Fluids and hydrothermal alteration assemblages in a Devonian gold-bearing hot-spring system, Rhynie, Scotland

2003 ◽  
Vol 94 (4) ◽  
pp. 309-324 ◽  
Author(s):  
M. Baron ◽  
S. Hillier ◽  
C. M. Rice ◽  
K. Czapnik ◽  
J. Parnell
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Hot Spring ◽  
Medium Temperature ◽  
Low Salinity ◽  
Major Fault ◽  
Spring System ◽  
Gold Bearing

ABSTRACTHydrothermal alteration at Rhynie, Aberdeenshire, Scotland, is concentrated along a fault zone, which juxtaposes surface deposits and the mineralised feeder zone to the Rhynie hotspring system. Mineralisation consists of breccias and veins filled with quartz, chert, calcite, K-feldspar and pyrite. Associated pervasive alteration comprises a high-temperature K-feldsparquartz-illite facies (formed at 250–350°C), a medium-temperature mixed layered illite/smectitequartz-K-feldspar-chlorite-calcite facies (formed at 150–200°C) and a low-temperature mixed layered illite/smectite-chlorite-calcite facies (formed at 100 to +150°C). The fluids responsible for mineralisation were mainly moderate- to high-temperature (Th =91–360°C), low-salinity (<0·2 to 2·9 wt.% NaCl eq.) H2O-NaCl-heated meteoric fluids comparable to modern and ancient hot-spring systems. The migration of these fluids was mainly restricted to a major fault zone bounding the Devonian basin. Fluids responsible for mineralisation, alteration and cementation elsewhere in the basin were low-temperature (Th 57 to 161°C), low- to high-salinity (<0·2 to 18 wt.% NaCl eq.) H2O-NaCl fluids, which resemble basinal brines.

Insights into chemical mobility in titanite driven by low-temperature crystal-plastic deformation

2021 ◽  
Author(s):  
Nicholas Udy ◽  
Michael Stearns
Keyword(s):  
Plastic Deformation ◽  
High Temperature ◽  
Low Temperature ◽  
Crystal Lattice ◽  
Trace Element ◽  
Fault Zone ◽  
Temperature Deformation ◽  
Icp Ms ◽  
Trace Element Contents ◽  
Element Contents

&lt;p&gt;The U-Pb system in titanite has been shown to be reset during a variety of high-temperature processes including high-temperature deformation, but post-deformation modification and recovery of crystal-lattice strain have so far made U-Pb equilibration mechanism from deformed titanites equivocal. Microstructures, including mechanical twinning and subgrain rotation recrystallization are more likely to be preserved at low-temperatures, but the systematics of chemical equilibration have not been established for these conditions. This study identifies progressive crystallographic misorientation and deformation twins in titanite porphyroclasts from the Wasatch Fault Zone, Utah, USA. The microstructures, mapped using electron backscatter diffraction (EBSD), developed at ~11 km depth during 300&amp;#8211;400 &amp;#186;C crystal-plastic deformation within the ductile fault zone. These microstructural maps were used to guide laser ablation-split stream ICP-MS analysis: U-Pb isotopes measured in tandem with major and trace element contents. Despite the low temperature, U-Pb and trace element contents in titanite equilibrated, at least partially, during deformation. Both major and trace elements in titanite also likely partitioned with a fluid and in response to the (re)crystallization of other mineral phases in the fault zone. Chemical zoning and crystal lattice recovery suggestive of fluid-aided recrystallization are absent, and the main mechanism for this resetting may instead be an enhancement of element mobility along microstructure dislocations. These processes are interpreted to record complex open-system behavior of titanite caused by crystal-plastic deformation during the initiation of the WFZ. This presentation will summarize the comparative analysis of microstructure by EBSD and titanite chemistry by LASS-ICP-MS, and how it bears on the understanding of elemental mobility in titanite during low-temperature crystal-plastic deformation.&lt;/p&gt;

Effect of Different Tempering Temperatures on Microstructure and Impact Property of 20CrMnTi Steel

