Recent massive sulfide deposits of the Semenov ore district, Mid-Atlantic Ridge, 13°31′ N: Associated rocks of the oceanic core complex and their hydrothermal alteration

Pertsev, A. N.; Бортников, Н. С.; Vlasov, E. A.; Bel’tenev, V. E.; Dobretsova, I. G.; Ageeva, Olga

doi:10.1134/s1075701512050030

Cited by 40 publications

(34 citation statements)

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“…Early surveys carried out during Russian cruises located and defined several extinct hydrothermal fields throughout the 13°30′N detachment using a deep‐towed self‐potential system, in addition to TV‐camera surveys and sampling [ Bortnikov et al ., ; Cherkashev et al ., ; Cherkashov et al ., ; Pertsev et al ., ]. These data and results clearly demonstrate that hydrothermal activity has been present in space and time throughout the exposed fault surface, from its termination near the ridge axis to the limit of the corrugated surface to the west.…”

Section: Geological Setting and Prior Workmentioning

confidence: 98%

“…These data and results clearly demonstrate that hydrothermal activity has been present in space and time throughout the exposed fault surface, from its termination near the ridge axis to the limit of the corrugated surface to the west. In addition to inactive hydrothermal fields, an active hydrothermal field (Semenov‐2) was observed [ Beltenev et al ., ; Cherkashov et al ., ; Pertsev et al ., ]. Hydrothermal deposits, which yield ages of up ∼100 kyr, show no apparent progression with age (e.g., in the direction of spreading), as older deposits are found near the axis, while the active site is >5 km off axis [ Cherkashov et al ., ].…”

Section: Geological Setting and Prior Workmentioning

confidence: 99%

“…The link between deformation and hydrothermal activity is further confirmed by a robust association along the Mid‐Atlantic Ridge (MAR) of oceanic detachment faults with both seismicity and hydrothermal activity [ Escartín et al ., ]. To date, all the OCCs that have been explored along the Mid‐Atlantic Ridge (MAR) are known to host active hydrothermal vents, show extinct hydrothermal deposits, or both (e.g., Logatchev, TAG, Semenov, Lost City, Rainbow, Ashadze, and Von Damm) [ Andreani et al ., ; Connelly et al ., ; Früh‐Green et al ., ; German et al ., ; Ondréas et al ., ; Pertsev et al ., ; Petersen et al ., ; Tivey et al ., ].…”

Section: Introductionmentioning

confidence: 99%

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Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Escartı́n

Mével

Petersen

et al. 2017

Geochem Geophys Geosyst

179

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Microbathymetry data, in situ observations, and sampling along the 13°20′N and 13°20′N oceanic core complexes (OCCs) reveal mechanisms of detachment fault denudation at the seafloor, links between tectonic extension and mass wasting, and expose the nature of corrugations, ubiquitous at OCCs. In the initial stages of detachment faulting and high‐angle fault, scarps show extensive mass wasting that reduces their slope. Flexural rotation further lowers scarp slope, hinders mass wasting, resulting in morphologically complex chaotic terrain between the breakaway and the denuded corrugated surface. Extension and drag along the fault plane uplifts a wedge of hangingwall material (apron). The detachment surface emerges along a continuous moat that sheds rocks and covers it with unconsolidated rubble, while local slumping emplaces rubble ridges overlying corrugations. The detachment fault zone is a set of anostomosed slip planes, elongated in the along‐extension direction. Slip planes bind fault rock bodies defining the corrugations observed in microbathymetry and sonar. Fault planes with extension‐parallel stria are exposed along corrugation flanks, where the rubble cover is shed. Detachment fault rocks are primarily basalt fault breccia at 13°20′N OCC, and gabbro and peridotite at 13°30′N, demonstrating that brittle strain localization in shallow lithosphere form corrugations, regardless of lithologies in the detachment zone. Finally, faulting and volcanism dismember the 13°30′N OCC, with widespread present and past hydrothermal activity (Semenov fields), while the Irinovskoe hydrothermal field at the 13°20′N core complex suggests a magmatic source within the footwall. These results confirm the ubiquitous relationship between hydrothermal activity and oceanic detachment formation and evolution.

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Section: Geological Setting and Prior Workmentioning

confidence: 98%

Section: Geological Setting and Prior Workmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Escartı́n

Mével

Petersen

et al. 2017

Geochem Geophys Geosyst

179

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“…Many seafloor massive sulfides in the recent oceans, including the largest and those with the highest Cu grade (Petersen and Hein, 2013;Hein et al, 2013), are hosted in the peridotite-dominated lithosphere with a thin and heterogeneous crust (Gràcia et al, 2000;Kelley et al, 2001;Petersen et al, 2009;Pertsev et al, 2012;Kostitsyn et al, 2013;Tucholke et al, 2013;Andreani et al, 2014;Ciazela et al, 2015), where melt-mantle reaction is likely more enhanced (Ciazela et al, 2017b). In on-land prospecting, the search for chalcophile deposits seeks regions with both an appropriately enriched source rock, and a mechanism for concentrating those elements in a deposit.…”

Section: Crust-mantle Transition Zones and Related Sulfide Ore Depositsmentioning

confidence: 99%

Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23°N, MAR)

