K-Ar dating of late Mesozoic volcanism and geochemistry of volcanic gravels in the North Huaiyang Be

来源 :科学通报 | 被引量 : 0次 | 上传用户:poshashajia
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
Two eruption episodes are identified through systematic field investigations and K-Ar dating of the lateMesozoic volcanic rocks in the North Huaiyang belt (NHB),Dabie orogenic belt, of which the earlier volcanic suitetermed Maotanchang Fm. (Fm.) occurring at Jinzhai,Xianhualing and Maotanchang, etc., was erupted from 149Ma to 138 Ma. The other named Xiaotian Fm. mainly dis-tributed at Xiaotian, Shucheng, etc., was formed between132 Ma and 116 Ma. During the eruption gap of the two vol-canic suites deposited a volcano-sedimentary conglomeratelayer, which are composed of the multi-compositional gravels, including the North Dabie orthogneiss complex (NDOC),volcanic gravels, etc. These volcanic gravels in the con-glomerate layer show identical geochemical and isotopic compositions (87Sr/86Sr(t) =0.7084-0.7092, (Nd (t) = 21.8-24.4) to the Maotanchang Fm. volcanic rocks (87Sr/86Sr = 0.7086-0.7102, (Nd = 19.2-24.4), but significantly distinct from those of Xiaotian Fm. (87Sr/86Sr = 0.7076-0.7084, (Nd = 17.2 - 19.2). K-Ar dating results of its underlying andoverlying volcanic sequences indicate that the conglomerate layers were deposite d at ~135 Ma. This suggests that the NDOC was rapidly exhumed to the surface dur ing or shortly before ~135 Ma and became the important provenance of the late Me sozoic volcano-sedimentary basins in the NHB. In combination with the regional v olcano-sedimentary correlation, we divided the Mesozoic stratigraphic sequence i n the NHB from base to top into Fanghushan Fm. (>160 Ma), Yuantongshan Fm. (/mid dle- lower segment of Sanjianpu Fm.) (160-149 Ma), Maotanchang Fm. (/Zhougongsh an Fm./upper segment of Sanjianpu Fm./Fenghuangtai Fm.) (149-135 Ma) and Xiaoti an Fm. (/Baidafan Fm./Heshidu Fm.) (135-116 Ma).
其他文献
The functional relation between theδ18O values in the shell of gastropod Gyraulus sibirica and the air temperature in the warm half-yearly period, and that bet
岩土勘察在岩土工程中起着决定性的作用。概述了岩土工程勘察各阶段的工作任务和岩土工程勘察技术管理中存在的问题,并有针对性的提出了解决现存技术管理问题的对策和办法。
最近年来,在珠宝市场上出现了用合成碳硅石充当钻石,以假乱真的现象,给珠宝商和消费者带来了极大的损失。这一情况引起了国内外珠宝检测机构的极大的警觉。基于这种情况,本文笔者
Study on two loess sections, one located at Wuwei near the Tengger Desert in northwestern China, another located near Ganzi at the southeast margin of the Tibet
随着数字测图理论与实践的进步,数字化测绘技术也逐步应用到地籍测量中,这就是数字地籍测量。其实质是一种全解析的、机助测图的方法,是一个融地籍测量外业、内业于一体的综
在前人系统的普查工作、区域地质成矿背景下,通过地质填图、槽探及钻探工作,大致查明矿区地质、构造、岩浆岩的基本特征及与铜银多金属的成矿关系。
本文结合自身多年工程经验,对钢结构施工中一些常见节点处理措施进行了简单的论述,以供同行参考。
高密度电阻率法与传统的电阻率法相比,成本低、效率高、方便、信息丰富,勘探效力显著提高,该方法对于研究区的浅层地层分布、地质构造等均可取得较理想的探查效果,为准确掌握水文
新世纪对水工建筑设计提出了更高的要求,在满足运行功能的前提下还要注重水工建筑物的外形美观和环境效果。文章从外观设计质量及水工建筑的主要内容谈起,就建筑设计中如何做到