Metamorphism of high-grade pelites in the Brabant Lake area, eastern La Ronge Domain, northern Saskatchewan

1992 ◽  
Vol 29 (8) ◽  
pp. 1686-1700
Author(s):  
Syed A. F. Abbas-Hasanie ◽  
John F. Lewry ◽  
Dexter Perkins
Keyword(s):  
Experimental Data ◽  
Water Pressure ◽  
Lake Area ◽  
High Grade ◽  
Minor Components ◽  
Early Proterozoic ◽  
Garnet Core ◽  
Facies Metamorphism ◽  
Lower Temperature ◽  
Recent Version

The Brabant Lake area mostly comprises Early Proterozoic clastic metasediments of the MacLean Lake belt, eastern La Ronge Domain, Reindeer Zone. The belt underwent upper amphibolite facies metamorphism, with sillimanite occurring in both psammitic and pelitic gneisses. Biotite + garnet + sillimanite + cordierite + quartz + K-feldspar + plagioclase parageneses suggest peak metamorphic pressure–temperature (P–T) conditions of 650–750 °C at 4–6 kbar (1 bar = 100 kPa) and [Formula: see text]. Both psammitic and pelitic gneisses underwent anatexis, which may have caused a reduction in water pressure. P–T conditions were also calculated by applying thermometry on the basis of garnet–biotite Fe–Mg exchange and barometry on the basis of garnet + plagioclase + sillimanite + quartz assemblages. The most precise garnet–biotite thermometer yielded temperatures of 608–758 °C (mean 690 °C). A more recent version, which incorporates the effects of minor components and nonideal mixing in both garnet and biotite, yielded a wider range of temperatures (565–826 °C), suggesting that imprecision in garnet–biotite thermometry may be due to disparate closing temperatures or disequilibrium. Application of several recent calibrations of the grossular + anorthite + sillimanite + quartz barometer produced a range of pressure estimates: three of these calibrations gave results compatible with documented mineral parageneses and experimental data, yielding 6.1 ± 0.5,6.1 ± 0.8, and 6.8 ± 0.9 kbar, respectively. Estimated mean pressures from another calibration are about 1–2 kbar higher. Peak metamorphic conditions at Brabant Lake are comparable with those experienced by metasediments of the Kisseynew Domain in Saskatchewan and Manitoba and other portions of the Reindeer Zone. Of 19 analyzed garnets from metapelites, 4 showed distinct chemical zonation. Garnet core growth appears coeval with syn-D2 peak metamorphic conditions; such cores yield the highest temperature estimates. Lower temperature estimates from garnet rims (range 610–660 °C, mean 630 °C) reflect retrogression under postpeak metamorphic conditions.

Paleoproterozoic reworking of an Archean thrust fault in the Hearne domain, Western Churchill Province: U–Pb geochronological constraints

2005 ◽  
Vol 42 (7) ◽  
pp. 1313-1330 ◽  
Author(s):  
K MacLachlan ◽  
W J Davis ◽  
C Relf
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Thrust Fault ◽  
Lake Area ◽  
High Grade ◽  
Facies Metamorphism ◽  
Minimum Age ◽  
Geochronological Constraints ◽  
Basement Deformation ◽  
And Control

The nature, timing and control of Archean crustal architecture on the distribution of Proterozoic reworking in Western Churchill Province are investigated in the Yathkyed Lake area, central Nunavut. The Tyrrell shear zone (TSZ) marks the boundary between the northwestern and central Hearne subdomains, respectively, in the hanging wall and footwall. Metamorphism and deformation in the hanging wall are ca. 2.66–2.50 Ga. Two episodes of metamorphism are recorded in a foliated granodiorite in the footwall, at 1818+5–2 and 1827 ± 5.6 Ma. The latter age is interpreted as the time of amphibolite-facies metamorphism and deformation in the footwall. A crosscutting dyke provides a minimum age of 1818 ± 2 Ma for this metamorphism and deformation. The TSZ is dominated by dextral oblique-slip shear fabrics. A suite of leucogranite dykes provide a maximum age of 1816 ± 2 Ma for dextral shearing. Dextral deformation is bracketed between 1815 ± 2 and 1811 ± 1 Ma, the ages of two other granitoid dykes. In an area of low dextral strain, there are proto-sheath folds related to Neoarchean thrusting. Paleoproterozoic transtensional shearing in the TSZ was localized along a preexisting late Archean thrust fault. The prior existence of this structure resulted in localization of penetrative Paleoproterozoic deformation in its footwall. This domain of high-grade Proterozoic deformation was uplifted in a regional, antiformal, metamorphic culmination, in part, by dextral-normal shearing along the TSZ. Penetrative basement deformation at depth played a role in transmitting farfield stresses related to the Trans-Hudson Orogen into its hinterland.

Where are the Eburnian–Transamazonian collisional belts?

