Regional metamorphism of late, the extensive development of migmatization. Regional metamorphism migmatization is the advanced stage.
The first period: sodium migmatization
Sodium mixed rock are mainly developed in the lower part of the ore-bearing rock series, ore layer are also scattered outcrop. This period rock mixed with white for the feature, a large white felsic veins, as a band, lenticular, intestinal shape along gneissosity metasomatic filling. This period the migmatization to filling, the low degree of mixing.
Phase second: potassium migmatization
The mixed rock is mainly developed in the upper part of the rock. Mixed rock is characterized by the appearance color to red light red meat, mineral particle size is coarse, for many, coarse, rock composition with microcline, as the product of potassium metasomatism. The period of migmatization " infiltrating". Rocks are mainly granitic gneiss and granite.
Regional metamorphism migmatization is the advanced stage. The stages of mineralization can be divided into two stages, namely alkaline metasomatism in early main mineralization period and, in late hydrothermal metasomatic metallogenic period mainly. In the early stage of metasomatic stage, accompanied by a variety of mixed rocks and granitic rock formation, in some ore bearing rock, can, corundum, garnet mica, apatite, nonmetallic minerals and some rare metal mineral formation.
Generally speaking, migmatization has two functions, one is to make iron enrichment, rich iron ore formation, and may cause the particles to bold, beneficiation favorable; two is the felsic or granitic veins or pegmatite dikes along the tectonic fissures interspersed through people in magnetite quartzite ore body, resulting in whole body dilution. The migmatization has two aspects of the role, but later shall mainly.
According to the ore deposit major elements, trace elements, rare earth elements, rock formation with water and hot water formation characteristics, which indicates that the formation of a more complex process. According to the ore component proportion and Niggli graphic rock protolith restoration, combining rock field characteristics, Dushan city to the rich iron ore region of rock formed in the active continental margin environment, its provenance has multiple characteristics (mainly terrestrial, followed by a submarine hot water to heat fluids and biological material added ).
In short, Dushan city to the rich iron ore ore material source in undersea volcano eruption, and in plane and vertical were shown to fold, the ore-bearing strata for five rock group Jingangku formation, metallogenic epoch of Neoarchean to early Proterozoic sedimentary environment of continental slope, lower near sea area, experienced more later deformation metamorphism, forming the pleats orebody. Therefore, deposit is a submarine volcano eruption sedimentary reformation type, belongs to metamorphic iron ore ferrosilicon formations.
The next step work problems:
( 1) strengthen the basic geological data collection and study. Because the area structure and metallogenesis is closely, the regularity of structural ore control is very obvious, should further strengthen the regularity of structural ore control research, combined with the actual data to find out faults, ore bodies were broken concrete location and fault distance, inferred ore bodies in the transformed space position, for future exploration basis, in order to effectively guide the prospecting work. At the same time, the fold structure often cause local orebody thickened, generally in the fold at the turning of multiply thickened, moreover is the same oblique reversal tight fold, orebodies obviously thickened, therefore, in the future exploration work should pay special attention to these sites.
( 2) strengthen the regional metallogenic system research, including the ore-forming material, ore-forming fluid, mineralization metallogenic dynamics, product, namely the source of a storage system, in particular the metallogenic epoch and metallogenic stages of research, elucidating the iron ore formation and distribution and enrichment, determine the exploration the best combination of signs and best method combination, for the iron ore prospecting bigger breakthrough promote the theoretical level and exploration technology.
( 3) from the stratabound ore deposit research perspective, Dushan city to the rich iron ore also belongs to the category, the only briefly mentioned, not in detail. Hope that future work in the use of stratabound ore deposit geology and metallogenic theory of the deposit in the area in detail research.
Key words: deposit; Jingangku formation; metamorphism; mineralization; Dushan City
