Application of tectono-geochemistry method for weak information extraction of Carlin-type gold deposits in Yunnan-Guizhou-Guangxi, SW China

Following decades of exploration of Carlin-type gold deposits in the Yunnan, Guizhou, and Guangxi provinces of China (known as the Dian-Qian-Gui Golden Triangle), surface mines are almost exhausted and undiscovered gold orebodies are deeply buried; thus, surficial geochemical information associated with concealed gold ore-bodies is poor. In this study, we compared methods of extracting this weak information based on soil geochemistry and tectono-geochemistry, and then applied the tectono-geochemical method to the Huijiabao and Nibao gold ore fields to evaluate its validity and identify favorable prospecting targets for deep-mineral explo-ration. We analyzed 8,842 soil geochemical samples and 4,049 tectono-geochemical samples from the Nibao gold ore field and its surroundings, and 253 tectono-geochemical samples from the Huijiabao gold ore field by sta-tistical analysis and geochemical mapping. Tectono-geochemical samples were less abundant, accounting for only approximately 60 % of the number of soil geochemical samples; however, the number and proportion of high-value samples were greater and the elemental content was typically higher. Primary geochemical infor-mation related to deep-seated Carlin-type gold orebodies is profoundly affected by structures such as faults, anticlines, joints, and fissures, and was effectively identified by the tectono-geochemical technique, which fo-cuses on tectonic and altered rocks. Conversely, soil geochemical information derived from these primary sources was significantly weaker because of the high mixing and homogeneity of elements during weathering. Eleven tectono-geochemical high composite anomalies of Au, Hg, Sb, As, and W were recognized in the east of the Nibao ore field, with Baogudi, Shuijingwan, Jiaozishan, Houzipo, Anzhe, and Hetaoshu predicted to be future targets of deep-mineral exploration. The Nayang-Yandengpo target was delineated according to high tectono-geochemical composite anomalies of Au, Hg, Sb, As, and Tl in the southeast part of the Huijiabao ore field, and nine concealed gold orebodies were identified at depths of 800-1,400 m through 37 boreholes, with a total gold resource of 16,338 kg and an average grade of 3.74 g/t. Successful case studies and applications demonstrate the effec-tiveness of tectono-geochemical information extraction method for detecting subtle signals from concealed orebodies, which will promote future deep exploration of the Dian-Qian-Gui Golden Triangle.