In the Zechstein copper deposits, Poland, Au and platinum-group elements are concentrated by a process of autooxidation and desulfurization of organic matter. Platinum-group elements, acting as catalysts of the autooxidation process, are concentrated at the border between oxicanoxic conditions, i.e., between kerogen and calcite, thucholite and calcite, black shale and white sandstone, etc. The gamma radiation accelerated and enhanced the process of autooxidation, and phosphates and borates coagulated noble metals from solutions. For these two reasons the highest Au and platinum-group-element-bearing contents (Au, up 3,000 ppm; Pt, 10-370 ppm; and Pd, 10-120 but sometimes up to 1,000 ppm) are present in a layer a few centimeters thick at the bottom of the black shale (platinum-group-element-bearing shale) when this shale is overlain by phosphates, borates, and thucholite-bearing shale.

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