Mineralization Law And Metallogenic Prognosis Of The Xiaoqinling Gold Ore Field

The Xiaoqinling gold mining area is the second largest ore concentrating area exploiting gold ore except the Jiaodong gold ore field. Determining mineralization and the deposit distribution law of the middle-deep ore body in the Xiaoqinling area has theoretical and practical significance for deep resource evaluation and prefect metallogenic theory of this type. On the basis of research results of previous scholars, this paper start with the typical deposit research, field survey and typical samples, identify under microscope, measuring element contents, summarized the mineralization and the deposit distribution law. I also set up the metallogenic model and ore forecast marks. The main achievement is as following:(1) The electron microprobe analysis results of the Au content of the sample from the magmatic rock and metamorphic rock in the Xiaoqinling area shows that the Au content of metamorphic rock is larger than that of magmatic rock. The cluster analysis of major elements and trace elements shows that Au occurs in sulfide and is freely soluble. Theδ34S value and content of Pb of the Yanshannian magmatic rock is close to those of Taihua metamorphic rock and Au ore, therefore the above three body have relationships in the genesis. The REE characteristics of all the Au deposits differ with those of granite, which reflect that there are no relationship of mineralization, and the mineralization sources are from amphibolites and gneissic rocks. The trace element characteristics show that the metallogenetic element Au and Mo lain on the first group and it is inferred that they have experienced hydrothermal alteration. To sum up, the metallogenetic sources are from the Taihua group stratum.(2)The paper classified the ore control faults into three types: The first is proceeding faults, which shows strong threading strain band; the second is the metalizing phase faults, in which ductility shear zone is changed from the brittle shear zone, and the shape is controlled by the faults; the third is after-metalizing faults, whose activity exists all through. The length is direct ratio to the intensity and scale of Au mineralization in the Xiaoqinling ore field. There are many dense and parallel corresponding faults and there is always a major structure with large resource. The non-homogeneity of Au grade shows the pulsating movement characteristics of there thermal fluid。(3)The mineralization fluid differ from fluid with high salinity and the son-crystal, and is same as the Yanshannian after-magmatic thermal fluid with low salinity and rich in CO2, H2O content, which reflect that the Au deposit formation is related to the activity of thermal fluid, and not directly related to the metamorphic process and migmatization. Through the contrast of typical deposits, the mineralization fluid is mainly magmatic fluid interfused by natural water. From the Wenyu body to the outside, the enclosure temperatures reduce gradually and the rock bodies control the mineralization temperatures and distribution.(4)Based on the analysis, the late period of Yanshannian is the major mineralization phase. Isotope data is timely measured, achieving an age of 200 Ma, which is accord with the age of joint of North China plate and Yangtze Plate. Therefore, the Xiaoqinling Au field is mineralized not only in the late Yangshannian, but in the indo-Chinese epoch.(5)According to the depth of super-large Au deposit in the world, the mineralization depth in the Xiaoqinling should be over 900 m. The scale of shear zone, attitude, size and length of ore body, rock alteration and so on are summarized and seven prospecting districts are determined and proved by drilling.