Table T1. Coring summary, Leg 197.
Table T2. Operations summary, Leg 197.
Figure F1. Location of Leg 197 sites and previous DSDP and ODP sites on the Emperor Seamounts (solid circles).
Figure F2. A. Preferred viscosity structure used to calculate hotspot motion from Steinberger and O'Connell (1998). A low-viscosity upper mantle is used to reproduce the Hawaiian-Emperor bend. A high-viscosity lower mantle is employed; otherwise, the relative motions between hotspots are greater than observations. Harvard tomographic model S12WM13 was used to infer mantle density heterogeneities. The gradual increase in viscosity was chosen to minimize disagreement with models based on postglacial rebound, which mainly constrain viscosity in the upper half of the mantle. B. The predicted motion of the Hawaiian plume between 90 and 43 Ma after Steinberger (2000). The model predicts a southward component of motion of ~10 mm/yr. This result is from the mantle flow at depth, which also tends to have a southward component of the same magnitude, partly due to a return flow opposite of Pacific plate motion in the model. The model predicts only a small relative motion between the Hawaiian and Louisville hotspots, in accordance with the age progressions observed along the two hotspot tracks. Other models with a lower viscosity in the lower mantle predict substantially higher flow speeds and substantially larger southward motion of the Hawaiian hotspot.
Figure F3. A. Average inclination values for three inclination group models from Detroit Seamount; error bars = 95% confidence intervals. The predicted inclination at 81 Ma based on prior Pacific apparent polar wander path (APWP) poles (Gordon, 1983) is also shown. B. Paleolatitude values with 95% confidence intervals for the inclination groups. The present-day latitude of the Hawaiian hotspot (solid line) is also shown. C. Estimated angular dispersion (S) of the inclination groups (solid line) vs. the predicted values for 45-80 Ma (dark field) and 80-110 Ma (light field) from McFadden et al. (1991). VGP = virtual geomagnetic pole. D. Orthographic projection of the colatitude (primary) for Detroit Seamount (star). The colatitude is distinct at the 99% confidence level (shaded) from previous 81-82 Ma poles (ellipses). Poles are derived from the following: 81 Ma (Gordon, 1983), 82 Ma (Sager and Pringle, 1988), and 33n (79.1-73.6 Ma) (Vasas et al., 1994). The sense of offset between the natural remanent magnetization data and the demagnetized (primary) data is the same as that between the new paleolatitude result and results based on prior Pacific pole positions. This is the expected effect if these previous pole positions are contaminated by secondary magnetizations. This figure is after Tarduno and Cottrell (1997).
Figure F4. Plot of latitudinal distance from the 43-Ma bend in the Hawaiian-Emperor hotspot track vs. age (light circles). Age data are not available for Meiji, Tenchi, and Jimmu Seamounts; their positions, based on a constant latitudinal progression, are shown for reference. Dark circles indicate positions after the difference between the present-day latitude of the 43-Ma bend and Hawaii is subtracted from each of the present-day latitudes of the Emperor Seamounts. In effect, we slide the Emperor trend down the Hawaiian chain so that the bend coincides with the position of Hawaii (inset). This reconstruction allows the following test. If the Emperor Seamounts record mainly motion of the Hawaiian hotspot, paleolatitudes should fall close to this corrected latitudinal trend; if the hotspot has been stationary, the paleolatitudes should fall close to the present-day latitude of Hawaii. Triangles = paleolatitudes of Suiko and Detroit Seamounts, with 95% confidence intervals. The null hypothesis that the paleolatitude result from the Suiko Seamount is drawn from the same population as the Detroit Seamount data can be rejected at the 95% confidence level using nonparametric tests (Kolmogorov-Smirnov). In the absence of a rotation of the entire Earth with respect to the spin axis, known as true polar wander (Tarduno and Cottrell, 1997; Cottrell and Tarduno, 2000b; Tarduno and Smirnov, 2001), the hotspot may have moved continuously southward at a rate of 30-50 mm/yr while the plate also drifted slowly northward (shaded area). This figure is after Tarduno and Cottrell (1997).
