Serpentinized Peridotite from the North Wall of the Puerto Rico Trench

Bowin, Carl; Nalwalk, A. J.; Hersey, J. B.

doi:10.1130/0016-7606(1966)77[257:spftnw]2.0.co;2

Cited by 56 publications

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“…However, the Tyrrhenian Sea rocks are very similar to highly refractory peridotites from modern, subduction-related trenches, such as the Puerto Rico, Tonga, and Mariana Trenches (Bowin et al, 1966;Bloomer and Hawkins, 1983;Bonatti and Michael, 1989).…”

Section: Island Arc/subduction Affinity Of Site 651 Mantle Peridotitesmentioning

confidence: 99%

“…data); (4) peridotites from modern arc/subduction-related zones, i.e., from the Puerto Rico Trench in the Atlantic (Bowin et al, 1966); and Tonga Trench in the West Pacific (Sharaskin et al, 1983); and (5) peridotites from Mediterranean ophiolite complexes for which an arc/subduction-related origin has been inferred, i.e., Vourinos in Greece (Moores, 1969) and Troodos in Cyprus (Beccaluva et al, 1980). The very low A1 2 0 3 content of Site 651 Tyrrhenian peridotites is paralleled only by peridotites from modern arc/subductionrelated zones, i.e., Puerto Rico and Tonga trenches, and from eastern Mediterranean ophiolites with inferred arc/subductionrelated origin, i.e., Troodos and Vourinos.…”

Section: Whole Rock Elemental Chemistrymentioning

confidence: 99%

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Peridotites Drilled from the Tyrrhenian Sea, ODP Leg 107

Bonatti¹,

Channell²,

Giraudeau³

et al. 1990

Proceedings of the Ocean Drilling Program

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Hole 651 A, drilled during ODP leg 107 in the Tyrrhenian Sea, bottomed in a 30-m-thick section of serpentinized peridotite. Site 651 was drilled on the eastern flank of a north-south trending basement high located along the axis of the Vavilov basin. Peridotite is overlain by a 136-m-thick basement section consisting of two distinct basalt units separated by a dolerite-albitite intrusive unit. Peridotite has a tectonitic texture and probably derived from the upper mantle; it was affected by a complex history of ductile and brittle deformation. High temperature (>700°C) hydrous metasomatism, which probably occurred at upper mantle levels and produced tschermakitic and Mg-hornblende, tremolite, and possibly chlorite, affected the peridotite. Lower temperature metamorphic events followed, which gave rise to talcquartz ± chlorite assemblages and to serpentinization. A relict primary assemblage consists of olivine, variable amounts of orthopyroxene, and spinel, implying that the rocks were originally harzburgite and dunite. Both bulk rock and relict primary mineral chemistry suggest that the peridotite is highly depleted, and chemically distinct from mantlederived peridotites from circum-Tyrrhenian ophiolites (North Apennine, Corsica), from passive margins and from the ocean basins. ODP Site 651 peridotite appears to have affinity with modern (Mariana, Tonga, and Puerto Rico Trenches) and ophiolitic (Troodos, Vourinos) arc-subduction related peridotites. It may represent a refractory upper mantle sliver which was affected by island arc/subduction systems inferred to have migrated southeast from Sardinia during the opening of the Tyrrhenian Sea.

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Section: Island Arc/subduction Affinity Of Site 651 Mantle Peridotitesmentioning

confidence: 99%

Section: Whole Rock Elemental Chemistrymentioning

confidence: 99%

Peridotites Drilled from the Tyrrhenian Sea, ODP Leg 107

Bonatti¹,

Channell²,

Giraudeau³

et al. 1990

Proceedings of the Ocean Drilling Program

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“…4-2). The dark rock was thought to be peridotite and led to two followup cruises to dredge for samples along these scarps [Bowin et al, 1966]. Dredging returned sedimentary rocks, variably altered basalt, and highly altered peridotite (serpentinite).…”

Section: Introductionmentioning

confidence: 99%

“…The north wall is marked by numerous scarps which are thought to expose the interior of the plate through large offset normal faults (Fig. 4-2) [Bowin et al, 1966]. During Cruise Chain 11 a camera lowing returned images of a veined dark rock with no sedimentary cover on the main scarp (Fig.…”

Section: Introductionmentioning

confidence: 99%

Geophysical and geochemical constraints on the evolution of oceanic lithosphere from formation to subduction

