Jianjin Cao

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.

Study of Particles from the Kafang Copper Deposit in Gejiu City, Yunnan

Samples were collected from the mining area, limestone area, and prospective area proximal to the Kafang copper deposit. The particles were analysed by the transmission electron microscopy (TEM) and the soil samples in the mining area were analysed by the X-ray diffraction (XRD). In the mining area and prospective area, metallic elements in the particles are Cu, Pb, Zn, As, Hg, and Co. Particles collected in the limestone area contain few metallic elements that exist in the ore minerals. Based on analysis of these particles, the following conclusions are made: (1) sizes of the collected particles are 20 – 300 nm; (2) the composition of the soil samples and the particulate samples are significantly different because particles in the particulate samples reflect an origin from geogas; (3) geogas particles have different elemental contents because of different physicochemical properties of the elements and physicochemical environment that the geogas particles experienced; and (4) the Kafang stratiform copper deposit is a granite-related hydrothermal deposit. Metallic elements in geogas particles occur in the ore minerals and have similar compositions to those of geogas particles in the sampling sites. The geogas particles most likely originate from concealed deposits. Supplementary material: EDS spectra of particles and coordinates of sampling points in the mining area, limestone area, and prospecting area are available at: https://doi.org/10.6084/m9.figshare.c.3820687