Host-rocks and alteration characters of the Baogutu porphyry copper-molybdenum deposit in Xinjiang, NW China.

The Baogutu porphyry copper-molybdeun in deposit locates in the Darbut magmatic are of the western Junggar. Based on the host rocks, alterations in stock and wall-rocks, and disseminated and network mineralization, together with Cu-Mo-(Au) association, the Baogutu deposit is a porphyry copper-molybdenum deposit. Our research recognized that the Baogutu intrusion is an intermediate porphyry with several lithologies and lithofacies. The host rocks are diorite, porphyaceous (quartz) diorite, (quartz) diorite porphyry, minor granodiorite, related breccias and various dikes. We have recoginized the four lithofacies that are central, principal, and order phases from centre outwards and the related breccias phase which occurs in inner stock and wall-rocks and overprints the earlier other three phases. Disseminated and network mineralization mainly Occurred inner the stock and minor in the outer wall-rocks. Alterations in stock and wall-rocks have overprinting zonation with blurry boundary. The alteration mapping in the Baogutu district shows that the three zones can be broadly distinguished according to the altered mineral assemblages. The concentric alteration zones from the inner Outwards are successively the overprinting zone of the K-silicate zone and the quartz-sericite zone, hornfelsed zone, and the propylitic zone, being similar to the Hollister-type alteration model. Quartz-sericite zone overprints both the K-silicate zone and the hornfelsed zone. The ore bodies mostly occur in the overprinting zones of the K-silicate zone and the quartz-sericite zone, locally Occurs in the hornfelsed zone. Our research suggests that the mineralization and alteration occurred in the Baogutu porphyry Cu-Mo deposit is closely related with the intermediate porphyry in which the deposit occurred.