Abstract
Sulfide ores were investigated along with ore-bearing and metalliferous sediments of the hydrothermal fields in the northern near-equatorial Mid-Atlantic Ridge (MAR) zone: Semenov (13°30–31′N), Ashadze-1 (12°58′N), Zenit-Victoria (20°08′N), and Peterburgskoe fields (19°52′N), discovered during legs 26, 32, and 33 of the R/V Professor Logachev FSUE PMGE. Biogenic carbonate and background sediments of this region were also examined. Lithological, biostratigraphic, and geochemical physical-chemical investigations methods were used. Mineragraphic and precision structural and chemical research of typomorphic minerals were carried out at various stages of lithogenesis. It was found out that most sulfide constructions in the Zenit-Victoria and Peterburgskoe fields, as well as the eastern field of the Semenov cluster, are located in biogenic carbonate sediments of the Holocene and Late Pleistocene ages and represent a new type of sulfide mineralization, unknown earlier in the MAR zone. This mineralization was formed by metasomatic replacement of biogenic carbonate sediments by ore minerals, simultaneously with diffuse percolating of hydrothermal solutions through the sediments.
Access provided by Autonomous University of Puebla. Download conference paper PDF
Similar content being viewed by others
Keywords
- Ocean
- Mid-Atlantic ridge
- Modern sulfide ores
- Ore-bearing sediments
- Biomineralization
- Hydrothermal
- Metasomatic
1 Introduction
Massive sulfide ores from the ocean are chimneylike ore mounds (black smokers) formed under highly forced hydrothermal fluids, which are vented on the seafloor in various geological settings, mainly in spreading zones of the mid-oceanic ridges. Sulfide mineralization hosted in recent sediments has been discovered near continents and in intracontinental rifts, such as in the Red Sea.
It is suggested that most ore material is supplied into marine sediments from hydrothermal plumes, which form in the ocean above active hydrothermal vents. The effect of hydrothermal solutions on sediments while the solutions seep through them has been much less studied.
Ore-bearing sediments formed under the effect of hydrothermal solutions have been studied most completely in the Red Sea rift zone (Baturin 1971; Pushelt and Laschek 1984; Bogdanov et al. 1986; Butuzova 1998, 2003) and in the rifts adjoining the North American continental block in the west: the Guaymas Basin in the Bay of California, the Middle Valley of the Juan de Fuca Ridge, Escanaba Trough, etc. in the Pacific Ocean (Curray et al. 1982; Gidrotermal’nye … 1993; Goodfellow and Franklin 1982; Kurnosov et al. 1994; Zierenberg et al. 1993; Lisitsyn et al. 1989; Geologicheskoe … 1990; Bogdanov et al. 1989, 2006). These processes have remained poorly studied until now in mid-ocean ridges, which are distant from continents and covered only with thin sedimentary cover.
We believe that the main reason for this situation is the generally agreed opinion that the formation of ore-bearing sediments predominantly occurs by sedimentation (due to destruction of surface hydrothermal structures and precipitation of the ore substance from suspensions of hydrothermal plumes). Another cause is the unilateral approach to studying ore-bearing and metalliferous sediments: commonly, specialists (lithologists, paleontologists, geochemists) explore their own field of expertise, applying methods used in that field. These methods do not always allow them to determine the nature of mineral components. These components can be hydrothermal-sedimentary (precipitating from hydrothermal plumes or formed by destruction of hydrothermal mounds and vents), authigenic (appearing in situ as products of postsedimentation transformations, including hydrothermal metasomatic alteration), terrigenous (coming from continents), and edaphogenic (products of ocean bed destruction).