Figure F5. A. Estimates of zonal quadrupole Gauss coefficients (g20) relative to the axial dipole (g10), from Livermore et al. (1984). Pacific data are rotated using a fixed hotspot reference frame (see model "B" in Livermore et al., 1984). Our proposed sampling covers the range where Livermore et al. (1984) propose a change in sign of the quadrupole term. B. Paleointensity determined from studies of submarine basaltic glass complied by Juarez et al. (1998). The proposed sampling covers the transition from the Cretaceous Normal Polarity Superchron (K-N) to the Late Cretaceous-Cenozoic mixed polarity interval. VADM = virtual axial dipole moment.
Figure F6. Compositional changes in magmas produced by the Hawaiian hotspot through time. The shaded field shows the range of published 87Sr/86Sr ratios of tholeiitic basalt vs. age and distance along the Hawaiian-Emperor chain. Note that data from Detroit Seamount are significantly less radiogenic than those at younger volcanoes. The circles with crosses connected by the thick dotted line show the trend in age difference between seamounts and the underlying ocean crust (from Keller et al., 2000).
Figure F7. Site 1203 survey 1, line 6, 5-km-long migrated time section. Data are bandpass filtered between 40 and 100 Hz. Hole 1203A is situated at about shotpoint 7780. Trace-to-trace distance = ~18.8 m; vertical exaggeration at the seafloor = ~3:1; bottom of hole = ~4.34 s two-way traveltime.
Figure F8. Summary of Site 1203 basement rocks and biostratigraphic ages with provisional downhole logging data for comparison. TD = total depth.
Figure F9. Close-up photograph showing partially altered glassy lobe margins with calcareous interlobe sediment (interval 197-1203A-41R-2, 0-18 cm).
Figure F10. Photomicrographs in cross-polarized light of zonation in plagioclase (Sample 197-1203A-35R-4, 47-49 cm [Piece 1F]). A. Field of view = 10 mm; photomicrograph 1203A-59. B. Field of view = 2.5 mm; photomicrograph 1203A-60.
Figure F11. Photomicrograph of the olivine-rich zone in Unit 16 (Sample 197-1203A-37R-3, 10-13 cm [Piece 1A]) (cross-polarized light; field of view = 5.5 mm; photomicrograph 1203A-22).
Figure F12. A. Total alkali content (Na2O + K2O) vs. SiO2 classification plot (from Le Bas et al., 1986) for volcanic rocks showing lava compositions from Detroit Seamount. The dashed line is the alkalic-tholeiitic dividing line for Hawaiian basalt. Lavas from Site 884 are tholeiitic basalt, whereas lavas from Site 883 are alkalic basalt, although Keller et al. (1995) inferred that prior to alteration these lavas were transitional between alkalic and tholeiitic basalt. Data for these two Leg 145 sites in this and all subsequent figures are from Keller et al. (2000) and M. Regelous et al. (unpubl. data). Lavas from Site 1203 range from tholeiitic, overlapping with Site 884 lavas, to alkalic, overlapping with Site 883 lavas. Most of the alkalic Site 1203 lavas have loss on ignition (LOI) >2 wt%. The volcaniclastite sample has high total alkalis, which is interpreted as a result of alkali gain during alteration. The two Site 1203 basalt samples in the tholeiitic field at <45% SiO2 are picritic as a result of olivine accumulation. B. Total alkali content (Na2O + K2O) vs. SiO2 comparing Detroit Seamount lava compositions with those from Mauna Kea Volcano (shield and postshield stage lavas-lower and upper shaded areas, respectively) on the island of Hawaii. Site 884 and some Site 1203 lavas overlap with the shield-stage tholeiitic basalt, whereas Site 883 and some Site 1203 lavas overlap with Hawaiian postshield alkalic basalt. The irregular line encloses postshield-stage lava erupted at Mauna Kea Volcano, Hawaii.
Figure F13. Ti/Zr abundance ratio vs. depth for Hole 1203A lavas. The alkalic basalt of Units 23 and 26 near the bottom of the hole have relatively low Ti/Zr ratios. This result contrasts with the classic Hawaiian trend of increasing alkalinity with decreasing eruption age during the transition from shield to postshield-stage volcanism.
Figure F14. Variations of loss on ignition (LOI), CaO, K2O, Na2O, Ba, and Sr with depth. Basaltic units are represented in blue and are labeled. Volcaniclastic units are represented in yellow.
Figure F15. Logging data summary for Hole 1203A. Circles plotted under bulk density, porosity, and P-wave log columns are values from discrete measurements on recovered core samples.
