Analytical/numerical modeling of komatiite lava emplacement and thermal erosion at Perseverance, Western Australia

We have applied a thermal-fluid dynamic-geochemical model to investigate the emplacement and erosional potential of Archean komatiite flows at Perseverance, Western Australia. Perseverance has been proposed as a site of large-scale thermal erosion by large-volume komatiite eruption(s), resulting in a 100-150-m-deep lava channel containing one of the world's largest komatiite-hosted Fe-Ni-Cu-(PGE) sulfide deposits. Using constraints based on field, theoretical, and geochemical data, we have modeled the emplacement of a range of flow thicknesses over felsic tuffaceous substrates with various degrees of consolidation and water contents. Thereto-mechanical erosion becomes more effective for substrates that are increasingly unconsolidated and water rich. For thereto-mechanical erosion to be responsible for the formation of the similar to100-m-deep, concave Perseverance embayment and the highly-contaminated (similar to10-20%) Perseverance komatiites, the most likely scenarios require emplacement of thick (e.g. greater than or equal to 10-30 m), turbulent, channelized liquidus or superheated komatiite lavas over a welded or unconsolidated submarine tuff. Flow distances must have been long (tens to hundreds of kilometers) and flow volumes must have been very high (hundreds to thousands of km(3)). Lava channels and tubes >110 km long have not been observed on Earth, but are consistent with those formed by low-viscosity lavas on Venus, the Moon, Mars and Io. Flow volumes are consistent with those in continental flood basalt eruptions and oceanic plateau Large Igneous Provinces, and may represent the initial outpourings of komatiite lavas from Archean mantle plume activity. (C) 2001 Elsevier Science B.V. All rights reserved.