Geological And Geochemical Characteristics Of Migmatite Type Uranium Deposit In The Yakou Area, Miyi Town, Sichuanprovince

Based on the key research project,"the research of the migmatitic uranium mineralization mechanism in Panxi area"?No.41472073?,NSFC?Natural Science Foundation of China?and“Metallogenic regularity and prospecting direction of the thermal liquid uranium deposits on the earth's axis in Kangdian Axis”,China Nuclear Geology,the author try to make researches on respects like regional geology,mining area geology,petrology and geochemistry of migmatitic uranium ore in Yakou area,in accordance with conclusions and data made by predecessors.The following major achievements and understandings are achieved:?1?From the ore-bearing wall rock,there are three kinds of ore in the Yakou area,namely:migmatitic schist ore,migmatite ore,biotite schist ore.According to radiological photography,uranium in the ore is mainly in the form of fine granular uranium,and distributes unevenly.paragenetic mineral assemblage is:quartz-feldspar-Mica?amphibole?-bitumen uranium-pyrite-chalcopyrite-pyrrhotite.?2?According to the characteristics of major and trace elements,the matrix?metamorphic rock?can be divided into two categories:one is oblique amphibolite,the other contains schist,gneiss and metamorphic sandstone.The protolith reconstruction shows that the oblique amphibolite is orthometamorphite,the original rock is of basic volcanic rock,the schist,gneiss,metamorphic sandstone are pararock,the original rock is defined as shale,clay rock,sandy rock,miscellaneous sandstone.?3?The types of trace elements in the wall rock are simple,generally including Cu,Sc,Bi and Th.The types of elements in ores and mineralized rocks are more complex than those in wall rock,all have great or obvious enrichment of U,Sc,Cu,Bi,Be and Th,which is quite similar to those in altered rocks,reflecting the close relationship between tectonic alteration and mineralization.In particular,there is no enrichment of Cu in the wall rock,but there are prominent or obvious enrichment of Cu in Ores,mineralized rocks and tectonic altered rock indicating that there may be a certain genetic connection between uranium and copper mineralization in the region.?4?From metamorphic rock to mixed lithified metamorphic rock,then to migmatite and to migmatitic granite,with the increasement of migmatization,the variation characteristics of major,trace and rare earth elements in various rocks in the area of Yakou region are as follows:?1?The obvious increase of the major element is K₂O and Na₂O,and the obvious decrease of the major elements are Fe₂O₃,MgO,CaO and TiO₂.?2?The content of trace elements like Co,In,Sc and Ni decrease distinctly,and the initial content of U is found in the mixed lithified metamorphic rock and new growing veins.?3?Comparing to metamorphic rock,the variation of?REE?LREE?HREE in the mixed lithified metamorphic rock is not obvious,which indicates that it has a certain inheritance.But the content of?REE and HREE in the migmatite are obviously increased,while in the content of?REE?LREE?HREE in the migmatitic granite are significantly reduced.?5?The variation characteristics of major,trace and rare earth elements in all kinds of ores,mineralized rocks and altered rocks in Yakou are:?1?From the comparison of ore,mineralized rock and altered rock with the major elements of the wall rock,in the process of uranium mineralization,the content of SiO₂ decreases obviously,while the content of MgO and TFe₂O₃ increases obviously,showing the uranium mineralization process is associated with the desiliconizing,Mg and Fe rich alteration metasomatism.?2?the variation characteristics of trace elements in altered rock and ore and mineralized rock are basically consistent,and their types and content of the elements are more than those of wall rock.Their trace element assemblage is U-Sc-Mo-Cd-Pb-Bi-Th.Compared with wall rock,the content of U,Cu,Co and In increase in the above rocks and minerals.?3?The content of rare earth elements in ore and mineralized rocks is significantly higher than that of its mineral-bearing wall rock,and all samples have high content of?REE,which reflects that the mineralization process in the area is accompanied by the increase of?REE.?6?From the diagram of the microelements and REE of the altered rock and the ore and mineralized rocks,they both have similar distribution patterns,which reflects the close relationship between tectonic alteration and uranium mineralization.?7?The uranium mineralization in this area is mainly influenced by tectonic and hydrothermal alteration.The hydrothermal alteration is closely related to metal-sulfide-mineralization.Especially in ore and mineralized rock and altered rock,there is a great or obvious enrichment of Cu in some samples,so the uranium mineralization is converted into Cu-U type mineralization in the Yakou area.?8?Compared with the characteristics of the migmatitic uranium ore in the Haita area,the ore-forming characteristics of Haita and Yakou area are different,whether the element content and the variation characteristic of the ore-forming wall rock,or the element species enriched in the ores,or the paragenetic mineral,showing that the ore-forming fluids in two areas may have some differences.