Geochronology of Serpentinized Harzburgite in Miaowan Ophiolite, Yangtze Block and Its Tectonic Implications
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摘要: 扬子陆核崆岭高级变质地体内出露一套强变形的基性-超基性岩岩石组合, 主要呈似层状、透镜状分布于崆岭群中, 该套变基性-超基性岩组合对扬子陆块早期构造演化过程具有重要意义.通过同位素稀释法(isotope dilution thermal ionization mass spectrometry, 简称ID-TIMS)获得该套岩石组合中蛇纹石化方辉橄榄岩全岩Sm-Nd等时线年龄为1063±12Ma, 说明Sm-Nd同位素体系可用于对超低含量、发生强蚀变作用的超基性岩样品进行定年.样品Nd同位素组成相对均一(εNd(t)值为6.90~7.32), 表明形成于封闭体系中, 其对应Nd同位素两阶段模式年龄为1.13~1.09Ga, 与形成年龄接近, 说明来自亏损软流圈地幔部分熔融.结合区域上已有的中元古代末期到新元古代早期构造岩浆事件研究, 认为在该时期扬子陆块可能由多个微陆块组成, 就扬子陆核而言, 其与扬子陆块西侧之间很可能存在分隔的大洋.Abstract: A series of strongly-deformed mafic-ultramafic rocks occur at the Kongling high-grade metamorphic terrain in Yangtze continental nucleus, scattering in the Miaowan Formation in layers and podiforms. This metamafic-ultramafic rock association is of great significance to the early tectonic evolution of Yantgze block. In this study, ID-TIMS whole-rock Sm-Nd isochron dating is carried out for the serpentinized harzburgite and amphibolite from this rock suite. The results indicate that the serpentinized harzburgite was formed at 1063±12Ma, showing that it is feasible to date tiny amount of heavily-altered ultramafic rocks by means of the Sm-Nd isotopic system. The comparatively uniform Nd isotopic composition (with εNd(t) value ranging from 6.90 to 7.32) indicates that they were formed in a closed system. Two-stage Nd modal age of 1.13-1.09Ga is close to their emplacement time, implying an origin of partial melting from depleted asthenospheric mantle. Combined with documented work on late Mesoproterozoic to early Neoproterozoic tectonic-magmatic events in the area, it is suggested that the Yangtze block may have been composed of several microcontinents at that time. There could have been an ocean separating the Yangtze continental nucleus from western Yangtze continental segment.
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Key words:
- Yangtze continental nucleus /
- Miaowan ophiolite /
- Sm-Nd isochron /
- isotope /
- geochronology /
- petrology /
- geochemistry
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图 1 崆岭高级变质地体南部庙湾地区地质简图
据彭松柏等(2010)修改
Fig. 1. Geological map of Miaowan area at the southern Kongling high-grade terrain
图 2 庙湾蛇绿岩蛇纹石化橄榄岩野外(a)及薄片照片(b)
Fig. 2. Field outcrop (a) and photomicrograph (b) of the serpentinized harzburgite in the Miaowan ophiolite
图 3 庙湾蛇绿岩蛇纹石化方辉橄榄岩-斜长角闪岩全岩Sm-Nd等时线
Fig. 3. Whole rock Sm-Nd isochron of the serpentinized harzburgites and amphibolites in the Miaowan ophiolite
表 1 庙湾蛇绿岩蛇纹石化方辉橄榄岩及斜长角闪岩Sm-Nd同位素组成
Table 1. Whole rock Sm-Nd isotopic composition of the Miaowan ophiolite
样号 样品 Sm(10-6) Nd(10-6) 147Sm/144Nd 143Nd/144Nd 2σ T2DM(Ga) εNd(t) zg94-1 蛇纹石化方辉橄榄岩 0.2821 0.7908 0.2157 0.513135 0.000009 1.11 7.13 zg94-2 蛇纹石化方辉橄榄岩 0.2042 0.5619 0.2197 0.513167 0.000010 1.10 7.20 zg94-3 蛇纹石化方辉橄榄岩 0.3915 1.0400 0.2276 0.513210 0.000012 1.12 6.97 zg94-4 蛇纹石化方辉橄榄岩 0.1798 0.5669 0.1918 0.512976 0.000015 1.10 7.29 zg94-5 蛇纹石化方辉橄榄岩 0.1038 0.3219 0.1950 0.513020 0.000013 1.06 7.71 zg94-6 蛇纹石化方辉橄榄岩 0.0679 0.2163 0.1899 0.512955 0.000021 1.11 7.13 zg94-7 