Precise Timing and Significance of Caledonian Structural Deformation Chronology in Southeast Qilian
-
摘要: 祁连山东南段呈北西-南东向展布着加里东期中祁连造山带和拉脊山造山带, 其基底为前加里东变质岩系, 在该变质结晶基底岩系中发育着菱形网格状韧性剪切带, 共轭韧性剪切带面对缩短方向的夹角为104°~114°, 其最大主应力方位为SW210°左右.在中祁连地块金沙峡和化隆地块科却两处韧性剪切带中的糜棱岩化岩石, 获取变质矿物白云母40Ar-39Ar坪年龄分别为(405.1±2.4) Ma和(418.3±2.8) Ma.这一年代学结果不仅确定了加里东基底变质岩系中韧性剪切带是加里东造山作用过程中形成, 更重要的是通过对基底韧性剪切带中变质变形岩石的年代学研究, 精确地限定了祁连山东南段的早古生代火山盆地(或岛弧盆地)、拉脊山小洋盆关闭的构造年代.这为造山带构造演化过程中盆地关闭时间的确定开辟了新的途径.Abstract: The middle Qilian orogenic belt and Lajishan orogenic belt of the Caledonian strike NW-SE direction in the southeast Qilian and its basement consists of Pre-Caledonian metamorphic rock series. The lozenge-cancellate-shaped ductile shear zone occurs in the crystalline basement, and the included angle of shortening direction of conjugated ductile shear zones ranges from 104° to 114° and the max principal stress direction indicates approximate SW210°. The 40Ar-39Ar plateau ages of muscovite obtained from the mylonitilization rock in ductile shear zone of Jinshaxia within middle Qilian massif and Keque in Hualong massif are (405.1±2.4) Ma and (418.3±2.8) Ma, respectively. The chronology data determine the ductile shear zones in Caledonian basement metamorphic rock formed through the Caledonian orogeny. Furthermore, the chronological study of basement rock determines precise forming period for the close of the Late Paleozoic volcanic basin (or island-arc basin) and Lajishan ocean basin. This offers a new approach to the determination of ocean basin closing time in the process of structural evolution of orogenic belt.
-
图 1 研究区地质简图、样品编号和年龄结果及对应的采样位置
1.中新生界/三叠系隆务河群; 2.上泥盆统牦牛山组、上泥盆统-上三叠统; 3.中奥陶统-下志留统、下奥陶统阴沟群; 4.寒武系-志留系/未分超基性岩; 5.蓟县系; 6.古元古界秦岭岩群、湟源岩群; 7.新太古界-古元古界化隆岩群; 8.上奥陶统花岗闪长岩; 9.中奥陶统花岗闪长岩; 10.下奥陶统闪长岩; 11.前加里东花岗岩; 12.前加里东花岗闪长岩; 13.加里东期背斜、向斜构造; 14前加里东期背斜、向斜构造; 15.加里东期挤压构造面理; 16.前加里东期挤压构造面理; 17.新太古界-古元古界化隆岩群挤压构造面理; 18.大断裂和一般断裂; 19.走滑构造/逆冲构造; 20.韧性剪切带
Fig. 1. Schematic geologic map of studying area, sample numbers and age data and corresponding sampling sites
图 2 李家沟及金沙峡地质构造剖面图
a.化隆地块李家沟-拉昂地质构造剖面; b.中祁连金沙峡观察点2229-2230地质构造剖面; 1.砂砾岩; 2.砂岩; 3.花岗闪长岩; 4.黑云母石英片岩; 5.花岗片麻岩; 6.条带状混合岩; 7.片麻岩; 8.大理岩; 9.韧性剪切带; 10.白云母测试年龄样及样品编号
Fig. 2. Geologic structural sections in Lijiagou and Jinshaxia
表 1 样品2229-1和7300-240Ar/39Ar逐段加热分析数据
Table 1. 40Ar/39Ar analysis data of processed heating to samples 2229-1 and 7300-2
-
[1] Berger, G. W., York, D., 1981. Geothermometry from 40Ar/39Ar dating experiments. Geochim Cosmochim Acta, 45: 795-811. doi: 10.1016/0016-7037(81)90109-5 [2] Chen, N. S., He, L., Sun, M., et al., 2002. Precise timing of the Early Paleozoic metamorphismand thrust deformation in the eastern Kunlun orogen. Chinese Science Bulletin, 47 (8): 628-631 (in Chinese). doi: 10.1360/csb2002-47-8-628 [3] Chen, N. S., Sun, M., Zhang, K. X., et al., 2000. 