Sites

Characterization

Minerals/

microstructures

Samples

Vesicular basanite

Mermoz-sacré cœur

Healthy and little altered basanite with microlitic porphyry texture composed of plagioclase, olivine and pyroxene. Plagioclases are in microlites and phenocrysts embedded in a mesostasis. The olivines, less abundant than the plagioclases, are in the form of phenocrysts and microcrysts generally enclosed by plagioclase microlites and surrounded by a crown of iddingsite synonymous with alteration. Pyroxenes are in the form of very small crystals between the plagioclase microlites. The rock also contains opaque minerals with a vesicular aspect.

Plagioclases+++++

Olivine+++

Pyroxenes++

Opaque minerals+

-vacuoles

-microfractures

Polarized light Natural light

Olivine (Ol)-Plagioclase (Pl)-Opaque minerals (O)-Vacuole (Vac)

Vesicular altered basanite

Fann-PE

Healthy basanite with microlithic to porphyritic texture. The plagioclases are colorless in natural light but with vivid staining in polarized light. They occur in large laths and show well visible polysynthetic macles. The plagioclase crystals show the beginning of a detectable alteration. The olivines are in the form of iddingsitised phenocrysts. Pyroxenes of clinopyroxene type are of variable size. The rock contains opaque minerals with a vacuolar aspect.

Plagioclases+++++

Olivine+++

Pyroxenes++

Opaque minerals +

-vacuoles

-microfractures

Polarized light Natural light

Olivine(Ol)-Plagioclase(Pl)-Pyroxene(Px)-Opaque minerals (O)-Vacuole (Vac)

Healthy basanite

Ngor

Basanite has a porphyritic texture. Plagioclase occurs as large laths with prominent polysynthetic macles. The olivines are in the form of phenocrysts and microcrysts surrounded by a crown of iddingsite synonymous with alteration. The phenocrysts show cracks that are sources of fluid passage. These fluids are at the alteration of the mineral. Pyroxenes are of variable size and are caught between the plagioclase laths. The rock also contains opaque minerals

Plagioclases+++++

Olivine+++

Pyroxenes++

Opaque minerals+

-macles

-microfractures

Polarized light Natural light

Olivine (Ol)-Plagioclase (Pl)-Pyroxene (Px)-Opaque minerals (O)-Vacuole (Vac)

Healthy basanite

Ouakam- mamelles

Poorly altered basanite with a porphyritic texture. Plagioclase is very present in large laths and shows well visible polysynthetic macles. Iddingsitized olivine is present as phenocrysts and microcrysts. The rock also contains opaque minerals and micrometric to millimetric vacuoles.

Plagioclases++++

Olivine++

Pyroxenes+

Opaque minerals

-macles

-microfractures

-vacuoles

Polarized light Natural light

Olivine (Ol)-Plagioclase (Pl)-Pyroxene (Px)-Opaque minerals (O)-Vacuole (Vac)