云南思茅盆地上白垩统勐野井组自形黄铁矿成因及地质意义
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摘要
云南思茅盆地位于特提斯成矿带东南段,上白垩统勐野井组是该区域一套广泛分布的含盐地层,该组内赋存有中国目前唯一的前第四纪固体钾盐矿床。对思茅盆地江城地区勐野井组石膏和黄铁矿样品,利用电子探针和质谱仪进行了主、微量元素和硫同位素分析,结果表明黄铁矿的n(S)/n(Fe)平均值为2.02,为硫富集型黄铁矿;黄铁矿的w(Co)/w(Ni)值为3.01~10.74,变化范围较大;黄铁矿的δ~(34)S_(V-CDT)值为-8.36‰~-3.36‰,平均值为-6.33‰,而石膏的δ~(34)S_(V-CDT)值为6.6‰~10.7‰,平均值为9.48‰。通过对黄铁矿n(S)/n(Fe)、w(Co)/w(Ni)、硫同位素以及石膏硫同位素进行分析,认为勐野井组石膏层在成岩期后受到了热液蚀变的作用,热液蚀变导致石膏被还原形成S~(2-),S~(2-)与热液带来的Fe结合形成了粒状黄铁矿。通过对思茅盆地江城地区勐野井组黄铁矿、石膏的成因机制研究得出,受印度板块俯冲活动控制,深部热液对该区上白垩统勐野井组内原生蒸发岩有明显改造作用并有多种金属矿物伴生。思茅盆地晚白垩世以来热液活动频繁,多期次的热液作用对盆地金属成矿有积极影响,对勐野井组钾盐有不利的改造作用,使得原生钾盐发生蚀变,普遍发生重结晶作用。
The Simao Basin is located in the southeastern part of the Tethyan metallogenic belt. The Mengyejing Formation containing evaporite successions in the Upper Cretaceous is widely distributed in this region. The Mengyejing Formation is currently the only pre-Quaternary solid potash deposit in China. Samples of gypsum and pyrite were collected from the Mengyejing Formation in Jiangcheng County in Simao Basin,and the analysisof major and trace elements and sulfur isotopes of these samples were performed by electron probe micro-analyzer( EPMA) and mass spectrometer. The results show that the S/Fe value of pyrite is 2. 02,showing that it belongs to a sulfur-concentration type pyrite. The Co/Ni values range from 3. 01 to 10. 74,and the varying range is larger. The δ~(34) S_(V-CDT)values of pyrite are in the range of-8. 36‰ to-3. 36‰ with an average of-6. 33‰,while the δ~(34) S_(V-CDT)values of gypsum are in the range of 6. 6‰ to 10. 7‰ with an average of 9. 48‰. The values of S/Fe,Co/Ni and sulfur isotope of pyrites and the values of sulfur isotope of gypsums suggest that the pyrite in the Mengyejing Formation in Jiangcheng County is formed in hydrothermal processes. The hydrothermal alteration causes the gypsum to be reduced to form S~(2-). S~(2-)formed the granulated pyrite combined with Fe from the hydrothermal fluid. Through this study of the genetic mechanism of pyrite and gypsum of the Mengyejing Formation,it comes to the conclusion that the primary evaporites of the Mengyejing Formation in the Upper Cretaceous might be experienced obvious alterations by deep hydrothermal fluids accompanied by several kinds of metals,which is controlled by the Indian and Asian collision,and the hydrothermal activities in Simao Basin recrystallized the potash minerals of the Mengyejing Formation,but might have favorable contribution to the metal deposition.
