M.-J. Yao’s scientific contributions

The authors discuss the ore-forming temperatures, orebody size and mineralization stages of the Qianhe gold deposit by using the thermoelectricity and decrepitation temperatures of pyrite from the deposit and evaluate the ore prospects at depths in the ore district by using mineralogical mapping. The study results show that the ore-forming temperatures of the deposit range from 222.3 to 360.1°C, indicating that the deposit is a mesothermal one. The thermoelectric properties of pyrite in all the levels are of the N type, with the total content reaching 81.4%. Spatially, the degree of erosion of the orebody shows the rhythmic feature, i.e. being from high to low and again to high, which indicates that the gold orebody is persistent form the 200 to 520 m levels and has a tendency to continue downward. There are mainly three types of decrepitation peak for pyrite, which correspond to the early, middle and late mineralization stages respectively.

The Qianhe gold deposit, Henan, is of tectonic alteration type. In this deposit, orebodies show gradational contact relationships with wall rocks with a vague boundary, but there is distinct difference in magnetic susceptibility among orebodies, wall rocks and various types of altered rocks. Systematic susceptibility measurements were made of altered rocks in various levels and along exploratory lines of the Qianhe gold deposit using a WCL-1 portable contact magnetic susceptibility meter. The susceptibility values of various kinds of typical altered rocks are in decreasing order as follows: chloritized rocks (Ch) → silicified-chloritized rocks (Si+ Ch) → chloritized-silicified rocks (Ch+Si) → K-feldspathized rocks (Kf) → silicified (Si) → pyritized-phyllic rocks (Py+Se+Si). Correlation analysis of the magnetic susceptibilities of altered rocks and degrees of gold mineralization indicates that there is a negative correlation trend between them. Profiles of magnetic susceptibilities of altered andesite along lines 78 and 83 and a vertical longitudinal projection map of magnetic susceptibilities and gold grade isolines in the ore district have been constructed, and the direction for looking for ore deposits at depth in the ore district has been predicted preliminarily.