Study On Effect Of Neotectonic Activity On Jiawu Gold Deposit Occurrence State

Jiawu gold deposit locates in Tongde- Zeku Indosinian Au, Ag, As, Sb, Hg metallogenic belt in Q inghai province, experienced multiple orogenic movement with superior ore- forming conditions, and after many explorations with multiple geological units for years, it is thought that prospecting breakthrough can be achieved by further exploration. However, during People’s Armed Police Force Gold’s exploration work from 2008 to 2011, the ore-occurrence condition of constructed exploratory trench, pit and drilling is not satisfactory. Preliminary analysis shows it may relate with orebody-break effect of neotectonic activity under strong uplift of the Qinghai- Tibet Plateau since Cenozoic. To ascertain ore prospect potentiality in Jiawu gold deposit, a study on neotectonic activity characteristic and its of gold orebody break effect is conducted, and has an important significance in both theory and engineering practice for scientific and reasonable deployment of the further exploration.Based on analysis on geologic, geochemical and tectonic characteristic, this paper is expected to reveal orebody-break effect of tectonic activity by study on neotectonic activity characteristic since uplift of the Q inghai- Tibet Plateau. Achievements are as followings:1. Topography and landform and tectonic deformation in Jiawu area are controlled by activie faults of I, II levels. Hazardous geological phenomena such as collapse, landslide, debris flow and country rock deformation are very common. Deep gully, valley-in- valley and Yellow River terraces are very developed. Neotectonic movement is very intense under background of uplift of Q inghai- Tibet Plateau since Cenozoic.2. Characteristics of element geochemistry field, synthetic geochemical anomaly, orebody’s existing environment and analysis of ore-forming processes in Jiawu area indicate superior metallogenic background and good prospecting prospect, and tremendous deep prospecting potential.3. Faults striking in NNW and EW are major ore-controlling structure, which can be divided into three levels of III, IV, V, and multi- level faults controll the occurrence of orebody jointly. These faults mainly thrust and right strike-slip under maximal principal stress in direction of N E since Cenozoic, and tectonic activity happens since 30 Ma of Quaternary.4. Fault activities’ orebody-break effect behaves as deformation of orebodies, even direct offset by thrusting,normal-slipping and strike-sliping, with an observed displacement of more than 3 m in surface. Orebody-break effect can be divided into three status: first one, fault activity results in orebody deformation, bending, or even reverse. Second one, fault activity of thrusting, normal-slipping and strike-sliping directly cut orebody, leading to a less continuty and regularity in distribution in deep. Third one, strong shearing effect of fault activity make the output form of the orebod y irregular, presented in sausage or lens shape, and thinning, even pinch out partially. Consequently, it leads to poor occurrence in footrill, drills designed according to surface attitude during revealing of orebody.5. For the situations presented above, it is suggested that drilling, adit, and pit layout density be increased in the next plan of exploration work, and deep drilling be carried out. Meanwhile, integrated geophysical and geochemical exploration work of large scale should be conducted, cooperating the surface rock geochemical survey of same scale, in order to guide verification of deep drilling.