Revealing the orogenic genesis of Huogeqi Cu-Pb-Zn deposit: Evidence from the machine learning-based data interpretation of pyrite geochemistry

Orogenic-type gold deposit is of great economic importance worldwide and its ore-fluid is believed to have poor ability in transporting base metals such as Cu, Pb, and Zn. However, increasing numbers of case studies have shown that base metal deposits can also form in similar geological processes as orogenic gold, and share similar characteristics with the latter. This leaves whether orogenic-type deposit is gold-only an open question for economic geologists. The shear zone-controlled Huogeqi Cu-Pb-Zn deposit is located in the north margin of the North China Craton. Although it is still debated whether this deposit is orogenic-type or of syngenetic origin, our previous geological, fluid inclusion, geochronological and stable isotopic studies have shown that it shares broad similarities with orogenic-type deposit. In this study, an alternative approach, the geochemistry of syn-ore pyrite coupled with supervised machine learning-based data interpretation, is employed to discriminate the genesis of this deposit. It is shown that the syn-ore pyrite is geochemically similar to those from orogenic-type deposits rather than VMS or sedimentary pyrite, and thus confirms the orogenic genesis and unambiguously exclude the syngenetic origin of this deposit from a different perspective. The results in this study support the view that orogenic-type ore-forming system can also form base metal deposit, which is consistent with the studies and simulation results by other researchers. In addition, since the pyrite can only record the geochemistry infor-mation in the final deposition of the mineral and eliminate the histories before the last deposition stage, the data interpretation of pyrite geochemistry by machine learning method is a powerful tool to discriminate the genesis of deposit, especially suitable for the deposits with multistage ore-forming processes.