Characteristics of the genetic mineralogy of pyrite and its significance for prospecting in the Denggezhuang gold deposit, Jiaodong Peninsula, China

Abstract

This paper reports the variation rules for the typomorphic parameters of the pyrite and the gold enrichment rules of the Denggezhuang quartz vein gold deposit at a large-depth scale, providing the mineral signs for deep prospecting prediction through detailed study of the characteristics of crystal’ habits, chemical composition, the thermoelectricity of pyrites, and mineralogical mapping. This paper primarily discusses the correlation between the mineralization intensity and the space-time evolution of the mineralogical parameters, clarifies the physicochemical conditions during gold mineralization, and provides information useful for deep mineralization prediction. We demonstrate that the crystal habits of the pyrites are very complex, primarily occurring as {100}, {210}, and their combinate form. {210} and {100}+{210} have positive correlations with gold mineralization, and {100}+{210} therefore can be useful for locating rich ore segments. The composition of pyrites is characteristically poor in S and rich in As. Their typical trace elements are composed of Mo, As, Pb, Cu, Bi, Zn, Au, Co, Se, Sb, Ag, Ni, Cr, and Te. The average contents of trace elements in pyrites from various stages show that the crystallizing temperature gradually decreased from an early stage to the metallogenic episodes. The precipitation and accumulation of Au and Ag occur primarily in the quartz-pyrite stage (III) and the polymetal minerals stage (IV). The occurrence rate of P-type pyrites (P(%)) is 83.52%. There is a larger dispersion of the thermoelectrical coefficient of pyrite (α) in the Denggezhuang gold deposit than in other deposits in the Jiaodong Peninsula. The electrical conductivity assemblage of pyrites from I to V is characterized by P⩾N→P>N→P≫N→P≫N→P⩾N, which is usually considered beneficial for mineralization. The relative contents of As+Sb+Se+Te and Co+Ni are closely correlated to P-type and N-type average values and their occurrence rates. According to the crystallizing temperature of pyrite, the mineralization intensity, and the denudation degree, the mineralization temperature of the Denggezhuang gold deposit is in the range of 150–322°C and is of a medium-low temperature. The orebody has already become denuded to the top-middle of the orebody, and the size of the orebody is larger than 900 m. Based on the vertical zoning of the thermoelectrical coefficients of pyrites and P-type pyrite mapping, it is suggested that the segment between −425 and −800 m may have exploration potential to the northeast of line 94 of the No. I2-2 orebody.