Fractionation trends in the Bay of Islands ophiolite of Newfoundland: polycyclic cumulate sequences in ophiolites and their classification

1977 ◽  
Vol 14 (5) ◽  
pp. 1156-1165 ◽  
Author(s):  
W. R. Church ◽  
L. Riccio
Keyword(s):  
Basaltic Magma ◽  
General Rule ◽  
Olivine Gabbro ◽  
Lower Velocity ◽  
Crystallization Sequence ◽  
Basaltic Rocks ◽  
Lower Temperature ◽  
High Velocity Layer ◽  
Velocity Layer ◽  
Temperature Crystallization

The fractionation range of the cumulate sequence of the allochthonous Bay of Islands ophiolite of the Western Platform of Newfoundland, measured in terms of the FeO(tolal)/MgO ratios of the liquids from which they were derived, encompasses entirely the range of known values exhibited by the overlying dikes and pillow lavas. Cryptic variations within the cumulate sequences are irregular, often inverse, and the crystallization sequences found in the cumulates suggest that they were formed from at least three different basaltic magma types, one of which is unusual in having given rise to co-existing highly aluminous clinopyroxenes and spinels. These features suggest that crystallization of the Bay of Islands plutonic rocks took place in an 'open system' magma chamber that was tapped repeatedly during fractionation to form dike rocks and lavas. Most of the cumulate rocks of the Bay of Islands ophiolite formed according to the crystallization sequence ol–cpx–(opx) or the sequence ol–plag–cpx–(opx). In contrast, the cumulate rocks of the Betts Cove ophiolite, located within the Fleur de Lys orthotectonic zone of the Newfoundland Appalachians, crystallized according to the sequences ol–opx–cpx and ol–cpx–plag. This difference in the nature of the cumulate sequences within the Bay of Islands and Betts Cove ophiolites is also reflected in the Ti characteristics of the basaltic rocks of the ophiolites, and in the morphology of the gabbroic units. Comparison with Mesozoic ophiolites suggests, as a general rule, that within ophiolite cumulate successions there is a tendency for ol–opx sequences to be followed by ol–cpx sequences, and for ol–cpx sequences to be followed by ol–plag sequences. Such a relationship may be related to processes involving remelting of lower-temperature crystallization products in a system open to either continuous or periodic additions of high temperature basaltic liquid. In terms of oceanic structures the Bay of Islands ophiolite corresponds to sonobouy model 2 of Christensen and Salisbury: the basal high velocity layer corresponding to the olivine-gabbro cumulate rocks, and the lower velocity 'gabbroic' layer to the upper part of the olivine-free cumulate sequence and overlying massive uralitized roof gabbro and dike rocks.

Imaging beneath a high‐velocity layer using converted waves

Geophysics ◽  
1992 ◽  
Vol 57 (11) ◽  
pp. 1444-1452 ◽  
Author(s):  
Guy W. Purnell
Keyword(s):  
High Velocity ◽  
Energy Partitioning ◽  
P Wave ◽  
Converted Wave ◽  
P Waves ◽  
Lower Velocity ◽  
S Waves ◽  
High Velocity Layer ◽  
The Waves ◽  
Velocity Layer

High‐velocity layers (HVLs) often hinder seismic imaging of deeper reflectors using conventional techniques. A major factor is often the unusual energy partitioning of waves incident at an HVL boundary from lower‐velocity material. Using elastic physical modeling, I demonstrate that one effect of this factor is to limit the range of dips beneath an HVL that can be imaged using unconverted P‐wave arrivals. At the same time, however, partitioning may also result in P‐waves outside the HVL coupling efficiently with S‐waves inside. By exploiting some of the waves that convert upon transmission into and/or out of the physical‐model HVL, I am able to image a much broader range of underlying dips. This is accomplished by acoustic migration tailored (via the migration velocities used) for selected families of converted‐wave arrivals.

