赣南隆坪萤石矿床成矿时代及成因初探:来自萤石Sm-Nd测年及黑云母电子探针的证据
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摘要
隆坪萤石矿床是赣南已探明的大型单一萤石矿床,矿体产于永丰复式岩体外接触带北东向硅化破碎带中。文章首次采用Sm-Nd等时线法对隆坪萤石矿进行测年和稀土元素分析,并对永丰复式岩体中黑云母矿物成分进行了系统的测试;获得了隆坪萤石矿的成矿年龄为158±3 Ma,与永丰复式岩体的成岩时代基本一致,表明该矿床萤石成矿作用与晚侏罗世岩浆活动关系密切。隆坪萤石矿中萤石轻稀土元素略富集,重稀土相对平坦,具微弱Ce正异常(δCe=1.08～1.11,平均1.09)和微弱Eu负异常(δEu=0.91～0.98,平均0.95),指示了萤石矿床的成矿流体经历了相对较高的温度。黑云母电子探针分析结果证实永丰复式岩体形成于相对高温、低压和高氧逸度的环境,岩浆起源于古老地壳物质的部分熔融,岩浆结晶分异晚阶段岩浆期后热液富含F等挥发分。隆坪萤石矿床形成于晚侏罗世,成因类型为岩浆期后热液充填型。
The Longping fluorite deposit is the large single fluorite deposit discovered in southern Jiangxi Province, China. The ore body occurs in the NE-trending silicified fractured zone within the outer contact zone of the Yongfeng complex. In this paper, for the first time, the Sm-Nd Isochronal method is used to estimate the age of Longping fluorite deposit, and rare earth elements and the mineral composition of biotite in the Yongfeng complex are systematically studied. The ore-forming age of the Longping fluorite deposit is 158 ± 3 Ma, which is consistent with the diagenetic age of the Yongfeng complex, indicating that the Yanshanian fluorite mineralization in this area was closely related to the Late Jurassic magmatism. The fluorite in the Longping fluorite deposit is enriched in light rare earth elements, and the heavy rare earth elements remain relatively unchanged, with weak Ce positive anomalies(δCe=1.08-1.11, average 1.09) and weak Eu negative anomalies(δEu=0.91-0.98, average 0.95), indicating that the ore-forming fluids of the fluorite deposit experienced relatively high temperature. The results of electron probe analysis of biotite show that the Yongfeng complex was formed in a relatively high temperature, low pressure, and high oxygen fugacity environment. The magma originated from the ancient crustal materials and the hydrothermal fluid was rich in F and other volatiles after the magma phase. The Longping fluorite deposit may have mineralized in the Late Jurassic, and the genetic type is hydrothermal filling after the magmatism.
The Longping fluorite deposit is the large single fluorite deposit discovered in southern Jiangxi Province, China. The ore body occurs in the NE-trending silicified fractured zone within the outer contact zone of the Yongfeng complex. In this paper, for the first time, the Sm-Nd Isochronal method is used to estimate the age of Longping fluorite deposit, and rare earth elements and the mineral composition of biotite in the Yongfeng complex are systematically studied. The ore-forming age of the Longping fluorite deposit is 158 ± 3 Ma, which is consistent with the diagenetic age of the Yongfeng complex, indicating that the Yanshanian fluorite mineralization in this area was closely related to the Late Jurassic magmatism. The fluorite in the Longping fluorite deposit is enriched in light rare earth elements, and the heavy rare earth elements remain relatively unchanged, with weak Ce positive anomalies(δCe=1.08-1.11, average 1.09) and weak Eu negative anomalies(δEu=0.91-0.98, average 0.95), indicating that the ore-forming fluids of the fluorite deposit experienced relatively high temperature. The results of electron probe analysis of biotite show that the Yongfeng complex was formed in a relatively high temperature, low pressure, and high oxygen fugacity environment. The magma originated from the ancient crustal materials and the hydrothermal fluid was rich in F and other volatiles after the magma phase. The Longping fluorite deposit may have mineralized in the Late Jurassic, and the genetic type is hydrothermal filling after the magmatism.
引文
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阳珊,姜章平,袁晓玲,等.2014.安徽金寨县沙坪沟钼矿成矿岩体矿物学特征及其成岩成矿意义[J].岩石矿物学杂志,33(2):243-254.
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周作侠.1988.侵人岩的镁铁云母化学成分特征及其地质意义[J].岩石学报,4(3):65-75.
Abdel-Rahman A F M.1994.Nature of biotites from alkaline,calcalkaline and peraluminous magmas[J].Journal of Petrology,35(2):525-541.
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Buddington A F and Lindsley D H.1964.Iron-titanium oxide minerals andsynthetic equivalents[J].Journal of Petrology,5(2):310-357.
Bierlein F P.1991.Rare earth element mobility during hydrothermal and metamorphic fluid-rock interaction and the significance of the oxidation state of europium[J].Chemical Geology,93(3-4):219-230.
Foster M D.1960.Interpretation of the composition of trioctahedral micas[J].Washington:US Geological Survey Paper,354-B:11-48.
Liu Y S,Gao S,Hu Z C,et al.2010.Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-N orth China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons of mantle xenoliths[J].Journal of Petrology,51:537-571.
Rieder M,Cavazzini G,D'Yakanov Y S,et al.1999.Nomenclature of the micas[J].Bulletin of Mineralogy,Petrology and Geochemistry,63(2):267-296.
Schreurs J.1985.Prograde metamorphism of metapelites,garnet-biotite thermometry and pro grade changes of biotite chemistry in high-grade rocks of West Uusimaa,southwest Finland[J].Lithos,18(2):69-80.
