Progressively Determine Prospecting Targets And Quantitative Forecast Of Baiyin Ore District,Gansu Province

The Baiyin ore district located in Gansu Province hosts the largest and most typical volcanogenic massive sulfide deposits in China. The development and utilization of its copper, lead and zinc resources has an important impact on China’s economic construction. However, after decades of continuously mining, the ore resources of this area have been nearly mined out which put a high pressure on us to increase its reserves. During decades of research and ore finding efforts, a lot of geology, geophysics, geochemistry and remote sensing works of this area have been done and a large amount of research data have been accumulated. Yet, the development and usage of these data currently is not sufficient and the prospecting results are not satisfactory. Thus, prospecting new ore bodies and searching for new resources in the deep and periphery of Baiyin ore district are both significant in theoretical and practical."5p" ore prediction and quantitative evaluation theory is a method of step by step system for mineral resources quantitative evaluation which based on researching geological anomaly of different scales to comprehensive prospecting information.As the prospecting level increased, the prospecting target area progressively smaller, the target level increased gradually and the prospecting success probability gradually increased. Base on the "5p" ore prediction and quantitative evaluation theory, with research and quantitative delineation of geological anomalies of different types, different scales, the combination of direct and indirect ore-prospecting information, and deeply and comprehensive analysis of multiple prospecting information, this thesis systematically established the "5p" ore prospecting and prediction model the Bainyin ore district and select different scales of ore prospecting and orebody finding areas, which provides the theory basis for resources exploration targets and ore prospecting task deployment in the peripheral and deep of the Baiyin ore district. Through above working, we obtained the following conclusions:1. Through the secondary development and extraction of the anomalous prospecting information of the1:1000000geological, geophysical and remote sensing data of the north Qilian region, this thesis set up the evidence comprehensive information prospecting model and quantitatively outlined the probable copper deposits forming area in this region. The results showed that copper deposits are mainly contained in the Ordovician (O), Cambrian (∈), Changcheng system(Ch), Silurian (S) and upper Devonian (D3) formation. The NW-NWW striking faults controlled the spatial distribution of formation and the ore deposits, copper deposits are mainly distributed in the scope of6km away with primary faults and15km with secondary faults. Basic-ultrabasic magmatic rocks also are closely associated with copper mineralization. Probable copper deposits forming areas are mainly distributed in the district of Sunan-Qilian-Menyuan which display in the middle of the study area, and sporadically distributed in districts of Akeshai-Subei, Nanbaxian and Guide-Xunhua. The overall distribution direction of these prospecting areas are the same with the regional tectonic direction and the distribution features of the basic-ultrabasic rocks.2. Through the analysis and extraction of the ore-prospecting information of the1:200000geology and aeromagnetic data of the Baiyin region, it turns out that the VMS ore deposit containing formation are mainly the basic volcanic rocks in the Ordovician, the Baiyinchang volcanic complex and metamorphic volcanic rocks in the Gaolan group. The VMS ore deposit are also found that they are mainly distributed in the range of2km away from the faults. Concealed faults, magmatic rocks and ring structure inferred by aeromagnetic data also played a important role in control the spatial distribution of these deposits. Combined with1:200000stream sediments geochemical anomalies, the comprehensive information evidence prediction models of the permissive VMS deposits finding area of the Baiyin region was established. And we determined that the Baiyin mines field and its peripheral, Laohushan-Zhuzuiyaba and Fuqiangbaop-Siyanjing area are the primary ore prospecting area, Shiqingdong-Duojiatan, Erdaowan and Luojiadazhuang-Yindonggou districts are the secondary ore prospecting area, and the district of Huangyakou, Tiebeigou, Yueshuiya located in the south of the study area are the third ore prospecting area. Besides, the paper analyzed the prospecting feasibility of these ore prospective area described above.3. Through the analysis and extraction of the1:50000geological anomaly of the Baiyin district, the results show that the deposits in this area are mainly contained in the Baiyinchang group (∈22) and Dajingzi group (∈23) of the lower Cambrian, and upper-middle Cambrian formation (∈23+4).The main ore containing lithology in these formations are quartz phenocryst tuff and basalt-basaltic tuff. It also shows that the ore deposits are mainly distributed in the range that2km away from the faults and the anticline axis, which implying that NWW striking faults and anticline controls the distribution of the volcanic rocks and the mineralization. Combined with geophysical survey and1:50000stream sediment geochemical anomaly analysis, the comprehensive information prospecting model of preferable ore-finding area was established. Using this model, the Baiyinchang mines field, Heishishan-Hengwan region and Shiqingdong-Duojiatan region are determined to be the primary ore prospection area, the Dilapai area adjacent to Heishichuan and Zhandonggou-Yingouguxia area are in the secondary place, and the eastern part of Heishishan, Xiongjiawan and Yiduqiang south area are in the third