scholarly journals Shannon Entropy as an Indicator for Sorting Processes in Hydrothermal Systems

Entropy ◽  
2020 ◽  
Vol 22 (6) ◽  
pp. 656
Author(s):  
Frank J. A. van Ruitenbeek ◽  
Jasper Goseling ◽  
Wim H. Bakker ◽  
Kim A. A. Hein
Keyword(s):  
Shannon Entropy ◽  
Chemical Elements ◽  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Short Wave ◽  
Hydrothermal Systems ◽  
Hydrothermal Processes ◽  
Primary Composition ◽  
Natural Mechanism ◽  
Measure Of Uncertainty

Hydrothermal processes modify the chemical and mineralogical composition of rock. We studied and quantified the effects of hydrothermal processes on the composition of volcanic rocks by a novel application of the Shannon entropy, which is a measure of uncertainty and commonly applied in information theory. We show here that the Shannon entropies calculated on major elemental chemical composition data and short-wave infrared (SWIR) reflectance spectra of hydrothermally altered rocks are lower than unaltered rocks with a comparable primary composition. The lowering of the Shannon entropy indicates chemical and spectral sorting during hydrothermal alteration of rocks. The hydrothermal processes described in this study present a natural mechanism for transforming energy from heat to increased order in rock. The increased order is manifest as the increased sorting of chemical elements and SWIR absorption features of the rock, and can be measured and quantified by the Shannon entropy. The results are useful for the study of hydrothermal mineral deposits, early life environments and the effects of hydrothermal processes on rocks.

scholarly journals “Trachytes” from Sardinia: Geoheritage and Current Use

2019 ◽  
Vol 11 (13) ◽  
pp. 3706 ◽  
Author(s):  
Nicola Careddu ◽  
Silvana Maria Grillo
Keyword(s):  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Building Stone ◽  
Step Method ◽  
Public And Private ◽  
Current State ◽  
Igneous Activity ◽  
Mineral Components ◽  
Granitoid Rocks ◽  
The Aesthetic

Sardinia was affected by an intense igneous activity which generated calc-alkaline products during the Oligo-Miocene period. The volcanic substance shows large variations, ranging from pyroclastic flow deposits, lava flows and domes. By composition, the deposits are all primarily dacites and rhyolites, with subordinate andesites and very scarce basalts. The rhyolite lavas show porphyritic and ash-flow tuffs. Ignimbrite structures are found in the dacitic domes and rhyolitic lavas. These rocks—commercially known as “Trachytes of Sardinia”—used to be quarried in all historical provinces, mainly in the central part of the island to be used as ornamental and building stone. They continue to be commonly used nowadays, but their use dates back to the prehistoric age. They are easily found in many nuraghi, “domus de janas”, holy wells, Roman works (mosaics, paving, roads, bridges), many churches built in Sardinia and practically in all kinds of structural elements in public and private buildings, such as walls, houses, and bridges. Contrary to the granitoid rocks, whose appearance is largely influenced by the mineralogical composition, the aesthetic feature of volcanic rocks is rather affected by the widest range of colors, structure and texture, i.e., shape, size and distribution of mineral components, porphyric index, etc. “Trachyte” is quarried opencast with the “single low step” method, with descending development, with prevalent use of double-disc sawing machines. Whenever the stone deposit allows higher steps, the chain cutting machine, in combination with diamond wire, becomes the preferred extraction solution. This study aims to at look Sardinian “trachytes” from a geoheritage perspective. After a geological-petrographic framework, the paper discusses the historical uses of “trachyte” in Sardinia. The current state of the art of “trachyte” quarrying, processing and usage in the Island is also described. An analysis of the “trachyte” production has been carried out. Finally, a consideration about how to enhance geotourism in the area is suggested.

