Sur l'origine des faciès de cargneules et de brèches rencontrées dans une coupe du Trias de la Vésubie, Alpes-Maritimes, France

A logged section of mostly Mushelkalk limestones (Middle Trias) in the Vesubie Valley is described. Cargneule a yellow-brown dedo-lomite, is superimposed on Triassic and possible tectonic breccias. In one locality cargneule appears to have formed along recent tree roots. Comparison with cargneules of the Alpine internal zones suggests that many external zone cargneules also formed by dédolomitisation as a product of recent weathering of gypsum and dolomite.Cette note décrit un profil banc par banc d'une série à dominante calcaire du Trias Moyen de la Haute Vésubie. Dans ce profil, des cargneules brun-jaune de dédolomitisation sont surimposées à des brèches qui pourraient être d'origine Triasique et tectonique. Dans certains cas, la cargneule ne s'est formée qu'autour de racines d'arbres récents. La comparaison avec les cargneules des Alpes internes suggère que beaucoup de cargneules des zones externes ont été également formées par dédolomitisation en produit d'altération météorique récente du gypse et de la dolomite.Richards M.T., Vearncombe J.R. Sur l'origine des faciès de cargneules et de brèches rencontrées dans une coupe du Trias de la Vésubie, Alpes-Maritimes, France. In: Géologie Méditerranéenne. Tome 11, numéro 3, 1984. pp. 283-286

Exploration of the Yandal gold province, Yilgarn Craton, Western Australia

The opening of the Yandal gold province during the 1990s provides a detailed case history of repeated exploration successes. First highlighted in 1992 with the discovery of the Bronzewing gold deposit, the resources of the Yandal gold province grew rapidly through the 1990s with a series of discoveries. By 2000, the gold endowment of the province was 470 tonnes (t), and it was producing 25 t Au p.a. from the Jundee, Bronzewing and Darlot mines. The exploration activities in the deeply weathered and mostly covered Archaean Yandal greenstone belt during this period set the standard for Australian gold exploration in deeply weathered terrains through a twofold approach that involved drilling 100 000 holes, and at the same time making a strong commitment to ore deposit research. Confidence came from an understanding of Archaean gold deposits and the regolith, including the effects of gold dispersion in the weathered zone and the necessity to properly penetrate the Cainozoic cover for effective drill testing. Special emphasis was placed on gold distribution, alteration, lithologies and structural geology, and these soon became the focus of both data collection and drill targeting during the exploration process. Aeromagnetic data provided the platform for interpolation between geologically constrained areas in this province of less than 10% outcrop. Rapid and effective communications and data handling were critical issues for managing large exploration programs involving many geologists in remote areas. © 2012 Australian Commonwealth Scientific and Industrial Research Organisation