Petrogenesis of Neoproterozoic Granitoids from the Wulian Region in the Sulu Orogen: Sr-Nd Isotopic Constraints
-
摘要: 五莲新元古代花岗岩类分布于五莲断裂以北, 动力变形强, 但变质程度弱, 仅达到绿片岩相.岩性以黑云正长花岗质为主, 少数为石英正长质.岩石中Sr同位素初始值的变化范围很广, 从0.697 306~0.753 765, 除了部分是由于源区的不均一或多源不同比例混合外, 岩浆侵位过程中或固结后的次生扰动可能也起着一定的作用.而它们的εNd (750 Ma) 均为负值且变化范围广(-3.1~-24.3), Nd同位素二阶段模式年龄从1.7~3.4 Ga, 均显示它们的源区以古老的地壳为主, 但具有多源混合的特征.推测五莲新元古代花岗岩类最可能的成因是太古代的TTG片麻岩(主要是其中的英云闪长质组分) 在压力约0.8 Gpa (相当于~25 km的中下地壳) 条件下发生部分熔融, 并混入了不同比例的年轻地幔来源物质.地幔来源物质的加入对于五莲新元古代花岗岩类的成因有重要的影响.Abstract: The Neoproterozoic granitoids in Wulian region are located north of the Wulian fault. They have undergone strong dynamic deformation but are slightly metamorphosed (green-schist facies). The granitoids are mainly biotite-syenogranitic in composition with minor quartz syenitic. The initial 87Sr/86 Sr ratios (ISr) are wide, ranging from 0.697 306 to 0.753 765. This may partially be ascribed to the inhomogeneity of magma source material or multi-source mixing with different proportions. Secondary disturbed after the granitic body's intrusion and concretion may also play a role, to some degree. The εNd (750 Ma) values of the granitoids are all lower than 0 and with wide ranges (-3.1 to-24.3), and the model ages (TDM) of two stages ranges from 1.7 to 3.4 Ga. This indicates that the parental magma of the Neoproterozoic granitoids in the Wulian region was primarily derived from crustal materials but with the mixed features of multi-sources. Therefore, the Neoproterozoic granitoids in Wulian have most probably been generated by partial melting of Archaean TTG gneisses (major tonalitic component thereinto) at pressures of about 0.8 Gpa (i.e. within the middle or the lower crust), and the addition of different proportions of mantle-derived juvenile materials. The addition of mantle-derived materials has been an important influence on the genesis of the Neoproterozoic granitoids in the Wulian region.
-
Key words:
- granitoid /
- Sr and Nd isotope /
- partial melting /
- Wulian /
- Sulu orogen
-
图 2 五莲片麻岩的地球化学成分图解
a.石英(Q)-碱性长石(A)-斜长石(P) 三角分类图解(Le Maitre, 1989); b.A/NK-A/CNK关系图; c. (Nb+Y)-Nb构造环境判别图(Pearce et al., 1984); d.La/Yb~Th/Yb判别图(Condie, 1989); e.稀土元素球粒陨石标准化曲线(球粒陨石数值据Boynton, 1984); f.不相容元素原始地幔标准化蛛网图(原始地幔数值据McDonough and Sun, 1995); 侵入岩系列的演化趋势据Lameyre and Bonin (1991); A.强碱性; B.适度碱性; C.二长质; D.钙碱性.资料来源: 薛怀民等(2005b); 黄洁等(2005)
Fig. 2. Geochemical compositions of representative samples from the Wulian gneisses
图 3 五莲新元古代花岗岩类的同位素组成
a.147Sm/144Nd与143Nd/144Nd关系图; b.Nd同位素初始值投影在εNd-时间演化图上(扬子基底TTG演化趋势据Gao et al., 1999); c.Sr同位素初始值与1/Sr关系图; d.Nd同位素初始值与1/Nd关系图.扬子基底TTG片麻岩资料据Gao et al. (1999)
Fig. 3. Sr and Nd isotopic compositions of the Neoproterozoic granitoid from Wulian
图 4 五莲新元古代花岗岩类的εNd (750 Ma) 与ISr关系图解
将扬子地台北缘随州地区晚元古代末期的辉长岩(Sr=166 μg/g, ISr=0.704 5, Nd=14.16 μg/g, εNd (750 Ma) =+4.6) 代表地幔组分.2个地壳组分, 地壳1为崆岭地区太古代的TTG片麻岩(Ames et al., 1996; Sr=143 μg/g, ISr=0.708 456, Nd=9.05 μg/g, εNd (750 Ma) =-33.9), 地壳2为韩国的一类地壳组分(Kwon et al., 1999)
