羌塘盆地沃若山地区上三叠统土门格拉组烃源岩沉积环境分析
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摘要
岩石学、沉积相、元素地球化学的综合分析结果表明,羌塘盆地沃若山地区上三叠统土门格拉组(T_3t)地层为三角洲沉积;整体富含水解性元素、Fe族元素以及上部砂岩Fe元素富集(高Fe/Mn比值)的特征表明古水体环境为较浅的河口-滨岸环境;CIA值(63.8~79)、ICV值(0.52~1.4)和Ga/Rb-K2O/Al2O3关系图解分析结果显示当时为风化强度中等、较温暖的半干旱—半湿润气候;Sr/Ba比值全部小于1(0.09~0.27),表明沉积水体为盐度较低的陆相淡水;根据V、U、Mo的含量比值,判断其为氧化-弱氧化的富氧水体环境。较为温湿的气候有利于生物的繁殖,但氧化-弱氧化的环境不利于有机质的富集,限制了该地区烃源岩发育:土门格拉组烃源岩的TOC含量为0.76%~1.46%(均值为1.04%),属中等品质的烃源岩。
This paper focuses on the study of the sedimentary environments of the source rocks from the Upper Triassic Tumengela Formation( T_3 t) in the Qiangtang Basin,Xizang,in the light of petrology,geochemistry and sedimentary facies analysis. The sedimentary environments of the source rocks in the Upper Triassic Tumengela Formation is assigned to the delta sedimentary facies. The enrichment of the hydrolytic elements,iron group elements,and the element Fe( Fe/Mn ratios) in the upper sandstones indicates the shallower river mouth to onshore environments. The values of CIA( 63. 8-79),ICV( 0. 52-1. 4) and Ga/Rb vs. K_2O/Al_2O_3 diagrams show the moderate weathering under the semi-arid to semi-humid climatic conditions. The Sr/Ba ratios are all less than 1( 0. 09 to 0. 27),indicating the low-salinity and fresh continental sedimentary environments. The V,U and Mo contents also indicate the anoxic-suboxic water environments. The warmer and wetter climates are beneficial to the reproduction of organisms,while the anoxic-suboxic environments are not constructive to the enrichment of organic matter. The low TOC values of 0. 76% to 1. 46%( mean value is 1. 04%) have disclosed that the source rocks should be assigned to the medium-quality source rocks in the study area.
This paper focuses on the study of the sedimentary environments of the source rocks from the Upper Triassic Tumengela Formation( T_3 t) in the Qiangtang Basin,Xizang,in the light of petrology,geochemistry and sedimentary facies analysis. The sedimentary environments of the source rocks in the Upper Triassic Tumengela Formation is assigned to the delta sedimentary facies. The enrichment of the hydrolytic elements,iron group elements,and the element Fe( Fe/Mn ratios) in the upper sandstones indicates the shallower river mouth to onshore environments. The values of CIA( 63. 8-79),ICV( 0. 52-1. 4) and Ga/Rb vs. K_2O/Al_2O_3 diagrams show the moderate weathering under the semi-arid to semi-humid climatic conditions. The Sr/Ba ratios are all less than 1( 0. 09 to 0. 27),indicating the low-salinity and fresh continental sedimentary environments. The V,U and Mo contents also indicate the anoxic-suboxic water environments. The warmer and wetter climates are beneficial to the reproduction of organisms,while the anoxic-suboxic environments are not constructive to the enrichment of organic matter. The low TOC values of 0. 76% to 1. 46%( mean value is 1. 04%) have disclosed that the source rocks should be assigned to the medium-quality source rocks in the study area.
引文
[1]王剑,谭富文,王小龙,等.藏北羌塘盆地早侏罗—中侏罗世早期沉积构造特征[J].沉积学报,2004,22(2):198-205.
[2]王剑,丁俊,王成善,等.青藏高原油气资源战略选区调查与评价[M].北京:地质出版社,2008.
[3]赵政璋,李永铁,叶和飞,等.青藏高原海相烃源层的油气生成[M].北京:科学出版社,2000.
[4]王羽珂,王剑,万友利,等.南羌塘坳陷古油藏带布曲组白云岩储层特征及控制因素分析[J].沉积与特提斯地质,2017,37(1):1-8.
[5]刘中戎,张佳伟.西藏羌塘盆地中生代晚期构造事件与油气的关系[J].沉积与特提斯地质,2017,37(2):23-29.
[6]彭清华,杜佰伟,谢尚克,等.羌塘盆地昂达尔错地区油苗生物标志化合物特征及其指示意义[J].沉积与特提斯地质,2017,37(3):59-65.
[7]张润合,斯春松,陈明,等.西藏羌塘盆地北部拗陷侏罗系层序地层划分对比及地质意义[J].沉积与特提斯地质,2015,35(2):1-7.
[8]陈文彬,付修根,谭富文,等.羌塘盆地上三叠统土门格拉组烃源岩生物标志物地球化学特征[J].现代地质,2014,28(1):216-223.