Massive sulfide deposits—ancient analogues of the contemporary oceanic massive sulfide ores—are thick stratiform bodies embedded, as a rule, in sedimentary and volcano-sedimentary rocks (Maslennikov 2006). This is similar to other type of deposits (cuprous sandstones and shales) formed under underground waters that emanated to submarine bottom sediments (Hoyningen-Huene 1963; Lur’e and Gablina 1972; Lur’e 1988; Rose 1976; White 1971). Both types are characterized by high concentrations of copper, lead, zinc, and rare elements and are the main sources for them. Enrichment in metals is explained by protracted circulation of ore-bearing fluids in sediments that serve as a barrier for metals (Gablina 1997), whereas venting of hydrothermal ore-bearing fluids in seawater results in their dispersion. Less than 5 % in the initial stage and up to 50 % in further periods are precipitated in sulfide mounds, which are formed on the seafloor near hydrothermal vents (Rona 1986; Gurvich 1998). The destruction of unstable massive sulfide ores under seawater began just after their formation (Gidrotermal’nye… 1993; Gablina et al. 2000).
In recent years, we and other researchers (Gablina et al. 2010, 2011, 2012; Dobretsova and Laiba 2009; Rusakov et al. 2013) obtained new data about the metasomatic effect of hydrothermal solutions on modern biogenic carbonate sediments of the Ashadze-1, Eastern (Semenov ore cluster), Zenit-Victoria, and Peterburgskoe ore fields of the Mid-Atlantic ridge (MAR), which led to the substitution of microfaunal shells of sediments by sulfides and other hydrothermal minerals, as well as to the formation of sulfide structures in them. This information is very important from both scientific and practical points of view, as the seepage of hydrotherms through the sediments might evoke precipitation of a larger part of the net load as well as the formation and preservation from destruction of a rich accumulations of sulfide ores.
2 Materials and Methods
Sulfide ores were investigated along with ore-bearing and metalliferous sediments of hydrothermal fields in the northern near-equatorial MAR zone: Semenov (13°30–31′N), Ashadze-1 (12°58′N), Zenit-Victoria (20°08′N), and Peterburgskoe fields (19°52′N), discovered during legs 26, 32, 33 of the R/V Professor Logachev FSUE PMGE, and carbonate, background sediments of this region. The investigations are based on a systematic approach to studies of the conditions of mineral and ore formation, which consists of a combination of lithological, biostratigraphic, and geochemical investigations. Mineragraphic, precision structures, and chemical research of typomorphic minerals, ore inclusive, were conducted at various stages of lithogenesis. The findings were compared with the data of direct measurements of Eh-pH parameters of ore-bearing and background sediments obtained during the leg. The main object of the research is the biogenic material of sediments, the mineral composition of which is uniform at the stage of sedimentogenesis within the ocean zone under consideration; these are calcite shells of dead plankton and benthos. Their different transformations may be associated with various conditions of diagenesis or superimposed processes.
3 Characterization of the Work Region
Ore fields are situated at the boards of the MAR rift valley in the area from 12°58.4’c.ш (Ashadze-1 field) to 20°08′N (Zenit-Victoria field) at depths from ~2400 to 4200 m (Fig. 1). Ore fields are composed of basalts, gabbro, peridotites, carbonate, metalliferous, and ore-bearing sediments with inclusions of sulfide ores.
The considered ore fields occupy a specific tectonic position: they are all situated in rift valley walls, with the Peterburgskoe field being found in the second ridge of the wall. Hydrothermal fields are characterized by developing metalliferous (Fecfs Footnote 1 ≥ 10 %, (Cu + Zn)cfs < 0.25 %), ore-bearing (Fecfs ≥ 10 %, (Cu + Zn)cfs ≥ 0.25 %), and carbonate (Fecfs < 10 %, (Cu + Zn)cfs < 0.25 %; CaCO3 ≥ 50–70 %) sediments. The thickness of carbonate sediments in this MAR sector does not exceed 1.5–3 m; ore-bearing sediments are no more than 0.5–0.6 m. Unaltered sediments are represented by calcite shells of foraminifers, coccolithes, and pteropods with admixture of clay and edaphogen material. According to the fauna assemblage, the age of the sediments is Holocene-Late Pleistocene (0–128 ka) (Gablina et al. 2011; Rusakov et al. 2011; Shilov et al. 2012).
