Abstract
The Easter microplate-Crough Seamount region located between 25° S–116° W and 25° S–122° W consists of a chain of seamounts forming isolated volcanoes and elongated (100–200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065°), to the present day general spreading direction (N 100°) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26°30′ S–115° W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges (< 2000 m high) bounding the Southwest Rift of the microplate consists of fault scarps where pillow lava, dolerite, and metabasalts are exposed. The degree of rock alternation inferred from palagonitization of glassy margins suggests that the volcanic ridges are as old as the shallow ridges bounding the Southwest Rift of the microplate. The volcanics found on the various structures west of the microplate consist of depleted (K/Ti < 0.1), transitional (K/Ti = 0.11−0.25) and enriched (K/Ti > 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)N = 1−2.5}, {(La/Sm)N = 0.4−1.2} and {(Zr/Y)N = 0.7−2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation (≈ 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25° S–118° W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (< 800 m depth) was formed by earlier (7–10 Ma) hotspot magmatic activity which also created Easter Island.
Similar content being viewed by others
References
Binard, N., Stoffers, P., Hekinian, R., and Searle, R., 1993, Intraplate “en échelon” volcanic ridges West of the Easter microplate: A hot spot origin,Mar. Geol. (submitted).
Bach, W., Hegner, E., Erzinger, J., and Satir, M., 1994, Chemical and isotopic variations along the superfast spreading East Pacific Rise from 6 to 30° S,Contr. Mineral. Petrol. 116, 365–380.
Baker, P. E., Buckley, F., and Holland, J. G., 1974, Petrology and geochemistry of Easter Island,Contr. Mineral. Petrol. 44, 85–90.
Bender, J. F., Langmuir, C. H., and Hanson, G. N., 1984, Petrogenesis of basalt glasses from the Tamayo region, East Pacific Rise,J. Petrol. 25, 213–254.
Bonatti, E., Harrison, C. G. A., Fisher, D. E., Honnorez, J., Schilling, J. G., Stipp, J. J., and Zentilli, M., 1977, Easter volcanic chain (Southeast Pacific): A mantle hot line,J. Geophys. Res. 82, 2457–2478.
Chen, C. Y. and Frey, F. A., 1985, Trace elements and isotopic geochemistry of lavas from Haleakala volcano, East Maui, Hawaii: Implications for the origin of Hawaiian basalts,J. Geophys. Res. 90, 8743–8768.
DeMets, C., Gordon, R. G., Argus, D. F., and Stein, S., 1990, Current plate motions,Geophys. J. Int. 101, 425–478.
Devey, C., Albarède, F., Cheminée, J. L., Michard, A., Muhe, R., and Stoffers, P., 1990, Active hot spot volcanism in the Society islands (West Pacific): Geochemical study,J. Geophys. Res. 95, 5049–5066.
Fisher, R. L. and Norris, R. M., 1960, Bathymetry and geology of Sala y Gomez, Southeast Pacific,Bull. Geol. Soc. Am. 71, 497–502.
Francheteau, J., Patriat, P., Segoufin, J., Armijo, R., Doucoure, M., Yelles-Chaouche, A., Zukin, J., Calmant, S., Naar, D. F., and Searle, R., 1988, Pito and Orongo fracture zones: The nothern and southern boundaries of the Easter microplate (Southeast Pacific),Earth Planet. Sci. Lett. 89, 363–374.
Fontignie, D. and Schilling, J.-G., 1991, 87Sr/86Sr and REE variation along the Easter Microplate boundaries (South Pacific): Application of multivariate statistical analyses to ridge segmentation,Chemical. Geol. 89, 209–241.
Frey, F. A., Green, D. H., and Roy, S. D., 1978, Integrated models of basalts petrogenesis: a study of quartz tholeiites to olivine melilites from southeast Australia utilizing geochemical and experimental petrologic data.J. Petrol. 19, 463–513.
Frey, F. A., Bryan, W. D., and Thompson, G., 1974, Atlantic ocean floor: Geochemistry and petrology of basalts from leg 2 and 3 of Deep-Sea Drilling Project.J. Geophys. Res. 79, 5507–5526.
Gallahan W. E. and Nielsen, R. L., 1992, The partitioning of Sc, Y and rare earth elements between high-Ca pyroxene and natural mafic to intermediate lavas at 1 atmosphere,Geochim. Cosmochim. Acta 56, 2387–2404.
