The Research Of Ralationship Between Alkaline Rock And Iron Of Ni-he Iron Deposit In Luzong Basin, Anhui, China

The Luzong volcanic basin of Middle-Lower Yangtze River metallogenic belt had discovered Ni-he Iron Deposit which is a large-scale ore deposit and contain 0.2 billions tons iron,0.13 billions pyrites,13 millions anhydrite. The main stage of mineralization related to diorite porphyry and the ore body located at the top of diorite porphyry. Basic the detail observation, there is another small-scale iron mineralization stage which located at monzonite porphyry. The ore mineralization of this stage lack of research and further study will be helpful to acknowledge the mineralization of this ore deposit as well as the mineralization of Luzong Mesozoic to a certain extent.On the basis of predecessors’ research and the field observation, indoors work, use the method of petrology, geochemistry et al., the geological characteristic especially the alkaline rock had been further study and had have a certain understandin.The intrusion mainly are diorite porphyry and syenite, furthermore there are dike rock such as trachyandensite, monzonite porphyry and syenite aplite et al..The metallic minerals of early iron mineralization are magnetite and pyrite, and the nonmetallic minerals are anhydrite, pyroxene, quartz, apatite and garnet et al.. The metallic minerals of lately iron mineralization are magnetite and pytite and the nonmetallic mineralization are pyroxene, biotite and apatite et al.. The alteration zone of Ni-he can be divided into three which are dark color alteration, superposition alteration and light alteration from bottom to top. Base the observation of field and microscope, combine with the research of generation between different minerals, the alternation of minerals, the relationship of wall rock alteration between mineralization, the stage of mineralization in this deposit can be divided into two hydrothermal stage. The early stage include pyroxene (garnet)-anhydrite-magnetite, chlorite-epidote-carbonate and argillite. The lately stage include alkali-feldspar, magnetite and pyrite.The lately mineralization of iron related to the intrusion of monzonite porphyry which is occurrence as dike and dissemination. monzonite porphyry, and the rock belongs to alkaline series which phenocryst is compose of albitization of andesine and orthoclase when the matrix is compose of orthoclase, oligoclase and less augite, biotite. In the course of albitization the iron content should be less-much-less from primary rock to alteration rock and ore-bearing rock when the age of them is consistent. The lately mineralization’s characteristic of lithogeochemistry show that the iron content of syenite aplite(alteration rock) far less than the monzonite porphyry(ore-bearing rock) and the age of them is nearly consistent which is show the course of sodium fluid from deep to shallow. It indicates that the enrichment of iron is closely relate to albitization.The result of LA-ICP-MS of zircon’s U-Th-Pb isotopic dating show that the age of diorite porphyrite is 132.7±1.4Ma when the monzonite porphyry is 131.5±1.4Ma. They are all products of Zhuanqiao circle. Combine with the relationship that the trachyandensite and the diorite porphyrite were cut by monzonite porphyry, and different mineral assemblage between two stage, the iron mineralization which relate to monzonite porphyry should be latter than the iron mineralization which relate to diorite porphyrite and belongs to the latest mineralization of Luzong. The characteristic of lithogeochemistry show that monzonite porphyry has a similar REE pattern with diorite porphyrite, it indicate that they have a same origin. And harker diagrams show that they have evolutionary relationship. The TiO2-AlO3-MgO genesis illustration of magnetite indicates that the formation of two magnetite relate to the intrusion of intermediate rock and influenced by hydrothermal lately.Combite with the predecessors’ research and research of this article, the mineralization of Ni-he Iron Deposit can be divided to Middle-Late Triassic Period deposition and Late-Zhuanqiao circle of Early Cretaceous. The Late-Zhuanqiao circle of Early Cretaceous include two stage.The stage one is the maily mineralization of Ni-he Iron Deposit which relate to diorite porphyrite when the mineralization of stage two relate to the monzonite porphyry. Monzonite porphyry and diorite prophyrite came from a same origin but different occurrence because of different stage of magmatic evolution and two stage magnetite all came from magnetite. The scale of lately mineralization is small, the reason may be:1,early iron mineralization which relate to diorite porphyrite take the most of iron and result of the poor of lately mineralization; 2,imonzonite porphyry has rich Na itself then lead to the poor of iron it can extraction; 3,the occurrence of exposure just a small part of alkaline rock, there is a big ore body in deep probably.Base the research had been finished, combine with the characteristic of other alkaline rock associate with iron in Luzong, the paper suggest that in the deep of Ni-he even Luzong, there is another stage iron mineralization which relate to alkaline. In the deep of Lu-zong still have a big potential of mineralization.