Geology of a vigorous hydrothermal system on the Endeavour segment, Juan de Fuca Ridge
- Univ. of Washington, Seattle (United States)
- Woods Hole Oceanographic Institution, MA (United States)
A high-precision, high-resolution geologic map explicitly documents relationships between tectonic features and large steep-sided, sulfide-sulfate-silica deposits in the vigorously venting Endeavour hydrothermal field near the northern end of the Juan de Fuca Ridge. Location of the most massive sulfide structures appears to be controlled by intersections of ridge-parallel normal faults and other fracture-fissure sets that trend oblique to, and perpendicular to the overall structural fabric of the axial valley. As presently mapped, the field is about 200 by 400 m on a side and contains at least 15 large (> 1,000 m[sup 3]) sulfide edifices and many tens of smaller, commonly inactive, sulfide structures. The larger sulfide structures are also the most vigorously venting features in the field; they are commonly more than 30 m in diameter and up to 20 m in height. Maximum venting temperatures of 375[degrees]C are associated with the smaller structures in the northern portion of the field are consistently 20[degrees]-30[degrees]C lower. Hydrothermal output from individual active sulfide features varies from no flow in the lower third of the edifice to vigorous output from fracture-controlled black smoker activity near the top of the structures. Two types of diffuse venting in the Endeavour field include a lower temperature 8[degrees]-15[degrees]C output through colonies of large tubeworms and 25[degrees]-50[degrees]C vent fluid that seems to percolate through the tops of overhanging flanges. The large size and steep-walled nature of these structures evidently results from sustained venting in a mature hydrothermal system, coupled with dual mineral depositional mechanisms involving vertical growth by accumulation of chimney sulfide debris and lateral growth by means of flange development.
- OSTI ID:
- 6937229
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 97:B13; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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