Geology Characteristics And Genesis Discussion Of Dajialiang Gold Polymetallic Deposit In Tianshui, Gansu Province

The Dajialiang gold deposit is located in the collision miscellaneous rock band between the North China Plate,Yangzi Plate and Tethys Old sea Plate.It is controlled by the regional Guanzizhen-Yuanjiaping and Niangniangba-Shujiaba structures and the associated secondary fault zones. It belongs to the Wenquan-Chaijiazhuang gold and silver metallogenic belt.It is clearly that the ore bodies are strongly controlled by strata and fault structures. Most of the ore bodies are found in the Sinian-Ordovician strata that are mainly composed of the metadacite. The Northeast F1 Main fault and the latter northwest-west secondary fault zones are ore-hosting structures, which are also the precipitation and the concentration of ore hydrothermal solution. There is strong ferritization alteration in the gold mineralization and the braunite alteration in the silver mineralization on the ground. While in the deep gold zone, it develops a lot pyritized phyllite alteration and carbonatation.Base on the studies, the ore forming is mainly related to the structures, ore-containing strata and acidic magmatic activity. The structures provide ore-transmitting channels and ore-bearing space, indicating that they are the most important ore-controlling factor. The third lithologie layer of Muqitan group offers the metallogenic materials. The Late Indosinian magmatic activity supplies enough fluid and energy. Through the process of repeated circular migration of the ore-forming fluid in the metallogenic structure system, the minerals generate precipitation, enrichment and mineralization. Regarding the alteration characteristics, the Dajialiang deposit is considered as the medium-low temperature hydrothermal gold deposit.