滇西北伊隆迈勘查区玢(斑)岩地球化学特征及地质意义

Geochemical Characteristics of Porphyrite and Porphyry of Yilongmai Exploration Region in Northwest Yunnan, and Its Geological Significances

为进一步找矿工作提供一定的地质依据,系统总结了勘查区玢（斑）岩的岩石特征,并分析探讨其岩石地球化学特征、成因及地质意义。岩石化学特征表明,该区玢（斑）岩SiO2含量为59.06%～68.62%,全碱（ALK）值为6.32%～7.35%,显示出富钾富钠的特点,铝饱和指数（A/CNK）为1.20～1.59,表现为过铝质;岩石中Rb、Ba、Th、U等大离子亲石元素富集,Nb、Ta、Hf等高场强元素亏损,高Sr值(340×10-6～868×10-6),低Y值(17.47×10-6～22.18×10-6)和Yb值(1.57×10-6～1.83×10-6)指示岩石类型为俯冲造山带钙碱性I型花岗岩系列;稀土总量(189.91×10-6～252.51×10-6)较高,明显富集轻稀土,且轻重稀土分馏明显（（La/Yb）N=14.82～22.3）,δEu值（0.79～0.87）表现出弱负异常。与区域格咱弧中酸性含矿岩体对比可知,它们在岩石地球化学特征上具有相似性,该区可能具有斑岩型矿床的成矿潜力。

In order to provide some geological basis for further prospecting work, summarized petrological characteristics of porphyrite and porphyry in the exploration region, explore geochemical characteristics, genesis and its geological significances. Geochemical features showed that SiO2 of porphyrite and porphyry are 59.06%～68.62%, the ALK values are 6.32%～7.35% show that the characteristics of enrich in potassium and sodium. The A/CNK values ranging from 1.20 to 1.59 indicate that they belong to the peraluminous attribute. These rocks are enriched in LILE, such as Rb, Ba, Th, U and depletion in HFSE, such as Nb, Ta, Hf. These have the high Sr(340×10-6～868×10-6) and low Y(17.47×10-6～22.18×10-6), Yb(1.57×10-6～1.83×10-6)content, indicating that these rocks belong to the subduction orogenic calc-alkaline granite and I-type series. These have high total REE(189.91×10-6～252.51×10-6), rocks are enriched in LREE and depleted in HREE and the fractionation is obvious（（La/Yb）N=14.82～22.3）. δEu values range from 0.79～0.84 show that the rocks are weak negative europium abnormalities. Comparied with the medium-acid ore bearing rock of the Geza arc, they are have similarities in the geochemical characteristics, and the exploration region may has the potential of porphyry deposit.