| Citation: |
GE Xiangying, MOU Chuanlong, MEN Xin, HOU Qian, ZHENG Binsong, LIANG Wei. 2024. Discussion on U-Pb dating and tectonic setting of K-bentonites in black shales of Wufeng-Longmaxi formations in the Sichuan Basin. Sedimentary Geology and Tethyan Geology, 44(3): 641-655. doi: 10.19826/j.cnki.1009-3850.2023.09004
|
Discussion on U-Pb dating and tectonic setting of K-bentonites in black shales of Wufeng-Longmaxi formations in the Sichuan Basin
-
Abstract
During the Late Ordovician–Early Silurian period, not only the black shales of the Wufeng and Longmaxi formations but also many K-bentonites were deposited in South China, and the presence of many bentonites indicated that intermittent volcanism had occurred in South China at this time. However, there are still disagreements over the source of the volcanic ash that formed the bentonites. In this paper, we investigated many Wufeng-Longmaxi shale sections from the Sichuan Basin and selected the bentonites with multilayer and larger thickness as the research objects, attempting to analyze the age of the bentonites, the duration of volcanic activity, and the source of the ash by integration of field investigation, mineralogy, major and trace element concentrations, and zircon geochronology. The bentonites have bold colors, some plasticity, with associated pyrites in field. XRD characteristics show that the bentonites are composed of clay and non-clay minerals. Clay minerals are dominated by the illite-smectite mixed layer and illite, whereas the non-clay minerals include quartz, albite, calcite, dolomite, and pyrite. Their geochemical compositions are characterized by high K2O content and low TiO2 content, LREEs are slightly enriched, HREEs are poor, with a strong negative Eu anomaly, and the Chondrite-normalized REE distribution is right-skewed. Zircon U-Pb dating by LA-ICP-MS yielded ages ranging from (448±2) Ma to (440.4±5.6) Ma, which suggested that volcanic eruptions in South China lasted for at least 8 Myr across the Ordovician–Silurian boundary. Application of various chemical discrimination diagrams (Nb/Y–Zr/TiO2, Nb–Y, Y+Nb–Rb, Zr–TiO2, Hf/3–Th–Ta, Nb/Yb–Th/Yb) implies that the bentonites were mostly from intermediate acid rocks and possibly originated from an island arc environment. The fact that the layer number and thickness of the bentonites gradually decreased from north to south, combined with the current understanding of the tectonic nature of South China, indicates that the volcanic ash was probably related to the subduction and closure of the Qinling Ocean on the northern border of the Yangtze Plate in the Early Paleozoic.
-
-
References
[1] Andersen T,2002. Correction of common lead in U-Pb analyses that do not report 204Pb[J]. Chemical Geology,192(1-2):59 − 79. doi: 10.1016/S0009-2541(02)00195-X [2] Bergström S M,Huff W D,Saltzeman M R,et al.,2004. The greatest volcanic ash falls in the Phanerozoic:Trans-Atlantic relations of the Ordovician Millbrig and Kinnekulle K-bentonites[J]. The Sedimentary Record,2(4):4 − 8. [3] Cabanis B,Lecolle M,1989. The La/10-Y/15-Nb/8 diagram-A tool for discriminating volcanic series and evidencing continental-crust magmatic mixtures and/or contamination[J]. Comptes Rendus de l'Academie des Sciences,309:2023 − 2029. [4] 曹熔,张姝婧,兰中伍,2023. 