| The Western Liaoning-Eastern Hebei gold metallogenic belt is located at the northern margin of north China craton and the eastern end of Yanliao metallogenic belt.It is one of the most important concentration area of gold mineralization in China,mainly consisting of three gold deposits concentration areas: Paishanlou,Erdaogou-Jinchanggouliang and Yuerya-Jinchangyu,and the gold deposits in this area are closely related to the Mesozoic granitoids.Taking three typical Mesozoic era granites,the Haitangshan rock body,the Xiduimiangou rock body and the Xiaoyingzi rock body as research objects,this paper studies the rock types genesis,source of magma,conditions of crystallization and indicative significance to mineralization by means of petrogeochemistry,petrography,and genetic mineralogy.The emplacement depth is estimated by methods of Mineral Geothermobarometry and the history of uplift and denudation is discussed.In addition,by comparing the depth of gold mineralization with the thickness of denudation after mineralization,the preservation status of gold deposits in the area after mineralization is analyzed,which provides a theoretical basis for the potential evaluation of gold deposits in the area.The genetic mineralogical study of the main petrogenic minerals in typical granitic rock bodies in the area shows that the amphibole-plagioclase equilibrium temperatures of the Haitangshan rock body,the Xiduimiangou rock body and the Xiaoyingzi rock body are respectively 670 ?,652 ? and 704 ?.The average depth of emplacement are 7.56 km,2.57 km and 4.84 km,respectively.The tectonic background of their diagenesis may be a post-collision environment transformed from compression to tension,and their magma is formed in the environment of medium temperature,rich water and high oxygen fugidity,which has good metallogenic potential.The comprehensive study of petrogeochemistry,petrophysiology and mineralogy shows that the Haitangshan rock body is a high potassium calc-alkaline,weakly peraluminous type I granite,and its magma is characterized by crust-mantlemixture.The origin of two disequilibrium textures between minerals,plagioclase complex zoning and the occurrence of biotite mantled by amphibole are discussed by cathodoluminescence and electron probe micro-analysis,which proved the existence of magma mixing.Since the large-scale gold mineralization from 138 Ma to 123 Ma in the western Liaoning district,the overall average denudation thickness is 1.7 ~ 2.7 km,which is less than the lower limit of the average gold metallogenic depth of 5km.Since the large-scale gold mineralization from 175 Ma to 159 Ma in the eastern Hebei district,the overall average denudation thickness is 4.8 km,which is less than the lower limit of the average gold metallogenic depth of 6.8km.Therefore,it is speculated that the gold deposits in the western Liaoning-eastern Hebei district have a good prospecting prospect at least within 2 km in the deeper part,and similar ore bodies with shallow ore bodies can be found. |
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