The Ashadze-1 hydrothermal field is represented by two ore bodies with relict and active hydrothermal constructions and ore-bearing sediments. The Semenov ore cluster contains both active constructions (North-Western hydrothermal field) and massive ores embedded in sediments (Eastern hydrothermal field). No active constructions have been revealed in the Zenit-Victoria and Peterburgskoe hydrothermal fields, whereas sulfide formations were recorded in topography in the form of small hills. The majority of the investigated sites are characterized by hydrophysical anomalies that indicate continuing hydrothermal activity. The age of sulfide ores, dated by the isotopic Th/U metod, ranges from <2–60 ka (Zenit-Victoria) to 37–124 ka (Semenov) (Shilov et al. 2012; Rusakov et al. 2013).
Most sulfide constructions in the Zenit-Victoria, Peterburgskoe, and Eastern fields of the Semenov cluster are located in sediments and represent a new type of sulfide mineralization, unknown earlier in the MAR zone. The mineralization was formed by metasomatic replacement of organic carbonate sediments by hydrothermal minerals, simultaneously with diffuse percolating of hydrothermal solutions through the sediments (Gablina et al. 2012; Rusakov et al. 2013).
4 Results
Sulfide ores have been most completely studied in Zenit-Victoria and Peterburgskoe hydrothermal fields. Here the ores are represented by scattered sulfide constructions composed of a porous pyrite-marcasite or sphalerite-marcasite (in Cu–Zn–Fe ores) framework. Chalcopyrite, sphalerite, copper sulfides, and, in rare cases, bornite develop in the most porous places of the framework. Opal, barite, and Fe–Si gel are most abundant among nonmetallic hydrothermal minerals.
Investigations have shown that sulfide constructions in sediments of the Zenit-Victoria and Peterburgskoe fields have certain features that distinguish them from tubular bodies of “black smokers” described in the literature, which were generated on the surface of the ocean floor (Gablina et al. 2012). Those features include the following:
-
1.
Unusual shape: streamlined pear- and mushroom-shaped, platy stratified (Fig. 2).
-
2.
Multichannel inner structure characteristic of “diffusers” (Fig. 2b).
-
3.
Hardening crusts in the roof and on the walls of structures—lithified sediments, commonly situated at channel outputs (Fig. 2a, c–f).
-
4.
Presence of relics of sedimentary layering in platy structures (Fig. 2f).
-
5.
Widely spread relics of microfossils replaced by ore minerals (Fig. 3).
-
6.
Conformity of the height of structures with the thickness of enclosing sediments.
-
7.
The presence of aragonite crusts with Fe and Mn hydroxides on the surface of sediments that contain sulfide formations or aragonite zones at the contact of sediments with sulfide structures (Fig. 4).
Within hydrothermal fields, metalliferous and ore-bearing sediments are spread in the form of spots, which is not consistent with the idea of a uniform precipitation of ore particles from hydrothermal plumes. They differ from background ones in their physical-chemical characteristics, by elevated content of ore components (Fe, Cu, Zn, and Mn), Si, Mg, metasomatic replacement of calcite tests by hydrothermal minerals, and development of near-ore mineral-geochemical zones.
Lateral and vertical zonation was established in the distribution of major rock- and ore-forming elements and secondary (hydrothermal) minerals in the sediments of the Ashadze-1 field. Hydrothermal minerals are represented by silicates (tremolite-actinolite, hornblende, serpentine, Fe–Mg-smectite, and, probably, polygorskite [sepiolite]), carbonates (Mg–Mn-bearing siderite), sulfides (pyrite, isocubanite), sulphates (millerite, barite, celestine), chlorides (atacamite, halite), and Fe and Mn hydroxides, which metasomatically substitute calcite in microfossil tests and form porous and crustified cement of the sediments. Pyrite, siderite, and Fe hydroxide and sulphate are most widespread newly formed minerals.
The following zones are identified according to the composition of the dominant secondary minerals:
-
(1)
A sulfide zone, which coincides with ore bodies
-
(2)
A zone of minerals with elevated magnesia content, which partly coincides with ore body 1, going beyond its contours in the west and southwest
-
3)
A zone with developing Fe–Mn crusts along the periphery of ore bodies 1 and 2.
