The Mid-Atlantic Ridge Near 45 °N. XVI. Serpentinized Ultramafic Intrusions

1971 ◽  
Vol 8 (6) ◽  
pp. 631-663 ◽  
Author(s):  
F. Aumento ◽  
H. Loubat
Keyword(s):  
Solid State ◽  
Hydrostatic Pressure ◽  
Upper Mantle ◽  
Sea Water ◽  
Mechanical Deformation ◽  
Ultramafic Rocks ◽  
Physical Conditions ◽  
Mid Atlantic Ridge ◽  
Directional Component ◽  
Solid State Recrystallization

Detailed descriptions of the mineralogy, petrography, geochemistry, and physical properties of serpentinized ultramafic rocks dredged from the Mid-Atlantic Ridge at 45° N support an interpretation of the events which affected these rocks after their original crystallization. Crystallization apparently took place in lopoliths emplaced at the Crust/Upper Mantle interface beneath the axis of the ridge under conditions quiet enough to permit gravity crystal differentiation and layering. The rocks were then fractured without hydration under high hydrostatic pressure, with a feeble directional component, possibly under conditions favoring solid-state recrystallization of interstitial minerals. Hydration (amphibolization) began during the last phases of intimate mechanical deformation and the commencement of rodingitic metasomatism. Further hydration resulted in multiple overlapping periods of serpentinization dependent on varying physical conditions. Hydrating fluids may have been derived both from juvenile waters and from sea water.

Distribution and evolution of uranium in the oceanic lithosphere

1979 ◽  
Vol 291 (1381) ◽  
pp. 423-431 ◽  
Keyword(s):  
Sea Water ◽  
Oceanic Lithosphere ◽  
Uranium Content ◽  
Major And Trace Elements ◽  
Ultramafic Rocks ◽  
Layer 2 ◽  
Secondary Enrichment ◽  
Layer 4 ◽  
Mid Atlantic Ridge ◽  
Fractionation Trend

Induced fission track techniques permit us to determine quantitatively the microscopic distribution of uranium in rocks, in their constituent minerals, and in percolating fluids. Both primary magmatic variations and secondary mobilization of uranium can be discerned. Concentrations of uranium in phenocrysts and fresh glasses of oceanic basalts and gabbros are very low (2-80 parts/10 9 ) and are comparable to concentrations in the same minerals of the associated ultramafic rocks. Variations with depth in D.S.D.P. holes show several distinct cyclic variations of uranium, accompanied by parallel trends in some major and trace elements. In Hole 332B (mid-Atlantic ridge, 36 °N), uranium and other elements can be shown to fall into two distinct groupings, each group following its own characteristic fractionation trend, suggesting that two distinct magmas differentiated independently beneath the median valley, the two magmas alternating in their contribution to the formation of oceanic layer 2. Earlier investigations of the uranium distribution in surface pillows and other dredged rocks exposed to sea water had shown that, owing to halmyrolysis, the uranium concentration increases systematically with distance from the axis of a midoceanic ridge. Subsequent investigations on rocks drilled from horizons deeper into oceanic layer 2 indicate that secondary enrichment or redistribution of uranium is confined to specific zones of altered basalt, near fractures, pillow and flow margins, and especially along horizontal planes of breccias and sediments in between massive flow where convective water circulation is thought to occur. Ultramafic rocks from the base of layer 3 and top of layer 4 are also enriched in uranium when hydrated by sea water during the process of serpentinization. A combination of these processes may double the uranium content of an oceanic lithospheric plate between the time of its formation and its eventual subduction.

Palladium, iridium, and gold contents of mafic and ultramafic rocks drilled from the Mid-Atlantic Ridge, Leg 37, Deep Sea Drilling Project

1977 ◽  
Vol 14 (4) ◽  
pp. 777-784 ◽  
Author(s):  
James H. Crocket ◽  
Yuko Teruta
Keyword(s):  
Noble Metals ◽  
Sea Water ◽  
Local Heating ◽  
Ultramafic Rocks ◽  
Gold Content ◽  
Secondary Alteration ◽  
Sea Floor ◽  
Mid Atlantic Ridge ◽  
Weak Trend ◽  
Drilling Project

