羌塘地块西南缘上侏罗统—下白垩统海相地层的发现
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摘要
通过1∶5万区域地质调查,在青藏高原羌塘地块西南缘鸡夯地区原划上三叠统日干配错群中新识别出一套上侏罗统—下白垩统地层。本文根据该套地层的岩石组合以及古生物面貌特征,初步探讨了该套地层的沉积环境和沉积相特征,对其中发育的玄武岩夹层采用锆石U-Pb(LA-ICP-MS)同位素测年方法,获得其年龄为118.3±2.1Ma。在发育的生物碎屑灰岩夹层中采集了珊瑚、双壳类、腕足、腹足类化石,化石资料显示该套地层形成于晚侏罗世—早白垩世。这是首次在南羌塘地块发现该时期海相地层,这一发现证明南羌塘地块在晚侏罗世—早白垩世时期海水并未完全退出,而是局部发育海相三角洲。
On the basis of 1 ∶ 50 000 regional geological survey,a succession of the Upper Jurassic to Lower Cretaceous marine strata has been recently recognized in the formerly Upper Triassic Riganpeico Group in the Jihang area,southwestern Qiangtang block,Qinghai-Xizang Plateau. The present paper gives a preliminary study of sedimentary environments and facies in the light of rock associations and palaeontological features in the marine strata. A LA-ICP-MS zircon U-Pb age of 118 ± 2. 1 Ma for the basalts in the marine strata and fossils data for the corals,bivalves,brachiopods and gastropods collected from the developed bioclastic limestones show that the marine strata were formed during the Late Jurassic to Early Cretaceous. The discovery of the Upper Jurassic to Lower Cretaceous marine strata has reflected that during the Late Jurassic to Early Cretaceous,the sea water still occupied the southern Qiangtang block,where the marine deltas were once developed in local parts.
On the basis of 1 ∶ 50 000 regional geological survey,a succession of the Upper Jurassic to Lower Cretaceous marine strata has been recently recognized in the formerly Upper Triassic Riganpeico Group in the Jihang area,southwestern Qiangtang block,Qinghai-Xizang Plateau. The present paper gives a preliminary study of sedimentary environments and facies in the light of rock associations and palaeontological features in the marine strata. A LA-ICP-MS zircon U-Pb age of 118 ± 2. 1 Ma for the basalts in the marine strata and fossils data for the corals,bivalves,brachiopods and gastropods collected from the developed bioclastic limestones show that the marine strata were formed during the Late Jurassic to Early Cretaceous. The discovery of the Upper Jurassic to Lower Cretaceous marine strata has reflected that during the Late Jurassic to Early Cretaceous,the sea water still occupied the southern Qiangtang block,where the marine deltas were once developed in local parts.
引文
[1]王剑,谭富文,李亚林,等.青藏高原重点沉积盆地油气资源潜力分析[M].北京:地质出版社,2004.1-317.
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[3]付修根,王剑,谭富文,等.藏北羌塘盆地油气地质勘探新进展[J].沉积与特提斯地质,2015,35(1):16-24.
[4]曹竣锋,宋春彦,付修根,等.藏北羌塘盆地羌资5井二叠系碳酸盐岩储层特征及影响因素[J].沉积与特提斯地质,2014,34(2):86-91.
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[13]白培荣,马德胜,熊兴国,等.北羌塘盆地托纳木地区下白垩统雪山组沉积相分析及油气意义[J].贵州地质,2014,31(4):307-313.
[14]陈文彬,贺永忠,占王忠,等.藏北南羌塘安多县鄂斯玛地区下白垩统孢粉化石Dicheiropollis的发现及其地质意义[J].地质通报,2012,31(10):1602-1607.
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[17]柳小明,高山,袁洪林,等.193nm LA-ICP-MS对国际地质标准参考物质中42种主量和微量元素的分析[J].岩石学报,2002,18(3):408-425.
[18]刘晔,柳小明,胡兆初,等.ICP-MS测定地质样品中37个元素的准确度和长期稳定性分析[J].岩石学报.2007,23(5):1203-1212.
[19]Liu Y S,Hu Z C,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chemical Geology,2008,257(1-2):34-43.
