Researches On Geological Characteristics And Geochronology Of Hongtugou Gold Deposit In Qinghai Province

The North Qilian Orogenic Belt lies between Qilian Plate and the Alashan Block,heading from north to west and from south to east.North Qilian orogenic belt have a peculiar geological background and Superior geological structure environment,so it is a important polymetallic mineralization zone in china.Hongtugou gold deposit is located in the middle of the North Qilian orogenic belt.The job of the theory research is not enough,especially deposit geological characteristics and geochronology.Based on the systematic collection and analysis of previous studies,with the analysis of electron pro?geochemistry?mineralography?geochronology and field investigation,The main achievements and new cognition as follows:(1)By systematic studying about geological characteristics of hongtugou gold deposit,we discover the the main mineralization and alteration characteristics,the association of Au element and other elements.(2)By studying the special annular serpentinite in the working area,based on the electron microprobe study,we find typical skarn mineral assemblage,which suggest the existence of skarn in hongtugou.Addition,we discuss the possibility of the existence of skarn-type gold deposits in hongtugou.(3)Study on the geochemistry shows that the basalt of the hongtugou owns the typical N-MORB and E-MORB features,suggesting that the basalt is the product of the expansion of the North Qilian Ocean.Based on U-Pb date,the author established tectonic-magmatic activity evolution process and the relationship between gold deposits.(4)By using zircon SHRIMP U-Pb isotope,we find that hongtugou gold deposit has three main magmatic activities: Proterozoic,early Paleozoic and Mesozoic thermal events.Mesozoic thermal events have a strong relationship with mineralization.(5)According to systems analysis,the main ore-controlling conditions of hongtugou gold deposit are the lithohorizon?structure?magmatic activity and wall rock alteration,especially tectonic zones in NW ?NNE and EW direction have strongest relationship with mineralization in the study area.(6)Based on studies stated above,the author summarizes metallogenetic model of hongtugou gold deposit and its exploration implications,this will be useful for the determination of the new ore prospecting target area.