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.
| Identifer | oai:union.ndltd.org:uno.edu/oai:scholarworks.uno.edu:td-2863 |
| Date | 16 May 2014 |
| Creators | Grassi, Leah R |
| Publisher | ScholarWorks@UNO |
| Source Sets | University of New Orleans |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | University of New Orleans Theses and Dissertations |
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