Figure F17. Photomicrographs showing titanomagnetite morphologies. A. Alteration of titanomagnetite to maghemite along cleavage planes and around rims in the weathered flow top of Unit 10 (Sample 197-1205A-24R-2 [Piece 19, 124-130 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-286). B. Alteration of titanomagnetite to maghemite in tholeiitic Subunit 19b (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-268). C. Alteration of titanomagnetite to maghemite in tholeiitic Subunit 19b (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-280). D. Typical titanomagnetite morphologies in the alkali basalt from Unit 20 (Sample 197-1205A-36R-5 [Piece 2D, 50-51 cm]) (reflected light; field of view = 1.25 mm; photomicrograph 1205A-283). E, F. Typical titanomagnetite morphologies in the alkali basalt (reflected light; field of view = 1.25 mm) (E) Unit 20 (Sample 197-1205A-44R-1 [Piece 5A, 87-88 cm]) (photomicrograph 1205A-284); (F) Subunit 19b (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (photomicrograph 1205A-281). G. Typical titanomagnetite morphologies in the alkali basalt of Subunit 19b (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (reflected light; field of view = 1.25 mm; photomicrograph 1205A-282). H. Lithologic Unit V conglomerate immediately above basement. Development of goethite in a hawaiite cobble; note that titanomagnetite is relatively unaltered (Sample 197-1205A-5R-2 [Piece 21, 101-103 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-182). I. Lithologic Unit V conglomerate immediately above basement. Distinctive morphology of groundmass titanomagnetite in the hawaiite cobbles; such dendritic forms are present in distinct zones that may be parallel or transverse to the plagioclase laths that define the trachytic texture (Sample 197-1205A-5R-2 [Piece 21, 101-103 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-287). J. Bireflectance of ilmenite and highlighting the development of ilmenite oxidation lamellae in titanomagnetite from Subunit 3b. Ilmenite oxidation lamellae are illuminated (Sample 197-1205A-13R-3, 27-29 cm) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-226). K. Bireflectance of ilmenite and highlighting the development of ilmenite oxidation lamellae in titanomagnetite from Subunit 3b. After rotating the stage 90, the ilmenite oxidation lamellae are not illuminated (Sample 197-1205A-13R-3, 27-29 cm) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-227). L. Ilmenite oxidation not restricted to lamellae in Unit 27. Ilmenite is illuminated (Sample 197-1205A-43R-2 [Piece 2A, 58-60 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-252). M. Ilmenite oxidation not restricted to lamellae in Unit 27. After rotating the stage 90, ilmenite is not illuminated (Sample 197-1205A-43R-2 [Piece 2A, 58-60 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-253). N. Early stages of maghemite (bright blue-gray) replacement of titanomagnetite (dull pink-gray) in the Site 1205 basement lava units: maghemite development along titanomagnetite cleavage planes in Subunit 12b (Sample 197-1205A-27R-5 [Piece 5, 103-105 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-224). O, P. Early stages of maghemite (bright blue-gray) replacement of titanomagnetite (dull pink-gray) in the Site 1205 basement lava units (reflected light; field of view = 0.25 mm): (O)maghemite development around the rim of and along a fracture in titanomagnetite in Subunit 26a; ilmenite oxidation lamellae are also evident (Sample 197-1205A-41R-5 [Piece 1A, 24-26 cm]) (photomicrograph 1205A-267). (P) maghemite development along titanomagnetite cleavage planes in Unit 27; one titanomagnetite crystal is unaltered (Sample 197-1205A-43R-2, 58-60 cm) (photomicrograph 1205A-254). Q. Early stages of maghemite (bright blue-gray) replacement of titanomagnetite (dull pink-gray) in the Site 1205 basement lava units: maghemite development along titanomagnetite cleavage planes and fractures in Subunit 30b; note that several crystals are unaltered (Sample 197-1205A-45R-1, 126-128 cm) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-265). R. Titanomagnetite inclusions in olivine from alkali basalt compared with groundmass titanomagnetite: two inclusions (arrows) in an olivine phenocryst in Subunit 3b (Sample 197-1205A-8R-1 [Piece 4, 59-61 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-192). S. Titanomagnetite inclusions in olivine from alkali basalt compared with groundmass titanomagnetite: four small inclusions (arrows) in a groundmass olivine crystal from Unit 20; note that the groundmass titanomagnetite exhibits extensive development of ilmenite oxidation lamellae (Sample 197-1205A-36R-5 [Piece 2D, 50-51 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205A-250). T. Opaque inclusions in olivine phenocrysts from tholeiitic basalt Subunit 19b. Olivine is completely altered and two Cr spinel inclusions have been completely replaced by titanomagnetite (pink-gray). One unaltered Cr spinel inclusion remains (dull blue-gray) (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (reflected light; field of view = 0.25 mm; photomicrograph 1205-288). U, V. Cr spinel in tholeiitic basalt Subunit 19b with rims of titanomagnetite after reacting with the magma (Sample 197-1205A-35R-4 [Piece 1C, 77-79 cm]) (reflected light; field of view = 0.25 mm): (U) photomicrograph 1205A-248; (V) photomicrograph 1205A-270. Click on letter or image for enlargement.