Ni-Mo-PGE Niutitang Formation, China

The Niutitang Formation is extremely enriched in an array of metals and provide a fantastic opportunity to study metal and semi-metal distributions and association at micron-scale in an organic matter-rich matrix. The mineralised black shale was deposited in a shallow marine environment during the Cambrian and is associated with phosphorite nodules.

The study aimed to investigate several outcrops of the polymetallic Ni-Mo-PGE sulphide ore layer, with a thickness between 5-20 cm. The enrichment in the highly organic matter-rich shale includes Mo, Ni, Se, Re, Os, As, Au, Hg, Sb, Pt and Pd and is often associated with carbonate-fluorapatite nodules (phosphorite nodules). Using a range of micro-analytical techniques (SEM, XRF, XANES, PIXE, EPMA) we were able to map the elemental distribution and zonation within the mineralised horizon and interpret mechanisms of enrichment.

The micron-scale investigation revealed association of Ni, As, Mo and Se with organic matter deposited during sedimentation and accumulation on the seafloor under euxinic conditions. The data supports previous studies suggesting organic matter deriving from organisms present in the water column played a crucial role in carrying, accumulation and precipitation of metals.

Publications/reports:

Pagès, A., Barnes, S., Schmid, S., Ryan, C., Paterson, D., MacRae, C., Laird, J., Le Vaillant, M., Fan, H., Wen, H., 2019. Micron-scale distribution of metals in Cambrian metalliferous shales, South China: Insights into local biologically driven redox disequilibrium, Chemical Geology, 528, 119283

Pagès, A., Barnes, S., Schmid, S., Coveney, R.M., Schwark, L., Liu, W., Grice, K., Fan, H., Wen, H., 2018. Geochemical investigation of the Lower Cambrian mineralised black shales of South China and the Late Devonian Nick Deposit, Canada. Ore Geology Reviews, 94, 396-413