serpentinized mantle peridotite and gabbroic intrusions
locally capped by lavas with or without intervening
sheeted dikes (e.g., Cannat, 1993; Figure 2a). This lateral
and vertical variability of slow-spread crust has been well
documented through ophiolite studies, seafloor geological
studies, geophysical surveys, and scientific ocean drilling
expeditions (e.g., Karson et al., 1987; Dick, 1989; Cannat
et al., 1995; Canales et al., 2000; Kelemen et al., 2007;
Blackman et al., 2011; Sauter et al., 2013; Ildefonse et
al., 2014; Lagabrielle et al., 2015). In this type of crust,
tectonics play a key role in crustal construction, through
detachment faulting (e.g., Escartín and Canales, 2011;
Figure 2b), which dominates the style of accretion over
~50 % of the Mid-Atlantic Ridge between 12.5
N and
35
N (Escartín et al., 2008). Long-living (~1–2 Ma)
detachment faults cap domal features, known as “oceanic
core complexes” or “megamullions,” where gabbroic
rocks, serpentinites, and fault-related material (e.g., talcamphibole schists) are typically sampled (e.g., Cann
et al., 1997; Tucholke et al., 1998; Escartín et al., 2003;
Ildefonse et al., 2007; MacLeod et al., 2009; Dick et al.,
2010). The magma-poor end-member for this style of
accretion is expressed at the ultraslow-spreading Southwest Indian Ridge by the nonvolcanic “smooth seafloor,”
where almost exclusively serpentinized mantle peridotites
are sampled (Cannat et al., 2006; Sauter et al., 2013).
Details of the detachment-controlled accretion mode
remain poorly constrained. In oceanic core complexes,
drill cores document a complex interplay between
magmatism, faulting, and hydrothermal cooling, which
is yet to be fully resolved (e.g., Blackman et al., 2011;
McCaig and Harris, 2012; Ildefonse et al., 2014).
Bibliography
Anonymous, 1972. Penrose field conference on ophiolites.
Geotimes, 17, 24–25.
Blackman, D. K., Ildefonse, B., John, B. E., Ohara, Y., Miller, D. J.,
Abe, N., Abratis, M., Andal, E. S., Andreani, M., Awaji, S.,
Beard, J. S., Brunelli, D., Charney, A. B., Christie, D. M., Collins, J., Delacour, A. G., Delius, H., Drouin, M., Einaudi, F.,
Escartín, J., Frost, B. R., Früh-Green, G., Fryer, P. B., Gee,
J. S., Godard, M., Grimes, C. B., Halfpenny, A., Hansen,
H. E., Harris, A. C., Tamura, A., Hayman, N. W., Hellebrand,
E., Hirose, T., Hirth, J. G., Ishimaru, S., Johnson, K. T. M.,
Karner, G. D., Linek, M., MacLeod, C. J., Maeda, J., Mason,
O. U., McCaig, A. M., Michibayashi, K., Morris, A., Nakagawa,
T., Nozaka, T., Rosner, M., Searle, R. C., Suhr, G., Tominaga,
M., von der Handt, A., Yamasaki, T., and Zhao, X., 2011. Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30
N. Journal of Geophysical
Research, 116, B07103, doi:10.1029/2010JB007931.
Boudier, F., Nicolas, A., and Ildefonse, B., 1996. Magma chambers
in the Oman ophiolite: fed from the top and the bottom. Earth
and Planetary Science Letters, 144, 239–250, doi:10.1016/
0012-821X(96)00167-7.
Canales, J. P., Collins, J. A., Escartín, J., and Detrick, R. S., 2000.
Seismic structure across the rift valley of the Mid-Atlantic ridge
at 23
20
0 N (MARK area): implications for crustal accretion processes at slow-spreading ridges. Journal of Geophysical
Research, 105, 28411–28425, doi:10.1029/2000JB900301.
Canales, J. P., Nedimović, M. R., Kent, G. M., Carbotte, S. M., and
Detrick, R. S., 2009. Seismic reflection images of a near-axis
melt sill within the lower crust at the Juan de Fuca ridge. Nature,
460, 89–93, doi:10.1038/nature08095.
Cann, J. R., 1974. A model for oceanic crystal structure developed.
Geophysical Journal International, 39, 169–187, doi:10.1111/
j.1365-246X.1974.tb05446.x.
