volcanic province), the Rhine Graben region of Germany, Damodar Valley
Coal Field (east India) and Rio Grande region of the USA is considered to have
been associated with the development of rift systems (see Chap. 4 ) . According to
modern concept, development of rift valleys and associated large scale volcanism,
are related to plume activities. Potassic volcanism in Indonesia, Ulleung Island,
Spain, Turkey, and Highwood Mountains of the United States is considered to be
subduction-related. Ultrapotassic volcanism in different parts of Italy (the Vulsini
complex, Vico, Phlegrean Fields, Vesuvius and Aeolian arc region) is either related
to partial melting of the subducted lithosphere underneath the European plate
(Edgar 1980) or related to rifting (Cundari 1980). Bianchini et al. (2008) supports
post collisional and intraplate Cenozoic volcanism in the rifted Apennines/Adriatic
domain. The K-rich volcanism of Alto Paranaiba province is considered to be
related to plume-related activity. Different tectonic processes pertaining to the

genesis of potassium-rich ma c and ultrama c rocks are described below.

14.1 Tectonism in European Volcanic Provinces

14.1.1 Development of the Rhine Rift Valley

Ziegler (1992) studied the Cenozoic rift system of western and central Europe. This
rift system is extended from the shores of the North Sea to the Atlantic coast of
North Africa over a distance of about 3,000 km. It comprises the Spanish Valencia
Trough, the Gulf of Lions, Saone, Limagne and Bresse grabens of southeastern
France, the Rhine, Ruhr Valley and Leine Grabens (Fig. 14.1 ).
The north - northeast-trending graben bifurcates near Frankfurt. The Leine graben
maintains the same strike direction of the Rhine Graben and the northwest-trending
Ruhr Valley graben. According to them reactivation of tectonic activity during
Permo-Carboniferous and Mesozoic resulted in the formation of fracture systems