ORIGINAL PETROLOGY AND TECTONIC SETTING OF META-VOLCANIC ROCKS FROM DAHONGSHAN GROUP, CENTRAL YUNNAN
Xu Qidong (China University of Geosciences, Wuhan 430074)
The meta-volcanic rocks in Dehongshan Group have been subjected to both regionally hydrothermal alteration of sea-water and regional metamorphism, so these rocks were changed in petrographic feature and chemical composition. Studies of immobile elements in the rocks show that these meta-volcanic rocks were tholeiite originally, and have geochemical characteristics of mid-ocean ridge environment,belonging to T-type MORB. The Cu-Fe mineralization of Dahongshan type in the rock group, which was rich in the metallogenic elements from the ocean crust,is in keeping with the original petrology and tectonic setting of these meta-volcanic rocks.