Ciążela

Koepke

Dick

et al. 2018

Geochimica et Cosmochimica Acta

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ABSTRACT:The Kane Megamullion oceanic core complex located along the Mid-Atlantic Ridge (23°30'N, 45°20'W) exposes lower crust and upper mantle directly on the ocean floor. We studied chalcophile elements and sulfides in the ultramafic and mafic rocks of the crust-mantle transition and the mantle underneath. We determined mineralogical and elemental composition and the Cu isotope composition of the respective sulfides along with the mineralogical and elemental composition of the respective serpentines. The rocks of the crust-mantle transition zone (i.e., plagioclase harzburgite, peridotite-gabbro contacts, and dunite) overlaid by troctolites are by one order of magnitude enriched in several chalcophile elements with respect to the spinel harzburgites of the mantle beneath. Whereas the range of Cu concentrations in spinel harzburgites is 7-69 ppm, the Cu concentrations are highly elevated in plagioclase harzburgites with a range of 90-209 ppm. The zones of the peridotite-gabbro contacts are even 2 more enriched, exhibiting up to 305 ppm Cu and highly elevated concentrations of As, Zn, Ga, Sb and Tl.High Cu concentrations show pronounced correlation with bulk S concentrations at the crust-mantle transition zone implying an enrichment process in this horizon of the oceanic lithosphere. We interpret this enrichment as related to melt-mantle reaction, which is extensive in crust-mantle transition zones. In spite of the ubiquitous serpentinization of primary rocks, we found magmatic chalcopyrites [CuFeS 2 ] as inclusions in plagioclase as well as associated with pentlandite [(Fe,Ni) indicate that the metal enrichment, increased sulfide modes, and potentially formation of small sulfide deposits could be expected globally along the petrological Moho.

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“…In addition, samples of OPG veinlets in amphibolite and gabbro, as well as massive OPG rocks, were dredged at 8 sites ( Fig. 1) [5]. The analysis of fresh lavas with quench glasses from 21 sampling sites showed that within the massif the composition of magmas of volcanic struc tures varied from normal (Nb N /Zr N = 1.…”

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confidence: 99%

Composition and origin of a K2O-rich granite melt in the Mid-Atlantic Ridge, 13°34′ N: Evidence from the analysis of melt inclusions and minerals of the gabbro-plagiogranite association

et al. 2015

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Participation of seawater in large scale convective circulation in the global system of mid ocean ridges is an important factor of heat and mass transfer resulting in cooling and hydrothermal alteration of the newly formed basic crust and precipitation of sulfide-poly metallic ores on the oceanic floor [1,2]. The deep zones of hydrothermal systems and the areas of hydro thermal-magmatic interaction are the least studied. It is suggested that the local partial melting of the basic crust under the influence of hydrothermal seawater derived fluids and the appearance of oceanic plagiog ranite (OPG), i.e., plutonic quartz-feldspar rocks with occasional pyroxene and hornblende, may be one of the extreme manifestations of such interaction [3,4]. However, there are other models of OPG origin: extreme differentiation of basaltic magma, phase sep aration of differentiated basaltic magma, magmatic assimilation, and partial melting of the hydrated crust [3]. Although the phenomenon of acid magmatism in the modern oceanic crust and paleoanalogs is of spe cial interest, the likely combinations of various petro genetic factors in the generation of OPG melts are poorly studied. In particular, the role of the basic crust composition is not clear.In this paper, we report the results of the study of an occasional biotite bearing gabbro-plagiogranite assemblage discovered in the Mid Atlantic Ridge (MAR), where the formation of the oceanic crust is significantly controlled by mantle magmas of the E MORB type enriched in incompatible elements. The composition of the granitoid melt was estimated by the study of melt inclusions in zircon, the bulk chemistry of OPG veinlets, and clinopyroxene/melt REE parti tioning.The gabbro-peridotite (strongly serpentinized) massif exposed in the footwall of the large offset low angle detachment fault in the range of 13°28′-13°35′ N on the western slope of the MAR was studied and sampled in three cruises of R/V Professor Logachev in 2007-2011 (Fig. 1). It is established that the structure of the massif is complicated by volcanic formations and a series of hydrothermal sulfide fields. In addition, samples of OPG veinlets in amphibolite and gabbro, as well as massive OPG rocks, were dredged at 8 sites ( Fig. 1) [5]. The analysis of fresh lavas with quench glasses from 21 sampling sites showed that within the massif the composition of magmas of volcanic struc tures varied from normal (Nb N /Zr N = 1.2; H 2 O (8) = 0.15 wt %; K 2 O = 0.04 wt %; 87 Sr/ 86 Sr = 0.7024) to sig nificantly enriched (Nb N /Zr N = 3.5; H 2 O (8) = 0.45 wt %; K 2 O = 0.7 wt %; 87 Sr/ 86 Sr = 0.7029) oceanic basalt.Biotite bearing OPGs were found at Sites 97 and 101, on the northern margin of the massif, at a dis tance of ~3 km from each other (Fig. 1). They occur as fine grained biotite-quartz-plagioclase veinlets in coarse graned gabbro. Gabbroids and hydrothermally altered mafic rocks prevailed among the dredged sam ples. Mafic rocks contain quartz-sulfide mineraliza tion. There are samples of massive biotite free OPG as well.S...

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Recent massive sulfide deposits of the Semenov ore district, Mid-Atlantic Ridge, 13°31′ N: Associated rocks of the oceanic core complex and their hydrothermal alteration

Cited by 40 publications

References 23 publications

Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Tectonic structure, evolution, and the nature of oceanic core complexes and their detachment fault zones (13°20′N and 13°30′N, Mid Atlantic Ridge)

Sulfide enrichment at an oceanic crust-mantle transition zone: Kane Megamullion (23°N, MAR)

Composition and origin of a K2O-rich granite melt in the Mid-Atlantic Ridge, 13°34′ N: Evidence from the analysis of melt inclusions and minerals of the gabbro-plagiogranite association

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