宣城水东地区中二叠统硅质角砾岩地球化学特征及其成因环境研究
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摘要
为研究长江中下游成矿带东部宣城水东地区中二叠统孤峰组中发育的一套硅质岩特别是其中的硅质角砾岩的成因,在详细的野外地质调查和室内岩石学研究基础上,对取自该套硅质岩中的7件硅质角砾岩、7件块状硅质岩和1件中薄层硅质岩样品进行了主量元素、微量元素和稀土元素地球化学分析。结果表明,硅质角砾岩和硅质岩的地球化学特征相似,其SiO_2含量高(93.70%~99.24%)、Al/(Al+Fe+Mn)值较高、轻稀土略富集、无明显铈异常和铕异常,显示非热液成因的特征。硅质岩的地球化学特征指示其主要为正常海水沉积成因,形成于靠近大陆边缘的沉积环境,受一定的陆源碎屑输入影响。硅质角砾岩的形成可能与江南断裂带活动影响有关,后期的海底热液对硅质岩进行叠加或动力学改造,并在局部形成角砾状构造。
Chert,particularly siliceous breccia,are well developed in middle Permian Gufeng Formation at Shuidong town,Xuancheng city,Middle-Lower Yangtze Metallogenic Belt. However,their origins and depositional environments remain controversial. Based on extensive field observations and petrography study of the siliceous breccia and chert,we analyzed major and trace elements of fifteen samples which include seven siliceous breccia,seven massive cherts and one thin-layered chert. These siliceous rocks have high SiO_2( 93. 70%– 99. 24%) and Al/( Al+Fe+Mn) ratios,and are characterized by slight enrichment of LREE without significant Ce and Eu anomalies,indicating that these rocks were bio-genetic and formed in an open continental margin environment with minor terrigenous clastic input. Meanwhile,the Jiangnan fault belt may play an important role in the formation of such chert. It could provide the passway for hydrothermal fluids that not only change the composition of chert but also trigger the formation of siliceous breccia.
Chert,particularly siliceous breccia,are well developed in middle Permian Gufeng Formation at Shuidong town,Xuancheng city,Middle-Lower Yangtze Metallogenic Belt. However,their origins and depositional environments remain controversial. Based on extensive field observations and petrography study of the siliceous breccia and chert,we analyzed major and trace elements of fifteen samples which include seven siliceous breccia,seven massive cherts and one thin-layered chert. These siliceous rocks have high SiO_2( 93. 70%– 99. 24%) and Al/( Al+Fe+Mn) ratios,and are characterized by slight enrichment of LREE without significant Ce and Eu anomalies,indicating that these rocks were bio-genetic and formed in an open continental margin environment with minor terrigenous clastic input. Meanwhile,the Jiangnan fault belt may play an important role in the formation of such chert. It could provide the passway for hydrothermal fluids that not only change the composition of chert but also trigger the formation of siliceous breccia.
引文
Adachi M,Yamamoto K,Sugisaki R.1986.Hydrothermal chert and associated siliceous rocks from the northern Pacific:their geological significance as indication od ocean ridge activity.Sedimentary Geology,47(1-2):125-148
Blatt H,Middleton G V,Murray R.1980.Origin of sedimentary rocks.Englewood Cliffs,N.J.:PrenticeHall,l-782
Bolhar R,Kamber B S,Moorbath S,Fedo C M,Whitehouse M J.2004.Characterisation of early Archaean chemical sediments by trace element signatures.Earth and Planetary Science Letters,222(1):43-60
