SEISMIC CONSTRAINTS ON SHALLOW CRUSTAL EMPLACEMENT PROCESSES AT THE FAST SPREADING EAST PACIFIC RISE

被引:110
作者
CHRISTESON, GL
PURDY, GM
FRYER, GJ
机构
[1] UNIV HAWAII MANOA, SCH OCEAN & EARTH SCI & TECHNOL, HONOLULU, HI 96822 USA
[2] WOODS HOLE OCEANOG INST, DEPT GEOL & GEOPHYS, WOODS HOLE, MA 02543 USA
[3] WHOI MIT JOINT PROGRAM OCEANOG, WOODS HOLE, MA USA
关键词
D O I
10.1029/94JB01252
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
We present the results of nine on-bottom seismic refraction experiments carried out over young East Pacific Rise crust. The experiments are unusual in that both the source and receiver are located within a few meters of the seafloor, allowing high-resolution determinations of shallow crustal structure. Three experiments were located within the axial summit caldera (ASC) over ''zero-age'' crust. The seismic structure at these three locations is fundamentally the same, with a thin (<60 m) surficial low-velocity (<2.5 km/s) layer, a 100 to 150-m-thick transition zone with velocities increasing hv similar to 2.5 km/s and a layer with velocities of similar to 5 km/s at a depth beneath the seafloor of similar to 130-190 m. The surficial low-velocity layer and transition zone are defined as seismic layer 2A, and the similar to 5 km/s layer is defined as the top of layer 2B. Both the surficial low-velocity layer and the transition zone double in thickness within similar to 1 km of the rise axis. We model layer 2A as the extrusive sequence and transition zone and the 2A/2B boundary as the top of the sheeted dikes. The primary implication of this interpretation is that the depth to the top of the sheeted dikes deepens from similar to 150 m to similar to 300 m within 1 km of the ASC. The thickening of the extrusive layer is interpreted to be due to lava that either overflows the ASC walls, is emplaced through eruptions outside of the ASC, or travels laterally from the ASC through conduits. The most probable cause for the thickening of the transition zone is sill emplacement outside of the ASC, either from magma that does not reach the surface in an off-axis eruption or magma that is transported laterally during the drainage process creating the ASC. We suggest that the mechanism controlling the magnitude and rate of the dike subsidence is the mechanism that determines the thickness of the extrusive section and the total thickness of layer 2A.
引用
收藏
页码:17957 / 17973
页数:17
相关论文
共 78 条
  • [1] THE VOLCANIC STRATIGRAPHY AND PETROGENESIS OF THE OMAN OPHIOLITE COMPLEX
    ALABASTER, T
    PEARCE, JA
    MALPAS, J
    [J]. CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 1982, 81 (03) : 168 - 183
  • [2] DSDP HOLE-504B, THE 1ST REFERENCE SECTION OVER 1KM THROUGH LAYER-2 OF THE OCEANIC-CRUST
    ANDERSON, RN
    HONNOREZ, J
    BECKER, K
    ADAMSON, AC
    ALT, JC
    EMMERMANN, R
    KEMPTON, PD
    KINOSHITA, H
    LAVERNE, C
    MOTTL, MJ
    NEWMARK, RL
    [J]. NATURE, 1982, 300 (5893) : 589 - 594
  • [3] DIRECT OBSERVATION OF A SECTION THROUGH SLOW-SPREADING OCEANIC-CRUST
    AUZENDE, JM
    BIDEAU, D
    BONATTI, E
    CANNAT, M
    HONNOREZ, J
    LAGABRIELLE, Y
    MALAVIEILLE, J
    MAMALOUKASFRANGOULIS, V
    MEVEL, C
    [J]. NATURE, 1989, 337 (6209) : 726 - 729
  • [4] GALAPAGOS RIFT AT 86-DEGREES-W .3. SHEET FLOWS, COLLAPSE PITS, AND LAVA LAKES OF THE RIFT VALLEY
    BALLARD, RD
    HOLCOMB, RT
    VANANDEL, TH
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH, 1979, 84 (NB10): : 5407 - 5420
  • [5] INSITU ELECTRICAL-RESISTIVITY AND BULK POROSITY OF THE OCEANIC-CRUST COSTA-RICA RIFT
    BECKER, K
    VONHERZEN, RP
    FRANCIS, TJG
    ANDERSON, RN
    HONNOREZ, J
    ADAMSON, AC
    ALT, JC
    EMMERMANN, R
    KEMPTON, PD
    KINOSHITA, H
    LAVERNE, C
    MOTTL, MJ
    NEWMARK, RL
    [J]. NATURE, 1982, 300 (5893) : 594 - 598
  • [6] VELOCITY POROSITY RELATIONSHIPS IN THE UPPER OCEANIC-CRUST - THEORETICAL CONSIDERATIONS
    BERGE, PA
    FRYER, GJ
    WILKENS, RH
    [J]. JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1992, 97 (B11) : 15239 - 15254
  • [7] MODEL FOR OCEANIC CRUSTAL STRUCTURE DEVELOPED
    CANN, JR
    [J]. GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1974, 39 (01): : 169 - 187
  • [8] OPHIOLITES, SEISMIC VELOCITIES AND OCEANIC CRUSTAL STRUCTURE
    CHRISTENSEN, NI
    [J]. TECTONOPHYSICS, 1978, 47 (1-2) : 131 - 157
  • [9] ELASTICITY OF MAFIC ROCKS FROM MID-ATLANTIC RIDGE
    CHRISTENSEN, NI
    SHAW, GH
    [J]. GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1970, 20 (03): : 271 - +
  • [10] COMPRESSIONAL AND SHEAR WAVE VELOCITIES AT PRESSURES TO 10 KILOBARS FOR BASALTS FROM EAST PACIFIC RISE
    CHRISTENSEN, NI
    [J]. GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1972, 28 (05): : 425 - +