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Controls on Heat Flow, Fluid Migration, and Massive Sulfide Formation of an Off-axis Hydrothermal System - the Lau Basin Perspective


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Schardt, C and Large, RR and Yang, J (2006) Controls on Heat Flow, Fluid Migration, and Massive Sulfide Formation of an Off-axis Hydrothermal System - the Lau Basin Perspective. American Journal of Science, 306 (2). pp. 103-134.

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A numerical model has been developed to investigate heat and fluid migration in a modem 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 (similar to 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.

Item Type: Article
Keywords: VHMS, VMS, seafloor convection, seafloor massive sulfide, black smokers, Lau basin, back-arc, ore genesis
Journal or Publication Title: American Journal of Science
Page Range: pp. 103-134
Date Deposited: 23 Aug 2006
Last Modified: 18 Nov 2014 03:11
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