Dear Gholamreza: magnesite formation in serpentinized peridotites is very common in the ophiolites of the Caribbean Coast Range and Margarita Island, and elsewhere in northern Venezuela. This is caused by the circulation of CO2 rich ground waters inside the fractures and joints in the serpentinite. Usually the magnesite is associated with white to orange opal nodules. Sometimes, the mineral is abundant and can be mined, such as happened decades ago at Loma de Guerra, in Margarita Island. Regards, Sebastián.
There is a large Magnesite deposit in Tuscany, originated from mantle degassing CO2 circulating in large fractures in Serpentinite. The Magnesite was quarried and mined from 1915 to approx. 1945. A rare cubic phase of Quartz (Melanoflogite) is present in the cavities in such large Magnesite lodes.
Here is a recent paper (free access) of this Magnesite ore:
Article Tectonically driven carbonation of serpentinite by mantle CO...
Tectonically driven carbonation of serpentinite by mantle CO2: Genesis of the Castiglioncello magnesite deposit in the Ligurian ophiolite of central Tuscany (Italy) - ScienceDirect
See E09 – Sparry magnesite in BCGS_MP-86 file on the web.
British Columbia deposit profiles are so far the best source for mineral deposit description data available on line. Concise and informative, just perfect.
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