Devonian alkalic basalt dikes of northeastern Newfoundland: evidence of a tensional environment

1978 ◽  
Vol 15 (5) ◽  
pp. 848-853 ◽  
Author(s):  
N. R. Jayasinghe
Keyword(s):  
Minor Element ◽  
Element Chemistry ◽  
Alkalic Basalt ◽  
Alkalic Basalts

A suite of diabase dikes intrudes granites and migmatites in the northeastern Gander Zone of Newfoundland. Rb–Sr dates on granites pre-dating and post-dating the diabases show that the dikes were emplaced in the Devonian. The mineralogy and the major and minor element chemistry of the dikes indicate that they are alkalic basalts that may have been intruded during a period of tension.

Chromite in greenstone lavas from the Kanakasu area, Nanjo Massif of the Mesozoic Mino terrane, central Japan

2002 ◽  
Vol 66 (4) ◽  
pp. 575-590 ◽  
Author(s):  
T. Agata ◽  
I. Hattori
Keyword(s):  
Chemical Composition ◽  
Oceanic Island ◽  
Island Arc ◽  
Basalt Magma ◽  
Central Japan ◽  
Compositional Zoning ◽  
Oceanic Ridge ◽  
Host Magma ◽  
Alkalic Basalt ◽  
Alkalic Basalts

AbstractChromite occurs together with olivine as phenocrysts in basalts of the Kanakasu greenstone body. Chromite forms inclusions within olivine phenocrysts; it also constitutes discrete phenocrystic grains scattered in the groundmass. The Cr and Ni contents of chromite-bearing olivine basalts are unusually high relative to the MgO content. This is probably due to the presence of phenocrystic chromite and olivine. The mineralogy suggests that the groundmass of the basalts is hawaiitic in composition. Chromite, generally, is unlikely to crystallize from differentiated magma such as hawaiite melt. The chromite and associated olivine phenocrysts are probably xenocrysts. Discrete chromite commonly shows compositional zoning that resulted from reaction with host magma; some chromite evidently changed in composition. Chromite embedded in olivine was shielded from reaction with host magma, and has preserved the original chemical composition. The composition of embedded chromite ranges: Mg/(Mg+Fe2+) 0.37–0.58, Cr/(Cr+Al) 0.47–0.64, Fe3+ 0.16–0.47 p.f.u., and Ti 0.034–0.13 p.f.u. The relatively high Ti and Al contents suggest that chromite crystallized from an alkalic basalt magma. The Cr/(Cr+Al) ratio is relatively high when compared to those of chromite in mid-oceanic ridge and island-arc alkalic basalts; the Kanakasu embedded chromite is chemically identical to chromite from Hawaiian alkalic basalts. The Kanakasu chromite was probably formed in an intraplate oceanic island.

Trace and Minor Element Chemistry of Alkali Feldspars in the Klokken Layered Syenite Series

1985 ◽  
Vol 26 (4) ◽  
pp. 952-970 ◽  
Author(s):  
R. A. MASON ◽  
I. PARSONS ◽  
J. V. P. LONG
Keyword(s):  
Minor Element ◽  
Element Chemistry ◽  
Alkali Feldspars

Minor element chemistry of leucite and pseudoleucite

1965 ◽  
Vol 35 (272) ◽  
pp. 596-603 ◽  
Author(s):  
C. M. B. Henderson
Keyword(s):  
Minor Element ◽  
Element Chemistry ◽  
Leucite Structure ◽  
Alkali Feldspars

SummaryLeucite and pseudoleucite invariably have lower K/Rb ratios and higher K/Sr and K/Ba ratios than the groundmasses of the rocks in which they occur. The distribution of Rb, Sr, and Ba between K-rich minerals (e.g. alkali feldspars) and the liquids from which they crystallize is generally such that Rb is impoverished and Sr and Ba enriched, relative to K, in the crystallizing phase. Leucite shows the opposite relationship and this is attributed to the leucite structure being sensitive to the size and valency of the ions replacing K.

Minor element chemistry of hemo-ilmenite and magnetite in cumulate rocks from the Sokndal Region, South Rogaland, Norway

2001 ◽  
Vol 86 (11-12) ◽  
pp. 1469-1476 ◽  
Author(s):  
Peter Robinson ◽  
Peter T. Panish ◽  
Suzanne A. McEnroe
Keyword(s):  
Minor Element ◽  
Element Chemistry
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