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Papers by Jacques Varet
Contributions to Mineralogy and Petrology, 1969
Bulletin De La Societe Geologique De France, 1966
The trachytes of Mont-Dore and the environs of Menet, in the Cantal [Central Massif of France] ar... more The trachytes of Mont-Dore and the environs of Menet, in the Cantal [Central Massif of France] are described and analyzed, along with their homogeneous inclusions and basement xenoliths. Two petrographic groups are identified within the trachytes; one is undersaturated and is allied to the phonolites, while the other is of the pantellerite type. The discussion of these latter rocks shows that they were derived from a trachytic magma and are sharply distinct from rhyolites.
Bulletin De La Societe Geologique De France, 1976
Bulletin De La Societe Geologique De France, 1976
Contributions to Mineralogy and Petrology, 1971
... The Crystallization of Ti-Rich Clinopyroxenes As shown by Verhoogen (1962) on the basis of th... more ... The Crystallization of Ti-Rich Clinopyroxenes As shown by Verhoogen (1962) on the basis of thermodynamieal considerations, the entry of Ti in clinopyroxenes (mainly in 6-coordination, or y-sites) is favoured by high temperature and dia'ectly controlled by alumininm and silica ...
Journal of Petrology, May 1, 1980
ABSTRACT
HAL (Le Centre pour la Communication Scientifique Directe), 2009
World geomorphological landscapes, 2022
Regional Geology Reviews, 2017
After this comprehensive description of Afar geology, another look at the geodynamic context can ... more After this comprehensive description of Afar geology, another look at the geodynamic context can be proposed. Recalling that Afar appears as a unique place on planet Earth, the following would be good subjects for further investigation: The process of break-up of a continent in an area of triple junction. The way continental drift develops from continental to oceanic rifting. How ridges progress and microplates form, deform and rotate. The pertinence and limits of the mantle plume models.
Chimie et expertise, 2020
Summary The East African Rift system is an exceptional feature on planet earth where plate tecton... more Summary The East African Rift system is an exceptional feature on planet earth where plate tectonics plays in extension within a continent, with hot mantle up-lift and high heat flows allowing for geothermal resources at shallow depth. Whereas the industrial development of geothermal energy is still embryonic, with a spectacular success in Kenya, particularly at Olkaria (600MWe installed), but developing fast thanks to appropriate tools, there is still a lack of appropriation of geothermal development at local level, as elsewhere in the world, where projects answering local needs with variety of usages prevail over large size units serving the electricity needs. The “geothermal village” concept was described in 2004, and several attempts to promote it could not reach a full success, despite the identification of numerous sites where local resource really fits the demand. The present usage is mainly handled artisanally, with geothermal steam condensation to produce water for agro-pas...
The Geology of the Arabian-Nubian Shield, 2021
Contributions to Mineralogy and Petrology, 1969
Bulletin De La Societe Geologique De France, 1966
The trachytes of Mont-Dore and the environs of Menet, in the Cantal [Central Massif of France] ar... more The trachytes of Mont-Dore and the environs of Menet, in the Cantal [Central Massif of France] are described and analyzed, along with their homogeneous inclusions and basement xenoliths. Two petrographic groups are identified within the trachytes; one is undersaturated and is allied to the phonolites, while the other is of the pantellerite type. The discussion of these latter rocks shows that they were derived from a trachytic magma and are sharply distinct from rhyolites.
Bulletin De La Societe Geologique De France, 1976
Bulletin De La Societe Geologique De France, 1976
Contributions to Mineralogy and Petrology, 1971
... The Crystallization of Ti-Rich Clinopyroxenes As shown by Verhoogen (1962) on the basis of th... more ... The Crystallization of Ti-Rich Clinopyroxenes As shown by Verhoogen (1962) on the basis of thermodynamieal considerations, the entry of Ti in clinopyroxenes (mainly in 6-coordination, or y-sites) is favoured by high temperature and dia'ectly controlled by alumininm and silica ...
Journal of Petrology, May 1, 1980
ABSTRACT
HAL (Le Centre pour la Communication Scientifique Directe), 2009
World geomorphological landscapes, 2022
Regional Geology Reviews, 2017
After this comprehensive description of Afar geology, another look at the geodynamic context can ... more After this comprehensive description of Afar geology, another look at the geodynamic context can be proposed. Recalling that Afar appears as a unique place on planet Earth, the following would be good subjects for further investigation: The process of break-up of a continent in an area of triple junction. The way continental drift develops from continental to oceanic rifting. How ridges progress and microplates form, deform and rotate. The pertinence and limits of the mantle plume models.
Chimie et expertise, 2020
Summary The East African Rift system is an exceptional feature on planet earth where plate tecton... more Summary The East African Rift system is an exceptional feature on planet earth where plate tectonics plays in extension within a continent, with hot mantle up-lift and high heat flows allowing for geothermal resources at shallow depth. Whereas the industrial development of geothermal energy is still embryonic, with a spectacular success in Kenya, particularly at Olkaria (600MWe installed), but developing fast thanks to appropriate tools, there is still a lack of appropriation of geothermal development at local level, as elsewhere in the world, where projects answering local needs with variety of usages prevail over large size units serving the electricity needs. The “geothermal village” concept was described in 2004, and several attempts to promote it could not reach a full success, despite the identification of numerous sites where local resource really fits the demand. The present usage is mainly handled artisanally, with geothermal steam condensation to produce water for agro-pas...
The Geology of the Arabian-Nubian Shield, 2021