西藏多龙矿集区硅质岩岩石地球化学、Si-O同位素特征及其构造意义  

Geochemistry,Si-O isotopic compositions and its tectonic significance of the siliceous rocks in the Duolong deposit,Tibet

作　　者：韦少港 宋扬[2] 唐菊兴[2] 侯淋[3] 贺文[3] 王勤[4] 林彬[2] 缪宇 旦真王修 李发桥 WEI Shaogang;SONG Yang;TANG Juxing;HOU Lin;HE Wen;WANG Qin;LIN Bin;MIAO Yu;DANZHEN Wangxiu;LI Faqiao(The First Monitoring and Application Center,China Earthquake Administration,Tianjin,300180;Institute of Mineral Resources Chinese Academy of Geological Sciences,Beijing,10037;School of Earth Sciences and Resources,China University of Geosciences,Beijing,10083;College of Earth Sciences i Chengdu University of Technology,Chengdu,610059;Tenth detachment of armed police gold forces,Kunming,650001)

机构地区：[1]中国地震局第一监测中心,天津300180 [2]中国地质科学院矿产资源研究所,北京100037 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]成都理工大学地球科学学院,成都610059 [5]武警黄金部队第十支队,昆明650001

出　　处：《地质学报》2019年第2期428-439,共12页Acta Geologica Sinica

基　　金：国家自然科学青年基金"西藏羌塘地体南缘铁格龙南超大型浅成低温热液型铜(金)矿床保存条件研究"(编号:41402178);中国地质科学院矿产资源研究所科技基础性工作专项(编号:2014FY121000);中国地震局第一监测中心科技创新主任基金项目(编号:FMC2018005)共同资助

摘　　要：多龙矿集区位于班公湖-怒江成矿带西段、羌塘地体南缘。本文通过对多龙矿集区出露的硅质岩进行系统地球化学研究,探讨硅质岩形成的沉积环境及成因。多龙硅质岩SiO_2含量为92.83%～93.97%,属于纯硅质岩;Si/Al值为48.98～49.56,MnO/TiO_2值为0.36～0.64,Al_2O_3/(Al_2O_3+Fe_2O_3)值为0.77～0.81;硅质岩ΣREE为30.83×10^(-6)～34.59×10^(-6),LREE/HREE值为6.71～6.93,球粒陨石标准化曲线为Eu负异常而Ce弱正异常的右倾型曲线,北美页岩标准化曲线为Eu和Ce均显示出弱正异常的平坦型曲线;微量元素均严重亏损,仅Cu、Pb等亲铜元素亏损幅度较对较弱,V值为7.83×10^(-6)～8.84×10^(-6),V/Y值为1.25～1.48,亦表明硅质岩形成的环境海底热液活动不强烈,沉积环境为大陆边缘环境。多龙硅质岩δ^(30) Si_(NBS-28)值为1.0‰～1.1‰,δ^(18) O_(V-SMOW)‰为20.3‰～20.8‰,表明多龙硅质岩为浅海环境中沉积形成的原生的生物成因硅质岩。综合分析认为,多龙硅质岩形成于中晚侏罗世-早白垩世早期,为形成于对稳定的洋盆闭合的大陆边缘沉积环境的生物成因硅质岩,暗示南羌塘地体南缘于中晚侏罗世-早白垩世早期处于陆缘弧环境,班公湖-怒江洋仍在北向俯冲消减,洋盆尚未完全闭合。The Duolong deposit is located on the western edge of the Qiangtang terrane to the northwest of the The Bangong-Nujiang suture zone in Tibet.Based on detailed geochemical research,this paper discusses the genesis and tectonic setting of siliceous rocks in the Duolong deposit.These siliceous rocks share SiO2 content of 92.83%?93.97%,Si/Al ratios of 48.98-49.56,MnO/TiO2 ratios of 0.36-0.64,Al2O3/(Al2O3+Fe2O3)ratios range from 0.77 to 0.81,suggesting that these rocks form at the continent margin and contain a relatively high proportion of terrigenous muddy sediments.They share total REE content ranging from 30.83×10^-6 to 34.59X10_6and LREE/HREE ratios ranging from 6.71 to 6.93.Both the chondrite-normalized and the North American shale-normalized REE patterns show that siliceous rocks are enriched with LREE,and have slightly positive Ce anomaly and negative Eu anomaly.Besides,their trace elements are badly depleted,except the chalocophile elements(Such as Cu and Pb).These siliceous rocks share V content of 7.83×10^-6-8.84×10^6 and V/Y ratios of 1.25?1.48.Moreover,these rocks haveδ^30SiNBS-28‰values(1.0‰-1.1‰)andδ18Ov-SM0W%values of 20.3‰-20.8‰,respectively.Comprehensive analysis shows that the Duolong siliceous rocks formed between the late Jurassic and the Early Cretaceous in a continental margin environment and belong to biogenic siliceous rocks.The southern Qiangtang terrane was in a continental margin arc environment between the late Jurassic and Early-Cretaceous.The Bangongco-Nujiang oceanic lithosphere was still undergoing northward subduction beneath the southern Qiangtang terrane and the oceanic basin have not closed completely at that time.

关 键 词：多龙矿集区 硅质岩 地球化学 岩石成因 沉积环境 西藏 

分 类 号：P588.2[天文地球—岩石学] P597[天文地球—地质学]