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一六钨矿大地构造位置位于南岭成矿带中段南缘,粤北曲仁盆地西南缘,是粤北地区近年来重要的找矿勘查成果之一。矿床为典型的矽卡岩矿床,矿体赋存于上泥盆统帽子峰组矽卡岩以及NWW向钾长石-石英-白钨矿脉和云母石英脉中。通过野外观察和镜下研究,本文将成矿过程分为矽卡岩期(A)和热液期(B),矽卡岩期可以分为早期矽卡岩阶段(A1)、晚期矽卡岩阶段(A2)、钾长石英白钨矿阶段(A3),热液期可以分为云母石英脉阶段(B1)和石英碳酸盐阶段(B2)。矿区包含4种类型的包裹体:含子矿物三相包裹体(Ⅰ型)、气液两相水溶液包裹体(Ⅱ型)、CO_2水溶液三相包裹体(Ⅲ型)、纯CO_2包裹体(Ⅳ型),Ⅰ型包裹体仅见于A3阶段;Ⅱ型、Ⅲ型以及Ⅳ型包裹体在A3和B1阶段石英中均有发育,在A3和B1阶段白钨矿中还发育Ⅱ型包裹体。A3阶段Ⅰ型包裹体完全均一温度为162~381℃,盐度为30.1%~45.4%(wt%NaClequiv,下同省略),Ⅱ型包裹体完全均一温度为154~363℃,盐度为1.49%~11.0%,Ⅲ型包裹体完全均一温度为290~390℃,盐度为2.20%~6.88%;B1阶段Ⅱ型包裹体完全均一温度为152~381℃,盐度为1.65%~9.32%,Ⅲ型包裹体完全均一温度为281~378℃,盐度为2.00%~8.82%。激光拉曼探针分析表明,A3阶段和B1阶段流体中存在H_2O、CO_2、CH_4和少量CO_3~(2-),指示流体处于还原的环境。包裹体完全均一温度—盐度关系图表明,数据点主要集中于三个区域:a区对应早期出溶成因的高盐度流体,b区反映流体发生了不混溶作用,c区反映早期高盐度流体与低盐度地下水混合特征。各区包裹体代表了岩浆期后残余原始流体不同阶段的演化产物。通过Ⅰ型包裹体计算得出的成矿压力范围为86.0~415.8MPa,用Ⅱ、Ⅳ型包裹体对成矿压力进行校正得出,A3阶段成矿压力范围为86~115MPa,成矿温度为176~279℃;B1阶段成矿压力范围为55~93 MPa,成矿温度为160~228℃,估算成矿深度范围为3.62~4.26km。研究认为,流体在演化早期存在局部高压,流体不混溶作用要比外来流体混入更早发生,而流体混入促进了流体的不混溶作用。流体物理化学条件的改变、外来流体混入以及流体不混溶作用是引起钨矿沉淀的主要原因。
The 16th Tungsten deposit is located in the southern margin of the mid-section of the Nanling metallogenic belt and the southwestern margin of the Qu’er Basin in northern Guangdong. It is one of the important prospecting and prospecting achievements in northern Guangdong in recent years. The deposit is a typical skarn deposit. Ore bodies occur in the Upper Devonian hatzifen skarns and NWW-to-K-feldspar-quartz-scheelite veins and mica-quartz veins. Through field observation and microscopic study, the mineralization process is divided into skarn stage (A) and hydrothermal stage (B), skarn stage can be divided into early skarn stage (A1), late skarn stage (A2) and potassium feldspar scheelite (A3). The hydrothermal period can be divided into mica quartz vein stage (B1) and quartz carbonate stage (B2). There are four types of inclusions in the mining area: trilaminar inclusions (Ⅰ), gas-liquid two-phase inclusions (Ⅱ), CO_2 aqueous three-phase inclusions (Ⅲ) and pure CO_2 inclusions Type I inclusions only occurred in A3 stage. Type II, III and IV inclusions developed in both A3 and B1 quartz and type II inclusions in scheelite A3 and B1. The complete homogenization temperature of type I inclusions in stage A3 is 162 ~ 381 ℃ and the salinity is 30.1% ~ 45.4% (wt% NaClequiv, the same shall apply below). The complete homogenization temperature of type Ⅱ inclusions is 154 ~ 363 ℃ and the salinity is 1.49 The complete homogenization temperature of type Ⅲ inclusions is 290 ~ 390 ℃ and the salinity is 2.20% ~ 6.88%. The complete homogenization temperature of type Ⅱ inclusions in stage B1 is 152 ~ 381 ℃ and the salinity is 1.65% ~ 9.32% The complete homogenization temperature of type Ⅲ inclusions is 281 ~ 378 ℃ and the salinity is 2.00% ~ 8.82%. Laser Raman probe analysis showed that H_2O, CO_2, CH_4 and a small amount of CO_3 ~ (2-) exist in the A3 and B1 phases, indicating that the fluid is in a reducing environment. The complete homogenization temperature-salinity diagram of the inclusions shows that the data points are mainly concentrated in three areas: a area corresponds to the high-salinity fluid of early dissolution origin, b area reflects the immiscibility of fluid, c area reflects the early high Salinity fluid and low salinity groundwater mixing characteristics. The regional inclusions represent the evolutionary products of different stages of the residual primary fluid after the magmatic period. The ore-forming pressure calculated by type I inclusions ranged from 86.0 to 415.8 MPa. Correcting the ore-forming pressure with type II and type IV inclusions, the pressure range of A3 stage mineralization was 86-115 MPa and the metallogenetic temperature was 176 ~ 279 ℃. The formation pressure in B1 is 55 ~ 93 MPa and the metallogenic temperature is 160 ~ 228 ℃. The estimated mineralization depth ranged from 3.62km to 4.26km. The study shows that there is local high pressure in the early stage of fluid evolution, and the immiscibility of fluid occurs sooner than that of foreign fluid. The fluid mixing promotes the immiscibility of fluid. Changes in the physical and chemical conditions of the fluid, the influx of external fluids and the immiscibility of the fluid are the main causes of the precipitation of tungsten ore.