Petrology of lavas from the Puu Oo eruption of Kilauea Volcano: III. The Kupaianaha episode (1986-1992)

Abstract

The Puu Oo eruption has been remarkable in the historical record of Kilauea Volcano for its duration (over 13 years), volume (`1 km 3 ) and compositional variation (5.7-10 wt.% MgO). During the summer of 1986, the main vent for lava production moved 3 km down the east rift zone and the eruption style changed from episodic geyser-like fountaining at Puu Oo to virtually continuous, relatively quiescent effusion at the Kupaianaha vent. This paper examines this next chapter in the Puu Oo eruption, episodes 48 and 49, and presents new ICP-MS trace element and Pb-, Sr-, and Nd-isotope data for the entire eruption (1983)(1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994). Nearly aphyric to weakly olivine-phyric lavas were erupted during episodes 48 and 49. The variation in MgO content of Kupaianaha lavas erupted before 1990 correlates with changes in tilt at the summit of Kilauea, both of which probably were controlled by variations in Kilauea's magma supply rate. These lavas contain euhedral olivines which generally are in equilibrium with whole-rock compositions, although some of the more mafic lavas which erupted during 1990, a period of frequent pauses in the eruption, accumulated 2-4 vol.% olivine. The highest forsterite content of olivines (F85%) in Kupaianaha lavas indicates that the parental magmas for these lavas had MgO contents of F10 wt.%, which equals the highest observed value for lavas during this eruption. The composition of the Puu Oo lavas has progressively changed during the eruption. Since early 1985 (episode 30), when mixing between an evolved rift zone magma and a more mafic summit reservoir-derived magma ended, the normalized (to 10 wt.% MgO) abundances of highly incompatible elements and CaO have systematically decreased with time, whereas ratios of these trace elements and Pb, Sr, and Nd isotopes, and the abundances of Y and Yb, have remained relatively unchanged. These results indicate that the Hawaiian plume source for Puu Oo magmas must be relatively homogeneous on a scale of 10-20 km 3 (assuming 5-10% partial melting), and that localized melting within the plume has apparently progressively depleted its incompatible elements and clinopyroxene component as the eruption continued. The rate of variation of highly incompatible elements in Puu Oo lavas is much greater than that observed for Kilauea historical summit lavas (e.g., Ba/Y 0.09 a -1 vs F0.03 a -1 ). This rapid change indicates that Puu Oo magmas did not mix thoroughly with magma in the summit reservoir. Thus, except for variable amounts of olivine fractionation, the geochemical variation in these lavas is predominantly controlled by mantle processes.Key words Hawaii 7 Kilauea Volcano 7 magma 7 Volcano plumbing 7 lava geochemistry 7 mantlemelting

The chemically zoned 1949 eruption on La Palma (Canary Islands): Petrologic evolution and magma supply dynamics of a rift zone eruption

“…Because the Kilauea system is almost continually supplied with new magma, geochemical differences among these three components are more subtle yet can be considerable in some cases. Not all erupted lavas pass through the summit reservoir, but mixing of distinct components within Kilauea's rift system is common [Garcia et al, 1996]. This results in more gradual variations in the composition of the erupted lavas, whereas the relatively abrupt changes typical for La Palma imply minimal damping of compositional fluctuations and by inference smaller magma bodies within the rift system [Albarbde, 1993].…”

Correlated Changes Between Volcanic Structures and Magma Composition in the Faial Volcanic System, Azores

“…Models dealing with the formation of volcanic rift zones and dike emplacement suggest a central accumulation zone of melts feeding a central volcano, from which sills and dikes intrude along rift zones depending on the local and regional stress fields (e.g., Gudmundsson, 1995;Garcia et al, 1996;Paquet et al, 2007;Gudmundsson et al, 2014). These models have in common that melts feeding both the central volcanoes and the associated rift zones form from the same shallow crustal reservoir.…”

“…The younger volcanic units on the island, in particular the Caldeira Volcano, likely cover older units, and in the absence of samples one might speculate that these may form compositional equivalents to the lavas erupted along the submarine rift zones. Thus, we suggest that a model like on Iceland (Gudmundsson, 1995) or Hawaii (Garcia et al, 1996) with a summit reservoir feeding both a central volcano and the rift zones is not applicable for Faial. Instead, the volcanic structures may be comparable to those observed on La Palma where the central volcano and the rift zone formed above distinct plumbing systems (Galipp et al, 2006).…”

“…For example, volcanoes at oceanic spreading axes are commonly elongated reflecting the intrusion of kilometer long dikes above which lavas erupt and build up volcanic ridges (Morgan, 1987). Studies of oceanic island volcanoes, e.g., Hawaii, Iceland, and the Canary Islands, have shown that extensional forces on different local and regional scales generate lithospheric pathways for the ascending melts (Garcia et al, 1996;Klügel et al, 2005a;Gudmundsson et al, 2014). However, little is known on how structural features or compositions of magmas change if an extensional component is present as a response to either changes in melting or tectonic regime.…”

Mécanismes de solidification des magmas basaltiques :

“…Tilling & Dvorak, 1993;Wright & Klein, 2008), due to the continuous monitoring of its activity by the Hawaiian Volcano Observatory since 1912. In addition, numerous pétrographie studies of the lavas from Kilauea have documented the complexity of the magmatic processes (Garcia et al, 2003;Garcia et al, 1996;Hofmann et al, 1984; Thornber, 2001). Kilauea is composed of tholeiitic basalt with minor olivine-rich tholeiite.…”