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The compositions of coexisting pyroxenes and garnet in the system CaO-MgO-Al2O3-SiO2 at 900°–1,100°C and high pressures (1981)

Perkins, Dexter ; Newton, Robert C.

Springer

Contributions to mineralogy and petrology 75 (1981), S. 291-300

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract The compositions of coexisting orthopyroxene, clinopyroxene and garnet in the CaO-MgO-Al2O3-SiO2 system are fixed at any givenP andT. Reversed hydrothermal experiments over theP/T range 15–40 kb/900°–l,100° C indicate that the garnet composition is nearly constant at Py86Gr14; the Alcontent and Ca/Ca+Mg values of the pyroxenes vary significantly, however: T P Wt. %Al2O3 $$\frac{{Ca}}{{Ca + Mg}} \times 100$$ °C kbar in opx in cpx in opx in cpx 900 15 3.55 2.92 0.72 47.05 900 30 1.62 0.92 0.81 47.30 1,100 20 1.11 0.92 1.22 45.20 1,100 40 1.26 0.88 0.81 45.64 The significant variation of A12O3 content with pressure supports its use as a geobarometer. The Ca/Ca +Mg values of coexisting orthoand clino-pyroxene have been used as a geothermometer. However, the present results show that the presence of A12O3 in the pyroxenes decreases significantly the mutual solubility of the pyroxenes, which may cause errors of up to 200° C if the A12O3 effect is ignored. Thermodynamic analyses of the experimental results for the reaction Mg3Al2Si3O12(gar) =Mg3Al2Si3O12(opx) yield average values ofΔH 0 andΔS 0 of 7.4 Kcal and 5.7 eu, respectively, which are in marginal agreement with calorimetric results. Similar analysis of our results for the reaction MgSiO3(cpx)=MgSiO3(opx) support earlier conclusions that MgSiO3 substitution in clinopyroxene behaves as a regular solution (Holland et al. 1979) and that Al substitution is quasi-ideal (Wood 1979). Application of the present results to garnet lherzolites from southern Africa yields a geotherm which is parallel to those previously proposed, although the indicated heat flow is greater. Similar rocks, from the Solomon Islands, show a much steeper geothermal gradient, as expected for an oceanic plate.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01166769

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Stability of the scapolite meionite (3CaAl2Si2O2 · CaCO3) at high pressures and storage of CO2 in the deep crust (1975)

Newton, Robert C. ; Goldsmith, Julian R.

Springer

Contributions to mineralogy and petrology 49 (1975), S. 49-62

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ISSN: 1432-0967

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences

Notes: Abstract The stability field of the end-member scapolite meionite was determined in piston-cylinder apparatus. Meionite has very high thermal stability at high pressures, exceeding 1500° C at 20 kbar. Below 6 kbar and 1270 ° C scapolite breakdown is subsolidus, to an-orthite + gehlenite + wollastonite + CO2, with a slope of 20 bars/degree. An extrapolation of existing thermodynamic data for CO2 permits calculation of ΔG F o =-2384.5 kcal/mol for meionite at 1270 ° C, very close to the value for 3 anorthite + calcite. Above 1270 ° C, scapolite begins to melt to An+Geh+Liq+CO2, and as pressure increases the melting curve steepens, the Geh and An being progressively replaced by Liq+corundum with Al in 6-coordination. At pressures 〉25kbar dp/dt becomes negative, corundum is the only crystalline product, and CO2 bubbles disappear from the quenched glass, indicating a solubility of CO2 under these conditions of about 5 wt. percent in the liquid. The subsolidus breakdown of meionite at high pressures to grossularite + kyanite + quartz + calcite nearly coincides with the upper pressure limits of anorthite. Thus scapolite is essentially limited to crustal rocks. In view of its great thermal stability, meionite can play a role as a primary mineral in deep-seated basic or intermediate magmatic processes. It is also likely that CO2 coming from the earth's interior will be captured by reaction with plagioclase and clinopyroxene. Scapolite has been noted in basic granulite inclusions from basaltic pipes in three continents. It seems probable that scapolite acts as a major storage site for CO2 in the deep crust.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00371078

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The immune response of inbred mouse strains to DNP-BGG (1977)

Newton, Robert C. ; Warner, Carol M.

Springer

Immunogenetics 4 (1977), S. 449-462

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ISSN: 1432-1211

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Abstract The immune response of six inbred mouse strains (SJL, A, C57BL/6, CBA, BALB/c, and DBA/1) to DNP56BGG was tested under three separate immunization schedules: 1 Μg DNP-BGG in 1 mg Al(OH)3 adjuvant, 50 Μg DNP-BGG in 1 mg A1(OH)3 adjuvant, and 1 Μg DNP-BGG in complete Freund's adjuvant. Individual serum samples were titered using a modified Farr assay. It was found that the first schedule allowed classification of the mice into responder (SJL, A) and nonresponder (C57BL/6, CBA, BALB/ c, DBA/1) strains. The second schedule produced quantitative as well as qualitative differences among the strains and allowed classification of the mice into higher-responder (SJL, A), intermediate-responder (C57BL/6, CBA, BALB/c), and low-responder (DBA/1) categories. When complete Freund's adjuvant was used in the third schedule, the differences among strains became insignificant. The sera from each strain were pooled and assayed for relative antibody affinity and IgM content. Both of these parameters were dependent largely on the dose of antigen and type of adjuvant used, rather than on the particular mouse strain being studied. The mechanism of adjuvant action, and possible cell interactions in the genetic control of the immune response, are discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01575680

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