广西箭猪坡矿床首次发现的石英脉型锡矿体特征及锡石微量元素地球化学意义

Characteristics of Quartz Vein Type Tin Orebody in the First Discovered Jianzhupo Deposit in Guangxi and Geochemical Significance of Trace Elements of Cassiterite

箭猪坡矿床是丹池成矿带南端的一个以铅锌锑为主的矿床,随着2012—2014年在箭猪坡矿床钻孔中石英脉型锡矿体的首次发现,打开了箭猪坡矿床新的找矿空间。新发现的锡矿体矿石矿物组合类型主要为锡石+闪锌矿+脆硫锑铅矿+黄铁矿+石英及锡石+脆硫锑铅矿+石英+方解石。箭猪坡矿床锡石呈自形-半自形粒状,锡石粒径多在0.1~0.2 mm,少数0.02~0.05 mm,分布在含硫化物的石英脉裂隙中。物相分析显示箭猪坡矿床锡主要赋存在锡石中,锡石物相占83.33%~100%。阴极发光(CL)图像显示箭猪坡矿床中的锡石经历了两期结晶作用:早期锡石(Ⅰ)和晚期锡石(Ⅱ),早期锡石CL荧光亮度较小,呈暗灰色至黑色;晚期CL荧光亮度较大,呈白色至浅灰色。锡石单矿物SnO2含量91.623%~96.288%,平均94.03%,杂质主要有Fe、W、In等,其中FeO含量0.02%~0.52%,WO3含量0.02~1.34%,In2O3含量0.476%~0.954%,Sn与FeO、In2O3呈负相关,锡石中FeO、WO3、Ta2O5、Nb2O5、MnO含量指示箭猪坡锡形成于中低-中温热液环境,成矿热液来源于高度分异演化的花岗质岩浆。通过与大厂矿田西矿带上部脉状锡矿体的类比分析,具有相似的成矿条件及矿物组合,推测所揭露的脉状锡矿(化)体相当于西矿带上部脉状锡矿(化)体,而下部的网脉状、似层状锡矿体尚未揭露到,由此预测箭猪坡矿床深部找矿空间及找矿潜力大。

Jianzhupo deposit is a Pb-Zn-Sb deposit at the southern end of Danchi metallogenic belt.With the first discovery of quartz vein-type tin ore body in the drilling hole of the Jianzhupo deposit in 2012—2014,a new prospecting space of Jianzhupo deposit has been opened.The newly discovered types of tin ore body mineral are mainly cassiterite+jamesonite+quartz+calcite and cassiterite+sphalerite+jamesonite+pyrite+quartz.The cassiterite in the Jianzhupo deposit is in the form of automorphic-semiautomorphic granules.The size of cassiterite is mostly 0.1—0.2 mm,a few 0.02—0.05 mm,which is distributed in the quartz vein cracks containing sulfides.The phase analysis shows that the tin in jianzhupo deposit are mainly hosted in cassiterite,the cassiterite phase accounts for 83.33%—100%.Cathodoluminescence(CL)images show that there are two stages of crystallization of cassiterite in Jianzhupo deposit:early cassiterite(Ⅰ)and late cassiterite(Ⅱ).The early cassiterite CL has a low fluorescence brightness,which is dark gray to black;The fluorescence of CL is bright,and it is white to light gray.The SnO2 content of cassiterite is 91.623%—96.288%,with an average of 94.03%.The impurities are mainly Fe,W,In,etc.of which FeO content is 0.02%—0.52%,WO3 content is mostly 0.02—1.34%,and In2O3 content is 0.476%—0.954%.Sn was negatively correlated with FeO and In2O3.The contents of FeO,WO3,Ta2O5,Nb2O5 and MnO in cassiterite indicate that Jianzhupo tin is formed in a low-medium-temperature hydrothermal environment,and the ore-forming hydrothermal fluid is derived from high differentiation evolving granitic magma.By analogy analysis with the vein-shaped tin ore body in the upper part of the West ore belt of the Dachang ore field,it has similar metallogenic conditions and mineral combinations.Ore(chemical)body,and the lower network vein-like,layer-like tin ore body has not been revealed,thus predicting the deep prospecting space and prospecting potential of the Jianzhupo deposit.