Figure F20. Structural, textural, and mineralogical features of Subunit 4A Cores 205-1253A-4R through 10R described in terms of veins, fractures, magmatic contacts, and voids and proportions of each mineral phenocryst. Core photographs illustrate representative features of Subunit 4A. Blue = medium grained, green = fine grained, yellow = microcrystalline, white = cryptocrystalline. A = aggregates, L = laths. Phenocryst percentage expresses mineral abundance over the full section length. Y = yes, evidence of voids. The number of plus or minus symbols rates the abundance of voids. Subunit 4A is further subdivided into Subunits 4A-1 and 4A-2 (see "General Description" in "Subunit U4A: Gabbro Sill" in "Petrology"). Magnetic polarity is also shown. A. Close-up photograph of veining within upper Subunit 4A-1 (interval 205-1253A-5R-4, 14-25 cm). B. Close-up photograph of the changes in grain size groundmass on a centimeter scale (interval 205-1253A-7R-1, 130-146 cm). 1, 6. Microcrystalline gabbro. 2. Cumulate fine- to medium-grained groundmass. 3. Microcrystalline groundmass. 4. Fine-grained groundmass with 10% pyroxene phenocrysts (1-mm size and subhedral). 5. Microcrystalline to fine-grained groundmass. C. Example of magmatic contact (interval 205-1253A-8R-1, 84-89 cm).

Figure F20. Structural, textural, and mineralogical features of Subunit 4A Cores 205-1253A-4R through 10R described in terms of veins, fractures, magmatic contacts, and voids and proportions of each mineral phenocryst. Core photographs illustrate representative features of Subunit 4A. Blue = medium grained, green = fine grained, yellow = microcrystalline, white = cryptocrystalline. A = aggregates, L = laths. Phenocryst percentage expresses mineral abundance over the full section length. Y = yes, evidence of voids. The number of plus or minus symbols rates the abundance of voids. Subunit 4A is further subdivided into Subunits 4A-1 and 4A-2 (see "General Description" in "Subunit U4A: Gabbro Sill" in "Petrology"). Magnetic polarity is also shown. A. Close-up photograph of veining within upper Subunit 4A-1 (interval 205-1253A-5R-4, 14-25 cm). B. Close-up photograph of the changes in grain size groundmass on a centimeter scale (interval 205-1253A-7R-1, 130-146 cm). 1, 6. Microcrystalline gabbro. 2. Cumulate fine- to medium-grained groundmass. 3. Microcrystalline groundmass. 4. Fine-grained groundmass with 10% pyroxene phenocrysts (1-mm size and subhedral). 5. Microcrystalline to fine-grained groundmass. C. Example of magmatic contact (interval 205-1253A-8R-1, 84-89 cm).