Bostr9m K,Peterson M N A.1969.The origin of aluminum-poor ferromanganoan sediments in areas of high heat flow on the East Pacific Rise.Marine Geology,7(5):427-447
David L K,Douglas H E.2001.Secular distribution of biogenic silica through the phanerozoic:Comparison of silica-replaced fossils and bedded cherts at the series level.The Journal of Geology,109(4):509-522
DiasS,Früh-Green G L,Bernasconi S M,Barriga F J A S,Seahma Cruise Team,Charles Darwin 167 Cruise Team.2011.Geochemistry and stable isotope constraints on high-temperature activity from sediment cores of the Saldanha hy drothermal field.Marine Geology,279(1-4):128-140
Douville E,Bienvenu P,Charlou J L,Donval J P,Fouquet Y,Appriou P,Gamo T.1999.Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems.Geochimica et Cosmochimica Acta,63(5):627-643
Girty G H,Ridge D L,Knaack C,Johnson D,Al-Riyami R K.1996.Provenance and depositional setting of Paleozoic chert and argillite,Sierra Nevada,California.Journal of Sedimentary Research,66(1):107-118
Hayashi K I,Fujisawa H,Holland H D,Ohmoto H.1997.Geochemistry of~1.9 Ga sedimentary rocks from northeastern Labrador,Canada.Geochimica et Cosmochimica Acta,61(19):4115-4137
Knauth L P.1994.Petrogenesis of chert.In:Heaney P T,Prewitt C T,Gibbs G V,eds.Silica:physical behavior,geochemistry,and materials application:Mineralogical Society of America.Reviews in Mineralogy,29:233-258
Maliva R G,Knoll A H,Simonson B M.2005.Secular change in the Precambrian silica cycle:Insights from chert petrology.Geological Society of America Bulletin,117(7):835-845
Masao K,Masamichi T,Hiromi N.2005.Sedimentary environments of the Middle Permian phosphorite-chert complex from the northeastern Yangtze Platform,China,the Gufeng Formation:acontinental shelf radiolarian chert.Sedimentary Geology,174(3-4):197-222
Mclennan S M.1989.Rare earth elements in sedimentary rocks:Influence of provenance and sedimentary processes.Reviews in Mineralogy and Geochemistry,21(1):169-200
Murray R W.1994.Chemical criteria to identify the depositional environment of chert:General principles and applications.Sedimentary Geology,90(3-4):213-232
Murray R W,Buchholtz Ten Brink M R,Gerlach D C,Russ G P,Jones D L.1991.Rareearth,major,and trace elements in chert from the Franciscan Complex and Monterey Group,California:Assessing REE sources to fine-grained marine sediments.Geochimica et Cosmochimica Acta,55(7):1875-1895
Murray R W,Ten Brink M R B,Gerlach D C,Russ G P,Jones D L.1992.Interoceanic variation in the rare earth,major,and trace element depositional chemistry of chert:Perspectives gained from the DSDP and ODP record.Geochimica et Cosmochimica Acta,56(5):1897-1913
Murray R W,Ten Brink M R B,Jones D L,Gerlach D C,Russ G P.1990.Rare earth elements as indicators of different marine depositional environments in chert and shale.Geology,18(3):268-271
Sugitani K,Horiuchi Y,Adachi M,Sugisaki R.1996.Anomalously low Al2O3/Ti O2values for Archean cherts from the Pilbara block,western Australia:possible evidence for extensive chemical weathering on the early earth.Precambrian Research,80(1-2):49-76