Subias I and Fernandez-Nieto C.1995.Hydrothermal events in the Valle de Tena(Spanish Western Pyrenees)as evidenced by fluid inclusions and trace-element distribution from fluorite deposits[J].Chemical Geology,24(3-4):267-282.
Sun S S and Mcdonough W F.1989.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J].Geologic al Society London Special Publications,42(1):313-345.
Williams-Jhons A E,Samoson I M and Olivo G R.2000.The genesis of hydrothermal fluorite-REE deposits in the Gallinas Mountains,New Mexico[J].Economic Geology,95:327-341.
Wones D R and Eugster H P.1965.Stability of biotite:experiment,theory and application[J].The American Mineralogist,50:1228-1272.
Zhang R X and Yang S Y.2016.A mathematical model for determining carbon coating thickness and its application in Electron Probe Microanalysis[J].Microscopy and Microanalysis,22(6):1374-1380.
方贵聪,王登红,陈振宇,等.2014.南岭东段北部花岗岩的萤石成矿专属性研究[J].大地构造与成矿学,38(2):312-324.
丰成友,黄凡,曾载淋,等.2011.赣南九龙脑岩体及洪水寨云英岩型钨矿年代学[J].吉林大学学报(地球科学版),41(1):111-121.
李长江,蒋叙良.1991.中国东南部两类萤石矿床的成矿模式[J].地质学报,(3):263-274.
林文蔚,彭丽君.1994.由电子探针分析数据估算角闪石、黑云母中的Fe3+,Fe2+[J].吉林大学学报(地),(2):155-162.
马莲花,蔡永丰,刘希军,等.2018.云南个旧卡房锡矿田花岗岩黑云母矿物化学特征及其成岩成矿意义[J].高校地质学报,(5):692-701.
王吉平,商朋强,熊先孝,等.2015.中国萤石矿床成矿规律[J].中国地质,(1):18-32.
谢应雯,张玉泉.1987.横断山不同成因类型花岗岩类岩石中黑云母的标型特征[J].矿物学报,3:55-64.
徐有华.2008.赣南萤石矿成矿地质条件及成矿预测研究[D].北京:中国地质大学(北京).
杨瑞栋,童日发,邵伟江,等.2013.赣南兴国旋卷构造区寻找富大矿床的思考[J].矿产勘查,4(2):121-130.
阳珊,姜章平,袁晓玲,等.2014.安徽金寨县沙坪沟钼矿成矿岩体矿物学特征及其成岩成矿意义[J].岩石矿物学杂志,33(2):243-254.
杨世文,楼法生,丰成友,等.2019.赣南晚侏罗世铝质A型花岗岩带及其意义[J].地质科技情报,38(3):12-29.
江西省地质矿产勘查开发局.2014.中国矿产地质志·江西卷[M].北京:地质出版社:700-707.
周作侠.1988.侵人岩的镁铁云母化学成分特征及其地质意义[J].岩石学报,4(3):65-75.
Abdel-Rahman A F M.1994.Nature of biotites from alkaline,calcalkaline and peraluminous magmas[J].Journal of Petrology,35(2):525-541.
Albuquerque C A R D.1973.Geochemistry of biotites from granitic rocks,Northern Portugal[J].Geochimica et Cosmochimica Acta,37(7):1779-1802.
Bau M and MollerP.1992.Rare earth element fractionation in metamorphogenic hydrothermal calcite,magnesite and siderite[J].Mineralogy and Petrology,45(3):23 1-246.
Buddington A F and Lindsley D H.1964.Iron-titanium oxide minerals andsynthetic equivalents[J].Journal of Petrology,5(2):310-357.
Bierlein F P.1991.Rare earth element mobility during hydrothermal and metamorphic fluid-rock interaction and the significance of the oxidation state of europium[J].Chemical Geology,93(3-4):219-230.
Foster M D.1960.Interpretation of the composition of trioctahedral micas[J].Washington:US Geological Survey Paper,354-B:11-48.
Liu Y S,Gao S,Hu Z C,et al.2010.Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-N orth China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons of mantle xenoliths[J].Journal of Petrology,51:537-571.
Rieder M,Cavazzini G,D'Yakanov Y S,et al.1999.Nomenclature of the micas[J].Bulletin of Mineralogy,Petrology and Geochemistry,63(2):267-296.
Schreurs J.1985.Prograde metamorphism of metapelites,garnet-biotite thermometry and pro grade changes of biotite chemistry in high-grade rocks of West Uusimaa,southwest Finland[J].Lithos,18(2):69-80.
Subias I and Fernandez-Nieto C.1995.Hydrothermal events in the Valle de Tena(Spanish Western Pyrenees)as evidenced by fluid inclusions and trace-element distribution from fluorite deposits[J].Chemical Geology,24(3-4):267-282.
Sun S S and Mcdonough W F.1989.Chemical and isotopic systematics of oceanic basalts:implications for mantle composition and processes[J].Geologic al Society London Special Publications,42(1):313-345.
Williams-Jhons A E,Samoson I M and Olivo G R.2000.The genesis of hydrothermal fluorite-REE deposits in the Gallinas Mountains,New Mexico[J].Economic Geology,95:327-341.
Wones D R and Eugster H P.1965.Stability of biotite:experiment,theory and application[J].The American Mineralogist,50:1228-1272.
Zhang R X and Yang S Y.2016.A mathematical model for determining carbon coating thickness and its application in Electron Probe Microanalysis[J].Microscopy and Microanalysis,22(6):1374-1380.