The tholeiite to alkalic basalt transition at Haleakala Volcano, Maui, Hawaii

1991 ◽  
Vol 106 (2) ◽  
pp. 183-200 ◽  
Author(s):  
C.-Y. Chen ◽  
F. A. Frey ◽  
M. O. Garcia ◽  
G. B. Dalrymple ◽  
S. R. Hart
Keyword(s):  
Alkalic Basalt

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.

Xenoliths in the alkalic basalt flows from Hualalai Volcano, Hawaii

1981 ◽  
Author(s):  
E.D. Jackson ◽  
D.A. Clague ◽  
E. Engleman ◽  
W.F. Friesen ◽  
D. Norton
Keyword(s):  
Alkalic Basalt

Feldspar relations in Icelandic alkalic rhyolites

1971 ◽  
Vol 38 (296) ◽  
pp. 503-510 ◽  
Author(s):  
Haraldur Sigurdsson
Keyword(s):  
Electron Probe ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
Potassic Feldspar ◽  
Acid Volcanic ◽  
Alkalic Basalt ◽  
First Time

SummaryAlkalic rhyolites with peralkaline affinities, bearing quartz and potassic feldspar phenocrysts, are described from Iceland for the first time. Evidence from electron-probe analyses of feldspar phenocrysts indicates crystallization in or near the thermal valley of the system SiO2-Or-Ab. Icelandic acid volcanic rocks are subdivided into alkalic rhyolites, belonging to transitional and alkalic basalt lineages, and the mildly calc-alkaline rhyolites of tholeiite lineages.

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.

Origin of Hawaiian tholeiite and alkalic basalt

Nature ◽  
1983 ◽  
Vol 302 (5911) ◽  
pp. 785-789 ◽  
Author(s):  
Chu-Yung Chen ◽  
Frederick A. Frey
Keyword(s):  
Alkalic Basalt
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