Figure F18. Photomicrographs of Sample 335-1256D-Run11-EXJB (Thin Section 13). Plag = plagioclase. A. Overview of a diorite patch in a fine-grained granoblastic aphyric basalt (cross-polarized light). An offshoot of the diorite crosscuts the granoblastic basalt, demonstrating that the diorite is intrusive. B. Subhedral amphibole (Amph) grows around clinopyroxene (Cpx). Clean, sharp grain boundaries between the amphibole and clinpyroxene indicate that the amphibole is of primary magmatic origin. C. Subhedral to euhedral zircon (Zrc).
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