云南播卡金矿区钠长岩地球化学特征及其地质意义

摘要

The Boka gold deposit is located in the Dongchuan ore concentration area,and belongs to Yunnan Proterozoic copper polymetallic mineralization belt.This paper reports the petrography,geochemistry and isotope features of albitite that is closely related to mineralization.Studies show that the mineral compositions ofalbitite are albite,pyroxene,biotite,and the major element characteristics indicate a high Na,alkali-enriched,metaluminous,alkaline-peralkaline rock.This albitite is characterized by low ∑REE,strong enrichment ofLILE(K,Rb,Nd)and LREE(La,Ce,Sm),and depletion of HFSE elements (Nb,Ta,U,Th).Based on Lr,ε Nd(t) isotopic geochemistry,it is suggested that Boka albitite was produced by magmatism of Middle Proterzoic continent rift in Huili-Dongchuan area,and it was derived from the deep mantle with the addition of some crustal materials in the magma source region.%播卡金矿床位于滇中元古代铜金多金属成矿带之东川矿集区.重点报道了区内与成矿密切相关的钠长岩的岩相学、岩石地球化学及同位素特征.研究表明,播卡钠长岩的主要造岩矿物有钠长石、辉石、黑云母,主量元素特征显示其为富碱、高钠、偏铝质的碱性-过碱性岩石.岩石的稀土元素总量低,相对富集轻稀土元素,明显富集大离子亲石元素K、Rb、Nd及轻稀土元素La、Ce、Sm,相对亏损高场强元素Nb、Ta、U、Th等.岩石的Ir值、εNd(t)值显示,其可能为中元古代晚期会理一东川一带大陆裂谷岩浆作用的产物,来源于深部地幔,可能有部分陆壳物质的参与.