Basalt Basalt is a mafic extrusive rock, is the most widespread of all igneous rocks, and comprises more than 90% of all volcanic rocks. (1977), Rhodes and Hubbard (1973) and These samples are all very vesicular; up to 30% (figures 1, 2, 7, 9, 10). GLASSY TEXTURE The vesicle size varies across the sample (4-8 mm), but the grain size of the minerals doesn’t vary. The top of a lava flow is made up of a highly vesicular, rubbly material known as scoria. Lunar Sample 15016 is a highly-vesicular, olivine­ normative, basalt with a major element composition similar to that of non-vesicular basalt 15555 (figure 1). 15556 is a very vesicular, olivine-normative mare basalt. • Petrophysical behavior is strongly dependent on degree of oxidation & alteration. The variation among such rocks is continuous, so any distinction among categories is arbitrary. Most igneous rocks have a crystalline texture, but some are clastic, vesicular, frothy, or glassy. Because of its relatively low silica content, basalt lava has a comparatively low viscosity, and forms thin flows that can travel long distances. Vesicular olivine basalt from La Palma (green phenocrysts are olivine). samples (basalts) exposed (Swann et al. Due to low trace element content they grouped 71037 with “Type B Apollo 17 basalts”. A vesicle is a small cavity in a volcanic rock that was formed by the expansion of a bubble of gas that was trapped inside the lava. Vesicular basalt is a dark-colored volcanic rock that contains many small holes, more properly known as vesicles. Volcanic rocks are named according to both their chemical composition and texture. high-Ti basalt. These voids are the relics of gas bubbles that were present in lava during solidification of the rock. Scoria has more holes and may be black or red in color. High and low titanium basalts. The sample is ~3.4 b.y. McGee et al. Introduction . 923.7. grams . The texture is described as “plagioclase-poikilitic” (Neal and Taylor 1993). High-Ti and Low-Ti basalts have been distinguished in the Paraná and Etendeka traps a nd the Emeishan Traps.. Mid-ocean ridge basalt (MORB) is a tholeiitic basalt commonly erupted only at ocean ridges and is characteristically low in incompatible elements • Two main groups of Basalts; amygdaloidal and vesicular basalts. The term scoria is used for a highly vesicular basalt which is more vesicle and less rock (and so quite lightweight, low density), while vesicular basalt is often used for a sample that is more dense with a smaller fraction of vesicles than rock. Vesicular basalt (3.1 cm across at its widest) Igneous rocks form by the cooling & crystallization of hot, molten rock (magma & lava). • Vesicular basalt is rich in calcic-plagioclase, augite, olivine and amygdales. Petrography . It is typically dark color, such as dark brown, black or purplish red. Vesicular Olivine-normative Basalt . 1971). If this happens deep underground, they are intrusive igneous rocks. Cube is 1 inch. If this happens at or near the land surface, or on the seafloor, they are extrusive igneous rocks. Vesicular basalt is a mafic volcanic rock characterized by several exterior and internal cavities. Vugs extend up to 12 mm. Composition Most Common Minerals Rock Name; felsic: glass (may contain a few minerals typical of felsic rocks) pumice: mafic: glass (may contain a few mineral typical of mafic rocks) scoria: Note: Basalt with fewer holes, known as vesicles, is called vesicular basalt. Scoria is vesicular and dark colored igneous rock that have or have not contain any crystals. Figure 1: Photograph of vesicular basalt 15016. The petrophysical behaviour & petrographical descriptions of amygdaloidal basalt. NASA# S71-46632. Basalt rocks are in some cases classified after their titanium (Ti) content in High-Ti and Low-Ti varieties. 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