Abstract:

Several Mopolymetallic ores have been explored and verified in the eastern Inner Mongolia area since 2004. The Wuhuaaobao Mo deposit in Honggeer area of Erlianhot is one of the new found ores. But, till now there are few studies about this ore deposit. The present paper deals with the geological features， the characteristics of igneous rock assemblages and  the results of LAICP MS zircon UPb dating. We propose that the metallogenic igneous rocks are quartz porphyry, granite porphyry and concealed finegrained adamellite.  The granodiorite exposed  on the surface is the surrounding rock. In TAS diagram, metallogenic igneous rocks are  plotted in subalkaline areas and in SiO2K2O diagram, belong to highpotasstic calcalkaline series. They are metaluminous with σ  between 1.913.29(average is 2.44) and A/CNK between 0.8761.013. Trace element abundances show  enrichment in Rb, K and depletion in Ba, Sr. High field  strength elements  show enrichment in Th, La, Ce, Nd, Zr, Ta, Hf, Tm, Tb, Yb and  relatively depleted in P, Sm, Nb and extremely depleted in Y. It reflects  the process of obvious crystallizationdifferentiation  and  proves that there is fractional distillation in LREE and HREE and LREE/HREE is 6.5214.76 which is much higher than average. According to δEu  ranges in 0.430.91, we inferred that there must have happened plagioclase fractional crystallization during the process of granitoid magma evolution  or  there were plagioclase  remnants in source region. The LAICP MS zircon UPb dating of quartz porphyry yielded an age of 139.2±3.4 Ma with MSWD of 1.9. All above, combined with tectonic setting discrimination and regional geological correlation, it is reasonable to conjecture  that the Wuhuaaobao Mo deposit was formed in  Early Cretaceous, namely, in the syncollisional stage of Mongolia microcontinent when merging with Siberia plate along the MongolianOkhotsk zone in Late Yanshan Epoch.

Key words: Wuhuaaobao Mo deposit, porphyry, meallogenic igneous rock assemblages, Early Cretaceous, syncollisional, MongolianOkhotsk