Fig. 4. εNd (750 Ma) vs. ISr diagram showing mixing correlation between the presumed mantle component and crustal components for the Neoproterozoic granitoid from Wulian
表 1 五莲新元古代花岗岩类的Rb-Sr和Sm-Nd同位素组成
Table 1. Rb-Sr and Sm-Nd isotopic compositions of Neoproterozoic granitoids from Wulian
-
Ames, L., Zhou, G., Xiong, B., 1996. Geochronology and isotopic character of ultrahigh-pressure metamorphism with implications for collision of the Sino-Korean and Yangtze cratons, central China. Tectonics, 15: 472-489. doi: 10.1029/95TC02552 Beard, J.S., Lofgren, G.E., 1991. Dehydration melting and water-saturated melting of basaltic and andesitic green stones and amphibolites at 1, 3 and 6.9kb. J. Petrol. , 32: 465-501. Borg, L.E., Clynne, M.A., 1998. The petrogenesis of felsic calcalkaline magmas from the southernmost cascades, California: Origin by partial melting of basaltic lower crust. J. Petrol. , 39: 1197-1222. doi: 10.1093/petroj/39.6.1197 Boynton, W. V., 1984. Geochemistry of the rare earth elements: Meteorite studies. In: Henderson, P, ed., Rare earth element geochemistry. Elsevier, Amsterdam, 63-114. Chavagnac, V., Jahn, B.M., 1996. Coesite-bearing eclogites from the Bixiling complex, Dabie Mountains, China: Sm Nd ages, geochemical characteristics and tectonic implications. Chem. Geol. , 133: 29-51. doi: 10.1016/S0009-2541(96)00068-X Chen, B., Jahn, B.M., Arakawa, Y., et al., 2004. Petrogenesis of the Mesozoic intrusive complexes from the southern Taihang Orogen, North China craton: Elemental and Sr-Nd-Pb isotopic constraints. Contrib. Mineral. Petrol., 148: 489-501. doi: 10.1007/s00410-004-0620-0 Cohen, A.S., O'Nions, R.K., Siegenthaler, R., et al., 1988. Chronology of the pressure-temperature history recorded by a granulite terrain. Contrib. Mineral. Petrol., 98: 303-311. doi: 10.1007/BF00375181 Condie, K.C., 1989. Geochemical changes in basalts and an desites across the Archean-Proterozoic boundary: Identification and significance. Lithos, 23: 1-18. doi: 10.1016/0024-4937(89)90020-0 Condie, K.C., 1997. Plate tectonics and crustal evolution. Butterworth-Heinemann Press. Corroll, M. J., Wyllie, P. J., 1989. Experimental phase relations in the system tonalite-peridotite-H2O at 15 kbar, implications for assimilation and differentiation processes near the crust-mantle boundary. J. Petrol. , 30: 1351-1382. doi: 10.1093/petrology/30.6.1351 Gao, S., Ling, W.L., Qiu, Y.M., et al., 1999. Contrasting geochemical and Sm-Nd isotopic compositions of Archean metasediments from the Kongling high-grade terrain of the Yangtze craton: Evidence for cratonic evolution and redistribution of REE during crustal anatexis. Geochimica et Cosmochimica Acta, 63: 2071-2088. doi: 10.1016/S0016-7037(99)00153-2 Holloway, J.R., Burnham, C.W., 1972. Melting relations of basalt with equilibrium water pressure less than total pressure. J. Petrol. , 13: 1-29. doi: 10.1093/petrology/13.1.1 