Thermal effects of ridge subduction

DeLong, Stephen E.; Schwarz, Wolfgang; Anderson, Roger N.

doi:10.1016/0012-821x(79)90172-9

Cited by 195 publications

(77 citation statements)

References 18 publications

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“…For Leg 125 boninite, the difficulty with the model as published by DeLong et al (1979) is that the temperature of the mantle wedge is too low to generate melt at shallow depths, because the wedge is cooled by subduction of the slab before the subduction of the ridge. This is true even in the modeled case of subduction beneath young (10-20 Ma) lithosphere.…”

Section: Ridge Subduction and Subduction Of Hot Lithospherementioning

confidence: 99%

“…DeLong et al (1979) consider this possibility, which was investigated more extensively by Defant and Drummond (1990) and Drummond and Defant (in press) (see appendix). They argue that the most fertile zone of melting lies at 23 to 26 kb and 770° C to 115° C, where dehydration and wet partial melting of the slab can occur together.…”

Section: Ridge Subduction and Subduction Of Hot Lithospherementioning

confidence: 99%

See 1 more Smart Citation

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Pearce¹,

Laan²,

Arculus³

et al. 1992

Proceedings of the Ocean Drilling Program

288

265

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Holes drilled into the volcanic and ultrabasic basement of the Izu-Ogasawara and Mariana forearc terranes during Leg 125 provide data on some of the earliest lithosphere created after the start of Eocene subduction in the Western Pacific. The volcanic basement contains three boninite series and one tholeiite series. (1) Eocene low-Ca boninite and low-Ca bronzite andesite pillow lavas and dikes dominate the lowermost part of the deep crustal section through the outer-arc high at Site 786. (2) Eocene intermediate-Ca boninite and its fractionation products (bronzite andesite, andesite, dacite, and rhyolite) make up the main part of the boninitic edifice at Site 786. (3) Early Oligocene intermediate-Ca to high-Ca boninite sills or dikes intrude the edifice and perhaps feed an uppermost breccia unit at Site 786. (4) Eocene or Early Oligocene tholeiitic andesite, dacite, and rhyolite form the uppermost part of the outer-arc high at Site 782. All four groups can be explained by remelting above a subduction zone of oceanic mantle lithosphere that has been depleted by its previous episode of partial melting at an ocean ridge. We estimate that the average boninite source had lost 10-15 wt% of melt at the ridge before undergoing further melting (5-10%) shortly after subduction started. The composition of the harzburgite (<2% clinopyroxene, Fo content of about 92%) indicates that it underwent a total of about 25% melting with respect to a fertile MORB mantle. The low concentration of Nb in the boninite indicates that the oceanic lithosphere prior to subduction was not enriched by any asthenospheric (OIB) component.The subduction component is characterized by (1) high Zr and Hf contents relative to Sm, Ti, Y, and middle-heavy REE, (2) light REE-enrichment, (3) low contents of Nb and Ta relative to Th, Rb, or La, (4) high contents of Na and Al, and (5) Pb isotopes on the Northern Hemisphere Reference Line. This component is unlike any subduction component from active arc volcanoes in the Izu-Mariana region or elsewhere. Modeling suggests that these characteristics fit a trondhjemitic melt from slab fusion in amphibolite facies. The resulting metasomatized mantle may have contained about 0.15 wt% water. The overall melting regime is constrained by experimental data to shallow depths and high temperatures (1250°C and 1.5 kb for an average boninite) of boninite segregation. We thus envisage that boninites were generated by decompression melting of a diapir of metasomatized residual MORB mantle leaving the harzburgites as the uppermost, most depleted residue from this second stage of melting. Thermal constraints require that both subducted lithosphere and overlying oceanic lithosphere of the mantle wedge be very young at the time of boninite genesis. This conclusion is consistent with models in which an active transform fault offsetting two ridge axes is placed under compression or transpression following the Eocene plate reorganization in the Pacific. Comparison between Leg 125 boninites and boninites and related rocks e...