The Simao Basin is located in the southeastern part of the Tethyan metallogenic belt. The Mengyejing Formation containing evaporite successions in the Upper Cretaceous is widely distributed in this region. The Mengyejing Formation is currently the only pre-Quaternary solid potash deposit in China. Samples of gypsum and pyrite were collected from the Mengyejing Formation in Jiangcheng County in Simao Basin,and the analysisof major and trace elements and sulfur isotopes of these samples were performed by electron probe micro-analyzer( EPMA) and mass spectrometer. The results show that the S/Fe value of pyrite is 2. 02,showing that it belongs to a sulfur-concentration type pyrite. The Co/Ni values range from 3. 01 to 10. 74,and the varying range is larger. The δ~(34) S_(V-CDT)values of pyrite are in the range of-8. 36‰ to-3. 36‰ with an average of-6. 33‰,while the δ~(34) S_(V-CDT)values of gypsum are in the range of 6. 6‰ to 10. 7‰ with an average of 9. 48‰. The values of S/Fe,Co/Ni and sulfur isotope of pyrites and the values of sulfur isotope of gypsums suggest that the pyrite in the Mengyejing Formation in Jiangcheng County is formed in hydrothermal processes. The hydrothermal alteration causes the gypsum to be reduced to form S~(2-). S~(2-)formed the granulated pyrite combined with Fe from the hydrothermal fluid. Through this study of the genetic mechanism of pyrite and gypsum of the Mengyejing Formation,it comes to the conclusion that the primary evaporites of the Mengyejing Formation in the Upper Cretaceous might be experienced obvious alterations by deep hydrothermal fluids accompanied by several kinds of metals,which is controlled by the Indian and Asian collision,and the hydrothermal activities in Simao Basin recrystallized the potash minerals of the Mengyejing Formation,but might have favorable contribution to the metal deposition.
引文
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[10]FAN W,WANG Y,ZHANG A,et al.Permian arc-back-arc basin development along the Ailaoshan tectonic zone:Geochemical,isotopic and geochronological evidence from the Mojiang volcanic rocks,Southwest China[J].Lithos,2010,119(3/4):553-568.
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[13]JIAN P,LIU D,KRONER A,et al.Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China(II):Insights from zircon ages of ophiolites,arc/back-arc assemblages and within-plate igneous rocks and generation of the Emeishan CFB province[J].Lithos,2009,113(3/4):767-784.
[14]XUE C,ZENG R,LIU S,et al.Geologic,fluid inclusion and isotopic characteristics of the Jinding Zn-Pb deposit,western Yunnan,South China:A review[J].Ore Geology Reviews,2007,31(1/4):337-359.
[15]曲一华,袁品泉,帅开业,等.兰坪—思茅盆地钾盐成矿规律及预测[M].北京:地质出版社,1998:1-50.
[16]刘成林.大陆裂谷盆地钾盐矿床特征与成矿作用[J].地球学报,2013,34(5):515-527.
[17]张远志.云南省岩石地层[M].武汉:中国地质大学出版社,1996:1-50.
[18]CHEN H,DOBSON J,HELLER F,et al.Paleomagnetic evidence for clockwise rotation of the Simao region since the Cretaceous:A consequence of India-Asia collision[J].Earth&Planetary Science Letters,1995,134(1/2):203-217.
[19]代堰锫,余心起,吴淦国,等.北武夷蔡家坪铅锌矿床硫化物特征、矿床成因类型及成矿时代[J].地学前缘,2011,18(2):321-338.
[20]李胜荣,陈光远,邵伟,等.胶东乳山金矿田成因矿物学[M].北京:地质出版社,1996:1-10.
[21]郑智杰,尹宏伟,张震,等.云南江城勐野井盐类矿床Sr同位素特征及成盐物质来源分析[J].南京大学学报(自然科学版),2012,48(6):719-727.
[22]黄智龙,陈进,韩润生,等.云南会泽超大型铅锌矿床地球化学及成因[M].北京:地质出版社,2004:1-10.
[23]张宇,邵拥军,周鑫,等.安徽铜陵新桥铜硫铁矿床胶状黄铁矿主、微量元素特征[J].中国有色金属学报,2013(12):3492-3502.
[24]陈光远,孙岱生,张立,等.黄铁矿成因形态学[J].现代地质,1987,1(1):60-76.
[25]ECKERT T,BARNES A,DHAWAN V,et al.A revaluation of the Co/Ni ratio in pyrite as geochemical tool in ore genesis problems[J].Mineralium Deposita,1979,14(3):353-374.
[26]佟景贵,李胜荣,肖启云,等.贵州遵义中南村黑色岩系黄铁矿的成分标型与成因探讨[J].现代地质,2004,18(1):41-47.
[27]高长林,吉让寿,秦德余.北大巴山地区沉积黄铁矿的硫、铅同位素及其构造学意义[J].中国区域地质,1995,14(2):158-163.
[28]陆红锋,刘坚,吴庐山,等.南海天然气水合物钻孔自生黄铁矿硫同位素特征[J].地学前缘,2015,22(2):200-206.
