新疆若羌—且末戈壁料软玉的地球化学特征及成因类型研究
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摘要
新疆和田透闪石集合体(软玉)矿带长约1300km,是世界上最大的软玉矿带。除传统上认识的山料和籽料外,在新疆若羌—且末地区也分布着大量的戈壁料软玉。以往对戈壁料软玉的研究主要集中在肉眼鉴定以及与人工仿制品的区别,对其来源、年龄以及成因类型等研究尚未开展。本研究采用电子探针、电感耦合等离子体质谱、氢氧稳定同位素质谱以及SHRIMP U-Pb测年等技术对若羌戈壁料的化学成分、矿物组成及年龄进行研究,在此基础上明确其成因类型。测试结果表明,若羌戈壁料主要由纤维状透闪石和阳起石(>95%)组成,并含少量(<5%)磷灰石、透辉石、绿帘石、铬铁矿等矿物。戈壁料颜色主要有深绿色、绿色、黄绿色、白色,除白色以外的颜色与其中的FeO含量(0.48%～2.92%)有关。样品全岩的化学成分与透闪石晶体化学组成类似,全岩稀土配分模式显示Eu负异常(δEu=0.09～0.66),LREE富集,HREE平坦,稀土总量(6.93～115.93μg/g)、Cr(68.8～119μg/g)、Ni(16.4～38.8μg/g)较低。戈壁料成矿流体中氢同位素δD为-24.94‰～-56.83‰,平均值为-40.14‰,显示其主要由岩浆水、大气降水组成。从戈壁料样品中分离出的锆石SHRIMP U-Pb年龄有四组(40～60Ma、480Ma、785Ma和1450～2460Ma),这些年龄可以约束戈壁料的形成时代。戈壁料软玉的地球化学和成矿流体组成与已报道的典型的镁质矽卡岩矿床中的软玉组成类似,其中400Ma左右的成矿年龄与报道的大部分和田区域的成矿年龄一致,多组成矿年龄也显示了软玉多期次成矿的特点。
BACKGROUND: The Hetian nephrite belt is the longest nephrite belt in the world at 1300 km. In addition to the traditional primary and placer nephrite, there is widespread Gobi nephrite in the Gobi desert of the Quoqiang district in Xinjiang.OBJECTIVES: To identify the origin, genesis, ages and types of Gobi nephrite.METHODS: Electronic Microprobe, X-ray Fluorescence, Inductively Coupled Plasma-Mass Spectrometry and sensitive high-resolution Ion Microprobe were used to examine the mineral assemblages, chemical composition and ages of Gobi nephrite. Based on these analyses, the genesis of Gobi nephrite was constrained.RESULTS: Gobi nephrite was predominantly composed of tremolite(>95%) with minor apatite, diopside, epidote and chromite(<5%). The color of Gobi nephrite was mainly dark green, green, yellow-green and white. The samples, with the exception of white, were related to the FeO content(0.48%-2.92%). The whole rock analysis suggested that both Gobi nephrite and tremolite had a similar chemical composition. All samples displayed LREE enrichment, flat HREE and negative Eu anomaly(δEu=0.09-0.66). Totally, all these samples had low content of REE(6.93-115.93μg/g), Cr(68.8-119μg/g), and Ni(16.4-38.8μg/g). δD(-24.94‰--56.83‰) of ore-forming fluids indicated that it was composed of magmatic water and meteoric water. SHRIMP U-Pb dating of zircons showed that there were four groups of ages: 40-60 Ma, 480 Ma, 785 Ma and 1450-2460 Ma. These ages could be used to constrain the formation ages of Gobi nephrite.CONCLUSIONS: The geochemistry and ore-forming fluid composition of the Gobi nephrite is similar to the composition of nephrite in the typical Mg-skarn deposit previously reported. The ore-forming age of 400 Ma is consistent with the mineralization age of most of the reported ages in the Hetian areas. The multiple age groups also indicate multi-stage mineralization of nephrite.