蛇纹石化方辉橄榄岩 0.1671 0.5075 0.1991 0.513008 0.000013 1.13 6.91 zg94-8 斜长角闪岩 1.3965 4.6985 0.1797 0.512891 0.000010 1.10 7.27 zg94-9 蛇纹石化方辉橄榄岩 0.2081 0.6534 0.1926 0.512962 0.000016 1.13 6.90 zg94-10 蛇纹石化方辉橄榄岩 0.3005 0.8356 0.2174 0.513150 0.000017 1.10 7.18 zg94-11 蛇纹石化方辉橄榄岩 0.2576 0.8665 0.1797 0.512880 0.000011 1.12 7.05 zg95-1 蛇纹石化方辉橄榄岩 0.0688 0.3534 0.1177 0.512446 0.000018 1.12 7.03 zg95-2 蛇纹石化方辉橄榄岩 0.0832 0.4213 0.1194 0.512466 0.000014 1.10 7.19 zg95-3 蛇纹石化方辉橄榄岩 0.1244 0.6591 0.1141 0.512425 0.000012 1.11 7.10 zg95-4 蛇纹石化方辉橄榄岩 0.0502 0.2427 0.1249 0.512493 0.000020 1.12 6.96 zg95-5 蛇纹石化方辉橄榄岩 0.0855 0.4759 0.1086 0.512390 0.000010 1.11 7.17 注：Sm、Nd含量根据ID-TIMS测量结果计算获得，误差＜5‰；计算εNd(t)值和两阶段模式年龄时，年龄值t采用Sm-Nd等时线年龄1063Ma；T2DM计算过程中参数(147Sm/144Nd)DM=0.2137，(143Nd/144Nd)DM=0.513150，(147Sm/144Nd)CC=0.1180(DM、CC分别代表亏损地幔和大陆地壳)；εNd(t)值计算过程中参数(147Sm/144Nd)CHUR=0.1967，(143Nd/144Nd)CHUR=0.512638. 
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[1] Bai, X., Ling, W.L., Duan, R.C., et al., 2011. Mesoproterozoic to Paleozoic Nd Isotope Stratigraphy of the South China Continental Nucleus and Its Geological Significance. Science in China (Ser. D), 54(11): 1665-1674. doi: 10.1007/s11430-011-4266-2 [2] Berkana, W., Ling, W.L., Qiu, X.F., et al., 2011. Early Neoproterozoic Arc Magmatism along the Northwestern Margin of the Yangtze Craton and Its Connection with the South China Block Evolution during the Rodinia Assembly. Mineralogical Magazine, 75: A54. [3] Cawood, P.A., Wang, Y.J., Xu, Y.J., et al., 2013. Locating South China in Rodinia and Gondwana: A Fragment of Greater India Lithosphere? Geology, 41(8): 903-906. doi: 10.1130/G34395.1 [4] Chen, K., Gao, S., Wu, Y.B., et al., 2013.2.6-2.7Ga Crustal Growth in Yangtze Craton, South China. Precambrian Research, 224: 472-490. doi: 10.1016/j.precamres.2012.10.017 [5] Chen, Z.H., Guo, K.Y., Dong, Y.G., et al., 2009. Possible Early Neoproterozoic Magmatism Associated with Slab Window in the Pingshui Segment of the Jiangshan-Shaoxing Suture Zone: Evidence from Zircon LA-ICP-MS U-Pb Geochronology and Geochemistry. Science in China (Ser. D), 52(7): 925-939. doi: 10.1007/s11430-009-0071-6 [6] Condie, K.C., 1998. Episodic Continental Growth and Supercontinents: A Mantle Avalanche Connection? Earth and Planetary Science Letters, 163(1): 97-108. http://www.sciencedirect.com/science/article/pii/S0012821X98001782 [7] Deng, H., Kusky, T.M., Wang, L., et al., 2012. Discovery of a Sheeted Dike Complex in the Northern Yangtze Craton and Its Implications for Craton Evolution. Journal of Earth Science, 23(5): 676-695. doi: 10.1007/s12583-012-0287-9 [8] Dilek, Y., Furnes, H., 2011. Ophiolite Genesis and Global Tectonics: Geochemical and Tectonic Fingerprinting of Ancient Oceanic Lithosphere. Geological Society of America Bulletin, 123(3-4): 387-411. doi: 10.1130/B30446.1 [9] Dilek, Y., Furnes, H., Shallo, M., 2007. Suprasubduction Zone Ophiolite Formation along the Periphery of Mesozoic Gondwana. Gondwana Research, 11: 453-475. doi: 10.1016/j.gr.2007.01.005 [10] Dong, Y.P., Zhou, M.F., Zhang, G.W., et al., 2008. The Grenvillian Songshugou Ophiolite in