Journal ArticleDOI
The Petrology and Geochemistry of the Azores Islands
TLDR
Forty lavas from the Azores Islands have been analyzed for 87Sr/86Sr ratios, major elements, first transition series metals, and LIL elements as discussed by the authors.Abstract:
Forty lavas from the Azores Islands have been analyzed for 87Sr/86Sr ratios, major elements, first transition series metals, and LIL elements The samples belong to the alkali basalt magma series but range from transitional hy-normative basalts from Terceira to basanitoids from Santa Maria Differentiated lavas include both typical trachytes and comenditic trachytes and comendites Major and trace element concentrations define smooth trends on variation diagrams, and these trends can be related to phases crystallizing in the rocks Systematic interisland differences are also apparent in these variation diagrams LIL element concentrations in island basalts are roughly twice as high as those in tholeiites from the adjacent Mid-Atlantic Ridge which transects the Azores Plateau 87Sr/86Sr ratios in lavas from 6 of the 9 islands range from 070332 to 070354, a range similar to that found in tholeiites from the Mid-Atlantic Ridge transect of the Azores Plateau This suggests that lavas from these islands and this portion of the Mid-Atlantic Ridge may be derived from a similar source However, lavas from the islands of Faial and Pico have 87Sr/86Sr ratios up to 070394 and ratios in Sao Miguel lavas range up to 070525, suggesting basalts from these islands are derived from a chemically distinct source Differences in the average LIL element concentrations of the least fractionated ridge tholeiites from the Azores Plateau and alkali basalts from the islands result from differences in extent of partial melting and residual mineralogy The alkali basalts are derived by roughly half as much melting as are the tholeiites Trace element concentrations in Azores peralkaline lavas preclude their derivation by partial melting of peridotitic mantle or basaltic crust; rather the data suggest they are produced by fractional crystallization of a basaltic parentread more
Citations
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Chemical and isotopic systematics of oceanic basalt : implications for mantle composition and processes
TL;DR: In this article, trace-element data for mid-ocean ridge basalts and ocean island basalts are used to formulate chemical systematics for oceanic basalts, interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone.
Journal ArticleDOI
Chemical and isotopic systematics of oceanic basalts. Implications for Mantle Composition and Processes
Journal ArticleDOI
The application of a ThHfTa diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province
TL;DR: In this paper, the effects of different types of bulk lower and upper crustal contamination of a within-plate alkali basalt on the Th, Hf, Ta and radiogenic isotope concentrations of the residual liquids are calculated in detail.
Journal ArticleDOI
Relationships between Lu–Hf and Sm–Nd isotopic systems in the global sedimentary system
TL;DR: In this paper, the authors report new Hf (and Nd) data for more than 100 sedimentary samples, recent to Archean in age, from a wide range of depositional environments.
Journal ArticleDOI
Sr and Nd isotope geochemistry of oceanic basalts and mantle evolution
TL;DR: Sr and Nd isotope ratios for 17 mid-ocean ridge basalts and for 11 oceanic islands and island groups are reported in this article, and the results are not explained by binary mixing of depleted and undepleted mantle reservoirs or variable magmatic depletion of a planetary reservoir, but support mantle evolution models involving re-injection of crust material into the mantle.
References
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Journal ArticleDOI
Determination of REE, Ba, Fe, Mg, Na and K in carbonaceous and ordinary chondrites
TL;DR: In this paper, the exact determination of REE and Ba abundances in three carbonaceous (Orgueil Cl, Murchison C2 and Allende C3) and seven olivine-bronzite chondrites were carried out by mass spectrometric isotope dilution technique.
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Origin of Basalt Magmas: An Experimental Study of Natural and Synthetic Rock Systems
H. S. Yoder,C. E. Tilley +1 more
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The genesis of basaltic magmas
David H. Green,A.E. Ringwood +1 more
TL;DR: In this paper, the results of a detailed experimental investigation of fractionation of natural basaltic compositions under conditions of high pressure and high temperature were reported, where a single stage, pistoncylinder apparatus has been used in the pressure range up to 27 kb and at temperatures up to 1500° C to study the melting behaviour of several basaltics compositions.
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143Nd/146Nd, a natural tracer: an application to oceanic basalts*
TL;DR: In this paper, the possibility of using 143Nd/146Nd as a natural tracer was examined by analyzing two Hercynian granitic rocks, one carbonatite, three alkali basalts and nine tholeiites.