BACKGROUND: The Hetian nephrite belt is the longest nephrite belt in the world at 1300 km. In addition to the traditional primary and placer nephrite, there is widespread Gobi nephrite in the Gobi desert of the Quoqiang district in Xinjiang.OBJECTIVES: To identify the origin, genesis, ages and types of Gobi nephrite.METHODS: Electronic Microprobe, X-ray Fluorescence, Inductively Coupled Plasma-Mass Spectrometry and sensitive high-resolution Ion Microprobe were used to examine the mineral assemblages, chemical composition and ages of Gobi nephrite. Based on these analyses, the genesis of Gobi nephrite was constrained.RESULTS: Gobi nephrite was predominantly composed of tremolite(>95%) with minor apatite, diopside, epidote and chromite(<5%). The color of Gobi nephrite was mainly dark green, green, yellow-green and white. The samples, with the exception of white, were related to the FeO content(0.48%-2.92%). The whole rock analysis suggested that both Gobi nephrite and tremolite had a similar chemical composition. All samples displayed LREE enrichment, flat HREE and negative Eu anomaly(δEu=0.09-0.66). Totally, all these samples had low content of REE(6.93-115.93μg/g), Cr(68.8-119μg/g), and Ni(16.4-38.8μg/g). δD(-24.94‰--56.83‰) of ore-forming fluids indicated that it was composed of magmatic water and meteoric water. SHRIMP U-Pb dating of zircons showed that there were four groups of ages: 40-60 Ma, 480 Ma, 785 Ma and 1450-2460 Ma. These ages could be used to constrain the formation ages of Gobi nephrite.CONCLUSIONS: The geochemistry and ore-forming fluid composition of the Gobi nephrite is similar to the composition of nephrite in the typical Mg-skarn deposit previously reported. The ore-forming age of 400 Ma is consistent with the mineralization age of most of the reported ages in the Hetian areas. The multiple age groups also indicate multi-stage mineralization of nephrite.
引文
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[9] 于海燕,阮青锋,孙媛,等.不同颜色青海软玉微观形貌和矿物组成特征[J].岩矿测试,2018,37(6):626-636.Yu H Y,Ruan Q F,Sun Y,et al.Micro-morphology and mineral composition of different color Qinghai nephrites[J].Rock and Mineral Analysis,2018,37(6):626-636.
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[13] 买托乎提·阿不都瓦衣提.和田玉戈壁料与仿戈壁料鉴定方法探讨[C]//中国珠宝首饰学术交流会论文集.北京:中国珠宝玉石首饰行业协会,2009:157-159.Abuduwayiti M.Hetian Nephrite Occurring In the Gobi Desert and Their Imitation[C]//Proceedings of China Gems and Jewelry Academic Conference.Beijing:China Jewelry and Jade Jewelry Industry Association,2009:157-159.
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[15] Black L P,Kamo S L,Allen C M,et al.TEMORA 1:A new zircon standard for Phanerozoic U-Pb geochronology[J].Chemical Geology,2003,200(1):155-170.
[16] Nasdala L,Hofmeister W,Norberg N,et al.Zircon M257—A homogeneous natural reference material for the ion microprobe U-Pb analysis of zircon[J].Geostandards and Geoanalytical Research,2008,32(3):247-265.
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[19] Ludwig K R.Squid 1.02:A User’s Manual[M].Berkeley Geochronology Center Special Publication,2001:1-21.
[20] Ludwig K R.User’s Manual for Isoplot 3.00:A Geo-chronological Toolkit for Microsoft Excel[M].Berkeley:Berkeley Geochronology Center Special Publication,2003.
[21] Liu Y,Zhang R Q,Zhang Z Y,et al.Mineral inclusions and SHRIMP U-Pb dating of zircons from the Alamas nephrite and granodiorite:Implications for the genesis of a magnesian skarn deposit[J].Lithos,2015,212-215:128-144.