Garbe-Schonberg, C.-D., 1993, Simultaneous determination of 37 trace elements in 28 international rock standards by ICP-Ms,Geostandards Newsletter 17, 81–97.
Green, T. H. and Pearson, N. J., 1985, Rare element partitioning between clinopyroxene and silicate liquid at moderate to high pressure,Contr. Mineral Petrol. 91, 24–36.
Hagen, R. A., Baker, N. A., Naar, D. A., and Hey, R. N., 1990, A SeaMARC II survey of recent submarine volcanism near Easter Island,Marine Geophys. Res. 12, 297–315.
Hanan, B. B. and Schilling, J.-G., 1989, Easter microplate evolution: Pb isotope evidence,J. Geophys. Res. 94, 7432–7448.
Hekinian, R. and Hoffert, M., 1975, Rate of palagonization and manganese coating on basaltic rocks from the rift valley in the Atlantic Ocean near 36°50′ N,Mar. Geol. 19, 91–109.
Hekinian, R., Thompson, G., and Bideau, D., 1989, Axial and off-axial heterogeneity of basaltic rocks from the East Pacific Rise at 12°38′ N and 11°26′–11°30′ N,J. Geophys. Res. 17, 17,437–17,463.
Hekinian, R., Bideau, D., Stoffers, P., Cheminée, J. L., Muhe, R., Puteanus, D., and Binard, N., 1991, Submarine intraplate volcanism in the South Pacific: Geological setting of the Society and Austral regions,J. Geophys. Res. 96, 2109–2138.
Hekinian, R., Bideau, D., Cannat, M., Francheteau, J., and Hébert, R., 1992, Volcanic activity and crust-mantle exposure in the ultrafast Garrett transform fault near 13°28′ S in the Pacific,Earth Planet, Sci. Lett. 108, 259–275.
Hekinian, R., Bideau, D., Hébert, R., and Niu, Y., 1994, Magmatism in the Garrett Transform Fault,J. Geophys. Res. (in press).
Johnson, K. T. M., Dick, H. J. B., and Shimizu, N., 1990, Melting in oceanic upper mantle: anion microprobe study of diaprides in abyssal peridotites,J. Geophys. Res. 95(B3), 2661–2678.
Langmuir C. H., Vocke, R. D., Jr., Hanson, G. N., and Hart, S. R., 1978, A general mixing equation with applications to Icelandic basalts,Earth Planet. Sci. Let. 37, 380–392.
Mahoney, J. J., Sinton, J. M., Kurz, M. D., Macdougall, J. J., Spencer, K. J., and Lugmair, G. W., 1994, Isotope and trace element characteristics of super-fast spreading ridge: East Pacific Rise, 13°23′ S,Earth Planet. Sci. Lett.,121, 173–193.
Maia, M. and Diament, M., 1991, An analysis of the altimetric geoid in various wavebands in the Central-Pacific Ocean: constraints on the origin of intraplate features,Tectonophysics 190, 133–153.
Mammerickx, J., Anderson, R. N., Menard, H. W., and Smith, S. M., 1975, Morphology and tectonic evolution of the East-Central Pacific,Geol. Soc. Amer. Bull. 86, 111–118.
Menard, H. W., Chase, T. E., and Smith, S. M., 1964, Galapagos Rise in the Southeastern Pacific,Deep-Sea Res. 11, 232–242.
Moore, J. G., 1966, Rate of palagonitization of submarine basalt adjacent to Hawaii,U.S. Geol. Surv. Prof. Pap. 550D, 163–171.
Morgan, W. J., 1972, Deep mantle convection plumes and plate motions,Amer. Ass. Petrol. Geol. Bull. 56, 203–213.
Naar, D. F. and Hey, R. N., 1986, East Rift propagation along the East Pacific Rise near Easter Island,J. Geophys. Res. 91, 3425–3438.
Naar, D. F. and Hey, R. N., 1989, Recent Pacific-Easter-Nazca plate motions, in Evolution of Mid-Ocean Ridges, IUGG, Symposium 8, AGU,Geophysical Monograph 57, 9–30.
Naar, D. F. and Hey, R. N., 1991, Tectonic evolution of the Easter microplate,J. Geophys. Res. 96, 7961–7993.
Okal E. and Casenave, A., 1985, A model for the plate tectonic evolution of the east-central Pacific based on SEASAT investigations,Earth Planet. Sci. Lett. 79, 99–116.
