藏北羌塘盆地侏罗纪含颗石藻黑色岩系地球化学特征与地质意义
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摘要
藏北羌塘盆地侏罗系发育一套富含有机质的黑色岩系,化石较为丰富而倍受地质学家关注。本文选择双湖地区毕洛错剖面,从有机地球化学和元素地球化学方面分析富含颗石藻黑色岩系特征。研究表明,研究区黑色岩系有机碳含量为2.84%～3.71%,氯仿沥青"A"含量为0.18%～0.29%。有机质类型为Ⅱ_1型,母质主要来源于浮游生物及少量陆生植物,T_(max)为429～435℃,显示该套岩系处于未成熟阶段。研究区样品的主量元素Si、Al、Ca等元素较富集,表明该套黑色岩系以陆源碎屑输入为主;V/Cr、U/Th、Ni/Co、V/(Ni+V)特征比值、U和Mo的富集以及Eu和Ce无明显异常,反映了该套黑色岩系主要沉积在弱还原环境,有利于有机质保存。以上研究表明,研究区含颗石藻黑色岩系为较好的烃源岩,保存条件较好,可以作为进一步勘探开发的有利烃源岩层。
A set of black rock series with rich-organic matters and abundant fossils, developed in Jurassic strata of the Qiangtang Basin in Northern Tibet, China, have been paid more attention by various geologists. In this paper, the coccolith-bearing black shales at the Biluo Co section of the Shuanghu area in the Qiangtang Basin have been selected to study their organic and elemental geochemical characteristics. The results show that their total organic carbon(TOC) contents change from 2.84% to 3.71%, and their chloroform bitumen "A" vary from 0.18% to 0.29%. The organic matters belong to the type Ⅱ_1, indicating that the organic matter was sourced from major plankton and minor terrestrial plants. T_(max) values varying from 429 oC to 435 oC indicating that the rock series are in immature stage. Furthermore, the major elements such as Si, Al, Ca and so on for samples are relatively enriched, showing that the black rock series are dominantly sourced from the terrestrial clastic input. The characteristic ratios of V/Cr, U/Th, Ni/Co, and V/(Ni+V), enrichments of U and Mo, and features of no obvious Eu and Ce anomalies show that the black rock series were mainly deposited in a weakly reduced environment which is beneficial to the preservation of organic matters. This study indicates that the coccolith-bearing black rock series are relatively good hydrocarbon source rocks, which are well preserved, for further prospective exploration of oil and gas.
A set of black rock series with rich-organic matters and abundant fossils, developed in Jurassic strata of the Qiangtang Basin in Northern Tibet, China, have been paid more attention by various geologists. In this paper, the coccolith-bearing black shales at the Biluo Co section of the Shuanghu area in the Qiangtang Basin have been selected to study their organic and elemental geochemical characteristics. The results show that their total organic carbon(TOC) contents change from 2.84% to 3.71%, and their chloroform bitumen "A" vary from 0.18% to 0.29%. The organic matters belong to the type Ⅱ_1, indicating that the organic matter was sourced from major plankton and minor terrestrial plants. T_(max) values varying from 429 oC to 435 oC indicating that the rock series are in immature stage. Furthermore, the major elements such as Si, Al, Ca and so on for samples are relatively enriched, showing that the black rock series are dominantly sourced from the terrestrial clastic input. The characteristic ratios of V/Cr, U/Th, Ni/Co, and V/(Ni+V), enrichments of U and Mo, and features of no obvious Eu and Ce anomalies show that the black rock series were mainly deposited in a weakly reduced environment which is beneficial to the preservation of organic matters. This study indicates that the coccolith-bearing black rock series are relatively good hydrocarbon source rocks, which are well preserved, for further prospective exploration of oil and gas.
引文
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[7]林金辉,伊海生,李勇,等．藏北高原双湖地区中侏罗统海相油页岩生物标志化合物分布特征及其意义[J]．沉积学报，2001, 19(2):287-291.
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[11]李永铁,谭富文,王剑,等．西藏羌塘盆地中侏罗世布曲期及夏里期岩相古地理与油气远景[J]．古地理学报, 2006, 8(4):500-501.
[12]蔡占虎．西藏南羌塘地区侏罗系地层特征及沉积环境分析[D]．成都:成都理工大学(硕士论文), 2014.
[13]陈建平,梁狄刚,张水昌,等．中国古生界海相烃源岩生烃潜力评价标准与方法[J]．地质学报, 2012, 86(7):1132-1142.
[14] Peters K E, Cassa M R.Applied source rock geochemistry[C]//Magoon L B, Dow W G.The Petroleum System:from Source to Trap.AAPG Memoir 60, 1994:93-117.
[15]杨万里,李永康,高瑞祺,等．松辽盆地陆相生油母质的类型与演化模式[J]．中国科学, 1981(8):1000-1008.
