Gold deposits, secondary

Occurrence.—The greater part of the world s gold is found in the metallic state either in primary deposits in veins in association with quartz, or as alluvial gold in secondary deposits in the form of dust, grains, fine leaves, or in larger pieces. 

Oxidation of sulfide minerals can occur naturally or as a result of mining activity. Arsenic-rich minerals around mines may, therefore, produce arsenic-rich drainage locally, but this tends to be attenuated rapidly as a result of adsorption of various arsenic species by secondary minerals. Some of the best-documented cases of arsenic contamination occur in areas of sulfide mineralization, particularly those associated with gold deposits. 

Delcorte, A., Medard, N., Bertrand, R. (2002) Organic secondary ion mass spectrometry sensitivity enhancement by gold deposition. A flZ. Chem., 74,4955 968. 

It is noteworthy that bornite, chalcocite and tetrahedrite-tennantite which are common minerals in Kuroko deposits occur in gold bearing Besshi-type deposits. Although these minerals are considered to be secondary minerals, depositional environments of these minerals are characterized by higher /s, and foj conditions. It is also noteworthy that these deposits are rich in pyrite rather than pyrrhotite. Probably, Besshi-subtype deposits in Shikoku formed under the higher fo and /sj conditions than the deposits characterized by pyrrhotite (Maizuru, Hidaka, Kii, east Sanbagawa). Such typical Besshi-type deposits (Besshi-subtype deposits in Shikoku) are characterized by simple sulfide mineral assemblage (chalcopyrite, pyrite, small amounts of sphalerite). Inclusion of bornite in pyrite is also common in these deposits. 

Dannetun P, Boman M, Stafstrom S, Salaneck WR, Lazzaroni R, Fredriksson C, Bredas JL, Zamboni R, Taliani C (1993) The chemical and electronic structure of the interface between aluminum and polythiophene semiconductors. J Chem Phys 99(l) 664-672 Ahn H, Whitten JE (2003) Vapor-deposition of aluminum on thiophene-terminated self-assembled monolayers on gold. J Phys Chem B 107(27) 6565-6572 Fisher GL, Flooper A, Opila RL, Jung DR, Allara DL, Winograd N (1999) The interaction between vapor-deposited A1 atoms and methylester-terminated self-assembled monolayers studied by time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and infrared reflectance spectroscopy. J Electron Spectrosc Relat Phenom 98-99 139-148... 

One form of heterogeneous immunoassay is called enzyme-linked immunosorbent immunoassay (ELISA). In one instance, electrochemical immunoassay was performed for anti-ferritin (antibody) in a PDMS/PMMA chip. First, DTSSP was self-assembled on the gold electrode deposited on the PMMA plate. Then horse spleen ferritin (antigen) was attached to the DTSSP layer. A 100-p.g/mL solution of anti-horse ferritin (rabbit serum) was added. Then a secondary anti-rabbit antibody (HRP-linked) was introduced. A substrate (4-CN) was finally added which was converted to a precipitate product. The precipitate caused a reduction... 

Haemochromatosis leads to an increase in the density of the liver parenchyma, which correlates with the accumulation of iron. CT scans reveal a remarkably dense and bright liver parenchyma with density values of up to +140 HU (so-called white liver). The deposition of 1 g iron results in a rise in density of 1 HU. (20) CT densitometry clearly facilitates effective control of therapeutic success in this storage disease. It is not possible, however, to differentiate pronounced secondary haemo-siderosis. Hyperdense values are also found in longterm gold therapy, in glycogen thesaurismosis and M. Wilson, or in chronic arsenic poisoning. 

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