Nonconventional Geochemical Exploration of Gold Deposits in Xinjiang and Henan Provinces, China

Abstract

This paper describes case histories of the use of the electric ion-extracting (CHIM) method and soil gas mercurometric surveys in search of concealed gold deposits, as well as the preliminary results obtained in the application of the newly developed geogas method in prospecting for concealed gold deposits. Experiments on the effectiveness of the CHIM method were carried out over a known gold deposit in the arid and semiarid Gobi desert of Xinjiang. A CHIM gold anomaly was revealed over the known orebody, with values tens to hundreds of times higher than the background. Two peaks were identified across the orebody; the peak value on the side to which the orebody was inclined was higher than that on the other side. Later, a CHIM survey was carried out along a 20-kilometer survey line and, consequently, quite a few CHIM Au anomalies were detected, with intensities ranging from 40 to 1000 ppb. The location of a test drillhole was determined on the basis of the CHIM gold anomaly and it intersected a concealed gold ore bed with an apparent thickness of 72 m and a grade of 1-9.37 g/t. A soil gas survey was performed over a known gold deposit and its margins in Shanggong, Henan Province. With 20 ng/m3 as the threshold, three soil mercury vapor anomalous zones were delineated, of which the No. I and No. II zones were coincident with gold anomalous zones delineated by a soil geochemical survey; the No. III anomalous zone, in an area not known to be associated with a gold deposit, was proved by trenching and drilling to be related to an auriferous rupture zone and gold orebody. These data permitted gold reserve figures to be increased. On the basis of the successful development of the geogas collector, the technique of instrument neutron activation analysis was used to replace the protoninduced X-ray emission technique and, as a result, distinct Au, As, Sb, and Zn multielement geogas anomalies were detected over two known concealed gold deposits. In this way, a new ore prospecting method is provided for the exploration of concealed gold deposits.