An assessment of soil geochemical methods for detecting copper-gold porphyry mineralization through quaternary glaciofluvial sediments at the WBX-MBX and 66 Zones, Mt. Milligan, North-Central British Columbia

Оценка геохимических методов исследования почв для обнаружения медно-золотой порфировой минерализации в четвертичных ледниково-флювиальных отложениях в зонах WBX-MBX и 66, гора Миллиган, северо-центральная часть Британской Колумбии.

This study is the second and final part of a Geoscience BC funded project (Project 2009-19) carried out by the author to test the effectiveness of a variety of commonly used chemical extractions at detecting mineralization through thick Quaternary glaciofluvial cover. In the first part carried out at the Kwanika Central Zone (Heberlein and Samson, 2010), results showed that conventional soil sampling (an aqua regia digestion of -80 mesh screened, upper B horizon) is ineffective at detecting the buried mineralization. Furthermore, laboratory specific extractions like MMI-M (SGS) and Ionic Leach (ALS-Chemex), Enzyme Leach and Bioleach (Actlabs) also performed poorly. These methods, which are widely recognized as being capable of detecting deeply buried mineralization in a variety of environments, did not produce convincing responses at Kwanika. In fact, none of the methods that tested the B horizon, the traditional soil sampling medium, did very well. The most robust responses for ore and pathfinder elements were found at the base of the organic layer in the Ah horizon. An aqua regia digestion carried out on samples from this layer identified high to moderate contrast apical or rabbit-ear responses for Cu, Au, Ag, W, As, Sb and Ca on both lines. A sodium pyrophosphate extraction performed almost as well, producing convincing responses for Cu, Au, Ag, As and U. The Kwanika study also demonstrated that soil pH and electrical conductivity measurements produced credible responses defining the position of the underlying mineralization. On one sample transect, mineralization was detected through 300 metres of cover consisting of up to 40 metres of Quaternary glaciofluvial deposits and an older post-mineral sedimentary basin. These results were obtained from an area withlittle surface disturbance as one might expect to find in a real exploration setting. <...>