Basalts and ultramafic rocks from holes 332B and 334 of Leg 37, DSDP, were analyzed for palladium, iridium, and gold by neutron activation. Averages obtained for the basalts are: Pd < 0.69 ppb, Ir < 0.025 ppb, and Au = 2.9 ppb. The samples include one representative of each of the main basaltic lithological units except for Unit III, hole 332B, which is represented by a suite of 14 samples. Averages of 43, 0.60, and 16 ppb were obtained for Pd, Ir, and Au respectively in two ultramafic rocks and a gabbro from hole 334.In comparison with basalts from mid-ocean islands such as Hawaii, Leg 37 sea-floor basalts are significantly depleted in Ir and Pd, but are similar in gold content. These differences may be related to differing degrees of alteration sustained by rocks from these differing environments.The depth profiles for Ir and Pd in hole 332B show no significant trends, but a weak trend of increasing gold content with depth is suggested. Variation of Ir and Pd in adjacent lithological units may be as great as a factor of 50. The Pd distribution in 14 samples from Unit III suggests that these differences probably reflect real differences in average metal content rather than sampling effects. Although alteration of Leg 37 basalts is weak, the low Pd and Ir contents and the variability from flow to flow suggest that reaction with sea water has leached Pd and Ir from these rocks. A possible complementary enhancement of some noble metals including Pd has been noted in the sediments immediately overlying mid-ocean rises. Although gold does not seem to be depleted in Leg 37 basalts there is evidence that the metal is easily mobilized by local heating accompanying igneous intrusive rocks.The average Au/Ir ratio of the Leg 37 basalts is four times higher than that of the ultramafic–mafic rocks of hole 334. Although part of this effect is probably due to secondary alteration, it is considered unlikely that the Leg 37 basalts and ultramafic rocks are petrogenetically related.

I. Ultramafic rocks - Peridotite—gabbro—basalt complex from the equatorial Mid-Atlantic Ridge

1971 ◽  
Vol 268 (1192) ◽  
pp. 385-402 ◽  
Keyword(s):  
Upper Mantle ◽  
Early Stage ◽  
Ultramafic Rocks ◽  
Metamorphic Rocks ◽  
Fracture Zones ◽  
Equatorial Atlantic ◽  
Isotopic Data ◽  
The World ◽  
Mid Atlantic Ridge ◽  
Liquid Fractionation

Rocks were dredged where the Mid-Atlantic Ridge is intersected by the Chain, Romanche, St Paul and Vema Fracture Zones, and from unfractured portions of the Ridge between 6 and 8° N. Peridotites are common at the fracture zones, but were found also in unfractured sections of the Ridge; harzburgites prevail, but lherzolites, dunites and plagioclase peridotites are also present. A variety of gabbros was recovered, generally above the peridotites, including norites, troctolites, quartz gabbros and theralites. The chemistry of these gabbros indicates a marked crystal-liquid fractionation, following both a ‘tholeiitic’ and an ‘alkali’ trend. The basalts show also both trends, but less markedly. Metamorphic rocks ranging from ‘greenschist’ to ‘amphibolite’ facies are found throughout the sections. Strontium isotopic data suggest that the peridotites (excluding St Peter-Paul rocks) are not related genetically to the associated gabbro-basalt, in a situation similar to that of alpine complexes on the continents. The peridotites are probably residual and were depleted of lithophile elements at some early stage of their history, before the opening of the Atlantic rift. It is postulated that in the upper mantle below the equatorial Atlantic a zone exists of residual, alpine-type peridotite, while the lower crust consists of a mixture of ultramafics and intrusive gabbros. The data indicate strong similarities between the Mid-Atlantic Ridge and alpine complexes from various parts of the world.

Fabrication and study the effect of the laser on the properties of the compound Tl2-xHgxBa2-ySryCa2Cu3O10+δ superconductor

2018 ◽  
pp. 168
Author(s):  
A. Kareem Dahash Ali ◽  
Nihad Ali Shafeek
Keyword(s):  
Transition Temperature ◽  
Solid State ◽  
Hydrostatic Pressure ◽  
Electrical Properties ◽  
Co2 Laser ◽  
Temperature Shift ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural And Electrical Properties

This study included the fabrication of    compound (Tl2-xHgxBa2-ySryCa2Cu3O10+δ) in a manner solid state and under hydrostatic pressure ( 8 ton/cm2) and temperature annealing(850°C), and determine the effect of the laser on the structural and electrical properties elements in the compound, and various concentrations of x where (x= 0.1,0.2,0.3 ). Observed by testing the XRD The best ratio of compensation for x is 0.2 as the value of a = b = 5.3899 (A °), c = 36.21 (A °) show that the installation of four-wheel-based type and that the best temperature shift is TC= 142 K  .When you shine a CO2 laser on the models in order to recognize the effect of the laser on these models showed the study of X-ray diffraction of these samples when preparing models with different concentrations of the values ​​of x, the best ratio of compensation is 0.2 which showed an increase in the values ​​of the dimensions of the unit cell a=b = 5.3929 (A °), c = 36.238 (A°). And the best transition temperature after shedding laser is TC=144 K. 