40Ar/39Ar and U-Pb age of metamorphic diorite body in the eastern Kunlun: Hornblende excess Ar and Paleozoic evidence of magma belt in eastern Kunlun. Chinese Science Bulletin, 45 (21): 2337-2342 (in Chinese). doi: 10.1360/csb2000-45-21-2337 [4] Chen, W., Zhang, Y., Ji, Q., et al., 2002. The magmatism and deformation times of the Xidatan rock series, East Kunlun Mountain. Science in China (Series D), 45 (Suppl. ): 20-27. [5] Fan, G. M., Zhang, K. X., Lin, Q. X., et al., 2004. Evolutionand characteristics of the Lajishan orogenic belt. Earth Science—Journal of China University of Geosciences, 29 (Suppl. ): 1-6 (in Chinese with English abstract). [6] Feng, Y. M., Cao, X. D., Zhang, E. P., et al., 2002. Structural, process and dynamics of West Qinling orogenic belt: A booklet of1∶1000000tectonic map of West Qinlingorogenic belt and neighbouring region. Xi'an Map Press, Xi'an, 26-31 (in Chinese). [7] Hames, W. E., Bowring, S. A., 1994. An empirical evaluation of argon diffusion geometry in muscovite. Earth and Planet. Sci. Lett. , 124: 161-167. doi: 10.1016/0012-821X(94)00079-4 [8] Harrison, T. M., 1981. Diffusion of 40Ar in hornblende. Contributionto Mineralogy and Petrology, 78: 324-331. [9] Qiu, J. X., Zeng, G. C., Zhu, Y. H., et al., 1998. Characteristics and latitudinal comparative research on the Early Paleozoic volcanic rocks of rifted orogenic belt and small ocean basin ophiolite suite from northern Qinling mountains and southern Qilian mountains. J. China Univ. Geol. , 4 (4): 393-405 (in Chinese with Englishabstract). [10] Sobel, E. R., Arnaud, N. A., 1999. Possible Middle Paleozoic suture in the Altyn Tagh, NW China. Tectonics, 18: 64-74. doi: 10.1029/1998TC900023 [11] Wagner, G. A., Reimer, G. M., Jager, E., 1977. Cooling ages deiverd fromapatite fission, mica Rb-Sr and K-Ar dating: The uplift and cooling history of the central Alps. Padovia. Uvi. Inst. Geol. Mineral. Mem. , 30: 1-27. [12] Xu, Z. Q., Yang, J. S., Jiang, M., et al., 1999. Continent subduction and uplifting of the orogenic belts at the margin of the Qinghai-Tibet plateau. Earth Science Frontiers, 6 (3): 139-151 (in Chinese with English abstract). [13] Yang, W. R., Deng, Q. L., Wu X. L., 2000. Faulting of Laji orogenic belt and its relationship to volcanic rocks and ophiolites. Geological Science and Technology Information, 19 (2): 5-11 (in Chinese with English ab-stract). [14] Yin, H. F., Zhang, K. X., 1998. Evolution and characteristic of the central orogenic belt. Earth Science—Journal of China University of Geosciences, 23 (5): 438-442 (in Chinese with English abstract). [15] Zheng, Y. D., Wang, T., Ma, M. B., et al., 2004. Maximum effective movement criterion and the origin of low-angle normal fault. Journal of Structural Geology, 26: 271-285. doi: 10.1016/S0191-8141(03)00079-8 [16] 陈能松, 孙敏, 张克信, 等, 2000. 东昆仑变闪长岩体的40Ar/39Ar和U-Pb年龄: 角闪石过剩Ar和东昆仑古生代岩浆岩带证据. 科学通报, 45 (21): 2337-2342. doi: 10.3321/j.issn:0023-074X.2000.21.018 [17] 陈能松, 何蕾, 孙敏, 等, 2002. 东昆仑造山带早古生代变质峰期和逆冲构造变形年代的精确限定. 科学通报, 47 (8): 628-631. doi: 10.3321/j.issn:0023-074X.2002.08.016 [18] 樊光明, 张克信, 林启祥, 等, 2004. 拉脊山造山带的大地构造演化特征. 地球科学———中国地质大学学报, 29 (增刊): 1-6. https://www.cnki.com.cn/Article/CJFDTOTAL-DZXE200201023.htm [19] 冯益民, 曹宣铎, 张二朋, 等, 2002. 西秦岭造山带结构造山过程及动力学: 1∶1000000西秦岭造山带及邻区大地构造图说明书. 西安: 西安地图出版社, 26-31. [20] 邱家骧, 曾广策, 朱云海, 等, 1998. 北秦岭-南祁连早古生代裂谷造山带与小洋盆蛇绿岩套特征及纬向对比. 高校地质学报, 4 (4): 393-405. https://www.cnki.com.cn/Article/CJFDTOTAL-GXDX804.003.htm [21] 许志琴, 杨经绥, 姜枚, 等, 1999. 大陆俯冲作用及青藏高原周缘造山带的崛起. 地学前缘, 6 (3): 139-151. doi: 10.3321/j.issn:1005-2321.1999.03.014 [22] 杨魏然, 邓清禄, 吴秀玲, 2000. 南拉脊山造山带断裂作用特征及与火山岩、蛇绿岩套的关系. 地质科技情报, 19 (2): 5-11. doi: 10.3969/j.issn.1000-7849.2000.02.002 [23] 殷鸿福, 张克信, 1998. 中央造山带的演化及其特征. 地球科学———中国地质大学学报, 23 (5): 438-442. -
下载:
点击查看大图
图(4) / 表(1)
计量
- 文章访问数: 3596
- HTML全文浏览量: 97
- PDF下载量: 6
- 被引次数: 0
