Gold with the symbol Au is an element of group IB which has an atomic number of 79 and atomic mass of 196.966655 making it one of the higher atomic number elements occurring naturally. The crustal abundance of gold is 0.004 and the metal is positioned between Ag and Rg. The terrestrial abundance of gold (0.005 ppm) is similar to that of platinum (Pt: 0.005 ppm) but, low compared with Cu (50 ppm), Ag (0.07 ppm), and the Au/Ag ratio is equal to 0.07. Gold is a siderophile group elements which displays some characteristics that relate it to chalcophile group elements.
Gold is a precious metal which is mined from Archean to Recent in age deposit types. The large variability in the geological setting of gold deposits suggests its transport and concentration by magmatic, hydrothermal and sedimentary possesses. It occurs alongside with platinum-group elements (PGE) and some heavy minerals like magnetite, ilmenite, garnet zircon, rutile, monazite and cassiterite (Frimmel, 2007). Gold combines only with tellurides, selenides and bismuthides (Boyle, 1987; Macdonald, 2007) and alloyed with Ag, Cu, Bi, Hg and PGE. Two types of auriferous deposits that include lode (or vein) deposits and placers are recognized (Boyle, 1987). The enigmatic quartz-pebble conglomerate deposits and the largest auriferous concentrations on earth are classified as modified paleo-placers closely related to lode deposits. Gold is widespread in low concentration in igneous rocks, it also occurs in primary hydrothermal in ore veins, in contact metamorphic deposits, in pegmatites, pyrite, arsenopyrite, quartz and other minerals (Korbel and Novak, 2001). Hydrothermal deposits (veins) associated with quartz and pyrite and placers deposits (Boyle, 1987) that derived from the weathering of gold-bearing rocks contain significant amounts of gold.
In its native state, gold occurs in tellurides and selenides (Boyle, 1987; Macdonald, 2007), and as inclusion in pyrite; it alloyed with Ag, Cu, Bi, Hg, and PGE. 197Au is only the one naturally occurring isotope of gold and the principal oxidation states of Au are + 1 (aurous) and + 3 (auric). Au is mainly present in the following complexes: [Au(CN)2]−, [AuCl2]−, [Au(OH)4]−, [AuCI4]−, [AuS]. The most common compounds include AuCl3 and HAuCl4; aurostibite and tellurides being the principal ore minerals of Au. Numerous Au and Au-Ag tellurides exist in which sylvanite, calaverite, petzite, krennerite and nagyagite are the most common occurring. Other auriferous compounds include antimonide (AuSb2), argentiferous gold selenide (Ag3AuSe2), uytenbogaardtite (Ag3AuS2) and bismuthide (Au2Bi).
Morphological changes in gold particles are attributed to hammering and abrasion (Youngson and Craw, 1999). Little shape modification is attributed to the mass transport of colluvial gold while significant changes are attributed to distance of travel, or time spent in fluvial systems and nature of bedrocks (Youngson and Craw, 1999). The general characteristics of gold grain morphology is indicative of transport distance (Townley et al., 2003).
The gold metal is among the most valued and sought-after commodity, which can be attributed to its malleability, resistance to corrosion and tarnishing and the glitter, makes it ideal for many jewelry purposes. Now, gold is finding industrial uses dues to its high resistance to chemical reaction, high conductivity, ductility and its rareness. The radioactive 198Au is used for medical diagnosis and radiation therapy for the treatment of cancer and rheumatoid arthritis (Armendariz et al., 2004; Macdonald, 2007), and as a tracer in industrial applications. Others use of gold include electronics, coins and decorative. Gold alloys are used in industrial applications such as electroplating, granulation, pressing and lamination.
The aim of this study is to investigate the geochemical distribution of gold, to determine the gold grains morphology and to examine the frequency distribution of elements associated with gold in stream sediment from Boyo area, situated within the Pan-African basement in Cameroon where important small-scale alluvial gold mining sites are found.