scholarly journals Carbonate Replacement as the Principal Ore Formation Process in the Proterozoic McArthur River (HYC) Sediment-Hosted Zn-Pb Deposit, Australia

2020 ◽  
Author(s):  
Sam C. Spinks ◽  
Mark A. Pearce ◽  
Weihua Liu ◽  
Marcus Kunzmann ◽  
Chris G. Ryan ◽  
...  
Keyword(s):  
Formation Process ◽  
Chemical Potential ◽  
Primary Control ◽  
Acid Dissolution ◽  
Ore Formation ◽  
Ph Buffering ◽  
Sequence Of Events ◽  
Key Characteristics ◽  
Sedimentary Carbonate ◽  
Chemistry Modeling

Abstract The McArthur River (HYC) Zn-Pb-Ag deposit in the Carpentaria Zn belt, northern Australia, is one of the world’s largest and most studied sediment-hosted base metal deposits, owing to its lack of deformation and preservation of sedimentary and ore textures. However, the ore formation process (syngenetic vs. epigenetic) is still a subject of controversy. In this paper we focus on key characteristics of the HYC deposit that remain unexplained: preservation of sedimentary carbonate (dolomite) and its association with Zn, and the role of thallium (Tl) and manganese (Mn) distribution in the orebody. Our findings demonstrate a sequence of events during ore formation: Tl is hosted almost exclusively within euhedral pyritic overgrowths around early diagenetic pyrite; sphalerite mineralization occurred after Tl-bearing pyrite overgrowths, in association with acid dissolution (replacement) of laminated and nodular dolomite across the subbasin; and outer rims are enriched in Mn on preserved dolomite at the dissolution reaction front in contact with sphalerite. New thermodynamic fluid chemistry modeling demonstrates the metal distribution and paragenesis can be explained by acidic, oxidized ore fluids entering the pyrite-dolomite host lithology, allowing reduction and pH buffering by acid carbonate dissolution, resulting in stepwise metal deposition in an evolving fluid. We argue this represents strong evidence for epigenetic ore formation at HYC. Furthermore, the primary control on ore deposition is not synsedimentary faulting in the subbasin; rather, the chemical potential of sedimentary carbonate within reduced, sulfidic lithologies appears to be of critical importance to precipitation of sphalerite.

Electron-beam patterning of materials with nanometer resolution

1990 ◽  
Vol 48 (4) ◽  
pp. 790-791
Author(s):  
S.D. Berger ◽  
J.M. Macaulay ◽  
L.M. Brown
Keyword(s):  
Formation Process ◽  
Material System ◽  
Hole Formation ◽  
General Sequence ◽  
Sequence Of Events ◽  
Similar Materials ◽  
Electron Beam Patterning ◽  
Common Observation ◽  
Underlying Mechanisms ◽  
Preparation Techniques

It was first reported in 1978 that intense electron irradiation of thin films of NaCl leads to the formation of holes with a diameter of the order of the probe. Since that time the same phenomena has been observed in a variety of materials, typical examples being AlF3, MgO and Al2O3. Quantitative and qualitative descriptions of the damage have been given by a number of workers in an attempt to understand the underlying mechanisms. While groups of chemically or structurally similar materials often show the same general sequence of events in the hole formation process, it is a common observation that polymorphs or different preparation techniques result in very different behavior, Furthermore, examples of hole formation have been given which appear to show characteristics specific to that material system.In an effort to gain insight into the hole formation process we decided to concentrate on a set of observations which are reasonably common.

scholarly journals BLEND-O-RAMA: BLENDING IN THE TITLES OF EPISODES OF ANIMATED TELEVISION SERIES FOR CHILDREN

2021 ◽  
Vol 18 (48) ◽  
pp. 53-69
Author(s):  
Jelena Danilović Jeremić ◽  
Keyword(s):  
Detailed Analysis ◽  
Formation Process ◽  
Structural Characteristics ◽  
Word Formation ◽  
Rich Source ◽  
Popular Press ◽  
Television Series ◽  
The Past ◽  
Television Shows ◽  
Key Characteristics

Often defined as a marginal word-formation process whose governing principles remain a matter of controversy, lexical blending has been examined from various perspectives over the past fifty years or so. Lexical blends have thus been described as (mostly) ephemeral linguistic creations, playful and witty, that are likely to occur in popular press, advertising, and product naming (Bryant 1974; Lieber 2010). Although we can nowadays understand the key characteristics of blends, in terms of their semantic, phonological and orthographic features, corpus-based studies of blends associated with particular types of discourse remain scarce. Television discourse is no exception. It has been cited as a rich source of blends (Mattiello 2013; Sams 2016), yet few have hitherto conducted their detailed analysis (cf. Andriani, Moehkardi 2019). Having noticed that blends frequently occur in the titles of episodes of animated television shows for children (e.g. Smeldorado in Inspector Gadget, The Three Smurfketeers in The Smurfs, Pinknic in The Pink Panther), we decided to investigate their structural characteristics. For this purpose, we collected a corpus of approximately 420 blends from the titles of animated series episodes, spanning 1950-2020. The analysis has shown that haplology and hyphenation feature prominently in the collected blends, as well as that several splinters are repeatedly used in their formation.

