scholarly journals Fingerprints of Kamafugite-Like Magmas in Mesozoic Lamproites of the Aldan Shield: Evidence from Olivine and Olivine-Hosted Inclusions

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 337 ◽  
Author(s):  
Ivan F. Chayka ◽  
Alexander V. Sobolev ◽  
Andrey E. Izokh ◽  
Valentina G. Batanova ◽  
Stepan P. Krasheninnikov ◽  
...  
Keyword(s):  
Low Temperature ◽  
Lithospheric Mantle ◽  
Melt Inclusions ◽  
Genetic Model ◽  
Aldan Shield ◽  
Essential Factor ◽  
Classification Schemes ◽  
The Mediterranean ◽  
Host Rocks ◽  
Potassic Magmatism

Mesozoic (125–135 Ma) cratonic low-Ti lamproites from the northern part of the Aldan Shield do not conform to typical classification schemes of ultrapotassic anorogenic rocks. Here we investigate their origins by analyzing olivine and olivine-hosted inclusions from the Ryabinoviy pipe, a well preserved lamproite intrusion within the Aldan Shield. Four types of olivine are identified: (1) zoned phenocrysts, (2) high-Mg, high-Ni homogeneous macrocrysts, (3) high-Ca and low-Ni olivine and (4) mantle xenocrysts. Olivine compositions are comparable to those from the Mediterranean Belt lamproites (Olivine-1 and -2), kamafugites (Olivine-3) and leucitites. Homogenized melt inclusions (MIs) within olivine-1 phenocrysts have lamproitic compositions and are similar to the host rocks, whereas kamafugite-like compositions are obtained for melt inclusions within olivine-3. Estimates of redox conditions indicate that “lamproitic” olivine crystallized from anomalously oxidized magma (∆NNO +3 to +4 log units.). Crystallization of “kamafugitic” olivine occurred under even more oxidized conditions, supported by low V/Sc ratios. We consider high-Ca olivine (3) to be a fingerprint of kamafugite-like magmatism, which also occurred during the Mesozoic and slightly preceded lamproitic magmatism. Our preliminary genetic model suggests that low-temperature, extension-triggered melting of mica- and carbonate-rich veined subcontitental lithospheric mantle (SCLM) generated the kamafugite-like melts. This process exhausted carbonate and affected the silicate assemblage of the veins. Subsequent and more extensive melting of the modified SCLM produced volumetrically larger lamproitic magmas. This newly recognized kamafugitic “fingerprint” further highlights similarities between the Aldan Shield potassic province and the Mediterranean Belt, and provides evidence of an overlap between “orogenic” and “anorogenic” varieties of low-Ti potassic magmatism. Moreover, our study also demonstrates that recycled subduction components are not an essential factor in the petrogenesis of low-Ti lamproites, kamafugites and leucitites.

scholarly journals Production of Didymella rabiei Pseudothecia and Dispersal of Ascospores in a Mediterranean Climate

2005 ◽  
Vol 95 (11) ◽  
pp. 1279-1286 ◽  
Author(s):  
E. Gamliel-Atinsky ◽  
D. Shtienberg ◽  
H. Vintal ◽  
Y. Nitzni ◽  
A. Dinoor
Keyword(s):  
Low Temperature ◽  
Environmental Conditions ◽  
Low Temperatures ◽  
Mediterranean Climate ◽  
Temperature Requirement ◽  
Trap Plants ◽  
Series Of Experiments ◽  
The Mediterranean ◽  
Stem Segments

Temperature and wetness conditions required for development and maturation of Didymella rabiei pseudothecia were determined in a series of experiments conducted in controlled-environmental conditions. Initial stages of pseudothecium formation occurred at temperatures ranging from 5 to 15°C. Incubation at low temperatures was essential for subsequent pseudothecium maturation. This requirement was satisfied for chickpea stem segments incubated at 5 or 10°C for three consecutive weeks or during periods of 3 or 5 days, separated by periods at higher temperatures. Following the low-temperature requirement, subsequent pseudothecium development was independent of temperature in the range tested (5 to 20°C). Wetness was essential for pseudothecium production: pseudothecia formed and matured on stem segments maintained continuously wet but also on those exposed to periods of three or five wet days, separated by dry periods. The dispersal of D. rabiei ascospores was studied using chickpea plants as living traps in the field. Trap plants were infected mainly when exposed during rain but also in rainless periods. Results of this study enabled us to describe the developmental events leading to the production of the teleomorph stage and the dispersal of ascospores by D. rabiei in the Mediterranean climate of Israel.

