Discovery and significance of cryptoexplosive breccia in Zhuhai area

Cryptoexplosive breccia is a type of brecci-like subvolcanic or hypovolcanic rock formed by hidden explosion in shallow or super-shallow conditions, which is closely associated with shallow to ultra-shallow intrusions or hypovolcanic intrusions in space and time, and its distribution is often controlled by regional deep faults. It has undergone multiple hydrothermal fluid alteration during its formation, providing favorable conditions for the formation of low-temperature, low-pressure metal deposits such as gold, silver, copper, manganese, uranium, etc., and can be used as a prospecting marker for subvolcanic-type gold, silver, copper and other polymetallic deposits. In this study, cryptoexplosive breccia was found both in outcrop and underground in Zhuhai area. And its lithological composition mainly consisting of greisen breccia and granodiorite breccia, both of which formed during the Yanshanian period, with diagenetic ages of 159.8 ± 1.7 Ma and 171.74 ± 1.11 Ma, respectively. This discovery is of great significance for the study of Mesozoic volcanic activities and the exploration of polymetallic deposits of cryptoexplosive breccia type in Guangdong Province.