John J. Naughton

Potassium-Argon Dating of Holocene Basalts of the Honolulu Volcanic Series

The potassium-argon method of geo-chronometry has been modified to enable the dating of young, normal volcanic rocks. It has been applied to the dating of the posterosional volcanics of the Honolulu Series, which include such well-known Hawaiian landmarks as Diamond Head and Punchbowl. Ages vary from about 30,000 yrs for the Koko rift zone lavas to about 800,000 yrs for the oldest member measured (Castle flow).

The chemistry of sublimates collected directly from lava fountains at Kilauea Volcano, Hawaii

Abstract During 1970, it was occasionally feasible to collect sublimate from directly above the lava fountain in the crater of Mauna Ulu on the east rift zone of Kilauea Volcano, when the level of the lava pool had dropped within the crater. Collecting equipment was suspended down the steep wall to a position above the fountain. Collections were made on quartz wool held within open-ended quartz tubes and, for silica detection, on stainless steel wool in a stainless steel tube. The main components in the sublimate were, in order of decreasing concentration for the best sample, Na, Ca, Al, Fe, Mg, K, B, Si, Ti, Zn, H + , NH 4 + , Cu, Ni in the form of sulfates, chlorides and fluorides. In order to investigate the forms in which the sublimate ions occur under different conditions of temperature and oxidation, the equilibrium compositions of the compounds most likely to be present were calculated. This was done for those important components for which thermodynamic data are available, using a computer program to calculate the minimum free energy for the mixture. The results indicate that, for primary conditions of high temperature and low oxygen partial pressure, the halides were the most likely form of the metallic compounds. Particulate sulfates appear under increasing oxidizing conditions caused by the access of air. These conclusions were reinforced by collections made from holes drilled through the thin crust of a lava lake formed during the same eruption.

Geophysical evidence for post-Miocene rotation of the island of Viti Levu, Fiji, and its relationship to the tectonic development of the North Fiji Basin

Geophysical studies of the island of Viti Levu, Fiji, show largeamplitude magnetic anomalies of up to 1500 nT to be located above the Tavua volcanic center. Field sampling of the volcanic rocks from the intrusive and extrusive centers of the volcano show the rock samples to have initial intensities of natural remanent magnetization of up to 380 A/m. Radiometric dating of fifteen oriented samples show an age range of 2.9 to 7.0 m.y.B.P, for the suite of rocks collected from the Mba basaltic group. Paleomagnetic analysis of the dated rocksshows declination vectors ranging from 325 ± 9° for an age of 2.9±0.2 m.y. B.P. to 290±4° for an age of 7.0±0.4 m.y. B.P. As a group, the paleomagnetic declination values of the samples systematically decrease with age. This decrease is attributed to progressive anticlockwise rotation of Viti Levu during the process of formation of the North Fiji Basin. A linear least squares analysis of the paleomagnetic data indicates that the island has rotated in an anticlockwise direction through 90° during the past 7 m.y. at a rate of 13.7° per million years. Declination values as low as 245° measured for some sites (not dated) suggest that anticlockwise rotation of Viti Levu and development of the North Fiji Basin could have commenced as early as 10 m.y. B.P. following the breakup of the ancient Solomons-New Hebrides-Fiji-Lau island arc. Large rotations of microplates may have occurred along other island arcs and marginal basin systems elsewhere in the Western Pacific and such rotational histories may reflect in detail the evolutionary development of these arcs and basins.

Some additional potassium-argon ages of hawaiian rocks: The Maui volcanic complex of Molokai, Maui, Lanai and Kahoolawe

Abstract Potassium-argon (K-Ar) ages have been determined for rocks from the group of volcanoes vicinal to Maui, Hawaii, in an effort to fill gaps left by previous dating work. Ages for tholeiitic samples from the main shield-building stage of the volcanoes varied in sequence from 0.83 m.y. for Haleakala to 1.84 m.y. for West Molokai volcano. Some differ significantly from ages reported previously. For the volcanoes studied, ages agree with the general Hawaiian trend of volcanoes becoming progressively older to the northwest (Fig. 1B). New determinations of K-Ar ages were made for the late-stage, alkalic volcanism on Kahoolawe (1.03 m.y.), and for the later post-erosional phases at Kalaupapa, Molokai (1.24 m.y.) and from a vent of the Lahaina Series on West Maui (1.30 m.y.). These last two, when compared with the dates of the main shield-building stages of the respective volcanoes, show that very extensive erosion of these Hawaiian volcanoes has taken place in the surprisingly short period of a few hundred thousand years. This is substantiated by evidence of similar rapid erosion on the islands of Oahu and Hawaii.