Temperatures of Neoproterozoic Regional Carbonate Alteration in the Eastern Desert of Egypt

2020 ◽  
Author(s):  
Arman Boskabadi ◽  
Tobias Kluge ◽  
Iain Pitcairn ◽  
Rabea Ali ◽  
Mokhles Azer ◽  
...  
Keyword(s):  
Low Temperature ◽  
Homogenization Temperature ◽  
Eastern Desert ◽  
Ultramafic Rocks ◽  
Wide Range ◽  
Two Samples ◽  
Ophiolitic Rocks ◽  
Clumped Isotope ◽  
Host Rocks ◽  
Different Sources

<p>Neoproterozoic ophiolites in the Eastern Desert (ED) of Egypt are pervasively carbonated and listvenitized. Two types of carbonation are recognized: 1) intergrown magnesite (and to lesser extent dolomite) with serpentine and talc that in cases form pure carbonate veins, and 2) cryptocrystalline magnesite veins filling the fractures crosscutting other ophiolitic host rocks. Few studies address the conditions of carbonate alteration of ultramafic rocks, especially the temperature of altering fluids. We employ clumped isotope thermometry on natural dolomite and magnesite from 17 variably carbonated ophiolitic rocks and veins in the ED. Five samples of antigorite-bearing serpentinite, talc-carbonate, and associated carbonate veins yield wide range temperatures of magnesite and dolomite between 213 to 426°C (285±73°C). These temperatures are comparable with previous fluid inclusion thermometry carried out on some of the vein samples (homogenization temperature between 225 to 383°C; Boskabadi et al. 2017). Ten samples of fully quartz-carbonate altered peridotites (i.e. listvenites) record even a wider range of clumped isotope carbonation temperatures between 90 and 452°C (227±112°C). In contrast, two samples of late-stage veins of cryptocrystalline magnesite record lower temperatures of 19 and 28°C. While the constraints on the pressure of carbonation are lacking, the wide range of temperatures for the carbonates in antigorite-bearing serpentinite, talc-carbonate, and listvenite lithologies suggest that carbonation probably occurred at variable depths, whereas the low temperature of cryptocrystalline magnesite veins points to conditions nearer the surface most likely associated with post-obduction processes. Therefore, different sources of carbon and CO<sub>2</sub>-bearing fluids should have been responsible for the formation of high- and low-temperature carbonates in the region.</p><p> </p><p>  Boskabadi et al. 2017. International Geology Review 59, 391–419.</p>

Low-temperature thermochronology of fault zones

2020 ◽  
Author(s):  
Takahiro Tagami
Keyword(s):  
Low Temperature ◽  
Fault Zone ◽  
Fission Track ◽  
Thermal Sensitivity ◽  
Fault Zones ◽  
Fault System ◽  
Vein Formation ◽  
Fission Track Thermochronology ◽  
Mineral Vein ◽  
Host Rocks

<p>Thermal signatures as well as timing of fault motions can be constrained by thermochronological analyses of fault-zone rocks (e.g., Tagami, 2012, 2019).  Fault-zone materials suitable for such analyses are produced by tectocic and geochemical processes, such as (1) mechanical fragmentation of host rocks, grain-size reduction of fragments and recrystallization of grains to form mica and clay minerals, (2) secondary heating/melting of host rocks by frictional fault motions, and (3) mineral vein formation as a consequence of fluid advection associated with fault motions.  The geothermal structure of fault zones are primarily controlled by the following three factors: (a) regional geothermal structure around the fault zone that reflect background thermo-tectonic history of studied province, (b) frictional heating of wall rocks by fault motions and resultant heat transfer into surrounding rocks, and (c) thermal influences by hot fluid advection in and around the fault zone.  Geochronological/thermochronological methods widely applied in fault zones are K-Ar (<sup>40</sup>Ar/<sup>39</sup>Ar), fission-track (FT), and U-Th methods.  In addition, (U-Th)/He, OSL, TL and ESR methods are applied in some fault zones, in order to extract temporal information related to low temperature and/or recent fault activities.  Here I briefly review the thermal sensitivity of individual thermochronological systems, which basically controls the response of each method against faulting processes.  Then, the thermal sensitivity of FTs is highlighted, with a particular focus on the thermal processes characteristic to fault zones, i.e., flash and hydrothermal heating.  On these basis, representative examples as well as key issues, including sampling strategy, are presented to make thermochronological analysis of fault-zone materials, such as fault gouges, pseudotachylytes and mylonites, along with geological, geomorphological and seismological implications.  Finally, the thermochronological analyses of the Nojima fault are overviewed, as an example of multidisciplinary investigations of an active seismogenic fault system.</p><p> </p><p>References:</p><ol><li>Tagami, 2012. Thermochronological investigation of fault zones. Tectonophys., 538-540, 67-85, doi:10.1016/j.tecto.2012.01.032.</li> <li>Tagami, 2019. Application of fission track thermochronology to analyze fault zone activity. Eds. M. G. Malusa, P. G. Fitzgerald, Fission track thermochronology and its application to geology, 393pp, 221-233, doi: 10.1007/978-3-319-89421-8_12.</li> </ol>

scholarly journals Geochemistry, Paragenesis, and Wall-Rock Alteration of the Qatruyeh Iron Deposits, Southwest of Iran: Implications for a Hydrothermal-Metasomatic Genetic Model

