黔西北猫榨厂铅锌矿床原位Pb同位素地球化学
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摘要
猫榨厂(猫猫厂—榨子厂)铅锌矿床是近年来黔西北地区深部找矿的一个成功实例,该矿床位于扬子陆块西南缘川滇黔铅锌成矿域的中东部贵州省赫章县境内,毗邻福来厂、天桥和板板桥等铅锌矿床。以往,该矿床以采地表砂矿和氧化矿为主,近年新发现的硫化矿体赋存于石炭系碳酸盐岩中,呈似层状、透镜状或脉状产出,层控特征明显。本次工作以新发现硫化矿体为研究对象,在系统矿物学观察的基础上,借助飞秒激光剥蚀多接收器等离子体质谱仪(fs LA-MC-ICP MS),开展方铅矿原位Pb同位素地球化学研究。结果显示,方铅矿原位Pb同位素组成变化范围较窄,~(206)Pb/~(204)Pb比值为18.755～18.775,~(207)Pb/~(204)Pb比值为15.780～15.799和~(208)Pb/~(204)Pb比值为39.413～39.477,暗示成矿金属来源单一或混合流体均一化程度较高。通过与潜在源区岩石Pb同位素组成特征对比,发现猫榨厂铅锌矿床的Pb金属主要由基底变质岩和盖层沉积岩共同提供,但地层沉积岩的贡献程度较基底岩石高。此外,猫榨厂与福来厂、天桥和板板桥硫化物的Pb同位素组成对比,显示自猫榨厂至板板桥,硫化物的Pb同位素组成逐渐降低,暗示随着成矿流体的演化或运移,高Pb同位素比值地层沉积岩的贡献比例逐渐减少。由于基底富含丰富的成矿金属,其贡献程度与矿床规模正相关关系明显。因此,综合分析认为,猫榨厂矿区深部和北东至板板桥一带仍有很大找矿潜力。
The discovery of the Maozhachang(Maomaochang-Zhazichang) Pb-Zn deposit is a successful case of deep ore prospecting in NW Guizhou in recent years. The Maozhachang deposit, which is adjacent to the Fulaichang, Tianqiao and Banbanqiao deposits, in Hezhang County, Guizhou Province, is located in the central-eastern part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province in the southwestern Yangtze block. Surface placers and oxidized ores were mined in this deposit in the past years. The newly discovered sulfide ore bodies occurred in Carboniferous carbonate rocks in stratiform, lenticular or veining with obvious strata-bound features. In this work, based on the systematic mineralogical observation, the in situ Pb isotopic geochemistry of galena by using femtosecond laser ablation multi receiver plasma mass spectrometer(fs LA-MC-ICP-MS) has been studied. The results show that in-situ Pb isotopic compositions of galena are varied within a narrow range, with ~(206)Pb/~(204)Pb ratios varying from 18.755 to 17.775, ~(207)Pb/~(204)Pb ratios varying 15.780 to 15.799, and ~(208)Pb/~(204)Pb ratios varying from 39.413 to 39.477, respectively, indicating a single source of ore metal or a highly homogenized mixture of ore-forming fluids. By comparing with the Pb isotopic ratios of possible source rocks of the Pb-Zn mineralization, we found that the Pb metal in the Maozhachang Deposit could be mainly sourced from both the basement metamorphic rocks and the cover sedimentary rocks, with the contribution of sedimentary rocks higher than that of the basement rocks. In addition, the comparison among Pb isotopic ratios of sulfides of the Maozhachang and Fulaichang, Tianqiao and Banbanqiao deposits shows that the Pb isotopic ratios are subsequent gradually decreased from the Maozhachang to Banbanqiao, suggesting that with the evolution or transport of ore-forming fluids, the contribution proportion of high Pb isotopic ratios' sediments to the fluids was gradually decreased. Since the basement rocks are rich in ore-forming metals, the degree of their contribution could be positively related to the size of the deposit. Therefore, it is believed that there is still great prospects for prospecting Pb-Zn resources in depth of the Maozhachang deposit and in Maozhachang-Banbanqiao area.