[9]杨日红,李才,杨德明,等.西藏羌塘盆地中生代构造岩相演化及油气远景[J].长春科技大学学报,2000,30(3):237-242.
[10]Tribovillard N,Algeo T J,Lyons T,et al.Trace metals as paleoredox and paleoproductivity proxies:An update[J].Chemical Geology,2006,232(1-2):12-32.
[11]和钟铧,李才,杨德明,等.西藏羌塘盆地的构造沉积特征及演化[J].长春科技大学学报,2000,30(4):347-352.
[12]Suttner L J,Dutta P K.Alluvial sandstone composition and paleoclimate,I.Framework mineralogy[J].Journal of Sedimentary Petrology,1986,56:329-345.
[13]Cullers R L.The controls on the major and trace element variation of shale,silt stones,and sandstones of PennsylvanianPermian age from up lifted continental blocks in Colorado to platform sediment in Kansas,USA[J].Geochimica et Cosmochim Acta,1994,58:4955-4972.
[14]Mc Lennan S M.A geochemical approach to sedimentary provenance[M]//GSA.GSA Abstracts with Programs.Boulder:GSA,1991,23(5):108.
[15]Korsch R J,Roser B P,Kamprad J L.Geochemical,petrographic and grain-size variations within single turbidite beds[J].Sedimentary Geology,1993,83:15-35.
[16]Kiminami K,Fujii K.The relationship between major element concentrations within sandstones from four turbidite sequences in Japan[J].Sedimentary Geology,2007,195:203-215.
[17]Benedict G L,Walker K R.古生代层序的古水深分析及其地球动力学意义[J].夏祖葆译.国外沉积相及古地理资料汇编(二),地质矿产部情报所.
[18]邓宏文,钱凯.沉积地球化学与环境分析[M].兰州:甘肃科学技术出版社,1993.
[19]Fedo C M,Nesbitt H W,Young G M.Unraveling the effects of potassium metasomatism in sandstones and paleosols,with implications for paleoweathering conditions and provenance[J].Geology,1995,23:921-924.
[20]Nesbitt H W,Young G M.Early Proterozoic climates and plate motions inferred from major elemental chemistry of lutites[J].Nature,1982,199:715-717.
[21]Fedo C M,Young G M,Nesbitt H W.Paleoclimatic control on the composition of the Paleoproterozoic Serpent Formation,Huronian Supergroup,Canada:a greenhouse to icehouse transition[J].Precambrian Research,1997,86:210-223.
[22]Cox R,Lowe D R,Cullers R L.The influence of sediment recycling and basement composition of evolution of mudrock chemistry in the southwestern United States[J].Geochim.Cosmochim.Acta,1995,59:2919-2940.
[23]Potter P E,Maynard J B,Depetris P J.Mud and Mudstones,Introduction and Overview[M].Berlin Heidelberg:Springer,2005.157-174.
[24]Sciscio L,Bordy E M.Palaeoclimatic conditions in the Late Triassic-Early Jurassic of southern Africa:a geochemical assessment of the Elliot Formation[J].J.Afr.Earth Sci.,2016,119:102-119.
[25]Hieronymus B,Kotschoubey B,Boulegue J.Gallium behavior in some contrasting lateritic profiles from Cameroon and Brazil[J].Journal of Geochemical Exploration,2001,72:147-163.
[26]Beckmann B,Fl¨ogel S,Hofmann P,et al.Orbital forcing of Cretaceous river discharge in tropical Africa and ocean response[J].Nature,2005,437:241-244.
[27]Ratcliffe K T,Wright A M,Montgomery P,et al.Application of chemostratigraphy to the Mungaroo Formation,the Gorgon field,offshore northwest Australia[A].Australian Petroleum Production and Exploration Association Journal(50th Anniversary Issue)[C].2010.371-388.
[28]韩永红,王海红,陈志华,等.耿湾-史家湾地区长6段微量元素地球化学特征及古盐度[J].岩性油气藏,2007,19(4):20-26.
[29]Algeo T J,Tribovillard N.Environmental analysis of paleoceano graphic systems based on molybdenum-uranium covariation[J].Chemical Geology,2009,268:211-225.
[30]Tribovillard N,Algeo T J,Baudin F,Riboulleau A.Analysis of marine environmental conditions based on molybdenum-uranium covariation——applications to Mesozoic paleoceanography[J].Chemical Geology,2012,324-325:46-58.
[2]王剑,丁俊,王成善,等.青藏高原油气资源战略选区调查与评价[M].北京:地质出版社,2008.
[3]赵政璋,李永铁,叶和飞,等.青藏高原海相烃源层的油气生成[M].北京:科学出版社,2000.
[4]王羽珂,王剑,万友利,等.南羌塘坳陷古油藏带布曲组白云岩储层特征及控制因素分析[J].沉积与特提斯地质,2017,37(1):1-8.
[5]刘中戎,张佳伟.西藏羌塘盆地中生代晚期构造事件与油气的关系[J].沉积与特提斯地质,2017,37(2):23-29.
