Characteristics Of Mineralization And Metallogenic Prognosis Of Skarn Fe Deposits In Pingshun Area, South Shanxi

Located in the south Shanxi province, Pingshun area is an important locality for skarn iron deposits in the North China. Pingshun's skarn iron deposits are rich in high-quality iron ore, having intrusive rocks with a great outcrop area, so it is advantageous to our study. With diverse shapes and different scale, the ore bodies are hosted along the contact belt between the intrusives and carbonate rocks. Folds, faults and contact zones are the dominating ore control and host structures. The ore type is monotonous magnetite. The mineralization and alteration are characterized by obvious zoning.The intrusive complex consists of rocks of the early stage and advanced stage in Pingshun area of south Shanxi. The intrusive rocks of the early stage are mainly composed of olivine gabbro-diabase, and the intrusive rocks of the advanced stage diorite-monzodiorite, while the later black unequal particle diorite is formed in their contact segment. A large amount of relict crystals of olivine, pyroxene and hornblender can be found in the early-stage intrusive rocks while a comparatively small amount of relict crystals exist in the intrusive rocks of advanced stage. Occasionally, we can see disequilibrium phenomenon of composition and structure in plagioclase. The rocks of the early stage and advanced stage are similar in some geochemical features such as low slicon and high magnesium, enrichment of light REE with a weak positive anomaly of Eu and depletion of heavy REE, enrichment of LILE, especially Sr, Ba and K and depletion of HFSE, especially Nb, Ta and Ti and enrichment of radiogennic lead (n(206Pb)/n(204Pb)=17.741～18.474, n(207Pb)/n(204Pb)=15.429～15.612). Petrological and geochemical characteristics of these two types of rocks indicate that they are comagmatics and originated from partially melting of EM, in which magma was formed with the high temperature fluid leading to partial melting of lower crust( especially TTG) ,in which granitoid magma were first formed and the mixed magma later. Finally the Pingshun complex was formed by fractional crytallization of magma. Based on the above-mentioned analysis, the metallogenic model is established.The formation of skarn ore deposits are tectonically controlled by Handan mantle plume in Pingshun area, and the original rocks of albitization rocks which are closely related to ore bodies are advanced stage intrusive rocks and it provides metallogenic material. The early intrusive rocks are metasomaticed by the later one ,and then iron-rich rocks are formed, at same time the later rocks related to ore deposits formed have 2-3 magmatic pulses, in which the hydrothermal solution contained serves as carrier of minerals. And the compressive stress and heat produced by hydrothermal solutions are dynamic forces for the migration of ore-forming materials. Based on the above-mentioned analysis, an ore-forming model of skarn iron deposits in the area has been constructed.By summing up the past geological data and field study, it is pointed out that the first and second tectonomagmatic belt with different mechanisms of emplacement have influence on the formation of ore deposits. The first belt belongs to positive emplacement mechanism. Within the pluton,the ore bodies show themselves as xenoliths, and there is the metallogenic potential far away from the contact zone between the intrusives and the carbonate rock while the second belt belongs to the passive emplacement mechanism. The xenoliths seldom occurs within the intrusive rocks, neither does the ore xenoliths. The iron deposits are mainly hosted along the contact zone between the intrusives and the carbonate rock, a minority within the carbonate country rocks. The anticlines formed under the condition of the positive emplacement are the important host structure.Based on studying the relationship between strata, magmatic rocks, construction, the contact zone, alteration zone and mineralization, it summarizes ore-controlling factors and metallogenic regularity and points out prospecting criteria. Then such methods as geological survey, magnetic survey are carried out to circle the prospecting such targets as Lugou, southern edge of Long Jianggou rocks, Luosai and Dongjiaoareas. All these provide basis for seeking deep concealed deposits and blind ore.further.