柴达木地块北缘牛鼻子梁镍铜矿床铂族元素和Re-Os同位素特征  

Platinum-group Elements and Re-Os Isotopic Characters of the Niubiziliang Ni-Cu Deposit in the Northern Margin of the Qaidam Block,Northwest China

作　　者：凌锦兰[1] 宋艳芳[1] 姜常义[1,2] 宋忠宝 赵彦锋[4] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]西安地质调查中心,陕西西安710054 [4]西北有色地质研究院,陕西西安710054

出　　处：《地质与勘探》2014年第1期138-144,共7页Geology and Exploration

基　　金：中国地质调查局地质矿产调查专项(编号1212011121089)资助

摘　　要：牛鼻子梁镍铜矿床是柴达木地块周缘新发现的一个岩浆硫化物矿床。该矿床所赋存的牛鼻子梁镁铁质-超镁铁质杂岩体出露面积约8km2,主要由橄榄岩、橄榄二辉岩、橄榄辉长岩、辉长岩组成。含矿岩石主要为橄榄岩和橄榄辉长岩。岩石和矿石的∑PGE含量(0.65×10-9～8.65×10-9)很低,可能是因为源区部分熔融程度较低导致的;在原始地幔标准化配分曲线图中,相对于Ni、Cu元素,PGE显示亏损,这是因为早期发生的硫化物熔离带走了大量PGE。星点状-浸染状矿石的(187Os/188Os)i比值为0.1944～0.5462,γOs值为56～338,显示在岩浆侵位和成矿过程中有较多地壳物质的加入。由于地壳混染而导致浸染状矿石Os同位素组成不均一,从而得出Re-Os等时线年龄(645Ma)大于岩体锆石年龄(367Ma)。The Niubizihang deposit is a newly discovered magmatic sulfide deposit, which occurs in the Niubiziliang mafic-utralmafic intrusion in the margin of the Qaidam block. The intrusion covers an area of about 8 km2 , and is mainly composed of peridotite, olivine websterite, olivine gabbro and gabbro. The major ore-bearing rocks are peridotite and olivine gabbro. The content of ∑ PGE （0.65 χ 10 -9 - 8.65 χ 10 -9 ） is very low probably due to the low-degree partial melting of mantle source. In the primitive-mantle normalized PGE patterns, the samples display depletion of PGE relative to Ni and Cu elements. The reason is that early segregated sulfide took away lots of PGE. The initial 1870s/188 Os ratio is 0. 1944 - 0. 5462, and γos is 56 -338, which show magma has involved more crustal material in the process of magma emplacement and mineralization. Because of heterogeneity in initial 1870s/188 Os ratios of disseminated ores caused by crust contamination, the Re -Os isochron age （645Ma） of disseminated ores is older than the zircon U - Pb age （367Ma） of the rock.

关 键 词：牛鼻子梁 铂族元素 Re—Os同位素 柴达木地块 

分 类 号：P618[天文地球—矿床学]