PECULIARITIES OF DISTRIBUTION AND COMPOSITION OF BETAFITE FROM DIFFERENT FORMATIONS OF THE ALDAN SHIELD (SAKHA-YAKUTIA)

2019 ◽  
pp. 8-15
Author(s):  
V. Guliy ◽  
I. Poberezhska ◽  
N. Bilyk
Keyword(s):  
Chemical Composition ◽  
Mineral Composition ◽  
Oxygen Isotopes ◽  
Carbonate Rocks ◽  
Aldan Shield ◽  
Mineralogical Composition ◽  
Significant Feature ◽  
Carbon And Oxygen Isotopes ◽  
Primary Composition ◽  
Geological Formations

Character of Nb and Ta distribution in the different geological formations of the Aldan Shield are given in this article. To get idea about betafite from different endogenic etalon formations the authors analyzed its well known locations in the pegmatites, skarns, carbonatites, metasomatites and late veins segregations. Geological setting and mineralogical composition of the apatite-bearing rocks from the Aldan Shield are described, and the most significant in scale metamorphosed carbonate and silicate varieties among them have been distinguished. Apatite mineralization in magnesium skarns and metasomatites is developed locally. Titanite and betafite are the main concentrators of Nb and Ta and apatite is typical accompanying mineral in the studied rocks. Betafite was detected in the pegmatite bodies from magnesium skarns and metasomatites of the Shield with irregular distribution within rocks rich and poor in apatite, but was not found in the most developed apatite-carbonate rocks which are regarded as ores of the Seligdar type, so it cannot be mineralogical indicator for this type of ores. Late carbonate generations are significantly enriched in light carbon and oxygen isotopes in contrast to positive δ13Ñ values in apatitecarbonate bodies of the Seligdar deposit and its family and the highest δ18Î values. We used these indicators to distinguish origin of the rocks with various carbonate generations, which have different amounts of betafite. Appearance of betafite is determined by primary composition of the initial rocks. Chemical composition of betafites from the skarns and metasomatites is similar, but with local variations. The most significant feature of the mineral composition is very low Ta content. Titanite is characterized by variable amounts of Nb and Ta in scale of sectors as well as within separate grains.

Entropy-based measure of uncertainty in past lifetime distributions

2002 ◽  
Vol 39 (02) ◽  
pp. 434-440 ◽  
Author(s):  
Antonio Di Crescenzo ◽  
Maria Longobardi
Keyword(s):  
Shannon Entropy ◽  
Lifetime Distribution ◽  
Residual Entropy ◽  
Residual Lifetime ◽  
Lifetime Distributions ◽  
The Past ◽  
Life Distributions ◽  
Measure Of Uncertainty

As proposed by Ebrahimi, uncertainty in the residual lifetime distribution can be measured by means of the Shannon entropy. In this paper, we analyse a dual characterization of life distributions that is based on entropy applied to the past lifetime. Various aspects of this measure of uncertainty are considered, including its connection with the residual entropy, the relation between its increasing nature and the DRFR property, and the effect of monotonic transformations on it.

scholarly journals II.—On the Origin of certain Banded Gneisses

1887 ◽  
Vol 4 (11) ◽  
pp. 484-493 ◽  
Author(s):  
J. J. H. Teall
Keyword(s):  
Flow Structure ◽  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Plutonic Rock ◽  
Parallel Structure ◽  
Present Purpose ◽  
Parallel Arrangement ◽  
Plutonic Rocks ◽  
Chemical And Mineralogical Composition

The term gneiss as generally used by geological writers signifies a rock of granitic composition in which a parallel structure in the arrangement of the constituents is more or less apparent. For our present purpose it is important to note that other plutonic rocks besides granite (e.g. diorite, gabbro, and peridotite) have their gneissose equivalents, so that, if we use the term gneiss in a structural rather than in a mineralogical sense, we may speak of diorite-gneiss, gabbro-gneiss, and so on. Now the parallel structure of gneissose rocks is of two kinds. It may consist (1) of a parallel arrangement of certain constituents (e.g. mica plates or porphyritic felspars), or (2) of an alternation of bands of varying chemical and mineralogical composition. It is agreed on all hands that a parallel structure of the first kind may be due either to the deformation of a mass of half-consolidated plutonic rock at the time of intrusion, in which case it is strictly analogous to the flow structure in many volcanic rocks, or to deformation produced by earth-stresses operating on the mass after consolidation.

