Zircon U–Pb Ages and Lu–Hf Isotope of the Dongchuan Group in Central Yunnan, China, and their Geolog

来源 :地质学报(英文版) | 被引量 : 0次 | 上传用户:heroic008
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
On the southwest margin of the Yangtze Block, the Dongchuan Group consists of slightly metamorphosed sedimentary rocks, including silty slate, argillaceous slate, clayey slate, arkose, dolomite, and minor volcanic rocks. To date, it is still a controversy over the depositional age and stratigraphic sequence of the Dongchuan Group. In this study, we analyzed five samples of meta-sedimentary rocks and one sample of meta-tuff from the Yinmin, Luoxue and Etouchang Formations of the Dongchuan Group in the Yuxi region for detrital zircon U-Pb ages and Lu-Hf isotope. The detrital zircon ages of the meta-sediments vary from 3073 to 1703 Ma, mainly clustered at three periods, from 1889 to 1840, 2490 to 2008 and 2878 to 2844 Ma. The youngest age peak of all the samples is ~1859 Ma, with the εHf(t) values of the zircons ranging from ?20.3 to +4.3 and more than 90% being negative, indicating that the Paleoproterozoic crustal accretion on the southwest margin of the Yangtze Block was dominated by reworking of the ancient crustal materials involved in the assembly and breakup of the Columbia supercontinent. Another important age range is between 2490 Ma and 2008 Ma, with εHf(t) values from ?14.7 to +8.9 and 70% of them are negative, suggesting that the magmatism in the source area was also dominated by reworking and recycling of the ancient crustal materials, with minor juvenile mantle substances added. The detritus was probably derived from the Paleoproterozoic crystalline basement in the south Yuxi region. The oldest peak age is ~2847 Ma and the εHf(t) values are from ?7.7 to +7.0 with 50% of both positive and negative values, demonstrating a possible ~2.85 Ga ancient continental nucleus on the southwest margin of the Yangtze Block and substantial growth in juvenile crust materials during this period. Besides, the weighted average age of the zircons from the meta-tuff of the Etouchang Formation is 1677 ± 14 Ma. Combining the previous research data and this study, we can constrain the depositional age of the Dongchuan Group in central Yunnan Province to the period from the late Paleoproterozoic to early Mesoproterozoic, slightly earlier than that of the Dongchuan Group in the Dongchuan area near to the southwest Sichuan Province. The depositional age of the Dongchuan Group is older than that of the Kunyang Group.
其他文献
目的:观察氯诺昔康的使用和术后炎性介质的变化的关系.方法:(1)实验性研究(experimental study)(2)观察对象:20例患胆石症的病人,均选择在连续硬膜外麻+静吸复合全麻下择期行
目的:比较针刺、电针和艾灸治疗膝骨关节炎(KOA)的临床疗效差异.方法:84例KOA患者随机分为针刺组、电针组和艾灸组,每组28例.针刺组予毫针针刺,取穴为患侧的内膝眼、犊鼻、鹤
目的:观察电针结合艾灸治疗肾阳不足型中风后尿失禁的临床疗效.方法:将60例肾阳不足型中风后尿失禁患者随机分为对照组和观察组,每组30例.对照组给予口服金匮肾气丸和缩泉胶
丰台区长辛店街道陈庄社区的老党员赵国才,一大早就戴上红袖标上街了,边搞卫生边巡逻。他说:“我要搞好环境卫生,我们这儿紧挨着园博园,街上每天都得干干净净的,要为园博会增
目的:观察芒针恢刺疗法对梨状肌综合征的临床疗效.方法:将100例梨状肌综合征患者随机分为普通针刺组及芒针恢刺组,每组50例.普通针刺组针刺患侧环跳、居髎、秩边、委中、阳陵
目的:我们从临床角度出发,以转化生长因子β1(TGF-β1),血管内皮细胞生长因子(VEGF)为指标,结合肾脏穿刺病理检查,对肾病综合征患儿进行了研究,旨在达到以下目的:1、探讨不同
【摘要】二类调查是以县级行政区域为调查单位之一,十年进行一次的森林资源调查,以满足县级行政区域下一步的森林经营方案、总体设计、林业区划与规划设计提供依据,做好森林二类调查工作具有重要意义。文章通过广西百色三好林业咨询服务有限责任公司与广西区林业勘测设计共同完成的乐业县2019年的二类调查,对森林资源调查工作进行分析,探讨森林二类调查内外业工作措施。  【关键词】森林调查;森林资源;二类调查;内外业
目的:观察电针“肾俞”对SAM P8小鼠海马区神经元超微结构及细胞周期蛋白依赖性激酶5(CDK5)、Tau蛋白的影响,探讨电针防治阿尔茨海默病(AD)的作用机制.方法:将5月龄雄性SAMP8
目的:研究青少年正常骶髂关节的X线及CT表现;评估JAS患者骶髂关节炎的X线及CT表现特征;比较X线平片及CT在诊断骶髂关节炎中的作用.结论:1.正常青少年(10岁~20岁)骶髂关节间隙
目的:分析古代医籍针灸治疗痰证的取穴思路,指导现代临床治疗.方法:以“痰”为检索词检索《中华医典》,根据纳入排除标准筛选文献,建立数据库,进行穴位及穴位与经脉、分布部