Stratigraphy and eruptive history of the Late Devonian Mount Pleasant Caldera Complex, Canadian Appalachians

1997 ◽  
Vol 134 (1) ◽  
pp. 17-36 ◽  
Author(s):  
S. R. McCUTCHEON ◽  
H. E. ANDERSON ◽  
P. T. ROBINSON
Keyword(s):  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Late Devonian ◽  
Crustal Material ◽  
Basaltic Rocks ◽  
Stratigraphic Subdivision ◽  
Mount Pleasant ◽  
History Of ◽  
High Level ◽  
Mafic Lavas

Stratigraphic, petrographic and geochemical evidence indicate that the volcano-sedimentary rocks of the Late Devonian Piskahegan Group, located in the northern Appalachians of southwestern New Brunswick, represent the eroded remnants of a large epicontinental caldera complex. This complex – the Mount Pleasant Caldera – is one of few recognizable pre-Cenozoic calderas and is divisible into Exocaldera, Intracaldera and Late Caldera-Fill sequences. The Intracaldera Sequence comprises four formations that crop out in a triangular-shaped area and includes: thick ash flow tuffs, thick sedimentary breccias that dip inward, and stocks of intermediate to felsic composition that intrude the volcanic pile or are localized along caldera-margin faults. The Exocaldera Sequence contains ash flow tuffs, mafic lavas, alluvial redbeds and porphyritic felsic lavas that comprise five formations. The Late Caldera-Fill Sequence contains rocks that are similar to those of the outflow facies and comprises two formations and two minor intrusive units. Geochemical and mineralogical data support the stratigraphic subdivision and indicate that the basaltic rocks are mantle-derived and have intraplate chemical affinities. The andesites were probably derived from basaltic magma by fractional crystallization and assimilation of crustal material. The various felsic units are related by episodes of fractional crystallization in a high-level, zoned magma chamber. Fractionation was repeatedly interrupted by eruption of material from the roof zone such that seven stages of caldera development have been identified. The genesis of the caldera is related to a period of lithospheric thinning that followed the Acadian Orogeny in the northern Appalachians.

scholarly journals The Low-Temperature Crystallization and Interface Characteristics of ZnInSnO/In Films Using a Bias-Crystallization Mechanism

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
K. J. Chen ◽  
F. Y. Hung ◽  
T. S. Lui ◽  
S. J. Chang ◽  
Z. S. Hu
Keyword(s):  
Low Temperature ◽  
Transparent Conductive Oxide ◽  
Crystallization Mechanism ◽  
Critical Factors ◽  
Interface Characteristics ◽  
Short Period ◽  
Higher Temperature ◽  
Low Temperature Crystallization ◽  
Lower Temperature ◽  
Temperature Crystallization

This study presents a successful bias crystallization mechanism (BCM) based on an indium/glass substrate and applies it to fabrication of ZnInSnO (ZITO) transparent conductive oxide (TCO) films. The effects of bias-crystallization on electrical and structural properties of ZITO/In structure indicate that the current-induced Joule heating and interface diffusion were critical factors for low-temperature crystallization. With biases of 4 V and 0.1 A, the resistivity of the ZITO film was reduced from3.08×10−4 Ω∗cm to6.3×10−5 Ω∗cm. This reduction was attributed to the bias-induced energy, which caused indium atoms to diffuse into the ZITO matrix. This effectuated crystallizing the amorphous ZITO (a-ZITO) matrix at a lower temperature (approximately170∘C) for a short period (≤20 min) during a bias test. The low-temperature BCM developed for this study obtained an efficient conventional annealed treatment (higher temperature), possessed energy-saving and speed advantages, and can be considered a candidate for application in photoelectric industries.

