Postvolcanic alteration and mobilization of uranium in the late jurassic volcanic rocks in northwest of Zhejiang province, China

Calc-alkaline volcanic rocks of Jiande formation in the northwest of Zhejiang Province were formed by four cycles of volcanic acivities and underwent many times of thermal events. There were two types of hydrothermal metasomatic alterations of the rocks in volcanic terrain, one developed in postvolcanic period and another in mineralization period. In the terrain of acid rocks, postvolcanic hydrotermal metasomatic alteration is mainly characterized by albitization and sericitization. It was this post-diagenetic plane type of metasomatic alteration that ought about the mobilization of uranium which originally existed in volcanic rocks in varied forms. Afterwards, the activated uranium was extracted from rocks by flowing hydrothermal solution, and therefore, the uranium concentration in the hydrothermal solution was increasing. In the alteration environment along the rift, the uranium was deposited from the hydrothermal solution