Analysis Of Geological, Geochemical Characteristics And Thegensis Of The Haoyaoerhudong Gold Deposit, Inner Mongolia Autonomous Region, China

Haoraoerhudong gold deposit is a typical black rock-hosted gold in the north margin of North China Block. This gold deposit has characteristics of great scale and low grade, as the detail report of reconnaissance in 2013 showed the average grade was only 0.82 g/t, but the proved reserve was 148.5 t, and it was considered as a greatest heap-leaching-type gold deposit in northern China. In this paper, the geological and geochemical studies of this gold deposit, including geological phenomena, isotope and rare earth elements, indicate ore-forming materials derived from strata activated and precipitated gold during the regional metamorphism and magmatic intrusion.(1)The wall rock in Haoraoerhudong gold deposit is black carbonaceous weak metamorphic rock in Mesoproterozoic Bilute Formation of the Bayan Obo Group, which is similar to black rock series. The orebody is hosted by the first and second segments of Bilute Formation in both wings of syncline, and has a characteristic of stratigraphic control. Gold mineralization occurs in the board and joint plate of carbonaceous slate.(2) Geological and geochemical profile survey found that the contents of trace elements Au、Ag、As are changing regularly in the profile,the closer to the intrusive,the higher the contents are. Especially the Au element,some even reach the industrial grade,that manifest the gold enrichment must have a connection with the basic vein rocks.(3) Trace elements of the samples can be divided in three groups as intrusive, surrounding rock and ore, which has been analyzed by correlation and cluster analysis. Correlation analysis shows that Au in orebody has negative relation with the elements of tail halo, and that Au in intrusion has positive relation with the elements of tail halo Cluster analysis sorts out Au-Ag-As as the combination of ore-forming element, which is identical with metallogenic indicative elements of carbonaceous slate. These phenomena jointly suggest that ore-forming materials derive from block rock series.(4) Combined with the main elements data, trace elements and rare earth elements, the comprehensive analysis shows that, The original rock of metamorphic rock in the Haoyaoerhudong gold deposit is sedimentary rock, the sedimentary environment shoud be continental margin arc, of ordinary sedimentary origin with a weak acid water.(5) The formation process of ore deposit could be divided into three stages, the first stage occur in middle Proterozoic, while basis of sedimentary happenned, and formed the ore source layer; The second stage, during the period between Neoproterozoic and the Late Carboniferous, there happenned the metamorphism, which made the ore-bearing formation; The third stage, by referencing isotope dating data, we know that the gold deposit formed at the same time of the Magma intrusion during Hercynian.