Metallogenesis of 150 similar to 140Ma porphyry-skarn CuMoFe (Au) deposit in Shanyang-zhashui ore concentration area, Qinling

Some CuMo, CuFe (Au) deposit, e. g. Chigou, Xiaohekou, Lengshuigou, Xiaguanfang, Yuanzijie and Xiaguanfang, distribute in the Shanyang-zhashui Paleozoic fore-arc basin of Mid-Qinling, Shaanxi Province. The rocks with the mineralization formed in 150 similar to 140Ma, belong high K calc-alkaline and shoshonite. The source region of the rocks are the mixture of lower crust and mantle, and formed in the extend stage of North China and Yangtze continental collision. Mineralization occurred in the contact zone of the Late Jurassic and Early Cretaceous rocks with Devonian and Carboniferous strata. Mineralization types are main skarn with little porphyry, some deposit with uniform skarn-porphyry metallogenic system. Mineralization combinations are CuMo, CuFe (Au) and Cu. Hydrothermal alterations in exocontact zone are skarnization and hornfielsization, while the alterations of endocontact occurred in rocks are silicification, potassic, sericitization, chloritization and argillation, the endoskarn is not well developed. Minerals in skarn are garnet, diopside, epidote and actionlite, etc. Garnets are main andradite and grossularite, diopsides are the main component of pyroxene. The early skarnization stage is featured by mainly andradite and grossular skarn, containing diopside, hedenbergite, magnetite and some copper minerals; and the late water-bearing silicate stage is of replacement of garnet skarn by chlorite, epidote, quartz, calcite and together sulfides precipitation. The latter is the main stage of copper mineralization. Chalcopyrite and bornite are the dominant ore mineral associated with mino rpyrite; magnetite are the dominant iron mineral with miner specularite. Although the skarn mineralization is the main type of Late Jurassic and Early Cretaceous deposit in Shanyang-zhashui ore concentration area. Appearance of porphyry copper mineralization in some skarn deposits implies that skarn mineralization of the study area having uniform porphyry-skarn ore forming system. Therefore, it is presumed there should be potential to find deep level porphyry-type Cu-Au mineralization targets, which has vital significance for mineral exploration in the area.