滇西北燕山期含矿花岗岩与全球埃达克岩地球化学特征对比

Comparison of Geochemical Characteristics Between Yanshanian Ore-bearing Granites in Northwest Yunnan and Global Adakites

为便于下一步找矿勘查研究,在前人研究基础上,收集并整理滇西北燕山期含矿岩体地球化学数据,结合现有研究成果,对滇西北地区进行整体性研究。根据数据筛选原则,绘制置信椭圆,计算相应交叠率,采用大数据方法,计算不同元素对比值,与全球埃达克岩对比,共获得图件65 536个。研究表明:燕山期岩体具有全球埃达克岩属性但又有其自身特点。某些元素比值(含Mo、Cu)较小且超出了全球埃达克岩的范围,说明Mo和Cu元素在该地区燕山期岩体中占据主导因素,富集程度较好。在K_(2)O/Mo-SiO_(2)/Cu、Na_(2)O/Cu-SiO_(2)/Mo、MnO/Cu-SiO_(2)/Cu和Na_(2)O/Zn-SiO_(2)/Mo等图件中,Mo、Cu元素与SiO_(2)、TiO_(2)、K_(2)O、Na_(2)O等拟合程度较好,具有一致的变化趋势,另外斑岩铜钼矿含矿流体作用和矿化作用不断演化,燕山期与含矿有关的花岗岩数据点偏离全球埃达克岩分布范围越远,其逸出程度也越大。该区燕山期含矿岩体与埃达克岩具有相似的产出背景,将埃达克岩的相关研究应用于该区,有助于进一步指导地质工作。

Sanjiang area in southwest China is an important area for geological research.On the basis of previous studies,through collecting and collating the geochemical literature related to Yanshanian deposits in the Geza island arc,418 representative geochemical data of ore-bearing rock masses in the area were obtained,including Xiuwacu tungsten-molybdenum deposit,Tongchanggou molybdenum-copper deposit,Relin molybdenum-tungsten-copper deposit,Hongshan copper-molybdenum deposit and Hongniu copper-molybdenum deposit.Combined with computer big data,referring to previous research methods and according to the principle of data screening,the data with SiO_(2) content greater than 56%and less than 90%(granite SiO_(2)>56%)were retained during screening.Excluding data with H 2O and LOI content greater than 7%and CO_(2) content greater than 3%(high H 2O and LOI content indicates strong alteration;high CO_(2) content indicates strong carbonation and calcitization).Remove some samples with abnormally high content of main elements,such as samples with Fe 2O 3>30%and abnomally high MnO content.Remove the data with abnormally high trace elements(sample retention).Draw the confidence ellipse and calculate the corresponding overlap rate.Meanwhile,the abnormal values in the study area(such as abnormal high values,abnormal low values,20 times higher than the average value of sample elements,etc.)were deleted during the study,the sample was retained and the negative value(which may exceed the detection limit)was deleted.The big data method was used to calculate the comparison values of different elements,and 65536 maps were obtained by comparing with the global adakites.The study shows that the Yanshanian rock mass has the global adakite attribute,but also has its own characteristics.Some element ratios(the denominator contains Mo and Cu)are small and exceed the range of global adakite,which indicates that Mo and Cu elements dominate the Yanshanian rock mass in this area and the enrichment degree is good.In maps such as K_(2)O/Mo-SiO_(2)/Cu,Na_(2)O/Cu-SiO_(2)/Mo,MnO/Cu-SiO_(2)/Cu,Na_(2)O/Zn-SiO_(2)/Mo,Mo and Cu fit well with most elements such as SiO_(2),TiO_(2),K_(2)O and Na_(2)O,and have the same trend of change,which indicates that the ore-bearing fluid and mineralization of Mo and Cu porphyry copper molybdenum ore are evolving continuously.The farther the Yanshanian granite data points related to ore-bearing deviate from the global adakite distribution range,the greater the escape degree.The Yanshanian ore-bearing rock mass in this area has a similar occurrence background to adakites.The application of relevant research on adakites in this area can further guide geological work.