Controls on heat flow, fluid migration, and massive sulfide formation of an off-axis hydrothermal system - The Lau basin perspective

Christian Schardt, Ross Large, Jianwen Yang

Research output: Contribution to journalReview articlepeer-review

15 Scopus citations

Abstract

A numerical model has been developed to investigate heat and fluid migration in a modern off-axis seafloor hydrothermal system, that is, hydrothermal activity and fluid discharge distal to an axial magma chamber emphasizing model geometry, rock/fault properties and fault distribution. The model is based on geophysical data and seafloor observations of the Lau back-arc basin and results suggest a different hydrothermal convection scheme than axial hydrothermal systems. Major hydrothermal activity is predicted to occur at topographic highs due to significant fluid migration along inferred basement topography off-axis with associated permeability differences. Major hydrothermal fluid discharge occurs at off-axis topographic elevated positions with temperatures (150°C - 450°C) and exit fluid velocities (∼4 m/s), in good agreement with seafloor observation and theoretical calculations. Heuristic mass calculations pertaining to the formation of massive sulfide deposits imply that a significant base metal sulfide deposit (5 Mt at 10% Cu + Zn) may form in less than 6,000 years, assuming a fluid containing a maximum of 10 ppm base metals and a deposition efficiency of 10 percent. The size and distribution patterns of massive sulfide deposits are determined primarily by fault distribution, provided that adequate fluid flow pathways and heat supply exist.

Original languageEnglish (US)
Pages (from-to)103-134
Number of pages32
JournalAmerican Journal of Science
Volume306
Issue number2
DOIs
StatePublished - Feb 1 2006

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