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[17]王成,龚庆杰,李刚,等．从南海沉积物中的主量元素比值变化看沉积物源区化学侵蚀变化[J]．海洋地质动态, 2007, 23(1):1-5.
[18] Goldberg E D, Arrhenius G O S.Chemistry of Pacific pelagic sediments[J].Geochim Cosmochim Acta, 1958, 13:152-212.
[19]刘刚,周东升．微量元素分析在判别沉积环境中的应用—以江汉盆地潜江组为例[J]．石油实验地质, 2007, 29(3):307-311.
[20] Prachiti P K, Manikyamba C, Singh P K, et al.Geochemical systematics and Preciousmetal content of the sedimentary horizons of Lower Gondwanas from the Sattupallicoal field, Godavari Valley, India[J].Int J Coal Geol, 2011, 88(2/3):83-100.
[21] Jones B, Manning A C.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones[J].Chemical Geology, 1994, 111(1/2):111-129.
[22] Algeo T J, Barry Maynard J.Trace-element behavior and redox facies in core shales of Upper Pennsylvanian Kansas-type cyclothems[J].Chemical Geology, 2004, 206(3/4):289-318.
[23] Chen L, Yi H S, Tsai L L-Y, et al.The Jurassic black shales facies from the Qiangtang Basin(northern Tibet):Rare earth and trace elements for palaeoceanographic implications.Acta Geologica Sinica, 2013, 87(2):540-554.
[24] Chen L, Jenkyns H C, Xu G W, et al.Preliminary nannofossil and geochemical data from Jurassic black shales from the Qiangtang Basin, northern Tibet[J].Journal of Asian Earth Sciences, 2016, 115:257-267.
[25] Touati Z, Haji T A.Redox, productivity and paleotectonic studies in the southern Tethyan margin of northern Tunisia[J].Marine and Petroleum Geology, 2019, 99:310-322.
[26] Hatch J R, Leventhai J S.Relationship between inferredredeox potential of the depositional environment andgeochemistry of the Upper Pennsyvanian(Missorian)Starkshale Member of the Dennis limestone, Wabaunsee County, Kansas, U.S.A[J].Chemical Geology, 1992, 99:65-82.
[27] Rimmer S M.Geochemical paleoredox indicators in Devonian-Mississippian black shales, Central Appalachian Basin(USA)[J].Chem Geol, 2004,206(3/4):373-391.
[28] Tribovillard N, Algeo T J, Lyons T, et al.Trace Metals Aspaleoredox and Paleoproductivity Proxies:An Update[J].Chemical Geology, 2006,232(1/2):12-32.
[29]毛瑞勇,张杰,冷济高,等．岑巩页岩气区块牛蹄塘组黑色页岩稀土元素地球化学特征及沉积环境分析[J]．矿物岩石, 2016, 36(4):66-73.
[30]涂光炽．低温地球化学[M]．北京:科学出版社, 1998:1-267.
[31]杨兴莲,朱茂炎,赵元龙,等．黔东震旦系—下寒武统黑色岩系稀土元素地球化学特征[J]．地质论评, 2008, 54(1):3-15.
[32] Boynton W V.Cosmochemistry of the Rare Earth Elements:Meteorite Studies[A].In:Rare Earth Element Geochemistry[M].Amsterdam:Elsevier,1984:63-114.
[2]叶和飞,罗建宁,李永铁,等．特提斯构造域与油气勘探[J]．沉积与特提斯地质, 1999, 20(1):1-26.
[3]伍新和,王成善,伊海生,等．西藏羌塘盆地中生界烃源岩探讨[J]．西北地质, 2005, 33(4):78-85.
[4]陈兰．藏北侏罗纪沉积相及黑色岩系有机地球化学研究[D]．成都:成都理工大学(硕士论文), 2003.
[5] Chen L, Xu G W, Da X J, et al.Chemo-and Biostratigraphy of the Jurassic Oil Shales from the Qiangtang Basin, Northern Tibet, China:A Case Study of the Toarcian Oceanic Anoxic Event[J].Acta Geologica Sinica(English Edition), 2017, 91(2):630-643.
[6] Chen L, Mattioli E, Da X J, et al.Calcareous nannofossils from the Jurassic black shales in the Qiangtang Basin, Northern Tibet(China):New records of stratigraphic ages and palaeoceanography[J].Newsletters on Stratigraphy, 2019, 52(1):55-72.
[7]林金辉,伊海生,李勇,等．藏北高原双湖地区中侏罗统海相油页岩生物标志化合物分布特征及其意义[J]．沉积学报，2001, 19(2):287-291.
[8]吴瑞忠,胡承祖,王成善,等．藏北羌塘地区地层系统[A]．青藏高原地质文集(9)[C]．北京:地质出版社, 1986:1-31.
