The Harp dikes and their relationship to the Helikian geological record in central Labrador

1977 ◽  
Vol 14 (12) ◽  
pp. 2683-2696 ◽  
Author(s):  
R. E. Meyers ◽  
R. F. Emslie
Keyword(s):  
Major Element ◽  
Mineral Chemistry ◽  
Olivine Gabbro ◽  
Crustal Extension ◽  
Hypabyssal Intrusions ◽  
Major Element Chemistry ◽  
The World ◽  
Basaltic Magmas ◽  
Basic Magmatism ◽  
Uplift And Erosion

The Harp olivine diabase dikes, of Neohelikian age, form an east-northeast trending swarm that cuts rocks of the Harp Lake Complex in central Labrador. The petrography, and rock and mineral chemistry of the dikes indicate that they are transitional in character between tholeiitic and alkalic compositions. The major element chemistry of the dikes is similar to basaltic magmas from other comparable continental settings and in particular closely resembles basalts and diabase sills of the Neohelikian Seal Lake Group.Correlation of the Seal Lake – Harp dikes magmatism is suggested with two other groups of hypabyssal intrusions of olivine gabbro east and southeast of the Seal Lake synclinorium (Michael gabbros and diabase dikes in the Mealy Mountains complex). All of this basic magmatism may have been related to a Neohelikian zone of continental rifting or incipient rifting. Intrusion and extrusion of basic magma under conditions indicative of crustal extension closely follows, or is associated with, uplift and erosion of anorogenic anorthosite–'granite' complexes in other places in the world and is inferred to be a consequence of a continuing evolving process of mantle–crust interactions; in Labrador, the process began in the Paleohelikian with intrusion of major anorthosite–adamellite complexes.

The (?) mid Triassic volcanic rocks of Lakonia, Greece

1982 ◽  
Vol 119 (1) ◽  
pp. 77-85 ◽  
Author(s):  
G. Pe-Piper ◽  
A. G. Panagos ◽  
D. J. W. Piper ◽  
C. N. Kotopouli
Keyword(s):  
Major Element ◽  
Volcanic Rocks ◽  
Low Grade ◽  
Potash Feldspar ◽  
Hypabyssal Intrusions ◽  
Major Element Chemistry ◽  
Plate Margin ◽  
Genetic Interpretation ◽  
Basic Rocks ◽  
Primary Minerals

SummaryThick subaerial volcanic sequences of probable mid Triassic age rest unconformably on Permo-Carboniferous limestones in the ‘Phyllite Series’ within the Gavrovo-Tripolitsa zone of the external Hellenide nappes. The volcanic rocks are varied in character. Pyroclastic rocks (often reddened) predominate, but minor basalt or andesite and rhyolitic hypabyssal intrusions and flows are also found. The rocks have experienced low-grade metamorphism and the only relict primary minerals are pyroxene and rare plagioclase in basic rocks and potash feldspar in acid rocks. The most important metamorphic phases are albite, chlorite, potassium mica, epidote, hematite, quartz and pumpellyite. Twenty-seven whole-rock major-element analyses suggest that there has been some exchange of Na2O and K2O for CaO during metamorphism, but that other elements have been relatively stable. A genetic interpretation of the rocks is attempted using published geochemical discriminator diagrams. The basic rocks are tholeiitic in major element chemistry and pyroxene composition. Trace element (Hf, Ta, Th, Ce, Yb) distribution suggests magma generation at a destructive plate margin.

The role of magma injection and crystal sorting in the formation of early gabbros at the Coldwell Complex, Ontario, Canada

2019 ◽  
Vol 56 (7) ◽  
pp. 715-737 ◽  
Author(s):  
Yong-hua Cao ◽  
David J. Good ◽  
Robert L. Linnen ◽  
Iain M. Samson
Keyword(s):  
Major Element ◽  
Mineral Chemistry ◽  
Ultramafic Rocks ◽  
Chemical Compositions ◽  
Olivine Gabbro ◽  
Additional Observation ◽  
Midcontinent Rift ◽  
Layered Series ◽  
Incompatible Elements

