Greyish-Black Rutile Megaclasts from the Nsanaragati Gem Placer, SW Cameroon: Geochemical Features and Genesis

Nguo Sylvestre Kanouo, Rose Fouateu Yongue, Shouyu Chen, Emmanuel Njonfang, Changqian Ma, Tanwi Richard Ghogomu, Jiangnan Zhao, Elise Sababa

Abstract


Greyish-black rutile megaclasts from the Nsanaragati gem placer in south western Cameroon display a wide range of lithophile and siderophile elements in LA-ICP-MS analyses. TiO2 abundances exceed 94 wt.%, with FeO (up to 4.2 wt.%), SiO2 (up to 1.5 wt.%) and Al2O3 (up to 1.8 wt.%) forming noticeable contents. Minor and trace elements with significant to moderate values (ppm) include Nb (965-4814), V (729-1846), Cr (495-756), Ta (44-180), and Zr (43-210). Nb/Ta ratios range between 10.0-44.9 and place the Nsanaragati rutile grains within the Niobium rutile. The measured contents for other elements including total REE are < 150 ppm, mostly falling below detection limits. Al2O3-MgO plots (wt.%) indicate that most rutile grains fall within a crust-derived rutile field, with rare plots in the mantle-derived field. Cr-Nb plots suggest the grains are related to rutile from metapelitic rocks, rather than metamafic rocks. Temperatures calculated from Zr in rutile thermometry range from 470 to 675°C, compatible with a likely crustal metapelitic source.

Full Text: PDF DOI: 10.5539/jgg.v4n2p134

Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.

Journal of Geography and Geology   ISSN 1916-9779 (Print)   ISSN 1916-9787 (Online)

Copyright © Canadian Center of Science and Education

To make sure that you can receive messages from us, please add the 'ccsenet.org' domain to your e-mail 'safe list'. If you do not receive e-mail in your 'inbox', check your 'bulk mail' or 'junk mail' folders.