Abstract:The Yaugjiazhangzi molybdenum field is located in Yaushan fold-belt on the northern margin of the North China platform. The well-known Bajiazi-Yangjiazhanzi molybdenum-polymetal minerogenic belt was formed as a result of activities and gradual evolution of Mesozoic magmas. Due to different emplacement depths of magmas, diverse host rock rnedia and varying rock-forming and ore-forming physicochemical conditions, a suite of metasomatic formations was developed which were different from but genetically closely related to each other, thus forming a unified metasomatic series in the Yangjiazhangzi ore field. The main metasomatic formations are described as follows: Metasomatic formation in the Yangjiazhangzi ore district: (1) metasomatic formation of medium-coarse grained granite, fine-grained porphyritold and granite porphyry; (2) quartz-alkali feldspar metasomatic formation: quartz-potash feldspar phase, quartz-potash feldspar-hornblende phase and quartz-potash feldspar-biotite phase; (3) pyritic felsite formation: quartz-sericite-pyrite phase; (4) magnesioskarn formation at the contact of. igneous rocks and dolomitic marble: diopside phase, chondrodite-clinohumite - phlogopite- magpetite phase, amesite-lizardite (talc) phase and brucite phase; (5) calciskarn formation: wollastonite-diopside phase, diopside-garnet phase, vesuvianile phase, zoisite, clinozoisite and epidote phase and tremolite-actinolite phase; (6) quartz-tourmaline formation in metamorphic hornstone. Alteration formation in the Lanjiagou ore district: (l) quartz-alkali-feldspar metasomat:ic formation: quartz-alkali feldspar phase, quartz-potash feldspar-biotite phase and quartz-potash feldspar- muscovite (hydromuscovite) phase; (2) greisen formation: quartz-potash feldspar-muscovite phase and quartz-muscovite phase; (3) pyritic felsite formation: quartz-sericite-amesite carbonate-pyrite phase; (4) quartz-sericite formation, chlorite formation, etc. The formation age of the main metasomatic series has been determined to be 1866-211 Ma, and the related mineralizations and alterations proceeded until Late Yanshanian. The formation temperature and acidity of calciskarn have been studied through examining paragenetic minerals. Calciskarn seems to have occured at 370-560℃ and in intermediate-weakly alkaline environment. Based on the distribution proportion of Fe, Mg, Al and other components in the association of pyroxene-garnet, the approximately estimated equation of the solution acidity has been obtained, and an investigation into the total basicity has been performed for the main altered zones, indicating that metals were precipitated in the largest gradient zone of basicity. Every metasomatic formation has its own geological environments, and each metasomatic phase is characterized by forming physicochemical conditions and the Yangjiazhangzi ore field underwent its specific mineral assemblage, rock-activity of components. On the whole, high temperature alkali metasomatic stage, calcimagnesium metasomatic stage and acid leaching stage with ore minerals mainly formed in acid leaching stage and later. Each metasomatic formation is accompanied by a specific minerogenic phase.
文章编号：
中图分类号：
文献标志码：
引用文本：
林文蔚.1987.辽西杨家杖子钼矿田的交代系列[J].矿床地质,6(1):22~34.1987.The Metasomatic Series of the Yangjiazhangzi Molybdenum Ore Field[J].Mineral Deposits6(1):22~34
图/表
