Structural control

The dry pans are a key but not the source to the kimberlite deposits in the north east of Limpopo Province. Sometimes the shallowest aphanitic kimberlite outcrops within them may lead attention to follow tens of kilometres fault strike. The pans are shaped by numerous phases of fault and conjugate shear along their margins. These faults themselves are rooted in the mantle near the deepest olivine phase transition, that itself has evolved at least prior to driving the Mesozoic-Cenozoic pan-continental rifting cycles, coupled with oceanic spreading. The remnants of these faults are to be traced into South America. Quartz boudins in granite, tear faults exhibiting dramatic elevation and pan hummocks with channel margin exposure of weathered kimberlite are some of the clues to the fault systems that have developed across the East African continent and created fables of correlative kimberlite age trends and southern Atlantic hot spot trails.
#kimberlite #rifts #mantle #structure

Dry pans

These dry pans, reminiscent of Roman architecture are just one part of a structural code that unravels the evolution of the Archaean Kaapvaal landscape. The ancient granite country host yields a variety of intrusions that have been deformed by fault movements evolved from some of Earth’s oldest failed rifting episodes. Precursor, pre-rift dolerite intrusions lay hidden beneath the hummocky pan floor. The pans are defined by fold and fracture sets that have formed across a dominant geometrical shear zone. The fractured pan margins bordering the Veldt repose in linear pillars of obedience to the faults that formed them millions of years ago. At the margins of the pan the soil profile reveals a basal clastic conglomerate borne from tear faults initiated along the shear margins. The lateritic profile is quite different to the marls seen in profile at the other end of the pan. These small basins were never to evolve further, but a view across the pan into the Veldt all but hides the passage of the shear zone across the landscape and into the distance towards the Highlands. Source mantle faults may have failed to rift this thick crust, but they did manage to emplace younger intrusions of different volcanic origin camouflaged, together with Kudu, under the Veldt canopy.
#structure #Earth #geology #exploration #mantle