| Citation: |
WANG Yi, DONG Lei, YE Chunlin, YANG Xuejun, LÜ Zhiwei, JIA Xiaochuan, HUANG Bo, CHEN Dongsheng. Zircon U-Pb age and geochemistry of Cretaceous metabasic rocks in Sewu area, Yarlung Zangbo River junction belt of Tibet, and their geological significance[J]. Geological Bulletin of China, 2020, 39(4): 459-470.
|
Zircon U-Pb age and geochemistry of Cretaceous metabasic rocks in Sewu area, Yarlung Zangbo River junction belt of Tibet, and their geological significance
-
Abstract
In recent years, new Cretaceous metabasic rocks were found in the vicinity of Sewu, Qiuduojiang Township, Qusong County, southern Tibetan Plateau, by regional geological survey.The rocks are extensively distributed in layers in B rock section of Songre Formation in southern Yarlung Zangbo River suture zone.A series of LA-ICP-MS zircon U-Pb samples, geochemical samples and thin section samples were collected for testing on the basis of detailed field work in order to find out the formation age and geochemical characteristics of these metamorphic rocks.All LA-ICP-MS zircon U-Pb samples belong to the Early Cretaceous.The geochemical characteristics of the major elements show that the rocks belong to the low-K (tholeiite) basalt series.The rare earth elements show that the plagioclase in the original magmatic rocks was less or not crystallized, and there existed a relatively high degree of fractionation between light rare earth and heavy rare earth.The high field strength elements are relatively obvious; the large ion lithophile elements are deficient, and the negative anomalies of Sr and Ba are obvious.It is considered that the metabasic rocks might have been derived from the soft fluid mantle.According to the high field intensity element diagram of stable enrichment, magma was contaminated by the crust in the process of emplacement and formation.According to the analysis of tectonic environment, the metabasic rocks have MORB characteristics, which might have been related to the interaction between the hot spots and the mid-ocean ridges on the passive continental margin of the New Tethys Ocean.Due to the strong metamorphism and deformation of the rocks, the composition of the original rocks can not be determined under the microscope.Field observation shows that they were probably similar to the characteristics of the volcanic rocks.If they were formed by volcanic eruption, they would play an important role in promoting the study of the southern part of the Yarlung Zangbo Suture Zone, and therefore the Cretaceous strata could be established.
-
Keywords:
- Yarlung Zangbo Suture Zone /
- Langjie Group /
- metabasic rock /
- zircon U-Pb dating /
-
-
References
[1] 云南省地质调查院.1:25万隆子县幅、扎日区幅地质调查成果与进展[J].沉积与特提斯地质, 2005, 25(1):115-118. [2] 董磊, 李光明, 黄勇, 等.藏南雅鲁藏布江结合带东段琼结杂岩早白垩世变辉绿岩地球化学特征及其地质意义[J].沉积与特提斯地质, 2018, (4):1-12. doi: 10.3969/j.issn.1009-3850.2018.04.001 [3] 孟元库, 许志琴, 陈希节, 等.冈底斯中段碱长花岗岩锆石U-Pb-Hf同位素特征及地质意义[J].中国地质, 2015, 42(5):1202-1213. doi: 10.3969/j.issn.1000-3657.2015.05.003 [4] Zhang C K, Li X H, Frank M, et al.Composition and sediment dispersal pattern of the upper Triassic flysch in the eastern Himalayas, China:significance to provenance and basin analysis[J].International Journal of Earth Sciences, 2017, 106(4):1257-1276. [5] Liu Y S, Hu Z C, Gao S.In situ analysis of major and trace elements of anhydrous minerals by LA-ICP-MS without applying an internal standard[J].Chemical Geology, 2008, 257:34-43. doi: 10.1016/j.chemgeo.2008.08.004 [6] Plank T.Constraints from Thorium/Lanthanum on sediment recycling at subduction zones and the Evolution of the Continents[J].Petrol., 2005, 46(5):921-944. doi: 10.1093/petrology/egi005 [7] 邓晋福, 刘翠, 冯艳芳, 等.