scholarly journals Applying spectral analysis for identification of alteration zones in north Saveh area, Iran

2020 ◽  
Author(s):  
Kazem Rangzan ◽  
Somayeh Beyranvand ◽  
Hoshang Pourkaseb ◽  
Hojjatollah Ranjbar ◽  
Alireza Zarasvandi
Keyword(s):  
Hydrothermal Alteration ◽  
Near Infrared ◽  
Thermal Emission ◽  
Spectral Response ◽  
Volcanic Rocks ◽  
Short Wave ◽  
Rapid Identification ◽  
Spectral Angle Mapper ◽  
Alteration Zones ◽  
The North

An extensive series of volcanic rocks are exposed in the north of Saveh city, Iran, which consist of phyllic, argillic and propylitic hydrothermal alteration types. For the purpose of the investigation, a FieldSpec3® spectroradiometer was used to measure the spectral response of the mineral content of these rocks. The spectral analyses of reflectance curve by The Spectral Geologist (TSG) software could discriminate kaolinite and montmorillonite (argillic), illite, muscovite, phengite and paragonite (phyllic), hornblende and chlorite, siderite (propylitic), hematite and goethite from the gossans. It also detected gypsum of hydrothermal alteration zones. The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) image, which was used for mapping the hydrothermal alteration minerals, contains the Visible and Near Infrared (VNIR) wavelengths between 0.52 µm and 0.86 µm, Short Wave Infrared (SWIR) wavelengths between 1.6 µm and 2.43 µm and Thermal Infrared (TIR) wavelengths between 8.125 µm and 11.65 µm with 15, 30 and 90 m spatial resolutions, respectively. For calibration of the ASTER images, the extracted spectra of different rocks and minerals were used for atmospheric and radiometric corrections. Mixture tuned matched filtering (MTMF) and Spectral Angle Mapper (SAM) were applied on ASTER data to map the hydrothermal alteration of minerals. The use of the spectroradiometry techniques in conjunction with other data exhibits the ability of these new methods for non-destructive and rapid identification of mineral types for more detailed investigation. The results show that the area has undergone different levels of hydrothermal alteration, so much so that phyllic, argillic and propylitic types of hydrothermal alteration are present in the study area. This may point to high potential and promising zones for the exploration of porphyry mineralisation.

Physical-Chemical Studies of the Process of Condensation of a Clinker-Free Binder

2022 ◽  
Vol 906 ◽  
pp. 47-52
Author(s):  
Maria Badalyan ◽  
Amalya Karapetyan ◽  
Hovsep Hoveyan
Keyword(s):  
Portland Cement ◽  
Calcium Hydroxide ◽  
Water Resistance ◽  
Volcanic Rocks ◽  
Mineralogical Composition ◽  
Free Lime ◽  
Hardening Process ◽  
Chemical Studies ◽  
The Difference ◽  
Physical And Chemical

The possibility of using a clinker-free binder as an alternative to expensive and energy-intensive Portland cement is being considered. The pozzolanizing effect of volcanic rocks is presented, where along with the binding of calcium hydroxide by silica to hydrosilicates, the binding of calcium hydroxide by “free” alumina to hydroaluminates also takes place. In the process of hardening of the clinker-free binder, the phase mineralogical composition of the formed new formations differs from the new formations that are synthesized during hardening of traditional Portland cement, which explains the difference in their properties. The new formations that are formed during the hardening process of clinker-free cements are mainly low-basic hydrosilicates, and alkaline aluminosilicates give the cast-in-place stone water resistance, frost resistance, waterproofing, etc., in a word, durability. Physical and chemical studies of the hardening process of clinker-free lime-igneous cements have been carried out, which indicates the possibility of replacing the energy-intensive Portland cement with cheaper clinker-free cement.