1990 ◽  
Vol 27 (10) ◽  
pp. 1382-1393 ◽  
Author(s):  
Jean Michel Bertrand ◽  
Emmanuel Ferraz Jardim de Sá
Keyword(s):  
West African ◽  
High Grade ◽  
The West ◽  
West African Craton ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
Nappe Tectonics ◽  
Pan African ◽  
Orogenic Belts ◽  
Lower Crustal

The reconstruction of Early Proterozoic crustal evolution and geodynamic environments, in Africa and South America, is incomplete if cratonic areas alone are studied. If the presence of high-grade gneisses is considered as a first clue to past collisional behaviour, 2 Ga high-grade gneisses are more abundant within the Pan-African–Brasiliano mobile belts than in the intervening pre-Late Proterozoic cratons. The West African craton and the Guiana–Amazonia craton consist of relatively small Archaean nuclei and widespread low- to medium-grade volcanic and volcanoclastic formations intruded by Early Proterozoic granites. By contrast, 2 Ga granulitic assemblages and (or) nappes and syntectonic granites are known in several areas within the Pan-African–Brasiliano belts of Hoggar–Iforas–Air, Nigeria, Cameroon, and northeast Brazil. Nappe tectonics have been also described in the Congo–Chaillu craton, and Early Proterozoic reworking of older granulites may have occurred in the São Francisco craton. The location of the Pan-African–Brasiliano orogenic belts is probably controlled by preexisting major structures inherited from the Early Proterozoic. High-grade, lower crustal assemblages 2 Ga old have been uplifted or overthrust and now form polycyclic domains in these younger orogenic belts, though rarely in the cratons themselves. The Congo–Chaillu and perhaps the São Francisco craton are exceptional in showing controversial evidence of collisional Eburnian–Transamazonian assemblages undisturbed during Late Proterozoic time.

scholarly journals Simultaneous Determination of Water Retention Curve and Unsaturated Hydraulic Conductivity of Substrates Using a Steady-state Laboratory Method

HortScience ◽  
2010 ◽  
Vol 45 (7) ◽  
pp. 1106-1112 ◽  
Author(s):  
Paraskevi A. Londra
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Hydraulic Conductivity ◽  
Water Retention ◽  
Water Pressure ◽  
Pressure Head ◽  
Laboratory Method ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Unsaturated Hydraulic Conductivity

For effective irrigation and fertilization management, the knowledge of substrate hydraulic properties is essential. In this study, a steady-state laboratory method was used to determine simultaneously the water retention curve, θ(h), and unsaturated hydraulic conductivity as a function of volumetric water content, K(θ), and water pressure head, K(h), of five substrates used widely in horticulture. The substrates examined were pure peat, 75/25 peat/perlite, 50/50 peat/perlite, 50/50 coir/perlite, and pure perlite. The experimental retention curve results showed that in the case of peat and its mixtures with perlite, there is a hysteresis between drying and wetting branches of the retention curve. Whereas in the case of coir/perlite and perlite, the phenomenon of hysteresis was less pronounced. The increase of perlite proportion in the peat/perlite mixtures led to a decrease of total porosity and water-holding capacity and an increase of air space. Study of the K(θ) and K(h) experimental data showed that the hysteresis phenomenon of K(θ) was negligible compared with the K(h) data for all substrates examined. Within a narrow range of water pressure head (0 to –70 cm H2O) that occurs between two successive irrigations, a sharp decrease of the unsaturated hydraulic conductivity was observed. The comparison of the K(θ) experimental data between the peat-based substrate mixtures and the coir-based substrate mixture showed that for water contents lower than 0.40 m3·m−3, the hydraulic conductivity of the 50/50 coir/perlite mixture was greater. The comparison between experimental water retention curves and predictions using Brooks-Corey and van Genuchten models showed a high correlation (0.992 ≤ R2 ≤ 1) for both models for all substrates examined. On the other hand, in the case of unsaturated hydraulic conductivity, the comparison showed a relatively good correlation (0.951 ≤ R2 ≤ 0.981) for the van Genuchten-Mualem model for all substrates used except perlite and a significant deviation (0.436 ≤ R2 ≤ 0.872) for the Brooks-Corey model for all substrates used.

