Ore-forming Geological Conditions Research Of Xiajiaping Gold Deposit, Tianshui, Gansu

The Xiajiaping Gold deposit is located in reversed S-shaped Collision orogenic miscellaneous rock band of the Western Qinling region. It is controlled by the regional structure and the associated secondary fracture. With the magmatic activity and the water-rock reaction between hydrothermal fluid and wall rocks, the metallic elements ultimately concentrate and mineralize, and it has extremely complicated ore-controlling and metallogenic characteristics.Base on the predecessor's works, detailed field geological survey and in-door research works, the paper begins with the geological characteristics of the regional, ore-field and mineral deposit, furthermore study the type, characteristic, space-time distribution and their internal relationship of tectonite (zone), structural feature, geochemical anomaly in mine area, and spatial relationship between mineralization belts or ore-bodies and fracture structures. Taking structural ore controlling as key point, the author study the relationship between ore-forming and ore-controlling factors including stratum, structure, magmatic rock and metamorphism, and analyse metallogenic epoch, fluid and material sources. Based on knowledge above, the paper establishes a metallogenic model focusing on structural ore controlling, and predicts metallogenic prospects.From the systematic studies, the ore forming mainly has something to do with fracture structures, ore-containing strata and magmatic activity. The fracture structures provid ore-transmitting channel and ore-bearing space, and it's the first ore-controlling factor. Metallogenic structure system formed by F1-ore-transmitting fracture structure and series of secondary ore-bearing fracture structures. The second lithologic layer of "a" rock segment of Liziyuan group offers the metallogenic materials; the Late Indosinian magmatic activity supplies enough fluid and energy, and impels hydrothermal cycle. Through the process of repeated circular migration, water-rock metasomatism of the ore-forming fluid in the metallogenic structure system, the minerals occur precipitation, enrichment and mineralization. The silver lead-zinc formation is at the late stage of the Au mineralization.