[22] Liu Y,Zhang R Q,Abuduwayiti M,et al.SHRIMP U-Pb zircon ages,mineral compositions and geochemistry of placer nephrite in the Yurungkash and Karakash River deposits,West Kunlun,Xinjiang,Northwest China:Implication for a magnesium skarn[J].Ore Geology Reviews,2016,72:699-727.
[23] Douglas J G.The study of Chinese archaic jades using non-destructive X-ray fluorescence spectroscopy[J].Acta Geologica Taiwanica,1996,32:43-54.
[24] Douglas J G.Exploring Issues of Geological Source for Jade Worked by Ancient Chinese Cultures with the Aid of X-ray Fluorescence[C]//Jett P.Scientific Study in the Field of Asian Art.London:Archetype Publications Ltd,2003:192-199.
[25] 刘喜锋,刘琰,李自静,等.新疆皮山镁质矽卡岩矿床(含糖玉)成因及锆石SHRIMP U-Pb定年[J].岩石矿物学杂志,2017,36(2):259-273.Liu X F,Liu Y,Li Z J,et al.The genesis of Mg-skarn deposit (bearing brown nephrite) and its Ar-Ar dating of phlogopite and SHRIMP U-Pb dating of zircon,Pishan,Xinjiang[J].Acta Petrologica et Mineralogica,2017,36(2):259-273.
[26] Ohmoto H.Stable isotope geochemistry of ore deposits[J].Reviews in Mineralogy and Geochemistry,1986,16(1):491-559.
[27] 张勇,魏华,陆太进,等.新疆奥米夏和田玉矿床成因及锆石LA-ICP-MS定年研究[J].岩矿测试,2018,37(6):695-704.Zhang Y,Wei H,Lu T J,et al.The genesis and LA-ICP-MS zircon ages of Omixia nephrite deposit,Xinjiang,China[J].Rock and Mineral Analysis,2018,37(6):695-704.
[28] Siqin B,Qian R,Zhuo S,et al.Glow discharge mass spectrometry studies on nephrite minerals formed by different metallogenic mechanisms and geological environments[J].International Journal of Mass Spectrometry,2012,309:206-211.
[29] Grapes R H,Yun S T.Geochemistry of a New Zealand nephrite weathering rind[J].New Zealand Journal of Geology and Geophysics,2010,53:413-426.
[30] Kostov R I,Protochristov C,Stoyanov C,et al.Micro-PIXE geochemical fingerprinting of nephrite neolithic artifacts from Southwest Bulgaria[J].Geoarchaeology,2012,27:457-469.
[31] Adamo I,Bocchio R.Nephrite jade from Val Malenco,Italy:Review and update[J].Gems and Gemology,2013,49:98-106.
[32] Bhattacharya A,Raith M,Hoernes S,et al.Geochemical evolution of the massif-type anorthosite complex at Bolangir in the Eastern Ghats belt of India[J].Journal of Petrology,1998,39(6):1169-1195.
[33] James O B,Floss C,McGee J J.Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in Lunar ferroan anorthosites[J].Geochimica et Cosmochimica Acta,2002,66(7):1269-1284.
[34] Charlier B,Auwera J V,Duchesne J C.Geochemistry of cumulates from the Bjerkreim—Sokndal layered intrusion (S.Norway):Part Ⅱ.REE and the trapped liquid fraction[J].Lithos,2005,83(3):255-276.
[35] 刘喜锋,张红清,刘琰,等.世界范围内代表性碧玉的矿物特征和成因研究[J].岩矿测试,2018,37(5):479-489.Liu X F,Zhang H Q,Liu Y,et al.Mineralogical characteristics and genesis of green nephrite from the world[J].Rock and Mineral Analysis,2018,37(5):479-489.
[2] Makepeace K,Simandl G J.Jade (Nephrite) in British Columbia,Canada[R].Program and Extended Abstracts for 37th Forum on the Geology of Indutrial Minerals,2001:209-210.
[3] ?apot W.Peculiar nephrite from the East Saian Mts (Siberia)[J].Mineralogia Polonica,2004,35:49-58.
