Hydrothermal alteration and mineralisation of basalts from the spreading zone of the East Pacific Rise (7°S–23°S)

Dill, Harald G.; Gauert, Christoph; Holler, Gerhild; Marchig, Vesna

doi:10.1007/bf01791387

Cited by 15 publications

(3 citation statements)

References 25 publications

(14 reference statements)

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“…The Ca/Na ratio of Type-M1 montmorillonite is -31, whereas Type-M2 is --1.4 (Tables 2 and 3). These results indicate that montmorillonite formed in a wide range of temperatures (50-200~ (Hayashi, 1989;Dill et al, 1992;Inoue, 1995). The MgO contents of the bentonites is higher than the source rocks.…”

Section: Clays and Clay Mineralsmentioning

confidence: 82%

Clay Minerals in Hydrothermally Altered Volcanic Rocks, Eastern Pontides, Turkey

Çelik

1999

Clays and clay miner.

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Abstract--Extensive hydrothermal alteration is observed around volcanogenic massive sulfide deposits. These deposits are related to Late Cretaceous volcanism in various parts of the Eastern Pontide province. Mineral assemblages resulting from alteration consist of mostly clay minerals and silica polymorphs, some sulfate minerals, and scarce zeolite minerals. The clay minerals are kaolinite, illite, and smectite. These minerals were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS), X-ray fluorescence spectroscopy (XRF), and differential thermal analysis (DTA)-thermal gravimetry (TG) techniques. The illite and the toseki deposits are a result of hydrothermal alteration of dacitic-andesitic volcanites. Two groups of bentonite deposits occur; the first mainly formed by hydrothermai solution whereas the second group resulted from halmyrolysis.The smectite in these alteration zones is generally montmorillonitic in composition and the interlayer cation is mostly Ca and lesser amounts of Na. The SiO 2 and F%O 3 contents of the hydrothermal bentonites are higher than those of the halmyrolysis smectites; however, the MgO content of both groups is similar. The Na20 and K~O contents of both groups are generally <0.5%. The hydrothermal bentonites are not plastic and have open honeycomb microtextures, although the halmyrolitic smectites axe plastic with ultrafine and rod-shaped textures. Illite, which contains some smectite layers, is a 1M polymorph, and has an asymmetry to the low-angle side of the XRD peaks. The impure illite deposits contain various combinations of smeetite, kaolinite and gypsum, galena, sphalerite, pyrite, goetite, and quartz. The illite has >35 wt. % A1203. The toseki raw material, which may be possibly useful as a porcelain raw material, is composed mainly of illite, kaolinite and quartz, or illite and quartz. The crystallinity of the kaolinite is poor.

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Section: Clays and Clay Mineralsmentioning

confidence: 82%

Clay Minerals in Hydrothermally Altered Volcanic Rocks, Eastern Pontides, Turkey

Çelik

1999

Clays and clay miner.

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“…Similar to pyrite, due to hydrothermal activity in the SOT, it is also challenging to indicate the specific source using iron oxides because it may be the weathering product of the hydrothermal origin of pyrite. At the same time, iron oxides are the main mineral facies of metal-bearing sediments [29] and are developed in hydrothermally altered basalt [30]. Therefore, the provenance of iron oxides is complex and varied.…”

Section: Provenance Indication Of Characteristic Heavy Mineralsmentioning

confidence: 99%

Heavy Mineral Compositions of Sediments in the Southern Okinawa Trough and Their Provenance-Tracing Implication

