富氟花岗岩体系岩浆流体内稀土元素演化规律的实验研究

Experimental Study on Evolution of REE in Magmatic Fluid Phase in the F-Rich Granite System

高温高压实验结果表明 ,随着富氟过铝花岗质岩浆分离结晶作用的进行 ,在与熔体相共存的流体相中 ,REE浓度呈有规律地变化 :当温度从 75 0℃下降至接近固相线 (5 70℃ )时 ,流体相中REE浓度逐渐降低 ,这一规律与REE在稀有金属花岗岩体上部岩相带中REE含量贫化的地质事实相一致。在富氟过铝质花岗岩体系中 ,REE易于分散进入某些造岩矿物 (如黑云母等 )和副矿物(如萤石和锡石等 )中 ,从而不利于REE形成热液矿床。

Experiments of fractional crystallization under high T P conditions demonstrate that during crystallization of F bearing alumina oversaturated granitic magma, an evolutional trend of REE concentrations in fluid phase coexisting with melt phase is observed: When temperature drops from 750℃ down to solidus (about 570℃), the REE concentrations gradually decrease. This phenomenon is consistent with the geological fact that REE contents in the upper zones of rare metal granites are lower than in the deeper zones. REE mostly tend to disperse in some rock forming minerals (such as biotite) and some ore forming minerals (such as fluorite and cassiterite). The rest of REE partition into fluid phase. The evolution characteristics of REE in the F rich alumina oversaturated granite system are not favorable for forming hydrothermal deposits of REE.