[4] Yui T F,Kwon S T.Origin of a dolomite-related jade deposit at Chuncheon,Korea[J].Economic Geology,2002,97:593-601.
[5] Harlow G E,Sorensen S S.Jade (nephrite and jadeitite) and serpentinite:Metasomatic connections[J].International Geology Review,2005,47:113-146.
[6] Liu Y,Deng J,Shi G H,et al.Chemical zone of nephrite in Almas,Xinjiang,China[J].Resource Geology,2010,60:249-259.
[7] Liu Y,Deng J,Shi G H,et al.Geochemistry and petrology of nephrite from Alamas,Xinjiang,NW China[J].Journal of Asian Earth Sciences,2011,42:440-451.
[8] Liu Y,Deng J,Shi G H,et al.Geochemistry and petrogenesis of placer nephrite from Hetian,Xinjiang[J].Ore Geology Reviews,2011,41:122-132.
[9] 于海燕,阮青锋,孙媛,等.不同颜色青海软玉微观形貌和矿物组成特征[J].岩矿测试,2018,37(6):626-636.Yu H Y,Ruan Q F,Sun Y,et al.Micro-morphology and mineral composition of different color Qinghai nephrites[J].Rock and Mineral Analysis,2018,37(6):626-636.
[10] Ling X X,Schm?dicke E,Li Q L,et al.Age determination of nephrite by in-situ SIMS U-Pb dating syngenetic titanite:A case study of the nephrite deposit from Luanchuan,Henan,China[J].Lithos,2015,220-223:289-299.
[11] Middleton A.JADE-Geology and Mineralogy[M]//O’Donoghue M.Gems.Oxford:Elsevier,2006:332-354.
[12] 张蓓莉.系统宝石学[M].北京:地质出版社,2006:365-374.Zhang B L.Systematic Gemmology[M].Beijing:Geological Publishing House,2006:365-374.
[13] 买托乎提·阿不都瓦衣提.和田玉戈壁料与仿戈壁料鉴定方法探讨[C]//中国珠宝首饰学术交流会论文集.北京:中国珠宝玉石首饰行业协会,2009:157-159.Abuduwayiti M.Hetian Nephrite Occurring In the Gobi Desert and Their Imitation[C]//Proceedings of China Gems and Jewelry Academic Conference.Beijing:China Jewelry and Jade Jewelry Industry Association,2009:157-159.
[14] Friedman I.Deuterium content of natural waters and other substances[J].Geochimica et Cosmochimica Acta,1953,4:89-103.
[15] Black L P,Kamo S L,Allen C M,et al.TEMORA 1:A new zircon standard for Phanerozoic U-Pb geochronology[J].Chemical Geology,2003,200(1):155-170.
[16] Nasdala L,Hofmeister W,Norberg N,et al.Zircon M257—A homogeneous natural reference material for the ion microprobe U-Pb analysis of zircon[J].Geostandards and Geoanalytical Research,2008,32(3):247-265.
[17] Compston W,Williams I S,Kirschvink J L,et al.Zircon U-Pb ages forthe Early Cambrian time-scale[J].Journal of the Geological Society,1992,149:171-184.
[18] Stern R A.High-resolution SIMS Determination of Ra-diogenic Tracer-Isotope Ratios in Minerals[C]//Cabri L J,Vaughan D J.Modern Approaches to Ore and Environmental Mineralogy.Mineralogical Association of Canada,1998:241-268.
[19] Ludwig K R.Squid 1.02:A User’s Manual[M].Berkeley Geochronology Center Special Publication,2001:1-21.
[20] Ludwig K R.User’s Manual for Isoplot 3.00:A Geo-chronological Toolkit for Microsoft Excel[M].Berkeley:Berkeley Geochronology Center Special Publication,2003.
