Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W

Herzig, Peter; Becker, K.; Stoffers, Peter; Bäcker, H.; Blum, N.

doi:10.1016/0012-821x(88)90115-x

Cited by 110 publications

(78 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Agrokipia B; Constantinou and Govett, 1973;Herzig, 1988;Hannington et al, 1998), demonstrates that it is typified by low concentration of all the elements with the exception of Cu (the average concentration is 0.6 % in the stockwork zone and 2.1 % in semi-massive ore). Copper content of Apliki stockwork type mineralization is comparable even with corresponding deposits with massive ore (e.g.…”

Section: Discussion -Conclusionmentioning

confidence: 99%

The geology of the northern part of the apliki Cyprus-type ore deposit

Antivachis

2017

geosociety

View full text Add to dashboard Cite

The Apliki copper deposit, in the Troodos ophiolite complex of Cyprus, is part of the Skouriotissa mining district. Mining activity at Apliki has resulted in the production of 1,650,000 tons of copper ore. The mineralization is hosted within the sequence of Lower Pillow Lavas of the Troodos ophiolite complex in the western part of the Solea graben. Plagioclase, pyroxenes (augite), magnetite and ilmenite, and rarely olivine are the main magmatic mineral components. The prevailing secondary minerals are celadonite, calcite, analcime and quartz which occur within amygdules or are dispersed within the rock matrix. The mineralized zone is bounded by two N-S striking sub-parallel faults and is, therefore, controlled by local structures which allowed access to the hydrothermal fluids. The basaltic Pillow Lavas at Apliki possess the same low-temperature regional scale alteration as the sequence of Lower Pillow Lavas of the Troodos ophiolite. In the mineralized zone the following facies have been identified: (a) A stockwork zone (b) Veins of amorphous silica (c) Veins of gypsum (d) Oxidized vein of massive mineralization ("red zone") (e) Oxidation zone The Apliki deposit is associated with cupriferous massive sulphide which has been mined out. The Apliki mineralization, presently exposed in the examined area, is a typical example of stockwork type sulphide mineralization, with more intense presence in the lower levels of the northern wall, where the semi-massive and massive ore are preserved. The stockwork ore is hosted within brecciated chloritized lavas. Weak silicification is observed in the upper parts of the brecciated lavas. Red jasper is spatially associated with the mineralized lavas and occurs as veins or openspace fillings within the mineralized zone. Pyrite, marcasite and chalcopyrite are the predominant ore minerals, whereas bornite, sphalerite, galena, and barite are accessories with quartz as the main gangue. Goethite, hematite, chalcocite, covellite, and Fe-, Cu-, Pb-, Al-, and Ca-sulphates were formed in the supergene environment. The sampling on the northern and southern wall, of the existing opencut, took place along a series of traverses based on a combined trench and rock-chip sampling method so to achieve the best representation of the samples taken. The spatial distribution of the major elements of the ore (Ag, As, Au, Cd, Co, Cu, Fe, Ni, Pb, S, Se, Sb and Zn) in the northern part of the opencut demonstrates an enrichment next to the western fault and at areas where the semi-massive ore is present. Similar work was carried out on the southern part with much lower concentrations, a fact that reflects the limited occurrence of disseminated ore in that region. The spatial distribution of the major elements throughout the Apliki deposit has demonstrated that the western fault may be the one which is the controlling structure, while the eastern one is the boundary for a gradational passage into the Lower Pillow Lavas. Gold grade does not exceed 0.1 g/t, while copper grades ranges between 0.01 to ...

