Scientists at the Geological Survey of India (GSI) have discovered, for the first time, "significant incidences" of gold associated with copper mineralisation in parts of Rudraprayag district of Uttarakhand.

"The gold values recorded from bedrock and stream sediment samples from the area are 475 ppb (parts per billion) and 1.42 ppm (parts per million), respectively," they have reported in the Current Science journal.

This part of Uttarakhand is in what is known as the "Lesser Himalaya" that is sandwiched, in the north, by the Main Central Thrust -- the major geological fault where the Indian Plate has been pushed under the Eurasian Plate along the Himalaya -- and in the south by North Almora Thrust.

The GSI scientists collected 355 samples from mineralised locales of Lameri-Koteshwar area of Uttarakhand. The gold and base metals were analysed at the GSI's chemical division in Lucknow.

"X-ray studies have indicated the presence of gold along with chalcopyrite, pyrite, sphalerite and galena in various samples," says the report, adding this "is the first record of in-situ gold incidence from the Rudraprayag area". Gold occurs as coarse, liberated particles and fine particles locked in pyrite and copper sulphide.

According to the report, the regions bearing gold are best exposed around Rudraprayag town in the Mandakini river valley. "Panning of stream sediments of Alaknanda and Mandakini rivers in Sumerpur-Ratura, Sari and Jugtoli areas revealed a few visible gold flakes."

The scientists also identified a cluster of five old workings in the form of shallow pockets around the Koteshwar area. "Near the old working site, one retort piece has also been recorded." Analysis of a sample of slag near the old working has yielded gold value of 45 ppb.

According to the GSI, gold is currently produced from three mines -- Hutti, Uti and Hirabuddni in Karnataka -- and, as a by-product, from the base metal sulphide deposits of Khetri in Rajasthan and Mosabani, Singhbhum, and Kundrekocha in Jharkhand.

Apart from the gold mines in the above-mentioned areas, some gold, although very small in quantity, is collected by "panning" from the sand and gravel of several rivers, including the Subarnarekha in Jharkhand and the Ambankadava Puzha and Chabiyar Puzha in Kerala.

Their finding on the occurrence of gold in alluvial deposits -- also called placer gold -- around Rudraprayag is indicative "of some probable potential auriferous (gold bearing) zone" towards the northern part of the region, the scientists say.