Vesicles in basalts, Newer Volcanics

This page documents some of the features recorded related to vesicle accumulation and flow as vesicle aggregates, exposed in pavement stones in the city of Melbourne. Key features are:

1. Pipes: simple and composite

2. Layers: irregular surfaces and gradient in vesicle sizes

3. Vesicles in fractures and in breccias

4. Drainage pipes

5. Complex features, including vesicular dykes

1. Pipes: simple and composite, longitudinal and orthogonal sections


Figure 1a) Numerous, closely spaced, vesicular circles: orthogonal sections to pipes.	Figure 1b) Pipes in sections close to parallel to their length.


Figure 1c) Circular cross sections of pipes.	Figure 1d) Detail.	Figure 1e) Dome of vesicle-rich magma.

Figure 1f) Complex cross sections of pipes comprising two magmas, one vesicular, the other not.	Figure 1g) Same as (1f).	Figure 1h) Very subtle, complex pipe forming an elliptic pipe, the left half of which is hardly visible.

Figure 1i) Yin and Yang pipe.	Figure 1j) Complex pipe on the left, but not elliptical like most others, but irregular in form.	Figure 1k) Starting plume from a trail of vesicles.

Figure 1l) Composite pipes.	Figure 1m) Composite pipes with internal complexity.	Figure 1n) Composite pipe.

Figure 1o) Longitudinal section of pipe marked only by concentration of vesicles at margins.	Figure 1p) Different sections.	Figure 1q) CAUTION: Some features may look like pipes in 2D but they are planar dyke-like features.

2. Layers: irregular surfaces and gradient in vesicle sizes


Figure 2a) Irregular contact between a vesicle-rich and vesicle-poor basalt.	Figure 2b) Notice vesicle diameter increase upwards towards the contact with vesicle-poor basalt.

Figure 2c) Irregular contact between a vesicle-rich and vesicle-poor basalt.	Figure 2d) Notice vesicle diameter increase upwards towards the contact with vesicle-poor basalt.

3. Vesicles in fractures and in breccias


Figure 3a) Thin vesicle-rich bands defining angular blocks (90 degree angles) of vesicle-poor basalt.	Figure 3b) Angular blocks of vesicle-poor basalt separated by vesicle-rich bands .

Figure 3c) Breccia formed by vesicle-poor basalt and vesicle-rich matrix (black stains are wet areas).	Figure 3d) Breccia formed by vesicle-poor basalt and vesicle-rich matrix (black stains are wet areas).

Figure 3e) Breccia formed by vesicle-poor basalt and vesicle-rich matrix(black stains are wet areas).	Figure 3f) Fractures forming a conjugate set (?) (marked as two black lines).

4. Drainage pipes


Figure 4a) Vesicle-rich pipe linked with a wider region, possibly a layer.	Figure 4b) On the right-hand-side there is a layer of bubbly-basalt (vertical on photograph). This is linked with an irregular network of interconnected narrow bands of bubbly basalt that trends horizontally on photo. The bands widen from left to right, and the bands merge leftwards.

Figure 4c) On the right-hand-side there is a layer of bubbly-basalt (vertical on photograph). This is linked with an irregular network of interconnected narrow bands of bubbly basalt that trends horizontally on photo. The bands widen from left to right, and the bands merge leftwards.).	Figure 4d) Same pattern.

Figure 4e) Detail of features above.

5. Complex features including vesicular dykes


Figure 5a) Merging of planar (2D)? vesicle-rich zones.	Figure 5b) Irregular vesicle-rich band, in both width and orientation.

Figure 5c) .	Figure 5d) .

Figure 5e) Splitting of a single central, wide band into two narrower bands. This is similar to the splitting of a dyke and suggests that these are planar features rather than pipes.	Figure 5f) Divergence or the splitting of a wide vesicle-rich band into two, akin to the splitting of a dyke tip.

Figure 5g) Complex features including a narrow fracture marked by two arrow heads in the high resolution version (double click on photograph). .	Figure 5h) Complex features.