The discovery of the Maozhachang(Maomaochang-Zhazichang) Pb-Zn deposit is a successful case of deep ore prospecting in NW Guizhou in recent years. The Maozhachang deposit, which is adjacent to the Fulaichang, Tianqiao and Banbanqiao deposits, in Hezhang County, Guizhou Province, is located in the central-eastern part of the Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province in the southwestern Yangtze block. Surface placers and oxidized ores were mined in this deposit in the past years. The newly discovered sulfide ore bodies occurred in Carboniferous carbonate rocks in stratiform, lenticular or veining with obvious strata-bound features. In this work, based on the systematic mineralogical observation, the in situ Pb isotopic geochemistry of galena by using femtosecond laser ablation multi receiver plasma mass spectrometer(fs LA-MC-ICP-MS) has been studied. The results show that in-situ Pb isotopic compositions of galena are varied within a narrow range, with ~(206)Pb/~(204)Pb ratios varying from 18.755 to 17.775, ~(207)Pb/~(204)Pb ratios varying 15.780 to 15.799, and ~(208)Pb/~(204)Pb ratios varying from 39.413 to 39.477, respectively, indicating a single source of ore metal or a highly homogenized mixture of ore-forming fluids. By comparing with the Pb isotopic ratios of possible source rocks of the Pb-Zn mineralization, we found that the Pb metal in the Maozhachang Deposit could be mainly sourced from both the basement metamorphic rocks and the cover sedimentary rocks, with the contribution of sedimentary rocks higher than that of the basement rocks. In addition, the comparison among Pb isotopic ratios of sulfides of the Maozhachang and Fulaichang, Tianqiao and Banbanqiao deposits shows that the Pb isotopic ratios are subsequent gradually decreased from the Maozhachang to Banbanqiao, suggesting that with the evolution or transport of ore-forming fluids, the contribution proportion of high Pb isotopic ratios' sediments to the fluids was gradually decreased. Since the basement rocks are rich in ore-forming metals, the degree of their contribution could be positively related to the size of the deposit. Therefore, it is believed that there is still great prospects for prospecting Pb-Zn resources in depth of the Maozhachang deposit and in Maozhachang-Banbanqiao area.
引文
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[16]Zhou JX,Luo K,Wang XC,et al.Ore genesis of the Fule Pb-Zn deposit and its relationship with the Emeishan Large Igneous Province:Evidence from mineralogy,bulk C-O-S and in situ S-Pb isotopes[J].Gondwana Research,2018,54:161-179.
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[19]曾道国,张应文,刘开坤.对黔西北猫猫厂-榨子厂铅锌矿区地质特征及找矿方向的几点不同认识[J].矿产与地质,2007,21(4):410-414.
[20]汤世凯,马筱,李学刚,等.黔西北福来厂铅锌矿床Pb同位素研究及地质意义[J].大地构造与成矿学,2012,36(4):549-558.
[21]Zhou JX,Huang ZL,Zhou MF,et al.Zinc,sulfur and lead isotopic variations in carbonate-hosted Pb-Zn sulfide deposits,southwest China[J].Ore Geology Reviews,2014,58:41-54.
[22]Li B,Zhou JX,Huang ZL,et al.Geological,rare earth elemental and isotopic constraints on the origin of the Banbanqiao Zn-Pb deposit,southwest China[J].Journal of Asian Earth Sciences,2015,111:100-112.
[23]Zhou J,Huang Z,Zhou M,et al.Constraints of C-O-S-Pb isotope compositions and Rb-Sr isotopic age on the origin of the Tianqiao carbonate-hosted Pb-Zn deposit,SW China[J].Ore Geology Reviews,2013,53:77-92.