Cann, J. R., Blackman, D. K., Smith, D. K., McAllister, E., Janssen,
B., Mello, S., Avgerinos, E., Pascoe, A. R., and Escartín, J.,
1997. Corrugated slip surfaces formed at ridge-transform intersections on the Mid-Atlantic Ridge. Nature, 385, 329–332,
doi:10.1038/385329a0.
Cannat, M., 1993. Emplacement of mantle rocks in the seafloor at
mid-ocean ridges. Journal of Geophysical Research, 98,
4163–4172, doi:10.1029/92JB02221.
Cannat, M., Mével, C., Maia, M., Deplus, C., Durand, C., Gente, P.,
Agrinier, P., Belarouchi, A., Dubuisson, G., Humler, E., and
Reynolds, J., 1995. Thin crust, ultramafic exposures, and rugged
faulting patterns at the Mid-Atlantic Ridge (22
–24
N). Geology, 23, 49–52, doi:10.1130/0091-7613(1995)023<0049:
TCUEAR>2.3.CO;2.
Cannat, M., Sauter, D., Mendel, V., Ruellan, É., Okino, K., Escartín,
J., Combier, V., and Baala, M., 2006. Modes of seafloor generation at a melt-poor ultraslow-spreading ridge. Geology, 34,
605–608, doi:10.1130/G22486.1.
Carbotte, S. M., Marjanović, M., Carton, H., Mutter, J. C., Canales,
J. P., Nedimović, M. R., Han, S., and Perfit, M. R., 2013. Finescale segmentation of the crustal magma reservoir beneath the
East Pacific Rise. Nature Geoscience, 6, 866–870,
doi:10.1038/ngeo1933.
Detrick, R. S., Buhl, P., Vera, E., Mutter, J., Orcutt, J., Madsen, J.,
and Brocher, T., 1987. Multi-channel seismic imaging of a
crustal magma chamber along the East Pacific Rise. Nature,
326, 35–41, doi:10.1038/326035a0.
Dick, H. J. B., 1989. Abyssal peridotites, very slow spreading ridges
and ocean ridge magmatism. In Saunders, A. D., and Norry, M. J.
(eds.), Magmatism in the Ocean Basins. London: Geological Society. Geological Society Special Publications, Vol. 42, pp. 71–105.
Dick, H. J. B., Lissenberg, C. J., and Warren, J. M., 2010. Mantle
melting, melt transport, and delivery beneath a slow-spreading
ridge: the Paleo-MAR from 23
15
0 N to 23
45
0 N. Journal of
Petrology, 51, 425–467, doi:10.1093/petrology/egp088.
Dunn, R. A., Toomey, D. R., and Solomon, S. C., 2000. Threedimensional seismic structure and physical properties of the
crust and shallow mantle beneath the East Pacific Rise at
9
30
0 N. Journal of Geophysical Research, 105, 23537–23555,
doi:10.1029/2000JB900210.
Escartín, J., Mével, C., MacLeod, C.J., and McCaig, A.M., 2003.
Constraints on deformation conditions and the origin of oceanic
detachments: The Mid-Atlantic Ridge core complex at 15
45′N.
Geochem Geophys Geosyst, 4, doi:10.1029/2002GC000472.
Escartín, J., and Canales, J. P., 2011. Detachments in oceanic lithosphere: deformation, magmatism, fluid flow, and ecosystems.
Eos, Transactions of the American Geophysical Union, 92,
31, doi:10.1029/2011EO040003.
Escartín, J., Smith, D. K., Cann, J., Schouten, H., Langmuir, C. H.,
and Escrig, S., 2008. Central role of detachment faults in accretion of slow-spreading oceanic lithosphere. Nature, 455,
790–794, doi:10.1038/nature07333.
France, L., Ildefonse, B., and Koepke, J., 2009. Interactions
between magma and hydrothermal system in Oman ophiolite
and in IODP Hole 1256D: fossilization of a dynamic melt lens
at fast spreading ridges. Geochemistry, Geophysics, Geosystems,
10, Q10O19, doi:10.1029/2009GC002652.
Gillis, K. M., 2008. The roof of an axial magma chamber: a
hornfelsic heat exchanger. Geology, 36, 299–302, doi:10.1130/
G24590A.1.
