scholarly journals Ba, Rb and Cs in the Earth's Mantle

1983 ◽  
Vol 38 (2) ◽  
pp. 256-266 ◽  
Author(s):  
Albrecht W. Hofmann ◽  
William M. White
Keyword(s):  
Mobile Phase ◽  
Aqueous Fluid ◽  
Oceanic Islands ◽  
Primitive Mantle ◽  
Partial Melt ◽  
Ocean Ridges ◽  
The Earth ◽  
Isotopic Abundances ◽  
Oceanic Basalts ◽  
Relative Abundances

Abstract In 166 isotope dilution analyses of Ba, Rb, Cs on fresh basalts from mid-ocean ridges and oceanic islands, Ba/Rb and Cs/Rb ratios are nearly constant. From this, we conclude that Ba/Rb and Cs/Rb ratios are essentially constant in the present-day mantle in spite of large differences in the degree of source depletion or enrichment. As it appears improbable that these ratios could be both constant and non-primitive, we propose that they are representative of the primitive mantle and of the present-day crust-mantle system. We explain this uniformity of relative abundances as follows: the mantle is depleted by subtraction of a mobile phase such as a partial melt or an aqueous fluid. In either case, a significant amount of the mobile phase remains in the residue. Ba, Rb and Cs are among the most highly incompatible elements. Therefore the mobile phase cannot fractionate these elements relative to one another but retains the source ratios of Ba/Rb and Cs/Rb. Also, the amount of mobile phase remaining in the residue is enough to dominate the Ba, Rb and Cs concentrations in the residue. Consequently, neither the mobile phase nor the residue, nor any other portion of the mantle that may be enriched by addition of the mobile phase, will be changed in their relative abundances of Ba, Rb and Cs, even though the absolute abundances of these elements may change by orders of magnitude.The primitive Ba/Rb = 11.3 and Cs/Rb = 12.6 x 10-3 lead to the following estimates for the primitive mantle: Ba = 6.9 ppm (taken from Jagoutz et al. [1]). Rb = 0.61 ppm and Cs = 7.7 ppb.Assuming the earth has a chondritic Sr/Ba ratio of 3.08, we calculate a Rb/Sr ratio of 0.029 for the earth. This corresponds to a present-day 87Sr/ 86Sr of 0.7045. This value lies near the lower limit of the ratios estimated from the correlation of Nd and Sr isotopic abundances in oceanic basalts.The Cs/Rb ratios is about a factor of ten lower than the Cl-chondritic ratio and a factor of three lower than the lunar ratio. This low terrestrial Cs/Rb ratio should be matched by similar values in the continental crust. However, the large range of Cs/Rb ratios found in the crust prevent us from obtaining a meaningful mass balance.

Evidence from ocean islands suggesting movement in the Earth

1965 ◽  
Vol 258 (1088) ◽  
pp. 145-167 ◽  
Keyword(s):  
Upper Jurassic ◽  
Oceanic Islands ◽  
Chemical Characteristics ◽  
Ocean Ridges ◽  
East Pacific ◽  
The Earth ◽  
The Pacific ◽  
Mid Ocean Ridge ◽  
Volcanic Islands ◽  
Ocean Ridge

Oceanic islands increase in age from the mid-ocean ridges towards continents and the andesite line reaching a maximum known age of Upper Jurassic. The Seychelles appear to be a continental fragment. Several pairs of lateral aseismic ridges extend from islands on the mid-ocean ridge to adjacent continents. Their continental junctions mark points on opposite coasts which would also fit if the continents were reassembled according to the criteria used by Wegener. As Holmes has shown each pair of ridges tends to have distinctive chemical characteristics. One possible explanation is that convection currents in the mantle rising along the mid-ocean ridges and sinking beneath trenches have carried the crust apart across the Atlantic, India and East Pacific Oceans. The lateral ridges may be approximately streamlines. Although Darwin showed that most volcanic islands sink, a few have been uplifted. Most of these lie a few hundred kilometres in front of deep trenches, suggesting that they may be on the crest of a standing wave in front of the trenches and that the crust is rigid. Of eleven straight chains of young islands in the Pacific ten get older away from the East Pacific Ridge. They could also be streamlines, fed by lava rising from deep within convection cells with stagnant cores. The regularity of ridges suggests non-turbulent flow.