火山灰锆石U-Pb定年在沉积岩定年上的应用[J]. 沉积与特提斯地质, 43(2):464 − 474. Cao R,Zhang S J,Lan Z W,2023. Application of zircon U-Pb dating of volcanic ash to dating of sedimentary rock[J]. Sedimentary Geology and Tethyan Geology, 43(2):464 − 474 (in Chinese with English abstract). [5] 陈诚,史晓颖,裴云鹏,等,2012. 鄂尔多斯南缘晚奥陶世钾质斑脱岩-SHRIMP测年及其成因环境[J]. 地学前缘,26(2):205 − 219. Chen C,Shi X Y,Pei Y P,et al.,2012. K-Bentonites from the Jinsushan Formation of Late Ordovician,Southern Ordos Basin:SHRIMP Dating and Tectonic Environment[J]. Earth Science Frontiers,26(2):205 − 219 (in Chinese with English abstract). [6] 陈世悦,李聪,张鹏飞,等,2011. 江南—雪峰地区加里东期和印支期不整合分布规律[J]. 中国地质,38:1212 − 1219. doi: 10.3969/j.issn.1000-3657.2011.05.008 Chen S Y,Li C,Zhang P F,et al.,2011. The unconformable distribution of Caledonian and Indosinian strata in Jiangnan-Xuefeng area[J]. Geology in China,38:1212 − 1219 (in Chinese with English abstract). doi: 10.3969/j.issn.1000-3657.2011.05.008 [7] 陈旭,戎嘉余,Rowley D B,等,1995. 对华南早古生代板溪洋的质疑[J]. 地质论评,41(5):389 − 400. doi: 10.3321/j.issn:0371-5736.1995.05.001 Chen X,Rong J Y,Rowley D B,et al.,1995. Is the early Paleozoic Banxi Ocean in South China necessary?[J]. Geological Review,41(5):389 − 400 (in Chinese with English abstract). doi: 10.3321/j.issn:0371-5736.1995.05.001 [8] 陈旭,张元动,樊隽轩,等,2010. 赣南奥陶纪笔石地层序列与广西运动[J]. 中国科学:地球科学,40:1621 − 1631. Chen X,Zhang Y D,Fan J X,et al.,2010. Ordovician graptolite-bearing strata in southern Jiangxi with a special reference to the Kwangsian Orogeny[J]. Science China:Earth Science,40:1621 − 1631 (in Chinese with English abstract). [9] Ge X Y,Mou C L,Wang C S,et al.,2019. Mineralogical and geochemical characteristics of K-bentonites from the Late Ordovician-Early Silurian in South China and their geological significance[J]. Geological Journal,54:514 − 528. doi: 10.1002/gj.3201 [10] 葛祥英,2012. 湘中湘南地区奥陶纪沉积相与岩相古地理[D]. 青岛:山东科技大学. Ge X Y,2012. Ordovician sedimentary facies and lithofacies paleogeography in Central and Southern Hunan Province[D]. Qingdao:Shandong University of Science and Technology (in Chinese with English abstract). [11] 葛祥英,牟传龙,余谦,等,2021. 云南大关新地2井奥陶−志留纪之交钾质斑脱岩岩石地球化学特征分析[J]. 中国地质, 48(3):911 − 924. Ge X Y,Mou C L,Yu Q,et al.,2021. Petrology and geochemistry of the K-bentonites at the Ordovician-Silurian transition in XD2 well,Daguan,Yunan Province[J]. Geology in China, 48(3):911 − 924 (in Chinese with English abstract). [12] Gromet L P,Haskin L A,Korotev R L,et al.,1984. The “North American shale composite”: Its compilation, major and trace element characteristics [J]. Geochimica et Cosmochimica Acta,48:2469 − 2482. doi: 10.1016/0016-7037(84)90298-9 [13] 胡艳华,刘健,周明忠,等,2009a. 奥陶纪和志留纪钾质斑脱岩研究评述[J]. 地球化学,38(4):390 − 401. Hu Y H,Liu J,Zhou M Z,et al.,2009a. An overview of Ordovician and Silurian K-bentonites[J]. Geochimica,38(4):390 − 401 (in Chinese with English abstract). [14] 胡艳华,孙卫东,丁兴,等,2009b. 奥陶纪−志留纪边界附近火山活动记录:来华南周缘钾质斑脱岩的信息[J]. 岩石学报,25(12):198 − 208. Hu Y H,Sun W D,Ding X,et al.,2009b. Volcanic event at the Ordovician-Silurian boundary:The message from K-bentonite of Yangtze Block[J]. Acta Petrologica Sinica,25(12):198 − 208 (in Chinese with English abstract). [15] 胡艳华,周继彬,宋彪,等,2008. 中国湖北宜昌王家湾剖面奥陶系顶部斑脱岩SHRIMP锆石U-Pb定年[J]. 