the Qinling Mountains, Central China: Implications for the Tectonic Evolution of the Qinling Orogenic Belt. Journal of Asian Earth Sciences, 32(3-4): 325-335. http://www.sciencedirect.com/science/article/pii/S1367912007002209 [11] Gao, S., Yang, J., Zhou, L., et al., 2011. Age and Growth of the Archean Kongling Terrain, South China, with Emphasis on 3.3Ga Granitoid Gneisses. American Journal of Science, 311(2): 153-182. http://adsabs.harvard.edu/abs/2008GeCAS..72Q1054Y [12] Guo, J.L., Gao, S., Wu, Y.B., et al., 2014.3.45Ga Granitic Gneisses from the Yangtze Craton, South China: Implications for Early Archean Crustal Growth. Precambrian Research, 242(1-2): 82-95. [13] Hawkesworth, C., Kemp, A., 2006. Evolution of the Continental Crust. Nature, 443(7113): 811-817. doi: 10.1038/nature05191 [14] Huang, T.Q., Li, J.F., Xia, B., et al., 2015. Petrology, Geochemistry, Chronology and Geological Stificance Tso Ophiolite in Middle Segment of Bangonghu-Nujiang Suture Zone, Tibet. Earth Science—Journal of China University of Geosciences, 40(1): 34-48(in Chinese with English abstract). doi: 10.3799/dqkx.2015.003 [15] Jiao, W.F., Wu, Y.B., Yang, S.H., et al., 2009. The Oldest Basement Rock in the Yangtze Craton Revealed by Zircon U-Pb Age and Hf Isotope Composition. Science in China (Ser. D), 52(9): 1393-1399. doi: 10.1007/s11430-009-0135-7 [16] Li, S.L., Wang, X.L., Duan, J.M., et al., 2012. Findings and Its Geological Significance of the Upper Devonian Ophiolite in Hujierte Area, Damao County, Inner Mongolia, China. Earth Science—Journal of China University of Geosciences, 37(1): 18-24(in Chinese with English abstract). http://www.researchgate.net/publication/287889641_Findings_and_its_geological_significance_of_the_Upper_Devonian_ophiolite_in_Hujierte_area_Damao_County_Inner_Mongolia_China [17] Ling, W.L., Gao, S., Zhang, B.R., et al., 2003. Neoproterozoic Tectonic Evolution of the Northwestern Yangtze Craton, South China: Implications for Amalgamation and Break-up of the Rodinia Supercontinent. Precambrian Research, 122(1-2): 111-140. http://www.sciencedirect.com/science/article/pii/S030192680200222X [18] Ma, Z.P., Xia, L.Q., Xia, Z.C., et al., 2004. Method of Ophiolite Geochronology Study and the Related Problems. Northwestern Geology, 37(3): 103-108 (in Chinese with English abstract). http://www.zhangqiaokeyan.com/academic-journal-cn_northwestern-geology_thesis/0201254329955.html [19] Peng, S.B., Kusky, T.M., Jiang, X.F., et al., 2012. Geology, Geochemistry, and Geochronology of the Miaowan Ophiolite, Yangtze Craton: Implications for South China's Amalgamation History with the Rodinian Supercontinent. Gondwana Research, 21(2-3): 577-594. doi: 10.1016/j.gr.2011.07.010 [20] Peng, S.B., Li, C.N., Kusky, T.M., et al., 2010. Discovery and Its Tectonic Significance of the Proterozoic Miaowan Ophiolites in the Southern Huangling Anticline, Western Hubei, China. Geological Bulletin of China, 29(1): 8-20 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTOTAL-ZQYD201001002.htm [21] Qiu, X.F., Ling, W.L., Liu, X.M., 2014. Correlation between the Mesoproterozoic Yangtze Continental