Convection tectonics: some possible effects upon the Earth's surface of flow from the deep mantle

1988 ◽  
Vol 25 (8) ◽  
pp. 1199-1208 ◽  
Author(s):  
J. Tuzo Wilson
Keyword(s):  
Land Surface ◽  
Angle Of Incidence ◽  
Gulf Of Aden ◽  
Upward Flow ◽  
New Techniques ◽  
Ocean Ridges ◽  
The Earth ◽  
Mid Ocean Ridge ◽  
The Subject ◽  
Ocean Ridge

Until a little more than a century ago the land surface not only was the only part of the Earth accessible to humans but also was the only part for which geophysical and geochemical methods could then provide any details. Since then scientists have developed ways to study the ocean floors and some details of the interior of the Earth to ever greater depths. These discoveries have followed one another more and more rapidly, and now results have been obtained from all depths of the Earth.New methods have not contradicted or greatly disturbed either old methods or old results. Hence, it has been easy to overlook the great importance of these recent findings.Within about the last 5 years the new techniques have mapped the pattern of convection currents in the mantle and shown that these rise from great depths to the surface. Even though the results are still incomplete and are the subject of debate, enough is known to show that the convection currents take two quite different modes. One of these breaks the strong lithosphere; the other moves surface fragments and plates about.It is pointed out that if expanding mid-ocean ridges move continents and plates, geometrical considerations demand that the expanding ridges must themselves migrate. Hence, collisions between ridges and plates are likely to have occurred often during geological time.Twenty years ago it was shown that the effect of a "mid-ocean ridge in the mouth of the Gulf of Aden" was to enter and rift the continent. This paper points out some of the conditions under which such collisions occur and in particular shows that the angle of incidence between a ridge and a coastline has important consequences upon the result. Several past and present cases are used to illustrate that collisions at right angles tend to produce rifting; collisions at oblique angles appear to terminate in the lithosphere in coastal shears, creating displaced terrane, but in the mantle the upward flow may continue to uplift the lithosphere far inland and produce important surface effects; collisions between coasts and mid-ocean ridges parallel to them produce hot uplifts moving inland. For a time these upwellings push thrusts and folds ahead of them, but they appear to die down before reaching cratons.

scholarly journals Partial melt or aqueous fluid in the mid-crust of Southern Tibet? Constraints from INDEPTH magnetotelluric data

2003 ◽  
Vol 153 (2) ◽  
pp. 289-304 ◽  
Author(s):  
Shenghui Li ◽  
Martyn J. Unsworth ◽  
John R. Booker ◽  
Wenbo Wei ◽  
Handong Tan ◽  
...  
Keyword(s):  
Aqueous Fluid ◽  
Southern Tibet ◽  
Magnetotelluric Data ◽  
Partial Melt

scholarly journals Editorial for Special Issue “Mineral Surface Reactions at the Nanoscale”

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 185
Author(s):  
Christine Putnis
Keyword(s):  
Surface Reactions ◽  
Experimental Studies ◽  
Analytical Techniques ◽  
Aqueous Fluid ◽  
Mineral Surfaces ◽  
Special Issue ◽  
Mineral Surface ◽  
Electron Microscopies ◽  
Interface Control ◽  
The Earth

Reactions at mineral surfaces are central to all geochemical processes. As minerals comprise the rocks of the Earth, the processes occurring at the mineral–aqueous fluid interface control the evolution of the rocks and, hence, the structure of the crust of the Earth during such processes at metamorphism, metasomatism, and weathering. In recent years, focus has been concentrated on mineral surface reactions made possible through the development of advanced analytical techniques, such as atomic force microscopy (AFM), advanced electron microscopies (SEM and TEM), phase shift interferometry, confocal Raman spectroscopy, advanced synchrotron-based applications, complemented by molecular simulations, to confirm or predict the results of experimental studies. In particular, the development of analytical methods that allow direct observations of mineral–fluid reactions at the nanoscale have revealed new and significant aspects of the kinetics and mechanisms of reactions taking place in fundamental mineral–fluid systems. These experimental and computational studies have enabled new and exciting possibilities to elucidate the mechanisms that govern mineral–fluid reactions, as well as the kinetics of these processes, and, hence, to enhance our ability to predict potential mineral behavior. In this Special Issue “Mineral Surface Reactions at the Nanoscale”, we present 12 contributions that highlight the role and importance of mineral surfaces in varying fields of research.