中国科学:D辑, 38(1):72 − 77. Hu Y H,Zhou J B,Song B,et al.,2008. SHRIMP zircon U-Pb dating from K-bentonite in the top of Ordovician of Wangjiawan Section,Yichang,Hubei,China[J]. Science in China (Series D), 38(1):72 − 77 (in Chinese with English abstract). [16] Huff W D,2008. Ordovician K-bentonites:Issues in interpreting and correlating ancient tephras[J]. Quaternary International,178:276 − 287. doi: 10.1016/j.quaint.2007.04.007 [17] Huff W D,2016. K-bentonites:A review[J]. American Mineralogist,101:43 − 70. doi: 10.2138/am-2016-5339 [18] Huff W D,Davis D W,Bergström S M,et al.,1997. A biostratigraphically well-constrained K-bentonite U-Pb zircon age of the lowermost Darriwilian stage (Middle Ordovician) from the Argentine Precordillera[J]. Episodes,20:29 − 33. doi: 10.18814/epiiugs/1997/v20i1/006 [19] Huff W D,Kolata D R,Bergström S M,et al.,1996. Large-magnitude Middle Ordovician volcanic ash falls in North America and Europe:dimensions,emplacement and post-emplacement characteristics[J]. Journal of Volcanology and Geothermal Research,73(3):285 − 301. [20] 姜尧发,唐跃刚,代世峰,等,2006. 浙江煤山二叠系—三叠系界线附近黄铁矿及其硫同位素组成研究[J]. 地质学报,80(8):1202 − 1207. doi: 10.3321/j.issn:0001-5717.2006.08.014 Jiang Y F,Tang Y G,Dai S F,et al.,2006. Pyrites and Sulfur Isotopic Composition near the Permian-Triassic Boundary in Meishan,Zhejiang[J]. Acta Geologica Sinica,80(8):1202 − 1207 (in Chinese with English abstract). doi: 10.3321/j.issn:0001-5717.2006.08.014 [21] Kolata D R,Huff W D,Bergström S M,1998. Nature and regional significance of unconformities associated with the Middle Ordovician Hagan K-bentonite complex in the North American midcontinent[J]. Geological Society of America Bulletin,110(6):723 − 739. doi: 10.1130/0016-7606(1998)110<0723:NARSOU>2.3.CO;2 [22] Kolata D R,Huff W D,Bergström S M,1996. Ordovician K-bentonites of eastern North America[J]. Geological Society of America Special Paper,313:1 − 84. [23] 刘宝珺,许效松,夏文杰,等,1994. 中国南方岩相古地理图集[M]. 北京:科学出版社. Liu B J,Xu X S,Xia W J,et al.,1994. Lithofacies paleogeography atlas of South China[M]. Beijing:Science Press (in Chinese with English abstract). [24] Liu Y S,Gao S,Hu Z C,et al.,2010. Continental and oceanic crust recycling-induced melt-peridotite interactions in the Trans-North China Orogen:U-Pb dating,Hf isotopes and trace elements in zircons from mantle xenoliths[J]. Journal of Petrology,51:537 − 571. doi: 10.1093/petrology/egp082 [25] Ludwig K R,2003. User’s manual for isoplot/EX version 3.00:A geochronological toolkit for Microsoft Excel[M]. Berkeley Geochronology Center Special Publication,1 − 70. [26] 罗华,何仁亮,蟠龙克,等,2016. 湖北宣恩县麻阳寨晚奥陶−早志留世龙马溪组斑脱岩LA-ICP-MS锆石U-Pb年龄及其地质意义[J]. 资源环境与工程,30(4):547 − 550. Luo H,He R L,Pan L K,et al.,2016. LA-ICP-MS Zircon U-Pb age and its significance of Late Ordovician-Early Silurian Longmaxi Bentonite[J]. Resources Environment & Engineering,30(4):547 − 550 (in Chinese with English abstract). [27] Ma J L,Wei G J,Xu Y G,et al.,2007. Mobilization and redistribution of major and trace elements during extreme weathering of basalt in Hainan Island,South China[J]. Geochimica et Cosmochimica Acta,71:3223 − 3237. doi: 10.1016/j.gca.2007.03.035 [28] 牟传龙,周恳恳,陈小炜,等,2016. 中国岩相古地理图集(埃迪卡拉纪−志留纪)[M]. 北京:地质出版社. Mou C L,Zhou K K,Chen X W,et al.,2016. Lithofacies paleogeography Atlas of China(Ediacaran–Silurian) [M]. Beijing:Geological Publishing House (in Chinese with English abstract). [29] 牟传龙,许效松,2010. 