Wednesday, January 30, 2008

GOLD IN THE COALS

GOLD IN THE COALS
By
DR. NITISH PRIYADARSHI

The origin of coal
Coal is a result of the accumulation and slow decay of plant remains in sedimentary strata. It undergoes in situ compaction under water with time, accompanied by biochemical processes such as decomposition due to bacterial action, dehydration, loss of volatile compounds (e.g. methane, higher hydrocarbons, carbon dioxide and nitrogen) and densification to form various ranks of coal depending on environmental conditions. In absence of atmospheric oxygen, the plant matter is further degraded by the action of anaerobic bacteria, which extract and utilize oxygen from organic molecules containing oxygen like lignin.
Gold in coals
Gold is an ultra trace constituent of coal and is rarely determined. There are early reports of gold in coal, for example it was detected in a coal from Wyoming, USA. About 1 ppm gold was found in some coals from Utah and upto 3 ppm gold in coal from Cambria, Wyoming-North Dakota, USA. Goldschmidt and Peters found 0.2-1ppm gold in some German coal ashes. Leutwein in 1956 mentioned some peats with rather high amount of gold.
There are some results (as parts per billion) for gold in coal, namely less than 1 to 10 for Australia, 1.0-2.5 for the Lithgow seam, NSW, Australia, 10-140 for Belgium, mean value for Bulgaria, 1-96 for Canada, 1.2-10 for the United Kingdom.
Recently samples of Jurassic and Paleogene brown coals and peat samples from the South-eastern region of the Western-Siberian platform were analyzed for gold by the neutron-activation method.
Mean content of gold in Jurassic coals is 30 ± 8 ppb, in Paleogene coals is 10.6 ± 4.8 ppb, and in peat is 6 ± 1.4 ppb. Concentrations of gold as high as 4.4 ppm were found in coal ash and 0.48 ppm in the peat ash. Coal beds with anomalous gold contents were found at Western-Siberian platform for the first time.
However, there is a need for much more data to clarify the situation.

Reference:
International Journal of Coal Geology Volume 68, Issues 3-4, 2 October 2006, Pages 127-134

Dr. Nitish Priyadarshi
Geologist
Email: nitish.priyadarshi@gmail.com
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