The Layered Series of the Midcontinent Rift related Coldwell Complex comprises thick sections of gabbro, without any known associated ultramafic rocks. It represents a major early intrusive unit of the Coldwell Complex and consists of thick accumulations of olivine gabbro and oxide augite melatroctolite. This study combines petrography, mineral chemistry, and lithogeochemistry to constrain the magma composition and petrogenesis of the Layered Series. The presence of cumulus orthoclase together with the observation that the Layered Series rocks plot in the alkaline field on a total alkali–silica diagram indicate that the Layered Series magma has an alkaline parentage. The stratigraphy of the Layered Series cannot be fully correlated between different areas using lithogeochemistry and mineral chemistry. This together with observed normal and reverse trends for mineral chemical compositions in different areas suggest that the processes related to magma emplacement and crystallization were different in different locations. The whole-rock concentrations of incompatible elements and the compositions of major minerals of the olivine gabbro and oxide augite melatroctolite units are chemically similar. However, major element lithogeochemistry is variable, dominantly due to differences in the abundances of olivine, clinopyroxene, plagioclase, and magnetite. An additional observation is that olivine and clinopyroxene are not in chemical equilibrium. Together, these observations are interpreted to reflect a combination of multiple injections of magma and crystal sorting in an open system.

The mineral chemistry and petrology of Tertiary pitchstones from Scotland

1998 ◽  
Vol 89 (2) ◽  
pp. 95-111 ◽  
Author(s):  
R. J. Preston ◽  
M. J. Hole ◽  
J. Still ◽  
H. Patton
Keyword(s):  
Trace Element ◽  
Major Element ◽  
Crustal Contamination ◽  
Mineral Chemistry ◽  
Lava Flows ◽  
Residual Glass ◽  
Pb Isotope ◽  
Isotope Data ◽  
Igneous Province ◽  
Basaltic Magmas

AbstractSub-silicic to silicic pitchstones are widespread throughout the British Tertiary Igneous Province (BTIP), with examples being found at all the major igneous centres. Both highly porphyritic and almost completely aphyric varieties occur, and take the form of sills, dykes and lava flows. Here we present previously unreported mineral chemistry data on phenocryst and microcrystallite populations from a number of pitchstones from throughout the BTIP. Phenocryst assemblages are completely anhydrous, comprising mixtures of plagioclase, sanidine, fayalite, orthopyroxene, pigeonite, ferroaugite, ferrohedenbergite and quartz. Microcrystallite assemblages are also diverse, consisting of sanidine, ferrohedenbergite, fayalite and, occasionally, almost pure end-member ferrosilite, as well as hydrous phases such as ferrohornblende and biotite. Textural and mineral chemistry observations support interpretations derived from whole-rock and residual glass major element analyses, together with whole-rock trace element and the available Sr-Nd-Pb isotope data, that the Tertiary pitchstones of Scotland are either the products of intimate mixing between a range of basaltic magmas with hydrous crustal melts, or were formed by the crustal contamination of basaltic magmas.

Major element chemistry of the geothermal sea-water at Reykjanes and Svartsengi, Iceland

1978 ◽  
Vol 42 (322) ◽  
pp. 209-220 ◽  
Author(s):  
Stefán Arnórsson
Keyword(s):  
Ground Water ◽  
Major Element ◽  
Sea Water ◽  
Geothermal Water ◽  
Ionic Exchange ◽  
Geothermal Waters ◽  
Major Element Chemistry ◽  
Element Chemistry ◽  
Geothermal Fields ◽  
Reykjanes Peninsula

SummaryHigh-temperature geothermal fields in Iceland represent localized anomalies of hot, altered rock in the uppermost part of the crust, which coincide with points of maximum tectonic/magmatic activity. These points correspond to the intersection of oblique fault swarms to the plate boundaries. Geothermal activity under mid-ocean ridges follows probably similar tectonic/magmatic anomalies.Due to high permeability sea-water invades the bed-rock of the Reykjanes Peninsula, Iceland, and is overlain by a variably thick lens of dilute ground water of meteoric origin. The variable degree of salinity of geothermal waters in the Reykjanes Peninsula has resulted from different degree of mixing of fresh ground water with the underlying sea-water-ground-water in the downflow zones around the geothermal fields. At Reykjanes the geothermal water represents heated sea-water without any freshwater mixing. The difference in the composition of sea-water or sea-water/fresh water mixtures and the geothermal waters is due to basalt/water interaction at elevated temperatures. The major-element chemistry of the geothermal water represents an equilibrium composition at the relevant aquifer temperatures. The activities of silica, calcium, sulphate, and carbonate are thus limited by the solubilities of quartz, anhydrite, and calcite. Fluoride activity is thought to be controlled by an ionic exchange reaction where it substitutes for hydroxyl groups in phyllosilicates. The ratios of individual cations and hydrogen ion are governed by ionic exchange equilibria with hydrothermal minerals, probably smectite and chlorite. The equilibrium pH for the Reykjanes and Svartsengi geothermal waters is 5·5 and 5·1 respectively. Sea-water will become somewhat acid upon heating to more than about 300 °C and equilibration with basalt, the acidity increasing with temperature.