[20]路远发.Geo Kit:一个用VBA构建的地球化学工具软件包[J].地球化学,2004,33(5):459-464.
[21]路凤香,桑隆康,邬金华,等.岩石学[M].北京:地质出版社,2002.
[22]刘昌实.岩石化学与多元统计[M].北京:地质出版社,1987.
(1)矿产调查研究所.西藏1∶5万埃永错东地区四幅区域地质调查报告.2015.1-273.
(2)江西省地质调查研究院.中华人民共和国区域地质调查报告1∶25万日土幅.2004.1-285.
[2]谭富文,王剑,王小龙,等.西藏羌塘盆地:中国油气资源战略选区的首选目标[J].沉积与特提斯地质,2002,22(1):16-21.
[3]付修根,王剑,谭富文,等.藏北羌塘盆地油气地质勘探新进展[J].沉积与特提斯地质,2015,35(1):16-24.
[4]曹竣锋,宋春彦,付修根,等.藏北羌塘盆地羌资5井二叠系碳酸盐岩储层特征及影响因素[J].沉积与特提斯地质,2014,34(2):86-91.
[5]王剑,付修根,李忠雄,熊松.北羌塘盆地油页岩形成环境及其油气地质意义[J].沉积与特提斯地质,2010,30(3):11-17.
[6]许建华,王准备.羌塘盆地侏罗系碎屑岩储集层综合评价[J].沉积与特提斯地质,2008,28(1):59-64.
[7]蒋忠惕.羌塘地区侏罗纪地层的若干问题[A].青藏高原地质文集(3)[C].北京:地质出版社,1983.87-112.
[8]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.
[9]朱丽霞,谭富文,付修根,等.北羌塘盆地晚中生代地层:下白垩统海相地层的发现[J].沉积学报,2012,30(5):825-833.
[10]方德庆,云金表,李椿.北羌塘盆地中部雪山组时代讨论[J].地层学杂志,2002,26(1):68-72.
[11]谭富文,王剑,李永铁,等.羌塘盆地侏罗纪末—下白垩统沉积特征与地层问题[J].中国地质,2004,31(4):400-405.
[12]金玮,王成善,李亚林,等.西藏双湖托纳木地区上侏罗统雪山组物源分析[J].大地构造与成矿学,2006,30(4):519-526.
[13]白培荣,马德胜,熊兴国,等.北羌塘盆地托纳木地区下白垩统雪山组沉积相分析及油气意义[J].贵州地质,2014,31(4):307-313.
[14]陈文彬,贺永忠,占王忠,等.藏北南羌塘安多县鄂斯玛地区下白垩统孢粉化石Dicheiropollis的发现及其地质意义[J].地质通报,2012,31(10):1602-1607.
[15]王立全,潘桂堂,丁俊,等.青藏高原及邻区地质图及说明书(1:1 500 000)[M].北京:地质出版社,2013.
[16]Yuan H L,Gao S,Liu X M,et al.Accurate U-Pb age and trace element determinations of zircon by laser ablation-inductively coupled.Plasma-mass spectrometry[J].Geostandards&Geoanalytical Research,2010,28(3):353-370.
[17]柳小明,高山,袁洪林,等.193nm LA-ICP-MS对国际地质标准参考物质中42种主量和微量元素的分析[J].岩石学报,2002,18(3):408-425.
[18]刘晔,柳小明,胡兆初,等.ICP-MS测定地质样品中37个元素的准确度和长期稳定性分析[J].岩石学报.2007,23(5):1203-1212.
[19]Liu Y S,Hu Z C,Gao S,et al.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chemical Geology,2008,257(1-2):34-43.
[20]路远发.Geo Kit:一个用VBA构建的地球化学工具软件包[J].地球化学,2004,33(5):459-464.
[21]路凤香,桑隆康,邬金华,等.岩石学[M].北京:地质出版社,2002.
[22]刘昌实.岩石化学与多元统计[M].北京:地质出版社,1987.
(1)矿产调查研究所.西藏1∶5万埃永错东地区四幅区域地质调查报告.2015.1-273.
(2)江西省地质调查研究院.中华人民共和国区域地质调查报告1∶25万日土幅.2004.1-285.