scholarly journals Healing and sealing of a simulated fault gouge under hydrothermal conditions: Implications for fault healing

1998 ◽  
Vol 103 (B4) ◽  
pp. 7421-7430 ◽  
Author(s):  
Martin P. Olsen ◽  
Christopher H. Scholz ◽  
Albert Léger
Keyword(s):  
Fault Gouge ◽  
Hydrothermal Conditions ◽  
Fault Healing

scholarly journals Clay minerals from the Arkitsa fault gouge zone, in Central Greece, and implications for fluid flow

2017 ◽  
Vol 47 (2) ◽  
pp. 616 ◽  
Author(s):  
D. Papoulis ◽  
D. Romiou ◽  
S. Kokkalas ◽  
P. Lampropoulou
Keyword(s):  
Fluid Flow ◽  
Clay Minerals ◽  
Fault Zone ◽  
Damage Zone ◽  
Fault Gouge ◽  
Hydrothermal Conditions ◽  
Core Zone ◽  
Damage Area ◽  
Central Greece ◽  
Alkaline Conditions

Clay minerals in shallow fault rocks are increasingly recognized as key to the mechanical and seismogenic behavior of faults and fluid flow circulation within the fault core and the surrounding damage zone. We therefore studied faultgouge mineralogy from samples derived from the ENE-trending Arkitsa fault zone, in east-central Greece, in order to testify if the fault is acting as a channel for fluid flow and whether the conditions that characterize the flow can be identified. Clay-gouge samples were collected within the fault core zone, as well as in the broader fault damage area. Consequently, the samples were analyzed by X-Ray Diffraction, SEM and Electron microprobe analyses. The minerals that were identified within the centre of the fault zone are: Montmorillonite, corrensite, illite, micro-calcite, dolomite, quartz, plagioclase and K-feldspars. The absence of corrensite, a clay mineral usually formed in hydrothermal conditions, in the samples from the broader fault damage area indicates that the circulation of hydrothermal fluids is mostly confined within and around the fault core zone. The assemblages within the fault gouge zone and especially the presence of corrensite, combined with the absence of laumontite, indicate hydrothermal alteration at neutral to alkaline conditions and a temperature range at about 100-150 oC.

Dynamics of CO2 emission from chernozems under agricultural use

2017 ◽  
Vol 4 (3) ◽  
pp. 43-49
Author(s):  
M. Miroshnychenko ◽  
O. Siabruk
Keyword(s):  
Carbon Dioxide ◽  
Agricultural Practices ◽  
Growing Season ◽  
Warm Period ◽  
Direct Seeding ◽  
Soil Tillage ◽  
Plant Residues ◽  
Hydrothermal Conditions ◽  
Organic Mineral ◽  
Mineral System

Aim. The comparison of the effect of hydrothermal conditions and various agricultural practices on the emission of CO 2 from chernozems in the Left-Bank Forest-Steppe of Ukraine. Methods. The dynamics of the intensity of carbon dioxide emissions from chernozem calcic (typical chernozem – in Ukrainian classifi cation) was studied during the growing season of 2011–2012. The observations were based on two fi eld experiments with various methods of soil till- age (6–7 years from the beginning of the experiment) and fertilization systems (21–22 years from the beginning of the experiment). Particularly, plowing at 20–22 cm, disking at 10–12 cm, cultivation at 6–8 cm and direct seeding using Great Plains drill were studied among the soil tillage methods. Mineral system (N 45 P 50 K 45 ), organic system (manure 8 t/ha) and combined organic-mineral system (manure 8 t/ha + N 45 P 50 K 45 ) were studied among fertilization systems. The intensity of CO 2 fl ux was determined using the non-stationary respiratory chambers by the alkaline absorption method, with averaging of the results during the day and the frequency of once a month. Results. During the warm period, the emission of carbon dioxide from the soil changes dynamically depending on temperature and humidity. The maximum of emission coincides with the periods of warm summer showers in June-July, the minimum values are characteristic for the late autumn period. The total emission losses of carbon in chernozems over the vegetation period ranged from 480 to 910 kg/ha and varied depending on the methods of tillage ± (4.0–6.0) % and fertilization systems ± (3.8–7.1) %. The changes in the intensity of CO 2 emission from the soil under different methods of soil tillage are associated with hydrothermal regime and the depth of crop residues location. The biggest difference is observed im- mediately after tillage, but in the spring period the differences are only 12–25 %, and after drying of the top layer of soil become even less. Direct seeding technology provides the greatest emission of CO 2 from chernozem, which is fa- cilitated by better water regime and more complete mineralization of plant residues on the soil surface. Annual losses of carbon are the least under disking of soil at 10–12 cm. The changes in the intensity of CO 2 emission from the soil under different fertilization systems are associated with the involvement of the additional organic matter from plant residues and manure to the microbiological decomposition. The greatest emission was observed under the organic- mineral fertilization system, which increased the loss of carbon by 7–8 % in comparison with the mineral system in the unfavorable hydrothermal year and by 11–15 % in the more favorable year. These differences are observed mainly during the fi rst half of the growing season when there is a clear tendency to increase the intensity of soil respiration. Conclusions. The hydrothermal conditions of the warm period of the year are decisive in the formation of the CO 2 emission fl ow from chernozems. Due to the improvement of agricultural practices, emissions might be reduced but not more that by 15 % of natural factor contribution.

A common precursor to both prebiotic and biological pathways to RNA nucleotides

2018 ◽  
Author(s):  
Andrea Pérez-Villa ◽  
Thomas Georgelin ◽  
Jean-François Lambert ◽  
Marie-Christine Maurel ◽  
François Guyot ◽  
...  
Keyword(s):  
Enzymatic Synthesis ◽  
De Novo ◽  
Life Forms ◽  
Hydrothermal Conditions ◽  
Modern Life ◽  
Ab Initio Simulations ◽  
Spontaneous Formation ◽  
Common Precursor ◽  
Open Issue ◽  
Anomeric Carbon

Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, <i>de novo</i> and salvage nucleotide enzymatic synthesis combines 5-phospho-α -D-ribose-1-diphosphate ( α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio simulations with mass spectrometry experiments, we compellingly demonstrate that nucleobases and α -PRPP spontaneously combine, through the same facile mechanism, forming both purine and pyrimidine ribonucleotides, under mild hydrothermal conditions. Surprisingly, this mechanism is very similar to the biological one, and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. These results suggest that natural selection might have optimized – through enzymes – a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.

A common precursor to both prebiotic and biological pathways to RNA nucleotides

2017 ◽  
Author(s):  
Andrea Pérez-Villa ◽  
Thomas Georgelin ◽  
Jean-François Lambert ◽  
Marie-Christine Maurel ◽  
François Guyot ◽  
...  
Keyword(s):  
Enzymatic Synthesis ◽  
De Novo ◽  
Life Forms ◽  
Hydrothermal Conditions ◽  
Modern Life ◽  
Ab Initio Simulations ◽  
Spontaneous Formation ◽  
Common Precursor ◽  
Open Issue ◽  
Anomeric Carbon

Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, <i>de novo</i> and salvage nucleotide enzymatic synthesis combines 5-phospho-α -D-ribose-1-diphosphate ( α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio simulations with mass spectrometry experiments, we compellingly demonstrate that nucleobases and α -PRPP spontaneously combine, through the same facile mechanism, forming both purine and pyrimidine ribonucleotides, under mild hydrothermal conditions. Surprisingly, this mechanism is very similar to the biological one, and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. These results suggest that natural selection might have optimized – through enzymes – a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.

Sign in / Sign up

Export Citation Format

Share Document