[21] Liu Y,Zhang R Q,Zhang Z Y,et al.Mineral inclusions and SHRIMP U-Pb dating of zircons from the Alamas nephrite and granodiorite:Implications for the genesis of a magnesian skarn deposit[J].Lithos,2015,212-215:128-144.
[22] Liu Y,Zhang R Q,Abuduwayiti M,et al.SHRIMP U-Pb zircon ages,mineral compositions and geochemistry of placer nephrite in the Yurungkash and Karakash River deposits,West Kunlun,Xinjiang,Northwest China:Implication for a magnesium skarn[J].Ore Geology Reviews,2016,72:699-727.
[23] Douglas J G.The study of Chinese archaic jades using non-destructive X-ray fluorescence spectroscopy[J].Acta Geologica Taiwanica,1996,32:43-54.
[24] Douglas J G.Exploring Issues of Geological Source for Jade Worked by Ancient Chinese Cultures with the Aid of X-ray Fluorescence[C]//Jett P.Scientific Study in the Field of Asian Art.London:Archetype Publications Ltd,2003:192-199.
[25] 刘喜锋,刘琰,李自静,等.新疆皮山镁质矽卡岩矿床(含糖玉)成因及锆石SHRIMP U-Pb定年[J].岩石矿物学杂志,2017,36(2):259-273.Liu X F,Liu Y,Li Z J,et al.The genesis of Mg-skarn deposit (bearing brown nephrite) and its Ar-Ar dating of phlogopite and SHRIMP U-Pb dating of zircon,Pishan,Xinjiang[J].Acta Petrologica et Mineralogica,2017,36(2):259-273.
[26] Ohmoto H.Stable isotope geochemistry of ore deposits[J].Reviews in Mineralogy and Geochemistry,1986,16(1):491-559.
[27] 张勇,魏华,陆太进,等.新疆奥米夏和田玉矿床成因及锆石LA-ICP-MS定年研究[J].岩矿测试,2018,37(6):695-704.Zhang Y,Wei H,Lu T J,et al.The genesis and LA-ICP-MS zircon ages of Omixia nephrite deposit,Xinjiang,China[J].Rock and Mineral Analysis,2018,37(6):695-704.
[28] Siqin B,Qian R,Zhuo S,et al.Glow discharge mass spectrometry studies on nephrite minerals formed by different metallogenic mechanisms and geological environments[J].International Journal of Mass Spectrometry,2012,309:206-211.
[29] Grapes R H,Yun S T.Geochemistry of a New Zealand nephrite weathering rind[J].New Zealand Journal of Geology and Geophysics,2010,53:413-426.
[30] Kostov R I,Protochristov C,Stoyanov C,et al.Micro-PIXE geochemical fingerprinting of nephrite neolithic artifacts from Southwest Bulgaria[J].Geoarchaeology,2012,27:457-469.
[31] Adamo I,Bocchio R.Nephrite jade from Val Malenco,Italy:Review and update[J].Gems and Gemology,2013,49:98-106.
[32] Bhattacharya A,Raith M,Hoernes S,et al.Geochemical evolution of the massif-type anorthosite complex at Bolangir in the Eastern Ghats belt of India[J].Journal of Petrology,1998,39(6):1169-1195.
[33] James O B,Floss C,McGee J J.Rare earth element variations resulting from inversion of pigeonite and subsolidus reequilibration in Lunar ferroan anorthosites[J].Geochimica et Cosmochimica Acta,2002,66(7):1269-1284.
[34] Charlier B,Auwera J V,Duchesne J C.Geochemistry of cumulates from the Bjerkreim—Sokndal layered intrusion (S.Norway):Part Ⅱ.REE and the trapped liquid fraction[J].Lithos,2005,83(3):255-276.
[35] 刘喜锋,张红清,刘琰,等.世界范围内代表性碧玉的矿物特征和成因研究[J].岩矿测试,2018,37(5):479-489.Liu X F,Zhang H Q,Liu Y,et al.Mineralogical characteristics and genesis of green nephrite from the world[J].Rock and Mineral Analysis,2018,37(5):479-489.