Geophysical evidence for hydration of the crust and mantle of the Nazca plate during bending at the north Chile trench

Ranero, César R.; Sallarès, Valentı́

doi:10.1130/g20379.1

Cited by 179 publications

(168 citation statements)

References 27 publications

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“…Ranero et al, 2003;Ranero and Sallarès, 2004;Li and Lee, 2006), and may proceed to depth greater than 20 km (depth of the 300°C isotherm in a 75-Ma-old plate) because of lower geothermal gradients and better water availability. By modeling seismic velocities of bending-related extensional faulting, Ranero and Sallarès (2004) predict a 20-km-thick mantle layer serpentinized to 17% for the Nazca plate at the North Chile trench. Based on geochemical data and modeling, Li and Lee (2006) estimate the paleo-serpentinization depth of the Feather River Ophiolite (subduction context) to be around 40 km.…”

Section: Results Of Mass Balance Calculationsmentioning

confidence: 99%

The Lithium, Boron and Beryllium content of serpentinized peridotites from ODP Leg 209 (Sites 1272A and 1274A): Implications for lithium and boron budgets of oceanic lithosphere

Vils¹,

Pelletier²,

Kalt³

et al. 2008

Geochimica et Cosmochimica Acta

118

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Despite the key importance of altered oceanic mantle as a repository and carrier of light elements (B, Li, and Be) to depth, its inventory of these elements has hardly been explored and quantified. In order to constrain the systematics and budget of these elements we have studied samples of highly serpentinized (>50%) spinel harzburgite drilled at the Mid-Atlantic Ridge (FifteenTwenty Fracture zone, ODP Leg 209, Sites 1272A and 1274A). In-situ analysis by secondary ion mass spectrometry reveals that the B, Li and Be contents of mantle minerals (olivine, orthopyroxene, and clinopyroxene) remain unchanged during serpentinization. B and Li abundances largely correspond to those of unaltered mantle minerals whereas Be is close to the detection limit. The Li contents of clinopyroxene are slightly higher (0.44-2.8 lg g À1 ) compared to unaltered mantle clinopyroxene, and olivine and clinopyroxene show an inverse Li partitioning compared to literature data. These findings along with textural observations and major element composition obtained from microprobe analysis suggest reaction of the peridotites with a mafic silicate melt before serpentinization. Serpentine minerals are enriched in B (most values between 10 and 100 lg g À1 ), depleted in Li (most values below 1 lg g À1 ) compared to the primary phases, with considerable variation within and between samples. Be is at the detection limit. Analysis of whole rock samples by prompt gamma activation shows that serpentinization tends to increase B (10.4-65.0 lg g À1 ), H 2 O and Cl contents and to lower Li contents (0.07-3.37 lg g À1 ) of peridotites, implying that-contrary to alteration of oceanic crust-B is fractionated from Li and that the B and Li inventory should depend essentially on rock-water ratios. Based on our results and on literature data, we calculate the inventory of B and Li contained in the oceanic lithosphere, and its partitioning between crust and mantle as a function of plate characteristics. We model four cases, an ODP Leg 209-type lithosphere with almost no igneous crust, and a Semail-type lithosphere with a thick igneous crust, both at 1 and 75 Ma, respectively. The results show that the Li contents of the oceanic lithosphere are highly variable (17-307 kg in a column of 1 m Â 1 m Â thickness of the lithosphere (kg/col)). They are controlled by the primary mantle phases and by altered crust, whereas the B contents (25-904 kg/col) depend entirely on serpentinization. In all cases, large quantities of B reside in the uppermost part of the plate and could hence be easily liberated during slab dehydration. The most prominent input of Li into subduction zones is to be expected from Semail-type lithosphere because most of the Li is stored at shallow levels in the plate. Subducting an ODP Leg 209-type lithosphere would mean only very little Li contribution from the slab. Serpentinized mantle thus plays an important role in B recycling in subduction zones, but it is of lesser importance for Li.

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Section: Results Of Mass Balance Calculationsmentioning

confidence: 99%

The Lithium, Boron and Beryllium content of serpentinized peridotites from ODP Leg 209 (Sites 1272A and 1274A): Implications for lithium and boron budgets of oceanic lithosphere

Vils¹,

Pelletier²,

Kalt³

et al. 2008

Geochimica et Cosmochimica Acta

118

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“…A slight decrease in middle and lower crustal seismic velocities trenchward probably indicates fracturing and possibly crustal hydration due to plate bending. Seismic velocities in the oceanic upper mantle systematically increase with plate age, though on corridor 2 they locally decrease trenchward, perhaps due to serpentinized mantle rocks [Ranero and Sallares, 2004].…”