Figure F16. Comparison of FMS images and wireline measurements (electrical resistivity, natural gamma ray, porosity, and density) with the core-derived lithology and logging lithology in basement.
Figure F17. Example of detailed FMS image displaying the transition between basement Units 7 (layered volcaniclastic sediment) and 8 (pillow lava).
Figure F18. Downhole and uphole run of the Goettingen borehole magnetometer. Intensities of the horizontal and vertical field are compared to the sequences of volcaniclastic sediment and lava flows.
Figure F19. Example orthogonal vector plot showing well-defined, stable magnetic behavior recorded by Site 1203 volcaniclastic sediment samples. A. Sample 197-1203A-24R-1, 30-32 cm. B. Sample 197-1203A-38R-2, 77-79 cm. C. Sample 197-1203A-38R-4, 94-96 cm. D. Sample 197-1203A-63R-5, 127-129 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F20. Example orthogonal vector plot showing well-defined, stable magnetic behavior recorded by Site 1203 basalt samples. A. Sample 197-1203A-25R-1, 29-31 cm. B. Sample 197-1203A-26R-1, 75-77 cm. C. Sample 197-1203A-31R-1, 65-67 cm. D. Sample 197-1203A-36R-3, 60-62 cm. E. Sample 197-1203A-37R-3, 113-115 cm. F. Sample 197-1203A-47R-4, 18-20 cm. G. Sample 197-1203A-55R-5, 17-19 cm. H. Sample 197-1203A-59R-4, 124-126 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F21. Histogram of inclination values derived from principal component analyses on alternating-field demagnetization data from Hole 1203A volcaniclastic sediment samples. DI = difference between the inclination of Hawaii and that of Detroit Seamount, Dl = difference in the latitude of Hawaii and the formative paleolatitude of Detroit Seamount.
Figure F22. Histogram of inclination values derived from principal component analyses on Hole 1203A basement basalt. DI = difference between the inclination of Hawaii and that of Detroit Seamount, Dl = difference in the latitude of Hawaii and the formative paleolatitude of Detroit Seamount.
Figure F23. Site 1204 survey 2 line 3, 4-km-long migrated time section. Data are bandpass filtered between 40 and 100 Hz. Hole 883F occurs at about shotpoint 3517, Hole 1204A at shotpoint 3549, and Hole 1204B at shotpoint 3555. Trace-to-trace distance = ~16.5 m; vertical exaggeration at the seafloor = ~3:1; bottom of Hole 1204B = ~4.35 s two-way traveltime.
Figure F24. Photograph showing rotated, broken sediment block overlying a thick interval consisting of a thin, faulted, very finely laminated bed and convoluted laminations, likely indicating slumping. The 2-cm brown beds of silty volcanic material alternate with finely laminated, bioturbated, and burrowed nannofossil chalk (interval 197-1204A-3R-2, 50-69 cm).
Figure F25. Recovery, age, and major lithologic features of basement units from Holes 1204A and 1204B. TD = total depth, G = fresh glass.
Figure F26. Photograph of Unit 1b breccia containing angular fragments of altered glass and vesicular basalt in a carbonate cement (Section 197-1204A-7R-1 [Pieces 5 and 8]).
Figure F27. Photomicrograph showing unaltered olivine and plagioclase laths in a glassy lobe margin (Sample 197-1204B-3R-2, 97-100 cm) (plane-polarized light; field of view = 0.625 mm; photomicrograph 1204B-138).
Figure F28. Photomicrograph showing unaltered olivine and plagioclase laths in glassy lobe margin (Sample 197-1204B-3R-2, 97-100 cm) (cross-polarized light; field of view = 0.625 mm; photomicrograph 1204B-156).
Figure F29. Abundance of Ti vs. Zr showing a near-linear trend for most of the lavas from Detroit Seamount. Basalt from Suiko Seamount defines a similar trend (data from M. Regelous et al., unpubl. data). Site 884 lavas and the two picrites from Site 1203 have the lowest abundances and the alkalic basalt from Site 1203 has the highest abundances of Ti and Zr.
