Characteristics and geological significance of particles on fractures from the Dongshengmiao polymetallic pyrite deposit, Inner Mongolia, China

Fault gouge samples were collected from deep-seated fractures in the Dongshengmiao polymetallic pyrite deposit. Fault gouge particles were analysed by transmission electron microscopy. Many particles were identified with sizes of 200 nm or less, such as carbon-bearing, gold, Pb-bearing or Zn-bearing mineral particles. Carbon-bearing particles included graphite, carbonate, organic matter and carbonate mixed with organic matter. Gold particles were found in fault gouge samples in the form of natural gold, which had not been previously observed. Other particles, such as Pb- and Zn-bearing particles, directly reflect the ore-forming elemental characteristics of the Dongshengmiao deposit. Based on analysis of these particles, the following conclusions made: (1) carbon-bearing particles were deduced to be able to provide additional information related to the deposit formation; (2) fracture-induced stress acted on particles based on the observed lattice deformations in the gold, graphite, dolomite and Fe-bearing particles and the uneven edges of many particles; and (3) information about concealed ore bodies can be more easily obtained through the study of fault gouge particles, which will make ore body exploration more efficient.