3D modeling of the porphyry-related Dawangding gold deposit in south China: Implications for ore genesis and resources evaluation

Abstract

The Dawangding deposit is a porphyry-related gold deposit in the Dayaoshan orogenic belt. Its formation is much more complex than typical orogenic gold and porphyry gold deposits. This complexity can cause great difficulty in getting correct exploration results. We applied a knowledge-driven and multi-constraint modeling approach to construct 3D geometric models of the orebodies and intrusions, and used the FLAC3D modeling to simulate the coupled mechano-thermo-hydrological (MTH) dynamics of the intrusions' cooling process. The 3D geometric features of orebodies as well as the distribution of Au reserves and Au grades in 3D space imply some important information for evaluating the deposit and for constructing computational models to understand the genesis of the deposit through geodynamic process modeling. Most orebodies are vein-shaped and located within the Dawangding porphyry intrusion, suggesting that the porphyry intrusions were the most important ore-controlling factor. The 3D shape and spatial distribution of orebodies and the intrusion indicate that the dominant orebodies are hosted by fractures that partly overlap the intrusion's contact zone. The computational dynamic modeling results demonstrate that the high dilation zones were formed by coupled MTH processes during syn-stretching cooling of the hot intrusions, and controlled gold orebodies. The 3D model of the Dawangding intrusion itself and the gold orebodies in the intrusion suggests that either densifying the exploration grid or increasing the exploration depth would likely increase the value of the Dawangding deposit The dynamic modeling shows a major high dilation zone at depth where no exploration work has been carried out and there is likely potential for discovering new gold orebodies.