Identification of a subduction zone component in the Higganum dike, Central Atlantic Magmatic Province: A LA‐ICPMS study of clinopyroxene with implications for flood basalt petrogenesis

Determining the primary compositions of continental flood basalts has proven allusive because of the masking effects of crustal contamination. The Higganum dike (Connecticut, USA) that fed the Talcott basalt of the Central Atlantic Magmatic Province hosts strongly zoned clinopyroxenes. The cores are Mg‐ and Cr‐rich, containing up to 1 wt % Cr2O3. The grains show optical and major, minor, and trace element continua between cores and their mantles and rims, indicating that the cores are early crystallizing phenocrysts, not xenocrysts. Laser ablation inductively coupled plasma mass spectrometry analyses of the cores were used to calculate liquid compositions of the most primitive component in the Higganum system and to make inferences about composition of continental flood basalt parental magmas. The Cr‐rich cores yield calculated liquids with Mg numbers of 63. The high‐Cr contents of these calculated liquids indicate the absence of significant clinoproxene or chromite fractionation. Olivine or orthopyroxene fractionation may have lowered the liquid Mg number but would not have significantly influenced the calculated incompatible trace element patterns. Extended rare earth element diagrams for the most Cr‐rich liquids show enrichment in incompatible elements, similar to arc basalts. Prominent negative Nb anomalies are present as are distinct positive Pb anomalies indicative of the influence of subduction zone fluids in the mantle source. Calculated liquid Ba/La values range from 3 to 30, also suggestive of fluid input. These data indicate that the mantle source experienced subduction zone fluid metasomatism. Subsequent crustal contamination is evident in bulk‐rock Nd and Sr isotopic compositions.

[1]  K. Lodders.  Solar System Abundances of the Elements , 2010, 1010.2746.

[2]  P. Richardson,et al.  A comparison of Eastern North America and Coastal New England magma suites: implications for subcontinental mantle evolution and the broad-terrane hypothesis , 2005 .

[3]  F. Ramos,et al.  Sr isotope disequilibrium in Columbia River flood basalts: Evidence for rapid shallow-level open-system processes , 2005 .

[4]  M. Norman,et al.  Trace-element distribution coefficients for pyroxenes, plagioclase, and olivine in evolved tholeiites from the 1955 eruption of Kilauea Volcano, Hawaiʼi, and petrogenesis of differentiated rift-zone lavas , 2005 .

[5]  H. Palme,et al.  Solar System Abundances of the Elements , 2003 .

[6]  F. Ryerson,et al.  New clinopyroxene-liquid thermobarometers for mafic, evolved, and volatile-bearing lava compositions, with applications to lavas from Tibet and the Snake River Plain, Idaho , 2003 .

[7]  P. Renne,et al.  The Central Atlantic Magmatic Province insights from Fragments of Pangea , 2003 .

[8]  S. Eggins,et al.  Hafnium isotope evidence for ‘conservative’ element mobility during subduction zone processes , 2001 .

[9]  J. Puffer.  Contrasting high field strength element contents of continental flood basalts from plume versus reactivated-arc sources , 2001 .

[10]  J. Baker,et al.  Resolving Crustal and Mantle Contributions to Continental Flood Volcanism, Yemen; Constraints from Mineral Oxygen Isotope Data , 2000 .

[11]  G. Jenner,et al.  Petrologic implications of trace element variation in clinopyroxene megacrysts from the Nograd volcanic province, north Hungary: A study by laser ablation microprobe-inductively coupled plasma-mass spectrometry , 1999 .

[12]  K. Johnson.  Experimental determination of partition coefficients for rare earth and high-field-strength elements between clinopyroxene, garnet, and basaltic melt at high pressures , 1998 .

[13]  J. Dostal,et al.  Geochemical constraints on the origin and evolution of early Mesozoic dikes in Atlantic Canada , 1998 .

[14]  J. Chesley,et al.  Crust–mantle interaction in large igneous provinces: Implications from the Re–Os isotope systematics of the Columbia River flood basalts , 1998 .

[15]  B. Wood,et al.  A predictive model for rare earth element partitioning between clinopyroxene and anhydrous silicate melt , 1997 .

[16]  J. Mahoney,et al.  Large igneous provinces: continental, oceanic, and planetary flood volcanism , 1997 .

[17]  J. G. McHone.  BROAD-TERRANE JURASSIC FLOOD BASALTS ACROSS NORTHEASTERN NORTH AMERICA , 1996 .

[18]  G. Jenner,et al.  Trace element partition coefficients for clinopyroxene and phlogopite in an alkaline lamprophyre from Newfoundland by LAM-ICP-MS , 1996 .

[19]  D. Günther,et al.  Inter-laboratory note. Laser ablation inductively coupled plasma mass spectrometric transient signal data acquisition and analyte concentration calculation , 1996 .

[20]  A. Brandon,et al.  Assessing subcontinental lithospheric mantle sources for basalts: Neogene volcanism in the Pacific Northwest, USA as a test case , 1995 .

[21]  W. Perkins,et al.  Measurements of trace elements in basalts and their phenocrysts by laser probe microanalysis inductively coupled plasma mass spectrometry (LPMA-ICP-MS) , 1995 .

[22]  eds. Rajesh K. Srivastava,et al.  Magmatism in relation to diverse tectonic settings , 1995 .

[23]  T. Wagner,et al.  Experimental and natural partitioning of Th, U, Pb and other trace elements between garnet, clinopyroxene and basaltic melts , 1994 .

[24]  E. Watson,et al.  High-pressure experimental trace-element partitioning between clinopyroxene and basaltic melts , 1994 .

[25]  M. Fisk,et al.  High-field-strength element partitioning between pyroxene and basaltic to dacitic magmas , 1994 .

[26]  C. Hawkesworth,et al.  Isotopic and Geochemical Constraints on the Origin and Evolution of the Columbia River Basalt , 1993 .

[27]  A. Philpotts,et al.  Wallrock Melting and Reaction Effects along the Higganum Diabase Dike in Connecticut: Contamination of a Continental Flood Basalt Feeder , 1993 .

[28]  S. Hart,et al.  Experimental cpx/melt partitioning of 24 trace elements , 1993 .

[29]  W. J. Pegram.  Development of continental lithospheric mantle as reflected in the chemistry of the Mesozoic Appalachian Tholeiites, U.S.A. , 1990 .

[30]  W. McDonough,et al.  Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes , 1989, Geological Society, London, Special Publications.

[31]  K. Cox.  The Karoo Province , 1988 .

[32]  R. Carlson,et al.  Flood Basalt Volcanism in the Northwestern United States , 1988 .

[33]  A. Philpotts,et al.  Differentiation of Mesozoic basalts of the Hartford basin, Connecticut , 1985 .

[34]  Mitsuru Ebihara,et al.  Solar-system abundances of the elements , 1982 .

[35]  W. M. Kaula,et al.  Basaltic volcanism on the terrestrial planets. , 1977 .