[29]蔡春芳,李宏涛.沉积盆地热化学硫酸盐还原作用评述[J].地球科学进展,2005,20(10):1100-1105.
[30]张建勇,刘文汇,腾格尔,等.TSR对气态烃组分及碳同位素组成的影响——高温高压模拟实验的证据[J].石油实验地质,2012,34(1):66-70.
[31]储雪蕾,陈锦石,王守信.安徽罗河铁矿的硫同位素温度及意义[J].地球化学,1984,13(4):350-356.
[32]胡古月,李延河,曾普胜.膏盐在金顶铅锌矿成矿中的作用:硫和锶同位素证据[J].地质学报,2013,87(11):1694-1702.
[33]肖昌浩.三江中南段低温热液矿床成矿系列研究[D].北京:中国地质大学(北京),2013.
[34]严育通,李胜荣,贾宝剑,等.中国不同成因类型金矿床的黄铁矿成分标型特征及统计分析[J].地学前缘,2012,19(4):214-226.
[35]帅开业.云南中、新生代地质构造演化与蒸发岩建造[J].现代地质,1987,1(2):207-229.
[36]SHEN L,LIU C,WANG L,et al.Degree of brine evaporation and origin of the Mengyejing potash deposit:Evidence from fluid inclusions in Halite[J].Acta Geologica Sinica,2017,97(1):175-185.
[37]曾普胜,李红,李延河,等.亚洲最大铅锌矿——三阶段叠加成矿的金顶巨型铅锌矿床[J].地质学报,2016,90(9):2384-2398.
[2]WANG L,LIU C,FEI M,et al.First SHRIMP U-Pb zircon ages of the potash-bearing Mengyejing Formation,Simao Basin,southwestern Yunnan,China[J].Cretaceous Research,2015,52:238-250.
[3]高翔,方勤方,姚薇,等.云南兰坪—思茅盆地勐野井钾盐矿床物质组分对成因的指示[J].地球学报,2013,34(5):529-536.
[4]刘群.中国中—新生代陆源碎屑:化学岩型盐类沉积[M].北京:北京科学技术出版社,1987:1-10.
[5]李玉英.河北高板河黄铁矿矿物形态及成因[J].河北地质学院学报,1994(6):523-535.
[6]METCALFE I.Palaeozoic and Mesozoic tectonic evolution and palaeogeography of East Asian crustal fragments:The Korean Peninsula in context[J].Gondwana Research,2006,9(1/2):24-46.
[7]METCALFE I.Late Palaeozoic and Mesozoic tectonic and palaeogeographical evolution of SE Asia[M]//BUFFETAUT E,GUNY G,LE LOEUFF J,et al.Late Palaeozoic and Mesozoic Ecosystems in SE Asia.London:Geological Society of London Special Publications,2009:7-23.
[8]METCALFE I.Palaeozoic-Mesozoic history of SE Asia[M]//HALL R,COTTAM M,WILSON M.The SE Asia Gateway:History and Tectonics of Australia-Asia Collision.London:Geological Society of London Special Publications,2011:7-35.
[9]SONE M,METCALFE I.Parallel Tethyan sutures in mainland Southeast Asia:New insights for Palaeo-Tethys closure and implications for the Indosinian orogeny[J].Comptes Rendus Geoscience,2008,340(2/3):166-179.
[10]FAN W,WANG Y,ZHANG A,et al.Permian arc-back-arc basin development along the Ailaoshan tectonic zone:Geochemical,isotopic and geochronological evidence from the Mojiang volcanic rocks,Southwest China[J].Lithos,2010,119(3/4):553-568.
[11]钟大赉.滇川西部古特提斯造山带[M].北京:科学出版社,1998:1-20.
[12]JIAN P,LIU D,KRONER A,et al.Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China(I):Geochemistry of ophiolites,arc/back-arc assemblages and withinplate igneous rocks[J].Lithos,2009,113(3/4):748-766.
[13]JIAN P,LIU D,KRONER A,et al.Devonian to Permian plate tectonic cycle of the Paleo-Tethys Orogen in southwest China(II):Insights from zircon ages of ophiolites,arc/back-arc assemblages and within-plate igneous rocks and generation of the Emeishan CFB province[J].Lithos,2009,113(3/4):767-784.