scholarly journals Offshore Geological Hazards: Charting the Course of Progress and Future Directions

Oceans ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 393-429
Author(s):  
Gemma Ercilla ◽  
David Casas ◽  
Belén Alonso ◽  
Daniele Casalbore ◽  
Jesús Galindo-Zaldívar ◽  
...  
Keyword(s):  
Volcanic Eruptions ◽  
Future Research ◽  
Geological Hazards ◽  
Future Directions ◽  
Sequence Of Events ◽  
Key Characteristics ◽  
Volcanic Islands ◽  
Slope Instabilities ◽  
High Level ◽  
Effective Integration

Offshore geological hazards can occur in any marine domain or environment and represent a serious threat to society, the economy, and the environment. Seismicity, slope sedimentary instabilities, submarine volcanism, fluid flow processes, and bottom currents are considered here because they are the most common hazardous processes; tsunamis are also examined because they are a secondary hazard generated mostly by earthquakes, slope instabilities, or volcanic eruptions. The hazards can co-occur and interact, inducing a cascading sequence of events, especially in certain contexts, such as tectonic indentations, volcanic islands, and canyon heads close to the coast. We analyze the key characteristics and main shortcomings of offshore geological hazards to identify their present and future directions for marine geoscience investigations of their identification and characterization. This review establishes that future research will rely on studies including a high level of multidisciplinarity. This approach, which also involves scientific and technological challenges, will require effective integration and interplay between multiscale analysis, mapping, direct deep-sea observations and testing, modelling, and linking offshore observations with onshore observations.

scholarly journals Fe-oxide concretions formed by interacting carbonate and acidic waters on Earth and Mars

2018 ◽  
Vol 4 (12) ◽  
pp. eaau0872 ◽  
Author(s):  
H. Yoshida ◽  
H. Hasegawa ◽  
N. Katsuta ◽  
I. Maruyama ◽  
S. Sirono ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Formation Process ◽  
Martian Atmosphere ◽  
Formation Mechanisms ◽  
Fe Oxide ◽  
Ph Buffering ◽  
Dense Carbon Dioxide ◽  
Meridiani Planum ◽  
Acidic Waters ◽  
Early Mars

Spherical Fe-oxide concretions on Earth, especially in Utah, USA, have been investigated as an analog of hematite spherules found in Meridiani Planum on Mars to support interpretations of water-rock interactions in early Mars. Although several formation mechanisms have been proposed for the Fe-oxide concretions on Earth, it is still unclear whether these mechanisms are viable because a precise formation process and precursor of the concretions are missing. This paper presents evidence that Fe-oxide concretions in Utah and newly found Fe-oxide concretions in Mongolia had spherical calcite concretions as precursors. Different formation stages of calcite and Fe-oxide concretions observed, both in Utah and Mongolia, indicate that calcite concretions initially formed within eolian sandstone strata and were dissolved by infiltrating Fe-rich acidic waters to form spherical FeO(OH) crusts due to pH buffering. The similarity between these Fe-oxide concretions on Earth and the hematite spherule occurrences in Meridiani Planum, combined with evidence of acid sulfate water influences on Mars, suggest that the hematite spherules also formed from dissolution of preexisting carbonate spherules possibly formed under a dense carbon dioxide early martian atmosphere.

scholarly journals Exploring and Modeling the Magma–Hydrothermal Regime

Geosciences ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 234
Author(s):  
John Eichelberger ◽  
Alexey Kiryukhin ◽  
Silvio Mollo ◽  
Noriyoshi Tsuchiya ◽  
Marlène Villeneuve
Keyword(s):  
Hydrothermal System ◽  
Temporal Evolution ◽  
Hydrothermal Systems ◽  
Primary Control ◽  
Relative Timing ◽  
Magma Chambers ◽  
Ore Formation ◽  
Close Coupling ◽  
Highly Active ◽  
Big Picture

This special issue comprises 12 papers from authors in 10 countries with new insights on the close coupling between magma as an energy and fluid source with hydrothermal systems as a primary control of magmatic behavior. Data and interpretation are provided on the rise of magma through a hydrothermal system, the relative timing of magmatic and hydrothermal events, the temporal evolution of supercritical aqueous fluids associated with ore formation, the magmatic and meteoric contributions of water to the systems, the big picture for the highly active Krafla Caldera, Iceland, as well as the implications of results from drilling at Krafla concerning the magma–hydrothermal boundary. Some of the more provocative concepts are that magma can intrude a hydrothermal system silently, that coplanar and coeval seismic events signal “magma fracking” beneath active volcanoes, that intrusive accumulations may far outlast volcanism, that arid climate favors formation of large magma chambers, and that even relatively dry rhyolite magma can convect rapidly and so lack a crystallizing mush roof. A shared theme is that hydrothermal and magmatic reservoirs need to be treated as a single system.