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Section: Ridge Subduction and Subduction Of Hot Lithospherementioning

confidence: 99%

Section: Ridge Subduction and Subduction Of Hot Lithospherementioning

confidence: 99%

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Pearce¹,

Laan²,

Arculus³

et al. 1992

Proceedings of the Ocean Drilling Program

288

265

View full text Add to dashboard Cite

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“…Other important features are: high-temperature metamorphism closely associated with near-trench plutons created by heat released through a slab window [DeLong et al, 1979;Iwamori, 2000]; and porphyry gold and copper mineralization often associated with adakitic rocks . When a ridge subducts under a continental margin, the diverging plates continue to separate creating a slab window that forms between the separating plates [Santosh, Kusky, 2010].…”

Section: P a L E O G E O D Y N A M I C Smentioning

confidence: 99%

A Silurian-early Devonian slab window in the southern Central Asian Orogenic Belt: Evidence from high-Mg diorites, adakites and granitoids in the western Central Beishan region, NW China

Zheng

Xiao

et al. 2018

Journal of Asian Earth Sciences

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“…Spreading ridge subduction should leave a distinctive mark on the structural and hydrogeologic processes in the overriding subducting crust, mantle, and where present, accretionary wedge (see for example references in Underwood, 1993). On land studies in convergent margin systems that have experienced past ridge subduction events, for example, portions of the Franciscan along California coast and the Shimanto belt of Japan, strongly suggest that ridge subduction is associated with an increase in the thermal maturation or metamorphic grade in the overthrust upper plate materials (Cloos, 1993;DeLong et al, 1979;Underwood, 1993). The enhanced thermal and fluid-rock interactions in the Franciscan in the Big Sur Region and the King Range in California (Underwood et al, 1989;Underwood et al, 1990) are also examples of the potential manifestations of past ridge subduction events.…”

Section: Introductionmentioning

confidence: 99%

A Summary of ODP Leg 141 Hydrogeologic, Geochemical, and Thermal Results

Brown¹,

Bangs²,

Froelich³

et al. 1995

Proceedings of the Ocean Drilling Program, 141 Scientific Results

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The subduction of the oceanic spreading center at the Chile Triple Junction is marked by a substantial thermal perturbation and marked changes in the hydrogeologic and aqueous geochemical regimes in the overthrust plate. Ridge subduction substantially changes the fluid chemistry in the wedge through variably hydrating the oceanic basement, accretionary wedge, and continental backstop. This generates positive anomalies in salinity and chloride values with respect to sea water. The wedge immediately above the subducted ridge also experiences greatly enhance diagenesis and cementation together with the influx of primordial mantle derived 4 He. Linear temperature and pore fluid chemistry profiles suggest a predominantly diffusive/conductive regime predominates in the interior eastern portion of the wedge and continental backstop region. In contrast, a vigorous and transient hydrogeolgic system within 5 km of the toe of the wedge at both Sites 859 and 863 generates spatially narrow, large, and complex anomalies in temperature and fluid chemistry. At the toe the vigorous hydrogeologic system may be variably influenced by the episodic expulsion of fluid from both the deeper parts of the wedge and oceanic basement driven convection systems. Structural and diagenetic observations are also consistent with a hydrogeologic regime that both evolves with time and that is dominated by episodic processes. In particular, studies of cements, mineralized veins, deformation bands, and Fe sulfide distribution suggest that above the subducting ridge (i.e., Site 863) the lithification in the wedge is greatly enhanced and that and periods of enhanced fluid expulsion are associated with local hydrofracture and dilation episodes.

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Thermal effects of ridge subduction

Cited by 195 publications

References 18 publications

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

A Silurian-early Devonian slab window in the southern Central Asian Orogenic Belt: Evidence from high-Mg diorites, adakites and granitoids in the western Central Beishan region, NW China

A Summary of ODP Leg 141 Hydrogeologic, Geochemical, and Thermal Results

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