CRUSTAL ACCRETION
135
locally capped by lavas with or without intervening
sheeted dikes (e.g., Cannat, 1993; Figure 2a). This lateral
and vertical variability of slow-spread crust has been well
documented through ophiolite studies, seafloor geological
studies, geophysical surveys, and scientific ocean drilling
expeditions (e.g., Karson et al., 1987; Dick, 1989; Cannat
et al., 1995; Canales et al., 2000; Kelemen et al., 2007;
Blackman et al., 2011; Sauter et al., 2013; Ildefonse et
al., 2014; Lagabrielle et al., 2015). In this type of crust,
tectonics play a key role in crustal construction, through
detachment faulting (e.g., Escartín and Canales, 2011;
Figure 2b), which dominates the style of accretion over
~50 % of the Mid-Atlantic Ridge between 12.5
N and
35
N (Escartín et al., 2008). Long-living (~1–2 Ma)
detachment faults cap domal features, known as “oceanic
core complexes” or “megamullions,” where gabbroic
rocks, serpentinites, and fault-related material (e.g., talcamphibole schists) are typically sampled (e.g., Cann
et al., 1997; Tucholke et al., 1998; Escartín et al., 2003;
Ildefonse et al., 2007; MacLeod et al., 2009; Dick et al.,
2010). The magma-poor end-member for this style of
accretion is expressed at the ultraslow-spreading Southwest Indian Ridge by the nonvolcanic “smooth seafloor,”
where almost exclusively serpentinized mantle peridotites
are sampled (Cannat et al., 2006; Sauter et al., 2013).
Details of the detachment-controlled accretion mode
remain poorly constrained. In oceanic core complexes,
drill cores document a complex interplay between
magmatism, faulting, and hydrothermal cooling, which
is yet to be fully resolved (e.g., Blackman et al., 2011;
McCaig and Harris, 2012; Ildefonse et al., 2014).
Bibliography
Anonymous, 1972. Penrose field conference on ophiolites.
Geotimes, 17, 24–25.
Blackman, D. K., Ildefonse, B., John, B. E., Ohara, Y., Miller, D. J.,
Abe, N., Abratis, M., Andal, E. S., Andreani, M., Awaji, S.,
Beard, J. S., Brunelli, D., Charney, A. B., Christie, D. M., Collins, J., Delacour, A. G., Delius, H., Drouin, M., Einaudi, F.,
Escartín, J., Frost, B. R., Früh-Green, G., Fryer, P. B., Gee,
J. S., Godard, M., Grimes, C. B., Halfpenny, A., Hansen,
H. E., Harris, A. C., Tamura, A., Hayman, N. W., Hellebrand,
E., Hirose, T., Hirth, J. G., Ishimaru, S., Johnson, K. T. M.,
Karner, G. D., Linek, M., MacLeod, C. J., Maeda, J., Mason,
O. U., McCaig, A. M., Michibayashi, K., Morris, A., Nakagawa,
T., Nozaka, T., Rosner, M., Searle, R. C., Suhr, G., Tominaga,
M., von der Handt, A., Yamasaki, T., and Zhao, X., 2011. Drilling constraints on lithospheric accretion and evolution at Atlantis Massif, Mid-Atlantic Ridge 30
N. Journal of Geophysical
Research, 116, B07103, doi:10.1029/2010JB007931.
Boudier, F., Nicolas, A., and Ildefonse, B., 1996. Magma chambers
in the Oman ophiolite: fed from the top and the bottom. Earth
and Planetary Science Letters, 144, 239–250, doi:10.1016/
0012-821X(96)00167-7.
Canales, J. P., Collins, J. A., Escartín, J., and Detrick, R. S., 2000.
Seismic structure across the rift valley of the Mid-Atlantic ridge
at 23
20
0 N (MARK area): implications for crustal accretion processes at slow-spreading ridges. Journal of Geophysical
Research, 105, 28411–28425, doi:10.1029/2000JB900301.
Canales, J. P., Nedimović, M. R., Kent, G. M., Carbotte, S. M., and
Detrick, R. S., 2009. Seismic reflection images of a near-axis
melt sill within the lower crust at the Juan de Fuca ridge. Nature,
460, 89–93, doi:10.1038/nature08095.
Cann, J. R., 1974. A model for oceanic crystal structure developed.
Geophysical Journal International, 39, 169–187, doi:10.1111/
j.1365-246X.1974.tb05446.x.
