GEOLOGY OF A VIGOROUS HYDROTHERMAL SYSTEM ON THE ENDEAVOR SEGMENT, JUAN DE FUCA RIDGE

被引:202
作者
DELANEY, JR
ROBIGOU, V
MCDUFF, RE
TIVEY, MK
机构
[1] UNIV WASHINGTON, SCH OCEANOG, SEATTLE, WA 98195 USA
[2] WOODS HOLE OCEANOG INST, DEPT CHEM, WOODS HOLE, MA 02543 USA
关键词
D O I
10.1029/92JB00174
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
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. Water depth in the vent field varies from 2220 to 2200 m. 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. The fractured basaltic substrate is primarily composed of well-weathered pillow and lobate flows. As presently mapped, the field is about 200 by 400 m on a side and contains at least 15 large (> 1000 m3) sulfide edifices and many tens of smaller, commonly inactive, sulfide structures. The larger sulfide structures are also the most vigorously venting features in die field; they are commonly more than 30 m in diameter and up to 20 m in height. Actively venting sulfide structures in the northern portion of the field stand higher and are more massive than active structures in the southern portion of the field which tend to be slightly to distinctly smaller. Maximum venting temperatures of 375-degrees-C are associated with the smaller structures in the southeastern portion of the field; highest-temperature venting fluids from the more massive 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. A different type of high temperature venting takes place from the upper sides of the structures in the form of ''overflow'' from fully exposed, quiescent pools of buoyant 350-degrees-C vent water trapped beneath over-hanging sulfide-sulfate-silica ledges, or flanges. These flanges are attached to the upper, outer walls of the large sulfide edifices. 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 the 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.
引用
收藏
页码:19663 / 19682
页数:20
相关论文
共 65 条
[1]   CHARACTERISTICS OF HYDROTHERMAL PLUMES FROM 2 VENT FIELDS ON THE JUAN-DE-FUCA RIDGE, NORTHEAST PACIFIC-OCEAN [J].
BAKER, ET ;
MASSOTH, GJ .
EARTH AND PLANETARY SCIENCE LETTERS, 1987, 85 (1-3) :59-73
[2]   EAST PACIFIC RISE AT 21-DEGREES-N - THE VOLCANIC, TECTONIC, AND HYDROTHERMAL PROCESSES OF THE CENTRAL AXIS [J].
BALLARD, RD ;
FRANCHETEAU, J ;
JUTEAU, T ;
RANGAN, C ;
NORMARK, W .
EARTH AND PLANETARY SCIENCE LETTERS, 1981, 55 (01) :1-10
[3]   INFLUENCE OF MAGMA CHAMBER GEOMETRY ON HYDROTHERMAL ACTIVITY AT MID-OCEAN RIDGES [J].
BRIKOWSKI, T ;
NORTON, D .
EARTH AND PLANETARY SCIENCE LETTERS, 1989, 93 (02) :241-255
[4]  
BUTTERFIELD DA, 1990, THESIS U WASH SEATTL
[5]   A SIMPLE MAGMA-DRIVEN THERMAL BALANCE MODEL FOR THE FORMATION OF VOLCANOGENIC MASSIVE SULFIDES [J].
CANN, JR ;
STRENS, MR ;
RICE, A .
EARTH AND PLANETARY SCIENCE LETTERS, 1985, 76 (1-2) :123-134
[6]  
DAVIS EE, 1984, 8417 EARTH PHYS BRAN
[7]  
Delaney J, 1984, EOS T AM GEOPHYS UN, V65, P973
[8]  
Delaney J. R., 1990, EOS T AGU, V71, P1609
[9]  
DELANEY JR, 1988, EOS T AGU, V69, P1497
[10]  
DELANEY JR, 1991, EOS T AM GEOPHYS UN, V72, P231