Volcaniclastic deposits from the North Arch volcanic field, Hawaii: explosive fragmentation of alkalic lava at abyssal depths
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Submarine explosive eruptions are generally considered to become less likely with increasing depth due to the increasing hydrostatic pressure of the overlying water column. Volcaniclastic deposits from the North Arch volcanic field, north of Oahu, have textural characteristics of explosive fragmentation yet were erupted in water depths greater than 4,200 m.
The most abundant volcaniclastic samples from North Arch are clast-supported with highly vesicular, angular pyroclasts. They are most likely near-vent pyroclastic fall deposits formed in eruption columns of limited height. Interbedded with highly vesicular pillow lava, they form low (50 to 200 m), steep-sided cones around the vents. Less common are stratified samples with graded bedding; one such sample includes a layer of roughly aligned, platy, bubble-wall glass fragments (resembling littoral limu o Pele) that may have been deposited by density currents. In addition to bubble-wall glass shards, numerous glass fragments with spherical, delicate spindle and ribbon shapes, and Pele's hair-like glass strands occur in the finer size fraction (<0.5 mm) of some samples. They are probably more distal fallout. Another sample, consisting of glass fragments dispersed in a marine clay matrix, was apparently reworked and deposited farther from the vents by bottom currents.
Glass compositions include low-(∼0.4-0.6 wt%) and medium-K2O (>0.6 wt%) alkalic basalt, basanite, and nephelinite. Sulfur and chlorine abundances are high, reaching a maximum of 1,800 and 1,300 ppm, respectively. The ubiquitous presence of limu o Pele fragments, regardless of glass composition, suggests that bursts of Strombolian-like activity accompanied most eruptions. Coalescing vesicles observed in larger pyroclasts and some pillow lava suggests accumulation of volatiles. Since the great hydrostatic pressure makes steam expansion impossible, a volatile-rich, supercritical magmatic fluid probably drove the eruptions. If these volatile-rich magmas had erupted in shallow water or subaerially, tall fountains would most likely have resulted. The great hydrostatic pressure (>40 MPa) limited fountain and eruption column heights.
KeywordsSubmarine explosions Strombolian Pyroclastic fragmentation Lava bubble wall fragments Alkalic basalt North Arch volcanic field Hawaii
DAC thanks JAMSTEC, particularly Eiichi Takahashi, Jiro Naka, Kozo Uto, and the Shinkai 6500 Team for support in mapping and sampling the North Arch volcanic field in 2000 and 2002. We also thank Naoto Hirano for his observations and sample selection during Shinkai dive S704 and Michelle Coombs for providing some glass analyses of the S704 flow samples. Summer intern Stella Maceri helped cut and describe some of these samples as part of a hyaloclastite study. Robert Oscarson assisted with microprobe and SEM analyses, and Jenny Paduan and Nadine Golden in producing Fig. 1 and 2. Constructive reviews by James White, Kathy Cashman, and Associate Editor Jocelyn McPhie improved the manuscript.
- Cas RAF, Wright JV (1987) Volcanic successions, modern and ancient. Allen and Unwin, London, pp 1–528Google Scholar
- Clague DA, Frey FA (1982) Petrology and trace-element geochemistry of the Honolulu Volcanics, Oahu: implications for the oceanic mantle beneath Hawaii. J Petrol 23:447–504Google Scholar
- Clague DA, Uto K, Satake K, Davis AS (2002) Eruption style and flow emplacement in the submarine North Arch volcanic field, Hawaii. In: Takahashi E, Lipman PW, Garcia MO, Naka J, Aramaki S (eds) Hawaiian volcanoes: deep underwater perspectives. Am Geophys Union Monogr 128:65–84Google Scholar
- Clague DA, Batiza R, Head JW III, Davis AS (2003a) Pyroclastic and hydroclastic deposits on Loihi Seamount, Hawaii. In: White JD, Smellie J, Clague DA (eds) Explosive subaqueous volcanism. Am Geophys Union Monogr 140:73–95Google Scholar
- Clague DA, Davis AS, Dixon JE (2003b) Submarine Strombolian eruptions on the Gorda Mid-Ocean Ridge. In: White JD, Smellie J, Clague DA (eds) Explosive subaqueous volcanism. Am Geophys Union Monogr 140:111–128Google Scholar
- Davis AS, Clague DA (2003) Hyaloclastite from Miocene seamounts offshore central California: compositions, eruption styles, and depositional processes, In: White JD, Smellie J, Clague DA (eds) Explosive subaqueous volcanism. Am Geophys Union Monogr 140:129–142Google Scholar
- Davis AS, Clague DA, Friesen WB (1994) Petrology and mineral chemistry of basalt from the Escanaba Trough, southern Gorda Ridge. US Geol Surv Bull 2022:153–170Google Scholar
- Eissen J-P, Fouquet Y, Hardy D, Ondreas H (2003) Recent MORB volcaniclastic explosive deposits formed between 500 and 1,750 m.b.s.l at the axis of the Mid-Atlantic Ridge. In: White JD, Smellie J, Clague DA (eds) Explosive subaqueous volcanism. Am Geophys Union Monogr 140:143–1408Google Scholar
- Fisher RV, Schmincke H-U (1984) Pyroclastic rocks. Springer, Berlin, Heidelberg New York, pp 1–472Google Scholar
- Hon K, Heiker C, Kjargaard JI (1988) Limu o Pele: a new kind of hydroclastic tephra from Kilauea Volcano, Hawaii. Geol Soc Am Abst Prog 20 (7):112–113Google Scholar
- Maaloe S, James D, Smedley P, Petersen S, Garmann LB (1992) The Koloa volcanic suite of Kauai, Hawaii. J Petrol 33:761–784Google Scholar
- Peng D-Y, Robinson DB (1979) The calculation of three-phase solid-liquid-vapor equilibrium using an equation of state. Advances in chemistry series 182, Am Chem Soc, Washington, DC, pp 185–196Google Scholar
- Vergniolle S, Mangan M (2000) Hawaiian and Strombolian eruptions. In Sigurdsson H, Houghton BF, McNutt S, Rymer H, Stix J (eds) Encyclopedia of volcanoes. Academic Press, San Diego, pp 447–461Google Scholar
- Wohletz KH (2003) Water/ magma interaction: physical consideration for the deep submarine environment. In: White JD, Smellie J, Clague DA (eds) Explosive subaqueous volcanism. Am Geophys Union Monogr 140:25–49Google Scholar