New orogenic type gold occurrences in the Uyanga ore knot (Central Mongolia)

Ariunbileg Sodov,Olga Gaskova,Otgonbaatar Dorjsuren,Battushig Altanbaatar,Oyunchimeg Tumen-Ulzii,Altansukh Gankhuyag,Dagva-Ochir Lkhagvasuren,O Chudaev,O Shouakar-Stash,R Harmon,R Millot,Y Kharaka

doi:10.1051/e3sconf/20199808020

Abstract

The Khangay-Khentey belt is located in central Mongolia (Central Asian Orogenic Belt). The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentaryErdenetsogtformation. The new Burgetei, Ult and Senjit gold occurrences were studied. The rocks of theErdenetsogtformation have an irregular gold content: 0.96 g/t Au is determined in quartz vein (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hgand Sb content up to 8.5 ppm and 39 ppm respectively. The Au content of arsenic pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). The ore-mineral assemblages in the new gold occurrences reflect the differences between three explored sites, formed in the course of fluid evolution during the water-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact.

Highlights

The classical theory implies that orogenic Au deposits are formed during the late stage of orogeny and are typically hosted by the rocks of greenschist to amphibolite metamorphic grade that may be spatially related to granitoid intrusions [1,2,3]
The primary ore occurrences of the Uyanga gold ore knot district of the Khangay gold zone are hosted in volcanogenic-sedimentary rocks of the lower-middle Devonian Erdenetsogt formation
This work used the field data sampled from the exploration trenches in the Burgetei, Ult and Senjit gold occurrences of the Uyanga ore knot district in 2016

Summary

Introduction

The classical theory implies that orogenic Au deposits are formed during the late stage of orogeny and are typically hosted by the rocks of greenschist to amphibolite metamorphic grade that may be spatially related to granitoid intrusions [1,2,3]. Arsenopyrite and pyrite represent the most abundant sulphide minerals that occur in association with the Au mineralization, which formed from low salinity, CO2-bearing, reduced and near-neutral pH fluids that show a wide range in fluid temperatures from about 200 to 500°C

Methods

Results

Discussion

Conclusion