Horning¹

2017

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This thesis investigates the evolution of the oceanic lithosphere in a broad sense from formation to subduction, in a focused case at the ridge, and in a focused case proximal to subduction. In general, alteration of the oceanic lithosphere begins at the ridge through focused and diffuse hydrothermal flow, continues off axis through low temperature circulation, and may occur approaching subduction zones as bending related faulting provides fluid pathways. In Chapter 2 I use a dataset of thousands of microearthquakes recorded at the Rainbow massif on the Mid-Atlantic Ridge to characterize the processes which are responsible for the long-term, high-temperature, hydrothermal discharge found hosted in this oceanic core complex. I find that the detachment fault responsible for the uplift of the massif is inactive and that the axial valleys show no evidence for faulting or active magma intrusion. I conclude that the continuous, low-magnitude seismicity located in diffuse pattern in a region with seismic velocities indicating ultramafic host rock suggests that serpentinization may play a role in microearthquake generation but the seismic network was not capable of providing robust focal mechanism solutions to constrain the source characteristics. In Chapter 3 I find that the Juan de Fuca plate, which represents the young/hot end-member of oceanic plates, is lightly hydrated at upper crustal levels except in regions affected by propagator wakes where hydration of lower crust and upper mantle is evident. I conclude that at the subduction zone the plate is nearly dry at upper mantle levels with the majority of water contained in the crust. Finally, in Chapter 4 I examine samples of cretaceous age serpentinite sampled just before subduction at the Puerto Rico Trench. I show that these upper mantle rocks were completely serpentinized under static conditions at the Mid-Atlantic Ridge. Further, they subsequently underwent 100 Ma of seafloor weathering wherein the alteration products of serpentinization themselves continue to be altered. I conclude that complete hydration of the upper mantle is not the end point in the evolution of oceanic lithosphere as it spreads from the axis to subduction. Chapter 1: IntroductionThe total water content of the oceanic lithosphere is the sum of the free water in pore spaces in the sedimentary cover and highly porous upper crust, chemically bound water in sediment clay minerals, chemically bound water in the upper and lower crust resulting from the precipitation of secondary hydrous alteration products, free water in fault zones, and bound water of hydrous minerals in the uppermost mantle resulting from serpentinization of peridotite. This thesis is focused on characterizing the location, extent, and timing of the processes that result in this alteration of the lithosphere.In Chapter 2 I focus on the alteration that occurs in the near axis region at an oceanic core complex located on the slow spreading Mid-Atlantic Ridge. At the Rainbow massif long-lived high-T hydrothermal venting h...

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“…Other data concern the petrology of some peridotites dredged from the outer wall of the Puerto Rico trench (Bowin et al, 1966) and mostly from the inner slope of the Mariana (Bloomer, 1983;Bloomer and Hawkins, 1983;Ishii, 1985;T. Ishii, pers.…”

Section: Introductionmentioning

confidence: 99%

Deformation History of Peridotites from Mariana Forearc, Conical Seamount, Leg 125

Girardeau¹,

Lagabrielle²

1992

Proceedings of the Ocean Drilling Program

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Abundant serpentinite seamounts are found along the outer high of the Mariana forearc at the top of the inner slope of the trench. One of them, Conical Seamount, was drilled at Sites 778, 779, and 780 during Leg 125.The rocks recovered at Holes 779A and 780C, respectively, on the flanks and at the summit of the seamount, include moderately serpentinized depleted harzburgites and some dunites. These rocks exhibit evidence of resorption of the orthopyroxene, when present, and the local presence of very calcic-rich diopside in veins oblique to the main high-temperature foliation of the rock.The peridotites, initially well-foliated with locally poikiloblastic textures, show overprints of a two-stage deformation history: (1) a high-temperature (>1000°C), low-stress (0.02 GPa), homogeneous deformation that has led to the present Porphyroclastic textures displayed by the rocks and (2) heterogeneous ductile shearing at a much higher stress (0.05 GPa). This heterogeneous shearing probably describes a single tectonic event because it began at high temperatures, producing dynamic recrystallization of olivine in the shear zone, and ended at low temperatures in the stability field of chlorite and serpentine. In a few samples, olivine shows evidence of quasi-hydrostatic recrystallization at a very high temperature. Here, we propose that this recrystallization was related to fluid/magma percolation, a process that can also account for the resorption of the orthopyroxene and for the late crystallization of diopside veins in the rock.The impregnation by fluid or magma, development of the main high-temperature, low-stress deformation, and subsequent migration recrystallization of olivine probably occurred in a mantle fragment involved in the arc formation. In addition, this mantle has preserved structures that may have formed earlier in the oceanic lithosphere upon which the arc formed.Heterogeneous ductile shear zones in the peridotites may have developed during uplift. The "cold" deformation may have taken place during diapiric rise of hot mantle that underwent subsequent serpentinization or gliding along normal faults associated with the extension of the eastern margin of the forearc.

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Serpentinized Peridotite from the North Wall of the Puerto Rico Trench

Cited by 56 publications

References 0 publications

Peridotites Drilled from the Tyrrhenian Sea, ODP Leg 107

Peridotites Drilled from the Tyrrhenian Sea, ODP Leg 107

Geophysical and geochemical constraints on the evolution of oceanic lithosphere from formation to subduction

Deformation History of Peridotites from Mariana Forearc, Conical Seamount, Leg 125

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