Cadmium, indium, tin, tellurium, and sulfur in oceanic basalts: Implications for chalcophile element fractionation in the Earth

2000 ◽  
Vol 105 (B8) ◽  
pp. 18927-18948 ◽  
Author(s):  
Wen Yi ◽  
Alex N. Halliday ◽  
Jeff C. Alt ◽  
Der-Chuen Lee ◽  
Mark Rehkämper ◽  
...  
Keyword(s):  
The Earth ◽  
Chalcophile Element ◽  
Element Fractionation ◽  
Oceanic Basalts ◽  
Cadmium Indium

Late Quaternary glacio- and Hydro-Isostasy, on a Layered Earth

1974 ◽  
Vol 4 (4) ◽  
pp. 405-428 ◽  
Author(s):  
J. Chappell
Keyword(s):  
North America ◽  
Late Quaternary ◽  
Oceanic Islands ◽  
Mantle Flow ◽  
Upward Movement ◽  
Last Deglaciation ◽  
Regional Effects ◽  
Relaxation Effects ◽  
The Earth ◽  
Hinge Zone

Isostatic response of the Earth to changes in Quaternary Times of ice and water loads is partly elastic, and partly involves viscous mantle flow. The relaxation spectrum of the Earth, critical for estimation of the mantle flow component, is estimated from published determinations of Fennoscandian and Laurentide rebound, and of the nontidal acceleration of the Earth's rotation. The spectrum is consistent with an asthenosphere viscosity around 1021P, and a viscosity around 1023P below 400 km depth. Calculation of relaxation effects is done by convoluting the load history with the response function in spherical harmonics for global effects, and in rectangular or cylindrical transforms for smaller regional effects. Broad-scale deformation of the globe, resulting from the last deglaciation and sea level rise, is calculated to have involved an average depression of ocean basins of about 8 m, and mean upward movement of continents of about 16 m, relative to the center of the Earth, in the last 7000 yr. Deflection in the ocean margin “hinge zone” varies with continental shelf geometry and rigidity of the underlying lithosphere: predictions are made for different model cases. The computational methods is checked by predicting Fennoscandian and Laurentide postglacial warping, from published estimates of icecap histories, with good results. The depth variations of shorelines formed around 17,000 BP (e.g., North America, 90–130 m; Australia, 130–170 m), are largely explainable in terms of combined elastic and relaxation isostasy. Differences between Holocene eustatic records from oceanic islands (Micronesia, Bermuda), and continental coasts (eastern North America, Australia), are largely but not entirely explained in the same terms.

Celestine discovered in Hawaiian basalts

2020 ◽  
Vol 105 (1) ◽  
pp. 52-57
Author(s):  
Michael O. Garcia ◽  
Eric Hellebrand
Keyword(s):  
Oceanic Islands ◽  
Sr Isotope ◽  
Fine Grained ◽  
Host Basalt ◽  
Mid Ocean Ridge ◽  
The Matrix ◽  
First Occurrence ◽  
Oceanic Basalts ◽  
Ocean Ridge ◽  
Isotope Analyses

Abstract We report here the first occurrence of celestine (SrSO4) in recent oceanic basalts. Celestine was found in moderately altered accidental volcanic blocks from Ka‘ula Island, a rejuvenated tuff cone in the northern Hawaiian Islands. This occurrence is novel not only for the presence of celestine but also for the absence of barite, the sulfate mineral most commonly found in oceanic hydrothermal deposits. Celestine was found lining vesicles and partially fillings voids within the matrix of several high Sr (2200–6400 ppm) Ka‘ula basalts. High-quality wavelength-dispersive microprobe analyses of celestine are reported here for near end-member celestine (>90%). The Ka‘ula celestine deposits are compositionally heterogeneous with large variations in Ba content (0.9–7.5 wt%) within single mineral aggregates. The most likely source of the Sr for celestine in the Ka‘ula basalts was the host basalt, which contains ~1200 ppm. This is about 10 times higher than normally found in mid-ocean ridge basalts and 4 times greater than commonly observed in Hawaiian basalts. Hydrothermal alteration by S-bearing fluids related to the eruption that transported these accidentally fragments probably mobilized Sr in the blocks. These S-rich solutions later precipitated celestine during or following the eruption. We were unable to confirm the origin for the Sr via Sr isotope measures because the Ka‘ula celestine was too fine grained, friable, and widely dispersed to be concentrated for Sr isotope analyses. Future studies of basalts from active volcanoes on oceanic islands, especially for basalts with elevated Sr contents (>1000 ppm), should be aware of the possible presence of celestine in moderately altered lavas.

