Situated in the SW Pacific, the Alaska-sized Ontong Java Plateau (OJP) represents the worlds largest LIP. Sub-aerial outcrops of OJP basement are present on the islands of Malaita, Santa Isabel, Ulawa, and Makira in the Solomon Islands. With OJP basement recovered by Ocean Drilling Program Leg 130 at Sites 803 (90 Ma) and 807 (122 Ma), the compositional uniformity of the erupted lavas is remarkable as is the apparent bimodality in ages. This is repeated in OJP basalts from the Solomon Islands. Two groups of basalts are found at 122 Ma - the Kwaimbaita and Singgalo Groups, and are present at Site 807, Santa Isabel, Malaita and Ulawa. The latter are enriched in the incompatible trace elements relative to the former. These groups are also distinguished isotopically. The 90 Ma basalts, found at Site 807, Santa Isabel, and Makira, are similar to the Kwaimbaita basalts. The new data from Makira indicate episodes of OJP volcanism at ~62 ma and ~34 Ma. In addition, MORBs and OIBs are stratigraphically intercalated with the OJP basement and a more fractionated variant of the Singgalo group, termed the Wairahito basalts. The OJP basalts from Makira, even though they are of different ages, preserve the groupings defined elsewhere on the OJP. These are interpreted in terms of plume volcanism at a mid-ocean ridge with the OIBs representing the plume tail component. In addition, PGE abundances in the basalts are interpreted to indicate a core-mantle boundary origin for the OJP plume.
Papers resulting from this research:
III and Neal C.R. (2004) LIP magma petrogenesis from source
to surface: Platinum-group element evidence from Ontong Java Plateau
basalts recovered during ODP Leg 192.
J. Geol. Soc. London, Special Volume on
Java Plateau (in press).
Neal C.R., and Castillo P. (2004) Compositional variability in lavas
from the Ontong Java
Plateau: Results from basalt clasts within the volcaniclastic sequence
Ocean Drilling Program Leg 192 Site 1184. J.
Geol. Soc. London, Special Volume on the Ontong Java Plateau (in press).
and Neal C.R. (2003) Using platinum-group elements
to investigate the origin of the Ontong Java
Plateau, SW Pacific. Chem. Geo.
Tejada M.L.J., Mahoney
J.J., Neal C.R., Duncan R.A., and Petterson M.G. (2002) Basement
geochemistry and geochronology of central Malaita, Solomon Islands,
with implications for the origin and evolution of the Ontong Java
Plateau. J. Petrol. 43, 449-484.
Neal C.R., Haggerty S.E., and Sauter V. (2001) "Majorite" and "Silicate Perovskite" mineral compositions in xenoliths from Malaita. Science 292, 1015-1018.
Neal C.R., Mahoney J.J., Kroenke L.W.,
Duncan R.A., and Petterson M.G. (1997) The
Ontong Java Plateau. In: Large Igneous Provinces: Continental, Oceanic, and
Planetary Flood Volcanism (J.J.
M. Coffin, eds), Geophys. Mono. 100,
183-216. American Geophysical Union.
Petterson M.G., Neal C.R.,
Mahoney J.J., Kroenke L.W., Saunders A.D., Babbs T.L., Duncan R. A.,
Tolia D., and McGrail B. (1997) Structure and
deformation of North and Central Malaita, Solomon Islands: Tectonic
implications for the Ontong Java Plateau - Solomon Arc collision, and
for the fate of oceanic plateaus. Tectonophysics
Nixon P.H. and Neal C.R. (1987) Ontong Java Plateau: Deep seated xenoliths from thick oceanic lithosphere. In: Mantle Xenoliths, ed. P. H. Nixon, 335-345. John Wiley and Sons.
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