Incrustations and fumarolic condensates at kilauea volcano, Hawaii: field, drill-hole and laboratory observations☆

Abstract Hawaiian volcanoes characteristically have but few of the many types of minerals found in incrustations of other volcanic areas. In Hawaii sulfates resulting from air oxidation of volatiles predominate, and fluorides produced during rock alteration by fumarolic gases are prominent. Halides are generally found where reducing conditions exist in fumaroles and lava lake drill holes. The most common mineral types are sulfur, opaline silica, gypsum, ralstonite, and thenardite. Minerals from the same deposit are found to vary markedly in the content of the less abundant components. Condensates from vapor issuing from fumaroles show little quantitative relationship in component content to incrustations deposited at the same fumaroles. It is believed that an energetically favorable isomorphic substitution of some elements in the crystal lattice of a depositing mineral may lead to the build-up of a high concentration of an element from a lean vapor. Equilibrium calculations applied to condensate studies give a good quantitative approximation to the concentrations of the elements found in natural systems, but when applied to incrustations they serve only to indicate general compositional relations. Laboratory studies have shown the important role of chlorides in metal transfer in the gas phase in high-temperature aqueous systems, but only in the absence of oxygen. These studies also demonstrated the important role of HF in rock alteration and in the transfer of silica.

Helium Flux from the Earth's Mantle as Estimated from Hawaiian Fumarolic Degassing

Averaged helium to carbon dioxide ratios measured from systematic collections of gases from Sulphur Bank fumarole. Kilauea, Hawaii, when coupled with estimates of carbon in the earths crust, give a helium flux of 1 x 105 atoms per square centimeter per second. This is within the lower range of other estimates, and may represent the flux from deep-seated sources in the upper mantle.

Age and origin of Truk Atoll, eastern Caroline Islands: Geochemical, radiometric-age, and paleomagnetic evidence

Geochemical, K-Ar age, and paleomagnetic data are presented for volcanic rocks from Truk Lagoon (7°20′N, 151° 15′E). Petrographic observations and 52 analyses for major and trace elements reveal 2 shield-building magma types—a mildly alkalic Truk Main Lava Series (TMLS) and a less alkalic Truk Transitional Lava Series (TTLS); and a post-erosional, highly silica-undersaturated, and incompatible-trace-element–enriched Truk Nephelinite Series (TNS). The TMLS and TTLS shield-building lavas give a mean K-Ar age of 10.9 m.y.; post-erosional TNS lavas are dated at 4.8 m.y. B.P. Paleomagnetic results for 15 stably magnetized sites give a paleopole of declination and inclination of 359.3°E and 8.8°30′, respectively, which suggests that Truk was formed 4.4° north of the equator. These data are consistent with a hot-spot origin for the volcanics of Truk Atoll.

Petrology and geochronology of volcanic rocks from seamounts along and near the Hawaiian Ridge: Implications for propagation rate of the ridge

Lavas from three seamounts along and three seamounts near the Hawaiian Ridge are petrographically and geochernically similar to lavas from the Hawaiian Islands. Rock types recovered include tholeftic and alkalic lavas. The composition of these lavas is virtually identical to that of lavas from the Hawaiian Islands. This indicates that the source composition and petrogenesis of lavas along the Hawaiian chain are very consistent. The three along-ridge seamounts are in areas where there were gaps in the radiometric age data base. New ages further document the linear age progression along the chain and define a new propagation rate of 9.6±0.4 cm/yr (which is identical to the present-day plate motion of the island of Hawaii). The near-ridge seamounts are Cretaceous in age (74–77 Ma) and are part of NNW-trending linear chains that predate and are unrelated to the NW- and N-trending Hawaiian and Emperor chains.

Some results from recent chemical studies at Kilauea volcano, Hawaii

The chemical surveillance of Kilauea volcano, Hawaii, has continued. No relationship has thus far been identified between the helium content of an associated fumarole and the activity at the volcano. Fume samples from Halemaumau crater in Kilauea caldera and from a fissure eruption that occurred nearby on the floor of the caldera during August 1971 were examined for their halogen (Cl and F) and sulfur contents. The ratio of Cl/F in fume showed an abnormal increase in samples taken at Halemaumau a month before the eruption. This change in ratio may be a helpful indicator of the onset of eruption in volcanic areas.

Rock Degradation by Alkali Metals: A Possible Lunar Erosion Mechanism

When rocks melt under ultrahigh-vacuum conditions, their alkali components volatilize as metals. These metal vapors act to comminute polycrystalline rocks to their component minerals. The resultant powder is porous and loosely packed and its characteristics may be compatible with the lunar surface as revealed by the Ranger photographs. If meteorite impact or lunar volcanism has produced vaporization or areas of molten lava, alkali erosion may have given dust of this character in adjacent solid areas.