2014 ◽  
Vol 900 ◽  
pp. 92-95
Author(s):  
Sheng Xu Liu ◽  
Yi Qiang Xiao ◽  
Ming Long Kang ◽  
Jian Min Zeng ◽  
Guo An Wang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Low Temperature ◽  
Fracture Morphology ◽  
Optical Microscope ◽  
Impact Property ◽  
Medium Temperature ◽  
The Impact ◽  
Type Of Fracture ◽  
Scanning Electron

The effect of different tempering temperatures on microstructure and impact property of 20CrMnTi steel has been studied on Zwick/roell Amsler PKP 450 pendulum machine, SU-8020 scanning electron microscope (SEM) and optical microscope. The results shows that the impact property of 20CrMnTi steel is dramatically improved after high-temperature tempering. However, the minimum value occurs when it was tempered at 350°C because of low-temperature tempering brittlement at this degree. The SEM fracture morphology was typical dimples after high temperature tempering, and the type of fracture was ductile fracture; the type of cleavage characteristic and quasi cleavage characteristic were generated on the fracture morphology at low-temperature and medium-temperature tempering respectively, and the type of fracture was brittle.

scholarly journals Structural and Mineralogical Characterization of a Fossil Hydrothermal System Located at the Outermost Front of the Southern Apennines Fold-and-Thrust Belt

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Paolo Fulignati ◽  
Fabrizio Agosta ◽  
Claudia Belviso ◽  
Giacomo Prosser ◽  
Antonio Lettino ◽  
...  
Keyword(s):  
High Temperature ◽  
Fault Zone ◽  
Hydrothermal Alteration ◽  
Hydrothermal System ◽  
Positive Anomaly ◽  
Thrust Belt ◽  
Hydrothermal Circulation ◽  
Geothermal Resources ◽  
Mineralogical Characterization ◽  
Fold And Thrust Belt

Aiming at investigating the hydrothermal circulation along the eastern flank of the Vulture volcano, along the outermost edge of the southern Apennine fold-and-thrust belt (ftb), we studied the fossil hydrothermal alteration that mineralized a transtensional fault that crosscuts volcanoclastic rocks in the Rapolla area. On the basis of structural, mineralogical, and fluid inclusion data, three main stages of activity of the hydrothermal system are documented. Stage 1 was produced by the circulation of fluids having low-pH conditions (pH ≈ 3-4) and relatively high-SO42- activity, as testified by the hydrothermal alteration mainly carried out by the alunite group minerals (particularly jarosite), which is typical of an advanced argillic alteration facies. Hydrothermal fluids were characterized by a high temperature of about 200°-210°C. These hot fluids altered and mineralized the matrices of pyroclastic rocks and sealed both burial-related and fault-related fracture networks. Later hydrothermal circulation (Stage 2) was recorded by opal A-rich veins present both within and outside the fault zone. The fluids responsible of opal A precipitation were characterized by lower temperature conditions, probably lower than 100°C. Current goethite mineralization takes place along the main slip surfaces of the study high-angle fault zone due to low temperature (<30°C) underground water circulation. This study highlights that a high-temperature hydrothermal system developed in the past within the transtensional fault zone of the Rapolla area when a high thermal anomaly was present. If we take into account that this area is still affected by a heat flux positive anomaly (90 mW/m2), we may infer that it has the potentiality to be considered an interesting site for future exploration devoted to the finding of medium-enthalpy geothermal resources at depth.

scholarly journals Impacto de las variaciones de temperatura diaria en la historia natural de los anuros tropicales

2016 ◽  
Vol 65 (1) ◽  
pp. 55 ◽  
Author(s):  
Manuel Hernando Bernal-Bautista ◽  
Jorge Luis Turriago-González ◽  
Francisco Antonio Villa-Navarro
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Variable Temperature ◽  
Developmental Time ◽  
Maximum Temperature ◽  
Medium Temperature ◽  
Variable Environment ◽  
Gosner Stage ◽  
C 23 ◽  
The Impact