Petrogenesis of the Boundary intrusions in the Flin Flon area of Saskatchewan and Manitoba

1977 ◽  
Vol 14 (3) ◽  
pp. 444-455 ◽  
Author(s):  
Eric C. Syme ◽  
Richard W. Forester
Keyword(s):  
Basaltic Magma ◽  
Molar Ratio ◽  
Chemical Characteristics ◽  
Olivine Gabbro ◽  
Metasedimentary Rocks ◽  
Metavolcanic Rocks ◽  
Flin Flon ◽  
Group 2 ◽  
The Town ◽  
Felsic Rocks

The Aphebian Boundary intrusions are a group of lensoid, ultramafic to felsic rocks which occur in a N–NW trending zone 10 km long by 4 km wide centred on the town of Flin Flon. The intrusions were emplaced into Amisk metavolcanic rocks and Missi metasedimentary rocks. Field relationships, petrography, and chemical characteristics of the Boundary intrusions indicate that they are composed of three compositionally distinct, sequentially emplaced groups. From oldest to youngest, these are (1) a mafic augite- and biotite-bearing mela-dioritic group, (2) a felsic group ranging from leucodiorite to granodiorite, and (3) an olivine-bearing (wehrlite to olivine gabbro) group. The mafic group crystallized at relatively high [Formula: see text] and [Formula: see text], such that successive differentiates have increasing MgO/FeO ratios. Molar ratio diagrams clearly indicate that fractionation of augite, minor magnetite, and possibly subordinate olivine can account for the observed chemical variation of approximately 80% of this group, whereas the olivine-bearing group could only have formed by crystal fractionation of subequal amounts of olivine and clinopyroxene, and minor magnetite. The felsic group is chemically similar to the post-Missi granodioritic plutons and cannot represent SiO2-rich residual liquids produced solely by fractionation of augite and olivine from a basaltic magma.

Low-temperature crystallization induced by excimer laser irradiation of SrBi2Ta2O9 films

2001 ◽  
Vol 16 (7) ◽  
pp. 1883-1886 ◽  
Author(s):  
Kwang Soo Seol ◽  
Hironao Hiramatsu ◽  
Yoshimichi Ohki ◽  
In-Hoon Choi ◽  
Yong-Tea Kim
Keyword(s):  
Low Temperature ◽  
Laser Irradiation ◽  
Excimer Laser ◽  
Precursor Film ◽  
Excimer Laser Irradiation ◽  
Low Temperature Crystallization ◽  
Lower Temperature ◽  
Substrate Temperatures ◽  
Induced Crystallization ◽  
Temperature Crystallization

Transition of a SrBi2Ta2O9 precursor film from amorphous to crystalline was inducedby excimer laser irradiation. Both fluorite and perovskite crystalline structures in suchfilms were obtained by excimer laser irradiation at substrate temperatures between 200and 500 °C. Either an addition of excess bismuth in the precursor film or an increasein the substrate temperature enhanced the formation of the perovskite structure in theexcimer laser-induced annealing process, resulting in the perovskite crystalline phase ata relatively lower temperature of 500 °C. Such a low temperature is preferred whenSrBi2Ta2O9 is used in ferroelectric devices. The mechanism involved in thislaser-induced crystallization is also discussed.

Preparation of Pb(Zr1−xTix)O3 powders from complex alkoxide and their lower-temperature crystallization

1992 ◽  
Vol 7 (4) ◽  
pp. 791-794 ◽  
Author(s):  
Toshimi Fukui ◽  
Chihiro Sakurai ◽  
Masahiko Okuyama
Keyword(s):  
Lead Acetate ◽  
Methyl Acetate ◽  
Particle Sizes ◽  
Ammonia Water ◽  
Lower Temperature ◽  
Temperature Crystallization

Pb(ZrxTix)O3 (PZT) powders of 0.2–0.4 μm particle sizes could be obtained from the complex alkoxides synthesized from lead acetate, Zr(OBun)4, and Ti(OEt)4. The powders crystallized to well-crystalline perovskite phases at a temperature as low as 250 °C, independent of the compositional ratio of the B site (Zr/Ti). For the preparation of powders, the complexing of alkoxides, addition of the second solvent such as acetone, acetonitrile, or methyl acetate, and base-catalyzed hydrolysis with ammonia water were essential.

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