Huang, J., Zheng, Y.F., Wu, Y.B., et al., 2005. Geochemistry of elements and isotopes in igneous rocks from the Wulian region in the Sulu orogen. Acta Petrologica Sinica, 21: 545-568(in Chinese with English abstract). Jahn, B.M., Cornicher, J., Cong, B., et al., 1996. Ultrahigh εNd eclogites from a UHP metamorphic terrane of China. Chem. Geol. , 127: 61-79. doi: 10.1016/0009-2541(95)00108-5 Koprubasi, N., Aldanmaz, E., 2004. Geochemical constraints on the petrogenesis of Cenozoic Ⅰ-type granitoids in northwest Anatolia, Turkey: Evidence for magma generation by lithospheric delamination in a post-collisional setting. International Geology Review, 46: 705-729. doi: 10.2747/0020-6814.46.8.705 Kwon, S.T., Lan, C.Y., Lee, T., 1999. Rb-Sr and Sm-Ndisotopic study of the Seoul granitic batholith in middle Korea. Geosci. J. , 3: 107-114. doi: 10.1007/BF02914266 Lameyre, J., Bonin, B., 1991. Granites in the main plutonic series. In: Didier, J., Barbarin, B., eds., Enclaves and granite petrology. Elsevier, Amsterdam, Netherlands, 3-17. Le Maitre, R.W., 1989. A classification of igneous rocks and glossary of terms. Blackwell, Oxford, UK, 193. Martin, H., 1993. The mechanism of petrogenesis of the Archean continental crust— Comparison with modern processes. Lithos, 30: 373-388. doi: 10.1016/0024-4937(93)90046-F Martin, H., 1994. The Archean grey gneisses and the genesis of the continental crust. In: Condie, K.C., ed., The Archaean crustal evolution. Elsevier, Amsterdam, 46-48. McDonough, W.F., Sun, S.S., 1995. The composition of the Earth. Chemical Geology, 120: 223-253. doi: 10.1016/0009-2541(94)00140-4 Pearce, J.A., Harris, N.B.W., Tindle, A.G., 1984. Trace element discrimination diagram for the tectonic inter pretation of granitic rocks. Journal of Petrology, 25: 956-983. doi: 10.1093/petrology/25.4.956 Rapp, R. P., Watson, E. B., 1991. Dehydration melting of metabasalt at 8-32 kbar: Implications for continental growth and crust-mantle recycling. Journal of Petrology, 87: 193-203. Roberts, M.P., Clemens, J.D., 1993. Origin of high-potassium, calc-alkaline, Ⅰ-type granitoids. Geology, 21: 825-828. Streckeisen, A., Le Maitre, R.W., 1979. A chemical approximation of the model QAPE classification of the igneous rocks. Neues Jahrbuch fur Mineralogie Abhandlungen, 136: 169-206. Taylor, S. R., McLennan, S. M., 1985. The continental crust: Its composition and evolution— An examination of the geochemical record preserved in sedimentary rocks. Blackwell Scientific, Oxford, 312. Wu, Y.B., Zheng, Y.F., Zhou, J.B., 2004. Neoproterozoic granitoid in northwest Sulu and its bearing on the North China-South China blocks boundary in east China. Geophysical Research Letters, 31, L07616, doi: 10.1029/2004GL019785. Wyllie, P.J., 1984. Constraints imposed by experimental petrology on possible magma sources and products. Transactions of the Royal Society of London, A310: 439-456. Xue, H. M., Dong, S. W., Liou, X. C., 2001. Geochemical