摘要
德兴铜矿是中国华南地区重要的大型斑岩铜矿,由朱砂红、铜厂和富家坞3个矿床组成。在系统的钻孔样岩相观察基础上,本文把德兴朱砂红花岗闪长斑岩划分为3种类型蚀变岩(钾化-黑云母化蚀变岩、绿泥石化蚀变岩、石英-绢(白)云母化蚀变岩),其主要标志性蚀变矿物依次为:钾长石(黑云母)→绿泥石→石英+绢(白)云母,且热液蚀变程度依次增强。以Al2O3作为不活动组分,通过Isocon分析法表明:随着热液蚀变作用的持续进行,蚀变程度的逐渐增强,主量元素(P2O5)行为较稳定,Na2O、Sr元素大量活化迁出;高场强元素Hf、Th、U、V、Co、Nb、Ta等表现为弱活动性或不活动性;成矿元素Cu、Pb、W显示出大量带入,表明热液流体和成矿流体可能属于同一流体系统。稀土元素均发生一定程度的活化迁移,其中绿泥石化蚀变岩的LREE、HREE均较原岩亏损,而石英-绢(白)云母化花岗闪长斑岩的LREE、HREE富集/亏损情况因样品而异,相对增量/减量变化幅度较大。各类蚀变花岗闪长斑岩球粒陨石化配分模式表现较一致,均为轻稀土相对于重稀土富集的右倾分布,极弱Eu负异常,曲线左陡右平缓,尾部轻微上翘,形似铲状,反映岩浆源区角闪石的分离结晶作用。蚀变花岗闪长斑岩的Y/Ho比值与球粒陨石的Y/Ho比值基本一致,表明Y-Ho在热液蚀变过程中未发生明显分离。弱蚀变花岗闪长斑岩具有较高Sr/Y比值、La/Sm比值以及中等Sm/Yb比值,暗示源区残留相主要为角闪石±石榴子石。
Dexing copper ore field,one of the most typical porphyry deposits in South China,is composed of Zhushahong,Tongchang,Fujiawu ore deposits.Based on petrographic investigation of drill core samples,the mineralized granodiorite porphyries at Zhushahong deposit are divided into three altered rock types,namely,the biotite-potassium feldspar alteration type,chlorite alteration type,and quartz-sericite（muscovite） alteration type.The alteration intensity of the three types rock changes from low through intermediate to high in sequence.According to the immobility of Al2O3,the Isocon analysis shows that during the hydrothermal alteration,the major elements（P2O5） as well as high field strength elements（e.g.Zr,Y,Nb,Ta and Hf） and transitional elements are almost immobile,while Na2O and Sr are strongly depleted.Metallic elements of Cu,Pb and W dramatically move in,indicating that the hydrothermal fluid responsible for alteration and the ore-forming fluid may belong to the same fluid system.The chondrite-normalized REE distribution patterns of all samples show typical flat to listric-shaped patterns and reflect crystallization of amphibole.In terms of net element gain and loss,chlorite alteration rocks have undergone net REE loss,while the muscovite-quartz alteration porphyries shows great difference,the behavior of LREE/HREE is contingent on the samples.The Y/Ho ratios are similar to those of CI chondrite,which indicates that Y and Ho show a similar geochemical behaviour during hydrothermal alteration.The granodiorite porphyry rocks have high Sr/Y and La/Sm ratios and medium Sm/Yb ratios,indicating a magma source with the residual phases of amphibole and/or garnet.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2012年第12期3869-3886,共18页
Acta Petrologica Sinica
基金
国家基础研究发展规划项目(2012CB416705)
中国科学院"百人计划"项目
国家自然科学基金项目(41272112
40872065)
江西铜业集团地质勘查项目联合资助
