Graben formation associated with recent dike intrusions and volcanic eruptions on the mid-ocean ridge

被引:71
作者
Chadwick, WW
Embley, RW
机构
[1] Oregon State Univ, Hatfield Marine Sci Ctr, Cooperat Inst Marine Resources Studies, Newport, OR 97365 USA
[2] NOAA, Hatfield Marine Sci Ctr, Pacific Marine Environm Lab, Newport, OR USA
关键词
D O I
10.1029/97JB02485
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
Grabens have been mapped immediately adjacent to recently erupted submarine lava flows on the Cleft and CoAxial segments of the Juan de Fuca Ridge (JdFR). The grabens are 10-100 m wide and 5-15 m deep and are located uprift and/or downrift of the eruptive vents that fed the flows. We interpret that these structures formed (or were reactivated) directly over the dike that fed the eruptions as it was intruding toward the surface. These graben structures are primary conduits for diffuse hydrothermal venting on the seafloor during the cooling of newly intruded dikes. The axial summit "graben" or "caldera" on the East Pacific Rise (EPR) in some locations has similar dimensions to the grabens observed on the JdFR, and we interpret that it too may be a dike-induced graben structure (although often buried by subsequent eruptions where it is narrowest). These grabens on the JdFR and the EPR are distinctly narrower and deeper than grabens that formed during well-documented dike intrusions on slow spreading rifts on land (Iceland and Afar). Mechanical modeling suggests that narrow grabens would form when a dike is at shallow depth where it imposes a high stress perturbation on the ambient stress state to cause faulting. Therefore the narrow grabens on the JdFR and EPR imply that a relatively high level;of horizontal compressive stress typically exists perpendicular to the ridges, and this must be overcome by high dike-induced perturbations to cause faulting. This is probably because gradual plate spreading rarely gets enough time to lower the compressive stress significantly due to the high frequency of dike intrusion events relative to the plate spreading rate. The dikes that do intrude in this environment must have relatively high internal magma pressure. Therefore the size and character of dike-induced grabens that form at the surface on intermediate to fast spreading ridges reflect the fact that volcanism dominates over tectonism in regulating the local stress state where a robust magma supply is available.
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页码:9807 / 9825
页数:19
相关论文
共 92 条
[11]   DYNAMICS OF CRUSTAL RIFTING IN NE ICELAND [J].
BJORNSSON, A .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1985, 90 (NB12) :151-162
[12]   SEISMIC ACTIVITY ASSOCIATED WITH THE SEPTEMBER 1977 DEFLATION OF THE KRAFLA CENTRAL VOLCANO IN NORTHEASTERN ICELAND [J].
BRANDSDOTTIR, B ;
EINARSSON, P .
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 1979, 6 (3-4) :197-212
[13]   Seafloor eruptions and evolution of hydrothermal fluid chemistry [J].
Butterfield, DA ;
Jonasson, IR ;
Massoth, GJ ;
Feely, RA ;
Roe, KK ;
Embley, RE ;
Holden, JF ;
McDuff, RE ;
Lilley, MD ;
Delaney, JR .
PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, 1997, 355 (1723) :369-386
[14]   LAVA FLOWS FROM A MID-1980S SUBMARINE ERUPTION ON THE CLEFT SEGMENT, JUAN-DE-FUCA RIDGE [J].
CHADWICK, WW ;
EMBLEY, RW .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1994, 99 (B3) :4761-4776
[15]   EVIDENCE FOR VOLCANIC-ERUPTION ON THE SOUTHERN JUAN-DE-FUCA RIDGE BETWEEN 1981 AND 1987 [J].
CHADWICK, WW ;
EMBLEY, RW ;
FOX, CG .
NATURE, 1991, 350 (6317) :416-418
[16]   SEABEAM DEPTH CHANGES ASSOCIATED WITH RECENT LAVA FLOWS, COAXIAL SEGMENT, JUAN-DE-FUCA RIDGE - EVIDENCE FOR MULTIPLE ERUPTIONS BETWEEN 1981-1993 [J].
CHADWICK, WW ;
EMBLEY, RW ;
FOX, CG .
GEOPHYSICAL RESEARCH LETTERS, 1995, 22 (02) :167-170
[17]  
CHADWICK WW, 1995, EOS T AGU, V76, pF410
[18]  
CHADWICK WW, 1996, EOS T AGU SF1, V77
[19]   Thermal fluxes associated with the 1993 diking event on the CoAxial segment, Juan de Fuca Ridge: A model for the convective cooling of a dike [J].
Cherkaoui, ASM ;
Wilcock, WSD ;
Baker, ET .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1997, 102 (B11) :24887-24902
[20]   TECTONICS OF THE EAST PACIFIC RISE NEAR 12-DEGREES-50'N - A SUBMERSIBLE STUDY [J].
CHOUKROUNE, P ;
FRANCHETEAU, J ;
HEKINIAN, R .
EARTH AND PLANETARY SCIENCE LETTERS, 1984, 68 (01) :115-127