[6]彭清华,杜佰伟,谢尚克,等.羌塘盆地昂达尔错地区油苗生物标志化合物特征及其指示意义[J].沉积与特提斯地质,2017,37(3):59-65.
[7]张润合,斯春松,陈明,等.西藏羌塘盆地北部拗陷侏罗系层序地层划分对比及地质意义[J].沉积与特提斯地质,2015,35(2):1-7.
[8]陈文彬,付修根,谭富文,等.羌塘盆地上三叠统土门格拉组烃源岩生物标志物地球化学特征[J].现代地质,2014,28(1):216-223.
[9]杨日红,李才,杨德明,等.西藏羌塘盆地中生代构造岩相演化及油气远景[J].长春科技大学学报,2000,30(3):237-242.
[10]Tribovillard N,Algeo T J,Lyons T,et al.Trace metals as paleoredox and paleoproductivity proxies:An update[J].Chemical Geology,2006,232(1-2):12-32.
[11]和钟铧,李才,杨德明,等.西藏羌塘盆地的构造沉积特征及演化[J].长春科技大学学报,2000,30(4):347-352.
[12]Suttner L J,Dutta P K.Alluvial sandstone composition and paleoclimate,I.Framework mineralogy[J].Journal of Sedimentary Petrology,1986,56:329-345.
[13]Cullers R L.The controls on the major and trace element variation of shale,silt stones,and sandstones of PennsylvanianPermian age from up lifted continental blocks in Colorado to platform sediment in Kansas,USA[J].Geochimica et Cosmochim Acta,1994,58:4955-4972.
[14]Mc Lennan S M.A geochemical approach to sedimentary provenance[M]//GSA.GSA Abstracts with Programs.Boulder:GSA,1991,23(5):108.
[15]Korsch R J,Roser B P,Kamprad J L.Geochemical,petrographic and grain-size variations within single turbidite beds[J].Sedimentary Geology,1993,83:15-35.
[16]Kiminami K,Fujii K.The relationship between major element concentrations within sandstones from four turbidite sequences in Japan[J].Sedimentary Geology,2007,195:203-215.
[17]Benedict G L,Walker K R.古生代层序的古水深分析及其地球动力学意义[J].夏祖葆译.国外沉积相及古地理资料汇编(二),地质矿产部情报所.
[18]邓宏文,钱凯.沉积地球化学与环境分析[M].兰州:甘肃科学技术出版社,1993.
[19]Fedo C M,Nesbitt H W,Young G M.Unraveling the effects of potassium metasomatism in sandstones and paleosols,with implications for paleoweathering conditions and provenance[J].Geology,1995,23:921-924.
[20]Nesbitt H W,Young G M.Early Proterozoic climates and plate motions inferred from major elemental chemistry of lutites[J].Nature,1982,199:715-717.
[21]Fedo C M,Young G M,Nesbitt H W.Paleoclimatic control on the composition of the Paleoproterozoic Serpent Formation,Huronian Supergroup,Canada:a greenhouse to icehouse transition[J].Precambrian Research,1997,86:210-223.
[22]Cox R,Lowe D R,Cullers R L.The influence of sediment recycling and basement composition of evolution of mudrock chemistry in the southwestern United States[J].Geochim.Cosmochim.Acta,1995,59:2919-2940.
[23]Potter P E,Maynard J B,Depetris P J.Mud and Mudstones,Introduction and Overview[M].Berlin Heidelberg:Springer,2005.157-174.
[24]Sciscio L,Bordy E M.Palaeoclimatic conditions in the Late Triassic-Early Jurassic of southern Africa:a geochemical assessment of the Elliot Formation[J].J.Afr.Earth Sci.,2016,119:102-119.
[25]Hieronymus B,Kotschoubey B,Boulegue J.Gallium behavior in some contrasting lateritic profiles from Cameroon and Brazil[J].Journal of Geochemical Exploration,2001,72:147-163.
[26]Beckmann B,Fl¨ogel S,Hofmann P,et al.Orbital forcing of Cretaceous river discharge in tropical Africa and ocean response[J].Nature,2005,437:241-244.
[27]Ratcliffe K T,Wright A M,Montgomery P,et al.Application of chemostratigraphy to the Mungaroo Formation,the Gorgon field,offshore northwest Australia[A].Australian Petroleum Production and Exploration Association Journal(50th Anniversary Issue)[C].2010.371-388.
[28]韩永红,王海红,陈志华,等.耿湾-史家湾地区长6段微量元素地球化学特征及古盐度[J].岩性油气藏,2007,19(4):20-26.
[29]Algeo T J,Tribovillard N.Environmental analysis of paleoceano graphic systems based on molybdenum-uranium covariation[J].Chemical Geology,2009,268:211-225.
[30]Tribovillard N,Algeo T J,Baudin F,Riboulleau A.Analysis of marine environmental conditions based on molybdenum-uranium covariation——applications to Mesozoic paleoceanography[J].Chemical Geology,2012,324-325:46-58.