Taylor S R,Mclennan S M.1985.The continental crust:its composition and evolution.Oxford:Blackwell,9-56
Yamamoto K.1987.Geochemical characteristics and depositional environments of cherts and associated rocks in the Franciscan and Shimanto Terranes.Sedimentary Geology,52(1-2):65-108
安徽省地质矿产局.1987.安徽省区域地质志.北京:地质出版社,1-200
程成,李双应,赵大千,颜玲.2015.扬子地台北缘中上二叠统层状硅质岩的地球化学特征及其对古地理、古海洋演化的响应.矿物岩石地球化学通报,34(1):155-166
戴圣潜,周存亭,储东如.2 005.1:25万宣城市幅(H50 C 002004)区域地质调查报告.合肥:安徽省地质调查院,1-223
何卫红,吴顺宝,张克信,卜建军.1999.下扬子区孤峰组放射虫化石带划分及环境分析.江苏地质,23(1):17-23
黄德志,邱瑞龙,吴言昌.2000.长江中下游前陆带南缘青阳-泾县一带印支运动的特征及意义.中国区域地质,19(1):52-58
黄虎,杨江海,杜远生,黄志强,黄宏伟,郭华.2012.右江盆地北缘上二叠统碎屑岩和硅质岩地球化学特征及其地质意义.中国地质大学学报,37(S2):81-96
黄虎,杜远生,杨江海,陶平,黄宏伟,黄志强,谢春霞,胡丽沙.2013.水城-紫云-南丹裂陷盆地晚古生代硅质沉积物地球化学特征及其地质意义.地质学报,86(12):1994-2010
孔庆玉,龚与觐.1987.苏皖地区下二叠统放射虫硅质岩形成环境探讨.石油与天然气地质,8(1):86-89,123-124
李双应,孟庆任,万秋,孔为伦,何刚.2008.长江中下游地区二叠纪碳酸盐斜坡沉积及其成矿意义.岩石学报,24(8):1733-1744
骆学全,张雪辉,孙建东,周宗尧.2015.萍乡-绍兴结合带铜多金属成矿规律研究报告.南京:南京地质调查中心,1-300
汤加富,侯明金,李怀坤,吴跃东,孙乘云.2003.扬子地块东北缘多期叠加变形及形成演化.大地构造与成矿学,27(4):313-326
夏邦栋,钟立荣,方中,吕洪波.1995.下扬子区早二叠世孤峰组层状硅质岩成因.地质学报,69(2):125-137
杨海生,周永章,杨志军,张澄博,付伟.2003.华南热水成因硅质岩建造的稀土元素地球化学特征.矿物岩石地球化学通报,22(1):61-64
曾允孚,夏文杰.1986.沉积岩石学.北京:地质出版社,1-190
张冠亚,杜远生,徐亚军,余文超,黄虎,焦良轩.2015.湘中震旦纪-寒武纪之交硅质岩地球化学特征及成因环境研究.地质论评,61(3):499-510
周旻玥,孔凡乾,韦龙明,白志强,董世爽,袁琼.2015.广西钦州石夹剖面硅质岩稀土元素地球化学特征.矿物岩石地球化学通报,2015,34(6):1262-1269
Blatt H,Middleton G V,Murray R.1980.Origin of sedimentary rocks.Englewood Cliffs,N.J.:PrenticeHall,l-782
Bolhar R,Kamber B S,Moorbath S,Fedo C M,Whitehouse M J.2004.Characterisation of early Archaean chemical sediments by trace element signatures.Earth and Planetary Science Letters,222(1):43-60
Bostr9m K,Peterson M N A.1969.The origin of aluminum-poor ferromanganoan sediments in areas of high heat flow on the East Pacific Rise.Marine Geology,7(5):427-447
David L K,Douglas H E.2001.Secular distribution of biogenic silica through the phanerozoic:Comparison of silica-replaced fossils and bedded cherts at the series level.The Journal of Geology,109(4):509-522
DiasS,Früh-Green G L,Bernasconi S M,Barriga F J A S,Seahma Cruise Team,Charles Darwin 167 Cruise Team.2011.Geochemistry and stable isotope constraints on high-temperature activity from sediment cores of the Saldanha hy drothermal field.Marine Geology,279(1-4):128-140
Douville E,Bienvenu P,Charlou J L,Donval J P,Fouquet Y,Appriou P,Gamo T.1999.Yttrium and rare earth elements in fluids from various deep-sea hydrothermal systems.Geochimica et Cosmochimica Acta,63(5):627-643
Girty G H,Ridge D L,Knaack C,Johnson D,Al-Riyami R K.1996.Provenance and depositional setting of Paleozoic chert and argillite,Sierra Nevada,California.Journal of Sedimentary Research,66(1):107-118
Hayashi K I,Fujisawa H,Holland H D,Ohmoto H.1997.Geochemistry of~1.9 Ga sedimentary rocks from northeastern Labrador,Canada.Geochimica et Cosmochimica Acta,61(19):4115-4137
Knauth L P.1994.Petrogenesis of chert.In:Heaney P T,Prewitt C T,Gibbs G V,eds.Silica:physical behavior,geochemistry,and materials application:Mineralogical Society of America.Reviews in Mineralogy,29:233-258
