Disturbance of the Sm-Nd isotopic system by metasomatic alteration: A case study of fluorapatite from the Sin Quyen Cu-LREE-Au deposit, Vietnam
文献类型：期刊论文
| 作者 | Li, Xiao-Chun1; Zhou, Mei-Fu1; Yang, Yue-Heng2; Zhao, Xin-Fu3,4; Gao, Jian-Feng5 |
| 刊名 | AMERICAN MINERALOGIST
 |
| 出版日期 | 2018-09-01 |
| 卷号 | 103期号:9页码:1487-1496 |
| 关键词 | Apatite metasomatic alteration Sm-Nd isotopes |
| ISSN号 | 0003-004X |
| DOI | 10.2138/am-2018-6501 |
| 英文摘要 | The Neoproterozoic (840 Ma) Sin Quyen deposit in northwestern Vietnam contains replacement Cu-LREE-Au orebodies in Proterozoic metasedimentary rocks. In this deposit, LREE-bearing minerals include allanite-(Ce), monazite-(Ce), chevkinite-(Ce), and fluorapatite. Fluorapatite from orebodies has undergone variable degrees of metasomatic alteration. Samarium-neodymium isotopic analyses were conducted on altered fluorapatite, and also on allanite-(Ce) and monazite-(Ce), to investigate whether such metasomatism can affect the Sm-Nd isotope system. Allanite-(Ce) and monazite-(Ce) have Sm-147/Nd-144 ratios ranging from 0.0359 to 0.0549, and Nd-143/Nd-144 ratios from 0.51147 to 0.51172. Their initial Nd-143/Nd-144 values at the time of mineralization range from 0.51126 to 0.51148, but mostly cluster between 0.51135 and 0.51145. Thus, the primary ore-forming fluids were relatively homogeneous in their Sm-Nd isotopic compositions. In the Sm-147/Nd-144 vs. Nd-143/Nd-144 diagram, the compositions of allanite-(Ce) and monazite-(Ce) generally plot along a Sm-Nd isochron of 840 Ma, implying that the Sm-Nd isotopic systems of these minerals were either closed or only slightly modified. In contrast, altered fluorapatite crystals have Sm-147/Nd-144 ratios varying from 0.0667 to 0.1348, and Nd-143/Nd-144 ratios from 0.51160 to 0.51199. The calculated initial Nd-143/Nd-144 ratios range widely from 0.51114 to 0.51141, with most values lower than those of the allanite-(Ce) and monazite-(Ce). In the Sm-147/Nd-144 vs. Nd-143/Nd-144 diagram, their compositions mostly plot below the 840-Ma Sm-Nd isochron. Petrographic observations and trace elemental analyses show that metasomatic modification of fluorapatite grains led to increases of their Sm/Nd ratios. The unaltered domains in the grains have Sm/Nd ratios varying from 0.114 to 0.200, with an average value of 0.161; whereas the altered domains have Sm/Nd ratios varying from 0.111 to 0.254, with an average value of 0.183. The increased Sm/Nd ratios can cause the calculated initial Nd-143/Nd-144 ratios to be lower than actual initial isotopic ratios, and can also result in compositional deviations from the reference Sm-Nd isochron. This study demonstrates that the traditionally assumed inert Sm-Nd isotopic system can be metasomatically disturbed due to changes in the Sm/Nd ratio. Therefore, care must be taken when interpreting the Sm-Nd isotopic data from apatite/apatite-rich rocks that have undergone metasomatic alteration. |
| WOS关键词 | RARE-EARTH-ELEMENTS ; TH-PB GEOCHRONOLOGY ; NORTHWESTERN VIETNAM ; FLUID METASOMATISM ; ACCESSORY MINERALS ; APATITE ; MONAZITE ; REE ; SR ; MICROANALYSIS |
| 资助项目 | NSFC[41473038] ; NSFC[41472068] ; NSFC[41525012] ; "CAS Hundred Talents" Project |
| WOS研究方向 | Geochemistry & Geophysics ; Mineralogy |
| 语种 | 英语 |
| WOS记录号 | WOS:000443196900011 |
| 出版者 | MINERALOGICAL SOC AMER |
| 资助机构 | NSFC ; NSFC ; "CAS Hundred Talents" Project ; "CAS Hundred Talents" Project ; NSFC ; NSFC ; "CAS Hundred Talents" Project ; "CAS Hundred Talents" Project ; NSFC ; NSFC ; "CAS Hundred Talents" Project ; "CAS Hundred Talents" Project ; NSFC ; NSFC ; "CAS Hundred Talents" Project ; "CAS Hundred Talents" Project |
| 源URL | [http://ir.iggcas.ac.cn/handle/132A11/88131]  |
| 专题 | 地质与地球物理研究所_岩石圈演化国家重点实验室 |
| 通讯作者 | Li, Xiao-Chun; Zhou, Mei-Fu |
| 作者单位 | 1.Univ Hong Kong, Dept Earth Sci, Hong Kong, Hong Kong, Peoples R China 2.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing, Peoples R China 3.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Wuhan 430074, Hubei, Peoples R China 4.China Univ Geosci, Fac Earth Resources, Wuhan 430074, Hubei, Peoples R China 5.Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Guizhou, Peoples R China |
| 推荐引用方式 GB/T 7714 | Li, Xiao-Chun,Zhou, Mei-Fu,Yang, Yue-Heng,et al. Disturbance of the Sm-Nd isotopic system by metasomatic alteration: A case study of fluorapatite from the Sin Quyen Cu-LREE-Au deposit, Vietnam[J]. AMERICAN MINERALOGIST,2018,103(9):1487-1496. |
| APA | Li, Xiao-Chun,Zhou, Mei-Fu,Yang, Yue-Heng,Zhao, Xin-Fu,&Gao, Jian-Feng.(2018).Disturbance of the Sm-Nd isotopic system by metasomatic alteration: A case study of fluorapatite from the Sin Quyen Cu-LREE-Au deposit, Vietnam.AMERICAN MINERALOGIST,103(9),1487-1496. |
| MLA | Li, Xiao-Chun,et al."Disturbance of the Sm-Nd isotopic system by metasomatic alteration: A case study of fluorapatite from the Sin Quyen Cu-LREE-Au deposit, Vietnam".AMERICAN MINERALOGIST 103.9(2018):1487-1496. |
入库方式： OAI收割
来源：地质与地球物理研究所
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