宁芜盆地宁藏中段次火山岩含矿性贝叶斯两组判别分析报告宁芜盆地位于淮阳山字型构造的前弧东翼与新华夏构造复合处，为地跨苏皖的中生代继承式陆相火山岩盆地。盆地明显受北北东及北西向断裂控制，呈北北向东延伸。边缘主要由三迭—侏罗系地层组成，中部则广泛分布火山岩系。火山岩系及少数下伏沉积岩系中发育有次火山岩，它们晚于该火山旋回侵入，并与火山岩在成分上相似。以fe、cu、s、p为主的多种矿产与次火山岩有直接关系。在宁芜中段取得31件次火山岩样品，其中1-15为含矿次火山岩及晚期脉岩，16-31为非矿次火山岩及侵入岩。每个样品分析sio2、tio2、al2o3、fe2o3、feo、mno、mgo、cao、na2o、k2o、h2o+等11项指标。原始数据见表2-1。表2-1原始数据样品/变量123456789101112131415161718192021222324252627282930154.1452.4856.4255.4857.1245.8643.8452.2854.7860.6657.9851.2464.2265.2558.6852.9055.9456.6954.3453.0758.5258.6654.7254.0262.3473.4672.2566.2067.3660.2620.890.880.820.800.750.880.600.660.890.640.810.850.650.550.650.920.861.060.820.801.011.000.850.680.550.020.250.230.360.65317.8617.3019.5916.6517.9814.2416.1815.3520.1215.7816.6516.7617.1717.1515.5018.8016.8415.2418.5417.4520.1519.4318.0618.7015.2813.0813.9413.4914.5915.5943.855.203.634.544.2513.802.857.041.554.864.609.721.821.933.536.353.1911.559.618.551.121.768.256.702.391.621.231.181.622.66第1页共3页54.396.032.255.233.847.833.881.743.133.124.647.611.332.056.223.585.191.530.553.611.731.733.463.185.711.111.821.862.344.3360.150.170.100.090.090.080.080.040.040.080.060.050.030.030.200.420.200.010.020.080.040.110.080.070.080.030.050.080.060.0673.462.571.543.032.042.562.222.832.842.143.142.901.691.662.092.092.941.230.761.902.642.551.101.622.140.170.521.511.652.2286.205.044.484.083.442.921.725.063.840.850.940.551.981.921.346.544.270.510.304.724.944.262.071.341.950.111.093.562.613.2795.365.727.826.006.256.445.004.006.144.705.318.008.258.043.902.894.123.340.656.147.006.717.086.703.250.480.770.263.904.12101.241.640.782.242.831.363.482.182.193.201.090.250.980.554.102.413.004.7911.540.830.770.631.881.464.007.596.324.804.394.78111.800.571.781.791.300.972.042.222.042.283.561.941.720.682.541.192.122.911.401.601.320.681.940.762.262.341.542.590.460.801/33148.121.2017.284.936.16.0.184.869.203.802.010.86经过30次迭代，得到有关参数如表2-2。表2-2由迭代法求出的各极小值角度fimin=2583996函数值rmin=9.228292e-02一类判别函数均值=3.041054二类判函数均值=-4.515806一类判别函数方差=3.145484二类判别函数方差=17.67206此时的线性判别函数的系数如表2-3。样品回代判别结果如表2-4。从回代结果看，90%以上的样品归类适当，仅有含矿类第二号样品（辉长闪安山玢岩，采自南山504孔），不含矿类第17号样品（角闪安山玢岩，采自莺子山龙王山组），第24号样品（钠长斑岩，采自李洼大王山组）三件样品归属有误。具体原第2页共3页因待查。当然，并不排除统计分析方法本身的概率风险。此外，从线性判别函数（表2-3）可以看到，对于判含矿与不含矿时的11项分析指标中，mno、na2o、mgo、h2o+及tio2起重要作用。对于含矿，前四项起正作用，最后一项起负作用。其中关于na2o的正作用可以理解为钠化蚀变是与铁的富集紧密相关联的。表2-3判别函数系数（b0）=64.3643（b1）=-0.9825（b2）=-18.3450（b3）=-1.5013（b4）=-0.8754（b5）=-0.8883（b6）=26.9320（b7）=2.8232（b8）=-0.3699（b9）=4.0971（b10）=1.9838（b11）=2.5511表2-4样品回代和判别结果样品号原类别判别函数值判别类别1234567891011121311111111111111.6365-0.85042.96914.77612.13642.86622.97043.99472.53801.82762.84345.84125.943012111111111112/31415111.62764.495911样品号原类别判别函数值判别类别161718192021222324252627282930312222222222222222-6.86641.5847-10.8404-9.0242-2.4931-3.8847-4.5430-0.10800.4634-2.3713-9.2601-12.7419-5.3852-2.4846-1.0441-3.25432122222212222222四、参考文献1.潘恩沛《判别分析》讲座笔记（未刊），1986年，西南冶金地质科学研究所。2.赶汉地质学院岩石教研室宁芜中段某些安山质火山岩、次火山岩岩石学特征及其与玢岩铁矿的关系，1978年，地质出版社《宁芜火山岩铁铜矿床会议选集》，第154-177页。3/3第3页共3页
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