Deep exploration of No.50 kimberlite pipe in Wafangdian, Liaoning Province: New advances and metallogenic model

The No. 50 kimberlite pipe, a diamond orebody of critical importance in China, is the only large-scale primary diamond deposit being exploited in Liaoning Province. It is renowned both domestically and internationally for its high grade and superior quality. Guided by recent insights into structural controls, an exploration project was implemented around No. 50 pipe for hidden ore bodies, utilizing a suite of advanced techniques, including 3D structural mapping, shallow seismic profiling, drilling, and a combination of borehole geophysical methods. This effort successfully led to the discovery of No. 50-1 kimberlite pipe, located approximately 1 000 meters beyond the original No. 50 pipe at a burial depth nearly 300 meters. Comparative analysis confirms that its characteristics are consistent with those of No. 50 pipe, supporting the interpretation that it is a structurally displaced block severed from the major pipe. Building upon this new discovery from the deep-seated exploration, the paper proposes a metallogenic model that integrates its tectonic setting and petrological characteristics. The model posits that within the lithospheric mantle of North China Craton, kimberlitic magmas intruded mantle peridotite. Diamonds, hosted within this mantle peridotite, were incorporated into the kimberlitic magma, facilitating its rapid ascent. Upon reaching sub-surface levels, explosive degassing and volatile expansion triggered rapid cooling and solidification, forming No. 50 pipe. Subsequently, thrust faulting dismembered the original pipe system, displacing a segment now identified as No. 50-1 pipe, while the primary root zone of No. 50 pipe remains undiscovered.