Abstract:

The Yangshan gold deposit，located in south Gansu Province，is a supper large fine-grained disseminated goId deposit recently found in China．Four discovered ore blocks of  the deposit all occur in Devonian epimetamorphised sandstone，phyllite or limestone．The ore belt is controlled by Anchanghe-Guanyinba fault as well as its secondary faults. The orebodies，being in lenticular or veinlike forms，are spatially related to plagiogranite． Pyrite and arsenopyrite are the main metallic minerals and native gold usually occurs in pyrite，arsenopyrite and clay minerals as micrograined inclusions(2～3μm)．Enrichment of Au，Hg，As，Bi，Sb in the ore is obvious and such elements show positive correlations with each other，
indicating that the forming of the Yangshan gold deposit is associated with the activity of hypothermal ore fluid containing Au，Hg，As，Bi，Sb．The decrease of these elements from the upper part to the lower part of the deposit show that the activity of the ore fluid becorne weak along with the depth．The δD value of quartz from the ore ranges from-60‰ to-72‰，andδ¹⁸O_H2O value ranges from 8.O‰～10.1‰，indicating the ore fiuid is mainIy composed of magmatic water．The δ³⁴S value of pyrite from the ore ranges from-2.2‰ to-0.7‰，which is greatly different  from that of pyrite in Devonian phyllite，suggesting the magmatic origin of the sulfur，therefore it is proposed that the Yangshan gold deposit is genetically related to
the magmatic thermal activity．

Key words: gold deposit, microelements, stable isotope, Gansu Province, the YangShan area