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

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. TiO 2 abundances exceed 94 wt.%, with FeO (up to 4.2 wt.%), SiO 2 (up to 1.5 wt.%) and Al 2 O 3 (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. Al 2 O 3 -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.

Rutile Mineral Chemistry as a Guide to Provenance of Red Sediments and Modern Sands of Bhimunipatnam–Konada Coast, Andhra Pradesh, East Coast of India

“…Electron probe microanalyzer data on rutile indicate that a large number of trace elements (Fe, Cr, Al, Mg, Nb, Ta) may substitute Ti in the rutile lattice [7][8][9][10][11][12][13][14][15] and the trace elements signature could be used as a provenance indicator. Detrital rutile geochemical studies by Meinhold et al, Stendal et al and Triebold et al [13,16,17] have demarcated the effectiveness of the method in identifying source and containing the metamorphic evolution of the hinterland.…”

Hydrocarbon Source Rock Potential of the Lacustrine Black Shale Unit, Mamfe Basin, Cameroon, West Africa

“…It is made up of three sub-basins; a west, middle and east sub-basins respectively separated by structural highs and that this basin generally shallows to the east. The basin is underlain and fringed by reactivated, fault-bounded granitogneissic rocks of the Pan-African Mobile Belt (550 ± 100 Ma) and are both intruded by Tertiary anorogenic and effusive basic intermediate rocks such as syenites, diorites, trachytes and basalts that belong to the CVL (Njonfang andMoreau,1996 andEyong et al, 2013). Wilson (1928,;Le Fur (1965), Dumort (1968) and Eyong et al.…”

“…It is oriented in a NE-SW trending direction, measuring 130km in length and a widest part is about 60 km and covering a total surface area of 2400 km 2 The basin stretches across the Cameroon-Nigerian boundary to join the Benue Trough in the west and is bordered by the Obudu and Oban Massifs, respectively in the north and south (Figure 2), while in the east, it narrows and disappears under the Bamenda Highlands which forms part of the Cameroon Volcanic Line (CVL). Preliminary geological studies; Wilson (1928), Le Fur (1965), Dumort (1968), Hell, Ngako, Bea, Olinga, and Eyong (2000), Eyong, (2001), Eyong (2003), Eyong, Wignall, Fantong, Best and Hell (2013), and geophysical surveys; Fairhead and Okereke (1987), Benkhelil (1989), Kangkolo andOjo, 1995, Manguelle-Dicoum, Nouayou, Tabod, andKwende-Mbanwi (1999), Fairhead, Okereke, and Nnange (2004), Ndougsa-Mbarga, et al (2007), Abolo (2008Abolo ( ), kangkolo (2008, Kanouo (2008), Tabod, Tokam-Kamga, Manguelle-Dicoum, Nouayou andNguiya (2008), Kanouo et al, 2012, Nguimbous-Kouoh et al, 2012, have indicated that predominantly thickly folded and fractured fluviatile to deltaic cross stratified conglomeratic sandstones, intercalated by thick beds of black organic rich lacustrine carbonaceous rocks and thin beds of carbonates and evaporites make up the Mamfe Basin sedimentary fill. Hydrocarbon prospectivity in the Mamfe Basin like any other basin must rely essentially on the presence of oil and/or gas-prone rock units which should have generated and expelled hydrocarbons.…”

Aptian-Late Cenomanian Fluvio-Lacustrine Lithofacies and Palynomorphs from Mamfe Basin, Southwest Cameroon, West Africa

“…The fossil content will ascertain the presence or absent of marine sediments among the lithologies studied and this may offer the key divide between a marine or continental source of the brines. The authors hope to contribute considerably towards the gradual construction of a verifiable stratigraphic framework and petroleum exploration activities that have just begun in this basin [23] [24].…”