scholarly journals Metals likely promoted protometabolism in early ocean alkaline hydrothermal systems

2019 ◽  
Vol 5 (6) ◽  
pp. eaav7848 ◽  
Author(s):  
Norio Kitadai ◽  
Ryuhei Nakamura ◽  
Masahiro Yamamoto ◽  
Ken Takai ◽  
Naohiro Yoshida ◽  
...  
Keyword(s):  
Tricarboxylic Acid Cycle ◽  
Hydrothermal Systems ◽  
Metal Sulfides ◽  
Hydrogen Electrode ◽  
Metal Production ◽  
Threshold Potential ◽  
Hydrothermal Processes ◽  
Autotrophic Metabolism ◽  
The Origin Of Life ◽  
Reductive Tricarboxylic Acid Cycle

One of the most plausible scenarios of the origin of life assumes the preceding prebiotic autotrophic metabolism in sulfide-rich hydrothermal vent environments. However, geochemical mechanisms to harness the reductive power provided by hydrothermal systems remain to be elucidated. Here, we show that, under a geoelectrochemical condition realizable in the early ocean hydrothermal systems, several metal sulfides (FeS, Ag2S, CuS, and PbS) undergo hour- to day-scale conversion to the corresponding metals at ≤−0.7 V (versus the standard hydrogen electrode). The electrochemically produced FeS-Fe0 assemblage promoted various reactions including certain steps in the reductive tricarboxylic acid cycle with efficiencies far superior to those due to pure FeS. The threshold potential is readily generated in the H2-rich alkaline hydrothermal systems that were probably ubiquitous on the Hadean seafloor. Thus, widespread metal production and metal-sustained primordial metabolism were likely to occur as a natural consequence of the active hydrothermal processes on the Hadean Earth.

Oxygen isotope evolution of volcanic rocks at the Sturgeon Lake volcanic complex, Ontario

2000 ◽  
Vol 37 (1) ◽  
pp. 39-50 ◽  
Author(s):  
E M King ◽  
J W Valley ◽  
D W Davis
Keyword(s):  
Oxygen Isotope ◽  
Volcanic Rocks ◽  
Isotope Ratios ◽  
Hydrothermal Systems ◽  
Superior Province ◽  
Volcanic Complex ◽  
Volcanic Stratigraphy ◽  
Oxygen Isotope Ratios ◽  
Ore Body ◽  
The Many

Igneous zircons from the Sturgeon Lake volcanic complex, host to several massive sulphide deposits in the Superior Province, Canada, have an average δ18O(zircon) of 5.4 ± 0.3‰ VSMOW (n = 9 rocks). These zircons are from units differing in age by 18 million years in the 2.7 Ga complex. There is no detectable interaction of high δ18O, supracrustal lithologies in the magma. Quartz from volcanic units beneath the largest ore body, the Mattabi deposit, has an average δ18O of 9.3 ± 0.6‰. Quartz phenocrysts from the Mattabi unit and overlying volcanics have elevated and heterogeneous δ18O values averaging 13.8 ± 0.9‰ and are not in magmatic equilibrium with zircons. The δ18O values of whole-rock powders range from 5.6‰ to 14.3‰ and follow the trend observed in the δ18O values of quartz. Healed microcracks are visible in cathodoluminescence images (but are not obvious optically) of quartz phenocrysts from units with high δ18O values and disequilibrium Δ(quartz-zircon) suggesting that recrystallization facilitates the elevation of δ18O. Quartz phenocrysts from volcanic units with Δ(quartz-zircon) values near equilibrium at magmatic temperatures do not display healed microcracks in cathodoluminescence. The elevated δ18O(quartz) values are not restricted to units hosting orebodies, but are seen in all rocks in the volcanic stratigraphy that postdate eruption of the Mattabi unit. Oxygen isotope ratios combined with physical volcanology studies suggest that impermeable volcanic layers control the size and location of the many hydrothermal systems that may have occurred in the Sturgeon Lake complex.

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