A re-examination of pseudoleucite from Spotted Fawn Creek, west-central Yukon

1969 ◽  
Vol 6 (1) ◽  
pp. 55-62 ◽  
Author(s):  
Dirk J. Tempelman-Kluit
Keyword(s):  
Experimental Data ◽  
Experimental Evidence ◽  
Water Pressure ◽  
Fluid Phase ◽  
Yukon Territory ◽  
Chemical Data ◽  
Partial Removal ◽  
West Central

New petrographic and chemical data for pseudoleucite from Spotted Fawn Creek and two new nearby localities in central Yukon Territory are presented and discussed in the light of recent experimental evidence on the origin of pseudoleucite. The petrologic, chemical, and experimental data suggest that natural pseudoleucite results from subsolidus breakdown of leucite under water pressure and that the space provided by this breakdown results in influx of the fluid phase that accomplishes partial removal of potash, enrichment in soda, and addition of water.

scholarly journals Characteristics Study of Photovoltaic Thermal System with Emphasis on Energy Efficiency

2018 ◽  
Vol 152 ◽  
pp. 01003
Author(s):  
Chuah Yee Yong ◽  
Mohammad Taghi Hajibeigy ◽  
Chockalingam Aravind Vaithilingam ◽  
Rashmi Gangasa Walvekar
Keyword(s):  
Experimental Data ◽  
Energy Efficiency ◽  
Solar Energy ◽  
Thermal Energy ◽  
Heat Energy ◽  
Thermal System ◽  
Electrical Efficiency ◽  
Pv Panel ◽  
Photovoltaic Thermal System ◽  
Lower Temperature

Solar energy is typically collected through photovoltaic (PV) to generate electricity or through thermal collectors as heat energy, they are generally utilised separately. This project is done with the purpose of integrating the two systems to improve the energy efficiency. The idea of this photovoltaic-thermal (PVT) setup design is to simultaneously cool the PV panel so it can operate at a lower temperature thus higher electrical efficiency and also store the thermal energy. The experimental data shows that the PVT setup increased the electrical efficiency of the standard PV setup from 1.64% to 2.15%. The integration of the thermal collector also allowed 37.25% of solar energy to be stored as thermal energy. The standard PV setup harnessed only 1.64% of the solar energy, whereas the PVT setup achieved 39.4%. Different flowrates were tested to determine its effects on the PVT setup’s electrical and thermal efficiency. The various flowrate does not significantly impact the electrical efficiency since it did not significantly impact the cooling of the panel. The various flowrates resulted in fluctuating thermal efficiencies, the relation between the two is inconclusive in this project.

THE EFFECT OF THE INTERACTION BETWEEN THE FILMS AND THE SUBSTRATES ON THE MICROWAVE PROPERTIES Of YBCO THIN FILMS

2007 ◽  
Vol 21 (18n19) ◽  
pp. 3224-3226
Author(s):  
LIBIN SHI ◽  
YUNFEI WANG ◽  
YUYANG KE ◽  
QUANWU WANG ◽  
ZHEN ZHANG ◽  
...  
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Resonant Frequency ◽  
Temperature Dependence ◽  
Surface Resistance ◽  
Microwave Properties ◽  
Microwave Surface Resistance ◽  
Microstrip Resonator ◽  
Lower Temperature ◽  
Xrd Patterns

The microwave properties of YBa 2 Cu 3 O 7- x / LaAlO 3 (YBCO/LAO) and YBa 2 Cu 3 O 7- x / MgO (YBCO/MgO) thin films have been investigated by microstrip resonator technique. The penetration depth λ0(0 K ) and the microwave surface resistance Rs can be obtained by analyzing the experimental data of the temperature dependence of resonant frequency, unload quality factor of the microstrip resonator. The stress in the two thin films can be obtained from their XRD patterns. The result shows that the stronger stress in YBCO/LAO thing film makes it have larger microwave surface resistance at lower temperature.

A model for the origin of the Lac St. Jean anorthosite massif

1976 ◽  
Vol 13 (2) ◽  
pp. 389-399 ◽  
Author(s):  
R. A. Frith ◽  
K. L. Currie
Keyword(s):  
Experimental Data ◽  
Partial Melting ◽  
Metamorphic Rocks ◽  
High Grade ◽  
Calc Alkaline ◽  
Grenville Province ◽  
Thermal Event ◽  
Anorthosite Massif ◽  
Mineral Assemblages ◽  
Potassic Rocks

An ancient tonalitic complex becomes migmatitic around the Lac St. Jean massif, ultimately losing its identity in the high grade metamorphic rocks surrounding the anorthosite. Field relations suggest extreme metamorphism and anatexis of tonalitic rocks. Experimental data show that extensive partial melting of the tonalite leaves an anorthositic residue. The same process operating on more potassic rocks would leave monzonitic or quartz syenitic residues. Synthesis of experimental data suggests that the process could operate at pressures of 5–8 kbar and temperatures of 800–1000 °C, which are compatible with mineral assemblages around the anorthosite massif. Slightly higher temperatures at the end of the process could generate magmatic anorthosite.Application of the model to the Grenville province as a whole predicts generation of anorthosite during a long-lived thermal event of unusual intensity. Residual anorthosite would occur as a substratum in the crust, overlain by high-grade metamorphic rocks intruded by anorthosite and syenitic rocks, while higher levels in the crust would display abundant calc-alkaline plutons and extrusives.

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