Ottonello, G., 1980, Rare earth abundances and distribution in some spinel peridotite xenoliths from Assab (Ethiopia),Geochim. Cosmochim. Acta. 44, 1885–1901.
Pearce, J. A. and Norry, M. J., 1979, Petrogenetic implication of Ti, Zr, Y, and Nb variations in volcanic rocks,Contr. Mineral. Petrol. 69, 33–47.
Pilger R. H. and Handschumacher, D. W., 1981, The fixed hotspot hypothesis and the origin of the Easter-Sala y Gomez—Nazca trace,Geol. Soc. Am. Bull. 92, 437–446.
Poreda R. J., Schilling, J. G., and Craig, H., 1993, Helium isotope ratios in Easter microplate basalts,Earth Planet. Sci. Lett. 119, 319–329.
Prinzhofer, A., Lewin, E., and Allégre, C. J., 1989, Stochastic implications of melting of the marble-cake mantle. Evidence from local study of the East Pacific Rise at 12°50′ N,Earth Planet. Sci. Lett. 92, 189–206.
Rusby, R. I., 1992, Gloria and other geophysical studies of the tectonic pattern and history of the Easter microplate, southeast Pacific, from Parson, L. M., Murton, B. J., and Browning, P. (eds),Ophiolites and their Modern Oceanic Analogues. Geol. Soc. Spec. Publication60, 81–106.
Rusby, R. I. and Searle, R. C., 1993, Intraplate thrusting near the Easter microplate,Geology 21, 311–314.
Schilling, J.-G., Sigurdsson, H., Davis, A. N., and Hey, R. H., 1985, Easter microplate evolution,Nature 317, 325–331.
Scientific Party, 1993, SO80, Geology of young submarine volcanoes west of Easter Island, South East Pacific,Marine Geology (submitted).
Schnetzler C. C. and Philpotts, J. A., 1970, Partition coefficient of rare-earth elements igneous matrix material and rock forming mineral phenocryst. II,Geochim. Cosmochim. Acta 34, 331–340.
Searle, R. C., Francheteau, J., and Cornaglia, B., 1993, New observations on mid-plate volcanism and the tectonic 22history of the Pacific plate, Tahiti to Easter microplate,Earth Planet Sci. Lett. (in press).
Searle, R. C., Rusby, R. I., Engeln, J., Hey, R. N., Zukin, J., Hunter, P. M., LeBas, T. P., Hoffmann, H.-J., and Livermore, R., 1989, Comprehensive sonar imaging of the Easter microplate,Nature 341, 701–705.
Sinton, J. M., Smaglik, S. M., Mahoney, J. J., and Macdonald, K. C., 1991, Magmatic processes at superfast spreading oceanic ridges: Glass variations along the East Pacific Rise, 13° S–23° S,J. Geophys. Res. 96, 6133–6155.
Stoffers, P.et al., 1989, Geology of Macdonald “hot spot”: Recent submarine eruptions in the South Pacific,Mar. Geophys. Res. 11, 101–112.
Stoffers, P.et al., 1992, Cruise Report SONNE 80a-Midplate III Oceanic Volcanism in the South Pacific,Berichte-Reports, Geol.-Palœont. Inst., Univ. Kiel. 58, 128 pp.
Sun S.-S. and MacDonough, 1989, Chemical and isotopic systematics of oceanic basalts: Implications for mantle compositions and processes, in:Magmatism in the Ocean Basins, eds. Saunder, A. D. and Norry, M. C.,Geol. Soc. Spec. Publication 42, 313–345.
Tarney, J., Wood, D. A., Saunders, A. D., Cann, J. R., and Varet, J., 1980, Nature of mantle heterogeneity in North Atlantic: evidence from deep sea drilling.Phil. Trans. R. Soc. Lond. A297, 179–202.
Thompson, G., Bryan, W. B., and Humphris, S. E., 1989, Axial volcanism on the East Pacific Rise, 10–12 NT, in:Magmatism in the Ocean Basins, eds. Saunders, A. D. and Norry, M. C.,Geol. Soc. Spec. Publication 42, 181–200.
Weaver, J. S. and Langmuir, C. H., 1990, Calculation of phase equilibrium in mineral-melt systems,Comput. Geosci. 16, 1–19.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hekinian, R., Stoffers, P., Akermand, D. et al. Magmatic evolution of the Easter microplate-Crough Seamount region (South East Pacific). Mar Geophys Res 17, 375–397 (1995). https://doi.org/10.1007/BF01227041
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01227041