scholarly journals How carbonate dissolution facilitates sediment-hosted Zn-Pb mineralization

Geology ◽  
2021 ◽  
Author(s):  
Weihua Liu ◽  
Sam C. Spinks ◽  
Matthew Glenn ◽  
Colin MacRae ◽  
Mark A. Pearce
Keyword(s):  
Carbonate Rocks ◽  
Carbonate Dissolution ◽  
Ore Formation ◽  
Hydrothermal Experiments ◽  
Sedimentary Carbonate ◽  
Ph Buffer ◽  
Water Saturated ◽  
Increasing Temperature ◽  
Critical Process

Most of the world’s Zn and Pb is extracted from sediment-hosted Zn-Pb deposits. The Zn-Pb deposits hosted in carbonate rocks are hypothesized to form by mixing of acidic metal-bearing brines with reduced sulfur-bearing fluids while dissolving sedimentary carbonate. To test the role of carbonate in this process, we conducted hydrothermal experiments simulating ore formation by reacting Zn ± Pb ± Ba–bearing brines with H2S and SO42– produced by native sulfur, with and without carbonate minerals (calcite or dolomite crystals), at 200 °C and water-saturated pressure. Sphalerite, galena, and barite (or anhydrite) crystals formed only when carbonate was present in the experiment, accompanied by carbonate dissolution. The textures of sphalerite clusters are similar to those observed in ancient and modern hydrothermal deposits. Thermodynamic modeling at 150 °C and 250 °C demonstrates that mixing of metal-rich brines and H2S causes most of the Zn in solution to precipitate as sphalerite only when carbonate dissolution occurs to buffer the pH, consistent with the experimental observations. The need for a pH buffer increases with increasing temperature, and different pH buffers may play a role for different deposit types. We propose that carbonate-buffered fluid mixing is a critical process for forming post-sedimentary Zn ± Pb ± Ba deposits in sedimentary carbonate rocks.

Fine Structural Changes in the Adenohypophyses of Rats Following Destruction of the Pituitary Stalk

1977 ◽  
Vol 35 ◽  
pp. 496-497
Author(s):  
K. Kovacs ◽  
E. Horvath ◽  
J. M. Bilbao ◽  
F. A. Laszlo ◽  
I. Domokos
Keyword(s):  
Structural Changes ◽  
Tissue Injury ◽  
Anterior Lobe ◽  
Uranyl Acetate ◽  
Male Rats ◽  
Pituitary Stalk ◽  
Sequence Of Events ◽  
Pituitary Glands ◽  
Electrolytic Lesions ◽  
Ultrathin Sections

Electrolytic lesions of the pituitary stalk in rats interrupt adenohypophysial blood flow and result in massive infarction of the anterior lobe. In order to obtain a deeper insight into the morphogenesis of tissue injury and to reveal the sequence of events, a fine structural investigation was undertaken on adenohypophyses of rats at various intervals following destruction of the pituitary stalk.The pituitary stalk was destroyed electrolytically, with a Horsley-Clarke apparatus on 27 male rats of the R-Amsterdam strain, weighing 180-200 g. Thirty minutes, 1,2,4,6 and 24 hours after surgery the animals were perfused with a glutaraldehyde-formalin solution. The skulls were then opened and the pituitary glands removed. The anterior lobes were fixed in glutaraldehyde-formalin solution, postfixed in osmium tetroxide and embedded in Durcupan. Ultrathin sections were stained with uranyl acetate and lead citrate and investigated with a Philips 300 electron microscope.

Desmosomal distribution in the epidermis of a non-contracting human skin equivalent

1992 ◽  
Vol 50 (1) ◽  
pp. 896-897
Author(s):  
L.X. Oakford ◽  
S.D. Dimitrijevich ◽  
R. Gracy
Keyword(s):  
Human Skin ◽  
Basal Layer ◽  
Skin Equivalent ◽  
Tissue Component ◽  
Intact Skin ◽  
Similar Sequence ◽  
Sequence Of Events ◽  
Suprabasal Keratinocytes ◽  
Human Skin Equivalent

In intact skin the epidermal layer is a dynamic tissue component which is maintained by a basal layer of mitotically active cells. The protective upper epidermis, the stratum corneum, is generated by differentiation of the suprabasal keratinocytes which eventually desquamate as anuclear comeocytes. A similar sequence of events is observed in vitro in the non-contracting human skin equivalent (HSE) which was developed in this lab (1). As a part of the definition process for this model of living skin we are examining its ultrastructural features. Since desmosomes are important in maintaining cell-cell interactions in stratified epithelia their distribution in HSE was examined.

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