show abstract

Section: Discussion -Conclusionmentioning

confidence: 99%

The geology of the northern part of the apliki Cyprus-type ore deposit

Antivachis

2017

geosociety

View full text Add to dashboard Cite

show abstract

“…Sin embargo, no todas las formas esféricas mencionadas en la literatura tienen las mismas características ni corresponden a las mismas causas. En este estudio se ha desechado todos aquellos datos existentes sobre formas esféricas que poseían tamaños superiores a 1 u, Yque han sido interpretadas como restos de algas o bacterias (La Berge, 1973;Fairchild et al, 1973;Horodyski y Donalson, 1983) o como productos de la precipitación inorgánica de sílice amorfa por cristalización esferulítica (Oehler, 1976;Herzig et al, 1988). Considerando el entorno de tamaño de las microesferas anteriormente descritas y sus características, hay también interpretaciones que aluden a un origen orgá-nico o inorgánico (Fox y Syren, 1983), que es la disyuntiva que se nos plantea en este estudio.…”

Section: Discussionunclassified

Untitled

Bustillo¹

1995

Estud. geol.

View full text Add to dashboard Cite

RESUMENUn estudio mediante MEB de silcretas miocenas opalinas formadas por silicificación de playas en un ambiente de «playa-lake» pone de manifiesto la existencia de una nueva microestructura de ópalo CT. Esta microestructura denominada en general fibrosa, se manifiesta por la presencia de multitud de fibras, filamentos o varillas formadas por la alineación de microesferas o microhemisferas que presentan un diámetro entre 0, l Y 0,2 1.1. Las fibras, filamentos o varillas tienen formas variables: rectas, curvadas, onduladas y «en horquilla», y presentan longitudes de hasta 10 11, aunque podrían existir longitudes mayores. La disposición organizada de las microesferas en filamentos o fibras, constituyendo la masa general del ópalo, y su parecido con microestructuras opalinas que han sido formadas por influencia bacteriana, hacen considerar esta hipótesis, aunque no se puede descartar totalmente un origen inorgánico por silicificación de sepiolita. Palabras clave: Microesferas, fihas, Opa/o CT, bacterias, si/cretas.ABSTRACT Electron microscope observations of opaline silcretes found in the playa of a miocene shallow lake reveal new opal CT microstructures. These microstructures are made up of fibres, filaments or rods, which are formed, in tum by coalesced microspheres or microhemispheres (0,1-0,2 11 diameter). They are up to 10 11 in length although larger ones could exist. They are straight, bent, wavy or even hairpin shaped. These microstructures comprise part of the opaline mass of the silcretes and are very similar to both neogenic opaline structures which are formed by bacterial intluence and to silicified biofilms. Therefore microbial mediation could exist in the genesis of this opal CT, although a possible inorganic origin by silicification of sepiolite is also considered.

show abstract

“…Equilibrium path calculations (Janecky and S eyfried, 1984) predicted abundant quartz may precipitate by mixing of hot solutions and ambient seawater. It was suggested (Herzig et al, 1988;Fournier, 1985) that some combination of conductive cooling and mixing account for the deposition of amorphous silica. The deposition of amorphous silica from >350°C solutions, carrying about 500 ppm SiO2, at the Endeavour Segment, Juan de Fuca Ridge, is due to conductive heat loss during the sluggish percolation of a seawater/hydrothermal fluid mixture through the walls of large sulfide structures (Canadian American Seamount Expedition, 1985).…”

Section: Precipitation Of Silicamentioning

confidence: 99%

“…By analogy with the hydrothermal cherts from the Nadan-Hechi of Guangxi, southern China, where there was no volcanic activity, and the Galapagos Spreading Center at 86°W, the temperature at which the Gusui chert formed could have been lower than 100°C. A temperature range of 29-64°C was obtained for the Nandan-Hechi chert (Chen and Chen, 1990) and 32-42°C for the Galapagos silica deposit (Herzig et al, 1988) by oxygen isotope measurements. These temperatures indicate a "white smokers", and are much lower than that of modern "black smokers" (Cann and Strens, 1982).…”

