广西大厂矿田大福楼锡多金属矿床地质与地球化学特征

位于大厂矿田东带的大福楼锡矿床是一个以产锡和锌为主、研究程度相对较低且规模较大的锡石硫化物型矿床。针对该矿床特征典型、研究薄弱、成矿条件优越及找矿前景可观等因素,对流体包裹体和硫同位素特征进行了研究。结果表明:大福楼矿床主要发育6种类型的流体包裹体(单相气相包裹体、单相盐水溶液包裹体、两相富蒸汽包裹体、两相富液体包裹体、含CO2相包裹体和含NaCl子矿物包裹体),包裹体大小一般为5～25μm,少数为30μm,主要呈多边形、米粒状、椭圆形、长方形以及不规则状,少数呈三角形以及半自形的负晶形。包裹体主要含Ca2+、Mg2+、K+、Na+、SO42-、Cl-和NO3-等液相成分以及CO2、CO、CH4和N2等气相成分。成矿流体属于Na(K)-Ca(Mg)-Cl型卤水溶液,呈弱酸性,包裹体中不含O2,表明成矿过程中没有游离氧的存在,而CO2、CH4和H2的含量相对较高,表明成矿流体具有较强的还原性。矿物中含NaCl子矿物包裹体的大量存在,显示成矿流体具有岩浆热液特征。包裹体中的氟对锡的迁移和沉淀起着非常重要的作用,而硫盐矿物的存在可能对锡的富集沉淀造成不利影响。硫同位素研究结果显示,矿石的δ(34S)值为-1.54×10-3～2.18×10-3,极差为3.72×10-3,均值为1.141×10-3,以正值为主,矿石δ(34S)值稍微偏离基性岩类硫的范围,而与陨石硫的同位素组成非常接近,具有重硫富集和典型岩浆来源的特征。锡矿硫元素可能部分来源于龙箱盖隐伏复式花岗岩体,显示

Geology and geochemistry of Dafulou tin-polymetallic ore deposit in Dachang ore field, Guangxi, China

The Dafulou tin deposit,located in the eastern of the Dachang ore field,is a large-scale cassiterite-sulfide deposit,of which the main mineral types include tin and zinc.Because of the typical deposit characteristics,weak research degree,excellent mineralization conditions and good prospecting potential,the fluid inclusions and sulfur isotopes were studied.The results show that there are six types of fluid inclusions(e.g.single-phase gas inclusions,single-phase brine inclusions,two-phase vapor-rich inclusions,two-phase liquid-rich inclusions,carbon dioxide-bearing,containing NaCl daughter minerals).The size of the fluid inclusion is 5-25 μm,yet 30 μm in the minority,whose shapes consist of polygon,rice-shape,oval,rectangular and irregular shape,but little in the shape of triangle and negative crystal.The liquid and gas components are composed of Ca2+,Mg2+,K+,Na+,SO42-,Cl-,NO3-and CO2,CO,CH4,N2,respectively.The fluid is characterized by the type of Na(K)-Ca(Mg)-Cl brine solution and weak acid,without oxygen existing,which suggests that the free oxygen does not exist.The high contents of CO2,CH4 and H2 indicate the strong reduction of the ore-forming fluid.A plenty of daughter minerals containing NaCl show the magmatic hydrothermal features of the fluid.The content of fluorine plays an important role to tin in the migration and precipitation,but the sulfur has an adverse effect on tin mineralization.The sulfur isotopes studies indicate that theδ(34S)values change from-1.54×10-3 to 2.18×10-3,with the maximum difference value of 3.72×10-3 and an average value of 1.141×10-3,dominated by the positive value.In the whole,theδ(34S)values deviate from the value scope of the magma and accord with that of the meteorite sulfur,characterized by the heavy sulfur-rich and typical magma source.In the Dafulou ore deposit the sulfur may be supplied by the Longxianggai concealed granite,which plays an important role in the mineralization.The tin ore is related closely to I-type granite.