贵州织金磷块岩型稀土矿含矿岩系REE地球化学特征与稀土富集
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摘要
贵州织金下寒武统戈仲武组(?1gz)磷矿富集大量稀土,但是磷块岩中REE富集机制问题尚不清楚。本文对贵州织金不同稀土含量区间(<262×10~(-6)、262×10~(-6)～527×10~(-6)、527×10~(-6)～761×10~(-6)、>761×10~(-6))的磷块岩的研究表明,磷块岩的稀土配分均显示出Ce负异常、Eu无明显异常、MREE富集以及富集重稀土元素Y的特征。(La/Sm)N-δCe及δPr-δCe图解显示织金磷块岩Ce异常为真实的Ce异常,代表磷块岩形成在氧化环境。但当时海水的氧化环境并不是控制MREE富集的决定因素。(La/Sm)N-SmN、(Gd/Yb)N-YbN散点图显示MREE富集是稀土在富集过程中稀土发生分异的结果。(Dy/Sm)N-δEu散点图以及Eu无明显异常说明织金磷块岩形成过程中可能无热水作用的参与。地史时期"老磷块岩"普遍存在重稀土亏损的特征。
A large amount of REE resources is enriched in phosphorites within the Lower Cambrian Gezhongwu Formation in Zhijin County, Guizhou Province. However, the REE enrichment mechanism in phosphorites is not clear yet. In this paper, the research on the Zhijin phosphorites with different REE content ranges(<262×10~(-6), 262×10~(-6)-527×10~(-6),527×10~(-6)-761×10~(-6),>761×10~(-6))indicates that REE patterns of all phosphorites show features of the Ce negative anomaly, no obvious Eu anomaly, MREE and Y enrichment.The(La/Sm)N-δCe and δPr-δCe diagrams show that Ceanomalies of the Zhijin phosphorites represent the real Ce anomaly which means the phosphorites were formed in an oxidized environment. However, the oxidized environment of seawater was not the decisive factor controlling the MREE enrichment at that time. The(La/Sm)N-SmN and(Gd/Yb)N-YbN scatter diagrams show that the MREE enrichment was resulted from the differentiation in the process of REE enrichment. The(Dy/Sm)N-δEu scatter diagram and no obvious Eu anomaly indicate that no hot water could be involved in the formation process of the Zhijin phosphorites. It's believed that "old phosphorites" of geological history are commonly characterized with the HREE depletion.
A large amount of REE resources is enriched in phosphorites within the Lower Cambrian Gezhongwu Formation in Zhijin County, Guizhou Province. However, the REE enrichment mechanism in phosphorites is not clear yet. In this paper, the research on the Zhijin phosphorites with different REE content ranges(<262×10~(-6), 262×10~(-6)-527×10~(-6),527×10~(-6)-761×10~(-6),>761×10~(-6))indicates that REE patterns of all phosphorites show features of the Ce negative anomaly, no obvious Eu anomaly, MREE and Y enrichment.The(La/Sm)N-δCe and δPr-δCe diagrams show that Ceanomalies of the Zhijin phosphorites represent the real Ce anomaly which means the phosphorites were formed in an oxidized environment. However, the oxidized environment of seawater was not the decisive factor controlling the MREE enrichment at that time. The(La/Sm)N-SmN and(Gd/Yb)N-YbN scatter diagrams show that the MREE enrichment was resulted from the differentiation in the process of REE enrichment. The(Dy/Sm)N-δEu scatter diagram and no obvious Eu anomaly indicate that no hot water could be involved in the formation process of the Zhijin phosphorites. It's believed that "old phosphorites" of geological history are commonly characterized with the HREE depletion.
引文
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[12]郭海燕,夏勇,何珊,等.贵州织金磷块岩型稀土矿地球化学特征[J].矿物学报, 2017(6):755-763.
[13]郭海燕.贵州新华磷（稀土）矿床稀土地球化学特征及控矿因素[D].贵阳:中国科学院地球化学研究所, 2017.
[14] Stine R A. Explaining normal quantile-quantile plots through animation:The water-filling analogy[J]. The American Statistician, 2017, 71(2):145-147.
[15]谭亲平,王学求.秦岭地区水系沉积物和岩石金元素时空分布研究[J].矿物岩石地球化学通报, 2017,36(05):824-8331.
[16] Tan Q P, Wang X, Xia Y, et al. Identifying ore-related anomalies using singularity mapping of stream sediment geochemical data, a case study of Pb mineralization in the Qinling region, China[J]. Geochemistry:Exploration, Environment, Analysis, 2018, 18(3):177-184.
[17] Shields G, Stille P. Diagenetic constraints on the use of cerium anomalies as palaeo seawater redox proxies:an isotopic and REE study of Cambrian phosphorites[J]. Chemical Geology, 2001, 175(1):29-48.
[18] Elderfield H, Greaves M J. The rare earth elements in seawater[J]. Nature, 1982, 296(5854):214-219.
[19] Shields G A, Webb G E. Has the REE composition of seawater changed over geological time?[J]. Chemical Geology, 2004, 204(1):103-107.
[20] Elderfield H, Pagett R. Rare earth elements in ichthyoliths:Variations with redox conditions and depositional environment[J].Science of the Total Environment, 1986, 49(86):175-197.
[21] Elderfield H, Sholkovitz E R. Rare earth elements in the pore waters of reducing nearshore sediments[J]. Earth&Planetary Science Letters, 1987,82(3):280-288.
[22] Bonnot-Courtois C, Flicoteaux R. Distribution of rare-earth and some trace elements in Tertiary phosphorites from the Senegal Basin and their weathering products[J]. Chemical Geology, 1989, 75(4):311-328.
