| Duobaoshan copper deposit is located in Daxing’anling forest swamp scenic areain Heilongjiang province. It is typical porphyry copper. The landform of this area isthe middle mountain, vegetation is developed in this area, certain difficulties werecaused in prospecting. Phytogeochemistry is relatively suitable for prospecting in thiskind of scenic areas. Exposed stratums of the copper deposit mainly are TongshanFormation and Duobaoshan Formation of middle Ordovician which constitute themain surrounding rocks. The copper ore bodies are controlled by3structures whichare structure in NW, arc structure in NW and structure in NE-NNE.Along with the frequent tectonic movements, there are kinds of magmaticactivities in Duobaoshan copper deposit, and the main magmatic activities are theones in middle Hercynian, late Hercynian and Yanshanian. The intrusive body isgranite. The contact zone of rocks is mineralized, and the alteration is developed. Themain kinds of alteration are propylitization, biotitization, potash feldspathization,silicification and sericitization, the alteration is closely related to Cu mineralization.Porphyry copper ore bodies mainly lie in alteration zones of quartz-sericitization. Theore types are dissemination, veinlet-dissemination and stringer.Considering the Duobaoshan copper deposit as mine area and the Duobaoshancopper deposit circumjacent area of Huma area as control plot, this paper conductedphytogeochemical exploration for mine area and its control plot. First of all, thequadrat survey was conducted for Duobaoshan area, showing that the favorablephytocoenosiums in Duobaoshan area are white birches, Mongolian oaks, larches,Korean pines, lespedeza and cotton grass. Secondly, the sample collection of rocks,soil, roots, stalks and leaves of plants was conducted for Duobaoshan mine area andits control plot, then the contents of13elements, which include Au, Ag, Cu, Pb, Zn,W, Sn, Mo, Bi, As, Hg, Co and Ni were analyzed. Since the contents of Au in plant are lower than the detection line, so analysis of the contents of12elements, whichinclude Ag, Cu, Pb, Zn, W, Sn, Mo, Bi, As, Hg, Co and Ni, were analyzed.With the methods of correlation analysis, clustering analysis and factor analysis,the correlation analysis for the contents of13elements which include Au, Ag, Cu, Pb,Zn, W, Sn, Mo, Bi, As, Hg, Co and Ni in rocks and soil in Duobaoshan copper depositarea was conducted. Through the analysis, it is concluded that Cu, Au, Ag, Mo, Coand Pb are related to the mineralization of porphyry copper, these5elements, whichinclude Cu, Ag, Mo, Co and Pb, can be considered as indicator elements ofphytogeochemical investigation for Duobaoshan copper deposit.Through the analysis of the contents of the5elements Cu, Ag, Mo, Co and Pb infavorable plants of Duobaoshan copper deposit area and control plot, it is discoveredthat the contents of indicator elements in mine area is larger than the contents incontrol plot, it shows that the contents of elements which are related to Duobaoshancopper deposit area were accumulated to a certain degree in plants, these indicatorelements could produce obvious abnormalities in the copper deposit area, suggestingthat using phytogeochemical survey is available.Through the analysis of the contents of elements for different favorable plants, itis concluded that the contents of the indicator elements of different plant samplesfrom Duobaoshan mine area are various, suggesting that different parts of plants havedifferent shielding effect to elements. Therefore, when the phytogeochemical isconducted, selecting effective indicator plants is very important. After the contents ofindicator elements of the favorable plants in Duobaoshan mine area were analysedand compared with each other, it is considered that lespedeza, white birches, larchesand Mongolian oaks have less shielding effect to elements and can be chosen aseffective indicator plants.Through the analysis of element contents in roots, stalks and leaves of plants inDuobaoshan mine area, the indicator elements Cu, Ag, Mo, Co, Pb have obviouslydifferent contents in different organs of plants, reflecting that the distribution of elements in different organs of plants is various, which means whenphytogeochemistry is conducted, the selection of the effective parts of sampling plantsshould be noted.Based on the summary of phytogeochemistry evaluation indicators such asabsorption coefficient, shielding coefficient and contrast coefficient, this paper cameup with total enriched coefficient and combination contrast coefficient as evaluationindicators, they were used in Duobaoshan mine area, reflecting that these2indicatorsare helpful to choose major indicator elements and advantageous sampling parts ofeffective indicator plants.Based on the systematic analysis of5evaluation indicators that includeabsorption coefficient, shielding coefficient, contrast coefficient, total enrichedcoefficient and combination contrast coefficient, this paper conducted the selection ofeffective indicator plants and sampling parts. It is considered that stalks of Mongolianoaks, stalks of white birches and roots of lespedeza can be considered as effectiveindicator plants and effective sampled parts of plants, in Duobaoshan copper depositarea. By comparing different indicators, it is considered that total enriched coefficientand combination contrast coefficient have better effect in the process of evaluation. |
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