Maliva R G,Knoll A H,Simonson B M.2005.Secular change in the Precambrian silica cycle:Insights from chert petrology.Geological Society of America Bulletin,117(7):835-845
Masao K,Masamichi T,Hiromi N.2005.Sedimentary environments of the Middle Permian phosphorite-chert complex from the northeastern Yangtze Platform,China,the Gufeng Formation:acontinental shelf radiolarian chert.Sedimentary Geology,174(3-4):197-222
Mclennan S M.1989.Rare earth elements in sedimentary rocks:Influence of provenance and sedimentary processes.Reviews in Mineralogy and Geochemistry,21(1):169-200
Murray R W.1994.Chemical criteria to identify the depositional environment of chert:General principles and applications.Sedimentary Geology,90(3-4):213-232
Murray R W,Buchholtz Ten Brink M R,Gerlach D C,Russ G P,Jones D L.1991.Rareearth,major,and trace elements in chert from the Franciscan Complex and Monterey Group,California:Assessing REE sources to fine-grained marine sediments.Geochimica et Cosmochimica Acta,55(7):1875-1895
Murray R W,Ten Brink M R B,Gerlach D C,Russ G P,Jones D L.1992.Interoceanic variation in the rare earth,major,and trace element depositional chemistry of chert:Perspectives gained from the DSDP and ODP record.Geochimica et Cosmochimica Acta,56(5):1897-1913
Murray R W,Ten Brink M R B,Jones D L,Gerlach D C,Russ G P.1990.Rare earth elements as indicators of different marine depositional environments in chert and shale.Geology,18(3):268-271
Sugitani K,Horiuchi Y,Adachi M,Sugisaki R.1996.Anomalously low Al2O3/Ti O2values for Archean cherts from the Pilbara block,western Australia:possible evidence for extensive chemical weathering on the early earth.Precambrian Research,80(1-2):49-76
Taylor S R,Mclennan S M.1985.The continental crust:its composition and evolution.Oxford:Blackwell,9-56
Yamamoto K.1987.Geochemical characteristics and depositional environments of cherts and associated rocks in the Franciscan and Shimanto Terranes.Sedimentary Geology,52(1-2):65-108
安徽省地质矿产局.1987.安徽省区域地质志.北京:地质出版社,1-200
程成,李双应,赵大千,颜玲.2015.扬子地台北缘中上二叠统层状硅质岩的地球化学特征及其对古地理、古海洋演化的响应.矿物岩石地球化学通报,34(1):155-166
戴圣潜,周存亭,储东如.2 005.1:25万宣城市幅(H50 C 002004)区域地质调查报告.合肥:安徽省地质调查院,1-223
何卫红,吴顺宝,张克信,卜建军.1999.下扬子区孤峰组放射虫化石带划分及环境分析.江苏地质,23(1):17-23
黄德志,邱瑞龙,吴言昌.2000.长江中下游前陆带南缘青阳-泾县一带印支运动的特征及意义.中国区域地质,19(1):52-58
黄虎,杨江海,杜远生,黄志强,黄宏伟,郭华.2012.右江盆地北缘上二叠统碎屑岩和硅质岩地球化学特征及其地质意义.中国地质大学学报,37(S2):81-96
黄虎,杜远生,杨江海,陶平,黄宏伟,黄志强,谢春霞,胡丽沙.2013.水城-紫云-南丹裂陷盆地晚古生代硅质沉积物地球化学特征及其地质意义.地质学报,86(12):1994-2010
孔庆玉,龚与觐.1987.苏皖地区下二叠统放射虫硅质岩形成环境探讨.石油与天然气地质,8(1):86-89,123-124
李双应,孟庆任,万秋,孔为伦,何刚.2008.长江中下游地区二叠纪碳酸盐斜坡沉积及其成矿意义.岩石学报,24(8):1733-1744
骆学全,张雪辉,孙建东,周宗尧.2015.萍乡-绍兴结合带铜多金属成矿规律研究报告.南京:南京地质调查中心,1-300
汤加富,侯明金,李怀坤,吴跃东,孙乘云.2003.扬子地块东北缘多期叠加变形及形成演化.大地构造与成矿学,27(4):313-326
夏邦栋,钟立荣,方中,吕洪波.1995.下扬子区早二叠世孤峰组层状硅质岩成因.地质学报,69(2):125-137
杨海生,周永章,杨志军,张澄博,付伟.2003.华南热水成因硅质岩建造的稀土元素地球化学特征.矿物岩石地球化学通报,22(1):61-64
曾允孚,夏文杰.1986.沉积岩石学.北京:地质出版社,1-190
张冠亚,杜远生,徐亚军,余文超,黄虎,焦良轩.2015.湘中震旦纪-寒武纪之交硅质岩地球化学特征及成因环境研究.地质论评,61(3):499-510
周旻玥,孔凡乾,韦龙明,白志强,董世爽,袁琼.2015.广西钦州石夹剖面硅质岩稀土元素地球化学特征.矿物岩石地球化学通报,2015,34(6):1262-1269