Anuran embryos and tadpoles are daily exposed to wide thermal variations in their ponds, with maximum temperatures at midday. The aim of this research was to study the impact of three daily variable thermal environments (with maximum experimental temperatures between 10:00 and 16:00 hours), on the survival, developmental time and body size of metamorphs of four tropical anuran species from lowland habitats in Colombia. A total of 50 embryos (Gosner stage ten) to metamorphosis (Gosner stage 46) of Rhinella humboldti, Hypsiboas crepitans and Engystomops pustulosus were exposed to each one of the three daily variable temperature treatments: high temperature (mean = 27.5 °C; maximum temperature = 34 ± 1 °C; range = 23-35 °C), medium temperature (25.5 °C; 29 ± 1 °C; 23-30 °C), and low temperature (24 °C; 24 ± 1 °C; 23-25 °C). For the other species, Espadarana prosoblepon, 40 embryos to metamorphosis were exposed to each one of the following thermal treatments: high temperature (mean = 22 °C; maximum temperature = 25 ± 1 °C; range = 18-26 °C), medium temperature (20.5 °C; 22 ± 1 °C; 18-23 °C), and low temperature (19 °C; 19 ± 1 °C; 18-20 °C). For all species, the thermal variable environment with the highest temperature showed the greatest accumulated survival, reduced significantly the developmental time from embryos to metamorphs, and the snout-vent-length of metamorphs. Therefore, under field conditions where ponds are exposed to thermally variable environments, the highest temperatures may promote a decrease in the period of time to metamorphosis, and a positive increase for the anuran survival; nevertheless, extreme temperatures were also found in the microhabitat of the species studied, higher than their upper thermal limits reported, which suggest a vulnerable situation for them and other tropical anurans from similar habitats.

scholarly journals SEBARAN SUHU DAN SALINITAS DI TELUK MANADO

2013 ◽  
Vol 9 (2) ◽  
pp. 70 ◽  
Author(s):  
Patrice NI Kalangi ◽  
Anselun Mandagi ◽  
Kawilarang WA Masengi ◽  
Alfret Luasunaung ◽  
Fransisco PT Pangalila ◽  
...  
Keyword(s):  
Surface Layer ◽  
High Temperature ◽  
Low Temperature ◽  
River Discharge ◽  
High Salinity ◽  
Vertical Profiles ◽  
Salinity Distribution ◽  
Low Salinity ◽  
Water Column Stratification ◽  
North Sulawesi

Penelitian ini bertujuan untuk mendeskripsikan sebaran suhu dan salinitas di Teluk Manado, Sulawesi Utara. Pengukuran suhu dan salinitas secara vertikal dilakukan di delapan tempat di teluk. Profil vertikal suhu dan salinitas memperlihatkan keberadaan pelapisan kolom air. Secara horizontal, kontur suhu dan salinitas di permukaan memiliki dua “kolam” massa air, yakni kolam yang bersuhu tinggi tapi bersalinitas rendah di bagian timur teluk dan kolam yang bersuhu rendah tapi bersalinitas tinggi di bagian barat teluk. Pada lapisan dalam, kontur suhu dan salinitas cenderung sejajar dengan garis pantai bagian timur. Kata kunci: suhu, salinitas, air sungai, Teluk Manado.   The objective of this research is to describe temperature and salinity distribution in Manado Bay, North Sulawesi.  The vertical measurements of temperature and salinity were done at eight locations in the bay.  The vertical profiles of temperature and salinity shows the existence of water column stratification.  Horizontally, temperature and salinity contours of the surface layer have two pools, i.e. a pool of high temperature but low salinity in the eastern part of the bay and a pool of low temperature but high salinity in the western part of bay.  In a deeper layer, the contours of temperature and salinity tend to be parallel to eastern coastline. Keywords: temperature, salinity, river discharge, Manado Bay.

Effect of heat stress during seed development and maturation on wheat (Triticum durum) seed quality. II. Mitochondrial respiration and nucleotide pools during early germination

1995 ◽  
Vol 75 (4) ◽  
pp. 831-839 ◽  
Author(s):  
L. Grass ◽  
J. S. Burris
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Low Temperature ◽  
Oxygen Uptake ◽  
Temperature Regime ◽  
Seed Quality ◽  
Energy Levels ◽  
Medium Temperature ◽  
Mitochondrial Structure ◽  
Temperature Regimes

