TY - JOUR
T1 - Interpretation of olivine zoning
T2 - Study of a maar from the San Francisco volcanic field, Arizona
AU - Van Kooten, Gerald K.
AU - Buseck, P R
PY - 1978/1/1
Y1 - 1978/1/1
N2 - Fe-Mg zoning in olivine represents a disequilibrium state that reflects the physical and chemical environment the mineral has experienced. Olivine crystallization is affected by changes in the magmatic environment. The types of profiles we have observed include (1) homogeneous crystals, (2) homogeneous cores and zoned rims, (3) zoning extending uniformly across the crystal, (4) composition profiles that change in steps across the crystal, and (5) irregular zoning resulting from alteration and oxidation. Stepped profiles appear to have resulted from episodic changes in the magmatic environment. Calculations show that the steps could have formed owing to changing pressure as magma pulsed toward the surface. Olivines from crater 160, a maar in the San Francisco volcanic field, Arizona, differ markedly in their zoning profiles. Comparison of separate flows indicates a common parent magma and suggests that a near-surface magma chamber did not exist. Probable correlations between a complex feeder dike and specific nearby flows were made.
AB - Fe-Mg zoning in olivine represents a disequilibrium state that reflects the physical and chemical environment the mineral has experienced. Olivine crystallization is affected by changes in the magmatic environment. The types of profiles we have observed include (1) homogeneous crystals, (2) homogeneous cores and zoned rims, (3) zoning extending uniformly across the crystal, (4) composition profiles that change in steps across the crystal, and (5) irregular zoning resulting from alteration and oxidation. Stepped profiles appear to have resulted from episodic changes in the magmatic environment. Calculations show that the steps could have formed owing to changing pressure as magma pulsed toward the surface. Olivines from crater 160, a maar in the San Francisco volcanic field, Arizona, differ markedly in their zoning profiles. Comparison of separate flows indicates a common parent magma and suggests that a near-surface magma chamber did not exist. Probable correlations between a complex feeder dike and specific nearby flows were made.
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U2 - 10.1130/0016-7606(1978)89<744:IOOZSO>2.0.CO;2
DO - 10.1130/0016-7606(1978)89<744:IOOZSO>2.0.CO;2
M3 - Article
AN - SCOPUS:0346946150
SN - 0016-7606
VL - 89
SP - 744
EP - 754
JO - Bulletin of the Geological Society of America
JF - Bulletin of the Geological Society of America
IS - 5
ER -