Cann, J. R., Blackman, D. K., Smith, D. K., McAllister, E., Janssen,
B., Mello, S., Avgerinos, E., Pascoe, A. R., and Escartín, J.,
1997. Corrugated slip surfaces formed at ridge-transform intersections on the Mid-Atlantic Ridge. Nature, 385, 329–332,
doi:10.1038/385329a0.
Cannat, M., 1993. Emplacement of mantle rocks in the seafloor at
mid-ocean ridges. Journal of Geophysical Research, 98,
4163–4172, doi:10.1029/92JB02221.
Cannat, M., Mével, C., Maia, M., Deplus, C., Durand, C., Gente, P.,
Agrinier, P., Belarouchi, A., Dubuisson, G., Humler, E., and
Reynolds, J., 1995. Thin crust, ultramafic exposures, and rugged
faulting patterns at the Mid-Atlantic Ridge (22
–24
N). Geology, 23, 49–52, doi:10.1130/0091-7613(1995)023<0049:
TCUEAR>2.3.CO;2.
Cannat, M., Sauter, D., Mendel, V., Ruellan, É., Okino, K., Escartín,
J., Combier, V., and Baala, M., 2006. Modes of seafloor generation at a melt-poor ultraslow-spreading ridge. Geology, 34,
605–608, doi:10.1130/G22486.1.
Carbotte, S. M., Marjanović, M., Carton, H., Mutter, J. C., Canales,
J. P., Nedimović, M. R., Han, S., and Perfit, M. R., 2013. Finescale segmentation of the crustal magma reservoir beneath the
East Pacific Rise. Nature Geoscience, 6, 866–870,
doi:10.1038/ngeo1933.
Detrick, R. S., Buhl, P., Vera, E., Mutter, J., Orcutt, J., Madsen, J.,
and Brocher, T., 1987. Multi-channel seismic imaging of a
crustal magma chamber along the East Pacific Rise. Nature,
326, 35–41, doi:10.1038/326035a0.
Dick, H. J. B., 1989. Abyssal peridotites, very slow spreading ridges
and ocean ridge magmatism. In Saunders, A. D., and Norry, M. J.
(eds.), Magmatism in the Ocean Basins. London: Geological Society. Geological Society Special Publications, Vol. 42, pp. 71–105.
Dick, H. J. B., Lissenberg, C. J., and Warren, J. M., 2010. Mantle
melting, melt transport, and delivery beneath a slow-spreading
ridge: the Paleo-MAR from 23
15
0 N to 23
45
0 N. Journal of
Petrology, 51, 425–467, doi:10.1093/petrology/egp088.
Dunn, R. A., Toomey, D. R., and Solomon, S. C., 2000. Threedimensional seismic structure and physical properties of the
crust and shallow mantle beneath the East Pacific Rise at
9
30
0 N. Journal of Geophysical Research, 105, 23537–23555,
doi:10.1029/2000JB900210.
Escartín, J., Mével, C., MacLeod, C.J., and McCaig, A.M., 2003.
Constraints on deformation conditions and the origin of oceanic
detachments: The Mid-Atlantic Ridge core complex at 15
45′N.
Geochem Geophys Geosyst, 4, doi:10.1029/2002GC000472.
Escartín, J., and Canales, J. P., 2011. Detachments in oceanic lithosphere: deformation, magmatism, fluid flow, and ecosystems.
Eos, Transactions of the American Geophysical Union, 92,
31, doi:10.1029/2011EO040003.
Escartín, J., Smith, D. K., Cann, J., Schouten, H., Langmuir, C. H.,
and Escrig, S., 2008. Central role of detachment faults in accretion of slow-spreading oceanic lithosphere. Nature, 455,
790–794, doi:10.1038/nature07333.
France, L., Ildefonse, B., and Koepke, J., 2009. Interactions
between magma and hydrothermal system in Oman ophiolite
and in IODP Hole 1256D: fossilization of a dynamic melt lens
at fast spreading ridges. Geochemistry, Geophysics, Geosystems,
10, Q10O19, doi:10.1029/2009GC002652.
Gillis, K. M., 2008. The roof of an axial magma chamber: a
hornfelsic heat exchanger. Geology, 36, 299–302, doi:10.1130/
G24590A.1.
CRUSTAL ACCRETION
135