Nucleus and the Shennongjia Area: Constraints from Zircon Geochronological and Hf Isotope. Geological Science and Technology Information, 33(2): 1-8 (in Chinese with English abstract). http://en.cnki.com.cn/Article_en/CJFDTotal-DZKQ201402002.htm [22] Qiu, X.F., Ling, W.L., Liu, X.M., et al., 2011. Recognition of Grenvillian Volcanic Suite in the Shennongjia Region and Its Tectonic Significance for the South China Craton. Precambrian Research, 191(3-4): 101-119. doi: 10.1016/j.precamres.2011.09.011 [23] Wu, Y.B., Gao, S., Zhang, H.F., et al., 2012. Geochemistry and Zircon U-Pb Geochronology of Paleoproterozoic Arc Related Granitoid in the Northwestern Yangtze Block and Its Geological Implications. Precambrian Research, 200: 26-37. http://www.sciencedirect.com/science/article/pii/S0301926812000046 [24] Xue, H.M., Ma, F., Song, X.Q., et al., 2010. Geochronology and Geochemistry of the Neoproterozoic Granitoid Association from Eastern Segment of the Jiangnan Orogen, China: Constraints on the Timing and Process of Amalgamation between the Yangtze and Cathaysia Blocks. Acta Petrologica Sinica, 26(11): 3215-3244 (in Chinese with English abstract). [25] Yang, C.H., Geng, Y.S., Du, L.L., et al., 2009. The Identification of the Grenvillian Granite on the Western Margin of the Yangtze Block and Its Geological Implications. Geology in China, 36(3): 647-657 (in Chinese with English abstract). http://www.researchgate.net/publication/282238702_The_identification_of_the_Grenvillian_granite_on_the_western_margin_of_the_Yangtze_Block_and_its_geological_implications [26] Ye, M.F., Li, X.H., Li, W.X., et al., 2007. SHRIMP Zircon U-Pb Geochronological and Whole-Rock Geochemical Evidence for an Early Neoproterozoic Sibao'an Magmatic Arc along the Southeastern Margin of the Yangtze Block. Gondwana Research, 12: 144-156. doi: 10.1016/j.gr.2006.09.001 [27] Zhang, C.H., Gao, L.Z., Wu, Z.J., et al., 2007. SHRIMP U-Pb Zircon Age of Tuff from the Kunyang Group in Central Yunnan: Evidence for Grenvillian Orogeny in South China. Chinese Science Bulletin, 52: 1517-1525. doi: 10.1007/s11434-007-0225-x [28] 黄强太, 李建峰, 夏斌, 等, 2015. 西藏班公湖-怒江缝合带中段江错蛇绿岩岩石学、地球化学、年代学及地质意义. 地球科学——中国地质大学学报, 40(1): 34-48. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX201501003.htm [29] 李尚林, 王训练, 段俊梅, 等, 2012. 内蒙古达茂旗胡吉尔特晚泥盆世蛇绿岩的发现及其地质意义. 地球科学——中国地质大学学报, 37(1): 18-24. https://www.cnki.com.cn/Article/CJFDTOTAL-DQKX201201005.htm [30] 马中平, 夏林圻, 夏祖春, 等, 2004. 蛇绿岩年代学研究方法及应注意的问题. 西北地质, 37(3): 103-108. doi: 10.3969/j.issn.1009-6248.2004.03.017 [31] 彭松柏, 李昌年, Kusky, T.M., 等, 2010. 鄂西黄陵背斜南部元古宙庙湾蛇绿岩的发现及其构造意义. 地质通报, 29(1): 8-20. doi: 10.3969/j.issn.1671-2552.2010.01.002 [32] 邱啸飞, 凌文黎, 柳小明, 2014. 扬子陆核与神农架地块中元古代相互关系: 来自锆石U-Pb年代学和Hf同位素的约束. 地质科技情报, 33(2): 1-8. doi: 10.3969/j.issn.1009-6248.2014.02.002 [33] 薛怀民, 马芳, 宋永勤, 等, 2010. 江南造山带东段新元古代花岗岩组合的年代学和地球化学: 对扬子与华夏地块拼合时间与过程的约束. 岩石学报, 26(11): 3215-3244. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB201011006.htm [34] 杨崇辉, 耿元生, 杜利林, 等, 2009. 扬子地块西缘Grenville期花岗岩的厘定及其地质意义. 中国地质, 36(3): 647-657. doi: 10.3969/j.issn.1000-3657.2009.03.011 -
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