华南地区早古生代沉积演化与油气地质条件[J]. 沉积与特提斯地质, 30(3):24 − 29. Mou C L,Xu X S,2010. Sedimentary evolution and petroleum geology in South China during the Early Palaeozoic[J]. Sedimentary Geology and Tethyan Geology, 30(3):24 − 29 (in Chinese with English abstract). [30] 牟传龙,周恳恳,梁薇,等,2011. 中上扬子地区早古生代烃源岩沉积环境与油气勘探[J]. 地质学报, 85(4):526 − 532. Mou C L,Zhou K K,Liang W,et al.,2011. The early Paleozoic sedimentary environment of hydrocarbon source rocks with petroleum and gas exploration in the middle-upper Yangtze region[J]. Acta Geologica Sinica, 85(4):526 − 532 (in Chinese with English abstract). [31] Mullen E D,1983. MnO/TiO2/P2O5:A major element discriminant for basaltic rocks of oceanic environments and its implications for petrogenesis[J]. Earth and Planetary Science Letters,62:53 − 62. doi: 10.1016/0012-821X(83)90070-5 [32] Nesbitt H W,Markovics G,1997. Weathering of granodioritic crust,long-term storage of elements in weathering profiles,and petrogenesis of siliciclastic sediments[J]. Geochimica et Cosmochimica Acta,61:1653 − 1670. doi: 10.1016/S0016-7037(97)00031-8 [33] Nesbitt H W,Young G M,McLennan S M,et al.,1996. Effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments,with implications for provenance studies[J]. Journal of Geology,104:525 − 542. doi: 10.1086/629850 [34] Pearce J A,Cann J R,1973. Tectonic setting of basic volcanic rocks investigated using trace element analyses[J]. Earth and Planetary Science Letters,19:290 − 300. doi: 10.1016/0012-821X(73)90129-5 [35] Pearce J A,Harris N B W,Tindle A G,1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks[J]. Journal of Petrology,25:956 − 983. doi: 10.1093/petrology/25.4.956 [36] Pearce J A,Peate D W,1995. Tectonic implications of the composition of volcanic arc magmas[J]. Annual Review of Earth and Planetary Science,23:251 − 285. doi: 10.1146/annurev.ea.23.050195.001343 [37] Pearce J A,Norry M J,1979. Petrogenetic implications of Ti,Zr,Y,and Nb variations in volcanic rocks[J]. Contributions to Mineralogy and Petrology,69(1):33 − 47. doi: 10.1007/BF00375192 [38] Robert S B,Merriman R J,1990. Cambrian and Ordovician metabentonites and their relevance to the origins of associated mudrocks in the northern sector of the Lower Palaeozoic Welsh marginal basin[J]. Geological Magazine,127:31 − 43. doi: 10.1017/S001675680001414X [39] 舒良树,2006. 华南前泥盆纪构造演化:从华夏地块到加里东期造山带[J]. 高校地质学报,12(4):418 − 431. doi: 10.3969/j.issn.1006-7493.2006.04.002 Shu L S,2006. Predevonian Tectonic Evolution of South China:from Cathaysian Block to Caledonian Period Folded Orogenic Belt[J]. Geological Journal of China Universities,12(4):418 − 431 (in Chinese with English abstract). doi: 10.3969/j.issn.1006-7493.2006.04.002 [40] 舒良树,2012. 华南构造演化的基本特征[J]. 地质通报,31(7):1035 − 1053. doi: 10.3969/j.issn.1671-2552.2012.07.003 Shu L S,2012. An analysis of principal features of tectonic evolution in South China Block[J]. Geological Bulletin of China,31(7):1035 − 1053 (in Chinese with English abstract). doi: 10.3969/j.issn.1671-2552.2012.07.003 [41] Su W B,He L Q,Wang Y B,et al.,2003. K-bentonite beds and high-resolution integrated stratigraphy of the uppermost Ordovician Wufeng and the lowest Silurian Longmaxi Formations in South China[J]. Science China (Series D),46:1121 − 1133. doi: 10.1360/01yd0225 [42] Su W B,Huff W D,Ettensohn