Hydrothermal exploration near the Azores Triple Junction: tectonic control of venting at slow-spreading ridges?

German, C. R.; Parson, L. M.; Team, Heat Scientific; Bougault, Henri; Coller, Dave; Critchley, M. F.; Dapoigny, Arnaud; Day, Charles; Eardley, D.; Fearn, A.; Flewellen, C.; Kirk, R. E.; Klinkhammer, Gary P.; Landuré, Jean-Yves; Ludford, E.; Miranda, Jorge Miguel; Needham, H. D.; Patching, John W; Pearce, Richard; Pelle, H.; Knœry, Joël; Rouse, I.; Scott, James M.; Stoffregen, P.; Taylor, Peter K.; Teare, D.; Wynar, J.

doi:10.1016/0012-821x(95)00224-z

Cited by 110 publications

(74 citation statements)

References 15 publications

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“…But while such a 665 hypothesis may be considered highly speculative in the modern day, we do note 666 that the past 20 years of exploration have helped to confirm what was once an 667 equally speculative hypothesis, also based on preliminary data-sets: that 668 tectonically controlled venting might be of importance along slow-spreading 669 ridges (German et al, 1996). From that historic perspective we eagerly 670 anticipate what the future exploration of Earth's slowest-spreading ridges might 671 bring!…”

Section: Rocks 641 642mentioning

confidence: 86%

Hydrothermal exploration of mid-ocean ridges: Where might the largest sulfide deposits be forming?

2016

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44Here, we review the relationship between the distribution of modern-day seafloor 45 hydrothermal activity along the global mid-ocean ridge crest and the nature of the 46 mineral deposits being formed at those sites. Since the first discovery of seafloor 47 venting, a sustained body of exploration has now prospected for one form of 48 hydrothermal activity in particular -high temperature "black smoker" venting -49 along >30% of the global mid ocean ridge crest. While that still leaves most of 50 that ~60,000km continuous network to be explored, some important trends have 51 already emerged. First, it is now known that submarine venting can occur along 52 all mid-ocean ridges, regardless of spreading rate, and in all ocean basins. 53Further, to a first approximation, the abundance of currently active venting, as 54 deduced from water column plume signals, can be scaled linearly with seafloor 55 spreading rate (a simple proxy for magmatic heat-flux). What can also be 56 recognized, however, is that there is an "excess" of high temperature venting 57 along slow and ultra-slow spreading ridges when compared to what was 58 originally predicted from seafloor spreading / magmatic heat-budget models. An 59 examination of hydrothermal systems tracked to source on the slow spreading 60Mid Atlantic Ridge reveals that no more than half of the sites responsible for the 61 "black smoker" plume signals observed in the overlying water column are 62 associated with magmatic systems comparable to those known from fast-63 spreading ridges. The other half of all currently known active high-temperature 64 submarine systems on the Mid-Atlantic Ridge are hosted under tectonic control. 65These systems appear both to be longer-lived than, and to give rise to much 66 larger sulfide deposits than, their magmatic counterparts -presumably as a result 67 of sustained fluid flow. A majority of these tectonic-hosted systems also involve 68 water-rock interaction with ultramafic sources. Importantly, from a mineral 69 resource perspective, this subset of tectonic-hosted vent-sites also represents 70 the only actively-forming seafloor massive sulfide deposits on mid-ocean ridges 71 that exhibit high concentrations of Cu and Au in their surface samples (>10wt.% 72 average Cu content and >3ppm average Au). Along ultraslow-spreading ridges, 73 3 first detailed examinations of hydrothermally active sites suggest that sulfide 74 deposit formation at those sites may depart even further from the spreading-rate 75 model than slow-spreading ridges do. Hydrothermal plume distributions along 76 ultraslow ridges follow the same (~50:50) distribution of "black smoker" plume 77 signals between magmatic and tectonics settings as the slow spreading MAR. 78 However, the first three "black smoker" sites tracked to source on any ultra-slow 79 ridges have all revealed high temperature vent-sites that host large polymetallic 80 sulfide deposits in both magmatic as well as tectonic settings. Further, deposits 81 in both types of setting have now been reveal...

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Section: Rocks 641 642mentioning

confidence: 86%

Hydrothermal exploration of mid-ocean ridges: Where might the largest sulfide deposits be forming?

2016

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“…From gravity and topography data, Scheirer et al [1997] estimate that the plateau's crust is twice as thick as surrounding crust, a thickening similar to that observed beneath the Reykjanes Ridge [Bell and Buck, 1992]. German et al [1996a] have proposed that the anomalously thick crust and associated higher crustal temperatures of the Reykjanes Ridge have prevented the tectonic segmentation common to slow spreading ridges, thus dampening hydrothermal activity. However, the degree of tectonism of the SEIR on the ASP Plateau is more similar to the Azores region: spreading segments are relatively short with complicated ridge offset geometries .…”

Section: Discussionmentioning

confidence: 97%

Detection of hydrothermal plumes along the Southeast Indian Ridge near the Amsterdam‐St. Paul Plateau

Scheirer

Baker

Johnson

1998

Geophysical Research Letters

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Abstract.A new self-contained profiling instrument, attached to 91 lowerings of waxcores and dredges along a 1600 km stretch of the Southeast Indian Ridge, found six sites having optical back-scatter anomalies indicative of hydrothermal plumes from high-temperature seafloor venting.At five other sites, back-scatter anomalies were less distinct, and at the remaining sites, anomalies were absent. These are the first documented hydrothermal sites along this intermediate-rate spreading center and are among the very few yet discovered in the Indian Ocean basin. Some profiles exhibit complex back-scatter anomalies suggestive of multiple sources of seafloor discharge. At one site, nearbottom temperature anomalies of-0.1 øC and the recovery of a vent-specific barnacle provide the first precise seafloor location of active venting in the deep Indian Ocean. Although this study is only reconnaissance in nature, venting along this portion of the SEIR appears to be significantly less than predicted by global correlations of plume incidence as a function of spreading rate. Nevertheless, these sites may be important as biological connections between distinct faunal assemblages of Atlantic and Pacific vent fields.

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“…The Rainbow massif is located in a small NTD of the MAR surrounded by en échelon nodal basins Parson et al, 2000] that offset the AMAR and AMAR minor segments of the ridge by 19.6 km in distance and 1.1 Myr in age [German et al, 1996]. Rainbow is one of a sequence of ten NTDs found south of the Azores; many of which host active or fossil hydrothermal systems .…”

Section: Geological Settingmentioning

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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Hydrothermal exploration near the Azores Triple Junction: tectonic control of venting at slow-spreading ridges?

Cited by 110 publications

References 15 publications

Hydrothermal exploration of mid-ocean ridges: Where might the largest sulfide deposits be forming?

Hydrothermal exploration of mid-ocean ridges: Where might the largest sulfide deposits be forming?

Detection of hydrothermal plumes along the Southeast Indian Ridge near the Amsterdam‐St. Paul Plateau

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

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