ON THE OCCURRENCE OF LOUGHLINITE (Na-SEPIOLITE) IN PANS OF THE NORTHERN CAPE PROVINCE, SOUTH AFRICA

Abstract

The occurrence of loughlinite (Na-sepiolite) in two pans (Koi Pan and Brak Pan) of the Northern Cape Province is reported upon. The presence of loughlinite within the pan sediments was confirmed by means of X-ray Diffraction analysis, which showed distinct reflections at 12.7 to 12.8 Å, which collapsed to 12.3 Å following Mg-saturation. This is the fourth reported occurrence of loughlinite worldwide and the first from South Africa. Loughlinite occurs associated with the mineral analcime, which was also reported from all previously described occurrences of the former. It is also interesting to note that all known occurrences of loughlinite are from playa-lake settings. We propose that the mineral formed authigenically under the saline and alkaline conditions of the pan environment, as is also deemed to have happened by some scholars in the Killik area, Turkey. Loughlinitization of sepiolite from sepiolite-bearing Kalahari calcrete occurring within the study area appears unlikely.

Deep subsurface mine stalactites trap endemic fissure fluid Archaea, Bacteria, and Nematoda possibly originating from ancient seas

“…This focuses the origin on marine/brackish water related source on the surface. The geological history of Southern Africa indicates two large windows of opportunity; one 350–250 myr ago during the initial existence stage of the inland Karoo Sea (McCarthy and Rubidge, 2005 ) and a second geological more recent period linked to the origin of the salt pans in South Africa (Roelofse, 2010 ). In the event of the Karoo Sea origin, the nematodes could have traveled to the deep subsurface from brackish coastal waters.…”

“…Salt pans are regularly visited by large flocks of birds and this constitutes a way M. parvella could have been transported from coastal areas to the inland after the disappearance of the Karoo Sea, as nematode transport by birds has been documented (Frisch et al, 2007 ). The oldest date for a salt pan known to us in South Africa was cited by Roelofse ( 2010 ) as 100 kyr. It is doubtful that this is the upper limit for the presence of salt pans in South Africa but in the absence of more rigid age data on salt pans, this second window of opportunity cannot be more exactly defined other than at least 100 kyr.…”