Prospection for gold and new occurrences of gold-bearing mineralization in the eastern Mongolian Altay

Abstract

Geological mapping and regional geochemical prospection on a scale of 1:50,000, covered an area of about 4,000 km 2 in the Zamtyn Nuruu region of the eastern Mongolian Altay. Northern part of the region is formed by the Lake Zone Terrane, the southern by the Gobi Altay Terrane; these two units are separated by the Bogd fault. The panned-concentrate heavy mineral survey was combined with the dry stream-sediment geochemistry, both being complemented by lithogeochemical sampling. The dry stream-sediment geochemistry proved to be a suitable method for regional prospection in semiarid to arid areas of Mongolia. The morphology and composition of placer gold grains were studied in order to estimate the distance from the primary source, and to constrain the nature of prospective primary mineral deposits. Based on the results of the regional geochemical survey and geological mapping, follow-up works were focused on prospective areas including the reconnaissance field works, detailed geochemical sampling, and geophysical measurements. New occurrences and signs of Au, Cu, Zn and (Ba)-As-Sb-Hg mineralizations were discovered. The ascertained goldbearing mineralizations are represented namely by Au and Au-(Ag) quartz veins in basic metavolcanic rocks of the Neoproterozoic Khan Taishir and volcanic rocks of the Permian Delger Khangay formations. Gold locally accompanies vein-disseminated base metal mineralization in some Proterozoic and Lower Palaeozoic formations. A prospective occurrence of clastic gold in Mesozoic conglomerates and sandstones was found at the northern edge of the Zamtyn Nuruu around the Samoandamba Uul. The geochemical survey has revealed a contrast in occurrence of ore indices between the two terranes formig the studied area. While the Lake Terrane and, especially, the Neoproterozoic Khan Taishir Formation are rich in gold and base metal showings, the Gobi Altay Terrane is barren.

Beyond the Great Wall: Gold of the Silk Roads and the First Empire of the Steppes

“…The foils from Gol Mod match the fragments from Egiin Gol, but those from Takhiltin and Shombuuziin are of lower quality and separated in two chemical groups. Placer gold in Mongolian Altai goes from high quality of nearly 100% fineness (Au content) at Ulaan Ul over Erdene Uul with 90–95% down to as low as 80.2% in Bayan Tolgoi . The fineness of native gold in quartz vein from this deposits ranges from 75% to 100%, some deposits showing two different qualities (for example, at Gobi–Altai Terrane 98% and 86%), which could explain both the variety and the separation into two groups of Takhiltin and Shombuuziin gold foils.…”

“…Placer gold in Mongolian Altai goes from high quality of nearly 100% fineness (Au content) at Ulaan Ul over Erdene Uul with 90−95% down to as low as 80.2% in Bayan Tolgoi. 40 The fineness of native gold in quartz vein from this deposits ranges from 75% to 100%, some deposits showing two different qualities (for example, at Gobi−Altai Terrane 98% and 86%), which could explain both the variety and the separation into two groups of Takhiltin and Shombuuziin gold foils. Gold of lower quality can be found but in deposits located far from Gol Mod.…”

Prospection for Copper Mineralization With Contribution of Remote Sensing, Geochemical and Mineralographical Data in Abhar 1:100,000 Sheet, Nw Iran / Poszukiwania Zasobów Rud Miedzi Z Zastosowaniem Zdalnych Technik Wykorzystujących Dane Geochemiczne I Mineralogiczne W Pokładzie Geologicznym Abhar 1:100,000 W Północno-Zachodnim Iranie

“…Finer (silt) fractions of alluvial sediments represent well the geochemistry of the drainage pattern and also reduce a "nugget effect" during sampling (Fletcher, 1997;Aichler et al, 2008). This method can be effectively used also in regional prospection for gold as shown by Xie & Wang (1991).…”

Correlation between Cu mineralization and major faults using multifractal modelling in the Tarom area (NW Iran)

“…The silt fraction of alluvial sediments is representative of the geochemistry of the drainage pattern and reduces the "nugget effect" during sampling (Fletcher 1997;Aichler et al 2008). Once material enters the stream, processes that move sediment also change its texture and geochemical composition.…”