Temporal and spatial variability of hydrothermal manganese and iron at Cleft segment, Juan de Fuca Ridge
摘要:
A unique data set for hydrothermal Mn and Fe was collected at Cleft segment on the Juan de Fuca Ridge between 1983 and 1991. The data set includes observations of focused and diffuse venting fluids and neutrally buoyant plumes formed by chronic and episodic venting. Manganese/heat and iron/heat ratios for plumes from the north end of the Cleft segment were combined with independently determined estimates of plume heat flux to yield annually averaged chronic venting fluxes for Mn of 0.36±0.17 mol s1 and for Fe of 0.61±0.34 mol s1. Over 6 years of plume measurements at North Cleft segment, observed episodic hydrothermal discharge accounted for 15% of the total vented Mn and 35% of vented Fe. The chronic fluxes for Mn and Fe at a second venting center located at the south end of the Cleft segment were estimated to be approximately equal to the fluxes at North Cleft segment. Chronic plumes at North Cleft segment are mixtures of focused and diffuse discharge that contribute heat, Mn, and Fe in variable proportions. Similar examination of South Cleft segment data strongly suggests the presence of an as yet unobserved venting source relatively depleted in Mn and Fe but contributing substantially to the overall heat. Temporal and spatial variations in the concentrations of Mn and Fe and in Mn/heat and Fe/heat ratios for focused seafloor vents were difficult to resolve within complex chronic plumes. Manganese/heat and iron/heat ratios of megaplumes suggest they may have derived from reservoirs of diffuse fluids while smaller event plumes may have formed by different processes and have properties similar to chronic plumes. The accurate assessment of segment-scale hydrothermal fluxes of Mn and Fe requires coordinated measurements of representative seafloor sources and the neutrally buoyant plume that integrates all seafloor discharge.
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关键词:
Experimental/ geochemistry geology iron manganese oceanic crust oceanographic regions seafloor phenomena terrestrial heat/ ocean thermal structure bottom temperature chemical composition midocean ridge mid ocean ridge seafloor geology geochemistry North Pacific spatial variability temporal variation hydrothermal vent Cleft segment Juan de Fuca Ridge AD 1983 to 1991 venting fluid neutrally buoyant plume heat flux Mn Fe/ A9150E Seafloor processes A9330P Pacific Ocean A9220C Chemistry of the oceans A9210M Thermohaline structure and circulation of the oceans A9135D Terrestrial heat A9135L Geochemistry/ Mn/el Fe/el
DOI:
10.1029/93JB02799
被引量:
年份:
1994
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