Section: Wide-angle Seismic Datamentioning

confidence: 98%

Untitled

2006

EoS Transactions

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“…Slow upper-mantle seismic velocities at the PeruChile, Kuril, and Middle America trenches have been observed and interpreted as evidence for a serpentinized mantle (Walther et al, 2000;Ranero and Sallares, 2004;Grevemeyer et al, 2007;Ivandic et al, 2010;Van Avendonk et al, 2011;Ivandic et al, 2008;Fujie et al, 2013;Lefeldt et al, 2012). Offshore Nicaragua where the outer rise is densely faulted, measured velocities range from 7.8 km/s (Walther et al, 2000) and 7.5 km/s (Ivandic et al, 2010;Ivandic et al, 2008) to as low as 6.9 km/s (Van Avendonk et al, 2011) ( Figure 5).…”

Section: Geophysical Properties Of a Hydrated Subducting Upper Mantlementioning

confidence: 99%

“…This seawater may fill cracks in the upper mantle with free water, react strongly with olivine in upper mantle peridotite, filling cracks and fault zones with serpentinite, and/or diffuse between fault zones, pervasively serpentinizing the upper mantle (Ranero and Sallares, 2004;Faccenda et al, 2009). …”

Section: Introductionmentioning

confidence: 99%

Evolution of oceanic margins : rifting in the Gulf of California and sediment diapirism and mantle hydration during subduction

Miller¹

2013

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This thesis investigates three processes that control the evolution of oceanic margins. Chapter 2 presents seismic images of a ~2-km-thick evaporite body in Guaymas Basin, central Gulf of California. In rifts, evaporites form under conditions unique to the latest stages of continental rupture, and the presence, age, thickness, and shape place new constraints on the history of early rifting there. Chapter 3 presents numerical experiments that show that diapirs can form in sediments on the down-going plate in subduction zones and rise into the mantle wedge, delivering the sedimentary component widely observed in arc magmas. Chapter 4 presents measurements of seismic anisotropy from wide-angle, active-source data from the Middle America Trench that address the hypothesis that the upper mantle is hydrated by seawater flowing along outer-rise normal faults. These measurements indicate that the upper mantle is ~1.57 to 6.89% anisotropic, and this anisotropy can be attributed to bendingrelated faulting and an inherited mantle fabric. Accounting for anisotropy reduces previous estimates for the amount of water stored in the upper mantle of the downgoing plate from ~2.5 to 1.5 wt%, a significant change in subduction zone water budgets. AcknowledgementsThis thesis punctuates my own transformation from student to new scientist, but it also marks a change from many other states of incipiency to nascence. In any transformation and in any new thing there is woe. This woe can be wisdom, but it can also be madness. Dan Lizarralde has a knack for sorting wisdom from madness, and he showed me how to see the difference and navigate the space in between. I am grateful that he took a chance on me, first as a summer student at WHOI and then as a graduate student, and he never stopped holding the proverbial carrot at just the right distance.Mark Behn and John Collins also understand wisdom and madness. They took an early interest in my work and have offered ceaseless encouragement since I first arrived at WHOI. They also provided the critical eyes that are essential to good science, and to the development of good scientists, and I am truly grateful for time I shared with these guys. Donna Shillington and Alison Malcolm had no hesitations about joining my thesis committee, and they have been nothing but supportive the whole time.I am lucky to have spent 5 months at sea with the fine officers and crews of the R/V Langseth, R/V Endeavor, and F/V Tiki. At WHOI, talented people like Jeff Dusenberry and Jonathan Murry kept our computers and code running. I am grateful that the folks in the education offices MIT and WHOI work hard to make the Joint Program the amazing experience it is. I am also thankful that the U.S. values scientists and students and supports us by giving grants like National Science Foundation (NSF) Division of Ocean Science (OCE) #824497 and NSF OCE-MARGINS #825178 and #841063 to Dan Lizarralde, as well as NSF Division of Earth Sciences #0652707 to Mark Behn.Camilo Ponton can talk science, but he was also there ...

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Geophysical evidence for hydration of the crust and mantle of the Nazca plate during bending at the north Chile trench

Abstract: Geology, v. 32, n. 7, p. 549-552, 2004. http://dx.doi.org/10.1130/G20379.1International audienc

Cited by 179 publications

References 27 publications

The Lithium, Boron and Beryllium content of serpentinized peridotites from ODP Leg 209 (Sites 1272A and 1274A): Implications for lithium and boron budgets of oceanic lithosphere

The Lithium, Boron and Beryllium content of serpentinized peridotites from ODP Leg 209 (Sites 1272A and 1274A): Implications for lithium and boron budgets of oceanic lithosphere

Untitled

Evolution of oceanic margins : rifting in the Gulf of California and sediment diapirism and mantle hydration during subduction

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