[24]Zhou J,Huang Z,Yan Z.The origin of the Maozu carbonate-hosted Pb-Zn deposit,southwest China:constrained by C-O-S-Pb isotopic compositions and Sm-Nd isotopic age[J].Journal of Asian Earth Sciences,2013,73:39-47.
[25]Zhang C,Wu Y,Hou L,et al.Geodynamic setting of mineralization of Mississippi Valley-type deposits in world-class Sichuan-Yunnan-Guizhou Zn-Pb triangle,southwest China:Implications from age-dating studies in the past decade and the Sm-Nd age of Jinshachang deposit[J].Journal of Asian Earth Sciences,2015,103:103-114.
[26]Zhou JX,Bai JH,Huang ZL,et al.Geology,isotope geochemistry and geochronology of the Jinshachang carbonate-hosted Pb-Zn deposit,southwest China[J].Journal of Asian Earth Sciences,2015,98:272-284.
[27]毛景文,周振华,丰成友,等.初论中国三叠纪大规模成矿作用及其动力学背景[J].中国地质,2012,39(6):1437-1471.
[28]周家喜,黄智龙,高建国,等.滇东北茂租大型铅锌矿床成矿物质来源及成矿机制[J].矿物岩石,2012,32(3):62-69.
[29]金中国,周家喜,郑明泓,等.贵州普定五指山地区铅锌矿床成矿模式[J].矿床地质,2017,36(5):1169-1184.
[30]崔银亮,周家喜,黄智龙,等.云南富乐铅锌矿床地质、地球化学及成因[J].岩石学报,2018,34(1):194-206.
[2]Zhou JX,Xiang ZZ,Zhou MF.The giant Upper Yangtze Pb-Zn province in SW China:Reviews,new advances and a new genetic model[J].Journal of Asian Earth Sciences,2018,154:280-315.
[3]金中国.黔西北地区铅锌矿控矿因素、成矿规律与找矿预测[M].北京:冶金工业出版社,2008,1-105.
[4]陈国勇,王亮,范玉梅,等.贵州五指山铅锌矿田深部找矿远景分析[J].地质与勘探,2015,51(5):859-869.
[5]温汉捷,周正兵,刘灵,等.贵州天柱大河边铅锌矿床的发现及其意义[J].地质通报,2017,36(7):1288-1293.
[6]刘幼平,张伦尉,杭家华.黔西北猫猫厂-榨子厂铅锌矿床深部找矿潜力分析[J].矿物岩石地球化学通报,2006,25(2):163-168.
[7]周家喜,黄智龙,周国富,等.黔西北赫章天桥铅锌矿床成矿物质来源:S、Pb同位素和REE制约[J].地质论评,2010,56(4):513-524
[8]金中国,周家喜,黄智龙,等.贵州普定纳雍枝铅锌矿矿床成因:S和原位Pb同位素证据[J].岩石学报,2016,32(11):3441-3455.
[9]周家喜,黄智龙,周国富,等.黔西北天桥铅锌矿床热液方解石C、O同位素和REE地球化学[J].大地构造与成矿学,2012,36(1):93-101.
[10]朱路艳,苏文超,沈能平,等.黔西北地区铅锌矿床流体包裹体与硫同位素地球化学研究[J].岩石学报,2016,32(11):3431-3440.
[11]周家喜,黄智龙,周国富,等.贵州天桥铅锌矿床分散元素赋存状态及规律[J].矿物学报,2009,29(4):471-480.
[12]熊伟,程鹏林,周高,等.黔西北铅锌成矿区成矿金属来源的铅同位素示踪[J].矿物学报,2015,35(4):425-429.
[13]肖宪国,黄智龙,周家喜,等.黔西北铅锌矿床成因研究中的几个问题[J].矿物学报,2011,31(3):419-424.
[14]程鹏林,熊伟,周高,等.黔西北地区铅锌矿床成矿流体起源与运移方向初探[J].矿物学报,2015,35(4):509-514.