Zhu

Zeng

2021

Minerals

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Heavy mineral assemblages have been widely used to effectively trace sediment sources. Heavy mineral assemblages are rarely used in research to trace sediment sources in the southern Okinawa Trough compared with geochemical proxies. In this study, the TESCAN Integrated Mineral Analyzer (TIMA) revealed the full-size heavy mineral assemblages in the five layers of the core sediment H4-S2 in the southern Okinawa Trough. During the past 700 years, the heavy mineral assemblages in the sediments of the southern Okinawa Trough were very similar to the East China Sea shelf/Yangtze River, mainly composed of mica and chlorite; dolomite; actinolite; and hematite/magnetite. The grain size distribution of heavy minerals is in the clay–sand range and mainly in silt. Actinolite and hornblende can indicate the supply of sediments from the East China Sea shelf/Yangtze River to the southern Okinawa Trough. Due to their complex sources, pyrite, epidote, and hematite/magnetite are not adequate indicators for distinguishing between the different provenance areas. Because previous studies have used a variety of analytical methods, especially using heavy liquids with different densities, dolomite cannot be used as a marker for sediments on the Yangtze River/East China Sea shelf. Therefore, the East China Sea shelf/Yangtze River is a vital provenance of sediments from the southern Okinawa Trough since the late Holocene period.

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“…In seafloor basalts, the primary (magmatic) Cu-mineral is chalcopyrite (Gitlin, 1985). In addition, hydrothermal fluid circulation at mid-oceanic ridges leads to alteration of the basement rocks with precipitation of Cu-sulfides as disseminated mineralization in veins (Dill et al, 1992;Alt, 1995;Teagle and Alt, 2004;Sharkov et al, 2007). Although no evidences of both magmatic…”

Section: Secondary Formation Through Low-temperature In Situ Alteratimentioning

confidence: 99%

Native Cu from the oceanic crust: Isotopic insights into native metal origin

et al. 2013

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Ocean drilling has revealed that, although a minor mineral phase, native Cu ubiquitously occurs in the oceanic crust. Cu isotope systematics for native Cu from a set of occurrences from volcanic basement and sediment cover of the oceanic crust drilled at several sites in the Pacific, Atlantic and Indian oceans constrains the sources of Cu and processes that produced Cu 0. We propose that both hydrothermallyreleased Cu and seawater were the sources of Cu at these sites. Phase stability diagrams suggest that Cu 0 precipitation is favored only under strictly anoxic, but not sulfidic conditions at circum-neutral pH even at low temperature. In the basaltic basement, dissolution of primary igneous and potentially hydrothermal Cusulfides leads to Cu 0 precipitation along veins. The restricted Cu-isotope variations (δ 65 Cu = 0.02-0.19‰) similar to host volcanic rocks suggest that Cu 0 precipitation occurred under conditions where Cu +-species were dominant, precluding Cu redox fractionation. In contrast, the Cu-isotope variations observed in the Cu 0 from sedimentary layers yield larger Cu-isotope fractionation (δ 65 Cu = 0.41-0.95‰) suggesting that Cu 0 precipitation involved redox processes during the diagenesis, with potentially seawater as the primary Cu source. We interpret that native Cu precipitation in the basaltic basement is a result of low temperature (20°-65 °C) hydrothermal processes under anoxic, but not H 2 S-rich conditions. Consistent with positive δ 65 Cu signatures, the sediment cover receives major Cu contribution from hydrogenous (i.e., seawater) sources, although hydrothermal contribution from plume fallout cannot be entirely discarded. In this case, disseminated hydrogenous and/or hydrothermal Cu might be diagenetically remobilized and reprecipitated as Cu 0 in reducing microenvironment. Highlights ► native Cu is a minor mineral phase in the oceanic crust ► Cu 0 precipitation is favored under anoxic, but not sulfidic conditions at pH ~ 7 ► Cu +-species are dominant in the basaltic basement ► Cu 2 +-species dominate in the solutions in the sedimentary layer ► Cu 0 precipitation in the basaltic basement is related to seawater-rock interaction ► sediment cover receives major Cu contribution from hydrogenous (seawater) source.

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Hydrothermal alteration and mineralisation of basalts from the spreading zone of the East Pacific Rise (7°S–23°S)

Cited by 15 publications

References 25 publications

Clay Minerals in Hydrothermally Altered Volcanic Rocks, Eastern Pontides, Turkey

Clay Minerals in Hydrothermally Altered Volcanic Rocks, Eastern Pontides, Turkey

Heavy Mineral Compositions of Sediments in the Southern Okinawa Trough and Their Provenance-Tracing Implication

Native Cu from the oceanic crust: Isotopic insights into native metal origin

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