Date of Award
Earth and Environmental Sciences
Dr. William Simmons
Mr. Alexander Falster
Dr. Karen Webber
The Usakos pegmatite, Namibia, is a highly evolved, rare-element LCT-type pegmatite. The pegmatite is emplaced in metasedimentary rocks of the Kuiseb formation. Ca and Al enrichment at the contact, B mineralization in the country rock and Sr mineralization in the core of the pegmatite are all evidence of interaction of the pegmatite melt and hosting country rock. K/Rb ratios within mica and feldspar are very low indicating a highly evolved melt. Tourmaline has a fractionation trend from Fe-rich at contact and intermediate areas to Fe-depleted in core regions and pockets. Columbite tantalite group minerals show a similar trend in fractionation, with columbite-(Fe) found near the pegmatite country rock contact and tantalite-(Mn) found in the core region. Trace element geochemistry from samples of pegmatite-country rock contact is enriched in light rare earth elements. Whole rock geochemistry provides evidence of the geochemically evolved nature of the pegmatite forming melt.
Grassi, Leah R., "A Geochemical Investigation of the Usakos Gem Tourmaline Pegmatite, Namibia" (2014). University of New Orleans Theses and Dissertations. 1803.