The genesis of the Chedu gold deposit in Nansha River area, Shaanxi Province

In this paper, the research work of the Proterozoic deposit in Nansha River area of Shaanxi Province was carried out, and the results show that the basalt volcanic tuff in Bikou Group 2^nd sub-group (Pt_2-3bk₂) is relatively rich in Sr, Ba, Rb, Ce, P and Sm, and depleted in Ta, Nb, Zr, Hf and Ti, exhibiting characteristics of calcium-alkaline volcanic arc basalt. There are two genetic types of the Proterozoic deposits, one is the strongly silicified rock type gold deposits related to the ductile shear zone formed by the Mesozoic thrust Nappe structure, and the other is the BIF type gold deposits related to the 2^nd subgroup volcanic tuff of the Meso-Neo Proterozoic period. According to composition analysis of single granular magnetite, the authors hold that magnetite has high TFeO (99.59% on average) content and very low TiO₂, MgO, A1₂O₃ and MnO content in gold magnetic quartz, which indicates that the banded magnetite in the Chedu magnetite quartzite gold ore is of sedimentary metamorphic type, i.e., belonging to quartzite type gold deposit. Hydrogen and oxygen isotope features of gold-bearing magnetite quartzite type gold ore show that δ¹⁸O water value is 12.34‰~12.45‰ (12.4‰ on average), and δD value is -112.6‰~-103.5‰ (-108.05‰ on average), consistent with BIF variation range of δD-type iron ore in Anshan-Benxi area (-129‰~-75‰), suggesting that quartz minerals in quartz rocks with gold magnetite have BIF characteristics.