Geological Characteristics Of A’nyemaqen Ophiolitic Melange Belt In Dongqinggou Area And Prospecting Prediction

Dongkehe ophiolite in Dongqinggou area located in A’nyemaqen ophiolitic belt in regional tectonic setting. There are many deposits(ore occurrences) in this ophiolitic belt, the Deerni large-scale copper deposit is the representative of these deposits, this belt is a great prospecting potential of precious metals and nonferrous metal metallogenic belt.This paper relys on the regional geological survey project and takes the orogenic metallogenic theory as a guide. Utility of field geological survey, profiling survey, samples collection and testing and isotope tracing, combination with data of petrography and mineralography of collected samples, this essay gives a further study on distribution, extension, scale, occurrence, mineral association of typical rock and petrographic characteristics of Dongkehe ophiolite, discussing on its geochemical characteristics and evolution process. On the basis of geological conditions, geophysical and geochemical anomalies data of Dongkehe ophiolite, this paper also gives a prediction of mineralization, and proposes a metallogenic model. This paper have achieved following understanding :Research on data of field geological mapping, petrology, petrography about Dongkehe ophiolite, it has been basically ascertained material composition, contact relationship and spatial occurrence of Dongkehe ophiolite. Dongkehe ophiolite have only existed metamorphic peridotite sequences( serpentinite, pyroxene peridotite) and a small amount of cumulate sequences, no lava sequence, according to the theory of the symbiotic sequence combination of the Trinity “ metamorphic peridotite-cumulate complex-lava”, which proposed by Steinman, it can be concluded that Dongkehe ophiolite have obviously suffered a strong transformation later stage.Research on structural trackway of Dongkehe area have showed that structure developed and deformed strongly in this area, and fold developed also in every slice, showed disordered generally(among the slices) and ordered locally(small slice-scale) fold type Non-Smith strata. Main structural deformation assemblages included fold-thrust fault combination, thrust- nappe structure, ductile et al, extending the cognition of the structural assemblage this area.Spectral analysis have showed that chloritization of serpentine have enriched of trace elements, such as Bi, Pb, Hg, As, W, Sb, Sn, Zn, pyroxene peridotite have enriched of Sn, Pb, Zn, W, Bi, As elements, depletion of Co and Ni elements relatively, it may be advantageous to mineralization elements aggregation of Co, Ni.Sr-Nd isotopic data have showed that affected the Sr isotopic composition of the serpentinized peridotite is not the alteration of the sea water, but the addition of the crustal material, it maybe represent recycling of terrigenous sedimentary rocks, continental crust and altered oceanic crust. Pb isotopic composition have indicated that the isotopic composition of the Pb of the serpentinized peridotite in this area is similar to that of the India ocean, and showed mixture of DMN and EMⅡ mantle componentAnalysis of geological characteristics, geophysical anomalies, geochemical anomalies, combination with high-accuracy ground magnetic survey anomaly and the anomaly of stream sediment survey,it is showed that intensity of As15 乙 1 Ni(Cr、Hg)of Ni, Cr, Hg, Co, Sb, Cu elements anomaly zone in Youhouqing area is high, and its range is large, Showing good superimposition between the nickel, cobalt and copper ore bodies found in this area. Youhouqing area is predicted key nickel, cobalt and copper deposits prospecting area.