[15]Bao Z,Yuan W,Yuan H,et al.Non-matrix-matched determination of lead isotope ratios in ancient bronze artifacts by femtosecond laser ablation multi-collector inductively coupled plasma mass spectrometry[J].International Journal of Mass Spectrometry,2016,402:12-19.
[16]Zhou JX,Luo K,Wang XC,et al.Ore genesis of the Fule Pb-Zn deposit and its relationship with the Emeishan Large Igneous Province:Evidence from mineralogy,bulk C-O-S and in situ S-Pb isotopes[J].Gondwana Research,2018,54:161-179.
[17]Zhou JX,Wang XC,Wilde SA,et al.New insights into the metallogeny of MVT Zn-Pb deposits:A case study from the Nayongzhi in South China,using field data,fluid compositions,and in situ S-Pb isotopes[J].American Mineralogist,2018,103(1):91-108.
[18]董家龙.黔西北猫猫厂-榨子厂铅锌矿区地质特征及找矿方向[J].矿产与地质,2005,19(1):29-33.
[19]曾道国,张应文,刘开坤.对黔西北猫猫厂-榨子厂铅锌矿区地质特征及找矿方向的几点不同认识[J].矿产与地质,2007,21(4):410-414.
[20]汤世凯,马筱,李学刚,等.黔西北福来厂铅锌矿床Pb同位素研究及地质意义[J].大地构造与成矿学,2012,36(4):549-558.
[21]Zhou JX,Huang ZL,Zhou MF,et al.Zinc,sulfur and lead isotopic variations in carbonate-hosted Pb-Zn sulfide deposits,southwest China[J].Ore Geology Reviews,2014,58:41-54.
[22]Li B,Zhou JX,Huang ZL,et al.Geological,rare earth elemental and isotopic constraints on the origin of the Banbanqiao Zn-Pb deposit,southwest China[J].Journal of Asian Earth Sciences,2015,111:100-112.
[23]Zhou J,Huang Z,Zhou M,et al.Constraints of C-O-S-Pb isotope compositions and Rb-Sr isotopic age on the origin of the Tianqiao carbonate-hosted Pb-Zn deposit,SW China[J].Ore Geology Reviews,2013,53:77-92.
[24]Zhou J,Huang Z,Yan Z.The origin of the Maozu carbonate-hosted Pb-Zn deposit,southwest China:constrained by C-O-S-Pb isotopic compositions and Sm-Nd isotopic age[J].Journal of Asian Earth Sciences,2013,73:39-47.
[25]Zhang C,Wu Y,Hou L,et al.Geodynamic setting of mineralization of Mississippi Valley-type deposits in world-class Sichuan-Yunnan-Guizhou Zn-Pb triangle,southwest China:Implications from age-dating studies in the past decade and the Sm-Nd age of Jinshachang deposit[J].Journal of Asian Earth Sciences,2015,103:103-114.
[26]Zhou JX,Bai JH,Huang ZL,et al.Geology,isotope geochemistry and geochronology of the Jinshachang carbonate-hosted Pb-Zn deposit,southwest China[J].Journal of Asian Earth Sciences,2015,98:272-284.
[27]毛景文,周振华,丰成友,等.初论中国三叠纪大规模成矿作用及其动力学背景[J].中国地质,2012,39(6):1437-1471.
[28]周家喜,黄智龙,高建国,等.滇东北茂租大型铅锌矿床成矿物质来源及成矿机制[J].矿物岩石,2012,32(3):62-69.
[29]金中国,周家喜,郑明泓,等.贵州普定五指山地区铅锌矿床成矿模式[J].矿床地质,2017,36(5):1169-1184.
[30]崔银亮,周家喜,黄智龙,等.云南富乐铅锌矿床地质、地球化学及成因[J].岩石学报,2018,34(1):194-206.