Diversity, Equality and Inclusion will promote the activities of female students in Japan

2020 ◽  
Author(s):  
Hodaka Kawahata
Keyword(s):  
Mineral Resources ◽  
Female Students ◽  
Male Students ◽  
Human Society ◽  
The Past ◽  
Ocean Ridges ◽  
The Earth ◽  
Wide Range ◽  
Opposite View ◽  
Global Carbon

<p><span>I got Ph.D. on the subseafloor hydrothermal system along the mid-ocean ridges. However, I changed my topics to global carbon cycle in the modern state and in the past when I was 35 year old. Therefore my research room has been interested in wide range of topics in geoscience: material cycle in the Earth’s surface, including C and water cycles, paleo and modern climate/environmental change and mineral resources. Since I believe that the real innovation has been carried out in human society and I think that some researchers have limited view of thinks, I have never strongly pushed the students to go to Ph.D. course. Therefore many highly competent students started to work at companies/ government after getting Master Degree. In spite of these circumstances, 22 students got Ph.D. at my research room during the last 25 years. The number is much larger than those of common geoscience research rooms at Japanese universities. Especially the female Ph.D.s (11) are just 50%, the largest in Japanese geoscience community. By the way, the relative abundances of female students in the JPGU participants and in Japanese Ph.D. course are around 30% and <20%, respectively. I have never invited female students, more than male students, on purpose. Every student at my research room receives equal good treatment. I am very often saying to the students, ”if you have any problem, please tell me. I do work for you.”. Female student at my laboratory mostly got Bachelor’s degree at the high rank university and therefore is very capable with her own opinion. I welcome her opposite view against me. Also she can give her frank opinion to our laboratory’s members although female people often have reserved attitude in Japan, which she would experience after leaving my research room. Although I have done nothing for special purpose, I respect Diversity, Equality, and Inclusions very much and take much care of her own effort to develop her ability and to cultivate her individuality. She has job that would stretch herself after Ph.D.. Currently 100% of female students at my laboratory, who would to become scientific researchers, succeeded in getting permanent/regular positions at Japanese universities/national laboratories. I have been saying that I would like to work for both male and female younger generations because I have one daughter and one son.</span></p>

A Discussion on volcanism and the structure of the Earth - Silica saturation in cenozoic basalt

1972 ◽  
Vol 271 (1213) ◽  
pp. 285-296 ◽  
Keyword(s):  
Experimental Work ◽  
Bimodal Distribution ◽  
Oceanic Islands ◽  
The Other ◽  
Solid Materials ◽  
Saturation State ◽  
The Earth ◽  
Earth Models ◽  
Cenozoic Basalt ◽  
Basaltic Lavas

Cenozoic basalts are conspicuously either over- or undersaturated with respect to silica. Undersaturated basalts are strongly dominant in the mediterranean areas and in oceanic islands other than Hawaii. Oversaturated basalts are strongly dominant in Hawaii and throughout the circumoceanic environment. Both over- and undersaturated basalts are abundant on the continents. Silica-saturated basalts are dominant only in the submarine ridges, where fresh representatives of either of the other saturation types are still unknown. Experimental work suggests that initial or early melting fractions of basalts or their plutonic equivalents or precursors would usually be either over- or undersaturated regardless of the saturation state of the starting material. The bimodal distribution of silica saturation in Cenozoic basalts is thus compatible with, and provides little basis for preference among, a variety of Earth models in which basaltic lavas are presumed to be early melting fractions of pre-existing solid materials.

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