scholarly journals Growth of Thermophilic and Hyperthermophilic Fe(III)-Reducing Microorganisms on a Ferruginous Smectite as the Sole Electron Acceptor

2007 ◽  
Vol 74 (1) ◽  
pp. 251-258 ◽  
Author(s):  
Kazem Kashefi ◽  
Evgenya S. Shelobolina ◽  
W. Crawford Elliott ◽  
Derek R. Lovley
Keyword(s):  
Electron Acceptor ◽  
Major Element ◽  
Solid Phase ◽  
Active Role ◽  
Sedimentary Environments ◽  
Major Element Chemistry ◽  
Wide Range ◽  
Structural Iron ◽  
Ferruginous Smectite ◽  
Freshwater Environments

ABSTRACT Recent studies have suggested that the structural Fe(III) within phyllosilicate minerals, including smectite and illite, is an important electron acceptor for Fe(III)-reducing microorganisms in sedimentary environments at moderate temperatures. The reduction of structural Fe(III) by thermophiles, however, has not previously been described. A wide range of thermophilic and hyperthermophilic Archaea and Bacteria from marine and freshwater environments that are known to reduce poorly crystalline Fe(III) oxides were tested for their ability to reduce structural (octahedrally coordinated) Fe(III) in smectite (SWa-1) as the sole electron acceptor. Two out of the 10 organisms tested, Geoglobus ahangari and Geothermobacterium ferrireducens, were not able to conserve energy to support growth by reduction of Fe(III) in SWa-1 despite the fact that both organisms were originally isolated with solid-phase Fe(III) as the electron acceptor. The other organisms tested were able to grow on SWa-1 and reduced 6.3 to 15.1% of the Fe(III). This is 20 to 50% less than the reported amounts of Fe(III) reduced in the same smectite (SWa-1) by mesophilic Fe(III) reducers. Two organisms, Geothermobacter ehrlichii and archaeal strain 140, produced copious amounts of an exopolysaccharide material, which may have played an active role in the dissolution of the structural iron in SWa-1 smectite. The reduction of structural Fe(III) in SWa-1 by archaeal strain 140 was studied in detail. Microbial Fe(III) reduction was accompanied by an increase in interlayer and octahedral charges and some incorporation of potassium and magnesium into the smectite structure. However, these changes in the major element chemistry of SWa-1 smectite did not result in the formation of an illite-like structure, as reported for a mesophilic Fe(III) reducer. These results suggest that thermophilic Fe(III)-reducing organisms differ in their ability to reduce and solubilize structural Fe(III) in SWa-1 smectite and that SWa-1 is not easily transformed to illite by these organisms.

Determination of major element chemistry in terrestrial waters from Antarctica by ion chromatography

1996 ◽  
Vol 739 (1-2) ◽  
pp. 257-263 ◽  
Author(s):  
K.A Welch ◽  
W.B Lyons ◽  
E Graham ◽  
K Neumann ◽  
J.M Thomas ◽  
...  
Keyword(s):  
Ion Chromatography ◽  
Major Element ◽  
Major Element Chemistry ◽  
Element Chemistry

Characterization of clays from the Foumban region (west Cameroon) and evaluation for refractory brick manufacture

Clay Minerals ◽  
2018 ◽  
Vol 53 (3) ◽  
pp. 447-457
Author(s):  
A. Pountouenchi ◽  
D. Njoya ◽  
A. Njoya ◽  
D. Rabibisao ◽  
J.R. Mache ◽  
...  
Keyword(s):  
Material Properties ◽  
Major Element ◽  
Raw Materials ◽  
Mineralogical Composition ◽  
Refractory Brick ◽  
Major Element Chemistry ◽  
End Products ◽  
Materials Used ◽  
Steel Mould

ABSTRACTThree clayey materials named MY3, KK and KG originating from the Foumban region (west Cameroon) were analysed to determine their granulometry, plasticity, major-element chemistry and mineralogy. Dilatometric and ceramic behaviour were also investigated. Clays were shaped by uniaxial pressing in a steel mould. Shaped samples were heated at 1300, 1400 and 1500°C. The end products were characterized in terms of their density, porosity and compressive strength. Raw materials differ in terms of their mineralogical composition, grain-size distribution, Al2O3 content and the nature and abundance of impurities inducing specific thermal behaviour during dilatometric analysis and sintering tests. The final material properties may be related to the main features of the raw materials used.

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