滇西腾冲大硐厂Pb-Zn矿床成因:来自稀土元素地球化学的证据  

Genesis of the Dadongchang Pb-Zn deposit in the Tengchong area of the western Yunnan:Evidence from the REE Geochemistry

作　　者：杨正香 邓明国[1] 牛春晖 贾桢 杨佳飞 杨正良 YANG Zhengxiang;DENG MingGuo;NIU Chunhui;JIA Zhen;YANG Jiafei;YANG Zhengliang(Faculty of Land and Resources Engineering,Kunming University of Science and Technology,Kunming 650221,China;The Second Institute of Geology and Mineral Resources Exploration,Gansu Bureau of Geology and Mineral Resources Exploration and Development,Lanzhou 730020,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650221 [2]甘肃省地质矿产勘查开发局第二地质矿产勘查院,甘肃兰州730020

出　　处：《矿物学报》2024年第1期97-110,共14页Acta Mineralogica Sinica

基　　金：国家自然科学基金项目(编号:42272078,41762009);云南省重大科技专项(编号:202202AG050006-3);云南省科技厅科技计划项目(编号:202305AT350004-2)。

摘　　要：腾冲大硐厂Pb-Zn矿床是西南“三江”成矿带腾冲地块东部具有代表性的矽卡岩型矿床之一,其成矿过程可划分为矽卡岩期(早、晚矽卡岩阶段)和石英-硫化物期(早、晚硫化物阶段)。方解石是该矿床中最主要的脉石矿物,其形成与铅锌矿密切相关。本文对主成矿期(石英-硫化物期)不同阶段方解石的REE特征与成矿早期(矽卡岩期)符山石、绿帘石以及大弯山单元花岗岩、大理岩和灰岩的REE特征进行对比研究。结果表明,主成矿期2个阶段方解石REE配分模式均为右倾型,∑REE分别为84.68×10^(-6)~125.58×10^(-6)和35.08×10^(-6)~38.24×10^(-6),LREE/HREE值为1.59~2.04和4.36~5.38,(La/Yb)_(N)值为1.12~1.81和4.01~5.72,(La/Sm)_(N)值为2.62~3.16和5.09~6.38,(Gd/Yb)_(N)值为0.64~0.97和1.22~1.30。2个阶段方解石的Yb/La-Yb/Ca投点位于岩浆成因与热液成因的交界部位,符山石、绿帘石、早硫化物阶段方解石和大理岩的Y/Ho值与大弯山单元花岗岩关系密切,晚硫化物阶段方解石的Y/Ho值介于大弯山单元花岗岩和围岩之间,暗示矿床主成矿期两阶段方解石皆为岩浆热液成因,成矿流体主要来源于岩浆热液,但成矿流体在主成矿期晚硫化物阶段的水岩反应过程中可能遭受了二叠系灰岩地层的强烈混染。从成矿早期到主成矿期δEu值分别为1.25~1.75和0.54~0.78,δCe值为0.85~0.94和0.94~1.05,氧化还原环境的转变可能是导致矿质沉淀的主要原因,后期水岩反应对矿质沉淀也存在少量影响。矿区中矿体离早白垩世花岗斑岩体较近,主要呈层状、似层状产于断裂的蚀变碳酸盐岩(矽卡岩)中,矽卡岩矿物自深向浅具有分带性。综合区域地质特征及矿床控矿因素分析,认为大硐厂Pb-Zn矿床属于矽卡岩型Pb-Zn矿床。The Dadongchang Pd-Zn deposit in the Tengchong area is one of the representative skarn type deposits in the eastern Tengchong Block of the"Sanjiang"metallogenic belt in Southwest China.The skarn period(early and late skarn stages)and quartz-sulfide period(early and late sulfide stages)in its metallogenic process have been identified.Calcite is the main gangue mineral in this deposit,and its formation is closely related to the Pb-Zn mineralization.In this paper,REE characteristics of calcites in different stages of main mineralization period(quartz-sulfide period)have been compared with those of vesuvianites and epidotes of the early mineralization period(skarn period),and those of the,Dawanshan unit granite,marble and limestone.The results show that calcites in two stages of the main mineralization period have right-declined REE distribution patterns,withΣREE contents of 84.68×10^(-6)~125.58×10^(-6) and 35.08×10^(-6)~38.24×10^(-6),LREE/HREE ratios of 1.59~2.04 and 4.36~5.38,(La/Yb)_(N) values of 1.12~1.81 and 4.01~5.72(La/Sm)_(N) values of 2.62~3.16 and 5.09~6.38,and(Gd/Yb)_(N) values of 0.64~0.97 and 1.22~1.30,respectively.Data of two-stage calcites are plotted in the interface fields of magmatic and hydrothermal origins in the Yb/La-Yb/Ca diagram.The Y/Ho ratios of vesuvianites,epidotes,calcites of the early sulfide stage,and marble samples are closely related to those of the Dawanshan unit granite samples,while the Y/Ho ratios of calcites of the late sulfide stage are varied between those of the Dawanshan unit granites and those of wallrocks.It is suggested that the calcite in two stages of the main mineralization period of the deposit is of magmatic-hydrothermal origin,and the ore-forming fluid is mainly derived from the magmatic-hydrothermal fluid,but the ore-forming fluid in the late sulfide stage of the main mineralization period could be strongly contaminated by the Permian limestone strata in the process of water-rock reaction.TheδEu values are 1.25~1.75 and 0.54~0.78,and theδCe values are 0.85~0.

关 键 词：稀土元素 方解石成因 成矿流体来源与演化 矽卡岩型Pb-Zn矿床 

分 类 号：P597[天文地球—地球化学] P618.4[天文地球—地质学]