2014 ◽  
Vol 2014 ◽  
pp. 1-25 ◽  
Author(s):  
Sina Asadi ◽  
Mohammad Ali Rajabzadeh
Keyword(s):  
Genetic Model ◽  
Wall Rock ◽  
Hydrothermal Activity ◽  
Low Grade ◽  
Wall Rock Alteration ◽  
Propylitic Alteration ◽  
Iron Deposits ◽  
Geochemical Analyses ◽  
Southwest Of Iran ◽  
Host Rocks

The Qatruyeh iron deposits, located on the eastern border of the NW-SE trending Sanandaj-Sirjan metamorphic zone, southwest of Iran, are hosted by a late Proterozoic to early Paleozoic sequence dominated by metamorphosed carbonate rocks. The magnetite ores occurred as layered to massive bodies, with lesser amounts of disseminated magnetite and hematite-bearing veins. Textural evidences, along with geochemical analyses of the high field strengths (HFSEs), large ion lithophiles (LILEs), and rare earth elements (REEs), indicate that the main mineralization stage occurred as low-grade layered magnetite ores due to high-temperature hydrothermal fluids accompanied by Na-Ca alteration. Most of the main ore-stage minerals precipitated from an aqueous-carbonic fluid (3.5–15 wt.% NaCl equiv.) at temperatures ranging between 300° and 410°C during fluid mixing process, CO2 effervescence, cooling, and increasing of pH. Low-temperature hydrothermal activity subsequently produced hematite ores associated with propylitic alteration. The metacarbonate host rocks are LILE-depleted and HFSE-enriched due to metasomatic alteration.

scholarly journals Dislocation interactions during low-temperature plasticity of olivine strengthen the lithospheric mantle

2019 ◽  
Author(s):  
David Wallis ◽  
Lars Hansen ◽  
Kathryn Kumamoto ◽  
Christopher Thom ◽  
Oliver Plümper ◽  
...  
Keyword(s):  
Low Temperature ◽  
Lithospheric Mantle ◽  
Dislocation Interactions

scholarly journals Mineralogy and Fluid Inclusions of the Cunas Emerald Mine, Maripí, Boyacá, Colombia

2021 ◽  
Vol 25 (2) ◽  
pp. 139-156
Author(s):  
Fernando Helí Romero Ordóñez ◽  
Andrés Felipe González-Durán ◽  
Javier García-Toloza ◽  
Jimmy Rotlewicz Cohen ◽  
Carlos Julio Cedeño Ochoa ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fluid Inclusions ◽  
World Market ◽  
Black Shales ◽  
Two Phase ◽  
Elevated Salinity ◽  
Liquid Co2 ◽  
Physicochemical Features ◽  
Complex Fluid ◽  
Host Rocks

The Cunas mine is currently one of the major producers of fine emeralds in Colombia; its emeralds typically display a magnificent green hue, which is highly appreciated in the world market. The mineralization is found in vanadium-rich black shales of the Muzo formation; emeralds occur in pockets within hydrothermal veins and breccias, consisting mostly of calcite, dolomite, albite, quartz, and minor pyrite, parisite-(Ce), and fluorite; hydrothermal alteration is pervasive and dominated by albitization and carbonatization. Emerald-hosted fluid inclusions are highly abundant and remarkably large and complex. Poly-phase inclusions are ubiquitous, occur both in emeralds and gangue minerals, and consist of two daughter crystals (typically halite and calcite or siderite; exceptionally parisite-(Ce)), a liquid brine, a CO2-N2-CH4-rich gas bubble, and occasionally minor liquid CO2. Vapor-rich inclusions were observed in quartz, and two-phase inclusions were identified in calcite and dolomite, thus suggesting a complex fluid evolution. Microthermometry analysis indicates the emerald-forming fluids were trapped at relatively low temperature ≈ 260-340°C and pressure ≈ 875-2400 kbar, with relatively high density —1.03 g/cm³—, and elevated salinity 39% NaCl eq. Wt.; other aqueous components detected include CaCl2, KCl, and FeCl2. Based on these data, we propose the emerald mineralization at the Cunas mine was originated by the mixing of two hydrothermal fluids of different sources; one fluid with high salinity derived from evaporite dissolution, responsible for the albitization of the host rocks; the second is a calcium-rich fluid evolved from connate waters, which was equilibrated by the interaction with calcareous and organic-rich wall rocks. As a result, emerald mineralization took place at structurally favorable sites where fluid mixing was promoted. The described geological and physicochemical features for the Cunas mine, are in agreement with an epigenetic sediment-hosted mineralization —Colombian-type— formed by the circulation and mixing of relatively low-temperature non-magmatic fluids.

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