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|Title:||Contributions to the Mineral Chemistry of Hawaiian Rocks. VI. Olivines in Rocks from Haleakala and West Maui Volcanoes, Maui, Hawaii.|
|Publisher:||University of Hawaii Press|
|Citation:||Fodor RV, Keil K, Bunch TE. 1977. Contributions to the mineral chemistry of Hawaiian rocks. VI. Olivines in rocks from Haleakala and West Maui volcanoes, Maui, Hawaii. Pac Sci 31(3): 299-308.|
|Abstract:||Phenocryst and groundmass olivine in 22 rocks of the tholeiitic,
alkalic, and nephelinicsuites from Haleakala and West Maui volcanoes were
analyzed by electron microprobe. Results and conclusions: Ranges for average
compositions of olivine phenocrysts and groundmass are, respectively. Fo73 _85
and Fo61 for the tholeiitic suite (only one tholeiite contained groundmass
olivine); Fo54_83 and Fo15_68 for the alkalis suite; and Fo73 _83 and Fo61 _66
for the nephelinic suite. In all suites, zoning extends these ranges substantially.
Phenocrysts are usually enriched in Fe, Mn, and Ca at their rims, and coexisting
groundmass olivine is richer in these same elements and depleted in Cr and Ni
contents. In the differentiated alkalic suite, Fe, Mn, and Ca increase, and Ni
decreases, from basalt to trachyte (mainly dependent on major element fractionation).
The tholeiitic and nephelinic suites can occasionally be distinguished
by higher Ca and lower Ni in olivine of the latter.
|Appears in Collections:||Pacific Science Volume 31, Number 3, 1977|
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