Origin and emplacement of Mariana forearc seamounts

Fryer, Patricia; Ambos, Elizabeth L.; Hussong, Donald M.

doi:10.1130/0091-7613(1985)13<774:oaeomf>2.0.co;2

Cited by 194 publications

(100 citation statements)

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“…A broad zone of serpentinite seamounts, each up to 2500 m high and 30 km in diameter, 50-120 km from the trench axis, occurs along the trench-slope break (outer-arc high) of the Mariana system. These seamounts are formed by the diapiric rise and protrusion of serpentinite bodies (Bloomer, 1983;Fryer et al, 1985b;Fryer and Fryer, 1987). In the Izu-Bonin forearc, a chain of serpentinite seamounts (up to 1500 m high and 20 km in diameter) is present < 50 km from the trench axis.…”

mentioning

confidence: 99%

Introduction

Taylor¹

1990

Proceedings of the Ocean Drilling Program

102

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mentioning

confidence: 99%

Introduction

Taylor¹

1990

Proceedings of the Ocean Drilling Program

102

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“…As suggested by Bloomer (1983) (C)The dragged down MORB has been meta morphosed in a region about 16 to 20 km deep and entrained into a rising serpentine diapir (Maekawa et al, 1992). The serpentinite diapir is considered to have been generated by the serpentinization of wedge mantle peridotite with fluid released from the subducting slab by com paction and dehydration reactions (Bloomer, 1983;Fryer et al, 1985). The uplifting force of the serpentinite diapir is considered to be gravitational instability (e.g., Ishii, 1985).…”

Section: Tectonic Modelmentioning

confidence: 99%

“…Numerous serpentinite seamounts are widely exposed in the forearc area along the Mariana Trench (Fryer et al, 1985). These seamounts are thought to have been formed by serpentinite dia pirs that originated from hanging wall peridotites above the subducting oceanic slab.…”

Section: Introductionmentioning

confidence: 99%

Origin of blueschist-facies clasts in the Mariana forearc, Western Pacific.

et al. 1995

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In the Mariana forearc region, blueschist-facies metabasite clasts have been recovered from a serpentinite seamount during Ocean Drilling Program Leg 125. To clarify the origin of these metamorphic clasts, major and rare earth elements (REE), Ba, and Sr were measured in seven blueschist-facies metabasite clasts. Two out of seven clasts have zig-zag REE patterns reflecting the lanthanide tetrad effect, suggesting intense interaction with sea water. The other five clasts, however, show REE patterns with light REE depletion similar to N-type mid-ocean ridge basalts. Barium and Sr enrichments, relative to light REE abundances, are not conspicuous and most clasts show Sr and/or Ba depletions, indicating that they have chemical affinity with mid-ocean ridge basalt. This result is supported by the similarity of the Ti02-A1203 systematics of the clasts to those of mid-ocean ridge basalts.These MORB-like clasts metamorphosed under blueschist-facies conditions must have been taken into uprising serpentinite diapir at a depth where materials from oceanic crust extensively accreted. Two possible sources for the MORB-like protolith of blueschist-facies clasts are considered: (1) the oceanic crust of the subducted Pacific plate, (2) oceanic crust trapped within the area between trench axis and volcanic front when the subduction of the Pacific plate started. The second possibility is likely because the subducting Pacific plate crust is overlain by 600-800 m of oceanic sediment which is not represented in the clast population. It is proposed that the clasts provide evidence of tectonic erosion of oceanic crust which was trapped in the Mariana forearc at the initiation of subduction.

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“…The occurrence of obvious flow structures (observed during SeaMark and diving surveys of the seamount [Hussong and Fryer, 1981;Fryer et al, 1985]) favors a gravity sliding origin for some of the observed structures. Geochemical and mineralogical analyses of serpentine sediments from Hole 778A reveal that significant sedimentary reworking and remobilization occurred on the flanks of the seamount in conjunction with gravitational sliding of the serpentine material (Lagabrielle et al, this volume).…”

Section: Regional Background and Previous Datamentioning

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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Origin and emplacement of Mariana forearc seamounts

Cited by 194 publications

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Introduction

Introduction

Origin of blueschist-facies clasts in the Mariana forearc, Western Pacific.

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

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