Figure F30. Example orthogonal vector plots showing well-defined, stable magnetic behavior recorded by Hole 1204B basalt samples. A. Sample 197-1204B-2R-2, 14-16 cm. B. Sample 197-1204B-14R-1, 14-16 cm. C. Sample 197-1204B-13R-4, 82-84 cm. D. Sample 197-1204B-17R-2, 104-106 cm. E. Sample 197-1204B-10R-1, 6-9 cm. F. Sample 197-1204B-15R-1, 11-13 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F31. Example orthogonal vector plots showing well-defined, stable magnetic behavior recorded by Hole 1204B diabase samples. A. Sample 197-1204B-7R-3, 139-141 cm. B. Sample 197-1204B-9R-2, 8-10 cm. C. Sample 197-1204B-8R-2, 21-23 cm. D. Sample 197-1204B-10R-4, 40-42 cm. E. Sample 197-1204B-11R-2, 38-40 cm. F. Sample 197-1204B-13R-3, 33-35 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F32. Site 1205 survey 3 line 4, 3-km-long, frequency wavenumber- or fk-migrated time section. Data are bandpass filtered between 60 and 150 Hz. Hole 1205A is at approximately shotpoint 4216. Trace-to-trace distance = ~9.9 m; vertical exaggeration at the seafloor = ~7:1; bottom of Hole 1205 = ~4.35 s two-way traveltime.
Figure F33. Photograph of conglomerate overlying basement showing clasts of hawaiite up to 8 cm in diameter embedded in a poorly sorted, fossiliferous sandy matrix (interval 197-1205A-5R-2, 9-25 cm).
Figure F34. Recovery, thickness, chemical composition, and major lithologic features of Hole 1205A basement units. TD = total depth.
Figure F35. Photomicrograph showing strain bands in trachytic texture in Unit 3b (Sample 197-1205A-10R-2, 73-75 cm) (cross-polarized light; field of view = 5 mm; photomicrograph 1205A-202).
Figure F36. Total alkali content (Na2O + K2O) vs. SiO2 classification plot for lava flows from Nintoku Seamount. The solid diagonal line is the alkalic-tholeiitic dividing line for Hawaiian basalt. Only two Site 1205 lava units (18b and 19b) are composed of tholeiitic basalt. All other flow units at Site 1205 and nearby DSDP Site 432 (M. Regelous et al., unpubl. data) are alkalic basalt. At both sites, conglomerates overlying igneous basement contain hawaiite clasts that are distinguished by their high total alkali (>6 wt%) and relatively high SiO2 content. Data for Suiko Seamount (Site 433), which is dominantly tholeiitic basalt (M. Regelous et al., unpubl. data), are shown for comparison.
Figure F37. Abundance of Y and Zr/Y vs. Zr content. In the Zr-Y panel the trends for East Pacific Rise (EPR) MORB (data from J.M. Sinton, pers. comm., 1998), three Hawaiian shields, and Suiko Seamount define a fan-shaped array of lines, but the trend for lavas from Nintoku Seamount crosscuts the trends for Suiko Seamount and the Hawaiian volcanoes. The Zr/Y-Zr panel shows that lavas from Nintoku Seamount display a wider range in Zr/Y than EPR MORB and Mauna Kea shield lavas. HSDP = Hawaiian Scientific Drilling Project.
Figure F38. Examples of Lowrie-Fuller tests (Lowrie and Fuller, 1971) conducted on Site 1205 basalt samples. ARM = anhysteretic remanent magnetization, SIRM = saturation isothermal remanent magnetization, AF = alternating field, SD = single domain, MD = multidomain. A. Sample 197-1205A-14R-2, 16-18 cm. B. Sample 197-1205A-19R-4, 143-145 cm. C. Sample 197-1205A-24R-2, 141-143 cm. D. Sample 197-1205A-27R-4, 44-46 cm. E. Sample 197-1205A-29R-3, 114-116 cm. F. Sample 197-1205A-35R-2, 36-38 cm.
Figure F39. Examples of isothermal remanent magnetization (IRM) acquisition and demagnetization (backfield IRM) used to calculate coercivity of remanence from Hole 1205A basalt samples. SD = single domain, MD = multidomain. A. Sample 197-1205A-14R-2, 16-18 cm. B. Sample 197-1205A-19R-4, 143-145 cm. C. Sample 197-1205A-24R-2, 141-143 cm. D. Sample 197-1205A-27R-4, 44-46 cm. E. Sample 197-1205A-29R-3, 114-116 cm. F. Sample 197-1205A-35R-2, 36-38 cm.
