Study On Process Mineralogy Of Heavy Calcium Calcite Mine In Shangfang Town Of Western Zhejiang

Ground calcium carbonate is grinded from natural carbonate minerals.As one of the most versatile inorganic fillers,ground calcium carbonate（heavy calcium）is widely used in rubber,plastics and papermaking industries.At present,with the rapid development of the downstream extension industry of heavy calcium,the domestic demand for heavy calcium resources is increasing.Therefore,strengthening the research of heavy calcium calcite,especially the process mineralogy research closely related to production,has a positive role in accurately evaluating the ore quality of calcite and rationally allocating mineral resources.The Shangfang Town of Western Zhejiang Province is located in the eastern section of the Jiangxi-Hangzhou tectonic belt,close to the tectonic suture zone between the Yangtze plate and the Cathaysia plate.Calcite deposits are widely distributed in the area,and it is an important heavy calcium resource base in my country.This article focuses on Daqiaotou calcite mine in Shangfang Town.By Process mineralogical index testing for different ore samples,as well as comparison with other calcite mines in Hezhou,Guangxi,different types and grades of ore were classified.Observations by hand specimens,optical microscope and scanning electron microscope were used to find out the difference in color,structure,grain size and mineral composition of different types of ores.Results of major and trace elements,C-O isotope,and other geochemical analysis were used to reveal influencing factors for ore process indexes of calcium calcite.At the same time,combined with the regional geological background,the metallogenic environment,material sources and metallogenic process of the Daqiaotou calcite deposit are discussed to constrain the genesis of the deposit is revealed.Through the above-mentioned research,the main conclusions of this article are listed below:（1）The Daqiaotou calcite deposit in Shangfang Town occurred mainly in the Carboniferous Huanglong Formation.According to petrographic characteristics,ores of this deposit are divided into three categories:marble,marbled limestone and limestone.The main mineral component of ores is calcite.With the increasing of the marbleization degree,the ores become more coarse and the color turns whiter,with the decreasing of impurities.Combined with heavy calcium industrial mineralogical indicators（hue Lab value）,the ore is preferably divided into two categories:red phase ore and blue phase ore.（2）The results of trace element test showed that the total amount of rare earth elements was low（the average value was 3.35 ppm）,and the differentiation of light and heavy rare earths was obvious.Light rare earths were enriched.Large ion lithophile elements Sr,Pb and high field strength elements Zr,Hf,U and Y were relatively enriched,and Nb,Th,Pr and Nd were relatively depleted.The higher Sr/Ba and salinity index（Z）values indicate that the protolith was formed in the shallow marine environment.TheδCe value of limestone in the mining area shows weak negative anomaly,and has high V/（V+Ni）value and higher U/Th value than that of marble,indicating that the original rock is formed in the reductive sedimentary environment.With the deepening of marbleization,the metallogenic environment transits from relative reduction to relative oxidation.（3）The C-O isotopic composition shows that the source of carbon in limestone is mainly the decarboxylation of organic matter,and the original rock is not affected by terrigenous clastic materials.The acidic magmatic intrusion in the Early Cretaceous provides a heat source for the formation of calcite and promotes the recrystallization of limestone.In addition,the formation process of marbleized limestone and marble also experienced the transformation of atmospheric water and magmatic hydrothermal fluid in the late stage,which improved the quality of ore（impurity reduction,mineral bleaching,and grain size increase）.（4）Whiteness and hue are important process mineralogy indexes for the industrial application of heavy calcium.Particle size is an important factor affecting the whiteness and hue of heavy calcium ore.When the mesh is 100～400,the whiteness and hue show a steep change trend,and when the mesh is over 400,the change trend slows down to a near level.Therefore,it is suggested that the particle size of whiteness test in the general industrial exploration index of calcite should be modified to 400 mesh（38μm）.（5）The results of ore comparison between Shangfang Town in Quzhou and Hezhou in Guangxi show that Hezhou ore is generally better than Shangfang Town ore in whiteness and color.In terms of self-shape,the ore in Shangfang Town is higher than that in Hezhou City;Mineral particle size,Hezhou ore is generally high;In impurity content,Hezhou ore is generally low;Chemical composition,Hezhou ore impurity elements（Mg O,Si O₂,Al₂O₃,etc.）slightly lower,more pure.（6）The experimental results show that the sample with high TFe₂O₃content has a slightly higher hue（ab）value,and the typical Hezhou red marble has a low TFe₂O₃content.However,the hue of the ore is not directly positively correlated with the content of TFe₂O₃,and the influence of green Fe²⁺and red-brown Fe³⁺may be completely opposite.With the increase of Fe³⁺content,the whiteness and L value of heavy calcium powder showed a significant downward trend.The a,b values showed a clear upward trend.Based on a comprehensive study,it is believed that Daqiaotou Mine in Shangfang Town is a deposit formed by shallow sea deposition and magmatic hydrothermal metasomatism.The crystallization degree,the impurity content of raw ore and the content of chromogenic element(Fe³⁺)are the main factors affecting the whiteness and color difference of heavy calcium ore.