关于火成岩常用图解的正确使用:讨论与建议[J].地质论评, 2015, 61(4):717-734. [8] Bienvenu P, Bougult H, Joron J L, et al.Morb Alteration:Rare-Earth Element/Non-Rare-Earth Hygromagmaphile Element Fractionation[J].Chemical Geology, 1990, 82(90):1-14. [9] 于云鹏, 胡培远, 李才, 等.西藏班公湖-怒江缝合带中西段早白垩世洋岛火山岩岩石学及地球化学特征[J].地质通报, 2016, 35(8):1281-1290. doi: 10.3969/j.issn.1671-2552.2016.08.009 [10] Wilson M.Igneous Petrogenesis[M].Netherlands:Springer, 1989:1-464. [11] Neal C R, Mahoney J J, Chazey W J.Mantle Sources and the Highly Variable Role of Continental Lithosphere in Basalt Petrogenesis of the Kerguelen Plateau and Broken Ridge LIP:Results from ODP Leg 183[J].Journal of Petrology, 2002, 43(7):1177-1205. doi: 10.1093/petrology/43.7.1177 [12] Xu J F, Castillo P R, Li X H, et al.MORB-type rocks from the Paleo-Tethyan Mian-Lueyang northern ophiolite in the Qinling Mountains, central China:implications for the source of the low 206Pb/204Pb and high 143Nd/144Nd mantle component in the Indian Ocean[J].Earth & Planetary Science Letters, 2002, 198(3/4):323-337. [13] 王金荣, 陈万峰, 张旗, 等.N-MORB和E-MORB数据挖掘——玄武岩判别图及洋中脊源区地幔性质的讨论[J].岩石学报, 2017, 33(3):993-1005. [14] 朱弟成, 莫宣学, 王立全, 等.新特提斯演化的热点与洋脊相互作用:西藏南部晚侏罗世-早白垩世岩浆作用推论[J].岩石学报, 2008, 24(2):225-237. [15] 王亚莹, 高利娥, 曾令森, 等.藏南特提斯喜马拉雅带内江孜-康马地区白垩纪多期基性岩浆作用[J].岩石学报, 2016, (12):18-42. [16] Hung Y, Cao H W, Li G M, et al.Middle-late Triassic bimodal intrusive rocks from the Tethyan Himalaya in south Tibet:Geochronology and tectonic implications[J].Lithos, 2018, 318/319:78-90. doi: 10.1016/j.lithos.2018.08.002 [17] Cao H, Huang Y, Li G, et al.Late Triassic sedimentary records in the northern Tethyan Himalaya:tectonic link with Greater India[J].Geoscience Frontiers, 2018, 1:273-291. ① 董磊, 王燚, 黄勇, 等.西藏古木加康地区1: 5万区域地质调查报告.中国地质调查局成都地质调查中心、四川省地质调查院, 2019. -
Access History
Figures(9)
Tables(2)
Export File
Citation
WANG Yi, DONG Lei, YE Chunlin, YANG Xuejun, LÜ Zhiwei, JIA Xiaochuan, HUANG Bo, CHEN Dongsheng. Zircon U-Pb age and geochemistry of Cretaceous metabasic rocks in Sewu area, Yarlung Zangbo River junction belt of Tibet, and their geological significance[J]. Geological Bulletin of China, 2020, 39(4): 459-470.
Format
Content
DownLoad:
-
Figure 1.
Tectonic maps of Sewucun area in Tibet (a, b) and geological map and sampling position(c)
-
Figure 2.
Field photographs of metabasic rocks
-
Figure 3.
Classification and discrimination diagrams of major elements
-
Figure 4.
Chondrite-normalized REE patterns(a) and standardized spider diagrams of trace elements from the primitive mantle(b) of metabasic rocks
-
Figure 5.
Zircon cathodoluminescence images and analytic point location of metabasic rocks
-
Figure 6.
Zircon U-Pb concordia diagrams and weighted average histogram of 206Pb/238U age of metabasic rocks
-
Figure 7.
Graphical illustrations of (Th/Nb)PM-(La/Nb)PM(a) and Nb/Yb-Th/Yb(b) of metabasic rocks
-
Figure 8.
Structural discrimination diagrams of metabasic rock
-
Figure 9.
Microscopic photographs of metabasic rocks