characteristics and their genesis of the granitic gneisses from southeastern Dabie Mountain. Acta Geologica Sinca, 14: 175-183. Xue, H.M., Liu, F. L., 2005a. Geochemical characteristics and genesis of plagiogneiss from the 0-2 000 m main hole of the Chinese Continental Scientific Drilling Project. Acta Petrologica Sinica, 21(2): 355-368(in Chinese with English abstract). Xue, H.M., Liu, F.L., Xu, Z.Q., 2005b. Geochemical characteristics of weakly metamorphosed orthogneisses outside the Wulian boundary fault along the northwestern margin of the Sulu UHP metamorphic belt and their protolith petrogenesis. Geology in China, 32(2): 249-258(in Chinese with English abstract). Xue, H.M., Liu, F.L., Meng, F.C., 2006. Major and trace element geochemistry of granitic gneisses from Sulu orogen, eastern Shandong Peninsula, Sulu orogen: Evidence for a Neoproterozoic active continental margin in the northern margin of the Yangtze craton. Acta Petrologica Sinica(in Chinese with English abstract, in press). Zhai, M.G., Cong, B.L., Zhang, Q., et al., 1994. The northern Dabieshan terrain: A possible andean-type arc. Inter. Geo. Rev. , 36: 867-883. doi: 10.1080/00206819409465492 Zhao, D., Cheng, L. R., Liu, M.X., 1995. The discovery of solenopora in the Wulian Group in the Jiaonan area, Shan dong, and its significance. Regional Geology of China, 14: 379-384(in Chinese with English abstract). Zheng, X.S., Jin, C.W., Zhai, M.G., et al., 1999. Petrochemistry and tectonic background of the grey gneisses in north Dabie terrane. Acta Petrologica Sinica, 15: 350-358(in Chinese with English abstract). Zhou, J. B., Zheng, Y. F., Li, L., et al., 2001. Accretionary wedge of the subduction of the Yangtze plate. Acta Geol. Sinica, 75: 338-352(in Chinese with English abstract). Zhou, J.B., Zheng, Y.F., Wu, Y.B., 2003. Zircon U-Pb ages for Wulian granites in northwest Sulu and their tectonic implications. Chinese Science Bulletin, 48: 379-384. 黄洁, 郑永飞, 吴元保, 等, 2005. 苏鲁造山带五莲地区岩浆岩元素和同位素地球化学研究. 岩石学报, 21: 545-568. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200503002.htm 薛怀民, 刘福来, 2005a. 中国大陆科学钻探工程主孔0~2000米斜长片麻岩的地球化学性质及成因研究. 岩石学报, 21(2): 355-368. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200502009.htm 薛怀民, 刘福来, 许志琴, 2005b. 苏鲁超高压变质带西北缘五莲断裂外侧浅变质花岗片麻岩的地球化学特征与原岩成因研究. 中国地质, 32(2): 249-258. https://www.cnki.com.cn/Article/CJFDTOTAL-DIZI200502009.htm 薛怀民, 刘福来, 孟繁聪, 2006. 苏鲁造山带胶东区段花岗片麻岩类的常量与微量元素地球化学: 扬子克拉通北缘新元古代活动大陆边缘的证据. 岩石学报(待刊). https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB200607003.htm 赵达, 程立人, 刘茂修, 1995. 胶南地区五莲群中管孔藻类的发现及其意义. 中国区域地质, 14: 379-384. https://www.cnki.com.cn/Article/CJFDTOTAL-ZQYD504.015.htm 郑祥身, 金成伟, 翟明国, 等, 1999. 北大别灰色片麻岩的岩石化学特征及大地构造背景. 岩石学报, 15(3): 350-358. https://www.cnki.com.cn/Article/CJFDTOTAL-YSXB199903002.htm 周建波, 郑永飞, 李龙, 等, 2001. 扬子大陆板块俯冲的构造加积楔. 地质学报, 75: 338-352. doi: 10.3321/j.issn:0001-5717.2001.03.007 -
下载:
点击查看大图
图(4) / 表(1)
计量
- 文章访问数: 3784
- HTML全文浏览量: 438
- PDF下载量: 13
- 被引次数: 0