Marzak and Oum-rabia wheat seeds were produced under three temperature regimes (20:15, 28:21, 36:29 °C) starting 10 d after anthesis through harvest. Nucleotide levels and respiratory activity of mitochondria isolated from imbibing embryos were determined. Mitochondrial structure from the radicle meristem region of imbibed embryos was examined under electron microscopy. Embryos from low-temperature treatments showed rapid accumulation of adenosine triphosphate (ATP) and higher energy levels and rates of oxygen uptake than embryos from high-temperature treatments. Embryos from medium-temperature treatments exhibited intermediate values. Parallel to these metabolic changes during early seed germination, results from electron microscopy revealed visible differences in mitochondrial structure. Mitochondria from the low-temperature regime were well developed with visible membranes and cristae; those from the high-temperature regime were degenerating. These results provide clear evidence of the influence of parent temperature conditions on the seed metabolism during early stages of germination. Key words: Embryo, mitochondria, nucleotide, oxygen uptake, vigor, wheat

Investigation of Buffer Layers for GaN Grown by MBE

2000 ◽  
Vol 639 ◽  
Author(s):  
Feng Yun ◽  
Michael A. Reshchikov ◽  
Paolo Visconti ◽  
Keith M. Jones ◽  
Dongfeng Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Electrical Transport ◽  
Topological Analysis ◽  
Buffer Layers ◽  
Structural Quality ◽  
Electrical Transport Properties ◽  
Medium Temperature ◽  
Aln Buffer

ABSTRACTThe structural quality of the buffer layer juxtaposed to the substrate is pivotal in attaining high quality GaN layers. In MBE deposition, low temperature, medium temperature and high temperature AlN buffer layers are at the disposal of the grower. There are quite a few reports, some discussing the benefits of high temperature buffer layers and others doing the same for low temperature buffer layers. The reports emanate from different laboratories; and due to stringent parameter control required, it is difficult to compare one type of buffer with another. To gain some insight, we undertook an investigation wherein these varieties of buffer layers were grown on nitridated sapphire substrate under similar conditions for a comparative analysis. In addition to the single buffer layers of both GaN and AlN varieties, some combinations of stacked buffer layers, including cases where these buffer layers were separated by GaN layers, were employed. Structural analysis by high resolution X-ray diffractometry and topological analysis by AFM were carried out to assess the quality of the epilayers grown on these buffers. Hall measurements at room temperature were carried out to characterize the electrical transport properties.

scholarly journals Early gold-bearing quartz veins within the Rivière-Héva fault zone, Abitibi subprovince, Quebec, Canada

2018 ◽  
Vol 55 (10) ◽  
pp. 1139-1157 ◽  
Author(s):  
Francis Guay ◽  
Pierre Pilote ◽  
Réal Daigneault ◽  
Vicki McNicoll
Keyword(s):  
Fault Zone ◽  
Thrust Fault ◽  
Fault Zones ◽  
Ductile Deformation ◽  
Vein System ◽  
Quartz Veins ◽  
Abitibi Subprovince ◽  
Major Fault ◽  
High Degree ◽  
Gold Bearing

The Malartic Lakeshore showing is a gold-bearing quartz vein system located within the major Rivière-Héva fault zone (RHFZ) of the southern Abitibi greenstone belt. This fault separates the 2702–2700 Ma felsic Héva Formation from the 2708 Ma mafic-ultramafic Dubuisson Formation. A swarm of thin diorite dykes with lamprophyric facies and gold-bearing quartz veins are present only on the Dubuisson side of the fault. The 30–70 cm thick gold quartz veins are boudinaged and folded. Veins are banded and associated with pyrite, chalcopyrite, galena, barite, and gold. The study area is characterized by a high degree of ductile deformation associated with the RHFZ and manifested by the southeast-trending “principal schistosity” (Sp). Stretching lineations plunge moderately to shallowly toward the southeast as a result of shortening followed by late directional shearing during a transpressive deformation. A sample from the Héva Formation yielded a zircon U–Pb age of 2698.2 ± 0.8 Ma, and a diorite dyke produced an age of 2694.3 ± 2.5 Ma. Quartz veins are crosscut by dykes, and both are affected by the Sp fabric, indicating an early emplacement with respect to the deformation. This situation contrasts with the orogenic gold veins found in association with major fault zones. A near-synvolcanic magmatic hydrothermal origin is proposed for this gold vein system. Because all subvertical units in the area are south facing, the presence of the older Dubuisson Formation over the younger Héva Formation is attributed to the RHFZ acting as a significant reverse or thrust fault.

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