Barite is a barium sulfate with the formula BaSO4.
Barite is often associated with fluorite and Pb-Zn (lead-zinc) mineralisation. Depending on the deposit, fluorite and barite are more or less abundant, and fluorite may even be absent. Like fluorite, most barite deposits occur at the unconformity between the Hercynian crystalline basement and sedimentary cover. The genetic processes involved are the same as for fluorite: brines (water produced by the evaporation of seawater) extracted Ba, transported and deposited barite and sulfides when they met fluids carrying sulfur in the form of sulfate or sulfide (H2S).
(See the model presented in the fluorite poster).
Source of barium, lead and zinc
- Barium, like lead, is mainly derived from potassium feldspars in granites and gneisses of the crystalline basement. These feldspars were altered during the formation of soils in the Permo-Triassic period (260-200 Ma), when, despite low relief, the sea was not present. The relief of the Hercynian mountain ranges had disappeared (Permian erosion), with France being very "flat", like today's Australian continent at that time.
- Zinc is thought to be derived from the alteration of black granite micas (biotites).
Barite has been mined in the following deposits in France:
- Chaillac (2.7 Mt, France's largest deposit),
- Southern Massif Central: Pessens (1.5 Mt), and Lacan (12), Font d'Arques (Albigeois: 34), Rouergue
- Les Porres (83) (1Mt)
- Les Farges (Ussel, 19) (0.5 Mt)
and in the Corbières.