Vertically, sulfide paragenesis is substituted by the hydroxide-ferruginous. Farther away from the ore bodies, the processes of dissolution and replacement of carbonate shells by secondary minerals in sediments fade (Gablina et al. 2010, 2011).
The sediments of the Semenov field also exhibit metasomatic substitution of foraminiferal tests by Fe and Cu sulfides and near-ore hydrothermal alterations. Vertical zonation is also recorded in the distribution of hydrothermal minerals in host rocks. In the upward direction, from the roof of the sulfide deposit toward the surface of the ocean floor, the sulfide-barite association progressively gives way to the hydroxide-ferruginous-sulfide-barite, barite-hydroxide-ferruginous, and atacamite-hydroxide-ferruginous associations (Rusakov et al. 2013). This zonation reflects an increase in the oxidation potential of porous solutions of sediments up the section as a result of the growing influence of seawater.
Ore-bearing sediments and host sulfide constructions of the Zenit-Victoria and Peterburgskoe fields were intensely altered, which is reflected in their lithification at the contact with ores, the development of secondary minerals in them (Fig. 5), a sharp decrease in Eh and pH values with respect to background, and an increase of porous water temperature. Simultaneously, the oxidation potential decreases (to negative values) while the acidity increases down the section, clearly indicating that acid-reducing hydrothermal fluids arrive to the sediments from below (Gablina et al. 2012).
In general, the following characteristics are typical of the studied objects:
-
1)
Reduction in the thickness of sediments occurring above sulfide constructions or enclosing them (probably due to dissolution of primary biogenic calcite).
-
2)
Development of pseudomorphs of ore and other hydrothermal minerals after microfauna tests in ore-bearing sediments (Gablina et al. 2011).
-
3)
Vertical and lateral mineral-geochemical zonation in ore-bearing sediments around ore bodies; the sedimentary section, from bottom to top, reflects an increase in the oxidation potential and pH up the sedimentary column and at the flanks of the ore fields (Fig. 5).
-
4)
A sharp difference of ore-bearing sediments from background sediments revealed by the physical and chemical characteristics of their interstitial waters; Eh and pH of ore-bearing sediments are close to the physical-chemical parameters of hydrothermal solutions (Gablina et al. 2012).
5 Conclusions
The described shapes and the inner structure of sulfide constructions (“diffusers”) suggest that their formation occurred under incomplete permeability of the environment, which hampered the spread of fluids (i.e., the diffusion mechanism of flow promotion). In sulfide ores, the presence of relics of the layered sedimentary structure and pseudomorphs of ore minerals after microfauna tests suggest the metasomatic origin of ore constructions. The biogenic calcite that composed the sediments dissolved during the test and was replaced by hydrothermal minerals. The ore-forming process can be associated with the influence on sediments of acid metalliferous low pressure fluids of diffusion type, which arrive from below through permeable zones in basalts. Mineralization occurred on the geochemical barrier in the zone of interaction among metalliferous fluids, seawater saturating the sediments, and biogenic sedimentary calcite that is unstable in the acidic environment. Carbonate bottom mud served both as a geochemical barrier (with the presence of reactive carbonate material) and a physical barrier, making rapid migration of ore-bearing solutions difficult and encouraging precipitation and accumulation of useful components. At the initial stages or at low pressure of fluids (e.g., in the “exocontact” of the already formed constructions), metasomatic replacement of isolated tests leads to the formation of ore-bearing and/or metalliferous sediments. The prolonged influence of hydrotherms brings about the complete replacement of sedimentary biogenic material and the formation of sulfide constructions in its place. The recycling of dissolved biogenic calcite occurs on the surface of sediments (the sea floor) in aragonite crusts, enriched in Fe and Mn hydroxides, or at the contact of sediments with sulfide structures (Fig. 4). The presence of hardening crusts of sediments in the roof and on the walls of the sulfide constructions indicates the increased temperature of leaking fluids. The occurrence of isocubanite among the newly formed hydrothermal minerals indicates a high temperature (>260 °C) of hydrothermal solution supplied to sediments (Vaughan and Craig 1978).
