Vertical distribution of elements in Deposit No. 1, Hat Creek, British Columbia: a preliminary study

Abstract

Four superimposed coal zones A, B, C, D, lie in the Hat Creek graben in folded and faulted Eocene strata. 65 samples from one central and representative drillhole are examined. AA analyses show Cu and Zn as having an inorganic affinity and increasing upward reflecting either a change in environment of deposition or a more selective sorption. SRF analyses show six elements increasing in abundance with depth (most pronounced first): Na, Ba, Si, Sr, Y, Mn, with 12 decreasing: Rb, Cr, K, Ni, Mg, S, Ti, Fe, Ca, Zn, P, Zr. Al does not vary. The pronounced upward increase in Rb might indicate the incorporation of increasingly silicic volcanic dust or sediment. K/Rb ratios however show an upward zig-zag variation while Ba shows negative correlation with K.Sr/Ba ratios for Zones A, B, D, are similar to those for granite. Ti/Al, Na/K, Ba/Sr, Rb/Sr and even the K/Rb ratios show that Zones A and D appear to be structurally distinct. Of the 15–20 major ‘stratigraphic’ coinciding highs and lows revealed in the element-depth variograms, 12–14 are in clean coal, 5–6 in carbominerite. The peaks may represent (a) the incorporation of volcanic ash or detrital sediment from different geological sources, or (b) the concentration or removal of elements by groundwater aided by previously high geothermal gradients. Missing core may represent the position of former watertables ‘drowned’ by repeated downward shifting of the graben. More detailed collecting should permit cycles of deposition to be distinguished. The coal zones can, elementally, be distinguished one from another but individually could be difficult to identify.