Abstract:

The Hardat Tolgoi Pb-Zn deposit is a medium-sized Pb-Zn deposit recently found in Erenhot-Dongwuqi polymetallic
ore belt along the suture zone between the North China plate and the Siberia plate. The granite relevant to the Pb-Zn mineralization
in the orefield is a concealed pluton. The LA-ICP-MS zircon U-Pb dating indicates that the granite was emplaced at 125±4.3
Ma and thus was the products of“ Yanshanian” magmatism. Detailed geochemical data show that the granite is composed of
weakly peraluminous (A/CNK= 0.99-1.08) rocks with low iron, high silicon, and high alkali contents (mostly Na<K). The granite
is enriched in large-ion lithophile elements (LILEs, such as Rb and K), Nd and Ta, but is depleted in high-field strength elements
(HFSEs, such as Nb and Ti), Ba and Sr. The chondrite-normalized REE pattern shows M type with tetrad effect and strong Eu
depletion (δEu=0.003~0.013). These results suggest that the alkaline feldspar granite belongs to alkalinity A type granite and was
formed in a post-orogenic tectonic environment. Nd-Pb isotopic compositions show that the alkaline feldspar granite was derived
from partial melting of the Mesoproterozoic upper crust.

Key words: alkaline feldspar granite, petrochemistry, Nd-Pb isotope, Hardat Tolgoi Pb-Zn deposit , Abaga Banner of Inner Mongolia