Figure F40. Example orthogonal vector plot showing well-defined, stable magnetic behavior recorded by Site 1205 basalt samples. A. Sample 197-1205A-13R-2, 39-41 cm. B. Sample 197-1205A-25R-2, 17-19 cm. C. Sample 197-1205A-26R-1, 117-119 cm. D. Sample 197-1205A-28R-3, 4-6 cm. E. Sample 197-1205A-29R-4, 126-128 cm. F. Sample 197-1205A-44R-1, 68-70 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F41. Histogram of inclination values derived from principal component analyses on Site 1205 lava flows compared to a synthetic Fisher distribution (Fisher, 1953) having the same precision parameter (k) as the experimental data.
Figure F42. Site 1206 survey 4 line 6, 2.5-km-long, finite-difference migrated time section. Data are bandpass filtered between 45 and 120 Hz. Hole 1206A is at approximately shotpoint 4947. Trace-to-trace distance = ~13 m; vertical exaggeration at the seafloor = ~4.25:1; bottom of Hole 1206A = ~2.25 s two-way traveltime.
Figure F43. Diagram summarizing the recovery, thickness, chemical composition, and major lithologic features of Hole 1206A basement units. TD = total depth.
Figure F44. Photomicrograph of Unit 6 euhedral olivine with unaltered interior and rims altered to iddingsite and green clay (Sample 197-1206A-18R-1, 49-51 cm [Piece 4]). A. Plane-polarized light; field of view = 0.625 mm; photomicrograph 1206A-358. B. Cross-polarized light; field of view = 0.625 mm; photomicrograph 1206A-359.
Figure F45. Total alkali content (Na2O + K2O) vs. SiO2 classification plot for basaltic lava flows from Koko Seamount. Data from Nintoku and Suiko Seamounts are shown for comparison. The solid diagonal line is the alkalic-tholeiitic dividing line for Hawaiian basalt. Only three Site 1206 samples plot in the alkalic basalt field.
Figure F46. Abundances of Na2O, K2O, TiO2, CaO, Al2O3, and Zr vs. MgO content for lavas from Koko, Nintoku, and Suiko Seamounts. All trends show an inverse correlation except for CaO in Nintoku Seamount lavas with <5 wt% MgO. Note that some lavas from Suiko Seamount contain up to 30 wt% MgO.
Figure F47. Examples of Lowrie-Fuller tests (Lowrie and Fuller, 1971) conducted on Site 1206 lava flow samples. ARM = anhysteretic remanent magnetization, SIRM = saturation isothermal remanent magnetization, AF = alternating field. A. Sample 197-1206A-3R-2, 99-101 cm. B. Sample 197-1206A-4R-5, 55-57 cm. C. Sample 197-1206A-9R-2, 29-31 cm. D. Sample 197-1206A-16R-5, 75-77 cm. E. Sample 197-1206A-22R-1, 117-119 cm. F. Sample 197-1206A-28R-1, 97-99 cm.
Figure F48. Examples of isothermal remanent magnetization (IRM) acquisition and demagnetization (backfield IRM) used to calculate coercivity of remanence from Hole 1206A lava flow samples. A. Sample 197-1206A-3R-2, 99-101 cm. B. Sample 197-1206A-4R-5, 55-57 cm. C. Sample 197-1206A-9R-2, 29-31 cm. D. Sample 197-1206A-16R-5, 75-77 cm. E. Sample 197-1206A-22R-1, 117-119 cm. F. Sample 197-1206A-28R-1, 97-99 cm. DC = direct current.
Figure F49. Example orthogonal vector plot showing well-defined, stable magnetic behavior recorded by Site 1206 basalt samples. A. Sample 197-1206A-3R-4, 59-61 cm. B. Sample 197-1206A-7R-4, 64-66 cm. C. Sample 197-1206A-16R-1, 33-35 cm. D. Sample 197-1206A-18R-2, 17-19 cm. E. Sample 197-1206A-20R-2, 85-87 cm. F. Sample 197-1206A-23R-1, 109-111 cm. Open squares = vertical projection of magnetization, solid circles = horizontal projection of magnetization.
Figure F50. Histogram of inclination values derived from principal component analyses of Site 1206 lava flows compared to a synthetic Fisher distribution (Fisher, 1953) having the same precision parameter (k) as the experimental data.