Our conclusions concerning superimposed metallization on Holocene-Late Pleistocene (0–128 ka) bottom sediments do not contradict the data on the absolute age of sulfide ores (from less than 2 to ~124 ka)Footnote 2 and the availability of recent hydrophysical anomalies above the Zenit-Victoria ore field, which indicate ongoing hydrothermal activity there (Shilov et al. 2012).
Notes
- 1.
/cfs—based on carbonate-free substance.
- 2.
The dating in the Petersburgskoe ore field of 176.2 ± 59 ka (Shilov et al. 2012) needs to be clarified.
References
Baturin GN (1971) Deepwater ore sediments of hydrothermal genesis. In: Zenkevich NA (ed) History of the World Ocean. Nauka, Moscow (in Russian)
Bogdanov YuA, Gurvich EG, Butuzova GYu et al (1986) Metalliferous sediments of the Red Sea. Nauka, Moscow (in Russian)
Bogdanov YuA, Khvorova IV, Serova VV, Gorbunova ZN (1989) Sedimentation in rift zone of the Juan de Fuca Ridge. Izv Akad Nauk USSR Ser Geol 5:26–35 (in Russian)
Bogdanov YuA, Lisitsyn AP, Sagalevich EG, Gurvich EG (2006) Hydrothermal ore formation on oceanic bottom. Nauka, Moscow (in Russian)
Butuzova GYu (1998) Hydrothermal-sedimentary ore formation in rift zone of the Red Sea. GEOS, Moscow (in Russian)
Butuzova GYu (2003) Hydrothermal-sedimentary ore formation in World Ocean. GEOS, Moscow (in Russian)
Curray JR, Moore DC et al (1982) Initial reports of DSDP, D.C.: U.S. Gov. Print. Off., vol. 64. Washington
Dobretsova IG, Laiba AA (2009) Formation of mineral carbonate in hydrothermal sulfide ore in MAR. In: Lisitsyn AP (ed) Geologiya morei i okeanov: Proceedings of the 18th International. Scientific Conference (School) on Marine Geology. 2:155–159. GEOS, Moscow (in Russian)
Gablina IF (1997) Formation condition of largy cupriferrous sandstone and shale deposits. Geol Ore Dep 39, 4: 320–333
Gablina IF, Mozgova NN, Borodaev, Yu S et al (2000) Copper sulfide associations in recent oceanic ores of the Logachev hydrothermal field (Mid-Atlantic Ridge, 14° 45′N). Geol Ore Dep 42, 4: 296–316
Gablina IF, Popova EA, Sadchikova TA et al (2010) Hydrothermal alterations of modern organic sediments at the Ashadze-1 hydrothermal field, Mid-Atlantic Ridge, 13° N. Dokl. Earth Sci 433(2):998–1002
Gablina IF, Demina LL, Dmitrenko OB et al (2011) Composition and secondary alterations of microfossils in sediments of the Ashadze-1 hydrothermal field (tropical Mid-Atlantic Ridge). Oceanology 51(3):476–490
Gablina IF, Dobretsova IG, Bel’tenyov VE et al (2012) Peculiarities of presentday sulfide mineralization at 19°15′–20°08′N, Mid-Atlantic Ridge. Dokl Earth Sci 442, 2: 163–167
Geology and Hydrothermal Activity of the Juan de Fuca Ridge (1990). In: Lisitsyn AP (ed) Nauka, Moscow (in Russian)
Hydrothermal Systems and Sedimentary Formations in Atlantic Mid-Ocean Ridges (1993). Lisitsyn AP (ed), Nauka, Moscow (in Russian)
Goodfellow WD, Franklin JM (1982) Geology, mineralogy, and chemistry of sediment-hosted clastic massive sulfides in shallow cores, Middle Valley, Northern Juan de Fuca Ridge. Econ Geol 88:2037–2068
Gurvich EG (1998) Metalliferrous Sediments of the Ocean. Nauchnyi Mir, Moscow (in Russian)
Hoyningen-Huene E (1963) Zur Paläohidrologie des Oberrotligenden und Zechsteins in Harzvorland. Ber Geol Ges DDR S.-H. 1:201–220