mentioning

confidence: 99%

“…Similar chert formations were found in the Late Jurassic through Santonian Nicoya Complex along the Pacific coast of Costa Rica (relatively near-shore environment, Hein et al, 1983) and Panama (Kuijpers and Denyer, 1979), in the Mesozoic Kelp Bay Group of southeastern Alaska , in the Cretaceous Shimanto Terrain (Orogenic belt, originally hemipelagic marginal and inter-arc basin), southwest Japan (Yamamoto, 1987), in the Ordovician Munsungun Lake Formation (volcanic arc) of northwestern Maine (Pollock, 1987), and in Devonian intraplatformal basin of northwest Guangxi province, southern China, where bedded cherts were derived from hydrothermal emanations (Chen and Chen, 1990;. (Hein et al, 1982;, Galapagos at 86°W (Herzig et al, 1988), Juan de Fucaridge (Canadian American Seamount Expedition, 1985), the Mid-Atlantic Ridge ) and the Taupo Volcanic Zone at Rotokaua of New Zealand (Weissberg, 1969).The following study focuses on the chert from the Gusui section, about 30 km to the north of the township of Hetai (Fig. 3.1).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Geochimie et mecanisme metallogenique du district aurifere de Hetai sud de la Chine =

Zhou¹

1992

View full text Add to dashboard Cite

The Hetai gold field, located in western Guangdong Province, is the biggest found in the Yunkai Terrain, southern China. The objective of this study is to characterize the geological and geochemical features of the Hetai gold field, to understand the geochemical behavior of gold in the history of mineralization, and to establish a reasonable metallogenetic model.The country rocks are principally metamorphosed Sinian (Late Precambrian) series, which developed in a medium or medium-low pressure metamorphic faciès series during the Caledonian period. The protolith is mainly pelitic or semi-pelitic rocks, intercalated with bedded cherts. Pétrographie evidence suggests that the bedded cherts within the Sinian strata are the product of a fossil geothermal system, which is favored by geochemical analysis. The cherts have a geochemical affinity to typical hydrothermal cherts.The migration pattern of impurity trace elements in source rocks can be described by a fractal structure of entrapment paths. Ideally there are two migration tendencies for trace elements. One is from within bulk solid cells toward various entrapment paths. The other is from a high temperature field to a lower one. High temperature accelerates the realization of these two tendencies. Diffusion is an important type of element reactivation, which is essentially a kind of oriented short-range mass transport within bulk solid cells and low rank entrapment paths.The ore is predominantly auriferous altered mylonites within hydrothermally altered ductile shear zones. At all scales, the characteristic pattern of shear deformation is anastomosing domains of higher deformation separating rhomboid domains of lower deformation. Hydrothermal alteration is both spatially and temporally associated with the development of the shear deformation system. The alteration products are principally quartz and sulfides. Gold precipitation is an integral part of the hydrothermal alteration system, and culminated during the formation of the second generation of sulfidation.Fluid inclusion study demonstrates that the primary ore-forming hydrothermal solution is a H2O-NaCl-CO2-dominated system, characterized by a low-salinity (about 1.5 -6 equiv. wt.% NaCl) and bearing CO2. Moderate-salinity aqueous fluid and CO2-I I dominated fluid were caused by CO2 effervescence and an unmixing of the primary hydrothermal fluid.The Hetai gold deposits are the result of the integration of polystage geological and geochemical processes. Sedimentation, regional metamorphism, granitic magmatism, deformation and hydrothermal activities, have all contributed to the formation of the gold deposits. During the Precambrian to Cambrian period, a thick potential source strata was deposited. Coeval hydrothermal activity may have participated in the preliminary enrichment of gold in the source rock. The Caledonian regional metamorphism played a basic role to redistribute the gold in the source strata. There are two general tendencies for gold to migrate during metamorphism. One is from within host...

show abstract

Hydrothermal silica chimney fields in the Galapagos Spreading Center at 86°W

Cited by 110 publications

References 30 publications

The geology of the northern part of the apliki Cyprus-type ore deposit

The geology of the northern part of the apliki Cyprus-type ore deposit

Untitled

Geochimie et mecanisme metallogenique du district aurifere de Hetai sud de la Chine =

Contact Info

Product

Resources

About