Figure F51. Red-brown soil containing planar laminations (interval 197-1205A-26R-3, 92-111 cm).
Figure F52. Well-formed zeolites recovered at Nintoku Seamount Site 1205 (Section 197-1205A-36R-2, 104 cm).
Figure F53. Well-defined dipping veins showing sinusoidal pattern in the DMT image of Site 1203 basalt.
Figure F54. Example of fractures and veins seen in FMS images.
Figure F55. History of rotation about the vertical axis for the magnetometer tool during the downhole and uphole run at Site 1203. BOP = bottom of pipe.
Figure F56. Schematic drawing (not to scale) showing the inferred volcanic environments for the volcanic sections drilled at Detroit (Sites 1203 and 1204), Nintoku (Site 1205), and Koko (Site 1206) Seamounts during Leg 197. The Detroit lava flows at Site 1204 and the lower part of the Site 1203 section were subaerially erupted (although shown as a submerged sequence following posteruption subsidence). The lava flows and associated tephra fall deposits in the upper part of the Site 1203 section were emplaced into a low-energy shallow-marine environment. The Site 1205 lavas were entirely subaerial, as indicated by numerous soil horizons between flows. The Site 1206 section at Koko Seamount consists of lava flows that have flowed from land into water in a nearshore environment. Subscript "A" indicates subaerial lava emplacement.
Figure F57. Total alkalis (Na2O + K2O) vs. SiO2 content showing shipboard Leg 197 data for lavas recovered from basement penetrations of Detroit, Nintoku, and Koko Seamounts. All samples are basalt except for the two hawaiite clasts from Nintoku Seamount that occur in a conglomerate overlying the basement. The alkalic-tholeiitic dividing line for Hawaiian basalt is from Macdonald and Katsura (1964). Fields for alkalic and tholeiitic basalt recovered from the shield of Mauna Kea volcano by the Hawaiian Scientific Drilling Project (data from Rhodes, 1996; Vollinger and Rhodes, unpubl. data) are shown for comparison. All data are given on a volatile-free basis with 90% of the iron as Fe2+.
Figure F58. A. Ti/Zr and alkalinity vs. depth in basement for basalt from Detroit Seamount (Site 1203), Nintoku Seamount (Site 1205), and Koko Guyot (Site 1206). Alkalinity is a measure of the deviation from the tholeiitic-alkalic dividing line in Figure F59; positive values indicate alkalic basalt (solid symbols) and negative values indicate tholeiitic basalt (open symbols). At Detroit Seamount, dominantly alkalic basalt, some with an anomalously low Ti/Zr = ~60, are overlain by tholeiitic basalt with Ti/Zr = ~100, only slightly less than the primitive mantle estimate. This stratigraphic sequence of basalt types is not expected during the late shield and postshield growth stages of Hawaiian volcanoes (Clague and Dalrymple, 1987). B. At Nintoku Seamount the lavas are dominantly alkalic basalt with two flows of intercalated tholeiitic basalt at ~200 m in the basement. This sequence of basalt types is similar to that of the postshield stage at Mauna Kea Volcano (Frey et. al., 1990, 1991). In contrast, at Koko Guyot, the lavas are dominantly tholeiitic basalt with a few intercalated lavas of alkalic basalt. This sequence is similar to the late shield stage growth of Mauna Kea Volcano that were recovered by the Hawaiian Scientific Drilling Project (Rhodes, 1996; Yang et al., 1996).
Figure F59. Photomicrograph of Unit 1 olivine phenocryst with chrome spinel inclusion (Sample 197-1206A-4R-3, 72-74 cm [Piece 4A]) (cross-polarized light; field of view = 5 mm; photomicrograph 1206A-304).
Figure F60. Photomicrograph of melt inclusions in plagioclase phenocrysts from a glassy lobe margin in Unit 3 (Sample 197-1203A-19R-2, 24-26 cm [Piece 3]) (plane-polarized light; field of view = 1.25 mm; photomicrograph 1203A-55).
Figure F61. Reflected-light photomicrograph of titanomagnetite (gray-brown) showing variable degrees of replacement by maghemite (light gray-blue) in the Site 1204 basement sequence (Sample 197-1204A-9R-2, 50-51 cm) (field of view = 0.25 mm; photomicrograph 1204A-125).
Figure F62. Complex vein filling (interval 197-1203A-36R-2, 116-135 cm).
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