Kurnosov V, Murdmaa I, Rosanova T et al (1994) Mineralogy and hydrothermally altered sediments and igneous rocks at Sites 856858, Middle Valley, Juan de Fuca Ridge, Leg 139. Proc ODP Sci Rep 139:113–131
Lisitsyn AP, Bogdanov YuA, Zonenshain LP et al (1989) Black smokers in the Bay of California. Izv Akad Nauk USSR Ser Geol 5:3–18 (in Russian)
Lur’e AM (1988) Genesis of Cuprous Sandstones and Shales. Nauka, Moscow (in Russian)
Lur’e AM, IF Gablina (1972) Sources of copper for the formation of mansfield-type deposits in the Western Ural Region. Geochem Int 10, 1:75–88
Maslennikov VV (2006) Lithogenesis and massive sulfide formation. IMin UB RAS, Miass (in Russian)
Pushelt H, Laschek D (1984) Marine Erzvorkommen in Roten Meer, Fridericiana. Zeitschrift der Universitet at Karlsruheno 34:3–17
Rona P (1986) Hydrothermal Mineralization in Seafloor Spreading Centers. Earth. Science Reviews, Mir, Moscow 20(1):1–104 (in Russian)
Rose AW (1976) The effect of cupriferous chloride complexes in the origin of red-bed copper and related deposits. Econ Geol 71:1036–1048
Rusakov V, Shilov VV, Dobretzhva IG et al (2011) Litochemostratigraphical horisons of upper pleistocene-holocene sediments of the Semenov ore cluster. In: Main Results in Russian Study of the Mid-Atlantic Ridge Processes in the First Decade of XXI. Russian Ridge’ 2011. IGEM RAS. Moscow, pp 68–70
Rusakov VYu, Shilov VV, Ryzhenko BN et al (2013) Mineralogical and geochemical zoning of sediments at the Semenov cluster of hydrothermal fields, 13°31′–13°30′ N, Mid-Atlantic Ridge. Geochem Int 51(8):646–669
Shilov VV, Beltenev VE, Ivanov VN et al (2012) New hydrothermal fields on Mid-Atlantic Ridge: Zenith-Victory (20°08′ c.ш.) and Peterburgskoe (19°52’ c.ш.). Doklady Earth Sci 442(1):63–69
Vaughan DJ, Craig JR (1978) Mineral chemistry of metal sulfides. Cambridge University Press, Cambridge
White WS (1971) A paleohydrologic model for mineralisation of the White Pine Copper Deposit, Norten Michigan. Econ Geol 66(1):1–13
Zierenberg R, Koski RA, Morton JL, Shanks WC (1993) Genesis of massive sulfide deposits on a sediment-covered spreading center, Escanaba Trough, Southern Gorda Ridge. Econ Geol 88(8):2069–2098
Acknowledgments
The material used in our studies was acquired during cruises of the R.V. Professor Logatchev, organized by the Polar Marine Geological Prospecting Expedition and financed by the Federal Agency of Subsurface and Natural Resources and Ecology of the Russian Federation. This work was financially supported by RFBR grants 08-05-00,799, 11-05-01117, and 14-05-00480.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2016 Springer International Publishing Switzerland
About this paper
Cite this paper
Gablina, I.F., Dobretsova, I.G., Popova, E.A. (2016). Biomineralization Processes During the Formation of Modern Oceanic Sulfide Ore and Ore-bearing Sediments. In: Frank-Kamenetskaya, O., Panova, E., Vlasov, D. (eds) Biogenic—Abiogenic Interactions in Natural and Anthropogenic Systems. Lecture Notes in Earth System Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-24987-2_5
Download citation
DOI: https://doi.org/10.1007/978-3-319-24987-2_5
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-24985-8
Online ISBN: 978-3-319-24987-2
eBook Packages: Earth and Environmental ScienceEarth and Environmental Science (R0)