摘要
报道了阿尔金东段北缘的古元古代晚期壳源火成碳酸岩全岩地球化学和锆石SHRIMP定年结果.它们明显切割围岩,以岩株状、岩脉状产出,包裹不同类型围岩包体.岩石主要由方解石、透辉石组成,含石英、长石等长英质矿物.岩石高CaO(20.56%～39.80%),SiO2含量变化较大(23.33%～54.06%),稀土总量低(TREE=28.36×10-6～63.01×10-6)、弱负铕异常(Eu/Eu*=0.69～0.83)、轻重稀土分离不强((La/Yb)N=9.20～16.85),相对富集大离子亲石元素Sr、Rb、Ba、Th,亏损高场强元素Nb、Ti、P.锆石具核-边结构,边部锆石普遍存在不明显的环带,具变质深熔锆石的结构特征,其207Pb/206Pb加权平均年龄为1931±18Ma.它们是高级变质作用条件下米兰岩群不纯大理岩深熔作用的产物.
This paper reports whole-rock geochemical compositions and zircon dating results of late Paleoproterozoic crustally-derived carbonatite in the northern Altyn Tagh.The carbonatite cuts contry rocks and occurs as stocks or dikes and contains different types of contry rocks.It is mainly composed of calcite,diopside,and a few silicate minerals(such as,feldspar,quartz,etc.).Samples of the carbonatite are characterized with high CaO contents(20.56%-39.80%),a large range of SiO2 contents(23.33%-54.06%),low TREE(28.36×10-6-63.01×10-6),weakly negative Eu anomalies(Eu/Eu*=0.69-0.83),moderately fractionated REE patterns((La/Yb)n=9.20-16.85).Compared with Sr,Rb,Ba,Th(LILE),the high field strength elements(HFSE),especially Nb,Ti and P,are strongly depleted.Zircons of the carbonatite show core-rim textures,and commonly show weakly zoning.SHRIMP U-Pb zircon dating result of the carbonatites is 1 931±18 Ma.All these threw lights on that the carbonatite are formed by the anatexis of impure marbles from Milan group.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2012年第5期929-936,共8页
Earth Science-Journal of China University of Geosciences
基金
中国地质调查局J46C001002(石棉矿幅)1:25万区域地质调查(修测)项目(No.200413000006)
关键词
火成碳酸岩
地质年代学
地球化学
岩石学
阿尔金北缘
derived carbonatite
geochronology
geochemical geochemistry
Petrology
northern Altyn Tagh.
