【摘要】 拉拉铁铜矿床是康滇铜矿带最大的IOCG矿床之一,过去曾一度被认定为海底喷流成因,现已逐渐被学者摒弃。然而,对于典型IOCG矿床的实例研究尚存在诸多疑问,特别是对拉拉地区广泛分布的钠长岩类与成矿关系的争议颇多。文中通过对拉拉小露天采场细碧角斑岩建造进行岩相学、地球化学和电子探针面扫描研究,发现其成矿期晚于细碧角斑岩建造形成时期,不存在火山喷发沉积成矿期。岩相学研究表明,角斑岩基质中既有原生钠长石呈残余斑晶产出,也有次生钠长石呈它形粒状交代原生钠长石现象,且角斑岩含矿量较细碧岩低;钠长石的电子探针面扫描显示磁铁矿沿钠长石四周分布,且晚期成矿流体具有富K和Al的特点,说明细碧岩受到了晚期构造变动的影响。成矿流体呈脉状侵入到细碧岩的片理中,在片理化带发育大量黑云母、白云母,并富集大量的金属氧化物、金属硫化物。地球化学显示,细碧角斑岩明显富集Nb、Ta、Zr和Hf,强烈亏损Ba、Pb、Sr和Ti,∑REE变化较大,成矿流体的Na含量较低且富含大量的K、Al、CO2和H2O。87Sr/86Sr初始比值为0.701 26～0.762 41,显示其受到了地壳混染影响。5件角斑岩εNd(t)值为-1.09～6.75,暗示流体上升途径亏损地幔—地壳的过程。成矿流体来自地下深处的岩浆房,不断上升至地壳,在上升过程中侵入到薄弱带或片理化岩石成矿,这一成矿过程类似于透岩浆流体模型。更多还原

【Abstract】 The Lala Iron-Copper Deposit,once considered submarine volcanic sedimentary mineralization,is now regarded by most scholars as one of the largest IOCG deposits in the Kang Dian copper belt.However,existing case studies of typical IOCG deposits had been problematic,at the center is the controversy over the widely distributed albitites and their relationship to mineralization in Lala area.Here,through petrographical,geochemical and scanning electron microprobe analyses of spilite-keratophyre formation in the Lala Xiaolutian pit,we confirm that the mineralization period was later than the spilite-keratophyre formation,therefore volcanic sedimentary mineralization did not occur.Our petrography data showed that both primary albite phenocrysts and secondary albites were in the keratophyre matrix;secondary albites replaced primary albites with small anhedral granular albites;and ore-bearing capacity of keratophyre was low.Electron microprobe analysis showed that magnetite is distributed along the albite,and the late ore-forming fluids are rich in K and Al,suggesting spilite was affected by the late tectonic movement.Moreover,the ore-forming fluid intruded into spilite foliation in a vein pattern,producing large amount of biotite and muscovite and enriching metal oxides and sulfides in the schistositilization zone.Geochemical composition revealed that spilite-keratophyre formation was significantly enriched in Nb,Ta,Zr and Hf,and depleted greatly in Ba,Pb,Sr and Ti;∑REE changed largely;and the ore-forming fluid had lower Na but higher K,Al,CO2 and H2 O contents.The initial 87 Sr/86 Sr ratio lied between 0.70126-0.76241,indicating it has been affected by crustal contamination.Furthermore,five keratophyre samples yielded aεNd(t)value of-1.09-6.75,consistent with a mantel-crust process,such that the ore-forming fluid formed initially in the deep magma chambers,ascended then to the crust and intruded into the weak zone or foliated rock.This process is similar to the transmagmatic fluid model.更多还原