F R,et al.,2009. K-bentonite,black-shale and flysch successions at the Ordovician–Silurian transition,South China:Possible sedimentary responses to the accretion of Cathaysia to the Yangtze Block and its implications for the evolution of Gondwana[J]. Gondwana Research,15(1):111 − 130. doi: 10.1016/j.gr.2008.06.004 [43] Su W B,Li Z M,Ettensohn F R,et al.,2007. Tectonic and eustatic control on the distribution of black-shale source beds in the Wufeng and Longmaxi formations (Ordovician–Silurian), South China[J]. Frontiers of Earth Science,1(4):470 − 481. doi: 10.1007/s11707-007-0058-6 [44] 苏文博,李志明,史晓颖,等,2006. 华南五峰组—龙马溪组与华北下马岭组的钾质斑脱岩及黑色岩系——两个地史转折期板块构造运动的沉积响应[J]. 地学前缘,13(6):82 − 95. doi: 10.3321/j.issn:1005-2321.2006.06.011 Su W B,Li Z M,Shi X Y,et al.,2006. K-bentonites and black shales from the Wufeng-Longmaxi formations(Early Paleozoic,South China) and Xiamaling formation(Early Neoproterozoic,North China)-implications for tectonic processes during two important transitions[J]. Earth Science Frontiers,13(6):82 − 95 (in Chinese with English abstract). doi: 10.3321/j.issn:1005-2321.2006.06.011 [45] Taylor S R,McLennan S M,1985. The Continental Crust:Its Composition and Evolution[M]. Oxford:Blackwell. [46] Teale C T,Spears D A,1986. The mineralogy and origin of some Silurian bentonites,Welsh Borderland,U. K.[J]. Sedimentology,33(5):757 − 765. doi: 10.1111/j.1365-3091.1986.tb01974.x [47] Winchester J A,Floyd P A, 1979. Geochemical discrimination of different magma series and their differentiation products using immobile elements[J]. Chemical Geology ,20:325 − 343. [48] Wood D A,1980. The application of a Th-Hf-Ta diagram to problem of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary volcanic province[J]. Earth and Planetary Science Letters,50(1):11 − 30. doi: 10.1016/0012-821X(80)90116-8 [49] 谢尚克,汪正江,王剑,等,2012. 湖南桃源郝坪奥陶系五峰组顶部斑脱岩LA-ICP-MS锆石U-Pb年龄[J]. 沉积与特提斯地质,32(4):65 − 69. doi: 10.3969/j.issn.1009-3850.2012.04.010 Xie S K,Wang Z J,Wang J,et al.,2012. LA-ICP-MS zircon U-Pb dating of the bentonites from the uppermost part of the Ordovician Wufeng Formation in the Haoping section,Taoyuan,Hunan[J]. Sedimentary Geology and Tethyan Geology,32(4):65 − 69 (in Chinese with English abstract). doi: 10.3969/j.issn.1009-3850.2012.04.010 [50] 熊国庆,王剑,李园园,等,2017. 大巴山西段上奥陶统—下志留统五峰组−龙马溪斑脱岩U-Pb年龄及其地质意义[J]. 沉积与特提斯地质,37(2):46 − 58. doi: 10.3969/j.issn.1009-3850.2017.02.006 Xiong G Q,Wang J,Li Y Y,et al.,2017. Zircon U-Pb dating and geological significance of the bentonites from the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation in western Daba Mountains[J]. Sedimentary Geology and Tethyan Geology,37(2):46 − 58 (in Chinese with English abstract). doi: 10.3969/j.issn.1009-3850.2017.02.006 [51] 熊国庆,刘春来,董国明,等,2021. 南大巴山上奥陶统五峰组−下志留统龙马溪组泥岩元素地球化学特征[J]. 沉积与特提斯地质,41(3):398 − 417. Xiong G Q,Liu C L,Dong G M,et al.,2021. A study of element geochemistry of mudstones of upper Ordovician Wufeng Formation and lower Silurian Longmaxi Formation in southern Daba Mountain[J]. Sedimentary Geology and Tethyan Geology,41(3):398 − 417 (in Chinese with English abstract). [52] 闫剑飞,余谦,刘伟,等,2010. 中上扬子地区下古生界页岩气资源前景分析[J]. 沉积与特提斯地质, 30(3):96 − 103. Yan J F,Yu Q,Liu W,et al.,2010. Perspectives of the Lower Palaeozoic shale gas resources in the middle-upper Yangtze area[J]. Sedimentary Geology and Tethyan Geology, 30(3):96 − 103 (in Chinese with English abstract). [53] 杨颖,2011. 