Ore prospects and ore exploration methods for metal deposits in the middle and lower Yangtze River valley

Abstract：This paper deals with the geological, geophysical and geochemical characteristics of ore deposits in the middle and lower Yangtze River valley and proposes the main targets of ore search at depth in the future, i.e.: hidden mineralized intrusions and related various types of orebody, large porphyry ore deposits in intrusions and stratiform deposits controlled by intrusions and the Wutong sandstone. It also discusses several main problems that should be solved in applications of geophysical and geochemical methods and emphasizes that we should bring into play the roles of integrated methods including the gravity method, magnetic method, induced polarization method, electromagnetic method and petrosonde, as well as several seismic methods and geochemical methods, which are closely combined with studies of geology and metallogenic characteristics of ore deposits. Some problems that should be paid attention to in applied tests of the methods are also discussed. Finally, the paper discusses the regional tectono-magmatic activity and metallogenic prospects from the tectonic evolution in the study region. The author thinks that: this region is the continent-continent collision-compression orogenic belt between the Yangtze plate and North China plate and its foreland area and strong lithospheric compression resulted in crustal thickening and extrusion and exhumation of deep materials, thus pushing the deep high-pressure (HP) and ultrahigh-pressure (UHP) metamorphic rocks to the shallow crustal level; HP and UHP minerals such as coesite formed at depth and molten mantle magma intruded upward simultaneously; large amount of calc-alkaline magma was generated and stored in the middle crustal level, and a long period of material exchange between the calc-alkaline magma and metallic materials in the middle and lower crust formed concentrated ore fluids, which entered the superficial layer of the crust through tensile faults that occurred in the late stage；finally after physical and chemical Processes occurred between the ore fluids and country rocks, metallic minerals were deposited to form ore deposits. A new tectonic model in the continent-continent collisional orogenic belt of the Yangtze plate and North China plate has been summed up.