[23] Morad S, Felitsyn S. Identification of primary Ce-anomaly signatures in fossil biogenic apatite:implication for the Cambrian oceanic anoxia and phosphogenesis[J]. Sedimentary Geology, 2001, 143(3):259-264.
[24] Goldberg E. Chemistry in the oceans[J]. Oceanography, 1961, 67:583-597.
[25] Piper D Z. Rare earth elements in the sedimentary cycle:A summary[J]. Chemical Geology, 1974, 14(4):285-304.
[26] Bau M, Dulski P. Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa[J].Precambrian Research, 1996, 79(1/2):37-55.
[27]伊海生,彭军,夏文杰.扬子东南大陆边缘晚前寒武纪古海洋演化的稀土元素记录[J].沉积学报, 1995(4):131-137.
[2] Ilyin A V. Rare-earth geochemistry of`old'phosphorites and probability of syngenetic precipitation and accumulation of phosphate 1 In memory of Richard P. Sheldon 1[J]. Chemical Geology, 1998, 144(3):243-256.
[3] Altschuler Z S. The geochemistry of trace elements in marine phosphorites:Part I. Characteristic abundances and enrichment[Z]. Special Publications of Sepm, 1980.
[4] McArthur J M, Walsh J N. Rare-earth geochemistry of phosphorites[J]. Chemical Geology, 1984, 47(3/4):191-220.
[5] Jarvis I, Burnett WB, Nathan Y, et al. Phosphorite geochemistry[J]. Eclogae Geol Helv,1994, 87(3):643-700.
[6] Donnelly T H, Shergold J H, Southgate P N, et al. Events leading to global phosphogenesis around the Proterozoic/Cambrian boundary[J]. Geological Society, London, Special Publications, 1990, 52(1):273-287.
[7] Baioumy H. Rare earth elements and sulfur and strontium isotopes of upper Cretaceous phosphorites in Egypt[J]. Cretaceous Research, 2011,32(3):368-377.
[8] Chen D F, Wei Q D, Liang Q, et al. Possible REE constraints on the depositional and diagenetic environment of Doushantuo Formation phosphorites containing the earliest metazoan fauna[J]. Chemical Geology, 2003, 201(1):103-118.
[9]高慧,杨瑞东.早寒武世早期贵州织金含磷岩系地球化学特征与成磷作用[J].地球与环境, 2005, 33(1):33-42.
[10]施春华,胡瑞忠.贵州织金含稀土磷矿床的Sm-Nd同位素年龄及其地质意义[J].地球科学, 2008, 33(2):205-209.
[11]施春华,胡瑞忠,王国芝.贵州织金磷矿岩稀土元素地球化学特征研究[J].矿物岩石, 2004, 24(4):71-75.
[12]郭海燕,夏勇,何珊,等.贵州织金磷块岩型稀土矿地球化学特征[J].矿物学报, 2017(6):755-763.
[13]郭海燕.贵州新华磷（稀土）矿床稀土地球化学特征及控矿因素[D].贵阳:中国科学院地球化学研究所, 2017.
[14] Stine R A. Explaining normal quantile-quantile plots through animation:The water-filling analogy[J]. The American Statistician, 2017, 71(2):145-147.
[15]谭亲平,王学求.秦岭地区水系沉积物和岩石金元素时空分布研究[J].矿物岩石地球化学通报, 2017,36(05):824-8331.
[16] Tan Q P, Wang X, Xia Y, et al. Identifying ore-related anomalies using singularity mapping of stream sediment geochemical data, a case study of Pb mineralization in the Qinling region, China[J]. Geochemistry:Exploration, Environment, Analysis, 2018, 18(3):177-184.
[17] Shields G, Stille P. Diagenetic constraints on the use of cerium anomalies as palaeo seawater redox proxies:an isotopic and REE study of Cambrian phosphorites[J]. Chemical Geology, 2001, 175(1):29-48.
[18] Elderfield H, Greaves M J. The rare earth elements in seawater[J]. Nature, 1982, 296(5854):214-219.
[19] Shields G A, Webb G E. Has the REE composition of seawater changed over geological time?[J]. Chemical Geology, 2004, 204(1):103-107.
[20] Elderfield H, Pagett R. Rare earth elements in ichthyoliths:Variations with redox conditions and depositional environment[J].Science of the Total Environment, 1986, 49(86):175-197.
[21] Elderfield H, Sholkovitz E R. Rare earth elements in the pore waters of reducing nearshore sediments[J]. Earth&Planetary Science Letters, 1987,82(3):280-288.
[22] Bonnot-Courtois C, Flicoteaux R. Distribution of rare-earth and some trace elements in Tertiary phosphorites from the Senegal Basin and their weathering products[J]. Chemical Geology, 1989, 75(4):311-328.
[23] Morad S, Felitsyn S. Identification of primary Ce-anomaly signatures in fossil biogenic apatite:implication for the Cambrian oceanic anoxia and phosphogenesis[J]. Sedimentary Geology, 2001, 143(3):259-264.
[24] Goldberg E. Chemistry in the oceans[J]. Oceanography, 1961, 67:583-597.
[25] Piper D Z. Rare earth elements in the sedimentary cycle:A summary[J]. Chemical Geology, 1974, 14(4):285-304.
[26] Bau M, Dulski P. Distribution of yttrium and rare-earth elements in the Penge and Kuruman iron-formations, Transvaal Supergroup, South Africa[J].Precambrian Research, 1996, 79(1/2):37-55.
[27]伊海生,彭军,夏文杰.扬子东南大陆边缘晚前寒武纪古海洋演化的稀土元素记录[J].沉积学报, 1995(4):131-137.
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