[14]XUE C,ZENG R,LIU S,et al.Geologic,fluid inclusion and isotopic characteristics of the Jinding Zn-Pb deposit,western Yunnan,South China:A review[J].Ore Geology Reviews,2007,31(1/4):337-359.
[15]曲一华,袁品泉,帅开业,等.兰坪—思茅盆地钾盐成矿规律及预测[M].北京:地质出版社,1998:1-50.
[16]刘成林.大陆裂谷盆地钾盐矿床特征与成矿作用[J].地球学报,2013,34(5):515-527.
[17]张远志.云南省岩石地层[M].武汉:中国地质大学出版社,1996:1-50.
[18]CHEN H,DOBSON J,HELLER F,et al.Paleomagnetic evidence for clockwise rotation of the Simao region since the Cretaceous:A consequence of India-Asia collision[J].Earth&Planetary Science Letters,1995,134(1/2):203-217.
[19]代堰锫,余心起,吴淦国,等.北武夷蔡家坪铅锌矿床硫化物特征、矿床成因类型及成矿时代[J].地学前缘,2011,18(2):321-338.
[20]李胜荣,陈光远,邵伟,等.胶东乳山金矿田成因矿物学[M].北京:地质出版社,1996:1-10.
[21]郑智杰,尹宏伟,张震,等.云南江城勐野井盐类矿床Sr同位素特征及成盐物质来源分析[J].南京大学学报(自然科学版),2012,48(6):719-727.
[22]黄智龙,陈进,韩润生,等.云南会泽超大型铅锌矿床地球化学及成因[M].北京:地质出版社,2004:1-10.
[23]张宇,邵拥军,周鑫,等.安徽铜陵新桥铜硫铁矿床胶状黄铁矿主、微量元素特征[J].中国有色金属学报,2013(12):3492-3502.
[24]陈光远,孙岱生,张立,等.黄铁矿成因形态学[J].现代地质,1987,1(1):60-76.
[25]ECKERT T,BARNES A,DHAWAN V,et al.A revaluation of the Co/Ni ratio in pyrite as geochemical tool in ore genesis problems[J].Mineralium Deposita,1979,14(3):353-374.
[26]佟景贵,李胜荣,肖启云,等.贵州遵义中南村黑色岩系黄铁矿的成分标型与成因探讨[J].现代地质,2004,18(1):41-47.
[27]高长林,吉让寿,秦德余.北大巴山地区沉积黄铁矿的硫、铅同位素及其构造学意义[J].中国区域地质,1995,14(2):158-163.
[28]陆红锋,刘坚,吴庐山,等.南海天然气水合物钻孔自生黄铁矿硫同位素特征[J].地学前缘,2015,22(2):200-206.
[29]蔡春芳,李宏涛.沉积盆地热化学硫酸盐还原作用评述[J].地球科学进展,2005,20(10):1100-1105.
[30]张建勇,刘文汇,腾格尔,等.TSR对气态烃组分及碳同位素组成的影响——高温高压模拟实验的证据[J].石油实验地质,2012,34(1):66-70.
[31]储雪蕾,陈锦石,王守信.安徽罗河铁矿的硫同位素温度及意义[J].地球化学,1984,13(4):350-356.
[32]胡古月,李延河,曾普胜.膏盐在金顶铅锌矿成矿中的作用:硫和锶同位素证据[J].地质学报,2013,87(11):1694-1702.
[33]肖昌浩.三江中南段低温热液矿床成矿系列研究[D].北京:中国地质大学(北京),2013.
[34]严育通,李胜荣,贾宝剑,等.中国不同成因类型金矿床的黄铁矿成分标型特征及统计分析[J].地学前缘,2012,19(4):214-226.
[35]帅开业.云南中、新生代地质构造演化与蒸发岩建造[J].现代地质,1987,1(2):207-229.
[36]SHEN L,LIU C,WANG L,et al.Degree of brine evaporation and origin of the Mengyejing potash deposit:Evidence from fluid inclusions in Halite[J].Acta Geologica Sinica,2017,97(1):175-185.
[37]曾普胜,李红,李延河,等.亚洲最大铅锌矿——三阶段叠加成矿的金顶巨型铅锌矿床[J].地质学报,2016,90(9):2384-2398.