Abstract:

Jianchaling gold ore deposit, located in the northeast edge of MianxianLüeyangNingqiang triangle
area, is associated with ultrabasic rock and the ore bodies occur in the goldbearing altering belt round the ultrabasic rock. Since the contentious understanding of mineralization, the subsequent exploration was influenced. Beginning with the geologic characteristics, orecontrolling factors and mineralization mechanism are discussed by measurement of major, trace and rare earth elements as well as S, H and O isotopic composition. The result shows that the deposit is controlled by ductilebrittle shear zone developed in the contact belt of ultrabasic rock and Sinian dolomite, and the mineralization is not only related with the ultrabasic rock, but also tightly with the granophyres. The emplacement of granophyres results in thorough alteration of the ultrabasic rock and the metallogenic elements to be released. Since δ³⁴S of pyrites in the ore, ultrabasic rock and dolomite is approximate to that in the granophyres, and shows definite regularity spatially, it is believed that sulfur in the ores is derived from the granophyres. Hydrogen and oxygen isotope composition of the ores lies between magmatic and meteoric water, and most of them gather together near the meteoric water line, which suggests that the hydrothermal solution originated from the granophyres and gradually turned into mixed water with the meteoric water added successively in. In view of the close relation between the deposit and granophyres and the appearance of fuchsite, it is considered that the deposit is formed between intermediate Indosinian and intermediate Yanshanian according to the isotopic ages.

Key words: ductile shear belt;granophyre, ultrabasic rock, mineralization, Jianchaling gold deposit, Lüeyang County, Shaanxi Province