Dike swarms of the west-central Arabian Shield: a key to its tectono-magmatic evolution.

Dike swarms and structural lineaments were investigated in the Hada Alsham area, west-central Arabian Shield of Saudi Arabia, using remote sensing, field observations, and geochemical analysis techniques. SPOT-7 digital satellite data were employed in the analysis of these structural lineaments and dike swarms. The extracted orientations of the structural lineaments and dike swarms confirm that they are approximately identical, trending mainly in the NNW–WNW, NE–ENE, and E–W directions. Based on field observations and cross-cutting relationships, these dike swarms can be geochronologically arranged (from oldest to youngest) as mafic NNW- to WNW-trending dikes, mafic NE- to ENE-trending dikes, felsic NE-trending dikes, and local mafic E–W dikes. Major and trace elements geochemistry indicates that the studied dike swarms are basalt, basaltic andesite, and rhyolite in composition. Trace and REE diagrams, as well as their immobile elemental ratios of the studied dike swarms suggesting their formation in a typical intraoceanic island arc setting. In addition, the felsic NE dikes may represent extensive fractionation of the mafic magma from which the mafic NE dikes were formed because their incompatible elements signatures are almost similar. All dike swarms were likely emplaced between 620 and 576 Ma, and during the post-collisional extension and relaxation, following the amalgamation of terranes (island arcs) during the collision between the East and West Gondwana. [ABSTRACT FROM AUTHOR]