[9]伊海生,林金辉,赵兵,等．藏北羌塘地区地层新资料[J]．地质论评, 2003, 49(1):59-65.
[10] Chen L, Yi H S, Hu R Z, et al.Organic geochemistry of the Early Jurassic oil shale from the Shuanghu area in northern Tibet and the Early Toarcian oceanic anoxic event[J].Acta Geological Sinica(English Eolition), 2005, 79(3):392-397.
[11]李永铁,谭富文,王剑,等．西藏羌塘盆地中侏罗世布曲期及夏里期岩相古地理与油气远景[J]．古地理学报, 2006, 8(4):500-501.
[12]蔡占虎．西藏南羌塘地区侏罗系地层特征及沉积环境分析[D]．成都:成都理工大学(硕士论文), 2014.
[13]陈建平,梁狄刚,张水昌,等．中国古生界海相烃源岩生烃潜力评价标准与方法[J]．地质学报, 2012, 86(7):1132-1142.
[14] Peters K E, Cassa M R.Applied source rock geochemistry[C]//Magoon L B, Dow W G.The Petroleum System:from Source to Trap.AAPG Memoir 60, 1994:93-117.
[15]杨万里,李永康,高瑞祺,等．松辽盆地陆相生油母质的类型与演化模式[J]．中国科学, 1981(8):1000-1008.
[16]邬立言,顾信章．热解技术在我国生油岩研究中的应用[J]．石油学报, 1986, 79(2):14-16.
[17]王成,龚庆杰,李刚,等．从南海沉积物中的主量元素比值变化看沉积物源区化学侵蚀变化[J]．海洋地质动态, 2007, 23(1):1-5.
[18] Goldberg E D, Arrhenius G O S.Chemistry of Pacific pelagic sediments[J].Geochim Cosmochim Acta, 1958, 13:152-212.
[19]刘刚,周东升．微量元素分析在判别沉积环境中的应用—以江汉盆地潜江组为例[J]．石油实验地质, 2007, 29(3):307-311.
[20] Prachiti P K, Manikyamba C, Singh P K, et al.Geochemical systematics and Preciousmetal content of the sedimentary horizons of Lower Gondwanas from the Sattupallicoal field, Godavari Valley, India[J].Int J Coal Geol, 2011, 88(2/3):83-100.
[21] Jones B, Manning A C.Comparison of geochemical indices used for the interpretation of palaeoredox conditions in ancient mudstones[J].Chemical Geology, 1994, 111(1/2):111-129.
[22] Algeo T J, Barry Maynard J.Trace-element behavior and redox facies in core shales of Upper Pennsylvanian Kansas-type cyclothems[J].Chemical Geology, 2004, 206(3/4):289-318.
[23] Chen L, Yi H S, Tsai L L-Y, et al.The Jurassic black shales facies from the Qiangtang Basin(northern Tibet):Rare earth and trace elements for palaeoceanographic implications.Acta Geologica Sinica, 2013, 87(2):540-554.
[24] Chen L, Jenkyns H C, Xu G W, et al.Preliminary nannofossil and geochemical data from Jurassic black shales from the Qiangtang Basin, northern Tibet[J].Journal of Asian Earth Sciences, 2016, 115:257-267.
[25] Touati Z, Haji T A.Redox, productivity and paleotectonic studies in the southern Tethyan margin of northern Tunisia[J].Marine and Petroleum Geology, 2019, 99:310-322.
[26] Hatch J R, Leventhai J S.Relationship between inferredredeox potential of the depositional environment andgeochemistry of the Upper Pennsyvanian(Missorian)Starkshale Member of the Dennis limestone, Wabaunsee County, Kansas, U.S.A[J].Chemical Geology, 1992, 99:65-82.
[27] Rimmer S M.Geochemical paleoredox indicators in Devonian-Mississippian black shales, Central Appalachian Basin(USA)[J].Chem Geol, 2004,206(3/4):373-391.
[28] Tribovillard N, Algeo T J, Lyons T, et al.Trace Metals Aspaleoredox and Paleoproductivity Proxies:An Update[J].Chemical Geology, 2006,232(1/2):12-32.
[29]毛瑞勇,张杰,冷济高,等．岑巩页岩气区块牛蹄塘组黑色页岩稀土元素地球化学特征及沉积环境分析[J]．矿物岩石, 2016, 36(4):66-73.
[30]涂光炽．低温地球化学[M]．北京:科学出版社, 1998:1-267.
[31]杨兴莲,朱茂炎,赵元龙,等．黔东震旦系—下寒武统黑色岩系稀土元素地球化学特征[J]．地质论评, 2008, 54(1):3-15.
[32] Boynton W V.Cosmochemistry of the Rare Earth Elements:Meteorite Studies[A].In:Rare Earth Element Geochemistry[M].Amsterdam:Elsevier,1984:63-114.
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