GEOLOGY, AGE, AND TECTONIC SETTING OF THE MESSINA LAYERED INTRUSION,LIMPOPO MOBILE BELT, SOUTHERN-AFRICA

Petrographic, structural, chemical, and Rb-Sr total-rock studies of the Messina Layered Intrusion of the Limpopo Mobile Belt show that this sill-like cumulus body formed approx. 3150 M.yr. ago from a tholeiitic magma, derived from a heterogeneous subcontinental mantle and crystallizing alternately plagioclase, olivine, and orthopyroxene. The Intrusion was emplaced at a high crustal level (less than 12 km depth) at the contact between a basement complex more than approx. 3780 M.yr. old and an overlying supra-crustal succession and also within the supracrustal succession itself. Subsequently, the Intrusion and the rocks with which it is associated underwent 4 major deformations, the first two of which formed schistosity. The Messina Layered Intrusion could be a remnant of a greenstone-belt terrain.-Authors