place.4. Based on the extraction of1:25000geological anomalous information of the Baiyinchang ore field, it was found that ore deposits are mainly distributed in upper and lower Baiyinchang group (∈22、∈22-1a、∈22-1c、∈21) and Dajingzi group (∈23b) of the lower Cambrian formation, the ore containing lithology is mainly quartz phenocryst tuff and basic volcanic rocks. At the same time, the deposits was found to be mainly located in the area0.6km away from the NWW, NE striking faults and anticline axis. The volcanic eruption center is the critical factor controlling the output of ore deposit, the region0.5km away from the quartz-sodium feldspar porphyry is also the favorable metallogenic area. High value area of the1:25000shallow source anomaly gravity shows NWW and NE distribution characteristics and medium to large VMS deposits are distributed in the negative value area. Combined with1:25000soil geochemical anomaly analysis, the comprehensive information prospecting model of potential mineral resource area was established. On the base of this model, the deep area of Zheyaoshan-Huoayanshan deposit and Xiaotieshan deposit, the connection area of the eastern and western Baiyin district are determined to the primary ore prospecting targets, and Shalaoba-Dalaoba-Yingouguxia, Fangmagou and Haoquangou-Baimawa area are the secondary prospecting targets.5. In order to explore the practical significance for rapid evaluation of prospecting of adsorption state metal ions measurement of the soil in thick loess layer coverage area, the experiment was undergone in Songjiatang and Southeast of the Xiaotieshan deposit area. The results show that this method is effect on ore prospecting under the arid and semi-arid environment of thick loess covering area in Baiyinchang. Main ore-forming elements Cu, Pb, Zn, Ag anomalies is obvious, and associated with anomalies of low temperature elements. The locations and elements of these anomalous are corresponding to the anomaly characteristics of the structure rock sampled in the same places. Through this method, several Cu, Bi anomalies and Cu, Zn, Sb anomalies are identified in Songjiatang and Southeast of the Xiaotieshan deposit, respectively, Which may be significant in ore prospecting in these area.6. Primary geochemistry elements halo of structure rock samples was used for ore prospecting in Baiyin ore field and its periphery area. In this study, a total length of18.7km of structure rock samples were collected and analyzed for trace elements characteristics. The results show that the content of elements of Cu, Pb, Zn, Ag and As of the structure rock samples were greater than its background value of this mining area, implying these elements are enriched in these samples. Cluster analysis identified that low temperature elements of Ag, Mo, the As and Sb are very closely associated, so as the main ore-forming elements Cu, Pb, Zn and Mn of this area, which is similarly to the nature of elements activities. By this method, several abnormalities were found in the mining area and surrounding area, and most of these anomalies locates in the extension part of the known ore deposits, showing that tectonic primary halos geochemical prospecting is useful in Baiyin mining area.7. Alteration zoning, ore structure and geochemical element distribution features of four new drilling (ZK2-1、ZK2-3、ZK10-1、ZK10-2) in this area were studied.The results show that, in the deep area, it is main developing disseminated copper mineralization, and chloritization alteration develops closely to the ore bodies and then surrounded by sericitization and siliconization. Elements distribution features show that the main ore-forming have multiple enrichment center, and correspond to the distribution of the ore bodies which show lateral echelon distribution trend characteristics. Besides, elements of Cu, Pb, Zn anomaly is consistent with the scope of main metallogenic belt, and Ag, As, Sb, Hg anomaly distributed in front of the ore bodies, while W, Sn, Mo, Bi distributed behind the ore bodies. And this paper obtained the elements axial zoning sequence of exploration section2:Ni-Co-As-Cu-Ag-V-Bi-Sb-Pb-Mo-Zn-Cd-Mn. Pb anomalies and (Pb+zinc)/Cu ratio of two deep drilling shows a increasing tendency, suggesting that it has the potential to find ore body in the deep area. Thus, deep drillings (especially pit drill) are required to control the deep ore body.8. Through secondary development and comprehensive analysis of large scale gravity, high precision magnetic survey data, combined with previous data, it was found that acidic volcanic rock class often forms regional gravity low, and most of the ore bodies form local gravity high in these regional gravity low. However, ore bodies buried more than500m don’t show gravity anomaly. High magnetic parts of the intersection parts of NWW and NE striking magnetic characteristic line around0nT are The favorable ore prospecting positions in the acidic volcanic rock outputting area. Combined with element zoning and main ore-controlling factors analysis, the geological, geophysical and geochemical comprehensive information prospecting model of the VMS deposit in the study area was established.9. Through extraction of large scale geophysical-geochemical prospecting information, metallogenic regularity study, combined with adsorption state metal ions measurement of the soil in thick loess layer coverage area, primary geochemistry elements halo of structure rock samples, and oxidation outcrop found in field reconnaissance, the areas of Zheyaoshan-Huoyanshan and Xiaotieshan-Tongchanggou deep mining areas, the connection area of Zheyaoshan Huoyanshan east, southeast of Xiaotieshan-Tongchanggou, Zheyaoshan-Huoyanshan west and Zheyaoshan-Huoyanshan north were delineated to be the perspective ore-bodies areas, which may benefit for resources prospecting in this ore filed.