『Abstract
　The Nyong unit is a greenstone belt at the NW border of the Archaean Congo craton. In this study, results of initial geochemical prospection for gold and platinum-group elements (Au-PGE) in pyroxinites, amphibolites, and their weathered products in the Nyong unit are reported from two areas, Lolodorf and Nyabitande.
　Garnet-bearing pyroxinites and pyroxinites devoid of garnet were investigated in the Lolodorf region. The main minerals in these rocks are clino/orthopyroxene + biotite + amphibole + feldspar±garnet±quartz±opaque minerals corresponding to a granulite facies assemblage. At Nyabitande region, garnet-bearing amphibolites and non-garnetiferous equivalents were identified. These have a granoblastic heterogranular texture, with associations of amphibole + plagioclase + quartz + opaque minerals + garnet±sulphides indicating the amphibolite facies. Both rock types are characterized by: (i) moderate SiO2, Al2O3, Fe2O3, CaO, MgO, Cr, V, Ni, Zn, Cu, Co, and Sc contents; (ii) low lanthanide contents with variable LREE-enrichment; and (iii) positive Ce and negative Eu anomalies. The (La/Yb)N ratios are only high in amphiboliters.
　The Au-PGE contents are low (25.1 to 120.9 ppb). Palladium and Pt are the most enriched PGE. These rocks are highly enriched in PPGE than in IPGE. The Pt/Pd ratios indicate that Pt is more mobile than Pd. They have positive Pd anomalies. The Pt/Ir, Pt/Rh, Pt/Ru, and Pt/Au ratios are variable, and indicate that Ir, Rh, Ru, and Au are more mobile than Pt.
　Weathered pyroxinites and amphibolites are also characterized by moderate SiO2, Al2O3, Fe2O3, and some transition trace metal contents. They are, in addition, marked by moderate REE contents and LREE-enrichment. The (La/Yb)N ratios indicate that weathered pyroxinites have more fractionated signatures than the weathered amphibolites. All the weathered samples have low Au-PGE contents with PPGE-enrichment. The Pt and Pd contents increase from the parent rock to the slightly weathered amphibolites contrary to the weathered pyroxinites.
　Mass-balance calculations reveal a strong accumulation of Fe, Mn, Ti, Al, some trace and rare-earth elements; and strong leaching of Au-PGE in several weathered samples.
　Pyroxinites, amphibolites, and their weathered products here, therefore, are not judged to have a favorable potential target for further Au-PGE exploration.

Keywords: SW-Cameroon; Nyong unit; Mafic-ultramafic rocks; Weathering; Geochemistry; Au-PGE exploration』

1. Introduction
2. Geographical and geological setting
3. Sampling and analytical techniques
　3.1. Sampling techniques
　3.2. Analytical techniques
4. Results
　4.1. Petrography and geochemistry of pyroxinites and amphiboles
　　4.1.1. Petrography
　　4.1.2. Geochemistry
　4.2. Petrology of weathered products
　　4.2.1. Morphology, mineralogy and distribution of major and trace elements
　　　4.2.1.1. Weathered garnet-bearing pyroxinites
　　　4.2.1.2. Weathered non-garnetiferous pyroxinites
　　　4.2.1.3. Weathered amphibolites
　　4.2.2. Geochemistry
　4.3. Genesis of mineralization
5. Mass balance evaluation
6. Discussion
　6.1. Petrography and geochemistry of pyroxinites and amphibolites
　6.2. Petrology of weathered materials
　6.3 Genesis of mineralization
　6.4. Mass balance assessment
7. Conclusion
Acknowledgments
Appendix A. Supplementary data
References