Solid-State Transition of Poly(butylene terephthalate) Induced by Mechanical Deformation

1980 ◽  
Vol 13 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Kohji Tashiro ◽  
Yuzo Nakai ◽  
Masamichi Kobayashi ◽  
Hiroyuki Tadokoro
Keyword(s):  
Solid State ◽  
State Transition ◽  
Mechanical Deformation ◽  
Butylene Terephthalate ◽  
Solid State Transition

Ordered Structures of Styrene Butadiene Block Copolymers

1967 ◽  
Vol 40 (5) ◽  
pp. 1526-1528
Author(s):  
Ed Vanzo
Keyword(s):  
Solid State ◽  
Block Copolymers ◽  
Mechanical Deformation ◽  
Solution Properties ◽  
Two Dimensional ◽  
Ordered Structure ◽  
Ordered Structures ◽  
Polymer Molecules ◽  
Cast Films ◽  
Styrene Butadiene

Abstract Anionically prepared block copolymers of butadiene and styrene exhibit solution properties which result from a two dimensional ordering of the polymer molecules. The most notable of these properties is the iridescent colors of toluene solutions which are dependent on concentration and abruptly change on mechanical deformation. Electron micrographs of the surface of cast films indicate that the ordered structure is retained to some degree in the solid state.

Colossal Barocaloric Effects with Ultralow Hysteresis in Two-Dimensional Metal–Halide Perovskites

2021 ◽  
Author(s):  
Jarad Mason ◽  
Jinyoung Seo ◽  
Ryan McGillicuddy ◽  
Adam Slavney ◽  
Selena Zhang ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Phase Transitions ◽  
Solid State ◽  
Hydrostatic Pressure ◽  
Metal Halide ◽  
Two Dimensional ◽  
Vapor Compression ◽  
Entropy Changes ◽  
Halide Perovskites ◽  
Solid State Cooling

Abstract Nearly 4,400 TWh of electricity—20% of the total consumed in the world—is used each year by refrigerators, air conditioners, and heat pumps for cooling. In addition to the 2.3 Gt of carbon dioxide emitted during the generation of this electricity, the vapor-compression-based devices that provided the bulk of this cooling emitted fluorocarbon refrigerants with a global warming potential equivalent to 1.5 Gt of carbon dioxide into the atmosphere. With population and economic growth expected to dramatically increase over the next several decades, the development of alternative cooling technologies with improved efficiency and reduced emissions will be critical to meeting global cooling needs in a more sustainable fashion. Barocaloric materials, which undergo thermal changes in response to applied hydrostatic pressure, offer the potential for solid-state cooling with high energy efficiency and zero direct emissions, as well as faster start-up times, quieter operation, greater amenability to miniaturization, and better recyclability than conventional vapor-compression systems. Efficient barocaloric cooling requires materials that undergo reversible phase transitions with large entropy changes, high sensitivity to hydrostatic pressure, and minimal hysteresis, the combination of which has been challenging to achieve in existing barocaloric materials. Here, we report a new mechanism for achieving colossal barocaloric effects near ambient temperature that exploits the large volume and conformational entropy changes of hydrocarbon chain-melting transitions within two-dimensional metal–halide perovskites. Significantly, we show how the confined nature of these order–disorder phase transitions and the synthetic tunability of layered perovskites can be leveraged to reduce phase transition hysteresis through careful control over the inorganic–organic interface. The combination of ultralow hysteresis (< 1.5 K) and high barocaloric coefficients (> 20 K/kbar) leads to large reversible isothermal entropy changes (> 200 J/kg•K) at record-low pressures (< 300 bar). We anticipate that these results will help facilitate the development of barocaloric cooling technologies and further inspire new materials and mechanisms for efficient solid-state cooling.

A suite of alkali basalts and gabbros associated with the Hare Bay Allochthon of western Newfoundland

1977 ◽  
Vol 14 (3) ◽  
pp. 346-356 ◽  
Author(s):  
R. A. Jamieson
Keyword(s):  
Oceanic Crust ◽  
Continental Margin ◽  
Upper Mantle ◽  
Ultramafic Rocks ◽  
Alkali Basalts ◽  
Crust And Upper Mantle ◽  
Bay Area ◽  
Close Proximity ◽  
Thrust Sheets

The Hare Bay Allochthon of northwestern Newfoundland consists of a series of sedimentary, volcanic, metamorphic, and ultramafic rocks which was emplaced over a Cambro-Ordovician continental margin as several thrust sheets. It probably represents a continental margin sequence overridden by oceanic crust and upper mantle. The Partridge Point gabbro, Cape Onion volcanics, and Ireland Point Volcanics, which now occur in the Maiden Point, Cape Onion, and St. Anthony tectonic slices respectively, appear to be closely related on petrographic and chemical grounds. Olivine, titanaugite, kaersutite, and plagioclase indicate that these rocks formed as a single suite of hydrous alkali basalts, possibly as part of a seamount near a continental margin. This relationship provides a link between the lower sedimentary and the upper igneous-metamorphic structural slices of the allochthon and implies that most of the transported rocks in the Hare Bay area evolved in close proximity to each other.

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