华南古−中生代关键地层界线附近斑脱岩锆石U-Pb年代学及成因[D]. 武汉:中国地质大学(武汉). Yang Y,2011. Zircon U-Pb Geochronology and Genesis of K-bentonite at the Paleozoic-Mesozoic Key Stratigraphic Boundaries of South China[D].Wuhan:China University of Geosciences(Wuhan) (in Chinese with English abstract). [54] 殷鸿福,吴顺宝,杜远生,等,1999. 华南是特提斯多岛洋体系的一部分[J]. 地球科学,24(1):1 − 12. doi: 10.3321/j.issn:1000-2383.1999.01.001 Yin H F,Wu S B,Du Y S,et al.,1999. South China defined as part of Tethyan Archipelagic ocean system[J]. Earth Science,24(1):1 − 12 (in Chinese with English abstract). doi: 10.3321/j.issn:1000-2383.1999.01.001 [55] 张娣,刘伟,周业鑫,等,2022. 扬子区西南缘奥陶纪末—志留纪初笔石生物地层对比及意义[J]. 沉积与特提斯地质,42(3):413 − 425. Zhang D,Liu W,Zhou Y X,et al.,2022. Biostratigraphic correlation of graptolites from Late Ordovician to Early Silurian on the southwestern margin of the Yangtze region[J]. Sedimentary Geology and Tethyan Geology,42(3):413 − 425 (in Chinese with English abstract). [56] 张国伟,郭安林,王岳军,等,2013. 中国华南大陆构造与问题[J]. 中国科学:地球科学,43(10):1553 − 1582. Zhang G W,Guo A L,Wang Y J,et al.,2013. Tectonics of South China continent and its implications[J]. Science China:Earth Sciences,43(10):1553 − 1582 (in Chinese with English abstract). [57] 周明忠,罗泰义,黄智龙,等,2007. 钾质斑脱岩的研究进展[J]. 矿物学报,27(3):351 − 359. doi: 10.3321/j.issn:1000-4734.2007.03.017 Zhou M Z,Luo T Y,Huang Z L,et al.,2007. Advances in research on K-bentonite[J]. Acta Mineralogica Sinica,27(3):351 − 359 (in Chinese with English abstract). doi: 10.3321/j.issn:1000-4734.2007.03.017 -
Supplementary Information
葛祥英-2024-附表 
-
Access History
Figures(9)
Export File
Citation
GE Xiangying, MOU Chuanlong, MEN Xin, HOU Qian, ZHENG Binsong, LIANG Wei. 2024. Discussion on U-Pb dating and tectonic setting of K-bentonites in black shales of Wufeng-Longmaxi formations in the Sichuan Basin. Sedimentary Geology and Tethyan Geology, 44(3): 641-655. doi: 10.19826/j.cnki.1009-3850.2023.09004
Format
Content
DownLoad:
-
Figure 1.
Tectonic framework of the South China Block (after Shu, 2012)
-
Figure 2.
The characteristics of the bentonites of the Wufeng-Longmaxi formations in typical sections of the Sichuan Basin
-
Figure 3.
XRD patterns of studied sample WXP-BT1
-
Figure 4.
Chondrite-normalized REE distribution patterns of samples from Wufeng-Longmaxi formations in the Sichuan Basin (normalization values after Taylor and McLenann, 1985)
-
Figure 5.
U-Pb concordia diagrams and cathodoluminescence (CL) images of typical zircons from the bentonites of Wuxingcun section, Zhenba, Shaanxi Province
-
Figure 6.
Zircon U-Pb concordia diagrams and cathodoluminescence (CL) images of the bentonites from Fenghuang section, Youyang, Chongqing City
-
Figure 7.
U-Pb concordia diagrams and cathodoluminescence (CL) images of typical zircons of the bentonites from Liangbai section, Zhenba, Shaanxi Province; Nanbazi section, Tongzi, Guizhou Province; Tianjiawan section, Daozhen, Guizhou Province
-
Figure 8.
The source magma and tectonic environment discrimination diagrams of K-bentonite samples from Wufeng-Longmaxi formations in the Sichuan Basin
-
Figure 9.
The thickness variation diagram of the K-bentonites in the Wufeng-Longmaxi formations from north to south in the eastern Sichuan Basin