Fig. 1. Reconstruction of the Iberia–Newfoundland rift to anomaly M0 (~ 121 Ma), based on the reconstruction of [54]. Onset of oceanic crust formation was interpreted to initiate around magnetic anomaly M3 (grey shaded area). Solid circles indicate locations of drill Sites (1276, 1277) during ODP Leg 210. Open circles indicate locations of peridotite highs, which were drilled during previous ODP legs 103, 149 and 173, respectively. Modified from [19].

Fig. 2. (a) Tentative geologic interpretation of the SCREECH 2 seismic reflection profiles [20] and [21]. The rough topography oceanwards of M3 marks apparent slow spreading oceanic basement. ODP Leg 210, Site 1277 cored about 80 to 100 m of apparent in-situ basement, just oceanwards of anomaly M1. (b) Detailed stratigraphy and recovery of Site 1277. The cores from the upper part show a complex assemblage of basalt flows interleaved with sandstones and mass flows containing clasts of mafic rocks and serpentinized peridotite and variably deformed gabbroic rocks. The lower 40 m is made of serpentinized peridotite and minor gabbroic to monzonitic veins.

Fig. 3. Photomicrographs from serpentinized peridotites from ODP Leg 210, Site 1277. All images are taken with crossed polarizers. (a) Serpentinized peridotite mylonite (7R-2, 17–20), cut by undeformed talc-rich veins (1), serpentine veins (2) and calcite veins (3). Note the extremely stretched, altered orthopyroxene (opx) in the centre of the image. (b) spinel and opx porphyroclasts, set in a (serpentinized) mylonitic matrix (7R-2, 17–20). (c) Opx porphyroclast with clinopyroxene (cpx) exsolution lamellae, partially replaced by calcite. Note that ghosts of cpx exsolution lamellae are preserved in calcite (9R-3 119–123). (d) opx porphyroclast, set in a matrix of dynamically recrystallized opx, cpx, spinel and olivine (4R-1, 11–14). (e) opx porphyroclast with coarse exsolution lamellae of cpx, surrounded by partially serpentinized spinel peridotite (ol, spl, opx, cpx) assemblages (4R-1 11–14). (f) Oxide gabbro with coarse cpx, plagioclase and ilmenite phenocrysts, and a finegrained cpx + Ti-hornblende matrix. Note the deformed twin lamellae of large plagioclase, and the undeformed, small neoblasts, indicating dynamic recrystallization (z01). (g) Idiomorphic zircon in small gabbro vein, together with apatite (ap), plagioclase (plg) and twinned Mg-hornblende (hbl) (9R-6, 68–71). (h) mafic igneous vein, with biotite (bt) and plagioclase (plg) (z36).

Fig. 4. (a) Compositional cross section of a small ( 0.25 mm) spinel grain. Cr# and Mg# are homogeneous in the core, but are affected by re-equilibration at the outer  50 μm (4R-1). (b) TiO₂ versus distance to small gabbroic dikes within the Newfoundland spinel harzburgites. Spinel TiO₂ > 0.2 wt.% is only observed within  2 mm from gabbroic veins. In all other samples, including breccias, TiO₂ is below 0.15 wt.%, precluding equilibration within the plagioclase stability field. Error bars indicate 1σ variation of at least 3 measurements on individual grains.

Fig. 5. (a) Cr# versus Mg# of spinels from the conjugated Iberia–Newfoundland rift. Cr# of Newfoundland spinels vary from 0.35 to 0.65. Note that the associated Mg# are generally low, thus precluding substantial low temperature Fe enrichment. Exceptions are related to mm-scale gabbroic veins, and dynamically recrystallized spinel in the matrix of 4R-1. (b) Cr# vs TiO₂ of spinels. Newfoundland spinels have TiO₂ contents below 0.15 wt.%. Spinels with TiO₂ > 0.2 are related to small gabbroic dikes. Note that high TiO₂ contents are found for all ODP sites from the Iberia margin, indicating equilibration in the plagioclase stability field. Shaded fields are from [37] (A), [25] (B), [8] and our unpublished data, (C) spinel peridotites, and (D) plagioclase peridotites. Data from Iberia from [16], [17], [18], [23] and [24].

Fig. 6. Cr# of cpx versus associated spinel in peridotites from the Iberia–Newfoundland rift. Light shaded field (A) are spinel peridotites from the Lena trough [25]. Dark shaded field (B) are spinel and plagioclase peridotites from the Eastern Central Alps ([8] and our unpublished data) (C) is from [26]. All samples from Site 1277 are aligned along the Cr# covariation trend for spinel peridotites, while many samples from Iberia show substantial deviation towards higher Cr# in spinel. This offset results from partial equilibration with plagioclase. Data sources and symbols as in Fig. 5.

Fig. 7. Spatial variability of spinel and clinopyroxene compositions across the Iberia–Newfoundland passive margin, reconstructed to anomaly M1 ( 123 My, after [19]). The samples represent a cross section of approximately 120 km between Site 1277 and Site 1068. (a) Spinel TiO₂ for spinel and plagioclase peridotites (excluding pyroxenites). Numbers indicate spinel analyses with TiO₂ < 0.15, in % of the total spinel analyses from the different peridotite sites (sources of data as in Fig. 5). (b) Calculated degree of melting after [27]: Only samples with coexisting cpx and low Ti spinel (TiO₂ < 0.15 wt.%) are considered. Note that spinels from Iberia indicate that there are remnants of fertile peridotite (e.g. degree of melting < 8% for some samples), while Newfoundland samples all indicate high degrees of melting. (c, d, e) Compositional variability of cpx coexisting with spinel (TiO₂ < 0.15 wt.%); Newfoundland cpx show the lowest Al₂O₃ and Na₂O, and the highest Cr#, indicating the most residual compositions of the Iberia–Newfoundland system.

Locations and petrological characteristics of samples from ODP Leg 210, Site 1277

(1) sb: sedimentary breccia with peridotite components; spm: serpentinized peridotite mylonite; gv: gabbroic veins.

(2) Denotes mineral textures: pc: porphyroclastic; gb: granoblastic.

(3) Sample depth of core 1W can only be estimated [19].

Major element concentrations (wt.%) in spinel from peridotites of ODP Leg 210, Site 1277

Each measurement represents an average of a single grain. Mg# (molar Mg/Mg + Fetot); Cr# (molar Cr/Cr + Al).

Per: spinels from peridotite, brec: spinels from breccias; n: number of analyses; 2σ: standard deviation of the mean.

Fe₂O₃ calculated by stoichiometry (3 cations, 8 charges).

Major element concentrations in olivine and pyroxene from peridotites of ODP Leg 210, Site 1277

Concentrations reported in wt.%; n.a. not analyzed; pc: porphyroclast core; gb: granoblast in mylonitic matrix;

exsol: exsolved from opx; n: number of analyses; 2σ: standard deviation of the mean.